Windows Phone Whatsapp .DB

Question: I have windows phone WhatsApp .db files which are messages.db, calls.db and settings.db. I want to view the messages and calls data. How is it possible?
Can anyone please help me. Thanks in advance.
By the way, I have tried whatsapp_xtract and it gives an error that input string must be of length 16. Help me, please.
Comment: I'm voting to close this question as off-topic because it has nothing to do with the Windows Phone platform
Comment: @kelvinelove I believe that this question is on topic because It deals about a problem specific to Windows phone OS. Whatsapp in other OS does not store the db files separately for Messages, call, etc... In Android there will be just a single msgstore.db file. This question refers to a Windows Phone in particular.
Comment: @KolappanNathan But isn't the **.db** format universal. I mean, its an SQLite database, which is the same thing irregardless of platform. The problem is more of a database file format issue, rather than being a Windows Phone platforms specific issue...!!!
Comment: @kelvinelove .db is a universal format. But I believe *how to open whatsapp chat files in Windows Phone?* is a valid question and it is only applicable to Windows Mobile.
Answer: I suggest that you download "WINAPP CRACK 2.0" from http://www.netup.in. This small program is available as a shareware and can process messages.db and calls.db files upto size of 1kb and unlimited when the premium version is purchased. It will show you all the messages with call records in a chronological order for all the backups prepared by Windows Whatsapp Mobiles. Try.

Windows Phone Whatsapp .DB


The less-known features

Question: Jukka has mentioned a feature (a page for more advanced searching) that I was not aware of. Are there other less-known features that you have found useful?
Answer: Stack Exchange has an experimental feature called timeline view (example).  It is useful when you want to know when a post was made, an answer was accepted, and so on (but be careful because it does not always show the complete history).  See my answer to another question for more details and a link to a user script which makes the timeline view easier to use.
Comment: I've found timeline view really useful to summarise recent activity.  This saves a lot of time when there are many long comment threads and answers for a question.
Answer: We have chat ! Specifically, http://chat.stackexchange.com/rooms/47/theoretical-computer-science takes you to a chat area for cstheory.
Answer: This is not a less-known feature but a less-known practice.  I hope that this belongs here anyway.
Changes of features and policies on Stack Overflow are listed in a thread on Meta Stack Overflow.  Note that not everything on the list applies to cstheory.stackexchange.com or meta.cstheory.stackexchange.com.  A Stack Exchange addict (unlike me) who is using a feed reader might want to subscribe to the feed for that thread to become a better Stack Exchange addict (unlike me).
Comment: This answer proves that you are a SO addict, actually a better one. ;)
Comment: @Kaveh: I clarified the answer a little in response to your comment. :)
Answer: Markup for tags.  They automatically link to the list of tagged questions.  This is sometimes useful on Meta and in tag wikis.  Examples:

[tag:graph-theory] → graph-theory (points to a tag on parent)
[meta-tag:scope] → scope (points to a tag on Meta; only available on Meta)
[tag:this-tag-does-not-exist] → this-tag-does-not-exist (also works for a nonexistent tag)
Comment: Doesn't seem to work in comments: [tag:graph-theory]
Comment: @Jukka: Too bad. :(
Answer: Hover the mouse on the following quote and

 you will see a spoiler text.

See Meta Stack Overflow for more information.  Not that I think that this is useful on cstheory.stackexchange.com.  :)
Comment: neat feature. might be useful if people start posting puzzle solutions.
Comment: This is a cool feature!
Answer: Meta Stack Overflow has a similar thread: Hidden features of Stack Overflow? by JosephStyons.  In particular, I like the following:

View the source of a post
Tooltip on hover on a link
Calendar
Answer: In the right sidebar, the date below "Latest Activity" is a link that takes you directly to the latest addition/change.
Comment: To supplement this answer, clicking the last-modified date/time of each question in a list of questions has the same functionality.
Comment: good finding! I have been hoping for this feature for a long time...
Answer: The review page.
Shows answers by new users. There is also a button under answers with negative or zero votes named "flag for removal".
Comment: Also contains an optional custom filter *Containing: "thank"*
and custom sorts: 1. Shortest first 2. Most commented 3. Reverse Order. I found it on [SO blog](http://blog.stackoverflow.com/2011/01/how-to-say-thanks-in-an-answer/).
Comment: How dumb of me! I've just found this feature and wanted to report it here. Thanks Kaveh for finding it early :)
Answer: I just noticed that there are a few short cuts for linking on the main site (particularly useful when commenting).

for Math.SE you can type [Math.SE] and it turns into Mathematics.
for FAQ you can simply write [FAQ] and it turns into FAQ.
Comment: @Tsuyoshi, posted a comment with a link to [Math.SE] where I forgot to put the url part. (ps: it seems that the trick also works for commenting on meta).
Comment: Wow.  This will be useful.  How did you find it?
Answer: The site's privileges page.
It show the reputation required for performing various task.
Comment: Yes, this is sometimes useful.  Also note that the number showing your reputation points (in the bar at the top of every page) is a link to it.
Comment: I didn't know that it is a link! :)
Answer: User League ranks users based on reputation gained during last year, quarter, month, week.
Comment: The page also has a table for the number of users in each reputation range.
Answer: data.stackexchange.com can be used to extract and query various types of information about the sites (posts, users, ...). Some popular queries can be found here.
Comment: The [data dump](http://data.stackexchange.com/theoreticalcomputersciencemeta/queries) is out!
Answer: I have recently found the filters to be a useful feature of stackexchange for following several sites.
For example, here is a filter I use.

The less-known features


Is the term Cushite used to refer to people of African descent?

Question: While reading the book of Numbers (I am a Christian, I don't know if it is referred to something else in Judaism), I came across the passage (Numbers 12:1-15) where Miriam and Aaron were speaking against Moses for taking a Cushite wife. I wanted to know if the term Cushite or Cushi is used to refer people of African descent, or specifically Ethiopia, or if not what exactly it does/did refer to. Obviously google gives results all over the map, it would be nice to get some real facts.
Comment: Because you're not Jewish?  We are open to all who have sincere questions, and I hope I've alleviated your initial fears.  I hope you enjoy the site.
Comment: Welcome to Mi Yodeya and thank you for bringing your question here!  I hope you enjoy the site.  By the way, the Hebrew name of the book of Numbers is "Bamidbar".  ("Numbers" is fine too, but if you're looking specifically for Jewish interpretations via Google, the Hebrew name might help.)
Comment: I just want to add that "Cushi" can have a pejorative context in Modern Hebrew; depending on the situation, it can be HIGHLY offensive to call someone that.  It doesn't sound like you're planning to use the word, but you should be aware of this.
Comment: All these are interesting arguments/comments. What one also should add to this is that Ethiopia also was used to extend beyond the red sea into Yemen. The two modern countries share history too. if you go to Rama/ Roha in Ethiopia you may wonder how the artifacts look similar to those in Yemen. In short it is a historical truth that Ethiopia (The land of Kush) was closer both to India and Israel in ancient times before its borders shrinked, so that it is quite possible for Moses to mary an Ethiopian woman. all the descriptions look like she is one of the tanned beautiful women out there.
Comment: @MonicaCellio thank you, I was afraid it would get downvoted and I would be chastised!
Comment: @gene This is true (https://en.wikipedia.org/wiki/Kingdom_of_Aksum) but the borders didn't extend that far into arabia. Too much desert.
Answer: See this comprehensive and well sourced paper on the topic by one of our site regulars. Cush was the son of Cham, and the grandson of Noah (Exodus 10:6), and according to the Midrash (Genesis Rabbah 36:7), he was cursed by his grandfather to be dark-skinned.
In terms of the location of the land of Cush, he writes:

"Cush" is commonly translated as Ethiopia, and "Cushites" are commonly understood to have been Ethiopians. However, most scholars agree that the Biblical geographic area referred to as Cush/Ethiopia was not only in the location of present-day Ethiopia, rather it spanned Northwest of present-day Ethiopia, including parts of the areas of present-day Ethiopia, Egypt, Somalia, Nubia, Eritrea, and the Sudan. The Midrash says (Exodus Rabbah,§10) that the plague of the frogs settled a border dispute between Egypt and Cush because the frogs did not pass the border, which showed where exactly the boundaries of each country laid. Indeed, it will be evident later that Cush was near Egypt. Nonetheless, Rashi (to Yoma 81b) translates "Land of Hindu" as the land of Kush. From here one sees that the terms "Kush" used does not necessarily always mean Ethiopia. In the beginning of the book of Esther (1:1), Scripture establishes that Ahasuerus was king from Hodu to Kush. The Talmud records (Megillah 11a) that Rav and Shmuel disputed whether Hodu and Kush are close to each other (Shmuel) or far from each other (Rav). The accepted translation of Hodu is India. If one is to assume that Kush refers to Ethiopia, how then could Shmuel say that Kush was close in geographical proximity to India? Rabbi Yaakov Emden (1697-1776) answers (see Hagahos Ya'avetz to Megillah 11a) that there are two places known as Kush. One "Kush" is in Africa and was Ethiopia, while the other "Kush" is in Asia was close to India. The dispute between Rav and Shmuel was which "Kush" the Torah referring to in describing the boundaries of Ahasuerus' rule. Indeed, an Asiatic mountain range known as "Hindu Kush" runs along the Pakistani-Afghan border.

