Category: Physics Page 9 of 11

A second crack at the nature of glass

On August 13, 2012

In Computers/Technology, Faculty, Field Research, Mathematics, Physics, Visualization

By Ashley Yeager

Glassblowers shape molten silica before the glass transitions from liquid to a more solid structure. Credit: handblownglass.com.

Patrick Charbonneau and his collaborators have taken another crack at understanding the nature of glass. Their latest simulations show that a key assumption of theoretical chemists and physicists to explain the molecular structure of glass is wrong.

Glass forms when liquids are slowly compressed or super-cooled, but don’t crystallize the way cooled water turns to ice. The liquidy pre-cursors to glass, like molten silica, do become hard like a solid, but the atoms in the material don’t organize themselves into a perfect crystal pattern.

The result is a substance that is as hard as a solid but has the molecular arrangement of a liquid — a phenomenon that scientists can’t quite explain, yet.

Previous theories assumed that at the transition point between a liquid and glass, the material’s atoms become caged by each other in a “simple” Gaussian shape. This same shape describes the distribution of people’s height in the U.S. and is known as a bell-shaped curve.

But new simulations, described online Aug. 13 in PNAS, suggest this assumption is wrong. The simulations model the interactions of glass particles in multiple dimensions and show the shape of the particle cage is much more complex than a Gaussian distribution.

The discovery is a “paradigm shift in the sense that so many people have been having the same, wrong, conception for so long, and they should now revisit that basic assumption,” says Charbonneau, a theoretical chemist at Duke. “The assumption was actually constraining how they thought about the problem.”

Even with a new shine on the way scientists think about glass, it is not clear how close or far the theorists are from writing an accurate description of what happens at the liquid-glass transition. But “the path to get there seems clearer than it has been in a long time,” Charbonneau says.

The next step in the research is to understand the relationship between glassy states of matter and those that are jammed, like pieces of cereal wedged in a grain hopper. Charbonneau and collaborators are already at work about how to study the connections between the two forms of matter.

Citation:
“Dimensional study of the caging order parameter at the glass transition.” 2012. Charbonneau, P., et al. PNAS Early Edition. DOI: 10.1073/pnas.1211825109

Reading between the lines of light

By Ashley Yeager

On August 10, 2012

In Computers/Technology, Engineering, Faculty, Nanotech, Physics

By Ashley Yeager

Harry Potter's invisibility cloak is not exactly what scientists have in mind for their light tricks. Credit: Warner Brothers.

The way we understand light is largely based on how we see it. To our eyes, light is like a stream of particles.

Scientists usually study these particle streams by measuring their wavelengths and how they interact with objects. But over the last decade, researchers have begun to realize that light particles can interact with objects within wavelengths too.

Now, scientists are looking inside wavelengths to control and manipulate light, which is transforming the traditional field of optics, according to Duke engineer David Smith and his colleagues.

They describe the changes to the field of optics in a review article appearing online Aug. 2 in Science, and they describe how, at a tenth or even a hundredth of the wavelength of visible light, the classic picture of how we see breaks down.

In this regime, streams of light particles can bend away from an object, essentially tricking the eye into thinking the object is not there. As a result, scientists can no longer think of light in terms of particle streams. Instead, they must think of it as a manipulation of electric and magnetic field lines.

Thinking of light this way, Smith and other scientists are beginning to understand how they can hide one object within another and even harvest energy. The new understanding “will be the design tool of choice” as scientists continue to play with the forces between electrically charged particles, the authors argue.

Citation:

“Transformation Optics and Subwavelength Control of Light.” Pendry, J., et. al. 2012. Science 337: 549-552.
DOI: 10.1126/science.1220600

Hot particles appear in Science

By Ashley Yeager

On July 19, 2012

In Physics

By Ashley Yeager

Protons and neutrons "melt" to produce a plasma of freely interacting quarks and gluons. Credit: RHIC/BNL.

