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Facebook authorization fails on iOS6 when switching FB account on device
Significance contradiction in linear regression: significant t-test for a coefficient vs non-significant overall F-statistic has two corollaries:   The gravitational attraction of a spherically symmetric body acts as if all its mass were concentrated at the center, and The gravitational acceleration inside the cavity of a spherically symmetric body vanishes.   Consider a spaceship floating freely in space. In a homogeneous universe, the combined attraction from all matter should cancel out, and the spaceship should stay motionless. Nevertheless, I'm free to divide the attraction into several parts originating from different parts of the universe: In the figure below, I've divided the universe into a red sphere centered on some arbitrary point (×) with my spaceship located at the edge of the sphere, plus infinitely many shells centered on the same point.  By corollary #1, the gravitational attraction of the red sphere equals that of all its mass centered at the point ×. By corollary #2, the combined acceleration of the spaceship from all mass in the green shell vanishes. The same can be said for the blue shell, the orange shell, and so on ad infinitum.  Hence my spaceship should start accelerating toward ×. By choosing the sphere large enough, I should be able to make it accelerate arbitrarily fast, and by choosing the location of × I can make it accelerate in any direction.    Of course this doesn't work, but why?  My best guess is that, even in an infinite universe, you can't keep adding spheres because you'll exit the observable universe, in which case there's no way to feel the gravity in part of the shell so that it's no longer symmetric. Perhaps also the expansion of the universe matters. But see the last two points below.  A few more things to consider:   The mass of the red sphere increases with the chosen radius $r$ as $r^3$, while the acceleration it generates is proportional to $r^{-2}$; hence the acceleration increases linearly with the chosen $r$. Our universe — the "Universe" — has an average density of some $10^{-29}\,\mathrm{g}\,\mathrm{cm}^{-3}$. Hence if I set $r$ equal to the radius of the observable Universe (46.3 billion light-years), the acceleration is a minuscule $10^{-7}\,\mathrm{cm}\,\mathrm{s}^{-2}$. If that bothers you, choose another universe where $\rho$ is ten orders of magnitude higher. Our Universe is not really homogeneous, but on large enough scales ($\gtrsim$ half a billion light-years) it seems it is. Still, the acceleration of the spaceship will be dominated by nearby sources. If that bothers you, choose a sufficiently homogeneous universe. On the scales we're considering, the Universe is not governed by Newtonian dynamics, but by general relativity. If that bothers you, use  instead — I think the issue is the same. If the issue is really that the size of the observable universe matters, then my intuition tells me that I can just choose an arbitrarily old universe where the asymmetric contribution from the most distant shells is arbitrarily small. If the issue is that the universe expands (so that gravity from the far side of a shell is somehow weakened, or "redshifted"), then my intuition tells me that I can just choose a sufficiently static universe. Generally accepted root mean square (RMS) error for rectifying topographic maps This is a generic inquiry on the common practice/standard for determining the acceptable values of RMS when georeferencing topographic maps.  Is there an absolute value?  Some literature suggests that it should be "less than or equal to 1/2 of the side of a cell which make up the total resolution of the image." error while loading shared libraries: libssl.so.1.1 (and libcrypto.so.1.1) As you can see I'm missing libcrypto and libssl files. I locked out myself from my server after running apt-update and apt-upgrade, I'm running this from web console, because ssh nor any other program won't work because of missing SSL files.  I tried removing and installing apt install openssl so did libssl-dev and/or compiling own openssl from a distro. None of these create the needed .so files, I ran locate, those files are not present anywhere on the server. There's also libssl1.0.0 which cannot be reinstalled and removing it would cause removal of 700MB of packages that would literally kill server and delete all data. The derivative of $x!$ and its continuity is the factorial of fractions and negative numbers defined? If yes, then what is its graph? Also please find its domain.  Our teacher said the factorial of a fraction is the fraction itself. He also said the graph is continuous but could not determine the derivative of $x!