What hoses for shallow point well?

Question: I've got a shallow point well w/pump where the tube (some sort of hard plastic) from the pump to the well has failed.  It developed a pinhole leak.  Question is, what do I need to replace it?  Is there a specific type of tube/hose?  I was considering making a temporary connection with a spare car coolant system hose I have, but when I prime the system it sees full utility water pressure (not sure what it is, but I'm sure I'm guessing it might be 60psi and I'm not sure that cooling system hoses are good for any more than around 2.0 bar).  Tips or tricks?
Comment: is the pump and well all part of the same model? You may be able to contact the original manufacturer for replacement or they can tell you what to buy.
Comment: Not exactly.  There's a Sears shallow jet pump attached to a generic tank, and the point well itself is just your standard driven point well made out of pipes.  There's no "brand" to the system as a whole.  I can try Sears, but the highest pressure is when then system is being primed.  I guess I need to know the typical pressure of "city water" and what pipes/hoses are rated to handle it...
Answer: Typically 100psi poly is used (it's a black flexible pipe with a blue stripe). You should be using brass or poly fittings. I personally avoid nylon, just because with the threaded parts it tends to have the tool grip worn down - it's especially a pain when you go to take it off years after it's been put on, and you need to apply a lot of torque: it tends to strip the fitting, rather than loosen it. Again, make sure the fitting you're using is rated for at least 100psi.
When you connect this pipe to the fittings, you'll need to heat it up (I prefer MEP gas but propane works as well) just enough so it can go on (you still need to apply a bit of force). If you heat it too much to the point it stretches, you'll weaken the pipe and probably cause a leak - if you do this, cut the end off and start over. Use two stainless steel gear clamps to ensure a reliable connection (you can usually get away with one -- but in an outside location like a well, an extra couple gear clamps is probably cheaper than the pain of having to do this repair again).
Wrap some black electrical tape around the gear clamps afterwards, especially if you have wires nearby. This reduces the chance of the sharp edges of the clamps rubbing against the wires and causing a short eventually (I've seen it happen - remember, these pipes will move a bunch every time the pump comes on). It also makes it easier to get the clamps off later, as they won't get full of mud and insects and whatever else. Inside, unless there are wires right next to the pipes, this generally isn't needed.
Most pressure systems are adjusted so they turn on at 40psi, and off at 60psi. The pressure tank in your house buffers this so the pump doesn't cycle constantly (which is hard on pumps). You want to use higher-rated pipes and fittings because sometimes pressure switches can fail and cause the pump to stay on. Most typical domestic pumps (up to 3/4 HP) can't produce above about 90psi, though it depends on several factors including the depth of the well and length of piping.

What hoses for shallow point well?


How is the Fez number cipher intended to be solved?

Question: Every walkthrough/guide/faq I've found for FEZ just has the answer to the number cipher, but not the steps you're supposed to take to solve it on your own. How is it intended to be solved?
Answer: I wrote an essay (with pictures!) explaining how I think the number cipher is intended to be solved.
How you should have solved the Fez number cipher
Here's the cliff notes:

Figure out 0-3 from the dimension diagram.
Figure out the set of symbols for 1-8 from the boiler room, although you don't know which ones are which.
See that 3 is not in the boiler room symbols, which means there must be multiple symbols for 3.
See the formulas in the classroom, and guess what the two horizontal lines mean.
Notice that overlaying images corresponds to adding numbers.
Figure out all the numbers, most importantly the all the single-limbs numbers.

And then you know everything. But steps 3-6 kinda have to be done on faith that you're on the right track, because you get no confirmation until the end. That makes this a really hard puzzle.
Comment: Not sure what the boiler room has to do with it. Thought my explanation was straightforward
Comment: @Sean: I suppose I'm looking for a much more pedantic walkthrough for each step of the reasoning. Figuring out the big points like the non-bijectivity and the adding notation aren't immediately obvious. Furthermore, guessing them doesn't get any confirmation until many steps later.


How prepared will I be to play Arkham Horror after reading just the Rulebook?

Question: I noticed the faq files for Arkham Horror are very large and are partially incorporated into the revised printing, but will I simply be doing some things outright wrong unless I review the faq first?  Will it be sufficient to use the faq as a reference and expect certain aspects of the game will be confusing and prompt me to look up the appropriate section?
Comment: While I agree with @recognizer (+1ed), I played the game a bunch before I knew of the FAQ. If it bothers you to relearn a bunch of rules, you probably want to follow it closely, but if you can take "Oh, I've been doing that wrong", then I'd say don't stress. I didn't answer because I actually feel like the answer is based somewhat upon how to play games and treat rules. My "answer" is not for everyone. Honestly, I reread the FAQ from time to time and find things I've done wrong. I think it unlikely one would remember every bit of the FAQ and the references to it are a little more scattered.
Comment: @Joey You (and people like you) should be fine then [in my opinion]=)
Comment: I personally am often content with giving myself 4 or 5 run-throughs of a game taking small stabs at clarification but not terribly long before making a quick ruling and writing down the question to research later and ask here on B&CG if necessary. It sometimes feels like the fastest way to reach full understanding in the medium term.
Comment: If you're really worried, you can do a solo game (maybe with two investigators) to make sure you figure out the obvious stuff before you try playing with a group of less patient people.
Answer: The best thing would be to learn the rules from someone who's very proficient in them, from their own experience playing. My experience, however, consisted of learning to play Arkham Horror with four friends who were all new to the game as well. In that case, I would suggest that anyone who has not played the game before at least attempt to read the entire rulebook and FAQ first.
If you don't have at least one person participating who's very conversant in the rules, then you'll probably be referring to the rulebook a LOT, not just checking the FAQ for clarifications. Note how long the "short" version of a quick reference guide in this answer is. It's pretty hard to explain the game concisely, and a lot of complications arise beyond the basic rules of the game. Naturally, the FAQ derives from those complications, and simply being aware of which characters, cards, etc have clarifications written about them will help you know whether to consult the rulebook or FAQ while playing. Don't expect to remember everything you read, there's just so much, but do everything you can to make it easier to refer to later.
If you consult some other questions on Arkham Horror, you'll see some comments about the importance of at least one player having the expertise to guide other new players. If you don't have that one expert player, then simply reading the rules AND the FAQ may not be enough to get everything right when first playing. So in short, you should read everything, and still be okay with the expectation that it may take a while to get it all right!
Comment: I mostly agree, but I'd look at it a bit differently. If no one has played before, you'll still have a good game, you'll just have to look at the rulebook (or possibly a cheat sheet/reference guide) a decent amount. Worst case, you'll realize later that you got a couple little things wrong. That seems totally fine, unless you're playing with really impatient people - in which case Arkham Horror probably wasn't the right game in the first place!


Is there a geoprocessing tool that I can use to find the closest road to a point on a map?

Question: I have a Network Dataset layer that I use to perform routing.  Even if a starting or ending point is not near a road in the Network Dataset layer, I still want to perform routing using those points.
Is there a way that I can get the routing to start at the nearest place on the ND, to the starting point, or end on the route at the closest place near the ending point?
Comment: this is ArcGIS?
Answer: ArcMap should do this for you automatically (snap off-network points to the nearest spot on the network) when you load locations into your analysis layer using the Network Analyst toolbar. If you need more control over which classes get locations snapped to them, you can do this in the "Layer Properties" window of your network analysis layer. See "Search tolerance and snapping environment" on this page:
http://resources.arcgis.com/en/help/main/10.2/index.html#//00470000003n000000
Answer: If I understand your question right, you have the Network Analyst extension, you should be able to snap your origin/destination points to the network automatically. If you look under the Network Analyst Options there are Location Snap Options. There is more information in this help page: http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//00470000003n000000
Hope that helps,
David
Comment: Thanks for your comment.  I didn't realize that there were settings in the Add Locations tool that I could use for this. Namely the Search Tolerance.
Answer: I was able to resolve this by changing the Search Tolerance of the Add Stops tool to a higher number.


Can a photo of a page of a copyrighted book be used commercially?

Question: Can a photo of a page of a copyrighted book be used commercially or released into the public domain for reuse?
Comment: Which juristriction?
Should be moved to law.se?
Comment: "photo of a page", as in, a reprography?
Answer: Generally, no. This is just reproduction and the copyright holder of the original work would retain copyright in the reproduction. In fact, if your photograph itself has little additional creativity and just reproduces the page, you might not have copyright in it yourself. This same situation applies to other creative works which may be under copyright, like paintings and sculptures.
Now, depending on other factors, you may be able to mount a fair use / fair dealing defense. One factor might be the portion of the work: if your page is an entire short story, or even the part with a key element of a factual report, that's pretty weak, while a random sample page might be considered okay — there's a point where the usage is "de minimis", which basically means "too small to matter". It's kind of surprising and counter-intuitive how small that has often been in court cases, though. You might want to consider how Google Books presents scans of works they don't have permission to show — they only show a few lines, not the whole page. Maybe they're erring on the side of caution — but maybe not.
But that's really out of scope for this site. The key thing is that a camera is not a magical device which wipes clean the creative slate.
Answer:
Can a photo of a page of a copyrighted book be used commercially?

It may be used commercially only if you have permission from the copyright holder of the original work to use a photo of that page for commercial usage.
Otherwise, the answer is, "No."


Transfering files using remote desktop Windows Server 2003

Question: I am trying to transfer files between the two Windows Server 2003 computers. I have already looked online and have selected the Disk Drives option Local Drives in the Local Resources tab. I still cannot see the other machine's drives from either the client or host. I believe this might be due to a security restriction in windows. What are the possible causes of this problem?
Answer: I usually just use Copy/Paste rather than looking for the drives in Explorer (as that can be pretty slow). Have you enabled clipboard sharing and tried to Copy/Paste the files.
Comment: It gives me this error: "Cannot copy Test: Windows cannot find '%1!|s!'. Check the spelling and try again, or try searching for the item by clicking the Sate button and then clicking Search."
Comment: @FranzPayer try enabaling Smart Card option in the resources tab.


