What happens to transactions in orphaned/forked blocks?

Question: From my investigation and reading a lot about this, it seems like the transaction is just removed and the ether returns back to some address. With Bitcoin, orphaned blocks are initially accepted by the network, but will be rejected once a longer blockchain is received that doesn't include the block. Is the same thing true in Ethereum?
Answer: The behavior in Ethereum is the same as in Bitcoin. At first the transactions seem to have gone through, but after a better chain is found it is as if the txs never happened.
Comment: Not true. The transaction gets back to pending state, it is not cancelled. Now, if another transaction from the same sender and with a higher nonce was accepted by then, then the first transaction will be effectively cancelled but because of the nonce, *not* because of the block being orphaned.
Answer: According to Ethereum White Paper transactions of orphan (uncle) will be added to the chain anyways.

As described by Sompolinsky and Zohar, GHOST solves the first issue of
  network security loss by including stale blocks in the calculation of
  which chain is the "longest"; that is to say, not just the parent and
  further ancestors of a block, but also the stale descendants of the
  block's ancestor (in Ethereum jargon, "uncles") are added to the
  calculation of which block has the largest total proof of work backing
  it.
Comment: I don't think you're answering the original question, but another one.  The OP is asking what happens to the transaction in terms of whether it affects the Ethereum state ("... ether returns back to some address").  Your answer explains that the uncle block is included in the POW calculation.  However, since the uncle is not an ancestor of the active tip, its transactions can't have been involved in transitioning the state.


What is the correct way to romanize ッジ?

Question: According to Wikipedia, ッチ is rendered as tch, not cch (etchi not ecchi). Logically I would think that ッジ would then be dj but there's no example of it. What is the correct way? dj or jj? Is there any comprehensive guide to Hepburn romanization that helps with this?
Answer: AFAIK cch => tch is the only exception defined in the Hepburn romanization system and its variants (such as パスポート式). All the other 促音 (っ) are expressed by repeating the same consonant. Specifically, I'm not aware of any romanization standard which uses dj. So if you want to strictly obey the rule, バッジ would be rendered as bajji even in the Hepburn system which is thought to be closer to English pronunciation. In 訓令式 this would be bazzi. IMEs accept both.
Traditional Japanese words occasionally have っち (eg, 八丁堀【はっちょうぼり】, 坊っちゃん, 湿地【しっち】), but probably there's no word that contains っじ/っぢ. Perhaps that's why there isn't any standard. There are many katakana combinations which are used to write loanwords but are not strictly defined in the traditional romanization systems (eg, ツァ, ティ, ドゥ). They are not suitable for writing non-Japanese-origin words in the first place.
Comment: For what it's worth, some people (myself included) don't like this aspect of these systems and will choose to always use a double consonant for geminate consonant (sokuon).
Comment: If that's what you really like, エッチ would be *echchi, not ecchi.

What is the correct way to romanize ッジ?


tranfser of electrons between two metals and a wire

Question: If you have a circuit of a battery, a Resistance and a light connected with a wire by example: in the middle the wire is cutted in two pieces. if you connect each piece of wire with a metal object and put those twee metal objects together so the current can flow to the resistance and the light.
How is it possible that the electrons can flow from the wire to one of the metal objects into the other metal object and again in the wire? I do understand how electrons move in metals and wires, but i don't know how the transaction of electrons between those components goes. Is it really that simple that electrons just can flow from one object into another of is the (kinetic) energy passed through when an electron clashes with the edge and that energie is passed through to the other object?
Comment: The details are, unfortunately, somewhat complicated, but in the most simplified version you can imagine that a metal is a bunch of positive metal ions in a lattice that are surrounded by a cloud (sea) of electrons. This electron cloud reaches all the way to the surface of the metal and when two pieces of metal touch, the electrons from one cloud can move into the other without a significant barrier. The average motion of these electrons is very slow, it's called the "drift velocity" and they move at fractions of a mm/s.
Answer: Metals consist of small crystals; within each crystal exists the "free electrons" which are shared by all of the atoms in the crystal lattice.  The number of free electrons per atom depends upon the details of the atoms, but is most often 1 or 2. The free electrons are visualized as "the electron sea" in the Drude model, devised ~1900, and is semi-classical. Introductory condensed matter texts often start with this model. The situation is slightly more complicated with alloys, but the same ideas hold.
In the electron sea the electrons are electrically shielded from each other by (a) the net positive charges of the ion cores and (b) the uncorrelated motions, essentially random, of the free electrons, which are described using the kinetic theory of gasses.
The crystal boundaries serve to impede the free flow of these electrons from one small crystal to the next, and also serve as scattering sites which continually randomize the motions.  The velocities of the free electrons are quite large.  When an external electric field is applied, it appears as a net "drift velocity" in the electron sea.  This is the current in that piece of metal.
When you bring two clean pieces of metal together all of the above is still true, but there is an additional restriction: each crystal has an effective "crystal voltage" on its interior, and for crystals of the same type it should be the same.  But when different metals are joined, the difference in the crystal voltage causes a voltage drop when going in one direction, and an increase in the other. This voltage difference is known as the Seebeck effect, discovered in 1821. Since the internal voltages change slightly with temperature, it is possible to measure temperature change electrically; this is the physical basis for the thermocouple.
So adding additional metal increases the total resistance of the circuit, depending upon the resistivity of the additional metal, its dimensions, and other properties.
The current is the net flow of electrons; each individual electron barely moves, but the effects are passed down the line.  With alternating currents for every move forward, there is a corresponding move backward -- hence no net motion from the electron drift at all.


"Front-End" technologies

Question: I'm a bit confused about what is considered "Front-End" (please see picture below).  I primarily work with Java, Node.js, PHP and SQL on the "Back-End" so to see these listed on a "Front-End" tab doesn't make much sense to me. I would think "Front-End" Java development for instance would be along the lines of Java Swing desktop app development.
Comment: That would be at best applet development, and we can nowadays safely pretend that never existed :)
Comment: @SethMcClaine I don't agree.  It's very clear and easy to me what is "Front-End" verses "Back-End".  I understand JavaScript and Java can be used on both of those ends but certainly "Front-End" JavaScript (i.e. AngularJS or jQuery) or Java (i.e. Swing) has a much different scope and code-base than "Back-End" JavaScript (i.e. Node) or Java (i.e. Spring Data or REST).  Could you relay a library or framework that's not specifically catered to "Front-End" or "Back-End" development? There very well might be one but all the ones I work with are specifically oriented towards "Front" or "Back" end.
Comment: Its basically the full-stack list, not specifically front-end.
Comment: I figured that but it still causes me to wonder..."Is this maybe Front-End Java development" since it's listed on a tab with heading "Front-End"
Comment: "applet development"?  How about Swing or JavaFX which are both "Front-End" technologies?
Comment: I would take front-end / back-end references with a grain of salt. As you will likely notice if you haven't already, where that line is cut really varies from person to person.
Comment: What about js frameworks, do the fall as front end or back end. Depends on the company, how they use them, what else the develop in that company. (The part that you started out with "I don't agree" kind of drive to my point, the line is drawn in different places for different people/companies)
Answer: As you note, the technologies listed in the chart aren't necessarily front-end technologies. They are technologies used by the highest-paid respondents who identify as "front-end developers". We probably could have been more clear here.
Comment: @cat Good catch. I pushed a fix. Will go live with next build =)
Comment: *"the technologies listed in the char"* Either you meant `char*` (but then it should be `const char*`) or chart, I'm not sure which

"Front-End" technologies


What can I do to someone falsely accusing me

Question: Let's say I get into an argument with someone. He falsely accuses me and I deny. He calls the police/local law enforcement of that place and it becomes clear that I was right. Now, what can I do to have him be punished for the time wasted/headache/other possible problems he caused? Can you introduce me to some readings/terms/webpages so I can learn more?
Comment: Depends on the jurisdiction, but probably nothing; see [this question](https://law.stackexchange.com/q/23506/4595) for a more serious example where the basic answer is 'your time and trouble will not be compensated'.
Comment: Different localities have different laws.  It might be helpful to list the city and country.  In the absence of information, maybe a local attorney would be a better resource
Answer: As noted in the comments, the correct answer depends upon where the conduct in question happened.
In most cases, nothing.
There is a qualified privilege from civil liability for reports made to public officials of alleged misconduct. The burden to overcome that qualified privilege is very high.
There may be a minor criminal charge if the police believe that the person making the report intentionally made a false report, but that would ordinarily not result in any compensation to you.
It is unclear from your question what the person making the accusation believed and that is critical to any civil or criminal liability. Simply being wrong is not in and of itself enough to give rise to either civil or criminal legal liability. Someone must know that their accusation is false (or at a minimum recklessly make an accusation without knowing whether it is true or false); if they sincerely believe their accusation, there is no liability even if the accusation arose from their negligence in most cases.
Also, notwithstanding the tag on your post, there would not be a false arrest in this case unless the police did not believe the person accusing you of a crime and arrested you anyway. Police are entitled to take someone accusing someone else of a crime at their word unless there is an obvious reason that they shouldn't believe them.


Valuing TRYUSD currency swap on Bloomberg

Question: Usually a leg in a swap is discounted using the corresponding OIS curve if the deal is collateralized and if collateral is posted in a different currency teh discounting happens with the corresponding CSA collateral curve. But for TRY I can see that both OIS and CSA curves are missing. I have seen that the TRY vs USD Basis curve has been used. Why is this curve being used specifically? Also I can see that TRY vs USD 3M curve is also present but the TRS vs USD Basis has been used to discount this leg.
Answer: Why did you not ask the help desk? F1 F1.
I think the answer is that it's simply a deficiency in BBG's system.
CSA curve is not built for TRY it seems. OIS should work though. May well be this curve also was not developed when you posted this.


