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If $x\sqrt{1+y}+y\sqrt{1+x}=0$ find $y'$ Postfix Domain Whitelisting in Combination with Sender Authentication I'd like to whitelist several domains in my Postfix configuration in such a way that all e-mails from those domains are accepted as long as they're properly authenticated using SPF and/or DKIM, should it be used by that domain. This means that e-mails coming from those domains should not be subjected to the usual DNSBL and Greylisting process, only to a SPF and DKIM verification.  Right now I have managed to save e-mails coming from those domains from the Greylisting milter by configuring a sender_access file and using the postmap utility to convert it to a suitable hash-database.  main.cf:  ... parent_domain_matches_subdomains = yes smtpd_recipient_restrictions =   permit_mynetworks   permit_sasl_authenticated   reject_rbl_client zen.spamhaus.org   reject_unauth_destination   check_sender_access hash:/etc/postfix/sender_access   check_policy_service unix:private/tumgreyspf ...   sender_access:  domain1.com OK domain2.net OK   I've found out about  and also found a , but it appears like that is a DNSBL-only measure and is only slightly helpful in my case. Drive shape key based on relative camera orientation? Is Dishonored an open-world game? I was considering whether or not to buy Dishonored, and watching gameplay of it on Youtube, when a thought popped into my head: is Dishonored free-roam? Can you go anywhere you want, similarly to Fallout or The Elder Scrolls? How do i prove invertibility of this linear transformation Let $T$ be a linear transformation from a vector space $V$  over reals into $V$ such that $T-T^2=I$. Show that $T$ is invertible How do I parse command line arguments in Java? What is a good way of parsing command line arguments in Java? How do electromagnetic waves travel in a vacuum? This is perhaps a total newbie question, and I will try to formulate it the best I can, so here it goes. How does an electromagnetic wave travel through for example, the vacuum of space?   I usually see that waves are explained using analogies with water, pieces of rope, the strings of a guitar, etc, but it seems to me that all those waves need a medium to propagate. In fact, from my point of view, in those examples the wave as a "thing" does not exist, it's just the medium that moves (involuntary reference to The Matrix, sorry).   But in space there is no medium, so how does a wave travel? Are there free particles of some sort in this "vacuum" or something? I believe , so supposedly there isn't a medium for the wave to travel through.   Moreover, I've seen other answers that describe light as a perturbation of the electromagnetic field, but isn't the existence of the field, potential until disturbed? How can it travel through something it does not exist until it's disturbed by the traveling light in the first place? (this last sentence is probably a big misconception by me). JSON+Node.js - Unexpected token o I read this book series in middle school. I believe that it would be classified as young adult fiction/fantasy. A girl has magical powers, and with her growing powers comes runes/tattoos in her arms. This is shown on every book cover. I know that one cover is blue. This one shows the girl in a black tank top and black pants. One is a yellow cover, with her in a dress (I think).  The girl has a friend/mentor, who she develops feelings for. The girl is the key to stopping a war between multiple factions/people. Each side is trying to use her to their advantage. I think the series was written in the early 2000s. Where did the "wheel" group get its name? The wheel group on *nix computers typically refers to the group with some sort of root-like access. I've heard that on some *nixes it's the group of users with the right to run su, but on Linux that seems to be anyone (although you need the root password, naturally). On Linux distributions I've used it seems to be the group that by default has the right to use sudo; there's an entry in sudoers for them:  %wheel ALL=(ALL) ALL     But that's all tangential; my actual question is: Why is this group called wheel? I've heard miscellaneous explanations for it before, but don't know if any of them are correct. Does anyone know the actual history of the term? How can I disable Alt-Scroll zoom in XFCE4 (Xubuntu) In XFCE4 desktop environments, alt+scroll wheel zooms my entire desktop. I'm finding this very annoying because sometimes I flick the scroll wheel to go to the top of a document then press the alt key for a some unrelated keyboard shortcut and find myself zoomed in so far I can't see anything at all. Is there any way to disable this feature? Do spell targets know they were targeted? Assuming a target of a Pathfinder spell did not see/hear/notice a caster casting the spell, do they know/feel they were targeted?  Is it relevant if the spell worked or not, if a save was involved (either successful nor not)? Does it depend on the spell?  Example: A cleric casts detect evil through a door. What do the NPCs on the other side know now? Using InDesign CS6, how can I simultaneously edit A4 and A5 versions of a poster? I'm on Adobe Creative Cloud, so I have the latest InDesign, and I'm attempting to design a poster for my choir's next concert. Traditionally, I've done this in Photoshop, in two separate files, however I've recently started using InDesign after converting to it to create wedding albums through Blurb.  I've created an A4 document, and created an alternate-layout for it in A5. I've then lined them up side-by-side, and I've added a black frame to the A4 page, to act as the black background for my page (by the way, feel free to advise on better ways to do this).  My assumption is that I've failed to understand how this works, as I was hoping that I'd magically get a black frame on the A5 version, and that I could use liquid layout to get this to automatically scale (along with all other elements), in order to create the two versions simultaneously.  All help/advice would be greatly appreciated! How does commands like ls know what its stdout is?  It seems ls is operating different depending on what the target stdout is. For example if I do:  ls /home/matt/tmp    the result is:  a.txt b.txt c.txt   However if I do  ls /home/matt/tmp | cat   the result is (i.e. new line per result):  a.txt b.txt c.txt   The process is passed a file descriptor 1 for stdout right? How does it determine how to format the result? Does the file descriptor reveal information? Why does this sort ignore the +/- character prefix? Can a US citizen leave and enter the US using a foreign passport? Get a "step-by-step" evaluation in Mathematica Are there any versions of t-SNE for streaming data? My understanding of  and the Barnes-Hut approximation is that all data points are required so that all force interactions can be calculated at the same time and each point can be adjusted in the 2d (or lower dimensional) map.  Are there any versions of t-sne that can efficiently deal with streaming data? So if my observations are arriving one at a time, it will find the best location on the 2d map to place the new observation, or continuously update all points on the 2d map to account for ht new observation.  Would this even make sense or does it go against the setup of t-sne. Information on month old flights Where can I get flight info for a flight a month ago for an insurance claim? Flight stat sites will only show a weeks worth of data. Have red shifted photons lost energy and where did it go?