What is the force that prevents an object in an accelerating inclined plane from rolling/sliding downhill?

Question: A ball on a stationary frictionless wedge would naturally roll down because of the component of its weight along the plane. But I read if the wedge is accelerated fast enough it would prevent the ball from doing so. For this to be true there must be a new force that acts on the ball and whose magnitude will depend on the acceleration of the wedge (since a certain acceleration must be reached). But I'm having trouble comprehending this new force. Is it the 'reaction' force to that of causing the acceleration or is it simply inertia and the ball is just trying to be the way it was? Or is it something else entirely?
 It also said that with enough acceleration the ball would slide up the ramp and fall over. I can visualize this but can't seem to explain it.
Comment: See also [Preventing a block from sliding on a frictionless inclined plane,](https://physics.stackexchange.com/q/35978) and [Preventing a block from sliding on a plane (with friction)](https://physics.stackexchange.com/q/52431)
Answer: A small correction - a ball on a frictionless wedge would not roll down, it would slide.
You are right - when the wedge accelerates to the right, it applies a force to the ball along the normal of the plane. This force can be thought of as having a horizontal and vertical component - and if the vertical component is equal to $mg$, the ball will only accelerate horizontally (that is the direction of the net component of force on the ball).

(note - the force F can be displaced along its line of action, so the dotted red and green vectors, which act on the center of mass of the ball, are just as valid as the solid ones that act on the bottom of the ball. But having them act on the center convinces you that these forces don't impart rotation on the ball).
If you accelerate the wedge even more, the vertical component of the reaction force will be greater than the force of gravity: you end up with a net force that points up. So the ball will move up the ramp (still not rolling, as it is frictionless...)


Images Unlinking in Illustrator

Question: My office is transitioning from Windows to Mac. Files which were created in Illustrator on the PC are showing up with images missing and their links broken. Same thing happens in reverse, if someone on a PC opens files made in Illustrator on the Mac the linked images will be unlinked for them. The images are stored on a central server and have not moved at all. What is causing this?
Comment: Hi there and welcome to GDSE! Unfortunately your question doesn't seem to be about graphic design so I have to vote to close it as "off-topic". Does your filenames contain forbidden characters like `< > : " / \ | ? *` or any other "funky" characters which could be interpreted differently on the two systems? Does the network drives have different names/letters? It's possible to see the path in Illustrator so you can compare it with the correct path in Explorer.
Answer: Sorry - before this gets closed as off-topic tech support - I've bee through this - it is the difference in how each OS expresses and reads filepaths, both symbolically as listed in the comment above and in how filepaths are parsed inside the OS - short answer is that there's no way round this - each time you jump OSes on the opening of the file, you'll need to repath if you want to see the images.
If you know, however, that one specific OS, "A"let's sayis the one which "matters" in that that's both where the designers live and where the files will reside when finally output, you can enact a policy in which folks on the other OS "B" don't repath when they make for example text-only edits, when the file's re-read into illustrator on OS "A", it shouldn't require repathing.
Hope that helps.
Answer: Link paths in all Adobe applications are absolute and not relative. Meaning they all reference the system they are on when initially creating the link. If the document moves, the absolute links break.
The only way to ensure links remain unbroken is to have all linked items on the same directory, and at the same hierarchy, as the working document and never work from a server.

Images Unlinking in Illustrator


In Crimson Peak, why did Thomas Sharpe fall in love with Edith Cushing?

Question: In Crimson Peak, Thomas Sharpe goes around the world collecting to be murdered rich wives. Why did he fall in love with Edith Cushing?
Answer: It's the same as asking "How can somebody fall in love?"
Still if we try to answer it from the film's perspective, one thing to be noted is that it will be purely speculative as we don't know the other contenders (his ex-wives). Still the bulletin points of speculation I can get are:

He never got intimate with his previous wives.
She was prettier than the other ones. Or she has more innocence to attract him.
He is tired of all these murders and his sister.

Otherwise we can just say that his sister never gave him space to fall for any other woman but this time he got it and fell in love with her.
Answer: Thomas chose Edith. Even when Lucille warned Thomas against choosing her. Lucille saw Edith as a legitimate threat to whatever it was they had. She was young, beautiful...brilliant. Even worse, Edith saw Thomas for more than what Lucille had envisioned for him. A prisoner in their mansion locked away together. Eventually, Thomas saw that too. But he was too much of a fool to stop it.


Is Sauron using his full power?

Question: So Sauron is a maia. The maia were forbidden to use their full power. But there is nothing that restricts Sauron of using the full extent of the maia power. It was said that the maiar were forbidden, but if they are only but forbidden then could a maia access all of the power? And we are talking about a fallen maia so Sauron using his full power would be logical.
Comment: i believe only gandalf and the rest of the "wizards" maia were forbidden the full use of their power? but regardless unless something physically prohibited sauron from using everything he possessed, we can assume he was operating with everything he had.
Comment: Is there some reason you suspect he might be holding himself back? He really does not seem like the type. And if you mean that he is *unable* to use his "full power" because the gods won't let him, then I'm not sure how that's different from just not having that power.
Answer: Yes, but that power was very limited compared to his former self. Sauron put most of his power into the ring when forging it, so when parted with it he is crippled...still an incredibly formidable foe, but not like he would be if he had the ring.
The reason the Istari(5 Maia sent to aid Middle Earth) didn't use their full power against Sauron was because they weren't allowed to. They were supposed to assists men, not save them.
Comment: @TheExtinctSurgeon Gandalf the White against a ringless Sauron could have defeated him...maybe.
Comment: -1 Tolkien stated that Sauron is not at all diminished when not possessing the ring. As long as it exists he has his power, when he actually holds it he is further enhanced compared to his native power.
Comment: Even Gandalf with full power could not have defeated Sauron
Comment: Whether he could or not is not made clear, as I recall. Do you have evidence for that statement?
Comment: @MattGutting When the Valar have the council to decide the Istari it is noted that because they will become of flesh they'll have physical restrictions, but that's part of the deal, not something the Valar forced on them. It's also noted that they aren't allowed to rule the wills of men, or try to match Sauron's power with power. There's nothing about actual restrictions placed by the Valar, just that they have rules in place.

Is Sauron using his full power?


Windows Server: How to configure DNS forwarders on a circuit with a dynamic IP address

Question: Here's the issue: Your connection to the internet is over a cheap circuit that doesn't provide a static IP address or public static DNS servers.  Your LAN is NATed behind a firewall appliance. You want to set up Active Directory and accordingly need to configure DNS and assign a static (NATed) IP address to the server.  Once you assign the static IP address however, your server no longer receives the addresses of public DNS servers from the router/gateway.  How do you configure your server to pick up the DNS servers issued up via DHCP from your router/gateway?
Answer: Don't bother with using your ISP's DNS. You're going to run a DNS server on your DC anyway, so just leave the DNS server configured to use root hints (as it is by default).
Comment: +1 Evan. You beat me to the punch by 6 seconds :)
Comment: sorry--didn't notice that this came in first
Answer:
If you're installing AD\DNS on the server, it should use a static RFC1918 address and not use a DHCP assigned address.
The AD\DNS server should point to itself for DNS.
All other internal clients should point to the AD\DNS server for DNS.
You don't need to set up the AD\DNS server to use forwarders. You can configure it to use only the root hint servers (which is what I recommend). You also don't need to and shouldn't configure the AD\DNS server to use the DNS servers from the router or from your ISP.

If I'm understanding your question, I have the same setup at home and I suspect many of the admins here do as well. I have an internal AD\DNS server with a static RFC1918 ip address. The server points to itself for DNS and is configured to use the root hint servers and not forwarders for external DNS resolution. All internal clients point to the AD\DNS server for DNS. My router has a single dynamic public ip address from my ISP. I host email and web sites for my domains on my server. I use a dynamic DNS client and service to keep my dynamic ISP ip address synchronized with my public DNS records for incoming email and web visitors. I have port forwarding set up on my router to forward web and email traffic to the internal RFC1918 ip address of my server.
Comment: root hints it is--I was looking at it from a forwarding point of view.
Comment: I prefer to use just the root hints for the reason that if you use forwarders and the forwarders have problems it will affect the ability of your internal clients to get external DNS records resolved. We all know that ISP's are not always on top of their game when it comes to stability, reliability, etc.


Is there a way to load a spreadsheet to jenkins?

Question: I'm trying to write tests to load a spreadsheet that populates users to a program site.
I was wondering if I can have a spreadsheet loaded to the site when the test runs on Jenkins.
To be more specific, the application takes a spread sheet by browsing its location. What I want to do, is specify the location of the file in test environment, is this possible?
Answer: I wrote an example project that uses Java and runs your tests on SauceLabs.   This project is executed using Maven and so you can load it in Jenkins.  Also, there is an included example of driving a test from a spreadsheet.


Normalized probability distribution from the Coulomb/Rutherford scattering amplitude?

