What is the reason behind that sometimes when I see new thing I feel that I have already seen them?

Question: I have googled it and I found that it is, because of good memory, but how it can be due to good memory as it didn't happen before. It happened to me many times, that I feel that the scene which is happening now, has already happened to me in my past. But it was a new scene in my life, so why does I feel like this? How is it possible that a same scene happens twice?. What is the reason behind it, that we feel something twice in our lives.
Answer: What you are talking about is a déjà vu, the feeling of familiarity even though the situation is not familiar at all. It is, in fact, a very common phenomenon. A high percentage of people report having had déjà vus. It is nevertheless hard to put a number to it, because the experiences and déjà vu definitions might be different. I have found numbers between 60 and 90% of the population.
The claim that this is a sign of a good memory is related to the view, that a déjà vu is not a false memory, because you actually realize that the situation should be unfamiliar to you (also mentioned here).
But how do déjà vus happen? There are several theories...
It seems clear that déjà vus are associated with activity in the temporal lobe (on the side of the brain). That's where memory is processed, especially episodic memory (things that happen - in contrast to learning a skill). People with epilepsy often report déjà vus right before a seizure that starts in the temporal lobe.
One theory, put forward in this paper, says that the memory and feeling of familiarity are processed in different areas and there is a false activation of the familiarity area during a déjà vu. The brain is not always working proberly, e.g. false sensations can happen, like hallucinations. So, the false activation of that familiarity center could give us the sense of familiarity in an unfamiliar situation.
Similar to this is the idea, that there might be a mismatch between perception and memory formation. When something we are experiencing right now is "leaking" into our memory due to false activation, we think that this has happened in the past. There is a problem with this explanation: despite having a strong feeling of familiarity during a déjà vu, people fail to give any context to when this previous event happened or which other events have preceded it. So, it doesn't seem to be perceived as a memory.
Another explanation could be a false combination of the experience with something that is loosely connected to it (like planning the trip, watching a movie with a similar scene, etc.). Our brain always tries to connect experiences. It might falsely identify something you've seen in pictures or read in a book as a real experience.
As you see, we still struggle to explain the phenomenon. It is caused by some error in the way our brain perceives a situation, writes or retrieves memory or processes familiarity. This error might be a wrong activation or wrong timing or the like.


App Script code to create documents in another Google Docs account

Question: I am trying to write an App Script code which is supposed to look at the Gmail account of the current user under which the script is run and take the email attachments and create new documents in a separate central user account. Is it possible for app script which is running under one account to create documents in another Google Docs account?
Answer: While you cannot directly create a file in another user's Google Drive account, you can change the owner of a document that's in the current user's account.
Refer to File.setOwner(user).


Does client get to keep unused logo designs

Question: I worked with a client who asked for a logo design, color palette creation and style guide in exchange for very, very little money. I presented four concepts, each with several iterations. The client chose, the project was completed and files handed off. Does the client have the right to keep the unused logos?? The ones they didn't select turned out to be the best, in my opinion...and given that they low-balled me on project fee, I don't feel that they should get all unused. What if they decide to use them in the future??
Comment: Possible duplicate of [Client buys logo but wants to buy other concepts too](https://graphicdesign.stackexchange.com/questions/92338/client-buys-logo-but-wants-to-buy-other-concepts-too)
Comment: Hi R.L., Welcome to GraphicDesign.StackExchange. We hope you enjoy sharing knowledge and experience here. From your question and your comments, your client is making progressively greater demands for little or no compensation—which leads to a parting of the ways unless an understanding is soon reached. You say you want to keep this client. At what cost to you and your continued peace of mind and sense of professional accomplishment?
Answer: Unless they mentioned that in the original briefing or in a contract, presumably they will only pay for the one they selected and that's the only thing they should be getting.
Comment: Lucian, thanks for your feedback. In this case, there wasn't a contract because I've worked with this client for so long. I know it's a bad idea not to start a project with a contract, but we've developed a decent working relationship for a few years now...so I guess since there wasn't a contract, they can't request/demand to keep additional, unused logos. I feel better about keeping them!
Comment: Every long-term working relationship will eventually get to a point when verbal agreements will not cover some particular situation. Then its a test for both sides on how this is resolved and if the relationship can move forward or not.
Answer: I personally keep all the unused versions, and don't feel the client has any right to anything except the one they paid for. Unused versions, especially if they are entirely different takes, could apply to a different (future) client and be used later.
Comment: Franko, I completely agree with you. Just needed other's feedback to validate my thinking on this matter. Thanks!
Answer: Ask yourself a simple question:
What explicit rights are granted (whether by contract or verbal agreement) when you and a client agree to you working on a logo for them?
They expect to pay for thinking / process / production design work, and they expect to pay for a logo or logo family, complete with alternate colour treatments (4-colour, duo tone, b&w, greyscale) all fonts (bespoke or bought w/ all rights) and a range of final output files (raster & vector), and for those final products they expect to have typical use rights for a logoset - any medium, any number of impressions / click throughs / views. They PAY for those use rights.
If they choose also to pay for similar rights to all presented alternative designs... sure, let 'em have 'em.
Absent payment explicitly FOR those non-selected designs? Yours as creator, free and clear.
Hope that helps clarify.
Comment: We are completely aligned, @GerardFalla! The client received the logo suite as mentioned in your post -- several color treatments, various file formats, stacked, horizontal orientation, etc. I will keep the rest of the unused logos to repurpose those concepts at a later time, or at the very least showcase in my portfolio. Thank you!!


Electric shock from pellet stove

Question: I accidentally let some hot pellets fly out of my pellet stove while stupidly cleaning the glass while it was on. The few pellets melted some of the carpet. I put them out with some water. When i went to try and pick them out of the carpet I leaned my hand on the stove a received a good shock. My pad under the carpet is solid concrete. After a bit of trial and error I found that I do not receive a shock while touching anything dry. I unplugged the stove and still received a shock. I pulled up some of the carpet and there is no wiring under the carpet. What could this possibly be?
Comment: Was it a static shock (single sharp snap), or an electric shock (sustained pulsating jolt)?
Answer:
I'd really stop testing this by shocking yourself.  (!)
If it happens repeatedly it's usually not static.
If it happens more when you're on water, probably not static.

You can use a non contact voltage tester (NCVT) to see if the stove frame is energized:

Just don't trust it too much, and test it on an outlet every time you use it to make sure it's working.
I'd use the NCVT to verify that the frame of the stove is energized, unplug the stove (carefully!) and test again.
If it's hot plugged in but OK unplugged, I'd call whoever installed or services the stove, otherwise call an electrician.
Comment: It takes pretty good juice to get a shock through damp concrete. I've gotten a tingle from 120v, and that is not something you want to mess with using your body once you find out the problem exists. A little better conduction is all it'll take to kill you.
Answer: If you're getting voltage when unplugged, check whether the chimney -- or its mounting hardware -- have contacted wires somewhere. You may have to play with circuit breakers and do some partial disassembly to isolate this.

Electric shock from pellet stove


Size of Controls

Question: I use elementary on a 13inch laptop with FullHD resolution. But much of the system is just too small for me.
The size of the system's Font I have already made greater with "accessibility" in the settings. Unfortunately the control elements (close / full picture) are still very small. The same applies to the icons in the system control and much else. Is there an easy way to change this? (I don't like the solution to reduce the resolution)
Answer: One other option would be to tell elementary to render everything at 2x, then scale your resolution down to 1.5x, as described here. This isn't an ideal solution - you'll still get some blurriness, and graphics performance may be a little slower - but it would solve the problem, and it would look better than just reducing the resolution.

There isn't an easy way to set up true 1.5x scaling on elementary. As you mentioned, changing the font size to "larger" helps a little (and will make icons a bit bigger), and changing the resolution would fix the problem at the expense of making things really blurry.
This post from elementary's UX architect explains why elementary provides 2x scaling but not 1.5x scaling.

Size of Controls


Can the default browser be upgraded without upgrading the whole OS?

Question: Can android 2.2 default browser be upgraded (without upgrading the whole OS) ?
Unfortunately, it is not available through Android market as far as I know.
Answer: You cannot update inbuilt browser even though your phone is rooted. Anyway you have some other good alternative browsers in market like Dolphin, Opera.
Answer: I am not sure if the browser can be updated, even with root. The best thing is to root your device and install a better ROM, if you are stuck on an old Android version and unhappy with the browser.


Single Response Spreadsheet (with multiple sheets) from multiple forms

Question: I have four surveys (google forms) from which I want responses to go to a single response spreadsheet (each on a different sheet).  It appears in the form view that I can select to have the response go to a new sheet in an existing spreadsheet, but when I select that option on the second form, I get a message saying that the spreadsheet is already in use.  How do I get this feature to work properly?  I want all the pre- and post- survey data in one single spreadsheet!!
Answer: Maybe this has changed in new Google Sheets because in the second and subsequent Forms it seems possible to select Responses, Choose response destination:

New sheet in an existing spreadsheet..., Choose:

find the Response Sheet for the first Form, Select and for this to work.


Is it permissible for a girl/woman to kiss the hand of an elderly non-mahram man out of respect?

Question: I want to know that can a woman kiss the hand of an elderly non-mahram man (Pir sahab) out of respect?
Comment: Possible duplicate of [Can I kiss or hug my friend's wife who is like a sister to me?](https://islam.stackexchange.com/questions/51044/can-i-kiss-or-hug-my-friends-wife-who-is-like-a-sister-to-me) as this comes under touching a non-mahram.
Comment: Who is a Pir Sahab? Is he called that due to his age something like grandfather?
Answer: No its not permissible, but its only permissible for men as it was a common practice in the history and of golden era.
Its not even permissible to shake hands and go in front of him without hijab, with the elderly peers if you want to perform bay'ah you need to be in hijab or behind of curtain and do the bay'ah.
As we can see in the books of ahadeeths, when women used to come for bay'ah then prophet Muhammad (Peace be upon him) not used to shake hands with them instead they used to do bay'ah wordily.
Comment: This ignores the fact that there are different of opinions about handshaking, and interpretation of the mentioned hadith.
Answer: Its best not to do that as Shriya prohibts Non Mahram contact of all sorts and if its kissing hands today tomorrow it could be other things as the Neyia of that even old man could be evil and my revert question to you is why are you going such places where you have to kiss some oldmans hand.?
Whynot just follow quran and saheeh sunna / hadith that being said a real shaikh or a man of Allah/religon will never allow you to touch him / kissing hand is far far beyond for such a man of faith and pioty if this quality is not in your Shaikh then you need to leave him.
May Allah protect all our sisters from harm and such men.