The essay explores many possible interpretations of Moshe's wife being called a "Cushite". Many explain that she was not actually Ethiopian, but was described as a "Cushite" as an expression of her beauty (see Rashi to Numbers 12:1).
Comment: just to be clear, it was Cham that was cursed, not Canaan. - see also Sanhedrin 108B http://halakhah.com/sanhedrin/sanhedrin_108.html
Comment: @Michoel Perhaps a secular source can provide some insight to the (admittedly already resolved) dispute of where exactly "Hodu to Kush" is. The Persian Empire at the time of Megilat Esther was the Achaemenid Empire. This spanned from Romania (north-west) to Lybia and Egypt (south-west) to the western edges of China and India (north- and south-east) A map can be found at http://sitemaker.umich.edu/mladjov/files/persia500nbc.jpg
Comment: Just to be clear, the Midrash says אותו האיש was cursed and from the context it appears it is referring to כנען, although one opinion in the Midrash says it was the direct result of his relations in the teivah and Rashi on that Midrash says it refers to the child who came out of that instance of relations. And Rashi in Sanhedrin 108b is very clear that the result of the black skin occurred to Kush, not Canaan.
Comment: It's also interesting to note that Hindu and Hodu sound similar.
Comment: Regarding the Kush that is near Hodu (The hebrew word for India/Hindustan)
http://en.wikipedia.org/wiki/Hindu_Kush
Comment: Interesting to note that Moshe's wife Tzipporah was not from Ethiopia, but rather from Midian which is not even near there. (This, of course, is assuming that the wife mentioned in Numbers 12:1 is the same woman as Tzipporah. Could be that she isn't?)
Comment: Rasag translates the phrase as "father of Canaan"
Answer: i find it interesting that people will quote sources from commentators thousands of years after the Tanakh, and historians later still, but no one points to a pretty clear Biblical reference on using Cushi to have it refer specifically to someone of a particular skin color:
Jeremiah 13:23
כג  הֲיַהֲפֹךְ כּוּשִׁי עוֹרוֹ, וְנָמֵר חֲבַרְבֻּרֹתָיו; גַּם-אַתֶּם תּוּכְלוּ לְהֵיטִיב, לִמֻּדֵי הָרֵעַ.  23
Can the Cushite change his skin, or the leopard his spots? Then may ye also do good, that are accustomed to do evil.
So it is definitely fair to assume that Cushi can mean someone who is black (or dark) skinned. We can argue all day long where the geography of the Cushites were considered to be.
Comment: #2. Since it is customarily used to refer to dark skin later in Jewish history rather consistently, it seems much more likely that the meaning of the word remained the same throughout. Your argument is akin to saying "If it says that Ezra was a scribe, how do you know scribe didn't originally mean an ignoramus?"
Comment: From your source how do you know cushi isnt reffering to an extremely pale nation?
Comment: #1. Leopards don't have white spots.


is there some device to make my laptop get wifi better (from a bigger distance)

Question: is there some device that I could connect to my laptop so that I could get wifi from a bigger distance ?
Comment: Use "legs" to move closer to the wifi access point.
Comment: @taspeotis is there another way, beneath moving closer ?
Comment: Use "legs" and "arms" and "hands" to move the wifi access point closer to your laptop.
Answer: It depends on what your situation is, but you can try this:

(Server) Add a gain antenna onto your wireless access point
(Client) Buy an external wireless adapter that allows you to connect an antenna, and then buy a large antenna for it.

You may also want to consider switching between 54a and 54g and artificially limiting the connection speed to get a more stable connection. You can also try a different channel to remove interference.
Answer: If you are using 802.11g then moving to 802.11n may help as the expected indoor and outdoor range is higher (~70m and ~250m respectively, compared to ~35 and ~120). Obviously this range can be affected by a great many things so if your current distance problem is due to bad interference or signal being blocked by big solid walls you might see little of the benefit, put the range potentially doubles when moving from G to N. See http://en.wikipedia.org/wiki/802.11#Protocols for more detail. Of course you would need to both upgrade your access point (by replacing it with a newer model that supports 802.11n and your laptop. You may be able to replace the internal wireless adaptor though this may affect your warranty, I suggest just getting a plug in adaptor (USB, PCMCIA, what-ever your laptop supports) instead.
As taspeotis recommends, improving the quality of your antennas can help quite a bit too in some circumstances.
If you are looking to extend the range in a particular direction and don't mind reducing the range in other directions than moving the access point, or if you can't because it is also your DSL router and needs to be near the inlet getting another AP that can sit further away from the rest of the equipment. Turn off the first one if you do that though, as they will interferer with each other otherwise (unless you can get the both to cooperate in a bridged mode). Sometimes moving the access point just a little can make a surprising amount of difference to reception at certain locations due to different patterns in interfering signals and the locations of signal blocking/reflecting structures in your environment. If you can't move your AP to where you want it due to lack of a convenient power socket, you could get a power-over-ethernet adaptor (see wikipedia for a general discussion, this is one example of a consumer targeted product and there are others on the market) - that way you only need a long network cable not a separate trailing power-line extender too.


How do I read peers.dat file to get a list of all peers seen or that bitcoind has connected to?

Question: In version 0.8.6 of Bitcoin, I see that peers.dat file is a custom database format declared in db.h:317 (class CAddrDB) and defined in dh.cpp:485. Any ideas on how I could go about reading the data from peers.dat with PHP or Python? I'd like to keep track of all peers that the bitcoin daemon sees and connects to.  Or is there a better way?
Answer: The easiest way to get peer information is via the JSON RPC interface has a command getpeerinfo.  Each peer returns a JSON object containing peer IP address info, connection time, version and subversion of the client.
You would probably be interested in this: Bitcoind API
Edit: Although this is not a way to read the database I presume that the data feeding the peers.dat file is pulled from both the IRC channels and the DNS seeds.  If you reported data on those nodes, you could use this data in combination with logs from the debug file to perhaps learn how your node discovered its peers.
Comment: Thanks, but that only lists the 8 peers I'm connected to.  I know that peers.dat contains a lot more data than that because:
1) it's rather large file (almost 1MB)
2) I see messages like the following in the debug.log:
"2013-12-30 03:05:34 Added 1 addresses from xxx.xxx.xxx.xxx: 62 tried, 14738 new"
Comment: "peers.dat is a flat file with a bitcoin-specific file format, unrelated to any database system." https://bitcointalk.org/index.php?topic=119525.msg1287284#msg1287284 looks like unless there's another implementation of it you would have to attempt to rebuild the code in the language you require.
Comment: I also found this: [Bitnodes](https://github.com/ayeowch/bitnodes).  I will investigate his code and learn from it.  Thanks!


Stable coins differences? (USDC - Coinbase / Circle, GUDS - Gemini, TUSD - Trust Token, PAX - PAXFUL, USDT - Tether)

Question: There has been a release of many stables coins recently. What are the differences from each? So far I know that Tether (usdt) is based out of the US banking system and everything else is in the US banking system and regulated. Also I read that the USDC and GUSD has a back door system to freeze and hold accounts if they wanted to. I wasn't sure if PAX had this same thing. What are all the listed pros/cons of each stable coin?
Answer: Indeed, USDC has a backdoor built in to allow for the freezing and/or seizure of funds if it is believed illicit activity is involved. In other words, any address can be blacklisted and funds frozen. Not very stable for a stable coin, right?
Comment: which stablecoin is the most "stable" out of all of them then?


Effect of Hanning Window on phase of FFT

Question: I'm calculating the beat of song through the frequency domain. I have 60 seconds of audio sampled at 48000Hz, multiplied by a Hanning window in the time domain. This gives me a resolution in the frequency domain of 1BPM, and I'm interested in frequencies from ~10 BPM to ~300BPM, which is only the first 300 bins of the 48000*60 bin length FFT. How does the Hanning window affect the phase of the song's beat? Using no window (really a rectangular window) results in a different phase than the Hanning window does.
Comment: Phase on its own is irrelevant. It only makes sense if you were to reconstruct the signal using an inverse transform (you don't), or you were comparing the signal to some other signal. Are you?
Comment: Not really working on this anymore, but I was comparing the phases of multiple audio files and trying to align them. It worked _okay_.
Answer: Recall that windowing in the time domain is the equivalent of convolution in the frequency domain. Multiplying a signal in the time domain with a Hanning window is the equivalent of convolving the frequency domain signal with the kernel [-1 2 -1]/4.
Thus, if $H(f)$ represents the (non-windowed) frequency response, a corresponding windowed frequency response would be:
$$H_w(f) = -0.25H(f-\Delta f) + 0.5H(f) -0.25H(f+\Delta f)$$
where $\Delta f$ is the frequency resolution - else you could write this (with $n$ being a frequency index) as:
$$H_w[n] = -0.25H[n-1] + 0.5H[n] -0.25H[n+1]$$
( windowed frequency response in terms of 'non-windowed' frequency response )
So the phase difference you are looking for is:
delta_phase = angle(Hw(n)) - angle(H(n))
Hope this helps
Answer: It't really more of a question of what the rectangular window is doing to your phase relationships, because it doesn't deemphasize the "edge effects" that occur at the beginning and end of your block of samples, which is the whole point of using a non-rectangular window.
Try this experiment: Do a number of FFTs with lengths ranging from 59*48000 samples to 60*48000 samples, using both window types. You'll find that the Hanning window gives much more consistent results than the rectangular window does. The two results will agree best when the length is close to an integer number of beats.
Comment: In terms of the audio, there's actually very little energy at 2.17 Hz, and the microphone and recording system aren't really designed to capture energy at such low frequencies. Musically, what we think of as "beat" is a pulsation in the overall energy level of the sound, and this is best extracted from the envelope data.
Comment: Thanks. Because changing the length affects the resolution and changes the frequencies, I did a linear interpolation of the phase using the bins just below and above 130 (which is the known BPM for this song), and I got this nice plot of frequency vs phase. With the Hanning window, they all overlap pretty well.
http://puu.sh/6zozE.png
Comment: Just out of curiosity, are you analyzing the audio signal directly, or the *envelope* of the audio signal?
Comment: I'm analyzing it directly. Would finding the envelope and analyzing that give more precise calculations? This is my first time analyzing real audio, but I think it should get rid of most of the high frequency components and leave the range that I'm actually interested in. Is that right?
Comment: Then I'll also try analyzing the envelope, thanks.
Comment: @DaveTweed Agreed. The "envelope" can simply be the rectified signal.