On July 20, readers of the journal Science are in for quite a treat — a clear, concise explanation of what matter looked like in the early universe and how scientists study it.

Science has “published very few articles in this field, as is generally the case in nuclear and particle physics, so it was a nice surprise when they invited us to write the piece,” said Duke theoretical physicist, Berndt Mueller, a co-author of the review article.

Subatomic scientists rarely try to present their latest discoveries in widely accessible terms, which may be why the journal does not run many articles related to nuclear physics, he said.

In the piece, Mueller and his co-author, Barbara Jacak, an experimental physicist at Stony Brook University, describe the most recent discoveries and remaining questions about matter in the early universe, a primordial soup called the quark-gluon plasma.

One of the most puzzling questions for physicists in this field how the subatomic particles that make matter — quarks and gluons — behave when they are “liberated,” or broken apart, as they were in the early phase of the cosmos. “We now know, thanks to the experiments at the Relativistic Heavy Ion Collider (RHIC), that they behave completely differently than theorists thought, but we only know some aspects, many others remain to be explored,” Mueller said.

The “big” question is what structure the primordial soup of quarks and gluons takes at extremely high temperatures‚ beyond two trillion degrees Celsius. “We don’t know. It’s somehow made up of quarks and gluons. It’s like saying that liquid water is made up of the elements hydrogen and oxygen, but not knowing that they form water, or H2O molecules, and that those again cluster in teaming little molecular clusters,” Mueller said.

Gold particles collide, forming a soup of quarks and gluons. Click the image to watch a more-detailed video about the quark-gluon soup.Credit: RHIC/BNL.

Answering the structure question may also help to better explain how some atoms at the opposite extreme of the temperature scale‚ a minute fraction of a degree above absolute zero, act as a nearly perfect fluid, flowing almost without resistance, just as the quark-gluon plasma does. The answer could also offer ways to comprehend black holes, string theory, and extra dimensions.

To make those connections, the authors argue that physicists will need to explore how quark matter evolves over a range of energies, temperatures and densities. They can use the Large Hadron Collider (LHC) in Europe to probe the universe’s primordial soup at the highest range of energies. But RHIC seems to be able to operate at the energy “sweet spot” for exploring the transition from ordinary matter to the quark-gluon plasma.

The scientists will talk more about future plans and research at RHIC and LHC at the Quark Matter 2012 conference in Washington, D.C. on August 12-18, which the Duke nuclear theory group helped to organize. Jacak, the leader of a 500-member international collaboration performing experiments at RHIC and a member of the National Academy of Sciences, will be at Duke on Sept. 5 to give a talk about hot nuclear matter research.

Citation: The Exploration of Hot Nuclear Matter. Jacak, B., and Mueller, B. 2012. Science. 337: 310-314.
DOI: 10.1126/science.1215901

Fermilab's final findings on Higgs, it exists

By Ashley Yeager

On July 2, 2012

In Physics

By Ashley Yeager

This graphic shows the simulation of a Higgs boson decay. Credit: Fermilab.

New data announced Monday by the Tevatron particle accelerator at Fermilab suggests the Higgs boson exists. But it will take results from experiments at the Large Hadron Collider(LHC) in Europe to establish a firm discovery of the particle.

Fortunately, you won’t have to wait long. LHC scientists are expected to release their latest Higgs results two days later, on July 4.

The new Tevatron data suggests that the Higgs particle has a mass between 115 and 135 GeV/c^2, or about 130 times the mass of the proton.

The estimated mass is calculated from data taken from two Tevatron experiments and aligns with LHC-based Higgs’ mass estimates announced in December 2011 and March 2012.

The Tevatron searches are “particularly sensitive” to the Higgs boson decaying to a pair of bottom quarks, said Bo Jayatilaka, a post-doctoral scientist working with Duke physics professor Ashutosh Kotwal. “This is the largest predicted decay of the Higgs boson at the masses being considered. The nature of collisions at the LHC makes it very hard to see this particular decay over background,” he said.

