system discription # uname -r 4.4.0-104-generic cat /etc/os-release NAME=&quot;Ubuntu&quot; VERSION=&quot;16.04.6 LTS (Xenial Xerus)&quot; ID=ubuntu ID_LIKE=debian PRETTY_NAME=&quot;Ubuntu 16.04.6 LTS&quot; VERSION_ID=&quot;16.04&quot; HOME_URL=&quot;http://www.ubuntu.com/&quot; SUPPORT_URL=&quot;http://help.ubuntu.com/&quot; BUG_REPORT_URL=&quot;http://bugs.launchpad.net/ubuntu/&quot; VERSION_CODENAME=xenial UBUNTU_CODENAME=xenial  apt 1.0.1ubuntu2.23 for amd64 compiled on Mar 25 2019 14:35:10  problem description of some unknown reason, my system failed into using apt to install any package with following details and any action with call apt to do some writing job will faile: apt install libalgorithm-diff-xs-perl --download-only -f Reading package lists... Done Building dependency tree Reading state information... Done You might want to run 'apt-get -f install' to correct these: The following packages have unmet dependencies:  libapparmor-perl : Depends: perl-base (&gt;= 5.22.1-9ubuntu0.6) but 5.22.1-9 is to be installed  libc6-dbg : Depends: libc6 (= 2.19-0ubuntu6.15) but 2.23-0ubuntu11.2 is to be installed  libc6-i386 : Depends: libc6 (= 2.19-0ubuntu6.15) but 2.23-0ubuntu11.2 is to be installed  libguestfs-perl : Depends: perlapi-5.18.2 but it is not installable  libhtml-parser-perl : Depends: perlapi-5.18.1 but it is not installable  liblocale-gettext-perl : PreDepends: perlapi-5.18.1 but it is not installable  libsocket6-perl : Depends: perlapi-5.18.2 but it is not installable  libsub-name-perl : Depends: perlapi-5.18.1 but it is not installable  libsys-virt-perl : Depends: perlapi-5.18.2 but it is not installable  libtext-charwidth-perl : Depends: perlapi-5.18.1 but it is not installable  libtext-iconv-perl : Depends: perlapi-5.18.1 but it is not installable  libtext-soundex-perl : Depends: perlapi-5.18.1 but it is not installable  libwin-hivex-perl : Depends: perlapi-5.18.2 but it is not installable  libxml-parser-perl : Depends: perlapi-5.18.1 but it is not installable  perl : Depends: perl-base (= 5.22.1-9ubuntu0.6) but 5.22.1-9 is to be installed         Recommends: rename but it is not going to be installed E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).  # apt-get -f install Reading package lists... Done Building dependency tree Reading state information... Done Correcting dependencies... failed. The following packages have unmet dependencies:  libalgorithm-diff-xs-perl : Depends: perlapi-5.18.1 but it is not installable  libapparmor-perl : Depends: perl-base (&gt;= 5.22.1-9ubuntu0.6) but 5.22.1-9 is installed  libc6-dbg : Depends: libc6 (= 2.19-0ubuntu6.15) but 2.23-0ubuntu11.2 is installed  libc6-i386 : Depends: libc6 (= 2.19-0ubuntu6.15) but 2.23-0ubuntu11.2 is installed  libguestfs-perl : Depends: perlapi-5.18.2 but it is not installable  libhtml-parser-perl : Depends: perlapi-5.18.1 but it is not installable  liblocale-gettext-perl : PreDepends: perlapi-5.18.1 but it is not installable  libsocket6-perl : Depends: perlapi-5.18.2 but it is not installable  libsub-name-perl : Depends: perlapi-5.18.1 but it is not installable  libsys-virt-perl : Depends: perlapi-5.18.2 but it is not installable  libtext-charwidth-perl : Depends: perlapi-5.18.1 but it is not installable  libtext-iconv-perl : Depends: perlapi-5.18.1 but it is not installable  libtext-soundex-perl : Depends: perlapi-5.18.1 but it is not installable  libwin-hivex-perl : Depends: perlapi-5.18.2 but it is not installable  libxml-parser-perl : Depends: perlapi-5.18.1 but it is not installable  perl : Depends: perl-base (= 5.22.1-9ubuntu0.6) but 5.22.1-9 is installed         Recommends: rename but it is not installed E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages. E: Unable to correct dependencies  Things i've tried:  I tried to remove packages like libalgorithm-diff-xs-perl, libtext-charwidth-perl... and all packages that will use them by order which block apt to work, and finally apt is ok to work, but that really takes time and can not be reused.
