How do I roast a whole duck so that fat drips out easily and the skin gets crispy?

Question: Duck is high in fat, so when roasting a whole duck you can end up with a lot of fat left with the duck inside the skin and soggier skin. How should the duck be prepared to avoid this?
Answer: Among poultry, duck is exceptionally fatty, and a lot of its fat is directly underneath the skin.  This can present a challenge when cooking, because we want the fat to render out and the skin to become crispy and delicious.
The most common way to do this, classically, is to:

Dock (or less commonly, score) the skin all over, to permit the fat an exit path (when doing this, be careful to cut through the skin into the fat layer, but hopefully not into the meat itself)
Roast at a relatively low temperature for to permit the fat time to melt and drip away; many recipes then finish on a higher temperature for crisping and browning

Like all poultry, salting the duck a day ahead, and then letting it sit in the refrigerator will also promote crispiness, but it is far less of a factor with duck which cooks and renders for a longer period of time.
Answer: I don't like greasy duck and after trying different methods found an indoor rotisserie and an adjustable bladed box cutter to be the solution. The box cutter allows you to make shallow cuts thru the skin only and as the duck turns slowly on the spit the melting fat bastes the duck resulting in a beautiful crispy non-greasy skin. (My mouth waters just thinking about it)
Answer: An effective method is to score the skin a bit and then steam the duck until most of the fat has melted, then roast at high temperature. I've seen many claims that this is the method typically used in Chinese and other eastern cuisines, but I can't confirm that from personal knowledge.


Audacity: calculate exact amplification

Question: Imagine I have 2 audio files. They contain same audio but one of them was amplified using Amplify effect of Audacity. I don't know the value used. Is it possible to calculate exact dB value used to change one file comparing it with original? How?
Answer: If the amplification was linear, and didn't result in clipping, then comparing any given peak value (in Audacity) between the two files will give you the information.
Answer: Try amplify in the second file.  The dB needed will bring it to the first files level.
Now if you compress or process the files otherwise the amount might be different than just amplify would use without the processing.
Note that while the levels are the same the loudness may well differ.
See LUFs to learn more about loudness standards and how they differ from levels.
Comment: Loudness standards have nothing to do with the OP's question.
Comment: So what.  I added a useful lagniappe in addition to the answer of the question.

Audacity: calculate exact amplification


Disable message autoselect in OS X Mail

Question: Is there a way to stop Mail from automatically selecting messages? For example when I delete a message, it will immediately select the next one and mark it read. Then if I don't want to read the message yet, I need to mark it as unread.
Comment: If you are not using Yosemite, try [this](http://apple.stackexchange.com/a/156570/54484) and increase the amount of time before a message is marked as read. If you are using Yosemite, there is no way to change the time before it is marked as read, and no way to prevent it from automatically selecting the next message.
Answer: Press option+delete or option+← to delete an email and not select the next email.
If you use an international keyboard: United states option key may be labelled alt and/or ⌥.
Comment: This should be the selected answer!
Answer: I'm afraid you can not change this behaviour in the Mail.app settings.

Edit: As @myhd pointed out, you can indeed change the behaviour with ⌥ + ⌫ Delete!
Answer: I, too, prefer that Mail.app not mark the next message as read. I am also using Yosemite. The only way that I know of to accomplish this is to hide the message viewer:
Mail => Preferences => Viewing tab => select 'Use classic layout'
Now the Mail window only shows the list of Mailboxes on the left (which is optional) and the messages in the current mailbox on the right. (You may need to drag the divider between the message list pane and the message viewer pane all the way down to the bottom of the window.) To view a message, double-click it in the list view and it opens in a separate window. From there, you can close, reply, forward, mark or delete it. If you delete it, the next message in the list is highlighted, but not marked as read until you open it.
Hope this helps.

Disable message autoselect in OS X Mail


Why do manwha more oftenly have colored pages then manga?

Question: Lately, I been reading quite some more manwha cause of their good stories. But I can't help but notice that manwha use a lot more colored pages, sometimes even fully colored volumes. Or just all pages color, why are color pages more commonly used in manwha then  manga? Is there a specific reason for this?
Comment: are you sure you're not talking about webtoons not manhwa? like manga, manhwa only gets coloured pages if it's a special edition or it's leading in the popularity votes similar to what's been shown in bakuman.
Comment: Are you sure that such things ain't Webtoons?
Comment: @Braiam Pretty sure yes. A sample would be the popular manhwa "Magician" by Kim Sarae.
Comment: To Love Ru is actually the only colored print I know about. Most manga(or much of anything else) are printed in black and white. Webtoons, being digital, are usually full-color. ReLife, being a webtoon, is full-color as well as many other web toons you may confuse as manga/other print.
Answer: There's the so called WebToon, which is most likely the one you refer to (and you are reading). Frankly speaking, printed color pages are not cheap. They cost a lot more than B&W page and are difficult to print correctly. With webtoons there's no such thing as "printing", everything is done digitally.
Manwha that is done in B&W completely due its distribution method (printed) which you will not see color pages (like Chevalier of the Absis, or ID which has some color pages as bonus), there's also webtoons that could be printed later on (like The Breaker/NW) and there are those that are not printed (almost all webtoons).
Is difficult to see a Manwha (or any printed media) in full color. The only case I know of is To Love る which is released later on after the black and white pages are released.
Is a matter of cost of distribution of the media, which is cheap for webtoons so artist can offer color pages.

In the example you gave, "Magician" by Kim Sarae, this is an original webtoon that is published using Naver.

A list of manwha that are in full color (MU): ~250 titles
All kind of manwha (full color and B&W) (MU): ~1500 titles

There are lots of black and white Manwha, just that are more difficult to find since they are distributed physically.
Answer: Actually, most manhwa aren't colored either. Along with some webtoons, only a few manhwa are colored.

The reason they aren't colored is because it takes a long time to create manga and manhwa, and it's a lot more expensive if each page is colored. Most of the creators start working alone without any financial support, thus making colored pages very difficult. Western comics are mostly made by large companies like DC or Marvel, and these companies have enough resources to make colored comics quickly.
Additional Resources:
If you'd like to confirm that manhwa is usually black and white, MyAnimeList has a list of manhwas for reference.
MyOtakuWay explains the difference between manga and manwa.
Searching for manga on MyAnimeList.net will let you see that most have just one author, not a campany or a staff.
Finally, ComicList is a list of comics where you can see that they are made by a company.
Answer: Long time ago before when there was no internet yet in this world, I always found Chinese comics (maybe weekly comics because they were thin) in full colour. I don't know why, but probably it's because of tradition.
In contrast, manga have no colours probably because of the Japanese mentality - they don't like to waste money etc. I'm saying this because, in national universities, even the copy paper there uses recycle papers. Not to mention the shounen magazines etc, that one's quality of paper is terrible, that's why they can sell a thick shounen magazines considerably cheap.


Is iCloud Backup issue will arise for applications build in lowers iOS SDK versions

Question: I developed my application using Xcode 4.0.2 and iOS 4 SDK.  Currently i am storing lots of documents and files in the Document Directory.
From iOS5 onwards, files and documents stored in the Document directory will be moved to iCloud automatically when they sync up with iTunes.
My question is whether it will affect the iOS applications build with SDKs like iOS4 or iOS3.
Are we need add additional code to disable the backup option in lower versions also like iOS 5.1 iCloud disable feature.
Answer: yes you need some additional code to prevent this back-up,please refer to the following link:
iOS 5.0.1 : How to verify that the folder is marked as "Do not back up" for iCloud?


Do I need a visa for Japan as a New Zealand Citizen?

Question: I'm from New Zealand and I am planning a trip to Japan next year. The flights I'm looking at have short layovers in Australia where I don't plan on leaving the airport so I don't think I need a visa for that, but will I need one for Japan?
Answer: As a New Zealand citizen you won't need a visa for Australia as you don't plan to leave the airport and will only be there for a few hours. If you do choose to take a longer layover (8+ hours) or leave the airport you can get a SCV visa on arrival by filling out a landing card.
You don't need a visa for Japan either as you are going for 90 days or less, but you will need an onwards/return flight as detailed in Timatic, the database used by airport staff:

The following are exempt from holding a visa: Nationals of New Zealand
  for a maximum stay of 90 days.
Important: Visitors not holding return/onward tickets could be refused
  entry.
Comment: note that some things (criminal record, untreated tuberculosis) may disqualify NZ citizens from a SCV; anybody who falls into those categories needs to make arrangements in advance.
Comment: I don't have a record or sickness so that's fine, thank you!
Answer: NZ citizen here.
You don't need a visa for Australia as you're in transit, and even to visit don't require one.
As a tourist in Japan, you need a flight/boat trip/etc out of the country, but otherwise can have up to 90 days.
Source: Have visited, transited and lived in Aus, and visited Japan four times, on a NZ passport.
Comment: Technically NZ citizens *do* need a visa to visit Australia, but most automatically qualify for a Special Category Visa on arrival. As I noted on Uciebila's answer, some NZ citizens don't qualify for a SCV and will need to make other arrangements.
Comment: @kelly summers Enjoy your stay + unless you go for the Olympics, better avoid that time, as it will be more crowded + expensice. Just in case you happen to check also elsewhere and get worried as you may see that a "tourist visa" is required. If so, the "tourist visa" refers to the permission to stay in Japan during max 90 days that you are "automatically" granted open arrival [unless you e.g. have some "bad past history" like having overstayed in Japan earlier, are under some criminal they want to arrest etc.] No preparations needed to get it.


