I'm in Germany and I need to get to the US. Since I'm not a US citizen or permanent resident, I can't travel directly because of the covid-19 travel ban. I want to find a country that  Isn't covered by the US travel ban, i.e. isn't listed at  Allows travel from Germany Has active air travel from Germany and to the US right now.  Does anyone know if such a country exists? Is there a list of different countries' travel restrictions that could help me find out? Alternatively, is there a way to spend 14 days at sea and then enter the US?
I'm a European citizen living in the US on a work visa. Due to some unfortunate circumstances, I need to urgently visit my home country. However I would like to get back to the US after my visit is complete. Flying from the US to Europe is not a problem as there are still daily flights between some city pairs. However going back could be tricky, as  anyone who has been in the Schengen area in the past 14 days from re-entering the country.   Is there a flight route that would let me from Europe to some country, stay there for 14 days and then fly to the US? Canada is out, as they've banned international visitors. Mexico seems to keep their border open, but I  any direct European flights from their airports. Almost every other country either suspended flights or doesn't allow foreign nationals to enter.
Prove that $\sum_{k=1}^{n}k\binom{n}{k}=n\cdot2^{n-1}$ I want to prove the following: $$\sum_{k=1}^{n}k\binom{n}{k}=n\cdot2^{n-1}$$ what I did is(use binominal): $$\binom{n}{k}X^k\cdot 1^{n-k} = (X+1)^n$$ $$k\binom{n}{k}X^k\cdot 1^{n-k} = k(X+1)^k-1$$ now I replace $k$ by $n$ and insert $X=1$ , I will get now $n\cdot2^{n-1}$ what you are suggesting? there is another way to do that? thanks! What is the unit of the coordinate system in PSTricks? If I use the following code, there two different kinds of units. One for the coordinate system used to declare \begin{pspicture} with (0,0) to (20,10), and the centimeter used in 4.2cm.  \begin{pspicture}(0,0)(20,10) \rput[lt](0.5,9){\psframebox[linewidth=1pt,framearc=0]{\parbox[c]{4.2cm}{\raggedright Text Goes Here...}}} \end{pspicture}   Can I use a unified dimension for both PSTricks objects and \parbox? Is a continuous function $ f\colon(0,\infty)\to R$, such that $f(x)\leq f(nx)$ increasing? Is it acceptable to say "fed up OF" - surely it should be "fed up WITH" or "bored WITH something" rather than "bored OF something"? I hear people using of when I have always thought it was with in the circumstances explained above.  It seems to be getting more common. Can we use curved spacetime to measure the one-way speed of light? This is related to  and  The idea is to shine a beam of light from a clock towards a heavy mass, like a black hole, in some manner such that the curvature of spacetime around the mass is sufficient to &quot;bend&quot; the light directly back to the clock. That is, to send the light along a self-intersecting geodesic using a sufficiently curved spacetime. Note that in this case the source and the detector are the same object, so no clock synchronization is required. Hypothetically, this should measure the one-way speed of light. None of the given refutations from the similar posts on this site are convincing. Here are some of the main refutations, as I understand them, and my counter to them: (1) In being curved by spacetime, the light is actually changing direction, hence this is not the one-way speed. To my understanding of General Relativity, the light travels along a geodesic; that is, a curve such that, ignoring technicalities of Differential Geometry, its tangent direction is constant. There is no reflection or acceleration. So in this sense, how can the light with a constant tangent direction be said to change direction? One might say that the path deviates from a straight line in Euclidean space, but given that spacetime is not Euclidean, has no , and has no global notion of direction, this is the only definition of straight or &quot;one direction&quot; that makes sense. Thus, either the light does not change direction and is &quot;one-way,&quot; or we need to be clearer about what exactly we mean by &quot;one-way&quot; in the context of General Relativity. (2) Such an experiment would be impossible or impractical. I think some posters were saying this because the original questions implied that the clock would have to be at the event horizon of a black hole, which is of course impossible or impractical; however, I don't think such an extreme closeness to the black hole is required. Given that the  of a black hole, where light orbits in a circle, is outside of the event horizon, shining the light at some distance outside of the photon sphere should be sufficient to curve the light back to the clock, regardless of the distance of the clock from the black hole (see my rough illustration). At the extreme, we could place the clock directly on the photon sphere, which should be theoretically possible. Regardless, the question is not about practicality, but whether the one-way speed is theoretically measurable.  