I have a  (the first version of what it's now called simply Traktor Audio 2)  The problem in settings it only sees one output, when there should be two (I need that for Mixxx etc.)  Also I want to be able set the sample rate to one of these: 44.1, 48, 88.2, 96 kHz or at least check which one is set.   Additionally if possible setting the latency would be an advantage.  Some info:  $ aplay -l **** List of PLAYBACK Hardware Devices **** card 0: HDMI [HDA ATI HDMI], device 3: HDMI 0 [HDMI 0]   Subdevices: 1/1   Subdevice #0: subdevice #0 card 1: TraktorAudio2 [Traktor Audio 2], device 0: Traktor Audio 2 [Traktor Audio 2]   Subdevices: 1/2   Subdevice #0: subdevice #0   Subdevice #1: subdevice #1  $ cat /proc/asound/cards 0 [HDMI           ]: HDA-Intel - HDA ATI HDMI                       HDA ATI HDMI at 0xfdcfc000 irq 45 1 [TraktorAudio2  ]: snd-usb-caiaq - Traktor Audio 2                       Native Instruments Traktor Audio 2 (usb-0000:00:1d.7-8)
I've got a NI Traktor Audio 2 sound card I'd like to get working with Mixxx, but I don't seem to have any success so far. The card seems to be supported in Ubuntu out of the box, and it seems to work well with ALSA, but I cannot select it in Mixxx and I'm not sure whether is something I can do to make it see it (e.g. through).  So for testing purposes, on the command line I can execute aplay to check each channel:  aplay -D plughw:2,0,0 test.wav   and  aplay -D plughw:2,0,1 test.wav   That works well: I can hear the test sound on each channel (A and B)  The relevant output for this card using aplay -D is:  hw:CARD=TraktorAudio2,DEV=0      Traktor Audio 2, Traktor Audio 2      Direct hardware device without any conversions plughw:CARD=TraktorAudio2,DEV=0      Traktor Audio 2, Traktor Audio 2      Hardware device with all software conversions   From those 2 items on the output, plughw is the one that works, whereas hw doesn't.  The problem is that Mixxx only lets me select the hw card, which does not seem to work. I'd like to be able to select the plughw card, which is the one that's working.  I've tried suspending Pulse Audio as suggested by , but that did not seem to work. I also played around with an .asoundrc file similar to the one  (which was for an older model of this sound card), but also without success.  Any ideas on how to make Mixxx show the right card (and channel, while we are at it)?  Thanks!
For the Pell's equation where $d=2$: $$x^2-2y^2=1$$ What are all the integer solutions to the equation. Apparantly there are infinitely many solutions, but how would I represent them in an expression? How would one create an iterative function (or iterator object) in python? I am not very well versed on set theory or syntax, but I thought I knew the basics.  However, in a book about databases I am reading now, the author uses $2^x$ to signify "a set of $x$."  For example, $2^{\text{dogs}}$ is a set of $\text {dogs}$, etc.    The author never really explained this or why he does it, I just picked up the meaning from context.    I am not sure why the exponent operator is used, nor am I sure what the number $2$ has to do with it.  The sets being represented are NOT powers of $2$ (in size)... they come in all sizes.  Is this a valid notation?  I have not seen it anywhere before... Eclipse is giving me a warning of the following form:     Type safety: Unchecked cast from Object to HashMap   This is from a call to an API that I have no control over which returns Object:  HashMap&lt;String, String&gt; getItems(javax.servlet.http.HttpSession session) {   HashMap&lt;String, String&gt; theHash = (HashMap&lt;String, String&gt;)session.getAttribute("attributeKey");   return theHash; }   I'd like to avoid Eclipse warnings, if possible, since theoretically they indicate at least a potential code problem.  I haven't found a good way to eliminate this one yet, though.  I can extract the single line involved out to a method by itself and add @SuppressWarnings("unchecked") to that method, thus limiting the impact of having a block of code where I ignore warnings.  Any better options?  I don't want to turn these warnings off in Eclipse.  