Does it make sense to use BitCoin to transfer money to yourself internationally?

Question: If you have a bank account in the US and an account in the UK, and you want to move money from one to the other, is Bitcoin a sensible way to do it, or are you better off using TransferWise or just doing an international wire transfer?
Answer: While in the US last year, I sent money to myself in Europe that way once, because it was significantly cheaper than using the legacy banking system.
I think it mostly comes down to whether you have easy access to a Bitcoin exchange from your bank account in the US and what amounts you are trying to transfer. It also depends on how urgently you need the money in the other country, and which country you currently are residing in.

Alternative 1 (if in UK): Use your US credit card to get Pounds from the bank, deposit those in your UK bank.
Advantage: Fast
Disadvantage: Currency exchange fee, fee for using CC abroad, (Deposit fee, if you have one)
Alternative 2: International Wire Transfer
Advantage: No manual involvement
Disadvantage: Takes several days, expensive (~$50), get lost sometimes
Alternative 3: PayPal
Advantage: Very fast, independent from residence
Disadvantage: ~3% exchange fee, % transfer fee, has to be withdrawn to Bank account
Alternative 4: Money transmitter
Advantage: Fast
Disadvantage: Needs to be picked up and deposited, expensive I think
Bitcoin:
Advantage: Can be cheap
Disadvantage: Takes a few days, manual involvement
Procedure:
• Consider buying Bitcoin locally if in the US, else buy Bitcoin from Exchange or Coinbase (each takes a few days until it is cleared, I think)
• Send Bitcoin to your account at an exchange in Europe
• Trade Bitcoin for national currency
• Withdraw to Bank account (usually a small fee applies).

Personal experience
Back when I did that last year, I was able to buy Bitcoin at a Bitcoin Meetup at Bitstamp spot-price. I transfered those to Bitstamp, traded, and ordered a withdrawal.
I had a confirmation that the money was headed to my bank account within 30 minutes, it arrived two days later. I actually made a few dollars on it, because the price had slightly increased between my local trade and the trade on Bitstamp.
Answer: To organize a wire from Europe to the US and back using bitcoin without fees, you can:

Open an account on KRAKEN.com do a IBAN/BIC wire to your kraken account (free!), takes 2-4 business days
Open an account on circle.com and register your US bank account
Buy bitcoins on kraken.com (very small fee, usually around 20 eurocents)
Transfer bitcoins from kaken.com to circle.com account
Withdraw bitcoins in USD from circle.com

I did not try it yet but the whole process should not cost you more than 50 eurocents. Of course you risk small losses/profits due to volatility of bitcoin prices. Also, I do not know what is driving the exchange rates at circle.com.
Comment: This seems to be an outdated answer. Circle.com no longer supports bitcoin.
Answer: Most big US banks charge 40-50$ in fees for international transfers and take a cut of the exchange rate. You might be able to lower this if you use a company like Usforex or Xoom, which I believe take around a 1-1.5% cut of the interbank rate plus a < 5$ fee.
And Bitcoin? I just transferred 1000$ from the US to Europe, from my wellsfargo account, via coinbase (bitcoin USD wallet), kraken (bitcoin EUR wallet) and a EUR bank account there.

Coinbase took 10$ in fees for the ACH money transfer from my bank account into the coinbase bitcoin wallet. It took around five days. I think Wellsfargo does not charge for ACH transfers when money is pulled.
Kraken requires 6 bitcoin confirmations, so the transfer Coinbase -> Kraken took 20 minutes. The trade bitcoin -> EUR then cost 0.34%, so 3.4 EUR. This fee can possibly be lowered to 0.1% by doing the transfer with a different type of electronic money, like litecoin, I haven't looked into that.
The SEPA transfer to the EUR bank account cost EUR 0.09 and took 4 days.

Now this is not the whole story, because I haven't figured out the cut the bank takes on the exchange rate and what the difference between the interbank rate and the US->Bitcoin->EUR rates is.
In total the bitcoin fees were less than 14 USD for 1000$, the bank transfer cost was at least 50$. The bank exchange rate spread can be around 1.5%, I have no idea what the spread in the case of bitcoin is, but probably lower.
The Bitcoin transfer took around 7 days, similar to what it takes to do a Usforex/Xoom transfer.
The bitcoin transfer takes a lot more manual clicking work. You have to transfer the money (1-2 minutes), do the bitcoin transfer (+wait 20 minutes), do a bitcoin/euro trade (+ wait 20 minutes), then do the 2nd transfer. Neither coinbase nor kraken can schedule any of this. You also can lose money if you delay any of this, as the exchange rates of bitcoin may change over time. That being said, the volatility of bitcoin at the moment is lower than the banking fees, even over weeks.
I think overall I prefer Xoom or Usforex like services for the occasional transfer, as it's so much easier to use. I hope someone automates the whole transfer one day with a program using coinbase's / kraken's APIs.
Comment: The rate on Google (which I think is the interbank rate) for $1000 is 893 EUR today. My Coinbase -> Kraken transfer got me 895.77 in the bank account, but that's only because bitcoin traded ~2% higher and I forgot to do my trade for two days. Sigh. This comparison is actually not that easy, also because Kraken does not send me reminder when the money arrived, so it's easy to forget. In the end, I actually made a profit from the transfer.
Answer: To make an international money transfer using bitcoins you need to figure out 2 things: 1. How to convert FIAT to BTC and 2. How to convert BTC to FIAT.

FIAT to BTC
Open an account on your local exchange. I find this resource useful: https://bitcoincharts.com/markets/list/ to find local exchanges.
You want to open an account on the local exchange because generally, it is cheaper and faster to transfer money locally. Once you have an account buying BTC is generally straightforward.

Things to keep in mind:

Make sure you open an account in an exchange and not a company that sits on top of an exchange. Exchanges generally charge from ~0.1 to 0.5% per transaction, while resellers generally charge above 1%.
Make sure to check out the spreads (the difference in buying and selling prices) on the exchange.  If daily trading volumes on an exchange are low, chances are the spreads are high and you might end up overpaying for your BTC.
You bank account name and your registered name on the exchange must match.

Sending BTC is straightforward.

BTC to FIAT
To convert BTC back to FIAT you need to register on an exchange in the receiving country.  You need to keep in mind exactly the same things as for point 1.
In addition keep in mind that most exchanges require 3-6 verifications before you can sell your BTC on the exchange. This takes on average 30 to 60 minutes and during this time you are exposed to the price volatility of Bitcoin.

To simplify the process of making international transfers using Bitcoin you can give finmates.com a try. This is my company.
We take your bitcoins and deliver local currency to your recipients and charge only 1%.
Having said the above IMO it makes sense to use BitCoins if:
1. The money transfer channel is not too bit (for example, not US/India), hence there is not a lot of competition and prices are high.
2. There are liquid exchanges at the both ends of the transaction (last time I checked spreads in Curacao (Caribbean islands) were around 10%.
3. You price conscious and make transfers regularly. IMO if you answer "yes" to these questions it makes sense to use BitCoins to make international money transfers
For a UK/US channel Transferwise charges ~0.5-1% depending on the amount (with a minimal of 2 Pounds or 3 USD). Hence IMO using Transferwise is easier and cheaper.


Would the City Hunter manga not be exported anymore?

Question: I've read the city hunter manga, which has about 193 chapters. But there are only 136 chapters available in my country. Did they stop translation and distribution of the rest of the chapters in foreign countries?
Comment: available where?
Answer: City Hunter on Wikipedia says there are 35 Volumes to the series originally running in Japan from 1985 to 1991/1992.
on the List of Chapters the final volume came out in April 1992 however chapter information stops at Volume 26 with Chapter 137 saying "(incomplete)" and with the inconsistent number of chapters per volume it's hard to extrapolate how many chapters there was by Volume 35. this relates to the Japanese release
the English Release appears to have more chapters per volume with Volume 5 ending at Chapter 44 - Gambling Queen, however judging by the names of chapters in the English version it appears some of the Japanese Chapters were split, such as Volume 4: Chapter 15 - A Lame Teacher in the Japanese version appears to match with the English Version's Chapters 29-31 - The Wacky Professor Part 1-3. As there are no ISBN numbers for the English Version after Volume 5 one can assume there are no Legal English versions released beyond Volume 5.
On City Hunter's Wikipedia Page, inside the right side info box under English publisher it says

NA
  Gutsoon! Entertainment (incomplete, defunct)

looking at Gutsoon! Entertainment's Wikipedia Page it says

On March 15, 2004, Gutsoon! announced that they will be placing their Rajin Comics brand on hiatus. Raijin Comics ceased publication with its July 2004 issue (issue #46) and the Raijin Graphic Novels line was subsequently cancelled as well.

this is also confirmed on City Hunter's Wikipedia Page

Attempts were made to license the series for the American comic market during the 1980s; however, Hojo insisted the manga should be released in the right-to-left format. In 2002 Coamix created an American subsidiary, Gutsoon! Entertainment. City Hunter was a flagship title in their Raijin Comics Anthology. Raijin switched from a weekly format to a monthly format before being cancelled after 46 issues.

