Creating Directional Flow Arrows for sewer lines?

Question: I am working for the Town of Yadkinville, NC and would like to know how to create a layer of directional flow arrows for sewer lines to be able to turn them on and off at will?
Comment: Is the From point of each polyline at a higher elevation than the To point?
Answer: Most of the sewer pipes I've seen have the directional arrow at the end of the line, but I had users that wanted the directional arrows along the entire line, at a reasonable interval.
It was a 2-layer symbol, with a cartograhic line, and then a Marker line symbol with an interval of 13.

Also, I just used 2 different feature layers of the same featureclass: 1 with the arrows and 1 without (sometimes I would tie each to different a scale range).
here's the symbol on a 9.3 layer (don't have time to sort out a style file). You should be able to add it, set the data source and go from there to tweak the symbol.
line-example-10.5.lyr
line-example-10.4.lyr
line-example-10.2.lyr
Answer: When you created your sewer network as long as it was built with an eye to topology you can symbolize with directional arrows.  Meaning, when editting, click for the first point of your line which will be uphill, then the second point to complete your line with the downhill.  Flow will be from uphill to downhill.  Creating the lines with flows in line is the most important step.
You can create your directional symbology from the properies of the line feature class.  Symbology tab, click the line symbol, Edit Symbol, select 'Cartographic Line Symbol' from the drop down, select the Line Properties tab.  You can choose which end of the line you want your flow arrows on (or the middle).
This is all assuming you are using ESRI products and are trying to do this on the desktop....


How to automatically send replies to Gmail (from a certain address) during business hours?

Question: My landlord has requested that I only send him or respond to emails during business hours. Is there a Google script that would automatically draft my response and send it to him during the next business day?
Often, I cannot simply send a message to him during business hours because I am busy during the day. I am not entirely sure why my landlord does not simply refuse to monitor his email address over the weekend or set up an automated reply system, but I would like to humour him in this request.
I know how to write a Google script that will send a canned reply to anyone who emails outside of a certain time frame, but I would like to set up the opposite, a way to ensure that my replies are only sent during a certain time frame.
Answer: Good news, since 16th-Apr-2019 you can schedule your emails in Gmail to be sent off exactly when you wish to:


Looking for a reference for highschool level readers

Question: I was wondering if there exists a book that talks to highschool level audience who wish to study pure mathematics for their undergraduate years. I'm not talking about problem solving kind of books (I've found a lot, since math competitions are very famous). But more like a book that talks of what to expect in, for example, calculus or algebra.
Comment: Some books worth looking at: [**Mathematics: Its Content, Methods and Meaning**](http://www.amazon.com/dp/0486409163); [**Mathematical Sciences: A Collection of Essays**](http://www.amazon.com/dp/0262030268) [(review of this book)](http://epubs.siam.org/doi/abs/10.1137/1012096); **Great Currents of Mathematical Thought** [Volume I](http://www.amazon.com/dp/0486495787) and [Volume II](http://www.amazon.com/dp/0486495795).
Answer: The book "How to think like a mathematician" by Kevin Houston. It was recommended reading during the summer before I enrolled in my undergraduate math program, and I found it incredibly helpful. It discusses how math at university level differs from math in high school. You get a nice introduction to what mathematicians mean by definitions, lemmas, theorems, and a number of different proof techniques. It's written specifically to help bridge the gap between high school and university, but it can also help when you want to see what math at university is like.
Comment: Thank you for this reference, I've gotten the book and I'm loving it
Answer: What is Mathematics by Courant and Robbins is what I usually recommend to my highschoolers, closely followed by The Mathematical Experience by Davis and Hersh.  Both of these would seem to fit the bill quite neatly - a good overview of topics like topology, abstract algebra, real analysis etc with some nice problems to work through (although not strictly necessary).
Answer: I find the books by William Dunham ("Euler: Master of Us All", "Journey Throug Genius", "The Mathematical Universe", there are others) very inspiring. Mostly at high-school level, but they require quite a bit of effort to really grasp the details. Aigner and Ziegler's "Proofs from THE BOOK" is a bit harder, but shows off many dazzling proofs. None are really about "what is math at college like", but they do show a bit of the history and some gems.


Another prefix - suffix - infix mix

Question:
My start shortens round about
  My ending settles doubt
  My middle means combined with
  My whole is always split
Comment: Just a doubt, is it *combined with* or *combine with*?
Comment: It is *combined with*.
Answer: I'll take a shot at this  with

 circumfix

My start shortens round about:

 cir as abbreviation for circa

My middle means combined with:

 cum, latin preposition of the intended meaning

My ending settles doubt:

 fix in the meaning of to establish, to set definitely. (Thanks to OnlyF I delved deep into Merriam Webster's and rephrased that.)

My whole is always split:

 staying in the theme, a circumfix always consists of two affixes, one placed at the start of a word, one at the end, so it's very literally split.
Comment: Nice one, you got them all first go :) Although there are more definitions of the ending which would make for a bit better fit, I think it's pretty much in the way you've written it down that it seems to not be such a good fit, to *** something can mean to rot13(gb frggyr qrsvavgryl, be chg vagb creznarag sbez), which settles doubt..
Comment: Oh, I got it? Cool. - But if this is the correct answer, it should be marked as such. As far as I can see, it's not marked. Apart from my browser may be playing dumb: Did your mark not get registered, or do you mean that it's still not complete?
Comment: No I was just leaving it for a bit in case you wanted to edit after my comment (not sure if you still can after accepting), but you'll get the tick soon in any case :)
Comment: Ah, OK. Well if you'd prefer that, I'll do.
Comment: That was a nice one, thanks. I liked the hints, and the overall consistency of the theme helps a lot to establish a good feeling for whether an answer fits well or not. So while trying around, there was always a good certainty that I was not quite there yet. Once I had it, it satisfyingly snapped right into place. I like that.

Another prefix - suffix - infix mix


Combining UV Maps for a Single Object

Question: I have a single object with two different UV Maps because it is a complex object and I wanted to unwrap different parts of it separately. I do not want to separate my object into pieces and recombine them because the object will be using bones, and I want the mesh to stay together. How do I combine the two UV maps for the single object?
Comment: Just work with separate UV islands . . ? Not sure what you are asking
Answer: I am assuming both UV maps are associated with the object?  You can create duplicates of all of your materials.  One material, let's call it A, will use UV map A; material B will use UV map B.  They will otherwise be identical.  You can set the UV map for the material using the "UV Map" input node.
You then need to define which vertices/faces are associated with each UV map.  I suggest using vertex groups to do this.  So you'll have vertex group A and group B.
Finally, you need to assign the right materials to the right vertices.  In edit mode, use your vertex group A to select all of the A vertices.  Then go to the material tab, select your material A in the slot list, and click "Assign."  Do the same for vertex group B/material B.
You'll need to repeat this process for each base material used by your object.
Answer: There is a free addon called 'Multi Object UV Editing' which you can download from github at https://github.com/ndee85/Multi-Object-UV-Editing
I am using this addon myself, it works like this: Select multiple objects and press the 'Multi Object UV Editing' button from the tool panel in the 3D view.

It will then temporarily combine your objects into one and open the UV editor as one. Once you are done editing and switch out of the edit mode (tab key) it will transfer the UV changes to the previously selected objects. It's pretty seamless.

Combining UV Maps for a Single Object


Which wood sources produce toxic smoke?

Question: So the title says it all. If I am scavenging wood in the wilderness, does some of it burn toxic? If so what kinds. This question is derived from this answer.
Comment: Also arguably all smoke is toxic, so it would help to mention in what kind of circumstances you'd worry about their toxicity. I.e. burning in a camp fire/fire place/indoor wood stove/... It also makes a big difference if you are having an open flame BBQ or will be suspending a lidded pot over the fire, etc.
Comment: This is going to be highly region specific... There are some tropical tree species that can be fatal (or at least really really nasty) if you inhale the smoke.
Answer: Yes, some sources create toxic smoke/fumes, notably:

Oleander
Rhododendron
Poison Ivy (smoke can cause lung damage in some cases)