Integration by Parts Question: Integrate $x^3e^x$

Question: Evaluate $$\int x^3e^x \mathrm{d}x$$
I tried to use integration by parts to do this and I let $u = x^3$ and $\mathrm{d}v = e^x \mathrm{d}x$. So I get $$\int x^3e^x \mathrm{d}x= \int x^3e^x \mathrm{d}x- \int e^x \cdot 3x^2\mathrm{d}x$$
How do I do this if my answer has the original integral in it?
Comment: Your integration by parts formula is wrong. The first term on the right does not have an integral.
Answer: A nice and quick way to visualize integration by parts (it could be a time-saver!):
$$\matrix{&\text{differentiate}&&& &\text{integrate}&\\
&x^3&&&&e^x&\\&&&\searrow^\color{red}{+}&&&\\&3x^2&&&&e^x&\\&&&\searrow^\color{blue}{-}&&&\\&6x&&&&e^x&\\&&&\searrow^\color{red}{+}&&&\\&6&&&&e^x&\\&&&\searrow^\color{blue}{-}&&&\\&0&&\rightarrow^{\color{red}{+}}&&e^x&} $$
You multiply the ends of each arrow, then place the corresponding sign and add everything up.
Comment: This is not only *a nice and quick way * ! It is beautiful !! Thanks for providing it.
Answer: The formula for integration by parts is as follows: $$\int u \ \mathrm{d}v = uv - \int v \ \mathrm{d}u$$
For your integral $u = x^3$ and $\mathrm{d}v = e^x\mathrm{d}x$ so we get that $v = \int e^x \ \mathrm{d}x = e^x.$
$$\int x^3e^x \mathrm d x = x^3e^x - \int3x^2e^x \mathrm{d}x$$
Apply integration by parts a couple more times and you should get the correct answer.
Answer: Your next step isn't accurate. This should be the next:
$$\int x^3e^x \mathrm{d}x= x^3e^x \mathrm{d}x- \int e^x \cdot 3x^2\mathrm{d}x$$
Remember, integration by parts states: $\int uv' = uv - \int vu'$
It follows from the product rule:
$$(u \cdot v)' = uv' + vu'$$
Subtract $vu'$ from both sides:
$$(u \cdot v)' - vu' = uv'$$
Integrate both sides:
$$\int (u \cdot v)' - \int vu' = \int uv'$$
The integral and differentiation operators are, by definition, inverses of one another, so the formula becomes:
$$uv - \int vu' = \int uv'$$
Therefore, $\int uv' = uv - \int vu'$
Answer: $$x^n\int e^x\ dx\ne\int x^ne^x\ dx$$
$$I_n=\int x^ne^x\ dx=x^n\int e^x\ dx-\int\left[\dfrac{d(x^n)}{dx}\int e^x\ dx\right]dx$$
$$\implies I_n=x^ne^x-nI_{n-1}$$
Answer: Hint: Notice that you are applying it (Integration by parts Formula) wrong. It should go as
$$\int x^3 e^x dx = x^3 e^x - 3\int x^2 e^x dx$$
Apply it twice and see what you find.
Answer: make the ansatz $\int x^3e^xdx=e^x(Ax^3+Bx^2+Cx+D)$ with the real numbers $A,B,C,D$
Answer: If you're curious, there's a pattern that emerges by looking at $\int x^ne^x dx.$
It's a good induction exercise to prove the following:
$$\int x^ne^x dx = \left[ \sum^n_{j = 0}\left((-1)^j \frac{n!}{(n-j)!} x^{n-j}\right)\right]e^x.$$


Can you capture an enemy settler before they settle the capital city?

Question: Could you take out a civilization before it starts by killing its starting settlers and warriors? On a duel map, could you do this and win without founding your capital either?
Answer: Theoretically, you could. If you somehow managed to capture a civilization's starting settler(s), you could eliminate them from the game very easily.
In practice, this will effectively never happen, as virtually every civilization will found their city on the first turn, and the game's start placement logic will avoid placing civilizations close enough to manage it.
Comment: Duel map size. 22 AIs. 41 city states. Enjoy =D
Answer: tl;dr: yes, you can do this, although it makes the game a bit confused.
This question made me curious, so I tried Affine's strategy of putting 22 civs and 41 city-states on the smallest possible map size. The game assigned me the Shoshone civ, which turned out to be perfect: their cities start with extra tiles, and they have a unique unit — the Pathfinder — that acts like (and replaces) the Scout but has the combat strength of a Warrior. Starting the game as the Shoshone, you get a Settler and a Pathfinder instead of the usual Settler and Warrior combo.
On my first turn, I founded a city, and its borders shoved Spain's starting units onto a little peninsula. I wasn't able to get my Pathfinder over to the Spanish Settler, but that Settler was too close to my city to found a city on its turn, and I was able to capture it on my second turn. I'm not 100% sure what happened to Spain's Warrior; it seemed like it just disappeared when I founded my city, but it could have been pushed onto a hex I couldn't see. I remained at war with Isabella for about ten turns, after which Spain just disappeared from the Diplomacy menu.
In the same game, I noticed that the Huns hadn't founded a city by turn four. I captured their Settler, but their Warrior ran away from me and the civ remained in the game. It took another four turns for me to track down that Warrior and attack it. The combat went normally; neither my Warrior nor the Hun Warrior was destroyed, though both took damage. Then, after I ended my turn, the Hun Warrior just disappeared off the map, without being attacked. When my next turn started, the Hun civ was no longer in the Diplomacy menu.
To test the second part of the question, I started a new game with the same settings, except that I had it start from the Classical Era instead of the Ancient Era. That means starting with a Settler, a Worker, a Spearman and a Pathfinder. I never founded a city. I was able to capture Venice's Settler on my first turn, and destroyed its military units over the next five turns. I didn't go after the Worker, though. It kept running around until turn 50, at which point I gave up hope that the game would consider the civ lost.
I did not have the "Complete Kills" option turned on.
Comment: What happened in the second game? Did nobody win?
Comment: Sorry, I didn't bother finishing it. About a dozen civs had established cities, so it would have taken non-trivial time to wipe them all out.
Answer: The AI will always settle their first city immediately. On higher difficulty levels they start with an extra settler so by the time you reach them you're probably going to be dealing with two cities.
In multiplayer games, if a player is going to be moving their settler before placing it, they will almost certainly protect it with their warrior (if they don't, more fool them).
And in case you're thinking of stealing that second settler for yourself, taking an enemy settler converts it into a worker (though ya know, free workers!)
Comment: Nice link, thx :)
Comment: Do you have a source for the extra settler thing?
Comment: @Sentry Yup, the [Civ Fanatcis forum](http://www.civfanatics.com/civ5/difficulties) has a handy table.


Ethereum performance using whiteblock

Question: I have recently heard about whiteblock testing platform, however, there is no details on how to build your own test. Do you have any idea about how to use it and how powerful the platform is?
Answer: I'm CTO of Whiteblock. We just opened the beta program for our SaaS testing platform. Needless to say, things have been pretty busy for us and we haven't even had time to update our website appropriately to share these details with the public.
Either way, if you need to set up a test net or have other specific testing needs, I'd love to give you a free trial of the platform if you're interested. In the meantime, please check out our website for more high-level details. Send me a message in the Telegram group so we can chat and get the ball rolling.
Comment: Thanks for the update. Yes I would like to try your platform to perform my own test.

Ethereum performance using whiteblock


What happens if I never receive my CA jury duty summons in the mail?

Question: This question is strictly hypothetical, but what happens if I never receive a Jury Duty Summons in the state of CA in the mail? Theerefore, I miss whatever trial/week I was assigned to,  because I never received the notification in the first place, through no fault of my own?
Comment: They use someone who did turn up.
Comment: I think the question is whether you would be punished for failing to appear.
Comment: How would you ever know that you were summoned?
Answer: According to my California county's Superior Court, Failure to Appear/Respond to a Jury Summons:

Pursuant to California Code of Civil Procedure Section 209, any
prospective juror who has been summoned for service, and who fails to
respond as directed and be excused from attendance, may be found in
contempt of court, punishable by fine ($1,500), incarceration (5 days)
or both.

There's no other information on the Jury webpages about beyond to call them if you miss the summons date. I suspect that if you did call them, they would just schedule for a new date.
I personally know people who have tossed all their jury summons and nothing has happened to them, but that may not hold true for all California counties.
Comment: @phoog Your statement goes to common practice and how the law is administered in fact. My comment goes to the case of someone aggressively seeking to punish you despite the fact that this is atypical, and suggesting that they would not prevail in doing so.
Comment: I am quite certain that failure to receive a summons, if believed by the court, would be a defense to this sanction.
Comment: @ohwilleke isn't that more or less implicit in "if you did call them, they would just schedule for a new date"?


Is it okay to have 2 definitions of the same term?