Perlbal For Upload Handling

Question: how and how well does perlbal handle uploads? does it take care of buffering the entire file to disk efficiently, and then pass arguments or headers to the backend describing the file? right now, im using nginx's upload module, but i'd like to use perlbal's X-REPROXY-URL capability to transparently serve files from a cdn.
Answer: Perlbal does have buffering of request bodies, but it doesn't do the high-level request body interpretation that the nginx upload module does. The primary motivation for the buffering in Perlbal is to avoid holding open a backend while a slow client uploads its file. Instead, Perlbal sucks up the entire file and only opens the backend request when the entire file has been received.
It is theoretically possible to make a plugin to do what that nginx module does, but as far as I know no-one has written such a thing yet.
Note that X-Reproxy-URL will redirect the backend connection to another host but the client still remains connected to the frontend Perlbal, so you may lose some of the benefits that a CDN usually provides in this setup, such as routing a client to a host that is close to the client on the network, because it will actually be your Perlbal connecting to the CDN rather than the client.

Perlbal For Upload Handling


What is the bandwidth of product of two signals?

Question: For signal $x(t)$ with bandwidth $B_x$ and signal $y(t)$ with bandwidth $B_y$, what will the bandwidth of the signal $z(t)=x(t)y(t)$ be?
Answer: The bandwidths simply add.
You can break down both signal into their sinusoidal components and pairwise multiply them. For every pair of sines you get the sum and difference frequencies. This is a simple consequence of the multiplication theorems for sine waves. The highest frequency of the product will be the sum of the highest frequencies in the individual signals. This is equivalent to a convolution in the frequency domain.
Comment: I think that the statement "The bandwidths simply add." needs some qualification since it does not necessarily hold for _all_ definitions of bandwidth that engineers might use.  If $B_x$ and $B_y$ are the _supports_ of $X(f)$ and $Y(f)$ respectively, then it is true that the support of $Z(f)$ will be $B_x+B_y$, but (i) support is not the only measure of bandwidth (do $99\%$ containment bandwidths add?), and (ii) in many signal models, the support of $X(f)$ and $Y(f)$ is $(-\infty,\infty)$ and so adding supports is meaningless.
Comment: Isn't multiplication in the time domain means convolution in the frequency domain? So how is it simply adding?


Do employers care about where you did your Bachelor if you have a Master's?

Question: I'm currently doing my Bachelor at EPFL, a top rated university for computer science (top 10-20 worldwide) but also very difficult. I was pondering whether or not I am wasting my time since I am planning on doing a Master's anyways somewhere, I may aswell go to an easier uni for my Bachelor and have more fun since I am young, then do my Master's at a good university. Or do employers care whether or not I completed my computer science bachelor at a top rated university in general?
Comment: "If I take an easier route, will employers respect it as highly?" - think about this. You know the answer :)
Comment: Very related: [Do employers care where you went to school?](https://workplace.stackexchange.com/questions/50356/do-employers-care-where-you-went-to-school)
Comment: Switching universities comes with its own hurdles. Syllabuses, teaching and grading styles can vary and if you switch you may have to expend significant effort adjusting to conventions within the new university. So it might not be a free win.
Comment: This really depends on which country you're in...not every place on earth cares about which university you went, but i would suggest going to a different university for your masters and being more relaxed there.
Comment: The quality of your bachelors absolutely influences the quality of the master's programme you will be able to get into. Secondly you should consider that an optimal route is bachelors, a few year's work, and then masters, if you follow that route you will need a good bachelors. Thirdly, there are a few top schools whose reputation will follow you _the rest of your life_. I don't really know if EPFL is such a school, but if you graduated from somewhere like MIT or Oxford that would still open doors for you decades later.
Comment: I'd consider adding a country tag (for where you're considering employment), but regardless of country, going to a prestigious university will open a lot of doors for you, and depending on the country, will keep a lot of doors from closing. I do know one or two companies that will not even look at a CV if it's not from the right universities (not that I agree with that, but that's reality for you)
Comment: That's up to the individual hiring manager, and many other cultural factors. I personally place very little value on formal education for the roles I hire for (software developers primarily, and related engineering roles), and the only time I care about your education is if I'm hiring for a junior/entry-level role and this is your first job...
Answer: It entirely depends on the employer, many will take notice. More sophisticated employers will definitely include it as part of the data considered when looking for new team members.
You should always choose the more academically rigorous and acclaimed path if you can. Part-time programs could be a good option if you need extra time for things like caring for a family member. Search for scholarships, provided by the school and other institutions to offset the cost. Downgrading your academic experience to have more time for goofing off seems like a bad trade-off over the long term.
Comment: It must be noted that the more work experience you get, the less relevant your academic prestige gets.
Answer: Your undergraduate university and major are good determinants of your first job post graduation. Employers generally have target schools for various reasons - academic rigor, regional affiliations, research collaborations, etc., so you will be exposed to better/different opportunities depending on the school you attend (you can easily research this aspect at your university's career center).
You got into the university because you had the raw intellectual ability to succeed there - working hard (early) will prepare you for your first job and in subtle ways later in your career.
Answer: I think all the other answers make a good point, however it's also worth noting that (most of the time) attending a better/more difficult university will likely also give you a better education. So even if an employer doesn't care at all about where you went, the extra technical knowledge you gain may make a difference.
If the reason the degree is more difficult is because the content is more difficult or there is more content in general. Then I'd say it does make a difference.
Comment: Also, a better bachelor will likely get you in a better Masters program, which will get you into better internships, which makes a huge difference.
Answer: A degree from a highly regarded university like the The Ecole polytechnique fédérale de Lausanne serve a lifelong purpose for you when you want a job.
It gets your job application noticed by human resource people and, to some extent, hiring managers.
It makes you stand out from the pile of applications and gets you the interview. When you go to the interview you can speak for yourself.
It doesn't matter whether it's a bachelor, master's or PhD. It works. If you want a long technical career this will help you.


Why don't airplane turbo piston engines have boost control?

Question: Why is it possible to over-boost piston aircraft engines? All turbo car engines have a wastegate that just vents pressure back to the intake, whereas in an airplane the pilot has to look at the manifold pressure gauge to protect the engine.
Answer: The majority of piston airplane engines are based on very old technology, before computerization was available. The vast majority of airplane piston engines are carbureted with manual mixture control, prop control and turbo control and the pilot has to manage all that plus carb heat manually.
New engine technology has been very slow to come into the piston market because certification costs are so high, and the market is so small. It would cost engine manufacturers millions to develop and certify new turbo-normalizing systems for these old engines and as there are probably only a few thousand turbo-normalized avgas piston airplanes in the world they would never recoup the costs.
There are modernized engines on the market with electronic fuel injection, computerized engine management with turbo-control, and single-level operation. These are slowly making inroads into the market but it's going to take time.
Answer: Some of the early, basic, turbocharged aircraft did have a manual waste gate control. "Turbo-normalizing" was designed to allow turbocharging at altitude and was not to be used a sea level. If not used properly, it would be possible to over boost the engine at low altitude but a "blow off valve" was incorporated to prevent damage to the engine.
N93641, 1973 Bellanca 17-31ATC Super Viking control panel showing manual waste gate control below throttle:
Answer: It is possible to overboost ANY turbocharged or turbo-normalized engine if handled improperly, aviation or otherwise.
Now a dedicated turbocharged engine generally uses an sutomatic waste gate to control the flow of exhaust gases through the turbo, thereby regulating the manifold pressure available to the engine.  They're also a little more ruggedly built that a normally aspirated engine specifically for that purpose.  That being said, they do have their limits and smooth throttle inputs are suggested to minimize the risk of an overboost condition below the turbo's critical altitude.
A lot of normally aspirated engines were turbo-normalized, that is fitted with an aftermarket STC turbo kit (The Bellanca above looks to have been fitted with a Rayjay STC turbo kit).  Older STC kits for turbo normalizing used manual waste gate controls which had to be adjusted manually and we're not cleared for used below 3000-4000 feet to prevent overboost.  Here pilot negligence does present an opportunity for over boosting and damaging the engine through failure to regulate the waste gate and or engage/disengage the turbo at low altitude.  There are s number of aftermarket STC turbo kits such as those made by Tornado Alley which do have automatic waste gates to reduce pilot workload such as those found on the Cirrus SR-22 Turbo and Mooney M20TN.
Answer:
Why it's possible to over-boost piston aircraft engines?

It's not. Unless the system is malfunctioning or not set up properly.

while in the airplane pilot has to look at the manifold pressure gauge
  to protect the engine.

This is simply not true. A pilot only has to look at the gauge to set the manifold pressure to whatever power setting he desires.
The turbo will never over boost. All piston turbo aircraft have had over-boost protection since day one. Most often by waste gate.
They are not controlled by computer. They use pressure controllers that sense manifold pressure and divert oil pressure to supply muscle to open the waste gate.
Comment: PA-44-180T Turbo Seminole has 2 over-boost  indication lamps. If you a low and cold and apply full throttle you will two red lights in the cockpit.
Comment: I'm fairly sure the Cessna T182 has a manual wastegate system and it is possible to overboost the engine. The newer T182T has automated it, though.


What are the teeth of the viperfish composed of?

Question: One of the viperfish's (genus Chauliodus) most unique traits is the transparent, needle-like teeth. Some other abyssopelagic fish (e.g. certain angler fish) have similar teeth. I'm curious as to what these teeth are actually made of. They clearly aren't made of bone, and from what I can tell from various fish skeletons, they decay fairly quickly with the rest of the fish.
Answer: They are not unique
The are made of enamel and dentine just like ours, Even the enamel in human teeth is translucent. Note viper fish are tiny so their teeth are likewise very small, so they can look transparent just by being translucent an small. Hydroxyapatite, the mineral enamel and dentine are made of is translucent. the difference is in the crystal structure,(teeth or often porous which leads to more scattering and less transparency similar to why dry paper is white and wet paper is translucent (also true of teeth)). Impurities or more precisely what else is present in the enamel and dentine are present has an effect as well, as teeth are not just hydroxyapatite.
Source for the composition of teeth.
source for the translucency and microstructure of teeth
Source discussing how translucency changes with mineralization in cow teeth.
Comment: Viperfish are not alone in having transparent teeth is is very common, but something on transparency and crystalography is a good idea.
Comment: This answer would be improved if it contained a citation to anything having to do with the viperfish or a discussion of the translucency of enamel in particular crystal alignments. In other words, I fear that providing a citation implies that the information in the rest of your answer is found in that citation, which it is not.