In these magazine serializations in Japan a Manga Series is generally released a chapter at a time in each issue so the 44 Chapters of the English Version run close to the 46 Issues of Raijin Comics
As for other countries there doesn't seem to be any data for their release however the Wikipedia page may only be detailing the original Japanese release and English because it itself is in English as Anime News Network list other countries that the manga series has been published in, however as i don't know any other languages getting data from another Language's Wikipedia will be a bit harder.
From the data we have on Wikipedia for City Hunter we can say that only up to Volume 5: Chapter 22 - The Game's Queen was officially localized in English as Chapter 44 - Gambling Queen. any other chapters in english that are floating around on the internet i would suspect to be scanlations.
scanlation status is not on topic here on Anime and Manga as such you probably wont find any information here as to any announcement by the scanlation circle why they have stopped, however possible reasons could be due to

Lack of access to the Raw Japanese Manga
Lack of Staff (scanlation circles shouldn't be profiting so the staff only works when they have the time)
Being told to stop by the publishers/mangaka (has happened if i recall, just not sure on the title)
Just a lack of interest in the series, this can be combined with Lack of Staff as Staff can leave individually when they lack interest.
Answer: It's available in Italian up to chapter 193, the full series. It's also available in French. The Italian version has the advantage of being quite cheap to buy, so I highly recommend you to do so you should be able to find it at any online bookshop, and when in doubt, amazon.it or amazon.fr may do the trick. I understand much of Italian being Spanish, so I could read it using the dictionary from time to time. If you don't know any Latin-based language, though, this may not help you, but at least Italian would be easier to understand than Japanese.
Comment: By online, cite a specific publisher/website. If it's an unofficial translations/scanlations, then you are not allowed to put it here as this site does not and will never support piracy. I would suggest revising your answer to include legal sources without duplicating information already mentioned in the previous answer.


Does port forwarding a port on one computer expose other computers in the network as well?

Question: I have read that port forwarding exposes your computer to security breaches. Does port forwarding a port on one computer expose other computers in the network as well?
Answer: You can consider your router the perimeter between those machines you trust and those you don't.  When you port-forward, you are permitting access from machines you don't trust to one that you do.  This automatically lowers the trust of your machine.  This is warranted because when you are port-forwarding you are saying that it is acceptable for a machine that you don't trust to influence the behaviour of one that you do trust, each time a connection is made to it.
While you may only permit access to a specific service on your machine and so influence should be confined to a known quantity (such as serving a web page), there are no guarantees that there are no exploitable vulnerabilities in the application you are allowing to be accessed by external parties.   If a vulnerability exists and is exploited, the worst case is that someone else has control of your machine.  If they have control of your machine, then they can use it as a jumping point to probe other machines in your network for vulnerabilities.
This is why in corporate environments, efforts are made to ensure that any machine that will be directly accessed from the internet is segregated from the rest of the network via firewalls.  This can help limit the ability of an attacker to get further into the network.
So this is the risk you must accept, and help better define the risk, you would need to examine the history of the application being exposed - how frequently critical vulnerabilities are uncovered, and how quickly they are addressed.
Mitigation strategies you can employ are about reducing your exposure.  This can be done by only port-forwarding when you want to use the service, or closing the application when not needed.
Answer: If we accept the assumption that opening a port to a machine allows that machine to be compromised, then yes. Every port on a machine is open to every other machine on the same network. So if opening port X to machine Y risks a compromise of machine Y, anyone who has compromised machine Y has access to port X on machine Z. So they can compromise machine Z too.
But this really just shows that talking in generalities such as "exposes to security breaches" is really just too vague to be useful. Plugging a machine in exposes it to security breaches. Dealing with non-quantified levels of risk leads to silly conclusions.
Comment: I agree, dealing with non-quantified information always leads to sillier or at least as silly conclusions then non-quantified information, but to understand anything I need to make assumptions. At least that is the fastest way of learning imo. Even if my assumptions are wrong, I think the most import thing is that you explicify hypotheses as much as possible in your mind and test them consequently. But will you only act on situations you can completely quantify?
Thanks for your answer! (and also of the other pple who commented)
Answer: No it does not - at least not generally. But if you forward some port to one machine there is a higher chance that this particular application gets attacked/exploited. During this it may run malicious code like a worm/trojan which then can spread in your internal network
Answer: Not really. Without port forwarding, incoming packets are dropped by the router because it cannot determine the destination. By forwarding ports, those packets are directed towards a specific machine. This is generally harmless. Your firewall will drop unwanted packets anyway. Even if it does not, no programs will be listening to that particular port and the packet will not affect the machine, of course with the exception of the program you had the port forward set up for in the first place, but that is intended behaviour.
The program you're using might have security flaws. An open port will allow an attacker to exploit these flaws. Not opening the port will add a level of protection by making the machine less accessible from the internet, but that itself is probably counterproductive. It is the equivalent of the very effective security measure of keeping a computer powered down forever.
Other machines in your network will not be exposed to such attacks; they are still inaccessible to the outside world, regardless of ports you may forward to their neighbours. The risk lies in the fact the exposed machine may be compromised. Machines normally protected by a layer of NAT will then be vulnerable because of an untrusted host on their local network.
In part, it is for this reason NAT is generally not regarded as a strong security layer anyway and punching holes in it should not put your network at risk. Nevertheless, it may be wise to set up a VPN instead of a port forward, in case your application is only used by trusted machines. More generally, be careful about which hosts are deemed trustworthy.


What's the difference between credit risk and counterparty credit risk?

Question: As the title reads, what is the difference between credit risk and counterparty credit risk? What are the key differences?
Answer: Credit risk is the risk for holding a risky bond. Counterparty risk is the risk that the counterparty will not be able to meet its contractual obligations if the credit event occur. For example, if you have a bond on AAPL and want to buy CDS to protect in case of bankruptcy (note you buy CDS from another counterparty -i.e. AIG- not the company), then credit risk reflects the possibility AAPL will not fully repay the bond, counterparty risk reflects the risk your counterparty (AIG) will not be able to pay you the amount it owes you if AAPL goes bankrupt.
Answer: Both 'credit risk' and 'counterparty credit risk' refer to the same type of risk, i.e. the risk that the opposite side of a contract will not honor its obligations to repay.
But 'credit risk' will be typically used in the context of traditional loans business, i.e. for practitioners 'credit risk' will be associated with lending a money to someone - here your total risk is known at the onset of a transaction, i.e. if you lend 1M USD to a company, then you cannot basically lose more than 1MM USD.
Whereas 'counterparty credit risk' will be used especially in OTC derivatives business where a contract value might be an asset or a liability over the lifetime of a contract and at the expiry, i.e. we do not know how much we could potentially lose over the life of a contract. To measure 'counterparty credit risk' boils down to finding an estimate on how much you could potentially lose assuming the counterparty does not pay at a given moment of contract life - this estimation is more challenging than in case of typical loans/guarantees.
References could be found in books of Brigo and Gregory.
Answer: There is no significant difference between the two. Both can be considered a financial risk, although credit risk appear to have a slightly broader view. You might also hear the term default risk used.
I suppose technically you could argue credit risk relates specifically to the extension of credit (a one sided risk), and counterparty risk relates to the risk in two sided transactions (e.g. credit swaps).
Ultimately, both are used to consider the loss due to opposing party in any transaction failing to live up to their obligation(s) on the basis of either ability or willingness.
You might also want to look into settlement risk, a non-financial risk also know as Herstatt Risk, which relates to the failure of a counterparty to deliver after you've delivered on your obligation.
Answer: I think the accepted answer gives the right insight, but I would like to add a further consideration: the difference between credit and counterparty risk is related to the main risk you are seeking compensation for when entering a trade. Indeed:

We might speak of credit risk when you enter a trade for which you are seeking compensation primarily for the risk that your counterparty might not pay you back: this is the case of a corporate bond for example, in which case you are first and foremost taking a view on the credit quality of the issuer.
We might speak of counterparty risk when you enter a trade for which you are seeking compensation primarily for some risk other than credit (equity risk, rate risk, etc.) but for which you are nonetheless exposed to the credit quality of a counterparty: this would be the case of any derivative transaction for example, in which you might be taking rate risk (e.g. interest rate swap) or equity risk (e.g. stock option) but which remains nonetheless a contract with a party which has to pay you at maturity $-$ hence subject to the risk the counterparty might default and not pay what they own you.
Answer: This is my take on the matter:
**

Credit risk

** - this can be defined as the risks of default on financial obligations from the extension of credit directly to a counterparty or indirectly through an instrument.
**

Counterparty risk

** - this can be defined as the risk of default from (i) the extension of credit or (ii) agreed contractual performance, which in most cases will carry financial obligations to the affected party/ies.
On this basis, it can be surmised that counterparty risk is a subset of credit risk.
Answer: Please read carefully.
I give you the use we have where I work but it might not be the correct one.
Credit risk will refer to spread moves.
Counterparty credit risk will focus on exposure and loss given default.


Can I make bone broth with bones without marrow?

Question: I bought some marrow bones from the butcher, roasted them, ate the delicious marrow.  I then decided to make broth out of it.  I've made broth many times with chicken carcasses, but not beef bones from which I have already eaten the marrow out of.  Anyone have experience making broth from beef bones without the marrow?
Comment: Hi Mega Man and welcome! I agree with you about the editing. Editing is meant to make improvements or clarify a question. In this case, however, I don't feel that the edit made any significant improvement to your question, nor do I see any problem with it as you wrote it. Therefore, I rolled it back to your original post.
Comment: I do not agree with the pedantic editing of this question.  It conveys no information more clearly now than it did previously.
Comment: Please read the corresponding Meta post [here](http://meta.cooking.stackexchange.com/questions/3329/why-are-people-here-messing-with-my-posts).
Answer: What you're proposing is similar to 'remouillage' ('rewetting'; sometimes called 'second stock').  It's a stock made from bones that have already been used to make stock.
It may not be quite as flavorful as you'd get from your first stock, but in your case, you haven't made stock with it, so any water-soluble bits that haven't been removed would still be on/in the bones.  And if the bones were roasted, they'll have extra flavor from the browning of the bits of flesh that can remain on the bones.
You'll also still get flavors from any vegetables you might use, so you can make a beef/vegetable stock.  Bonus points if they're also things that might have been trash -- parsley stems, the ends of onions, that sad looking pepper that you found in the back of your fridge, etc.  Growing up, my mom would keep a bag in the freezer of such things, and when she had a carcass, she'd toss it all in the pot and let simmer.**
This second stock can then be used in case where you might not want the full strength stock, but as you found, you can also reduce it to intensify the flavors (but if you do that, go light on the salt)
** She'd also make seafood stock from crab shells (including legs), or shrimp shells, tails and heads; her mother grew up in the Great Depression, and you learn to be frugal.
Comment: And if you want more examples of this frugal style, check out [Great Depression Cooking](http://greatdepressioncooking.com/Depression_Cooking/Welcome.html) and the [YouTube channel](https://www.youtube.com/user/DepressionCooking).  (no relationship, other than a fan who has the DVDs)
Answer: I'm afraid you won't have much flavor in a stock made from bones with no marrow.
Stock gets that delicious flavor not really from bones, but from the marrow and connective tissue on/inside the bones.  Most beef marrow bones don't have a great deal of connective tissue on them, and you've already eaten the marrow, so there's just not much left to flavor a stock.
Comment: You *might* get something closer to remouillage, a 'rewetting' of the bones.  (ie, making a second thin stock from the bones that had already been used for stock making).
Comment: @Joe i boiled the bones afternight (thanks for the term remouillage, that's a new one for me!), and then reduced ~3 lbs of marrowless bones, various spices to ~12 oz of glace and pleased to see that it gelled up nicely after reducing and refrigeration.
Comment: @Joe  Huh.  I'd never heard of that... I'd always heard that once you made stock from your bones, there *shouldn't* be anything left to extract a second time.
Comment: @Joe Since OP found your comment more helpful than my answer, perhaps you should post it as an answer so it can be accepted?
Comment: @senschen I started last night, then I fell asleep.