Question: (A bit difficult to describe what I mean without sharing my definitions, but I am cautious of posting them since this is regarding my thesis.) I had to provide a definition for a term I came up with. Since it is a complex matter, I provided one definition and then wrote "alternatively put:" and gave a second definition that describes it a bit differently and more elaborate. My advisor just put a question mark. I thought of merging both definitions together, but they are more or less different "views" of the term, so it didn't make sense. Is there an academically adequate way for me to keep both definitions of the same term?
Comment: Is this math? Lots of answers seem to assume it is.
Comment: Shouldn't the general answer to "what to do if my adviser puts a question mark" be "then talk to your adviser!"?
Comment: Consider the seven definitions of a [matroid](https://en.wikipedia.org/wiki/Matroid#Definition).
Answer: If they are "views" then they are hardly "definitions". A definition should be precise. If you want to give two statements, which might occur in math, you need to be able to prove equivalence.
If they merely overlap in meaning then there may be cases in which one applies and the other doesn't. In informal language that is probably fine, but in a dissertation that is unlikely to be the case. It is hard to "define" goodness for example.
Note that something like a metaphor or analogy isn't a definition. A definition needs to distinguish what is and what is not conformable.
I'll go along with your advisor and put a question mark.
You can choose one, perhaps, or unify them formally, but two is too many.
If the same term is used in your field in two distinct ways then it may be defined differently for different aspects. But in such a case you will need to be extremely clear when you use one definition or the other. What is it that distinguishes them?
Comment: *If they are "views" then they are hardly "definitions".* Counterpoint: https://en.wikipedia.org/wiki/NP_(complexity)#Formal_definition Though I do agree that the thesis should probably pick a single thing and call it the definition.
Comment: @JordiVermeulen That doesn't sound like a difference to me. If multiple definitions aren't provably equivalent, there's been a mistake.
Comment: @user541686 the difference in that example is that all those different definitions are provably equivalent.
Comment: @user541686 Well, the first one is *the* definition, and is why it's called NP. The second one is not so much a definition as a result saying that something is in NP if and only if it satisfies these conditions. And it's often more convenient to check NP-ness using the result than the definition.
Comment: @wizzwizz4 I just meant that in some mathematical settings, there are different "views" of a certain concept that are provably equivalent (e.g. NP-ness by Turing machine, or by certificates). Sometimes one view is more convenient for whatever it is you're doing, and that's fine, because they're all the same. It's different in some other sciences, where the same term may have multiple definitions that are *not* provably equivalent, but subtly different.
Answer: Echoing @Buffy's good answer, and emphasizing a certain point: even if there is no truly "correct" order of logical development of the ideas (meaning what is a definition, versus consequence of definition), you probably need to pick one... Then perhaps prove that another "definition/characterization" is equivalent, or, possibly, is equivalent when both characterizations apply(?).
After proving such an equivalence, then we can forget the (possibly artificial) logical ordering that we used at the beginning (to avoid circular reasoning...)
Comment: I often write definitions like "The following are all equivalent: def1, def2, def3.  We call anything satisfying any one of these equivalent conditions a ____".  Then prove the equivalence.
Answer: Here is a familiar example of how to write equivalent definitions,
Lemma 1.3.4: For any set $A \subset X$ the following two conditions are equivalent:
(a) The complement $X-A$ is open in $X$.
(b) Any sequence $(x_n)$ in $X$ with limit $x$ that has all $x_i \in A$ also satisfies $x \in A$.
Proof: Yadda yadda yadda QED.
Definition 1.3.5: The set $A \subset X$ is said to be closed in $X$ to mean it satisfies one and therefore both of conditions (a) and (b) above.
Answer: I guess you can give multiple definitions, as long as you then explain why there are multiple definitions. For example, I can imagine if you are talking about "fatigue" you could say "for engineers, fatigue means... But when sports scientists use the term, they mean... The difference is interesting because...."
Basically, you don't want your readers to be puzzled by what's going on. If your supervisor (who is an expert) is puzzled, then everyone else will be too. Have a bash at rewording it, and run it past your supervisor again.
Answer: What field is this? If you're doing qualitative work, it wouldn't be out of line to provide an elaborated definition and a more concise (TL;DR) version of the same concept. The shorter definition may be shorthand for the former. The shorter version could also be a more abstract concept that would meet with wide agreement (and be easy to grasp, maybe even by non-academics), while the longer version is a detailed description of exactly what does and doesn't fit into the concept. Indeed, when doing quantitative analysis in the social sciences, it's very common to give a conceptual definition, followed by a definition that operationalizes the concept for the analysis in question.
Comment: The definition of "definition", and the uses of definitions, vary by field. For example, I used to do research on democracy, and there are literally dozens of different definitions of it. Most everyone agrees that a "democracy" is a country ruled through elections, but there are all sorts of nuances, like who can vote, how free the press is, and how fair elections are. When there are no true bright lines between categories, you can't construct perfect definitions. OTOH, for quantitative analysis, I'd need a very specific definition, which might depend on what's feasible given imperfect data.
Comment: You aren't describing a "definition" but an explanation or, perhaps, an analogy. If the shorter "definition" really defines the concept, what use is the longer one?
Answer: A definition must be comprehensive and unambiguous.

If you need a second definition, it can mean that your first "definition" is still ambiguous, that you still need to be more precise. In that case, it means that the first "definition" was actually not a definition. So it would not be okay to have two definitions. Work harder on the first definition.

Another case is if you have readers from very distinct fields who have distinct jargons which makes that some of them who aren't familiar with the jargon of the first definition (assuming it is a true unambiguous definition) don't really understand it. In that case, a second definition can be interesting as long as it's just a sound paraphrase. But the best solution remains to find a definition whose words are understandable by everyone.

TL;DR. It's always a bad idea to have two definitions. However, it can be interesting to present equivalences. That is the fact that one term in a specific field corresponds to another word in another field. This can allow to jump from one field to another field and connect knowledges together.
If you want to help people better understand what your object is by explaining things about it, by stating some consequences of its existence, or by telling its origin, etc. it doesn't stand in the "definition" part but in the rest of your text parts (etymology, origin, consequences, corollaries, theorems, etc. as it depends on your working field).


Are questions on weather balloons on topic here?

Question: I'm planning a high-altitude weather balloon project (to around 100000 feet) some time down the line and I have some questions I need to ask before doing so. Since there isn't Weather Ballooning Stack Exchange (yet!) can I post questions about it here? It's sort of aviation anyway haha.
Answer: I think we have enough balloon questions already to say that balloons in general are on topic here, so the question is if there any reason why weather balloons specifically should not be. IMO, if the question is about the balloon itself or how to operate it then yes, it's on topic; if it's about the mission or the activity that the balloon supports then the answer is (generally) no, unless that mission is clearly aviation-related itself.
Questions about constructing, operating or navigating the balloon would be on topic, unless perhaps you ask about generic gas/buoyancy calculations that are not specific to aviation. Questions about meteorology instrumentation, data processing or other aspects of the balloon's mission would be off topic.
There's a possible grey area here, because weather balloons and weather in general are very important and relevant to aviation so arguably the mission could also be aviation-related in some scenarios. But I think that's the same with most things  and individual questions can always be voted on or off topic, whatever we think about the subject in general.
Perhaps a clearer example would be a hot air balloon used for safari tourists in Africa. Questions about constructing, launching, navigating, retrieving and generally operating the balloon itself would be on topic. Questions about what animals to look for, good game areas to launch in, how much to tip your pilot, the ethics of photo safaris vs. shooting safaris etc. would all be off topic.
But as always on StackExchange, if in doubt just post your question and see what the response is.
Comment: i would also add that FAA/NTSB regulatory questions on balloons (manned or unmanned) would be on-topic
Answer: Depending on the question (required notams during launch for example) you may find better answers at earthscience.SE.
Comment: I very much doubt anything under the Karman line or purely atmosphere bound will be on topic on space.SE
Comment: Well, I meant more technical questions such as calculating balloon ascent rates, drift, and communication systems.
Comment: @shortstheory and why wouldn't the people that launch such balloons routinely (a subset of meteorologists) not know these things?  Questions about weather balloons would be on topic at [earthscience.se].
Comment: Oh! I think I missed the point of what Earth Science SE was about, no offence to the good people there. Does it fit on Space Ex SE?
Comment: Besides, earth science SE is not getting nearly as much traffic as we are.
Comment: @shortstheory Stuff like calculating the ascent rate of a gas-filled balloon (the generic case), or cluster balloons might be on topic here (or equally so on [physics.SE]) - It sounds like something you'd find described in the FAA's balloon handbook. Specifically weather-ballon-related stuff (I can't think of a convenient example but "you'll know it when you see it") is a bit more sketchy.


How can I set the Accept Header for a link on a web page?

Question: This is mostly an ivory tower question, since I can easily just make a new URL endpoint.  But basically, I'd like to be able to serve up CSV when the user has the Accept header configured to include text/csv.  That's trivial on the server side, but on the client side I don't know how to set the Accept header unless I'm using XHR or some other "non-browser" client.  Is there a way in HTML to set the Accept header in a link or in JS to set the Accept header when using window.location?
Comment: +1, this would be a good use of the protocol features.  Unfortunately, you're not going to be able to get the browser to set what it accepts on a normal link.
Comment: I think this is a HTML defect. If we would be able to set the accept and accept-language headers on the HTML links, life would be much easier. E.g. you would not need to put that info into the URL to make the content cacheable, crawlable, etc... Sharing links would be much harder though...
Comment: That's what I figured @Brad.  Doesn't hurt to ask though :)
Answer: I figure I might as well put this here for the next thousand people looking at the post.  You cannot do it.
Comment: It's sorta funny to me that anyone thinks that answer has anything to do with this question.  It works, for a different question.
Answer: Update:
I will leave my original answer below for posterity, but I now see that I didn't really answer the question. There isn't a way to do this "natively", the best approach I can think of would be to use a data uri (http://en.wikipedia.org/wiki/Data_URI_scheme) and have AJAX do the work for you:
// aware that you didn't mention jQuery, but you can do this with or without
var download = function(){
    var mime = this.getAttribute('data-mime-type');
    $.ajax({
        accepts: mime,
        success: function(data){
            var uri = 'data:'+mime+';charset=UTF-8,' + encodeURIComponent(data);
            window.location = uri;
        }
    })
    return false;
}

With the same idea used in the example below:
Download CSV
document.querySelectorAll('a[data-mime-type]').onclick = download;

Original Answer
There is no built-in way to force an 'Accept' header on a link (via HTML or Javascript). I think you could pull this off fairly easily using a very small amount of server & client-side code though. Should be easy in any language, my example is PHP:
function get_accepted_headers() {
    $headers = apache_request_headers();
    if(array_key_exists('Accept', $headers)) {
        $accepted = explode(',', $headers['Accept']);
        return $accepted;
    }
    return array();
}

Add a data-accept attribute to your download links:
Download CSV
Then attach a click event handler to ensure that the user accepts the specified content type:
// will end up with something like: ["text/html", "application/xhtml+xml", "application/xml;q=0.9", "image/webp", "*/*;q=0.8"]
var user_headers = <?=stripslashes(json_encode(get_accepted_headers()))?>;
var click_header_check = function() {
    var accept = this.getAttribute('data-accept');
    if(user_headers.indexOf(accept) == -1) {
        console.log('User does not explicitly accept content-type: %s', accept);
        return false;
    }
    window.location = this.href;
    return;
}

// attach the event listener
document.querySelector('a[data-accept]').onclick = click_header_check;

Not sure if this is what you were looking for, but hope that it helps.
Comment: Yeah, as far as I can tell this doesn't answer the question at all, since the stuff in the fake Accept don't get sent to the server.  IE to be clear, I want to OVERRIDE what the browser says
Comment: I suppose I was confused about the question, it appears you want a link to send a different request header and that isn't possible outside of using an XMLHttpRequest and using `window.location` to 'redirect' user to a `data:...` url
Answer: For those still interested, there is a way to do this in pure javascript.
The following code uses JQuery (https://jquery.com/) and FileSaver.js (http://purl.eligrey.com/github/FileSaver.js/blob/master/FileSaver.js) though you could write the respective parts yourself:
//in case of non binary data use:
var type = 'text/xml';
var url = 'http://your_url_here/'
$.ajax({accepts:{text:type},
        url:url,
        processData:false,
        dataType:'text',
        success:function(data){
                saveAs(new Blob([data], {type: type}),'filename.txt');
            },
        error: function(){
               // Handle errors here
            }
    });


pineapple houseplant tipped and stem disturbed at ground level

Question: When returning my pineapple plant to its usual spot, the central stem almost snapped at ground level.  I propped up the plant with a stake, but want to know if there is anything else to do to ensure the plant recovers.  Thanks for your help.
Comment: Do you have pictures maybe?
Answer: Since this pineapple has a central stem you seem to be indicating that it has reached maturity and has produced a stem with a heavy pineapple fruit on top, and this weight with its leverage has caused the break during the move. So we know that basically, despite the unfortunate break the plant has come close to end of life, will continue to ripen the fruit, produce pups at the side at soil level and the centre will die out shortly.
The staking is a good idea and will likely carry the plant through to the end. It will keep the fruit clear of the soil. Likely there will be enough resources in the thick stem to continue to nourish the fruit to the end despite the break unless it has become completely separated. Once removed from the mother plant the fruit cannot ripen much more than it already is.
Once the fully mature fruit can be separated from the mother plant the broken stem can be removed (eliminating the need for the support stick) and composted, then focus on allowing the pups to gain some traction so that they can be cut off and repotted separately to start the new round of plants.


