Difference between Entity framework self tracking entities vs Unit of work

Question: What is the difference between using Entity framework self tracking entities and implementing Unit of work architecture? As i understand both are keep tracking of the objects, one db call for commit changes. So i cant figure out the difference of those. can some one point me about what should used in which case?
I'm using entity framework 5 with WCF service application.
Answer: The purpose of self tracking entities is that you don't need to keep the DbContext/ObjectContext alive to track changes to the entity object(s).  The main feature of this is you can send an entity to another process (or host entirely, such as another WCF service on another host) that makes changes to the entity object, then returns that entity object to the calling process with change tracking still intact.
UoW coordinates changes made between multiple entity objects (greatly simplified explanation).
Answer: According to the MSDN, Self Tracking Entities are no longer Recommended

STEs No Longer Recommended
We no longer recommend using the STE template, it continues to be
  available to support existing applications. Visit the N-Tier page for
  other options we recommend for N-Tier scenarios.

http://msdn.microsoft.com/en-us/data/jj613924.aspx


"boundary" vs "interface"?

Question: I am working with biofilm and there are many documents talking about boudary conditions while others talks about interface or both of boundary and interface. So, boundary and interface are the same (in numerical analysis) or not? why and examples?
Answer: I'm not particularly familiar with biofilm literature.  But in most computational literature, the border of the entire domain of a problem are usually referred to as the boundary.  Outside of a boundary, there are no nodes, elements, or anything else under consideration.
The entire domain may also be subdivided into smaller regions.  Some of these regions share edges on the boundary of the domain.  However, some of these regions share borders between each other that are not boundaries of the domain.  Usually these regions have different material properties or different relevant physics and may also have different meshes.  The borders between any two regions in a domain are usually referred to as interfaces.
Comment: In multiphase flow, the boundary between phases is usually referred to as an "interface" to distinguish it from the actual physical boundaries surrounding the system.
Comment: @PoBo: That is true.  Sometimes, the interface condition is also referred to as a boundary condition.  But it is a boundary condition of the subregion, as opposed to the boundary condition of the domain.
Comment: In some literatures, I found that the authors use the term "interfaces" to indicate the geometry position/properties between 2 fluids/phases/something else... However, when they need to use a boundary condition on these interfaces, they call them boundary in term "boundary condition" (not "interface condition" ^^). So, generally, 2 terms are only different about their meaning, is that right?

"boundary" vs "interface"?


What's the connection with Back to the Future movie?

Question: In the movie 'A Million Ways to Die in the West' Dr. Emmett "Doc" Brown from 'Back to the Future' appears in one of the scene with his time machine.
What is the connection with that old movie?
Comment: Huh? What connection? A joke maybe?
Answer: Just a cameo which only raised a bit of inconsistency.

This film takes place in 1882 and is inconsistent with the Back To The
  Future timeline, which places Doc in the west during 1885 and
  later.(Source: Wikipedia)
Answer: Back to the future was(is) a very popular movie, there is no real importance or connection except to give you a few kicks


Are electron shells probability distributions?

Question: I know that orbitals are probability distributions. Are electron shells probability distributions too?
Answer: Short Answer:
No.
Long Answer:
First, strictly speaking, the orbitals themselves in the quantum mechanical sense are not probability distributions.  They are eigenfunctions $\Psi_i$ of the Hamiltonian as defined by the time-independent Schroedinger equation $H\Psi_i=E_i\Psi_i$.
The probability distribution function $p(\vec r)$ for electrons is generated by summing the products of the eigenfunctions and their complex conjugates for all occupied eigenfunctions at a given 3-D point $\vec r$ and dividing by the total number $N$ of electrons in the system:
$$
p(\vec r) = \frac{1}{N}\sum_{occ}{\Psi_i^*(\vec r)\Psi_i(\vec r)}
$$
Note that $p(\vec r)$ is simply $\frac{1}{N}$ times the electron density function $\rho(\vec r) = \sum_{occ}{\Psi_i^*(\vec r)\Psi_i(\vec r)}$.
To be fair, prior to a detailed introduction to the quantum mechanical description of electronic structure, the distinction between the electronic wavefunction $\Psi(\vec r)$ and the electron density function $\rho(\vec r)$ is typically not clearly established in chemistry instruction, so your having conflated them is quite understandable.
Second, again strictly speaking, electron shells are not probability functions.  While Pushkar Soni is correct that the principal quantum number for a given electron approximately indicates the 'electron shell' to which it is assigned, the indistinguishability of electrons (among other factors) in general prohibits unambiguous translation of quantum number information into the real-space function $\rho(\vec r)$.  The best we can do is to interpret electron shells as corresponding to certain features of the structure of $\rho(\vec r)$. Offhand, I know of at least two ways of qualitatively identifying 'electron shells' from $\rho(\vec r)$.
First, as Geoff Hutchinson notes, the radial distribution function $r^2\rho(r)$ shows local maxima that can be interpreted as electron shells.  Note that  $\rho(r)$ in the r.d.f here is a function only of $r$, the distance from an isolated atom/nucleus; the angular dependencies (on $\theta$ and $\varphi$) have been integrated out.
Second, Bader's QTAIM describes how the Laplacian of the electron density, $\nabla^2\rho(\vec r)$, exhibits minima in 3-D space at positions corresponding to the notion of electron shells.
Comment: Good answer. But could you please correct the second sentece in the Long Answer: $\Psi_{i}$ is an eigenfunction of *the Hamiltonian*. It is also a solution of the time-independent Schrödinger equation, but its not an eigenfunction Schrödinger equation since it is just a nonsense. ;)
Comment: @Wildcat Very good point.  Looks like someone else beat me to the edit, though. :-)
Answer: In order to understand you should know the differences between shell, sub-shell and orbital.

Shell represents the main energy level occupied by the electron. It is given by the principal quantum number (n). For example , if n=1, the electron is present in the first main shell, called K-shell. if n=2, the electron is present in the second main shell, called L-shell and so on..
Sub-shell represents the sub-energy level occupied by the electron (as main energy level is considered to consist of a number of energy sub-levels ). it is given by azimuthal quantum number. subshell corresponding to l=0,1,2,3 are represented by s,p,d,and respectively.
Orbitals you know it well.
You may understand it like this-

when n=1 we have only s subshell
when n=2 we have s and p subshell
for n=2 we have s,p and d subshell and so on.

Now, s, p and d and f have certain regions, which we call orbitals. which are probability regions as you know. Here is the link for you,

http://en.wikipedia.org/wiki/Atomic_orbital
Must watch the video associated with it named [atomic orbitals and periodic construction]

Last but not the least- we certainly not have electron shells probability distribution. its only orbitals. shells are created by scientists to study the atom systematically but they have physical significance too (i mean here the subshells and orbitals lie).
it seems you are not clear with - shell, sub-shell and orbitals.
you should first check out what they actually means in order to understand.
Comment: I'd suggest adding some discussion of the [radial distribution function](http://chemwiki.ucdavis.edu/Physical_Chemistry/Quantum_Mechanics/Quantum_States_of_Atoms_and_Molecules/8._The_Hydrogen_Atom/The_Wavefunctions to discuss how the  orbital probability lines up with the older concept of a "shell."
Answer:
Electron shell is well described into the old quantum mechanics developed by Bohr, see Atom Bohr model
Probability distribution is well described into the modern quantum chemistry, see Quantum mechanics, general description

Therefore, both definitions are not comparable among them because each one belongs to different theory conceptions.
Comment: -1 Uh no. If you take the [radial distribution function](http://chemwiki.ucdavis.edu/Physical_Chemistry/Quantum_Mechanics/Quantum_States_of_Atoms_and_Molecules/8._The_Hydrogen_Atom/The_Wavefunctions) $r^2 R^2(r)$, you find peaks for each radial wavefunction that correspond somewhat reasonably to the "shell" concept.
Comment: Even more directly, Bader's QTAIM, which is built off of the electron density $\rho$ -- which is *precisely* the **probability distribution** of electrons in a system -- recovers the 'electron shell' phenomenon via the [negative Laplacian of the electron density](http://www.chemistry.mcmaster.ca/aim/aim_5.html), $-\nabla^2\rho$.


Prevent a single host from consuming entire bandwidth?

Question: We have a linux router providing internet connectivity to several PCs. It's currently using shorewall to help make the iptables setup easier. Is there a way I can set it such that any individual host is prevented from using the entire line? I'm thinking setting the limit at 80%: So any one PC can't use more than 80% of bandwidth, thus if someone is downloading/uploading large files, the connection isn't completely overwhelmed.
Answer: Take a look at the Linux advanced routing and traffic shaping HOWTO, which has a section bandwidth management.  It looks like the HOWTO is unmaintained, but it's still a good place to start.  The Traffic control HOWTO also has good information.
Answer: Shorewall allows limitatin per source aswell as per destination IP. For details see the official homepage http://www.shorewall.net/ConnectionRate.html


How much alcohol remains in strawberries soaked in alcohol?