A Fraction field problem

Question: Let $R$ be an integral domain (in particular commutative ring) with identity and let $X$ be a sub field of $R^{frac}$ (fraction field of $R$). Is it true that there exists a sub ring $A$ of $R$ such that $X=A^{frac}$?
Comment: @MartinBrandenburg I'm confused, in wxu's counterexample the ring is a UFD.
Comment: But this *is* true when $R$ is UFD (or PID).
Answer: It is not true.
Consider $\mathbb{Q}[x,y]\subset \mathbb{Q}(x,y)$, let $K=\mathbb{Q}(\frac{x}{y})$. If there exists a subring $A$ of $\mathbb{Q}[x,y]$, such that the fractional field of $A$ is $K$, then $A\subset \mathbb{Q}[x,y]\cap K=\mathbb{Q}$. Contradiction.

Edit: Here is a proof for $\mathbb{Q}[x,y]\cap K=\mathbb{Q}$.  Suppose $f(x,y)\in \mathbb{Q}[x,y]\cap K$, then $f(x,y)=\frac{g(x/y)}{h(x/y)}$ with gcd$(g(t),h(t))=1$. Then we have $f(x,y)h(x/y)=g(x/y)$. If $h(t)$ is not constant, say $\alpha\in \overline{\mathbb{Q}}$ is a root of $h$, then let $x=\alpha, y=1$, we have $0=g(\alpha)\neq 0$. so $h(t)$ is a constant. Hence $f(x,y)=g(x/y)$, now comparing the degree of $y$, it is easy to see $g(x/y)$ must be a constant. We are done.
Comment: There we go, nice and simple.
Comment: @rschwieb, thank you~
Comment: Quite ingenious, wxu!
Answer: wxu has given a nice example in above to show the claim is incorrect. To clarify that it is far from being true, the following example show it is not true even if the domain is a principal ideal domain.
Let $k$ be any field, $A$ be the polynomial ring $k[X]$ and $F$ be the field $k(X)$ of rational fuctions. For any positive integers $m$ and $n$, take the subfield $X=k(x^m+x^{-n})$. Then we can check that $X\cap A = k$ by some computation. Therefore, this will be another counter-example in which $A$ is even a principal ideal doamin.
Answer: This is a comment for ding8191.
Let me interpret that $k[x]\cap k(x^m+x^{-n})=k$ for any positive integers $m,n$ with the same method.
Suppose a polyonmial $f(x)=\frac{g(x^m+x^{-n})}{h(x^m+x^{-n})}$ with $g,h$ having no common factor. Then $f(x)h(x^m+x^{-n})=g(x^m+x^{-n})$. Then if $h$ is not a constant, say $\alpha\in \overline{k}$ is a root of $h$, since the equation $x^m+x^{-n}=\alpha$ can be solved in $\overline{k}$, say $\beta$ is root of it. Then let $x=\beta$, we get $0=g(\alpha)\neq 0$, contradiction. Thus $h$ is a constant. Hence we may assume $f(x)=g(x^m+x^{-n})$, in this case, $f$ must be constant too! We are done.
With this method, we can find more subfield $K$ of $k(x)$, such that $k[x]\cap K=k$.

Aside:
If $n=m$, consider the ring map $k(x)\to k(x)$ sending $x$ to $x^{-1}$, we can immediately see that $k[x]\cap k(x^n+x^{-n})=k$.
In fact, we can decide all subfield $K\subseteq k(x)$ such that $K\cap k[x]=k$.
Claim: Let $r(x)\in k(x)$. If $r(x)\notin k[x]$ and $r(x)^{-1}\notin k[x]$, then $K=k(r(x))$ is a subfield of $k(x)$ such that $K\cap k[x]=k$. Convesely, if $K\cap k[x]=k$, then $K=k$ or $K=k(r(x))$ for some $r(x)\in k(x)$ such that $r(x)\notin k[x]$ and $r(x)^{-1}\notin k[x]$.
Proof. By luroth theorem, every $k$-subfield of $k(x)$ is of the form $k(r(x))$ for some $r(x)\in k(x)$. So it suffices to prove the statement that if $r(x)\notin k[x]$ and $r(x)^{-1}\notin k[x]$, then $k(r(x))\cap k[x]=k$.
Suppose $f(x)h(r(x))=g(r(x))$, with $(g,h)=1,h\neq 0$. Then we can find an $\beta\in \overline{k}$ such that $r(\beta)=\alpha$ is a root of $h(t)$ if $h$ is not a constant. Contradiction. Thus $h$ is a nonzero constant. In this case, if $g$ is not a constant, then $r(x)$ is integral over $k[x]$, but $k[x]$ is a normal ring. Hence $r(x)\in k[x]$. Contradiction again.
If either $r(x)\in k[x]$ or $r(x)^{-1}\in k[x]$, it is obvious that $k(r(x))\cap k[x]\neq k$ if $K\neq k$.
We are done!

A Fraction field problem


relative merits of presentism, eternalism and the growing block universe

Question: What are the relative merits of the different philosphies of time. Presentism states that only the present now exists, a la Julian Barbour. Eternalism posits an object spacetime stage where everything is already laid out simultaneously. The growing block universe states that only the present and past exists, but the future remains open, with the present flowing into the future, crystalizing it. Is timeless being or temporal becoming more fundamental?
Comment: If you cannot formulate the question in a logical positivist way, so that one can distinguish by an experiment or by an observation between the different options, than as far as science is concerned you might as well believe that the present doesn't exist, only one future moment does, in particular, 5:54 PM, Dec 13, 2034. There is no meaning I can see to questions without empirical consequence, and this is a prime example.
Comment: This is not a question, its just the fishing for some chat. -1 and vote to close as not a real question.
Comment: @Georg: I agree with your assessment of the question, -1, but this is something that non-physicists ask physicists all the time, because they want to recognize perceptual reality in physical reality, and they are annoyed that this is not obvious. So the answers might not be so terrible in principle.
Comment: This could be a great question -- any chance we could persuade you to develop this just a bit further?
Comment: "If you cannot formulate the question in a logical positivist way ..."  Nonsense. There are many valid ways to view properly formed questions besides the logical positivist view.
Answer: Change, the flow of time, is obviously real. An objective universal "now", stretching across the universe, is obviously at odds with relativity. So I vote for "process eternalism": all times are equally real, and "coexist" (in some sense of the word "exist"), but they all exist in the mode of becoming, not in the mode of "timeless being".
The individual experience of time is not an experience of the whole of space at once, and not even an experience of a whole life at once: it is of a narrow individual state, that becomes another such state, that becomes another state, and so on until the end of life. Presumably this has to do with persistence-through-change in whatever part of the brain is the physical locus of consciousness. You are something, you came into existence, your existence is a series of changes in state, and eventually you will cease to exist.
For purposes of visualization and calculation, we can spatialize time, and think of your history as a "line" in space-time. We can even think of the histories of all the matter there ever was in space-time, as a "bundle" of such timelike lines. But we know from personal experience that the mode of being of our personal world-line is the mode of "becoming"; the world-line of a material object is made of the changes that happen to it ("made of time", one could say, though time itself is then "made of" change), and this applies to us too.
There are considerable difficulties in subsuming all the actual details of contemporary physical theory into this ontology. If we could canonically decompose the space-time history of the universe into a number of bounded "world-volumes" of narrow spatial width and finite duration, we could then say that each world-volume represents an elementary process, the persistence through time of a fundamental entity. For example, in a process-eternalist account of a cellular-automaton ontology, you could say that each cell has its own history and thus its own "local time". But it's hard to say what the "persistent fundamental entities" in the real world might be (D0-branes?).
By way of concluding, I would emphasize a few things. First, there is a limit to what physics can tell you about ontology and this is an example. Modern physics has been ontologically cut loose from phenomenological space and time; one is free to posit any sort of ontology, or no ontology at all, so long as you can start with empirical data, place it into the theoretical framework, and eventually get quantitative predictions which can be translated back into empirical consequences. This has given people the conceptual flexibility to dream up relativity and quantum mechanics, but it has also cut the ties between space and time as they are known in experience, and space and time as they are represented in mathematical physics. When physicists are asked to talk about the nature of time, they tend either 1) to use a fuzzy version of the intuitive concept of time, but with some alterations to acknowledge physics 2) to reify however they personally think about the mathematics, and say that space-time "is" an unmoving four-dimensional block, or (more rarely) that reality "is" an operator algebra, etc 3) say that reality is beyond time, or even beyond space and time, and that the nature of time is something for cognitive scientists and neuroscientists to figure out.
However, I think one must respect the subjective appearance of the world, if one wishes to do ontology. It is the one thing we do know to exist. For this discussion, this means that if we are going to talk about time, we have to respect the nature of time as revealed in experience, and that means the reality of change - of "becoming". Any ontology which denies that becoming is real, can be instantly falsified. Instead, one should use the reality of becoming (and the reality of the rest of phenomenology) as a clue to the nature of the reality that is described formally in our physical theories. Our experience is showing us part of the "true nature" of a very small part of the physical world (i.e. the little portion of brain in which consciousness resides). In the present instance, it is telling us that time is real. But as I remarked at the beginning, presentism (as well as the "growing block universe") is a problem from the perspective of relativity. Thus I opt for the peculiar compromise of process eternalism.
Comment: I downvoted this too quickly--- I think this basically answers the question--- the ontology is one of many free inventions which you are allowed to choose arbitrarily, so long as it matches experience. If you make an edit, I will remove the downvote (sorry).
Answer: You left out relationism. In relationism, time is not independent of the configurations matter makes. Point of fact, time is none other than what clocks -- made up of matter -- read. It makes no sense to ask what if the clock reads out the wrong time from the 'actual' time because there is no actual time. If there are many many clocks, and nearly all of them agree except one, then it can be said that clock is synchronized wrongly. It makes no sense to ask what if all the clocks are synchronized wrongly if they all also happen to agree with each other.
The past in relationalism is none other than what the configurations of matter forming memories and records say the past is. if they all agree, that's what the past is. If most agree except one or two memories and records, those of them are suspect, and we go with the majority rule.
Time is not a container or a spatialized line where material events can be positioned into a timeline of history. That is a bad metaphor brought on to us by our language and brain structure. Time emerges from the configurations of matter itself.
Answer: Your question depends upon which interpretation of quantum mechanics you choose. The many worlds interpretation is compatible with both eternalism and presentism because all the branches are included. Interpretations with collapsing wave functions in real time tend to tie in with the growing universe interpretation, but not eternalism because how the wave function will collapse can only be determined probabilistically. Consciousness causing collapse interpretations tend to favor presentism at the time of consciousness.
Comment: The many worlds and CCC interpretations are basically interchangable--- CCC was just a reinterpretation of many worlds by Wigner to isolate and remove the question of "existence". Again, the notion of "existence" has no positivist manifestation.
Answer: Durationless instances do not exist. What we subjectively call now always has a temporal extent. It takes time to think, time to perceive, and time to act. This immediately rules out presentism. No clock has infinite resolution.
The flow of time is a nonexistent illusion with neurological underpinnings. When you process a spoken language sentence or listen to a melody, what happens is the auditory perceptions are cached into the phonological loop of working memory and stored in a linearized fashion. That is to say, not linearly in the brain, but when replayed in working memory, the contents of the phonological loop are played out sequentially in the same order in which they are first recorded. However, if you were to look into the brain, all you will see are the contents of the phonological loop all co-existing at the same instant. Ditto for visual motion as the brain also has a similar cache for visual motion and changes. The take home lesson is time all lies in your mind.
Time is not a measure of change because change can only be detected if the memory cache contains differing copies of the same object, or informational representations thereof, co-existing simultaneously. This is most readily apparent in visual change-blindness. A huge visual change is unnoticable if a brief flash is presented between changes. Once again, it is all in your mind.
Preverbal children live in a timeless world. It is only after learning language with its tenses and aspectual structure that they form a model of time in their minds. Roughly speaking, it looks like a timeline.
Causation lies in the mind. Certain kinds of correlations that are presented together to the brain under certain conditions are automatically assigned a causal cause-and-effect relation by the brain itself. Correlations between events exist, but causality only lies in the mind.
Comment: -1: Having been around preverbal children, you are totally off. They have a sense of time just as we do, unless you look at 1-3 months, where their brains are not myelinated, and they look like they are constantly high.