I'm not sure of a comprehensive list, but be wary of any poisonous wood / shrub, it's probably more likely to burn toxic. As pointed out in the comment, unless you can identify vines well then it may be a good idea to stay away from all of them - dead ones are hard to identify.
In addition, be aware that any wood containing sap (pine for instance) will tend to spit, so don't cook directly on such a fire, otherwise your food may get coated! These are generally OK to use if your food is well above the fire though.
I also wouldn't use any processed wood that may contain glue, varnish etc. - highly likely it could burn toxic. I know this is for a survival situation, but sometimes you can come across "easy" treated wood that's been dumped off someone (old furniture for instance.) I wouldn't just immediately grab it, especially if you're using it for cooking.
Comment: I think I would generalize Ivy to all vines.  Some are safe to burn, but dead vines are just too hard to identify. (+1 all the same)
Comment: @RussellSteen Very good point - updated!
Comment: Do you have a citation for toxic smoke or fumes from Rhododendron wood?
Answer: At The Wood Database is a table of 235 wood types—intended for woodworkers—which indicates the irritation reactions, type of irritations (skin, eyes, respiratory), and irritation potency.  It should be helpful to infer which woods might be poor choices to burn and breathe.
For example, Douglas-fir irritates all three areas but at low potency.  Reactions include irritant, giddiness, runny nose, splinters go septic, nausea.  The details say that reactions to Doug-fir are quite uncommon.
At the other extreme is Australian Cashew Nut which causes irritant, skin lesions, nosebleeds of maximum potency.  Surprisingly, Western Red Cedar has the same severe irritation ratings (and I love sawing it up and deeply inhaling the aroma).
Comment: @KenGraham:  Thanks for the edits.  It was quite late when I typed that.
Answer: Sumac is a known toxic burning wood of North America. You are not to use it with the preparation of food.
Comment: Could you add some references to back up your statements.
Comment: @ShemSeger not sure why you think it does not answer the question.  While Kens request for references is good.  [Sumac is toxic and can grow into small trees that can reach a height of 1–10 m (3.3–32.8 ft). ](https://en.wikipedia.org/wiki/Sumac#Toxicity_and_control)
Answer: As noted in a comment, all wood can be considered to release toxins in the smoke when burned. You may be exposed to more toxic smoke if you burn hotter fires.
Wood contains a lot of chemicals, and burning it involves a lot of chemical reactions. Different chemicals burn off into the smoke at different temperatures.
I do not smoke food, but my understanding of food smoking is that lower temperature smoke is better for smoking meat.
I have read that more toxic chemicals tend to smoke out at much higher temperatures, approaching or exceeding 1000 degrees F (540 C). This is especially relevant to those using home-made wood charcoal, as the chemicals which burn at lower temp are already driven off, so you are more likely to be burning a hotter fire with less pleasant smoke. Likely less smoke overall, but that smoke may be made of more toxic chemicals.
I have made some good quality charcoal and plan to try some crafts next year such as pottery, melting down steel, or making some glass; these require very high temperatures (please use extreme caution and do your research if you follow suit). When I recently found out that late-stage smoke may be more toxic, that was concerning to me. If I do these projects, I will need to avoid the smoke as much as possible.
I recall a few articles which discuss the higher-temp toxic smokes, but I do not remember how to get at them now. I will update this answer within a day or two after I track down the reference links.
Answer: There is nothing wrong with burning rhododendron, as long as it is seasiond, it burns hot and fast, so you will need a large pile or mix with other longer burning logs,  it's tangled nature makes it sometimes difficult to harvest, it's is commonly burned in areas where it is plentyfull and invasive. In green wood, it has traces of toxin however when dried it is quite safe to burn
Comment: When you post an answer that contradicts a highly voted answer, it will be better accepted if you include supporting references.
Comment: Related: https://outdoors.stackexchange.com/questions/7100/are-rhododendron-and-mountain-laurel-truly-toxic-to-burn-in-a-campfire/7104#7104

Which wood sources produce toxic smoke?


what is the translational motion with the velocity of the center of mass?

Question: and that is the internal motion relative to the center of mass?
could give me some examples?
desire to relate since I need to find out what is the kinetic energy in the center-of-mass of two particles, one moving and one stationary.
Note: they collide
Answer: The center of mass of a two-particle system is, by definition, at position
$$x_\textrm{com} = \frac{m_1 x_1 + m_2 x_2}{m_1 + m_2}.$$
The relative position of your particles relative to the CoM can be found by substracting the position of the CoM:
$$x'_1 = x_1 - x_\textrm{com},\ x'_2 = x_2 - x_\textrm{com}.$$
That should help you get started. Try differentiating those expressions to come up with how velocities relate, and what the kinetic energy would be.


At what minimum distance the direction at which eyes point becomes parallel?

Question: This is very similar, but different than this question about focus, let me explain why it's not a duplicate at all.. That other question is about the distance of EACH individual eye FOCUS, this one is about VERGENCE, focus plays no role in this question, here what matters is the angle formed between the direction each eyes points. When objects are close to our noses, eyes get cross-eyed. As objects get further away, the eyes get more parallel, so called wall-eyed. There must a distance just become totally parallel, I deduce this by analogy to what happens to the focus, for which the distance is 6 m as this answer says. What is the corresponding distance for vergence?
I couldn't find the answer in the relevant wikipedia article on vergence.
Answer: Mathematically, the eyes are parallel when they fixate at, and only at, infinity. Now, because of noise, there is a distance after which it's not really going to make a difference (otherwise you would be able to tell the distance between stars at night). There are 2 parts for your question. First, at what distance it doesn't matter because the eyes won't stay still enough to accurately maintain this vergence angle. Second, at what distance it perceptually makes no difference because you can't tell if the object is closer or not. Concretely it means looking at the distance where each of these metrics is smaller than detection threshold (the value below which your performance on a detection task is lower than a specified value). Conveniently, Chopin et al. (2016) measured both values (these numbers can of course be found in older papers too).
For the first question, they measured vergence noise of 225 arcsec (or 225*pi/(60*60*180)=0.0011radians). The distance for which vergence becomes smaller than that is approximately 55 meters (vergence~=IPD/FD, with IPD interpupilary distance of approx 6cm). So farther than that you wouldn't be able top tell whether they fixate at infinity or not.
For the second question they measured relative disparity thresholds. Relative disparity is the difference in vergence angles between 2 points. So for relative disparity angles lower than threshold you cannot tell whether point A is closer or farther than point B. They unfortunately don't report the exact value but from the graph it looks like 300arcsec, corresponding to a distance of about 40 meters. In other words, after this distance you can't tell whether an object is farther than where you look at.
Finally, you could also ask: at what distance can't I tell whether an object is at infinity or not? The distance of a point in isolation is called absolute disparity, and is known to be much worse than relative disparity (i.e. it is much easier to compare the distance of 2 points than to report the distance of a single point in isolation). This distance turn out to be quite shorter. From the same paper the absolute disparity threshold is about 3000arsec (again, they unfortunately don't report the exact value). This gives a fixation distance after which you cannot tell whether you fixate at infinity or not of about 4 meters.
This is all very approximate and making lots of assumptions but I hope this more or less answer your question.
Chopin, A., Levi, D., Knill, D., & Bavelier, D. (2016). The absolute disparity anomaly and the mechanism of relative disparities. Journal of vision, 16(8), 2-2.


What happens to nonce in transactions?

Question: When is the nonce generated? What parts of a transaction can be changed after the nonce was generated? How is the nonce connected to a transaction's children/parents?
Answer:
The last step, after bundle and tips have been set up, is calculating a nonce matching the minimum weight magnitude (MWM). On the mainnet, MWM is 14, which means the transaction hash has to have 14 trailing 0-trits.
None. Transaction hash is calculated by absorbing all transaction trytes and create a 81 characters transaction hash. This means, if you change any characters, it will give you a complete different transaction hash.
It is not connected. Nonce only affects that transaction (not the bundle, and not other transaction in the bundle).

For how a transaction were generated in IOTA, you can take a look at this article: In-depth explanation of how IOTA making a transaction (with picture)
Comment: `trunkTransaction` and `branchTransaction` are part of the transaction trytes, aren't they? You said the transaction hash is calculated by absorbing the whole transaction trytes. So how is the nonce not connected to branch and trunk?
Comment: branch and trunk are part of a transaction. But what Louie says is still true. Transactions in a bundle are atomic units on their own. They are chained via trunkTransaction. But the nonce always relates to a single transaction. So in a bundle with 5 transactions you'd have 5 nonces, one for each transaction.
Comment: Yes, trunk and branch are parts of the transaction, but in that transaction, that is just an 81 characters string, nothing else. Nonce will only care about its transaction, not others (e.g. the "trunk transaction" itself, nor other transaction in the bundle)

What happens to nonce in transactions?


Used sesame oil instead of soy sauce - can I rescue marinade?

Question: I am making panko chicken, for which I marinate the chicken in low sodium soy sauce and lemon. I ran out of the soy sauce and needed an additional 2 tbsp of it. I remembered I had bought a small bottle of it but it was a different brand. I accidentally poured sesame oil. Now I don't know what to do. Can I make something else from the mixture, and what other ingredients should I then put in?
Comment: Is this just in the marinade? Doesn't the oil float? You could probably just spoon most of it off the top... I don't know that it will really hurt anything. Anyway, the recipe for your "panko chicken" would be helpful.
Comment: Was this regular sesame oil, or toasted sesame oil?  (toasted is much more strongly flavored)
Comment: You should also use better titles when writing a question. I have edited it (pending review)
Answer: You don't need to rescue the marinade, sesame oil isn't going to ruin it, just add more soy sauce to get the saltiness you need. Sesame oil isn't going to impart much flavor to the meat in the marinade However, if you plan to use the marinade as a sauce then keep in mind that

Sesame oil is not going to add much flavor to the meat while it is marinaded, however is will add a lot of flavor to the cooked result, perhaps too much
That much oil could make your end result a bit greasy in texture
Sesame oil has a low smoke point and will burn and produce off flavors if added to the bottom of a hot pan, I recommend adding it to liquid

I would suggest if you plan to use the marinade as a sauce just add a little bit of it and add soy separately to the dish to make up for it.
Answer: There is absolutely nothing wrong with sesame oil. You will get a slightly different flavor. As it's an oil, you may want to reduce the amount of oil elsewhere.
Having slightly less soy sauce than described in you recipe doesn't really affect anything (apart from additional soy flavor).
Comment: Harmless if it is untoasted sesame oil (which nobody would mistake for soy sauce drunk!). Toasted is a very potent aromatic.
Answer: 2tbsp of sesame oil is a lot, if it is toasted sesame oil (the variant most easily mistaken for soy sauce). Certainly too overwhelming for a japanese style dish, you crossed the border to korea(n food) here. Consider finding a recipe for a korean (eg bulgogi) marinade, and add the rest of the needed ingredients too...


Execute a file from nerdTree

Question: With the default file explorer (netrw) you can press x to open a file or directory with the system default application. Is there an easy way I can do the same with nerdTree? I can't find the option. Thanks.
Comment: You can maybe try `gx` since it's basic Vim functionality and I assume it's worth a shot.
Comment: It works with the files (at least it did open firefox with .html files) so it's something but It would be great if it also worked with folders. Netrw opened nautilus when I executed folders.
Comment: Hmm. But I, and I think you too, have looked through the whole documentation of NERDTree. I guess you can ask the developers directly in their issue tracker
Answer: In NERDTree, press m to bring up the NERDTree Menu, and then you should see an option, labeled o, to open the current node with the system editor associated with that file or directory. If that doesn't work for you, create an issue in the NERDTree repo.