I am not sure what caused this error, but here is what the whole error says, and also this is sitting as a notification, and preventing me from updating any software using Update Manager - Please provide some assistance or tell me how to figure out what to do to fix it.  Could not calculate the upgrade  An unresolvable problem occurred while calculating the upgrade.  Please report this bug against the 'update-manager' package and include the following error message: 'E:Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.'
Continuous bijection from $(a,b) \to S^1$? Using the uncertainty principle to estimate the ground state energy of hydrogen I have been reading through this  of the ground state energy of hydrogen  and others like it. In this one it says it is using the uncertainty principal but then proceeded to use the following: $$pr=\hbar$$ But why is it not using: $$pr=\frac{\hbar}{2}$$ which is more in line with the uncertainty principle and what comes earlier in the derivation. Which hydroxyl from either the phosphate or the glycerol is taken during synthesis of a phospholipid head? Since drush 9 (drupal 8.4 requirement), alias @sites does not seem to be implemented anymore (or yet ?).  $ drush @sites cr The alias @sites could not be found.   Is this a way to get the same behavior that does not consist of typing my 300 alias in a config file ? Blender 2.80 system Req + GPU req Can someone please let me know the minimum system requirements and GPU requirement to run blender 2.80 and eevee smoothly?   Also please let me know the optimum system requirements for the purpose of    environment modeling Game development charachter modelling and animation   Also if someone can suggest me a good desktop/laptop for personal use that is compatible with blender 2.80 in a low budget.  Any help will be much appreciated.  Thanks in advance! Center of mass in a straight rod I got an assignment to prove that in a straight homogeneous rod, you can always choose a coordinate system in such a way that  $$\int_S x_1 \, dx_1 \, dx_2=0 $$  $$\int_S x_2 \, dx_1 \, dx_2=0 $$  $$\int_S x_1x_2 \, dx_1 \, dx_2=0$$  where $S$ is the cross section of the rod  Now, intuitively, I can understand that the first two expressions basically state that if you find the mass center of the rod, then all you have to do is to put the origin of the coordinate system in the mass center, and the integrals turn out to be zero. What I'm curious about is whether or not this is a good enough of an explanation, and also, a hint on how to obtain the third equality. Where can I ask a question about finding general software that meets certain requirements? I have a list of requirements for a program, but I don't know what program meets these criteria. That's about general-purpose software, for example, not a programming IDE or statistical workbench, questions about which would certainly go to respective sites.  Is this question appropriate on Stack Overflow? Where should I ask about it? On Super User or elsewhere? Proving identities (mod $pq$) using Fermat's little theorem? Error When Create Drupal Commerce Product Display Dragging files into blender INT(5) vs SMALLINT(5): numbers in parenthesis after the numeric type In MySQL table definitions is there a different between INT(5) and SMALLINT(5)?  Or do they both represent the same size? Query Activity for ORDER BY xxx DESC LIMIT Let $X$ be a space that satisfies the hypotheses used to construct a universal cover $\overline{X}$. Let $\pi = \pi_1(X)$ and consider the action of the group $\pi$ on the space $\overline{X}$ given by the isomorphism of $\pi$ with $\text{Aut}(\overline{X})$. Let $A$ be an abelian group and let $\mathbb{Z}[\pi]$ act trivially on $A$, $a \cdot \sigma = a$ for $\sigma \in \pi$ and $a \in A$.  Now, assume that $X$ is a CW complex. How do I see that $\overline{X}$ is a CW complex such that the action of $\pi$ on $\overline{X}$ induces an action of the group ring $\mathbb{Z}[\pi]$ on the cellular chain complex $C_*(\overline{X})$ such that each $C_q(\overline{X})$ is a free $\mathbb{Z}[\pi]$-module and$$C_*(X; A) \cong A \otimes_{\mathbb{Z}[\pi]} C_*(\overline{X})?$$ $24\mid n(n^{2}-1)(3n+2)$ for all $n$ natural problems in the statement. For some of the apps I've developed (then proceeded to forget about), I've been writing plain SQL, primarily for MySQL.  Though I have used ORMs in python like , I didn't stick with them for long.  Usually it was either the documentation or complexity (from my point of view) holding me back.  