What Happens if Hive Web Shuts Down?

Question: I've been hearing a lot of good things about Hive Web as a wallet. Apparently it's pretty secure, open source, and only requires that you keep a 12-word phrase safe. That said, what if they ever decided to shut down Hive Web suddenly? Would all your BTC go down with it, or could you simply spin up an instance of their open-source web server to regain access to your wallet?
Answer: You could most certainly spin up your own server :) Included in the Github repo is a Vagrantfile that uses Ansible to deploy and provision an instance of hive-js. This can be handy not only for creating a local test instance, but also for deploying to more public environments such as DigitalOcean or AWS.
Alternatively, because Hive Web implements BIP32/BIP39, other wallets implementing the same standard should allow for compatible 12-word seed phrases to be moved between clients. In addition to being a high priority item for Hive OSX, it seems that most if not all Bitcoin wallet developers are striving to implement these same standards.
If all else fails, you could use something like http://bip32.org/ to manually recover your master extended key and sweep the funds elsewhere.
Answer: Hive closed and I have been looking for a way to retrieve my wallet. I used iOS app called Bread Wallet http://breadwallet.com

Download the app
Enter your 12-word phrase
Wait 10-15 minutes as it does the magic
See your wallet

At this point do whatever you like with your BTC. Convert to another wallet or just user Bread Wallet.

What Happens if Hive Web Shuts Down?


How to estimate times during Sprint Planning?

Question: I have 6 user stories for a sprint of 14 days. I have the detailed description in the stories for what the team needs to develop, and the team is new to scrum. (this would be their 2nd sprint). The only thing I haven't done so far is to assign an estimate to the stories, using a systematic approach. (like a point system). I want to start with Agile planning poker approach, but how do I assign a number of days after the developer assigns a size (number, color etc) to a story? My point is why do we need to have a point system if we are eventually going to estimate in terms of days?
Answer: The idea of story points is that allow you to measure how much you typically do in a sprint. Then you use this measurement to determine the capacity of future sprints.
Say you are about to start a sprint. Your team has a choice between two ways of estimating how much work will go in the sprint:
Time based estimating
The team looks at each story and works out how long they think it will take to complete. They also calculate how much time is available in the sprint. They add stories to the sprint until the sum of the estimates on the stories added equals the time they believe is available.
Story points estimating
The team estimates stories using relative sizing. They could use small/medium/large or they might use the Fibonacci sequence numbers (1, 2, 3, 5, 8, 13). The actual values used are not important. What is important is that stories requiring a similar amount of effort have similar estimates. e.g. two stories estimated at 5 points will take roughly the same amount of work to complete.
Now the team just gets on with doing some work. But the clever bit is they measure how much they get done in a sprint. They then use this measurement to determine their capacity for future sprints.
Say the team works for a sprint and completes 20 story points. There is a good chance that in the next sprint they will also do around 20 story points (as long as their sizing is consistent).
Notice how time is never mentioned. It is simply relative sizing and measuring how much gets done.
Answer: I think you're doing it wrong. You shouldn't bother assigning the number of days to the story. Your team has 14 days to work on the stories. So estimating points to stories is your way to decide how much work can be completed during those 14 days. If the total points for a single sprint is too big or too small (you know this by reflecting to past sprints), then adjustments to the amount of stories might be required so that you can deliver what you "promised" in 14 days. I believe that's the way to go in implementing Scrum. Assigning number of days for stories based on their size is a step not required; it's not even useful.
PS: If you need to do time tracking, that's another story. Try reading this Q&A for a start: Scrum - Is a good practice to set the remaining work of a Sub-task?
Answer: You'll be hard pressed to actually estimate how many stories you can do in the 2nd sprint. Particularly with a new team. Use it as an opportunity to practice point estimation and then use the the number of points completed (deployed to production) to determine how many points to pull into the 3rd sprint.
Here's the thing though... A single sprint's worth of data is practically worthless. A single data point just isn't enough to accurately forecast. They'll also be wrong about how big stories are.  They won't agree about how big stories are. Problems will happen, expect it and don't knee jerk when they fail to finish as many points in the 3rd, or when they finish twice as many in the 4th. It's going to take time for a new team to find the sweet spot and their rhythm, but they will... eventually.
For perspective, it took my team a dozen iterations to achieve a stable,  predictable, forecastable capacity. That's six months. Don't expect miracles. Just record the data, reflect, and adapt accordingly.


How would I find a hot spring?

Question: I've been looking at a map of the hot springs in my state, and near my area there are 4 in a 60 mile range. These hot springs all are lined up in a straight line, and so my incredibly wishful thinking is that there is another undiscovered (or at least, secret) hot spring somewhere along that line. I will live there next summer, so I'll get plenty of chances to go hiking and exploring the area. If such a treasure does indeed exist, how can I maximize my chances of finding it?
Comment: The geology will decide where a spring could be, if they are in a straight line then it's likely a fault line. So simply follow the fault line! A geological map would help too, but that will depend on your country.
Comment: What hot springs are you referring to? After posting my answer, now I really want to see if I can't dig up some stratigraphic maps for you area and identify some possible search areas.
Comment: To cover the area much faster than walking a fly over (early morning, colder the better) with a thermal imaging camera would be worth a shot. Could do this with a drone very easily or hire a fixed wing (with pilot) for an hour.
Answer: Walk the line on a humid very cold still morning.  If the hot spring is of any significance -- e.g. enough surface to get in, and enough flow to be hot, -- you should get a plume of steam rising off the water.  This will likely require an air water temperature differential of at least 40 degrees F to be visible.
I have seen 'steam' (fog) tendrils off of lakes with a 20 F degree differential, but they were fairly insipid.
You can check this by going to one of the known hot springs, and seeing what sort of conditions are required for reasonable visibility.
If you have a friend with a plane, you may be able to check more quickly from the air.
Method 2.  The forest service uses some satellite (don't know which one) to spot forest fires when small looking at the earth in IR.  See if the known springs show up in IR on the views from this satellite. If they do, track the fault line.
This method will give you a false positive for every furnace chimney and badly insulated shack, but comparing locations with a visible light image of roads and access points will weed most of these out.  Note:  Remote buildings that are too bright may be a grow-op.  Proceed with care.
Comment: When walking a area with springs or seeps. Hot or cold. Keep a eye out for change of flora. A damp or wet area will have different flora than the dryer area around it. Even if you do not see surface water.
Comment: Great suggestions! Unfortunately the other springs didn't show up on the IR map I found.
Comment: Given the weather, have you checked if existing springs give themselves away with plumes?
Answer: It helps to know what is going on underground when looking for geological patters. Hot springs are of course geothermally heated by pockets of magma in the crust that are relatively close to the surface. Understanding the underlaying strata and ground water patters are essential to accurately predicting where hydraulic phenomena will appear. At the very least you need a stratigraphic map so you can examine fault structures and determine where layers of porous rock intersect with faults, the surface, and also where aquatards may inhibit ground water flow.
As others have already indicated here, the fact that the hot springs you are observing are in a line suggests that they are over a fault line, likely an area of tectonic uplift. If you were to examine the stratigraphy of the areas where the known hot springs are, you could identify which layers of strata the heated groundwater is permeating to the surface from, and then locate other areas along that line where those same layers intersect with the surface again.
I'll confess that reading a stratiographic map isn't that easy, but if you can even get a vague idea of where you might suspect undiscovered springs will appear based on the geology and geography, it will greatly reduce your search area.
Without conducting a geological survey with a team of geologists, the next best thing to do is to go bush whackin' away from the beaten trail, using the suggestions that @Sherwood gave you in their answer. An IR thermal imager would be handy to bring along with you, you can get relatively affordable ones that attach to your iPhone.
It's no simple task to actually go out and find natural resources. Which is the number one reason why geologists are able to get jobs other than just teaching... Most of the time when people stumble onto hot-springs it's because they're looking for something else. Lots of springs are discovered by hunters and trappers this way.
Good luck finding your personal secret hotspring, I'm sure you'll have fun exploring the untamed bush whether you find one or not.
Example of stratigraphic map:
Comment: I didn't even go into anticlines or synclines in my answer, but my example image shows a pretty clearly defined syncline in the middle, right where moose lake is, which gives me reason to believe that the Agwv strata is impermeable (my inner geology nerd is really coming out in this answer).