Execute a file from nerdTree


Do pilots of airliners and jumbos do a walk around preflight check for every flight?

Question: Do pilots of airliners and jumbos do a walk around preflight check for every flight?  How do pilots of large airliners and jumbos do sumping.  If its not a requirement because of aircraft design, why not implement the same design attributes to smaller and ALL other aircraft?
Comment: Sampling to check for water accumulation in the fuel
Comment: Note that "being really big" is a design attribute, and implementation for small aircraft is not practical.
Comment: Sumping? You mean taking fuel samples?
Comment: Modern jet transport aircraft have a water scavenge system which mixes water from the bottom of the tanks back into the fuel. Water draining is usually only necessary weekly. This system would incur too much weight and use too much energy on small aircraft versus the time it saves.
Answer: NO, not all airline pilots do a walk-around for every flight.
At my airline, maintenance personnel do a "Pre-Departure Check" (PDC) before each flight from all main bases on all wide body aircraft. (A330, B767, B777, and B787)
The PDC includes:
1) a walk around
2) a check of critical systems
3) a signature in the Journey logbook
As a result pilots very rarely do a walk around on the wide body aircraft.
If we happen to land somewhere without company maintenance, then a walk around would be done by the pilots. If it were an ETOPS flight, we would also have to make an entry in the Journey Log Book stating that the APU oil level was checked by noting the EICAS APU Oil Quantity reading.
In addition to the maintainance walk around, the ramp crew also does a quick walk around inspection just prior to push back.
Comment: Interesting, would you say that your airline is the exception rather than the rule? I know pilots from British Airways and Qantas who have to do walkarounds themselves even at their home base.
Comment: I honestly don't know what other airlines do. I usually do long haul ETOPS flights and assume that other airlines would also require a maintainance sign off before an ETOPS flight. I would expect that maintainance persnonel would do a walk around during this inspection. Do British Airways and Qantas pilots also do walk arounds on ETOPS wide body flights?
Comment: Further on Ben's comment, I know Cathay Pacific pilots do that as well. I don't know the exact sign off procedure, but they have many long hauls and presumably ETOPS flight.
Comment: Certainly widebodies, ETOPS I don't know for sure. I'll add that it's usually the cruise relief pilot who gets the job (especially when it's raining...)
Answer: Yes, pilots of airliners do a walk around to visually check the aircraft before every flight, just like pilots of smaller planes do. A quick YouTube search brings up quite a few videos which explains the process.
The short version is, for items that are on the ground or within reach of the pilot, comparatively detailed checks are performed. For items that are beyond reach, a visual inspection is performed.
Due to the design of the aircraft, some checks that are possible on smaller aircrafts are impractical on airliners. For example you cannot move the flaps and elevators by hand. However, you can move them by using the yoke in the cockpit, once hydraulic power is on. There is a sensor which displays the position of the control surfaces in the cockpit. In a small aircraft, the pilot will move the yoke, then turn his head around to visually inspect the control surfaces are deflected to the correct direction.
Comment: A walk around is performed, but not necessarily by a pilot. See Mike Sowsun's answer.
Comment: "items that are on the ground or within reach of the pilot" For some planes [not much falls into that category](https://upload.wikimedia.org/wikipedia/commons/2/2a/Engine_of_Jet_Airways_Boeing_777-300ER.jpg).
Comment: Every flight? Even if you have a very short turn-around?


Add Windows 11 tag

Question: I noticed while writing a question about Windows 11 that we don't have a Windows 11 tag.  Since Windows 11 released this morning, the tag should be made for people who have questions about Windows 11.
Answer:
Since Windows 11 released this morning, the tag should be made for people who have questions about Windows 11.

Windows 11 was announced it was not actually released.  However, I already created it, it's a shell of a tag since most of the stuff that exists in the Windows 10 tag cannot be added to the tag at this time.
I also created a Windows 11 Preview tag which matches the Windows-10-Preview tag.
Comment: We can use the Windows-Insider tag to properly tag questions about preview builds of Windows 11.  We probably should have avoided creating a Windows 11 tag this early, since it's not released, and won't be for several months.  However, there have already been nearly 6 questions, specifically about it probably would have been created by somebody else.
Comment: I'm wondering if the windows-11 tag should, for the moment, be merged and synonymised with the windows-11-preview tag. For the moment all there is are previews, there is no de-facto Windows 11 release.
Comment: @spikey_richie - I immediately regret answering that first TPM question
Comment: @Mokubai - If we do that cannot be reversed?  What happens in 4 months when it is released?  It's a pain but we could just handle that cleanup manually.  There can't possibly be that many questions about TPM requirements for Windows 11 :$
Comment: @Ramhound it would mean that existing and current new questions would all be tagged as "preview", but we can break the synonym later or even merge or retag existing questions into the new tag when it is properly released. For now all we really have are "previews" so from a technical standpoint it seems "right" that everything relating to it is tagged that way.. future me can deal with 4 months away, chump deserves everything he gets.
Comment: @Mokubai - Future me likes the idea; Past me immediately regretted it making the preview tag first. Ancient me figured (better someone who could do a minimum text description than someone who wouldn't go to that effort). Present me is 3 stooging himself.
Comment: "There can't possibly be that many questions about TPM requirements for Windows 11 :$" - They're coming in thick and fast.

Add Windows 11 tag


RSA encryption with private key and decryption with a public key

Question: When using the RSA cryptosystem, does it still work if you instead encrypt with the private key and decrypt with the public key? What about in the case of using RSA for sender authentication?
Comment: Encryption with the private key is part of RSA signatures. But just like we don't use plain RSA for encryption, we don't use plain RSA for signing. Actual signature schemes use padding and hashing.
Comment: @HumamShbib: Your question is too vague for an answer. However, computing ${\tilde m}^d\bmod n$ (where $\tilde m$ is a _padded_ representative of message $m$, $d$ is the private exponent, and $n$ is the public modulus) is used a part of RSA signature of message $m$, including sometime for the purpose of sender authentication. See [PKCS#1](ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.pdf) or [ISO/IEC 9796-2](http://webstore.iec.ch/preview/info_isoiec9796-2%7Bed3.0%7Den.pdf) for proper signature schemes.
Comment: It works, but it is not secure. Don't do it.
Comment: Since no one mentioned it so far: By definition of the encryption scheme, the modulus $n$ is part of the public key. If you just have $d$ and no $n$, you can't "encrypt". About interchangeable $e$ and $d$: Yes it works, but usually $e$ is chosen to be small. This is okay. An easy to guess $d$ is not.
Comment: @PaŭloEbermann thank you, but what I meant is that does the private key encryption in RSA is exclusively applied in sender authentication? because RSA is a public key cryptography and the encryption is done with a public key rather than a private key.
Comment: @fgrieu I would not point to 9796 unless it is absolutely necessary, there are too many pitfalls
Comment: BTW, if you disclose the modulus of the RSA key pair to multiple parties, and then use a public key with a standardized exponent (3 or the fourth number of Fermat, 65537) for decryption, then **anybody** can decrypt the message. You should at least use a fully randomized exponent, but there are still pitfalls (e.g. padding, as mentioned) if you do.
Comment: @CodesInChaos *But just like we don't use plain RSA for encryption, we don't use plain RSA for signing.* Could you give any reference?
Comment: @PiotrDobrogost Check [PKSC#1](http://www.rsa.com/rsalabs/node.asp?id=2125) for secure padding schemes.
Answer: Mathematically it work just fine. "Encrypt" with the private key, "decrypt" with the public key. Typically, however, we say sign with the private key and verify with the public key.
As stated in the comments, it isn't just a straight forward signing of the message $m$. Typically a hash function and padding is involved. Also, often one has a separate key pair for signing.
As you can see, there are a number of caveats, but in general you are correct, it is used for sender authentication.
Comment: I'm probably splitting hairs, but "encrypt with the private key" is not a valid cryptographic operation. That usually get translated into a Signature Scheme with Recovery (or indicates that's what the OP wants).
Comment: Encryption is done with public key only, since the key is public, and only the holder of private key can decrypt it. If message is encrypted with private key, then everyone can decrypt it, since the public key is public. The point of encryption is that only the authorized recipient is to get the message, otherwise there's no point encrypting the message; save the time & computing resources, and just display the message to the public!
Answer: Asymmetric encryption and signing are entirely distinct concepts. The security and construction requirements are completely different. (Encryption for instance, needs to be an injection, whereas signature verification needs to be a surjection towards the verified message space. As a further hint of how they are intrinsically different, note that it lasted quite a bit of time before ID-based encryption could be designed, whereas ID-based signatures were there from the beginning.)
To put it simply: there is no meaning for (understand definition for) the wording "encrypt with the private key". How would you do it?
By way of example, take the ElGamal encryption scheme: $s$ is your private key, $g^s$ your public key. To encrypt $m$, you draw a random $r$ and compute the ciphertext $(g^r,m*g^{r*s})$. Now, let's be practical: you've got this nice library implementing ElGamal. The API for encryption says the function takes two arguments: a message and a public key, that is a group element $g^s$ for some secret number $s$ and some group generator $g$. Now how do you "encrypt with the private key" $s$? You feed the function with $m$ and $s$? It does not comply with the API and it might even crash.
Then let's be theoretical: how do you sign with the ElGamal encryption?
Eventually, this misconception probably arise from the specifics of the underlying mathematical structure of RSA (which has both signature and encryption variants, and where a private key of the same form can be used for decryption or signature, and the corresponding public key used for encryption of signature verification). But even there, a standard-compliant implementation will not allow you to "decrypt with the public key". Due to padding indeed, there is no way decryption will succeed. For the particular case of RSA, see also there.
So if you need to sign, use the signing function of a signature scheme with a private key.
And if you need to encrypt, use the encryption function of an encryption scheme with a public key. After all, that's what they were designed for.
Comment: Why does a signature need to be a surjection? Does that mean that every byte-string of a given length should be a valid signature of something?
Comment: I meant, the public function in an encryption scheme must basically be an injection (so that one can always decrypt) whereas the public function in a signature scheme must basically be a surjection (so that one can always sign).
Answer: The two keys $(e,m)$ and $(d,m)$ in the RSA key pair are fully equivalent, in that $e$ and $d$ can be arbitrarily chosen integers (in the interval $0..m-1$) as long as they fulfill the well-known congruence $ed \equiv 1 \mod \phi(m)$. You can swap them and nothing will change.
A key becomes public the moment you (as the key generator) decide to disclose it, possibly to attackers too. By consequence, the one you decide not to disclose becomes the private key.
When you use the key pair for confidentiality purposes, you typically want everybody to be able to send confidential messages to a receiver, so that only such receiver can interpret them. In such case, everybody shares a key (which will be the public one by the definition above, used for encryption), whereas the receiver has got the one which is not shared with anybody else (which must be the private key, used for decryption).
The idea of using the public key for decryption undermines the very purpose of having a scheme in place for confidentiality as defined above. Why should you do encryption at all if anybody (including the attacker) can undo it?
If you are thinking "Maybe I could securely distribute the public key only to the intended receiver", then you are not disclosing any key at all, and the definition of public and private do not hold anymore: you use RSA as a sort of secret key cipher like AES.
On the other hand, when you use the key pair for authentication purposes, you typically want everybody (including any forger) to be able to establish with certainty that a message really comes from a certain originator, and not from anybody else. In such case, everybody shares a key (which is again the public one, used for verification), whereas the originator has got the one which is not disclosed to anybody else (which must be the private key, used for signing).
In the same way as before, using the public key for signing is contradictory.
Finally, it should be noted that the public key (in either case) takes a special form (3, 65537, etc). That is purely for efficiency purposes (since the key must be public anyway, why don't we pick one that is computationally easy to deal with?), and it is not related to security.