Question: I know that the alcohol content of food that is prepared with alcohol is a tricky study, as evidenced by the fact that food left out overnight stored overnight loses, by one study, 30% of its alcohol content.  Several weeks ago I had some chocolate dipped strawberries that had been soaked in liquor before being dipped in chocolate.  I thought I could taste alcohol, but my dining companion didn't taste it.  So it wasn't a strong flavor.  Is there any information out there on how much alcohol may have been transferred to the strawberries?
Comment: Interesting question. From experience, if they're soaked overnight in golden grain, they are *very* alcoholic. But I'd guess this is a function of time and % alcohol.
Comment: @yossarian - in this case they definitely weren't very alcoholic, so I'm guessing not overnight.
Answer: I don't think this has a single answer: The amount of alcohol would depend on the alcohol content of  the soaking liquor or liqueur, soaking time, temperature of chocolate, and how thick the strawberry was.
I suspect uncut strawberries would take at least several days to fully absorb alcohol and reach equilibrium, but the surface should take up alcohol fairly quickly. If they are cut up, exposing the more porous interior, I imagine an overnight soak would be sufficient to reach maximum alcohol content.  The enormous, bloated mutant strawberries you sometimes see at stores could take considerably longer than others to absorb their maximum alcohol.
Alcohol is much more volatile than water, so the immersion in warm, melted chocolate would remove some alcohol, but once the chocolate cools, it should trap any remaining content.
The flavor of alcohol is easily masked by other flavors at under 20% content; this could explain why your friend didn't taste it, but you did.  It's quite possible the strawberries packed a sobriety-busting punch, but it was disguised by the chocolate and fruit tastes.
Comment: Thanks for the comprehensive answer.  In this case they were definitely whole and soaked in tequila, and they were the typical large grocery store type rather than small, good fresh-off-the-farm berries.  I'm curious, though, by your statement in bold - you are saying that the alcohol was under 20% of the entire berry + chocolate and so the flavor may have been masked?
Comment: @justkt: I think 15-20% alcohol content *sounds* right, but bear in mind this is an educated guess at best.  I'm basing this on was going on % alcohol by volume in beverages, thinking of port, sherry, liqueurs, and mixed drinks where the alcohol content is 15-20%, but the alcohol flavor is weak or imperceptible.  At 25%+, the alcohol flavor is quite clear.
Comment: That also depends on the palate of the person eating it and the quality of the alcoholic beverage.


What type of problems can mapreduce solve?

Question: Is there a theoretical analysis available which describes what kind of problems mapreduce can solve?
Answer: In Map-Reduce for Machine Learning on Multicore Chu et al describe "algorithms that fit the Statistical Query model can be written in a certain "summation form," which allows them to be easily parallelized on multicore computers." They specifically implement 10 algorithms including e.g. weighted linear regression, k-Means, Naive Bayes, and SVM, using a map-reduce framework.
The Apache Mahout project has released a recent Hadoop (Java) implementation of some methods based on the ideas from this paper.
Answer: For problems requiring processing and generating large data sets. Say running an interest generation query over all accounts a bank hold. Say processing audit data for all transactions that happened in the past year in a bank. The best use case is from Google - generating search index for google search engine.
Answer: Many problems that are "Embarrassingly Parallel" (great phrase!) can use MapReduce. http://en.wikipedia.org/wiki/Embarrassingly_parallel
From this article....
http://www.businessweek.com/magazine/content/07_52/b4064048925836.htm
...
Doug Cutting, founder of Hadoop (an open source implementation of MapReduce) says...
"Facebook uses Hadoop to analyze user behavior and the effectiveness of ads on the site"
and...  "the tech team at The New York Times rented computing power on Amazon's cloud and used Hadoop to convert 11 million archived articles, dating back to 1851, to digital and searchable documents. They turned around in a single day a job that otherwise would have taken months."
Answer: Anything that involves doing operations on a large set of data, where the problem can be broken down into smaller independent sub-problems who's results can then be aggregated to produce the answer to the larger problem.
A trivial example would be calculating the sum of a huge set of numbers.  You split the set into smaller sets, calculate the sums of those smaller sets in parallel (which can involve splitting those into yet even smaller sets), then sum those results to reach the final answer.
Answer: The answer lies is really in the name of the algorithm.  MapReduce is not a general purpose parallel programming work or batch execution framework as some of the answers suggest.  Map Reduce is really useful when large data sets that need to be processed (Mapping phase) and derive certain attributes from there, and then need to be summarized on on those derived attributes (Reduction Phase).
Answer: You can also watch the videos @ Google, I'm watching them myself and I find them very educational.
Answer: Sort of a hello world introduction to MapReduce
http://blog.diskodev.com/parallel-processing-using-the-map-reduce-prog
Answer: This question was asked before its time. Since 2009 there has actually been a theoretical analysis of MapReduce computations. This 2010 paper of Howard Karloff et al. formalizes MapReduce as a complexity class in the same way that theoreticians study P and NP. They prove some relationships between MapReduce and a class called NC (which can be thought of either as shared-memory parallel machines or a certain class of restricted circuits). But the main piece of work are their formal definitions.


Periodic differentiable function

Question: If $f(x)$ is a differentiable function on the real line and periodic with period $T$ does it have at least two stationary points in $(0,T]$?
Answer: Yes. If $f$ is constant, then every point is stationary. Otherwise the image of $[0,T]$ is a closed interval (since $f$ is in particular continuous), and therefore $f$ has at least one global maximum and at least one global minimum. We know that maxima and minima of a differentiable function are stationary points. The maximum and minimum are different points because $f$ is not constant. If one of them are $0$ (and therefore outside $(0,T]$), just consider $T$ instead -- that will also be a global extremum because $f$ is periodic.
Answer: Yes. Consider $g(x)=f(x)-f(x+T/2)$. Since $f$ is differentiable, it is continuous, and hence $g$ is continuous. Now $g(x+T/2)=f(x+T/2)-f(x+T)=f(x+T/2)-f(x)=-g(x)$. Thus there is at least one zero of $g$ by the intermediate value theorem. But $g(x)=0$ implies $f(x)=f(x+T/2)=f(x+T)$, and then by the mean value theorem there are two points $\xi_1,\xi_2$ with $x\lt\xi_1\lt x+T/2$ and $x+T/2\lt\xi_2\lt x+T$ with $f'(\xi_1)=f'(\xi_2)=0$.

Periodic differentiable function


Syncronisation tool for dropbox replacement

Question: I have several Linux-PCs I want to be synced. I have a server exporting a filesystem via nfs, ftp or sshfs. I mount them to ~/syncenc. With encfs they are mounted to ~/sync. Working directly in this directory is fine as long as the computer is online. But some are Laptops that should keep their home directory local, but sync when online. Both the local as the remote data can change, of course. Also I a file is moved one side it has be move on the other as well, same for dirs. The software should be FOSS.
I'm looking for a software that can do that.
So far i found: https://secure.wikimedia.org/wikipedia/en/wiki/Comparison_of_file_synchronization_software but the table is rather incomplete.

rsync - does not work bidirectional does it?
unisono - cannot exclude files, there for useless (you cant sync a/b with a recursivly, obviously) also it cannot detect rename/move operations.
Dir Sync Pro - Cannot detect rename/move operations, not suitable.
iFolder - Wikipedia says something about P2P. ?? Also it seems to depend on a special Serversoftware.
Answer: Since you seem to be on Linux, you might look at http://www.sparkleshare.org ... seems to be maturing well and has good Linux / Mac / Android support. Windows and iOS are lagging for now, but if you don't need them it might do the trick for you.


Impala no heat at Idle

Question: I have 2006 impala that randomly will blow cold air at idle. Sometimes if I stop at redlight the heater will blow cold air. If I get the engine above idle by reving the engine to about 1K rpm it starts to blow warm again. The temp gauge remains at the normal spot on the gauge. The radiator and expansion tank are at the correct levels.
Comment: I had this problem with my 2007 Impala. The dealership service dept. told me I needed a new head gasket ($1800). I took it to a private mechanic who fixed it for $30 by bleeding the cooling system and filling the recovery bottle. I think that if I check the coolant levels more frequently and keep that overflow jug full, (like the guy above said) I can even save the $30 charge next time.
Comment: Do not think its the water pump..had mine replaced also the thermostat...problem still there. Did not notice till now, with the cold weather. Will try the top up of coolant if needed.
Answer: It turns out the problem is pretty common with 3.5L Impalas. For some reason these engines lose coolant. Some blame is placed on head gaskets, some blame Dex-Cool. What ever the cause, refilling via the overflow jug can leave an air pocket in the cooling system. The cure is to fill via the pressure cap right to the top. Recheck the level after several heat/cool cycles. Then never let the overflow jug get empty.
Comment: thank you for the information no heat at idle on 2007 chevy impala with 3.5 engine
i flush system and bleed air from system . heat ok now thank again..
Answer: Possible stuck thermostat.  The "normal" indication on factory temperature gauges cover a huge range.  My Eclipse has a factory gauge and an aftermarket gauge.  The factory gauge settles in at "normal" for a 160-200 degree range (normal temp is 185).  At 160 the car barely makes any heat in the cabin, at 185 it's got decent heat, and at 200 it can light your feet on fire.  :-)
Could also be a failing water pump, but that mode of failure is not one I've heard of very often.
Comment: The water pump crossed my mind also. I have ruled out the thermostat (in my head anyway) because the gauge never waivers once the engine is warmed up and the heat returns almost instantly once the rpms increase.
Answer: No heat or hot air during idle is the result of air gap in the heater core. Open hood, driver side fire wall you will the see the heater core rubber hoses. Remove the two hose clamps. Disconnect both hoses from the metal extension tubes (not the hose clamps located at fire wall, these are to difficult to reach). Use a funnel and fill both heater core hoses with 50/50 Dex-Cool (it does not take much, maybe 8 to 12 oz). Reconnect both hoses and reconnect both hose clamps. Fill overflow reservoir to proper level. Fill radiator to proper level. Now you will have heat at idle.
Answer: I have this same problem, and I can tell you exactly what it is. GM vehicles use the coolant DEX-COOL, which is the purple color coolant. In the impala's if the coolant hasn't been changed for a while the dex-cool will leave deposits, or get thick is easier way to think about it. When it runs through your heater core, that silt like deposit will clog the heater core.   If it acts like mine did, when the car is idling it will not produce any heat but when you drive there is no problem with the heat. This is because the higher RPM's will allow for the fluid to move through the heater core and produce heat. To fix this you need to flush the heater core backwards and forwards to unclog the heater core. There are two hoses on the right side of the engine, which connect from the top right under the plastic cover to the fire wall. The hose on the left is the inlet and the hose on the right is the OUTLET. Disconnect the hoses from the engine and use a garden hose with a spray tip on it. Put the tip in the right hose and spray water through it. You will see a thick dark purple fluid come out of the other hose. When you see the water come through clear, then switch to the left hose and repeat. do this several times, and make sure your letting the water run through it for at least 30sec to 1min. reconnect the hoses, and replace the lost coolant then bleed the air out of the system.    ON THESE CARS IT IS VERY EASY TO LEAVE AIR IN THE SYSTEM BECAUSE WHERE THE HOSES ATTACH TO THE ENGIN IS THE HIGHEST POINT OF THE COOLING SYSTEM AND NOT AT THE CAP. You may have to do this several times, and if it continues, then there has probably been too much damage to the heater core and will need to be replaced.
ALSO, if the coolant is bad enough the whole engine will need to be flushed, and if you don't have the knowhow to do that, I would recommend to take it to a mechanic to have this completed as all components of the cooling system including the reservoir need to be cleaned, flushed and refilled.
Answer: To anyone having poor heat or over heat problems with chevy motors 3.5l v6 and 3.4l and any other close to these. Go to Route 66 hot rod high friggin heat problems I did this on my chevy uplander.with a 3.5l v6 cost me under $20 and about half hour of work not 2or 3k at dealer go read this try it I have good heat and was able to bleed all air to get rid of overheat problem. Give it a try
Comment: Welcome to Mechanics.SE! Please post the relevant portions of the article you are referencing. This is to protect this answer for future users with the same problem who may not be able to find the articles as links can change, move, or go away completely.
Answer: change thermostat that will fix problem. our 2007 impala had no heat @ idle before replacing
Comment: This is a wild guess.