Question: My question appears elementary, but I have been pretty vexed trying to answer it precisely. Can one use the Rutherford/Coulomb scattering amplitude to get a finite, normalized momentum-space distribution for the outgoing particle state?
Specifically, consider an incoming wave packet $\psi_{in}(\vec{k})$ which is, let's say, a Gaussian in momentum $\vec{k}$ centered around some $\vec{k}_0$. Say this is a charged particle and it scatters off a classical Coulomb potential $V(r) = \alpha/r$. Naively, one would write the outgoing wavefunction as something like
$\psi(\vec{k'}) = \psi_{in}(\vec{k'}) + i \int d^3\vec{k} \ f(\vec{k'},\vec{k}) \delta(E_{k'}-E_k) \psi(\vec{k}) $
where the amplitude depends on the angle $\theta$ between $\vec{k}$ and $\vec{k'}$ as
$f(\vec{k'},\vec{k}) \sim 1/(1-\cos \theta)$.
As is well known, this thing diverges as $\vec{k} \to \vec{k'}$, so the integral blows up there, so the total cross section is divergent, and so on. That's fine. But one could ask for eg. the probability distribution
$dP(\vec{k'}) = |\psi(\vec{k'})|^2 d^3\vec{k'} \ \ \ \ (*)$
but it appears to be singular at every $\vec{k'}$ that's in the support of the incoming wavefunction, since at each such value the forward part of the amplitude diverges.
Is there a way to get around this and produce a finite distribution? What's particularly confusing is that one can actually invoke the optical theorem and show that, formally, $(*)$ integrates over all $\vec{k'}$ to unity, but on any finite region of $\vec{k'}$-space, the integral looks divergent!
(As a special case, consider the incoming packet to be a delta function $\psi_{in}(\vec{k}) = \delta(\vec{k} - \vec{k_0})$. Then the probability to scatter into any solid angle that doesn't include the forward direction $\theta = 0$ is manifestly finite, and you can use the optical theorem to write the probability for scattering into a small solid angle $\delta \Omega$ which includes the forward direction as $P = 1 - \int_{S^2 / \delta \Omega} d\Omega \frac{d \sigma}{d \Omega}$, i.e. as 1 - (the probability to scatter into any other angle). But if instead we consider an incoming wavepacket that has some finite support, this kind of trick doesn't seem to work...)
Answer: Just in case anyone was left hanging here, I think I'm satisfied for the time being by the "Coulomb wave functions". These things are exact, normalizable solutions to the Schrodinger equation with a plane-wave boundary condition. They aren't exactly of the form given above here, with a scattering amplitude in them, but you can form initial wavepackets and get well-defined answers that take forward scattering into account.


assembly find min max values

Question: My problem here is that using an input file where the first integer defines how many integers are in the file, (minus that one) and then sums all the integers, followed by finding the highest and lowest integers and printing them out.
My error is that the highest integer is not being found. I instantiated the high variable in the beginning with 0 so that it should be updated during the first pass, and it's never being updated, yet my lowest value is found and printed without problem, therefore I assumed my problem lay hidden in my jumps, but nothing I seem to change, or comment out changes my output. It must be a simple error, but I'm not very familiar with assembly and it's giving me a lot of problems.
<code>;; NASM program to read from cmd line arg, open file, read first line, and print first line to screen
;;  Uses fopen, fscanf, and printf
;; For help using the stack to write subroutines, consult the assembly lecture "Stack Basics and Procedure Calls"

;; nasm -f elf cfunctions.asm
;; gcc -o output cfunctions.o -m32
;; output input.txt

%include "mine.inc"

extern printf
extern fopen
extern sscanf
extern fscanf

%define STDIN 0
%define STDOUT 1
%define SYSCALL_EXIT  1
%define SYSCALL_READ  3
%define SYSCALL_WRITE 4

global main

section .data

read_char:  db 'r', 0
format:     db "%d",10,0
filename:   dd 0
file_pointer:   dd 0
number:     dd 0
string:         db "The integer is %d",10,0
sumString: db "The sum is %d",10,0
lowString: db "The lowest number is %d",10,0
highString: db "The highest number is %d",10,0

section .bss

  temp resb 8; reserves a lot for the manipulated item
  low: resb 2 ; reserves 2 bytes buffer for low, because if theres a low under 65k i'll be so mad!!
  high: resb 8; reserves a lot for a big number
  sum: resb 8 ; reserves a lot for the sum
  size: resb 2; only need a word for ints 1000 (hopefully)

section .text

main:

  ; instatiate the min and max values
  mov eax, 65535
  mov [low], eax ; starts the low really high
  xor eax,eax; sets eax to zero
  mov [high], eax ; high is now zero

    ;; Get the filename, pointer to input filename is returned, will equal 0 for an invalid filname
    push    dword filename  ; Push address of the pointer to the filename
    call    GetCommandLine  ; Return address pushed to stack, Go to line 72, GetCommandLine
add esp, 4      ; Resets stack value (equivalent to 'pop' inst)

;; (You need to insert code here to error check filename)

;; Open the file using fopen
;; Equivalent to eax = fopen("input.txt", "r") if programmed in C
push    dword read_char ; "r" to open a file for reading
push    dword [filename] ; filename from cmd line arg
call    fopen
add     esp, 8

;; Error check fstream returned from fopen
cmp eax, 0
je  Exit
mov [file_pointer], eax

;; Read a value from the file using fscanf
push      dword number  ; Address of 'number'
push    dword format    ; %d to read an integer
push    dword [file_pointer] ; fstream from fopen
call    fscanf
add     esp, 12

  mov ecx, [number] ;
  mov [size], ecx ;

  xor ecx, ecx

loopFile:

  ;; Read a value from the file using fscanf
      push    dword number  ; Address of 'number'
  push    dword format  ; %d to read an integer
  push    dword [file_pointer] ; fstream from fopen
  call    fscanf
  add     esp, 12

  ;; sum is calculated here
  mov eax, [number]
  mov [temp], eax ; temp is now the current number from the file
  add [sum], eax ;

  ;; lowest is calculated here
  mov ebx, eax;[temp]
  mov ecx, [low]
  cmp ebx,ecx ; compares if temp is less than lowest
  jl lessThan

  jmp highest ; test2 maybe it's not jumping

highest: ;; higest is calculated here
  mov ebx, eax; [temp]
  mov ecx, [high]
  cmp ebx,ecx
  jg higherThan

  jmp count ; test2

;; Print every int in the file
count:
    push    dword [number]
    push    dword string
    call    printf
    add     esp, 8

;count:
;counter of how many ints left
  mov ecx, [size]; moves into ecx
  dec ecx ; decreminte ecx
  mov [size], ecx ;

  cmp ecx, 0;
  jg loopFile ; jumps to the beginining of the loop

  ;; prints the sum
  push dword [sum]
  push dword sumString
  call printf
  add esp,8

  ;; prints the lowest
  push dword [low]
  push dword lowString
  call printf
  add esp,8

  ;;prints the highest
    push dword [high]
  push dword highString
  call printf
  add esp,8

Exit:
    mov     EAX, SYSCALL_EXIT
        mov     EBX, 0
        int     080h
    ret

lessThan:
  mov ebx, [temp]
  ;mov ecx, [low]
  ;mov ecx, ebx
  mov [low], ebx ; moves lowest into low
  jmp highest ; jumps to next comparison

higherThan:
  mov ebx, [temp]
  ;mov ecx, [high]
  ;mov ecx,ebx
  mov [high], ebx ; moves highest into high
  jmp count

GetCommandLine:

;; Macros to move esp into ebp and push regs to be saved
         Enter 0
         Push_Regs ebx, ecx, edx

;; Initially sets [filename] to 0, remains 0 if there's an error
         mov ebx, [ebp + 8]
         mov [ebx], dword 0

;; Get argc (# of arguments)
         mov ecx, [ebp + 16]

;; Checks the value of argc, should be 2 (a.out and input.txt), includes the if statement macro
     cmp ecx, 2
     if ne
        jmp gcl_done
     endif

;; Get argv[0] ("a.out"/"cfunctions" or the executable, this is not used in the project)
;; Consult slide 6 of Stack Basics... lecture
 mov ecx, [ebp + 20]    ;  ptr to args ptr
 mov ebx, [ecx]     ;  argv[0]

;; Get argv[1] ("input.txt")
     mov ecx, [ebp + 20]    ; ptr to args ptr
     mov ebx, [ecx + 4] ; argv[1]

;; Set the filename pointer arg on the stack to the address of the filename
     mov edx, [ebp + 8]
     mov [edx], ebx

gcl_done:
;; Macros to return
     Pop_Regs ebx, ecx, edx
     Leave

;; Return
     ret
</code>
Comment: Your `low` variable is too small. Make it a dword.
Answer: As Frank Kotler mentioned, the problem was that my low variable needed to be declared as a full 8 bytes. I believe when accessing memory, values were overlapping and changing my low value when storing new values in that accessed memory, but changing my low to 8 bytes fixed my problem.

assembly find min max values


Does gravitational lensing violate Fermat's Principle that light must travel in straight lines?

Question: Does bending of light due to warping of space violate Fermat's Principle or is it that in the principle light goes in a straight line with respect to space (taking space as the reference) and in Relativity that reference itself is bending and so does the light?
Answer: Fermat's principle is a bit more complicated than what you state: it says that in travelling from $A$ to $B$, light will go along the paths that will minimize the time taken to get there - and these may or may not be straight lines. (See e.g. Wikipedia.)
That said, the gravitational lensing of light does not operate quite like that. Since it is in vacuum, Fermat's principle demands that light travel locally in straight lines, which indeed it does: it travels in a null geodesic. However, since spacetime itself is curved, the path appears to bend with respect to the flat-space metric you'd have without the Sun's presence.
Answer: Well, needless to say that in curved space, one should use Fermat's principle for a curved space, which for instance is worked out in my Phys.SE answer here. The solutions are geodesics wrt. the optical path length. They satisfy a ray equation. It was shown in my Phys.SE answer here that this ray equation correctly accounts for the bending/deflection of light.


What's the silliest configuration mistake you ever made?

Question: You are a System Admin/Consultant and you have to deploy an application working fine on dev machine, but as soon as you deploy it on the production machine it does not work. What is the silliest configuration mistake you ever made?
Comment: this should be community wiki
Answer: I'm not sure these are silly enough, I must've done worse...
Almost 20 years ago, I was helping set up a new office and was getting the Internet connection going, setting up an HP/Apollo workstation as the main DNS server.  I learned the hard way about the need to include the . at the end of FQDNs.
While changing some connection in the server room and simultaneously in a wiring closet, I hooked the switches up in a loop.  It took a few seconds for the ports to saturate, and a few more to unplug the last few connections.
Comment: I think anyone who has ever hand-edited a zone file has done the "missing dot" thing at least once :-)
Answer: Worst configuration mistake that springs to mind: Renumbering a server and making sure to adjust all my server's Listen directives, my IP-Based vhosts, and the system's network configuration...
...then rebooting and realizing I didn't update the local firewall to pass traffic for the new network.  DOH!
Answer: I dont know if this counts or not.  We were on a very tight budget and needed to run 10 new CAT5 runs to a location in the middle of a concrete floor.  There wasnt any under-floor conduit available and the ceilings were cathedral with no crawlspace.  There was a row of low-hanging florescent light fixtures directly over the location where the CAT5 needed to be installed.  I proposed that we run the cat5 out of a wall at fixture-level, then run a piece of conduit 25' across the top of the fixtures to a column.  Then down the outside of the column to a box.
This looked and worked beautifully for years....until maintenance was called in to change one of the florescent tubes....access to the light was via the top of the fixture...which is where I had mounted 25' of conduit.
That light still had not been replaced.
Answer:
Configure router for RADIAS authentication
Think you have tested failback to LOCAL auth but havn't really because as that point in time your RADIUS and LOCAL passwords were the same
Need to move RADIUS server to a less secure network to allow normal users to vpn in via the firewall
Decommission Old RADIUS server
forget about router, never change RADIUS config
Try to log into the router ...