OneNote 2010 bullet indenting

Question: In OneNote 2007, when you typed a dash and pressed space, you'd get a bulleted list. The same thing happens in 2010, except it indents the bullets over. I find this very annoying and have not been able to figure out how to turn it off. When working on old notebooks from OneNote 2007, the old paradigm is used, but not on new notebooks from 2010. Is there a way to revert the behavior back to the way it was in OneNote 2007? Thanks.
Answer: If you wish to disable auto bullets & numbering permanently, click Tools -> Options -> Editing and remove the checkmark from Apply numbering/bullets to lists automatically.
This is a direct paste from Link

OneNote 2010 bullet indenting


How to proceed end to end with iota on Bitfinex (e.g., store them in Keepass)?

Question: I am quite a newbie and got some iota. I'd like to store them, but I don't know how to even get them out of Bitfinex. I could transfer them to another wallet. Can somebody explain the whole process
Answer: Your goal is to instruct Bitfinex to broadcast a transaction to the tangle. One that sends the IOTA balance Bitfinex is storing for you (under their seed) over to an address generated under your seed.
What is a seed
A seed is the password you use to manage your balance on the IOTA network. This network is like a database of password-protected balances called the tangle. The homebanking app used to consult the tangle & place transactions is called a local wallet.
Your IOTA tokens always reside on the tangle, on addresses generated under your seed (think bank accounts).
How do I get my own seed
IOTA is conceived to be decentralized and as such, there is no-one to "give out" seeds or anything like that.
So whenever you require a new seed you just make one up and use it to log in to the tangle. Once you use it, it's yours - simply because it's nigh impossible for someone else to pick or guess the same one. It really is that straight-forward.
You just have to keep in mind that your seed won't just have to look random — it has to be cryptographically random in order to withstand the brute force of quantum computing in just a few years…
The IOTA foundation recommends the use of a specialized password generator to ensure true randomness of your seed. Heed this advice and your funds will be very secure indeed.
Step-by-step

You need your own seed. A generator recommended by the IOTA development team itself is Keepass. Refer to this post for a step-by-step on how to generate a seed with Keepass.
Install the latest version of IOTA's local wallet just like you would any other application. Choose light node when asked.
Open IOTA Wallet & log in using the seed Keepass generated for you. You should always keep your seed to yourself. Never share it with anyone or paste it anywhere but a trusted local wallet.
Click on receive and then on the address shown in order to copy it to your clipboard. You can also click the Attach to tangle button, but that's not really necessary.
It's time to head on over to Bitfinex, to their Withdraw section. Pick IOTA and paste your receive address into the recipient's field. Refer to their guide or iotaprices.com for detailed instructions. Make sure to properly confirm the transaction (captcha & email) and be patient for them to actually broadcast your transaction to the tangle.
Answer: First off, you don't store IOTA in KeePass, KeePass is a password manager and is unrelated to IOTA. IOTA is stored in the Tangle, which you can access using a seed and a wallet.
So the steps for withdrawing your IOTA from Bitfinex are the following:

Install IOTA light wallet following this guide: https://iotasupport.com/gui-lightwallet.shtml
Generate(or think of) a secure seed, see https://iotasupport.com/gui-newseed.shtml
Use your seed to log in to your wallet and generate a receive address
Follow the official Bitfinex guide to withdraw IOTA to your wallet, using the receive address generated above. https://support.bitfinex.com/hc/en-us/articles/115003291345-How-do-I-withdraw-cryptocurrencies-

Remember to share your seed with nobody and keep it absolutely save.
Answer: The best way to generate a Seed is via Keepass (Windows) or KeepassXC (Linux).
Very important is to change the seed after creation, so you don't fully rely on the generation algorithm. The advantage over the Linux terminal is, that you don't have to copy/paste it. You can store it directly and safly in Keepass.
For newbies I recommend following sites:
Lightguide
CryptoViking: first Steps


Export Survey Results to Excel option not in Action Menu

Question: I have a survey and all the needed results. I need to export the results to excel, though in the process of setting up the survey I changed or removed the Overview.aspx page/view. Now when I add a webpart like the overview.aspx, everything is the same except when I go to the Action button "Export to Excel" is not an option. How do I get that option back? If I can't get that option on a webpart back how can I get the results of the survey exported to excel?
Comment: i tried it through the View All site contents method but still dont' the export to excel option, any ideas please?
Answer: I had a similar problem where the export option was not visible in the action menu. As workaround, I found that if I accessed the survey from Site Settings ==> View All Site Content ==> My Survey then the export button is available.
Answer: None of the above should be necessary. The "Action" options are dependent on the view used. Open the "Overview" view, click "Actions" and the export option magically appears.
There's no way anyone would know this so this is a good example of the bad design / UX that plagues Sharepoint.
Answer: I have not found a way to do this either.
But I found one workaround:
To avoid having to open each response to see the selection made, I found that the RSS feed view at a least contained the value chosen.  From there I copied the feed into excel and cleaned it up.
I tried attaching the list in Ms Access - but it isn't an available list to choose.
If there isn't a way to get at the values in a response, I don't think I'll use this template again.
The above suggestion to find the export option didn't work for me either.
If you go the "rss feed" method, be sure you allow RSS for the list, pick your columns and adjust the item limits to meet your needs.  Find this under survey settings > communications > rss feed
Answer: You can right click on the overview screen and choose export to excel. A new window will pop up. Click on "show a graphical summary of responses" which should open the graphical response page with yellowish arrow tags click on the arrow shown in the picture and it should turn into a green check box This should select all of your survey questions and auto format them for excel. All you have to do is click import at the bottom of the page.
Answer: Hint: make sure to use the Internet Explore Browser the it works!
Answer: I had same problem in my Sharepoint 2010.
I was harrasing Google to get me an answer but with no luck.
Then I decided I will create RSS feed out of the responses, and then the option to export to Excel appeared in my Action lists. Propably it gets the settings about the columns to export from RSS settings.
Good luck.
Answer: I added a new view to the survey results page and set it as the standard. Afterwards I deleted and the thereby also the standard view. After selecting "Overview" as the standard, the Export to Excel button reappeared
Answer: Here is the solution. http://danssharepointblog.blogspot.com/2013/10/how-to-create-export-to-excel-button.html
I will now follow this fellow's blog!


