In Texas is it okay for a person to post photos on a commercial website of private property without the owner's permission?

Question: We hired someone to build decks on our property.  He did not do a good job, finish the job, etc.  He took photos and posted them on his company website.  Is there anything I can do to have them removed?
Comment: It would make a difference if the contractor is claiming that photos of work done by other people are actually of his work; but pictures of his work on his website do not need your consent.
Answer: The owner of the premises can prohibit what they like on their property, including photography from their property. They have no control of  photography of their property from someone else's property.
In the circumstances, the contractor was there with your permission and, unless you said otherwise, such permission would reasonably include the right to take photographs. He took photos (and they are his photos, not yours) so he can do what he likes with them.


Most important tells

Question: I would like to start to play poker at casino near my home. I usually play on line. I would like to know which are, in your opinion, the most important tells to take care at brick and mortar poker.
Answer: Probably the chip glance as the flop, turn, or river come out. Indicates they hit the flp/t/r in some way and their initial intention is to bet.
A chatty player is almost always a good hand, especially on the river when your contemplating a call against a player.
Shaking hands when betting is usually a monster, not a bluff.
I'm far from an expert but I think most would agree these are ones seen often and are pretty reliable.
Comment: On the flip side, my experience has been that if a player is being really chatty facing a bet and they shove over the top, they rarely have it.
Comment: Another valuable one is the "is it my turn"? from a usually inattentive player...indicates strength.
Answer: Giving off:

Know your stack size before the hand starts and who you have covered.  Don't wait for a good hand to count.
Use the same mechanics.  If you bet left handed then always bet left handed.
Rest your hands in the same spot.
Don't announce your bet some times.  Do it the same way every time.  Annie Duke caught a tell in player announced raise to the dealer when he was bluffing.  Another pro caught a tell of player used smaller denomination chips when it was a bluff.
If you are going to check your cards on the flop then always check
your cards. A flop came up three diamonds and a guy immediately checked his cards.  Sammy Farah at the end of the hand said you have queens and one red.  You checked to see if it was a diamond and he was right.
Wait your turn pre to check your cards.  Be in a body position to play the hand. Don't sit up tall after you hit a monster.
Take the same amount of time to make an action.  Don't rush a bluff
to look strong.  If you insta call it means you probably have piece of it but did not smash the board.  You did not even consider a raise.
If it is a fold then go ahead and fold. If you think they might be bluffing you but you don't even have a bluff catcher then take the standard time.
Don't ask the player for count some times and some times ask the
dealer.
Don't talk.
Don't try and give off fake tells!

Read

Do they act different. Do they act more confident some times? Was that a bluff or a monster.  Notice the tell and know what it means are not the same.
Starting out I think you should more remember the betting pattern
then what they showed.
Comment: I like this one. Those small tips are pretty serious. I remember my last quite-evident tell: When having pocket rockets I tended to turn my eyes away every sight. Damn. It was a hard week to me.
Answer: Single stand alone tell is really not enough to get any good advantage.
You need to observe, if the player you are focused on try to act and bluff you, or not. Many players just try to hide their emotions and do not act, while many others try to signal tells that are opposite to their hand strength.
Caro's book of poker tells is really great source of information about this topic.

Most important tells


How to change date format correctly? (1899-Dec-30 error)

Question: I would like to use date format for "Modified" field YYYY-MM-DD instead of the default MM-DD-YYYY. So I created a calculated field with the code:
<code>=TEXT(Modified,"yyyy-mmm-dd")
</code>
But at about 70% of the case the result is 1899-Dec-30 (That is not correct). This is based on an auto generated field so it can't be blank. Also if I modify again the value is still wrong. But if I edit and save the item without any modifications, the value is correct. The oroginal "Modified" field is always correct. I suspect the calculated field run faster than the original, so while the original's value is not calculated yet the calculated field somehow get this wrong result, but not sure. I tryed:
<code>=IF(ISBLANK(Modified),"",TEXT(Modified,"yyyy-mmm-dd"))
</code>
And looks like with this the error is not appear, but I tested only about 50 time so not sure and even if it is solved, I don't understand why. Also I never got "" result just the field started to display the correct result what is suspicious. I think with the additional calculations the calculated field runs slower than the original so it have time to get it's value, so the calculated one can get good result, but this is only a hypothesis. Do u have any idea what could it be?
Answer: It seems that a date value never is blank, but zero.
I made it working with this:
<code>=IF(Modified<1,"",TEXT(Modified,"yyyy-mmm-dd"))
</code>


dripping sound in ceiling when central heating gets warm

Question: I am a complete novice about plumbing so apologies in advance. Basically I have noticed that, when my central heating warms up I hear what sounds like a dripping noise in the ceiling. This seems to start slow, speed up then slow down. After a few seconds it will start again and so on, as long as the central heating is on. Once I switch off the heating it takes about half an hour for this dripping noise to stop completely. Is this likely to be a leak or is there another explanation?
Answer:
is this likely to be a leak?

If it has been happening for more than a week and there is no sign of water, like a discoloured or damp patch on the ceiling or wall, then no.

is there another explanation?

When pipes heat up, they expand, as they expand they rub against the woodwork or other material they are fixed to. Frctional forces cause the pipe to be trapped until accumulated expansion pressure is enough to overcome friction momentarily. This produces a series of annoying but harmless clicks, taps, knocks or bangs.
Comment: I may have a similar issue but haven't nailed it down yet. What kind of contractor can be brought in for listening / diagnosing dripping sounds? It would be worth a contractor fee to reassure myself that the sound is harmless if I knew who to ask. Is it an HVAC person or plumbing or general contractor (or other) that would be best-suited?


How to edit .asec file?

Question: How to edit .asec or compare two .asec files witch are stored by app at location mnt/.android_souce/app name.asec.
This file get updated whenever data connection is on / while using app to upload and download app data .
This folder not able to access on non rooted Phone but can able to access on pc with usb .
What are capable software that can read and writing easily .asec file ?
Comment: You really need to give more details about these files and about what you already tried. Just right now, your question is really really unclear. So, try to clarify it and explain what you already tried.
Comment: I am playing a online multi player game (example:- war),
Comment: I am playing a online multi player game (example:- war), this war game created a file at locagion Mnt/sdcard/.android_secure/war.asec. this file allwase update when i paly war game . i guess that war.asec file containtes my game data like my level.gold coins . etc. I want to know that can i read and edit this file?  . thanks for yours in trust in my question.
Answer: The ASEC file is a TwoFish encrypted container which in turn is a dm-crypt volume that gets mounted by Linux's device mapper at /mnt/asec/[app_id] (The AppID is based on the package name). The 128-bit key to the container can be found in /data/misc/systemkeys but this file requires root access for reading. You can read exactly how the encryption works here. Moving on, the mounted volume will contain an unencrypted apk of the application. In order to change the desired data, it's necessary to understand where the data is stored and how it is done. For that, the application will have to be reverse-engineered by either decompilation - list of tools - or by disassembly to smali and posterior debugging using tools such as apktool and androguard.
Sometimes, these steps can be bypassed as the app uses a database file in it's directory (usually /data/data//) that you can edit with any SQLite editor, such as SQLite Debugger or using the sqlite3 set included by default in Android, or keeps the relevant information in memory in a way that is trivial to change it with a memory editor such as GameGuardian. However, the data can be stored server-side and transmitted through the network when app is started and then kept in memory in a not easily modifiable way so that in order to be able to change it, you will need to not only reverse-engineer the application but also to intercept and modify the traffic it receives in order to transmit the new information to the application.
Comment: Technically, GooglePlay transmits the encrypted parameters and apk, thus the apk downloaded from the Play Store would be different from the one you retrieve using the method above (see last paragraph of reference number one - Encrypted Apps and Google Play). But if considering only the end result, the answer is no.
Comment: Thanks sir for yours quick and valuable respons . 1st of all i want to tell you that i am a mechanical engineer so i don't have much knowledge about programming but i have common sens so i can do a lot if someone as like you guide me properly.                                       I am sure that this the only file is changing all the time i have taken backup 2 times like when i wans haveing 10 money and 8 money file so how i can compare this 2 files to findout changing factor to modifiy it? Once again thanks to u
Comment: Would the unencrypted apk be any different than the apk downloaded directly from google play? (Assuming the apk wasn't a paid-for app)

How to edit .asec file?


Why do people say "break a leg" to actors?

Question: Frequently, before going on stage, someone will say "break a leg" to an actor, which is a peculiar acting saying meaning "good luck!"  How did this expression come about?
Comment: Because all actors are mad?
Comment: A good example of this is in the play/movie ["The Producers"](http://en.wikipedia.org/wiki/The_Producers_%281968_film%29), though there have been allusions to the superstition in a number of plays.
Answer: According to Wikipedia, the term:

reflects a theatrical superstition in which wishing a person "good luck" is considered bad luck. The expression is sometimes used outside the theatre as superstitions and customs travel through other professions and then into common use. Among professional dancers, the phrase "break a leg" is replaced with "merde".

The article goes on to mention several theories about the actual origins of this expression. The one that is often mentioned (as far as I have heard), is called the Opposite Meaning theory. It says,

People in theatre consider it bad luck to wish an actor good luck, so instead they wish the opposite, by saying "break a leg!".

Another theory claims that the phrase has Greek origins:

In the time of Ancient Greece, people didn't applaud. Instead, they stomped for their appreciation and if they stomped long enough, they would break a leg. Or, some would have it that the term originated during Elizabethan times when, instead of applause the audience would bang their chairs on the ground—and if they liked it enough, the leg of the chair would break.[12]

Still another claims that the origins are, in fact, Yiddish:

Some etymologists believe it to be an adaptation from the Yiddish translation into German. The phrase "Hatsloche un Broche" (הצלחה און ברכה) ("success and blessing") had been calqued from the German phrase "Hals- und Beinbruch" ("neck and leg fracture"), because of near similar pronunciation.