Finding out my current LDAP server type

Question: How can i find out if my current LDAP sever type is Standalone, Master or Replica (slave)?
I am using OpenLDAP on SLES 11.
Comment: ...by looking at your configuration files?
Answer: In your slapd.conf file, you can check if there is any information about syncprov (thus, your server is a Master), or syncrepl (it would be a slave), which are modules made for replication.
If you're not sure, you can have a look in the current configuration of your server, by binding yourself on cn=config, and searching in the configuration of your "hdb" or "bdb" (or wathever) database if there is one of these two modules loaded.

Finding out my current LDAP server type


How is regression testing tracked as part of a Sprint? Is it a user story or a task?

Question: How is regression testing tracked as part of a Sprint? Is it a user story or a task? We always do regression testing as part of a sprint; however, there is question on whether we track as a task attached to one story in JIRA. Or is this a separate user story in each sprint?
Answer: Each user-story should be deliverable by itself independently, because this way you can deliver customer value even if you didn't fully finish the Sprint. Atleast this should be the goal, a lot of teams use INVEST to safeguard this goal. This should mean any testing is part of user-story, maybe as a sub-tasks, but it should be finished before the story is finished. It should be DoneDone.
This means if you have 5 stories you will do 5 times your regression test in a Sprint. Hence why most Agile teams focus on automating all the regression testing. Now if you would have the regression testing at the end of your Sprint as a single task/story you might not be able to deliver anything or worse take shortcuts on your testing and deliver lower quality in the end.
On Scrumboards (E.g. JIRA) you could also add an extra column named "Testing" and when ever a story end-up here you do the regression testing. Do make sure it has a low WIP-limit. Still I prefer parallel testing and not postponing it till the end of the story and certainly not the Sprint.
Also read:

https://less.works/de/less/technical-excellence/index.html
http://agiletester.ca/agile-testing/
Answer: In my personal opinion, regression testing is a task.

A user story, by definition, is a description of a software feature from an end-user perspective.

Regression testing has nothing to do with end-user.
Having said this, one may argument, from tester point of view, an end-user is a developer or another tester, so it potentially is a user story as well.
Regardless of what it is, the most important aspect is to have everyone within your Agile team to reach an universal agreement whether regression testing is a task or user story and stick with your final decision.
Comment: A task part of the user-story. Sorry, but anyone advocating separate testing activities (tasks or stories) in an Agile way of working is missing the point. Unless the team has learned from experience (long time, months rather than weeks) that this is optimal for their flow and product, but most of the times its just a shortcut leading to unfinished and untested work.
Answer: Regression testing is tracked is one of two ways:

By tracking when feature/bug tickets are done and knowing that each one includes the writing of tests that will then remain as regression tests going forward. I consider this the preferred approach as you get much better tests, they are actually written and context switching is reduced.  I also recommend dev/qe pairing with test design and writing in parallel with application changes.
By setting aside a separate time for regression testing which can be either manual or (ideally) updating automated tests to reflect the change in functionality.
Answer: Regression testing if worked by a single person then, it should be task because as definition, "A story is something that is generally worked on by more than one person, and a task is generally worked on by just one person. A user story is typically functionality that will be visible to end users. ... These tend to be things done by one person." So we can conclude it should be a task.


Priors for log-normal models

Question: I am trying to determine what the most appropriate non-informative priors are for the two parameters of a log-normal distribution (for an accelerated failure time model).  I had been working with a normal prior on the mean of the logged data (or log-normal prior on the median), and an independent normal prior on the  log of the sd of logged data (or log-log normal prior on the dispersion).  It seems to me that the parameterization of the second parameter is quite informative on the natural scale of the parameter but I am pretty new to this. Any ideas on better ways to approach this?
Answer: When I'm trying to be relatively uninformative, I have tended to use a uniform prior on $\ln \sigma$ and specify an upper bound, which corresponds to $p(\sigma) \propto 1/\sigma$ over a finite range—relatively uninformative, and equal to Jeffreys' prior over the range (not equal to what the Jeffreys prior would be if you knew there was an upper bound on $\sigma$ and what it was.)  If the posterior piles up against your upper bound, you can increase it and rerun, unless you have some strong reason for choosing that upper bound.  This was suggested by Andrew Gelman in the Prior distributions for variance parameters paper here.  (Some of the other articles in this issue of Bayesian Analysis are possibly relevant too, hence the link to the journal page.)
However, recently I've tried the beta-prime prior suggested in the first response to
Weakly informative prior distributions for scale parameters and that worked out well for me also.    Importance sampling on the output of the MCMC indicated that the differences between the posteriors of the parameters of interest using the two priors were trivial, which, after all, is what you want when you're trying to be relatively uninformative - and it gets you away from that annoying specification of an upper bound on $\sigma$.
This question and answer may also be relevant:
Random effect on scale parameter
Answer: In the absence of a particular desired form of prior, often people use conjugate priors; the conjugate prior for $\sigma^2$ in the normal would be inverse gamma. You can choose anything from highly uninformative (an improper prior like $1/\sigma^2$ is often used and is a limiting case of the Inverse Gamma), through mildly informative, to a fully informative prior (such as one based on a previous study).
I believe the Jeffreys prior is $1/\sigma^2$. The nice thing about Jeffreys priors is they don't depend on your parameterization (if you transform the parameter, the Jeffreys prior 'follows' it so that everything corresponds).
http://en.wikipedia.org/wiki/Inverse-gamma_distribution
Answer: Jeffreys in his book on probability describes what noninformative priors he would use for scale parameters.  He uses improper priors (i.e. prior density functions that do not have a finite integral).  Here is an amazon link to the book. http://www.amazon.com/Theory-Probability-Classic-Physical-Sciences/dp/0198503687/ref=sr_1_1?s=books&ie=UTF8&qid=1339588187&sr=1-1.

Priors for log-normal models


How can I insert a customized emoticon in SMS? Galaxy S2

Question: Just wondering if is it possible to insert a customized emoticon in SMS.
I get only those :-) default ones. I'd like to use smth like :) or :-x or 8-)
Answer: Depending on the keyboard you are using, the SMS emoticons will show up in the bottom right (where the enter key usually is). If you long press on the key, you will get a pop-up of other emoticons you can use. Using :) is the same as :-) so they wont show that one.
You can send any emoticon you want, but if who you send it to doesn't "change it" to an image, they will only see the normal "8-)" version.
Answer: First go to type a text, then tap the ?123 key then press the 1/3 key twice and you will be shown a page full of emotions.
Alternatively, you can download another SMS app such as Handcent.
Answer: An alternative keyboard like Smart Keyboard has similar support. It also allows a user to customise which smileys are shown and to edit them. A user can also specify whether they prefer an ENTER key or a SMILEY key to be shown. Long-pressing shows a pop-up with smileys.
Note that these are punctuation marks and not images. If the user's SMS app can convert these punctuation marks into graphical image smileys, then the recipient will see those, else he/she'll see the text characters.
Answer: You could use GO Keyboard app, instead of the stock keypad. It has an advanced setting which allows you to pick from the following styles:
:)
:-)
:^)
:o)
GO SMS Pro app is even better. It lets you display emoticons as cute images, but it's good only if the other user also has GO SMS Pro.


Really Bad posture now hurting me whats the best solution?

Question: Hi i am 17 year old and have been using computers since age of 11. I had bit lower back pains but never bothered to inquire about it. I have sat most of my life and now i am 17 since 2 years my back strength is too weak i cant even stand erected for long time i have to lie down or sit. My weight has also increased and problems have become worse. Daily in morning my shoulder neck and back is paining at least for fifteen minutes and my chest feels short of breath. My posture has become very odd (I have added pictures). This is indirectly affecting my work and studies a lot my self confidence has also decreased. I need proper guidance for improving my posture and strengthening my back. Thanks for help in advance. I really appreciate everyone's help.
Comment: Also see https://fitness.stackexchange.com/questions/6994/i-have-extremely-bad-posture-what-can-i-do/7015#7015
Answer: We can't provide a full life-routine for you to follow, as we'd need to diagnose a lot more than what we can see in the picture, and the paragraph you wrote. But I'll touch on the most immediate pitfall I see, and provide some further learning resources.
After that, it's up to you to seek out a qualified physician, or a physical therapist to help you.
The anterior pelvic tilt
When we sit a lot - and I mean a LOT - our hip flexors will do what's called "adaptive shortening". Essentially, they realize that in the seated posture, they don't have much room, and they get sort of squished together, and the react by making themselves shorter to avoid the tension.
This causes the anterior pelvic tilt, where the front of your pelvis is pulled down, which pushes your rear upward. This, in turn, can very quickly cause lower back pain because it's like a big pinch.
More info and guidance:

https://www.youtube.com/watch?v=K-CrEi0ymMg
https://www.youtube.com/watch?v=u1sfPfsESDQ

Note: The guy in this video is very well educated in anatomy, physical therapy and personal training, and in this way he separates himself from most of the fitness gurus of YouTube. In fact, I advise you to scroll though his entire library, and watch any video that applies to you.
Answer: As Alec mentioned, it's anterior pelvic tilt and it's a common result of our sit-on-butt lifestyle. It takes a long time to develop, and it will take a long time to resolve fully. Some general notes I would make:

Don't just start "lifting weights", follow a proper strength training program.
Don't fall victim to the "1 & 23 problem" whereby you spend one hour a day exercising and the rest sitting down or laying down.

You need to build strength (via a proper program) and change your lifestyle. Instead of sitting down, get a stand up desk. Go walking for lunch, ride your bike or walk to something instead of driving, and basically try to get out of the seated position as often as you can.
Your body will adapt to whatever you throw at it. Start providing it stimulus it needs in order to get stronger and healthier.


