Please feel free to change the title of this question since I'm not sure if it's fitting.  For example, I'd like to draw a rule with the same height as the thickness of a frame line of a standard tcolorbox.  I had a look at the tcolorbox package code, and I assume that the line leftrule/.store in=\kvtcb@left@rule is somehow essential for what I want. But if I try  \documentclass{article}  \usepackage{tcolorbox}  \begin{document}  \noindent\rule{\textwidth}{\kvtcb@left@rule}  \end{document}   it doesn't work and LaTeX returns the error ! Undefined control sequence..  So my more general question is: How can I access package internal values like this to use them in my document?
Many LaTeX “hacks” begin with \makeatletter and end with \makeatother. What do these commands do?
What is the rule for adjective order? I remember being taught that the correct order of adjectives in English was something along the lines of "Opinion-Size-Age-Color-Material-Purpose."  However, it's been a long time and I'm pretty sure I've forgotten a few categories (I think there were eight or nine). Can anyone fill them in? Do I need a Kuwait transit visa as an Indian national? I am an Indian national and passport holder, traveling from New Delhi to Frankfurt (via Kuwait) and back with Kuwait Airways. I see no Terminal change for the onward and return journeys. I have no plans to leave the airport due to short layovers.  Do I need a Kuwait transit visa? What levels-up Psi-abilities? How to install Google Chrome How do you install Google Chrome on Ubuntu? I've seen $d(xy) = y(dx) + x(dy)$, but I don't understand the principle behind it and memorizing it is lame.  Can anyone explain what is going on here?  For example from physics, $$F = {{dP} \over {dt}}$$ $$F = {{d(mv)} \over {dt}}$$ $$F = {{v(dm) + m(dv)} \over {dt}}$$ Since $$dm = 0$$  $$F = {{m(dv)} \over {dt}}$$ Since $$a = {{dv} \over {dt}}$$ $$F = ma$$ How could we improve our planned post notice improvements? Megan has written a .  I've seen a bunch of discussion about it on chat - but it feels like having it purely on the blog is a little clunky.  So specifically - what does the MSE community feel about the proposed post notices for closed questions? What's missing, or what should be added? What are some of the lessons we've learnt that could be helpful here? Why does $1+2+3+\cdots = -\frac{1}{12}$? $\displaystyle\sum_{n=1}^\infty \frac{1}{n^s}$ only converges to $\zeta(s)$ if $\text{Re}(s) &gt; 1$.  Why should analytically continuing to $\zeta(-1)$ give the right answer? String comparison in Python: is vs. == match first column of file a with paragraphs of file b I have 2 files. The first, fileA looks like  TCONS_00000066  XLOC_000030     -       u       q1:XLOC_000030|TCONS_00000066|0|0.000000|0.000000|0.000000|0.000000|- TCONS_00000130  XLOC_000057     -       u       q1:XLOC_000057|TCONS_00000130|0|0.000000|0.000000|0.000000|0.000000|- TCONS_00000395  XLOC_000206     -       u       q1:XLOC_000204|TCONS_00000393|0|0.000000|0.000000|0.000000|0.000000|-   FileB looks like:  &gt;TCONS_00000001 gene=XLOC_000001 AGATGAGCTGGTGGGGATGCTCTAAGAGAACGAGAGAAGCACAGAGCAGATAAACCACACCCACAGGCAC CACCGTCCTTGTTGGTAATGAAGAAGACGAGACGACGACTTCCCCACTAGGAAACACGACGGAGGCGGAG ATGATCGACGGCGGAGAGAGCTACAGAAACATCGATGCCTCCTGTCCAATCCCCCCATCCCATTCGGTAG TTGGATTGAAGACTACCGAATAAGAGAAGCAGGCAGGCAGACAAACCCTTGAACCAAGGAGTCCTCGCTG AGGAAGCTTTGGATCCACGACGCAGCTATGGCCTCCCCGCCCACCAGGCCGCCAGCCACAACCAGCTGAC TAGGTCGCATGCATCATCAGATTTCAATCTCCCTTCGTTCCCTGTCCCTAATCCAATACCAATAGGGAGC AATCAGCTGCTCCTCGACGGCGAGGGAGATGTCGTCGGCCGCGGGCCAAGACAACGGAGATACCGCTGGG GACTACATCAAGTGGATGTGCGGCGCCGGTGGCCGTGCGGGCGGCGCCATGGCCAACCTCCAGCGCGGCG TTGGCTCCCTCGTCCGTGACATTGGCGACCCCTGCCTCAACCCATCCCCCGTTAAGGGGAGCAAAATGCT CAAACCGGAAAAATGGCACACATGTTTTGATAATGATGGAAAGGTCATAGGTTTCCGTAAAGCCCTAAAA TTCATTGTCTTAGGGGGTGTGGATCCCACTATTCGAGCTGAAGTTTGGGAATTTCTTCTTGGCTGCTATG CCTTGAGTAGTACCTCAGAGTATAGGAGGAAACTAAGAGCTGTTAGAAGGGAAAAATATCAAATTTTAGT TAGACAGTGCCAGAGCATGCACCCAAGCATTGGTACAGGTGAGCTTGCTTACGCTGTTGGATCAAAGCTA   Now, fileA contains selected transcript numbers in the first column and fileB contains sequences of all transcripts. I want to scan fileB for the first column of fileA and print the trailing sequences of matching transcripts along with the transcript number. Can a wealthy investor invest in or make a deal with a company before it goes public / IPO? Can a wealthy investor invest his money in any company before it goes public / IPO? I am referring to a recent Goldman Sachs and Facebook deal worth $450 Million at a valuation of $50 Billion dollars.   