I'll give you 3 guesses as to how successful that was.
Luckily we only setup LOCAL authentication for serial line access (hey if you have access to the box to plug into the serial port ... well we all know the rule about physical access and security)
Answer: How about this?

Configured the Web site fine, but accessing a .aspx file gave "404 - File or directory not found". ASP.NET Web Service Extension was not enabled.
In IIS 7, you are planning to install SSL Certificate and under Request Certificate under Country code you don't see your country code. It can be added manually.
You complain, Web site hosted in production is having high CPU problem. Forgot to diable debug="true" in web.config


How to implement a unique ERC20 token for different assets

Question: I am trying to implement a way to tokenise real estate property. When a new property is added to the platform, the goal is to create a new instance of a Property and also create a new ERC20 token associated with that property.
I'm wondering what would be the best way to achieve this structure.
One solution I was working towards was having a contract erc20Factory, however, having multiple tokens would mean having a way to identify them and adding identification such as 'id' in every function would no longer meet the ERC20 standard. Is there another way to establish such association?
Would it be feasible for Property to store the address of its ERC20 token as an identifier?
Answer: Super feasible and makes sense.  I'd have both an ID and an address as identifiers.  You could even have the ID be a hash of details of the property so people don't try and mint different tokens for the same property.


How to Enable Search Engine Friendly URL's in Magento2?

Question: I am looking to use SEO friendly urls. What would be the best approach to do so?
Answer: As per official documentation presented here https://docs.magento.com/user-guide/catalog/catalog-urls.html:
Products

The URL key should consist of lowercase characters with hyphens to separate words. A well-designed, "search engine friendly" URL key might include the product name and key words to improve the way it is indexed by search engines. The URL key can be configured to create an automatic redirect if the URL key changes.

Categories

To prevent search engines from indexing multiple URLs that lead to the same content, you can exclude the category path from the URL. Another method is to use a canonical meta tag to let search engines know which URLs to index and which to ignore. By default, Magento does not include the category path in product URLs.

Also, please read the whole documentation on that link in order to understand the context and the appropriate settings.


How do I add mods to Minecraft on Xbox360?

Question: I play Minecraft on my Xbox360. I want to add mods on my Xbox360 but how do I do that? I would like to play the Pixelmon mod on my Xbox360 because I like Pokemon, but I don't know how.
Comment: Hello, I cleaned it up for you this time, but in the future please mind the spelling, and avoid typing in all caps. Also leave out the hashtags, they do nothing here. While we do not necessarily expect everyone to post in *perfect* English, we do request that some effort is made to write to the best of your ability in order to maintain a high standard of quality on our site. Please (re)read though the [tour](http://gaming.stackexchange.com/tour) and check out our [help pages](http://gaming.stackexchange.com/help) if you haven't already.
Answer: Modding in the console community is a rare instance. To allow modifications to your current game, you would require a JTagged console. Keep in mind that having a tampered console is against the Terms and Conditions enforced by minecraft, and you face the risk of receiving a console ban.
If you are interested in the use of modifications in microsoft, you may want to invest in a version of minecraft for the PC, as it fully supports mods. There is far less hassle, and you won't be banned.
Also, with that said. There are very select few modifications opened to the Xbox Minecraft community, as modifying the game is far more complicated than it would be on the PC platform.
Comment: "Unlikely" the only thing the games have in common is the theme and the name. One is written in java (which is quite friendly to being modded) and the other in C++ (which is uhm, not friendly to being modded except in ways the programmers build in explicitly)
Comment: Additionally, mods are typically built to run on specific versions of Minecraft - running a mod designed for version **1.7.x** on older (1.6.x) or newer (1.8.x) versions of Minecraft will often result in errors, crashes, and unintended behavior. As the Pixelmon mod is being developed for PC, it is unlikely that they have a version that is compatible with console-specific Minecraft builds (even if it were possible to mod the console version at all).


Why multiplication by numeral system base and raising to corresponding power converts any numeral system integer to decimal only

Question: I am not very good in math so I apologize if my question is too simple and does not belong here...
Why an integer in numeral system X can be converted to decimal by multiplying it's digits to X (meaning base of the numeral system) which is raised to corresponding power (0,1,2,3 etc)?
I mean that it seems like it is a universal way to convert any numeral system to decimal. But why there is no similar formula (involving multiplication by the base + exponents) to convert an integer of any numeral system to an integer in any numeral system?
Thanks!
Comment: Not sure this is clear.  Do you mean something like $137=1\times 10^2+3\times 10^1+7\times 10^0$?  If so, an analogous formula does hold for other bases.
Comment: Yes, that exactly what I meant. But could you give an example of conversion from binary to duodenary system using the same approach? Thanks
Comment: Conversion between bases isn't as simple as all that.  Think about decimal to binary, say.  you need to find the largest power of $2$ less than or equal to the given number, subtract that and repeat.  Simple, but not a closed formula.
Answer: There is such a formula. There is nothing peculiar about base $10$. Suppose that you this number: $1\,332$, which is supposed to be a number written in base $4$. And suppose that you want to exprees it in base $6$. So, you compute $2$, $3\times4$, $3\times4^2$ and $4^3$, but you express them in base $6$. You'll get $2$, $20$, $120$, and $144$ respectively. Then you sum them (doing all computations in base $6$, and you'll get the answer: $330$.
Comment: Ok, got it. Formula is the same for conversion to any other numeral system and my confusion was related to the EXPRESSION of the result in decimal system. So the result of conversion can be expressed in any required numeral system. Thanks for great explanation!
Comment: Yes, that's right.
Comment: Apparently this formula does not convert between numeral systems at all. It just simplifies conversion by breaking down a number to addends. By addends I mean each digit of a number multiplied by base raised to a power corresponding to this digit position. Like number 123 in base 10 can be represented as 100 + 20 + 3. Then each addend can be converted to any numer system one by one and a sum of these converted numbers expressed in required numer system will be a converted number.. It is more natural and easy for us to convert it to decimal.


Magento : Change Stock Availability From Dropdown to Text

Question: I want to change Stock Availability of product in backend, from drop down to text area to add custom text for product. My version is Magento 1.9.2.
Answer: I made an attribute called "customstock"
Then in public_html/app/design/frontend/base/default/template/catalog/product/view/type/default,phtml
I changed the code to
<?php if ($_product->isAvailable()): ?>

<?php echo $this->__('Availability:') ?> <?php echo $this->__('In stock') ?>

    <?php else: ?>

<?php echo $this->__('Availability:') ?> <?php echo $_product->getData('customstock'); ?>

    <?php endif; ?>


jQuery: Remove inline "display:none"

Question: I'm trying to figure out how to remove some inline styles from the current menu item in the navigation that jQuery is adding on hover. After hover, I want to still see the current menu item but the jQuery is adding display:none/
I added "display:block;" to the CSS for .current-menu-item but when hovering on nav, the jQuery is trigged and that is overridden by inline style="overflow: hidden; display: none;" in

Opportunities

Repro:
 1. Go here: http://clients.weinsteinau.cgvcreative.com/opportunities/

Note that the menu item that corresponds to the page appears below the navigation
Hover over nav
Note that the name of the page disappears from the navigation

Expected:
Hovering over nav should trigger all items to appear. After hover, the current menu item should retain display:block so it's still visible to the user.
I appreciate any help. Thanks!
Answer: Use !important, this will help overwrite inline styles from CSS here you can find more more information.
Here is how I fixed your CSS:

 /* line 90, ../scss/_nav.scss */
 .navigation ul li ul li.current-menu-item,
 .navigation ul li ul li.current_page_item,
 .navigation ul li ul li.current-page-ancestor {
   display: block !important;
   color: red;
 }

jQuery: Remove inline "display:none"


Why is this topological gate mentioned in Raussendorf et al. 2007 a CNOT?

Question: I read a Paper about quantum error corrections. I don't know why this is a CNOT gate. How to calculate this kind of CNOT gate as a topology form?
Answer: There are a variety ways of showing this, depending on your prior knowledge. The simplest is to know that you can convert a braiding diagram into a ZX calculus graph by changing each ring into a connected component of nodes of the same type and putting edges between components whose rings are of opposite type and linked:

becomes

which is the same as (by contracting adjacent nodes of the same color and discarding self-edges, which doesn't change the operation of the graph):

which is the same as (by discarding degree 2 nodes, which has no effect on the operation):

Which, if you're familiar with the ZX calculus, is the standard CNOT graph. You can evaluate as a tensor network to see that it corresponds to the unitary matrix of the CNOT.
Alternatively, what you can do is show that the topological construction supports parity sheets corresponding to the stabilizer tableau of a CNOT operation:
$$\text{Tableau}(CNOT) = \begin{array}{r|cc|cc}
& X_c & Z_c & X_t & Z_t \\
\hline
c & X & Z & & Z \\
t & X &   & X & Z \\
\end{array}$$
For example here is the parity sheet of the $X_c \rightarrow X_c X_t$ entry:

The main rule you need to know, in order to find these sheets, is that they can be extended through space arbitrarily but can only terminate on boundaries of the same type. So in this quick sketch above the rule I was following is that the "red" sheet could only terminate on the dark boundary, and I found a way to link a top-left tube to a bottom-right and bottom-left tube while respecting that rule.
I've given a talk going into this in more detail: https://www.youtube.com/watch?v=1ojXEEm_JiI
Comment: Thank you for your rich reply. I watched your video, really interesting. But I am still thinking about how to use a mathematical method to get this CNOT gate... It is my first time to see this kind of topology for gates.


Title of TV series or movie with four armed humanoid creatures?