How to save a render image as JPEG with white background instead of default black background at alpha transparent areas?

Question: My render image has a transparent background and when i save it as PNG RGBA every thing is OK. But when i want to save as JPEG format which doesn't support alpha transparency, save it as black backgroud at transparent areas.
How to save a render image as JPEG with white background instead of default black background at transparent areas?
Just like when i save the render image as PNG RGBA format and open it in GIMP and save as JPEG format which change transparent background to white.
Is anyway in blender without using Nodes?
Comment: Any particular reason you don't want to use nodes? They are very flexible and allow for doing  things precisely such as this..
Comment: My solution in Blender 2.8 is plane with emission material behind. Environment background and compositing methods generates aways grey background or too much light. Other thing: Is there somewhere in blender nodes tip for type of input/output types? For example: alpha output 0-255 or 0-1.0?
Answer: No, but it's quite simple to do with nodes..
In the compositor (press ⎈ Ctrl← Left arrow), enable Use Nodes in the header and add an alpha over node (⇧ ShiftA> Color):

The color in the top slot is the color which will be used instead of transparency.
Now transparency will be automatically filled in with white (or whatever is in the top socket) when the scene is rendered.
Comment: I am now interested in Render Layer. I wonder if you can put png image sequences with transparent backgroung into that node Render Layer. I am going to test it out myself. Thanks for post above.
Comment: Additionally, make sure you apply the following settings: [Properties > Render Properties > Film > tick "Transparent"] and [Properties > Render Properties > Color Management > View Transform > Standard]
Answer: You can change the background color by modifying the environment by going to the World tab in the Properties pane.
In cycles, change the environment surface color.  Turn off everything except camera in in the Ray Visibility panel to prevent the environment from affecting your scene.

If you're using Blender Internal renderer, then instead of setting ray visibility, you'll need to set the alpha chanel to display the sky color.

The downside of all of this is that you lose the ability to control lighting using the sky map.  If that's a problem, the using the compositor to add a backdrop to your renders is the way to go-and this kind of task makes for a good introduction to the compositor.


In PHP, how do you code with scalability in mind?

Question: I know this may be a general question, but what exactly goes into scaling for all the users you will encounter, even if not in the next few months? I did some research and most of what is done is server side, with caches and other similar stuff. Any points in the right direction would be helpful.
Answer: "Even if not in the next few months" smells like premature optimization. Don't do that:

It's not worth it. Many people, when realizing a project, believe that their project will be the second Facebook. Then they release it, and then they notice that ten visitors per month is the best they can do. Spending less money and time on optimizing for further scalability and more time thinking about the project itself would help.
It's like with bottlenecks and profiling: you always have an impression that you know perfectly well where the bottleneck is, and in most cases, you discover that you were wrong when profiling. Do your application first. See how is it used. Profile it. Gather BI data. Gather performance metrics. Analyse it. Check if your analysis was right. Make the predictions about the future, based on your analysis, then optimize for scalability what you really need to optimize.

For example, a scalable web application must be able to be hosted on several servers. The last project I've done for my customer was intended to be scalable. There was a choice: either we spend 1.5 months more in order to make the web app work on several servers, or the customer buys a high quality server (one machine only) and the web app is hosted on this machine only. It was much less expensive to buy an expensive server, counting both the direct cost (price of the server vs. price of 1.5 months of work) and the long term savings (power consumption of one high quality server vs. power consumption of several low-end servers). Now the app is running for a few months, and according to the metrics, if there would be a problem with scalability one day, it would concern in first place the database, and in second place the network infrastructure (switches, routers, etc.).
Now, an application may be more or less scalable on several points:

Database: according to my personal experience, most scalability-related problems come from the database. Hopefully, there are plenty of ways to make the database scalable for every industry-grade database engine, and even before that, there are plenty of ways to improve the database structure and to optimize the queries. Caching helps too.
Network: bandwidth can be a real issue in some configurations, and sometimes you can't do anything about it without doing expenses you can't afford. To avoid being blocked on this level, you can optimize the visual design of the website in order to have less images or better compressed images, optimize the layout of the page, reduce the HTTP requests (through CSS sprites), reduce the quantity of HTML code sent (through AJAX), etc. HTTP compression is a must-have. Browser caching too, but your metrics may show that many clients have an empty cache.
CPU and memory usage: porting an application to be hosted by several servers can be painful too, both on infrastructure (hardware) level and on application (software) level. To avoid this, use extensive caching and profile the application, removing progressively the bottlenecks.
Comment: Thank you very much. Currently I am not developing for that in mind. Coincidentally, I am actually going to just gather info to see where things go. I was just curious what others know, but thanks for the advice!
Comment: I see. I modified the answer to address better your concern.
Answer: Scalability is very much language agnostic, so there is no PHP specific thing for it. Key factor is to have decoupled subsystems, communicating via language agnostic protocols (so for example if you have to call webservice from your PHP code, don't use PHP's serialize, but rather JSON, even if both components are currently both implemented in PHP). This will allow you to replace components with other alternatives, perhaps developed in other technologies.
You can find many examples of scalable architectures implemented using PHP on highscalability.com blog
Comment: @Andy: purpose of `serialize` is to serialize state of object to string. Synonyms for serialization used in other languages are marshaling or pickling. Problem with that kind of serialization is, that it's language specific. That's why well defined standards like JSON are better for passing data to web services.
Comment: I see what you are saying, so essentially split the work up. I appreciate the advice.
Comment: I looked at the php doc on serialize. I am not too familiar with it. What its is purpose if you don't mind me asking?
Comment: I will not link specific posts becuase they might be biased, but just do some search on SOA (Service Oriented Architecture) and Distributed Systems. Libraries and guidelines on PHP is lacking on the internet.
The easiest way to start is with a Messaging infrastructure and Event Driven Design.
Comment: Oh yes, I was actually wondering how I would store certain information server side, and I guess this helps me on that end. Just to make sure, say I would like to store cookie information server side, the way I would do it would be using serialize? Thank you very much!
Answer: Worrying about scalability now is probably not worth it: if your project takes off and hits the mark from where you cannot scale by adding more hardware, you'll have enough cash rolling in to fund more thorough measures; if it doesn't, then any effort you make now is a waste of your time and resources.
That said, there are a few things you can and should do to keep your application maintainable, and if you follow these guidelines, factoring in scalability will be much easier later on in the game. An ideal solution will allow you to swap out the entire data storage code with only minimal changes to the program logic and no changes at all to the presentation code.


What is meant by Gene Expression Level?

Question: I am new to BioInformatics, I want to know what is gene expression level and how it is determined.. Anyone who can answer this silly question.
Comment: Are you familiar with the concept of `gene expression` but not `gene expression level` or you're not familiar with the concept of gene expression? You might want to have a look at [wikipedia > gene expression](https://en.wikipedia.org/wiki/Gene_expression) or at any intro course to molecular genetics.
Answer:
"Gene expression level" is an imprecise and partially ambiguous term
  that should be avoided.

Many (but not all) genes have the information to produce proteins†, but there is no need for this information to be used at any given time — it depends on the requirements of the organism or cell. For example the DNA of lung cells contains the information to produce the protein chains of haemoglobin, but it is never used in those cells. We can say that "the gene is not expressed".
So the absence of expression is fairly easy. However, for a protein-coding gene the meaning and quantitation of expression is more difficult. That is because in expressing the information in the gene the DNA is first transcribed into mRNA by RNA polymerase, and then that information that encodes a protein can be translated into protein on the ribosome.
The word level refers to quantification, and is a sloppy substitute for quantity or perhaps rate (quantity produced in unit time) or perhaps relative quantity.
But the main difficulty is whether in quantifying gene expression you measure the quantity of mRNA synthesised under standard conditions or the quantity of protein produced.
If you are a bioinformatician encountering this term, my bet is that it is in relation to the currently (2018) popular RNA-Seq technique, which in fact provides relative measurements of the quantity of RNAs of different types produced under standard conditions. This is generally expressed in units called FPKM — Fragments Per Kilobase of transcript per Million mapped reads. The difference between this technique and the northern blotting mentioned by @Hawkeye, is that the latter is used to detect a single mRNA, whereas RNA-Seq applies to all the mRNAs that are present in a sample.
In the field of proteomics, it is possible that the term is being used in relation to the amount of protein produced, which may be roughly quantified by two-dimensional gel electrophoresis.
†Some genes encode RNAs that do not encode proteins (ribosomal RNAs, transfer RNAs, RNAs involved in splicing and in modification of rRNA, microRNAs etc.). The expression of the genes for these will end with the synthesis of the RNA.

What is meant by Gene Expression Level?


Find a website at some geographical location

Question: The http responses returned from my server are very slow. After testing a number of things out, I suspect some router along the way has implemented a firewall to inspect higher level protocol data, possibly http protocol data. In order to determine whether that is true, I would like to access a website that is hosted by my server provider that is located at the same location. Is there a way to figure out the domain name of some server located at the same location? All I have to go on is the IP address of my own server, so I assume that that some website should exist that uses an address within a range of the one mine is using.
Answer: Found this cool tool: http://reverseip.domaintools.com/
Unlike most other reverse IP address tools, this lists the actual domain of site and not the service provider's domain.