Jayatilaka, who heads one of the Higgs analysis groups at Fermilab, said the Tevatron results “give a glimpse into this important decay channel of bottom quarks substantially earlier than the LHC will be able to.” It will require much more data to see this decay at LHC, he said.

The Tevatron stopped taking data in the fall of 2011, so the new Fermilab-Higgs results are final. As a result, “the most complete Higgs picture will emerge by putting together the pieces of the jigsaw puzzle from both Fermilab and CERN,” Kotwal said.

Lab "cloud" goes global

By Ashley Yeager

On June 15, 2012

In Computers/Technology, Faculty, Genetics/Genomics, Mathematics, Physics

By Ashley Yeager

A network of individual computers are linked through a server. Credit: TAS Software

The National Science Foundation has awarded computer scientist Jeff Chase $300,000 to move a computer cloud he now has in his lab to the university’s campus network, and beyond.

Chase has been building the cloud to improve server networks. In his new model, servers, the computers that process requests and deliver data over a local network or the Internet, have become critical, public infrastructures with open, flexible, secure, robust and decentralized control.

The work, once reproduced outside of the lab, will let Duke scientists across campus and throughout the world to more easily connect to one another through existing networks and to share computational services and access data, according to Tracy Futhey, Duke’s vice president for information technology and chief information officer.

Based on software-defined networking and other technologies, the new, on-demand cloud services will be launched through a distinct network that connects science resources, such as the large datasets generated in physics and genomics experiments.

The project is part of the NSF-funded Global Environment for Networking Innovation, or GENI.

Chase’s work was also recognized on June 14 when the White House launched an initiative, US Ignite, to develop a publicly available system of advanced networks based on important contributions from GENI scientists. Duke is among more than 60 universities across the country that has participated in the project.

Betting on Bayesball

By Ashley Yeager

On June 13, 2012

In Behavior/Psychology, Faculty, Lecture, Mathematics, Physics, Science Communication & Education

By Ashley Yeager

Derek Jeter, upper left, and Alex Rodriguez, lower right, anticipate a grounder in a 2007 game . Credit: Wikimedia.

New York Yankees shortstop Derek Jeter has five golden gloves. Alex Rodriquez, a Yankees shortstop and third baseman, has three.

It wasn’t a surprise then when Sayan Mukherjee asked a crowd at Broad Street Café who was a better mid-fielder and Jeter got a few more cheers.

The question, and response, prompted Mukherjee, a statistician who studies machine learning, to launch into a discussion about intuition and statistics in sports, specifically in baseball. Mukherjee spoke on June 12 as part of Periodic Tables: Durham’s Science Café.

He admitted he was a Yankees fan, which elicited some booing. Laughing it off, he then showed a complex statistical equation his colleague, Shane Jensen at the University of Pennsylvania, and others use to calculate a player’s success at fielding ground and fly balls.

On the next slide, Mukherjee showed the results. Rodriquez was clearly on top, and Jeter closer to the bottom. “Jeter doesn’t have as big a range as other players, that’s all I’m suggesting,” Mukherjee said.

Of course, these statistics, called sabermetrics, aren’t new to Jeter and other players. The numbers, based on Bayesian statistics, are exactly what the Oakland A’s baseball team used in 2002 to build a winning team. And, when new numbers came out in 2008, the stats ranked Jeter fairly low as a defensive player. He responded by saying there was a “bug” in the model.

“He has a point. The exact conditions for each play are not the same, so it’s hard to truly compare them,” Mukherjee said. The equation, however, is a way to measure factors of the game, rather than rely on intuition, and statisticians are trying to add more factors to make the model more realistic. The next factor they want to add will account for the different designs of ballparks, Mukherjee said.