What's the difference between a package and bundle?

Question: I seemingly see the words package and bundle used interchangeably in Apple documentation referring to a special folder in the file system that the user sees as document (iWork Pages document) or application (Pages.app). I know one can view the contents of a package or bundle by right clicking on one of these special files and clicking Show Package Contents. Which suggests to me that both are are a type of package. So is a bundle a special type of package?
Answer: From Apple's Bundle Programming Guide

Although bundles and packages are sometimes referred to interchangeably, they actually represent very distinct concepts:
A package is any directory that the Finder presents to the user as if it were a single file.
A bundle is a directory with a standardized hierarchical structure that holds executable code and the resources used by that code.

Also

The Finder considers a directory to be a package if any of the following conditions are true:
The directory has a known filename extension: .app, .bundle, .framework, .plugin, .kext, and so on.
The directory has an extension that some other application claims represents a package type; see Document Packages.
The directory has its package bit set.

In code with bundles and packages are manipulated by the same NSBundle class
Answer: A package and a bundle have/have had similar structure. A package is a "file" that is operated on by the OSX Installer. These days packages have been flatten into an xar archives. Packages are also "files" created by some Apple applications, where the file is actually a directory with multiple supporting files. A bundle contains executable code, an application (.app) is a bundle. Plugins are also bundles.


Build and deploy asp.net MVC WCF application

Question: I am fairly new to creating deployments for projects.
I have a asp.net MVC web application and WCF service layer (5 services).
Our QA team needs to get latest build packages to test the application.
At the moment we have command line build scripts which gets the latest source, build with the Visual Studio and copy those build outputs to IIS and Services folder(Services are hosted as Windows services).
What would be the recommended way to do this? We have TFS builds, but we are not using those build outputs at the moment.
What would be the recommended way to set up a deployment for these projects?
Answer: You should automate your deployment pipeline.
You can use TFS builds in conjunction with Web Deploy or with Octopus to achieve this goal.


Change surface's apparent color based on light depth from source

Question: I'm trying to find a way to color the surface of objects depending on the light depth from the light source, but only in appearance to the camera. I have one light source in the scene, and I want any surface that could hit that light directly to be colored red, and look red to the camera regardless of angle, but reflect as if it was white. Then any light that is hit by that reflection to be colored green (the light bounce max is 2 so that would be the end of it). So far, I have tried using the light path node to basically make conditional sections for if if something was a camera ray, what the ray depth was, etc, but since it starts counting from the camera, I'm not sure if that would work. Is this possible with cycles?
Answer: I'm not 100% sure what you mean, but try something like this - the light is white, it makes the object with the material (the cube) appear red, but reflect white ("mirror" plane below) and any red light that would be cast as a "secondary bounce color transfer" appears green instead of red (cast on both the bottom "mirror" as well as on the white sphere). I used an emission shader for the green to make it more pronounced, but you can use diffuse as well - the effects just aren't as prominent.


redirect root domain name to amazon s3

Question: My domain is rather long. I need to use it without www.
All the info I find on the net is about cnames.
How do I redirect the whole domain to an amazon s3 bucket, not only a subdomain?
Answer: Amazon recently announced support for root domain hosting via S3.  The instructions for setting this up can be found here.  Note that you will have to setup two buckets to accomplish this, and that you will have to use Route 53 for your DNS hosting.
Answer: Try wwwizer
What you need to do is to create a cname www pointing to your s3 bucket url (bucket name will need to match) and then create an A record to the ip given by wwwizer.
Another way is to use a url redirecting service or use a free web host (like godaddy's ad supported hosting) and on the index file issue a redirect to www.yourdomain.com.
There might be other solutions that rely on finding out the ips of the amazon s3 front end servers but they are error prone.

redirect root domain name to amazon s3


Higher point semi-classical Virasoro conformal blocks

Question: I am looking for references of higher point semi-classical Virasoro Conformal blocks. I know of one paper where two heavy and arbitrary light operators(https://arxiv.org/abs/1601.06794) have been considered, and another paper with 5-point correlator(https://arxiv.org/abs/1512.07627) is considered. But I am particularly trying to find references/attempts with all equal dimensional operator light correlators. Are there any?
Comment: Could you be more specific? Can you give the arXiv numbers of the papers you are mentioning? You want all operators with the same dimension: light or heavy? What about the exchanged operators?
Comment: I have edited the question accordingly. I am looking for n-point arbitrary light operator correlators. Although I am not completely clear, but I thought that in large c limit the main contribution comes only from  identity exchange, but I might be wrong, so I have omitted that part in the question.
Answer: In the light limit, there is no reason for the identity exchange to dominate. If all operators are light, including exchanged operators, an $N$-point block is a simple integral over $N-3$ variables. The case $N=4$ is given by formula (2.12) of https://arxiv.org/abs/1109.6764 , whose generalization to $N\geq 5$ is straightforward. It should also be possible to generalize the hypergeometric representation (2.13), I am not sure if this has been worked out explicitly. For $N=5$ this seems to be formula (2.10) of your reference https://arxiv.org/abs/1512.07627 .


Weird white space in illustrator CC 2018 when using pen or brush tool

Question: I need help getting rid of these white spaces connected to the lines I'm drawing. Ive tried it with no fill but I cannot get rid of them. please help!
Comment: as far as I can tell, this is a fill on the shape. Check to make sure you actually have the shape selected and then switch it to no fill.
Comment: https://helpx.adobe.com/illustrator/tutorials.html
Answer: The objects have the fill of white, you have to change it to "no fill"
Select the paths, then click the   or hit /)
(you will have to select the paths in order to change the color of the fill or stroke)
Comment: You must've changed the Stroke, you need to change the fill
Comment: when I change it to no fill it just turns the line into a red line and doesn't appear when its not selected.
Comment: when i do that the white space disappears but my lines become thicker and changing the weight of the stroke doesn't do anything. I'm sorry I'm new at illustrator.
Answer: Select one of the line shapes and turn off the white fill.
That brush has a thickness independent of stroke. If you want to use brushes you can change the diameter of a calligraphic brush after double clicking the brush in the Brushes panel.
I'd just draw those lines again with the pen or line tool so the stroke works. When starting out regular lines (paths) are easier than brushes. Draw the lines, select the stroke again in the tool panel, with stroke selected you can control thickness and color.
If you want your stroke pointy you can select that under profile at the bottom of your stroke panel.


Desperate for recognition of this car, only picture, stole something right out my mailbox. difficult to recognize, small crossover 2000-2023

Question: please any car brand or information is welcome. security cam footage of vehicle of whom someone stole something from my mail. I know my cars, but there isn't much to go on. Probably a crossover or hatchback, Iv'e lost faith in it being an SUV. looked at all major SUV types can't find it. Not likely to be Mercedes, BMW, Japanese, Korean, Chevy or any other major SUV. think it is a hatchback, and no software can find it because it is too distorted.
Comment: Welcome to Motor Vehicle Maintenance & Repair! This is a small SUV or crossover, though I can't place it. I've seen the styling before, but everything I look at does not match the upswept headlight lense and small side marker which is bent and follows the round wheel arch. I thought it might have been an Mazda CX3, as the wheels look right, but it doesn't have the marker on the side.
Comment: 2021 ish Nissan Murano???
Answer: You're looking at a semi-recent BMW X2 crossover SUV.  I know you said it wasn't a BMW, but that particular X2 model has a badge on the D pillar that is unique to it.  Comparing against images online, you can also note the slight wraparound the headlights have into the fender along with the obnoxiously large sunroof which is an option on that model.
I remember the first time I saw one of these in person and was shocked at why they would stick that badge on the D pillar at all because it looks so out of place and is such a distinctive feature of that model.
Comment: thanks, looks like you're correct. i thought it was a bmw suv, but i didn't look at crossovers. thanks, this is valuable information as it is a rare vehicle. And a serious matter.
Comment: Going a bit deeper because people that steal suck - it looks like either a first or second generation 2018-2023 based off of 2 things.  The headlight profile in the current generation does not match this and the wheels are unique to the first and second generations.
Comment: Thanks. It is very difficult to track down registration without a vin or plate, but if the fbi can do it, so can I with some help from the police . I have turned in the photo and knowledge of the model has helped I appreciate it so much!


What tools and/or equipment is needed to replace the cylinder head on a 2003 Chevrolet Trailblazer 4.3L V6?