What happens to chiral Majorana edge fermions near quantum phase transition in p+ip superconductors?

Question: In the weakly-coupled BCS regime two-dimensional chiral (p+ip) spinless superconductors and superfluids posses a chiral gapless fermionic Majorana state localized near the boundary. This gapless edge mode is a direct manifestation of the topological quantum phase transition present in this system. Indeed the boundary is the line which separates two topologically different phases, it is localized in the region where the gap closes. My question is what happens to the edge states if we tune fine-tune the bulk value of the chemical potential to the critical one, i.e. approach quantum criticality in the bulk. The gapless fermions should penetrate into the bulk, right? What happens to their chiral and Majorana property?
Answer: At the critical point, the bulk gap is closed, and there is nothing to prevent the edge state from penetrating into the bulk. So the gapless mode simply merge into the bulk. The modes (of opposite chirality) from both edges will mix. Both the chirality and Majorana property will be "canceled out" by the mixing.
Comment: Thank you for the answer. Do you know if this mixing of opposite edge modes near criticality was studied in detail in some geometry (e.g on the disc or stripe)? If yes, a reference would be welcomed.


What do you call a facial gesture?

Question: What do you call a facial gesture? I thought about it and I can't think of a single word to refer to it. It's not a facial expression, because it's not an expression, but a gesture that can accompany any facial expression. For example, someone licking the upper lip. That's a gesture, but you can look aroused, sad, angry while doing it, so it's not a facial expression.
Comment: Who keeps trying to close and downvote these?  Blackbird has a reasonable confusion based on a lack of clarity in the references researched.  These are great questions because they require a deep familiarity with language that no dictionary can provide.
Answer: It would still be considered a facial expression. It can be used to describe both individual movements and signals (like winking or smirking) and also the collective expression of the whole face conveying an emotion or state (like scared or inebriated). The individual expressions are also known as a form on non-verbal communication.

What do you call a facial gesture?


Circuit Simulation Software

Question: I'm getting back into hobbyist electronics after a very long hiatus and was wondering what the current state of circuit simulation software is. What is the industry standard for macs or PCs? What are the open-source alternatives?
Comment: kinda duplicate? http://electronics.stackexchange.com/questions/1206/what-are-the-freeware-spice-simulators-available
Comment: @endolith, I think they are similar, but I see this showing up in search, I am going to edit the title, I hope Brian is okay with it?
Comment: This also may be a better community wiki that people will continue to update and vote on in the long term, that is your option brian. If you would like to get a specific answer and accept it then the question is correct how it is.
Comment: Totally ok with the title change, I don't think I have enough rep to mark this community wiki.
Comment: @brian, you cannot mark community wiki. Do you have a specific answer that you are looking for?
Comment: No I'm not looking for a specific answer, I'd rather it be community wiki.
Answer: LTspice is free and works well for switching power supply designs.
I also use Paul Falstad's Circuit Sim for concepts.
When it comes down to designing power supplies (which is pretty much the only thing I use circuit simulators for) I usually rely on application notes and already designed supplies. If they use LT parts, I might try and optimise the design. WEbench by National Semiconductor is quite good, but I wish it gave you more freedom.
Comment: Falstad sim is broken, see http://electronics.stackexchange.com/questions/11082
Comment: @markrages: Not any more than others http://electronics.stackexchange.com/a/11098/142
Comment: @endolith actually, many commercial circuit sims use different tricks to try to converge on stable values.
Answer: Well some programs I've had chance to work are Multisim and Proteus (form what I've seen, I'd put them in "industry standard" slot (disputed for Multisim), as even the cheapest versions seem to be very expensive).
They are generally nice and come with large libraries of components. They are also point and click, so you just select item from the list of items and place it on the circuit board.
They also come with virtual lab instruments such as multimeter, oscilloscope and so on, so you can see how each part of the circuit behaves. Another interesting thing in Multisim is that you can use for example input form computer's microphone and redirect it to the virtual circuit or connect speaker of the circuit to computer's speaker.
They also come with some microcontrollers, but selection is very limited in Multisim (some PICs only, if I remember correctly, but I never used that feature much). Proteus is supposed to be better, but I haven't used it much.
Both programs were very easy to use.
One limitation I found in Multisim which I couldn't circumvent is that only 4 wires can connect to each joint, so sometimes circuits can look a bit messy.
As for the free software, I haven't had good experiences in that field. I've tried to use gEDA, but it proved to be too complicated for me.
There is also gnucap, but I haven't had any experience with it.
There's also this list form Wikipedia that could be interesting.
Comment: Multisim is not industry standard. It is actually targeted at education. NI does not use the software for their on development, they get theirs from mentor graphics.
Comment: @Kortuk♦ Well, I thought it was since several engineers I talked to told me they use it all the time. Still, it's nice to hear information from other sources too.
Comment: I am impressed you got the Star, you do not need to do that to reference me, that just says I am a mod. Second, I could understand thinking that. NI does not use it that way, and When I was at NI week they were clearly trying to make it an educational standard, not a professional one. It is not bad, but the ones I am more used to have signal integrity and many other nice features that I actually need regularly.
Answer: The industry standard is PCs with Windows and all the major simulation packages support it.  No one that I know or have heard of in industry does any circuit simulation on Macs.  Linux is more common than OS X.
Comment: Really need both a Linux and Windows OS nowadays to get the best tools.
Comment: Why the down vote?  That answers part of the question.
Comment: people get angry about statements like that, but i have to agree.
Comment: @tyblu: What are the "best tools" that only run on Linux?  What's wrong with running it in a virtual machine?
Comment: @endolith, There is nothing wrong with VM's. In fact, I consider it to be a superior option to dual-booting or having separate PCs, and is what I do (Linux, running Win in VM). I love easy access to scripting libraries (UNIX), machine customizability (incl. security), and possibility for low overhead (satisfies my OCD). For some reason I like ext3/4 more than NTFS, too, though my reasons are likely outdated.
Answer: I use the SPICE supplied with the Pulsonix PCB software I use. It's actually SIMetrix SPICE, and a free version is available here. It has a very good reputation.
LTSpice is very popular, and is free.
Answer: If you've got an iPad, iCircuit is pretty neat. Needs a few updates but it's obviously the way forward for this kind of thing.
Comment: It's basically a modification of Falstad's circuit sim: http://www.falstad.com/circuit which I use often.
Comment: Seems it's available for the iPhone too - but it's expensive.
Answer: I use MacSpice with OSX. It is completely text (netlist) and command line-based, though it produces decent graphical output. I'm not a SPICE expert, but apparently this one is done well, whatever that means.
I like it.
Answer: LT Spice has been mentioned more than once, and I'll add that not only is it free and of high performance, but the user base is unusually active and helpful. Others such as TINA are out there, but you won't find the degree of help if you need to figure out how to stick handle around tricky modelling issues (eg. using tanh as an approximation for functions that are not differentiable).
There are also printed books available, if the dead-tree format appeals to you.
Answer: Not clear if you also want digital circuit simulation, but I've found a free version of the software I used to use when I was in digital ASIC design:
http://bleyer.org/icarus/
Both Verilog and VHDL were competing for the industry standard designation back then, and I suspect that they still are.
Answer: Check out http://www.partsim.com/, it's free and has full SPICE simulation engine, web-based schematic capture tool, and graphical waveform viewer
Answer:
I've tried Quite universal circuit simulator QUCS it is open source, multi platform and very easy to use.

Analysis types include S-parameter (including noise), AC (including noise), DC, Transient Analysis, Harmonic Balance (not yet
  finished), Digital simulation (VHDL and Verilog-HDL) and Parameter
  sweeps.
Comment: Why did you include the banner in your answer. What value does it add?
Comment: @DmitryGrigoryev We remember more when we see things. It's nice and it helps to identify the software.

Circuit Simulation Software


How can one estimate wave drag?

Question: Wave drag is an especially high drag above mach 1, but I've found it hard to find source materials to estimate it. I'm looking to estimate how to design better for wave drag by estimating how it would affect my flight in the transonic region Mach 0.8 - 1.2.
Comment: Welcome to Aviation.SE. Speeds up to Mach 1 are subsonic by definition and do not have wave drag. You might want to simplify your question to focus on one aspect. It requires several answers in its current form, and this site tends to like one at a time.
Comment: @Pilothead As you increase speeds past about Mach 0.6 you enter the transonic regime where areas over which flow acceleration occurs (such as wings) may encounter sonic or supersonic flow
Comment: Hey @Pilothead, thanks for the heads up. Thanks for welcoming me , and I have simplified the question and perhaps I'll add the other elements in another question.
Answer: Usually wave drag $c_{d_w}$ starts becoming relevant at the drag divergence Mach number $M_{DD}$, which is defined as
$$\left.\frac{\partial c_{d_w}}{ \partial M}\right\vert_{M=M_{DD}}=0.1 \tag{1}$$
Or in words, the Mach number at which the wave drag coefficient versus M has a gradient of 0.1
Lock$^1$ has derived an empirical formula that shows the development of $c_{d_w}$ after the critical Mach number, $M_{cr}$, which is the number at which the flow becomes locally supersonic on the wing:
$$c_{d_w} = 20(M-M_{cr})^4 \tag{2}$$
If we apply the definition of $(1)$ to $(2)$ we obtain:
$$M_{cr} = M_{DD} - \left(\frac{0.1}{80}\right)^{1/3} \tag{3}$$
As you can see, the value of $M_{DD}$, is a little bit higher than the value of $M_{cr}$. First you get local super sonic flow, but the drag does not increase rapidly, as you further increase the Mach number, the drag starts to increase significantly, and you reach $M_{DD}$. See this image, where $M_{DD}$ is denoted by $M_{CDR}$.