How does size/complexity of a project impacts efficiency of a user centered design process?

Question: Which approaches help for small/middle/large scaled software projects?
I'm working sometimes on projects with 50-100developers (+other stakeholders) over several years and I'm still unsure if ucd would be the best (standalone) approach.
Comment: This is a very opinion based question IMHO, not to mention UCD doesn't apply to anything and everything, thus without further information on teh project(s) it's almost impossible to answer
Comment: We can not treat this forum, covering the emerging and subjective field of UX- as other stablished, objective fields such as programming. Creativity and design are big part of the field hence it is not always a right or wrong answer to questions. Many answers to some still valid questions can be based on opinion and personal experience which is not always destructive. in particular since the filed still suffers from limited num of of reliable sources in some aspects.
Answer: The size and complexity doesn't affect the efficiency of a UCD process. The way you implement the UCD process does, and it needs to be optimized depending on the size and complexity of the project, not in terms of what needs to be done (you should still aim to do research and testing), but just how it needs to be done (since you may have different project timeline and budget constraints).
The common dilemma for the project manager these days seems to be trying to do LEAN + AGILE + UX, and for organisations that are finding its feet in transforming or adopting one particular approach, trying to do all three at the same time is probably going to be biting off more than they can chew. I suggest trying to become leaner first if you have large and complex projects, then try to be agile with development implementation strategies then work some UX design approaches into the mix.
Answer: I do not believe one process is 'the' process. Any organization depending on the culture, knowledge, experience, and maturity in UX can adapt a whole process or parts of it. UCD, Usability engineering and other approaches also emphasize that it is not necessary to keep the whole process and part of them can be adapted based on the needs of the organization.
The more important issue in my view is how the selected process or practices fit into the current organization, and the existing processes.
I have spent some time studying different organizations and how they approach UX. I have found it much more complex to use UCD in bigger organizations with different internal stakeholders that have different views on UX, different motivations, and different priorities. It is often the case that these views are conflicting. One example is the tension I have observed between designers and product owners in agile settings. This is even more difficult in companies that are not 'market-driven', or do not have 'competitors'. In such cases, showing the value of UX is more challenging.
In cases where UX practices or processes are selected and introduced without taking the whole context into account the conflicts tend to increase and power struggles appear.
I believe a successful approach to UX, and assuring good UX in products can only be successfully (Effectively and efficiently) achieved when the current working development processes  are taken into account when introducing UX practices (UCD has for instance a list of these practices and how they map to different stages of SW development).
In my view, UX literature has not sufficiently explored the organizational aspect of implementing such processes and practices. Merely focusing on the process has the risk of 'ripple-effect' when introducing that into an organization. There is more risk that other stakeholders like developers show resistance towards the process. I believe any person who is concerned with working with UX in development organizations should  have an eye on 'organizational change' issues.


Multiple Half-lap Jig for Grid Work

Question: I'm making a gate from 2x2 material.  I want to build-in a half-lap grid. I came up with a jig to use with my router that involves laying the 2x2 side by side in a box 1 1/2" deep  then attaching at 90 degrees, a series of 1 1/2" template pieces with a 1 1/2" space between each template piece.  As you can see in the photo, I'm able to get results but not consistently enough for my needs.  I would like to do this on the table saw with some sort of jig similar to a finger joint jig but would need to make two cuts per crosscut.  An inch and a half dado set would be perfect but not an option. Maybe using such thick material makes a jig impossible.  Any input would be appreciated.
Comment: There's no reason you can't do what you want successfully with a router, in fact I think this should be the preferred method for a couple of reasons. Can you identify the source of your consistency issues? You're ganging them together to cut multiples correct, is the squareness of the fence the issue? Or is it maybe that the workpieces aren't firmly clamped so some or all can shift just a hair during the operation? If you get everything dialled in and tight this should be a dream job for the router, resulting in the cleanest, most consistent half laps of any technique bar using a CNC :-)
Comment: Graphus-- I'm thinking you are right and I may need to make heavier templates and generally tighten the jig connection to the material.  I really appreciate your comments, Thank you.
Answer: So to start by clarifying the issue...if you have a normal finger-joint jig with a stop block the same size as your dado stack there is no way to reference the first cut on each board.  Since the stock is wider than the dado stack you'd need two passes, one for the "leading" edge of the half-lap and one for the "trailing" edge.  Once the first dado is made on each board you can make the next dado by aligning the stop block on the two sides of the previous dado.
I think the solution will be to have a second, movable reference block whose width is the difference between your stock width and your dado stack width.  You'll then make your first cut with the new block set against the jig's stop and the end of the work piece against the new block.
 Then your second cut with will be with the end of the work piece against the jig's stop.  (Note that for this use of the jig the jig's stop should be the stock width plus the new block's width away from the blade.)
For example, say you've got a 3/4" dado stack and your stock is 1" wide.  You'll need a stop block 1/4" wide.  Your first cut (with the new block) will be from 1" to 1 3/4" from the end of the work piece, and the second cut (without the new block) will be from 1 1/4" to 2" from the end of the work piece.  (I'm not using your exact dimensions because I think this makes it clearer what is happening...)
Comment: FYI, I've never done this myself, so if I'm missing something here please let me know...
Comment: SaSSafraS1232 - I think you may have the answer.  I'll have to do a drawing before I can see it clearly.  Thank you for your help.
Answer: I did something similar to make book shelves for paper backs.
For a given set, I clamped all the verticals together, then made two passes with a radial arm saw to define each side of the cut.  Did the same for the shelves.  Took out the wood between with a chisel. Since the baseof each cut was buried in the joint, I didn't care if that was rough.  My shelves weren't designed to have shelves flush with risers.  I wanted to use 1x4 material (3/4 x 3.5) and a paperback is about 5" wide,so the shelves were proud of the risers by 1.5"
You can define the edges of the cut with a regular saw blade, then make a series of passes with a dado to clean out the middle.  Make a few extra pieces during the first stage, so you have test pieces to dado.
Comment: Hello Sherwood,  Thank you for your input.  I haven't had time to get a jig together but I will incorporate your suggestions.  Thanks again.
Answer: The jig you want for this looks like this

There is a set screw on the end not shown on the picture to set the thickness of the saw blade (done once when you make the jig). When using the jig you just clamp
around the piece that you want to cut a groove for and that's it for setup. No calculations, just using the jig's two different lengths as end stops for the inner/outer cuts and then rip away the waste in between.
There is a build description on this web page and a corresponding video.

Multiple Half-lap Jig for Grid Work


I am looking to isolate an inverter when power from a generator is applied- debounce relay?

Question: I have tried to find specific info on this scenario with no luck
The situation is this;
Off grid power system 12v battery store runs 12v lights etc. and an inverter for things difficult to run or convert.
I have a relay which energizes from the generator output and disconnects the inverter (so I'm not trying to push two unsynchronized ac signals in the same circuit)
The theory seems good, but I have managed to fry two inverters and I think this is due to a quick on/off switching of the relay as the generator powers down causing spikes and knocking out the output stages of the inverter.
It would be good to isolate the inverter completely, i.e 12v input side and ac output side- but I feel like a debouncing type circuit is needed on both relays
Any ideas/suggestions as to the simplest (and cheapest!) way of sorting this would be greatly appreciated.
Comment: Have you considered a SSR?
Answer: I believe that what you might really need is a changeover contact then neither grid/AC nor inverter output can be connected together. When AC resumes the relay, in sequence, disconnects the inverter and milli seconds later reconnects the AC to the load.
There may also be another problem that you haven't considered and that is when you disconnect the inverter output when it's supplying a high current to the load. This may cause some back emf (due to the inverter output filter) and this may "hurt" the inverter.
Anyway, it's worth trying the changeover relay and if it still gives problems then you'll have to find a way of ramping down the inverter output voltage to a safe level before disconecting and reconnecting the AC.
Comment: Thanks Andy.The intention would be to not have anything powered by the inverter when the generator is started- so hopefully that's not a problem. The switch on the inverter could be changed for a relay though?
I appreciate your time to answer the question.


How can I make the dimensioning of a temperature monitoring circuit?

Question: I need to design a circuit to measure temperatures in the range 15-40 degrees C (this will later be the basis for a regulator of a peltier-element for a fridge).
I tried a circuit using the bandgap-reference of 2 transistors, but it did not work. Now I would like to use a circuit with a transistor used as a diode. I could only come up with a transistor (with B and C connected together), in series with a resistor (for a supply voltage of 12 V I will choose a resistor of 11.3...12 k). But I think this circuit is too simple.
I also found this circuit, but I don't know how to make the dimensioning of the components.
Answer: The easiest is to get a off the shelf temperature sensor IC.  These are cheap and plentiful, and do a much better job than you can cobble together on your own.  These devices are available with a voltage output you can run into the A/D of your micro, or with a digital interface like IIC or SPI.
Trying to make your own just doesn't make sense, especially if you have to come here asking how.
If cost is a overriding concern, then the cheapest temperature sensor is probably a thermistor and pulldown resistor.  These things have a large temperature response, so all you need is those two components to directly drive a A/D input of the micro.  Another advantage of thermistors is that they can be thru hole and thereby mounted standing off the board up to a few 10s of mm.  That can help in measuring air temperature and being less sensitive to board temperature.
The downside of cheap thermistors is that they aren't very accurate.  This method is appropriate for measuring temperature to decide how hard to run a cooling fan, but not for controlling a environmental chamber to ±½°C.
Comment: After trying some circuits which didn't work (the voltage didn't change with temperature), I just connected a transistor (B and C together) with a resistor (12k for an input voltage of 12 V) and measured the BE-voltage. It had a variation, as expected, of about 2 mV per degree). I think I should amplify this voltage, so that it would be easier to interpret, but I am not sure how (if I need anything other than an opamp). Afterwards, I will use a comparator to feel the difference between the measured voltage and a reference voltage and thus make the PWM command.
Answer: You'll want to drive the diode (or diode connected transistor) with a current source.  10uA is a nice value.  An easy(accurate) current source can be made with a voltage reference, opamp and resistor.

