MongoDB: how to search for fields in a collection
Get names of all keys in the collection
Is 20 watts of electricity dangerous? I have a few circumstances which invlove someone being shocked with 20 watts of electricity and whether it would be deadly. So here they are:   Would 1000 volts at 20 miliamperes of AC (2MHz frequency) be dangerous or deadly? Would 1000 volts at 20 miliamperes of DC be dangerous or deadly? Would 10 Kilo volts at 2 miliamperes of AC (2MHz frequency) be dangerous or deadly? and Would 10 Kilo volts at 2 miliamperes of DC be dangerous or deadly?   Thanks for everyones help. I'm used to creating Java Edition Minecraft maps, where NBT can be used to set many different block, item, and entity properties, like an item's CanPlaceOn/CanDestroy list, a chest's items, and more! To open my maps up to more players, I've started creating maps on Minecraft Bedrock Edition as well. But NBT is inaccessible from commands in BE, which I knew before, but didn't know how much of a problem I would have creating these complicated command chains. One of the things that I've always been doing is giving players items with custom item names, lores, enchantments, and other properties. But there is a problem. All this would have been done in NBT in Java Edition. In Bedrock, NBT is inaccessible from commands, meaning the commands I used in JE don't work. Are my dreams crushed? How do I make my textures show in cycles? I am admittedly new to Blender, and of course cycles. I am working on a scene and I have textures set to my objects that render with internal engine just fine. However, when I go into cycles, everything is greyish. I have two light sources that should be sufficient (I think), I just don't know what I'm doing wrong. This is a screenshot of the cycles result. Google Maps Location History is showing an incorrect location I have a major problem that I hope someone can help with. On my Google Maps feature under my Location History it shows a location that I was never at at any point, but when my wife happened to see that location she doesn't believe me that the GPS could be wrong and pinpoint that location if I was never there.  I was first wondering myself how could that could be possible if I was never there or my phone was never at that location that was 35 miles away from me and second is there any way I could prove the GPS being wrong? Can I contact Google Maps and can they give an official printout of that certain day and every location I was? I really need to prove my honesty to her and hope there is a way. using a:hover to change the color of an image How can I use the "signature" function in Preview on Mac Mini with no camera? I have a Mac Mini with no attached camera. I would like to use the feature of Preview that allows you to insert a signature. This relies on taking an image of your signature using an isight/facetime/webcam. I do not have on.  I do have a MacBook pro on which I use the signature function. Is there a way to copy a file from the the MacBook Pro to the Mac Mini to enable this function on the Mini? When can I make opportunity attacks? command not found and syntax error near unexpected token Code block is not properly formatted when placed immediately after a list item Consider the following piece of Markdown code:  This is some regular text.      &gt;&gt;&gt; def factorial(n):     ...     return 1 if n &lt; 2 else n * factorial(n - 1)     ...   * This is a list item.      &gt;&gt;&gt; def factorial(n):     ...     return 1 if n &lt; 2 else n * factorial(n - 1)     ...    Notice that the second code block is preceded by a list item.   Why is the factorial code not properly formatted under these circumstances? To demonstrate the problem, I'll insert the Markdown code show above:    This is some regular text.  &gt;&gt;&gt; def factorial(n): ...     return 1 if n &lt; 2 else n * factorial(n - 1) ...     This is a list item                 def factorial(n):       ...     return 1 if n &lt; 2 else n * factorial(n - 1)       ...               This applies to numbered as well as unnumbered lists. iPhone Passcode for Powering Off We have Godaddy's Dedicated server. but we are facing problems with this server. after on 400-500 active users server randomly timeout or kill users. we this it's error with IIS. We did conversation with some server experts they said there is some issue with IIS. but nobody can resolve this issue. i share a screen shoot of analytic of active users. Please help us. Someone who just thinks they know what they're talking about What is a word or phrase that means a speaker (or writer) is talking about something they know very little about, but they think they know more than they do?  An example: If you read diet message boards, you get dozens of people saying ‘Eat 6 small meals a day,’ or ‘Eat 3 big meals, but don’t snack,’  or ‘Eat more/less protein/carbs/fat.’ Each person is sure they are knowlegable enough to give good advice, but real experts(dieticians or researchers, for example) are rare.  I want a word to describe this attitude.  Bullshit is close, but someone bullshitting usually knows they aren’t an expert, they just want to convince the listener they are.  Also, I’d prefer something politer than bullshit. I want to synchronise two folders in real time under Windows 7.  