Source
The value of $M_{DD}$ can be estimated using:
$$ M_{DD} = \frac{K_A}{cos \Lambda} - \frac{t/c}{cos^2 \Lambda} -\frac{c_l}{10cos ^3\Lambda} \tag{4}$$
With

$\Lambda$ is the sweep angle
$t/c$ the relative thickness of the section lift coefficient
$c_l$ the section lift coefficient
$K_A$ the airfoil technology factor (a correction factor denoting the quality of the airfoil). Typical values for the airfoil technology factor are 0.87 for an NACA 6-series airfoil section or 0.95 for a supercritical section.

So the workflow is as follows:

Estimate $M_{DD}$ using $(4)$
Derive $M_{cr}$ using $(3)$
Determine the development of $c_{d_w}$ using $(2)$.

For more info, see this link and this link
$^1$ Hilton, W.F., High Speed Aerodynamics, Longmans, Green & Co., London, 1952, pp. 47-49
Note, this method is only for estimating the wave drag coefficient around the drag divergence Mach number, I'm not sure to what Mach number it provides an accurate estimate
Comment: I'm sorry to be a nuisance, but should the third term be divided by 10? as in 10cos^3(lambda) on the bottom? Also, thank you, this is extremely useful, and is helping me no end with my own calculations
Comment: @AlastairWyllie This is Dave Korn's formula for airfoil wave drag extended to the swept wing by W.H. Mason. The "10" can actually be anything between 7 and 10 to best match experimental results.
Comment: thanks a lot for all the formulae and the info. You've been super helpful and I will look into the book as well.
Comment: @RajathPai You're welcome. As you can see your question has been 'on hold', because it's a very broad question. As such, other people can not answer to it anymore. Very broad questions are difficult to answer, please focus on one question per post. You can edit the question to make it more specific and then it can be reopened again. If you have any other doubts concerning how to improve your question let me know. If you want to ask another (different) question on an aviation topic, please make a new post.
Comment: I already edited it and reduced it once. I will try to reword it and be more specific. Thank you for your advice.
Comment: I think the second and third terms in equation 4 should have negative signs on them, increasing thickness decreases divergence Mach no, as in Korn's relation
Comment: @AlastairWyllie well spotted, I've edited it.
Comment: @AlastairWyllie, again correct. Apparently I'm very bad at copying formulae from my own thesis :)
Comment: Interesting! Thank you!

How can one estimate wave drag?


What would I see with a telescope of 70mm aperture , 300mm focal length and maximum magnification of 150x

Question: What would I be able to see with 70mm aperture telescope with 300mm focal length with maximum magnification of 150 x?
Comment: It really depends on 1) if it's an excellent or lousy telescope, 2) if it has an excellent or lousy mount, 3) if the seeing conditions and sky brightness in your area is excellent or lousy, 4) your degree of patience and willingness to learn how to use it. btw 70 mm, f=300 mm means it's f/4.3 which is pretty short. You would also need a 2 mm focal length eyepiece to get 150x, or a 4 mm eyepiece and 2x Barlow so something doesn't sound right about those numbers. If it's urgent you need to buy it, better not.
Answer: It's 70mm aperture, so the maximum useful magnification will be 165x.
If you have a 4mm eyepiece, you will have 75x magnification, and at that, you can expect to see rings of Saturn, moons of Jupiter in good conditions. Venus will show phases. I can't say much about Mercury.
You can see many surface features of the Moon. The view will be particularly good at 150x. You will have to use a 2x Barlow for that. Remember, the view will be good in good "seeing".
If you are in dark sky away from light pollution, you can expect to see many globular clusters and nebulas particularly, the Orion Nebula.


What does the frequency of my miner mean?

Question: What does the clock frequency of my miner mean. I can change it but how does it affect performance? For BFGMiner when I start my Gridseed I can press 'C' to change it.
Comment: Are you referring to a specific config file parameter, like `–bmsc-freq`? If so, you should add it to your question. Adding more detail to your question would be appreciated, and would be more helpful to others who might have the same question.
Comment: No the clock frequency. Updated
Answer: I believe that is just a parameter to allow you to control the clock frequency (usually measured in MHz) of your miner. You can see a sample list of configurations for CGMiner here.
There is an inherent trade-off here. A higher frequency means a higher hash-rate but more energy consumption and wear-and-tear on your hardware. For example, this site shows a sample chart of different frequencies and hash rates for a particular piece of hardware. It's up to individual miners to figure out what the right trade-off between performance and energy consumption is for them.


Can you help me identifying this circa 1910 airplane with tail number 72?

Question: Circa 1910 airplane with tail number seventy two
(Click for larger image)
Answer: It is a Wright, allright, but more probably an EX. The EX was a modified Model R, which in turn was a modification of the Model B. The R and the EX were single seaters, whereas the B would seat two.
Picture of a Model B replica, as taken from its Wikipedia article:

Picture of a Model EX, taken from this site.

The EX was the model used by Cal Rodgers for his epic transcontinental flight. Note the lengthened tail and the closer wings, which allowed to reduce rigging wire and, thus, drag. The "72" shows the same features, so I think it is a Wright Model EX.
Comment: @VerticalLiquid: It's good to know that collectors like you value those historic documents - if it weren't for you, the picture might not exist anymore. Not everyone takes so much care to preserve historic collections like [Dean Putney](https://www.kickstarter.com/projects/deanputney/experience-world-war-i-through-a-german-officers-p?lang=de), after all.
Comment: Really appreciate all the help. I am so curious what the "72" is indicative of and what field it was in (empty grandstands in background) but I fear this may never be known. Thanks again guys :)
Comment: @VerticalLiquid: It is obvious from marks in the corners that the picture was in an album - do you still have the album? This might give more context.
Comment: Unfortunately I am an old photo collector and this was purchased by itself. I would love to have that album however ;)
Comment: Thank you for the kind words Peter. It can be an expensive hobby but worth it. I find myself burning up the "whale oil" many nights going through my albums.
Answer: Looks very much like a Wright Model R. Some information can be found here, a picture from that site below:

(source: wright-brothers.org)
Comment: Looks very close, but the "72" has a bigger wing: Outside of the props, the Model R has only one pair of struts, but 72 has two.
Comment: @PeterKämpf indeed, you appear to be right.


Usage of comma of full stop in direct speech

Question: My daughter asked me if this is correct or not - "We've first got to put the shelves together, then find a way to put them up," said Hermione, in a matter-of-fact tone of voice. - my answer was direct speech ending with comma doesn't look correct, but her answer sheet says this as correct answer. I can't explain her why, googling didn't work out. Please help.
Answer: The opposite is true — this article explains in more detail but generally you use a comma after direct speech. The only time this rule does not need to be followed is if the direct speech ends with a question mark or an exclamation point.
Comment: Please do not answer questions that are off-topic on this site. The appropriate response to such a question is to flag it as off-topic or (if applicable) to for migration to a site where it is on topic.


How does the efficient market hypothesis fit with the rapid changes in prices?

Question: The price of IBM changes from second to second, but there's no way that actual news about IBM is coming out that fast. The information available about IBM changes a lot more slowly than its share price. If I am to believe that the market is setting the price at exactly what IBM is worth, how can the "true price" of IBM be changing so quickly?
Answer: It depends on which form of EMH you're considering as to provide a rationale.
Strong-form EMH could or would assert there's private information potentially changing hands that agents are acting on to cause the price movement.
Semi-strong form EMH would suggest all available public info (eg, the news you reference WRT IBM) is immediately incorporated into share price, nullifying any ability to extract a profit.  The reality, as the other user noted in his/her response, is that this information is often incorporated imperfectly in practice, whether that be at a lag or in an overeaction at its release.
Answer: You're right. The "true price" should only jump when news arrives but in practice, market participants need time to arrive at a new equilibrium, i.e. the market needs some time until it is clear how the news affects the price. Therefore, you see more adjustments taking place and more trading after arriving news.
The description above gives some reasoning why prices changes in a more noisy way and don't simply jump. After all, it's just a theory and does not translate to real life with 100%. Indeed, you could view the stock price as a noisy proxy for the true price. This is in particular true for high-frequency data where there is a lot of market microstructure noise.


How to control temperature in NVE molecular dynamics

Question: I want to simulate a molecular system at a certain temperature. It would be best if it could be implemented by NVT molecular dynamics. However, if one were to use a NVE simulation (like velocity Verlet), how could I fix the temperature, or let the temperature only fluctuate a little bit around the desired value?
Comment: By definition, an NVE ensemble does _not_ have fixed temperature.
Comment: You need to use a thermostat algorithm. Any and every textbook on simulation covers thermostats. I recommend that you spend some time in the library... Try Frenkel & Smit and/or Allen & Tildesley
Answer: In my quite limited knowledge, there is no straightforward way to simulate a system with $NVE$-ensemble and get a (nearly) constant temperature.
You could approach this problem by starting with an $NVT$-ensemble. Set up the system, run energy minimization, generate velocities and use the velocity rescaling method until you are close to the wanted temperature. Once you are close to $T_{wanted}$, switch to a more gentle method, like Berendsen weak coupling or use a thermostat, such as Nose-Hoover.
After the system has thermalized, you can switch to $NVE$ and run the production simulation.
I don't have the privilege to post any links, but a simple google search with the keywords 'NVE MD simulation temperature control' will provide a good amount of references.
Answer: It depends on what you mean by $NVE$; if you want to do dynamics in a constant energy ensemble, and you consider the total system energy to be composed of the sum of kinetic and potential energies of your system, one can contemplate three ensembles: $NVE_{tot}$, $NVE_{kin}$ and $NVE_{pot}$, where the total, kinetic and potential energies are conserved, respectively, for all time.
Temperature, in the MD sense, corresponds to the instantaneous kinetic energy of a system. However, there are no constraints placed on the kinetic energy of the system in the $NVE_{tot}$ ensemble (other than summing with the potential energy gives a constant value for all times).
In contrast, the isokinetic ensemble, $NVE_{kin}$, requires that the kinetic energy, and therefore the instantaneous temperature, remains constant for all time, which appears to be what you want. Tuckerman discusses the various schemes one can use in his book quite comprehensively.


