Ubuntu bluetooth won't turn on
ubuntu 18.04 LTS bluetooth [0cf3:3004] discovery not working
I have a simple circuit:    The max rating (current) of the LED is 30mA.  How can I work out what the resistance of the resistor needs to be? By using ohm's law I found it to be \$3V/0.03A = 100 \Omega\$. However using software called , and trial and error I got the minimum possible resistance to be 36&Omega;. However, if I use a 35&Omega; resistor, then the LED breaks. Is the software wrong, or (more likely) am I doing something wrong? removeGroup() in QGIS 3 I am updating a plugin from QGIS 2 to 3.  I need to iterate through the groups (the names are dynamic) and remove them with their respective child layers.  I need to get a list of groups and then iterate through the groups and delete them.  The original code is as follows:  legend = self.iface.legendInterface() group_names = legend.groups() rev = self.groups[:] rev.reverse() ...     for i, group in enumerate(rev):         legend.removeGroup(group)   I replaced self.iface.legendInterface() with QgsProject.instance().layerTreeRoot() but group_names = legend.groups() fails with the message 'QgsLayerTree' object has no attribute 'groups'   What is the proper container of the groups and how do I access the collection; and, once found, how do I delete those groups?  A search for information on how to remove groups from a layer tree in QGIS 3 has proven fruitless. I have 2 partitions (Windows and Ubuntu 13.04) and I am asked which one to boot each time I turn on my computer.  I want to install Ubuntu 13.10 to the entire disk.  I do not mind if all previous Ubuntu/Win data are lost.  How can I do that? How to switch between Ubuntu and Windows 7 without a reboot I have installed windows 7 and then Ubuntu 11.04. Now I want to know how I can switch from Ubuntu to Windows 7 and from Windows 7 to Ubuntu without restarting the computer. Why is the application of probability in  (QM) fundamentally different from its application in other areas? QM applies probability according to the same  as in other areas of physics, engineering, etc.  Why is there a difference?  Naively one would assume one of these possibilities:   It is not the same probability (theory?) It is a matter of interpretation (of the formalism?) Something else?   Many answers (which I am still studying) focus on the fact that the combined probability of two mutually-exclusive events in QM is not equal to the sum of the probabilities of each event (which holds classically by definition). This fact (appears to) makes the formulation of another probability (a quantum one) a necessity.   Yet this again breaks down to assumed independent, if this is not so, the "classic probability" is applicable (as indeed in other areas). This is one of the main points of the question. Uninstall apps locked by phone vendor WinForms Global Exception Handling? Create WiFi hotspot on ubuntu The unique style of the diagrams at  has an informative but nice hand-drawn touch. I guess they are actually drawn by hand but just recently on our partner site for Mathematica someone asked how to draw a similar diagram such as this one with Mathematica's plot functions ().    Now without Mathematica this should be possible as well but I have a hard time getting the details right. Can such a diagram be created in TeX with a similar design? My first attempt does not look particularly great but here it is (the font is from ):      \documentclass{standalone}     \usepackage{tikz,color}     \usepackage{pgfplots}     \usepackage{fontspec}     \setmainfont{Humor-Sans}      \begin{document}     \begin{tikzpicture}     \pgfplotsset{every axis/.append style={line width=1pt}}      \begin{axis}[%         axis x line=bottom,         axis y line=left,         xtick={1.2, 2.9, 4.5},         xticklabels={-3 days, -1 day, 5 minutes},         yticklabels={}     ]     % 1st plot     \addplot [cyan!80!white, samples=200, domain=0:6] {0.05*rnd+3+(sin(deg(x))^2)/sqrt(x)*exp(-(x-2))};     % white background for 2nd plot     \addplot [white, samples=200, domain=0:6,line width=4pt] {0.05*rnd+0.4*x+2+x^2*sin(deg(x))^2*exp(-x)};      % 2nd plot     \addplot [red!80!white, samples=200, domain=0:6] {0.05*rnd+0.4*x+2+x^2*sin(deg(x))^2*exp(-x)};      \end{axis}       \node at (2.7,4.6) {downhill};     \draw  plot[smooth, tension=.7,line width=2pt] coordinates {(1.2679,5.5206) (1.9454,5.493) (2.4017,4.9261)};      \end{tikzpicture}      \end{document} How do I upgrade from 14.04 LTS to 16.04.1 LTS? So, today is July 21st and . gives me an option to download 16.04.1 LTS. However, attempting to upgrade gets me this message -  $ sudo do-release-upgrade Checking for a new Ubuntu release No new release found   What is wrong? Does it matter that I am running apt-get update behind apt-cacher-ng?  