Question: So, I was away for a few months and when i returned, my vehicle had a cracked cylinder head. Long story, but i got a replacement cylinder head. I know a little about cars, but far from a master mechanic. I need to know exactly what tools and/or equipment will be needed to get the job done. And if at all possible, if someone may know or has some type of step by step guide on the replacement process. I could definitely use it. Also, what all exactly needs to be replaced other than the head. I got a gasket set along with the cylinder head itself. Do i need to also get new bolts or use the old ones? Sealants that need to be used? Any fluids need to be drained beforehand? The timing chain information? Crankshaft info? I just need all of the NEED-TO-KNOW that anyone could possibly offer me. Thanks.
Comment: Welcome to Motor Vehicle Maintenance & Repair!
Answer: You need (at a minimum):

A metric socket set (ratchet, breaker bar, sockets) - 1/2" drive is probably best
Hand tools (pliers, metric wrenches [combination wrenches], gasket scraper)
Torque wrench which matches your socket drive size - 1/2" drive will detect the torque needed for reassembly (3/8" won't go high enough).
Straight edge and feeler gauge to check flatness of the block deck surface
Containers to catch liquids like coolant
A Haynes manual or the like, which will provide you all the specifics

If I didn't put that last line in there, I'd be here all day trying to decipher exactly what you need to do. A repair manual like Haynes or Chiltons may not be the absolute best, but it will provide you the step-by-step you need for tear down and reassembly, along with the specs needed for torque and the like. Consider it a tool in your arsenal which is crucial for what you're trying to do.
Along with the parts you already have, you most likely need new head bolts. The rest of the bolts should be reusable, unless they break. You'll also need a new exhaust manifold gasket for the side you're taking apart. Be careful when taking the bolts/studs out of the head ... they have a tendency to break due to heat cycles and rust.
Unless you are replacing the timing chain, which you shouldn't need to, you don't have to worry about it or the crankshaft. You won't go into that part of the engine while replacing the head.
Comment: In addition to Haynes and Chilton manuals, an online resource called Alldata is also available. It includes all the data that professional mechanics access including step by step instructions for repairs. You can get a short-term one month subscription for a single make-model-year for only $20. https://www.alldata.com/diy-us/en
Comment: Thank you so much for all your help


What is the difference between `dd`, `cp` and `rsync`?

Question: Besides the explanations from the man pages and --help information, in which way do the commands dd, cp and rsync differ when used to copy files? In which context is each of these superior to the others, for some definition of 'superior', so that it should get preference of use?
Comment: Although I agree that the question is extremely broad and doesn't show that the man pages were actually read, the answer received seems to address it fairly well.  For this reason, I think it should not be closed.
Comment: Thanks for this comment. I have read the --help and man pages but I don't see an advantage in 'showing' that I have done it. The purpose of the question is indeed to eschew the technical jargon and have guidance around it. Which jargon may be daunting confusing to the novice. We have received a pretty thorough and to-the-point answer.
Answer: They are completely different animals that better fit on different file or device manipulation cases:
dd
This command was created as a "copy and convert" utility, originally intended for converting files between the ASCII, little-endian, byte-stream world of DEC computers  and  the  EBCDIC,  big-endian, appearing at the first time on Unix Version 5. It became the de facto command utility to manipulate everything that can be mapped as a file inside your Unix-like operating system(clone a disc, backup of mbr, clone a disk as file, copy some blocks of one device file, write an image to a usb stick..), and piped to other commands, the sky is the limit. One alternative to this software is the dcfldd command.
dd related stuff:

Is there a way to determine the optimal value for the bs parameter to dd?
11 Awesome DD Commands
6 Examples to Backup Linux Using dd Command (Including Disk to Disk)
What does dd stand for? - Could be "Dataset Definition" or "Copy and Convert" and was renamed to dd only because cc was reserved for the C compiler. It is up to choose one of the naming theory ;)

cp
Make copy of files and directories. This is a more "higher" level of abstraction, where you can copy directories recursively, without caring about block size, file conversion, etc. It is a better tool to deal with "1-to-many" cases of file copy, ownership, symbolic link follow, recursively copy, and verbosity. However, it has it's limitations like dealing with file changes, remote copy, and those things better handled by rsync.
cp related stuff:

Is it possible to see cp speed and percent copied? - Specific case there rsync is a better tool to local copy files ;)
Difference Between cp -r and cp -R (copy command)

rsync
Can to copy files inside the same computer, but it's features are more useful on remote copy scenarios. Some of the features are ownership handling/manipulation, more easy "exclude" expressions for a better copy, file checksum to see if a file was already copied, delete origin files during or after copu, the use of a "transparent shell" by invoking the protocol wanted using a specific URI(ssh://, rsync://...), pipelining and other stuff that create optimized environment for remote mirroring things.
rsync related stuff:

rsync all files of remote machine over SSH without root user?
Rsync filter: copying one pattern only
Rsync - 10 Practical Examples
How to Backup Linux? 15 rsync Command Examples

Further Reading:

dd vs cat — is dd still relevant these days?
Comment: **dd** is also nicknamed Disk Destroyer
Comment: I read somewhere _"block transfer vs file transfer"_. Probably dd is the former while cp and rsync are both the latter. That refers to what it is doing under the hood, but possibly that also affects its performance in some way would be interesting to know.


how to mount ipod touch 4th generation 16gb

Question: i am used to the easy way on windows. just open the itunes and voila your work is done. here it is a bit different i see. i tried using rhythmbox and also downloaded gpod. but seems like Rhythmbox only supports upto 3rd generation ipods. My being the 4th gen. i am unable to load files or even mount it easily.For this i have downloaded gtkpod ipod manager. but cant really understand nothing. can you please help, and tell me how to go about it :(
Comment: duplicate of http://askubuntu.com/questions/25908/how-to-mount-my-ipod-touch-4g, which has a good answer.
Answer: Try this : (http://www.simplehelp.net/2007/07/07/how-to-use-gtkpod-to-manage-your-ipod-in-ubuntu/)
Works for me :)
This is a bit outdated - Skip the installation instruction and go to step 2 of "Using gtkpod".
Answer: Currently, there doesn't seem to be an open-source way to put audio onto a 4th gen iPod touch.
I tried gtkpod and banshee, but both are based on libgpod.  That wiki page indicates that the current (0.8.0) release only has read-only support for iPod touch 4th gen.
I ran into the same problem as you, with a 4th gen ipod touch. (except maybe you weren't even getting read-only support). The GUIs do a terrible job at alerting you to the fact that your changes can't be saved. :/


Citing translations

Question: For this answer, and I'm sure others, I copied the english translation from the iTalmud app. Should I cite it at the bottom of the quote?
Comment: Is it their own, or did they get it from somewhere? (+1, good question, not [an agreement-that-you-should-cite type of +1](http://meta.judaism.stackexchange.com/faq#vote-differences).)
Answer: Whenever I quote translated passages, I try to make it clear where the translation came from (including if it was mine), either with a note or simply by linking to the translation in the citation.
There are three reasons that I do (and advocate) this practice:

All translations embed assumptions and interpretations, and it's important to acknowledge this fact and that the translation you're reading represents a particular take on the text.
If the translation was by me, I want to make it clear that the translation you're reading is no more reliable than the rest of the answer (really a specical case of the previous reason).
If the work of translation was done by someone else, it makes sense to give due credit for that work. As it says in Avot 6:6, "One who says something in the name of its speaker brings redemption to the world ..."

As precedent for this practice, I'll point out that the MLA recommendation for citing the Bible includes "In your first parenthetical citation, you want to make clear which Bible you're using (and underline or italicize the title), as each version varies in its translation ..."
Answer: Whenever I quote the Soncino, I make a note of it. See here for one example:
Shimi Ben Geira was Shlomo's Teacher?
I also link to the translation.

Citing translations


Length of a seconds pendulum

Question: I would like to construct a seconds pendulum. The length of a 1/2 Hz pendulum is 994 mm. My question, is that length the distance to the center of mass? And how does the density of the arm effect the period? e.g.; will the length a steel arm and weight be different than an aluminum of wood arm and weight?
Comment: If the weight of the arm is not negligible compared to the end mass the pendulum is called a "physical pendulum".  Google that and you'll readily find the formula.  As a practical matter you should make the length trimable and adjust to achieve the desired period. (The real physical calculation will make the arm slightly shorter)
Answer: The formula which the seconds pendulum is derived is the simple gravity pendulum.
The simple gravity pendulum assumes a few things when you derive the solution to the differential equation.

The arm is massless and does not stretch or compress.
There is no air resistance/friction opposing the motion.
It is a point mass
The angle of movement is small

(there are some other assumptions; but those are the key ones for what you are asking).
It is modeled as a single point of mass on an arm with no weight.  This means that if the mass of the arm can't be ignored; it will affect the equation.  In this case, we have a very long arm that ideally will support the pendulum without stretching or compressing, so it will need to be somewhat strong; and is therefore likely to have noticeable weight.
With a real sized pendulum bob on a weightless arm, you would need to have $994 \  mm$ from the pivot point to the centre of the pendulum bob; because it is the centre of mass of the pendulum where the simple gravity pendulum equation is derived.  When the arm weight is important, it will raise your centre of mass closer to the arm from the middle of the bob.  It also may create substantial differences due to the moment of inertia; as we are no longer a point mass; but instead a rotating rigid body.
You will have to consider the weight and geometry of your arm + bob to determine the centre of mass.  The tricky part will be designing the two in a way so that the centre of mass is $994 \ m $ from your pivot.  It may take trial and error.

Length of a seconds pendulum


The cost of Exchanging $50k

Question: Walk me through buying 50k in BC using cash in Dallas and exchanging BC for cash in the SF bay area 3 days later. Specifically with attention  to costs and fees, and maintaining anonymity via in person transactions or whatever method is most relevant to maintaining anonymity.
Comment: Just don't... the chance you lose it is way too big. As not all amounts can be easily converted to cash and even if so, you still need to withdraw it somehow... so you would just get it back on the bank account it came from. Probably a LOT less then you have put in though due to fees and stuff.
Answer: If for cash means you want paper then it is possible only theoretically - you sell it in the same way as cucumbers or gas to the people that want to buy it. You just need to find them and it will be hard because if you don't want to do it online means you are afraid of something: fake banknotes, money laundering, etc.
Answer: Finding an Exchange
I'm not sure if there are walk-in exchanges in Dallas, but the Bitcoin site is a good place to start a search. Most exchanges take a couple of days to set up and verify your account, so just walking in and purchasing $50k of Bitcoin is unlikely.
Cost
Your specific fees will depend on the exchange that you choose. Generally you should plan on the purchase costing around $1k. You shouldn't have any fees associated with selling, apart from the transaction fee, which should be less than $30.
Anonymity
When Bitcoin began it offered a great deal of anonymity, as there was very little regulation. It's use as the primary currency for illegitimate transactions on sites such as Silk Road has brough regulation which errodes anonymity. Now exchanges will require photo identification (not uncommon for them to ask for more than one form as well) prior to doing business with you.
Hypothetically speaking, I believe its still possible to use Bitcoin with some anonymity. Its unrealistic to think that you'll be able to achieve this with a quick $50k cash transaction. If anonymity is important, you may have a look into Monero.
Volitility
If you're planning to use Bitcoin specifically to transfer funds, then you'll need to be aware of volatility. There are many speculative traders betting for or against the Bitcoin, which means that the price can (and does) move rapidly. 10% movement in a day isn't uncommon. The longer it takes you to sell your coins, the less likely it is that they'll be worth the same amount you paid. For the amount that you're asking about, you could easily lose or make a few thousand dollars in 3 days.