The Phrase Finder (hat tip to Unreason) has even more theories on how the term came to be. They note that:

'Break a leg' also means, 'make a strenuous effort'. There are many references to the phrase used that way, which pre-date the earliest theatrical good luck charm meaning.

So the theories they offer stem from this. For example, the following things could be related to "breaking a leg":

Put on a performance good enough that you will have to bend your knee in a bow or curtsey to acknowledge the applause.
Impress the audience so much that you will need to bend down to pick up the coins they throw onto the stage.
Pass out onto the stage to receive a curtain call (the side curtains on a stage are known as legs).
Go on stage and have your 'big break'.

Note that still, nobody knows the exact origin of the phrase, but some are more plausible than others.
Comment: http://www.phrases.org.uk/meanings/break-a-leg.html has few other possible etymologies
Comment: @Unreason Thank you for that link--I have added it to my answer, and credited you.
Comment: And how common is this idiom? Will it be understood outside theatrical environment?
Answer: It's a superstition; wishing a stage performer "good luck" will cause them to have bad luck, so instead the person tells the performer to have the worst luck commonly thought of; literally breaking a leg on stage would be a very bad thing, considering "the show must go on".
Comment: It reminds me of _in bocca al lupo_ ("in the jaws of the wolf") used in Italian to wish good luck.
Answer: Saying "good luck" in theatre is considered bad luck. Just like saying "Macbeth" is considered bad luck or a bad omen.  (Instead of saying "Macbeth", people will refer to it as "The Scottish Play")
Break a leg
Comment: On that note... http://www.youtube.com/watch?v=h--HR7PWfp0
Answer: Someone told me that a "leg" was a part of the mechanism that raised and lowered the curtain, the idea being that you could get so many curtain calls, your very popularity would end up breaking the leg of the curtain.  I find this extremely implausible but thought I'd pass it along.
Answer: I like the "Vaudeville" theory from Theatre Superstitions". Steppenwolf Theatre Company. Retrieved 2012-06-30. that uses the "leg line" as its basis:
In the days of Vaudeville, companies would book more performers than could possibly make it onstage, but would only pay those who performed.[19] Since the Renaissance, legs have been used as part of the masking in proscenium theaters, which remain the most popular style of theater to this day.[20] Thus, to make it on stage, one had to enter the line of sight of the audience or "break a leg", to be paid
Answer: My Director just explained to us that the curtains hanging either side of the stage are called "legs" in theatre touching the legs is a big no no!
The expression "break a leg" means to walk past the legs (curtains) to come on stage! hence breaking through the legs!
Comment: Very appealing hypothesis, and one that's not pure conjecture. Could you provide a reference that says theatre curtains are called *legs*?
Answer: Break a leg may stand for run, go, rush, don't have second thoughts, you've got what it takes to win. It is like hit the road, hit the ground running, hit the ceiling etc. which shouldn't be taken literally.
It is one of those idioms that is transportable and not necessarily originating from the showbiz. It's for assuring and motivating actors even more than "good luck".
Answer: My own theory is that the English "Break a leg" comes from Jewish theater.  In Hebrew, "Baruch alechem" means "Bless everyone."  It's easy to imagine how, in America, "Baruch alechem" might facetiously be rendered "break a leg."
Comment: Ooh, I really like this. Could you provide a link which testifies that the Hebrew expression really means "bless everyone"?
Comment: Actually it's better translated as *Bless you*, which is even more apposite. It would be nice to have some corroboration from American theatre (theater?) though.
Comment: *Aleichem* (עֲלֵיכֶם) means "be with you" -- most famously in the expression "Sholom aleichem", *peace* be with you, or in Arabic, Salaam alaikum. *Baruch* ( בָּרוּךְ) means "blessing" (most famously in Arabic as the name of a recent US president).
Answer: Had heard that during Shakespeare's time only the rich could afford to go to the theater.  Shakespeare however felt the poor should be allowed to see plays and made sure during this time that the poor would only be charged a penny to get into the theater and were made to stand not sit around the stage, front and center.  The story goes on to say they would be in such amazement being able to view these productions their mouths would hang open to the point they would drool onto the stage making it slippery for the actors causing them to slip and fall and potentially break a leg
Comment: Hmm. Do you have a reference for that?
Answer: I had heard that in early theatre the lead actors study or stand in would say it to the lead actor, hoping he would get to fill in for the lead actor if he broke his leg or any thing that would get him to go on in his place .
Answer: I heard that a famous actor long ago, broke his leg during his performance, but In the tradition of
"The show must go on", he persevered and gave the greatest performance of his career.
Comment: Do you have any idea who this was?
Comment: I've heard of football /soccer players who have continued playing a match with fractured bones, torn hamstrings etc., so as a story  it's quite plausible. However, simply stating "you heard" this story offers the OP, and everybody else, very little to go on. (Note that I didn't provide any names) It could also be that this incident happened long after the idiom had been established.
Answer: I say break a leg mean example a comedy so funny you slap top
Of thigh so hard laughing you could break a leg.thus meaning have a good show.
Comment: Hi Arthur, and welcome to ELU. Citing a reference to support your belief would make this a better answer. Otherwise this can be seen as just your opinion, and we try to give answers with some kind of authoritative reference here. Since you're here, please have a look at the [site tour](http://english.stackexchange.com/tour)
and visit the [help center](http://english.stackexchange.com/help) for guidance on how to use this site.


Freezer temperature

Question: I checked my freezer temp., when it was somehow empty the thermometer indicated range between -20 to -4C (depend on opening and closing the door) and when I put stuff inside (50% full) indicated -6 to -10C, I have located the thermometer in the freezer, my fridge is a 12ft regular refrigerator and freezer with separate door, the refrigerator works well, my concern is if the thermostat or timer works? since I could not reach -18C when there are stuff in the freezer
Comment: How long did you give it to come to equilibrium after filling it? If it had to freeze half its volume worth of food, it might take quite a while, but eventually it should come to the same temperature as it would empty. Also, assuming you can't control freezer and fridge temperature separately, what temperature is your fridge holding?
Answer: -18C (0F) is ideal, but freezer temps fluctuate, usually with -18C at the low end of that fluctuation. It sounds to me that your freezer is fine. Your food will be fine while you scope out and buy a thermometer that you can move to different parts of your freezer, like this:

Note from that picture that the "safe" zone includes a range just below freezing. The ideal temp of -18C is about quality, not safety.
One like this takes a bit of installation, but it monitors the temperature of your freezer constantly, without you having to open the door to read it: $25 Refrigerator/Freezer Monitor
For more information from a very reliable (if very conservative) source, see what the FDA has to say.
Comment: This is a very minor point, but there are a few bacteria types that cause foodborne illness which can grow (very slowly) even at 30-32F, depending on the texture of the food.  It's hard to note that on a thermometer dial, but you do want to keep everything in your freezer at least at 29F (-2C) or below for food safety reasons.  Of course, if your freezer gets warmer than that, you'll likely see the significant degradation of food quality due to temperature cycling before any bacterial hazards would grow enough to be significant.

Freezer temperature


Finitely generated soluble groups with uncountably many maximal subgroups

Question: Is there a finitely generated soluble group with uncountably many maximal subgroups? Any classification of such groups?
Comment: We can't expect any classification... maybe it would sound more reasonable to ask about the class $C_1$ of f.g. solvable groups having only countably many maximal subgroups, its subclass $C_2$ of f.g. solvable groups all of whose maximal subgroups are finitely generated, its subclass $C_3$ of f.g. solvable groups all of whose maximal subgroups have finite index. All these classes are stable under quotients. Probably the inclusions $C_1\supset C_2\supset C_3$ are strict although I have no example in mind right now to prove it, and $C_3$ includes all nilpotent-by-polycyclic f.g. groups.
Comment: And in turn to classify such groups (those f.g. solvable with countably many maximal subgroups), it is no restriction to assume that the intersection of all maximal subgroups is trivial. This yields some reduction: e.g., a group with this property has all its nilpotent normal subgroups abelian.
Comment: PS: regarding my first comment, an example of group in the class $C_2\smallsetminus C_3$ is the wreath product $\mathrm{Sym}_3\wr\mathbf{Z}$. It contains $L=\mathrm{Sym}_2\wr\mathbf{Z}$ as a maximal subgroup, of infinite index so is not in $C_3$. That it belongs to $C_2$ is not hard: using that $V=\mathrm{Alt}_3^{(\mathbf{Z})}$ is a simple $L$-module, one gets that if $M$ is a maximal subgroup, either it contains $V$ or is isomorphic to $L$ and hence is finitely generated. In the first case, we get a maximal subgroup of the quotient $L$, which is nilpotent-by-polycyclic, hence of finite index.
Answer: Yes, there is a finitely generated soluble group with uncountably many maximal subgroups.
Fix an odd prime $p$. Denote by $F_p$ the field on $p$ elements, $C_2$ the cyclic group on $2$ elements. Let $A$ be the set of functions from $\mathbf{Z}$ to $\{-1,1\}$. Let $M$ be the free $F_p$-module on the generators $(e_i)_{i\in\mathbf{Z}}$. Consider the lamplighter group $L=C_2\wr\mathbf{Z}$, with generators $u,t$ with $u^2=1$ and $u$ commuting with its conjugates.
For every $f\in A$, endow $M$ with a structure of an $L$-module, where $t$ acts by the shift $e_i\mapsto e_{i+1}$ and $u$ acts diagonally by $u\cdot e_i=f(i)e_i$. We write it as $M_f$ to emphasize the dependency on $f$.
Each $f\in A$ can be viewed as a bi-infinite word in the letters $\pm 1$.  Let $A'$ be the set of "universal" sequences, that is, those sequences for which every finite word occurs at least once. Then if $f\in A'$, the module $M_f$ is a simple module. Indeed, consider any nonzero element $w=\sum_{i=k}^l a_ie_i$ with $a_k,a_l$ nonzero. Then by the assumption, we can find some conjugate $u'$ of $u$ mapping $e_i$ to $-e_i$ for all $i = k, \dots, l - 1$ and $e_l$ to $e_l$. Then $u'w + w = 2 a_l e_l$ generates $F_p e_l$. In turn using $t$ we get all the other basis elements.
Let $N=F_p[L]$ be the group algebra. Then mapping $1$ to $e_0$ defines a surjective $F_p[L]$-module homomorphism $p_f:N\to M_f$. Let $I_f$ be its kernel. We claim that
Elements of $L$ can be written as $g=(t^n,P)$ with $P$ a finite subset of $\mathbf{Z}$. Let $\delta(g)$ be the corresponding basis element of $N$. Then $$p_f(\delta(t^n,P))=p_f((t^n,P)\delta(1,\emptyset))=(t^n,P)e_0$$ $$=(t^n,\emptyset)(\prod_{i\in P}f(i))e_0=(\prod_{i\in P}f(i))e_n.$$
In particular, $p_f(\delta(1,\{i\}))=f(i)e_0$, and $p_f(\delta(1,\{i\})-\delta(1,\emptyset))=(f(i)-1)e_0$. In particular, $\delta(1,\{i\})-\delta(1,\emptyset)\in I_f$ iff $f(i)=1$. This shows that $f\mapsto I_f$ is injective.
Since $A'$ is clearly of continuum cardinality, this shows that $(I_f)_{f\in A'}$ is a family of continuum cardinality of maximal submodules of $N$.
Therefore, in the group $N\rtimes L$ (which is solvable of length 3, generated by 3 elements), we have a family $(I_f\rtimes L)_{f\in A'}$ of maximal subgroups, of continuum cardinality.
Of course we can pull this back to any group having $N\rtimes L$ as a quotient, such as the free solvable group of any length $\ge 3$ on $\ge 3$ generators.

