December 15, 2010

Tangling the microscopic ladder

If a ladder had more than one rung at each step, it would look awkward and would be a bit dangerous to climb. Ladders in the microscopic world were thought to be similar in structure, having only one particle, or rung, in each step in the lattice of a crystal.

But theorists have conceived of structures where multiple particles could sit at one lattice site and have now simulated how these structures might form and behave for a range of temperatures, pressures and densities.

The result seems to defy the idea that repulsive forces typically keep particles apart. But “nature is not as simple as it appears,” says Patrick Charbonneau, a theorist jointly appointed in the chemistry and physics departments at Duke.

In simulations of cooled, compressed particles, he and his colleagues, Kai Zhang and Bianca Mladek, identified particles that began to mingle and overlap to occupy the same lattice site, rather than move away from each other.

Details of the work appear in the Dec. 10 issue of Physical Review Letters.

“We’re not sure how these overlaping particles would look in nature,” Charbonneau says. But confirmation of the theory could improve scientists’ understanding of exotic matter, like Bose-Einstein condensates and electron bubble crystals, or even the interactions among chain-like molecules, such as certain polymers and dendrimers.

December 10, 2010

Gesture-Based Interfaces: My Research

Blogger Vansh Muttreja (Class of  2012 B.S.E. Electrical and Computer Engineering and B.S. Economics) updates us on his research:

Over the past three months I have been working on some very interesting projects as part of Duke SyNRG (Systems Networking Research Group) which is led by Dr. Romit Roy Choudhury, Nortel Networks assistant professor of electrical and computer engineering.

The goal of our research is to bridge the gap between physical and virtual interfaces, and to make collaboration much easier and intuitive. A lot of times we notice that the screen size of our desktop or our phone is not feasible when we need to work on multiple applications. Thus, it is much more convenient to project the data on the wall using a projector, or in our case, using palm-sized pico-projectors.

Pico-projectors are proliferating rapidly and by next year we expect to see phones with built-in projectors. Imagine the possibilities!

We've come up with two novel applications for pico- projectors. The first is called Virtual White Board, which enables multiple users to remotely and simultaneously edit white boards in real time. Everyone using their respective physical white boards becomes part of a network. Now these users, wherever they may be located, can write and draw on their white boards using a color marker in their natural way, and the information is simultaneously projected on all the boards in our virtual network. Here is a screenshot of a remote tic-tac-toe game being played by two users on boards in different physical locations.

The second program we developed is called Smart Transfer. Some jobs like design projects and architectural techniques require the user to work on a bigger screen. We wanted to enable the user to directly interact with the projection screen. So we implemented a system in which a person can use a laser pointer as a point-and-click device and directly work on the projection screen. The laser pointer is now effectively a mouse for the projected screen.

The final aim was to make collaboration and file transfer between devices more instinctive. So we came up with a design in which a user can simply use the laser pointer to select a file he wishes to transfer, and perform an intuitive ‘flicking’ gesture towards the device he wants to transfer the file to. For example, imagine there is one computer to the left of our parent screen, and one computer to the right. A simple selection of file and flicking gesture to the right will initiate file transfer to the computer on the right and to the left if the flick is directed towards the left. This is especially advantageous for transferring standalone objects such as images within a document. So multiple people collaborating on a word document can intuitively and easily share charts, images, text etc. present within their document.

December 2, 2010

A Bang-Up Job In Geneva

For the past three weeks, the Large Hadron Collider, or LHC, hasn’t been slamming protons together, but not because it's broken again. Instead, the world’s most powerful particle accelerator is bashing around heavier particles. The goal is to create a new state of matter — the quark-gluon plasma — and the first results seem to indicate success, says Steffen A. Bass, a theoretical nuclear physicist at Duke who's a quark-gluon enthusiast.

A quark-gluon plasma is an extremely hot, dense soup made of the basic building blocks of matter, hence its name. It likely resembles matter as it would have been in the first microseconds after the Big Bang. Scientists want to create it to study the plasma’s evolution into the kind of matter that makes up the Universe today.

Despite its theoretical promise, the quark-gluon plasma has been hard to cook up. Several labs, including Brookhaven’s RHIC, have tried. But a definitive recipe and result hasn’t come easy, even when the temperature of the New York-made soup of gold particle collisions was approximately four trillion degrees Celsius. It took RHIC several years of running until it could confirm the observation of a quark-gluon plasma.

Now, the lead-on-lead collisions at the LHC in Geneva show similar quark-gluon plasma characteristics.

When the heavy particles collide, for example, concentrated jets of particles form. As the jets bang around in their hot, dense environment, they lose energy, a phenomenon called jet quenching. Two weeks ago, one of LHC’s instruments, ATLAS, recorded that the jets lost more energy than ever observed before. Now, followup data suggests that the quantity of quenching can only be explained if a really hot quark-gluon plasma was actually created, Bass says.

Bass, an expert on quark-gluon plasma, adds that the LHC reports indicate the machine has created a plasma soup that is tens of trillions of degrees Celsius, nearly 30 percent hotter than the RHIC’s plasma. The LHC’s version also has a higher energy density. In actual food terms, the Swiss soup would have nearly three times more calories than a same-sized bowl of Brookhaven’s soup.

Yet, the LHC plasma is still a nearly "perfect fluid," meaning it doesn’t contract heat and has almost no viscosity, a surprise to most physicists. They thought that at higher temperatures the soup would turn from a liquid into a gaseous plasma.

But there’s one piece of evidence that would nail down the LHC’s substance as a definite quark-gluon plasma—a particular form of decay of the soup from quarks and gluons back into protons, neutrons and other forms of matter called parton recombination. The data may already be there, Bass says, and if it is, recombination would be a “dead giveaway” of a substance thought to have existed only in the early Universe.

Duke physicist Berndt Mϋller, Bass and their graduate students plan to “dig deeper” into the data in the coming weeks, he says, adding that they’ll have plenty of time too. Another round of lead smashing won’t be done for at least a year, maybe even two. After a one year tune-up in 2011, the LHC is going back to proton smashing and the relentless search for a particle called the Higgs boson.