I dropped my Nikon D3200. Camera still turns on, but the lens wont attach to the body. It looks like something at the bottom of the lens might be broken; not the actual lens, but a small black circle type of thing. Anybody has any idea how much something like that will cost to repair?
I dropped my camera while on holiday last summer. Thankfully, my camera wasn't damaged but the kit lens has lost the ability to autofocus and the UV filter and 58mm to 52mm filter step-down (I use it to attach a fisheye filter to the lens) I had on its end are stuck and won't come off.  I've replaced the lens with an 18-200 zoom lens so I don't especially need it. I was wondering if it was worth getting the lens looked at and possibly repaired?  I've heard many places will charge you £50 or so just to look at the lens and given the cost of the kit lens I'm not sure it's worth it.
This is a  about DoS and DDoS mitigation.   I found a massive traffic spike on a website that I host today; I am getting thousands of connections a second and I see I'm using all 100Mbps of my available bandwidth.  Nobody can access my site because all the requests time out, and I can't even log into the server because SSH times out too!  This has happened a couple times before, and each time it's lasted a couple hours and gone away on its own.  Occasionally, my website has another distinct but related problem: my server's load average (which is usually around .25) rockets up to 20 or more and nobody can access my site just the same as the other case.  It also goes away after a few hours.  Restarting my server doesn't help; what can I do to make my site accessible again, and what is happening?  Relatedly, I found once that for a day or two, every time I started my service, it got a connection from a particular IP address and then crashed.  As soon as I started it up again, this happened again and it crashed again.  How is that similar, and what can I do about it? What happens to Zhang ziyi (Jen) in  when she jumps off the cliff .. she dies? becomes immortal? Just before jumping what does she want Lo to become - a master?  Why does she jump off, guilt? Invariance of a maximally entangled state under unitary operation $U \otimes U^\dagger$ Apparently the (d-dimensional) maximally entangled state, $|E \rangle = \sum_{i} |ii\rangle /\sqrt{d}$ is invariant under operations of the form $U \otimes U^\dagger$. I want to prove this result, which amounts to showing that  $$\left(\sum_i U | i \rangle \otimes V |i \rangle = \sum_i | ii \rangle \right)\Rightarrow (V = U^\dagger )$$  I have no idea how to even start. I suppose it's some simple linear algebra result, but I don't see it. A hint would be appreciated. So I had 20+ Pokemon on my account and today when I tapped on the app, it brought me back to the original screen when you first start playing. My friend who signed up tested using my username when she first started and my username was unavailable, meaning the account still exists. I don't have the password for the account, but I do have the email. So I wanted to know if it was possible to log back into an account? When I launch nautilus from terminal the following error is printed and nautilus doesn't open up.  (nautilus:25179): GLib-GIO-CRITICAL **: g_dbus_interface_skeleton_unexport: assertion 'interface_-&gt;priv-&gt;connections != NULL' failed  (nautilus:25179): GLib-GIO-CRITICAL **: g_dbus_interface_skeleton_unexport: assertion 'interface_-&gt;priv-&gt;connections != NULL' failed Could not register the application: Timeout was reached  (nautilus:25179): Gtk-CRITICAL **: gtk_icon_theme_get_for_screen: assertion 'GDK_IS_SCREEN (screen)' failed  (nautilus:25179): GLib-GObject-WARNING **: invalid (NULL) pointer instance  (nautilus:25179): GLib-GObject-CRITICAL **: g_signal_connect_object: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed   What could be the problem?? No sound and flash videos play super fast after daily update I just updated my 11.10 Ubuntu from the regular auto updater. After I restarted my laptop I have no sound and the videos in YouTube (and other websites) play super fast.  Not sure if it has something to do with the case, but since last night I get hd0 out of disk error before the grub screen and on the login screen I have some delay before I can type my password. In the console I see errors like these: status: {DRDY err}.  I could say the errors have something to do with the sound problem and the flash player, but if this happened when I got the hd0 error, not now after the regular daily update.  