Note: 3 is the minimal derived length. Indeed, finitely generated metabelian groups have maximal subgroups of finite index, hence there are at most countably many. This holds more generally in finitely generated nilpotent-by-polycyclic groups.
Comment: Thank you for the nice construction. It is very helpful.
Comment: Note: this construction is described in: A. Arikan, G. Cutolo, D. Robinson. On groups with countably many maximal subgroups. J. Group Theory 21 (2018), no. 2, 253-271. (Currently available [here](http://www.dma.unina.it/~cutolo/papers/JGT18.pdf))


How to add logo in Modern Team Site

Question: How can I add a logo in Modern Team Sites?I can't found out any information about it.In documentation it says that it is possible but from where? In settings I can't found that option.
Answer: The below is the "official way to go", but at the end is a suggestion to check for a quick logo change.
Modern Team Sites can't be customized through the settings-menu. Instead, to customize Modern Team Sites, you need to upload required files and assets and apply the changes by executing the ApplyTheme method. To specifically change the logo of a Modern Team Site, you need to use the Groups Graph API and define the logo in there.
See more about Applying custom theme to "modern" team site and SharePoint PnP including the method for logo changing.

There's a suggestion that you can change your logo by accessing the default logo at Site Assets stored with the name __siteIcon__.jpg. By replacing this file with an identically named filed you could apply your own logo to the site.
Answer: For a Modern Team Site you have to go to the Site Assets folder and upload the site logo there. It must be name __siteIcon__.jpg and must be a jpg for it to work.

Upload your new file and overwrite the existing file. Wait a few seconds and hit CTRL+F5 to clear the cache and there you have it.
Answer: although the page for changing the logo isn't listed in the site settings, it is still there and you can access it directly with its url:
https://contoso.sharepoint.com/_layouts/15/prjsetng.aspx
however when you create a Team site with the SharePoint link from the app launcher, it will be attached to a O365 group, and it is the O365 Group logo that will override your site logo
so in order to change the logo go to the Admin center > Groups > and change the logo of your group there
it can take some time to sync to your site (i was able to force the sync by removing the default acronym logoin the prjsetng.aspx)

How to add logo in Modern Team Site


Dissolving metal reductions

Question: Could reduction of an organic compound by reacting it with sodium dissolved in $\ce{NH3}$ still proceed if a metal such as aluminium were used instead of sodium? I'm not sure about the aluminium amine or amide structure that would be formed.
Comment: Aluminium does not react with anhydrous ammonia even at 500 degrees C. However I don't have a particularly good explanation why Al doesn't dissolve. It may be due to Al forming a thin protecting film on the surface; but from [here](https://books.google.co.uk/books?id=NAABS5KrVDYC&pg=PA389#v=onepage&q&f=false) it seems that the films only form when you have some water (so it's presumably Al2O3)

You can dissolve Ca, Sr, Ba, Eu, and Yb in liquid ammonia, as well the alkali metals. All of these elements have relatively low ionization energies.
Comment: To me it seems, that aluminium is the odd one out. According to [Yu Qiu, Lian Gao](http://www.sciencedirect.com/science/article/pii/S0955221903000141) it seems that AlN is formed and ammonia is split. I only read the abstract though. I remember vaguely from when I tried the birch reaction, my lab colleague almost dissolved a whole iron/copper spatula by accident.| @J.LS Care to write up an answer.
Comment: Thanks I wasn't sure some things work in theory but not in reality!
Comment: What if aluminium amalgamate was used? Or if naoh and a nitrate salt were used with the regular aluminium?
Answer: Is there a goal here? If you wanted to react aluminium with concentrated aq ammonia, you would get hydrogen but the rate would be proportional to temperature.  However, this would be quite a poor way to create a reductive environment and as someone has already alluded, aluminium and sodium hydroxide or a strong mineral acid is better. From what I've seen, if you use alkali, a catalyst is needed.
Ethylamine can be more conveniently used in place of ammonia.
Calcium can also be used in reductions.I think I've also seen Indium, but that seems a bit expensive.
Comment: The goal is to reduce a carboxylic acid or alcohol to the alkane using aluminium :)
Answer: Sodium in anhydrous ammonia liberate a solvated electron for reductions and produce sodium amide.
If you do the same in the lab with aluminium then the chance is big that nothing would happen because the oxide layer on the aluminium surface and the fact that ammonia is a toxic gas that you don't smell at high concentrations.
Nothing will happen if you just put aluminium in aq. ammonia. You need to transform aluminium in another form with a strong acid to make it reactive.
The answer is no.
Comment: I don't see how the toxicity of ammonia is relevant. Perhaps you could add a bit more detail about why the reaction doesn't take place and how you can make it take place as you seem to be implying in the third paragraph.
Comment: [Welcome to chemistry.SE!](http://chemistry.stackexchange.com/tour) If you had any questions about the policies of our community, please visit [the help center](http://chemistry.stackexchange.com/help).

Dissolving metal reductions


Carto legend colours not showing in embed?

Question: Carto legends are showing no colours in the bullets after manually adjusting colours in the HTML window -- but only in IE. No issue in other browsers. Has anyone else seen this?
Answer: That is a known bug in CARTO in which it doesn't display correctly the legend colors in IE browser. You can find the reported bug in this issue


setSQL not working in CartoDB API?

Question: I'm trying to use CartoDB API to retrieve a dataset from my account to a heatmap. I want to filter the data using SQL. The problem is the following: the sql query does not always work when using the on done callback. However, it does work when I set it from the console using the map variable (where I stored the layer).
cartodb.createLayer(map, layerUrl)
.addTo(map)
.on('done', function(layer) {
    map.layer = layer;
    layer.getSubLayer(0).set(subLayerOptions); // sql is inside here
    map.invalidateSize(true);
}).on('error', function() {
    console.error("Cannot create layer");
});

EDIT
I wrote another cartodb code in the example, the actual sentence which sets the sql is this one: layer.setSQL(subLayerOptions.sql); (as it is a heatmap and the torque layer seems not to have the getSubLayer function).
To clarify my question, the result I'm obtaining is the same as if I don't set the query in the done callback (as I assume it is using the sql I have in the map I created from CartoDB SaaS). It is ignoring the query passed through javascript. I remark that if I set it later it works fine, it just needs some time to load the first time so I assume the problem is around that but I haven't find it yet.
EDIT 2
Sometimes the fix is just to zoom in and out. In this cases the data seems to be loaded but the interface is not refreshing.
Comment: Please ask your new edited comments in a new question if the first one was solved.
Comment: It was not answered, I just added information I found that could help solve the issue.
Comment: If you could share your code or create a repo to have a look. Because with this info I cannot replicate your problem. Be careful with `subLayerOptions.sql`, if this is a local file your code will not work.
Answer: With the little info you have told us the only thing I came up is removing map.layer = layer. Also I do not know what are you trying to do with map.invalidateSize(true);. Nevertheless, I have created a working example about setting the options of a sublayer. And the sql query works every time! :-)
Comment: Sometimes my maps are initialized while hidden and when I show them up the size is wrong, so I invalidate it to fix the problem.

setSQL not working in CartoDB API?


What is the price of an ask order bought if a bid order is placed at a higher price?

Question: What is the price of an ask order bought if a bid order is placed at a higher price? For example, if there exist two ask orders at $50 and $49, and I place a bid order at $50 of an amount larger than amount of the two ask orders, will I buy the $49 ask order at $49? Or will I pay $50 for both orders, losing $1 on the lower one?
Answer: If you bid a higher price than a buy order, you will purchase that buy order at the ASK price, you won't pay more than they were asking for. Your order will fulfill all sell orders up to the amount and price you set your bid. This is known as a limit order.
If you requested to buy more coins than the $49 sell order, you would fulfill that order at $49 and then buy the rest at $50.
See also: How will Mt.Gox select matching orders if asking for a price that is higher than available prices
Answer: When a new order is added to the order book, it will first be matched against already existing bids and offers. The older orders take precedence: you match them at what you saw on the order book. If there are multiple orders at the same price, they are prioritized oldest first.
In your specific example where you bid with a larger amount on an order book that has offers at $49 and $50, you would buy the offer at $49, then the offer at $50, and the remainder of your bid would be added to the order book for someone else to be matched with a sell order.