The cost of Exchanging $50k


Whats the best advice to progress onto TT bars?

Question: Ive just started TT on my road bike and looking at slowly adding components to improve my time....aero bars seem next logical step but need some advice on how to progress? Thank you
Comment: Consider that every dollar you spend tt-ifying a road bike is money you can't put into a dedicated TT bike.    Look on ebay for cheap used clipon aero bars - don't buy new.   If you like the posture then consider buying a TT bike.
Answer: I followed a similar path.  I was road riding then entered into a couple of TT's.  I soon thereafter bought aerobars off of Ebay.  Riding at that angle is different and takes a little getting used to.  I then decided to get a TT bike, but instead of just buying one, I bought a frame and all parts on line, mostly from Ebay, scouring for the best prices on what I wanted that were either slightly used (mostly) or new.  I ended up saving almost $4,000 doing it this way instead of buying a ready to go bike and I learned a lot in the process.  I did have my local bike shop put it all together for around $100.
Good luck.
Answer: There is plenty of info on web about this topic.
The general consensus is that aero bars give the biggest time improvement per dollar spent. See this Cycling Tips article, which goes on to say that the next bang-for-buck improvements are: a skin suit, shoe covers, aero helmet, TT wheels.
There are a few things to consider though.

Aero bars will mess with your bike fit, so get a fitting done to a) take full advantage of them, and b) avoid injuries. You'll probably lift your seat and move it forward a tad.
Aero bars are less useful on hilly / twisty courses. Do your research on this.
This Bike Radar article discusses these and more issues. And this Cycling-Inform article rehashes the general advice.

Happy racing!


How can I view diffs or at least older versions of specific files with etckeeper?

Question: So I'm using etckeeper on my machine running Debian 9.1 with KDE and would like to view diffs (or if that isn't yet implemented: past versions) of specific files. How can I do that?
Answer: By default, with etckeeper, /etc is a git repository, so you can use git tools to view its contents (and the changes). For example, you can use gitk (after installing it) to browse the repository's history, and if you want to focus on a specific file, you can specify it on the command line:
cd /etc
gitk apt/sources.list &

Since you're a KDE user, you might find qgit nicer.
Comment: Will use that in the future. It didn't work now as I didn't initialize the database as I thought it would do that on its own - especially as I noticed how several .git folders were created automatically via some other tool. I didn't know it needed to be configured first because there was nothing on its website nor a popup / wizard after installation. But I guess people are used to reading the man pages for tools.
Comment: @Seamus in terminals I use `tig`.
Comment: It's generally useful to read at least the [`README`](https://etckeeper.branchable.com/README/) (which in this case is quite good).
Comment: `gitk` looks like a great tool to use w/`etckeeper`. I wondered if there was a CLI-only version available as my Raspberry Pi is the "zero graphics"/Lite distro. There are some promising ideas covered in this [thread on SO](https://stackoverflow.com/questions/5361019/viewing-full-version-tree-in-git); this one in [particular :)](https://stackoverflow.com/a/18287861/5395338)
Answer: I just use git log and git show or git diff.  e.g.
# git log --oneline /etc/squid/squid.conf
907df30 saving uncommitted changes in /etc prior to apt run
a612769 daily autocommit
6d45b99 saving uncommitted changes in /etc prior to apt run
0f21707 daily autocommit
9a95a9b saving uncommitted changes in /etc prior to apt run
b2518f4 daily autocommit
338b4a7 daily autocommit
862d5e6 committing changes in /etc after apt run
ff6a8fd daily autocommit
2d64d79 saving uncommitted changes in /etc prior to apt run
7e3bb0e Initial commit

# git diff a612769 907df30 /etc/squid/squid.conf
diff --git a/squid/squid.conf b/squid/squid.conf
index 0e08217..e630ed9 100644
--- a/squid/squid.conf
+++ b/squid/squid.conf
@@ -7876,9 +7876,3 @@ forwarded_for off
 #  not all I/O types supports large values (eg on Windows).
 #Default:
 # Use operating system limits set by ulimit.
-
-#httpd_accel_host virtual
-#httpd_accel_port 80
-#httpd_accel_with_proxy on
-#httpd_accel_uses_host_header on
-

If I wanted the full contents of a specific revision of a file, I'd use git ls-tree (to get the sha1 of the file blob) and git cat-file to output it.  e.g.
# git cat-file blob "$(git ls-tree a612769 /etc/squid/squid.conf |
                       awk '{print $3}')" > /tmp/squid.conf.a612769


How can I log Messages out of a Google Talk account in High Sierra?

Question: High Sierra removes Google Talk support for Messages. That's not really Apple's fault, as Google is migrating all Google Talk functionality to Hangouts and doesn't allow third-party clients to connect to Hangouts. But after upgrading from Sierra on a machine that was logged in to a Google Talk account, Messages is still connected to that account and receives messages but can't send them. How can I log Messages out of this account which is now useless? It doesn't show in the Accounts tab of the Messages preferences.
Answer: This might help https://apple.stackexchange.com/a/107120.
I would do the different steps and then start from scratch. Or... you might try checking what each file in those directories do and see if yo can delete the account manually.
If you try the each file method, it appears that the file <code>~/Library/Preferences/com.apple.iChat.Jabber.plist</code> contains the Google Accounts. If you see your account delete it and relaunch Messages.
Important: Please backup your files before doing something that might harm your OS. ALWAYS. I've learned this the hard way. It's always easier to copy back files than to have to fix something from scratch.
Answer: You don't see Google under Internet Accounts?
If so disable Messages.
If not, sign out/remove Google out of accounts and then sign back in.
Comment: Google is in Internet accounts, but there's no Messages option to delete.
Answer: I upgraded to High Sierra and found that my Google Talk account stopped receiving messages automatically (fixed in newer version maybe?), so not sure if this works, but I have a couple suggestions:
1) Try removing your Google account from Internet Accounts completely and making sure that you don't keep receiving messages.
2) If that's not enough, open Keychain Access and do a search for keys with the name Google in them. You can view and copy the passwords and info to a text file if you would like a backup. Delete any that you find.
After you do either of those, make sure to go to Internet Accounts and either add it back or re-enter the password for your Google account. Hope this works for you!
Comment: I can't remove my Google account, because I have many gigabytes of Gmail emails and a slow Internet connection. It would take days to redownload them all.
Comment: I see. That wasn't in the original question, so I didn't know. Maybe still worth a try if you are able to use a faster connection at some other location (work, friend's house). Or you could locally archive the emails and only download new ones.
Comment: Can you take your Mac to starbucks or the apple store? If its not a macbook, then I can understand. But you should delete the account and reinstall it. Starbucks or the Apple Store has pretty decent wifi speeds.


Have any clones married?

Question: I know that clones were made to fight for the Republic during the Clone Wars, and that's all they were used for. But after Order 66, there wasn't anyone to fight against anymore. So did any clones settle down, maybe even marry afterwards?
Comment: No, they all had short lifespans. I'm guessing they were all dead in a matter of years.
Comment: Cut Lawquane got married but he'd deserted and was mentally ill; http://starwars.wikia.com/wiki/Cut_Lawquane
Comment: Canon only or is Legends acceptable?
Comment: @Null Legends is ok.
Answer: In canon, the only clone who got married (that I'm aware of) is Cut Lawquane, who deserted and married a Twi'lek named Suu before the Clone Wars ended.
In Legends, there are a few clones who got married.
The most notable is, of course, Boba Fett, who married Sintas Vel a few years after the Clone Wars (although Boba certainly didn't "settle down" as a result of his marriage). (Obviously, Boba himself is fully canon, but his marriage is present only in Legends.)
All the others I know of are from Clan Skirata.

Fi Skirata married a human Mandalorian named Parja Bralor at the end of the Clone Wars.
Null-11 Ordo Skirata married a Republic Treasury Audit Division agent named Besany Wennen. They married before the Clone Wars ended but survived the war and presumably settled down to live a quiet life.
Clone commando Darman Skirata married a Jedi named Etain Tur-Mukan near the end of the Clone Wars, and they had a son together. However, she was killed shortly after Order 66.

Since we know that some clones married it's reasonable to assume that others did as well -- we just don't know much about the clones after the end of the Clone Wars.
Comment: A clone married a Jedi? She must have deserted
Comment: There were married clones in Thrawn trilogy. But I don't think they were clones from the GAR - I think Baron Fel's clones.

Have any clones married?


can't install runit after DEBIAN_FRONTEND=noninteractive install -y gcc

Question: I hope to install gcc and runnit automatically.
But when I "sudo apt-get install gcc" it comes up a dialog to make choose the configuration.
So I use
sudo DEBIAN_FRONTEND=noninteractive apt-get install -f -y --force-yes --no-install-recommends gcc

and then I use the same way to install runit
sudo DEBIAN_FRONTEND=noninteractive apt-get install -f -y --force-yes --no-install-recommends runit

But unfortunatly Error occur:
It shows
start: Unknown job: runsvdir
dpkg: error processing runit (--configure):
subprocess installed post-installation script returned error exit status 1
E: Sub-process /usr/bin/dpkg returned an error code (1)

And my system is a clean Ubuntu10.04 . I can install runit if I don't install gcc noninteractiv.
Hope someone can help me.
Thanks!
Comment: I have solved this problems. It's beacuse my sources.list is too old.
Answer: This bug is solved before. Update source.list will be OK


Would centrifugal force simulate gravity for fish?

Question: We know that in zero gravity; you can simulate gravity with centrifugal force.  This works great for people, but if you had fish in a body of water, would the fish be subject to simulated gravity?
Comment: Yes. Centrifugal force acts on everything, just like gravity.
Answer: There are many processes in aquatic life that work, based on gravity.