Postdoc in reputed university vs Assistant professor in below average university

Question: I am a fresh Ph.D. scholar. I have applied for several academic jobs and recently I got acceptance for a Postdoc position in a university (world QS rank 71) and an assistant professorship offer in a university which is not among top 1000 university in the world but known as an average university in my subject area.  Being a fresh Ph.D. scholar what should be my priority? For both positions, the contract is 2 years. Which job experience, postdoc or AP, will give me better chance to get a better position after 2 years?
Comment: It's probably worth explaining what it means that the AP position has a contract of two years.  Is it not a tenure-track/continuing position?  You can't get good advice on the job titles alone; you have to consider duties (especially teaching), etc.
Comment: @MBK That sounds like a giant red flag to me.  Unless that department is where you want to be forever, I wouldn't do it.
Comment: what is your subject area?
Comment: @krebto Computer science
Comment: @ben for AP the contract can be extended after every 2 years. It's a newly established department; HOD told me that besides teaching responsibilities I may expect a lot of administrative and managerial responsibilities. For postdoc position I will work on two projects along with 1 PhD and 1 MS student.
Comment: @MBK You should add the details in your comment into the question. What your responsibilities will be as a postdoc and assistant professor are quite relevant to the question.
Comment: I just checked the University that is 71st on QS...please DONT go there, you will destroy your life
Comment: What are your long-term goals? Advice would differ depending on whether you're looking for somewhere stable to raise a family or to publish as much research as possible.
Comment: The fact that the AP position is only two years is very suspicious. The danger is that you spend two years doing lots of teaching and administration and little research, which means you will struggle to get another academic job afterwards. Unless the AP position is permanent (or tenure-track), I would definitely prefer the postdoc in terms of career advancement.
Answer: A good boss (both personally and scientifically) is everything. Try to find out where you will get the best (direct) supervisor/professor because that is where you will most likely be both happier and more productive.
Answer: University ranking offers almost no information; you need to look at the quality and reputation of the departments that are offering you jobs.  For the sake of answering the question, let's assume that you have a postdoc offer from a reasonably strong CS department (KU Leuven qualifies) and an assistant professor offer from a mediocre department. I also assume that you eventually want a faculty position in a strong department---neither of your current offers qualifies.  Finally, let's assume these are the only two options you are willing to consider.
Take the postdoc.
First, moving from a weaker department to a stronger department is significantly harder than moving in the other direction.  Hiring committees will make snap judgments about you based on the reputation of your current department; all else being equal, applications from stronger departments are more successful.  (Of course, all else is never equal.  And the fact that people shouldn't make snap judgments like this is irrelevant.) Same goes for funding applications and conference/journal publications.
Second, weaker departments (at least in the US) have less (or no) expectation of faculty research, and therefore provide fewer resources for research. Those resources include strong graduate research-active colleagues, and (most importantly) time. Weaker departments tend to have higher faculty teaching loads with weaker (or no) TA support, and you've already been told to expect a large administrative workload.
In short, if you accept a position in a significantly weaker department, you are likely to be less productive, and the research you do publish is likely to be valued less.  This discrepancy will offset any benefit from accepting a faculty position earlier.
Comment: _(I worked in 2 top 10 EU universities)_ — Europe and the US have _very_ different faculty hiring practices and politics.  That said, I'm not proposing "university credentials without papers", but the exact opposite.  Taking a faculty position with fewer resources and a higher teaching load _means publishing less_.  Conversely, taking the postdoc _means publishing more_.
Comment: I downvoted for many reasons. One is that you usually have more opportunitis to get grants and students as associate professor, leading to more papers, possibly some last author papers. And you get leadership experience. All of these are very important to get further grants and better jobs. So I think your idea of how hiring committees work is not right, and most certainly not true for many hiring committees.
Comment: _One is that you usually have more opportunitis to get grants and students as associate professor_ — Not in my experience, but this may vary by field. (My field doesn't have "last authors".) — _I think your idea of how hiring committees work is not right_ — I've been on my department's hiring committee for about 15 years, including three as committee chair, and most of my former PhD students hold tenure-track faculty positions.
Comment: Downvoter: Care to explain your disagreement?
Comment: In the hiring committees I have seen, people are judged mostly on their research output: the number of papers and the reputation of the journals. If you already got a grant this is a big plus. Some grants require people to have a permanent position. My personal experience is that a good boss massively increases research output, a top 10 university (I worked in 2 top 10 EU universities) does not. Especially as a young postdoc you need papers, not "university credentials without papers", hence my own answer and downvote of this one. I also think your bold "take the postdoc" is much too direct.
Answer: I think you should think about the final result that you plan to achieve at the end of this work. For example, the goal is to publish as many scientific articles in the best journals as possible. Then you must assess your abilities and resources to achieve this goal (based on your experience during PhD). If you think that you have enough strength to generate ideas and publish good articles in good journals, then professorship is for you. If you are not ready for an independend job and needs some supervision, then go for a postdoc.
Comment: @levgen Thank you for your answer. I can generate results independently. However, being part of a research group which is already producing good results will definitely increase my capacity to publish more. The question here is what is more beneficial for a fresh PhD? 2 years of AP experience in an average university (less publication but independent job experience)  or  2 years of postdoc in reputed university (more publication but not an independent job experience)
Comment: @MBK Again, if you are sure that working as an assistant professor will not lead to a sharp drop in your performance, I would choose a professor. If there are doubts about the ability to work completely independently, then go for a postdoc. At the same time, the university's rating itself is not so important for your case in my opinion.
Answer: If the Assistant Prof. position will eventually lead you to tenure and if you feel confident you can manage it, you should go for it.
A postdoc in a reputable university doesn't mean anything if you don't end up publishing good papers, which of course you can't know in advance.
In the end, the job of a postdoc is to find a stable position, and you have been given the opportunity to reach it through the Assistant Prof. contract.
Answer: At the end, both are job. Based on your previous research achievements, e.g., number and venue of publication, you can choose PostDoc or Asst. Professor. It's not only about independent research, many factors are related. Also be aware that this short term Asst Prof. deals with overloaded teaching assignments, in that sense, PostDoc will bring your own research identify.


Ground beef meat colors seem different these days

Question: Why is it that in the "good old days" (I've been cooking/ buying/butchering for 6 decades) freshly ground meat was red until prolonged oxygen exposure turned it brown (store-bought, packaged meat was a bit greyer...darker red on the outside and nice pink/ red on the inside). Today I notice the opposite, red on the outside and grey on the inside. Why is this happening?
Comment: Likely a change to nitrite regulations. Here is Ireland:  https://www.fsai.ie/faq/use_and_removal_of_nitrite.html   We do it in US too.
Comment: I've noticed the same, but I can't remember if that's true of all of the places that I get meat from, or how it's packaged (eg, the strange puffy packs where it's a plastic container w/ a fused plastic sheet on top, vs. the old fashioned shrink-wrapped ones ... or chubs or heavier plastic like cryo-vac (the last two which would've been done at a factory rather than the local store ... and might've been done in a low-oxygen environment) )
Comment: @WayfaringStranger : that'd affect sausages ... but to the best of my knowledge, supermarket ground beef is just ground meat and fat ... no other additives.
Comment: @Joe My food science is from the early 80's. Things may have changed with hamburger. I was told nitrite was commonly used, but people did start complaining about it back then. Perhaps its just in processed meats now.  https://indianapublicmedia.org/amomentofscience/meat-stays-red-myoglobin-nitrites/
Comment: @Joe you'd be surprised what's put in to make it look "better" for sale, especially in the US and Canada (the EU has very strict regulations and any additives would have to be listed on the packaging, but who reads the packages of supermarket meat anyway...).
Answer: The color of meat comes from the pigment myoglobin. Freshly cut meat shows a purple-red color. When exposed to air, myoglobin forms oxymioglobin, providing an attractive cherry-red shade. However, long exposure to air and store lighting lead to the formation of metmyoglobin, which is brownish-red.
The inside part of the meat can show a more greyish color due to the lack of contact with oxygen.
The industry uses some techniques to control / cover the oxidation of myoglobin up to metmyoglobin and keep a nice red shade for a longer time.

Modified atmosphere packaging (MAP): to avoid complete oxidation of the meat and final brownish/greyish color (that does not look appealing anymore); some gases like carbon dioxide and nitrogen are used to decrease the content of oxygen and to slow down this process. Therefore, the outside doesn't turn grey that fast. For more information please refer to: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4093050/
Color additives: in Europe, minced meat is a product category that is subject to contain color additives according to the Regulation (EC) No 1333/2008. E.g. the category "burger meat" can contain carmine or carminic acid (red color extracted from crushed bugs and stabilized with aluminium salts...), whereas other categories within the group may not be allowed to contain such color additives but natural colors or vegetable extracts. Nowadays many meat producers are switching to red beet or radish extracts to enhance the red shade of fresh minced meat in fresh sausages, meatballs, etc. while keeping "clean label".
In the US there is a list of commonly used meat additives (https://www.fsis.usda.gov/wps/portal/fsis/topics/food-safety-education/get-answers/food-safety-fact-sheets/food-labeling/additives-in-meat-and-poultry-products/additives-in-meat-and-poultry-products)

Note: nitrites and nitrates are food preservatives not used in fresh meat but in cured and/or processed meat.


What is the actual purpose of MVC?