Question: I am looking for the name of a tv series or movie in the 70s, feels very British, that had some human-like creatures (maybe smaller than normal humans) that had four arms.
Comment: This is very vague, are there *any* other details you can add?
Comment: The tone of the show/movie felt like a little like the Gerry Anderson series, U.F.O., but perhaps a tad darker.
Comment: I'm looking for something like that too. The four armed alien was humanoid and the second pair of arms were small like a child's arms set under the normal adult arms. The alien used these to shrink people and would leave them in a small case. The miniaturized people would be used to produce energy, somehow. But like the original poster said, it was like a 50's or 60's sci fi flick, I remember it as being Japanese though. But it was definitely dark.
Comment: That movie is called "Wild, Wild Planet."
Answer: The short-lived American sci-fi comedy Quark had a female four-armed space "telephone switchboard operator".
Comment: I will check that out, but I remember the show having a darker tone, more menacing...and perhaps even a little gothic like as if it was a Hammer film.
Answer: The movie you're thinking of is called, "The Wild, Wild Planet," from 1965. It's actually kinda sick and messed up for a movie of that period. It's an Italian film. It was the first of a series of four films set on the Gamma 1 space station, that took place in the same universe. One of the movies was more-or-less remade as the infamous Japanese film, "The Green Slime."
Here's the trailer for the movie
Comment: The ones in the trailer don't look all that short, but it is a decent guess, and a movie I'd never seen before. That said, it looks like JP discarded it in comments for the initial question.
Answer: Unfortunately, the description is still vague enough to cover a lot of ground.  For example, I bet you could find alien monsters-of-the-week with three, four, or more arms in more than one episode of "Voyage to the Bottom of the Sea", "Lost in Space", "Space: 1999", at least one of the "Star Trek" shows, any of the 60 or 70 years of "Doctor Who" shows, and so on.  The 1960s and 1970s saw a series of Mystery Science Theatre-worthy US/Italian/Japanese sci-fi coproduction films (including the infamous "Green Slime") that could fit the bill.  The description might fit the 80s cult horror film "The Gate" (kids play a heavy metal record backwards, open a gate to hell, and unleash a horde of little gremlin-things led by a giant 4-armed monster).  Multi-armed clay-mation nasties were standard fixtures the Harryhausen mythology films (Sinbad, Jason and the Argonauts, etc.) and elsewhere ("Equinox", for just one example).  I think the Martians from the short-lived 1980s "War of the Worlds" television show might also fit.
Any chance of remembering anything special about the outfits the creatures wore, the things they did, the setting or plot, or anything like that, which might narrow things down a bit?


My transaction failed due to running out of gas. Can I recoup this money?

Question: My transaction failed due to running out of gas. Can I recoup this money?
I was trying to send to Monaco card via my token wallet. Below is the transaction id. For some reason, it charged me £159 for sending £99 dollars. Could someone please help me out, as i am clueless as to what to do.
https://etherscan.io/tx/0xda8c0b80d8e240a83c8f6b067c4656babeb13e8e0ece4fd4292aa06252f1285c
Answer: That transaction had a very high gas price specified (0.000025 Ether, 25,000 GWei), while currently transactions are getting confirmed for much lower (0.000000002 Ether, 2 GWei). And the transaction only specified a max of 25,000 gas units, which is pretty low. So, your transaction burned up the maximum amount (25,000 * 0.000025 = 0.625 Ether), and still failed, unfortunately.
Those funds are gone, unfortunately. Whatever client you were using should have calculated the amount of gas units needed more accurately, and should have let you set the price per gas unit much, much lower than that. Send that transaction to the support team of the wallet you were using to send it, as that is likely a bug they should fix in their code, so others don't encounter it too.
Comment: This answer seems to imply that the 'out of gas' was in some way the result of the gas price specified. This is not correct. gasPrice has nothing to do with how much gas is used. Think of it this way: if you pay $1,000 a gallon for a gallon of gas you can still travel 25 miles. Same as if you paid $1 for a gallon. Gas gets consumed by the gallon. Price has nothing to do with it. The reason the transaction failed is because it didn't have enough gas. The reason it cost so much is because you paid too much per gas.
Comment: Yes, there are two problems that combined in this transaction to make it a problem. Your last two sentences are a great summary of the two issues!
Answer: I'm sorry, but no, when the gas limit is hit the transaction is cancelled and you lose the entire gas amount as the transaction fee, ~$161 in your case.  This sucks, but is an important behavioral incentive in the network.
You can see your details here:
https://etherscan.io/tx/0xda8c0b80d8e240a83c8f6b067c4656babeb13e8e0ece4fd4292aa06252f1285c
Comment: I've been trying to understand ridiculously high gas costs or rather how my Ethereum Wallet sets them, and more importantly how new users can avoid accidentally getting gouged.   I've seen ranges for simple transactions cost between .5 Ether and 2 Ether and my client doesn't allow changing the cost to anything reasonable.   I can see new users easily falling victim to such high costs.  Finding this post just supports my concerns that it is possible to pay way too much for a simple transfer.  Can you clarify what you mean by "behavioral incentive"? It sounds like this is bad, but by design.
Answer: Yes a costly mistake, but I bet I won't do it again. I got burned on 7 contracts before I learned. Chalk it up to a loss and make another contract while it's cheap, because I don't know about you but I plan to help take ethereum past bitcoin
Comment: That's the spirit !
Answer: No, unfortunately. I recommend you one thing:
For testing purposes, visit remix.ethereum.org
In the "Run" panel make sure you select JavaScript VM
Every time you run a transaction, you'll be able to see an estimated gas cost by inspecting the contract information created in the console.


Is there a way to get old posts from a blog regularly via an RSS feed?

Question: I know many blogs that posted really good stuff a few years back but have become inactive now. I want to read the posts but it is very inconvenient to go to the blog's website daily and read one post and remember which ones you have read. So, is there a service that can periodically deliver these old posts (say one per day or week) as an RSS feed/email?
Comment: Unlikely, but not impossible. RSS Feeds are usually generated by the blog-site itself. An "external site" would need to know "internal structures" of that site to do so, or the feed most likely results in "random order". Not all blogs e.g. present time stamps with their articles – or if they do, in very different ways, so that's pretty hard to achieve.
Answer: RSS/ATOM feeds are generated by the website as @izzy mentioned up there. The related CMS allows you to select how many recent posts should be available in RSS feed link. If you select a big number, that'll generate a giant XML file which will make it tedious for the readers to access and browse the items, therefore the common thing with websites or blogs is that they choose to display a small number of the most recent items in the feed, e.g. 10, 20.
However there may be occasions where you might want all items in the feed URL. I was working on a podcast app that used the RSS link to parse and display the items, and I wanted it display all episodes of the podcast. What I did was to ask the blogger to change the number of items for the feed, save that XML file that contained all the items from the beginning up to now, and upload it on my own server. Writing a script, I could check the RSS link for the new items, and if any, have the script write it into the file on my server and keep it updated. Doing this, I'll have an XML/RSS link having all the upcoming items forever!
I know it's a bit complicated, but if you're planning to be able to read the current posts in the future, you can do something similar, but if you want the already-expired items in the RSS, then it'll be a bit difficult without getting in touch with the blog author.


Formal epistemology starting point

Question: After an introductory course in logic (propositional and predicate calculus) and the article on the SEP, where and how should one start studying formal epistemology?
Comment: Ignore the "answer" below for starters. Learn a bit of probability theory, a bit of inductive logic, a bit of modal logic. Check out the recommendation above as well as articles in [this collection](https://smile.amazon.com/Readings-Formal-Epistemology-Sourcebook-Philosophy/dp/3319204505/ref=sr_1_3?ie=UTF8&qid=1522113392&sr=8-3&keywords=formal+epistemology) (many of which should be freely available).
Comment: Maybe useful: Vincent Hendricks, [Mainstream and Formal Epistemology](https://books.google.it/books?id=Bjnje5u2q9cC&printsec=frontcover), Cambridge (2006) and [Readings in Formal Epistemology: Sourcebook](https://books.google.it/books?id=LpBPDAAAQBAJ&pg=PR3) (2016).
Answer: I don't understand what you mean by formal epistemology.
If you want to create new knowledge the knowledge you create often doesn't fit in to existing formalisms. So if formal epistemology involves describing the creation of knowledge in terms of formalism, then it's not going to be any use in most interesting cases.
As far as the use of logic in epistemology is concerned, a lot of the field is still enamoured with inductivism and the idea of justification despite the enormous unsolvable problems with such approaches and the existence of a viable alternative:
Deduction vs Induction -- are they equally valid?
Do all epistemologies suffer from the "regress of justifications" problem?
My main recommendation is to read the references given in the answers I cited above.
Comment: This is a really bad answer. If you don't know what formal epistemology is, then you're not qualified to comment. Your second paragraph is nonsense, while the third paragraph is patently false. And the fact that your "main recommendations" are your own answers on this site is just gross. -1
Comment: Oh, you've read "books about epistemology"? You must be qualified to make sweeping claims about the entire field without a shred of evidence, then. I guess my first comment was way out of line. (To anyone who happens to read this in the future, please bear in mind that crackpots who make claims like "This entire discipline rests on mistakes that no one but me is smart enough to recognize" should simply be ignored.)
Comment: I have read books about epistemology. The authors of most of those books have in general started with a mistake, have ignored criticism of that mistake and have proceeded to write a vast body of material that solves no real problems.
Comment: @aduh The mistakes have been recognised by other people, e.g. - by Popper and some others who took account of his ideas. The books I have read about epistemology include Howson and Urbach's "Scientific Reasoning: The Bayesian Approach", Bovens and Hartmann, "Probability Theory: The Logic of Science" By Jaynes and many others. Unfortunately when people ignore problems with their position, I can't provide specific quotes from them about the problem they don't mention. All I can do is point out that there are accounts of the problem and there are solutions.