Air bubbles float up.
Water levels separate based on temperature, because hotter water is lighter than colder water.
Oxygen moves from the surface down to lower levels as the water circulates.
Detritus sinks to the bottom, where it can decompose, allow plants to grow in it, etc.

Both these processes cause turn over of the body of water and create circulation patterns.  Centrifugal gravity simulation would help with this. Some of these matter more in large bodies of water vs small bodies of water, and pumps could be used to help simulate some of it.
Comment: Another gravitational effect is orientation. Fish have gas filled floatation bladders which keep them upright and neutrally buoyant.  In microgravity, fish would be oriented randomly since there is no "up".


People waiting in a building to be taken to a new future/planet

Question: They've all answered an ad or something, and paid a lot of money for a ticket, this is their 'only' chance. The main character begins to think it's all been a ripoff, there's no such thing as aliens or space travel or whatever, gets impatient and leaves the building. When he comes back they've all gone and he has missed his opportunity. I read it about 25 years ago in a collection. Any ideas?
Comment: @user14111 - I had never seen that. Could you provide an example?
Comment: @user14111 - well feel free to edit it to a better phrase. You're clearly more familiar with it than I am
Comment: @user14111 I don't think there's any *opposition* to it, per se. It's just that to someone not familiar with everything you've mentioned above, "sf" looks like an abbreviation of "sci-fi" which hurts readability of the post and can be safely expanded.
Answer: "Of Missing Persons" by Jack Finney. See this question and answer. First published in the March 1955 issue of Good Housekeeping. The ISFDB bibliography page lists some collections you might have read it in.
the main character begins to think it's all been a ripoff, there's no such thing as aliens or space travel or whatever, gets impatient and leaves the building...

The dark barn was silent now, except for our breathing. Time ticked away, and I felt an urge, presently, to speak to whoever was next to me. But I didn't quite know what to say, and I began to feel embarrassed, a little foolish, and very aware that I was simply sitting in an old and deserted barn. The seconds passed, and I moved my feet restlessly; presently I realized that I was getting cold and chilled. Then suddenly I knew—and my face flushed in violent anger and a terrible shame. We'd been tricked! bilked out of our money by our pathetic will to believe an absurd and fantastic fable and left, now, to sit there as long as we pleased, until we came to our senses finally, like countless others before us, and made our way home as best we could. It was suddenly impossible to understand or even remember how I could have been so gullible, and I was on my feet, stumbling through the dark across the uneven floor, with some notion of getting to a phone and the police. The big barn door was heavier than I'd thought, but I slid it back, took a running step through it, then turned to shout back to the others to come along.

when he comes back they've all gone... ?? he has missed his opportunity.

It took four or five seconds, no longer, fumbling at that door, to heave it open again. But it was four or five seconds too long. The barn was empty, dark. There was nothing inside but a worn pine bench—and, in the flicker of the lighted match in my hand, tiny drifts of what looked like damp confetti on the floor. As my mind had known even as my hands scratched at the outside of that door, there was no one inside now; and I knew where they were—knew they were walking, laughing aloud in a sudden wonderful and eager ecstasy, down into that forest-green valley, toward home.
Comment: I can recall reading that story thinking I'd consider myself better off staying, since the society formed by that (inane) selection test would be full of people who valued faith over common sense.  ..shudder.
Comment: Uh... are those "tiny drifts of damp confetti" the remains of the protagonist's companions?  Maybe he dodged a bullet, and didn't realize it.
Answer: James Patrick Kelly's "Standing in Line With Mister Jimmy" was published just shy of 25 years ago, in 1991.  It appeared in IASFM and later in Kelly's collection Think Like a Dinosaur.  The plot is about a street kid and his faithful electronic companion, Mr. Jimmy, standing in line with hundreds of other people to pass through a mysterious doorway to an unknown fate—potentially relocation to a wonderful new planet.

At the end of the story, the protagonist elects to not take his chances on the door after all.
Comment: The part about "repatriation" is confusing. You mean to say that the "wonderful new planet" on the other side of the doorway is actually the home planet of the people standing in line?
Comment: OK, I read the story. They don't buy tickets to go through the door, they just have to be appropriately dressed. Varied speculations about where the door leads do not include passage to another planet; closest is one man who thinks he's going to an L5 space colony.


Why is lemon mixed with water considered alkalizing water?

Question: The benefits and facts of alkaline water are often skewed due to the marketing of companies and uneducated hype for the innocent idea of unlimited potential. I wanted to know the specific reactions occurring when mixing water and fresh lemon slices that lead to water becoming alkalized (higher in pH).
Comment: I'm voting to close this question as off-topic because we don't do lists on chem.SE.
Comment: It doesn't and I have no idea why you'd think so.
Comment: @Todd A reaction mechanism is essentially a list of equations; the particular wording of a question should not play such a big role here. (the question even was tagged with reaction mechanism.) This question is not only very much on topic here, but also asking to fact check some the garbage science claims by the marketing industry. As a science community I believe it is our duty to clear up such claims with real facts. As a side note: "We don't do lists" is essentially the "too broad" close reason. I am voting to leave this question open. I will also upvote it.
Comment: Lemon water should be slightly acidic, not basic, due to the citric acid.
Comment: I removed the reference to lists
Comment: @Martin-マーチン - Thanks for clearing that up. Retracting VTC and upvoting.
Answer: The claim that lemon water is alkaline is simply wrong.  However, that hasn't stopped people from claiming that it's true:

Lemons are an incredibly alkaline food, believe it or not. Yes, they are acidic on their own, but inside our bodies they're alkaline (the citric acid does not create acidity in the body once metabolized). As you wellness warriors know, an alkaline body is really the key to good health.

Every sentence above is wrong.  Lemons do not turn alkaline inside the body.  They are not an alkaline food.  Citric acid creates neither alkalinity nor acidity in the body when it is metabolized.  An alkaline body is not the key to good health.  In fact, if your body were more alkaline by only 0.5 pH units from its usual state, you would probably die from it.

I wanted to know the specific reactions that occur when mixing water and fresh lemon slices [...]

There aren't really many reactions that occur.  Lemon juice is mostly water.  Mixing the lemon juice present in lemon slices with more water just dilutes it.  Lemon juice is acidic, due to the presence of citric acid and other acids.  Diluting will very slightly lower the acidity.  None of that has any relevance to the pH inside a mammalian body, which is exquisitely regulated by other mechanisms.
I don't know why people make up weird claims that lemons are an "alkaline" food, but those claims, sadly, are out there everywhere.
Comment: *"I don't know why people make up weird claims that lemons are an "alkaline" food"* Because they sell. The people marketing these stuff probably know that it's all rubbish.
Answer: I'm an undergrad chemistry major, and I know some about the subject. The reason that people (falsely) believe that lemons somehow "turn alkaline" in the body is because drinking a lot of lemon juice slightly raises the pH of urine. The real reason this occurs is because the citric acid forms a buffer with citrate (which is found in the renal system I believe) and prevents urine from changing pH. It cannot change the pH of your blood. Nothing you eat changes your blood pH. If you eat a whole bunch of antacids (which are alkaline) you would neutralize your stomach acid and definitely have digestive issues, but it would not change your blood pH.


What happens when we have $e^{H}$ with $H$ an operator?

Question: Suppose that we have a hermitian operator. Let's take for example the Identical operator $I: I\Psi=\Psi$. What does the operator $e^{I}$ do? does it result in $e^{\Psi}$ or something else? What happens if we replace it with the momentum operator $p$?
Comment: See https://physics.stackexchange.com/q/574621/50583, https://physics.stackexchange.com/q/133758/50583 for more discussions of exponential operators
Answer: You can Taylor-expand it just like you would a polynomial. Given the definition of the exponential function as a Taylor series, $$ e^{ax} = 1 + ax + \frac{(ax)^2}{2!} + \frac{(ax)^3}{3!} + \cdots,$$
you can generalize it to operators. Accordingly, the exponentiation of an operator, say the Hamiltonian $\hat{H},$ can be written as an infinite series of operators:
$$ e^{\hat{H}} = \mathbb{I} + \hat{H} + \frac{\hat{H}^2}{2!} + \frac{\hat{H}^3}{3!} +  \cdots$$ where the first operator on the right-hand-side is the identity operator: $\mathbb{I}: \mathbb{I} \psi = \psi.$
Of course, the choice of the operator is arbitrary, and as far as I know, it does not need to be Hermitian or unitary. In Quantum Mechanics, exponentiated operators serve the role of generators of motion in time or in a Hilbert space. For instance, the momentum operator $\hat{p}$ exponentiated as
$e^{- i \, \textbf{x} \cdot \hat{p}/\hbar}$ represents a translation in position when applied to a wavefunction $\psi(x).$
Comment: The reason that this is a sensical definition is that a lot of identities from the exponential function can be proven using the Taylor series. So this carries over nicely to the operator definition. Try to 'proof' $\frac{d}{dx}e^{ax}=ae^{ax}$ using the Taylor series for example. A notable exception is that $e^{\hat A} e^{\hat B}\neq e^{\hat A\hat B}$. The Baker-Campbell-Hausdorff formula describes why and how this fails. https://en.wikipedia.org/wiki/Baker%E2%80%93Campbell%E2%80%93Hausdorff_formula
Comment: Another important exception: if $\hat H(t)$ depends on a parameter $t$ in such a way that $\left[\hat H(t), \tfrac{\mathrm d\hat H}{\mathrm dt}(t)\right]\neq 0$, then $ \tfrac{\mathrm d}{\mathrm dt}\left[e^{\hat H(t)} \right]\neq  \tfrac{\mathrm d\hat H}{\mathrm dt}(t) e^{\hat H(t)} $. This is why [time-ordered exponentials](https://en.wikipedia.org/wiki/Ordered_exponential) need to be used for the formal solution of the Schrödinger equation.
Comment: The series definition really only works for bounded exponents. For the general proper definition see https://physics.stackexchange.com/q/574621/50583.
Answer: Functions of operators are understood as Taylor expansions. Thus, in the case of an exponent:
$$
e^{\hat{A}} = \sum_{n=0}^{+\infty} \frac{\hat{A}^n}{n!}
$$
Comment: Though in the case where the operator is diagonalizable, we can also take the more direct approach $f(A)\vert\psi\rangle:=f(a)\vert\psi\rangle$ for eigenstates $\vert\psi\rangle$ of $A$ with eigenvalue $a$ and then extending linearly to all other states. This approach also works for functions which do not have a series representation.
Comment: The series definition really only works for bounded exponents. For the general proper definition see https://physics.stackexchange.com/q/574621/50583.
Comment: This is the first time I see this approach, but it does make sense.