Question: I've seen a lot of stuff that describes how it's done, but not a lot that tells WHY it's done. Is it just a way to keep the code readable, or is there a better reason?
Answer: It's about Separation of Concerns.  Basically, you want your software components to do one thing, and one thing only.  If your components start doing more than one thing, code gets hard to read, things become more complicated than they need to be -- basically an app turns into a big plate of Spagetti Code.
The Models contain the business logic, represent the things in your application.  The views present the data to the user.  The controllers decide what to do with the various user actions.  When you stick to that, the code is easy to read because things are as simple as possible.
MVC is a popular pattern, but it's not the only one out there. MVVM is also popular.  As long as you separate your concerns, pick any design architecture that suits you.
Answer: The actual purpose of MVC is to separate your views from your controller and model. In other words, it is a design pattern is a structure for keeping display and data separate to allow each to change without affecting the other. By saying so, it is mostly used for GUI stuffs. Thus it essentially contains three things. The Model contains what is often called
business logic, or all the data and information manipulated by your system. The
View contains the objects that display the data, and the Controller manages the
interaction with the user and mediates between the Model and the View.
In many modern GUI toolkits, view and controllers are somewhat inter-related and thus cannot be fully separated. For example, a button is a controller but it needs to be displayed in the screen.
Answer: There is also other things I haven't seen mentioned here. Yes, a design pattern prevents the problems and difficulties of spaghetti code. No longer do you have to deal with a chunk of code, adventuring through hundreds or thousands of lines to get to the piece of code you want. But there are other reasons as well: Since your code is divided into multiple sections, communications of developers will have an easier time, addressing and therefore solving a problem. A design pattern also helps developers to program accordingly to DRY. An example of this is the layouts in Laravel, which helps you not using the same piece of html code again and again.
Make sure to check out this link for more info: Design Patterns
Answer: Thats a big question I don't have time for that big of an answer, so I'll try to keep it short.
The primary reason is like you said for keeping the code readable and manageable.  The separation of these main components model, view and controller help to create more reusable code that is easier to understand because each piece has a distinct purpose.  The model representing the objects or data within the system and containing the code for the actions that can be performed on those objects.  The view of course encapsulating the layout and design that allows you to view that data.  And finally the controller that allows you to navigate from view to view, action to action.
If you have ever dealt with a large system of code that married the three of these together, you will have seen the typical copying of large chunks of redundant code that was not quite what was needed for the next task.  These models are built in such a way that they are more generic making them more reusable than it was inline.  That is you dont have SQL statements scattered throughout your scripts instead it is consolidated.  The same is true of HTML being scattered in code, very undesirable and hard to edit and maintain.
Hope that helps.
Comment: Wow! You started your answer saying 'don't have time for the big answer' and look! your's is the longest one! :D
Comment: Ah now that is not a big answer compared to the question.

What is the actual purpose of MVC?


A question about /t/ + fricative /r/ vs /tr/ affrication

Question: So in most accents of English, /r/ is fricated when it follows /t/ and /d/ word-initially, and in some it has become a full affricate /tʃ/.
If you were going to look at a spectrogram of this, how could you measure the degree of frication of /r/? I'm looking at the affrication of /tr/ and /dr/ and need to know how it differs from just /r/ being fricated.
Answer: The short answer is that there is no difference. Phonetically speaking, an affricate is just a  stop closure followed by a period of frication, so [t] plus frication is the same as an affricate. The distinction between an affricate and a stop-fricative sequence is really a phonological one, where the former behaves as a single phoneme and the latter behaves as a sequence of two phonemes. See the related question: Is there a difference between an affricate and a plosive+fricative consonant cluster?
In the case you are talking about, we know there are two phonemes at play--/t/ and /ɹ/. Following the conventions that linguists use for bracketing, this sequence doesn't strictly speaking "become" /tʃ/, since that would indicate one phoneme sequence becoming another phoneme entirely, which only makes sense in a discussion of diachronic change; in a synchronic context, it's more accurate to say that the underlying sequence /tɹ/ is sometimes realized as something like [tʃɹ] (note the square brackets, indicating a phonetic realization). See the related question:  Why are /t/ and /d/ sometimes affricated before /ɹ/ in English? Technically, it is the aspiration associated with the initial /t/ that is turning into a fricative, so from a phonological point of view it might make more sense in all cases to think of this process as the affrication of the /t/ rather than the "fricativization" (or spirantization) of the /ɹ/. In practice, however, it might be difficult to say where the /t/ ends and where the /ɹ/ begins in the spectrogram, since the tongue usually gets in position for the /ɹ/ before voicing kicks in, i.e., during the apiration/fricative noise.
As for how to "measure" the degree of frication in the /tɹ/ on a spectrogram, it's not clear how you would quantify such a property, but the main visual difference between frication noise and aspiration noise is that formant structure is visible in the latter but not in the former.
Comment: I do have experimental experience with this phenomenon, and it's true that there is a lot of variation from speaker to speaker. It is also true that there is often formant structure visible after the frication noise, but often the formant structure is only apparent in the _transition_ from the consonant cluster into the following vowel (so if the following vowel is [i], for example, F2 and F3 are steeply rising coming out of the frication noise). Depending on one's labeling scheme, that transition could be considered part of the /ɹ/ or not.
Comment: It is also true that the degree of lip rounding and retroflexion will affect both the distribution of frication noise and the loci of the formants, and often one sees a downward-sloped center of gravity in the noise that "fades into" the second and third formants, which tend to bunch together at a relatively low part of the spectrum under these conditions. It is thus not always straightforward to decide whether noise in the spectrogram should be characterized as frication or aspiration, and even when it is clear that both are present, it is not always clear where to draw a line between them.
Comment: In that case, since /ɹ/ is phonetically [ɚ̥], there should be visible formants in the spectrgram of [tʃɹ]. Also, both /ʃ/ and /ɹ/ are rounded, and the onset and length of lip rounding should be visible as well, and measurable, as well. My guess -- based on zero experimental experience -- is that the individual variation will swamp the /tɹ/ ~ /tʃ/ variation, which is to say some people consistently hear the difference and some never do and some can under certain conditions. And everybody's convinced they do, so nobody notices the difference; like /θ/ ≠ /ð/, which always comes as a shock.
Comment: I have another question which is more specific about the same subject. When you look at a spectrogram of an affricated realisation of "tree", you can see the period of frication and then there (at least in the examples I'm looking at) is the /r/ which is showing formants as is usual for an approximant. However, all the literature I've read has said that if the /r/ follows a voiceless stop (i.e. /t/), it becomes devoiced. When I look up what a devoiced approximant looks like, it says it's more like a fricative and less like an approximant. But in 'tree', I'm still seeing it as approximant. Why?
Comment: @user3604 I have some ideas, but it might be best for you to post this as a separate question and include some screen caps of the spectrograms in question.


Why does decreasing ion channel density result in an action potential not firing?

Question: I'm pretty confused, when i run a simulation of an action potential reducing the sodium and potassium channel densities gradually over time results in an action potential not being fired, and when i only reduce sodium channel density it stops the action potential from firing even faster. My question is why? what role does density have in firing an action potential?
Answer: It is very straightforward. More the density of sodium channels, more the influx of sodium ions. More the influx of sodium ions, more the depolarization. If there are sufficient sodium channels, then the large influx of sodium ions will cause membrane depolarization above the threshold value, thus resulting in firing. If the density of channel is reduced, the depolarization value will not cross the threshold. Thus causing a net change in membrane potential, but not firing.
Potassium channel acts in coordination with sodium channel. Only if there is an influx of positive sodium ions into the cell, potassium channel will act and release potassium ions outside the cell in order to maintain the membrane potential. If sodium channel is reduced, no further processes happen, thus no firing.
Comment: Actually, the depolarization can still cross the threshold given sufficient synaptic input even with a reduced sodium channel density.

Also, in the case where only sodium channel density is reduced, the rate of sodium influx will be lower than the rate of potassium outflux and hence action potentials will be harder to produce


Why are countries in the Gulf rich but lagging in technological innovation?

Question: Countries in the gulf are oil rich. But they are lagging in R&D sector. Governments do not spend much on R&D. Most countries employ foreign contractors or import technologies.
What is the reason?
Comment: I would guess it's a variation of the CEO Money Machine.  The folks in charge have all the money they need, and attempting to "innovate" would only threaten their positions.
Comment: It may be instructive to consider the "resource curse" of places like West Virginia.  Coal has arguably kept them poor.
Answer: Update
Resource Curse literature attempts to address the issues you are raising, take a look at here and here.
Here is an interesting example of a technology transfer case.
Original answer
They do, in fact, have increased the share of R&D spending by a huge margin in the past 5 years. Some of these countries see commerce, trade and tourism as more central to their development than other aspects of development.
The number of Arab students on government scholarship in the West has been on the rise and many western universities have opened branches in the Middle East, especially in the Gulf countries. In the past, only the rich kids of Arabs were able to go to universities in the West. By default, these kids, did not bother working as scientists or educators, they, probably, stayed in the west or became entrepreneurs.
Today, with the help of government scholarships, the ordinary folks can send their kids for education, and hopefully, these kids will bring the science to the other ordinary folks in their respective countries. Remember, technological shock is not so fast and abrupt as we assume in the models, it take decades to have a measurable effect in practice.
As younger 'kings' and 'princes' are involved in politics, there are signs of greater investment in education and science.
Here is the chart of R&D spending to GDP ratios in the Gulf countries.
In the countries, where younger generation have more say in politics, there the spending on R&D has been higher than in those where older 'kings' rule. See the chart, Qatar and UAE have had higher R&D shares, but the data is limited for these countries.
Answer: There is a great deal to consider when discussing resource rich countries. Countries that rely on a single sector have less diverse economies, which can lead to a number of issues (especially if the price of a particular resource drops).
Additionally, resource rich countries tend to have unstable governments, which makes it difficult to diversify and grow the economy. Some of these governments are dictatorships and some are run by those who are wealthy as a result of having a stake in the resource. These particular issues tend to spawn corruption and abuses in a way that is not usually seen in other governments.
Of course these are broad generalizations, but they are important.
To address your question specifically, I would suggest that there is a reliance on foreign contractors because the necessary skills are not in abundance within the country itself. Since the countries rely on a single resource, most jobs and education are tied to the resource, which means limited available skills. Additionally, if one of these countries wants to develop technologies within the country, it would need to import tons of resources, probably more so than other countries that have multiple resources. My guess is that at this time, importing  technologies is more efficient.
This isn't to say that gulf countries don't invest in R&D, they do. It just looks different than in other countries.
Answer: Oil-rich country "resource curse" is merely symptoms, not the root cause of the poor R&D. It is a fallacy once you inspect the fact: US, Russia are both oil-rich country.
Technologies advancement is a culture of a collective and organic development process, a stable society(that doesn't burn and kill the scientist), critical thinking (breakthrough that will overthrow the previous finding), motivation incentive and lots of available wells trained "manpower" on the field, government policies on fundamental science.
Just look into human history, you will notice there is little progress in technology until the 18-century industrial revolutions: it is the synergy of all the above factors that lead the technologies boom.
Now take any gulf oil exporting countries and compare facts in the checklist, you will find there is a huge gap of each factor when compared to technologies advanced country. First, suppression of female rights, cut the science production to half (FYI, lots of modern scientific breakthrough are from the female scientist). Lack of top-notch scientist (as guidance), challenging cultures and persistency (many scientists that win nobles prize have their papers rejected by prominent science paper). Such countries government also lack the vision to invest in fundamental science.
Comment: There is a big debate: Joel Mokyr has been working on the cultural and ideological aspects of technological progress. Bob Allen has also been exploring the underlying drivers of technological progress, but he focuses more on the economic aspects i.e. wages, prices and incentives. Resource curse literature is another strand trying to offer answers to the puzzle. There is, as you suggest, no definitive factor that could explain why these countries are not on the technological frontier. But, I can see a wind of change on the horizon as younger generation is getting more say in politics.