Is it legal to make emergency landing on roads?

Question: Recently I've seen many videos of planes landing on car road. Is this legal? Does this only apply to only USA or even other countries?
Comment: You really need to specify the jurisdiction. It could differ between countries (e.g. Finland has (or had in the late '80s) areas of road set up as fighter airstrips), or in the US, between states.  I used to work for a farmer who regularly used the road in front of his house as a runway, without any apparent legal problems.
Comment: In an emergency, you should throw away all rulebooks and do whatever you needed to do in your best judgement to minimize fatalities and injuries. Nobody is going to blame someone trying to do their best in a real emergency. At the most, you may have to pay compensation for damages, but that's civil, not criminal, and that's why you get insurance.
Answer: In the USA, when an airplane is in the air, it is governed by Title 14 of the Code of Federal Regulations, also known as the Federal Aviation Regulations (FARs). FAR 91.3(b) gives the pilot in command authorization to deviate from any flight rule necessary to meet an emergency: if that pilot needs to land on a road to meet an emergency, it is certainly legal as far as the FAA is concerned.
In fact, for private flights in small airplanes, the FAA doesn't bother much at all about specifying where you choose to land. There are no regulations about it at all.
The FAA's authority to regulate stops when the gear touches the ground, though. The road, or field, or waterway, or whatever you might be landing on usually belongs to someone or some government entity. Government entities often have laws against landing aircraft in certain places like roads or waterways, but just as often, they don't. It depends on which government. But in all cases I have ever seen, if such a regulation exists, so does an exception that starts, "except in cases of emergency...."
Answer: If you are in an emergency situation and think landing on a road is the safest option for everyone, you might as well do so. Usually grass areas or fields are preferred due to the fact that roads usually have more obstructions (traffic signs, street lights, bridges, cars,...) than fields, which might only have a fence or similar.
Example: If you lose engine power over a city or densely populated area, roads are probably the safest option. When losing engine power above a agriculture area, you most probably would avoid roads as best as possible and pick a field with little vegetation.
I'm not sure about the legal side but I think if you have an emergency and need to land immediately, nobody will prosecute that emergency landing legally. However, if you land on a road without having an emergency, it probably will be prosecuted in most countries.
Comment: @LeonardTan Airliners usually have enough redundancy (multiple engines and systems) to be able to reach an airport for emergency landing. If they lost all engines right after takeoff for example, they would most probably simply crash into the ground ahead. I don't think airline pilots would ever consider landing on a road as there is no road capable (big enough) to land a proper airliner on it. Doing that would only risk more lives.
Comment: Downvoted and flagged as Not an answer. The question is "Is it legal?", your answer can be summed up to "Maybe, I have no idea, do it if you need it". There is no attempt at all to answer the real question.
Comment: @rauberdaniel: It has been done, for instance https://en.wikipedia.org/wiki/Southern_Airways_Flight_242
Comment: @rauberdaniel IIRC there are certain major highways that were designed to act as backup/emergency airstrips.
Comment: do you know if a airliner needs to make a emergency landing and they are no near to any airport or water?
Comment: @nick012000 Interesting. Do you know where that is?
Comment: @nick012000, we have some such around, but they are military backup airstrips—there is concrete divider between the lanes that has to be pulled away before it can be used for aircraft operation, plus the car traffic has to be stopped. So it is completely unsuitable for emergency landing.
Comment: @JanHudec The main reason they're by now unsuitable are the overhead road signs. When designed and built, those roads did not have those, and were wide enough for the aircraft of the day. The center barriers needed only be removed to allow aircraft access to the other side of the road which was to be used as parking space and taxiways, not to allow them to land on it.
Comment: @jwenting, it depends on which one. The one I know is just two lanes in each direction, so it was not wide enough without removing the barriers even at the time it was built.
Answer: In most western jurisdictions, wherever a pilot decides to land is considered by the regulator to be an "aerodrome", from an aircraft operating perspective.  A lake (on floats), a field, a back country road; the regulator doesn't care unless say, the operation violated a regulation about putting putting people or vehicles or buildings in danger.
The rub is who owns the "aerodrome" and what they may have to say about it.  You may decide to land on dirt road, and the national regulator probably doesn't care either way (nothwithstanding any specific regulations banning certain operations), but the municipality that owns the road may not be too pleased.  This gets a lot of Ag operators in trouble from time to time because they operate from dirt roads a lot.
Landing on a highway? If it's an emergency, anything goes and worry about the consequences later.  If it was discretionary (non-emergency), and you came close to cars or people, you will likely be busted on endangering life and limb.  On the other hand, if you do a discretionary landing on a highway with nobody around, it might just be dealing with the state/province, or whatever jurisdiction looks after the road, who decides to impound your plane... if you get caught.
Answer: In a bonafide emergency it is legal to land anywhere. That's a decision made by the pilot in command, and not lawyers (thankfully).
Answer:
Necessitas non habet legem
Necessity knows no law

This principle is known pretty much all around the world. In an emergency, you may  choose to do things that are normally forbidden. However, that does not mean that you are exempted from any rules. You are still responsible and liable for your emergency actions.
Assume a simple case: you are pilot of a small plane. The engine dies. You cannot find an airport within your gliding range. There is no free area. The only possibility is a highway. You decide to land on that highway.
If you are in an emergency, and if there is no other - better - alternative, you may choose to land on the highway.
If everything goes well, and you cause no further damage: congratulations! There will be no prosecution for landing on the highway.
What could possibly go wrong?

Maybe there is an investigation, and authorities conclude that there was an airport in reach, or that you could have recovered your engine if you had followed the check list, or they believe that you faked the emergency for the sake of getting Youtube clicks, etc. Either way, if your case is not credible, you might loose your certificate.

There may be damage on your plane. Anything from a few scratches to a total loss. Hopefully, this damage is covered by an all risk insurance. The insurance company will scrutinize your case and try very hard to find anything that you could have done better and avoid paying.

You might have caused material damage to third parties. Your 3rd party liability insurance will have to cover - unless they can show that you have caused the damage through gross negligence. In that case they can try to wriggle out of their liability. Another financial hazard is the liability ceiling. If you cause a damage of several million $€¥, you might become broke for the rest of your life.

Now to the worst part. In your emergency landing, you are touching some cars or pedestrians. You did not foresee or want that, but unfortunately you killed them. You will face a trial. The court knows that you had good intentions and possibly be mild with you. It is also possible that the court is convinced that your decision was a bad one and that they will punish you for killing these people.

For the last point, let's assume you are PIC of an airliner. You have 200 people on board. You are convinced that you can save all of them, but you have to sacrifice a very small number of uninvolved people on the ground. This is not legal - you are not allowed to sacrifice anyone else to protect your passengers, no matter how odd are the numbers. You would face a trial, possibly with a tough outcome.

Summary
A pilot in a dead or alive situation will not care about losing his certificate, some fines, or financial consequences. Surviving the flight and bringing the passengers down safely would be everything. However, an emergency situation  does not exempt one from responsibility and liability. Sacrifying uninvolved bystanders is not acceptable.
Disclaimer
Legislation differs from country to country.
This post is for your entertainment only. Do not quote me after landing on the highway. Don't refer to me after an emergency landing on the Red Square.


When would it be lawful and professionally ethical in the US for a medic to sign with his sole name a medical report that the patient himself wrote?

Question: If a patient writes a medical report about himself, and gives it to his medic to sign with his sole name, under what conditions is it lawful and professionally ethical for the medic to sign it?
Comment: Is the report correct?
Comment: Perhaps OP means that the report is only signed by the medic/doctor. That is, there's no information that the patient wrote it.
Comment: Sole name means his name only, not jointly with anyone else, and not saying it was written by anyone else.
Comment: Why the term "sole name"?  Most people have more than one name.
Answer: When they agree with everything written there and don't want to add anything. Signing a report didn't mean you authored it: it means you authorize it.
Comment: In general, yes, but I was wondering whether this would contravene the professional rules of the American Medical Association. In particular, asserting something that they haven't observed, rather than saying that that is what the patient has informed them. Certainly some sets of professional rules do not allow that.
Comment: @TheEarth the OP never suggested that the conditions haven't been observed, just that the medic didn't write the report. As an aside, many things cannot be observed and are generally reliant on patient reporting eg chronic pain, insomnia etc.
Comment: Sure, many symptoms come without signs. I doubt there's a problem if a medic signs a patient-written report that says only what the medic himself might say. I once hired a lawyer to send a letter and it was fine with him that I wrote it. But do professional ethics say that a medic's report must make clear when symptoms (or an absence of symptoms) are described that are unobserved by the medic and only reported by the patient? I was hoping someone would answer who had knowledge of medical ethics in the US and could refer to relevant documents. Professional rules are usually quite strict.
Comment: This answer may be terse, but I think it is correct. It is ethical and legal to do, "when they agree with everything written there". (And, by the way, professional rules are actually usually extremely lenient as applied in real life, far more lenient in most cases than legal rules.) I recognize that sourcing would be better however. They are also often vague. https://web.stanford.edu/class/siw198q/websites/reprotech/New%20Ways%20of%20Making%20Babies/EthicVoc.htm


If I Google my name, the first result is someone else's (inappropriate) profile. Is there anything I can do?