Edit.. I should add that there are a lot of power supply connections and bypass caps missing from the above schematic.  (for R1 try two 1 Meg's in parallel (1% or better).. with more time than money you can futz with the R's )
Comment: Perfect floating voltage sources like that are *hard* to find.
Comment: @ConnorWolf,  I think almost any voltage reference will work.. I've done it with REF02's and REF102's.  http://www.digikey.com/product-search/en?x=0&y=0⟨=en&site=us&keywords=ref02


What happens when a new instance of a contract is created?

Question: I was wondering what happens when a user wants to create a new instance of a contract. Is a copy of the contract created from the contract that was first created on the blockchain, but given a different address and is stored as a new contract on the blockchain? Does something change with the initial contract deployed on the blockchain?
Answer: Two deployments of the same contract code are unrelated.
It's analogous to installing Microsoft Word on two different computers. The same code is running in two places, but that's the extent of the connection.
Comment: So let's say that there is a contract for an auction already in the blockchain. If a user would like to create his own auction, he would still call the constructor from the initially deployed contract and create a copy of that contract but with his address?
Comment: No, he would copy the code, paste it into Remix or the like, compile it, and deploy it. He would not interact with the other contract at all.
Comment: Ok interesting. Is it possible to make a smart contract work in a way that every user with an address uses the same contract. Like for the auction example, can a user create an auction and the auction he created is mapped to his particular address, and when another user creates an auction it is mapped to his address, without the need of creating new contracts?
Comment: Yes, the EVM is Turing complete, so you can write whatever code you want in a contract.


Why do we assume weight acts through the center of mass?

Question: The weight of a body acts through the center of mass of the body. If every particle of the body is attracted by earth, then why do we assume that the weight acts through the center of mass? I know that this is true but I can't understand it. Does it mean that the earth does not attract other the other particles of the body ? Wouldn't it mean that girders would not need any support at the periphery if we erect a pillar at the center?
Comment: Gravity acts at all points of a body. In classical mechanics, you can invoke the concept of the center of mass in order to view the situation more compactly, as it could rule out the unnecessary details about the size or shape of the rigid body under consideration. Instead of a bulky body motion, you can simply illustrate it as a simple particle motion, where the point particle represents the center of mass (or the entire) system, without failing any associated dynamics related to it.
Comment: @unnikrishnan I think you ought to expand the comment into an answer.
Comment: Weight acts at the center of mass of a rigid body because "center of mass" is defined as the point where the weight action is centered.
Comment: I'm confused about your second question. Do you mean to say that you want to erect a pillar at the center of the earth?
Comment: I think u misunderstood that. So gravity acts through center of mass of a body but then why do girders bend at the periphery even if the gravity acts at the center?
Comment: This question has more about the ideas discussed here. http://physics.stackexchange.com/q/95234/37364
Comment: "Wouldn't it mean that girders would not need any support at the periphery if we erect a pillar at the center?" - but this is true! Take a drinking glass and put a piece of paper on top of it so it doesn't fall off. Now the paper isn't supported at the periphery, only by the "pillar" at the centre, yet it doesn't fall down. You will run into a separate problem if you try to support heavy things at the edge of the paper (or girder) of course because it will bend.
Answer: The other answers here, which show that gravity does not exert a torque on an object, are correct. However, they rely on the following implicit step of logic to get to the answer the OP wants:
An object that has a force acting on it, but no torque acting on it appears as if it is being pulled from its center of mass.
This is true in the case of ideal rigid bodies only. In the case of elastic objects, OP is absolutely correct, in that gravity does indeed act on each individual particle in the object. This is why girders bend under their own weight, among other things.
Comment: I think this answer is not correct. Generally the centre of gravity does not coincide with the centre of mass **unless the gravitational field is uniform**. When that is the case, CG and CM coincide regardless of the rigidity of the body. For  bodies much smaller than the Earth, the gravitational field is uniform to a good approximation. The rigidity of the body has nothing to do with the matter. It is a Red Herring. Gravity acts on all particles of the body whether it is rigid or elastic.
Comment: Considering his question was about girders, which typically aren't planet-sized, there is only one relevant approximation here, which is the one I specified. You are technically correct, though.
Comment: The curvature of elastic objects under gravity is quite complicated, and likely beyond my powers of explanation this early in the morning (greetings from UTC -5). Maybe this will help? https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.me.berkeley.edu/~lwlin/me128/BeamDeflection.pdf&ved=0ahUKEwis6LmOkZzRAhVE2oMKHW7vDY0QFggfMAE&usg=AFQjCNFq8o6qdHoASfNHdH7nnumOOqJyPw
Comment: Girders would bend even if pulled from the center of mass.  A better example would be a two by four held up on your shoulder bending even when you're supporting the center of mass.
Comment: Hence why I said, "bending *under their own weight*". That eliminates any doubt as to where it's being pulled.
Answer: As a point of clarification which perhaps has not been made as clearly in the other answers: No, the weight of a body does not act through the center of its mass, and no such assumption is necessary. However, one can show (see the answer by @tomph) that the sum of all gravitational forces (which indeed do act on any small part of the body) can be replaced equivalently by a single force through the object's center of mass, if that object can be thought of as rigid. The "equivalently" in this statement refers to the fact that, when we calculate e.g. the forces required to hold such an object in place (by "pillars", say), the result will be exactly the same whether we use the single weight force acting through its center of mass or the actual weight distribution of the object.
In short, the model of the single force acting through the center of mass is a very convenient simplification, but it's neither a necessary assumption nor does it reflect reality. As others have said, once we want to describe the behavior of deformable bodies or discuss interior load distributions in a body, this model is no longer adequate or useful, or even correct, as pointed out by @probably_someone.
Comment: One cannot actually show this in general because it's wrong. It's true (a) at the surface of a planet, where the gravitational force is uniform throughout space and (b) for spherically symmetric bodies on scales where gravity is not uniform. These account for the vast majority of cases that come up in real life.
Comment: Two answers: First, I think you would have to consider my answer in the context of the question it was addressing, which was clearly a question by someone without a high level of formal training (and I will note that this is not meant as a slight). For the scenario this person had in mind, I am willing to bet that my answer was appropriate without going to great lengths to establish the conditions under which it hold (and can is "true").
Comment: As a second answer, taking a more formal perspective, if we consider the $L_2$-space of all square-integrable force density distributions, then my answer is "generically true", in the sense that it is true for all possible force density fields in the above set, with the exception of a subset of measure zero (the subset comprising the distributions that produce a finite moment with zero net force).
Answer: The fact that a weight of a body seems to act on its center of mass is a direct consequence of the weight being a parallel force field (obviously assuming that the body is small enough for the field $\textbf{g}$ to be constant over it).
Consider for simplicity a discrete system formed by N particles, each of mass $m_i$. The total external force acting on this system is
\begin{equation}
\textbf{F}_{tot} = \sum_{all \,particles} \,m_i  \textbf{g} = M \textbf{g}
\end{equation}
where $M$ is the total mass of the system.
In order to prove that the body is not rotated around its center of mass by its weight alone we consider the torque exterted by weight with respect to the center of mass:
$$
\tau _{cm} = \left(\sum_{all\,particles} m_i \textbf{r}'_i\,\right)\times\,\textbf{g} = \left(\sum_{all\,particles} m_i (\textbf{r}_{i} - \textbf{r}_{cm})\,\right)\times\,\textbf{g} = (M\textbf{r}_{cm} - M\textbf{r}_{cm})\times\textbf{g} = \textbf{0}
$$
where the primed coordinate are with respect to the center of mass.
Thus, as you can see, the weight of a body exerts no torque on the body. From these result we can infer that, of course, every particle constituting the body is subject to weight, but the total effect is exactly the behaviour the body would have if the weight acted only on a particle having the mass of the total system and located in the center of mass.
Comment: I'm pretty sure it's also true for non-constant gravitational fields as long as they are conservative (curl = 0), not sure how to show that though.
Comment: @JasonS Mmh. Are you saying that any conservative field has the same kind of effect?
Comment: @JasonS and what about the electric equivalent? For example, an electrostatic field ($\nabla \times \textbf{E} = 0$) has a non-zero torque on an electric dipole, with respect to the center of the dipole itself, $\textbf{p} \times \textbf{E}$.
Comment: Maybe not then.  I guess this means that tidal forces can exert a torque on a rigid body?
Comment: @tomph Could you just tell me how you get $\textbf{(r prime)}_{cm}=(\textbf{r}_{cm} - \textbf{r}_i)$  ?
Comment: @TheCrypticCat it is by definition, or you could simply draw a diagram and see it is true
Comment: @tomph I kinda drew the diagram. Isn't $\textbf{(r prime)}_{cm}=(\textbf{r}_i-\textbf{r}_{cm}  )?$ (Forgive me if I am sounding like a moron).
Comment: @TheCrypticCat oh sure. You are totally right, thanks, I overlooked at it. Nevertheless it does not change the demonstration, but it was fair to point that out. Edited the answer
Comment: Is it true for any kind of force though? Does any force exerted on a body always act through the center of mass of the body?
Answer: First of all, lets look at the difference between center of mass and center of gravity in a general case.
Center of mass of a rigid body is a hypothetical point where the whole mass of the body is "assumed" to be concentrated. It's not actually true that the mass is concentrated only at a single point of he body. The distribution of mass is balanced around the center of mass and the average of the weighted position coordinates of the distributed mass defines its coordinates. If the body has a uniform density throughout, then the center of mass lies at the centroid of the body.
Now, center of gravity is the average location of the "weight" of the body, whereas the center of mass is the average location of the "mass" of the body. Hence, in general, the center of mas and center of gravity of a body are not equal. However, in a uniform gravitational field (a point on earth is a very good approximation where your body lies), these two points coincide due to the fact that the weight, $W=mg$, where $m$ is the mass of the body and $g$ is the acceleration due to gravity. This means that if we set the constant $g$ as one, or express weight in terms of $g$, then weight is numerically equal to mass. So, center of mass coincides with the center of gravity here.