Before I came to the code, it was simpler, but still provoked warnings:  HashMap getItems(javax.servlet.http.HttpSession session) {   HashMap theHash = (HashMap)session.getAttribute("attributeKey");   return theHash; }   Problem was elsewhere when you tried to use the hash you'd get warnings:  HashMap items = getItems(session); items.put("this", "that");  Type safety: The method put(Object, Object) belongs to the raw type HashMap.  References to generic type HashMap&lt;K,V&gt; should be parameterized. Accessing laptop's hard drive when OS won't boot Why have a letter in a word when it’s silent in pronunciation, like the b in debt?  Can anyone please clarify my uncertainty here? Process substitution and pipe I was wondering how to understand the following:     Piping the stdout of a command into the stdin of another is a powerful   technique. But, what if you need to pipe the stdout of multiple   commands? This is where process substitution comes in.   In other words, can process substitution  do whatever pipe can do?   What can process substitution do, but pipe cannot? Unable to mount Windows (NTFS) filesystem due to hibernation Is it possible to create an  shader in Cycles? Specifically for something like , , , etc.. Function ereg() is deprecated Where to find the checksums of Ubuntu ISO images? I just downloaded the ubuntu-10.10-desktop-i386.iso, and am having a hard time burning it, so I'd like to check that the file is intact, but I cannot find the md5sum of the file.    Is there a URL or official FTP mirror which includes the md5sum of the Ubuntu disk images? I'm a little confused as to whether I should install Ubuntu on its own partition on my hard drive, use VirtualBox or another virtualization package to install it, or use Wubi to install it directly on top of my current OS (Win 7). I definitely want to learn and use Ubuntu, so this is not just for playing around with it.   Also, if I choose to partition, should I partition the hard drive myself or should I let the Ubuntu installation menu do it for me? I understand that I am going to need a main partition, for Ubuntu's core components, and also a swap partition. Then there is the option to add a partition for "home"- I don't understand what combination of these partitioning options I should choose, or whether it is better to partition in Windows before I install Ubuntu or just partition my hard drive when I install Ubuntu itself How do I make my program watch for file modification in C++? I have the following code that will remove lines with the pattern banana and 2 lines after it:  sed '/banana/I,+2 d' file   So far, so good! But I need it to remove 2 lines before banana, but I can't get it with a “minus sign” or whatever (similar to what grep -v -B2 banana file should do but doesn't):  teresaejunior@localhost ~ &gt; LC_ALL=C sed '-2,/banana/I d' file sed: invalid option -- '2' teresaejunior@localhost ~ &gt; LC_ALL=C sed '/banana/I,-2 d' file sed: -e expression #1, char 16: unexpected `,' teresaejunior@localhost ~ &gt; LC_ALL=C sed '/banana/I,2- d' file sed: -e expression #1, char 17: unknown command: `-' Raised index of partial derivative I am having a really hard time wrapping my head around component notation for tensor fields. For example, I do not know exactly what the following expression means $$\partial_\mu\partial^\nu \phi, \tag{$\#$}$$ where $\phi$ is a scalar field. On the one hand $\partial^\nu=g^{\lambda\nu}\partial_\lambda$ where $g_{\mu\nu}$ is the Minkowski metric, and hence we could write explicitly $$\partial_\mu\partial^\nu \phi=\sum_{\mu,\nu,\lambda}g^{\lambda\nu}\partial_\mu \partial_{\lambda}\phi=\sum_{\mu,\nu}\partial_{\mu}\partial_{\nu}\phi=\partial_\mu\partial_\nu\phi. \tag{$*$} $$ On the other hand, we may think of $\partial_\mu\partial^\nu=g(\partial_\mu,\partial^\nu)=\delta_\mu^\nu;$ so that $\partial_\mu\partial^\nu\phi=\phi?$ Maybe? I am actually not sure of what this would mean. I am really confused. Any help is appreciated. Edit: To give context of where this expression comes from: I was computing the Lagrangian $$\mathcal L=\frac{1}{2}(\partial_\mu\phi)(\partial^\mu \phi) $$ considering an infinitesimal spacetime translation $x^ \mu\to x^\mu-\alpha a^\mu$. The scalar field thus transforms like $\phi(x)\to \phi(x)+\alpha(\partial_\mu\phi(x))a^\mu.