Question: Unless you include my middle name in the search, a few of the links that come up aren't my profiles, but profiles of people who have the same name. One of them is an Instagram that does not give off the impression I want employers to have of me. Will this harm my job search? And is there anything I can do to make the situation better for myself?
Comment: Relevant article: [job-searching when you share a name with a porn star](http://www.askamanager.org/2014/06/job-searching-when-you-share-a-name-with-a-porn-star.html)
Comment: You could provide a URL for your Facebook or LinkedIn profiles, I have seen forms where there are fields for that. Then the employers will not have a doubt whether or not the profile belongs to you.
Comment: You should probably talk to Instagram about it, see if there is any action you can take with them.
Comment: Is your name extremely unique to the point that an employer would assume the top hits in a google search are for you?
Comment: If this is really is a concern. You could always add a picture to your CV. Unless the other person also looks like you. However there are plenty of discussions whatever adding a picture is a good thing or not.
Answer: Most recruiters (and intelligent people in general) understand that an internet search for a person's name will likely turn up hits for more than one person. I wouldn't get too worked up about it unless your name is very unique.
You can take preemptive steps when you provide your information to someone (this is best done verbally, and only if you are aware that people actually do confuse you with the others of your name out there):

If you search for my name on the internet, just remember, I'm the one from Sometown. There are a few other John Doe's that usually show up ahead of me in searches.

You should search for your name occasionally to be aware of what might be popping up so you can forewarn someone if there is something you wouldn't want to to be falsely associated with.
Better yet, you can provide some more direct search tips to help them. Provide the URL to your LinkedIn profile, or to your own website or blog, or StackExchange profile, or wherever you have good information about yourself that you are in control of.  Of course, this assumes you've got more there than just your name and a picture (especially in LinkedIn profile).
A recruiter will probably start at whatever place you give them, and will probably go from there, but at least you've given them enough background information in your first reference that they should be able to identify you in other contexts.
And of course, take the time to make sure your online presence portrays you in the light you want to be seen in. Lock down the privacy settings on any social media where you might have posted things that you don't want potential employers to come across.


How would I go about measuring an analog signal on my arduino mega that has both positive and negative voltages

Question: I have a signal that fluctuates between -70mV and 50mV. How would I get the arduino to read this.. Ultimately I am trying to graph the data in real time so it looks like this.

https://i.stack.imgur.com/a8zIE.jpg
Comment: i don't think an arduino has much sensitivity (precision) between such close values. I would use an op amp to amplify it to ~0-5v, after it went through a voltage sum circuit, a dual op amp like the 358 will  let you do both with one chip.
Answer: You need to amplify your signal and add 2.5V as a "virtual ground" for the amplification. This gets a little tricky, since you need a low-impedance VCC/2 source to feed the amplifier as a virtual ground.  This would require a unity-gain buffer fed from a voltage divider:

simulate this circuit – Schematic created using CircuitLab
Now you use that to feed the amplifier:

simulate this circuit
The gain is set by 1+(RF/RG), or 11 in this case, giving you -0.77V to +0.55V.
There is a simpler option, though. (There is another intermediate option but the editor lost it and I can't be bothered to spend the time recreating it).
This method does come at a cost, though: it inverts the signal. The -0.07 becomes 0.07 and the 0.05 becomes -0.05, and multiplied by the gain and added to the offset:

simulate this circuit
Here you get a transformation from -0.07V - +0.05V to +0.7V - -0.5V.  That means that in software you then have to invert the value (simply subtract it from 0 after removing the DC offset).
You're basically shifting some of the complexity out of the circuitry and into the software.
Personally I use the inverting amplifier (the last circuit) because the virtual ground current is near zero, so you don't need a low impedance VCC/2 voltage source. It's also easier to create more sensible gains (like 10x) than the non-inverting amplifier, which always has 1 added to the gain.
Comment: Your second circuit doesn't have a well defined DC working point.
Comment: Quite possibly not. I was having a nightmare of a time with the editor. It kept wiping stuff out and crashing and deleting circuits.
Comment: @EdgarBonet The op-amp was upside down in the non-inverting second stage... oops...
Answer: Here is my try at this: if your voltage source doesn't mind sinking
something like 150 µA, you could try something like this:

simulate this circuit – Schematic created using CircuitLab
This should map the input range [−70 mV, +50 mV] to
[0.04 V, 4.06 V].


What is the proof that the existence of one-way-functions implies $P \neq NP$?

Question: I am not an expert in this field, but I have read that the existence of one-way functions implies $P \neq NP$. Since there seem to be so many different definitions of one-way-functions and I have not seen a proof  I wanted to ask if someone knows where to read this, or knows the proof.
Please if you give a proof, also give a precise definition of which version of "one-way-function" you use. The proof can of course be detailed, the detailed, the better! :)
Thanks!
Comment: Suppose, for the sake of contradiction, that $P=NP$ and there is a one-way function $f$. You know $f$ is computed by a poly-size circuit. Given $y$, can you think of a way to find $x$ with $f(x)=y$?
Comment: Checking whether a given circuit has a satisfying assignment is an NP-complete problem.
Comment: I guess the poly-size circuit problem is in NP, so since by assumption P=NP, we can solve the poly-size circuit problem in polynomial time and thus invert $f$ which contradicts the assumption that $f$ is one-way. But I didn't know of the connection of $f$ to the poly-size circuit problem. Do you have any reference for this?
Comment: Assuming $P=NP$, there is an algorithm that takes as input a circuit computing a function $f : \{0,1\}^n \to \{0,1\}$, outputs $x$ with $f(x)=1$ if such an $x$ exists, and runs in time polynomial in $n$ and the size of the circuit.
Comment: Ok, but how does one construct an $NP$ complete problem given a one-way-function (Definition of Wikipedia)?
Comment: If a function is one way then its inverse is at least as hard as an NP complete problem.
Answer: $P \ne NP$ if and only if worst-case one-way functions exist.
Reference:
Alan L. Selman. A survey of one-way functions in complexity theory. Mathematical systems theory, 25(3):203–221, 1992.
Comment: it would be helpful to sketch out/ summarize some of the proof.
Answer: If P=NP, every polytime computable 1-1 function $f$ has a polytime computable inverse:
$\{(x,y) \mid \exists z\ |yz| \leq poly(|x|) \land f(yz)=x \}$ is NP.
We can find a $y$ such that $f(y)=x$ by starting with the empty string as$y$ and greedily adding the following bits using this NP oracle.
Answer: Let $f:\{0,1\}^* \rightarrow \{0,1\}^*$ be a OWF and define $L_f = \{(x,y)\in \{0,1\}^* \times \{0,1\}^*:$ there exists $z$ such that $f(xz)=y\}$.
I construct the following non-deterministic Turing machine:
$A((x,y)):$"Non-deterministically guess $z$. return ACCEPT if $f(xz)=y$ and REJECT otherwise"
$A$ makes a single call to $f$ which is OWF and therefore runs in polynomial time. $A$ decides $L_f$ therefore $L_f \in NP$.
Assuming $P=NP$, there exists a deterministic polynomial time decider $A'$ such that $A'((x,y)) = ACCEPT \iff A((x,y)) = ACCEPT$. Using $A'$ I construct $f'$ which inverts $f$ in deterministic polynomial time. First, I define a helper function $h:(\{0,1\}^*,\{0,1\}^*) \rightarrow \{0,1\}^*$ the following way:
$h(x,y) = $
\begin{cases}
    h(x0,y),& \text{if } A'(x0, y) = ACCEPT\\
    h(x1,y),& \text{if } A'(x1, y) = ACCEPT\\
 x  & \text{otherwise}
\end{cases}
$h$ is a recursive function that tries to add a single bit $b$ to $x$ in every iteration. If $A'$ accepts $xb$, that means there exists some $z$ such that $f(xbz) = y$. In this case, $h$ recalls itself with $xb$. Once $|z| = 0$ I know parameter $x$ contains the preimage of $y$ and the DTM $A'$ would reject both $(x0,y)$ and $(x1,y)$. In this case $h$ returns $x$. $h$ runs in deterministic polynomial time in $|xz|$ since at every iteration $|x|$ grows by 1 on account of $|z|$. At every iteration $h$ calls $A'$ which runs in polynomial time, making the total runtime of $h$ polynomial.
Using $h$ I define the function $f':\{0,1\}^* \rightarrow \{0,1\}^*$ such that $f'(y) = $ "Initialize $x$ to be empty and return $h(x,y)$". $f'$ inverts $f$ in deterministic polynomial therefore $f$ is not OWF, reaching contradiction.
In conclusion, if there exists a OWF, then $P \neq NP$.
Comment: Every point in my answer is a necessary logical step.
Comment: That's exactly what I did.
Comment: It was already hinted under the question. Your answer is too long for this basic question imo. Anyone who has seen a reduction from search to decision should be able to fill out the rest.
Comment: Not on this site. Have you checked [help/on-topic]? If someone cannot fill in the gaps like these then probably they should ask the question on our sister site [cs.se] in place of here.
Comment: If P=NP, any polytime computable 1-1 function has a polytime computable inverse. The proof is not even a paragraph: $\{(x,y) \mid \exists z\ |yz| \leq poly(|x|) \land f(yz)=x \}$ is NP. We can find a $y$ by starting at empty string and greedily adding the following bits using this NP oracle.


conceptual model, mental model, roadmap and framework

Question: i'm a little confused about the concept of this words. conceptual model, mental model, roadmap and framework. is there anyone who can explain to what this words means. and more importantly what is the difference of them?
Answer: Those are two sets of related but different concepts; mental/conceptual model, and framework/roadmap.
The difference between a mental model and a conceptual model is described well in this article.
Mental Model v Conceptual Model

A mental model represents a person's thought process for how something works (i.e., a person's understanding of the surrounding world). Mental models are based on incomplete facts, past experiences, and even intuitive perceptions. They help shape actions and behavior, influence what people pay attention to in complicated situations, and define how people approach and solve problems.
A conceptual model is the actual model that is given to the user through the interface of the product. Going back to the iPad ebook example, you have a mental model about what reading a book will be like in the iPad, how it will work, what you can do with it. But when you sit down with the iPad, the "system" (the iPad) will display what the conceptual model of the book app actually is. There will be screens, and buttons, and things that happen. The actual interface is representing the conceptual model.