Why do we assume weight acts through the center of mass?

As I have quoted in the above paragraph, the weight of a body, in general acts through the center of gravity, not the center of mass, However, a body on the surface of earth feels a uniform gravitational field and so the center of gravity coincides with the center of mass.
The center of mass is a hypothetical point where the whole mass of the body is assumed to be concentrated. Its not actually the point where the whole mass is accumulated. The mass (the amount of matter) spreads continuously throughout the body. But, when it comes to study the motion of a body, which we do actually by studying the variation in the position coordinates associated with the body with respect to time, the COM is really helpful. But, how do we associate coordinates to a body? If the body is bulky, then you can't actually specify the coordinates, instead you specify the volume of the body it occupies in the space. But, you may know that this "volume" is completely irrelevant and unnecessary for a rigid body to explain its dynamics.
To avoid such difficulty, we make use of the center of mass. You can plot the trajectory of the body in the space by tracing down the motion of the center of mass of the body as a function of time. This approach does not fail any dynamics of the body under consideration. So, we could attach the coordinates (frame of the body) on the center of mass of the body.
Gravity acts at all points of the body. The concept of center of mass allows one to study the body or a system of bodies (which I think as the most useful purpose of the concept of center of mass) in a more compact way by simplifying the problem (or by deleting unwanted details). You can assume (on Earth) that the weight of the body acts through the center of mass. An important aspect of this consideration is that the center of mass of a rigid body does not change during its motion. Also, if you consider the complex cases, for example, a two body problem, which can be resolved to a one body problem (that's really a great relief) by invoking the center of mass.
If you are not convinced in the ease of doing this approximation, consider a body moving through a gravitational field under the influence of some external force. try to resolve the Force components to get the resultant force. Without the concept of center of mass, you need to resolve it for the entire points (or particles) constituting the body.
Answer: Force that acts on the center of mass does not exert any torque on an
extended body.   So, gravity 'acting on the center of mass' means a force
that accelerates, but does not rotate, its target.
There is tidal torque on
the Earth by the Moon, but this is because the Earth is not a rigid body, and
changes shape (and weight distribution) with tides.   That means that the
Earth is effectively polarized by a gravity field, and that polarization
(tidal lobes) slows the Earth while adding to the Moon's orbital angular
momentum.   This is not due to gravity directly, but due to the time-dependence of
Earth's shape change (it isn't a time-reversible effect, though a
conservative force field, like gravity, is).
There is clearly torque, too, in a Cavendish apparatus Cavendish torsion balance where the two objects are designed to act against a torsion spring by gravity force.  So, the claim of action on the center of mass is sometimes false.
One can argue, of course, that a point mass exerts no
torque on a rigid object, because no equal-and-opposite torque can
meaningfully be exerted on the point object by gravity.  It is difficult,
though, to generalize that argument.
Answer: By definition of the center of mass is the point whose acceleration is found by $$\vec{a}_{cm} = \frac{1}{m} \vec{F}_{net}$$
In fact, gravity acts on all the bodies and as far is the linear motion of the center of mass the location of where the force is acting doesn't matter. The location of where a force is applied only matters for the rotational motion.
Take a free floating bar in space and apply a load on one end of it. The body is going to translate and rotate. If you work out the equations you will see that the translation of the center of mass does not depend on the location of the force.


How can I import a Google Sketchup model with textures?

Question: I'm using Unity 4 and trying to import a SketchUp Model into Unity and other Engines - but I can't get it to import correctly. Can anyone help me out?
Comment: What, exactly, doesn't work?
Comment: No, dont work...
Comment: When I put the 3d model gives it to me without the Texture
Answer: A quick Google search reveals this question over on the Unity forums, the steps provided there are as follows:

Sketchup Standard version or Pro Version - v8 or higher:

1 Create/open the model with Google Sketchup
2 Align the faces of the model (In the Monochrome mode--> the bright side should be up/front)
3 Export in .dae format (Default settings!)

Blender - v3.55 or higher:

4 Open the .dae file with Blender (If you want to see the textures - switch to texture rendering mode)
5 Export to .fbx (Default settings)

Unity - v3 or higher:

6 Create a new folder for your models (within the Assests tab) - Recommended
7 Create a Folder called "Textures" within the new folder
8 Drag/Import your model textures into the textures folder
9 Drag/Import your .fbx model in the new folder (same layer as the "Textures" folder)

If you have done everything right, you should see a materials folder
(near the textures folder)  If you drag your object into the scene it
should be fully textured If something is invisble - you have aligned
the faces wrong (go back to step 2)
PS: If you have Google Sketchup pro - you can skip the blender part

The basic idea being that you'll need to export through an intermediate format to get the textures working. Another step by step tutorial is available here, which includes images to make things easier.
Comment: I did not understand this part: Align the faces of the model (In the Monochrome mode--> the bright side should be up/front)
Comment: View the question on the Unity forums, you'll find that question answered.
Comment: Unity can also import .dae files perfectly fine, and will convert them itself, so the Blender step is probably redundant.


Making Web config connection strings more generic

Question: I need to deploy my MVC (Web api2.0) applications into QA then after passing, into production.  My apps access several SQL databases.  I cannot set security=integrated in either QA or Production so I set it to False but need to include the UID and Passwords in the web config files.  I know I am missing something here but how can I make process more secure and more generic so that I do not need to recompile between Dev - QA - Production and do not need to place the credentials in the web config?
Answer: Encrypt them, copy the encryption results in your config, then decrypt.  Here's one way to do that:
Encrypt and decrypt a string


Sodium potassium balance in a cell

Question: In a resting cell at steady state, is sodium influx or potassium efflux higher according to the concentration gradients and permeability, and given that the sodium potassium ATPase is active?
Answer: If potassium ions were alone inside and outside of the cell, they would be tended to diffuse along out of the cell due to high gradient inside. Because of potassium ions have positive charge, potassium lose would cause negativity inside. Within a few seconds, potential loss would rise enough to be able to stop potassium exit out of the cell. Because against decreasing concentration gradient, there would be reverse direction electrical gradient increase so these forces have to be balanced somewhere. For a large mammal nerve cell , needed potential gradient is about-94 millivolts.
We can assume similar concepts for sodium ions also. This time direction will be outer to inner side of cell. And this makes a positive potential (about +61 millivolts) due to gaining positive ions .
When we calculate total diffusion potential for only one ion, Nernst equation is used. For ions more than one we have to use Goldman equation, which is more complicated , instead.
Goldman equation consists of three factors:

Electrical charge for each ions.
Permeability for each ions.
Concentrations inside and outside of the cell for each ions.

Major factor on this resting potential is membrane permeability. For potassium ions, membrane permeability is about 100 times more than sodium ions. Because potassium leakage channels makes potassium leakage more easier than sodium. When we put this factor on Golman equation, we find resting potential about-86 millivoltes which is closer to potassium diffusion potential.
(source:Wikipedia)
(source:KhanAcademy)

Sodium potassium balance in a cell


Composite Deck Surface Mount Post Bracket

Question: I noticed that for wood decks, there are surface mount deck brackets for the 4 x 4 posts.  I just resurfaced my wood deck with composite.  I have been unable to find those brackets for composite deck material.  Are there surface deck mount posts for composite?
link to the wood version
Comment: Why do they need to be different? Do your new posts have different dimensions?
Comment: No, they are 4x4.  I have never worked with composite material before.  It seems to be more pliable than wood.  I was scared that it wouldn't be as rigid.
Answer: These brackets will also work for composite material. The composite material might be harder on a cheap drill bit, but so long as you can drill a hole through the deck, you can mount a bracket to it.