He added, though, that these stats don’t really put players’ jobs at jeopardy. Judging by the crowd’s first response, people obviously still rely on intuition when it comes to picking their favorite players. The cold, hard numbers therefore affect how players approach their game – ie Jeter’s post-2007 season focus on a training program to combat the effects of age, Mukherjee said.

The data also affect people betting on the games. “Betting is huge, in any sport,” Mukherjee said, and the numbers, it seems, can affect how people choose to risk their money, but not their team loyalty.

Student Profile: Jack Matteucci

By sa160@duke.edu

On June 13, 2012

In Computers/Technology, Physics, Students

By Nonie Arora

It may be summer, but student scientists are still on the job. Rising Trinity junior Jack Matteucci is heading to CERN in a few weeks to join the many scientists working with data from the Large Hadron Collider.

A Simulated Collision Producing a Higgs Boson Particle, Wikimedia Commons

Scientists working with data from the Large Hadron Collider are trying to determine whether the Higgs Boson, the so-called “God particle” exists. While the Higgs Boson has been called the “God particle” by some because it is currently the last predicted particle in the Standard Model to be observed, physicists are less fond of the name. “There is no doubt that it’s a huge missing piece to the puzzle, accounting for the observed phenomenon know as invariant mass, but it by no means explains everything about particle physics,” Matteucci says.

Einstein’s famous E= mc^2 showed a relationship between mass and energy. According to Matteucci, the Higgs Boson and its associated field would account for certain observed nonsymmetrical weak interactions, which would explain why certain particles have an inherent mass apart from the energy from their motion.

When collisions happen in Large Hadron Collider, thousands of protons collide and sophisticated computer programs must separate these interactions. After these interactions have been separated, data analysts like Matteucci enter the picture. He will be using ATLAS computing to analyze decay processes of elementary particles and confirm particle interactions.

Jack Matteucci

“During these interactions a plethora of particles are created and destroyed within tiny fractions of milliseconds which decay and lead to secondary products,” Matteucci explained. “Then, scientists try to backtrack to information about primary particles.”

While the collective effort is huge, the data is still analyzed one person at a time and interactions have to be confirmed thousands of times, according to Matteucci.

At Duke, Matteucci works under the guidance of Al Goshaw, the James B. Duke professor of physics. He’s also collaborating with Meg Shea and Yu Sheng Huang to build a cosmic ray detector. Cosmic rays are high-energy particles from the sun. Particles are produced from the interaction of the sun’s radiation and the Earth’s atmosphere. The team in Goshaw’s lab believes this detector will be very reliable and will be used to test more precise, future detectors.

April 17 — Goo, Goop, Gack (and Snot!)

By Karl Bates

On April 10, 2012

In Chemistry, Engineering, Nanotech, Physics, Science Communication & Education

Gooey, goopy materials and a lecture about the wonders of snot are the stars of a family-friendly, hands-on evening of science on the Duke University campus from 5–8 p.m. on Tuesday, April 17.

A quivering mass of cornstarch "oobleck." Image by Collin Mel Cunningham via Flickr

The event will be in the Fitzpatrick CIEMAS building on Duke’s West Campus. Public parking is available in the Bryan Center structure on Research Drive, near the Duke Chapel.

Faculty and students will share experiences with oobleck cornstarch polymers, origami that folds itself magically, and ‘soft matter,’ which is a polite term for other kinds of goopy stuff.

The evening also features tours of facilities including the DiVE virtual reality simulator, and a guest lecture, “The Science of Snot,” by Dr. Richard Superfine of UNC-Chapel Hill’s physics department.

All this edutaining fun is sponsored by The Materials Research Science and Engineering Center of the Research Triangle, a collaborative effort of Triangle universities funded by the National Science Foundation. It’s also a part of the state wide North Carolina Science Festival being held April 13-29.

