What imperial machine screw has a diameter of 4.5mm and a thread pitch of ~1mm?

Question: I lost one of the screws of my grandpa's rocking chair. I live in Germany and cannot figure out which kind of nefarious imperial screw this is. According to my measurements, the diameter is exactly 4.5 mm and the length (head included) 30 mm. However, this is not M4.5. I measured a thread pitch of 1.04 mm which arguably results in a thread density of 24 TPI (threads per inch). I assumed it was something like #9-24 UNC but those screws do not seem to exist (at least Wikipedia does not mention them and none of the retailers specialized in imperial screws have them). Do they exist in the US?
Comment: The exact length of 30 mm gives credence to my hunch it is a metric screw. I have never heard of a 9/24 machine screw, bolt or pitch form.
Comment: Not asked, but that type of screw is commonly called an "oval head machine screw".
Answer: A friend of mine pointed out that #9-24 UNC is actually a standard size – it is far from common these days (mind this is an old piece of furniture). Here is a table from 1916:

The listed diameter of 0.176 inch amounts to 4.48 mm – well within my range of measurement error.
Now that this is cleared up, the real struggle will be to find one of these ancient screws, with sufficient length, more than 100 years later… in Germany.
On a side note: I did read the other answers and I appreciate them. I got my hands on a #10-24 UNC screw, but it does not fit.
Answer: Machine screws below 1/4" are mostly found in even numbers.
Assuming a thread pitch of 24, it's likely a #8 or #10. Their diameters are listed as 4.166mm and 4.826mm, respectively.
Since M4.5 screws are only commonly made with .5mm and .75mm pitches, I'd lean toward the 10-24.
Answer: I ran into the same situation.
There is not a #9-24 screw( that I know of) use 10-24 screws. if it does not fit, then buy a 10-24 tap and re-tap the thread.
Problem solved.
Answer: There is no #9 screw size, it will be 8-24 or 10-24. 8-24 would be 4.06mm and not likely to fit your measurements because sometimes thread cutting results in slightly SMALLER diameters, but not larger. #10 would be 0.19" or .483mm diameter, so that fits your scenario better and 10-24 screws are much more common that 8-24.


L^p Idempotent multipliers in 2 dimensions

Question: This question is suggested by that about L^p multipliers (and the answer by Michael Lacey in particular).
Let E be a measurable set in the plane and XiE its characteristic function. We say E is an Lp multiplier set iff the translation invariant operator F(Tf) = XiE F(f) (F = Fourier Transform), extends to a bounded operator on L^p (it is a-priori defined on the Schwartz Class or L^2\cap L^p).
For example in dimension 1 every interval is an L^p multiplier for every p except 1 and infty.
The situation strongly differs in the 2-dimensional case, as highlighted by the solution of the ball multiplier conjecture by C. Fefferman: the ball B is a strict L^2 multiplier (not L^p for p\neq 2) and the same is true for every set with an appropriate curvature.
I was wondering whether more generally something can be said about the interval of p for which E is an L^p multiplier, in terms of the "geometry" of E, in dimension 2 or higher.
Answer: The only result along these lines that I am aware of is due to Vebedev and Olevskii (Idempotents of Fourier multiplier algebra. Geom. Funct. Anal. 4 (1994), no. 5, 539--544. ). Their result states that if a set E \subset R^d does not agree (almost everywhere) with an open set, then it can not be a L^p multiplier for p \neq 2.


Transaction confirmation

Question: How does transaction confirmation work in bitcoin-qt? I suppose, client does not have addresses index with balance on each of them (because there is not such console/bitcoind commands). Looking through all of the blocks - it is too slow.
Answer: Transaction processing is a function of mining.  Each time a block is found observed transactions become included in the block chain and get one confirmation.  The Bitcoin protocol is designed to have an adjusting difficulty to ensure that blocks are not generated at a speed greater than that>   This ensures the gradual distribution of new coins into the economy as well.  So long story short this is the model that Bitcoin uses and it is one of the few shortcomings of performing transactions.
Comment: That's fine. But what happens if I send transaction, which are moving 1 BTC from address1 to address2 (address1 has only 0.5 BTC)? Miners will check it? What if I am a miner, and include this transaction in my own block?
Comment: The bitcoin nodes check all of the transactions in a block and will reject the block if it contains an invalid transaction.  Each transaction must reference an unspent output in order to transfer coins.  If your wallet has just 0.5 BTC, then it does not have an unspent output of 1.0 BTC and the transaction cannot be created.  Note that all transactions are public and are contained in the blockchain, not in your wallet.
Comment: So, bitcoin-qt/bitcoind has ability to quicky check unspent output on particular address? Does they contain index with all addresses and unspent output on them?
Answer: As transactions occur, the client tracks their effects on its own balances. If you add a new account, it will have to scan all unspent outputs to find any for that account.

Transaction confirmation


How to check for mesh overlap?

Question: I'm creating a level editor in Unity. I need to detect when an object is intersecting another as I don't want to allow the user to place an object when it is colliding with something else.
In the below diagam, there is a corner road piece and a tree. The dashed red line represents the mesh bounds of the road and the blue dashed line represents the mesh bounds of the tree.

My current approach is to use Physics.OverlapBox with mesh.bounds. In the diagram, visually, it is clear that the tree does not overlap the road. However, the bounds do overlap, therefore I cannot place the tree there.
Whats the best way to check if they are actually colliding in an efficient way? The level editor could potentially have thousands of objects.
EDIT:
I have since tried using Physics.ComputePenetration. Primitive-primitive checks work ok, primitive-mesh collider checks work ok, but mesh collider-mesh collider checks fail. From what I understand a concave mesh collider cannot interact with another concave mesh collider. Is there a workaround for this or must I momentarily make it convex before checking overlap? I just don't want to lose the accuracy of the concave collider.
Comment: Tests with concave colliders are vastly more expensive than convex ones, so it's usually a good idea to decompose your concave colliders into multiple convex or primitive pieces wherever possible.
Answer: To solve this I first use Physics.OverlapSphere to get the nearby colldiers. Then for a more precise calculation I use Physics.ComputePenetration.
However, some of my assets utilize concave mesh colliders. As stated in the docs, a concave mesh collider cannot collide with another concave mesh collider. To fix this, I momentarily make the mesh collider convex before calling the overlap sphere.
Comment: If your issue is solved, could you mark your answer as correct, to prevent it from being bumped to the homepage?

How to check for mesh overlap?


Is there any free vector editing software?

Question: Is a free vector editing software similar to Illustrator?
Answer: Yes, there are several. My go-to software is Inkscape mainly due to its stability: https://inkscape.org/en/
There's also the drawing tool from OpenOffice/LibreOffice if you feel like you need to create vector art in a Microsoft Word style interface.
If you need CMYK support there's SK1, though I personally haven't tried it so I can't vouch for it: http://sk1project.org/
Comment: I took a look at the latest Inkscape and it looks like it now supports CMYK. So I highly recommend giving Inkscape a try.


In W-OTS, is it trivial to forge smaller N values?

Question: Just read about W-OTS. Since the signature is the private key hashed 256-N times, is it trivial to forge a signature with a smaller value for $N$ when having access to original signature? I.e. just hash it one more time and it represents 9-1, etc.
Answer: W-OTS has a checksum that ensures that kind of attack doesn't work.
In essence, the checksum is the sum of the value of every other component subtracted, so that if you hash one component one more time, you need to find a pre-image of a component of the checksum.
Basically, it looks a bit like this:
<code>[ - | - | - | down | checksum up ]
</code>
Related: https://crypto.stackexchange.com/a/63903/36960


OpenOffice - combined roman and arabic numerals page numbers

Question: I am putting the final touches on my Master's Thesis, and the format I need to use requires that all pages before the table of contents be numbered with roman numerals, and all following pages be numbered with arabic (regular) numbers.  I can only figure out how to use one or the other, not both in the same document.  thank you for your assistance.
Answer: This OpenOffice page  contains the information on changing page numbers from latin to arabic numerals and on how to restart page numbering at 1 again. (I understand you already no this bit)
To combine the two types of numbering, you need to make a new page style, choosing the desired numbering format and then applying this new page style to your target pages.
See for detailed information in the index of the help pages under "page styles;creating and applying".
Make sure to add the pagenumber field again to the footer in your new page style.


How can I clean water stains off my shower stall?

Question: It is all glass (transparent) but has become translucent because of salt stains (slightly hard water). What is the best way to clean without using harsh chemicals? My toddler is allergic to harsh chemicals like Ammonia.
Comment: People don't have allergies to harsh chemicals, they have allergies or sensitivities to specific things. "Harsh chemicals" is a generalization with little meaning. If the types of products you use in your home are important for your son's well being you should take him to an allergist to find out exactly what he is allergic to.
Answer: Ammonia is not the right chemical anyway. Try vinegar; if that's too much of a chemical for you, get out a razor blade and start scraping. Or rinse after using it....
Once you have it clean, use a squeegee to remove any water from it before it dries after each use to keep it clean.
Answer: This really depends on the exact cause of your water issues.  When I buy a house with a lot of build up on the glass I try the following steps in pretty much this order:

Hot vinegar on paper towels.  Stick paper towels on door.  Note that when using vinegar you can ruin nearby towels/clothing.
Hot vinegar/Dawn/baking soda paste.  Rub it on door, let sit for 10-15 minutes and hit it with a heavy pad.  If the glass is flat I would suggest a few SOS pads.
Lemon juice.   The acids in lemon juice tends to break down the things vinegar doesn't.
Then we are on to CLR and whatever we find at store.