Update: Essentially what this argument boils down to, I think, is that the average speed of light along a single self-intersecting geodesic may differ from the average speed of light along a non-geodesic self-intersecting path, which is always c. Put that way, however, it does seem a little ridiculous. It is hard to see how the anisotropy of the speed could be defined in such a way as to be consistent with this pathological case. Presumably, we could approximate a single self-intersecting geodesic with a non-geodesic path arbitrarily closely, so, logically, the average speeds over each path should be approximately the same, i.e., c. Furthermore, how would the &quot;preferred direction&quot; of the speed of light behave around a black hole, for instance? Regardless, I still think this experiment does actually solve the problem for the given notion of &quot;direction&quot;. Though the problem is usually posed in the flat spacetime of Special Relativity, with a global notion of direction, so the apparent unanswerability of this question should be seen as a limitation of Special Relativity only, which is then solved by General Relativity. On , I have my favorite tags filter. I setup email notifications for it and now I'm thinking I overdid it on the frequency. Trying to change the settings, I clicked on the edit link in the email notifications box to the right, except nothing happens. There are no JavaScript errors and the HTML for the link is simply &lt;a class=&quot;edit&quot;&gt;edit&lt;/a&gt;. This seems like unfinished planned feature. Update: Using Chrome Version 29.0.1547.66 m Same on Firefox 23.0.1  Both edit links are not working. Further Update Events capture:  Update 2014-02-03: Here's what the subscription tab in the network profile looks like. I would like to know if there is some way to share a variable or an object between two or more Servlets, I mean some "standard" way. I suppose that this is not a good practice but is a easier way to build a prototype.  I don't know if it depends on the technologies used, but I'll use Tomcat 5.5    I want to share a Vector of objects of a simple class (just public attributes, strings, ints, etc). My intention is to have a static data like in a DB, obviously it will be lost when the Tomcat is stopped. (it's just for Testing) HtmlSpecialChars equivalent in Javascript? Unable to install Ubuntu on Lenovo Y500 Can I remove receipts from imported products from my passport? I have recently imported books into Canada from Japan.  As I bought in excess of 5000¥, the purchase was tax free and the receipt was stapled to my passport and stamped.  Since I've now come back to Canada and no issues occurred with my imports, Is it safe to remove the receipts from my passport?  As it was stamped and stapled, there will remain a trace that something was there. Could this cause problems when I return to Japan at a later time? Prove that $C\exp(x)$ is the only set of functions for which $f(x) = f'(x)$ I was wondering on the following and I probably know the answer already: NO. Is there another number with similar properties as $e$? So that the derivative of $\exp(x)$ is the same as the function itself. I can guess that it's probably not, because otherwise $e$ wouldn't be that special, but is there any proof of it? I'm building a child theme and it currently has a very simple &lt;head&gt; section in header.php:  &lt;head&gt;   &lt;meta charset="&lt;?php bloginfo( 'charset' ); ?&gt;"&gt;   &lt;meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1"&gt;   &lt;title&gt;&lt;?php wp_title( '|', true, 'right' ); ?&gt;&lt;/title&gt;   &lt;link rel="profile" href="http://gmpg.org/xfn/11"&gt;   &lt;link rel="pingback" href="&lt;?php bloginfo( 'pingback_url' ); ?&gt;"&gt;   &lt;!--[if lt IE 9]&gt;   &lt;script type="text/javascript" src="&lt;?php echo get_template_directory_uri(); ?&gt;/js/html5shiv.min.js"&gt;&lt;/script&gt;   &lt;![endif]--&gt;    &lt;?php wp_head(); ?&gt; &lt;/head&gt;   I'm guessing wp_head() is responsible for the second &lt;title&gt; element (it appears just there in the final HTML), but other things I've read say this is impossible.  Should I be removing the &lt;title&gt; from my header.php, or should I be adding something to my functions to remove the title from wp_head() (eg. remove_action('wp_head', 'title') ?  Or should I be doing something else altogether? What is the difference between public, protected, package-private and private in Java? In Java, are there clear rules on when to use each of access modifiers, namely the default (package private), public, protected and private, while making class and interface and dealing with inheritance? How extended must my extended paper be? Consequence of the Hahn-Banach Theorem From wikipedia's page on the Hahn-Banach Theorem:  If $V$ is a normed vector space with linear subspace $U$ (not necessarily closed) and if $z$ is an element of $V$ not in the closure of $U$, then there exists a continuous linear map $ψ : V → K$ with $ψ(x) = 0$ for all $x$ in $U$, $ψ(z) = 1$, and $||ψ|| = dist(z, U)^{−1}.