Roadmap and frameworks are much broader terms, but I have put them into the UX context I think you're talking about - essentially your roadmap is your plan for how to deliver, and a framework is the set of constraints you have to operate within.
UX Roadmap v Framework

A UX Roadmap is a game plan to achieve your product or site goals. It starts with your desired result of a seamless and delightful user experience and takes into account all of the UX research required to achieve it. Think of it as a blueprint for your research that includes a strategic overview, the different kinds of studies needed to satisfy research goals, a proposed timeline of deliverables and other key elements that enable your success.
A framework is a set of functional, predefined, reusable components that can be bundled in a specific working solution.


Is there a way to prove ownership of a transaction?

Question: Is it possible to prove that you are the sender in a transaction?
Prove this to 3rd-parties, not only the receiver.
Comment: possible duplicate of [How can I use message signing to prove that I have private keys for many different accounts?](http://bitcoin.stackexchange.com/questions/7413/how-can-i-use-message-signing-to-prove-that-i-have-private-keys-for-many-differe)
Comment: possible duplicate of [How does sign message work?](http://bitcoin.stackexchange.com/questions/3898/how-does-sign-message-work?rq=1)
Answer: You cannot "own" a transaction. But you can own the private keys for one or more of the addresses from the inputs of the transaction.
A (regular) transaction must be signed with the private keys of the addresses of all the inputs. So if you own one of the addresses, the transaction could not have been verified without you, which may count as "ownership" if you want to call it that way.
Proving that you own an address can be done by signing a message using the private key of that address. Most wallets provide signing functionality. Just agree on a message, something like "I, [name with which the other party knows you], am the owner of address [address from the input]." After signing, you can send the message and the signature to the other party and he will be able to verify your ownership of the private key.
Answer: Yes, it is possible. You would do that by signing a message using the private key of the address which you sent the transaction from. Bitcoin-QT offers this functionality by clicking the button called "Sign Message". Anybody can then verify that the message could only have come from the owner of said address.
To ensure privacy, you would perhaps not want to put private information into that message, but rather announce to the third party that you will send them a message with some sort of passphrase (or ask them what passphrase they would like you to use), e.g. "This verifies my ownership - 54123" and then later on, send them exactly that message signed by using your private key.
Comment: What address would you use to sign the message? There's no "sender" address in a transaction, only inputs/outputs.
I think a good solution would be to use the change address, but how do you determine what the change address is?
Comment: The "sender" address is the one, that you had previously received the inputs to. I.e. the receiving address of the transaction that gave you the bitcoins that you are now spending. The change address is not useful in this case, because nobody has a way of knowing whether you sent the change of the transaction to yourself or to a third party. If you don't know which address the inputs belonged to, you can easily find out by checking the transaction id on a block explorer such as blockchain.info.
Comment: So I can be sure that all the addresses from all inputs belong to the same private key/person?
Comment: Maybe not belong but they have access to the private key (think of a service sending coins on behalf of someone else, they have control of them but they do not belong to them in reality)
Answer: Yes, you can prove you are the transaction's sender, by signing an arbitrary message with the transaction sender's private key.
Here is an example using Electrum 3.3.6.

Navigate the menu bar: Tools -> Sign/Verify message.
Fill an arbitrary message (ex: This is a test message.)
Enter the sender's address for that transaction (ex: 1Hs7hQQs8cQVGLoTrNjDuXqRRpfGCwLEeh)
Click the Sign button. This will generate a signature for this message, using the sender's private key, if you own it.
Send the transaction ID, message, sender address and signature to whoever needs proof you are the sender. They will be able to check your signature, with the Verify feature, or any equivalent tool they may use.


Can anyone protect my question (What does "TTY" stand for?)

Question: Can anyone protect my question?  Because there are samlier question to it like this one that is protected! That has less upvotes!
Answer: I have protected that question but you must have to read why a question should get protected
https://askubuntu.com/help/privileges/protect-questions
Its doesnt matter its having low/high votes. If that have some significance to wide area of Ask Ubuntu users, then to protect it we used to protect the Question.
So the others(new users) who are intended to do some mess cant even touch them unless they do some contribution and earn a minimum reputation.

Can anyone protect my question (What does “TTY” stand for?)


How to obtain the h-index or number of publications for a given academic as a function of time?

Question: Services like Google Scholar can provide you with the h-index of a given author at present. Is there a way or a service that provides a time series of the h-index (or the number of publications) as a function of time, or even provides a plot of this time series?
Comment: Are you interested *specifically* in the Google Scholar citation data, or would a visualization of the h-index as measured by, for instance, Scopus also do?
Comment: Scopus also works, it can be any service. I am aware that different sites provide different measures of h-index that are not consistent between themselves. Any would suffice to get the general gist of h-index evolution.
Answer: Scopus has an author search option. You can then examine a range of graphs that show academic output over time. Many universities have a subscription to Scopus.
As with any citation and  publication based metrics, the values are contingent on the citations and publications included in the underlying database. Scopus is fairly broad, but there is quite a lot of quality control. So the numbers will be quite a bit smaller than for example Google Scholar. Another option might be PublishOrPerish which is a downloadable free program which uses Google Scholar as the underlying data source.
Below I show an example for Albert Bandura (one of the most highly cited psychology researchers) using Scopus.
Citations per year

Documents by year

h-index by year
I could not see any easy way to just get the h-index by year. However, the h-index tab, does allow you to filter on different years. So you could manually, change the end year and repeatedly obtain the h-index to see how it went up each year.
Answer: I am not actively aware of any tool that does this, although I vaguely remember seeing such timelines for various bibliometrics tools. However, if you are able and willing to do a little bit of coding, it should be reasonably easy to code this up yourself.
For instance, SCOPUS has an API that you can use to get all citation data for an author. From there, you should be able to can just browse the publications that cited this year to year backwards, remove all publications whose publication date is after the date you are currently looking at, and recompute the h-index. A Python script to this end should be quite easy to set up.


How to bring a cat from Mexico to United States on a flight?

Question: I have US citizenship, my wife is a Mexican citizen working on her visa. She has a cat she can't live without and I am trying to figure out how to get it up here. Do I just talk to the airport and pay a fee?
Answer: According to the CDC, import requirements for pet cats are pretty relaxed. However, additional requirements may apply based on the destination state, county, or city.
For information about flying with a cat, contact your airline. They will probably have different rules depending on whether the cat is accompanied (considered personal baggage) or not (considered cargo). I flew my cat domestically (within New Zealand) on a 1.5 hour flight unaccompanied, so I had to pick him up at the cargo depot at the destination, rather than regular passenger baggage claim. There will probably be more paperwork required for international pet transport.
Answer: Here are the rules for taking pets to México.  Note that this is a consulate in Canada, and I am Canadian.  It will be slightly different coming from the United States or elsewhere (likely just veterinary association membership, but ensure you check).
When we did it, we went to the vet and got proof of health, rabies shots, and deworming - and proof of all of that!  Keep ALL your paperwork, make 2 copies, keep one at home and take the originals and a copy with you.
As Greg Hewgill mentioned, ensure you've done everything the airline wants done first.  In our experience, that means mentioning and paying for Pet carry when purchasing the tickets (and do this early, there is a limit on number of pets allowed on each flight).
With us, the cats travelled under the seat as our personal items. Larger pets will have to be picked up at baggage claim after immigration.  Before customs, in the baggage claim area or on the way, there is a SAGARPA booth, where the agents will review the animal and  your paperwork, and either approve it or require a local veterinary assessment.  You will get your papers back, but they will take a copy of them for their records.
Expect this to take time, especially if there is a lineup - if there are two people travelling, have one get in line with the pets and the paperwork, and send the other one to pick up baggage and come back.
Expect the airline checkin counter (either for local onward travel, or when returning) to review all the paperwork before issuing boarding passes as well.  This is why I recommend bringing two copies, in case SAGARPA takes one set, or you misplace it, or it gets used for something else accidentally.
Also: know what the requirements are in your home country for bringing pets back.  In Canada, it's an on-site veterinary review, and that isn't cheap.


Mini CD in Mac Mini

Question: How does one get a mini CD out of a Mac Mini? It got stuck in there pretty deep and I'm scared to take the drive and shake it. I tried getting it out by "levering" w/ a pen clip but that didn't help. Help me please!
Comment: what MrU said - or a credit card with double-sided tape, or even a post-it note.  On the subject of notes… please note you can't put mini CDs in a slot-loader. afaik, only the Wii is designed to take them.
Answer: Tweezers? I use tweezers often in our car, which the cd player's eject function won't work.
But since yours is so "deep" down, can you still see it? If not, well, slim tweezers?
If you can still see it, you should be able to use the tweezers.
-------------------------------
Another way is maybe a hook fashioned out of a plastic sheet? take a slim but sturdy sheet, cut it so that it fits into the drive, and fold a small fold along one end. The fold will act like a hook and grab onto the drive.
Insert the plastic folded end first, facing down. try to get the plastic on top of the disc so the fold slides over the top and unfold behind it. The fold should "catch" the disc and then you can pull it out.
Hope this helps.
Comment: next time, use a designated mini cd adapter - They look like normal sized discs with a slot in the middle to hold the mini cd in place

Mini CD in Mac Mini


Windows Fine-Grained Password Policies (FGPP) - Set Policy Duration

Question: Trying to determine if there's a way to configure an FGPP(the policy itself) to last/be enforced only for a specified period of time or ideally, until a triggering event occurs.  E.g., create temp pwds for a group w/ a 10-day expiry FGPP, but only have that FGPP in place until the pwds expire in 10 days, or they change their pwds (then revert to the domain "Max-Pwd-Age" etc. policy).
Answer: FGPP provides password policies, but does not to my understanding provide a means of applying to groups, OU's, etc. only for a defined period of time.
That said, I am curious why a group would have a temporarily shorter (assuming your domain setting is longer than 10 days :) )password age?
It seems to me the only way to accomplish this would be to apply a FGPP to an OU, then use an AD-automating method to periodically test the accounts' last password change value and move it to another OU based on that. I am not an AD "expert" but I am aware of tools that may make doing so possible.
Comment: Thx Sean, yeah I'm not seeing many ways to handle this.  Was thinking scheduled task also. seems to be the only way to handle this, but thx for confirming.  FYI by "group", I meant a group of users to which FGPPs would be applied individually.  We have an app upgrade req to temporarily change users' pwds en masse to get some stuff to work post-upgrade, but those pwds must return to being "interactive" (user-driven/responsible,) soon after.