$. Visually stunning math concepts which are easy to explain Since I'm not that good at (as I like to call it) 'die-hard-mathematics', I've always liked concepts like the  or the , which are easy to understand and explain but are mathematically beautiful at the same time.  Do you know of any other concepts like these? Password Protect QGIS project On a shared computer, I have a QGIS project which links up to a PostGIS database that contains my data. If a user wants to access layers from the db, they have to enter the db credentials, so that's OK.   However, I have previously logged on and imported layers from my db into QGIS, and manipulated them in QGIS (styling options based on meta-data, etc.)... Anybody who opens my QGIS project can view these layers in QGIS, and can therefore see the data I wish to be protected in my db.  Is there a way to password protect my QGIS project? Font corruption: lines through characters I have a problem where a one-pixel high white line is displayed through certain letters of text. Almost always only a single character type is affected at once, and only in one font size (though that size can change over time). Most of the time things are fine, but this happens several times a day. It happens frequently in Firefox, but system dialogs, menus, etc. can also be affected. It's been happening ever since I upgraded to 10.10. Only restarting seems to fix it.  Two examples (in the first, only the larger "r" is corrupted):     Any help would be appreciated, thanks.  Edit: I've since noticed that I can (sometimes) make the fonts appear correctly by zooming in/out all the way and returning to the default in Firefox (one or two steps, then going back, does nothing) seems to make the problem go away temporarily.  Edit 2: I figure it's worth noting that the solution below doesn't fully work for me any longer (I'm now using Ubuntu 11.10). It does significantly reduce the frequency of this problem occurring.  Edit 3: Still around in 12.04. The fix provided by Vanni works perfectly now for me, but apparently doesn't for some.  Edit 4: This seems to be an xorg problem, with Vanni's answer fixing it for many Intel video cards. I've had this occasionally happen with AMD graphics cards in 13.10 and 14.04, but very rarely (only two or three times). Getting a closed form from $\sum_{i=1}^{n-1} \sum_{j=i+1}^{n} \sum_{k=1}^{j} 1$ Will Windows 10 Technical Preview be upgradable to final release? Is there any information about if Windows 10 Technical Preview will then be upgradable to the final release ?  I'm asking that because I would like to use it on my primary PC (I'm aware of the risks but I accept them), in place of Windows 8.1 But I'd like to avoid to reinstall all after the release of the final version. Simple as the title states: Can you use only Java commands to take a screenshot and save it?  Or, do I need to use an OS specific program to take the screenshot and then grab it off the clipboard? This is something I just realised I don't entirely know the answer to, so I'm going to ask it here as I think it's interesting.  In most non-scientific writing on depth of field, diagrams generally show camera and subjects as being perfectly parallel, e.g.    However, is this a more accurate representation of the focal plane?    Are there ways to optically alter the shape of the focal plane?  Note: Obviously these diagrams are two dimensional, but I'm assuming in the second diagram the shape would be spherical with the sensor at the center. I am making a test where I am asked to add the missing words.     [...] chair is [...] useful piece of furniture.    I would have said that a is the missing word in both the cases, but the test says the words I should have added are the and a respectively.     [...] last time I saw [...] bear, I was travelling in [...] Europe.   I would have added: nothing, a, nothing. The correct answer is: the, a, nothing.  Why is the the correct article to use in both the sentences? Possible Duplicate:          Can anyone offer me advice on how to clean my camera's sensor?   Should I do this myself, or take the camera to a professional? Is it precarious, or easy with the right amount of care?   I have a Nikon D3000 that has a small dot off-center of the sensor. I believe it is dirt, and I would like to remove it. I'm tempted to use a cotton-bud, but I'm afraid that I might damage the sensor.  The dot appeared after a trip to a tropical area where the camera became wet. I took the lens off and a lot of moisture, and possibly some dirt, went into the camera. The lens became fogged-up.  When I returned from my trip I ran a hair dryer for (air only, without heat) 10 minutes through the battery compartment, believing this would circulate around and dry the camera. Consequently, I noticed many speckled dots around the sensor. I also believe there's a subtle but persistent haze when I look through the lens, but I could be wrong.  