How did the lighter elements end up in the center of the solar system? Solar System Formation

Question: The previous generation of stars famously are the origin of all the heavier elements (up until iron?) in the solar system. So a big portion of the solar system mass actually is made up of Carbon, Silicon, Iron and the like because of that. But in the center, and only in the center, there is a star with presumably almost no heavy elements inside. How can that be? Am I wrong about the actual mass concentrations or is there really an imbalance, i.e. is the element distribution really lighter towards the center of the solar system? I would presume that the previous generation of stars just ended in a more or less uniform cloud of debris, from which the solar system formed. But if so, why aren't there star systems where the star has a very different composition and is kind of a spluttering, dirty fusion machine (metaphorically, I mean)?
Answer: The solar system contains very little of elements heavier than Helium - less than 2% by mass.
This is reflected in the chemical abundances measured in the photosphere of the Sun. i.e. The Sun does contain heavier elements.
Your question is the wrong way around; it is not that the heavier elements have not sunk into the middle, it is that the vast majority of hydrogen and helium that was in the same place as the planets when they formed, did not end up as part of the planets. In fact, even this is only partially true. The mass of planetary material in the solar system is also dominated by the hydrogen and helium in the gas giants.
So the conundrum is only why the smaller planets don't have a similar composition to the Sun. The answer to that is temperature and gravity. A small, hot planet just doesn't have the gravity to retain fast moving hydrogen and helium atoms, unless they are trapped in some compound (like water!).
Thus, the small planets close to the Sun are depleted of light elements.
Comment: @lthz - Another way to look at it: The vast majority of the hydrogen in the  universe has never been in a star. See [What percentage of the hydrogen today has never been in a star](https://astronomy.stackexchange.com/questions/19385).
Comment: @lthz Yes, that is certainly true, but more importantly, the debris from those stars is mixed with a much greater quantity of material that has never been part of a star.
Comment: Oh I see, thanks! So does that effectively mean that really only a slight portion of matter was fused in the early stars before they became unstable?
Answer: Toward the end of a stars lifecycle the star looses the ability to continue using hydrogen ect). To power itself, it begins to, (in a desperate attempt to live.) Create heavier elements such as iron. Now iron can't certainly not sustain a star.
As such the iron destroys the star, thus marking the end of its life cycle.
Small amounts of iron probably exist in stars, (from the universes point of view.) But it's not enough to actually effect the star it's in.
Iron is of course not the only things starsform that ultimately kill the star, I'm just using it as an example here.
None the less stars are quite interesting, just as anything else in space.
P.S. This is just my vary basic understanding of space, and I'm learning a lot on this website.
Have a nice day/night.
Comment: I understand your enthusiasm but it really doesn't add anything relevant.
Comment: This doesn't really address the OP's question, which is about the spatial distribution of heavy elements.
Comment: Welcome to StackExchange. In answers, we're generally looking for more complete answers informed by a deeper understanding of the subject matter. If you're not familiar with this field but you still want to contribute, you might have better luck asking questions about things you find hard to grasp as you learn. You can also contribute to other Stack Exchange sites when you *are* familiar enough with the subject matter to provide an in depth answer. Good luck.


Where to change GRASS GIS wxGUI language?

Question: I use GRASS 6.4.2 on Russian version of Windows 7 x64. As I start wxGUI it is shown in Russian. But I don't like its translation and want to work with English interface. I have no clues how to solve it.
Answer: We have recently added a language selector in the graphical interface. This is
currently under testing in GRASS 6.4.3.
For now, you can upgrade to GRASS 6.4.3svn but installing this version:
http://wingrass.fsv.cvut.cz/grass64/
In the wxGUI:
Settings --> Preferences --> Appearance --> Language Settings
It should solve your problem.
Comment: Just FYI: there are still some issues which we probably solved a few hours ago :) So all should be then available in the upcoming GRASS GIS 6.4.3.


Are there any DNA viruses with junk DNA in them?

Question: I know mimiviruses and pandoraviruses have orphan DNA - DNA that is not found in other species - but this is DNA that codes for proteins. I am not able to find out if they contain junk DNA. By junk I mean DNA that does not have ANY function at all. Sort of like the junk DNA in the human genome put there by retroviruses, DNA that just sits there, doing nothing, just going along for the ride.
Comment: The terms junk DNA and non-coding DNA mean very different things. Non-coding DNA would include the part of a promoter that binds RNA polymerase but is not transcribed and other similar and regulatory regions that bind proteins (and also strictly speaking the parts of a gene that encode the untranslated regions of a mRNA transcript). Junk DNA can be taken to mean functionless DNA, although that begs the question whether it is DNA that has a function that has not been elucidated. Could you please clarify what you mean and amend your title accordingly.
Comment: To help get an answer to the "junk" part of your question, you might be interested in a similar question I asked about parasitic code in viruses: https://biology.stackexchange.com/questions/92829/do-any-known-viruses-contain-junk-or-parasitic-genomic-information
Comment: I should have been clearer. By junk DNA I mean functionless DNA that is known to do nothing. Not promoter regions or regulatory sequences. On a related note, are there retroviruses that infect other virues - that insert their own code in the code of a bigger virus? If so, can some of this code get deactivated or mutated over time to become functionless?
Comment: Best not to use the word code for genomic DNA. First because of the confusion with the genetic code, which is a cypher; second because you're interested in non-coding DNA. How can you envisage a virus infecting a virus? Think about the nature of viruses. And if you include transposons as junk DNA you are stretching things as they encode the ability to transpose themselves.
Answer: Viruses typically don't have junk DNA-so to speak because of their tiny size. When the particles (of virus) are so small, there really isn't any space for "junk" or extra DNA.
That being said, while viral DNA replication, there may be some errors that may make the virus DNA unable to code for proteins or "junk". While this is an interesting proposition, the mutations that occur in almost cases do not make non functional proteins but mutated proteins which make the viruses more virulent (more true in case of RNA viruses...which mutate a lot faster).
Regarding virus infecting virus, putting its own code it "kind of happens" but not as you would expect. I am listing 2 such examples here-

There are some viruses called satellite viruses and viroids which depend on "donor" larger viruses for some of the proteins they need for replication. This means a satellite virus can survive in a host only if the donor virus is present.

In animals like pigs, when different strains of Influenza virus infect together, while virus assembly genetic material (RNA) of one strain can enter into the other....creating completely novel strain.

Hope that answers your question. Please feel free to ask for clarification. Thank you and have a nice day.


Why isn't the Eucharist of protestant churches considered valid by non-protestants?

Question: The Catholicism and Orthodox churches do not recognize the Eucharist of protestant churches. Why not?
Comment: Many Protestant churches reject transubstantiation of Christ at the Eucharist and may disfavor the priest's role in the sacrament.
Comment: Welcome to the site. This is good question. I edited it for grammar.
Comment: possible duplicate of [On what grounds does the Catholic church reject sacraments of protestant denominations?](http://christianity.stackexchange.com/questions/5116/on-what-grounds-does-the-catholic-church-reject-sacraments-of-protestant-denomin)
Answer: As far as both Catholics and Orthodox are concerned, you need a validly ordained priest to confect the Eucharist.(see e.g. CCC, ¶1411) As far as they are concerned, none of the churches that originate from the Reformation period have what is required for a valid priesthood (i.e. bishops in unbroken tactile succession from the Apostles(see CCC, ¶1576)), so the Eucharist cannot be validly celebrated by these churches.
This may look uncharitable on the surface. In reality, the Catholics and Orthodox could not accept the validity of Protestant Eucharists without significantly altering their own doctrine.

On another related point, it's worth noting that Catholics and Orthodox do not even properly consider the Protestant churches "Churches" in the proper sense: they are referred to technically as "ecclesial communities" precisely because they have not preserved the sacramental priesthood and therefore the Eucharist:

According to Catholic doctrine, these Communities do not enjoy apostolic succession in the sacrament of Orders, and are, therefore, deprived of a constitutive element of the Church. These ecclesial Communities which, specifically because of the absence of the sacramental priesthood, have not preserved the genuine and integral substance of the Eucharistic Mystery cannot, according to Catholic doctrine, be called "Churches" in the proper sense. Responses to some questions regarding certain aspects of the doctrine of the Church)
Comment: @Flimzy References have indeed been added.
Comment: @nick012000 Yes to an extent, but that's not the question here.
Comment: With the exception of some groups (like the Anglican communion), the problem is further that even if they had a valid priesthood, their conception of communion is incompatibly different.
Comment: This is a good answer, but would be improved with references, if possible.
Comment: Protestants would argue that they have maintained the priestly succession, because in their view, *all* Christians are priests, which is why they call their church leaders things like "pastors" or "ministers" instead.
Comment: @eques That's a distinct (though clearly related) issue.
Comment: It's distinct, but a complete answer on this question should address both facets
Comment: @eques Well, go ahead and write one, then. But I disagree with the idea that Protestant theologies of the Eucharist are relevant to the question of validity.
Comment: It certainly is though. It's in the two paragraphs of the CCC before the one you cited. If you have a different conception of what the Eucharist is, of course the Catholic Church won't recognize it as valid.
Comment: @eques As I say, do write an answer if you think it's relevant. As it happens, I disagree, on the grounds of *ex opere operato*; it certainly isn't a question with a clear answer.
Comment: Let us [continue this discussion in chat](https://chat.stackexchange.com/rooms/112632/discussion-between-eques-and-lonesomeday).
Answer: It's clearly because Catholics believe that the bread and wine are the physical Body and Blood of Christ. Protestants do not. So, therefore, it's a fundamentally different ritual in Protestant churches.
The 1896 Papal Bull declaring all Anglican denominations to be "null and void" was after hundreds and hundreds of years of disagreement on the fundamental nature of the eucharist. I am of the opinion, as an Anglican, that it is merely symbolic and demonstrates our devotion to Christ to do exactly as he said to do when we remember him, for thousands of years.
That's why. Personally, I think it's best not to raise the issue with Catholics. It's not a salvation-killer (is there such a thing, ah a topic for another thread) or anything, after all.
Comment: This is better than your last post I commented on. And it is correct too. I'm glad to see you are showing an interest in the site.
Comment: It's worth pointing out that the situation with Anglicans is complex, much more so than with, say, Presbyterians. Plenty of Anglicans have Catholic beliefs about the Eucharist, and many would not consider themselves Protestant.
Comment: @lonesomeday Yes, if I recall correctly, an Anglican may choose to accept or reject transubstantiation, where a Catholic must accept it as a central doctrine.
Comment: "It's clearly because Catholics believe that the bread and wine are the physical Boyd and Blood of Christ." Some protestant churches hold this view, too, so that's clearly not the answer. Even if that were the answer, it's not at all *clear* that it is--please provide references.
Answer: The question of validity turns on the view of the Eucharist at Mass.  For Catholics, they understand the Eucharist to be an actual sacrifice.  And to have an actual sacrifice, one needs a sacrifice at an altar with a duly ordained priest.  So yes, "valid" requires a priest, but the whole point is their view that the wine/bread changing into blood/body is to sacrifice it.