Here is the update history log from /var/log/apt/history.log   Start-Date: 2012-04-03  10:04:39  Commandline: aptdaemon role='role-commit-packages' sender=':1.71' Upgrade: python-aptdaemon.gtkwidgets:amd64 (0.43+bzr697-0ubuntu1, 0.43+bzr697-0ubuntu1.2),  libvlc5:amd64 (2.0.1+git20120329+r134-0~r35~oneiric1, 2.0.1+git20120402+r146-0~r36~oneiric1),  python-aptdaemon:amd64 (0.43+bzr697-0ubuntu1, 0.43+bzr697-0ubuntu1.2),  vlc-nox:amd64 (2.0.1+git20120329+r134-0~r35~oneiric1, 2.0.1+git20120402+r146-0~r36~oneiric1),  vlc-plugin-notify:amd64 (2.0.1+git20120329+r134-0~r35~oneiric1, 2.0.1+git20120402+r146-0~r36~oneiric1),  aptdaemon:amd64 (0.43+bzr697-0ubuntu1, 0.43+bzr697-0ubuntu1.2),  python-aptdaemon-gtk:amd64 (0.43+bzr697-0ubuntu1, 0.43+bzr697-0ubuntu1.2),  vlc:amd64 (2.0.1+git20120329+r134-0~r35~oneiric1, 2.0.1+git20120402+r146-0~r36~oneiric1),  aptdaemon-data:amd64 (0.43+bzr697-0ubuntu1, 0.43+bzr697-0ubuntu1.2),  vlc-data:amd64 (2.0.1+git20120329+r134-0~r35~oneiric1, 2.0.1+git20120402+r146-0~r36~oneiric1),   python-aptdaemon.gtk3widgets:amd64, 0.43+bzr697-0ubuntu1,0.43+bzr697-0ubuntu1.2),  libvlccore5:amd64 (2.0.1+git20120329+r134-0~r35~oneiric1, 2.0.1+git20120402+r146-0~r36~oneiric1),  vlc-plugin-pulse:amd64 (2.0.1+git20120329+r134-0~r35~oneiric1, 2.0.1+git20120402+r146-0~r36~oneiric1) End-Date: 2012-04-03  10:05:15 My &quot;hat&quot; is shown twice in my answer, once in my sig, and again above. MacOS 10.14.6; Safari Version 14.0.2 (14610.3.7.1.10) Suppose $X$ is a finite set and $f : X \to X$ is a function. Then $f$ is injective if and only if $f$ is surjective. Suppose $X$ is a set and $f : X \to X$ is a function.  If $X$ is a finite set, prove that $f$ is injective if and only if $f$ is surjective. Show that when $X$ is an infinite set, the statement is not true in general.   For that, let $X = \mathbb{R}$ and find a function $f: \mathbb{R} \to \mathbb{R}$ which is injective but not surjective, and a function $g: \mathbb{R} \to \mathbb{R}$ which is surjective but not injective  My attempt at the first part   Suppose that the function is surjective but not injective. Let $a,b \in X$ such that $f(a)=f(b)$ but $a \not =b$. Now since this is a finite set mapping to itself then there are not enough elements in $X$ to map to $X$ since two elements were used to map to one element, thus the function can't be surjective. Therefore if the function is surjective it is also injective.   Now suppose that the function is injective but not surjective. Let $a \in X$ such that $f(b)\not =a$ for all $b \in X$. Since the function was assusmed to be injective each $a \in X$ must map to an element of $X$, thus must have two elemetns in $X$ mapping to the same element in $X$. Hence the function can't be injective, therefore if the function is injective it must be surjective.   Would an exponetial function work for injective but not surjective since can't map to negative numbers. And an example of a function that is surjective but not injective could be a log function since none of the negative numbers get mapped to anything?   Also I'm having trouble seeing why it has to be finite for the first part to work. I understand it has something to do with the pigeonhole principle but its not that clear to me. How do I interpret the results of a regression which involves interaction terms? If I have a linear regression of the form:  $$y \sim 1+\beta_1x_1 + \beta_2x_1x_2,$$  where $x_2$ is a Boolean variable depending on another variable $x_{2cont}$, a positive variable:  $$x_2 = \begin{cases} 1 &amp; \mbox{if } x_{2cont} &gt; 5 \\ 0 &amp; \mbox{if } 0 &lt; x_{2cont} \le 5. \end{cases}$$  And I got regression results. How shall I interpret the regression results?  esp. how shall I interpret the two coefficients I get from this regression,  $\beta_1 \text{ and } \beta_2$? I am trying to follow the best practice design patterns for triggers but get the error Constructor not defined: [CaseTriggerHandler].(). What am I missing?  Trigger  trigger CaseTrigger on Case (before insert, before update, before delete, after insert, after update, after delete, after undelete) {      CaseTriggerHandler handler = new CaseTriggerHandler();      //Before Insert     if(Trigger.isInsert &amp;&amp; Trigger.isBefore){         handler.OnBeforeInsert(Trigger.new);     }     //After Insert     else if(Trigger.isInsert &amp;&amp; Trigger.isAfter){         handler.OnAfterInsert(Trigger.new);     }     //Before Update     else if(Trigger.isUpdate &amp;&amp; Trigger.isBefore){         handler.OnBeforeUpdate(Trigger.old, Trigger.new, Trigger.newMap);     }     //After Update     else if(Trigger.isUpdate &amp;&amp; Trigger.isAfter){         handler.OnAfterUpdate(Trigger.old, Trigger.new, Trigger.newMap);     }     //Before Delete     else if(Trigger.isDelete &amp;&amp; Trigger.isBefore){         handler.OnBeforeDelete(Trigger.old, Trigger.oldMap);     }     //After Delete     else if(Trigger.isDelete &amp;&amp; Trigger.isAfter){         handler.OnAfterDelete(Trigger.old, Trigger.oldMap);     }     //After Undelete     else if(Trigger.isUnDelete){         