Calculate time difference between times past midnight
How do I calculate a time delta in my Google Spreadsheets?
"I couldn't but laugh" - correct or not? Can there be a notification for bounties started on questions you've asked or answered? Browsing folders with more than 100000 images bases and binary I can not figure this out.   I started off by making a table and putting the base(2) on one side, the number in the middle and the remainder in the third row and for 2010 I got 11111011010 but I cant find the next two numbers please help and please explain in detail.  Thank you =)   to express 2010 in base 2, we use exactly 8 ones and 3 zeros. find the next two integers in base 2 that use the same number of ones and zeros Retrieving Maxwell's equations from the minimum action principle I'm currently working at the start of Alexei Tsvelik's book Quantum Field Theory in Condensed Matter Physics. I'm kinda stumped on a few essential steps.  Starting with the action:  $$S = \int dt \int d^3 x \mathcal{L}_{\mathrm{EM}} = \int dt \int d^3 x \left( -\frac{1}{4} F_{\mu \nu} F^{\mu \nu} + j_\mu A^{\mu}\right).$$  In the absence of any sources $j_\mu = 0$ and $c=1$, which after pulling in the negative sign implies  $$S = \frac{1}{2}\int dt \int d^3 x  \,\,\left(E^2 - B^2\right)$$ The next step is to take $\vec{E} = -\vec{\nabla} \phi + \partial_t \vec{A}$ and $\vec{B} = \vec{\nabla} \times \vec{A}$. Letting $\phi = 0$ and directly inserting these into the above yields:  $$S = \frac{1}{2} \int dt \int d^3 x  \,\left( (\partial_t \vec{A})^2 - (\vec{\nabla} \times \vec{A})^2 \right) $$  Now considering $\vec{A} = \vec{A}_0 + \delta \vec{A}$ as some minimal change in our vector potential, with $\vec{A}_0$ gives a minimum for the action and putting this into the above expression we have: $$\delta S = \int dt \int d^3 x \left(\partial_0 \vec{A}_0 \partial_0 \delta \vec{A} + \left(\vec{\nabla} \times \vec{A}_0\right)\cdot\left(\vec{\nabla} \times \delta \vec{A} \right) \right)+ \mathcal{O}(A^2)\,\,\,\,\,\,\, (1)$$ where I have the term  $$\mathcal{O}(A^2) = \int dt \int d^3 x \left( (\partial_0 \vec{A}_0)^2 + (\partial_0 \delta \vec{A})^2 - (\vec{\nabla}\times\vec{A}_0)^2-(\vec{\nabla}\times \delta\vec{A})^2\right)$$  The next step is where I lose our author and go from "Oh ok I get this" to "completely clueless". He rewrites $\delta S$ as:  $$\delta S =  \int dt \int d^3 (\delta x) \vec{A} \mathcal{F(\vec{A}_0)}+ \mathcal{O}(A^2)$$  where $\mathcal{F} = \frac{\delta S}{\delta A}$. What is the purpose of $x\to \delta x$ in the above expression? Is the functional derivative $\mathcal{F}$ a vector quantity? He has it bolded with a bolded $\vec{A}$ in the above expression. One last question takes the above expression further. We assume $\delta \vec{A}$ vanishes at infinity, as it should, and integration by parts yields:  $$\delta S =  -\int dt \int d^3 x \left( \partial^2_0 \vec{A}_0 - (\vec{\nabla} \times \vec{\nabla})\times \vec{A}_0  \right)\delta \vec{A}\,\,\,\,\,\,\,\, (2)$$ How exactly did we go from (1) to (2)? Thanks I appreciate your time! How to validate an email address using a regular expression? I have this MySQL query using  that is the following:  SELECT *  FROM data_tbl WHERE AES_DECRYPT(data_point,'aBcDeF')='data_1';   I've figured out as much that the equivalent in Postgres 11 is  (F.25.4. Raw Encryption Functions) and the query would look something like this:  SELECT *  FROM data_tbl AND decrypt(data_point,'aBcDeF','aes')='data_1';   At least, the documentation for both leads me to believe that these are equivalent.  The data was dumped from MySQL and imported into PostgreSQL.   The data-point field in MySQL is type varbinary(255) and the values all show BLOB in MySQL Workbench.  The data_point field in Postgres is type bytea and the values all show [binary data] in pgAdmin.    Whether those data types are equivalent, I admit, I'm not sure.  The MySQL query works and finds a record based on he criteria. The PostgreSQL does not, although the record is in there. So it seems like one of three things:   The data types (varbinary(255) vs bytea) are not equivalent The data does not match (BLOB vs [binary data]) are not equivalent The functions (AES_DECRYPT vs decrypt()) are not equivalent   I did try to decrypt the value in PostgreSQL just to see what it is in a readable format by first trying:  SELECT decrypt(data_point, 'aBcDeF', 'aes')  FROM data_tbl;   But that just returned [binary data] for all the rows.  