Customers grid issue

Question: whenever i select more then 20 records from the filter in the magento admin customer->all customers i have seen this issue
http://prntscr.com/n73cu6
I have tried and i can revert the filter to 20 but when i click on seeing the next 20 customers i face this issue again . is there any way to fix this issue ? I have tried almost every thing every single thing from the google help all commands are done indexer,upgrade,static-content etc every thing .
Comment: does your customer grid having custom/additional column ?
Answer: Try the below git commit. Hope it will help you
https://github.com/magento/magento2/pull/14905

Customers grid issue


Organ donation compatibility based on DNA

Question: As far as I know, multiple tests are made before organ transplant to determine matching. Would it be possible to do the matching based on the DNA of the patients, rather than the actual serum antigen/antibody? If yes, is it any better/cheaper/easier?
Comment: Since the DNA is not recognized by the immune system (in contrast to surface molecules), this wouldn't make much sense.
Comment: @Chris but the these molecules are coded by the DNA, aren't they? I know there are post translation modifications (including immune cell maturation), but I was wondering how important/predictable are they
Comment: @Zeller If you are trying do test if a chair exists, why would you look for a carpenter rather than a chair? Sure there might be DNA markers, but whilst it's cheaper and (presumably) quicker to do the more appropriate method, why would you need/want to do a DNA test? (That is not necessarily a rhetorical question)
Comment: I'm trying to find a better solution for organ transplant matching based on genetic data instead of immunology. Assuming that if all the genes are know for both the donor and the acceptor, it is possible to determine the match. I haven't researched too much as the idea came up today, but I'd like to know if it is theoretically possible. Maybe going to the gene level, you can avoid multiple tests, predict/prevent chronic rejection and so.
Answer: @zeller
The better answers are being sought in a field called Regenerative Medicine.
A number of techniques have been tried, among them 3D printing of organs and dissolving the cells from a donor organ leaving the collagen scaffolding, then reseeding the organ with a patients stem cells in a bioreactor.
Most of these technologies, unfortunately, are in the proverbial 20 years from now category, which means that there are an incredible number of technical and biological challenges to overcome, but the ideal result would be organs with the patient's own cells and therefore no rejection or need for immunosuppressant therapies post transplant.
A nobel prize was awarded a few years back to Shinya Yamanaka for creating Human Induced Pluripotent Stem Cells. A technology like this would be the likely source of the stem cells necessary to seed these organs, however there have been problems with these cell lines including their tendencies to become neoplastic and form cancers.
So for at least the near and medium term the best alternative is to find organs that are as close a match as possible for Major Histocompatibility Complexes, and as Moderator Chris said, the best way to do this matching is to test for the cell surface proteins, as these are what will be the targets of immune cells. Also an organ has a very short life span after the donor dies to be usable. Sequencing is much slower than the protein screening that is in place today. You run into ethical questions regarding keeping someone on life support for the sole purpose of harvesting their organs.
And we still wouldn't be 100 percent sure that even people with the same alleles for these molecules express them in the exact same way as there may be slight differences in the post translational modifications that are made. The human immune system has evolved to detect small variations and as such we would still need to test the proteins, even if we found allelic matches. People get autoimmune diseases all the time, so there is no guarantee that even allelic matches would not be rejected.
Comment: It's not really (directly) related to this question as such, but you have listed a lot of different approaches & you do appear to still be active in here, so I just wanted to ask if you know of any suggestions of this approach in any available literature? https://biology.stackexchange.com/questions/79881/could-bone-marrow-transplants-be-used-to-prevent-tissue-rejection-of-trans-speci
Answer: The human genome is 3 billion letters long.  Most of that sequence has nothing to do with tissue rejection.  Only a handful of genes relate to tissue rejection, so those are what one might want to sequence, but even having the sequence doesn't necessarily tell you how the proteins are shaped, and it's protein shape that determines how they interact with each other.
Comment: But the different alleles of each protein, or gene, is what determines compatibility. That could be easily tested. The thing is it is cheaper to analyse serum than Next Generation Sequencing.
Comment: The SHAPE of the proteins is what determines compatibility, and that can't be predicted now from sequence alone. Anyway, next generation sequencing takes a week, PCR and sanger sequencing of 10 genes would take 48 hours.
Comment: It is the shape, sure, but the alleles are already known. If we look for compatibility we just have to identify them, not predict their structure. And I don't know where you got that NES takes a week. NES takes about half a day depending on jow much you have to mount and sequence (providing you have the equipment in your lab).


Is is possible to save blocks from one mailing to reuse in another mailing using CiviCRM Mosaico?

Question: I have two different newsletters – a monthly one to our full mailing list and a weekly one every other week to a smaller group. They use different templates so I cannot simply reuse a weekly issue as a monthly issue or vice versa, but I often need to repeat selected blocks (Mosaico) of content in both. At the moment, I am laboriously copying each element (title, text, button text, button link, image) from one mailing to the next, but this is really time-consuming.
Is there a way to copy a block from one mailing into another mailing, eg by copy and paste or saving to a library?
Answer: One way that I  am aware of is to click into a block in one mailing and then select the "Source" button

That will bring up the HTML source code dialog window
You could copy this, and then paste it into a block on the other mailing and assuming there are no fundamental differences in the template's stylesheet, it should look the same.


How difficult will it be to determine, get and apply latest patches to Solaris 8

Question: I have a Sun Ultra Enterprise 2 running Solaris 8 (Generic_108528-11). This hasn't had any patches applied for years. I just now got the configuration right for connecting to the internet through my Verizon router. I want to get an uptodate browser (it's currently running Netscape 4.76!) but I suspect that I'll need to have the latest (or perhaps the last) patches created for Solaris 8 applied in order to have a current browser work. How difficult will it be to determine what patches I need and the get and apply them?
I've considered upgrading to a newer version of Solaris but I don't think any newer version that will run on this box is available on CD; everything is on DVD and I don't even know if I could replace the CD-ROM drive with a DVD drive.
I'm pretty much a novice when it come to Solaris or Unix when it comes to administration.
Comment: FYI: Probably the CD drive is SCSI, you can get SCSI DVD drives. Easiest way to find out would be to open the case and look...
Comment: Thanks derobert. I know it's SCSI. The question is whether or not a SCSI DVD drive will operate when connected to this box. Perhaps the fact that it's SCSI means that the fact that DVD didn't exist when this box was designed doesn't matter.
Comment: no particular experience with that system, but SCSI DVD drives speak the same protocol and are the same device class as CD drives. You may need adapters, of course, depending on the SCSI physical interfaces involved.
Answer: If you're paying for a support contract, it should be very easy to download the latest Solaris 8 recommended patch bundle from the Oracle Support website and install it using the included script & instructions in that bundle.
Oracle does not make Solaris 8 patches available without paying for a support contract, and is scheduled to stop producing Solaris 8 patches in October 2014 (over 14 years from when the OS was first released in February 2000), but will
still charge for access to get existing patches after that date.
Comment: OK @alanc. I'm beginning to wonder if I'm wasting my time trying to make use of this box. If I can't update the current OS or install a new one, what's the point? I guess Oracle can't give away Solaris 8 patches if they have customers who are paying for them.
Comment: @Tom there is a Debian sparc port, if you just want to use the hardware. Not too useful if the goal is to learn Solaris, though.
Comment: You could try installing Solaris 9, but it may be a frustrating [experience](http://www.rainsbrook.co.uk/sun/Sun-e2/). You would still need to pay for patches though. The hardware could well run for a while. they were built really well.


Overcome 2 monitor session limitation in Cisco VSS

Question: Is there a way to overcome Cisco's 2 monitor session limitation on a VSS 6500 without the use of a network tap?
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 can post and accept your own answer.
Answer: If it's like most of the hardware switches, no.  Only one "monitor session" can be active at a time, 'tho the configuration can store two.
Using vlans and external filtering hardware (gigamon?) you could have one session dumping all the traffic you want to see, but that's still one session. (and a network tap would be cheaper)
Answer: Unfortunately no.
Anue Systems makes a very slick solution which allows you to pass in all your span or tap traffic and then "switch" that traffic based on your rules to your various tools that would typically utilize a span port.
I'm sure there are other vendors that provide a similar solution but I was impressed by this particular one.
Comment: If we're throwing in companies to help with things like this then I think [Gigamon](http://www.gigamon.com/) deserve a mention. :)
Comment: [Net Optics](http://www.netoptics.com/) has a similar product but the interface could definitely use some improvement.
Answer: On the Cisco 6500/7600 Platform, you have two additional mirroring options that can be used along with, or to replace SPAN. The advantage of these two alternate methods is that the mirroring is performed in hardware (ASIC) so it does not impact the CPU like SPAN does.  The downside to these mirroring techniques is they can only mirror inbound on the interfaces. With the smart planning of multiple source interfaces, or an entire VLAN, you can still get bidirectional traffic if necessary.
For L2 interfaces (switchports or VLANs where routing is not occuring on the switch) use VACL Capture Note that this does require a rule in the Vlan map to allow all traffic, be careful to not block traffic other than the traffic you are mirroring!
For L3 interfaces (L3 ports, SVIs, subints) use MLS IP IDS. This does not require the CBAC or firewall modules, it works on a base 6500.
Answer: If its vlan traffic look into setting up VACL captures.


Can small airplanes be towed (or carried) as cargo to be dropped at some other location by air?