$ Plugging thins into the Lagrangian yields the term I am referring to. Edit 2: The change in placement of indices are actually my doubts. I try to elaborate. I do not have any background in using indices to talk about tensors. I am used to interpret the expressions $\partial_\mu$ as the local vector field defined in some chart (local coordinates). I think about vector fields $X$ as abstract section of the Tangent bundle, which restricted to local coordinates can be expressed as $X=X^\mu\partial_\mu$. In the context of QFT, as far as I understand, the symbol $\partial_\mu$ denotes  $(\partial_t,\nabla)$ in the local coordinates $(t,x,y,z)$. So that $\partial_\mu\phi=(\partial_t \phi,\partial_x \phi,\partial_y\phi,\partial_z\phi)$. This was supposed to be my justification on why I wrote the summation on $\mu$ and $\nu$ in $(*)$, but now I note that this only applies when $\mu$ or $\nu$ appear twice, indicating the scalar product; which leads me to the last remark. I think of $g_{\mu \nu}$ as the component of the matrix $$g=\begin{pmatrix} 1&amp;0&amp;0&amp;0\\ 0&amp;-1&amp;0&amp;0\\ 0&amp;0&amp;-1&amp;0\\ 0&amp;0&amp;0&amp;-1\\ \end{pmatrix}$$ which represents the pseudo-Riemmanian metric, which by definition acts on tangent vectors, i.e. linear combinations of the $\partial_\mu$ applied to a point. This is where my doubt comes, in which was the right way to interpret the notation; in particular what is the expresion $(\#)$ in explicit coordinates? I've just installed Ubuntu 14.04 and am trying to install php 5.3. But when I run   apt-get install php5    it's installing php 5.5.9-1ubuntu4. I need to use php 5.3 in the system because the application I'm working on is built with php 5.3.   How can I achieve this? Prove that $f'(a)=\lim_{n\to\infty}\frac{f(b_n)-f(a_n)}{b_n-a_n}$ under some conditions Prove that $f'(a)=\lim_{n\to\infty}\frac{f(b_n)-f(a_n)}{b_n-a_n}$, with $f: (k_1,k_2)\to\Bbb R$ differentiable at $a\in (k_1,k_2)$, $\lim b_n=\lim a_n=a$, and $a_n&lt;a&lt;b_n$.   My attempt: Im trying to write the above equality as a particular case of this other equality that hold by any interior point $a$  $$f'(a)=\lim_{h\to 0}\frac{f(a+h)-f(a-h)}{2h}$$  Because $a_n&lt;a&lt;b_n$ then I can write  $$f'(a)=\lim_{n\to\infty}\frac{f(b_n)-f(a_n)}{b_n-a_n}=\lim_{n\to\infty}\frac{f(h_n+a)-f(a-j_n)}{h_n+j_n}$$  Where $h_n=b_n-a&gt;0$ and $j_n=a-a_n&gt;0$, where these two new sequences tends monotonically to zero.  Now my problem: my thought is that $h_n$ and $j_n$ are particular sequences then I can build a sequence $k_n$ such that $j_n$ and $h_n$ are subsequences so I can write:  $$\{h_n:n\in\Bbb N\}\subset\{k_n:n\in\Bbb N\}\text{ and }\{j_n:n\in\Bbb N\}\subset\{k_n:n\in\Bbb N\}$$  (I can build this $k_n$ by example doing $k_{2n}=h_n$ and $k_{2n-1}=j_n$) and then I have the desired expression  $$f'(a)=\lim_{n\to\infty}\frac{f(b_n)-f(a_n)}{b_n-a_n}=\lim_{n\to\infty}\frac{f(k_n+a)-f(a-k_n)}{2k_n}$$  My question:   Is this proof right? In particular Im unsure of the implicit statement "if the limit exist for $k_n$ then it must exist too for the particular case with $h_n$ and $j_n$". The use of two sequences, $h_n$ and $j_n$ in the limit make me unsure about the validity of this manipulation and assumption. There is a simpler/different way to prove the same?   Thank you in advance. Reading from text file until EOF repeats last line How to access the Index Of A Generic.List By Reflection? ok, ive a class and i pass an object as property.  the object that i pass is a List&lt;X&gt;  in my class im trying to access the Object index by reflection BUT I CAN'T!!!   Example:  this class works i just wrote down the part i want to show you and i need help.  class MyClass {     private object _recordSet;     public object RecordSet     {         get { return _recordSet; }         set { _recordSet = value; }     }      public string Draw()     {         system.reflection.Assembly asem = system.reflection.Assembly.getAssembly(_dataSource.GetType());          object instance;          instance = asem.CreateInstance(_dataSource.GetType().UnderlyingSystemType.FullName);          //to access de Count of my List         int recordcount = int.Parse(_dataSource.GetType().GetProperty("Count").GetValue(_dataSource,null));          //i need to do a          for(int cont = 0; cont &lt; recordCount; cont++)         {             _dataSource[cont].Name; // &lt;-- THIS PART IS NOT WORKING!!! because i cant access the Index Directly.... WHAT TO DO!! ???         }     } } Can I list the resources in a given package?