Then I came across  to use convert_from as in:  SELECT convert_from(decrypt(data_point, 'aBcDeF', 'aes'), 'SQL_ASCII') FROM data_tbl;   However, I just get this error:  ERROR:  invalid byte sequence for encoding "UTF8": 0xcf 0xf5 SQL state: 22021   So at this point I'm stumped as to how to resolve the primary issue. The primary issue being doing the equivalent of AES_DECRYPT but in PostgreSQL 11. The last error message isn't so much an issue, but it is likely related to decrypt() not returning the same results.  Any suggestions? Vertically centered horizontal rule filling the rest of a line? I'd like to have a horizontal line extending from the end of the text on a line to the right margin. So far I've found \hrulefill and \leaders\hrule\hfill, but these draw a line that's flush with the baseline of my text — how can I get it to be vertically centered? Which LaTeX to install on Linux? Which LaTeX distribution would you recommend for using on Linux from command line? I am looking for one with most complete coverage of packages. After drinking an energy drink, there are little yellow and white bars above the health bar. What are those? What do they represent? Proving $f(x,y,z)=\big(\frac{x}{a+x+y+z}, \frac{y}{a+x+y+z}, \frac{z}{a+x+y+z} \big)$ is injective Let $a\in \mathbb{R}$, $a\neq 0$, and $E=\{(x,y,z)\in \mathbb{R}^3:a+x+y+z\neq 0\}$ and $f:E\rightarrow \mathbb{R}^3$ defined by $$ f(x,y,z)=\big(\frac{x}{a+x+y+z}, \frac{y}{a+x+y+z}, \frac{z}{a+x+y+z} \big) $$ Show that $f$ is injective.    I've been trying to prove it directly by showing that if $f(x_1,y_1,z_1)=f(x_2,y_2,z_2)\Rightarrow$ $x_1=x_2, y_1=y_2,z_1=z_2$. But I get a system of equations which I'm find difficult to deal with. Any help would be greatly appreciated. "Needs cleaned" or "needs to be cleaned" Is the uncertainty principle a property of elementary particles or a result of our measurement tools? Prevent abstract environment to reset pagenumbering I want to prove that the distance between incentre and orthocentre is $$\sqrt{2r^2-4R^2\cos A\cos B\cos C} $$here $r$ is inradius and $R$ is circumradius. I considered $\triangle API$ ($P$ is orthocentre and $I$ is incentre). I could find  $AP=2R\cos A$, $AI=4R\sin\frac{B}{2}\sin\frac{C}{2} $ and $\angle PAI=\angle \frac{B-C}{2}$. So applying cosine rule I got $$PI^2=4R^2+16R^2\sin^2\frac{B}{2}\sin^2\frac{C}{2} -16R^2\cos A\sin\frac{B}{2}\sin\frac{C}{2}\Bigg(\cos\frac{B}{2}\cos\frac{C}{2}+\sin\frac{B}{2}\sin\frac{C}{2}\Bigg)$$ How to proceed form here ? It seems i'm not gonna find an answer for this question which does not use LHopital's rule. How do you prove limit of (lnx)/x approaches 0 as x moves toward infinity WITHOUT using LHopital's rule? Travelling on Business visa to UK for tourism purposes The Download CSV link seems broken in SEDE query result window I've created   which works nice. I would really like to download those results as an CSV file. Therefor I click on the provided link on the right hand side of the screen called Download CSV. The result is:  The webpage cannot be found  https://data.stackexchange.com/stackoverflow/csv/202355?UserId=187606 I expected: A file in CSV format. It looks like a regression of  Queries without a parameter work as advertised. Can this be fixed? nmake fatal error U1034: syntax error : separator missing I'm having trouble understanding what I'm doing wrong here: I'm trying to set up two network Locations, one for my home network via my cable modem and a second for Wi-Fi tethering via my mobile phone. What I'd like to be able to do is change the Location (under the Apple menu &gt; Location) and have my Mac automatically connect to the proper Wi-Fi network: either my home network SSID or my WiFi tethering SSID. I defined two locations, switched between them, and set the preferred network list for each location. But when I change the preferred network list for one Location, it changes the list for the other Location as well! Am I doing something wrong or is it really not possible to maintain a separate list of Preferred Networks for each network Location? It seems doubtful it's not possible since just about every other netrok setting depends on the location... I am using OS X 10.7.2.