Impala no heat at Idle


Better to run one relay or two, given equal total bandwidth?

Question: For example, would it be more helpful to the network to setup one relay that had 4TB  of bandwidth, or two relays that each had 2TB? Does the answer change depending on the amount of bandwidth each relay would have?
Answer: One relay with 4TB, with the relay using up the 4TB quota as fast as possible.
Faster relays are more attractive to traffic, so the network is better off if you move that 4TB in a week then hibernate for 3 weeks than if you throttled down the bandwidth to keep the relay active all month.
Plus, a single relay is easier to administer.
Comment: That sort of answers [a different (but related) question](http://tor.stackexchange.com/q/6115/6868), though. What if both relays could have 25 TB, so that they could both be fast the entire month? Would it still be better to run one at 50 TB, or would two balance the traffic better?
Answer: One relay is probably better, both for performance and anonymity (assuming the relays would run on the same machine).
Performance: There's no obvious performance gain by running two relays with half the bandwidth, since you should add the other relay to the MyFamily and thus only one relay would be used per circuit. Additionally, a second relay would add overhead and maintenance work.
Anonymity: By running more circuits over one relay, the individual circuits get a better anonymity as long as the relay isn't compromised (the same reason why being a relay improves the anonymity for your own browsing).
If you plan to run two relays in geographically seperate locations, that could be worth it, though.
Comment: Afaik, the main advantages of running two geographically seperate relays would be to (1) spread the bandwidth availability better, so people around the globe get similar performance and (2) if your hosting company decides to hand access to the relay over to some 3rd party (gov. agency or the like) only half the bandwidth is compromised.
By running both relays at the same place, these advantages are negated, so there's no reason to split, as long as one VPS is capable of handling the whole traffic.
Comment: I wasn't planning on them being geographically separate, but they would be on different VPSs with the same host. Does that make any difference?


No Olam Habah for these?

Question: At the end of Gemorah (Tractate) Sanhedrin, there is discussion of people who are not Zocheh to get into Olam Haba (Gan Eden). Is there a comprehensive list somewhere of people mentioned throughout Talmud and commentaries who have been cursed in this way?
Comment: mc, Welcome to mi.yodeya, and thanks very much for your interesting question! We'd love to have you as a fully-registered member, which you can accomplish here: http://mi.yodeya.com/users/login
Answer: Rambam (Laws of Teshuvah 3:6ff) gives the following list. (All of them are referring to people who know that what they're doing is wrong. The average nonobservant Jew nowadays is in an entirely different category, "tinok shenishba.")

Minim: people who deny Hashem's existence, or who hold heretical beliefs about Him (basically, who don't accept one or more of the concepts covered in the first five of the Rambam's Thirteen Principles of Faith)
Apikorsim: people who deny the connections (via prophecy and Divine knowledge) between Hashem and humanity (basically, the concepts covered in Principles 6, 7, and 10)
Deniers of the Torah: people who deny parts of the Torah or its mitzvos (basically, Principles 8 and 9)
Deniers of the Resurrection or of the coming of Moshiach (basically, Principles 12 and 13). (I wonder, by the way, where Principle 11, that Hashem rewards good and punishes evil, would fit in this taxonomy.)
Mumarim: habitual transgressors of a particular mitzvah (when done to provoke Hashem rather than out of passion), or apostates who abandon Judaism entirely
People who cause others to sin, whether by force or by persuasion
People who separate themselves from the community (remaining aloof when they are in trouble)
People who sin openly and brazenly, "like Yehoyakim"
Informers (who hand over Jews, or their possessions, to non-Jewish authorities who will not give them due process)
People who lord it over the community and make themselves feared, "not for the sake of heaven" but for selfish motives
Murderers
People who speak lashon hara
People who extend their foreskin (to conceal their circumcision)

Then he lists several other things of which the Sages say that one who habitually does these also loses his share in Olam Haba:

Making up a derogatory nickname for someone
Using such a derogatory nickname
Embarrassing a person in public
Getting honor for oneself at the expense of someone else's embarrassment
Treating Torah scholars lightly
Treating one's teachers lightly
Treating Chol Hamoed lightly
Desecrating sacred objects

He concludes, though, that these exclusions are not absolute: one can always do teshuvah as long as he is alive.
Furthermore, there is an extensive discussion in a letter by the Lubavitcher Rebbe zt"l, in which he argues (based on many sources) that even people in these categories who have not done teshuvah still have a way out, just that it is a lot more difficult. But ultimately, "lo yidach mimenu nidach" - no Jew is ever truly lost.
Answer: In the Koren Siddur with Rabbi Sacks commentary, it states at the addition at the end of Perek Aleph of Pirkei Avot "Rabbi Chananya Ben Akashia omer" ... that the Rambam says "It is a fundamental principle of the Jewish faith that if a person fulfills even one of the 613 mitzvot fully and properly, without ulterior motive but simply for its own sake and out of love, he merits a share in the World to Come."
now i'm not sure if i answered your question, or created a new one... such as if someone committs one of the above sins but also does mitzvot then what happens to his share in Olam Haba. I have no idea!

No Olam Habah for these?


Why do some airfields not have manned ATC towers?

Question: I was wondering why some airfields, for example Tatenhill Airfield (EGBM), don't have anybody in their ATC towers?
Comment: You might get more understanding by editing your question to explain why you think there would be someone in the tower?
Comment: as far as I can see, Tatenhill Airfield doesn't even have a building that resembles a tower. https://goo.gl/maps/mMHja
Answer: One of the biggest reasons to not man a tower is (not unsurprisingly) costs.
Many remote airports only have a few movements per day, and a permanent staff in the tower makes it even more difficult keep the operation economically viable.
For this reason, remotely staffed towers are being developed now, and for instance Örnsköldsvik airport (ESNO) in Sweden has just received approval from the Swedish Transport Agency to operate with a remote tower:

The system's sensors are installed at Ornskoldsvik Airport but traffic
  is remotely controlled from Sundsvall, Sweden.
Answer: In the case of Tatenhill, the field was previously used by the RAF. Evidently the original control tower was replaced by a previous operator, which explains why there is still a control tower there. But currently it is a private field, where the amount of traffic doesn't warrant operating the control tower.
Information from NATS lists a Tatenhill Radio frequency that provides A/G (air to ground) service during certain hours. YouTube videos suggest no tower services.
There are many airports in similar situations, that do not operate a control tower (whether or not they have one), or only operate at certain times, when there is not enough traffic for a control tower to be needed. VFR rules give pilots the responsibility to "see and avoid" each other in these areas, and announce their intentions on the appropriate frequencies.
Also, see the related questions to the right, especially: What's the process for an uncontrolled airfield to become controlled/towered?
Comment: It shows in [Blue](http://skyvector.com/?ll=52.814149241638525,-1.7647231459668087&chart=301&zoom=1)  on the VFR maps, which is supposed to indicate a manned airport.   Magenta icons are supposed to indicate untowered airports.  Is the map wrong?
Comment: I understand, thats a great help, thankyou
and thankyou abelenky
Comment: @abelenky It appears that there is a frequency but not providing tower service, I've edited with more info.


Why is ATP the preferred choice for energy carriers?

Question: Why is ATP the most prevalent form of chemical energy storage and utilization in most cells?
Comment: It might be worth while having a look at [this](http://academic.evergreen.edu/curricular/m2o2006/seminar/westheimer.pdf) great article by F. H. Westheimer _Why Nature Choose Phosphates_, published in _Science_ in 1987
Comment: the energetics of the phosphate hydrolysis is more or less similar for most NTPs. Compared to GTP, ATP requires one less enzyme for its synthesis. Pyrimidine triphosphates are also high energy molecules but have specialized roles.
Comment: Thats an interesting paper, thanks for recommending it. IF someone wants with no access through a university wants to read this paper, see here: http://academic.evergreen.edu/curricular/m2o2006/seminar/westheimer.pdf
Comment: I wonder if oxygen has anything to do with it? See MH Zhou's theory [here](https://www.researchgate.net/post/Why_did_evolution_favor_ATP_and_not_GTP_TTP_or_CTP): "Please look at and compare the chemical structures of adenine and ATP vs guanine...the oxygen level on [early] Earth was below 0.1% as compared to 20% nowaday. Therefore, adenine was far earlier than guanine appearred on Earth by billions of years on early Earth. It is because, adenine has no oxygen atom in its structure, whereas guanine has 1 oxygen atom in its structure...."
Comment: Although ATP is certainly the most common triphosphate *synthesized*, GTP is quite commonly used to drive reactions: GTP provides 2/3 of the energy for protein synthesis, which is a major energy expenditure for most cells. So I would argue the preference for ATP over other NTPs is not as strong as it might seem at first glance.
Comment: The academic.evergreen.edu link is broken, but the Westheimer paper still lives at http://archives.evergreen.edu/webpages/curricular/2006-2007/m2o2006/seminar/westheimer.pdf
Answer: I really like this question as it is such a fundamental underpinning of all life on the planet, yet there is such sparsity of actual information on its origins and why selection rewarded ATP use over anything else. Here I am talking generally since no specific studies exist in ATP vs other candidates.
A lot of the below information is taken from a relatively old article mentioned in the comments by TomD that discusses: "Why nature chose phosphates." by Westheimer, 1987. The article is very influential and has been cited over a thousand times since publication. Another article that came out in the same year that this question was asked "Why nature really chose phosphate." by Kamerlin et al., 2013
Some of the below arguments are more convincing than others, but all of them should be thought of when attempting to answer this question.
Summary.