"Permission denied" when running macOS installer from command line

Question: I'm trying to install High Sierra to an external drive, from a system which is running Mojave. I can't run the GUI installer (it warns me about trying to install an older version of the OS), so I'm trying to use the command line instead.
My system has SIP disabled and I've connected an empty, Mac OS (Extended, Journaled) formatted SSD via USB and named "macOS". I run the following:
sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/startosinstall --converttoapfs NO --agreetolicense --volume /Volumes/macOS

This gives the following output:
By using the agreetolicense option, you are agreeing that you have run this tool with the license only option and have read and agreed to the terms.
If you do not agree, press CTRL-C and cancel this process immediately.
Preparing to run macOS Installer...
Permission denied
Any ideas why permission is denied even though I'm using sudo and have SIP disabled?
Comment: Have you tried using the flash drive installer?
Answer: What worked for me is:
sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/startosinstall --volume /Volumes/macOS --converttoapfs NO

As it will then show you the license to review.


what benefit is it to clearing the Drupal cache now that I have Varnish in front of Drupal?

Question: Our site has Varnish in front of Drupal for anonymous user page requests so that these pages are cached.  I know how to clear the Varnish cache within Varnish but my question is what benefit is it to clearing the Drupal cache now that I have Varnish in front of Drupal?
Comment: It all depends.  To answer the converse, one case would be where you have a large site and Varnish caching pages for a short length of time and then using Drupal's cache for longer periods of time.  This way Varnish can keep everything that is actively used fresh and in memory, and rely upon Drupal to quickly serve up pages from its cache when necessary.  In this case, clearing the Drupal caches would remove potentially stale pages when Varnish came back to ask for more.
Answer: Whenever Varnish Cache expires it asks Drupal to give it the rendered page. Drupal in turn sees if it can server the page from the Cache. If yes it will server from the cache, else it will regenerate the page.
In short, when you clear the Drupal Cache,

No changes are visible to end users for whom the content is served from Varnish.
When the Varnish Cache expires, it will fetch the content form Drupal. Now that you had cleared the Drupal cache, instead of serving from the cache the page will be rebuilt.


VNC Server without X Window System

Question: Will a VNC server work without X Server installed? I know vnc works with X Server, but what about without it?
Comment: If you want to use VNC without having X being started visibly on the server, you could have a look at Xvnc.
Answer: No you'll typically need X installed on the server you're remoting into using VNC since it merely is displaying an X desktop back from this server.

In computing, Virtual Network Computing (VNC) is a graphical desktop sharing system that uses the Remote Frame Buffer protocol (RFB) to remotely control another computer. It transmits the keyboard and mouse events from one computer to another, relaying the graphical screen updates back in the other direction, over a network.

This bit might be what confuses people:

Note that the machine the VNC server is running on does not need to have a physical display. In the normal method of operation a viewer connects to a port on the server (default port 5900).

When they mention "Display" they're talking about a physical monitor. The remote server still requires that X be installed and configured so that GUI desktops can be run.
What about Xvnc, X11vnc, and vncserver?
Xvnc
Xvnc is a X11 server that you can run standalone, but it will still require a desktop to operate it, otherwise when you launch it you'll be presented with just a black window. So Xvnc doesn't technically require X to be installed since it contains its own X server.

So Xvnc is really two servers in one. To the applications it is an X server, and to the remote VNC users it is a VNC server. By convention we have arranged that the VNC server display number will be the same as the X server display number, which means you can use eg. snoopy:2 to refer to display 2 on machine 'snoopy' in both the X world and the VNC world.
Normally you will start Xvnc using the vncserver script, which is designed to simplify the process, and which is written in Perl. You will probably want to edit this to suit your preferences and local conditions. We recommend using vncserver rather than running Xvnc directly, but Xvnc has essentially the same options as a standard X server, with a few extensions. Running Xvnc -h will display a list.

$ export DISPLAY=localhost:1.0
$ /usr/bin/Xvnc :1 -ac -auth "/root/.Xauthority" \
    -geometry "1200x700" -depth 8 -rfbwait 120000 \
    -rfbauth /root/.vnc/passwd 2> /root/.vnc/ServerDaemon.log &
$ /bin/sleep 10
$ /usr/bin/fvwm 2> /root/.vnc/fvwm.log &

x11vnc
Where Xvnc contains its own X server, x11vnc does not. It's a VNC server that integrates with an already running X server, Xvnc, or Xvfb. It does have the unique feature of being able to connect to things that have a framebuffer.
excerpt

x11vnc keeps a copy of the X server's frame buffer in RAM. The X11 programming interface XShmGetImage is used to retrieve the frame buffer pixel data. x11vnc compares the X server's frame buffer against its copy to see which pixel regions have changed (and hence need to be sent to the VNC viewers.)

excerpt

It allows remote access from a remote client to a computer hosting an X Window session and the x11vnc software, continuously polling the X server's frame buffer for changes. This allows the user to control their X11 desktop (KDE, GNOME, XFCE, etc.) from a remote computer either on the user's own network, or from over the Internet as if the user were sitting in front of it. x11vnc can also poll non-X11 frame buffer devices, such as webcams or TV tuner cards, iPAQ, Neuros OSD, the Linux console, and the Mac OS X graphics display.
x11vnc does not create an extra display (or X desktop) for remote control. Instead, it uses the existing X11 display shown on the monitor of a Unix-like computer in real time, unlike other Linux alternatives such as TightVNC Server. However, it is possible to use Xvnc or Xvfb to create a 'virtual' extra display, and have x11vnc connect to it, enabling X-11 access to headless servers.

vncserver
vncserver is just a frontend Perl script that helps ease the complexity of setting up VNC + X on remote servers that you'll be using VNC to connect to.

vncserver is used to start a VNC (Virtual Network Computing) desktop. vncserver is a Perl script which simplifies the process of  starting an Xvnc server.  It runs Xvnc with appropriate options and starts a window manager on the VNC desktop.

References

Virtual Network Computing - Wikipedia
Comment: The Xen hypervisor provides a VNC server to access the terminal of a guest without requiring X on either the host or guest. I think it might be this package  https://packages.debian.org/wheezy/xcp-vncterm. I am not sure this would work without Xen. There is also https://github.com/proxmox/Vncterm which doesn't seem to require X.
Comment: May be this should be helpful? https://github.com/ponty/framebuffer-vncserver
Answer: If you are not running X11 (X) but using the framebuffer, there is framebuffer-vncserver. https://github.com/ponty/framebuffer-vncserver
This works well, with the exception that it does not support input. This is easy to work around, by directly injecting input on the server side.

VNC Server without X Window System


Low pass sequencing has been reported to detect common variants. How low can one go and get reliable data? Is 2X pass sequencing analysis possible?

Question: I would like to use low pass sequencing to replace a genotyping chip to be able to detect variants up to 0.1 % allele frequency in available population data. What is the minimum depth I can opt for to retain the confidence of base calls? Can GATK be used to analyse this data?
Answer: This is a good idea - low pass sequencing has shown to be better than genotype arrays for things such as GWAS or QTL mapping.
The primary way of processing low-pass sequencing data is to use imputation - partciularly methods such as GLIMPSE or QUILT and a large reference panel such as the HRC or TopMed in order to refine the genotype calls.
This is a figure from the GLIMPSE paper showing how you can retain variants of different frequencies at different levels of sequencing depth.

And a similar image from the QUILT paper:

You might also want to check out some of the methodology in this paper http://m.genome.cshlp.org/content/31/4/529


Does a microwave oven disinfect food?

Question: Imagine I am preparing food -- just about to put it into a microwave oven --  and some of it falls on the floor. Assuming it got some bacteria or other organisms (viruses?) on it, will the microwave processing disinfect it? What about worm eggs? As I understand, any living organism, given enough exposure to microwaves, degenerates. Is this true?
Comment: http://cooking.stackexchange.com/questions/32055/why-microwaves-do-not-kill-harmful-bacteria-as-well-as-boiling
Comment: A little off topic, but I'll share anyway I have some old artifacts of wood with evidence of active worms. After putting them in a 1200 watt oven for 10-12 minutes all evidence of wood worms disappeared, that was several years ago. My assumption was that the water in the live worms was heated to a lethal temp. Obviously size was a constraint, although a commercial oven should be easy to find. Not for painted objects probably.
Comment: That amount of usual pathogen does not matter unless you clean up the floor with food... Yes microwave will disinfect the food, it is used for pasteurization.
Answer: Microwave ovens can indeed kill bacteria in food by heating them to high temperatures. For example, this article found that microwave heating could kill all of the Salmonella bacteria in a chicken thigh sample:

The effect of microwave heating on Salmonella Enteritidis inoculated
  on fresh chicken was investigated using a microwave oven (800 w) to
  determine the destruction of Salmonella Enteritidis isolated from
  chicken carcasses, in relation to the time of heating at two power
  settings: high (power level 10) and medium (power level 6); The
  relationship between heating time and temperature was also been
  studied. The destruction was 6.4 log cycles at time 95 sec for the
  high power level, and 5 log cycles at time 140 sec for medium power
  setting. After 110 sec for higher power level, no survival of
  Salmonella Enteritidis was detected in samples (100g), but at 140 sec
  for medium power level, these food pathogens were still present.