Formal epistemology starting point


An intuitive proof of Prokhorov's theorem

Question: I just want to understand why tightness condition implies that the measure sequence would admit a converging subsequence. I wonder if someone can explain to me how Prokhorov's theorem is proved intuitively without too much analysis formalism. Why not being able to escape to infinity warrants convergence?
Comment: Kindly state the version of Prokhorov's theorem that you know, so that others can begin their answer without confusion of notation etc. Also, it helps (but is not necessary) if you've seen a formal proof of Prokhorov's theorem.
Answer: I always thought the example given in Billingsley 's book was illustrative as to why tightness is needed for this result. Consider the sequence $F_n$ of distribution functions
(or the associated probability measures on $\mathbb{R}$) corresponding to $Unif(-n,n)$ random variables. In this case every subsequence converges to the limiting "extended distribution function" $F_\infty(x)=1/2$. Notice that this CDF does not correspond to a probability measure on $\mathbb{R}$, and intuitively why this is occurring is that the mass of the distributions of $F_n$ is escaping to infinity. In general it can be shown that every sequence of CDF's must have a subsequence converging to some sort of "extended distribution function" like the example above (this is usually called Helly's selection theorem). Tightness it turns out is a necessary and sufficient condition to imply that this extended distribution function corresponds to a probability measure. See the below slides regarding Helly's theorem.
https://faculty.math.illinois.edu/~psdey/MATH561SP19/week10.pdf
Comment: The link is broken

An intuitive proof of Prokhorov’s theorem


Connection and curvature using differential forms

Question: I am trying to understand how one would use differential forms to calculate the components of the connection and the curvature tensor given a metric. Can anyone point me to relevant resources for the same? I have a basic understanding of differential geometry.
Comment: see also [Textbook on Differential Geometry for General Relativity](https://physics.stackexchange.com/q/266451)
Answer: There is an example of deriving the Schwarzschild metric using tetrad formalism in Wald's General Relativity. Note that he uses abstract index notation instead of differential forms notation, however this is purely a notational difference on his part, the procedure is completely analogous.

The general methodology is however as follows:
1) Cartan's first equation of structure is $$ T^a=d\theta^a+\omega^a_{\ b}\wedge\theta ^b. $$ For a torsionless connection, this is $$ 0=d\theta^a+\omega^a_{\ b}\wedge\theta^b, $$ where $\theta^a$ is the covielbein and $\omega^a_{\ b}$ is the connection form.
If the connection is also metric compatible, then we have $$ (d^\nabla g)_{ab}=dg_{ab}-\omega^c_{\ b}g_{ac}-\omega^c_{\ a}g_{cb}=0, $$ which imply that for an orthonormal/rigid frame ($g_{ab}=\eta_{ab}$) we have $$ \omega_{ab}=-\omega_{ba}, $$ so in this case the connection form is $\mathfrak{o}(1,3)$-valued (skew-symmetric when both indices are lowered or raised).
We know from pseudo-Riemannian geometry, that the torsionlessness and metric compatibility condition determine the connection uniquely, so together with the antisymmetry condition, Cartan's first structure equation can be used to calculate the connection.
2) The equation $$ 0=d\theta_a +\omega_{ab}\wedge\theta^b $$ consists of 4 2-form equations. By writing out the basis expansion of $\omega_{ab}$ explicitly, you can obtain all the connection 1-forms (I have purposefully lowered everything, as the antisymmetry condition can be used more effectively this case).
3) To calculate the curvature, the second structure equation of Cartan is directly utilized: $$ \Omega_{ab}=d\omega_{ab}+\omega_{ac}\wedge\omega^c_{\ b}. $$
Basically, everything's known here, so you can just plug in everything and calculate separately $\Omega_{01},\Omega_{02},\Omega_{03},\Omega_{12},\Omega_{13}$ and $\Omega_{23}$. You're done.
Notes:

It is preferable to express the differential form using the coordinate basis, so what you'll get for the connection form for example is $\omega_{\mu\ b}^{\ a}\mathrm{d}x^\mu$.
Calculating the connection form is the "hard" part here - it is only slightly easier/faster than using the coordinate basis formula for the Christoffel symbols - however calculating the curvature is MUCH easier. In the coordinate basis approach you need to manually ennumerate all independent components and calculate them, which is a hassle, while here you only need to calculate six 2-forms, you are essentially bundling together multiple calculations efficiently into strings of components.
Comment: Thank you uldreth for your answer. I will read the section from Wald. I think the differential forms method is good in the way that components that are zero are automatically eliminated unlike the coordinate approach where one needs a bit more work.


Current 'Users Online' Script

Question: What is the best script to use for showing the current visitors or guests Online?
Thanks!
Answer: As @Ryan Smith suggested, this greatly depends on the implementation details of the website. I'm sure that there is a off-the-shelf framework offering a storefront application with all the bells and whistles (such as the types of scripts you are mentioning); however, these can range anywhere from being free and open source, or very expensive.
Implementing a script like this yourself isn't very difficult. Assuming that you're keeping track of the users on the website in some form of data store (typically a backend database) you could do something like this:

When the page loads, fire a JavaScript that makes an Ajax request
Have the page that's the target of the Ajax request select a count of the number of rows in the table storing the active users. Return this result.
When the request completes, have the Ajax callback insert the number into the DOM in whatever place you'd like.

You can set this process to repeat at certain intervals so that the pages containing the script are dynamically updated showing a relatively up to date count of the number of users online.
Answer: I think it all depends on how your tracking who's online within your application.
Usually, when someone logs-in, you create a session for them that you could iterate through based on whatever language you are using.
You have to keep in mind that HTTP is a stateless environment, so determining when someone is online is largely subjective as to your opinion as to how long ago they logged in.

Current 'Users Online' Script


jquery cycle IE7 transparent png problem

Question: I'm having trouble getting jquery cycle to work when I have transparent png files in IE7
It's fine in Firefox and Chrome but in IE (version 7) I get a black colour where
the png transparency is during the fade.
Can this be made to work right?
Answer: unfortunately, though IE7 supports transparent PNG's, only one filter can be applied to an element at a time.
What is happening in your application is that IE7 is applying the alpha filter to your PNG, and is then asked by jQuery to apply another alpha filter for the fade. This has visible results like you said.
The way to get around this is to nest your png inside a container and then fade the container. Sort of like this:

Another way to get around this is this simple jQuery plugin that i used because i couldn't change the structure. I would give attribution but I honestly cant remember where i found it.
/* IE PNG fix multiple filters */
(function ($) {
    if (!$) return;
    $.fn.extend({
        fixPNG: function(sizingMethod, forceBG) {
            if (!($.browser.msie)) return this;
            var emptyimg = "empty.gif"; //Path to empty 1x1px GIF goes here
            sizingMethod = sizingMethod || "scale"; //sizingMethod, defaults to scale (matches image dimensions)
            this.each(function() {
                var isImg = (forceBG) ? false : jQuery.nodeName(this, "img"),
                    imgname = (isImg) ? this.src : this.currentStyle.backgroundImage,
                    src = (isImg) ? imgname : imgname.substring(5,imgname.length-2);
                this.style.filter = "progid:DXImageTransform.Microsoft.AlphaImageLoader(src='" + src + "', sizingMethod='" + sizingMethod + "')";
                if (isImg) this.src = emptyimg;
                else this.style.backgroundImage = "url(" + emptyimg + ")";
            });
            return this;
        }
    });
})(jQuery);

NOTE Originally the plugin was written to fix PNG transparency in IE6 but I modified it to work with your problem in IE6+.
Sidenote: I cant remember off the top of my head but i think that IE8 may have the same problem. Correct me if i'm wrong :)
Comment: Yes it appears IE8 also has this problem
Comment: I can also confirm that this is a problem in IE8, just in case anyone is still having doubts.
Comment: I would give this significantly more than +1, if I could.
Comment: have you tried dd_belatedPng (http://www.dillerdesign.com/experiment/DD_belatedPNG/)? It uses VML and should work with the fades (e.g. filter:alpha(opacity=n));
Comment: Amazing dude you are awesome.
Comment: @DavidMurdoch Unfortunately, that does not work for IE8 unless you force compatibility mode to emulate IE7 which seems a bit backward.
Comment: The first method works in IE8 (and 7?) if the outer container has an opaque background color. Otherwise, no joy. Kind of defeats the purpose of using PNGs with transparency.
Comment: Not sure what my issue was with the jQuery plugin method, but I wrote a plugin based on [an answer to a related question](http://stackoverflow.com/questions/1204457/how-to-solve-hack-fading-semi-transparent-png-bug-in-ie8/4126528#4126528) and noticed that it's basically the same as this. I probably screwed it up some how before. Here's [my version](https://gist.github.com/1318344).
Answer: This has been driving me mad for the last few days! Finally found a decent solution that works pretty well.
Add this to your CSS:
img {
    background: transparent;
    -ms-filter: "progid:DXImageTransform.Microsoft.gradient(startColorstr=#00FFFFFF,endColorstr=#00FFFFFF)"; /* IE8 */
    filter: progid:DXImageTransform.Microsoft.gradient(startColorstr=#00FFFFFF,endColorstr=#00FFFFFF);   /* IE6 & 7 */
    zoom: 1;
}
Credit: Dan Tello
Comment: I tested several other fixes and found they made IE slow, with this one it is blazing fast
Comment: This worked great for me on IE8 - I did not test on IE7.  The other solutions in this thread did not work in my case.  Thanks!
Comment: So far the only fix that has worked without fail for me! Thanks!
Answer: Try adding
cleartype:  true,
    cleartypeNoBg:  true
to your cycle jquery arugments.
It should be fine now :)
Comment: This combined with using png8 works for me on IE7, but not on IE8 - as with rjmunro, I get a thin black border during the transitions.
Comment: For us, that didn't work while the images are acutually transitioning. The black appeared during the fade, then disappeared after.
Comment: Why this isn't the best answer is beyond me. This is the solution to the problem.
Comment: This saved the day for general HTML slides in JQuery Cycle for me. Thanks a lot!
Answer: Coupled with the "wrap the image in a div / fade the div" tactic previously mentioned, using this line of CSS will fix the IE issue:

#div img {
    filter: progid:DXImageTransform.Microsoft.AlphaImageLoader (src='../images/bubble_intro_ph1.png');
}
Answer: For me it worked to just include the filter property with blank value in jQuery's .animate()function
Maybe this will work for you, too.
$("#btn").animate({opacity:1,"margin-left":"-25px", filter:''});

Comment: this just disables the animation all together, but fixes the image-problem. Fine for me as a solution :)
Answer:
Internet Explorer 7 has some issues
  with fading transparent PNGs. If
  you've gotten to the this page because
  you're seeing a black border where the
  transparent edges in your PNG are,
  then here are some tips for fixing the
  problem:

Do not fade the element directly, but fade a parent container
  holding the PNG. This may mean you
  need to add a wrapper element to your
  code.
Give the parent element a background color.
Lastly, if you're still having problems, try giving your parent element
  the old zoom: 1 trick. Give the
  parent element a style declaration of
  zoom: 1 (either via CSS or an inline
  style.) This will force IE to give the
  element hasLayout—which tends to fix
  all sorts of weird display issues in
  IE.

