AWS Signature Version 4 Using Named Credentials
Accessing AWS S3 via a REST API (Apex callout with a Named Credential)
How is dark energy consistent with conservation of mass and energy? I initially thought that dark energy must in some way violate conservation of mass and energy since the component of the energy density of space that comes from dark energy is constant, and space is expanding. Therefore, as space expands the energy in the universe that comes from dark energy would increase. I presumed the source of this energy was not coming from the conversion of other types of energy to dark energy, so it must violate conservation.  I decided to Google this and came upon this article:    It says that dark energy does NOT violate conservation and quotes Carroll, Press, and Turner (1992):  "…the patch does negative work on its surroundings, because it has negative pressure. Assuming the patch expands adiabatically [i.e. without loss or gain of heat], one may equate this negative work to the increase of mass/energy of the patch. One thereby recovers the correct equation of state for dark energy: P = – ρ c2. So the mathematics is consistent."  Is there a way to explain this in layman's terms? (The blog attempted to do this, but it was very unclear to me.) More specifically, can you explain where my initial train of thought described above fails when I erroneously concluded that dark energy violates conservation?  Thank you. msbuild, defining Conditional Compilation Symbols I'm possibly just blind, but is there a command line to specify conditional compilation symbols in MSBUILD?  I currently have this Line in my buildscript:  SET MSBUILD=C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\MSBuild.exe SET CONFIG=Debug %MSBUILD% /p:Configuration=%CONFIG% /p:OutputPath=..\..\output source\MyProject\MyProject.csproj   And I'd like to add a condition. In Visual Studio, i can just go into Project Properties => Build => Conditional compilation symbols, but I have not seen that option for msbuild?  Bonus Karma if you know if I can completely override all symbols already specified in the .csproj files to make sure that only the conditionals from my Buildscript go in. I have an integrated webcam in my laptop. I know that it works and that ubuntu recognized it because at installation it asked if I wanted a photo taken for some kind of image associated with my account. When I look in system settings, I do not see any webcam in the hardware section. I would like to disable the webcam like you can do in Windows, but as I can't find it in my hardware section, how can I disable it? I cannot even unplug it as it is integrated into the monitor. Am I looking in the wrong place?? I am using 12.04 What is the number of automorphisms (including identity) for permutation group $S_3$ on 3 letters? What is the number of automorphisms (including identity) for permutation group $S_3$ on 3 letters?  I believe the answer for this is 6. As we can write the group elements as below   (a)(b)(C) (ab)(c) (ac)(b) (bc)(a) (abc) (bac)   Can we generalize that for any $S_n$ onto $n$ the number of automorphisms will be $n!$ Also I cannot find this anywhere in my text, can we have a permutation $S_n$ onto $m$ where $n\neq m$? (for eg: is it possible to have a permutation group say $S_5$ on say 2 elements?) I am a graduate student in mathematics who would like to learn some classical mechanics. However, there is one caveat: I am not interested in the standard coordinate approach. I can't help but think of the fields that arise in physics as sections of vector bundles (or maybe principal bundles) and would love an approach to classical mechanics or what have you that took advantage of this.  Now for the questions:   Is there a text book you would recommend that phrases the constructions in classical mechanics via bundles without an appeal to transition functions?   What are the drawbacks to this approach other than the fact that it makes computations less doable? (if it does that)   Are there benefits to thinking about things this way, ie would it be of benefit to someone attempting to learn this material to do it this way? How do I copy vertex groups from one object to another? So, I decided that a previous project contained exactly what I needed to expedite a new project, so I appended the appropriate objects form the previous project to the new one. This was great, because I didn't have to define new materials, &amp;c.   Regrettably, though, I found out that when it came to vertex groups, where it would have been as helpful to be able to copy vertex groups from one object to another as it was to copy materials, I couldn't figure out how to do so.   Am I looking for a feature which does not yet exist?  NOTE: I did not expect the vertex groups to have assignments in the target objects, but it would have been handy not to have had to retype 25 names. How to pack the game files into one without using any file compressor? Well, one example is this file of the game The Sims 2 for PS2: quickdat.arc. The file contains this .arc extension, but it's no one an archive file and it contains some data of the game inside. How can I do this? Put so many files in one?  How to do something like this? All the game files inside one without using a file compressor? Problem about a process with bins of balls When I choose the Connection Type in VPN Connections, I have only PPTP and I can't find OpenVPN, but I already installed it via terminal with the command sudo apt-get install openvpn easy-rsa  Why I can't find it? Prove that $ S=\{0\}\cup\left(\bigcup_{n=0}^{\infty} \{\frac{1}{n}\}\right)$ is a compact set in $\mathbb{R}$. Prove that $ S=\{0\}\cup\left(\bigcup_{n=0}^{\infty} \{\frac{1}{n}\}\right)$ is a compact set in $\mathbb{R}$, but $\bigcup_{n=0}^{\infty} \{\frac{1}{n}\}$ is not a compact set.   (Can we use definition of compact set for this problem? ) I bought a Magic the Gathering display box today with cards from the new edition Innistrad. Unfortunately one of the cards in a booster pack was damaged. It is not just a simple scratch - one corner is bent and a small part of the card is missing. According to different trading platforms this card would be worth about 6 Dollars minimum in mint condition. So it is not really expensive but also not totally worthless.  What can I do about this? Can I obtain a replacement card from the producer (WotC) or from the store I bought it from? How can I prove that the card was damaged when I opened the booster pack? I am sure I am not the first person who got a damaged card from a booster pack. How are such issues usually handled? Does C# have anything comparable to Python's list comprehensions? Create subdomains on the fly with .htaccess (PHP) I am looking to create a system which on signup will create a subdomain on my website for the users account area.   e.g. johndoe.website.com  I think it would be something to do with the .htaccess file and possibly redirecting to another location on the website? I don't actually know. But any information to start me off would be greatly appreciated.  Creating a sign up area is not the problem - I have done this many a time. I am just unsure where to start with the subdomain. "India has" or "India have" Segmentation Fault when attempting to print value in C c++ get registry key returns only one char Focus existing terminal with `Ctrl-Alt-T` shortcut Is there a way (eg. a binary hack into Finder) to stop it from creating .DS-Stores on LOCAL Volumes?   I am using Leopard, therefore these don't work:    (requires Lion)  (requires Snow Leopard)   Also,  slows down my computer. Often I need two (or more) map frames in map layout to present different data next to each other. It is easy to make multiple map frames in QGIS Print Composer. BUT...  It is in the nature of my work that very often I need to update some map frames because data I am presenting in map changed or I need to add/remove layer, change scale, projection etc.  So if I create one map frame, lock it (Lock layers for map item), create second map frame with different layers, scale,projection etc. and than realize I need to change something in first frame, I can't find a simple way to do it...  To simply do that in Mapinfo, there are more Map Windows, in ArcGIS there are multiple Data Frames. What is in QGIS to achieve that? Is it true that an ideal is primary iff its radical is prime?