However if this is an ongoing issue at your house I suggest using an auto glass sealant like RainX so that the buildup is much much slower.
Answer: Couple things I have used that work well and are fairly mild are Barkeeper's Friend Soft Cleanser and Simple Green Clean Building Concentrated Bathroom Cleanser along with a blue scotch sponge. It's important to leave either cleaner on the glass for a while before you start scrubbing to let it work. The more you leave it on the easier it is to clean.
Neither one has a very strong scent to it. If you keep the window open and rinse everything well when you're done I don't see how that could be an issue but I'm not a doctor.
Barkeeper's friend is oxalic acid and citric acid. MSDS lists it as a moderate health hazard. It's very good at getting rid of heavy buildup. Once you get it clean the easiest way to to keep it clean is to squeegee the glass after every shower. 0 chemicals.
The Clean Building Bathroom Cleaner is from a line specifically developed to be safer. The MSDS lists it as a slight health hazard. Dwell time is very important for this one. Spray it on and let it sit on the glass for a good 15-30 minutes then scrub lightly with a blue scrub sponge. Be careful cleaning the glass, they do break. If your build up is very bad you may need to let it sit on the glass longer and come back and respray every so often to keep it wet. May need multiple cleanings but once you get it clean it's easier if you clean it regularly.
I've been using the Clean Building for a while now because it works well for me and you only mix about 1oz or so per spray bottle so it's very cheap in the long run.
Answer: You can also try a shot of vinegar concentrate poured into a small bowl with water.
Answer: If you are sure it is hard water deposits- CLR. If it is soap film (and it might be)- cleanser with phosphoric acid.
Close the door and keep your sensitive child (really, all kids) out. Rinse and repeat ad nauseum... then ventilate.


Number of Pandemic players?

Question: Why is the original Pandemic set for up to 4 players when there are 5 role cards?
Comment: Not a direct answer but I've had fun playing the game with 5 people (though still choosing from the modern 7 roles).  It affects the balance a bit but not in a consistent way (more turns in a round hurts you, but higher variety of roles helps you). Don't be afraid to try with 5 and tweak as you find the bias.
Answer: When the game is started the roles are shuffled together and each player is dealt a random role. Having more roles then players allows for some greater variations in the game as you will not always get the same roles in every game which can change how you play the game. You can see in the rules how it deals with the extra roles. Also it should be noted that in the current edition there are 7 roles for 4 players in the base game.
Comment: Additionally, the game feels slower the more players you have - for example Tom Lehmann mentioned [here](https://boardgamegeek.com/thread/1075895/pandemic-base-game-lab-6-players-and-other-questio) that 6 players was definitely bad in terms of down time between turns in testing.
Answer: After you play the game a number of times, you'll notice that the combination of roles affects the flow of the game. The 5th role increases replay value and prevents the game from becoming too repetitive.
Pandemic has expansions, however, which allows for more players. One such expansion, "Pandemic: On the Brink", has 5 players and includes 7 new role cards.
The base game and subsequent expansions rely on additional role cards -- as well as other added game mechanics -- to keep the game interesting.

Number of Pandemic players?


ExpressionEngine Related Pages Navigation

Question: I have a problem with ExpressionEngine (specifically v2.5.2) and the EE forums are closed today for some reason which is the reason I am posting here. Hopefully someone can help out anyway.
I have a channel set up in EE called "Static Pages" which contains all the data for my static pages (Obviously). The channel also has a relationship field called {static_parent_page}. I used this relationship field to build my navigation so you can have subpages under which ever page you choose as the parent page using this relationship field.
eg. I create a page called "Parent Page" and another two pages called "Subpage 1" and "Subpage 2" and on the Subpage 1 & 2 entries I set "Parent Page" in the {static_parent_page} field and they appear in the navigation like this:
-Parent Page
---Sub Page 1
---Sub Page 2
Anyway, I hope that makes sense.
Onto my problem. I want to be able to go to the "Parent Page", which has two columns, one is a sidebar and the other is the main content. In the sidebar I want a link to the Parent Page at the top and underneath that links to the related subpages as well.
I believe I have sorted that out my using {related_entries} tag but when I go to one of the sub pages the parent page link is still displayed but the other related subpages disappear.
SO...(I think I have made this more complex than it needs to be, apologies) basically I want the sidebar to display:
-Parent Page
---Sub Page 1
---Sub Page 2
Regardless of whether you are on the "Parent Page", "Sub Page 1" or "Sub Page 2".
Any ideas?
Thanks in advance,
Ben
Answer: Without being able to see your template code, I would say try to set dynamic="off" in the template.
Comment: Without template code we won't be able to help you much, have you considered using a navigation management module such as navee?
Answer: Purchase and use the Structure Module. It was built for the exact purpose you describe, including generating navigation dynamically.
Side note: In EE 2+, the dynamic parameter needs to be set to "no" instead of "off."


Black Beatles and the Mannequin Challenge

Question: The "Mannequin Challenge" is a new viral video meme where people freeze in place like mannequins, without camera tricks.  Most of the videos use the song "Black Beatles," by Rae Sremmurd.  But how did "Black Beatles" become the theme for the Mannequin Challenge?
Comment: Hi. I have no idead what you are talking about, could you add more details, links for people like me?
Comment: Can you please post an example of what you are talking about.
Answer: I've seen articles that suggest that the craze originated from a segment of the original "Black Beatles" video where the band freezes like mannequins, but upon investigation, this seems to be incorrect.  There is a live video of the band doing the challenge onstage during the song, but this seems to have been recorded AFTER the challenge started to gain momentum.
It's probably most likely that one of the early versions of the video used that song, and that later versions imitated the early one --that's usually how these viral memes work.  When the video of the actual band doing the challenge surfaced, it probably solidified the connection.


Probability of Random number selection

Question: Suppose you are asked to pick any random real number.
Then you have a choice to pick any number between -∞ and +∞, i.e, infinite numbers.
The probability that you select a particular number n = 1/∞ = 0.
Which means that you did not select any number. How is it possible?
Answer: Two misconceptions might be at play here: that to pick something at random always means picking something uniformly at random; and that to pick an object at random means that one picks any specific object with positive probability.
Regarding the first point, consider that one cannot pick uniformly at random, say, a positive integer, since the probability $p_k$ to pick $k$ would not depend on $k$ in $\mathbb N$ and the common value $p$ of these probabilities $p_k$ should solve the equation $\sum\limits_{k\in\mathbb N}p=1$, which has no solution.
A way out of this conundrum is to use nonuniform distributions, like a geometric distribution or a Poisson distribution or any other from a plethora. Then $p_k$ does depend on $k$ and one can achieve the condition $\sum\limits_{k\in\mathbb N}p_k=1$.
Regarding the second point, consider the uniform distribution on the interval $[0,1]$. A random number $U$ chosen according to this definition is such that $x\leqslant U\leqslant y$ with probability $y-x$ for every $0\leqslant x\lt y\leqslant1$. In particular, $U\leqslant\frac12$ happens with probability $\frac12$, $\frac13\leqslant U\leqslant\frac12$ happens with probability $\frac12-\frac13=\frac16$, and so on, but $U=x$ happens with probability zero, for every $x$.
This kind of remark, and others, led to the idea that additivity was a desirable feature of a probability, but only when restricted to countable collections.
Answer: The logic you have described only works (still, informally) with countable sets. That is why a measure-theoretic approach was needed to formalize the probability over general sets. Namely, you define the class of "obserable events" (formally, a $\sigma$-algebra of subsets of the original set) and define probability for these events only.
This probability is a measure and it formalizes the notion of being random. Namely, if you ask me to choose a random number, I can choose $0$ or $\sqrt{2}$ with probabilities $0.5$ for each of them, since being "random" is not a formal notion. The formal notion is a probability distribution.
Even for countable sets, how would you define randomness? Namely, it's clear that if we consider a finite set with $n$ elements then the a "natural" interpretation of being "random", I guess,  means that any element can be picked up with probability $\frac1n$. But what if there are infinitely many elements? You can still forget about measure theory and define just a probability to pick up each of these elements. But how should one define the probability to pick up $1$ or $2$ or $n$ from $\mathbb N$ in a "random" way?
Answer: probability of selection of any random real number is one...
intuitively, if you have to choose any real number between 1 and 5, you practically don't have an option of not choosing that number. which means you will choose a number between the finite defined range. since there is no other condition on the properties of the number being chosen, the probability of choosing any real number between 1 to 5 is 1.
same soln. can be extended to the infinite case...
a more germane case is putting some property on selection, example- choosing a multiple of 5 on the real number [1,5]. here, the probability is undefined since there are infinite real nos. between 1 and 5. as above, this can be extended to the infinite cae with same results.
Answer: actually probability ( tends )-> 0 if the sample space( tends ) -> infinite, but not exactly zero
Comment: For the future, you may read [this](http://meta.math.stackexchange.com/questions/5020/mathjax-basic-tutorial-and-quick-reference) to improve your formatting.

Probability of Random number selection


Is there any benefit of using multiple lists to store documents versus a single library in large lists?

Question: Background:
We are migrating a legacy system into Sharepoint and will look to migrate around 300 000 documents. There is some metadata which inherently diferentiates the documents from eachother.
Currently I have chosen to have 5 subsites with a doc library in each to essentially split the documents up roughly based on the metadata, however they all use the same content type.
I have written a custom interface for querying the data without the use of the default list views by using SPSiteDataQuery. My queries will always return < 5000 items as a lot of the number of documents in the list are actually versioned so throttling should not be an issue.
Question:
Is there any point splitting up the doc libraries?
Is there an issue with putting all the docs in a single list with regards to performance?
I'd rather have them in a single list and use SPQuery. It would also make other operations I need to perform easier to implement without having the libraries in different places.
Sharepoint can apparently store up to 30 million items in a list. Am I worrying needlessly about 300 000 docs in a single list? We are NOT using any folders or item level permissioning either
Answer: I don't think there is any point in splitting up the libraries given your use case if they all share the same content type and metadata.
But how big are these files?  Are you taking into account SharePoint's maximum recommended content database size of 200GB?
Comment: they are small docs in the region of 50kb each. Yes the content database size has been considered and wont be a problem.


Did Galen Winsor swim in a spent fuel pool of a nuclear power plant?

Question: It is claimed here from minute 50 onwards. Also he claims that he drank 2l of the water and that he ate some uranium.
Answer: If the claims of Mr. Winsor are true that he worked as a safety manager in a nuclear plant, it is highly unlikely that he was actually able to accomplish anything that would have legitimately given him a lethal dose of radiation.