Source: Fading a 24-bit transparent PNG in IE7+
Unfortunately, this means that it's impossible to have transparent PNGs fading in over a transparent background, since you have to apply a background color to the parent element in order for the transition to go smoothly, i.e. without the black pixels. background: transparent won't work (since transparent isn't really a color). :(
Answer: I'm loading some png's dynamically into the DOM... this worked for me: http://www.twinhelix.com/css/iepngfix/
Answer: I've got the ultimate solution for this damn IE-PNG-BlackBorderProblem when using fading or other jQuery effects. It is working in every IE > 6 even in IE8!:

Download jQuery's pngFix at: http://jquery.andreaseberhard.de/pngFix/
Modify this script by searching:
if (jQuery.browser.msie && (ie55 || ie6)) {
and replace it with:
if (jQuery.browser.msie) {
create a blank.gif (1x1 transparent gif)
put a:
.pngFix( {blankgif: '< relative location to the blank.gif >'} );
at the end of the line where you perform jQuery effects eg.
$('#LOGO').animate( {'top': '40%', 'opacity': '1.0'}, 2500 ).pngFix( {blankgif: './library/img/blank.gif'} );
make sure that all pictures have been loaded before you use jQuery effects within your document ready function by using the .load event on the window DOM-Element:
$(document).ready( function() {
$(window).load( function() {
$('#LOGO').animate( {'top': '40%', 'opacity': '1.0'}, 2500).pngFix( {blankgif: './library/img/blank.gif'} );
});
});
Load page in IE8 and feel happy ;-)
You can see it in action on http://www.claudworks.net

No ugly dark borders anymore around some animated PNGs in IE.
Answer: I had this problem with Drupal Views Slideshow using the Fade transition on transparent PNGs.
I stumbled across the following quasi-solution totally by chance. I don't know why it works, but the drawback is it essentially removes the cross-fade envelope in IE (it doesn't appear to visibly affect FF or Safari):
Views Slideshow will print something like the following as part of its output:

I hid views-field-field-photo-fid:
.views-field-field-photo-fid { width: 0px; }

Not perfect but maybe good enough till I find a better solution. You can take a look at the development site: http://acupuncture2.polishyourimage.com/
Answer: I'm also using Weezy's solution but doesn't play nice with IE7. The effects is even worse.
When assigning jQuery opacity-property to animate-function instead of Black-Border-Bug it generates a Black&White-Border-Bug :-P So I did the following for IE8;
In the head IE8 conditional comment with the HTC behavior on class .fixpng especially for htc.

changed HTC-file to IE8pngfix.htc. Changed line 75 in the .htc to

!/MSIE
  (8)/.test(navigator.userAgent

It's actually double-filtered, first IE conditional and then in htc, but what the hell!
I found that because htc could interfere with jQuery. Example;

  [div id="tooltip" class="fixpng"]

Had to change $(div#tooltip).css({opacity: 0}) to display:none in CSS and set display: 'block' in hover-event.
So if anybody has found a working solution for IE7 I would be really happy. All the workarounds /hacks above don't work for me. About IE6 I don't care any second.
Answer: Ok so I took Darko Z suggestion about the div. In the end this is what I had to do to be able to get jQuery Cycler fadeing FX to work on IE with drupal 7. Instead of placing an  tag I used divs and applied the.png to the background of the image along with
So I changed this:

to this:

then in the css I did:
.fademe{ width:640px; height:330px;}
#TAB1{ background: #999 url(http://mysite/IMG/bio_640x330.png) no-repeat;}

and it works for now =D.
Hope it helps,
Defigo
Answer: I found the fix to this bug, simply add the following to the wrapping div and to the img and other elements (e.g. h1,h2,p)
#div, #div img {
    background:none !important;
    filter:none !important;
}

This will fix it
Comment: This does work if you don't miss out the !. Also background property is not necessary.
Answer: This drove me mad for a couple of days and I finally stumbled across Unit's PNG fix. http://labs.unitinteractive.com/unitpngfix.php - works with Cycle and stopped me from switching to a JPEG solution!
It needs a bit of tinkering to target specific PNGs in the cycle div, but she works!
Answer: Hoping to help somebody else who encounters this problem:
I had transparent .png backgrounds (tiled) on a few divs on my page and when I activated the jquery cycle plugin, those transparent areas became screwy. They lost some of their transparency.
My solution was to simply make the tiles much bigger, so there really is no tiling at all. There is a small trade off for file size, but it fixed the problem.
Answer: I rewrited the fadeIn and fadeOut methods. It seems I don't get the black color on PNG image. No parent div is needed. Still you use as jQuery.
http://www.pagecolumn.com/javascript/fade.htm
Answer: If you can afford to sacrifice a bit of image quality, you can save the images as PNG-8 instead of PNG-24, then apply the fix mentioned by Prosini, i.e.
cleartype: true, cleartypeNoBg: true

and that should work. With PNG-24, I was still getting a bit of black border during the transitions.
Answer: While not specifically limited to the cycle plugin, this may help others. I came across this stream in my attempt to find a solution to .animate() transparent/translucent png files.  I had the issue of a black border occurring in both IE7 and IE8.  The images appear fine until I attempted to use JQuery to animate the opacity...
$('#my-png-img').stop().animate({opacity:0.0},3000);

I went thru a number of the solutions and unfortunately, none of them were ideal.  While this stream is a bit dated, it may help someone else still searching to piece together a solution. I ended up using the Twin Helix solution (http://www.twinhelix.com/css/iepngfix/) with a bit of a tweak.  I'm not a huge fan of .htc files but that's beside the point.  I edited the iepngfix.htc file (~line 75) to trap for IE7 and IE8.  I changed...
!/MSIE (5\.5|6)/.test(navigator.userAgent) ||

to
!/MSIE (5\.5|6|7|8)/.test(navigator.userAgent) ||

From there I followed the general instructions (see demo) including adding this bit to my CSS
/* IE PNG Fix */
img, div, a, input {
    behavior: url(/_css/iepngfix.htc)

}

In addition and as others have mentioned,  I had to nest my image in a container...

Then I applied .animate() effect to the containing div.  A bit constraining however, this was the only way I was able to get fading to work consistently.  In one case, I even found that the transparency issue affected animating the opacity on a transparent .gif file.  Oh and, whether I used .fadeIn()/.fadeOut rather than .animate() made no difference.
Comment: This doesn't work for me. My images are applied via the css background property, so I can't "wrap" them in a div.
Comment: FWIW, .fadeIn() and .fadeOut() just call the .animate() function internally in jQuery.
Answer: Weezy's solution worked for me!
I tweaked the .htc file further, and changed this line:
var bgPNG = bgSrc.match(/url[("']+(.*\.png[^\)"']*)[\)"']/i);

to:
var bgPNG = bgSrc.match(/url[("']+(.*\.fixme.png[^\)"']*)[\)"']/i);

By doing this, the .htc script will ignore all .png files unless they end with .fixme.png (for example "transparant.fixme.png").  I intended this to speed up the script a little and ensure that only problem .pngs are fixed (the ones you must have transparant).
I use other .pngs which are not transparant, and therefore don't need this script to run against them.
Answer: The best fix is unitpngfix.
Include it in your script and be sure to provide the path to your 1px by 1px transparent gif. Voila!
Answer: This is all pretty hectic stuff you're being asked to do. All very coding codingsky.
Here's my suggestion. IE will not allow a png background above a colored background to live in peace, like so...

Notice the first div is z-index 2(on top of 2nd div).
This can be simplified by putting your bgColor in the background css in the 1st Div and doing away with the second div. This solves the problem of the black areas. I had this problem myself.
The only way I can see you having a problem where you can't use this method is where you have the need to overlay two png background images over one another and fade simultaneously. Don't do that. You'll need to animate each one after one another.
Answer:
Define a solid background color to your image:

    .container img {
         background-color: white;
    }

Define the background-image css property of your image to its src attribute:

    $('.container img').each(function() {
         $(this).css('background-image', $(this).attr('src'));
    });

Advantage: you don't need to change your markup
Disadvantage: sometimes applying a solid background color is not an acceptable solution. It normally is for me.
Answer: To solve this issue simply add:
"filter" : ""
to your .css() or .animate() and it'll fix a number of IE related issues.
Answer: The most reliable solution is to not use pngs in fading style animations in <IE9 browsers.
I tried nearly every "fix" and variation of a fix available that I could find for this issue and had no success. The solution I used was to export pngs that were going to have fading-style animations applied to them (ie, fadeIn/fadeOut) to gifs and do a conditional replacement for <IE9. Although the gifs don't look as good as pngs in a modern browser, they look a hell of a lot better than the way IE8 and earlier render pngs, and this method works reliably. You still get to display nice pngs for capable browsers and when the fix is applied nothing else gets broken; most of the png hacks are known to break other css properties. Your code might look something like this:
$(document).ready(function ()
{
      if ($.browser.msie && parseInt($.browser.version, 10) < 9)
      {
          $(".myClass, .myOtherClass").each(function (val)
          {
              var backgroundValue = val.css("background-image");
              backgroundValue.replace('.png', '.gif');
              $(this).css("background-image", backgroundValue);
              //you could just as easily do this with 'img' tags
          });
      }
}