ATP has ancestral dominance. Most other reasons derive from this.

Alternative phosphate groups or other molecules may not provide enough energy.

Alternatives may be toxic.

Other molecules, particularly phosphates, are used for inefficient high energy bursts.

Pi is a "good" leaving group.

Phosphates are fundamentally able to be regulated through electrostatic manipulation.

ATP synthase can efficiently reattach the Pi to ADP.

Lots of Pi available to organisms because of it's ancestral dominance ("if it ain't broken, why fix it?" is at play).

ATP can provide more energy if needed; it's scalable to the situation. (ADP becomes AMP + Pi)

Easily usable by a variety of proteins.

Why ATP?
ATP is an efficient and relatively easily biosynthesised molecule that can fulfil multiple biochemical roles. Cells do have alternative energy carriers, some with more specialised roles, however, ATP is ubiquitous throughout our cells and inter-cellular spaces. There aren't a wealth of resources explaining why ATP is any better than other compounds, however, there is plenty of reasons why the phosphates are required.
Why not the alternatives?
Citric acids and their derivatives are a good candidate, with deductible groups and high bioavailability but they simply don't give enough energy to stabilise genetic material.
Another tribasic candidate is arsenic acid. This is a fundamentally toxic compound, though, which isn't particularly great for living things.
There are other phosphates too, and they are used in many organisms. In biology, they have specific functions, and not used as the general energy carrier. For example, creatine triphosphate provides a high energy phospho- anhydride bond, that is often used to quickly and anaerobically regenerate ATP, useful during high rate muscle activity for contraction.
GTP is structurally very similar to ATP. GTPases are used more to initiate cellular signalling pathways. It is sometimes used as an energy source. This is a good example of an alternative energy carrier.
Over the years, many proteins have specialised with a specific shape, and this chance is the primary reason behind ATP over GTP. In other words, the choice of ATP over GTP is primarily down to cellular preference of molecular shape. One of them had to emerge as being more widely used, and it was ATP that 'won'.
Efficiency and simplicity.
The reaction was once thought to be a relatively simple nucleophilic displacement. From the 2013 paper:

...this simplicity is deceptive, as, even in aqueous solution, the low-lying d-orbitals on the phosphorus atom allow for eight distinct mechanistic possibilities, before even introducing the complexities of the enzyme catalysed reactions.

Traditionally one will be taught that ATP is such a chemically efficient way of storing and transporting energy. This is due to the ATP->ADP & Pi hydrolysis reaction. The phosphate groups in ATP are full of negative charges and these are repelling one another. This means that the third phosphate is a great leaving group and breaking the phospho- anhydride bond is a favourable reaction. ...
...But the story is a lot more complicated than that. The above explanation isn't really satisfying because those same negative charge forces are repulsive of the nucleophile that is attempting to complete ATP->ADP & Pi. A more comprehensive explanation would go along the lines of 'although a negative charge repulsion exists between the nucleophile of the protein and the phosphate, that high energy barrier can be overcome by electrostatic manipulation'. This allows an "on-off switch" for the hydrolytic reaction by tweaking the electrostatic environment. This is another great regulatory tool that the phosphates provide. This regulatory feature is important for signal and metabolic/catabolic cascades.
When it comes to 'rebinding' the Pi to ADP, it is fairly easy since ADP seldom covalently binds to anything, which would require a lot of energy to recover the ADP. This also helps the bioavailability of free ADP to ATP synthase, an incredibly efficient enzyme, that uses membrane proton gradient to drive the production of ATP. Talking about actual numbers is difficult here as there is only data available from Rat hepatocytes. Who is to say mammals are representative of all organisms? The estimates of energy of hydrolysis range from ΔG˚ = -48 kJ mol-1 to -30.5 kJ mol-1. Note that these are considerable, but not exceptional values, so it's easy for many different proteins, that need not be very specialized, to break the bond all over the body. I couldn't even find the numbers for the synthase reaction per ATP, but a single ATP synthase can produce up to 600 ATP per minute.
The final point of this efficiency is that the elements in ATP are very abundant and established in the biosphere making it readily available. This makes the phosphates a convenient biomolecule.
Multi-functionality.
ATP is ubiquitous in the body, but in some cases more energy is needed than there are ATP available. In these times of need, ATP can be used to produce more energy, breaking another phosphoanhydride bond to become AMP+2Pi. AMP however is typically a signalling molecule.
With the low activation energy required to break the phosphoanhydride bond, a multitude of enzymes, far too many to list here, can make use of ATP in order to gain energy towards the activation energy for many other functions.
Comment: I think this answer mixes up the advantage of phosphates as energy carriers with the predominance of ATP. The case for phosphates is nicely made by Westheimer's 1987 paper; but there is little reason to suppose that ATP is chemically special compared to, say, GTP --- the prevalence of ATP over other triphosphates is likely just an evolutionary coincidence. And the argument that ATP is "a great biomolecue" because it is "abundant in the biosphere" is obviously circular.
Comment: I really like how the top two answers start with their opposing views on whether or whether they do not like the question.
Comment: It seems like you just accidentally explained why AMP is a signalling molecule. AMP signals low energy.
Comment: @Roland Great points, but allow me to elaborate that when I say that abundance makes it a "good" biomolecule I am not making a circular argument. Once any compound establishes itself in the primordial soup and is propagated, it is more convenient/probable that molecule is used than an alternative. This is a valuable point, and is less circular than it would first appear.
Answer: I don't like this sort of question because I don't think it can really be answered and I'm very suspicious of arguments that seem to claim ATP is the only or even the best solution to the problem. Nature generally demonstrates that there is more than one way to kill a cat, but if one way works adequately you don't always need to look for another.
This is not necessarily the case, of course, if we consider an example from the postulated RNA World — which I shall presently — catalysis using RNA was supplanted in most cases by catalysis using proteins. So sometimes a better solution provides an evolutionary advantage, and sometimes if things work well enough they stick as the limiting factor is elsewhere.
So I tend to the view that ATP worked, so it stuck. It was probably chance it wasn't GTP or CTP or UTP, as these work as energy sources in signal transduction, phospholipid synthesis, and glycogen synthesis, respectively.
But this raises the question of the function or necessity of the purine or pyrimidine ring in the nucleoside triphosphates. As far as I can see the answer is this serves no indispensible function. (Sure, it binds to enzymes — but all sorts of other structure are able to do this.) So I would like to fly the following kite (which must have been flown before, although I am not aware of a reference).

A nucleotide triphosphate (ATP) became the preferred energy source in
  metabolism after a mechanism of RNA synthesis evolved that used NTPs as
  substrates.

When the synthesis of RNA evolved to use the free energy of hyrolysis of a 'diphosphorylated extension' of its structural building block (NMP), a system of using a related hydrolysis was extended to metabolism. Note that I say 'related', as RNA synthesis (like other macromolecular syntheses) hydrolyses the alpha-beta phosphodiester bond (releasing pyrophosphate), whereas in metabolism it is generally the beta-gamma bond that is hydrolysed (releasing orthophosphate).
The hydrolysis of ATP would have displaced what it is thought to have been a pre-replication system(s) of energy generation because it would presumably have been better and allowed integrated energy metabolism. (The energy demands of replication would have been large.) But that doesn't mean it's the best conceivable method — working well and being convenient could have been enough.
Footnote
Although not part of my argument, there is another key molecule in metabolism that has what may be considered a 'useless' adenosine component — NAD (and NADP). The redox guts of this is the nicotinamide ring. Did this evolve from a form that was initially part of a ribozyme — perhaps involved in the formation of deoxyribose when the RNA genome was being displaced by the DNA genome?
Comment: I'm not convinced that ATP is used more often than the other nucleotides because of chance. In the early stages of cellular evolution, there must have been competition for the nucleotide that gave the highest fitness, and it turned out to be ATP. Why? That's a very good question.
Comment: @rhody  You are quite justified in feeling that the answer to this unanswerable question is not chance. However, what is not justified, in my opinion, is the assumption that a non-chance answer is of the type you assume, namely that NTPs were the best molecule for the job, and that ATP was the best of the NTPs. In the latter case it could be e.g. that ATP was the 'cheapest' to synthesize, or that purines bound better to ribozymes than pyrimidines. And if NTPs were a consequence of the RNA structure of the genome, then selection occured at RNA, i.e. it was not 'pure chance'.
Answer: Preface
I have already provided an answer to this question, addressing one aspect of it: why a nucleotide triphosphate — rather than any other molecule — was the choice for an energy carrier. In that answer I suggest that the choice of ATP, rather than any GTP, CTP or UTP, was mere chance.
This second question has, in fact, been posed, but was regarded — incorrectly in my opinion — as a duplicate. I have recently become aware of research that suggests to me a possible reason for the preference of ATP over other NTPs, and, as it is independent of my previous answer, I would like to present it as a separate answer.
Why ATP rather than other NTPs?
I am starting from the assumption of an RNA world in which some sort of RNA genome had developed the ability to replicate and exhibit enzymic activity. The ribosome, and especially ribosomal RNA, can be regarded as a fossil of such a world. Harry Noller, in a review of this topic in Science in 2005, considers the bases that are involved in base-pairing in the many RNA double-helical loops, and those that are unpaired in such loops. Many of the latter are involved in ternary interactions in the rRNA, which has an overall protein-like structure. A significant fact that he mentions about the bases that are unpaired in the helical secondary structures is their skewed distribution:

"However, the unpaired bases are not distributed evenly among the four bases. In Escherichia coli 16S rRNA, for example, the proportions of unpaired bases for G, C, and U are 31%, 29%, and 33%, respectively, whereas 62% of As are unpaired, a tendency that extends to other functional RNAs."