As the Second Vatican Council says: "That more perfect form of participation in the Mass whereby the faithful, after the priest's communion, receive the Lord's Body from the same sacrifice, is warmly recommended."
CCC 1388

For Protestants, they do not view the wine/bread at communion as a sacrifice.  They believe Christ offered Himself once for our sins.

[The high priest Jesus Chrst] [w]ho needeth not daily, as those high priests, to offer up sacrifice, first for his own sins, and then for the people's: for this he did once, when he offered up himself.
Heb 7:27

Nor yet that he [Christ Jesus] should offer himself often, as the high priest entereth into the holy place every year with blood of others; For then must he often have suffered since the foundation of the world: but now once in the end of the world hath he appeared to put away sin by the sacrifice of himself.
Heb 9:25-26

Note that Christ offered Himself, as against those priests who offer blood of others.  Christ no longer suffers.
So, while the answers mention the idea of a so-called "bloodline" of duly consecrated bishops and priests traceable back to apostles, the point of that "bloodline" was not mentioned.  The Catholic Church believes their Mass is a sacrifice that requires a valid priest, while Protestants believe in Christ's sacrifice done once and offered solely by Himself.
Answer: In 1896, Pope Leo XIII issued a papal bull Apostolicae Curae declaring all Anglican ordinations to be "absolutely null and utterly void".  This is because of they changed the form of ordination rites in such a way as to render them invalid.  This means the Anglicans don't have valid orders and therefore they cannot confect the Eucharist.  Changes to the rites of ordination did not occur during the Great Western Schism.
Comment: @thedarkwanderer Ok. My point is that Leo XIII's bull is of dubious relevance here.
Comment: Unfortunately, while this is true of Anglicans of the 19th century, it is not true of Anglicans today. A number of schismatics from the Netherlands (including validly ordained bishops) joined the Anglican Church and they *did* have valid orders. Right now their orders' validity is as clear as paste.
Comment: Except the Catholic Church's position has not effectively altered on that point -- clerics received into communion (via the Pastoral Provision) who were formerly Anglican are ordained absolutely not conditionally.
Answer: There are two related aspects

Lack of valid priesthood (also indicated in @lonesomeday's answer). "Only validly ordained priests can preside at the Eucharist and consecrate the bread and the wine so that they become the Body and Blood of the Lord." Catechism of the Catholic Church #1411. The Fourth Lateran Council in 1215 declared "Indeed no one can perform this sacrament except the priest duly ordained" (DH 802 cited in Ludwig Ott's Fundamentals of Catholic Dogma, p 422)

Difference in concept (As outlined in @Ztucker's answer) The question uses the term Eucharist, but that is not broadly used by Protestant Churches. Catholics (and Orthodox) believe the Eucharist to be the Body and Blood of Christ really and substantially present. "That in this sacrament are the true Body of Christ and his true Blood is something that 'cannot be apprehended by the senses,' says St. Thomas, quoted in Catechism of the Catholic Church #1381. In contrast, Protestants either believe it to be purely symbolic or possibly a consubstantial presence, but certainly not a sacrifice.

Both of these concepts must be understood for a complete answer. In contrast to the claim of "ex opere operato" (from the work having been worked), the lack of priesthood alone is not sufficient. If a validly ordained Catholic priest went and celebrated a Protestant communion service (e.g. a Lutheran one), no valid Eucharist would result due to a defect in the required form, matter and intention. For a valid Eucharist to occur, the correct matter (unleavened wheat bread and grape wine without additives) must be used, the correct form (specifics words used in consecration) and the correct intention (at least to do what the Catholic Church intends, but more specifically to turn the bread and wine into the Body and Blood of Christ and offer it). The principle of "ex opere operato" means that the spiritual result of the act depend not on the individual holiness of the minister or recipient but depend on the act itself (the opposite is "ex opere operantis" -- from the work of the one doing the work").


Undo accepting the answer

Question: When I accept someone's answer to my questio, then this user gets +15 reputation while I get +2 reputation. What will happen if I undo my decision? And what if I further acept somebody's else answer? I'm asking here while I don't want to make experiments.
Answer: Here is a comprehensive description of actions which lead to reputation change, and by how much: https://meta.stackoverflow.com/questions/269653/why-did-i-gain-lose-reputation-can-i-audit-my-reputation-history
So: when you unaccept an answer, you get -2 and the answerer gets -15. In other words, you reverse what happened when you accepted. Same deal if you then accept someone else's: you get +2 and that answerer gets +15.
Comment: I just had an "interesting" experience - my answer was unaccepted, and the poster accepted his own answer, a relatively minor variation of my answer. :-/ I feel it's borderline behaviour, especially as I recalled how poster nagged me for details...

Undo accepting the answer


Where do I find data to start a graph data structure to practice on?

Question: I am interested in learning firsthand about graph data structures but have no data to put into the database. Can anyone recommend a source for a beginner to find graph data? (Preferably a source that has nothing to do with Facebook.)
Answer: When I was in the same position as you, I was very happy to find Knuth's Stanford Graphbase (SGB). He supplies not only a library for working with graphs, but also some data sets to play with. My favorite one was the 5-letter English words dataset. You can use your programming language of choice to generate an undirected graph where two words are neighbors if and only if they differ by exactly one letter. So, for example, "bread" and "broad" are neighbors, but not "bread" and "bleak".
As proposed in the book/documentation (you can buy a printed copy on Amazon, it's quite interesting), you can then play games like "Word Ladders", where players try to find the shortest path between words. Implementing these games will give you an excuse to experiment with shortest-path algorithms, breadth-first searches, etc. Knuth actually provides an implementation of such a game (using his library) in the file ladders.w in the SGB tarball.
There is another data set provided on the SGB webpage: a graph with the adjacencies between the contiguous United States and DC. I cannot include the hyperlink because I'm new to this site.
Note: the library was written using CWEB, a tool for literate programming (again, cannot include link, so google it). If you want to actually use the SGB library, you will need to install CWEB; if you want the documentation, you will need CWEB and TeX.
Comment: You should be more precise then about what you want in your question.
Comment: I have taken a data structures course so am somewhat familiar with the basic concepts, like Dijkstra's shortest path,linked-lists,sorting algorithms etc. I'm now looking into the site, although I have to admit I am looking for data more along the lines of bus routes, financial stuff, anonomized consumer data etc. Something a little more exciting where a cool statistic or tendency might emerge.
Answer: Try the boost graph library, it's extensively documented and, it is used by CGAL, which is a computational geometry library, which allows for graph visualization (e.g. 2D Segment Delaunay graph or 2D Apollonius Graphs visualisation). If you want to visualize your graphs, CGAL might be a good thing to try. It works with OFF file format, but you can convert it to STL or something else using meshconv.
Answer: The data for Algorithms by Sedgewick and Wayne is available at http://introcs.cs.princeton.edu/java/data/.


How to prove closure property of regular languages using regular expressions?

Question: I know that we can prove closure of two regular languages under operations like union, intersection, concatenation etc. by constructing NFAs for them but how to do the same thing using regular expressions, specifically proving that reversal of a regular language is closed using regular expression?
Comment: By far the easiest way to show that regular expressions are closed under reversal is to convert to an NFA, reverse that and convert back, which is exactly what you don't want to do. Although it's surely possible to prove that regular expressions are closed under reversal without going via automata, I suspect it would be sufficiently horrible and unenlightening that there'd be no reason to ever do it.
Comment: @david-richerby I strongly disagree with your first comment. If you convert your "easiest way" to an algorithm, its complexity will be much worse than with the algorithm given by Vor.
Comment: Sure. It's a perfectly reasonable question.
Answer: You can prove it using this approach:
if $E$ is a regular expression then you can recursively define its reverse in this way:

if $E = \emptyset$ then $E^R = \emptyset$
if $E= (E_1)$ then $E^R = (E^R_1)$
if $E = a \in \Sigma$ then $E^R = a$
if $E = E_1 \cdot E_2$ then $E^R = E^R_2 \cdot E^R_1$
if $E = E_1 \cup E_2$ then $E^R = E^R_1 \cup E^R_2$
if $E = E_1^*$ then $E^R = E^{R\,*}_1$

You can prove that each "step" is correct and after a finite amount of transformations the procedure ends. At the end you get a regular expression (recursively built from $E$) that defines $E^R$.
Comment: Since $\cup$ is also commutative you have now shown that the reverse of a language given by a regular expression is represented by the mirror image of the original expression! (Well, assuming you view the expression as a tree with operators in the nodes.)
Comment: This proof method is called *structural induction*.
Comment: Its much more abstract view please give me some detail.
Comment: @Rouftantical: very informally: you can define the reverse of a regular expression $E$ (that represents a regular language $L_E$)  using another regular expression $E^R$ which is built recursively (that represents a regular language $L_{E_R}$); for all strings $w$, $w \in L_E$ if and only if $w^R \in L_{E^R}$.
Comment: @HendrikJan: Yes, you're right!


how to test facebook app for different scenarios

Question: how to test a facebook app for different use cases. i will take a simple example here:
assuming i have a facebook app which just does the login to a site.
now, how do i handle/ test different use cases in this:
1) user is already connected to the site and logging in again using her facebook account
2) user is a first time user and want to login to my site through his facebook credential and she a) allows the app to access her details b) deny the app to access her details
these are the very basic test cases but there could be more depending upon what exactly what we want to do with that app and the site.
so my question is how does one test all these scenarios ? if i use my facebook account once then it doesn't allow me to test the other scenario (like if i once allow an app then it doesn't allow me to test the 'deny' scenario)
thanks in advance
dev
Answer:
You can use test users for manual or automated testing.


