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Dinyar Rabady
Works at CERN
Attends University of Vienna
Lives in Geneva, Switzerland
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Dinyar Rabady

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A matter of scale

I'm not usually much of a fan of the Fahrenheit scale, but as this graphic illustrates, it does produce convenient numbers for the purposes of discussing the weather.

(Image credit unknown; Googling it produces many hits.)

#sciencesunday

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Special offer from Google today: run a 2-minute security check on your account (which is really a good idea anyway) and get a free 2GB of Drive storage space. If your Google account matters to you -- your GMail, YouTube, Google+, Drive, and so on -- this is something worth running every few months.

And after you do that, go enable 2-step verification. (https://www.google.com/landing/2step/) It's the single best thing you can do to protect your account from being compromised. 
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#pixelpushing

And then this guy got Windows 3.11 running in the Javascript-powered emulation environment in Chrome, followed up by having it run both Mosaic and Netscape 1.0 for the full mid-90s experience, and I was all like...
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Tagging +Peter Poier because we were discussing this quite a while ago.
 
As we continue to search for planets beyond our Solar System, we are starting to find worlds that we might actually be able to stand upon. And in honor of this, the folks at JPL have produced some travel posters for these brave new worlds, available as free high-res downloads from their site.

http://planetquest.jpl.nasa.gov/media_categories?category=6

Kepler-186f, the one pictured below, is my favorite because it captures some interesting physics. It orbits a red dwarf about 500 light-years from Earth, and it was the first planet discovered which is potentially suitable (in terms of things like temperature) for life as we know it. But life would be different in some interesting ways.

One of the reasons is that photosynthesis would be a bit different. Plants on Earth are green because their leaves contain chlorophyll, a chemical which absorbs sunlight and turns that energy into excited electrons. Those energetic electrons are then fed into the entire photosynthesis system, and ultimately that energy is stored in the form of sugars and used to sustain the plant's life. The reason chlorophyll is green, though, comes down to three diagrams.

The first is the solar spectrum, that is, the color of light the Sun shines.

http://en.wikipedia.org/wiki/File:Solar_Spectrum.png

The X-axis of this graph shows the wavelength of light, from ultra-violet on the left to infra-red on the right; the Y-axis shows how bright the Sun is in each of those colors. As you can see, the Sun shines fairly evenly in the entire band between about 500 and 700nm, which is exactly the set of colors that the human eye can see. (No coincidence! Our eyes have evolved to see sunlight, not x-rays, because there aren't that many x-rays around to see by) 

There are two graphs here: the yellow curve shows the color of sunlight itself, and the red curve shows the color of the light we see at sea level. The difference is that the atmosphere absorbs some colors of light but not others. For example, the fact that the red curve is way below the yellow curve at the far left is because ozone in the upper atmosphere is very good at absorbing UV light -- the reason why it protects us from skin cancer.

The second diagram is the absorption spectrum of chlorophyll:

http://en.wikipedia.org/wiki/File:Chlorophyll_ab_spectra.png

This graph uses the same X-axis, but the Y-axis shows how effective chlorophyll is at absorbing light of each color. There are two curves because there are actually two different kinds of chlorophyll: the green kind (chlorophyll-A) which is most prevalent, and the red kind (chlorophyll-B) which often stays behind after the green one has left, giving autumn trees their color. The bumps on the left actually aren't very interesting, since the Sun doesn't produce much light in those colors -- they're there because it's hard to design a chemical which doesn't absorb those colors. (For various technical quantum mechanics reasons) The sharp spikes on the right are what makes chlorophyll so important to photosynthesis, and for chlorophyll-A, that spike happens at a wavelength of 680nm, smack in the middle of where sunlight is the brightest. For comparison, sunlight is the brightest at 665nm.

As it turns out, the chlorophyll molecule is fairly flexible and complex, and small modifications to it would likely lead to "pseudo-chlorophyll" molecules with their peaks in different places, which we'll come back to in a moment.