Linux - Create ftp account with read/write access to only 1 folder

Question:
Possible Duplicate:
Linux - Create ftp account with read/write access to only 1 folder

Hey guys....
I have never worked on linux and dont plan on working on it either - The only command I probably know is "ls" :)
I am hosting my website on Eapps and use their cpanel to setup everything so never worked with linux.
Now I have this one time case - where I need to provide access to a contractor to fix the CSS issues on my website. He basically needs FTP (read/write) access to certain folders.
At a high level - this is my code structure

/home/webadmin/example.com/html/images
                               /css
                               /js
                               /login.php
                               /facebook.php

/home/webadmin/example.com/application/library
                                      /views
                                      /models
                                      /controllers
                                      /config
                                      /bootstrap.php

/home/webadmin/example.com/cgi-bin

I want the new user to be able to have access to only these folders

/home/webadmin/example.com/html/js
/home/webadmin/example.com/html/css
/home/webadmin/example.com/application/views

He should not be able to view even the content of other folders including files like bootstrap.php or login.php etc
If any sys admins can help me set this account up - will really appreciate it. Thanks
Answer: If this is possible and how to do it depends on the software that running there and the permissions you have. Most likely the best way is to ask the tech support to do it for you.
Comment: Well I have root access


USPTO patent search database no longer secure over web SSL https

Question: Does anyone know how to do a safe query of the: USPTO Patent Application Full-Text and Image Database (AppFT)?
When queries to the database essentially go across the web either to your VPN host or your client browser on your PC.  Previous to 2017, it WAS secured utilizing SSL.
Quick search web address - http://appft.uspto.gov/netahtml/PTO/search-bool.html
Without inadvertently revealing IP when narrowing down the search to final patent #'s and classifications ?  Many time one must get very specific to identify prior artwork or patent #'s.
Is no longer hosted at USPTO using any type of SSL (https://) security, it appears to be open text from the host end.  No amount of VPN protection from the client can secure the connection (end to end) either.
Google patents does host all their patent database on SSL server,  But then again its google,  They probably already have the entirety of your IP before you thought of it.
Thank you.
Answer: You might try  Espacenet,  The Lens or PatentScope - all are https
Comment: +1 for The Lens.


Can the Torah Scroll be opened while still inside the Aron Kodesh?

Question: I can't imagine for what reason, but can a Torah Scroll be opened while still in the Aron Kodesh? In other words, must a Torah Scroll always be removed from the Aron Kodesh in order to open the Torah Scroll?
Answer: There is no documented reason not to open a Torah Scroll while still inside the Aron haKodesh.
Actually, many Sefardim communities seem to have the custom of opening the Torah Scroll while still inside the Aaron haKodesh before taking it out and parading it to the Bimah; often still open so all can peer into it.
Personally I roll the Sefer Torah to its correct place while it's standing in the Aaron HaKodesh and nobody has ever commented on the [im]propriety of this. Admittedly, לא ראיתי אינו ראיה - missing evidence is not a [good] proof.
Comment: Thanks for (indirectly) confirming that what I do is what you do and it seems OK. I guess we're both *Ba'alei Kri'ah*?
Comment: @DanF - in this case I do it with the title of _Shames_ (Beadle). I lein but once a week (שבת מנחה) but in another shul.


How long should I take to tell an employer my decision?

Question: I'll have my first face to face interview soon and I have a few questions. Do I have to accept or reject the offer on the spot or is it okay to ask for some time? How long do you think I should take to reply?
Comment: You should never accept or reject an offer on the spot.
Answer:
Do I have to accept or reject the offer on the spot or is it okay to ask for some time?

It is OK to take some time to decide. Most (all actually) interviews I've had have been this way.

How long do you think I should take to reply?

It is highly probable that they will tell you by when they expect your answer. You should then make up your mind and decide by that time, so you can convey your answer by the date given.
You will then have until that date to decide among the other offers or options you have lined up.

Some useful posts that you may consider reading, regarding the handling of multiple offers, some with different expected times of response, etc., include:

How do I coordinate the process of pursuing multiple job opportunities at the same time?
How can I delay job offer acceptance?
How long can I wait to respond to a job offer?
Comment: @HorusKol those are perhaps edge cases (especially the reasonable one). However, if a short time frame is given to accept OP will have to take that into the equation, along with other offers lined up, and see what's best for them (drop this one in favor of another possible offer? go for this one dropping the others? that would be case specific)... I think there are several questions that specifically address what you pointed out, I'll see if I can include some of them in the answer. Thanks for the feedback :)
Answer:
Do I have to accept or reject the offer on the spot

Offers on the spot are quite rare. Typically you talk to a number of people and they need some time to integrate the data (means "talk about you"). They often run multiple candidates and don't make a final offer until they have interviewed them all and ranked them. Then they will offer in order of the list. It's much more likely that there is a significant time gap between the interview and an offer, decline or simply just nothing. Even if they want to hire you, there is often also a bit of back and forth on the details (timing, comp, benefits, relo, equity, contracts, ...) before the formal issue gets offered
Getting an offer on the spot is a clear indicator that you are very strong candidate, so it's a good problem to have.

is it okay to ask for some time?

Yes. One week is fairly normal and can often be extended with the right reasons (and candidate). However, it's better to analyze the situation up front and make sure that you know what your own decision criteria are. If you have done your up front research properly and nothing overly surprising happens at the interview, you should be able to make a decision quickly. Primarily you should take this time to study the details of the offer, carefully read all the contracts and agreements you are supposed and work through any adjustments and/or misalignment.
Blanket Advice: never sign anything that you haven't carefully read and that you are sure you fully understand.
Answer: My experience (the Netherlands, Belgium). Normal is one week to think about it, longer might be seen that you're not so interested.
Normally after interview, employer takes one week to decide. After that he sends you a contract, or in person. You take one week to decide/draft changes to the contract (always draft changes, even if they are just secondary. You meetup to sign the contract, or do it digitally. Up to the signing part you can still refuse the job offer (as long as you didn't say anything verbally or writtenly that you would accept the contract).


Distortion treatment?

Question: I've been seeing this distortion treatment popping up everywhere lately and was curious if anyone knew how or could point to some resources? I've tried a google search but can't find anything relevant. I've also tried the flag/wave effects in Illustrator but it looks like a cheap recreation.
Answer: On Photoshop: text layer, could be with transparent or white background:

Make a PSD file the same size as the text layer with a B&W gradient (50% gray is static, black and white will be displaced right and left):

For the gradient use guides on the part of the text you want to get the distortion

Back to the text layer, Menu Filter > Distort > Displace, after click on OK, the program will ask the file for the distortion, is the PSD gradient file.

Et voilá!
Comment: The only problem with this is that now your text is rasterized.
Comment: You can keep the editable text converting the Text Layer to Smart Object.
Comment: Yeah but thats does not help now your text is pixels and that is relly really bad for print, font aliasing  etc etc. But its fineif all you do is design pixels.
Answer: I would just use the Warp Tool (Shift+R)
Take some text and select it all (make sure it's converted to outlines)and then using the warp tool, just brush across it (hold down Shift to make it go straight)
You can adjust the intensity of the tool by double clicking (I ad mine pretty high)

Play around with where you brush with the warp tool (how many times etc.) until you get the desired effect.

After playing with the settings etc. for a couple minutes, this is what I achieved:
Comment: I don't think that this is an eloquent solution. Too much distortion on the top and bottom halves.
Comment: @Ovaryraptorov it depends on the size of the brush and the strength.
Comment: Turns out that because Beziers aren't second degree continuous you get really undesired behavior when you convolve it with another bezier. Interesting data point for using higher order nurbs cirves.
Answer: Here is an old answer which also applies to this question.

The Envelope Method
You can accomplish some of the desired goal here using Illustrator's Envelope Distort. First, create your text. Next,
  make a rectangle and then using the Mesh Tool (U) click in the middle
  to turn this rectangle into a mesh. You can edit the mesh points to
  create some waves. Then make sure your text and mesh are both selected
  and use Menu > Object > Envelope > Make with Top Object to warp the
  text to the mesh. This works with objects that do not curve around to
  show a back side. Yet, this can too be approximated by doing more work
  and slicing your text into front/back pieces and warping them both to
  connect in the same place in a visually-acceptable way.

This shows a basic text wave distortion with top mesh object.
  https://i.stack.imgur.com/pqt09.png

Distortion treatment?


What does the blinking of the cpu address bus actually means?