What pain point does Intelligent Children Design Pattern solve?

Question: In absence of this pattern, downcasting is needed in the derived classes. My question is does this pattern solve only the problem of downcasting? And why is downcasting bad compared to the alternative offered by Intelligent Childrean Design Pattern?
Answer: Intelligent children is used when there are two base classes at the root of separate but related class hierarchies. For example Widget and WidgetRenderer are the base classes and ListBoxWidget needs to be used by the draw() method of the ListBoxWidgetRenderer. So the draw() method will want to downcast the Widget pointer.
Downcasting is generally frowned on, so every fresh reader will have to be convinced that it's okay in a given situation. With this pattern the right pointer is made available at the right type.


WCF Named Pipe Security and Multiple User Sessions?

Question: I have setup a WPF application that is single instance using a Mutex, this allows for the application to run within each user account if you are using user switching.  The application sets up a WCF named pipe so that I can communicate to the single instance from another process (i.e. when the second process runs before it terminates due to the Mutex).
I would like to know if anything should be done (best practices) to secure the named pipe?
Also I would like to know if the named pipe messages would reach all running processes within the system or only within current user session.  If the named pipe is sent system wide then what would be the best implmentation to restrict the communication to the current users session?
Answer: Named pipes in WCF are not accessible from the network and no encryption is required to secure them. However, WCF services are not secure against the attack mentioned by romkyns.
I suggest you read this posts:
Exploring the WCF Named Pipe Binding - Part 1
Exploring the WCF Named Pipe Binding - Part 2
Exploring the WCF Named Pipe Binding - Part 3
Exploring the WCF Named Pipe Binding - Part 4
about the security problems involved.
In short WCF allows ANY process to masquerade itself as the service and:

Either simulate the service OR
Eavesdrop and tamper data assuming that the rogue process itself connect to the service. However, if the service uses access security to check the identity of the calling user this may not be possible.
Comment: @jesusduarte Late, but the links are back.
Answer: Named pipes imply that the communication is point-to-point on the same machine.  I believe that it is secured by default, but since communication is never leaving the machine, even on the same network, that security isn't the biggest thing to worry about - at least in regards to the communication between a named pipe component and its consumer.
Check out "Programming WCF Services 2nd Edition" by Juval Lowy.  Chapter 10 is all about component security.  On page 514, he writes "there is no sense in using Message security over IPC, since with IPC there is always exactly one hop from the client to the service.  The chart on that page shows that Transport security is turned on by default for named pipes.
Answer: This paper on named pipe security discusses the topic in a lot of detail.
In short, if you're not careful you could allow a malicious program running with standard user permission to exploit a pipe to elevate itself to the same privilege level as the named pipe server.
I'm afraid I don't know whether the WCF implementation is secure against this type of attack by default.


Cascoded/Bootstrapped Transimpedance Amplifier

Question: I've come across an interesting transimpedance amplifier toplogy, that reportedly reduces voltage and current noise and compensates for large photodiode capacitance. However, as I'm working with an avalanche photdiode, and I need to bias it with at least 65V - how exactly would I be able to adapt the circuit for such high voltages?
Comment: It looks to me that this biases the photodiode at about -9 volts - maybe lowering the -15 volt rail will get more reverse bias?
Answer: Your source, of course, is http://www.electrooptical.net/www/frontends/frontends.pdf.
A direct adaptation is fairly simple. Rbias should be connected to -15, as shown, but the 20K resistor must be tied to a separate bias voltage, Vb. For a given diode bias voltage Vd, Vb = 1.67 Vd. In your case, this would call for a Vb of about -100 volts.
All of this supposes that you need the performance. Do you? What photodiode current level are you expecting? What is the photodiode capacitance when biased? How much bandwidth do you need? What SNR do you need? Go back to the article. Start with your expected current level and desired output voltage. This determines the value of the transimpedance amplifier resistance. Now use this, along with the diode capacitance and the input capacitance of your op amp, to model a simple TIA with a small feedback amplifier. Calculate the bandwidth. Is this adequate? If so, go no farther. There is an old saying: those who ask for more bandwidth than they need get what they deserve.
Comment: +1, for citing the source and, even more, for the saying about bandwith. I should put a poster with this slogan above my 50 MHz vintage scope (556) that works as good as new for most things even today...
Comment: My issue currently is not so much with the bandwidth, but the noise magnitude. My application would require a few dozen kHz, despite the APD responding in the ps range. The fact that the APD has a huge capacitance (320 pF) and a verly low dark current (~0.15 uA, looking to measure changes around 0.8 uA) made me afraid of noise isses. I've come across this design because I was looking for a low noise transimpedance solution, and it did seem a rather effective one. Right now however I suspect I would be able to achieve that with a simple TIA as long as I carefully choose a low noise op-amp.


How to make 2 diffrent networks in router ping each other

Question:
Hello i have this 2 routers how i can make them ping each other and alos the devices connected to them
Comment: This configuration doesn't make any sense if those IP addresses are configured on the link between the routers. The routers should have a shared network on the point to point link.
Comment: As Teun has mentioned the general practice would be to use a /30 for the interconnection with both routers existing on the same /30 subnet. This scenario is not viable as is, both routers need to share a subnet in order for ping or any type of layer 3 communication to take place. Years ago when I was newer Teun downvoted many of my questions or comments, that being said he knows his stuff ;).
Answer: Routers need to have interfaces on a common subnet in your example.  If the addresses you show are for the common link, they are not in the same subnet.
You can either:

Change router1's interface to 10.2.1.2/30, or
Change router2's interface to 10.1.1.2/30
Answer: Routers need to share an IP subnet with each other in order to communicate. If you use a link-only subnet you can use a /31 subnet mask, e.g. 10.1.1.0/31 and 10.1.1.1/31. A /30 subnet wastes 50% of its address range.
Since there seems to a another subnet behind Router1 that Router2 can't see, make sure you add an appropriate static route to R2, or set up a routing protocol.
Answer: I solved it i putted a serial connection between the 2 routers with 2 diffrent subnets and addes it to the ospf and the ping wotk in all places


Ubuntu Software Center does not work Ubuntu 16.10

Question: I´m completely new to Linux and Ubuntu and I tried to install chrome. But when I tried to open the .deb file with the Ubuntu Software App it did not work. When I open the app manually it won´t load the icons, it´s showing just three gray points.
That´s what I see when I open the Sofware Center
My problem is, that I can open it (and all solutions in the internet seem to be if you can not open it), but I can´t even see what software I could install. The start menu is there and seems to be normal, but if I want to choose a category this appears and if I try to install a special software it just loads and loads and loads...
So, I tried sudo dpkg -i google-chrome-stable_current_amd64.deb, but I got an error that because of dependency-problems the file can not be configurated.
I hope somebody knows what I did wrong or missed to do and can help me,
thank you
Comment: Possible duplicate of [gnome-software on Ubuntu 16.04 doesn't work](https://askubuntu.com/questions/761745/gnome-software-on-ubuntu-16-04-doesnt-work)
Answer: You have 2 alternative ways to install .deb files.
1)Using Gdebi
This is a GUI application that handles with installing .deb files to the system. You can download it using the command:
sudo apt-get install gdebi

After you installed the app simply go to the application that you want to install, right click and choose "open with Gdebi" by using Open with option.
2)Using terminal
You can always install downloaded .deb files by using:
sudo dpkg -i yourprogram.deb

Be carefull that you need to be on your directory that .deb file is located. You can right click in file manager and choose the option "open Terminal here".
With that you automatically get to the directory in the terminal and you only will need to copy&paste the command I wrote it.
Try these methods and give us feedback that your problem is solved.
Comment: OK, I tried option one. The window of Gdebi opened and I got an error at status which I was able to fix, but now I got another one: dependency not realizable: gconf-service
What does that mean? And how can I fix that?
Comment: @LuaMia Do you have a good Internet connection ? Other topics related to this problem says that you have to download the dependencies even that you're installing .deb files offline.


Best practice for using application wide TraceSource

Question: So I have an application where I will be using tracing for logging application activity/errors etc. Most information will go in a log file whereas some errors will go in event viewer too. This application will have lots of classes.
What is the best way of using TraceSource in this case? Should I create a singleton wrapping TestSource class or is there any better way of doing it?
Answer: I agree to some extent with @Valdis - log4net and NLog are two examples of very powerful logging frameworks that offer a great deal of flexibility and relatively easy to use configuration (NLog is probably easier to configure than log4net).  However, I don't think that is necessary to completely avoid TraceSource.  TraceSource is built in so you avoid an extra dependency.
If you are using TraceSource I don't think that a single application wide static TraceSource object is the way to go.  I would recommend using more TraceSources, possibly even one per class (that might be overkill, but is a common pattern when using log4net and NLog).
I have put more details in an answer to your other question about when to use more than one TraceSource in an application.
Answer: are you strict to use built-in .net eventing and logging infrastructure? I would encourage to use some of the 3rd parties (like logging from Enterprise Library). those are more flexible, more configurable and you do not have a headackes like these - you just write:
<code>Logger.Write(...)
</code>
Comment: @Valids: unfortunately that's what i have to used at this point


Bitcoins sent to wrong address

Question: I've make a mistake: unfortunately I've write my Bitcoin(s) from The Ledger to a wrong unknown adress. Is there any way to recover this mistake ?
Comment: Does this answer your question? [What happens if I mistype the address when making a payment?](https://bitcoin.stackexchange.com/questions/194/what-happens-if-i-mistype-the-address-when-making-a-payment)
Answer: No, you can't get it back as you don't even know to whom the address belongs. Even if you knew the owner of the address it's his, her, etc. decision to transfer it back.
Answer: Basically no. Because bitcoin is a untrackable(?) and unrefundable currency.
It's your luck if you get it back by finding the owner of the addr.(literally impossible) and requesting him to give your funds back.
But it's his decision also it's not illegal because it's your fault and he didn't do anything. Lets say it's illegal still there's a small chance that he'll get caught and you'll get your funds back because its untrackable(?).
Sorry for you.

Bitcoins sent to wrong address