Classical force keeping electron in orbit around proton in hydrogen atom

Question: In terms of Classical Physics, what force would be required to hold an electron in orbit around a proton, i.e., an hydrogen atom?  I have done a calculation, but need verification.
Comment: What's your calculation?
Comment: Embarrassing, but I simply took the Bohr Radius, and plugged it into the Coulomb force equation!  I know.
Comment: Countt010, I am trying to get a thumbnail calculation for A Level students, such that they can appreciate the idea of producing protons for use in a collider.  I know I have oversimplified, but...
Answer: I've made a numerical answer to complement the existing answer, with some sanity checks along the way.  I trust that you know that this is entirely a toy universe, and none of this stuff has very much meaning, as said in the other answer.
Speaking entirely classically, an electron orbiting a proton will feel a Coulomb force of:
$$F=-\frac{e^2}{4\pi \varepsilon_0 r^2}.$$
If the electron is staying at constant $r=r_B$, then this force must be balanced by another force.  The magnitude of this force is found by plugging in the right constants, as:
$$F=8.24\times 10^{-8}~N.$$
Sounds small right?  Consider the acceleration this force would correspond to, through Newton's second law as:
$$a= \frac{F}{m} = 9.05 \times 10^{22}~m s^{-2}.$$
Now that is huge!  But that's of course understandable.  Consider this force coming from centripetal acceleration by being in circular motion, then the velocity the electron would be moving at would be:
$$v=\sqrt{\frac{F r}{m}} = 2.18 \times 10^6~ ms^{-1}.$$
That does of course mean the electron orbits ~$10^{15}$ a second, around a tiny tiny amount of space.  To get an electron travelling at $2.18 \times 10^6 ~ms^{-1}$ to completely change its velocity vector $10^{15}$ a second is going to require a mighty acceleration.
Comment: Yes, I do know this is not valid.  However, as an exercise in thought, leading to an analysis of why it is not valid, it is a useful entree for my students.  As you point out, and I also calculated this, the acceleration is, er..., quite large.  But thanks for your time.
Answer: The classical model (planetary model) states that, in a similiar manner to planetary orbits, where the gravitational force is balanced by the centrifugal force, the electron is held in balance of electric force and centrifugal force.
This theory fails, as we know, because accelerating charges radiate, thus losing energy and inevitably falling into the nucleus.
This problem is solved in the quantum viewpoint- the energy of an electron around the atom is quantized. First came the bohr model which was simply a quantized version of the planetary model (only certin radii are allowed). Then came the de-Broigle model, where the electron takes it's wave-like form and can only be found in radii where it can form a standing wave.
The modern conception is that of orbitals- the electron is merely a probability density around the atom, which behaves according to the different spherical harmonics.
Comment: Electron isn't probability density. Density, wawefunctions etc. are only ways to describe it's behavior.
Comment: @Mithoron I think this is more a discussion of semantics- the probability density is as much "the electron" as the particle is- until it isn't measured, it is superposition-ly "smeared" on the entire distribution


Areca Palm isn't thriving the way I expected

Question: So, here's a photo of my dypsus lutescens. As you can see from above, the plant is very much alive, and new leaves (?) are sprouting. However, they immediately drool. It's as if the weight of the leaves is too heavy for the thickness of the stalks. So instead of having it growing vertically, as I usually see them doing, it's growing horizontally and occupying the area around (not above) it.

I keep the soil relatively moist, although the top 2 inches look... weird. As if it has some kind of mould? Not sure. I used a fork to get rid of the clumps, and the deeper soil seems normal. You can observe some leaves with brown tips, which might indicate underwatering. There's also some browning of the stalks, that can point towards a fungal or bacterial disease?
The plant is kept inside, with indirect lighting (4m and 2m away from windows A and B). The temperature is always between 23 and 26ºC; humidity is usually less than 50% (London, UK); not ideal. The coffee shop right across the street has some luxurious Areca Palms, and I would say that the light it gets there is way less than mine (but maybe the artificial lighting in the ceiling helps them). The hardness of the water here is crazy (25 <= DH < 50) though.
My current plan is to repot it (try to get rid of that mould like appearance in the soil). I have a feeling that I will find some rotten roots. The overall plant size is not that big, but I can observe dark roots coming out from the drain holes. I am also thinking in potentially use some physical help (a cord?) around the stems/stalks to force them to stay vertical.
What would you recommend?
Answer: Much more light, remove the stones and odd things that are on top of the soil
No need to repot, just water less
Comment: Yup, move to the window or expect it not to thrive. Could add 2 cups of fresh soil on top, too.


Isometric embedding of a genus g surface

Question: Can a genus $g$ surface with constant negative curvature and $g>1$ be isometrically embedded in $\mathbb{R}^4?$
Comment: Relevant: https://math.stackexchange.com/questions/1528046/can-a-hyperbolic-surface-be-isometrically-embedded-into-mathbb-r4
Comment: You might be interested in [this question](https://mathoverflow.net/q/37708/21564) and its answers.
Comment: Is there any example or counter example?
Comment: So, is this an open problem?
Answer: The Nash-Kuiper Theorem implies the answer is yes if you only require the embedding to be of class $C^1$.  However, I believe the actual visualization problem for $g\geq 2$ (that is, producing the embedding in this case) is an open problem (unlike the visualization of the $C^1$-embedding of the flat torus, which has a $C^\infty$-isometric embedding into $\mathbb{R}^4$).
Since the smallest known $C^\infty$-embedding for the hyperbolic plane is $\mathbb{R}^6$ I would guess the answer is no for a genus 2 hyperbolic surface (but as far as I know it is open).  Note it is a theorem of Hilbert that the hyperbolic plane cannot be $C^r$-embedded into $\mathbb{R}^3$ for $r\geq 2$.  Later Efimov generalized this to closed hyperbolic surfaces.
I believe these facts and references may be found in:
Isometric Embedding of Riemannian Manifolds in Euclidean Spaces by Qing Han, and Jia-Xing Hong.
Comment: There are visualizations of the Nash--Kuiper embeddings here: http://hevea-project.fr/
Comment: That's a confusing place to put the link: the smooth flat embedding of the torus in R^4 and the C^1 flat embedding of the torus in R^3 aren't related at all.
Comment: There isn't really any difference between the $g=1$ and $g\geq 2$ cases for the Nash--Kuiper construction of C^1 isometric embeddings; their method works for an arbitrary metric without regard to its curvature.  I'm fairly certain that if one can render a flat torus in R^3, then one can render any surface with any metric in R^3, though the people at Hévéa might know better. (+1 btw)
Comment: @JohnPardon Sure, I know the method works theoretically in general, but actually doing it is computationally complicated (which is why it hasn't been done).
Comment: @JohnPardon Thanks for the link. However, I already knew about the flat tori and Nash spheres from Hevea; I referenced one in my answer.  It is the hyperbolic ones for closed surfaces of $g\geq 2$ that are not presently visualized (as far as I know).
Comment: @JohnPardon I was trying to contrast the situation for $g=1$ and $g\geq 2$ (minimal smooth embedding vs visualization of $C^1$-embedding).  Sorry if it confused you.  I made an edit that hopefully makes my intent more clear.  Thanks for the comment.
Answer: I don't know the answer to your question, and I wouldn't be surprised if it were open. You may be interested to know that any compact Riemannian two-manifold $(V, g)$ admits a $C^{\infty}$ isometric embedding $V \to \mathbb{R}^5$. See Gromov's Partial Differential Relations, pages 298 - 303.


"Either A, or B, or both"

Question: I want to say that it's possible that at least one of {A,B} is true, and possibly both of them are true. Is it correct to phrase it as "either A, or B, or both are true".
Comment: I don't agree - I think it's covered rather in the 'Either vs. among' thread at http://english.stackexchange.com/questions/59148/either-vs-among (where tchrist and FumbleFingers point out that 'either' _may_ be used when there are more than two alternatives).
Comment: Either or both of A and B are true.
Comment: I think this is perfectly acceptable, and less confusing than some of the alternatives proposed.
Comment: [on hold] the question is a dupe of http://english.stackexchange.com/questions/13889/does-either-a-or-b-preclude-both-a-and-b
Answer: Mathematical logic speaks of an exclusive-OR and an inclusive-OR. Typically parents offer exclusive-OR choices to their children. ("You can have either cake or ice cream"; "...but not both" is implied.) You can say "Either a or b, but not both" to clarify an exclusive-OR, or "Either a or b, or both" to clarify an inclusive-OR. The "but not both" or "or both" in a sense wraps around the whole "either a or b" part.
Answer: Typically you would list them in order with commas and leave off "or" until the last item, as in:
"either A, B or both are true"
Keep in mind that there are those who prefer a comma after B as well:
"either A, B, or both are true"
Comment: *Either* is typically reserved for two options. Some people will object to using it for three, as in your examples. (Whether or not they have a point, is a separate issue, it's just something to be aware of.)
Answer: Since "or" is neither logically or commonly exclusive, "A or B" expresses exactly what you're aiming for.
If you're getting into troubles about clarity I would suggest rephrasing the particular sentence in a way that leaves no doubt:

Maybe I will open the door to my right or my left

could translate to

I might open any of those doors
Answer: Usually just "A or B" implies what you want, but if you want to clarify that meaning is not exclusive, you can use and/or.
Answer: The multiple form would be: 'Any or all of A and B are true.'

"Either A, or B, or both"


Has anyone had any difficulty upgrading from Entity Framework 1 to Entity framework 4?

Question: I'm looking at a project that has been developed and maintained with Entity Framework 1 that is relatively stable at this point.  I'm wondering if people have ever migrated a project like that to EF 4 and if anyone can share any particular difficulties they may have had.  I know there are a lot of benefits to look forward to but I'm trying to assess the risk involved if I upgrade.  Will it create a lot of unexpected behavior for someone who is accustomed to EF 1? Any input would be appreciated.
Answer: This is the only significant problem I've had. It may or may not affect you. There's a workaround, but it's annoying.
If you're using pregenerated views you'll need to manually change your build events to use the .NET 4.0 EdmGen.


What comes first—verb or adverb?

Question: Do you say,  to effectively communicate or would you say to communicate effectively. As ENL learner I get this confused quite often. Thanks.
Comment: It depends on the context. Both types occur and there's no difference in meaning. But those are just remains of clauses; you need a full sentence to decide which one to use. That's what speakers do -- decide what to say next; at speed.
Answer: "To communicate effectively" is the preferred option, as it avoids splitting the infinitive.
Splitting the infinitive means that a word intrudes between "to" and the verb (in this case, "communicate").
Comment: but of course the "rule" about splitting infinitives is hotly debated and often ignored. So don't be surprise to see it the other way around.  As in the original Star Trek intro:  ". . ., to boldly go where no man has gone before."
Comment: The rule is often debated, but most editors will correct split infinitives in text for publication if there is no advantage to the split. In the Star Trek example, there was an advantage of dramatic emphasis.