Swimming in the pools is actually a fairly standard practice among workers servicing spent fuel pools.  Divers are used to inspect the submerged fuel rods for damage, and are protected from radiation by the water itself.  As it turns out, water is actually a very good radioactive shield, and divers are safe as long as they don't get too close.
On August 31st, 2010, a diver servicing the Leibstadt nuclear reactor accidentally handled a radioactive piece of tubing on the floor of the pool.  The diver was very deep in the pool and did not hear his radiation alarm go off upon picking up the object and putting it in a transport basket.  The worker received a large dose to his hand, but was otherwise OK.  As can be seen from the report, there was no loss of life or serious injury from the incident, and it appears that this was a case where the diver had picked up a piece of debris from one of the fuel rods and moved it with his hand.

Behavior of spent nuclear fuel in water pool storage
This report was put out in 1977 regarding the protocols and safety of storage of spent fuel rods within pools.  The report itself is very long, but after skimming through it for about a half an hour there are a couple of things to point out.

The average pool from the limited pictures and data in the report indicate that these pools are typically at least 28 feet deep, requiring the use of diving equipment in order to reach the bottom.

The amount of radiation in the water is typically measured in the 10s to 100s of nanoCuries/mL of water.  Thanks to this handy document from the Army Corp of Engineers, nanoCuries are about the same amount of radiation emitted by consumer products.  Two liters of water from one of these pools would be emitting approximately 200 microCuries.  While this is well above what is allowed to be sold in stores, this is approximately 1/5th amount of radiation given off as from a brain or liver scan.

In terms of eating uranium, chances are that if he did, in fact eat Uranium, he did not eat enough of it to cause any lasting impact on his body.  Ironically, the primary danger of eating uranium is not radioactivity, it is toxicity.  According to the CDC...

Natural and depleted uranium have the identical chemical effect on your body.
The health effects of natural and depleted uranium are due to chemical effects and not to radiation.

A cursory reading of the CDC report on uranium says, simply, the toxicity will kill you before the radiation does.  So any possible consumption of uranium on the part of Mr. Winsor must have natually been low enough that he did not poison himself chemically, as evidenced by the fact that he was still alive to record the video.

While this is not as scientific as some of the other sources, Randall Munroe of XKCD posted a What If? article a few years ago regarding swimming in a radioactive fuel pool.  Some of my initial research came from references in this article, but his conclusions are similar to mine.
Comment: Thanks, so he could have done it... But are there no news reports about this?
Comment: He absolutely could have done it, but there is nothing special about what he claimed he did.  He effectively went for a swim, drank some slightly dirty but not overly dangerous water, and ate some poison, but not enough to cause damage.  I wouldn't expect there to be any news reports because there isn't anything special about what he claimed to do.  **I** would swim in a nuclear fuel rod pool and drink the water if I needed to.  The things he claimed to have performed weren't dangerous.
Comment: Well I do not know about the press back then, but  something like this would be reported by today's press. Because it is quite funny to jump into the pool to make a point about nuclear power plant safety.
Comment: Again, I feel that is doubtful that anyone would cover it besides it possibly being a click bait piece.  The video is presented as a claim that there is a conspiracy to prevent the spread of nuclear power by making the claim that nuclear power is not dangerous; however the evidence presented in the video does nothing to contradict what is known about the dangers of nuclear power and radiation.


Portrait lens for Canon T1i

Question:
Possible Duplicate:
What is a good Canon lens to take portraits?

I have a Canon Rebel T1i camera. I am thinking of buying a Canon EF 50mm f/1.8 II lens for portraits. Is it the right lens for portraits? If not what other lenses would you recommend.
Comment: Also see helpful information at [Which focal-length lens is is usually used for portrait photography?](http://photo.stackexchange.com/questions/916/which-focal-length-lens-is-is-usually-used-for-portrait-photography) and [Is it worth it to have the 50mm f/1.8 Canon lens?](http://photo.stackexchange.com/questions/4047/is-it-worth-it-to-have-the-50mm-f-1-8-canon-lens)
Answer: The Canon EF 50mm f1.8 II is a great "starter" prime lens in my opinion. Perfect for portraits when mounted on the Rebel due to the crop factor conversion.  The lens itself feels really cheap and was cumbersome to manually focus for me personally; I found the focusing ring too narrow. The bokeh is good but quite busy due to only 5 (non-rounded) aperture blades. Despite all this, the images this lens yields are good and sharp.
Comment: FWIW, the number of aperture blades affects the shape of out-of-focus highlights, but the "busyness" of bokeh is more influenced by the rendering characteristics of the optics.
Answer: The 50mm f/1.8 will take fine portraits, however don't assume that the 50mm is the only length at which a lens is suitable for portraits. Nearly any lens longer than 35mm can be used to good effect, and the longer a lens is, the more "flattened" the distances involved become (which can be handy).
I've used various focal lengths to take portraits, ranging from 35mm to 200mm. It all depends on what you want creatively and how far away (or close) you need to be from (to) your subject. (I mention this because some subjects have a very large personal space -- it may be better to use a longer lens to avoid infringing upon this space and making them uncomfortable.)
For candids, distance is often key. I've made some of my best candid shots at focal lengths of more than 100mm (and often 150 or 200mm). This is because the subject often doesn't even know the image is being taken.
The 50mm f/1.8 is practically disposable, both due to its cost and cheap make. In one way it is nice, because if it is broken, it isn't expensive to replace. However, if you want something with better manual focus and a better make, look at the 50mm f/1.4 or either of the 85mm variants. (85mm might be a little long, depending on what your intentions are.)
Don't forget that with a T1i, you have a cropped sensor. This means a 50mm lens gives the same effective view as 85mm on a full-frame sensor. Essentially this means that in short spaces you may not have the flexibility to capture what you want, but in normal spaces you should be fine.
Answer: I would recommend that you also take a look at the 50mm f/1.4. As far as I can understand from reviews, apart from the larger aperture, it is also of better build quality. Don't know what the price difference is though.

Portrait lens for Canon T1i


What happens to Omar Sy's character "Barry"?

Question: Of all of the loose ends left by Jurassic World, the biggest question I am left with is what happens to Barry?  One of the raptors is trying to get him while he takes cover in a log, and Chris Pratt's Owen catches the raptor's attention, and leads them away.  To my recollection, Barry is not seen again during the movie.
Comment: @jmassey60 If I remeber correctly, we see him again at the end of the film helping out injured people with Owen.
Answer: I watched the film again last night, and you do in fact see Barry one more time, in the Costa Rican first aid camp, for just a little less than 2 seconds, and he said something to someone off screen.  I could not make out what he said, was about 2 words or so.  I guess maybe we might see something in a sequel or an interview or something, but my guess is that it will just be assumed that he

somehow knew he was safe from the other three raptors (not having seen one hit with a rocket) and the Indominus Rex,
jogged the substantial distance back to the raptor paddock through the unfamiliar woods in total darkness,
found an operational vehicle and drove to the main compound,
and flew out on the last available evacuation vehicle, the helicopter that Lowery called in.

I am dissatisfied with this, but that's the fault of the movie, and I doubt it'll ever be covered in any more detail.
Answer: Usually, these are always the scenes that get the snip during the edited process.
I can think one example off the top of my head: In Watchmen, there is quite a significant character 'Hollis Mason' who plays the original 'Nite Owl'. In the cinema version, he is never heard from again after a scene with Daniel (new Nite Owl). However, in the directors cut, there is quite a chunky and gruesome death scene that was cut out of the final film. Why? Time restraints maybe?
I think the answer to your question is: The scene was shot but likely to have been cut out, as although Barry had quite a bit of screen time, he isn't a significant character. (Much like Hollis Mason)
Comment: That does answer the question of "why did we not see his rescue/escape/death", but I was pretty sure that was the case.  What I don't know, and can't find any real answer on, is "what happened".  I disagree with the analogy of Watchmen's Hollis Mason, because his death adds nothing to the story other than being faithful to Moore's comic.  After all, he would have died 12 hours later in the explosion even if he hadn't been bludgeoned to death, and Dan would have made no different decisions about stopping Adrian.  Barry's fate has impact on the inevitable sequel and remains the only name lost.
Comment: @jmassey360 Well, maybe it's elaborated in some possible Director's Whatever Extended Cut.


Can piano studies be played as a performance piece?