So chlorophyll has evolved (or rather, creatures have evolved to produce this one particular molecule) to very efficiently absorb light of exactly the color that the Sun produces the most of. Why does this make chlorophyll green?

Imagine that you shine sunlight on some chlorophyll. The chlorophyll absorbs the 680nm light; in fact, if you want to be precise about it, you can flip the chlorophyll graph upside-down (that is, replace it with 1-absorption, to instead show how much light it lets through) and multiply it by the sunlight curve, to see what color of sunlight bounces off of it. Light bouncing on chlorophyll would look just like the incident sunlight, but with another gap in it, corresponding to the colors that chlorophyll absorbs away for its own purposes. 

Because chlorophyll's absorption peak is so sharp, you can basically imagine this as light with the 680nm part of it removed. What color is 680nm? It's a bright red. And that brings us to the third diagram, namely how the human eye sees color:

http://en.wikipedia.org/wiki/Color_vision#mediaviewer/File:Cone-fundamentals-with-srgb-spectrum.svg

Color vision works by having three kinds of "cone" receptor in the eye: one which sees red, one green, and one blue. (These are called L, M, and S in the diagram for obscure reasons) This diagram has the same X-axis again, and now the Y-axis shows how sensitive each cone type is to each color. So for example, if you shine pure 680nm light onto an eye, that stimulates the red cone some, and the blue and green cones not at all, which the eye reads as "red." If you shone 580nm (yellow) light instead, that would stimulate both the red and green cones a lot, but the blue cone not at all, which our brain interprets as "oh, that must be yellow."

(Incidentally, that's also why color-combination tricks work. If you shine both red and green light on a point, it looks yellow to your eye. If you look at the monitor you're reading right now with a magnifying glass, you'll see that each pixel is actually three little pixels -- one red, one green, and one blue -- and that a yellow pixel has red and green lit but not blue, taking advantage of the same illusion to show you all the colors)

So back to plants. Sunlight on its own tends to stimulate your red and green cones a lot, but not much blue. (Take a look at the steep drop-off on the left of the sunlight diagram, and how that overlaps with what the blue cone sees) That's why the Sun normally looks yellow. But sunlight bouncing off chlorophyll -- i.e., what you see when you stare at a plant -- is missing a bunch of its red light, so it only stimulates green. And that's why plants look green.

(Incidentally, when you look at the eye-sensitivity chart, you might notice that the red and green cones are right next to each other, but the blue cone is off by its lonesome. This isn't a coincidence: many species only have red and blue. The green cone only shows up in some species, and because it's just like red but a little off, small differences in color in the range that they both hit therefore look very different to us. That gives us tremendously high frequency sensitivity in the greens: 490nm and 500nm light look really different, while 650 and 660nm are nearly indistinguishable. That's really useful when you need to recognize different kinds of plant!)

So back to Kepler 186f: its star is a red dwarf, which is smaller, dimmer, and redder than our own sun. We could repeat the entire calculation above using its color of starlight, and what you discover in this case is that efficient Keplerian chlorophyll would be absorbing light off in the infra-red. Doing the same subtraction of reflected light, we find that Keplerian chlorophyll under Keplerian skies would look deep red to our eyes.

And since our eyes have evolved to see green at high resolution, not red, Keplerian fields would look very strange to us -- almost uniform in color, with motion hard to see, because our eyes aren't adapted to seeing fine shades of red.

You can actually do this calculation for any kind of star, and you'll find that the color of "local chlorophyll" will range from red (for red dwarfs), through green (for stars like our own), out to yellow (for slightly blue stars). It never gets beyond that, because stars beyond "slightly blue" have a very short lifespan, and would never be around for long enough to develop their own native flora anyway.

So when you're going out traveling among the stars, expect a fairly wild color show.