How would I find a hot spring?


only 1 tile visible in GE after gdal_translate -of KMLSUPEROVERLAY

Question: I have a 3-band ASTER scene in any of several formats (PCIDISK, GeoTIFF, Imagine), already reprojected to the geographic coordinate system. I can view and manipulate the scene successfully in PCI Geomatica and ESRI ArcMap. I want to create a KMZ version of it, and following in part this other GIS StackExchange post, I tried using:
<code>gdal_translate -of KMLSUPEROVERLAY myscene.tif myscene.kmz
</code>
but the result is invisible in Google Earth (although it zooms to the correct area). It remains invisible when zooming way out and way in, except that the lower-left tile of the 16 tiles it created does show up when zooming in. It, however, is completely black as it is in the no-data collar around the image data.
Also, if I unzip the KMZ and open any of the individual tile KMLs that were created, they open just fine, and the ones that are not in the collar show the correct image data. So I suspect there's something wrong in the way the output KMZ was formed (which uses Regions and NetworkLinks, KML elements I have not worked with before). But I don't know whether this is due to input data or format problems, to incorrect or missing parameters to gdal_translate, or something else. I've tried several input formats with the same results each time.
Tips and suggestions (if not outright answers!) much appreciated!
Answer: Looks like this is a bug in GDAL 1.9.0, and fixed in 1.9.1:
http://trac.osgeo.org/gdal/ticket/4527


Designing a hash function from first principles rather than depending on heuristics

Question:
Is there a general method to design a cryptographic hash function (with desired properties) from first principles? That is, is there a general process for constructing such functions? I get the impression that Merkle–Damgård construction simplifies the process by allowing collision-resistant compression functions to be used, but are there any general ways of finding "good" compression functions other than by using trial-and-error?
In the entries to the most recent NIST challenge, it seemed to me as if the teams were using very different approaches based on different heuristics, and then essentially testing their functions against many inputs, tweaking parameters, and after that iterating until all evidence pointed to their functions as being secure.

To what extent is this an accurate summary of their approaches? I would really appreciate a reference to a thesis or other publication on this subject.
Comment: Construction of collision-resistant compression functions from block ciphers is well-studied. Davies-Meyer, Matyas-Meyer-Oseas, Miyaguchi-Preneel and Hirose constructions are common. The [Wikipedia article on compression functions](https://en.wikipedia.org/wiki/One-way_compression_function#Construction_from_block_ciphers) covers that. One problem is, construction of practical block ciphers from first principles is not an exact science.
Comment: There exist [hash functions based on conjecturally hard problems](https://en.wikipedia.org/wiki/Security_of_cryptographic_hash_functions#Provably_secure_hash_functions), such that breaks of the hash function imply efficient algorithms for the problem.
Answer: You should design your hash on the bit level.
Regardless how you design your hash, at the end of the day you have a $m$ booleans functions for each output bit from an arbitrary $n$ bits of input.
Some properties of boolean functions
All your output bits will be some boolean function of your input bits.
All boolean functions can be turned into the so called algebraic normal form (ANF), which means your input bits are combined using AND and XOR operators only.
XOR operator is just addition modulo 2. AND operation is just multiplication modulo 2. And these operations are usually denoted with multiplication and addition respectively. In modulo 2 arithmetic addition and subtraction are the same operation, so don't be surprised when I use + when talking about differences.
The modulo 2 arithmetic forms a field, which means all your usual algebraic identities you know are true.
So now the operation of your cipher is just a system of $m$ equations for $n$ bits of input.
Due to nature of modulo 2, a lots of things cancel. Powers cancel: $0^n = 0$, $1^n = 1$. Even coefficients cancel: $x + x = 2x = 0$.
This means the equations for the output is simpler: The only possible coefficient is 1 (or 0 which means a missing term). And all of them is on the first power.
Nonlinearity
If you try to make a cryptographic hash function that only uses XOR and shifting, the equations will be linear even after infinitely many rounds, now the analyst is just a single Gauss elimination away from solving it and now they have the ability to create arbitrary preimages.
In order to avoid that, you need to make your equations non-linear by using the AND operator. Hashes do all sorts of shifting and XOR-ing but this non-linear step is what makes them secure.
But having non-linear terms are not enough. You must make sure the attacker cannot effectively cancel out the non-linear terms out of your equations by fixing some inputs to 1 or 0. Also you need to make sure the terms will not cancel if the attackers takes the difference of two equations. If you have the formula $xy + x + y$ for one and another formula $xy + y + z$ for another bit. Adding these two will give $x + z$ which is now linear and allows the attacker to solve it to get the relationship between two out bits.
Every independent linear equation an attacker can create will reduce the security of your hash with 1 bit. One way to mitigate this is making sure all the functions for the output bits contain different terms. In the previous example if we replace the $xy$ to $xz$ to the second formula. Adding together will not yield linear equation then. But if the attacker fixes the $x$ to a constant value then it becomes a linear equation. This is probably the most challenging part of designing your hash.
Balance
Another thing to consider is balance. You want your hash behave like the so called random oracle. This is important if you want your hash useful as a cryptographically secure random number generator for example. You should make sure all your bits in the resulting hash have 50% chance to be 1. The XOR operator have a very good property that makes it possible: in $a + b$, if either term have 50% chance to be 1, the entire expression will have 50% chance to be 1. To prove this let's consider $A$ and $B$ the probability that $a$ and $b$ are 1 respectively. The probability that $a + b$ is 1 is: $A(1-B) + B(1-A)$. That is either $A$ is 1 and B is 0, or $A$ is 0 and $B$ is 1. If we expand this we have: $A + B - 2AB$. Substituting 0.5 for $A$ gives: $0.5 + B - B = 0.5$. So as long as you can ensure there is at least one term in the final equations that has 50% chance to be 1 independent from other terms, then that will ensure your function is balanced. The simplest way to achieve this, is making sure at least one first order input bit term appears in the functions of all output bits and it will anchor the 50% chance.
Strict avalanche criterion
The next thing to consider is the strict avalanche criterion (SAC).  This means if you change any bit (or more generally any bit pattern) in the input, all bits in the output must have 50% chance to change. Failing to do so can give information to the attacker about the input, and makes your hash vulnerable to differential cryptanalysis. Let $H(x)$ the original hash, let $H(x + \alpha)$ the hash of the changed input. In $H(x) + H(x + \alpha)$ the changed bits will be set. You must make sure this function is balanced too so any bit has 50% chance to be set. Let's se what it means. Let x be the bit we changed. Let $xy + xz + yz$ the expression we test. Let $\bar x$ be the flipped $x$. So the test expression will be: $(xy + xz + yz) + (\bar xy + \bar xz + yz) = xy + xz + \bar xy + \bar xz = (x + \bar x)y + (x + \bar x)z = y + z$. Basically terms that doesn't cointain $x$ will be removed, and $x$ will will be removed from terms that contain $x$. This implies that in order to reach SAC it's a necessary condition that  every output bit depends on every input bit. If there is an output bit that doesn't depend on some input bit, your hash will fail to demonstrate SAC if that bit is flipped.
So now how can you make sure that $H(x) + H(x + \alpha)$ is balanced? There is a class of boolean functions that ensure that. They are the so called bent functions. The simplest bent function is just $xy$ where $x$ and $y$ are independent bits. These bent functions can be combined together by adding them up, so $ab + cd + ef + gh$ will be a bent function too ($a$-$h$ are independent bits). There are other more complex construction too (but I didn't find good examples). So if you want to have SAC, use bent functions. But bent functions come with a drawback: they can't be balanced. There will be a $2^{-n/2}$ bias releative to the 50%.
But this bias approaches zero as the number of bits reaches infinite.