Question: I've learned that Etudes are performance pieces, but what about piano studies like Hanon and Czerny?
Comment: Note that the word *étude* literally means "study".
Answer: Well pretty much anything can be played as a performance piece but many of them would be very dull to listen to.  Personally I find Hanon extremely boring and I believe many other people do too.  Czerny less so but still there is not enough in most of them to make then sufficiently interesting for the listener in a concert setting.
Having said that there is a huge list of studies - usually called Etudes - by great composers which work well as performance pieces.  All of Chopin's and Liszt's Etudes as well as much of Scriabin, Kapustin, Busoni and many others.
So to directly address your question.  You can play anything as a performance piece but you will not attract many listeners if the piece is not intended for that purpose.  "Etude" and "Study" are often used interchangeably so that is not the distinction you should use.  It comes down to the quality of the music and it's usually obvious if a piece is just a mechanical exercise or a well-constructed and interesting-to-listen-to piece of music.
Hope that helps.
Comment: Just to be clear: *étude* is just *study* in French.
Comment: My first time seeing pianist Cecile Licad was at a concert whose primary focus was Chopin's first book of Etudes (Opus 10), and I was totally blown away by the way it seemed like she was pouring music out of the piano.  Definitely concert-worthy pieces.
Comment: the preludes of J.S.Bach (welltempered piano) are often played in small concerts and might be considered aswell as études, after all there where meant as such.
Comment: Czerny created _lots_ of pieces for beginners. I think many are nice dance forms or short binary forms comparable to baroque suites or something like dance sets from Schubert. Not concert hall material, but certainly intended for entertainment.
Comment: There will be a lot of  études containing more music than some sonatines.
Comment: How can you forget about the études of Burgmüller? :-)
Comment: Just to add my two cents; the six suites for cello by Bach were considered as nothing more than etudes for a long time by cellists around the world until one of them, I forgot his name, recorded them and then they became huge concert pieces that both performers and publics alike just love.
Answer: I have taken a few works from Czerny, slowed them down and played them as prelude pieces in church.  One day a woman commented how gorgeous a piece was that I played and I told her it was by Czerny.  She immediately called a meeting of the liturgy committee and had a bylaw drawn up stating that the organist shall NOT PLAY FINGER EXERCISES for worship and they presented me with a list of acceptable composers.  That next Sunday, I played several of Bach's two part inventions.  Bach was an acceptable composer.  I didn't have the heart (or stupidity) to tell them that the choir anthem that week was written by an atheist (Rutter).
I will be playing a concert on a theater organ this June and am deliberating playing a Czerny piece because it sounds really cool with the xylophone and bell stops.
Comment: I got complaints for playing Bach inventions before church as a prelude, saying all I was doing was playing scales and arpeggios.
Comment: @Malcolm Kogut which Czerny pieces did you play?
Comment: The one that got me in trouble was #45 in THE ART OF FINGER DEXTERITY op. 740 in Ab. From the same book #7 in C. The key is to play them slowly with much feeling, maybe roll or arpeggiate the LH and don't play the huge scales or arpeggios at the end. I played #32 as a postlude on the organ with all the stops pulled.  That one was really cool. I have three or four of these books which I have culled from. Slow with feeling is key to faking the music worshipers out.
Answer: The word etude  means study. Most were composed for specific techniques formerly on harpsichord, then, when piano made its debut, for all the new techniques that were available. Czerny, Cramer, Bertini were prolific for the piano, Kreutzer and Rode for violin.
Chopin and Debussy took this writing to a different level, with their Etudes de Concert, and Liszt went even further, both in difficulty and Romantic quality. The latter ones, I guess would be ripe for performance. Although earlier ones were specifically for learning techniques, which is what studies are for, after all, any could be  and have been used as performance pieces. It rather depends on the player and the audience.
Hanon and Czerny could well feature if one wanted to show particular facets of playing prowess to a selected audience - or could be segued into an interesting pastiche.
EDIT: not certain, but dynamics probably don't play a great part in studies. However, applying some of your own would perhaps make them much more like performances.
Comment: Etudes are where one learns to actualize dynamics!
Comment: @RichardBarber - in some cases, but most are for technique. Just checked my Hanon, The Virtuoso Pianist - not a dynamic in sight. If they were going to be anywhere, that'd be where.
Comment: Well I am no virtuoso pianist.  I'm from the school of thought that equalizes dynamics to the other musical factors, having studied the clarinet in my youth.  Even the most technical of etudes (Kroepsch) must be performed with utmost exactitude with regard to dynamics. I studied Kroepsch and Rose under a few teachers, and all of them expected as much during the lesson. Studies born without and played without dynamics should definitely /not/ be heard in recital.
Answer: The short answer is yes, it can.
A better question is "Is this a good idea?", and only you can answer that. Try recording yourself playing the study and listen back to it, perhaps back-to-back with some other piano music you enjoy listening to. If you find it horribly dull, or much less enjoyable than the others, perhaps don't play it as part of a performance.
Answer: Definitely yes, but only if approached as a performance piece rather than as a study to begin with.
I feel compelled to explain what I mean by this. In theory, the above distinction should be redundant. We are musicians, and in theory, interpreting music should always be much more than simply reading notes from a sheet.
In practice, however, most people setting off to play a 'study' piece, approach it in a very different mindset to that of something that they would consider a 'musical' composition in its own right. People typically approach a study as a technical challenge, and feel satisfied that they 'mastered' the study when the technical element that it is supposed to teach (usually, but not always, one of a physical nature) has been 'mastered'. The result in musical effect is a piece that sounds technically challenging and possibly awe-inspiring, but ultimately clunky to listen to in the musical sense.
You will find that if you discard this mindset, and approach the piece from a musical perspective, all but the most boring studies (and sometimes even those!) suddenly take on a life of their own, and become very musical and interesting pieces to perform, with lots of exciting stuff happening beyond the purely technical stuff. Czerny was one of my favourite composers to perform back when I used to be a pianist, and I always got great feedback on the melodies and interesting musical patterns involved, because I always tried to make that my focus and consider the piece as a whole, rather than a the sum of its 'technical' aspects, serving only as a 'show-off' exercise. There's some really nice gems in Czenrny's etudes that really bring out beautiful music when approached with this mindset, but could easily be reduced to a salad of notes if approached only for their technical challenge.
I feel that, perhaps the reason Chopin's etudes traditionally tend to be considered as more 'performance' pieces than Czerny's, is a) because Chopin has earned the reputation of having more 'musical' pieces, such that even his etudes tend to be approached from the musical standpoint to begin with, thus more easily achieving a performance mindset and quality, and b) because some etudes aren't actually that technically challenging to begin with (at least not in the physical sense -- many of Chopin's etudes are exercises in producing a specific musical effect, such as the standing out of an inner melody, rather than technical exercises in speed or finger stretch).
Finally, just to get a bit more provocative here, I will directly contradict the (currently) accepted answer as regards Hanon. If you simply approach it as practicing slightly more elaborate scales, then of course there's no performance value there. But this goes directly against what it means to be a musician. A good pianist / musician can find musical meaning and bring about beauty, even in a Hanon study. It's all about the interpretation, and how you approach a piece. Alas, part of the bigger problem here is that even professional teachers and performers tend to approach these simply as 'finger strength' exercises, so there's not that many positive examples out in the wild to be inspired from. But if you make a point of trying to bring out the music even in something as simple and structured as a Hanon study, it will serve you a lot better in the long run than if you approached them purely as 'finger stretching exercises'.
Answer: There is no rule for what should or should not make it into a performance.  If your audience begins to leave the room or fall asleep, you may have gone wrong somewhere, and I am not sure that's even true.
I have given on one occasion a recital strictly made of Etudes & Study pieces.  In that concert, the only reason why I played some Czerny & Hanon pieces was to help listeners appreciate the genius of other composers like Chopin, who could write study pieces that were also masterpieces as opposed to sounding "just" like studies.
Note also that Liszt wrote some Etudes named "Concert Etudes" where the explicit intent was for them to be performance pieces.  In fact, these are more about performance than studies, unlike the work of Chopin, who focused very much on one or a few specific technical challenges in each of his Etudes.  Making the beauty comes out of an Etude is what makes his body of work on Etudes unsurpassed in my opinion.
Answer: Anecdotally, one exception of a composition as a drill for a guitar master (so I am told) was designed for drills and mastery of
the concert guitar solo work "Recuerdos de la Alhambra" by Francisco Tàrrega. Transposition to piano would take the skill of Art Tatum.


Messenger required for Shaloch Manos?

Question: Does Shalach Manos require a Messenger and why?
Answer: The Binyan Tzion, questions if you are Yotzei the Mitzva of Mishloach Manos if you bring it yourself, since Mishloach implies that you must send it with a Shaliach. Others like the Eishel Avrohom and Rav Shlomo Kluger hold that you are certainly Yotzei if you bring it personally. Sending it is a leniency that the Anshei Knesses HaGedola allowed. Moreover you can only make a Shaliach for something that you can do yourself. If you can't give Mishloach Manos by yourself you wouldn't be able to make a Shaliach.
Comment: Your last point is paradoxical. If the Hachamim enacted it to be done specifically through an agent then it would work through an agent. It is a mitzvah dirabanan and the rule of kol detikun rabanan k'ein d'oraisa tiknu is only regarding a mitzvah modeled after an actual d'oraisa concept. On a Yomtov celebrating Torah Shebaal Peh it is appropriate to have a mitzvah that is complete hiddush and not modeled on a di'oraisa.
Comment: Great point again
Comment: Sources? [15 characters]
Answer: The Dvar Avraham chelek 1:13  brings a shittah from a reading in the Ran that one needs to use a agent to fulfill mitzvah.
The Kaf Hachaim 695:41 writes the opinion of  Binyan Tzion (Gershon gold sourced) and says that the Torah uses the term send in diffrent cases(Noach,Avraham)but was not done through a agent and he holds one does not need one to fulfill the mitzvah.

Messenger required for Shaloch Manos?


Can the Antminer S3 mine Bitcoin using Scrypt algorithm?

Question: Because I can use my PC to mine Bitcoin using the Scrypt algorithm. I use NiceHash. They have an option to select which algorithm we want to use. So I was wondering, once I get my Antminer S3, is it possible to point it to NiceHash's Scrypt stratum and mine using the Scrypt algorithm?
Answer: No. Bitcoin does not use Scrypt, so you cannot use something that mines Scrypt to mine Bitcoin. Furthermore, the Antminer S3 is a Bitcoin miner, it can only mine SHA256d coins, such as Bitcoin. So it cannot even use the Scrypt algorithm or mine any coins that use Scrypt.
Comment: So how does Nicehash work? They have an option to mine using the Scrypt algorithm (bitcoin), and when I use it, my hashing speed jumps from 11 MH/s to 1.7GH/s
Comment: Nicehash will use your hashrate to mine some coin other than Bitcoin, and then convert the earnings to Bitcoin for you.


Can I use US bank issued credit/debit cards in Canada?

Question: I will visit Toronto this summer. I have a US VISA credit card and a US MasterCard debit card. Do stores there usually accept these two cards? If so, which one has the cheaper transaction fee, or are both expensive and it's better to use cash?
Answer: Almost all stores will accept both these cards. Mastercard and Visa are accepted everywhere credit cards are accepted in Canada which is most places. Some stores are cash-only or debit only but not many of them are left.
Whichever one will have the lowest fee will depend on the particular card you have. When you got each card, it will have come with a cardholder agreement. On it, each one will specify the foreign transaction fee charged. This is a percentage of the sale, usually around 2.5% but there exists cards with 0% and I have seen up to 3.5%. If you no longer have the agreement, go to the website of each bank that issues your cards and look for the information there.
It is good to have cash for things like bus fares and small items but getting cash only means that you paid the transaction fee ahead of time when you did the conversion. You usually would have to pay it again even to convert unspent foreign currency, although some places have a buy-back contract that lets you get back converted currency up to a certain number of days after you converted with them.
Debit card transactions on the other hand do not usually work between Canada and the US. You may use your US debit card to withdraw cash from most Canadian ATMs which will give you a good rate plus some fees. For small withdraws fees are usually steep since there is often a flat amount plus a percentage.
Comment: Note: the debit-only places won't take US debit cards since they function through the credit card network in Canada.  Canadian debit cards are on the Interac network and do not work on the credit card network.  (Some banks have credit-card-like debit cards now too but they function on Interac in Canada, and using the credit card network when outside the country.)
Comment: @JimMackenzie I've found that a lot of places that have "no credit" signs actually do accept my card if I ignore the sign and just swipe my credit card. But maybe that's just in Vancouver.
Comment: There are a couple of good no-annual-fee credit cards that have no foreign transaction fee -- the Barclay Uber Mastercard comes to mind (and it has pretty good cash back rewards, too). I myself use the First Tech FCU Platinum Mastercard, because it has true chip+PIN, which means it's guaranteed to work everywhere in Europe.
Comment: I was in Canada this September and October and felt no need whatever to have cash. Everywhere took my US debit cards without a problem, except for a few places without contactless where I had to use chip+signature. Of course I'm lucky and have a rare US debit card with contactless, too, which also worked perfectly and I did not have to sign. Google Pay with the same card worked as well. I did not use any buses though.