handler.OnUndelete(Trigger.new);     } }   Handler      public with sharing class CaseTriggerHandler {      private boolean isExecuting = false;      public CaseTriggerHandler(boolean isExecuting){         this.isExecuting = isExecuting;     }      public void OnBeforeInsert(List&lt;Case&gt; newCases){         //EXECUTE BEFORE INSERT LOGIC     }      public void OnAfterInsert(List&lt;Case&gt; newCases){         //EXECUTE AFTER INSERT LOGIC     }      public void OnBeforeUpdate(List&lt;Case&gt; oldCases, List&lt;Case&gt; updatedCases, Map&lt;Id, Case&gt; CaseMap){         //BEFORE UPDATE LOGIC     }      public void OnAfterUpdate(List&lt;Case&gt; oldCases, List&lt;Case&gt; updatedCases, Map&lt;Id, Case&gt; CaseMap){         //AFTER UPDATE LOGIC     }      public void OnBeforeDelete(List&lt;Case&gt; CasesToDelete, Map&lt;Id, Case&gt; CaseMap){         //BEFORE DELETE LOGIC     }      public void OnAfterDelete(List&lt;Case&gt; deletedCases, Map&lt;Id, Case&gt; CaseMap){         //AFTER DELETE LOGIC     }      public void OnUndelete(List&lt;Case&gt; restoredCases){         //AFTER UNDELETE LOGIC     }      public boolean IsTriggerContext{         get{ return isExecuting;}     } } How do you force Chrome pages/tabs to crash using JavaScript? python3 is not supporting gtk module How to find the most famous questions on Stack Overflow? How to find questions with   most comments most votes most viewed   I have seen following question, but seems like there is no easy way.   Is there way to bookmark a page so that the same URL can be used to update data (which will be very seldom) at each hit? In formal logic, how is it possible for an argument with a contradictory conclusion to be valid? I've recently been trying to introduce myself to formal logic, and I've hit a stumbling point:  In the text I'm reading, a valid argument is defined as "an argument in which it is impossible for the premises to be true and at the same time the conclusion false."  The text then later prompts me to declare whether it's possible for an argument to be valid with a contradiction for a conclusion. The answer key then claims that yes, it is in fact possible, but offers no further explanation. I'm also supposed to create an example.  I just can't wrap my head around this one.  Here's the example I've worked up, is this a valid argument?   If grass is green then it is raining.  If water is wet then it is not raining.  Therefore: It is raining and not raining.   My head hurts. $f$ is surjective iff it has a right inverse: using the axiom of choice and errors in ProofWiki Ubuntu 14.04 doesn' t boot after upgrade from 12.04 installed inside Windows 8.1 I have Ubuntu 12.04 installed like an app on windows 8.1 (Ubuntu 12.04 allow to be installed like an app in Windows 8.1 and it can be removed when you don't need it any more from Control Panel). Usually, to chose what os to boot when you start the laptop, you can choose between windows 8.1 and Ubuntu after windows logo appeared at start up and that was ok until I made this upgrade. Now when I try to choose Ubuntu the laptop try to boot it but, after that full colored screen is showed the screen go black and this messages appear:  mount: mounting /dev/loop0/ on /root failed : Invalid argument mount: mounting /dev on /root/dev failed: No such file or directory mount: mounting /sys on /root/sys failed: No such file or directory mount: mounting /proc on /root/proc failed: No such file or directory Target filesystem doesn' t have requested /sbin/init No init found. Try passing init = bootarg.  BusyBox v1.21.1 (Ubuntu 1:1:21.0-1ubuntu1) built-in shell (ash) Enter 'help' for a list of built-in commands  (initramfs) _   I don' t know what to do after this screen appears. Please help ! Why can't we see infrared light? No Wifi, HP Pavillion 15 Ubuntu 14.04 Often while playing Pathfinder, my group will run into problems where rules for 3-dimensional play simply don't exist, so far as we can find. Arguments will come up over things like carrying-capacity, movement speed, area-effects, and a variety of other things.  Simply put, are there rules for 3D play for Pathfinder, and if so where can I find them? I noticed that the paper size invoked by a4paper is not working right in my examples:  \documentclass[a4paper,11pt,oneside]{article} \begin{document} Test \end{document}   I checked with Preview.app and it tells me the paper size is 21.59 cm × 27.94 cm. A4 should be 21.0 cm × 29.7 cm.  When I use \usepackage[a4paper]{geometry} I notice a different size of the paper (it gets narrower) and Preview.app says: 21.01 cm × 29.71 cm, which seems right. I can reproduce this exact behavior with every class: article, book etc., scrartcl, scrreprt, etc., g-brief2 except memoir which gives me 21.01 cm x 29.71 cm    Is there something wrong or am I missing something?