My summary is no way exhaustive.
As the time passes and more and more attacks are discovered so new hash designs need to satisfy more and more conditions, balance, SAC and nonlinearity is a good starting point but probably not enough (I don't know all attacks).
Comment: Do you mean SAC or just avalanche effect? SAC's tricky to prove...
Comment: @PaulUszak I meant SAC. I know it's hard to prove, but it's probably easier to start from primitives (bent functions), that demonstrate SAC and mix your bits such that bentness is preserved (in that way you will have SAC and BIC (bit independence)) too.
Answer: Unlike physics, you cannot have formal definition of primitives in a system that is inherently probabilistic.  In the case of hashes in particular, you want some "random looking" output for an input.  The reason that the Merkle–Damgård construction is so popular is that it allows for a simple analysis of a single block in the chain of the hash construction, which is true for every other hash construction as well.  In semiconductor physics, I can use first principles to derive everything in my drift, diffusion transport equations; however, in cryptographic hashes, you have a probabilistic nature that is different from that of the tangible facts that one expects from a first-principle system.  (even if I consider the probabilities of the quantum space because there's convergence that one does not see in cryptography)
For these reasons, I would say that there have been no "first principles" definitions in cryptography in the same way that one sees in the classic sciences.
Answer: Designing something from first principles just requires inspiration, genius and madness.  Look at:
SHA1("Hello wil3"/0x0a) = a45cc70b69b168e6010b6d1fe2fc9fd358b031ff
The main requirements are simply that it's one way, collision and preimage resistant.  There's nothing fundamentally linking the two sides of this equation otherwise.  There's also nothing (so far) in quantum or gravitational theory (essentially everything) that suggests a hash has to even have a block.  Nothing at all. A stream cipher doesn't and that's cryptographic.  No block means that the need for Merkle–Damgård disappears in a puff of logic.
The best cryptographic example of invention I can think of is the sponge. Read about PANAMA and RADIOGATUN which led to the evolution of innovative spongy hashes. Although to understand the thought processes, you'd probably need to interview the team members.
Parameter tweaking through heuristic rules is commonplace.  This is one of the best examples I've seen of an evolved (rather than procedural) design.  It's an antenna (honestly):-

It's glaringly apparent that this was incrementally evolved, rather than designed by a white collar radio engineer with a slide rule.  It even looks like the route of a hill climbing technique.  Such optimisation was also used to design S boxes, and had positive results. The main issue with these approaches is the danger of local optimums within the value function.  Adding more and more bits to the SHA block width is still not as optimal as the completely different approach of Keccak.  That leap requires a human.  There's an interesting and vaguely similar discussion in From hash to Cryptographic hash.
But on the substantive issue, no, there aren't any short cuts to invention. I'll suggest a biography of  Leonardo da Vinci, Alan Turing or Isaac Asimov.  You're asking for a reference on how to create.  Generally that's reserved for God, but there are a very few lucky individuals.
Comment: This answer doesn't seem to address the question, and some of the points it makes are wrong/misleading.`The main requirements are simply that it's one way and has good preimage resistance` - the requirements are collision resistance, preimage resistance, and second preimage resistance.

`Why couldn't a hash be bijective?` because it by definition compresses an arbitrarily sized input to a finite sized output.
Comment: The crux of the question seems to be `are there any general ways of finding "good" compression functions other than by using trial-and-error?` and `I would really appreciate a reference to a thesis or other publication on this subject.`. You would probably want to talk about (at least) differential cryptanalysis, while preferably sharing a link to a publication detailing why it is relevant. Admittedly, "first principles" is seemingly not a well defined term. But the [comment by Luis Casillas](https://tinyurl.com/y7tbd2wp) is possibly on the right track.


homotopic between two maps imply the homotopy between their mapping cone

Question: Recall the mapping cone of a map $f: X\rightarrow Y$ is defined as the space $C_f: X\times [0, 1]\dot{\cup} Y/\sim$, where $\sim$ is the equivalence relation given by $(x, 1)\sim f(x)$ and $(x, 0)\sim(x', 0) $ for all $x, x'\in X$. Show that if $f, g: X\rightarrow Y$ are maps such that $f$ is homotopic to $g$, then the spaces $C_f$ and $C_g$ are homotopy equivalent.
In the first attempt to solve it, I tried to define natural maps between $C_f$ and $C_g$ that could induce homotopic inverse of each other, but I have not got the answer. When I check Hatcher's book ``Algebraic Topology", I find that I could directly use proposition 0.18 on page 17. But after I read the proof, I find it still does not provide us the homotopy inverse maps between $C_f$ and $C_g$ directly.
So, my first question is:
Can we find a natural homotopy equivalence between $C_f$ and $C_g$ without using the process provided in proof of proposition 0.17 mentioned above?
I want to ask a more general or soft problem, since I am a beginner to learn algebraic topology, when I am asked to prove some spaces are homeomorphic (or homotopy equivalent) or some maps are homotopic, the first thing come to mind is apply the definition of homeomophism or homotopic etc, so I have to find certain specific good maps, but it seems really hard to me in some situations, just as the situation above.
Take another problem for example, prove that $\frac{S^1\times [0, 1]\dot{\cup}S^1}{(z, 0) \sim z^2}$ is homeomorphic to the Möbius band. My first attempt is to prove $\frac{S^1\times [0, 1]\dot{\cup}S^1}{(z, 0) \sim z^2}$ is homeomorphic to $\frac{S^1\times [0, 1]}{(z,0) \sim(-z,0)}$, this time I can easily give the homeomorphism, but when I tried to find some natural homeomorphism from the latter to the Möbius band, which is defined as $\frac{[0, 1]\times[0, 1]}{(x, 0)\sim(1-x,1)}$, it is very hard for me, and finially I have to do some cutting and gluing operation to prove they are homeomorphic without giving a specific map.
So, My second question is:
Are there any suggestions when facing these situations? To be more specific, I mean when one tries to find some natural maps, but it is not easy at all.
Comment: I'd like to point out that this is proved in much detail in proposition 3.2.15 in Arkowitz's Introduction to Homotopy Theory.
Comment: You may find helpful the more leisurely approach in Chapter 7 of my book "Topology and Groupoids" (http://pages.bangor.ac.uk/~mas010/topgpds.html)  See also the comments in http://mathoverflow.net/questions/96071
Answer: Hint for the first question. Given the cone $\Gamma X$ of a topological space $X$, you can cut it in the middle : $\Gamma X \simeq X_1 \cup X_2$ with $X_1 \simeq \Gamma X$, $X_2 \simeq X\times[0,1]$ and $X_1 \cap X_2 \simeq X$.
Given $f,g \colon X \to Y$ homotopic by $H \colon X \times [0,1] \to Y$, you could now be able to define a map $$M_g \to M_f$$ which will be (easily) a homotopy equivalence.


The meaning of early ray termination and front-to-back traversal in ray tracing

Question: I'm new to computer graphics. These days I've been trying to understand how ray tracing using an acceleration data structure works. I came across the term "early ray termination" several times, I looked it over the internet several times too, but I haven't been able to find a satisfactory explanation of it.
What does it mean to terminate a ray early, and why do we have to do it?
Besides, I noticed that the term "front-to-back traversal" is mentioned almost every time there's a mention of "early ray termination".
Concretely how does front-to-back traversal work (in the case of a kd-tree for example) ?
Answer: Front-to-back traversal is the idea that when traversing a ray through the acceleration structure, we want to examine nodes that are in front, i.e. closer to the camera, before other nodes. If you only want the first intersection with a surface (as usual in ray tracing), then if you get an intersection in the front node you don't need to traverse any nodes behind it; as any possible intersection there would be later than the one you already found. This saves time.
For example, in a kd-tree, at each node you have a splitting plane dividing space into two child nodes. You would first descend to the child closer to the camera, and only if no intersections are found there do you descend to the other child.
Early ray termination seems to be a term used in the context of volume rendering. When you're traversing a ray through a medium that attenuates light, such as fog, smoke, cloudy liquids, etc., then beyond a certain distance there is no possibility of the ray having any more effect on the image. If you have thick fog with a visibility of 10 meters, then an object 11 meters away cannot be seen.
You can precalculate the distance at which the attenuation reaches 99% or so (it never quite reaches 100%, but approaches it exponentially). There is no reason to intersect the ray against objects farther than that, so when using the acceleration structure, you can simply discard any nodes beyond that distance. In effect, the ray becomes a line segment terminated at a fixed length. If it doesn't hit anything within that length, there's no point checking further. (Another case where limited-length rays are handy is for shadow rays. You only want to trace them back to the originating light source; any intersections beyond that are irrelevant for the shadow.)
Comment: @user2651062 Normally you would have built the whole tree before you start traversing it. Your comment makes it sound like you're trying to build and traverse at the same time? Or else what do you mean by "future child nodes"? In any case, you have to traverse all child nodes that intersect the ray or segment. If it intersects the left child, you descend into the left child and repeat the process for its children. You might need to descend into both children if they both intersect the ray/segment.
Comment: Thanks @NathanReed. 1 more question. Say I want to traverse the tree breadth first, I am at level 0 (i.e at the root of the tree, I haven't divided the tree yet, I have a bounding box including all the scene primitives). I divide the bounding box along an axis such that the left child node is the one closer to the camera. Then I find that a certain ray R intersects the left node. R should be early terminated with regard to the right child node and to all of its future children nodes. But I still have to test the intersection of R with the future children nodes of this left node, am I?


How can I get attachments to work if I don't have threads on my lens?

Question: there are a few lens attachments (fisheye and pinhole) that I would love to have, but my one lens doesn't have threads that I could use to attach the fisheye/pinhole. Is there any way I could still attach these, or would it just be worth buying a whole lens? The camera I use is a Nikon D3000, and currently I'm using the lens it came with the most, 18mm-55mm, (which is the one that doesn't have threads) but I also have an AF-S Nikkor-Zoom 55mm-200mm that HAS threads, but I don't use that one nearly as much. Any help would be greatly appreciated. Thank you.
Comment: Get your threads back by removin the filter that is already on the lens! Generally lenses without threads lack them for vignetting reasons and some accept slip-in filters at the rear.
Answer: The kit D3000 comes with the 18-55mm f/3.5-5.6G AF-S DX VR Nikkor Zoom Lens I believe. According to the Nikon website it accepts 52mm screw-on filters. You should have no problem adding 52mm screw on filters or attachments such as macro filters or wide angle lenses(example).
If you have multiple lenses that you would like these attachments to work with, you can get step up/step down rings that let you use other thread sizes together. For example you could get a step up from a 52mm filter to a 77mm filter and use 77mm attachments on multiple lenses.
Note that these lens attachments many times come with severe trade-offs as far as quality goes, but they are very inexpensive typically. The other option would be to get a dedicated lens for fisheye or macro work.
Answer: There are some clip on attachments. I have a Raynox dcr-250 which is a clip on macro adapter, quality is undoubtedly less than a dedicated macro lens but then the price is also considerably less and its "good enough".
You will need to worry about clearance between the attachment and your lens, I bought it for my Nikon P7100 along with a Polaroid adapter tube which extends just beyond maximum lens reach so that macro lens and camera lens do not collide.


What are the good and bad cholesterol ?