How can you SSH into your raspberry pi with x11 forwarding enabled on mac?

Question: I've been trying to connect to raspberry pi over ssh on a mac and then open the desktop using startx. I know on a windows you can use putty and xming but both of those are windows programs only. Is there a way that I your x11 forwarding on mac when using ssh with my pi? I already know how to ssh using the terminal and have also tried Spackle. Any suggestions will be appreciated.
Answer: If you want to display X11 apps on your Mac desktop, you don't run startx from the pi - that will attempt to start it on the pi's screen.  Instead, run an X11 server on your Mac, configured to allow remote connections.  Then, on the Pi, set your DISPLAY environment variable to point to the Mac's server.
In my case (macOS Sierra 10.12.6), I downloaded and installed XQuartz (version 2.7.11 (xorg-server 1.18.4)).  Then, in the X11 Preferences, on the Security tab, check the "Allow connections from network clients" box.  Finally, issue an appropriate xhost command to allow your pi to connect (xhost + will work fine if you trust everybody on your LAN - probably OK at home but bad for any kind of public network).
At this point, you can ssh to the pi as you always do, without any special kind of X11 forwarding.  In there, set the DISPLAY environment variable to point to your Mac's X server. For example, if the Mac's IP address is 192.168.1.10 and the X server is display 0, you would export DISPLAY=192.168.1.10:0
With this done, X11 apps on the pi will send their output to the Mac.
If you log in to the pi from multiple computers, you can add code to your .bashrc (or .login if you use tcsh) to set DISPLAY based on the IP address you logged in from.  Or you can just use the -Y parameter of ssh.
Of course, the XQuartz app must be running whenever you try to log in.  Otherwise, the X11 communication won't have anywhere to go and you won't see any graphics.
Answer: X11 is no longer included with OS X. XQuartz libraries are available, but I know of no  tools which use these for ssh.
I suggest you install VNC on the Pi (I use tightvncserver) and access from the Mac like
open vnc://firstname.lastname@example.com:5901

Comment: Thanks for the help. I so have X11 downloaded on my mac. I was trying to avoid vnc. Thanks once again for your help.
Comment: If you are worried about VNC security, then port forwarding can be used to send the VNC traffic from localhost (the Raspberry Pi) to your OSX session.  VNC is a lighter weight solution than opening a ssh connection and typing startx, since the former sends an image whereas the latter passes a lot more information over the network.
Comment: Check out this page: http://elinux.org/RPi_Remote_Access#Running_a_remote_GUI
Comment: You don't need any tools that use XQuartz *for* ssh.  Just run XQuartz, which will open an xterm window.  Then type in your `ssh` command (with -Y) from there.  Or SSH from any other window and set your DISPLAY variable appropriately.  VNC works great, but it consumes display resources on the Pi, which you may not want to do if you don't have to.
Answer: I had the same problem, and have a solution working now, but it needs a little refining (I can't get it to run in anything other than full screen).
My Mac is an iMac 27in, and I'm using a Pi model 2 with the latest Raspbian image.
I have Quartz and thus X11 installed on the iMac because I need this for the Dia program.
From the iMac terminal, I ssh to the Pi with the -X option (so ssh -X firstname.lastname@example.com).
After entering the password, I get several messages including one about auth key data, but I just ignore these for the moment.
Once at the prompt on the Pi, as user pi, I just enter lxsession (and again, some messages go past) then the big Raspberry appears in the middle of my screen and I have the Raspberry Pi's desktop. I need to use "cmd+opt+A" to get back to the OSX desktop, and I'm still working on how to get a more "manageable" window, but it most certainly works !
My motivation for doing this was to get it working WITHOUT any additional software, and it is working well for me, even though most of my time is spent in a terminal.
Another option that also works well is to install xrdp on the Pi, then use the Microsoft Remote Desktop app from the App Store (I know, it sounds strange) but this also works really well, but it does mean installing extra software.
My OSX has just been upgraded to El Capitan, but I did most of this originally on Yosemite.
Good luck
Simon
Answer: You don't have to set the DISPLAY variable if you use xfowarding via SSH by adding -Y to your ssh command on the Mac!


What is the difference between asteroids, comets and meteors?

Question: Some celestial objects seem to be referred to as asteroids, some as comets, and some as meteors or meteorites.
What is the distinction between all of these different objects? Are any of them the same?
Answer: The objects you are refering to are actually two different objects: asteroids and comets. Meteor and meteorite are other names for an asteroid, at a given time of its interaction with our planet. We'll get to that.
So first, what is the difference between an asteroid and a comet?
A comet is a small solar system body that display a "coma" (an atmosphere of a sort) and sometimes a tail passing close to the Sun. They are mostly made of ice and dust, as well as some small rocky particles. We distinguish two kind of comets, with short or long orbital period. The short orbital period ones originated from the Kuiper Belt, a region composed of small bodies beyond the orbit of Neptune. The long orbital period ones originated from the Oort cloud, a scattered disk of icy planetesimals and small bodies laying around our solar system.
An asteroid is a small body, composed mostly of rocks and metals. In our solar system, they can be originated from the asteroid belt, laying between Mars and Jupiter, or from the orbit of Jupiter (the Jupiter Trojans), or from actually almost everywhere in the Solar System.
A small asteroid ('meteoroid') that enters the Earth's atmosphere becomes a meteor, what we also call a "shooting star".
Eventually, a meteor that was massive enough not to be completely distroyed entering the Earth's atmosphere and hitting the ground is a meteorite.
Comment: @SarahofGaia No, as noted in the answer a "shooting star" is a meteor.
Comment: A "shooting star" can also be a comet, right?
Comment: "A small asteroid ('meteoroid') that enters the Earth's atmosphere becomes a meteor, what we also call a 'shooting star'."              ____________________________                                                                                But comets much more often than asteroids provide the material for meteor showers. Comet 1P/Halley is identified as the source of the Eta Aquarids and the Orionids; Comet 109P/Swift-Tuttle is the source of the Perseids; and Comet Thatcher is the source of the Lyrids. I suppose that comets more often than asteroids produce meteors.
Answer: Asteroids are what are called minor planets - small inner solar system rocky bodies. Especially between Mars and Jupiter.
Comets typically have highly elliptical orbits but they don't have to. The key defining feature of a comet is that it has a gaseous atmosphere and a tail when it passes close to the Sun. Comets are generally loose aggregations of ice, dust, rocks etc.
Meteoroids are very small rocky or metal bodies, from a single particle up to about 1m diameter. If they hit the atmosphere, the visible glowing trail of particles is called a meteor. And if it hits the ground it is called a meteorite.
Answer: Asteroids and Meteoroids are very different in size. Asteroids are huge usually about few kilometers big.
Whereas Meteoroids can be so small from centimeters to about few meters wide.
Both are very different in size. Sometimes, when two asteroids collide they might throw away few percentage of their rock which falls into planets as meteorites.


What's the efficiency of hub gears compared to derailleurs?

Question: What's the efficiency of hub gears compared to derailleurs? I know that hub gears are not as efficient. Apart from being heavier, how much will I lose in performance if I use hub gears?
Comment: Weight should not affect efficienty, which is a measure of energy input vs. energy output. A bike can be heavy (require more energy to move), and even so be efficient (not wasting energy with friction, flexing, etc.)
Comment: Are you looking for numbers or an approximation? If the former, I suggest you mention a particular hub.
Comment: I think he's saying that both lower efficiency and higher weight will "lose in performance", which is true, assuming a route that isn't totally flat and isn't almost all downhill.
Answer: A lot depends on the rider and what you mean by efficiency.
It is easy to keep a hub gear running well for years, but an unmaintained derailleur will become inefficient very quickly.  A hub gear allows the chain to be fully enclosed, for all but the most dedicated cyclist; an enclosed chain will be more efficient as it will be cleaner and better oiled.
An enclose chain allows you to arrive at work, with clean cloths and no need to change, this can save lots of time.  Not having to spend time adjusting a derailleur or cleaning your chain also increase the efficiency of your life.
However it takes longer to remove the wheel if you have hub gears and an enclosed chain.
Gear shifting efficiency. This is most important in cities with many traffic lights to stop at. With a derailleur, you must shift before you stop, or you'll be starting in a high gear. With an IGH, you can forget about shifting while you are braking, and just select the right gear for the next acceleration a second before you start pedaling. It's a huge difference for a commuter, irrelevant for a racer.
Personally I think on a road bike:

Hub gears are more efficient if you wish to use a bike to make lot of short trips as part of your day to day life.
But derailleurs are more efficient if you consider going fast on a bike to be very important and are willing to put the work into the bike that is needed to keep it in a very good state of maintenance.