I want to know what is the procedure and how are these valuations made prior to the company going public? Is is possible that an investor could raise capital from investment banks, private equity, or commercial banks to re-invest in a pre-IPO deal at some valuation?  Knowing that angel investors don't provide so much money, can they play their role here with a normal investor? What is the difference between String.Empty and "" (empty string)? Scale-dependent displaying of a layer using OpenLayers plugin? When I am creating a layer in QGIS the layer position/lines does not stay the same when I zoom in closer than, it seems like 1: 1000. I am adding 2 images to explain the problem. The moment I zoom in closer than 1: 1 000 then the original layer does not display correctly anymore.  Please, can you assist in this matter? Are battery packs allowed in hand luggage? When flying, are you allowed to bring battery packs / power banks? I'd like to bring my ACC 10400mAh Power Bank on several flights. What is the equation for the tension on the ends of a cable suspended at different heights? I'm looking for an equation to find the tension on the ends of a cable suspended between two poles (one higher than the other) with no load but the cable itself.    I determined that the tension would be different on each end, that the shape of the suspended cable would be a  truncated at one end, and that the following would be the variables necessary in the equation:   cable weight cable length vertical distance between ends horizontal distance between ends   Some links that could be helpful: I am trying to grab the capital letters of a couple of words and wrap them in span tags. I am using  for extract and wrapping purposes, but it's not outputting anything.  preg_replace("/[A-Z]/", "&lt;span class=\"initial\"&gt;$1&lt;/span&gt;", $str) When to use "have" and "have got" Deriving the conditional distributions of a multivariate normal distribution We have a multivariate normal vector ${\boldsymbol Y} \sim \mathcal{N}(\boldsymbol\mu, \Sigma)$. Consider partitioning $\boldsymbol\mu$ and ${\boldsymbol Y}$ into  $$\boldsymbol\mu = \begin{bmatrix}  \boldsymbol\mu_1 \\  \boldsymbol\mu_2 \end{bmatrix} $$ $${\boldsymbol Y}=\begin{bmatrix}{\boldsymbol y}_1 \\  {\boldsymbol y}_2 \end{bmatrix}$$  with a similar partition of $\Sigma$ into $$  \begin{bmatrix} \Sigma_{11} &amp; \Sigma_{12}\\ \Sigma_{21} &amp; \Sigma_{22} \end{bmatrix} $$ Then, $({\boldsymbol y}_1|{\boldsymbol y}_2={\boldsymbol a})$, the conditional distribution of the first partition given the second, is  $\mathcal{N}(\overline{\boldsymbol\mu},\overline{\Sigma})$, with mean $$ \overline{\boldsymbol\mu}=\boldsymbol\mu_1+\Sigma_{12}{\Sigma_{22}}^{-1}({\boldsymbol a}-\boldsymbol\mu_2) $$ and covariance matrix $$ \overline{\Sigma}=\Sigma_{11}-\Sigma_{12}{\Sigma_{22}}^{-1}\Sigma_{21}$$  Actually these results are provided in Wikipedia too, but I have no idea how the $\overline{\boldsymbol\mu}$ and $\overline{\Sigma}$ is derived. These results are crucial, since they are important statistical formula for deriving Kalman filters. Would anyone provide me a derivation steps of deriving $\overline{\boldsymbol\mu}$ and $\overline{\Sigma}$ ? Thank you very much! I understand if I boot from a live cd  I can see all the system logs under System > Administration > File Log Viewer   I have a major error with a disk not mounting and I want to trace i tback to the last time it did work and what may have corrupted the ext4 filesystem on it.  So within the File Log Viewer Where do I start examining? How to know if a time series is stationary or non-stationary? My question is the same as . I put my stackexchange flair at the bottom of my sites:     And get a &quot;profile for Ninsuo on Stack Exchange, a network of free, community-driven Q&amp;A sites&quot; link instead of my nice flair. By opening Firebug, I can read the following error:  Or as text:  NetworkError: 500 Internal Server Error -   I did not tried to update a new picture - just in case you want to get further first. Good luck!