It transpires that many of these 'unpaired As' are involved in what are called Type II A-minor nucleoside interactions, which are illustrated in Fig 3. of that paper, below:

In the legend to this figure Noller points out that:

These precise lock-and-key minor-groove interactions between (usually) an adenosine and a Watson–Crick base pair are found extensively in 16S and 23S rRNA. They were first observed in crystal packing of the hammerhead ribozyme and in the P4-P6 domain of the group I ribozyme. A-minor interactions play an important functional role in monitoring codon-anticodon interaction by the ribosome via their unique stereo-chemical fit to Watson-Crick base pairs.

From this I conclude that adenine has unique structural properties that would allow it to form a more precise and stronger interaction to base-pairs in a ribozyme RNA than the other three bases. One of the features of any ribozyme involved in using an NTP to drive chemical reactions would have been to bind the NTP. (We see this in contemporary proteins with the Rossman Fold which binds adenine.)
The greater suitability of the adenine of ATP for this role may be why it, rather then GTP, CTP or UTP, became the major (I would assume initial) choice for energy carrier.
Comment: If this idea has been expressed before, I apologize for not acknowledging the fact. Let me know. Otherwise, you read it here first.


Is the Fine Stucture constant constant?

Question: I have read that the fine structure constant may well not be a constant. Now, if this were to be true, what would be the effect of a higher or lower value? (and why?)
Comment: On a related note: it's already known that the fine structure constant varies with the energy scale of the particles involved in measuring it (renormalization group evolution), which is why we sometimes call it the "coupling parameter" instead. But that's not what the article is talking about.
Comment: Here is a link to Chad Orzel's post about why he is skeptical about these results : http://scienceblogs.com/principles/2010/09/_httpksjtrackermitedu20100907e.php
Comment: There has been a lot of work lately on this topic. In [this paper](http://arxiv.org/abs/1008.3907) evidence for an (apparent) variation of $\alpha$ on cosmological scales is presented. There are also a few papers by Paul Davies on this. One is sadly behind a Nature paywall. Another one can be found on [arXiv](http://arxiv.org/abs/0708.1783)
Comment: Related: http://physics.stackexchange.com/q/21721/2451
Answer: Another thing that would be changed by a varying fine structure constant would be that it would alter almost every electromagnetically mediated phenomenon.  All of the spectra of atoms would change.  What would also change would be the temperature at which atoms can no longer hold onto their electrons, since the strength of attraction between electrons and the nucleus would change.  This would then change the redshift at which the universe becomes transparent.  The end result would be that the cosmic background radiation would be coming from a different time in the universe's history than otherwise thought.  This would have consequences for the values of cosmological parameters.
Once you alter phenomena in this stage of the universe's history, though, you have to be quite careful to not disrupt the current predictions for how much hydrogen, helium, and heavy elements there are in the universe (while creating nuclei depends mainly on the strong interaction, electromagnetism does have something to do with determining the final energies of the nuclei, and so can't be completely neglected--changing the fine structure constant changes these cross-sections).  Current theory predicts these things with great accuracy, and changing things around, particularly particle physics parameters that govern the length of the neucleosyntheis era (which overlaps with, but is a subset of the time at which the universe is opaque) potentially make these observations not agree with theory.
Comment: @Jerry: The physical effect would be negligible. But the fact that $\alpha$ _changes at all_ - if confirmed - would prove some cosmological theories and disprove others, so scientific effect would be quite significant.
Comment: While all you say is true, current theories cannot exclude possible variation of $\alpha$ in time although the upper limit for this variation (given by experimental data) is about $10^{-16}$ per year.
Comment: @gigacyan:  Which means that the effect is pretty much negligible (and probably zero), considering that the universe is ~$10^10$ years old, unless this is somehow the mechanism for inflation or something like that.
Comment: @Jerry, your TeX got messed up, so you might want to re-post the comment.
Comment: Ah, I meant ~$10^{10}$.  :)
Comment: @gigacyan:  I don't think it would do anything significant to change cosmology if it was that small of an effect--what observable consequence would appear?  It might have consequences for particle physics, though, since if $\alpha$ is a scalar field, then you need a new electroweak theory.
Comment: Cheers, I sometimes wonder what the effect/affect (never really sure which one to use) of changeing constants would be. Thanks for all your help!
Answer: Many very accurate measurements seem to imply that the fine-structure constant has been totally constant, within the error margin, since the Big Bang. And the few experiments that suggested otherwise have problems. Theoretically, it's likely that the fine-structure constant is completely constant.
However, if you imagine that the fine-structure constant changes a bit, many things become different. For example, the stability and lifetimes of the neutron and nuclei will change abruptly. The modified fine-structure constant will also influence many other "constants" that define particle physics - such as the ratios of particle masses, fine-structure constants for other forces, mixing angles, and others - but you would have to describe what (dimensionless parameters) you want to keep fixed while you're changing the fine-structure constant.
From an "anthropic" viewpoint, it is important to notice that chemistry (minus nuclear physics, the care about isotopes etc.) would remain largely unaffected. It's because the atoms exist in the non-relativistic limit, and the fine-structure constant only determines the (order-of-magnitude estimate of the) speed of electrons in the atoms. Because the fine-structure constant is much smaller than one, the electrons in atoms may be approximated by non-relativistic mechanics. That would still be true if you e.g. doubled the fine-structure constant. So the ratios of the atomic frequencies etc. would remain pretty much unchanged, even if you doubled alpha, up to small corrections and splittings of the spectral lines (which are called the fine structure for a good reason).
It is even plausible that as complicated molecules as the DNA could continue to work unaffected even if alpha were changed by many percent or dozens of percent, despite the fact that the functioning of the DNA depends on small detailed in energy differences. If the units were redefined properly, the world of biochemistry would be pretty much unchanged. However, that's because the quantum electrodynamics with electrons only depends on one dimensionful parameter only - the electron mass - and one dimensionless one - the fine-structure constant that moreover defines a different scaling for space and time in the non-relativistic limit. If you considered the behavior of high-energy physics which has many other elementary particles, a change of alpha would surely make a difference.
Best wishes
Lubos
Answer: This is a purely speculative idea, but it seems to me that the fine-structure "constant" is actually a measure of the compressibility of the vacuum. In a theory of quantum gravity, the structure of the vacuum (on which quantum fields are defined) and that of the background geometry are necessarily interrelated, in the sense that the vacuum can be thought of as a condensate of quantum geometrical excitations.
If the large-scale geometry of the universe can indeed be given a description in terms of such a condensate then the material properties of the condensate would show fluctuations over long distances. One of these would be the "vacuum" compressibility or $\alpha$.
Caveat Emptor: There are a few key notions that must be elaborated on before the above argument can begin to stand on its own. These are:

What is a "quantum geometric condensate" and why should the vacuum of the standard model have such a description?
A elucidation of the precise sense in which one can think of $\alpha$ as a measure of the compressibility (or some other "material" characteristic) of the ground state of the resulting condensate.

The first proposition is one I firmly believe in, not least because of what what I have learned through my own research. The second is something I am hazy on at present, though I have a strong intuition that such a description exists and is even natural.
I realize, that in the absence of a clearer explanation of these two issues I am asking the reader to believe in my reasoning based more on a "gut feeling" than anything else. This might be too much to digest for some. However, if for whatever reason, you are willing to give some credit to this line of reasoning then a cosmological variation in $\alpha$ is all but inevitable.

Is the Fine Stucture constant constant?


NLog mySQL target configuration

Question: I am trying out NLog to use mySQL table. I seem to have the configuration set correctly however I am getting the following error (capturing exceptions in NLog).
2012-10-10 17:09:20.0200 Error Error initializing target Database Target[slogger] System.Configuration.ConfigurationErrorsException: Failed to find or load the registered .Net Framework Data Provider.
   at System.Data.Common.DbProviderFactories.GetFactory(DataRow providerRow)
   at System.Data.Common.DbProviderFactories.GetFactory(String providerInvariantName)
   at NLog.Targets.DatabaseTarget.InitializeTarget()
   at NLog.Targets.Target.Initialize(LoggingConfiguration configuration).
I think that this error is related to the statement "The parameter name should be a provider invariant name as registered in machine.config or app.config" in the database target configuration page however I am not certain how to correct the error. I have the mySQL DLL referenced in the application.
Following is my configuration:

Please let me know what I am doing incorrectly and how to change. I really appreciate help. This is really a cool app!
Thanks
Ray
Answer: try changing the dbProvider to this

dbProvider="MySql.Data.MySqlClient.MySqlConnection, MySql.Data"

NLog mySQL target configuration


What should I do if someone put a lot of work into answering my question - but I left out important information?

Question: Someone put a lot of work into answering my question here . Then I discovered that the behaviour only occurred when I was using a BindingNavigator and I had neglected to mention this in my question.  Is there some way I can send points for the effort?
Comment: Have you upvoted the answer yet?
Comment: 10 points to Gryffindor... I mean, to spajce ;)
Comment: Ah! I have now.
Comment: Great! Can you please post your comment as an answer?
Answer: This happens a lot
Leave a comment on their answer and wait for them to edit.
If you want to reward them for their time and their answer seems merit-able, than you can upvote the answer at your own discretion.

If it doesn't actually answer your question, than you shouldn't mark it as the answer.
The primary purpose of answers getting marked is for the benefit of future visitors whom will also be looking for answers to the question you've posted, and the get the most benefit if the marked answer is actually the answer.
Answer: Another option is to create a bounty on your question if you feel they went way beyond your expectations in answering your question. Offering a bounty takes away a chosen amount your reputation and awards it to the person of your choice. An overview of the rules regarding bounties can be found here.