(I also like hub brakes for the same reason)
Comment: Rolling up your pant leg also allows you to arrive at work with clean clothes. :)
Comment: Third aspect of efficiency: **Gear shifting efficiency**. This is most important in cities with many traffic lights to stop at. With a derailleur, you must shift before you stop, or you'll be starting in a high gear. With an IGH, you can forget about shifting while you are braking, and just select the right gear for the next acceleration a second before you start pedaling. It's a huge difference for a commuter, irrelevant for a racer.
Comment: @StephenTouset For some reason, I never see people with rolled up pant legs in winter...
Comment: "An enclose chain allows you to arrive at work, with clean cloths and no need to change" So does tucking your trouser leg into your socks. Or using trouser clips. Either of those works just fine in winter.
Comment: @cmaster I'd counter that experienced commuter cyclists likely will learn to downshift before stopping. It's one of those fundamental cycling skills. That said, you're correct that hub gears can shift while stationary.
Comment: @WeiwenNg Sometimes, you need to perform an emergency stop. Show me the chain-shifter that manages to do an emergency stop *and* shift down - no problem with an IGH (shift after stop). Also, I'd argue that shifting gears before you stop is as much a bike skill as shifting gears is a car driving skill: The later is almost unheard of in the USA where virtually all cars are automatic, but in other countries where manual gears are abundant, the statement is considered true. Same for bikes: It's only a basic bike skill as long as you equate bike with chain shift. *But IGH bikes are bikes as well*.
Comment: @cmaster You're not looking hard enough.
Answer: In 2001, Kyle and Berto published a comparison of the mechanical efficiency of several configurations of derailleur and internally-geared hubs in Human Power, which you can find here. Among the systems tested were a Shimano MTB derailleur system, a Sturmey-Archer 3-speed hub, the Shimano 7-speed Nexus hub, and the 14-speed Rohloff hub.
MTB derailleur systems are (now) known to be less efficient (more lossy) in terms of power transmission than "road bike" derailleur systems. In particular, note fig. 12 in the cited link, which compares average efficiency at three different levels of power for the internally-geared and MTB derailleur system. As shown in the figure, the three derailleur-type drivetrains (a Shimano 27-speed, a Browning 4-speed, and a Browning 12-speed) were more efficient than the other drivetrains tested, all of which used planetary-geared rear hubs. Spicer (2000) has measured the power transmission efficiency of an ideal chain driven system at about 98%, so that is what you would expect the maximum efficiency to be.
Answer: It depends on the model you get, but the efficiency is generally comparable.  Derailleurs that are in really good condition and properly lubed will be more efficient, but marginally, and will often be less efficient due to real world conditions.
At least that's what the wiki says:
http://en.wikipedia.org/wiki/Hub_gear
I have one road bike with a 3x9 derailleur, a smaller bike with a 7 speed nexus, and a brompton that actually has a hub AND a derailleur for a low/high gear.  The other considerations (tire size, pressure, etc) probably matter far more than the gear.  For easy shifting and maintenance, hubs, no question.
Newer hubs are generally considered more efficient (Shimano Alfine vs Nexus, that sort of thing).  Also, Shimano has an 11 speed coming out that has a different type of lube than usual, and is supposed to have improved efficiency, but I don't think we'll know much till its out.
Then there's the Rohloff.  Way too expensive to buy, but shows what a good hub can pull off:
http://hubstripping.wordpress.com/speedhub-rohloff/
Comment: I own a Rohloff and don't think it is way expensive to buy. Not only it costed the same as the parts I didn't have to buy (crankset, rear and front deraileur, cogset, shifters, etc.), but also the drivetrain lasts longer. It is not perfect, but it is worth for anyone that will crush the miles from it.
Comment: Some experimental results for derailleur systems here: http://www.ihpva.org/HParchive/PDF/hp50-2000.pdf Summary: smaller cogs are less efficient.
Comment: The 11-speed will be oil lubricated, rather than grease.
Answer: Let's say, in The Netherlands were the majority of bikes are used as a means of personal transportation the vast majority of gears are hub gears. The main reason is their very low maintenance, and of course the fact that you get a proper chain cover. For use as means of transportat
Answer: There was a recent study done on this by FahrradZukunft magazine, which is nicely summarised in this excellent article. The results are summarised in the following graph:

The dark pink line represents a singlespeed transmission which is around 97% efficient (a typical figure quoted for a derailleur system is slightly lower at 95%).
As you can see the efficiency of the hub gears depends which gear you're in, as a different number of moving parts can be engaged for each. Overall the Rohloff speedhub is the clear winner, with the Nuvinci CVT hub coming in last. As the article says, at a 200W power output this equates to a difference of 22 watts, which is pretty significant.
Personally I've found the drag from hub gears to be noticeable if not huge, but a price worth paying on an all-year commuting bike for example.
Answer: In general, it depends on the hub and the cyclist. My gut and my experience with the two 3-speed hub geared bikes I own (SRAM and Nexus hubs) suggests to me that not much in the way of pedaling energy is sacrificed.
Answer: I don't know how much is lost, but there is definitely some. I lose speed more quickly coasting with my hub (Nexus 7) than with a freewheel design. This is confirmed by turning the crank on a tuning stand and seeing how much more quickly the wheel stops turning than with a freewheel.
Similarly, on the tuning stand, if I slowly spin the crank backwards, the wheel will start to rotate backwards which never happens with a freewheel (or at least to much less an extent).
Both of these tell me that the hub is creating a bit more internal resistance than the bearings and ratchet mechanism on a freewheel do.
The chart posted above would indicate that internal hubs maybe lose 2.5% of efficiency compared to a derailleur.
That and the slightly higher weight are probably why racers all use derailleurs.
Comment: Welcome to [bicycles.se] @Danny. Thanks for having a go at answering one of our questions. We recommend that new members take the [tour] to make best use of the site, and especially to understand how it's different from a chat site.
Answer: I can only compare the basic Shimano Acera and Deore (3x8) deraileurs to the Rohloff 14-speed hub, but these are my observations relating to efficiency. There's a distinction here between pedalling efficiency and gear-shifting efficiency. I'm going to mention both as I don't know which one you meant.
On the Rohloff hub

In the majority of gears it doesn't feel like there's any loss of pedalling power compared to a direct-drive fixed gear bike (subjective, I know). Gears 7 and 12 make some noise and seem a little less efficient.
Changing gears is always impossible if significant force is on the drivechain.
A short pedalling pause is required to shift gears.
It is possible to change to/from any gear when stationary or coasting.
Gear inches change between gears is simple and predictable (roughly the same percentage per click).

On a derailer

A small amount of pedalling power seems to be lost to the jockey wheel. This is significant only if it gets dirty or one of the shifters is misaligned. Several gears are noisy/inefficient due to chain angle.
Changing gears is sometimes tricky if there a large force on the drive chain. It depends on which change is being made, some are really easy and smooth, others need some care.
No pause to fast, gentle pedalling is required to shift gears.
Only possible to change gears when pedalling.
Two shifters means that shifting quickly to a predictable-length gear a skill that requires a bit of thought.

YMMV, but I find the Rohloff to be efficient and simple to use. We use it on a tandem, so it may be that the pause needed when shifting is less distruptive on a solo bike.
However, I also expect that an experienced racer would be able to shift their high-spec gears much more quickly and efficiently than any hub gears and that this might mean that deraileurs are the only option for racing. That and the fact that you can't seem to connect them to brifters.
Answer: In my ~1 month experience with the Deore (11 speed?) internally geared hub compared with well-maintained derailleur systems of comparable quality and newness, the internally geared hub has a noticeable amount of internal loss. Note that this test was carried out about a year ago. I ended up returning the bike.
First test (idle loss): turn the crank a few times and get the wheel to spin, see how long it continues to spin. This will tell you how much energy is lost in the hub. In my experience the loss is noticeable.
Second test (loss under power): using a similar gear ratio, turn the crank at a fixed speed for about a minute, you will get an idea of how much energy input is needed to keep the wheels turning at a fast, steady pace. Compare the two energy inputs.
Answer: I set the same electric bicycle up using a Bafang 1kw mid drive anf a thumb throttle.
I ran.3 different gear set ups with same final drive ratios.
1st set up was with a Shimano Nexus 8, top speed was 43mph. Sluggish.
2nd was with a Sturmey Archer. Top speed 45mph
I ran it with a derallier and got 49.5mph.
Max rpm on the moyor was the same for all 3 with a full battery.
This is actually quote a big % change. While it only lools like a 4.5mph increase, the energy required to.go.those extra mph is quite significant.
Remember to double your speed neefs 8x the power...so an extra 4.5mph is probably over 10 % more power to the wheel rather than absorbed by the gear system.
I agree  they are nice and.tidy but I now build all my electric.bikes with derallier. I get noticably more miles per battery...about 10% more coincidentaly !
Answer: There are various studies of this. Some have quoted them. The objective answer is that hub gears are generally less efficient than derailleurs.
My bike last year was a Ridgeback World Journey, a heavy steel tourer with an Alfine 8 hub and drop bars.
This summer I made up a tourer using a Ridgeback Panorama Deluxe. Still a heavy steel tourer. I didn't pay much attention to the component weight.
Both bike are very similar, but the Panorama is a 3x9 derailleur, the World Journey is Alfine 8. So effectively the same bike with different transmissions.
Here is a numberless, but still objective answer. With the bike in a stand, I can spin the back wheel and let it go. The derailleur wheel will continue spinning for a very long time, the hub gear will slow quickly.
Subjective answer - the derailleur bike rides a lot better. Exploring a Scottish island this summer I could pedal a little and then coast for a long time, even on the flat. I could never do that on the hub gear bike. I think I could feel the drag.
The overall difference in weight of the two transmission systems is not that great, apparently. But with the hub gear all the weight is at the back end. I swapped the tyres between the two bikes, so at one point had both back wheels off. Again numberless, but there was a huge difference in weight. This heavy back end makes the bike 'feel' sluggish, I think.
I've always had hub gear bikes in the past. It seems like a great idea, and changing gear while stationery is useful. Combined with roller brakes it could be the ultimate commuter (I've got a Carrera Subway 8, that has exactly that setup).
But they have many drawbacks:

The gear range will be narrower than a derailleur set. Might not matter where you are, but bottom gear isn't really low enough on my Alfine.
They feel, to me, 'sluggish'.
The back end is heavy, and if you have rear panniers, VERY heavy, so increasing chances of pinch flats and needing higher tyre pressure.
Changing the rear wheel for flats is difficult. You can't have a QR, and you need to carry something to unhook the cable (at least with Shimano). So you have more tools to carry, specifically a 15mm spanner and a 2mm allen key. On the bike stand it's a bit awkward. In the dark/rain it would be a horrible job. Is a horrible job, I've done it.
You have very limited choice of changers if you want to use drop bars.


How do Marxists account for fiat money?