For more information on this event and the NC Science Festival, go to: http://www.ncsciencefestival.org/event/duke-goo/

Neutrinos change their flavors, again

By Ashley Yeager

On March 8, 2012

In Lecture, Physics, Science Communication & Education

By Ashley Yeager

Two anti-neutrino detectors at Daya Bay, shown here prior to the pool being filled with ultrapure water. Courtesy of Roy Kaltschmidt, Lawrence Berkeley National Laboratory.

Elusive particles called neutrinos can change their flavors, just like the Wrigley Company trying out a new taste of Starburst candy.

Now, physicists say they have gotten the best glimpse yet of the most elusive change in neutrino flavors. The result is the “missing piece in the puzzle to understand the phenomenon of how the particles transform,” said University of Wisconsin-Madison physicist Karsten Heeger, a collaborator at the Daya Bay experiment.

He announced the new result at a symposium at Duke on March 8. The team has also submitted a paper on the result to Physical Review Letters.

Neutrinos are elementary particles that come in three flavors — muon, electron and tau. In past experiments, physicists have measured two of the ways that neutrinos can change flavors.

But no one had seen the third transformation yet. “It revealed itself in the disappearance of electron-flavored antineutrinos over a distance of only two kilometers at the Daya Bay experiment,” Heeger said. An anti-neutrino is the anti-matter counterpart of a neutrino.

By observing the change over short distances, the physicists have measured the “mixing angle,” called theta one-three. Measuring the angle will help them design new experiments to better understand why matter predominates over antimatter in the universe.

Last year, physicists at the T2K neutrino experiment in Japan said they had seen hints of neutrinos flipping flavors in a way to give them theta one-three. But the experiment was interrupted when Japan was hit by an earthquake and tsunami on March 11, 2011. Their results at that point did not have enough significance to constitute a discovery in particle physics.

In the new neutrino experiment, Heeger and his collaborators looked for anti-neutrinos coming from the six nuclear reactors at the Daya Bay Nuclear Power Plant in southern China. The team built and installed six anti-neutrino detectors in the mountains near the plant. Three of the detectors sit only about 500 meters from the plant, while the other three sit 1700 meters from it.

The nuclear reactors produced tens of thousands of electron antineutrinos. Recording the particles’ signals, the scientists found that the far detector registered six percent fewer electron-flavored particles. The deficit, according to Heeger and his collaborators, is the signal for the elusive neutrino flavor changes in neutrinos. He thinks there is less than a 1 in 3.5 million chance that the result happened by random chance.

Another hint of the Higgs, maybe

By Ashley Yeager

On March 8, 2012

In Faculty, Physics, Visualization

By Ashley Yeager

This cartoon shows a "line-up" of possible suspects for the Higgs boson. Click image for a larger view. Credit: Mark Kruse, Duke University.

Scientists may have spotted the Higgs boson again.

But, Duke physicist Mark Kruse says Fermilab has made its latest announcement prematurely.

Physicists have been searching for the Higgs for more than 40 years, hoping to find it and at last explain how mass in the universe is created.

Last year, the Fermilab team announced no significant hint of the particle when it had analyzed about 80 percent of the data from its two Higgs-hunting instruments, CDF and DZero.

Now, after adding the remaining 20 percent of the data, and some analytic improvements, the team is suggesting that Fermilab has seen the particle.

The signal, however, would be “almost fantastically high” if seen with other Higgs detection methods, Kruse says. He is on one of the committees reviewing the analyses from Fermilab’s CDF experiment and once led the instrument’s Higgs Discovery Group.

He also works at LHC, where teams made a similar announcement last December.

A “tremendous amount of work” has gone into the latest Fermilab results, Kruse says. But, the team could have waited for upcoming improvements in the CDF and DZero studies and also worked to better understand the discrepancy between the lab’s latest results and those from last year.

This might, of course, all be sorted out soon, he adds. But, “my feeling is that it was a little soon to make this announcement with the suggested claims we made, without the full results and proper understanding of the present analyses.”

This “rush to announce” mentality may also create a certain amount of distrust in the public eye, Kruse says.