Note: Commenting out the files in apt.conf.d that used apt-cacher-ng did not make a difference.  Edit: Explanation for possible duplicates:  deals with upgrade from 12.04LTS to 14.04LTS. My question is specific to 14.04 LTS to 16.04.1 LTS upgrade. Old answers, while good for archival purposes are less relevant in a fast changing package like ubuntu. Moreover none of the answers answer what is wrong. The link  pointed out is mentioned in one of the comments. This Q &amp; A is more helpful for people upgrading today than the work around mentioned in "". outline object effect How can I achieve an outline effect similar to the ones found in League of Legends or Diablo III?      Is it done using a shader? How? I would prefer answers that are not tied up to any particular engine but one that I can adapt to whatever engine I'm working on. Mapping key combination with xmodmap I'm trying to achieve the following mapping keycode 135 = &lt;Ctrl-C&gt;  Is it possible to achieve this in some way? Determining if an Object is of primitive type I have an Object[] array, and I am trying to find the ones that are primitives. I've tried to use Class.isPrimitive(), but it seems I'm doing something wrong:  int i = 3; Object o = i;  System.out.println(o.getClass().getName() + ", " +                    o.getClass().isPrimitive());   prints java.lang.Integer, false.  Is there a right way or some alternative? Rearranging display order of attribute table fields using QGIS? I have 4 copies of the Hot Questions widgets.  Sometimes, possibly after they reload on their own, I can only tap to open the last widget I added. If I tap on the question of any others nothing happens.  If I refresh each one then tapping works on the one I refreshed. How to insert code with accents with listings? I'm trying to insert source code in LaTeX with using listings, but my code has accents and pdflatex gives me this error:  Unicode char \u8:�\expandafter not set up for use with LaTeX.   This is a code the reproduces the error.  example.tex  \documentclass{article} \usepackage{listings} \usepackage[utf8]{inputenc} \usepackage[spanish]{babel}  \begin{document}  \lstinputlisting[language=C++]{code.cpp}  \end{document}   code.cpp  // Código con una tilde   What can I do to generate the PDF correctly? Do there exist two primes $p<q$ such that $p^n-1\mid q^n-1$ for infinitely many $n$? We can prove that there is no integer $n&gt;1$ such that $2^n-1\mid 3^n-1$. This leads to the following question:     Is it true that for every pair of primes $p&lt;q$ there are only finitely many integers $n$ such that $p^n-1\mid q^n-1$? Are there two primes $p&lt;q$ and an integer $n&gt;p+q$ such that $p^n-1\mid q^n-1$?Is it true that if $n&gt;6$ then $2^n-1\nmid 5^n-1$?   Edit: Here are some examples: \begin{array}{ll} 2^{36}-1\mid 41^{36}-1, &amp;3^{12}-1\mid 97^{12}-1,\\ 5^{6}-1\mid 37^{6}-1, &amp;7^{4}-1\mid 151^{4}-1. \end{array}  Now I prove there is no integer $n&gt;1$ such that $2^n-1\mid 3^n-1.$  Proof: Denote $A=2^n-1$ and $B=3^n-1$. If $n$ is even then $3$ divides $A$ but not $B$, a contradiction.  If $n$ is odd then $A\equiv -5\pmod {12}$. Since every prime greater than $3$ is $\equiv \pm1,\pm5 \pmod {12}$, some prime factor $p$ of $A$ must be congruent to $\pm5 \pmod {12}$. As $p \mid B$, we have $3^{n+1}\equiv 3 \pmod p$. Since $n+1$ is even, we get $(\frac{3}{p})=1$, a contradiction again. What does the leading semicolon in JavaScript libraries do? Why avoid increment ("++") and decrement ("--") operators in JavaScript? I am really having trouble working a problem in my course. I will post it and then add what I have thought etc.  Let p be an odd prime, then using the Euclidian Algorithm, calculated the GCD of of $x^{p-1}-1$ and $x^2+1$ in $\mathbb{Z} / p\mathbb{Z}[x]$  Also, how does $p=1 (mod4)$ tell us that  $-1$ is a square in $\mathbb{Z} / p\mathbb{Z}$, infact that $-1$ is a square here if and only if $p=1(mod4)$.  My thoughts:   I know that $$x^{p}-x=(x)(x-1)(x-2)…(x-(p-1))$$ and so that in this sense our roots will be the congruence classes of $1,2,…p-1$  and also that $$x^{p-1}-1=(x-1)(x-2)…(x-(p-1))$$  But I get lost when trying to apply the EA to these polynomials,  like how can I do it when p is arbitrary?  Preferably id like to be able to understand/see how to do the first part first i.e. using division with residue and then move on to the second part. Any insight/hint or solution to this would be great,  Thank you all  Update:  When I try to do division with residue, I just get  $$x^{p-1}-1=(x^2+1)(x^{p-3}-x^{p-5}+x^{p-7}-x^{p-9}...)$$  for example,  $p=7$  $$(x^{6}-1)=(x^2+1)(x^4-x^2+1)$$  for $p=11$  $$(x^{10}-1)=(x^2+1)(x^{8}-x^{6}+x^{4}-x^{2}+1)$$  which for specific cases tells me that 1 is the gcd, but I dont know how to generalize that for the case with arbitrary prime p.