Question: LTV predicts that fiat currency, which requires zero labor to produce, should have zero value. Empirically, fiat currency does not have zero value. How do Marxists account for this. The to responses I have gotten so far are that labor does go into printing(though very little in comparison to the price) and that fiat currency is merely a token of money. In which case what is the money in this regard and how can any of this be empirically tested?
Comment: I think you'll get a better answer at [politics](https://politics.stackexchange.com/)
Answer: Marx's theory of product-value is often called a "labour theory of value" though he never used it himself to describe his "law of value". He also had a theory of exchange-value to try to explain market phenomena.
Marx did have a theory of the materialisation of labour in gold. But fiat or credit money has no intrinsic value (if it did then it would not be fiat), though it does have an exchange value, broadly speaking the value that can be acquired by spending it.  Marx argued that the use of money obscured the real value ("congealed labour-time") involved in transactions and exchanges.
That is not really testable, but what may be testable is the extent that relative prices of different commodities reflect the labour involved in their production, and if so whether these reflections are of average or marginal labour, and what causes changes in relative prices over time.  Whether you would want to is another question: it is all a bit 19th century.
Comment: Appreciate the reply. Is their any way you know of in which I could get a hold of the studies that have tested this price to labor value comparison that show evidence of this being the case?
Answer: There is nothing which exists in the human world, which does not require labor. Fiat money is by far no exception to that. It requires an state with many institutions to secure the money, so people can trust in the value of it. It requires bank houses and a lot of technology and real work to manage the financial processes. Marxian economics is very materialistic. The material background of most "pure" econonomic phenomens, is often ignored by the mainstream. For marxian economics fiat money has definitely value of "congealed labour-time" and not only the value of the printed paper.
Today we live in the age of information and data. So we know a lot things similar to fiat money. How a society determines the value of something is in the power of the society, not in the thing itself. The average required  labour time is an theoretical more philosophical tool, which still is not easily applicable to known, maybe any, economy.

How do Marxists account for fiat money?


Software/Web Application for Sharing Code Snippets Internally

Question: Does anyone know of a web app and/or software that can be installed and run locally to share code snippets?
We would like to encourage code reuse and re-factoring within our organization but using sites like http://snippets.dzone.com/ or http://pastebin.com/ wouldn't work very well in this scenario because we want to keep this private. Visual Studio has support for code snippets but that's geared more towards individual developers and not for group sharing.
Does anyone have any suggestions for an app/tool that might accomplish this goal?
Comment: possible duplicate of [Open Source PasteBin ?](http://stackoverflow.com/questions/3909251/open-source-pastebin)
Answer: you can use http://codetidy.com/ or https://gist.github.com/


Help! Turn php link data into url OR hide edit link in post admin OR hide drafts for all users except admin?

Question: My website allows users to upload events via an upload process incorporated into a customised front end page.
As an event uploader, I also want users to have access to the dashboard where they can view the events they have posted.

I ideally want to remove access to edit.php - I don't want users to be able to edit / or reach post.php, at all through their dashboard. I only want them to upload events through the customized front end upload.

SOLUTION POSSIBILITY 1
I could disable edit for the contributor role completely and still have a way to show posts to the event listers from their dashboard, if I could just learn how to add this info to the menu in the admin side bar in the form of a button in the dashboard (for all users). This code came from a link I found in a widget:
<a href="<?php echo get_author_link( $echo = false, $current_user->data->ID; ?>LINKED TEXT HERE

I tried to add it using AG Custom admin add menu button funtion, but it didn't work.
The above would be the ideal solution for me as there'd be no access to edit.php through url link for this role.
One set back is that showing the posts in the fron end, shows an edit button when the post is still a draft. I would like to remove the EDIT button from the front end page they view, I think it only appears in draft status as this role can't edit published posts (I will have to double check that). Even if it's the users post I don't want them to be able to edit it once it has been submitted, as I only want what I originally approve to be published.
I reckon I could work that out myself (In single probably?)bugt if anyone can help whilst I think of it that would be great!
SOLUTION POSSIBILITY 2
So - if I use role manager to completely prevent editing, that removes all access to the edit.php. which is fine in the instance above (if I can add that link to show all authors posts into the admin sidebar).
But I really do want event uploaders to be able to view a list of their events and view each one. Edit.php seems a good second best place for that to happen if I can't link to a list in the front end as in the exp above, as the events are already listed at edit.php, as is the view facility. I just don't want to allow a link through to edit, and there is that link in the title of the post until I have approved it!!
I thought if I could disable the link through to edit a post. (through to post.php) which is incorporated into the title of each row in the table of posts (or events in my case) then that would stop people from accessing that screen. BUT I would then, though, have to solve that the screen would still be accessible if they pasted in '/edit.php' to the url. I have removed quickedit and edit, and edit from the bulk filter at the top of edit.php.
SOLUTION POSSIILITY 3
Another possible fix takes advantage of the fact that once a post is published (approved by me) by a contributor, this link on the post title in edit.php screen actually disappears!
So alternatively, if someone knew a code I could paste into functions within the theme or even the core files, (i don't mind, either way, I'm desp!) to make it possible for only admins to posts of draft status in their post list in edit.php, so once a contributor posts an event in the front end, it doesn't appear in their own post screen until it becomes published (when I have approved it), then that would also solve my problem!
Thank you so much for your time! I utterly am stuck, I can't find a solution to any of these options, this as far as I can get with each!
I would be so SO grateful if there was anyone out there who could help me with this challenge, I am truly stumped.
I'm not a php expert, but I'm handy and have a reasonable grasp, and am good at finding solutions and amending ones from others to match my unusual needs, etc. I have spend ages on this one and just had to wave the white flag! I'll eagerly look out for any tips from our there in the big wide world !
Thanks again
Kaye
.......................................................................................
Other notes:

I'm using wordpress v3.1.1
I use manage readers own posts
I have hidden the media library so contributors see only their own piccies.
I use role manager to deal with role limits
I also use rolescoper to deal with category limits
I use adminize and global screen options to tailor screen
I use AG custom admin to help tailor admin screen
Along with a heap off other functions and plugins.

I would very much like to allow event uploaders access to a dashboard, so I don't want to hide the whole dashboard as a solution to this problem of hiding access to editing (or POST.php) in the back end.
Comment: Have you found a solution for this? Although you go into great lengths to explain your issue, it's being kind of hard to understand you final goal... Wouldn't a custom Dashboard widget solve the problem? *(listing all the user's posts/events)*
Answer: As far as I understood this right, you want to disable the possibility to reach any other side aside from the dashboard.
Well, then here's a short plugin for you:
<?php
! defined( 'ABSPATH' ) AND exit;
/* Plugin Name: (#45989) »kaiser« Allow Dashboard only access */

function wpse45989_access_dashboard_only()
{
    if (
        ! isset( get_current_screen()->id )
        OR 'dashboard' !== get_current_screen()->id
        )
    {
        // Lets limit this to only specific user roles
        if ( current_user_can( 'ROLE_NAME_HERE' ) )
            exit( wp_redirect( admin_url() ) );
    }
}
add_action( 'current_screen', 'wpse45989_access_dashboard_only', 100 );


Cross-platform interactive ebook in iBooks Author

Question: I'm attempting to create a choose-your-own-adventure ebook in iBooks Author. However, in formats other than the mac store, the links do not work. I can export it as an epub but the links will only work in iBooks. How do I fix this?
Answer: This is a case where a very user-friendly tool works well on only one platform.
Before I say anything else, you should have learned how to create and edit links in HTML. Also, it might help to use css which allows you to force a new page. Sample code here: http://www.paulsalvette.com/2012/04/adding-page-breaks-for-your-kindle.html (Keep in mind that ebook support for page breaks has improved but is still lacking in Google play books).
Creating hyperlinks in HTML for epub files is extremely simple. Unfortunately ibooks author probably generates a lot of hard-to-edit code (I'm guessing).  If you can unzip the .epub (an epub is just a zip with its suffix renamed to epub), you can probably make those changes manually. But that might be a lot of trouble.
Actually if you're testing the links, you could probably test with Adobe Digital Editions or the Readium in Chrome
I don't know why you choose ibooks author, but you probably would have had more luck with creating your ebook in sigil. You need to test the html files before you make an epub file.
One thing. I am a gigantic fan of CYOA, but here are 2 things you should know:

"Choose your own adventure" is trademarked. I would call it a "maze story" which is not trademarked.  I think there are some bona fide CYOA stories as ebooks, but I think the publisher created an app to host those stories. (By the way, looking over the print CYOA is very interesting. you can appreciate the artistic choices. I blogged about the series here (skip down a bit)).
This author Rudolf Kerkhoven has created some interesting (and successful) maze stories in Kindle. Check out "The Adventures of Whatley Tupper"
Comment: If the OP is using any of the more advanced features of ePub with iBooks Author, then they won't be able to fix this with Sigil because iBooks Author uses a modified version of ePub 3.0 and Sigil can only handle ePub 2.0 (it actively breaks ePub 3.0 files).


How to formulate a chord on the piano?