However, the main issue is balancing the amount of microwave exposure. Heating the food for too long will result in the food becoming dehydrated or burned, and heating it for too short a period of time will result in food poisoning.
This paper shows that insufficient microwave exposure can and will lead to food poisoning if there is a large amount of bacteria inside the food:

Leftover samples of a savoury rice dish consumed by all six ill
  persons contained 6×103/gm Salmonella enteritidis PT4. The rice salad
  comprised boiled rice, raw carrots, eggs, cheese and curry powder. The
  curry powder and remainder of the pack of six eggs were negative on
  microbiological analysis. The rice dish had been prepared by heating
  in a 500 W microwave oven with a rotating turntable on full power for
  5 min.
Comment: So in essence, microwaves don't kill bacteria / viruses. Heating does.
Answer: I'm no expert, and this is more of a physics answer rather than biology. The microwaves will not reach all of the food. This is why you get hot and cold spots. The rotating plate mitigates this to some extent, but not all of the food will receive a blast. However heat will slowly spread throughout the food. If the contaminated bits are hot enough for long enough it should be OK, but I wouldn't rely on this.
Comment: Can you provide citations to back up your claim?
Comment: Not even the surface will be covered. The microwaves don't have a problem penetrating the surface, the problem is due to the wavelength only some areas get their molecules excited by the waves. This explains it better than I can: https://what-if.xkcd.com/131/
Comment: Yeah, the warming of the food is extremily non-uniform, but I thought that at least the surface area gets enough radiation. And still - how much does it take to kill a bacteria? A colony of them? Is that heat that can kill them, or do microwaves affect them? ...and I bet if I asked this on Physics SE, they'd said, this one is for Biology :D.. Somehow my questions always fall in between SE sites :/ funny thing..
Answer: Keep in mind that microwaves kill organisms via heat, and in particular, heating mainly water.  This is contrast to ionizing radiation, for example as obtained from the cobalt used in commercial food radiation.
If the pathogen does not contain, or is not sufficiently adjacent to liquid water, or is not sensitive to heat, it may persist.
As an explanation, a microwave generates heat because microwave oven peak frequency emissions (~2.45 x 10^9 Hz) (reference) are able to excite water molecules.  The physics of that are actually quite complex, but at a high level, water doesn't really exist appreciably as H20.  Rather, it is better described at STP as HOH (hydrogen hydroxide) or more accurately, H3O+ OH- (hydronium hydroxide).  All those ionic and van der Waals' forces (reference) allow water to have a high specific heat (i.e. a small bit of water can contain a lot of heat).  That water heat (via predominantly conduction) heats the rest of the food.
The importance of this is that in order for a microwave oven to sterilize anything, including food, both of the following must be true:

The target must be raised to a sufficiently high temperature.
That temperature must be maintained long enough to adequately disrupt the homeostasis or (in the case of a virus or prion) structure of the pathogen.

And these predominantly depends on water being present (though some fats and sugars can also efficiently absorb microwaves).  If there is insufficient liquid water present, the microwaves would inefficiently heat the dry food, and as a consequence could fail to achieve a sufficient kill temperature.  (In contrast to liquid water, ice has a much lower resonance with microwaves, which is why the defrost cycle of a microwave uses lower energy and switches on and off to allow heat conduction to even things out and minimize hot and cold spots).
Some pathogens would not likely be killed by a consumer microwave oven:

Bacteria which form spores often require very high heat, above the boiling point of water, so in a microwave, those spores (e.g. Bacillus anthracis, Clostridium botulinum) would be unlikely to reach those temperatures (as additional microwave energy would convert the water to steam at STP, rather than raise its temperature).
Prions are also notoriously difficult to destroy.  In fact, when a patient with CJD has neurosurgery, typical hospital policy is to throw away the entire surgical instrument tray, because there is no adequate sterilization procedure available, period.  (You're unlikely to find prions in your kitchen unless your name is Hannibal Lecter, but I include them for completeness.)

Finally, there are two main routes by which pathogens in food make you ill.  The first is an active pathogen (e.g. live bacteria or replicating virus) acting within your body.
The second mode is that of preformed enterotoxins. While the OP asked about food on the floor (presumably of short duration), the title is directed to disinfecting food.  From a food safety perspective, many common bacteria (most classically Bacillus cereus) produce toxins which persist even after they have been killed and the toxins can survive high heat.  Microwave radiation and the expected heat produced would not destroy these molecules, and would not render the food safe.  This would also apply for many chemical substances potentially present on a typical kitchen floor.
All that said, in 2014 microbiology research done at Aston University suggested that there is actually a decreased risk of eating food dropped on the floor if you follow the five-second rule.
Answer: Yes, you are right. If the food just fall on the floor and you microwave it, maybe that could kill most of bacteria or disinfect virus. bacteria are living organism, normally can't tolerate over 100 ℃, and virus' protein coats are not stable too.
However! maybe there are Spores which are generated from gram positive bacteria, the power of microwave or oven can't disinfect all of them. And also, the toxic chemicals on the floor, which might from your floor cleaners or be generated by bacteria, maybe microwave or oven are not strong enough to denature them. In biological lab, we use autoclave, 121℃ and 1.2 kg / cm² pressure over 15 mins, to kill bacteria spores. And it can't clean toxic chemicals. To be noted, there is not pressure function in normal housse using oven and microwave!
Comment: What do you mean by "spot"? Did you mean "spores"?

Does a microwave oven disinfect food?


Emission Spectrum of Hydrogen and Helium?

Question: Why do hydrogen and helium have different emission spectra? I thought that emission spectra were the result of electrons 'jumping' from one energy level to the next - since hydrogen and helium both have electrons on n=1, l=0 and only there, why are their emission spectra different?
Comment: Hydrogen has a nuclear charge of +1, but helium has a nuclear charge of +2. So although each has one electron the spectra are not the same.
Answer: We have solved the Schrödinger equation for hydrogen-like atoms such as $\ce{H}$, $\ce{He+}$, $\ce{Li^2+}$, $\ce{Be^3+}$, and $\ce{B^4+}$. The energy levels are neatly arranged:
$$E_n = - \frac {E_0} {n^2}$$
where:

$E_n$ is the energy of the $n$-th energy level
$n$ is a positive integer ($1$, $2$, $\dots$)
$E_0 = 13.6~\mathrm{eV}$

This is possible because we only need to consider two particles: the nucleus which has a positive charge and the electron which has a negative charge. We only need to consider the interaction between those two particles. Also, the nucleus is not moving, which simplifies some calculations
However, for higher atoms such as helium, where there are more than one electron, the Schrödinger equation contains two terms for the two nucleus-electron attractions and a term for the electron-electron repulsion. The term for the electron-electron repulsion makes things difficult because both electrons can be moved. That term makes the equation impossible to solve analytically.

For hydrogen, the energy of an energy level is determined solely by its principal quantum number. That means, the $2s$ orbital has the same energy as the $2p$ orbital (ignoring the virtual particle effect).
This is not true in higher atoms such as helium. The energy levels of helium can be seen here:

(The energy levels of hydrogen is on the right of the diagram for comparison.)
Here, the azimuthal quantum number has an effect on the energy of the energy levels, which makes for more possible differences between energy levels, which makes for more lines as well as different on the emission spectrum.
Comment: Note that for 'Hydrogenic' atoms such as $\ce{Li^{2+}}$ the energy equation should be modified slightly to $E_n=-Z^2R/n^2$ where *Z* is the atomic number and *R* the Rydberg (which you label as $E_0$ and is $R_{\infty}=13.6057 \pu{eV} = 109737 \pu{cm^{-1}}$ ) but varies slightly as it depends on reduced mass (for nucleus of mass *M*, $R=R_{\infty}(1+m_e/M)$. The $Z^2$ terms is why the energy is so much lower for helium than hydrogen
Answer: Electronic energy level for $\ce{H}$ and $\ce{He}$ are different because in $\ce{He}$ nucleus there is two proton and for $\ce{H}$ it has single proton.
As their energy are different they require different amount of energy to excite them, so different spectra comes out with different wavelength.


How to tell if a polarizing filter is too damaged?