Basically, I want to monitor a folder and synchronise each change (new files, changed files, deleted files) to another drive. It has to be in real time, so it gets synchronised instantly when a change happens. A one-direction synchronisation is enough.  I tried Microsoft's , but it does only syncing by hand or scheduled (thus not satisfying the "real-time" requirement).  Can this be achieved with Windows 7 itself? If not, are there other methods of doing this? Intuitive explanation for formula of maximum length of a pipe moving around a corner? For one of my homework problems, we had to try and find the maximum possible length $L$ of a pipe (indicated in red) such that it can be moved around a corner with corridor lengths $A$ and $B$ (assuming everything is 2d, not 3d):    My professor walked us through how to derive a formula for the maximum possible length of the pipe, ultimately arriving at the equation $L = (A^{2/3} + B^{2/3})^{3/2}$.  The issue I have is understanding intuitively why this formula works, and exactly what it's doing. I understand the steps taken to get to this point, but there's an odd symmetry to the end result -- for example, is the fact that $\frac{2}{3}$ and its inverse are the only constants used just a coincidence, or indicative of some deeper relationship?  I also don't quite understand how the formula relates, geometrically, to the diagram. If I hadn't traced the steps myself, I would have never guessed that the formula was in any way related to the original problem.  If possible, can somebody give an intuitive explanation as to why this formula works, and how to interpret it geometrically?    Here's how he found the formula, if it's useful:  The formula is found by finding the maximum possible length of the pipe by expressing the length in terms of the angle $\theta$ formed between the pipe and the wall, and by taking the derivative to find when $\frac{dL}{d\theta} = 0$, which is the minimum of $\frac{dL}{d\theta}$ and is therefore when $L$ is the smallest:  $$ L = \min_{0 \leq \theta \leq \frac{\pi}{2}} \frac{A}{\cos{\theta}} + \frac{B}{\sin{\theta}} \\ 0 = \frac{dL}{d\theta} = \frac{A\sin{\theta}}{\cos^2{\theta}} - \frac{B\cos{\theta}}{\sin^2{\theta}} \\ 0 = \frac{A\sin^3{\theta} - B\cos^3{\theta}}{\sin^2{\theta}\cos^2{\theta}} \\ 0 = A\sin^3{\theta} - B\cos^3{\theta} \\ \frac{B}{A} = \tan^3{\theta} \\ \theta = \arctan{\left( \frac{B}{A} \right)^{\frac{1}{3}}} \\ $$  At this point, we can substitute $\theta$ back into the original equation for $L$ by interpreting $A^{1/3}$ and $B^{1/3}$ as sides of a triangle with angle $\theta$ and hypotenuse $\sqrt{A^{2/3} + B^{2/3} }$:  $$ \cos{\theta} = \frac{A^{1/3}}{ \sqrt{A^{2/3} + B^{2/3} }} \\ \sin{\theta} = \frac{B^{1/3}}{ \sqrt{A^{2/3} + B^{2/3} }} \\ \therefore L = A^{2/3} \sqrt{A^{2/3} + B^{2/3} } + B^{2/3} \sqrt{A^{2/3} + B^{2/3} } \\ L = (A^{2/3} + B^{2/3}) \sqrt{A^{2/3} + B^{2/3} } \\ L = (A^{2/3} + B^{2/3})^{3/2} \\ $$  The equation for the formula for the maximum length of the pipe is therefore $L = (A^{2/3} + B^{2/3})^{3/2}$. Regex to strip lat/long from a string Anyone have a regex to strip lat/long from a string? such as:  ID: 39.825 -86.88333 Choice of ECC curve on USB token I would like to get a USB token to secure my keys. My use case is protection of 3 GnuPG keys that I will be using 10 times per day at least. I plan to create a new key ring from scratch. Because ECC seems more future-oriented than RSA, this is what I chose to use. I'm wondering which USB token to choose as well as which curve.  On  it is said that many people think curves recommended by the NIST or defined by Brainpool have a doubtful origin; therefore, they recommend the non-standardized Bernstein’s Curve 25519. On  one poster says that    He is not aware of any profound criticism of Brainpool curves, and Bernstein’s Curve 25519 is hard to protect against side-channel attacks when implemented in embedded devices.   As a result, I'm a bit lost as to which key/curve to choose. Open a direct file on the hard drive from Firefox (file:///) I have a small PHP system I created for myself. This system contains a few .doc and .docx file documents. I want to be able to open them directly from the browser without downloading them.  I created a link: &lt;a href="file:///c:/mysite/myfile.docx"&gt;myfile&lt;/a&gt;. But Firefox does not open the link. href="http://localhost/myfile.docx" works fine - it offers me to download the file.  Any ideas on how I can do it? Do I need to change something in the Firefox options or security settings? Factoring $x^n + y^n$ over the integers UNetbootin is stuck in an "Automatic boot in 10 seconds" countdown loop I made a bootable Windows 7 USB using UNetbootin, and when I try to boot from the bootable USB and select the Default boot menu entry, it gets stuck at the UNetbootin boot menu and it keeps repeating an Automatic boot in 10 seconds... message in an endless countdown loop. Selecting Press [Tab] to edit options and editing the options has no effect. When I go back to the boot menu, it keeps repeating the same countdown loop.   I've tried redoing the UNetbootin extraction, but I still have the same issue. I just updated my Moto X to latest and greatest Android 4.4 KitKat (I even did full factory reset just to be sure) and now I'm trying to install  but unable to do so, I'm getting following error:     Unknown error code during application install "-24"   Please advise.