Question: I play guitar, and am attempting to teach myself the piano. Which notes from a scale form the chord on the keyboard? Is there a common rule for this?
Comment: What kind of chord?  There are many varieties, and they all exist on the guitar as well.
Comment: which notes from a scale form a chord isn't anything specific to a guitar or keyboard so I'm not sure I understand the question as asked. Are you asking how to *voice* a particular chord? e.g. *which* C, E and G to play if playing a C major chord?
Answer: Any keys you like. A chord in just two notes played at the same time, although typically three or more is used. Now, most combinations will sound bad of course (at least for a certain value of bad, it's all subjective) so the question rather needs to be specified into which chord you mean.
The rules to form nice sounding chords are complicated, but it's the same rules as for guitars, but because of the difference between the instruments you would typically not do the notes in the same order, or at least you would have the notes repeated higher and lower.
So the C Major on a guitar would for example be "E C E G C E", while on the piano you would just take "C E G". These are both C Majors, although there are complicated naming systems to actually name the guitar chord something more complicated, as it has an extra low E.
Pianos are both easier and more difficult than guitars. There are no barre chords you can just move up and down. On the other hand you can move every chord up and down with just minor modifications in how you hold your hand, which are needed because the black keys aren't regular.
So there are less chords to learn, you don't have to learn G Major separately from C Major, but you will have to learn to transpose the chords, which comes with practice, I'm told. :-)
Answer: Open up the piano so you can see the strings.  They are laid out just like the frets of a guitar.
A friend of mine actually learned to play the piano this way as a little kid.  He studied the strings instead of the keyboard.  He didn't know anything about music theory -- not even the names "major" and "minor" -- but he noticed that a certain kind of chord (what we call "major") always looked a certain way: a hammer, skip three, next hammer, skip two, next hammer.  Another kind (what we call "minor") was upside-down:  hammer, skip two, hammer, skip 3, hammer.
Comment: Right, you need to think of each key on the keyboard in sequence, forgetting that they are black or white. Then it becomes simpler.
Comment: Hammer, skip two, hammer, skip 3, HAMMER TIME! (sorry, couldn't resist)
Answer: The first, third, and fifth. For example:
C major scale: C D E F G A B C
C major triad: C E G
Comment: But, is it the only way? What if I want my chord to have more than 3 sounds(wikipedia says, that chord have at least 3 notes)
Comment: @Agares: No, that's just the basic major/minor chords.
Comment: Well, then you have a different chord than a simple major or minor triad.
Comment: If you learn about [scale degrees](http://www.folkblues.com/theory/scale_degree_text.htm), the principles of making chords will start to click.
Comment: @rshallit: Yes, you would. Nothing in the question is limited to the major and minor traids.
Comment: I thought the question read that way. "Which notes from a scale form *the* chord on the keyboard" sounds like "Which notes from (for example) an A major scale form an A major chord on the keyboard?"
Comment: @Agares Are you talking about doubling notes? Any given major barre chord on guitar has three pitches, but six notes are sounding: one for each string. On piano, you can sound as many chord tones as you can reach with your hand, but some combinations sound better than others.
Answer: The most common chords used in western music are tertian chords. This means that they are built up in thirds from their underlying scale. Take the C Major scale:

    C D E F G A B

Now, starting with C, move up in thirds (skipping a note each time)

    C   E   G   B

This gives you the notes of a "C Major 7th" chord. Why is it called a 7th chord? Because it contains the 7th note of the scale:

    C D E F G A B
    1 2 3 4 5 6 7
                ^

Why is it called a "Major" chord? Because the 3rd (E) and the 7th (B) are both major intervals.
Pick a different mode (or scale) and you get a different chord. Triads are 3 note chords, built in the same way (in thirds from the root). A scale with a minor third (Eb is a minor third above C) will be a minor chord*. Here's some further reading on chord theory:
http://en.wikipedia.org/wiki/Chord_(music)#Secundal.2C_tertian.2C_and_quartal_chords
* It could be a diminished chord, but I am assuming diatonic harmony here rather than diminished.
Answer: Of course a Chord is any combination of notes played together so that's pretty broad.
Most piano players and composers approach piano chords from music where the chords are explicitely written out in sheet music notation. For people learning jazz, there are chord dictionaries and methods where most chords are listed in several notations.
What I will do is to suppose you want to play on piano songs you know on the guitar already.

The best way to translate your knowledge of chords from guitar to piano is to have two books, one is a guitar chord dictionnary giving conventional names of chords that you know. The other is a piano chord dictionary, sorted by chord name that you will try to play on your piano and learn and variate, etc.

Here is a way to see piano chords from a guitarist perspective

On the two instruments certain intervals in a chord do not give the same feeling or atmosphere or effect. That's often true with chords such as seconds and ninths. So you will end up using a related chord on the other instrument with a little twist added or removed. You could try to make up rules about that but that would soon be artificial.
The most immediate difference between chords on a guitar and chords on a piano is that on a guitar the chords are based on modifications of the basic relations between strings:

E A d g b e'

by putting fingers on the frets in a certain order, you add or substract semitones to the member of this arrangement.

These 6 strings cover 2 full octaves end to end ! To do the same thing with a piano you would need 2 hands. Compared to guitar chords, most piano chords for songs are cluttered so that they can fit the left hand (and sometimes a bit of the right hand). When a pianist wants to understand guitar chords he has the same perspective problem in reverse: he tries to group on one octave all the notes and usually he can't because he will run short off fingers and strings.
On a guitar, certain tonalities and chord types are really easy because you can take advantage of the basic fourths between the strings. Another trick is of course the capodastro to change the basic tuning and transpose. The disadvantage is that certain chords and tonalities are very difficult or require a barré to shift easily. Sometimes you have to exclude some strings.
On a piano, you rely much more on your muscle memory, practice and training to be able to shift any song a few semitones up or down. At first sight, the ground is a lot less uniform than guitar, with the inegal number of white keys and black keys inside the octave. On the other hand, shifting one octave is almost instantaneous and the range is impressive: you are your own bass and you are not limited by the number of frets, the size of your fingers and the hole of the guitar to explore in the high register.

Another thing you can do (it is fun but it takes time, it is a way to explore the keyboard) It is a bit cumbersome, it is a lot more practical to do that on paper if you know and can read sheet music notation. Or find a drawing of a piano keyboard and make diagrams of the chords that way: it is the equivalent of a tablature for the piano, but learning traditional music notation is a real asset:

First, recon the keys corresponding to guitar strings on the piano. Try to play them all at once with your two hands. Try to be comfortable with finding and placing them. Your left pinky must be on the low E. That's confortable to have E-A-d on the left and g-b-e' on the right
Second, think as with a tablature of the chord (but use only the position of the dots, not the number indicating the finger to use on a guitar), starting from low E and going to e' :

If the string is not used in the chord, lift the finger on the piano.
If the base fret of the chord you know is, say, the 4-th one, shift all your fingers 4 keys on the right (all keys, black and white count), one finger at a time
Move each finger further right according to the number of the fret where the string is dotted  (if the dot is on the fret #6, move it 2 further keys right)

Check that what you do is right by ear or compare with your guitar.
Third, try to regroup some of the keys in the left hand, substracting one octave if necessary and redundant notes one octave apart if necessary.
Shift the whole one or two octaves toward the bass to take advantage of the piano's range so that chords and melody are clearly separated.

You can do the same thing if you know sheetmusic notation : write the guitar chord in sheet music notation (you can start from a tablature applying the same principle than in the game with fingers on the piano or looking at your fingers if you know how to name a note you play on the guitar) then add or substract an octave to certain notes so that it fit in your left hand.
Answer: If I am reading your question correctly, I believe you are referring to the type of chords besides just the chords.
The question as to the basic chords are answered by others already so I will just extrapolate.
My advise is to forget about scales if you want the fast track to getting chords. It will just like touching your nose the other way around. We can get back to the scale theory behind it later. In my profession, I strife to make learn as simole as possible for my 5000+ student in my 25 years of teaching. I hope this helps you.
Just think in terms of semitones (or half-steps in American Terms) and sharps and flats. With only 9 formulas, you can create at least 144 chords. There is absolutely nothing complicated with forming chords if you do it this way. Peel open your eyes and ears.
You already learnt that Chords are formed by pressing the Root note, next note 4 half steps up and then 3 half steps up. ie. C E and G in C chord. You can get every other major chords by using this R - 4 - 3 formula.
Now, to get the minor chord, just flatten the middle note (i.e. E flatted to E flat). So Cm chord = C Eb G. I do not want to use R - 3 - 4 because by doing so, you end up memorizing 12 formulas at least. I just want you to remember 9 for the time being)
For the suspended chord, just sharpen the middle note (i.e. E sharpened to F) Sharpen means raise the note 1 half step. So for Csus or Cs4 or Csus4 = C F G. You will get this is "McGyver's theme"
For the Diminished Fifth chord, just flatten the rightmost (fifth) note (i.e. G flatted to G flat). So Cm chord = C E Gb. It is most commonly used in m7-5 like in Cm7-5 which is C Eb Gb Bb. It will most commonly be used as Bm7-5 when playing songs in A minor key. Bm7-5 = B D F A. When playing Dm E7 Am progression, replace the Dm with Bm7-5 and you will get the an even more beautiful color to your song.
For the Augmented 5th chord, just sharpen the fifth, rightmost note (i.e. G sharpened to G#) So for CAug or C+5 or CAug5 = C E G+. You will find this is "Greatest Love of All" and "James Bond Theme"
Now for the 6th, 7th and Major 7th. Basically it means:
For 6th ADD a note 2 half steps from the 5th note. C6 will result in C E G A. You will find these sweet sounding chords prevalent in Hawaiian songs.
For 7th ADD a note 3 half steps from the 5th note. C7 will result in C E G Bb. These chords with "unfinished" feelings alway appear in pairs with root chords. I.e. G7 with C chord in C key; C7 with F Chord in F key; etc.
For Major7th ADD a note 4 half steps from the 5th note. CMaj7; CMaj;CM7 will result in C E G B. You will find these big broad sounding chords prevalent in Movie Themes to give you the big countryside feelings. You will also find it in songs with minor keys long root chord progressions like Feelings which goes Am - AmM7-Am7-Am6-Dm...
For Diminished Chords, this is a special exception. All the 4 notes are 3 half steps apart. ie. Cdim = C Eb Gb A. You will find these weird sounding chords prevalent in Hawaiian and Jazz songs as a passing chord ie. C C#dim Dm G7.... or C Ebdim Dm G7..... One of Bach's songs also uses this (I forgot the name) which is commonly used in Dracula Vampire movies. Try it out and see.
For all the above, you will see that all these adds to the color of sound and like an artist, these are your shades that will help you paint your masterpieces. How you use them will determine the quality and output of your music.
With the above, you can create 144 chords at least. Test it out as below
Major (try out all the 12 chords)
Minor (try out all the 12 chords)
7th (try out all the 12 chords)
m7th (try out all the 12 chords)
m7-5 (try out all the 12 chords)
dim (try out all the 12 chords)
6th (try out all the 12 chords)
7th (try out all the 12 chords)
Maj7  (try out all the 12 chords)
Dim (try out all the 12 chords)
Aug5 (try out all the 12 chords)
Sus4  (try out all the 12 chords)
With so much 144 colors, you should have enough to paint your masterpieces. Only after mastering these, we worry about the 9ths, 11ths, 13ths later.
Enjoy!!!

How to formulate a chord on the piano?