Dominos as logic gates
And the Domino half-adder
Gettin' Wired: Your Civic Duty
Voting-day giveaways. Krispy Kreme giving away free donuts. Ben & Jerry’s giving away free ice cream (between 5 and 8 p.m.) and Starbucks giving out free coffee. Ostensibly to those sporting “I voted” stickers.
However …
Handy said there is a federal statute that prohibits any reward for voting.
Starbucks’ good deed can be perceived as paying someone to vote, and that’s illegal, Handy said.
“The way it is written, it expressly prohibits giving any kind of gift,” Handy said.
Handy said the intent of the statute is aimed at special interest groups trying to influence who and how people vote.
To fix the situation, Starbucks had agreed to give a tall cup of coffee to anyone who asks on Election Day.
But how is a Starbucks to know that you’ve already gotten a free coffee at another location? Or a donut, or ice cream? Shoot, a feller could have a pretty good time in Vegas with all that stuff! Just stay below the lethal dose.
Relatively Special
Lorentz Transformations at Backreaction
Modern Silly Knees-Bent Running About Advancing Behavior
Seems like the winner depends more on luck rather than skill
Belated Conference Greetings
I’ve been seemingly running in quicksand ever since returning from the 7th Symposium on Frequency Standards and Metrology, what with the pileup of work while I was away (and everything seemingly breaking during that period of time) and getting ready for our clocks to leave the nest. But now, as I’m burning up my comp time from all that, I’ve had a chance to look back.
The conference was really good, as conferences go. A little over 100 people attended, from labs around the world. I knew perhaps a third of them already (though a few probably did not remember me) and met a few more. I didn’t see any glitches except for one or two instances of technical difficulties, which speaks volumes for the organizers and support staff, because you just know there were issues, and since they didn’t become visible it means they were solved quickly. The accommodations were very nice and the food was decent as far as dining hall food goes. The whole thing came in under the government-rate per diem, and the government is actually pretty stingy about such things.
Many of the talks encompassed the recent push into optical transitions for timekeeping; the microwave transitions used in the established clocks of today run at something a little less than 1010 cycles per second, but an optical transition will be about 4 orders of magnitude higher in frequency. Even if your detection can’t be done to the same level of precision, owing to lower light levels and fewer atoms, the higher frequency represents 2 or 3 orders of magnitude improvement in the overall measurement. The enabling technology for this has been the octave-spanning optical frequency comb, made by pulsed lasers in some nonlinear medium. If you consider the time width of the pulses Fourier-transformed in the frequency domain, you see a whole bunch of laser frequencies separated by the pulse repetition rate, so it looks like a comb. As I’ve mentioned before, you can use these individual frequencies to interrogate atoms, meaning you can measure some narrow clock transition. This becomes really useful when the comb spans an octave, so the low-frequency end can be frequency-doubled and referenced to the high-frequency end, making the comb stable. The repetition rate can be tied into some stable RF or microwave source, and now you know what each frequency is to a very high level of precision. A lot of labs are now doing this.
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Vindicated
… and it feels so good
Per my previous observation, this phenomenon has now been properly represented.
more music charts
Splitter
A physics-based puzzle game in which you have to guide your character to the goal by cutting wooden objects and joints.
Dude, It's Physics
The Physics of Surfing (Part One: Dropping In)
[P]addling by itself doesn’t get you into the wave, because you actually cannot paddle as fast as the wave is moving, and you need to match the speed of the wave if you want to ride with it. In order to catch up to that wave speed, it’s necessary to use the gravitational potential energy of the wave. The trick is to obtain sufficient speed by paddling that, as the wave travels under you, your board begins to fall down the face. As you drop down the front of the wave, the gravitational potential energy you gain is converted into kinetic energy. Soon you are travelling as fast as the wave. In fact, if you continue to drop to the bottom of the wave, you’ll be moving faster than the wave — and if you don’t cut into the face, you might temporarily outrun it.
Say "Cheese"
Ultrafast Lasers Show Snapshot Of Electrons In Action
In a paper to appear in the Oct. 30 issue of Science Express, the online version of the journal Science, the CU team describes how they shot a molecule of dinitrogen tetraoxide, or N2O4, with a short burst of laser light to induce very large oscillations within the molecule. They then used a second laser to produce an X-ray, which was used to map the electron energy levels of the molecule, and most importantly, to understand how these electron energy levels rearrange as the molecule changes its shape, according to Kapteyn.
1/Problem
Optics basics: Inverse problems at Skulls in the Stars.
Plenty of other techniques exist for measuring the internal structure of objects, using a variety of different types of waves. Magnetic resonance imaging (MRI) subjects a patient to an intense magnetic field, and makes an image by measuring the radio waves emitted when the field is suddenly switched. Ultrasound imaging uses ultrasonic waves to probe the soft tissues of the human body, and is used in mammography.
Each of these techniques is quite different in its range of application, but all require nontrivial mathematical techniques to reconstruct an image from the raw scattered wave data. These mathematical techniques are broadly grouped into a class of problems known as inverse problems, and I thought it would be worth an optics basics post to discuss inverse problems, their common features, and the challenges in solving them.