Tor and remote desktop viewing

Question: If I am using tor for anonimity, does this prevent staff at a place of employment or an educational institution from remotely viewing my desktop and seeing what I am doing on Tor? If so how can I get around this?
Comment: Tor masks your traffic as it leaves your computer, it doesn't protect you from applications installed on your computer by other administrators. If you are looking for an answer to the second part of your question, I suggest removing the Tor bit as it is irrelevant.
Answer: If someone else has software installed on the computer you are using that allows them to view your screen than Tor will not prevent them from doing so.
If used correctly Tor will make it very difficult to associate your internet traffic with you and people snooping on that traffic will not know you are the one it is directed to. But, if an attacker has spyware on your computer that wont matter. They will presumably already have access to your computer and be able to see and record everything you are doing.
Potential alternatives are to use Tor on your own computer that doesn't have spyware installed on it by an educational institution. However, if you are using a school computer and internet connection there is no real way to garuntee that you aren't being snooped on.
Answer: In general, if you can't trust the computer that you are using, you should expect no privacy whatsoever. Just as Tor cannot protect you against someone looking over your shoulder at your screen, it cannot protect you against an administrator viewing through Remote Desktop, or the "commercial spyware" programs that many institutions install on their computers which are capable of taking screenshots and logging keystrokes.
The main purpose of Tor is to make it hard for the websites you are accessing to figure out who or where you are, and for your ISP/anyone watching your network traffic to see what websites you're trying to access. It does not protect you against software on your own computer.
There is really no way around this other than to use Tor (or VPN) on a computer that you own and trust, preferably one on which you've fresh-installed the operating system yourself.
Comment: I would hesitate to equate VPN to Tor.

Tor and remote desktop viewing


Questions about rooting a tablet device for making kiosks

Question: My company's looking at the option of using Android tablet for making kiosks. The thing is, the majority of the native settings must be blocked from the user, and very limited apps and utility will be exposed to the customer. From the looks of it, a custom ROM would be the perfect solution, but that requires some arbitrary device be rooted. But then rooting voids warrantee, and this is meant to be a commercial product, so some kind of warrantee is needed. Is there an alternative method? Or what's the legality of commercial rooting?
Comment: I've added the [tag:kiosk-mode] tag to your question. You might like to start by looking at the existing top questions in that tag.
Answer: For a solution like a kiosk you would use dev hardware where you have full access to the hardware (JTAG for example) and then you would push your own Android build with root access enabled and then push the ROM to the dev board.
That said, for a kiosk type deployment you would NOT want root access available. Therefore when you push your ROM root would not be enabled.
I think your confusing root access and an unlocked bootloader.
By a dev board and learn how to build your own ROMs. :)
Comment: Thanks! I'll be learning Android dev in the process of this project, so this world is still very new to me. Would you kindly elaborate what you said? Is it then not practical to convert existing tablets like the Samsung Tab for this purpose?
Answer: Did you have a look at applications such as KioWare and SureLock Kiosk Lockdown? These seem to be able to put your device to a kiosk environment. Im certain there are more alternatives for this purpose out there.
Another option would be to implement your own home screen application. This answer from stackoverflow might help with that.
cheers!
Answer: You could use SuperLockLite Secure Kiosk if you have Samsung device. Have a look at this free app, it does not require rooting of phone.


Dependence of solar irradiation through the atmosphere on Sun's altitude

Question: I want to show that the higher the Sun's altitude, the higher the solar irradiation through the atmosphere, through simple experiments. However, I don't have the instrument that measures irradiation. Is there a good approach?
Comment: Which kind of energy? Without specifying what you're talking about, it will be hard to help. I suppose you think of solar irradiation onto the atmosphere. Then you must specify a wavelength-range, as the atmosphere is in various parts of the spectrum transparent or opaque.
Comment: @AtmosphericPrisonEscape Thanks for pointing out. And yes, I meant *solar irradiation*. But I just want to know a simple experiment without regard to things like wavelength-range.
Comment: Are you asking about the change in incident light received as the  sun's height above the horizon changes?  If so, then you should say "through" the atmosphere instead of "onto".
Answer: I believe you could use pyranometer data at various elevations to get a non-spectral measurement of the total irradiance received at the Earth's surface.  From here: http://en.wikipedia.org/wiki/Pyranometer

A pyranometer is a type of actinometer used to measure broadband solar irradiance on a planar surface and is a sensor that is designed to measure the solar radiation flux density (W/m2) from a field of view of 180 degrees.
  Pyranometers are frequently used in meteorology, climatology, solar energy studies and building physics. They can be seen in many meteorological stations - typically installed horizontally and next to solar panels - typically mounted with the sensor surface in the plane of the panel.

If you want something more accurate, a pyrheliometer or radiometer is used.  From http://www.esrl.noaa.gov/gmd/grad/starmeas.html

Direct solar irradiance is the solar radiation that passes directly though the atmosphere from the sun without being scattered or absorbed by the atmosphere. Typically it is measured on a surface that is kept normal to the direction of the center of the sun's disk. That surface is held normal to the sun's position by a solar tracker. Pyrheliometers are most commonly used to measure total direct solar irradiance. The most accurate measurements of this quantity are obtained from absolute cavity radiometers which serve as calibration standards and are being increasingly used operationally.
Comment: I'm sorry, I omitted to write the **sun's** altitude, and thank you so much for your answer.


Representing hierarchical data (C++)

Question: Say we have 2 Classes: Account and Contact like this:
class Account {
    string Id;
    string Name;
}

class Contact {
    string Id;
    string FirstName;
    string LastName;
}

An account can contain many contacts. This data is managed in a class "DataManager" which acts as the repository for the rest of the program. There are 2 main requirements:

For an Account, I need to retrieve a list of its Contacts
For a given accountId or contactId I need to retrieve the respective Account/Contact. The retrievement of a contact should work, even if I don't know which Account the contact is assigned to. Like this
Contact c = dataManager.GetContact(contId);

I discussed with a colleague the following 2 options to implement the Account-Contact relation in C++:
Option 1: Store hierarchically
... the Account class would contain a map of contacts. Key of that map would be the ContactId. The DataManager would store a map of accounts:
class DataManager {
    Account& GetAccount(string accountId);
    Contact& GetContact(string contactId);

    map<string, Account> accounts;
}
class Account {
    map<string, Contact> contacts;

    Contact& GetContact(string contactId);
    list<reference_wrapper<Contact>> GetContacts();
}

Problem: The implementation of DataManager:: GetContact would need to iterate over all account's contacts. As an alternative, I could store a map of contactId -> accountId in the DataManager to quickly dereference the account that contains the required contact.
Option 2: "Flat" storage"
In this solution, the objects are all stored in the DataManager. The account class only stores the Id's of its contacts.
class DataManager {
    map<string, Account> accounts;
    map<string, Contact> contacts;

    Account& GetAccount(string accountId);
    Contact& GetContact(string contactId);
}
class Account {
    map<string, string> contactIds;
    list<string> GetContactIds();
}

Problem: To get a list of all contacts of an account, the calling code (-> in real: some code in the DataManager) needs to iterate over the list of contactIds retrieved by the Account object and collect the respective contact objects from the DataManager.
Option 2.1 Reference wrapper
What about containers using reference_wrapper instead of string contactId? (as suggested by @Caleth)
What to do?
Which of these options seems more legit to you - or do you suggest a different solution?
Comment: What about containers using `reference_wrapper` instead of `string` contactId?
Answer: I suggest that design:
class DataManager {
  map<string, Account> accounts;
  map<string, Contact*> contacts;
  Account& GetAccount(string accountId);
  Contact& GetContact(string contactId);
}
class Account {
  map<string, Contact*> contacts;
  list<Contact*> GetContactIds();
}

So, you can access contacts of an Account directly.
Note: It is better to use reference wrappers as @Caleth commented or shared pointers instead of raw Contact pointers.

Representing hierarchical data (C++)


Low temperature PCR

Question: We're trying to do emulsion PCR using HA-coated polystyrene beads and we're noticing that the beads are seeing drastic issues with thermal degradation above 90C. As PCR has an unfortunate requirement of requiring a high temperature, I was curious about what options are out there to reduce the temperature during PCR denaturation or to stabilize the beads.
Comment: That's true, but there is a diminishing return on additives (at least DMSO) in which after a certain threshold either the polymerase will no longer function or the reaction will shift towards non-specific priming.
Comment: Unfortunately melting temperature of nucleic acid is an intrinsic property of the molecule. Do you need to use polystyrene as a substrate? Perhaps silicon or glass are better suited for this in situ PCR.
Comment: Well you can change the melting temperature using additives like DMSO and betaine. Unfortunately, the beads have to be coated and the polystyrene seems to be the best for the downstream steps so we would prefer to stick with polystyrene before re-optimizing everything else.
Comment: If there was an easy solution, I wouldn't be asking it on SE.
Comment: I've seen PCR melt temps as low as 92 C. It's too low a temp to melt, but do they become fluid > 90 C?
Answer: Perhaps isothermal amplification is possible (NASBA)?
Amplification of DNA also seems possible (NASBA at biomerieux).
Answer: Look at chemical hydrogen bond breakers.  Guanadine hydrochloride is included in the buffer conventionally to compete with the the hydrogen bonds that form the double helix.  Other hydrogen bonders like Propionamide and 2-Pyrrolidone can weaken the helix and I would think lower the melting point of the bonds.
How much the Tm is affected would depend on the concentration of the breaker in the buffer.  It might not be possible to lower the temperature this much and you may loose specificity - you might be able to squeeze a few more degrees if the oligos can't get any shorter.
Comment: Doesn't this accomplish the same thing as DMSO?
Comment: i think a few molar salt will also do it, or just amping up the Gu in the solution, but the paper also tries to estimate specificity and fidelity of the PCR reaction with different compounds so that you don't get as much error with increased bond breaking.  In the extreme concentrations of adding bond breakers, you get no double helix formation at all.
Answer: Update (21/09/17) as the answers are a little outdated by now:
Isothermal amplification methods are fairly well established by now and commercially available. They tend to amplify DNA at temperatures of around 56°C.