What comes first—verb or adverb?


How to test your deferred deep link in iOS

Question: I have an app in which i have to use deeplink and deferred deep link.
I'm able to debug deeplink in my app but how to debug deferred deeplink in my iOS app.
How would i know what value I'm getting in launchoptions when freshly installing the app from appstore and how can i debug deferred deep link while in development ?
Is it possible to debug deferred deep link in development without making it to appstore?
Answer: According to Branch.io, which we use a lot, you can manually replicate the process without the App Store.  When they say "Branch link" just use your own link:

Deferred deep linking is simply deep linking into an app that is not
yet installed. Once the app is installed, the context is preserved and
the user's first app-open will have the deep link data from the
original Branch link. To test this, uninstall the app from your
device, click the Branch link, and manually launch the app from Xcode.
You should be routed to the correct content within your app.

https://help.branch.io/developers-hub/docs/ios-testing
Answer: In debug mode you can click on your branch link (maybe you can copy this link on a notes page or send it to yourself on whatsapp) and it will open the link on safari and redirect you to appstore (Don't install the current app from appstore).
Post this you can simply run the app on your device connected to your system via xcode. This will have the same effect as a deferred deeplink. (you can debug this in your app delegate, just make sure you are on the same network.. wifi or 4g as branch uses this for fingerprinting and might not run the deferred deeplink if this changes between the time you clicked on the link and launched the app via xcode.)
If you wan't to test as to how it will behave in production enviornment you can use test flight for the same. (Click on link and once it opens in safari install the app via test flight)


Is it possible to kill all scripts on a webpage after loading the page in Firefox?

Question: Is it possible to disable all scripts on a website after a certain time? For example, I would like to load a webpage and have it load executing whatever scripts it wants. However, I would like to disable all scripts from running after the page loads manually. Now, I can bring up the inspect and debugger screen and pause script execution, but that does not allow me to look at the webpage without scripts running. It grays out the webpage. Is there a way to actually copy text from the webpage while also pausing/disabling all scripts?
Answer:
Enable the command line of the Browser Console (it is disabled by default)
Load the webpage
Open the Browser Console, type or copy and paste the following line and press Enter

gBrowser.selectedBrowser.browsingContext.allowJavascript = false;

The setting is tab-specific, and persists navigation. You can always set JavaScript on again, by applying true
Also, since this is not documented it can change anytime. In fact it changed recently, and this code will work only with Firefox 92 and onwards
Answer: Chrome has the javascript Switch, you just wait for the page the load then turn off javascript: https://chrome.google.com/webstore/detail/toggle-javascript/cidlcjdalomndpeagkjpnefhljffbnlo
Firefox has Javascript Switcher with pretty much the same functionality but remembers the last position you left it in per site: https://addons.mozilla.org/en-US/firefox/addon/quick-js-switcher/?utm_source=addons.mozilla.org&utm_medium=referral&utm_content=search
Comment: The addon does not allow for disabling JavaScript without reloading the page as far as I understand.
Comment: Sorry, the Chrome one does.
Comment: @Viktor try https://addons.mozilla.org/en-US/firefox/addon/javascript-control/reviews/?utm_content=search&utm_medium=referral&utm_source=addons.mozilla.org it has the same icon as the chrome version so I assume it works the same and wont reload
Comment: @8vtwo unfortunately that Firefox addon also reloads after disabling JavaScript.


Managed Package "This extension depends on the package you are trying to uninstall. force-app"

Question: I'm attempting to uninstall a managed package and I'm getting this error. I'm tearing my hair out trying to figure it out. Any thoughts?
Comment: Do you have multiple packages installed in your org? Is one of them called "force-app"? The message suggests you have a package which depends upon the package you're attempting to uninstall.
Comment: There is no package called 'force-app' that I can see.
Comment: Can you share a screenshot of your Installed Packages screen? You're not in a packaging org, are you?
Answer: Had something similar to this and I raised a case. Check this link.
It is also weird because the force-app is a folder on the DX that contains all files related to a project, org, etc ...


Calculated value column

Question: In SharePoint foundation 2010 can i add a new calculated value column where the calculation are based on when another column is modified ?
Comment: Individual column modification dates are not stored (Just whole list items). They can be derived from versioning or through the use of Event Receivers but this is not possible through a simple calculated column. Perhaps if you share what you are trying to accomplish we can help you find a suitable solution.
Comment: basically i want to calculate the duration for a chain of tasks to be completed, and if it meets the estimation provided but to detect the exception i want to add to the calculation when that column was modified
Answer: Out of the box, SharePoint won't tell you when a specific column was modified. You only know when the item was last modified (Modified field).
To track changes on a specific column, you would need to duplicate it and run a workflow that checks for updates. Not a simple design.
Here is how it would work:

add two more columns hidden from the users: CopyColumn and CopyModified
on item change, the workflow compares Column with CopyColumn
if the values are different it means that the user has modified the column. Calculate the time difference between Modified and CopyModified, then update CopyModified and CopyColumn for the next round
if the values are the same, no action, just stop the workflow
Comment: ok thats a new idea , how it can be done ?
Comment: I have added more details to the answer.
Answer: Yes, you can see this link for possible formulas - http://msdn.microsoft.com/en-us/library/bb862071.aspx
Comment: thanks but this not what i need, i need column C to calculate value from column a and add for example the date column b was modified in
Comment: Please write a case you want to have. You can for example have something like - '[Column1] * 6 + MONTH([Column2])' where column1 is number and column2 is date. Also you can combine values into a string.
Answer: Agree with Christophe. SharePoint has no column level changetracking (just like there's no column level security). A list item is the deepest object in SharePoint you can bind events etc. to. My current client wanted to be able to see (and track, for auditing) purposes these column changes as well.
We implemented an ItemEvenReceiver that writes all fields for which the AfterProperties value of a column didn't match the BeforeProperties value of said column to a database.
Another option would be to have a list identical to the source list and copy the item to that list on every update (or just the date and the old and new value of the column in question).
And another option would be to add a column ColumnBModified to your list and setting that column to the current time when the BeforeProperties value of a column does not match the AfterProperties value.
All options require code (ItemEventReceiver)

Calculated value column


Anyone success which In App Purchase ANE for Adobe air?

Question: I have tried two versions of In Freshplanet
and StickSports
but both of them failed. When I try to get product info, no error throws out, just empty array returned in success handler. Is there anyone success with In App Purchase in Flash? Following are my info:

Bundle ID matchs App ID. YES.
One binary version was uploaded to Appstore and rejected later. YES.
in app purchase Product status: Ready to submit and Waiting for review(two products).
Correct product ID: I tried both full and short one: "testproduct" and "APP_BUNDDLE_ID.testproduct" but both fail.
Comment: You might find more in app purchase ANEs here: http://www.as3gamegears.com/category/air-native-extension/
Answer: http://distriqt.com
Very easy to set up with clear instructions. Also supports Google Play Store.
App currently in the Apple App Store using the ANE.
https://itunes.apple.com/gb/app/prime-mover/id595928344?mt=8


How strictly should the 300dpi rule be followed?

Question: I am designing a magazine where we have spreads for photography. We have around 275 ppi for those. I'm not sure how a 275ppi would look on print. Does it matter a lot for a picture as big as a double US letter size spread? How hard and fast is the 300dpi rule? What is the least one could risk?
Answer: Not strictly at all. There is in fact almost no difference between 275 PPI and 300 PPI. The biggest risk is that you get moire on your screens, which is more or less a hit or miss thing.
Also you should try out stuff on actual paper to see how much the PPI affects things. You can easily get almost no difference between a 250 and 300 PPI image. YMMV.
Answer: The formula to work out required dpi is as follows:
Lines Per Inch (LPI) x 1.6 = DPI
So...

For a screen with 85 Lines Per Inch.... 85 x 1.6 = 136dpi (common newspaper lpi)
For a screen with 150 Lines Per Inch.... 150 x 1.6 = 240dpi (common offset lpi)
For a screen with 175 Lines Per Inch ..... 175 x 1.6 = 280dpi (common magazine lpi)
For a screen with 300 Lines Per Inch ..... 300 x 1.6 = 480dpi (high-end "gallery quality")

I most commonly use 240ppi as a bare minimum resolution for most offset work, since a 150LPI screen is the most common frequency in general offset.
There are, of course, occasions where a higher LPI frequency is used and more PPI is beneficial.
There's really no such thing as "too much" ppi. This is generally why 300ppi is used as a standard - it covers the broadest range of possible screen frequencies and is an easy round number to remember.
Comment: ... and humidity in the press room can vary by ±20%... and "Todd" the pressman can be having a bad day... there are *always* particular variables for a particular case.  It's just not possible to think in black and white terms for questions like this. I gave a general rule of thumb.. is it perfect for *every* instance, no... however I also alluded to that in the answer :)
Comment: Altough, the formula ia more like **1.6-2.2 x LPI**, which in turn is not much info as, A) you can affect the LPI, B) some devices do not have LPI's and C) even if your machine has higher LPI does not mean the image needs to be using tha absolute maximum quality...
Comment: Agreed +1, 300 dpi is more of a rule of thumb than anything.
Comment: It's interesting that no one mentions WHY resolution of a digital image (which is not measured in dpi, but is ppi) should be considered in terms of halftone screen frequency. Something you might want to look up (TL for here).

Also, I would disagree with "there's never too much dpi."  You can choke a RIP. You can wind up with soft focus with higher dpi than necessary for the screen frequency. You can produce files that are unmanageable if they have to be transmitted through email or other methods with limits in the megabytes.
Comment: If your concern is print production, you can't *also* be concerned with file size and email. That is just contradictory thinking in my opinion. There are plenty of electronic delivery methods which do not make file size a concern. Quality should be the primary issue where print production is concerned.
Comment: @user8356 Because it would require you to actually  understand how printing works, which most people can not be bothered to do.