If you want to play with what different wavelengths of light look like, this site has a simple slider:
http://academo.org/demos/wavelength-to-colour-relationship/

To read more about color vision, start at:
http://en.wikipedia.org/wiki/Color_vision

And for photosynthesis, start at:
http://en.wikipedia.org/wiki/Photosynthesis

Incidentally, the planet's name simply means that it's the sixth (f) planet out from the 186th star studied by the Kepler planetary survey.
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Some better info for those fooled by the "cancer is just bad luck" headlines. 
GrrlScientist: Please, journalists, get a clue before you write about science
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Nashville's chief of police got an angry letter from a citizen about why he had been so kind to protesters -- serving coffee and hot chocolate instead of threatening to arrest them. The chief wrote back and published his letter, and I highly recommend it, as a thoughtful short essay about civil society, the relationship of citizens, government, and police, and about how people form their social perceptions. 

Via +God Emperor Lionel Lauer.
When a pro-cop citizen wrote the Nashville Police to express his "frustration and outrage" at the city's peaceful handling of recent Ferguson protests, Chief Steve Anderson reminded the letter-writer of a simple fact: "The police are merely a representative of a government formed by the people for the people—for all people."
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So Microsoft sat on a bug report about a remotely exploitable bug in Active Directory which potentially allows attackers to take control of the whole system? (And even now didn't fix all Windows versions). More proof that Google is absolutely right with their automatic disclosure policy (after three months) with Project Zero.
Windows admins: Patch now, unless you run 2003, in which case you're out of luck.
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lol
 
Via +Lea Kissner, a novel encryption protocol from Stack Overflow:

function encrypt($string){
    return base64_encode(base64_encode(base64_encode($string)))

Finally, there's a 192-bit replacement for the venerable rot26 protocol. Sure, it won't run in O(0) like rot26 will, but for applications where you can sacrifice the speed, it's a perfectly viable alternative.

LGTM. Ship it.
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The acclaimed graphic artist and journalist Joe Sacco on the limits of satire – and what it means if Muslims don’t find it funny
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Trifft es doch voll und ganz.. 
 ·  Translate
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+Jordan Peacock shared this fairly searing indictment of the USAF's aircraft purchasing and priority decisions, and I think that at its heart, it's quite right. The A-10 is an extremely effective and reliable aircraft; it flies more sorties and performs more useful functions in modern warfare than pretty much anything else. But as the article says, while the USAF's primary actual jobs today are close air support and small bombing raids, what the USAF wishes its primary job were is high-speed dogfighting and stealth bombing runs, and so it wants to pour money into things like the F-117 and F-35.

There are three aircraft which the USAF flies which I really admire: the A-10, the B-52, and the F-16. The first two, speaking as an engineer, are honestly extraordinary craft: the B-52 has been in continuous service since 1955, and is expected to keep flying until 2040 at least; there are even individual aircraft which have been commanded by three generations of the same family. Cheap, simple, and stupid are not bad things in design: in fact, being nearly indestructible and working in any conditions you might want, unobtrusively but reliably, are some of the highest goals which any device can hope to attain. The A-10, likewise, is a brute-force stupid design which does exactly what it's supposed to. It doesn't look like anyone's idea of graceful, but it's also basically a flying platform for a giant gun which can get the crap beaten out of it and still fly home, which is basically exactly what people need. The F-16 is important because heavy bombers like the B-52 need a fighter escort in order to function; but unlike its successors, the F-22 and F-35, the F-16 basically works.

It's very easy to become enthralled with speed, agility, and stealth, but this is the sort of nonsense that becomes popular only in an organization which isn't being really tested on its efficiency and skill. Resource limits come from politics, not practicality, and as a result the USAF has invested a tremendous amount of money in aircraft which are basically fancy research prototypes, X-planes, not reasonable production designs. And they show no signs of changing course.