Determining if patent is international?

Question: I am currently looking into patent US20110202766. I am new to patent law and I would like to know if the given patent is US-only, or international. How can I find out about where does a given patent apply?
Answer: Granted, enforceable patents are territorial limited. So a U.S. patent allows its owner to control the making, selling, using and importing into the U.S. In this case you are referencing an application that may or may not have resulted in one or more U.S. patents (looks like it hasn't as of March 2013). The inventor could have filed counterpart applications in other countries or with international bodies that can lead to patents elsewhere. One way to look into this is to look up the application it the EPO's database called Espacenet by the US application number. When you find it you will see a selection to the left called INPADOC family. Clicking on that brings up a list of all the related documents known to that international database. Besides the US application it shows one with a "WO" number. That is a PCT application. It is possible to go from a PCT application to "real" filings in 140+ locations. To look up PCT data and other international info go to WIPO's Patentscope search engine.
You might also search Patentscope for applications by the same inventor.
The application you are interested in got a non-final rejection in December 2012. You can look up the history in USPTO Public PAIR.
Comment: Non final rejection doesn't mean much. Most applications get rejected at first.
Comment: Interesting. So that's what "Non Final Action Mailed" means? So that means that I should be asking the person claiming to hold the patent rights some more concrete proof that their patent is indeed enforceable? At any rate, thanks for the great answer!
Comment: Please look up that application yourself in Uspto public pair (google it). There may be some related application that resulted in a patent but the number you provided is an application NOT a patent. Applications have a number that the first 4 digits are a year. Like 2011.

Determining if patent is international?


Should I create a new tag?

Question: There's a bunch of words in my question that don't have tags yet. Can I just add them all?
Comment: I created this Q&A because I just got done cleaning up a bunch of singleton tags that probably should have never existed.
Comment: Y'all I just cleaned up another ~20 tags. Please be careful with tagging. A good number of them were easily avoidable spelling mistakes.
Answer: Before you create that new tag, stop and consider the following:

Note: The example questions used here are intentionally basic and should not be taken as a guideline for what is appropriate to ask on the site.

1. Is this a useful way to categorize the question?
For example, if your question is "Why do rockets sometimes explode?", then rockets and rocket-explosion are probably both good tags, because someone looking in those categories is probably interested in that type of question.
However, let's say the body of your question says, "Some rockets have exploded in the air and others on the launchpad." air would not be a helpful way to categorize the question. Someone looking at questions about air is probably not interested in why rockets explode. In fact, launchpad may not be helpful either. Unless the question is seeking specific information about launchpad explosions, someone looking at questions about launchpads is probably not interested in why rockets explode either.
2. Is this concept useful for space exploration?
For example, if your question is "Do burgers taste different in space?", burger is probably not a useful tag. Short of some surprising turn of events (e.g. Bigelow launching a burger shop in space), there are probably not going to be a lot of questions about burgers on the site, and even if there were a few someone is unlikely to go looking for a burger category unless they already know about those questions. Consider: food
3. Will this tag get used again?
Categories are only useful if they gather a collection of related questions. Let's say your question is "Will the Laser Corp SuperZapBolt laser be used on the new satellite?" You might think lasercorp-superzapbolt passes #1 and #2, after all lasers aren't an unusual topic in space exploration. However, consider whether it is really likely that someone will be asking about this specific laser again. Has it been used on multiple existing spacecraft or very prominently on a well-known spacecraft? If not, it's probably not going to attract any other questions, and you should just stick with laser.
4. Is there an existing tag that is fairly equivalent in terms of categorizing the question?
For example, if your question is "What caused this conflagration on the ISS?", and you're considering adding a conflagration tag, you should probably check to see if fire exists first.
5. Is the tag spelled right? Are you sure?
Similar to #4, this is about how well you check for existing tags. Please be absolutely certain you are using the correct spelling for all the words in your tag. Google them and copy and paste the exact spelling. Make sure tags with the correct spelling don't already exist. Also, keep in mind that we standardize on US English spellings for tags.
Comment: A particular example of #3 are tags that are made for specific missions.  What typically happens is that some mission is launched that week, someone asks a question about that mission, and suddenly we have a new tag that never gets used again.
Comment: @DrSheldon Yes, exactly this. Please consider how major the mission is before making a specific tag for it.
Answer: The flipside here is called burnination, where the community removes tags. It's worth reading what the overall methodology is, but you should pay attention that tags must be clear
We recently reversed a tag synonym because [neo] was potentially vague. I've seen that happen a lot, where a tag goes with an acronym or simple name, and thus you wind up with multiple meanings for the same tag. An excerpt can help, but not all users will see them (they don't show up on mobile), let alone read and obey them.
Comment: Good addendum! Thanks!

Should I create a new tag?


Is it correct to have categories as filters?

Question: I am currently working on an internal search application where users will be able to search within the repository. We have categories and authors for segregating different documents. There can be different filters once I change the tabs as well as shown in image 2. Is it correct to have categories as filters? Also, how do I show filters that appear within categories?
Comment: Did I understand you correctly in that the categories you list in the left hand column correspond with the tabs? So that Category 1 can be either Images or Users, for example?
Answer: This is a great 2009 article from UX Matters about filtering search, categories and drilling down into those categories are absolutely fine filters when implemented correctly, the biggest takeaway from the article is to make sure your users always have a way to get back.
Comment: Including a key quote from the article in your answer, supporting your assertion, would be good.
Answer: My recommendation: NO, do not present categories as filters.
Rather, to solve this problem, I recommend my clients to make two main result templates, based on the market leader's (google.com's) behaviour:

One Main results template where categories are presented as group results. This template is without filters.
One Category results template where results within a category are represented with filters.

This also solves your second question: How to show filters that only appear within certain categories. The answer is to wait until the user has clicked a group, thereby informing the service what category she is interested in. This, again, is a design pattern derived from google.com.
If you do multiple test searches on google.com (1, 2, 3) you will oftentimes see that on the first search results page, results from one type of source (images, videos, news, tweets, map results, shopping, facts etc. etc.) are represented together in a group. Some refer to these as Google's OneBoxes. The purpose is intuitive disambiguation; to guide the user to the desired repository by way of providing examples, as opposed to forcing them to read labels and try to understand your information architecture.
As part of an open source project I have illustrated template #1 here. Below are three of the suggested group results (OneBoxes). These groups all have potential, individual filters, and these filters are shown only when the particular group is selected, taking the user to template #2.
In the original template the results are responsive. Based on Bootstrap.


Can the Montevideo interpretation of quantum mechanics do what it claims?

Question: Partly inspired by the great responses to a my previous physics.SE question about "reversing gravitational decoherence, today I was rereading the intriguing papers by Gambini, Pullin, Porto, et al., about what they call the "Montevideo interpretation" of quantum mechanics.  They've written lots of papers on this subject with partly-overlapping content; see here for a list.
The overall goal here is to try to identify, within the (more-or-less) known laws of physics, a source of decoherence that would be irreversible for fundamental physics reasons, rather than just staggeringly hard to reverse technologically.  One can argue philosophically about whether anyone should care about that, whether such a decoherence source is either necessary or sufficient for "solving the measurement problem", etc.  Here, though, I'm exclusively interested in the narrower issue of whether or not such a decoherence source exists.
Gambini et al.'s basic idea is easy to explain: quantum-gravity considerations (e.g., the Bekenstein bound) very plausibly put fundamental limits on the accuracy of clocks.  So when performing a quantum interference experiment, we can't know exactly when to make the measurement---and of course, the energy eigenstates are constantly rotating around!  So, for that reason alone (if no other!), we can think about any pure state we measure as "smeared out a little bit" into a mixed state, the off-diagonal entries in the density matrix a little bit less than maximal.
More precisely, Gambini et al. claim the following rough upper bound for the magnitudes of the off-diagonal elements.  Here, T is the elapsed time between the beginning of the experiment and the measurement, Tplanck is the Planck time, and EA-EB is the difference in energy between the two things being kept in superposition (so that $\frac{E_A - E_B}{\hbar}$ is the Bohr frequency).
(1) $\left| \rho_{offdiagonal} \right| \lt \exp \left( -\frac{2}{3} T_{planck}^{4/3}T^{2/3} \left( \frac{E_A - E_B}{\hbar} \right)^{2} \right).$
If EA-EB were equal to (say) the mass-energy of a few million protons, then (1) could certainly lead to observable effects over reasonable timescales (like a second).
Now, it might be that there's an error in Gambini et al.'s analysis or in my understanding of it, or that the analysis relies on such speculative assumptions that one can't really say one way or the other.  If so, please let me know!
If none of the above holds, though, then my question is the following:
Can the bound (1) really do anything like the work that Gambini et al. claim for it---that is, of preventing "macroscopic interference" from ever being observed?  More concretely, is it really true that anything we'd intuitively regard as a "macroscopic superposition" must have a large EA-EB value, and therefore a relative phase between the two components that rotates at unbelievable speed?  In principle, why couldn't we prepare (say) a Schrödinger cat in an energy eigenstate, with the alive and dead components having the same energy (so that EA-EB=0)?  Would such a state not constitute a counterexample to what Gambini et al. are trying to do?
Answer: Jorge Pullin sent me an email responding to my question and to Ron Maimon's criticisms.  In case people are interested, I'm posting it here with Jorge's kind permission.  I particularly appreciated his clarification that the Montevideo interpretation is not really an "interpretation" at all, but new physics that makes new and different testable predictions.  In particular, in Jorge and Rodolfo's view, the argument they give involving clocks is "motivational" in character; they're not claiming it as a derivation from accepted principles of quantum gravity.  --Scott