Question: I dropped my CPL onto some rocks and it's a bit scratched up. There's no obvious effect in a (very cursory) look at the photos, but are there tests I can do to see if the damage has a visible effect?
Answer: You can test the polarizing effect by placing a non-circular polarizing filter in front, you should be able to place it at an angle that almost eliminates light transmission. However I highly doubt that the scratches will have an effect on it's ability to filter polarized light!
As already stated scratches on the front of a lens typically have a minimal impact on image quality: here's a very good example.
Answer: The end of the lens is extremely out of focus, it takes a lot of damage to be immediately visible. One test I've heard of is to attach a few strips of post-it paper to the front of the lens - you'll barely be able to see the difference.
The most likely effect will be a slight blurring of the image. Take a couple of pictures of a static scene using a tripod, one with the filter and one without. If you can't see the difference, it's time to stop worrying.
Comment: heck, I've one lens with a chip out of the front element. There's no visible effect on the produced images (tbh, it's an 87mm front element and the chip is maybe 5mm long on the very edge, so out of the path of most if not all light reaching the filmplane)
Answer: Shoot a photo so that a light source is in the frame to test if a damaged filter (or lens front element) has visible effect. Look for extra flare or streaks shaped like the scratch(es).
I've heard of fixing the flare by painting over the scratch with a marker, but haven't had a chance to verify it. You might want to start out with a whiteboard marker to test.
Also, try using big F number which will make image defects more perceptible.


Oxygen-gtk theme on ubuntu 12.04

Question: I tried to use the oxygen-gtk theme on ubuntu 12.04, but it didn't work properly, only the menus. The windows looked like win95/98 :D
I know that the best way to use that is to use Kubuntu, but I found it really buggy...
So, is there a way to use that theme on Unity?
Answer: I think i found something similar, a person with the same problem as you asked this question a while ago. Check it out here: KDE theme in Ubuntu Unity , if it helps.
Enjoy Ubuntu!

Oxygen-gtk theme on ubuntu 12.04


public databases of IP addresses which are involved in illegal/gray-area activities

Question: I just received a /24 IPv4 network from my ISP. This very same /24 network was previously used by some hosting provider and if I made a quick scan of those 256 IPv4 addresses agains some DNSBL databases, then many of the addresses were listed there. This made me wonder are there other such public databases for different threads than spam? For example maybe some CERTs or other organisations have such (public) databases where they list IP addresses involved in botnets or hosting (regularly) web-servers which serve malware.
Comment: I'm slightly confused about your question. However, yes, there is. There are RBLs for all sorts of malicious reasons. Whether it be spam, scanning host, brute force attacks, etc.  Many custom (some private some not) RBLs exist for which match a pattern of unwanted behavior.
Comment: Ok, thanks! Could you name some specific RBLs which are for fighting against some other malicious activities than spam?
Comment: Well, I would suggest you google for specific RBLs you might want.  If you want to block against bruteforce attempts, you're better off using something like fail2ban.  AlienVault has their Open Threat Exchange(OTX) that has something of an RBL catalog if you will.  They have a Python library that you might be able to leverage their OTX with but I'm not sure.  I know its primary purpose is for supplementing their AlienVault USM platform.
Answer: The MXToolbox blacklist checker is a good place to start.
You can follow that up by reading some of the lists hosted at iblocklist.com particularly including the dshield list, and then some of the others.
Perhaps also look at the sources of "bad IP lists" in the Emerging Threats and Snort IDS/IPS rulesets.
Comment: Snort can, at minimum, check against the DShield blocklist as part of the rules.
Comment: agree about MXToolbox.  Good resource all around.
Comment: Thanks! I used a custom script which worked similarly to MXToolbox blacklist check, but I checked only against around 10 DNS based email blacklists. Lists on iblocklist.com were useful! Are there "bad IP lists" distributed with Snort? Or what did you mean?
Comment: Do you mean this list: http://feeds.dshield.org/block.txt? Are the IP addresses in this list responsible for DDoS attacks? Spreading worms? Some other malicious activity? I tried to find this information from DShield website, but I couldn't find it.
Answer: Robtex is an online tool that will give you various information about an IP or netblock.  I prefer the "old robtex" version of the site, which is still available at the top next to the other links.  The other linked resources will also have useful information from those vendors (McAfee, Google, Virustotal, etc.) about their perception of your netblock.
Good luck!
Comment: Yeah, that's why I don't like the "new robtex" as much, you have to click on the "old robtex" link after you click through.  E.g. punch in 126.96.36.199 in the main bar, click the entry that has "126.96.36.199" (link is ?dns=220.127.116.11), once you've got that, you can click "check 188.8.131.52 on: old robtex".  When you scroll down, there's a section titled "Blacklists".   https://www.robtex.com/en/advisory/dns/8/8/8/8/
Comment: All I was able to find with Robtex were whois database records and DNS PTR records when I searched for subnets. Am I using this tool wrong or doesn't it provide any other information? Just for information, I found the [Google Malware Distribution database](https://www.google.com/transparencyreport/safebrowsing/malware/?hl=en), which is quite interesting. Allows one to search for websites which distribute malware.


If Parker was possessing Josh throughout the whole movie, why didn't he just kill Josh's family?

Question: In Insidious Chapter 2, if Parker was possessing Josh throughout the whole movie, why didn't he just kill Josh's family right off the bat instead of waiting until close towards the end of the movie?
Answer: As far as I'm aware, the movie didn't give a neat explanation for this, but from what we do know, it was always Parker's mother driving him to kill, and although Parker clearly enjoyed killing, we have to assume he wanted to continue his killing spree 'on the quiet' like before, just under the identity of Josh this time. Killing the family would only attract attention and make it difficult for him to stay in possession of Josh.
This is at least backed up by the first bit of dialogue we hear from Parker (via the possessed Josh):

I wanted to stay so much longer... the feeling of being alive again. You cannot comprehend how good it feels. To breathe. To eat. All the little things that you brush off, like a fly. But she wanted me to kill you. She wouldn't stop. Wouldn't stop pushing me to do it.
Answer: As far as I think, Parker and the other dead's desire was only to possess alive people's bodies, escape hell and live again. But when everyone got to know that Josh was in fact possessed by Parker, Parker didn't find any other solution to keep him alive again only to kill anyone who makes an obstacle in his way.


Voldaren Pariah is exiled while transforming

Question: What happens if Voldaren Pariah is exiled while transforming? Does it still force target player to sacrifice 3 creatures? Also if it is returned from exile, does it returned already transformed and if it does, does its triggered ability go on the stack then?
Comment: Can you clarify what you mean by "while transforming"? The answer is assuming you mean "after activating the activated ability, but before that ability resolves". Once it has actually "started to transform", it will transform no matter what; it can't be exiled "while transforming".
Answer: There are two possible outcomes, depending on when the Volarden Pariah is exiled. These are the only two possibilities; you can't do anything while the Pariah is transforming.
While the activated ability is on the stack
In this case, the Pariah will never transform, and the triggered ability that would make the opponent sacrifice creatures never goes on the stack.
The relevant rules are these:

112.7. The source of an ability is the object that generated it. The source of an activated ability on the stack is the object whose ability was activated. The source of a triggered ability (other than a delayed triggered ability) on the stack, or one that has triggered and is waiting to be put on the stack, is the object whose ability triggered. To determine the source of a delayed triggered ability, see rules 603.7d–f.

201.4. Text that refers to the object it's on by name means just that particular object and not any other objects with that name, regardless of any name changes caused by game effects.

400.7. An object that moves from one zone to another becomes a new object with no memory of, or relation to, its previous existence.

If we put these all together, we see that the instruction "Transform Volarden Pariah" really means "Transform the object whose ability was activated". And when the Pariah is exiled, it becomes a new object, so the original object doesn't exist, and the "Transform" instruction just does nothing. Since it never transforms, the triggered ability on the back face never triggers, and the opponent doesn't have to sacrifice three creatures.
After the activated ability resolves
Once the activated ability resolves, the triggered ability on the back face immediately goes on the stack, because rule 116.2a says

Triggered abilities can trigger at any time, including while a spell is being cast, an ability is being activated, or a spell or ability is resolving. (See rule 603, "Handling Triggered Abilities.") However, nothing actually happens at the time an ability triggers. Each time a player would receive priority, each ability that has triggered but hasn't yet been put on the stack is put on the stack. See rule 116.5.

And rule 112.7a says

Once activated or triggered, an ability exists on the stack independently of its source...

So, even if the Pariah is exiled while the triggered ability is on the stack, the ability still f the resolves, and forces the opponent to sacrifice three creatures.
If the Pariah re-enters the battlefield
In either case, the Pariah will enter the battlefield face-up. Rule 711.8 says

A double-faced card enters the battlefield with its front face up by default. If a spell or ability puts it onto the battlefield "transformed," it enters the battlefield with its back face up.

And rule 400.7 (quoted above) says that it doesn't remember its previous existence, so there's nothing that would change what it does from the default.
Answer: target player does not have to sacrifice 3 creatures as this is what happens
1. you sacrifice 3 creatures to transform it
2. Activated ability goes on the stack
3. pariah is exiled
4. Ability resolves
5. the ability states:

when this creature transforms into Abolisher of Bloodlines

From the comprehensive rules

406.2. To exile an object is to put it into the exile zone from whatever zone it's currently in. An exiled card is a card that's been put into the exile zone.

At this point it is no longer a creature but a card in exile meaning that target player won't have to sacrifice anything
When it returns to the battlefield it will be a voldaren pariah and nothing will happen because when a card is moved to an other zone it becomes a new object meaning it will not remember anything that happend before, meaning that it will not remember that you transformed it so it will not be transformed
This is stated in the comprehensive rules here

400.7. An object that moves from one zone to another becomes a new object with no memory of, or relation to, its previous existence.
Comment: Isn't the ability that's resolving in step 4 "Transform Voldaren Pariah"? This ability fizzles because it's not on the battlefield anymore, so it never actually transforms. The trigger of "when this creature transforms..." is never actually triggered.
Comment: In steps two and four do you mean the activated ability instead of trigger? If you wait until the trigger goes on the stack it is too late.
Comment: I Have changed it
Comment: @Matt It doesn't 'fizzle' (countered due to lack of legal targets), it just does nothing (because the transforming the Pariah is an illegal action it is ignored, but the game still tries to do it)
Comment: This answer is about half right. As Matt mentioned, it's the activated ability that resolves on step 4, and it fails because the object you would have transformed doesn't exist, not because it's "no longer a creature" (so, 112.7 and 400.7 are more relevant than 406.2). And while it's true that it re-enters front face-up, it also never was transformed, so saying it "doesn't remember" is misleading.