Question: I have question about cholesterol, as I know we can get cholesterol using vegetables and meat, so what is good and what is bad ?
Comment: @xusr the comment as written makes a fine answer - it's referenced and all.
Comment: Whats wrong with question ?
Comment: Possible duplicate of [What is/are the molecular differences between HDL and LDL cholesterol?](https://biology.stackexchange.com/questions/5152/what-is-are-the-molecular-differences-between-hdl-and-ldl-cholesterol)
Answer: Original Answer (posted originally as a Comment)
It is now accepted that high cholesterol causes atherosclerosis. Cholesterol a major component of the plaques that block arteries. 'Good' and 'bad' cholesterol refer to the way cholesterol is transported in the bloodstream.
'Bad' cholesterol is cholesterol in the form of low density lipoproteins or LDL, and 'good' cholesterol is in the form of high-density lipoproteins or HDL.
Or at least that is how it used to be. It is still accepted that high concentrations of LDL in blood promote atherosclerosis, that is high levels of LDL may still be considered 'bad', but drugs that specifically raise the levels of HDL have had serious adverse effects.
Check out this great article: Cholesterol and Controversy: Past, present and Future by  Jeanne Garbarino, especially the section on "Deconstructing Cholesterol: "Bad" is still bad, but is "good" still good?". It is hard to know what the current position is. And check out the work of Brown and Goldstein.
Edit
Goldstein, in his Nobel lecture, famously said (see here)

Cholesterol is a Janus-faced molecule. The very property that makes it useful in cell membranes, namely its absolute insolubility in water, also makes it lethal. For when cholesterol accumulates in the wrong place, for example within the wall of an artery, it cannot be readily mobilized, and its presence eventually leads to the development of an atherosclerotic plaque.

Cholesterol may be synthesized in the body, or obtained from the diet.  The site of biosynthesis is mainly the liver. Cholesterol and fats (triacylglycerols) are transported in the bloodstream as lipoprotein particles, which may be roughly described as a lipid core surrounded by a protein coat, and may be viewed as a mechanism for transporting insoluble fat molecules (by 'coating' them with a soluble protein exterior).
There are five main classes of lipoprotein particles (see, for example, Berg): chylomicrons, very low density lipoproteins (VLDL), intermediate-density lipoproteins (IDL), low-density lipoproteins (LDL), and high-density lipoproteins (HDL)
Cholesterol (and fats) are transported from the liver to other tissues in the form of low-density lipoproteins (LDL).  High-density lipoproteins, on the other hand, pick up cholesterol and fats in the blood and from specialized cells and transport them to the liver. Hence the names 'bad' and 'good' cholesterol.  (In reality, of course, things are more complex than this simple scenario: for a very readable account, see Berg).
The ratio of 'bad' to 'good' cholesterol, ie the ratio of LDL to HDL may be used diagnostically, and a healthy LDL/HDL ratio is about 3.5 (see Berg), but in view of the studies cited by Garbarino a low ratio due to high concentrations of HDL (rather than low LDL) might not be so great either. In fact, if LDL is in check, there may be no benefit to raising HDL (Garbarino article).  But I suppose the physicians will always find a way to waffle (and to charge for the privilege).
It is a common misconception that plants do not contain cholesterol. (My original answer to this question attempted to promulgate this nonsense). In particular, plant membranes do contain cholesterol. However, the amount of cholesterol in plants is low compared to that found in animals (Behrman & Gopalan, 2005).  But it is certainly not zero. The nucleus of maize shoots contain significant amounts of cholesterol, for example (Kemp & Mercer, 1968).
This great reference, Cholesterol in Plants, by Behrman & Gopalan (2005) suggests that the following paragraph should be inserted into biochemistry texts.

More than 250 steroids have been described in plants.
  Of these,  perhaps  sitosterol,  which  differs  from  cholesterol by an ethyl substituent at position 24, is the most
  common.  But  plants  also  contain  cholesterol  both  free
  and esterified. Cholesterol occurs as a component of plant
  membranes  and  as  part  of  the  surface  lipids  of  leaves
  where it is sometimes the major sterol. The quantity of
  cholesterol is generally small when expressed as percent
  of  total  lipid.  While  cholesterol  averages  perhaps  50
  mg/kg total lipid in plants, it can be as high as 5g/kg
  (or more) in animals.

A great generalization is the following (Behrman & Gopalan, 2005)

Prokaryotes do not contain cholesterol

These authors also suggest that one of the reasons for the common misconception that plants do not contain cholesterol is "legalities of food labeling that allow small quantities of cholesterol in foods to be called zero".
I suppose we should not be too surprised that plants can make cholesterol. They can of course, make steroids, the Mexican yam being the original source of a precursor of a particularly important one.
A key enzyme in the biosynthesis of cholesterol is HMG-CoA reductase, which is the target for statins, and these drugs  may be used to lower serum cholesterol levels (but there may be side-effects).
One interesting thing about the biosynthesis of cholesterol is that the final cyclization step requires oxygen which has lead to much philosophical and evolutionary debate (see, for example, here).
Finally, another quote from Goldstein

Cholesterol is the most highly decorated small molecule in biology. Thirteen
  Nobel Prizes have been awarded to scientists who devoted major parts of their
  careers to cholesterol. Ever since it was first isolated from gallstones in
  1784, almost exactly 200 years ago, cholesterol has exerted a hypnotic fascination for scientists from the most diverse domains of science and medicine
Comment: You cite: "While cholesterol averages perhaps 50 mg/kg total lipid in plants, it can be as high as 5g/kg (or more) in animals." That is a factor of 100. How can this make you consider your first answer "promulgating nonsense"? Quantities do not count?
Answer: The question as stated is unclear as to what is being asked.
If the question is whether ingested cholesterol from whatever source is good or bad, then the answer is that dietary cholesterol is superfluous to human nutrition since it can be synthesized by the liver, and the latest guidelines suggest to keep intake as low as possible.

While adequate evidence is not available for a quantitative limit for dietary cholesterol in the 2015-2020 Dietary Guidelines, cholesterol is still important to consider when building a healthy eating style. In fact, the Dietary Guidelines states that people should eat as little dietary cholesterol as possible. 1

The main source of dietary cholesterol is overwhelmingly from animal sources. A meta-analysis published in August 2017 of vegetarian diets found that

Of the 8385 studies identified, 30 observational studies and 19 clinical trials met the inclusion criteria (N = 1484; mean age, 48.6 years). Consumption of vegetarian diets was associated with lower mean concentrations of total cholesterol (−29.2 and −12.5 mg/dL, P < 0.001), low-density lipoprotein cholesterol (−22.9 and −12.2 mg/dL, P < 0.001), and high-density lipoprotein cholesterol (−3.6 and −3.4 mg/dL, P < 0.001), compared with consumption of omnivorous diets in observational studies and clinical trials, respectively. Triglyceride differences were −6.5 (P = 0.092) in observational studies and 5.8 mg/dL (P = 0.090) in intervention trials. 2

concluding that plant based diets reduced total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol ( as the latter is used in reverse cholesterol transport so with less circulating cholesterol there is naturally less to transport ) but triglycerides were unaffected.
So, if you eliminate animal based foods (and therefore the main source of dietary cholesterol) then the studies suggest you are likely to improve your lipid profile which is presumably one reason for the guidelines.

https://www.choosemyplate.gov/2015-2020-dietary-guidelines-answers-your-questions
Association between plant-based diets and plasma lipids: a systematic review and meta-analysis https://academic.oup.com/nutritionreviews/article/75/9/683/4062197

What are the good and bad cholesterol ?


Proportion of dark matter/energy to other matters/energy at the beginning of the universe?

Question: What was the proportion of dark matter/energy to other matters/energy at the moments after the beginning of the universe (standard Big Bang model)?
Comment: What do you mean by "moments"? Are we talking seconds, minutes, ...? The very early universe was a busy time with a  lot of different reactions going on. After about the first hour or so things settle down a lot and [it gets very easy to describe](http://en.wikipedia.org/wiki/Chronology_of_the_universe).
Answer: It is important to remember that very early ($10^{-10}$ seconds) on in the universe history there was no distinction between dark matter and normal matter as it is expected that all the forces were unified and there would be no difference between dark matter particles and normal matter particles since there were "no particles" in the classic sense. Recall that in QFT particles are excitations of fields, but if all the fields were coupled then there would be no difference between dark matter and non-dark matter. Also at very high energies, the excitations wouldn't last long enough to be meaningful.
If one takes inflation into account, I suppose the ratio of energy in the primordial matter fields vs. inflationary fields would depend on the exact model of inflation.
Answer: This question doesn't have a "correct" answer yet because we simply don't know what dark matter is.
That aside, assuming dark matter consists of particles (WIMPS for example), the LHC hasn't turned up any sign of dark matter production yet.  Since the number of locations in the Universe that are able to reach LHC energies are very limited compared to the overall Universe, it's likely that nearly all of the dark matter today was produced very shortly after the big bang.  There simply aren't enough energetic processes to be generating the quantity of dark matter we think there is today.  That is, assuming a WIMP model of dark matter, the vast majority of the particles we estimate there are today are primordial remnants of the big bang.
Of course the above doesn't apply to other models.  For example, here is a paper exploring primordial black holes as the source of dark matter.
Comment: This doesn't really address the OP's question, which is about the proportions of the different things in the early universe.
Answer: In an FRW cosmology, we have a scale factor $a$. For example, if $a$ grows by a factor of 2, galaxies have gotten twice as far away as before. The contribution to the stress-energy tensor from radiation goes like $a^{-4}$, from massive particles $a^{-3}$, and from a cosmological constant $a^0$, i.e., it's constant. For these reasons, the universe has gone through three epochs: radiation-dominated, then matter-dominated, and now a vacuum-dominated epoch in which dark energy is dominant.
It's true that we don't know much about dark matter and dark energy, but we do know that dark matter consists of massive particles (otherwise you can't make the models fit the observations) and that the equation of state of dark energy is very close to that of a cosmological constant (Carnero 2011, Allen 2008, Biesiada 2011). For these reasons we can expect that dark energy and dark matter played negligible roles in the early universe.
Allen 2008, http://arxiv.org/abs/0706.0033
Biesiada 2011, http://arxiv.org/abs/arXiv:1105.0946
Carnero 2011, http://arxiv.org/abs/1104.5426