Let us start with your own question. We believe it is answered in this paper of Paz and Zurek.
Quantum limit of decoherence: Environment induced superselection of energy eigenstates.
Juan Pablo Paz (Buenos Aires U.), Wojciech Hubert Zurek (Los Alamos). Nov 1998. 4 pp.
Published in Phys.Rev.Lett. 82 (1999) 5181-5185
DOI: 10.1103/PhysRevLett.82.5181
e-Print: quant-ph/9811026 [quant-ph] PDF
In fact our approach may be considered as a completion of the environmental decoherence
approach. Paz and Zurek have shown that the pointer basis is defined by the eigenvectors of the interaction Hamiltonian and the self-Hamiltonian. It is not clear if pointer states can be defined among the eigenstates belonging to the same eigenlevel of the dominant Hamiltonian. If that were the case our axioms would not lead to the production of events for a Schroedinger cat that would involve states of that type.
As for the points raised by Maimon, there are several, some explicit, some implicit, so we
will try to treat them separately:
a) His first point is that there is no relative phase in two interacting systems because underlying the theory is ordinary quantum mechanics. We think this is a misunderstanding of what we do.  Or perhaps we did not explain it clearly. Although one talks of an "interpretation of quantum  mechanics" the Montevideo interpretation has new physics, described by the modified Schroedinger equation we have. This is clear, for instance, when we formulated it axiomatically. Incidentally, a convenient place to find our papers is at http://www.montevideointerpretation.com
As a result systems lose relative coherence. One can motivate the new physics in the impossibility to observe precisely ordinary quantum mechanics, and we did so in some
of the papers, but at some point one has to admit it is new physics. The new physics emerges naturally from the relational descriptions that are suitable for generally covariant theories like general relativity. We showed in the paper by Torterolo et al. that in such a context the only thing one can compute are conditional probabilities between observables that evolve in the unobservable time. One could extend that calculation including a second clock. But even if one prepared both clocks in the same initial state, after some time the clocks will disagree on the times assigned to each measurement, contrary to what Maimon claims.
b) As for his point of the photons, if one could put the screen very very far away, we contend that indeed interference would disappear. But obviously in any feasible experiment
the effect is too small to observe. We wish it would be easier, then it would make the whole paradigm experimentally testable. Unfortunately the only way to see the effect is to have Schroedinger cat type states with huge energy differences compared to what is available at the atomic level. Those are not easy to find in the lab.
c) As for the kool aid part, we agree with you as well. I doubt very many people, apart from some string zealots, will claim that string theory solves the problem of time in generally covariant systems. Let alone the fact that the real universe is not AdS!
Answer: No it cannot. This is not an interpretation, nor a new theory, it is a misunderstanding. The papers are vacuous, and not in an interesting way.
What time is it?
The basic idea is that we don't know what time it is, really. So we make a probability distribution for what time it is, and this changes the phase of the wavefunction by an amount proportional to however much we don't know the time. Then the authors claim that this uncertainty introduces a decoherence phenomenon into the Schrodinger equation, because the phases of energy eigenstates are shifted by an uncertain amount.
This is just plain wrong. The reason is that although we don't know what time it is, we know from the author's assumption that there is a consistent Schrodinger time (this is one of their axioms) that whatever time it is, it's the same time for any two things in the theory. So while there is an uncertainty in the phase of an isolated system from not knowing what time it is, there is no uncertainty introduced in the relative phase of two interacting systems, and there is no decoherence caused by this uncertainty, except through mistakes in analysis.
Mistakes
These mistakes are subtly introduced by making a separation between "observer" and "system", and introducing the probability distribution for the clock reading only in those cases where the observer is interacting with the system, and when observers are interacting with each other, not when systems are interacting with systems.
For example, suppose you have a photon split by a beam splitter, with one part going through some glass, then through a double slit to measure interference. This will work, the beams stay coherent, because the photon that gets through doesn't excite any irreversible quantum in the glass. Notice that the glass is large and macroscopic, though.
Anyway, once the photons interfere, you get a pattern that doesn't give a hoot about what time it is, just on the relative phase-difference between the two photons, the path-difference in the optical system. So the photon didn't care that we don't know what time it is for the glass, because it just goes through the glass and not, and whatever time it is, it interferes with the other photon, which doesn't care what time it is either, because it's the same time as the other photon.
Note that the photon interacted with this enormous glass, and all the atomic absorption and emission events had to coherently come together even though for the glass, we don't know what time it is. The relative coherence is maintained throughout.
So when does the problem of time show up in these papers? It shows up when the observer entangles with the system, and at this point, the authors declare that the uncertainty in what time it is shows up as an uncertainty in the phase of the system that the observer measures.
If there is a second observer measuring something else, they introduce an uncertainty in the second observer's time. But then when the observers come to talk, the authors pretend that the two observers phase-shifts are uncorrelated, when in fact the uncertainty in what time it is is exactly the same for the two observers, because it is an uncertainty in the same global t variable that they both don't know.
So whatever the t-uncertainty for each observer, the coherence effects between the two observers are not washed out, unless you make the assumption that the actual global t is different for the two observers, an assumption that is at odds with the postulates of the theory, that there is a global time ticking down there underneath it all.
There is no problem of time in S-matrix theory
Constrary to the authors' claims, string theory solves the problem of time definitively and for good, that's the whole point. The solution was the motivation for Heisenberg to introduce S-matrix theory in the first place, it allows you to make a theory in cases where space and time are unreliable.
An S-matrix theory doesn't give a detailed history of the events in the interior of spacetime, it only relates things on the boundary to other things on the boundary. It doesn't have a real local non-asymptotic time variable at all, so it can't describe time-dependent phenomenon, like the formation and evaporation of a quantum black hole in detail. This is why we are in the embarassing position of having essentially exact quantum description of forming and evaporating black holes while at the same time not being able to answer some of the simplest questions about this process.
So if you make a string scattering calculation, or an AdS/CFT calculation using boundary states, you don't have a problem of time on the interior, you can't, because time on the interior just doesn't appear in the description. It is at best reconstructed approximately from the quantum state on the boundary.
You might say "but then what about the problem of time on the boundary!", but the boundary theory is non-gravitational, and it doesn't have a time problem either. This is the miracle of string theory, and this is what makes it the only plausible candidate for quantum gravity--- the philosophical problems completely evaporate in S-matrix, it is as if they never existed.
You might object that there is a t-variable on the perturbative string world-sheet, but this is an artifact of the perturbative theory, of describing the string scattering process in detail using intermediate states, which you then interpret as localized in time. This interpretation is not completely good, you can't associate local operators to the string. If you do string field theory, you need to do it in light cone, and then the string story becomes more or less local along the light-front, but the light-front time variable is going diagonally in space time, and the string field is only telling a local story in the transverse coordinates to the light-cone pair. It stays nonlocal in the light-cone pair (time and one other coordinate).
If one were given the correct exact string S-matrix in our vacuum, there would be no t-variable in the S-matrix, only the S-matrix in and out state which does not reference any clocks at all. You might object that the S-matrix gives you phase shifts in outgoing waves, and to measure these phase shifts you might think you need a clock, but this is not so, since the relative phase between two states can be determined in principle by perfoming a second much-later scattering which can be approximated as two separate scatterings, and allowing the scattered products in different direction to interfere with each other to make fringes. The phase shifts of the original scattering now show up in the k-directions of the bragg diffraction of the two waves, and you can reconstruct the phase shift information from complicated scattering matrix data in principle without needing a clock on the interior, just by considering a more complicated in state.
This is exactly what you do for a photon--- you scatter it off a double slit to turn the difference in phase shift into a spatial diffraction pattern. This is not obscure at all, although it is hopeless to describe the appropriate s-matrix elements in detail for any realistic experiment.
This means that the problem of time cannot even be stated in S-matrix theory, and time is not treated differently from space, because neither is treated at all. This is the greatest virtues of string theory, and it is the reason that the S-matrix program was able to make such surprising progress in quantum gravity, which was not its original goal.
Comment: Thanks, Ron.  Offhand remark: to those who haven't fully drunk the Kool-Aid yet, not being able to state the problem of time, since you don't treat space or time at all, might not sound like such a wonderful "virtue"!  I.e., if you want to say various things we care about are just "illusions," then the question shifts immediately to *explaining* those illusions and figuring out their basic properties, which you admit hasn't been done yet in the case of AdS/CFT.
Comment: ... regarding string theory kool aid, which I drink with no reservation, reconstructing time and space from boundary data is indeed the main sticking point in accepting S-matrix theory, and it is why it took two decades from 1940-1960 before the theory could really take off. The 1960s literature is entirely devoted to the problem of reconstructing local physics from S-matrix data, and it is possible, although extremely difficult and philosophically involved. Although the "illusion of space" is not completely worked out in AdS/CFT, it is worked out enough to know for sure it works.
Comment: Moving on to your criticism of Gambini et al.: I imagine their response would be, sure, in the case of the photon travelling through glass, you'll see the interference for exactly the reasons you say. But when trying to superpose two *macroscopic* bodies, the situation is substantially different because of the huge energy differences involved (cf wolfgang's answer). Is there any merit to that claim? (For this question, let's forget about whether everything is "really" unitary in some boundary description to which we don't have access; I'm only interested in limits on actual experiments.)
Comment: @ScottAaronson: The problem is that their hypothesis of fundamental decoherence is not justified by the mechanism they give--- not knowing what time it is. For observing coherence, you only need to know that there is a global time in which all phenomena are coherent. This is a postulate in their method, and if they omitted this postulate, and said that there was a real fundamental decoherence due to gravity, it wouldn't be necessarily inconsistent, but it would probably conflict with experiment (but it might be possible, it's just not what they do).
Comment: OK, thanks.  I understood them to be saying: when you superpose two bodies with a huge difference in energy, the Bohr frequency condition implies that the relative phase between them really is rotating at an enormous speed, which then means that you really do need to know what time it is to great precision if you want to measure anything about the phase.  This argument might still be wrong, but I don't see how one can refute it by pointing to their assumption of a global time ticking underneath everything.  (And incidentally, I didn't see where they ever discussed two observers.)
Comment: @ScottAaronson: The way you refute it is by noting that the uncertainty in the time only becomes important when you compare the _relative phase_ between two different systems, and the uncertain time has to be different for the two systems in order for the decoherence to wash out. If the time is secretly the same between the two systems, the decoherence doesn't happen, the phase coherence is the same as ever, regardless of any uncertainty in the value of the global time. You need relative fluctuations in time to get decoherence. This is not mentioned in their paper, for obvious reasons.
Comment: When you say "two different systems", are you talking about A and B where a|A>+b|B> is our superposition?  If so, then suppose t is exactly the same for both A and B, *but* the relative phase between them evolves like exp(i*omega*t), where omega is something enormous.  Then why *wouldn't* we need to know the global time t to a precision ~1/omega, in order to detect the coherence between |A> and |B> in an experiment?
Comment: @ScottAaronson: Because you don't need to know the time precisely to turn the relative phase into an interference fringe. Even if you don't know the exact time for the photon, you know the phase-difference along the two paths, and so you know the shift in interference fringes. When you measure phases, you turn the interference into spatially resolved peaks and troughs that don't care about the time, because the coherence is along certain directions regardless of the exact time. To measure the phase-difference, you don't measure the phase of the combined system precisely and look at your watch.
Answer: I did not read these papers as "quantum-gravity considerations" but about limits imposed by (quasi)classical gravitation on quantum experiments. They discuss mainly clocks (*) but I think for this discussion it is easier to consider distance measurements:
In an interferometer the distances between mirrors etc. have to be controlled with great precision to see an interference pattern. In order to control the distances between mirrors one needs to make them heavier and the limitation from (quasi)classical gravitation is that the mirrors cannot form a black hole.
So I think it misses the point to state that "you get a pattern that doesn't give a hoot about what time it is".
If one would perform an interference experiment with macroscopic bodies the effective wavelengths would be at or below the Planck length and one could not place the mirrors with sufficient precision to see anything. I think this is the kind of issue they are talking about and not a new quantum gravity theory. The fact that the S-matrix can be calculated in string theory is great, but does not really have anything to do with this imho.
(*) I guess the reason they consider clocks is because they want to get universal quantitative bounds on decoherence times and not just qualitative statements about a particular interference experiment.
Comment: The issue I have with this interpretation (which is close to what they suggest, replacing time with space) is that it assumes that there is a decoherence caused by the uncertainty in the gravitational metric background. If this background is coherent vacuum, there should be no uncertainty at all. I understand the experimental setup makes it hard to measure interference for macroscopic objects, but if you have a zero-temperature mesoscopic grain, you should be able to observe interference when it is at rest, and then boost the whole system to a velocity where the wavelength is trans-Planckian
Comment: If they suggested the cosmological horizon has thermal gravitons that you can't shield, I would be on board--- I do think that the deSitter horizon makes it difficult to define quantum coherence for a deSitter universe, and I believe the proper description of dS space is by a thermal statistical ensemble, and no pure state. But the bounds from gravity alone in flat space are not consistent with an interpretation that gravity leads to fundamental decoherence.
Comment: In my example the issue is the uncertainty in the position of the mirror(s) (which has to withstand the recoil of the photon or Schroedinger's cat) and not uncertainty about the metric.
Comment: Also, if you move the particle (or Schroedinger's cat) very slowly through the interferometer to increase the wavelength, then the payoff is that the experiment takes much longer and you need to fight decoherence that much longer. If G & P did their calculation correctly (which I did not check) then there is a limit to what you can achieve by slowing down the particle or cat.