Looking for a remote flash trigger for Sony

Question: Can anyone recommend a wireless flash set up for Sony A200 camera/Sony F58-AM flash unit?
Answer: You'd use the pop-up as a trigger; it will provide TTL control of the F58-AM. The only thing you're missing, really, is the off-camera shoe (to mount it on a lightstand) and that's the same unit as the Minolta/KonicaMinolta OC-1, so you may be able to pick one up fairly cheaply on the used market. If you don't want the on-camera flash to influence the lighting, you can put a bit of card in front of it (it doesn't have to be white card) -- as long as even a little bit of light leaks from the pop-up, it should be enough to control the remote flash.
Comment: Not too happy with the reliability of this solution.
Comment: Unfortunately, the only TTL alternative is to go wired. There is a PC adapter that will let you use standard third-party wireless equipment, but it doesn't have a shoe (it's meant for studio lighting) so you'd need to McGuyver a kit together at both ends (camera and flash) to make it work. Minolta's pro solution (on the 9/9000 series cameras) used an on-camera PC socket.
Comment: Just an update: the [Phottix Odin TTL radio triggers come in a Sony/Minolta flavor](http://www.phottix.com/en/studio-accessories/phottix-odin-ttl-flash-trigger-for-sony.html).
Answer: Your other option is a radio trigger like the Cactus v4 trigger with a hot shoe adapter to provide the interface. I don't know anything about the adapter, there may be others around as well, but the Cactus triggers are okay, not great, but okay, and generally work in a reasonable range for home studio fun (I have them and have used them on studio strobes).
Comment: So there is nothing with a Sony/Minolta fit of repute?
Comment: Not that I'm aware of, but that doesn't mean there isn't one. Of the most well known, it appears they're strictly standard hot shoe size. Minolta, in this instance, I think made a bad mistake and Sony has perpetuated.
Comment: Update: obviously, Sony's had a rethink and stopped the perpetuation since their most recent hotshoes are now iso-compliant.
Answer: Pixel and Phottix radio flash triggers have Sony/Minolta hotshoe versions, but you can just use hotshoe adapters with any manual radio triggers, since TTL communication doesn't matter. If you need TTL over radio the Pixel Kings and Phottix Odins both have Sony/Minolta hotshoe versions (but they obviously don't support the newer Sony iso-compliant hotshoe flash gear).


Can a spark ignite hydrogen?

Question: Can a spark ignite hydrogen? Also, what about the tip of a cigarette? I've heard that hydrogen is very explosive. Thanks
Comment: H2 is not explosive. Appropriate mixes of H2 with O2 or possibly Cl2 can be explosive.
Answer:
Can a spark ignite hydrogen? Also, what about the tip of a cigarette?

Yes, if the $\ce{H2(g)}$ concentration in oxygen or air is greater than about 4% not only will it burn, but most likely explode. You should avoid all heat sources when dealing with it, including direct sunlight. Just so you know, hydrogen safety datasheets include words such as "extremely flammable" and "DANGER" in red capital letters.
Besides its high flammability, another thing that makes it so dangerous is that you can barely see its flames when there's a high oxygen concentration, as seen below. It also reacts violently (A.K.A. explodes) with most oxidizing compounds, so you should be careful where you are storing it.
A rocket engine at full thrust. There's a barely visible bluish flame below it, that's the hydrogen-oxygen mix used as fuel.
Answer: Actually hydrogen is not at all explosive. The mixture of hydrogen with oxygen (also air) is. As you know hydrogen is stored as liquid (high pressure cylinders) and it's perfectly stable. You can mix it with any amount of argon heat it as high as you want and nothing will happened. OK, if you reach temperature as high as on the Sun then it will explode, but that's an nuclear fusion (i.e. physics not chemistry). On the other side the mixture of hydrogen with oxygen can very easily by ignited by an electric spark or a cigarette.
Comment: Even at the Sun's core temperature Hydrogen is incredibly stable. After all, the Sun hasn't burned even half its Hydrogen after all these billions of years, and that's despite the presence of C,N and O catalysts.
Comment: This is slightly misleading. If you ha a room completely filled with hydrogen then, yes, a spark would not ignite the hydrogen. But few such rooms exist. What if you have a balloon filled with pure hydrogen? Then that is highly flammable and can be ignited with a spark despite the hydrogen being pure. It won't *explode* but it will burn. The same balloon filled with an oxygen/hydrogen mixture will explode violently.
Answer: Hydrogen is flammable only when mixed with oxygen, hence this can be mixed with compressed oxygen in petrol engines (hydrogen gas & oxygen gas) to be used as fuel.
Answer: I have accidentally blown up a small container with a mixture of hydrogen, oxygen and the water I was using to extract the gasses. Well I was using DC electricity to get the gasses and there was a spark that happened in the small container and it was a violent explosion and so loud people were driving around looking to see where it came from. I was lucky not to be hurt. There were pieces of the plastic container embedded in the wood framing of my garage. It wasn't much gas either.

Can a spark ignite hydrogen?


Windows 7 does not recognize filesystem on external harddisk which works on any other PC

Question: I have Windows 7 installed on a PC, and try to attach a external 2.5" Seagate 320GB harddisk. The PC itself is perfectly able to see this disk, and even boot from it on startup. There is onyl one partition on this disk, type NTFS, and it can be quickly found on any other PC in Windows.
When I boot into Windows 7 on this PC, and attach this external hard drive (remember, it's not a hardware problem, this PC is even able to boot from this disk!), it is quickly recognized by Windows, but the partition type is unknown, Windows only detects one partition that has no type or name, nor a drive letter in the Disk Management console.
The problem is persistent, tried many reboots, shudowns, but the problem persists.
Answer: May be in this PC USB port has no power to start HD properly. Try to connect HD using short cable or cable with 2 USB connectors.


How to rollback and override to a specific date within a Time Machine backup

Question: my situation is kind of weird. I've totally crashed my system yesterday after installing bootcamp/windows 8.1 (bad partition format). Fortunately, I have a full backup Time Machine on a Drobo 5D (firewired). Since Drobo 5D need specific drivers to read data, I could not reinstalling the OS from Time Machine Backup.
So I have reinstalled a fresh OSX El Capitan from scratch. After created the user and installing drobo drivers, I have bound the Drobo 5d Time Machine backup Disk to the Time Machine OSX service. I've done this because I though it was the way to do it... Error! When I went to restore, I have not seen my old data but just the new installation.
When I go to directly within Drobo Backuped Disk, I see All Past Folders AND new Folders.
I've tried to restore the backup user with migration tool App but no success, the same user as the fresh install, not the old one (with all my apps).
Now I think I've corrupted my backup. Is there a way to rollback this issue?
Answer: I've found a solution. Just delete the undesired folders. Delete and recreate the "latest" alias to the desired date (folder named by date). Boom! Backup is available from that datetime.


Is it legal to sell a software which will scan user files with multiple antiviral engines located on remote server?

Question: I have an idea for a software, which will allow users to upload their files for antivirus scan, receive scan results and perform corresponding action on user end. Is it legal to do so, taking that the antiviral software itself will not be distributed (i.e. i will buy and install it only on my server)?
Comment: "Is Business model X legal" is way too general a question to be susceptible of a meaningful answer.  The answer is "it depends."  Are you writing the software?  Do you have licenses to use it in this way?  Are there any patents that prevent you from doing this?  etc...
Comment: You have two questions -- "is it legal to provide a service where files are uploaded and processed" and a second "can I use software licensed for a single user or computer"  -- the first is Yes, the second is dependent on the terms in the license.
Answer: You will have to read the license of the anti-virus software. Or better yet, ask a good lawyer to read that license.
What you are planning is a commercial use of the software, so any protections that the law might give to a consumer won't apply to you. When you use the software commercially, you are fully responsible for claiming with the words of the license.
Answer: Especially the first answer gives a good indication, but there is even more you have to keep in mind.
First you need to find out, what you are allowed to do with the Software you plan to use. Most companies have different licenses for Personal Use and Commercial Use. You will have to check the company's license for this. For example, you could try to find out if there are companies that offer licences where you 'pay-per-file' for example. This will keep your costs low in case of low interest in the product.
Second, you will have to think about other legal requirements, such as e-commerce requirements (what information are you required to give to the consumer, what can they expect from your product, to what extent can you guarantee the findings of your service?).
Third, and this part is getting increasingly important. What personal information will you process of the customer? Will you process everything, or is some information send to the software distributor as well? Will you hire a VPS? Or have a physical server?
Concluding, there are two (maybe three) important parts of your company. You will have to establish contracts with the Software distributor about the use of its software. Depending on the sort of server you use, you will have to arrange contracts with a cloud company. Third, you will have to standardise the contracts with the consumer/company about the service you are delivering. All of this should be complemented with providing the consumer/company information about how its personal information is being used.
I hoped to have provided you a sufficient answer. Don't hesitate to ask more if you want to know more.