Question: Is there any present technology where a large plane can carry a small plane (or multiple small planes) and drop it midair where the small plane deploys itself? This would be very good from defense point of view, where small fighter jets with limited range could be dropped off by large airplanes with very long range.
Comment: Related answer: [Can a fighter jet land on a modified airliner](http://aviation.stackexchange.com/questions/9854/can-a-fighter-jet-land-on-a-modified-airliner/9856#9856)
Comment: This might be worth reading: https://en.wikipedia.org/wiki/Parasite_aircraft
Answer: If you are talking about externally carrying/deploying other aircraft, this has already been done with the B-52 (albeit for testing purposes) carrying the X-15.
I'm not too sure about having an aircraft drop out of a cargo bay such as the C-130.
On a side note military gliders were used extensively during WW2 and some were capable of carrying light tanks. The gliders were usually towed behind larger bombers to give them the required altitude and speed. They were used because of their wooden construction allowing a stealthy approach due to the reduced radar signature.
Comment: I doubt stealth was the reason. Many gliders were used only once. Wood is light and cheap. Steel would be heavy and aluminum to expensive.
Comment: Both steel and aluminum were also "strategic materials" required for the production of other essential materiel (tanks, ships, guns, field equipment, powered aircraft). The gliders were used primarily because they could get heavier equipment like jeeps and artillery into the field, and also because the ability to glide meant that the C-47 tow craft didn't have to overfly German territory (or at least not as deeply), which protected the more valuable powered planes. Bombers were rarely used as tugs for many reasons, primarily that they were way too valuable for actually delivering ordinance.
Comment: Stealth was a benefit of gliders but mainly because of their silence at low level approaching the target. Other reasons to use them included: they only needed to be able ditch  safely on rough ground without a care for taking off again (over powered transports landing); were able to offload a unit ready to fight (over powered transports dropping paratroopers); required less training of both pilots and passengers (over paratroopers).
Comment: Wood was a surprisingly good material for aircraft bodies and wings. Just reference the *de Havilland Mosquito* fighter bomber, aka *the Wooden Wonder*,which was surprisingly robust, perhaps more so than similar metal aircraft.Aircrew particularly enjoyed it because opposing machine gun fire went straight through rather than rattling around inside as shrapnel, significantly reducing casualties. Link: https://en.wikipedia.org/wiki/De_Havilland_Mosquito
Comment: Stealth technology was not really a subject in WW2 (the Ho-229 being the sole noteable exception). The use of gliders required air superiority (Germany on the Eastern Front, Allies over Normandy), and the very limited range would put the tow craft on the radar anyway. The "antidote" for radar at the time was chaff or active jamming, not avoidance. Gliders were build of (cheap) wood because they were strictly one-way craft.
Answer: Parasite aircraft is a concept that has been considered.
During the era of the zeppelins several countries experimented with launching fighter aircraft from airships, mainly as a way to get the fighter crafts to a relevant altitude while conserving fuel.  However none of these projects where realized before the end of WWI.
During WWII soviet used Tupolev TB-3's to carry I-16 dive bombers, a culmination of experiments started during the 1930's. Some of Japan's kamikaze crafts where also launched as parasite aircraft.
In an escort role Germany experimented with parasite craft solutions as a way to bypass the very short operational range of rocket powered fighters, but these experiments where ultimately judged unsuitable.
The extreme range of US strategic bombers in late WWII and early cold war lead US to consider parasite fighters as an escort solution.  However these attempts where eventually scrapped in favour of aerial refueling, as this was considered a safer option.
Source: https://en.wikipedia.org/wiki/Parasite_aircraft
Comment: Welcome to Aviation SE, Taemyr. Could you please add the gist of the link directly. If links go stale, your answer would lose most of its value as it is.
Comment: @PeterKämpf Attempted to include the gist of the article.
Comment: It's worth noting that, today, the escort fighter is obsolete. Today, we use cruise missiles, fighter-bombers and/or stealth, depending on the circumstances. A bomber that would require escort in a defenced airspace, such as a B-52, is only used once air superiority is achieved so no escort is needed.
Comment: @Vladimir At least in US practice, there are no nuclear bombs dropped by non-stealth bombers. US B-52s just use cruise missiles; bombs are only used on fighter-bombers and B-2s.
Comment: @VladimirF The nuclear bomber is largely obsolete; it's vulnerable on the ground and hard to get to the target. The retaliatory strike comes from submarines.
Answer:
small fighter jets with limited range could be dropped off by large airplanes with very long range

That sounds like a one-way mission.
Some Zeppelins and some US Navy airships did carry small aircraft that could be both launched and, importantly from the pilot's perspective, recovered in mid-air.
However in the modern world, the approach you describe is not used.
If fighters are needed beyond normal operational range of their bases, air forces will either use in-flight refuelling or create a forward operating base nearer the mission target. Aircraft carriers are a popular solution to this requirement, if adequate time is available.
Comment: +1 for mentioning that it's usually desired to get the fighters _back home_ at some point.
Answer: Since your question is about the tech, it very much does exist in a few forms at least for aircraft of varying size.
The Bell X-1 (the plane that broke the sound barrier) was a mid flight deploy from a B-29. This was a result of its low fuel load it could not really get its self off the ground and then have enough fuel to break the sound barrier.

This became common for a lot of the high speed test crafts developed over the years. Up through the X-15 (the fastest thing out there)

The first space shuttle tests were done by flying the shuttle to altitude on a modified 747 and deploying it for an unpowered decent so the tech is there even for large craft.

The more modern Space Ship One also uses this configuration to get it to altitude easier.

The tech is there and has been used over the years. Now to the more realistic question "would you do it" most likely no. As you mentioned there is a case for small limited range planes being deployed at distance but the simpler solution to that is a mid-air refuel. This accomplishes the range extension and allows the plane to get back home. The other option is a drop tank which also extends the range of a plane.
Note: Another kinda of cool solution to the problem was to weld 2 planes into one like the North American F-82 Twin Mustang.

Comment: Also, it's not unknown to tow a sailplane from one airport to within gliding distance of another.
Answer:
This would be very good from defense point of view, where small fighter jets with limited range could be dropped off by large airplanes with very long range.

Parasite aircraft as a way of increasing the range of fighters has been tried repeatedly, with everything from airships to heavy bombers as the mothership.  It turns out to be much harder than it sounds, and has generally been abandoned in favor of dedicated tankers and mid-air refueling.
Answer: Germany had some (very) limited success in WWII with the Mistel concept, which is basically the opposite of what you mentioned:
The smaller of two craft was the piloted one, the bigger craft being an explosive-carrying drone -- like a really big glide bomb. The most common combination was a Fw-190 figher/bomber carrying a Ju-88 drone.
Answer:
where a large plane can carry a small plane (or multiple small planes) and drop it midair where the small plane deploys itself

In addition to those concepts, let us not forget the Goodyear Inflatoplane, which was designed specifically to be dropped from aircraft, inflated, and flown away.
Designed for pilot rescue, the idea of dropping an aircraft in and flying it out was revealed to be ultimately impossible when one considers pilots in a Vietnam jungle.


How safe is the bowline knot in different situations?

Question: The bowline knot (picture below, source) has a great reputation as a very safe knot. Is it really completely safe in all situations and loads, or are there use cases where it may fail?
Comment: Just as a security note concerning the phrasing of the question: This knot can not be called a very safe knot, certainly not a completely safe knot (the existence of such a thing is generally debatable). Due to several deadly accidents (ring loading as described in answers) it was a nogo-knot for a long time in europe and is still not a standard knot to teach in climbing.
Comment: In addition to the other great answers, there is a 1-handed method for tying the bowline around your body, which could come in handy if your other hand is busy hanging on. A good thing to know!
Answer: The bowline knot is very safe if loaded correctly. This is the usual, safe way to load it:

The chair foot is the body (sorry for not offering naked models), the part of the rope leading away from the picture will take the load. In this use case the knot should hold perfectly. On the other hand, you might get the idea to use the bowline knot to create a sling, say to rappel down from a tree:

This is wrong and if you rappel down from that carabiner you might get yourself killed, because the knot can slip when loaded "sideways", pulling the main loop apart. There are other similar wrong use cases, all depending on the knot being able to hold when pulled sideways – which the bowline knot isn't.
This was discovered during an investigation of a fatal fall in Germany in the 1960s. The case went to the court and after that the Germans have done a series of tests on the knot to realize that it can indeed slip under side load, which is why it's considered unfit for climbing today. See Pit Schubert, Sicherheit und Risiko in Fels und Eis.
Comment: @DavidR, you're right, but the problem is that the bowline is often presented as a knot that can't slip no matter what. And unstated non-obvious assumptions (such as that you don't load the knot sideways) are *very* bad when talking about safety. Even in my answer I say that the first option is perfectly acceptable and further discussion here should make the case completely clear. Main thing is that people know the dangerous case.
Comment: Agreed.  Could you edit the title to address this?  'Sideways' loading is actually a general issue with a certain class of knots, including both the bowline and figure-8 (i.e., either of the 2 popular knots a climber might use to tie in with will fail catastrophically when sidways loaded).  I feel like this answer would be more appropriate to a differently worded question, so it would help people think about the issue clearly.  If you did that, I would delete my current answer, and write up a different one about identical issues with the figure-8.  That could actually be pretty helpful.
Comment: Every knot could fail if you construct a scenario that it wasn't designed for.  Perhaps you could rephrase the question as "is the bowline appropriate for 'sideways' loading of the main loop?".  My concern is that you asked a very broad question about a knot, then wrote a (well structured) answer about a very specific miss-application of that knot.  This is troubling to me because someone new to knots might draw the wrong conclusion (bowline is BAD) because of a miss-application (what you document is that sideways loading is BAD, which, really, applies to other knots too).
Comment: I have edited the question to sound less alarmist. I didn't want to go to the completely general case of loading different types of knots, but I think you can still slip the information about the figure-8 into your answer quite nicely.
Comment: @zoul: This is my first time seeing this question/answer and my first thought with that carabiner load is "wrong". I can see the bowline being ripped apart loaded like that.
Answer: In the context of rock climbing, compared to a figure-8 knot, bowlines are:

About as strong under ideal circumstances

BUT:

Can come untied on their own when unloaded
Are more difficult to visually inspect (important, because climbers frequently rely on partners to check their knots, and may be tying and untying knots when they're tired and / or distracted).