What is this humanoid moose monster?

Question: I am trying to recall the name of a creature I saw in an early d&d game, certain it was before 2e, but don't recall if it was in a core book or an adventure, or other supplement.
It was a humanoid with a mooselike head (snout, antlers). It had a spit attack (acid or poison I think), and possibly some charm type ability.
I've looked at creature lists and some core books (Rules Cyclopedia, monstrous compendium), but haven't found it.  It had a stat block page with a black and white picture of the head I think.
Comment: I love the fact that there are so many different moose monsters in D&D that it's hard to work out which one you're looking for.
Answer: Thanks to the other answers, I figured out the creature. It was an actaeon, a defender of woodland creatures from Mystara campaign setting.  I misremembered its breath weapon: instead of acid, its breath weapon polymorphs foes into forest creatures.
Answer: Reindeer head instead of moose, but maybe a Shatjan?

It has an ice-based breath weapon instead of acid, but no charm. This specific printing is from The Horde, a FR splat-book from 1990 (2e), but there may be earlier iterations I'm not familiar with.
Answer: The only thing I could find that matches your description (in part) is a Wendigo.
These often are presented as a humanoid body with either Elk horns, or an Elk head & horns (or moose), but not always. The only stats I could find were from Pathfinder, and did not involve a spit attack from what I could see.
It was also in Fiend Folio for 3e but I found no stats (I do not have access to this book).
Although both of these are later than you recall seeing them, the Wendigo is from Native American mythology so it is not unlikely that it was included in some past editions. Though I can find no proof of this.
Comment: Some brief research indicates that the wendigo wasn't published in the AD&D era in hardcover, but it was published at least twice in *Dragon* Magazine. However, neither are moose- or elk-like. The March 1987 (page 51) wendigo is just a human who has tasted too much human flesh, and looks like a savage human. The Oct 1988 (page 32) Wendigo is described as a Unique being, and *"Everyone who sees Wendigo sees him differently, since Wendigo's form reflects a person's deepest fears."* Notably, most First Nations traditions say wendigo are spirits or look human, so that might just be Pathfinder.
Comment: True, which is why I mentioned that was the only place I founds stats. However the Wendigo is from Native American culture and may have appeared in earlier editions (It was in 3e for instance). I will adjust my answer
Comment: Pathfinder is seriously post 3.5 E, he did encounter the monster far before 3.5 was a dream in the head of its makers.
Answer: Could you be thinking of the Peryton? That has the form of a large bird of prey, with the head and antlers of a stag. Their shadow is that of a humanoid, which could cause confusion. However, the version in the AD&D1e Monster Manual does not have a spit attack.

What is this humanoid moose monster?


A problem about functions

Question: $f(x)$ is continuous on interval [1,2], and its derivative exist on [1,2], and we have $f(1)=f(2)=0$. Prove there exists at least one point $a, a \in  [1,2] $ such that
${f(a) \over a}=2007f^{'}(a)$.
Answer: Given the conditions, and $h(x)$ a continuous function
then you can find $\xi$, such that
$h(\xi)f(\xi)=f'(\xi)$
define then $g(x)=e^{-\int h(x)\mathrm{d}x}f(x)$ and because $f$ is zero
at $1,2$ so is $g$ so you can apply rolle's theorem.
So given similar condition is if you can convert your equation in the
previous form you can apply rolle's theorem. In the specific case $h(x)=\frac{1}{2007x}$
Answer: Define $g(x)=x^{-1/2007}f(x)$ on $[1,2]$ and apply Rolle's theorem to $g$.

A problem about functions


Should we keep the question about GLBSE protected?

Question: The recent question about the GLBSE closing down was protected by me. However, some believe the protection was unwarranted. Should we keep this question protected?
Answer: I think protection is warranted to prevent significant abuse/misuse. While I don't know which number counts as "significant", I think we're just not there yet.
Just downvote + comment any inappropriate answer.
Comment: I would tend to agree that we're not at an abusive point just yet, but rest assured the mods will be keeping a close eye on this question. The moment we're spending too much time moderating one question it will get protected :)
Answer: I believe this question should be protected. For not we have 3 answers with reputation 1 - one is just a random comment, one is making claims without giving sources, and one being balanced, but a bit uninformative. I'd rather avoid the mess of the first two types of answers by keeping the question protected.


Please identify this vintage bike - peculiar frame

Question: Helping out a friend to identify this bike, it's got quite an interesting frame and is located northern nsw, Australia. Haven't been able to see a name or printing on it. It has 3 blue stars down the front under the Handle bars. If anyone knows or has seen a bike like this, am keen to work out it origins. Thanks
Comment: I can't say that I've ever seen anything like it.  Unfortunately missing detail, but appears to be a pretty old bike (40-50 years old) with a standard (for the time) coaster brake.  There likely is a brand name ("Bendix", "New Departure", et al) stamped on the brake arm (coming off the rear axle and bolted to the chain stay).  This brand might give some hint as to the bike's ancestry.
Comment: Australian stuff tends to be a lot more regionalised than other markets.  Malvern, Malvern Star, and Southern Star are common Aussie bike brands.
Comment: Beautiful frame! You are sure to get looks on the street if you end up restoring it.
Answer: The three stars are the logo for "Malvern Star" which is an Australian brand that has been operating since 1902.
https://en.wikipedia.org/wiki/Malvern_Star
http://www.malvernstar.com.au/


Is there a way to add variants to a mini panel?

Question: I am trying to organize my content as follows, but I am not certain if it is proper to use variants (if there are variants for mini panels) this way.  Suppose I have a page A.  I would like to easily re-use A as a block in other pages, say as a block with a portion of the content of A and a read more link and placed in a sidebar of the front page.  Note that I want to do this for a few hand-selected pages, and I hope these blocks can be moved around easily like panes.  So I was thinking if I can do the content of A in a mini-panel A', and use A' in both A and the front page.  But that way I must have two ways to render the mini-panel A'.  So how do I add variants to A'?
Comment: How are you create the page in the first place? Is it a panel page a view page or simply a node?
Comment: They will be panel pages, and the site uses panels a lot, so I tend to look for a panels-solution.
Answer: Minipanels don't support variants, however, you can achieve a similar result by adding visibility rules to show/hide minipanel panes on certain pages, according to specified conditions.
Though more simple options are possible, an example using PHP for a visibility check is here


Working on files in the cloud

Question: Files I wrote on my desktop using 12.04 with Libreoffice and saved in Word format are in my Ubuntu One folder. I thought I could edit them away from home, as I do on Sky Drive. But when I opened one it only downloaded it to my laptop (which is using 11.10 and Abiword). Do I have to edit the file and then upload it back to the cloud? Will it then replace the original?
Answer: Short answer: Yes, no and yes.
Slightly longer: Ubuntu One provides only a storage cloud, no editing tools.
I just realized that you probably didn't add your notebook as a device to UbuntuOne and so no automatical syncing will take place at all. So that would need to be done first.
Then if you edit the file on your notebook and save it it should get automatically synced back to UbuntuOne and then to your other system. (This doesn't apply for a smartphone, UbuntuOne Files for Android provide only downloading the files).

Working on files in the cloud


Creation vs Evolution

Question: Are the belief in creation and the theory of evolution mutually exclusive? Does holding of one necessarily mean not holding the other? If not please share some examples.
Comment: The problem is that the 'duplicate' question has been frozen because it was not a question fit for this site. So, if this question is a duplicate then it must also be a unsuitable question and must be closed on that basis. If it is suitable it is not a duplicate.
Answer: Not necessarily. There are christians on all parts of the spectrum. I see them as 2 main camps.
#1 mutation/natural selection exists but only to a point
There are many christians that will accept parts of the constructs of evolution such as natural selection via environmental pressure and/or artificial selection but quote the scripture "God made the beasts of the earth after their kind" to illustrate that one species can never turn into another. They say a dog will always be a dog no matter how much you breed it to have long hair or a squashed nose. The don't believe that new information or bio-mechanical function can arise from random mutations like gene repetition/deletion, copy errors, etc. They point out that creatures like dogs that are bred down certain paths have always lost information not gained. Now this group of Christians can either believe in an ancient universe or a 6-10k year one but all will state that life is about 6-10k years old. They also like to point out that that there as been no documented examples yet of NEW function arising from selection pressure.
#2 Everything happened according to science but God started/nurtured it
This is a belief held by many modern Christians. It combines predestination in varying degrees as a lens to view reality. The most 'hands-off' interpretation says that God stacked the deck a certain way (the weightings of various physical laws, vacuum energy etc) before he exploded the gigantic soup of particles and started off the universe down the track of star and then planet formation and eventually life. The other end of the predestination spectrum is that you and I were conceived of before the Word spoke the universe into existence. Every facet of chemical reactions, evolution, mutation was planned so as to produce you and everyone else so as to participate in eternity with our Creator.

Creation vs Evolution


How to have iTerm2 hotkey window slide up and down instead of fading

Question: I'm using iTerm2, and my hotkey window used to slide down and then back up. A while ago, the animation changed to having it fade in and out. Is there any way to get it to go back to sliding? I prefer that animation.
Comment: damn only three votes! my life depends on this!!!
Answer: Sorry, I had to take that out because it didn't work well on Mac OS 10.10. It is generally unhappy about windows being outside the bounds of the screen and it led to some ugly problems.
Comment: Is this still an issue with Mac OS 10.14? It appears to default to fading in, but sliding off screen when dismissed.
Comment: The logic was revamped in 3.1. It fades if the offscreen frame would intersect a different display, or if the window is not attached to an edge of the screen (e.g., a normal window or a full-screen window, but not a top-of-screen window)


How to point out the real answer when another was selected by the question's author?