I see it like this: use an ORM for portability, plain SQL if it's just going to be using one type of database. I'm really looking for advice on when to use an ORM or SQL when developing an app that needs database support.  Thinking about it, it would be far better to just use a lightweight wrapper to handle database inconsistencies vs. using an ORM. Site hosted on EC2 / Amazon held hostage with private key I have a new client whose previous developer has left her high &amp; dry with her site on Amazon/EC2. He holds the private key to the instance, and though she has full access to the Amazon control panel (she's paying $300/mo for a site that has like 3 visitors per week) she doesn't have any way to get her content off and move to a new host.  I'm not familiar with AWS and am not sure how to help her. The site's group/file permissions are screwed up on the server so exporting the content/database via her WordPress control panel isn't working.  Any ideas on how to help her? Thanks! Making yogurt at home is a fairly straight-forward process.  Heat milk to 180F (82C), cool that milk to at least 110F (43C), add live cultures, usually in the form of yogurt with said cultures, incubate, then chill.   There are several variables in the process, some of which are: The fat content of the milk (I typically use whole), how long to hold the milk during the initial heat step, how long it takes to cool the milk, the temperature of the incubation step, and the length of time for incubation, to name a few.  While length of time for incubation, and temperature at this stage, clearly contribute to sourness, I am trying to nail down the variable that contributes to a creamy texture.  I'm not referring to breaking or clumping, as described in .  My yogurt comes out smooth.    My initial hypothesis is that holding the milk for a length of time at the initial 180F(82C) (rather than immediately removing from heat and/or chilling) has an impact on final texture. Any thoughts or experience that might inform my hypothesis? Can we define flat connection on any given smooth manifold? For example, a sphere $S^2$ in $\mathbf{R}^3$ is apparently not flat with respect to the Euclidean connection, but can we define a flat connection and thus with affine charts on $S^2$? Is it possible to unwrap materials made in Vertex Paint? I painted an group of objects in Blender using the Vertex Paint and was wondering if it would be possible to unwrap the mutliple materials(when the objects are joined together using Ctrl+J)? Do I have to paint it all over again? Boundary conditions for calculus of variations in phase space and under canonical transformations This might be a stupid question, but I just don't get it. In Hamiltonian mechanics when examining conditions for a $(\boldsymbol{q},\boldsymbol{p})\rightarrow(\boldsymbol{Q},\boldsymbol{P})$ transformation to be canonical one starts with $$ \dot{q}_ip^i-H(\boldsymbol{q},\boldsymbol{p},t)= \dot{Q}_iP^i-\bar{H}(\boldsymbol{Q},\boldsymbol{P},t)+\frac{d}{dt}W(\boldsymbol{q},\boldsymbol{Q},t)$$ where $\bar{H}$ is the transformed Hamiltonian, and $W$ is the generating function (now a function of $\boldsymbol{q}$ and $\boldsymbol{Q}$). This term shouldn't break Hamilton's principle, since $$ \delta\int_{t_1}^{t_2} dt\frac{d}{dt}W(\boldsymbol{q},\boldsymbol{Q},t)=\delta W(\boldsymbol{q},\boldsymbol{Q},t)|_{t_2}-\delta W(\boldsymbol{q},\boldsymbol{Q},t)|_{t_1}=0-0=0 .$$ But I don't see why the variation of $W$ should disappear at the endpoints (say at $t_1$). Expanding leads to: $$ \delta W(\boldsymbol{q},\boldsymbol{Q},t)|_{t_1}=\left(\frac{\partial W}{\partial q_i}\right)_{t_1}\underbrace{\delta q_i(t_1)}_{=0}+ \left(\frac{\partial W}{\partial Q_i}\right)_{t_1}\delta Q_i(t_1)=\left(\frac{\partial W}{\partial Q_i}\right)_{t_1}\delta Q_i(t_1).$$ $\boldsymbol{Q}$ is itself a function of $\boldsymbol{q}$ and $\boldsymbol{p}$, so $$ \delta Q_i(t_1)=\left(\frac{\partial Q_i}{\partial q_k}\right)_{t_1}\underbrace{\delta q_k(t_1)}_{=0}+\left(\frac{\partial Q_i}{\partial p_k}\right)_{t_1}\delta p_k(t_1)=\left(\frac{\partial Q_i}{\partial p_k}\right)_{t_1}\delta p_k(t_1). $$ It seems as if we also needed the variation of $\boldsymbol{p}$ to vanish at the endpoints, and I don't get this because (at least in cartesian coordinates) $\boldsymbol{p}=m\dot{\boldsymbol{q}}$ and the velocity can be different along the original and the varied orbitals even at the endpoints (they can point in totally different directions), so in general $\delta \dot{\boldsymbol{q}}(t_1)\neq 0$. What am I doing wrong? Can someone help me with this, please?