Both the figure-8 and a bowline (and its variations) will fail if loaded in the manner your picture indicates.  Any knot is only useful for the scenarios it was designed for, and part of knot-craft is knowing what the knots are designed to do, not just how to tie them.
Comment: +1 - The bowline is great for a lot of things, just not holding a person's life.
Comment: I'm going to try and find recommendations from link-able authorities, but its a little complicated because most "authorities" are either books I don't have with me, are groups like the AMGA, which don't put a lot of information free online.
Comment: Although the double bowline (aka bowline on a bight...depends how you tie it) is great with a yosemite backup or double overhand backup, but still harder to visually inspect and much less common than the eight.
Comment: absolutly, agreed... I wasn't sure how to addres the "yosimitee bowline", there are a couple variations I've seen (they all double the initial loop and all tie the end off with a half hitch, but sometimes the end-strand passes back through the knot, so that its on the climbing end, sometimes it ends in the main loop of the bowline), I wasn't sure if / how to address that, because I was hesitant to recommend one or the other.
Comment: What's the "Yosemite backup"? Are you talking about a half-hitch or an overhand knot tied in the bitter end around the standing end after tying the bowline? I know about the "Yosemite **finish**" but I've never seen or heard that regarded as a **backup**. All it does is move the tail so that it points away from the tie-in point.
Answer: In addition to zoul's excellent answer, the Bowline has another drawback in that it can come loose (or even undone) after repeated load/unload cycles (i.e. weighing and unweighing the rope).
This means that the bowline is not as good as the figure-8 to use to tie-in a climber, especially for multi-pitch climbing, gym climbing, etc... (That said, many good climbers do use the bowline to tie in.)
Answer: None of the photos show the bowline with the loose end tied off. In this (untied off) form the knot is unsafe as there is a strong chance of slippage. It's also easy to tie badly with fatal consequences. On the plus side its possible to tie one single handed in about 4 seconds.
When tied off with a single or better double hitch though then this knot is pretty safe, for most situations it still would not be my knot of choice though.
The Bowlines best application is possibly tree or post belays, but even here after moderate loading it can be hard to untie and a better choice would be round turn + 2 half hitches.
For heavy loading situations the double figure of eight (or fig 9 for super heavy) is a better knot but lacks the ease of set up.
Comment: I speak from the 30 yrs climbing and 10 yrs Industrial Rope Access experience. if you're looking for linkable references though not sure.
Answer: In the first instance, the simple #1010 Bowline (as shown by the OP) - is not and never was intended for climbing. Its sort of like asking; "Is a Lamborghini sports car suitable to drive off road in very rough terrain?" Clearly, the answer is "No".
The simple #1010 Bowline was 'invented' hundreds of years ago for nautical (sailing) purposes. It was not designed (or intended) for life critical applications such as rock climbing.
There are many different types of 'Bowlines'.
If you are going to select and use a 'Bowline' for life critical applications, you should select a type that is 'inherently secure'. Inherently secure knots do not require any form of 'backup stopper knot' to make them secure.
Inherently secure 'Bowlines' include:

The EBSB Bowline; and
Harry Butlers Yosemite Bowline variant; and
Scott's locked Bowline; and
Lee's link Bowline.

All 'Bowlines' have the advantage of being Post Eye Tiable (PET) and totally jam resistant.
Comment: What makes PETness an advantage?


Early 2013 Retina display on Late 2013 MacBook Pro 13 inch compatibility

Question: Does a MacBook Pro 13 inch Retina late 2013 work with an early 2013 Retina display? As far as I know just the webcam cables are different. Does that mean that the display works just without the webcam (which I don't need)?
Answer: Browse ifixit.com and you can see ifixit's part numbers for these two 13" Retina MacBook Pro machines.
The "Display LVDS cables" on the two MacBooks carry the same ifixit part numbers. The two models' "Screen Assemblies," however, show different ifixit part numbers.
Because the screen part numbers are different, I think the answer to your question is "Probably not."
If I were in your shoes and really wanted to resurrect my MacBook Pro, I'd look for the specific part that fits your model MacBook Pro, or a used MacBook Pro of the same model from which you could remove and reuse its screen.


Make a variation in Sibelius

Question: I'm writing a sonata for piano. And I'm writing it in the Sibelius app.
I've finished the first movement. I want to write the next movement after the first movement in that project. But I don't know how.
I mean I wanna write a new score in a project with new starting.
Comment: Do you mean that you want to write two consecutive movements in the same file?
Comment: @Dekkadeci yes.
Answer: If you want to start a new movement, or new piece in a collection of pieces, you'll need to do a few things:

make sure you have a page break at the end of the previous movement (or at least a line break). To do a page break, select the last barline of the previous movement and press Cmd-A (on a Mac, let me know if you need PC shortcuts).
create a bar number change, set to number "1" and put it at the beginning of the new movement.
put a final barline at the end of the previous movement.
when putting the new key-signature and time-signature at the beginning of the new movement, go to more options and deselect allow cautionary. This stops the change of key and time-signature appearing at the end of the previous movement.
you could also choose to have the full instrument name at the beginning of the new movement. This is quite useful in a score with several instruments; it is probably not necessary for a solo piano sonata. The easiest way to do this is to select the last barline of the previous section, open the inspector and select Section end.
you will need to add a new title, and will also need to drag the first stave of the new movement down a bit, to make room for the title.

This answer tells you what you need to do. Let me know if you also need all the shortcuts or menus to do all these things. As far as I know there isn't a way to do all this with one operation.
Comment: Yes please. May you say the Windows shortcuts?

Make a variation in Sibelius


They made Solomon the son of David king the second time. How?

Question: 1 Chronicles 29:22
And they ate and drank before the LORD on that day with great gladness. And they made Solomon the son of David king the second time, and they anointed him as prince for the LORD, and Zadok as priest.
Answer: Six chapters earlier in 1 Chronicles 23:1

When David was old and full of years, he made his son Solomon king over Israel.

A parallel account of this twice declarations is in 1 Kings

1:34
There have Zadok the priest and Nathan the prophet anoint him king over Israel. Blow the trumpet and shout, 'Long live King Solomon!'

1:39
Zadok the priest took the horn of oil from the sacred tent and anointed Solomon. Then they sounded the trumpet and all the people shouted, "Long live King Solomon!"

So there was no doubt that Solomon was the king. It served as a warning to Adonijah, Solomon's older brother.
Answer: There is an important distinction between what happened at Solomon's first and second anointing.
Solomon's first anointing recorded in 1 Kings 1:32-40 was hurriedly arranged by king David to avert the crowning of Adonijah.
It was very important that Israelite kings rule as vice-regents of God almighty and recognize that fact, 1 Sam 8:7, 8, 24:6, 2 Sam 19:21, 1 Chron 28:5, 2 Chron 9:8, 13:8, Ps 5:2, 44:4.  Thus, kings could not be anointed by mere men but had to be appointed by God and fully recognized by the people.  Thus, it was that Solomon had to have a more complete recognition that he was king by ALL the people.
Thus, the second anointing was to ensure this was the case - all Israel was invited to the ceremony complete with feasting and planned celebrations.
We have an almost identical situation with king Saul many years earlier in 1 Sam 11:14, 15.
Benson arrives at the same conclusion:

They made Solomon king the second time — The first time was, when he was made king during Adonijah's conspiracy, (1 Kings 1:34,) on which
occasion it was done in great haste, and in the presence of only a few
of David's servants; but now in the presence of all the great men of
Israel, the princes of the tribes, the captains of thousands and
hundreds

Similarly, Barnes:

King the second time - Solomon's first appointment was at the time of Adonijah's rebellion (marginal reference). As that appointment was
hurried and, comparatively speaking, private, David now thought it
best formally to invest Solomon a second time with the sovereignty, in
the face of all Israel.
Answer: Yes and what do we SEE in the letter to the Hebrews that says: Unto them who look for Him (being Jesus) a "Second Time" He will appear with no mention or reference to sin but appearing to them to expedite a complete deliverance to a Salvation being readied to now be revealed in this last of the last of times Amen
Comment: Take a tour of the site to understand how it is different. Use more evidence, reference, and avoid very short answers. https://hermeneutics.stackexchange.com/tour
Answer: What it is, Thomas, is these two stories (1K 1, and 1C 29) are reports of the same, not separate events. When you explore the details of each narrative, yes, this is the case, up to and including putting Zadok in the seat of Abiathar. The distinction, instead, is as follows. A number of ANE kingdoms made use of vicegerency as a needful if not somewhat defensive mechanism of state, and also typically in the forms of both viceregency and viceroyalty, which is generally what is meant by coregency. Judah later did, while Israel did not, because Judah was the more vulnerable by far. The duties and functions of a viceregent were of the administrative sort, lower level stuff, but his authority was understood to be unquestioned in such matters, and death of the king would still be expected to see the viceregent accede to regency. The viceroy on the other hand, though also typically a prince, is intended to take on more serious matters of state including warfare. Nebuchadrezzar is believed to have held such an office. And sometimes, as in the case of Solomon, a shift will occur from the lower to the higher level, formally, which is to say advancing from viceregency to viceroyalty. This is what his having been made king a second time means.