Question: I have created a question on how to have "synonyms" context menu in Libreoffice Writer. I was concerned mostly by British English so, a comment to this question was the correct answer. But in fact that answer already existed to a similar question specifically asking about English UK (here). Only that it was not the answer that was selected as definitive in that case, while the one selected doesn't in fact work (anymore). How to confirm and highlight what the correct answer is?
Comment: Just went though and did a bit of...cleanup. Cheers!
Comment: @Marco Ceppi: In cleaned up question I was asking about different languages, not just about British. Also, the case of synonyms for British involved a bug, and I guess that is a separate question/answer. I still need a general as well as detailed answer to the question: "how to have synonyms for different languages" - that is: French, German, Romanian, Spanish etc. For some languages the option is there just by adding languages in "Language Support", for others like French, you need a separate extension, for others this is not available either. But now that question is closed. I don't get it.
Comment: @Marco Ceppi: it is pretty clear to me that if two questions have a common answer, it doesn't mean that this answer is the definitive or the complete one for both, so it doesn't mean that the two questions are clones. The more particular one (related just to UK English) may become redundant if the more general one  gets a very detailed answer that would include UK English, but that is hardly a reason to close the one that is the most inclusive and possibly most useful. i was still expecting new answer there: what to do? create new questions on separate languages??
Comment: @Marco Ceppi: in this sense that  question should be closed but for a different reason: http://meta.askubuntu.com/q/5467/47206
Answer: The best thing you can do is leave a comment on the incorrect answer indicating that it no longer works and vote up the correct answer. You could also leave a comment on the question for the OP - and he can verify that the new answer works and mark it as accepted if he is still around.
Comment: what about editing the answer, to add that info, instead of just a comment - when one has the privilege?
Answer: Since the existing answer is just a link to another post that then links to some blog that is out of date, it's clearly incorrect.
As George indicates, a courtesy comment is nice, but at the end of the day if it's wrong, vote accordingly and the author will either fix it, or delete it.
Personally, I think the accepted answer is not that good even when it was correct. As for your original question we should mark that as a duplicate of the original and then just concentrate on making sure the correct content floats to the top.
Comment: maybe my question that relates to any different language is not a duplicate to the one that only asks for British synonyms. i just added an answer to mine regarding French and expect new answers for other languages


What to expect when tearing up carpet?

Question: What should I expect when I tear up carpet? My brother's dogs have stained my carpets with their pee and poop, he also has tracked in grease from his work boots and stained it with tattoo ink. I want to tear up my carpet and do something different on the floor. Was thinking just painting and sealing the concrete and put down some throw rugs. What's easiest for someone who doesn't have a lot of experience in this type of thing?
Comment: The first thing I wold recommend is to make sure you are wearing a good charcoal filter respirator (not just a dust mask).  That stuff is going to STINK when you start tearing it up.
Comment: When I helped remove the carpet in my apartment, they had used tack strips not carpet glue, I found dirt composed of decomposed carpet mixed with dust.
Answer: expect stains, smells, and possibly mastic/glue.
If you're looking for an 'industrial loft' feel, clean it up the best you can and then just cover it with some high-end concrete/floor paint...or epoxy. It'll be rough, but practical.
For a more finished looked, hire someone with a concrete grinder to grind off the bad top layer of glue, dog pee and what-have you. Come back and then apply an acid stain to the entire thing. When finished, give it a seal coat. That's what we did with our basement floor and, at least for me, I love the look.
Comment: Thanks for the input! I want to start doing this as soon as possible, with all the humidity in the air it is bringing the smell back up, BAD.
Answer: I'm not sure if your question is, 'What am I likely to find under my carpet,' or 'What should I do after ripping up carpet?'
If the question is the former, the answer is absolutely anything depending on the age and history of your house. I know people who have ripped up carpet to find concrete, wood floors, and in one case magnificent hardwood that polished up real nice.
It sounds like you know there's concrete under there, but I think some unknowns would be whether it is stained or not, and whether there are any big cracks in it from the foundation settling. You can pull up carpet in an inconspicuous corner and peek, but if you rip it all up I try to be ready for anything, and make sure you have the budget to deal with some surprises.
Comment: As far as I know it is supposed to be concrete, I bought the house in 2007. The house was "re-done" according to my realtor after Hurricane Ivan tore through Pensacola, FL. I don't think she even knew what to find in the house to be honest with you.
Answer: After removing the old carpet and tack strips, spray the stains with Kilz, patch cracks if there are any, and paint the whole concrete floor with floor paint to make sure no stains gets embedded in your concrete floor in the future. Since you live in Florida, laying new carpet is not your best option due to weather and high humidity. Use floating vinyl planks instead: they are easy to install. You can do it yourself and save big. They are very durable and cheaper than hardwood while having the same look. Easy to clean and maintain too.

What to expect when tearing up carpet?


Does Monero have zero-conf?

Question: Is there such a thing as zero-conf in Monero and if yes, then how does it work?
Is it supported by the Monero client?
Answer: You're probably referring to the concept where a vendor will accept payment, even when the payment has not been included in a block.  Sure, that works the same way in Monero that it does in Bitcoin.  The transaction in question will be visible in the mempool.  When the vendor sees the transaction in the mempool, he may decide to release goods to the customer.
Answer: Monero transactions are pretty similar to Bitcoin ones regarding this: you see them on the network, they linger in the txpool till mined, the block they're in can be reorganized, and the more blocks on top of it, the less likely it is to happen.
The Monero wallet offers the get_transfers RPC, which has a pool input field. When set to true, any transaction to your address in the txpool (ie, not yet mined) is returned. There's a double_spend_seen field for the returned transactions. If true, it means another transaction was seen which double spend at least one input of the original transaction. In that case, you'll probably want to not accept that transaction until it's actually mined.
Answer: Currently the best implementation is the Point of Sales payment system Kasisto. Here is an example of usage: https://i.stack.imgur.com/ejR1J.jpg
See also this question : What is Kasisto?

Does Monero have zero-conf?


Welcome to our new pro tem moderators!

Question: Thanks to everyone who participated in the recent nominations to select new moderators. We're always happy to see the community being proactive and getting involved in who is leading their site. Now, I'm happy to announce that your site has two new pro tem moderators who have stepped up and volunteered their time to help lead this site to success. Here they are:

I'd also like to thank two of our past moderators for everything they've done for this site up until this point. Their moderator status is being removed at this time as well:

Good luck to the new moderators, and good luck to the site as a whole!
Answer: Welcome to the new moderators! :D
I'll be glad to assist you if and when needed, just let me know.*

*Possibly by ping, I can't hear your voices. :P

Welcome to our new pro tem moderators!


Pendulum and simple harmonic motion

Question: I have a physical pendulum that, for small oscillations, can be modeled with the simple harmonic motion approach. In determining the motion equation, I need to figure out the amplitude: I know that the pendulum has length $L$ and is released from an initial angle of $\theta = 15.0°$. My intuition suggest me that the amplitude can be calculated as $A = L\,\sin\,\theta$, but the solutions book actually uses the formula $A = r\,\theta$ (where in this case $r = L$). But the last formula is used to calculate the arc of circumference, so I wonder if it is the right way to do it and why.
Comment: $sin\theta = \theta$ for small values of $\theta$ but I would not consider $\frac{\pi}{12}$ small enough for that approximation.
Answer: Why would you consider the amplitude to be equal to the horizontal displacement? There's also a vertical displacement, which is arguably more important, without vertical displacement there would be no oscillation, since the potential energy would remain the same. Or take for example a torsion pendulum:

You wouldn't describe the amplitude as $r\sin{\theta}$, because that would give an amplitude of zero when the pendulum swings 360 degrees. It makes more sense to say that the amplitude is equal to the length of the path the pendulum travels, i.e. the length of the arc.
Comment: You make some good points about the horizontal and vertical displacements.
Answer: Your intuition is correct, $A=L\sin \theta$ is strictly the right answer.
But, note that $\theta$ is (sort of) small. And for small angles:
$$\sin \theta \approx \theta$$
The arc length is almost equal to the horizontal distance for small angles.
You even wrote "for small oscillations" in the text yourself, and exactly that is only necessary to add to the discription in order to make this simplification. Then many future formulae that may be derived, are much simpler - but are only valid at small angles.
Comment: @BillN Good point! Of course, SI units are *always* the case.
Comment: It's useful to point out that $\theta$ is measured in radians for the small angle formula to work.  Beginning students often forget about the proper units.
Answer: The pendulum would be a simple harmonic oscillator only if the angle from which it is released is very small. It will be actually an angular simple harmonic oscillator but since the angle is small the motion can be considered almost linear. So it can be said a linear simple harmonic oscillator. For large angles, it would be an angular oscillator but not a simple harmonic oscillator. So the only time it makes sense to talk of an amplitude of its harmonic linear motion is when the angles are small. For small angles, $L\sin\theta \approx L\theta $.
If the angle is not small then the oscillation can not be considered as a linear oscillation at all and the only amplitude that would make sense is its angular amplitude - i.e. $\theta$ itself. Or you could consider it oscillating in a plane with the horizontal amplitude being something and vertical amplitude being something else and so on... but that is an unnecessary complication.
Answer: It depends what is being defined as the 'displacement' of the pendulum, which is what you are really asking about.  Amplitude is maximum displacement.
The angular displacement $\theta$ of the string or rod could be used.  Since the length $L$ is constant (and the CM is assumed to be at the end) this is equivalent to the arc length $s=L\theta$ along the path of the bob.
Alternatively you can define 'displacement' as the horizontal distance $x=L\sin\theta$ of the bob from the vertical line through the pivot.
The confusion is caused (I think) by the fact that the motion is not strictly SHM whichever of $\theta(t)$ or $s(t)$ or $x(t)$ you use.  Each is approximately SHM only for 'small' displacements.  If one of these were exactly SHM, we would ignore the other options and there would be no confusion.

Pendulum and simple harmonic motion