I have a son, 13 years old, who needs his laptop for school for better writing, etc. But naturally he wants to play with it after working.  Are there any programs or packages for safety on the internet? A program limiting the time on the web and filtering the webpages would be great.
Does anyone know of a good way to set up some sort of parental controls so that one user account is subject to them, but not another?  A couple of friends of mine use Ubuntu and have kids (7 to 10 years old) who use the family computer. They'd like to have some blocking of adult sites. They're not going to supervise all the time, which I know might be ideal, but there we go. And they're not particularly technical, so they don't want to have to run scripts to turn the parental controls on and off regularly, but they can cope with having different accounts for different people. I haven't found a great way of doing this. I am pretty technical, so I'm happy to spend some time at the command line to set it up, but then it needs to just work.  Please don't just link to DansGuardian. If your answer doesn't address the different user account aspect, I will vote it down. If you want to talk about general parental controls that apply to all users then please start a new question - I'm sure that plenty of people would be interested in it, and I'll link to it from this question.
How can I create a coffee cream effect with Photoshop? Today I would like to create a coffee cup with the cream floral on it as a text by using Photoshop. It looks like you order a cup of hot cappuccino and the bartender will draw a flower with cream on the surface of coffee but now I want to make it like a text to present a tittle.     I just need to do the cream text effect, no need to draw the whole cup of coffee since i can't use some images. So anyone can tell me how to do this cream effect on Photoshop.  Thanks in advance for any feedback! Spacing issue for newenvironment wrapper of equation environment If I create a custom environment based on the equation environment, I get a spacing issue: the next line of text after my environment closes doesn't start on the left margin.  Example code:  \documentclass{article} \begin{document} \newenvironment{myenv}{\begin{equation}}{\end{equation}} \noindent $| \leftarrow$ this is the left margin. \begin{myenv} e ^{i \pi} + 1 = 0 \end{myenv} $| \leftarrow$ this isn't the left margin. \end{document}   Output:    Removing the newline after \end{myenv} solves the spacing problem, but the resulting code is not readable.  Of course, in this example I could just use the equation environment itself. My real issue involves a more complex custom environment that suffers from the same problem, and which also includes an equation environment within it. What's a word for someone who is constantly asking for same thing? Hi I'm looking for a word for someone who is constantly asking for something and keeps wanting updates about it. The closest words I can think of is pushy and, to a lesser extent, annoying. But clearly these words don't directly mean what I intend. Present tense for future events Why does it sound perfectly natural to say Our flight leaves tomorrow at 6pm but weird to say It rains tomorrow at 6pm? What kind of scenario, if any, could make the rain sentence sound natural? Image uploads from the editor strip preceding line breaks Recently, using the image uploader in the post editor has starting stripping preceding line breaks; placing the image directly after any previous text instead of at the current cursor position. This means that the inserted image is placed inline as part of the previous line of text rather than in a new paragraph as it did previously...  Before inserting the image (note the cursor position):        After inserting the image:        This also happens after the Markdown for a horizontal rule, which destroys the rule and gives us a bunch of hyphens followed by an image instead:        Seems the behaviour is a bit inconsistent... Sometimes I get the behaviour shown above and sometimes it leaves a single newline, I'm not sure when or why but single line breaks are ignored in Markdown so the rendered result is the same regardless.  Obviously it's useful to be able to have inline images, but I'm pretty certain most images aren't intended to (and shouldn't) be. Loading a package conditionally Non in front of hyphenated adjective Why is inductance (L) proportional with turns-square (N²)? We start from the   $$ \mathbf{\nabla} \times \mathbf{B} = \mu \mathbf{J} + \overbrace{\mu \epsilon \dfrac{\partial \mathbf{E}}{\partial t}}^0. $$  We take surface integration of both sides, for the surface (\$s\$) inside the mean path (\$c\$) of the core.  $$ \int_s \left( \mathbf{\nabla} \times \mathbf{B} \right) \cdot d\mathbf{s} = \mu \int_s \mathbf{J} \cdot d\mathbf{s} $$  We use the  to rewrite the left hand side; where \$c\$ is in the same direction with the magnetic flux \$\Phi\$.  $$ \oint_c \mathbf{B} \cdot d \mathbf{\ell} = \mu N I $$  (The integral on the left hand side results \$NI\$, because there are \$N\$ different wires on the winding.)  The magnetic field density inside these kind of cores are considered to be uniform. So, we can write  $$ B \ell_c \overset\sim= \mu NI \implies B = \dfrac{\mu NI}{\ell_c}; $$  where \$\ell_c\$ is the mean path lenght of the core.  We can find magnetic flux from the magnetic flux density we have found by using the cross sectional area of the core \$A_c\$.  $$ \Phi = BA_c = \dfrac{\mu NIA_c}{\ell_c} $$  By definition, inductance is the amount of magnetic flux generated per applied current, that is  $$ L \overset\triangle= \dfrac{\Phi}{I}. $$  So, we find inductance of the system as  $$ \boxed{ L = \dfrac{\Phi}{I} = \dfrac{\dfrac{\mu NIA_c}{\ell_c}}{I} = \dfrac{\mu NA_c}{\ell_c} }. $$  But, all other sources () give inductance of an inductor like this as  $$ L = \dfrac{\mu N^2A_c}{\ell_c}. $$  What is the mistake I did in my derivation? Please explain in detail. If a function is a combination of other functions whose derivatives are known via composition, addition, etc., the derivative can be calculated using the chain rule and the like. But even the product of integrals can't be expressed in general in terms of the integral of the products, and forget about composition! Why is this? Verbless sentence I thought I heard my teacher said: 'Don't construct a sentence without a verb.'  Is there such rule in english grammar?     She looks like 70 years old. Perhaps older.   How about the question above? Is it correct? Is there any book that can be used references for wide range of topics in grammar(including syntax, morphology et cetera)? I have finished oxford grammar in use recently and think it wasn't enough for me. Product of pairwise coprime integers divides $b$ if each integer divides $b$ Let $a_1....a_n$ be pairwise coprime.  That is $gcd(a_i, a_k) = 1$ for distinct $i,k$, I would like to show that if each $a_i$ divides $b$ then so does the product.  I can understand intuitively why it's true - just not sure how to formulate the proof exactly. I want to say if we consider the prime factorizations of each $a_i$, then no two prime factorizations share any prime numbers.   So the product of $a_1...a_n$ must appear in the prime factorization of $b$.  Is this correct?  Or at least if if the idea is correct, any way to formulate it more clearly? Does decrease in temperature affect mass $E=mc^2$? My understanding of Quantum physics and String Theory is very basic and I don't yet have a grasp on the maths, but in my research I have come up with a question.  Does a decrease in temperature also signify/create a decrease in mass?  I am quite willing to believe the concepts I think I am beginning to understand are totally misconceptions on my part.  But, as I see it mass is a product/mark of disruption to the Higgs field as a particle moves.  If these particles are ultimately composed of vibrating Strings, their mass is given by the rate at which they vibrate and how it interacts with the Higgs field.  I don't have any idea if, as the temperature (as we know it) approaches 0k, the string/quark/sparticle would change its state in any way or if the changing of the state of the String would change what type of particle it represents.  It seems I'm more full of questions than answers, but that's why I love these topics!  I know what I'm learning is new if the best and brightest are still working on the 'basics' to just make their systems work :). A composite integer n is a Carmichael number if the only Fermat   witnesses for $n$ are those $a \in \mathbb Z_n^+$ which are not   coprime with $n$. The smallest example of such a number is $561 = 3 ·  11 · 17$   I think I understand the definition, but I don't quite understand why is the smallest Carmichael number is the above mentioned number. Please clarify. Get client IP address via third party web service How to use z-index in svg elements? mongodb $exists always returning 0 PHP generate file for download then redirect How Do Dementors Communicate with Wizards? Only half of the display works, can I set to display only in that region? I have a Macbook with a cracked screen, only the top left half of the screen works, is there anyway to reduce the screen resolution, keep the DPI the same, and thus have the entire OS visible in the top left section of the screen which works?  The below photo demonstrates what I mean, with parts of the creen totally unusable, it would make sense to be able to display the whole screen in the remaining usable part. What if my State / Country doesn't have a Ubuntu LoCo Team? How can I start one? I know what an Ubuntu Team is and , but what can users do if their area doesn't have a LoCo team?