Question:
I'm currently running NOP   on a Z80A cpu. All it does it flash some led, I expected it to flash 1 by 1.
The led are place from address 16-0
Comment: At such low clock rates you are most likely seeing undefined behaviour. 1 Hz is way below chip's operational frequency which is into megahertz range.
Comment: The original Z80 is not all static by any means. In fact, it is famous because of being non static. It won't work below its minimuim clock rate. To achieve DC to max clock rate operation, you need the CMOS version of the Z80.
Comment: @Algimantas No - The Z80 is famous for its all-static design and should run at clock frequencies even lower.
Comment: Note there's more going on on the address bus than simply instruction fetch addresses: during state transitions T3 and T4, the Z80 pushes the contents of the (incrementing) R register onto the address bus for dynamic memory refresh. You'll probably not be able to distinguish the two overlapping increments from each other. What have you done to the rest of the CPU signals?
Comment: @BrianH  oh actually I'm looking for the reason why it blink. I'm beginner to electronics so sorry If I use the wrong term. I hook up my z80 with a 5v power supplied by a Arduino. The digital bus are connected to ground with a 100k ohm resistor. The  clock speed is at 1hz. (From my Arduino, it goes high and delay 500ms and goes low and delay another 500ms and repeats)
Comment: @Algimantas - There are so many versions of Z80 chips from so many vendors that there might be some around that get into hickups when clocked too slow. Some were known to be picky with the "low" time. Single stepping works much better by supplying an e.g. 1MHz clock and stopping the CPU using /WAIT
Comment: Depending on the speed you run your CPU with you might or might not see anything blinking.
Comment: Hi and Welcome to Retrocomputing StackExchange. It would be helpful if you added a couple more details to your question, such as how is the NOP instruction being fed to the Z80 and how are you clocking the Z80.
Comment: @BrianH now it just blinks all the led on and off, not really sure what's going on. Earlier on it blinks different led.
Comment: @tofro yeah, sorry, I commented without googling. It seems like people had success running Z80s with button clicks providing clock signal.
Answer: Algimantas's answer is partly correct - the pins will begin to count in binary as these represent the 16-bit program counter (PC). But they also present an 8-bit I register, and 8-bit Refresh (R) counter.  Thus there is a different pattern on the upper 8 address lines than the "expected" straight binary pattern.
There are two things going on, an opcode fetch, and a refresh cycle. The LEDS are actually showing the contents of the PC register followed by the I register on the upper 8 bits of the address bus and R is on the bottom 8 bits.  It is further complicated by the length of the different registers.
See I AND R REGISTERS.  What they do.
More detailed explanation:  The Z80 fetches opcodes with a a cycle named "M1" which is 4 clocks long.  The PC is presented on the LED's during clock cycles T1 and T2.  A refresh cycle also occurs during T3 and T4 of all M1  cycles.   In T3 and T4,  the address pins present the contents of the 8-bit I register (interrupt page register) on the upper 8 bits, and the lower 8 bits is the R-register that also increments after each opcode fetch.
The R and I registers will start at 00 and the Z80 PC will start at 00000 on reset.  For the first 256 (Edit: actually 128) cycles, the LED will show  the I + Refresh and the PC RAM memory addresses in perfect sync.
But at cycle 128 (0x080), the pattern will change. The Refresh register will have wrapped around back to 0x00, so the pattern will change as shown below
Address bits in Hex:
0x0000 M1 cycle (opcode fetch)
0x0000 Refresh cycle is made from I (00) + R (00)
0x0001 M1 cycle (opcode fetch)
0x0001 R
0x0002 M1 cycle (opcode fetch)
0x0002 R
<and so on...>
0x007f M1  cycle (opcode fetch)
0x007f R  they both still match.
0x0080 M1  cycle (opcode fetch)
0x0000 R <=- refresh register has wrapped around
0x0081 M1 <= but the Program Counter does not.
0x0001 R <= refresh is now at a count of 1
0x0081 M1 <= but the Program Counter = 0x81
<and so on...>

Comment: The R register doesn't increment up to FF, but up to 7F, then it goes back to 0. The highest bit of this register is not altered by the refesh logic. It only can be changed by a LD R,A instruction. So the sync between memory address and refresh address is only kept for the first 128 M1 cycles.
Comment: Thanks for the correction! It's been a long time ( 40 years) since I worked at Mostek on the Z80 testers
Comment: If you want to see the memory refresh alone, provide a `HALT` instruction instead of `NOP`.  That will stop the `PC` advancing (more correctly, it will stop the CPU putting the new `PC` onto the address bus).
Answer: The LEDs show individual bits of address that is currently accessed. This is a binary representation and each combination of on/off LEDs corresponds to different address.
Since you are giving it a hardwired NOP instruction, the address grows sequentially like this:
0000 0000 0000 0000
0000 0000 0000 0001
0000 0000 0000 0010
0000 0000 0000 0011
<and so on...>
1111 1111 1111 1111

After that it rolls over back to all zeros. If you gave it some real code that does something, the LEDs would not grow sequentially due to branches in code. They would also show memory addresses being accessed for reading or writing.
Comment: Please also note that the high (?) bits of the Z80 address bus are used by the Z80-built-in D-RAM refresher. So I would expect to see 0000h, 0100h, 0001h, 0200h, 0002h, ... at the address bus.


Growing avocado from seed

Question: The first time ever my avocado seed grew a root so when it got really long I planted it and then nothing and I thought I had killed it so while in the dirt I broke off part of the seed just to find out it is fine and green so just wondering is it ok with half a seed?Thanks Karen.
Comment: While life often finds away, I believe this would not be ideal and greatly reduces the chance of the plant fully germinating - you may be better off trying to grow another one from seed.  Some tips - It can take a LONG time to start growing (sometimes months) - keeping the seed emersed in water in a warm (24c + environment) can help.  Sometimes "scarring the seed" can help, eg by sanding off some of the skin or soaking in dilute Hydrogen peroxide can also stimulate growth.   Don't transplant the seed until the plant has a 15cm long stem and leaves - again, this can take a long time.
Comment: You did not describe your sowing method. Many do germinate it in a jar, let the roots develop in water, and then pot it directly in the soil. To their amazement, the tree is shocked and even may die. They don't understand that roots which developed in water for too long have a hard time adapting to soil. Did you grow your seed first in water, or was it soil from the start? Did you keep the rootball intact if you used soil?
Answer: There are two versions of "is it OK?"   First, is it ever possible?  That depends on what part of the seed remains.  A non-compound seed like avocado has only one epicotyl, or embryo plant.  If what's left lacks an epicotyl, the seed can never sprout.  On an avocado, the epicotyl looks like the tip of a tube, and depending on the stage of the seed's maturity may even include tiny yellow/white leaves.  There's a drawing of the inside of an avocado seed at http://www.inspiredbymygarden.com/germination-of-seeds/.
Second, how good an idea is it to use part of a seed, even if it might be possible?  Not very.  Most of content of an avocado seed, or of most of the grains and other seeds we eat, is starch.  It is food for the baby plant until the new plant has roots and leaves to feed itself.  You're starting your plant on a starvation diet.  It may or may not survive.
Recommendation:  Eat another one of those delicious fruits and start with a whole seed!
Comment: P.S.  Simply because the inside of a particular seed, in this case avocado, is chemically a starch doesn't make it safe food for humans.  Just so there are no misunderstandings!  Don't eat avocado seeds.
Answer: Its definitely got less of a chance of making it now then it did before it was damaged, but if I were a betting man, and I am, id say as long as that tap root isn't damaged, and conditions are ideal, its probably going to make it.
    Some advice though, dont baby it. If you do, and thats the only reason it survives, your going to have a weak tree. Avocado's are already fairly picky about climate and stress levels. If your just growing it to grow a tree, it will be fine no matter what, I guess, but if your hoping to get fruit off of it, id plant another tree.
      Also, not sure if you're aware, but most avocado farmers trees, are grafted. There are a lot of reasons for that, main one being that they want consistency in thier crop. Another reason is because they can sometimes not fruit, ever. Or sometimes take up to 10 or even 15 years to bear fruit. I have even heard 20 years, but if you graft a branch off of a tree with a particular fruit that you like, onto a solid root stock, that tree will bear fruit in, id say 3 years, tops. Probably quicker in ideal conditions. They also have a weird way that they pollinate and reproduce naturally, which I wont get into because im not sure I grasp it entirely. It has to do with temperature, and the flower functioning as both a male and a female organ, but not at the same time. Heres an article to better explain.
https://www.agric.wa.gov.au/spring/growing-avocados-flowering-pollination-and-fruit-set
     My point is, It is because of this, that id not only plant about 3 or 4 trees, but id go with grafted trees, not trees from seeds. Id scrap the whole idea of a seed altogether (unless the seed is grown for its root stock). That way you can also get trees proven to be climatized to your local environment. Id also suggest getting a tree that is grafted from a tree that you've tasted the fruit from, and you liked it. When avocados are cross pollinated, you never know what your gonna get, and avocados have quite a range of possible flavors, and not just the ones that you can buy in the store. Those are the ones that taste good, some dont.
      Also, when you see flowers, dont be too excited. It produces a ton of flowers in hopes of attracting pollinators, but most of them wont become fruit. Most of them are strictly an attractant.
      Avocados are a lot of work but they can be very rewarding. Especially if you love avocados as much as I do. Good luck.
Answer: My first avocado seed also broke when I planted it. However, I did wait until it was 2-3 inches tall and had a long root before I put it in soil. I planted it in soil that was made for propagating seedlings as well. In addition, I placed the broken half of the seed as close to its original position as I could. I'm not sure if that helped, but it's been over a year and my avocado plant is still growing strong. Looking much more like a mini tree now.
So yeah, my advice would be to keep that one growing, and start a backup seedling just in case :) You need two avocado plants in order for them to actually produce fruit anyways.

Growing avocado from seed