It's worth noting that the photos are fine, with no evidence of distortion or blurring. The camera is now dry and it's been months since this happened. But the dot on the sensor has been there since, like an itch I can't rub. How do I reference the only element in a singleton set? You can turn any element $n$ into a singleton set by adding braces, $\{n\}$. Is there an inverse to this operation, such that if I know the set is a singleton set I can easily reference its element?  For example, say I have the set $A = \{5,6,7,8\}$, and then some process that iteratively eliminates all but one element of $A$, and then I want to see what 10 plus the resulting element is, how could I write that?  The only way I can think of is by referencing the first element by its index, e.g., $10 + A_1$. Is there another way to do it though? In my case the elements of $A$ are already indices, so I would have to index an index, like $10 + x_{A_1}$. Which is not the worst thing in the world, I was just wondering if there is a better way. I am looking for a word that would describe someone who always goes out of their way to take their time and do a good job. Sort of the opposite of half-assing something.  I am looking for something that is more about a work ethic than a technically proper way of doing things. Something like canonical or protocol would not be a good fit. Long story short  I have two computers: a laptop and a desktop computer. Both have Windows 7 on them.  I buy the Windows 8 Pro upgrade. To see if it screws up anything, I install it on my laptop as a guinea pig. I intend to use Windows 8 for my main computer, my desktop, but I want to test it on the laptop, so I know I don’t risk losing access to my desktop and the data on it. I never use my laptop, and only used it, because it already has a Windows 7 installation on it.  The problem  At some point, I must have entered the license key on my laptop, because when I go to the activation screen on my desktop, I get this:    Uh-oh. I can’t use the key on my desktop. Now how the hell do I transfer the key from my laptop to my desktop computer?  Answers and suggestions so far  Let’s just say that I tried everything possible to get some answers on this matter. The best response I got from Microsoft is this:     To install Windows 8 on your desktop, do the following:         Uninstall Windows 8 on your laptop   Afterwards, install Windows 8 on your desktop   If it won’t activate, call product activation at (...)      I am not a fan of that last point. The error message does allude to such a solution, however:     If you’ve reinstalled Windows or made changes to your hardware recently, you may be able to use your current key.   The question  My main question is this: has anyone been in a similar situation, and if so, what did you do to resolve this?  Failing that, what is the proper way to   uninstall the Windows 8 installation on my laptop, and reinstall the Windows 8 installation on my desktop?   Ad 1  I have already tried using the “reset” feature on my laptop, but that only resulted in a new Windows 8 installation that was already activated. But which is the right way to uninstall the installation in a way that allows me to use the license key on the desktop computer?  Ad 2  Which is the proper way to reinstall the Windows 8 installation on my desktop computer? Why do I even have to reinstall it in the first place?  I won’t get around to do this, until my USB key with 3.0 support arrives in the mail, but it is going to be a while, until I find a assuaging response to the best way to go about this anyway. Deep cloning objects I want to do something like:  MyObject myObj = GetMyObj(); // Create and fill a new object MyObject newObj = myObj.Clone();   And then make changes to the new object that are not reflected in the original object.  I don't often need this functionality, so when it's been necessary, I've resorted to creating a new object and then copying each property individually, but it always leaves me with the feeling that there is a better or more elegant way of handling the situation.  How can I clone or deep copy an object so that the cloned object can be modified without any changes being reflected in the original object? Reading an Excel file in PHP I'm trying to read an Excel file (Office 2003). There is an Excel file that needs to be uploaded and its contents parsed.  Via Google, I can only find answers to these related (and insufficient topics): generating Excel files, reading Excel XML files, reading Excel CSV files, or incomplete abandoned projects. I own Office 2003 so if I need any files from there, they are available. It's installed on my box but isn't and can't be installed on my shared host.  Edit: so far all answers point to  and/or  about how to use it. How to activate quota for users on folders?