Wikipedia entry on Loop-mediated isothermal amplification.
For the more tech-savvy, an open research article on
loop-mediated isothermal amplification in Nucleic Acids Research.
Link to a commercially available product using isothermal amplification: ANSR (Disclaimer: I work for this company)

Low temperature PCR


Pot bound Acers with dropping leaves

Question: I have two Acers which are around 13 years old, they are in despair as they need re-potted but we are finding it hard to get a pot bigger than the one they are already in. They are already looking like they are dying and it would really upset me to loose them, is there any way to save them? One has started to drop leaves and I am starting to panic. Any advice greatly appreciated.
Comment: Many plants are quite happy being potbound and just slow down their growth. We need some pictures to really answer your question.
Answer: Some people root prune their Acers every time they become root bound.  It involves cutting off about 1/3 of the roots, then planting them back into the same pot.  This means you have to be very good on watering, never letting them dry out the first year.  Always keeping the soil nice and moist.  Not wet.
Winter is the best time to do root pruning.
How to root prune your maple
Comment: I second the root pruning approach.
Answer: Unfortunately, there's not much you can do because, as you suspect, it's likely they've run out of root room. If you can't find larger containers, they can be transferred to the ground, but that is best done in autumn; done now, you'd need to keep them well watered right up until winter begins.
Shrubs and trees in containers cannot stay contained forever (unless they are small shrubs), so they're really only relatively temporary potted plants. You can try trimming back a bit, but that needs to be done carefully so as not to destroy the natural shape. If you do trim back, remove any loose soil at the top and replace it with fresh potting soil and add a basic fertilizer (with an NPK of something like 7-7-7), preferably a liquid one at this time of year if you're in the northern hemisphere because it's really a little late to give fertilizer now. Keep well watered, because the soil to root ratio will be out of balance, meaning there's insufficient unoccupied soil to retain water. Really, though, the best option is larger containers or transferring to the ground.
Comment: Thank you for your reply. I guess I have been nervous to do anything with them in case I killed them, but I guess they will die anyway.

Pot bound Acers with dropping leaves


Does any data go into SSD from bootable OS USB (besides OS itself)?

Question: I made a bootable OS 10.6 in my external HD with Disc Utility's partition & restore functions (with the "source" (as OS disc) and "destination" method...)
And I used that to do a clean OS install on a new SSD.
I then found out I need to return this SSD because of some issues.
So, before returning, I'm just worried, did any of my personal data go into SSD from my external HD? All I did was to use the HD's OS partition to install OS on the SSD. The HD has another partition that is a time machine backup, but I didn't use that for SSD. This HD had been used as various data backups before I made any partitions in it. I guess what I'm trying to say is, can data that's currently on another partition or was stored in the past on the whole HD unknowingly transfer into the SSD by just fresh-insalling OS?
Answer: If you used installed OS X on your SSD from a bootable hard drive partition that was cloned from an install DVD, nothing else residing on your hard drive will be copied over without you knowing about it.
The only time user data is copied over onto a new drive is when transferring from a Time Machine volume or a disk in Thunderbolt/Firewire Target mode - something that cannot happen without your knowledge or consent.


Grand Audio Engineering/Mixing and Mastering Course?

Question: Does anyone know of a course or playlist that shows someone how to get into the world of mixing, mastering. I'm a complete noob and would like to learn about that stuff but I don't know the first thing. Is there a course out there which takes someone through the beginner to expert faze of getting the maximum amount of sound out of your recordings? That would be incredible, if such a thing exists. So if someone does know of this kind of thing would they be so kind as to link me to it? A free course would be incredible but that may be asking for too much so don't hesitate if the course costs money, a redirection would just be awesome! It doesn't even need to be a course, even a book or DVD series would be better than nothing. Anything to get me off my feet really.
Comment: Expect to take five to ten years of learning and practicing before your recordings really start to shine. It's like learning a musical instrument. It takes a lot practice time to become good at it. It is also fun and rewarding.
Comment: Yes, it is not an overnight thing at all. But if you work hard and smart, you can get good results within a year and then build on that.
Answer: There are thousands of options. Here are some:
Books

Mixing Secrets for the Small Studio by Mike Senior
Recording Secrets for the Small Studio by Mike Senior
Behind the Glass by Howard Massey
Fundamentals of Musical Acoustics by Arthur Benade
Handbook for Sound Engineers by Glen Ballou
Here, There and Everywhere: My Life Recording the Music of the Beatles by Geoff Emerick (Note that the techniques pioneered in recording The Beatles at Abbey Road form the basis of virtually all music production that followed. This is worthwhile reading regardless of you opinion of The Beatles or the type of music you want to record.)

Web Resources

Sound on Sound
TapeOp
ProSoundWeb

Fora (Forums)
I highly recommend you start off by reading only and not posting on a forum you are new to.

The TapeOp Message Board (TOMB) (best resource in this whole post, sorry Sound.SE)
Sound Design Stack Exchange (Beta)
Right here (music.stackexchange.com)

Other

Berklee College of Music Courses on coursera.org

The number two thing to do to learn to record music
The second most important thing to do if you want to produce music is to learn to play a musical instrument. It doesn't matter if it's an accordion or a zither, a balalaika or a hurdy-gurdy. Learning to play any instrument (even just cowbell) will both give you an understanding of how music works and something to record when you are alone. Which brings us to...
The Number One Thing to Do to Learn to Record:
Record!
Do you have a smart phone? Then you can start recording today! Just start recording things. If you know a musician or band or you are a musician, start recording them or yourself. If you have a computer, get Audacity (free) or Reaper ($60) or Live Intro ($99) or anything and start playing around with it. Learning to record is like learning a musical instrument. Reading and research help, but...
The only way to really learn is to practice.
Most of the people who recorded your favorite albums started out with a cassette tape deck and a burning passion. Many of them never went to any kind of school for audio production. Some of them won Grammies before there was any such thing as schools for audio production. Stop reading this and go do it!
Comment: Oh wow, now that is an impressive answer! Thanks a bunch! It's exactly what I was looking for.
Comment: Yes, this is a great answer. The only thing I would take exception to is the recommendation to learn a musical instrument. There are already many people who can play musical instruments and don't now how to record themselves and/or don't have the money to pay someone else to record them. I recommend you consider the audio mixer to be your musical instrument and get enough skill and gear together so that you can record all of the indie bands in your area for free until you are good enough that somebody wants to pay you.
Comment: @SimonWhite I can't find any references right now, but I've read several times that many engineers recommend learning some instrument and they use that knowledge frequently. I've learned several instruments and have used almost all of that knowledge. At least learning a lot of music theory is invaluable and the best way to learn theory is along with an instrument. Setting up click tracks and editing are two things that every engineer does that are made easier when you know an instrument and/or theory. Playing in a band helps a lot with understanding how everything should fit together.
Comment: @SimonWhite As a recording engineer, you have to work with musicians and producers (who are usually also musicians). Being able to talk to both musicians and producers effectively is much easier to do when you know an instrument. Most people who are music production engineers got into it at least party because they love music. There's not better way to experience the full breadth of music than to learn an instrument. I stand by my recommendations.
Answer: To give one more addition to Todd's excellent answer. Video tutorials are even better suited to learning about audio recording over books or other written content IMO because you can hear the techniques they are teaching in action and how it affects the sound, which you simply cannot get from written text.
A youtube channel I highly recommend is The Recording Revolution. It covers an wide range of topics and techniques and is very beginner friendly. He even did a series where he recorded and mixed a song using only $300 worth of recording equipment in total (not including instruments) to show what you can do with very little money. It really is a fantastic resource.
https://www.youtube.com/user/recordingrevolution/videos
Comment: Great recommendation and great website. You really have to remember that you want to be an audio engineer, not a gear collector. I highly recommend that beginners only rent gear for the first while (if you have a music store with rentals in your area) because so much gear is low-quality and/or not appropriate to your needs.


Server process with PHP+MySQL

Question: I am new to web programming, and I am developing a simple appointment app with PHP + MySQL. Is there a simple way to add a background process on a timer (to send out daily appointment reminders, for example)? This could be done easily in another language, but I want it to run on shared hosting with only PHP.
Answer: Your host may or may not approve of this. You can write a PHP script for use on the command line and make a crontab entry to run it periodically. If you don't have command-line access to the PHP interpreter, you could write the script to run in the web server and hit it with wget or curl, also using a crontab entry.
Comment: +1 for using cron on a local machine + public-facing script on the remote machine.  Remote-cron is a cool idea.
Answer: If you have a Linux webhost, you might be able to use a cronjob (to automatically run a script periodically)--even on shared hosting.  Some webhosts with shared web hosting allow you to create cronjobs via cPanel (or whatever they use).
That would really be your best bet, as opposed to creating a background process on the server, which the webhost probably would not be very kind about.  So definitely check and see if you can use cron.
Answer: I work in a place where I cannot set a cron job so I made a page that when viewed it checks the time since the last time it did a list of jobs.  If the time since job last run is over a set threshold it runs the list of jobs.  Then I set up a scheduled job on a computer that I know is on all the time and connected to the internet and would open the page every 10 minutes.  Worked pretty constantly.  Got the idea from Joel on a stack overflow podcast episode.

Server process with PHP+MySQL