$  How is this a consequence of the Hahn-Banach Theorem? Cross tabulation of two categorical variables: recommended techniques Where does Minecraft for Windows 10 store its data? Bad substitution: no closing "`" in a heredoc / EOF I'd like to print a man style usage message to describe a shell function like this output man find:  NAME        find - search for files in a directory hierarchy  SYNOPSIS        find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression]  DESCRIPTION        This  manual  page  documents the GNU version of find.  GNU find searches the directory tree rooted at each        given starting-point by evaluating the given expression from left to  right,  according  to  the  rules  of        precedence  (see section OPERATORS), until the outcome is known (the left hand side is false for and opera‐        tions, true for or), at which point find moves on to the next file name.  If no  starting-point  is  speci‐        fied, `.' is assumed.  OPTIONS   I am facing an error message on the ` character. Following simple script shows the error:  ~$ cat &lt;&lt;EOF `.' EOF  bash: bad substitution: no closing "`" in `.'   I though heredoc was a cool way to echo strings by pasting them without having to escape its content such a quotes, etc... I assume I was wrong :/  Can someone explain this behavior please? Can heredoc accept ` character?  Edit 2: I accepted the answer of quoted here-document  &lt;&lt;'END_HELP', but I finally won't use it for this kind of complete manual output as  does   Edit 1: (For future reads) the limit with using quoted here-document is that is prevents to use tput in the here-document. To do so, I did the following:   unquoted here-document, for tput commands to be executed prevent the "bad substitution" error by escaping the backtick instead use tput within the  here-document   Example:  normal=$( tput sgr0 ) ; bold=$(tput bold) ;  cat &lt;&lt;END_HELP # here-document not quoted ${bold}NAME${normal}        find - search for files in a directory hierarchy  ${bold}SYNOPSIS${normal}        find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression]  ${bold}DESCRIPTION${normal}        This  manual  page  documents the GNU version of find.  GNU find searches the directory tree rooted at each        given starting-point by evaluating the given expression from left to  right,  according  to  the  rules  of        precedence  (see section OPERATORS), until the outcome is known (the left hand side is false for and opera‐        tions, true for or), at which point find moves on to the next file name.  If no  starting-point  is  speci‐        fied, \`.' is assumed. END_HELP  unset normal ; unset bold ;   Here, note the escaped backtick that was source of error:  \`.' Same Video on each face, but with different time delay? iam looking for a way to - like the title says - i want to put the same video on each face, but with different time delay.  In other words, i want to create a kind  of videowall.  i found :  #---------------------------------------------------------- # File multi_material.py #---------------------------------------------------------- import bpy  def run(origin):     # Create three materials     red = bpy.data.materials.new('Red')     red.diffuse_color = (1,0,0)     blue = bpy.data.materials.new('Blue')     blue.diffuse_color = (0,0,1)     yellow = bpy.data.materials.new('Yellow')     yellow.diffuse_color = (1,1,0)      # Create mesh and assign materials     bpy.ops.mesh.primitive_uv_sphere_add(         segments = 16,         ring_count = 8,          location=origin)     ob = bpy.context.object     ob.name = 'MultiMatSphere'     me = ob.data     me.materials.append(red)     me.materials.append(blue)     me.materials.append(yellow)      # Assign materials to faces     for f in me.faces:         f.material_index = f.index % 3      # Set left half of sphere smooth, right half flat shading     for f in me.faces:         f.use_smooth = (f.center[0] &lt; 0)  if __name__ == "__main__":     run((0,0,0))   But it didn't really work out for me, it creates a red sphere and sends      Traceback (most recent call last):   File "\Text", line 36, in      File "\Text", line 28, in run AttributeError: 'Mesh' object   has no attribute 'faces' Error: Python script fail, look in the   console for now...   to the console. Also i didn't know how i could add the delay in there.  Hope you can help me out with this! :) SSL certificate for a public IP address? I just tried buying a Comodo Positive SSL but it was rejected due to not supporting a public IP address, but instead they only support a domain name.  Does anyone know any SSL certificate provider that supports public IP address instead of a domain name?  My company has a dedicated server hosted with a web hosting company, which is used for running a bugtracker for multiple projects (for multiple clients). Since it's only used for a bugtracker, we don't need a domain name (our clients access it by typing the public IP in their browser).