An honest reckoning is hard to come by, but if I were to pop my head up and ask "what can the Air Force most usefully provide," it would instead be partitioned functionally:

* Close air support, at scales ranging from the nano (bug-sized) to the A-10.

* Blowing stuff up from a long way away, at scales ranging from "blow up that car over there" to "blow up that city over there." 

* Carrying things from place to place, especially places where it's hard to get at things like fuel and landing strips, or where the intervening airspace is full of people who don't like you, at scales from the personal ("we need more medical supplies!") to the major logistical. ("We need to move 100,000 troops and all related equipment")

* Communication and surveillance capability, at scales from nano ("fly into that room and tell me what's in it") to global. ("Show me any missiles flying anywhere in the world right now")

Each of these naturally translates into a combination of manned and unmanned aircraft. But the aircraft you end up seeing as the primary drivers of such a mission aren't fancy fighter jets: fighters are support aircraft, meant to protect bombers and cargo planes and the like as they move through hostile territory. You end up building a system around "flagships" like the A-10.

It's time to stop looking at fancy toys and start thinking seriously about what these things are for.
KUWAIT CITY—This has been a classic week in the defense procurement industry. The armed services are trying to boost their worst aircraft, the totally worthless F-35, by trashing their best, the si...
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Heh.
Your scientifically accurate horoscope for 2015: "The position of the stars and planets will not affect your life in any way, shape, or form, whatsoever."

Source: http://boingboing.net/2015/01/03/your-scientifically-accurate-h.html
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You're taking all the fun out of it.
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Currently
Geneva, Switzerland
Previously
Vienna, Austria
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CERN Building 40-3-B01 1211 Genève 23 Switzerland
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Work
Occupation
PhD student at the CMS Experiment at CERN
Employment
  • CERN
    PhD student, 2012 - present
    Work on the upgrade for the CMS Level-1 trigger.
  • Catalysts
    Java developer, 2012 - 2012
    Work on a anti-phishing mail server acting as a relay between customers on Austria's biggest platform for classified ads.
  • Institute of High Energy Physics of the Austrian Academy of Sciences
    Undergrad working on the Trigger of the CMS Experiment, 2011 - 2012
    Development of a protocol buffer-based communications protocol on top of TCP/IP.
  • University of Vienna
    2008 - 2011
    Teaching assistant for the Physics for Biologists lab course.
  • Caritas Vienna
    2005 - 2008
Education
  • University of Vienna
    Physics, 2012 - present
    Work on upgrading parts of the Level-1 Trigger of the CMS Experiment. This involves development in VHDL as well as C++.
  • University of Vienna
    Physics, 2006 - 2012
    Emphasis on software in high energy physics with some courses taken in Computational Physics.
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Dinyar Rabady's +1's are the things they like, agree with, or want to recommend.
Joe Sacco: On Satire – a response to the Charlie Hebdo attacks | World n...
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Join our 1.3 million other students today and learn programming and big data to advance your knowledge and career in programming. Udacity co

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Paperman
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We came in the afternoon for a snack and while there were plenty of tables free were only allowed to sit at the last high-table if we didn't want a full meal. The place is very dark and decorated with christmas lights all over. After waiting for the waiter to take our order for 20 minutes we left.
Public - in the last week
reviewed in the last week
We very much enjoyed our stay at Glen Oaks. We stayed in the Queen Room which was very nicely furnished. The prices are steep, but this was expected for the region.
Public - in the last week
reviewed in the last week
I had the red beef curry which was very good. The service was friendly and prompt.
Public - 3 weeks ago
reviewed 3 weeks ago
71 reviews
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Map
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The cappuccino is very good. The staff seemed slightly overwhelmed, but very friendly all the same!
Public - 3 weeks ago
reviewed 3 weeks ago
We had an excellent burger here and the beer on tap was great! The service was fast and friendly.
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reviewed 3 weeks ago
Very nice place with friendly staff. Especially the beef is highly recommended.
Public - a year ago
reviewed a year ago