Allegory of the cave and Forms?

Question: In my philosophy class, the professor told us about the allegory of the cave and how it relates to the Forms. From what I understood, regular people only see shadows of the Forms; but by doing philosophy, one can free himself from the chains and catch a glimpse of the Forms. Which Forms can philosophers catch a glimpse of?
Comment: True ideas and even wikipedia gives such description. But one can argue against, personal interpretations would be opinion-based. Maybe reference request could be on-topic.
Comment: See [Plato's theory of *forms*](https://en.wikipedia.org/wiki/Theory_of_forms#Evidence_of_Forms).
Comment: And see the post : [Plato Cave Allegory](https://philosophy.stackexchange.com/questions/38689/plato-cave-allegory).
Comment: See Plato's [*Phaedo*, 65a-66a](http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0170%3Atext%3DPhaedo%3Asection%3D65a).
Comment: The library can be your secret weapon. Seriously. Reference section. Encyclopedias of Philosophy. Some come in multiple volumes.
Answer:
"Which forms can philosophers catch a glimpse of?"

Especially those of the Good the True and the Beautiful (In Platonic philosophy, or traditional Political Philosophy). The whole discussion in Plato's Republic, so called in the translation, is on the form of Justice which is a part of the Good. It's basically the question: What is the best way to behave? The ordinary man adjusts to convention and vogue mindlessly, but the philosopher holds back, withdraws into death as it were, and from there surveys the idea of Justice attempting to find its highest annunciation, to determine it as a principle to guide one's deeds: Socrates thus says: The Just is what improves human beings. To follow this wouldn't suit most men, and, in fact, Thrasymachus grows enraged and frightens Socrates by turning beet red when he hears of this idea (provided we interpret this as anger and not a "blush" as is often supposed). So, he is is like the ones who would kill the man who comes back down from the sun of the idea proper, into the region where the shadow, the opinion that Justice is the "advantage of the stronger party" is regnant.
This by no means exhausts the interpretation of the passage, but I give an initial indication of the subject matter only.
Answer: If any specific Form is apprehended by the escaped prisoner it is the Forms of the Good, which Plato symbolises as the Sun at Rep. VI.508e-509a. So far as I can see, the text indicates no other particular Form. And - Plato is full of surprise - it may not indicate a Form at all. This is a point for later.
Here's a standard summary :

At Republic 514 a I Plato makes Socrates introduce the Cave as 'an illustration of our human nature in reference to education and want of education'. He tells
   us that the men chained in the Cave can see nothing but the shadows on the
   rock face in front of them which are cast by puppets being moved along the top
   of a low wall behind the prisoners, beyond which a fire is burning. Likewise
   they can hear no sound save the echo of voices uttered by the puppet operators
   behind this wall. Such prisoners are said to be homoious hemin ['like us] in being able to see
   only shadows of themselves and shadows of the phenomena. Yet, if someone
   were to turn such a prisoner round bodily and oblige him to look at the fire and
   the objects on the wall and compel him to recognize these things from their
   familiar shadows, the prisoner would still consider those shadows seen earlier
   to be truer than the objects now shown him.
In 516 a-d it is also suggested that such a prisoner would resent being
   released and dragged up into the daylight outside the cave where he had always
   been kept, and that he would temporarily be blinded by the unfamiliar light.
   But later his eyes will perceive shadows and reflections by day and the stars and
   moon by night. Then finally he will look up at the sun, and recognize it as the
   source of light causing the seasons and all the other phenomena he observes. (R. G. Tanner, 'ΔΙΑΝΟΙΑ [dianoia]  and Plato's Cave', The Classical Quarterly, Vol. 20, No. 1 (May, 1970), pp. 81-91: 85.)

If, which is not clear, the stars and moon or other things itemised here refer to particular Forms there is absolutely no indication of which Forms they are.
The peculiarity of the 'Form of the Good'
The above account, which is standard, assumes that what we call 'the Form of the Good' really and truly is a Form. There are grounds for caution here.
The Forms are distinguished as having 'being and reality' - they are the 'objects of knowledge' - unlike sensible particulars and everything in the sense-based world. Yet the Form of the Good (he tou agathou idea), is beyond the being and reality (epekeina tês ousias) of the Forms (VI.508e2–3 & 508b8-10). A natural reading of this is that what we call 'the Form of the Good' is not itself a Form, since it transcends the Forms.
On this reading, the escaped prisoner does not apprehend any of the Forms but only the Sun which, symbolising the Good, is beyond them in being and reality.

Allegory of the cave and Forms?


What do I lose when reducing bit depth?

Question: I am concerned about the losses when converting flac files from 24bit to 16bit.
Does it reduce quality or add noise or what?
Answer: Technically it does reduce the quality, yes. It should not add any perceivable noise. Will you notice the difference? Try it and see. I don't expect you will. 16bit is CD quality, ie pretty good considering how most people listen to music these days.
Some reading if you want to understand more:
http://www.presonus.com/news/articles/sample-rate-and-bit-depth
A nice image from that page describing it:
Comment: NIcely explained Mark : ) Bit depth only really makes a difference when professionally designing sound to be played on High quality multimedia such as film, gaming etc
Comment: Mark Durham is right, but keep in mind that when you lower the bit depth; the lower the volume of your sound, the lower the quality. So if you can normalize or maybe even compress/limit your original high quality sound it will help a bit. Or you could split the loud and less loud parts in different files and normalize them independently. Sorry for posting a new answer. i can't comment until i have 50 rep.
Comment: the pedant in me suggests that it does add noise, by the very fact of reducing quality. I agree that you may not notice it, depending on the audio, the bit-depth change etc, but there will be added noise.
Comment: @RoryAlsop I wonder? It could well be the case, even though we are unlikely to hear the difference. I'll re-word that bit of by answer.
Answer: As long as you dither, you'll be fine; it can overcome the dynamic range limitations of if you had recorded 16-bit.
Scroll down this page for more info on bit depth/dithering (I suggest reading the whole page):
http://people.xiph.org/~xiphmont/demo/neil-young.html
Answer: If the FLAC files are not meant to be used for further sound design, and are recorded at reasonable levels, you don't lose anything important.  The dynamic range of 16-bit sound is very high - roughly 100 dB (how dither affects this makes the answer not quite as straightforward as you'd thing it is).
If you are truly concerned about the audiblity of bit depth on files like that, the best way to reasuure yourself is to test for yourself.  Get a free ABX comparator like FooBar, put in a file at 16 bit versus one at 24 bit, and listen for a difference.  Here's another blind test already set up that you could try:
http://ethanwiner.com/BitsTest.html
I have pretty good hearing, checked with blind tests here: http://www.audiocheck.net/blindtests_index.php
I can assure you that unless you're planning to further process the sound or the sound in the file is very very quiet, you won't lose anything important.  If the sound is very quiet, normalize it first and then you can reduce the bot depth without losing anything important.

What do I lose when reducing bit depth?