Is there any evidence that supports glycolysis in mitochondria or chloroplasts?

Question: Glycolysis is known to be a part of cellular metabolism undergone by both eukaryotic and prokaryotic cells, whether under aerobic or anaerobic conditions. As the endosymbiotic theory states that mitochondria and chloroplasts were once bacteria that lived apart from eukaryotic cells, do they have any enzymes or compounds suggesting that they once did glycolysis?
Comment: On aspect of the endosymbiontic theory is that genes were transferred from the endosymbiont/new organelle to the nucleus of the host cell. Does your question include such transferred genes or only the ones remaining on the mitochondrial/plastid genomes?
Answer: A search of UniProt returns no reviewed, mitochondrially encoded genes involved in glycolysis. There are some unreviewed entries, but a brief perusal of the associated publications suggests to me that these have all been incorrectly annotated (as one may expect from unreviewed entries).
Interestingly, Rickettsia prowazekii, an obligate intracellular parasite and the modern species thought to be most closely related to mitochondria, also has no glycolytic enzymes:

Genome sequences of organisms enjoying an endosymbiotic lifestyle are at risk. The activities of homologous nuclear genes may render genes of the endosymbiont expendable and as a consequence they become vulnerable to obliteration by mutation. Good candidates for such purged genes in Rickettsia and mitochondria are genes required for amino-acid biosynthesis, nucleoside biosynthesis and anaerobic glycolyis. These and other genes would have been deleted when an ancestral genome first lived in a nucleated cell. Once genes essential to a free-living mode are lost, the endosymbiont becomes an obligate resident of its host.

Andersson SGE, Zomorodipour A, Andersson JO, Sicheritz-Pontén T, Alsmark UCM, Podowski RM, Näslund AK, Eriksson A-S, Winkler HH, Kurland CG. 1998. The genome sequence of Rickettsia prowazekii and the origin of mitochondria. Nature 396:133-140.


How can I seal between a concrete patio and a brick wall?

Question: I have patio that's connected with brick from my house. Where the brick and the patio meet there is a crack along the entire perimeter. Its a fairly small no larger than a hairline crack. I'd like to seal that but i'm not sure what I would use to seal? I can attach photos for better understanding if need be. Thank you.
Comment: Please [take the tour](https://diy.stackexchange.com/tour) to learn what to do next.
Comment: you need a picture to get this answered right
Answer: Urethane or silicone caulk are the usual, but there are others that remain flexible. Read some labels at your hardware store. Flexibility is crucial, so don't use latex. If you have a lot of seasonal movement (frost heave), caulk might not be a good idea anyway.
Either match color or go with clear. Use as small a bead as possible and avoid smearing it out onto either surface by cutting a fine, angled point on the tube and pressing firmly.
Comment: Thank you for the quick response. I'm very much an amateur so I have to ask. Is there a specific brand that is better than others? Also, I live in Michigan so yes I do deal with frost. If not caulk what other options are there?
Comment: Brand recommendations are off-topic here. Go with the more well-known ones and you should be fine. If I had other options for such a situation I'd have mentioned them. Since the crack is so small you're limited. Frankly, I wouldn't worry about it unless you have reason.
Answer: Urethane caulk would be the go-to product, but hairline cracks are a bit of a problem.
If your crack was, say, 10mm wide and with temperature variations it widens or shrinks by, say 2mm, then that's only +/-20% width variation. Urethane caulk is elastic, so it'll stretch and squeeze and stay in.
However if you have a hairline crack, say 0.5mm wide, and temperature variations make it widen by only 1mm, then that's +200% width, and the caulk won't be able to stretch enough to stay attached to both sides of the gap.
If you want to seal it for cosmetic purposes, then just use caulk. But if you want it to be watertight to prevent water infiltration you really need to know what caused the crack, if it is going to widen in the future or not, etc.


System monitoring tool

Question: Having switched to linux(ubuntu studio) I gathered that there would not be something like the task manager on windows to watch in real time how much ram is consumed and what the cpu usage is. What is a GUI tool that would allow me to observe the amound of RAM and CPU usage in real time?
Answer: Where did you "gather" this ? There are several programs for Ubuntu, some even preinstalled that are exactly doing this:
The default GUI app is called Gnome System Monitor.

For the terminal, there should be top preinstalled, but I prefer htop, that is a bit more fancy and has some nice extra features ....
sudo apt-get install htop

or glances
sudo apt-get install glances

There are also some Indicator applets: indicator-multiload or indicator-sysmonitor should work.

See some reviews at OMG!Ubuntu.
Compare with this post at AskUbuntu.
Answer: I like gkrellm for this.
CPU by core or all-total, i2c monitors for temperatures/fan speeds/voltage/etc, disk i/o by whole or partition or disk, network in/out with connect/disconnect buttons for dial up, RAM monitor and swap space monitor, date/time, uptime, monitor the /proc file system, and new mail message monitor, and more.
Lots of windowing options - always on top, always on bottom, etc. Can be started when desktop loads.
Daemon component to run on remote machines so you can watch via the local GUI client and monitor multiple servers, etc.
Here's a screenie of my current system and gkrellm

System monitoring tool


Bluetooth Wifi Bridge

Question: I have seen many articles online about using a phone or computer to act as a Bluetooth-WiFi(internet) bridge, where you can share the internet connection with other devices over Bluetooth. But I have not seen any generic stand alone devices that would allow this same function. I have seen ones for specific IoT devices that allow Bluetooth light bulbs and such to be accessed over WiFi but not a generic one. Has anyone seen such a device?
Answer: Bluetooth is a proprietary technology which is managed by the Bluetooth SIG.  Unlike "Wireless A/B/C/N/AC", which is the networking technology standardized by IEEE, Bluetooth is tightly managed by this group and specific patents are required when making something Bluetooth compatible.  This means that the "stack", which manages to what and how a device can connect to other BT devices, is often proprietary to the device itself.
You can experiment with this by purchasing a Chinese-local Bluetooth headset designed for phones and trying to pair it with a Dell laptop that has integrated Bluetooth.  Chances are, your device won't pair, and you'll have to download the Chinese company's BT stack to your computer and install it.  This often interferes with the existing stack that comes with Windows and may create new problems.
This, and the inherent short range of BT, are why you see devices that will take commands via WiFi and relay them via Bluetooth, but not accept commands via Bluetooth and convert them to a traditional WiFi signal.  It takes a machine with a compatible BT stack and its own connection to a wireless network of some sort via its own wireless adapter.  That's why you're seeing the articles that you're seeing; they do exactly that.
Obtaining the BT patent and permissions to build a router that does this specifically and selling it as a consumer item faces hurdles manufacturers wouldn't want. BT is intended for short-range, so any product like that would immediately catch flak from misunderstanding consumers for being terrible once they're out of the same room.
A Bluetooth Router which can connect to your WiFi router, however, does exist. If you read the Amazon reviews for it, you'll find that the low-star reviews all involve problems I've described here (failure to pair due to BT stack, range issues past 30 direct feet, etc.).
Your best bet is probably to use a computer or phone that will manage its BT-connected peripherals as peripherals and just give other things access to those peripherals via Wi-Fi.
Comment: Thank you for detailed answer. But even that router is only designed to control specific devices or to extend the range of existing connections.  When using a phone or computer, you are able to give the Bluetooth device internet access without knowing or caring what that device is doing over the connection. That is what I am attempting to locate. I could design and build my own, but it would be nice if there was something off the self that would do this

Bluetooth Wifi Bridge


Can't enable CrossfireX on 2 Diamond Radeon HD 5870

Question: When I start Catalyst Control Center (CCC) and open AMD CrossFireX Configuration, the identify GPU button is disabled.
Both cards are detected by Windows, CPUZ and GPUZ. CCC context menu shows 6 video outputs (3 per videocard (2 DVI and 1 HDMI)).
Here's my set up:
Motherboard: Intel DP55WG (claims to support both SLI and CrossFireX) (with the latest BIOS)
CPU: Intel Core i7 860
GPU: Two Diamond Radeon HD 5870 (one in PICE x16 2.0 slot running at x8 2.0 and another in x8 2.0 slot running as x8 2.0). One CrossFire bridge is properly installed. PSU is properly connected.
Memory: 16GB (4x4GB Corsairs CL9)
OS: Windows 7 SP1 x64 Ultimate
I tried disabling one of the monitors and rebooting. Tried putting the CF bridge on a different connector - same difference.
I'm a bit at a loss.
Answer: Ok. Problem solved - the solution was as dumb as the problem. I had to completely uninstall and then reinstall the same AMD ATI Catalyst driver...