Tag Archive | "Department of Physics"

Physics Professor Wins Air Force Grant

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Physics Professor Wins Air Force Grant


By Andrew Boryga
Special to UM News

Wang

He Wang

He Wang, an assistant professor of physics, joined the University of Miami College of Arts and Sciences just last August but she is already making big waves.

Late last year, Wang was notified that she won a grant from the prestigious 2017 Air Force Office of Scientific Research (AFSOR) Young Investigator Research Program (YIP) to continue investigating the potential application of next-generation LEDs, solar cells, transistors, and lasers.

YIP is a research grant award that is open to scientists and engineers at research institutions across the United States who received a Ph.D. or an equivalent degree in the last five years and who show exceptional ability and promise for conducting research.

The objective of the grant is to foster creative research in science and engineering, enhance career development of talented young researchers, and increase their opportunities to recognize and tackle significant challenges in the fields of science and engineering.

Wang’s winning proposal was titled “Structure-Photophysics-Function Relationship of Perovskite Materials.”

Her research focuses on investigating device physics and photophysics of organic and organic-inorganic hybrid optoelectronic materials. In layman’s terms, optoelectronics is the study and application of electronic devices and systems that source, detect, and control light. An example would be solar cells or LED devices.

Wang said she is excited about the award.

“I have been studying these subjects for some time and I look forward to using the resources of this grant to gain even more insight,” she said.

She tunes the structure of thin films comprised of these materials, uses laser spectroscopy to understand dynamics, and combines her knowledge of physics and engineering to think about the potential application of next-generation LEDs, solar cells, transistors, and lasers.

In her proposal for YIP, she focused on studying a new classification of materials associated with this field: organic-inorganic hybrid perovskite materials. Perovskite is a specific type of crystal structure found in materials that can be used for solar cells and LED technology.

Over the course of the next three years, she will use aspects of physics, chemistry, materials science, and engineering to study the fundamental behavior of these materials and what they could possibly be used for in the future.

This will be a continuation of the research she began when she entered Princeton University as a graduate student in 2008. After receiving her Ph.D. in electrical engineering at Princeton in 2013, she was a postdoctoral fellow in physical chemistry at UC Berkeley for nearly three years before joining the College of Arts and Sciences’ physics department.

There were over 230 proposals for the YIP last year and grants were awarded to just 58 scientists and engineers. In total, these young researchers received $20 million, or $360,000 per winner. The grant is spread out over the course of three years and can be used to support research, hire personnel, and acquire any necessary lab equipment.

 

 

 

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Sub-Second Seizures

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Sub-Second Seizures


UM physicist studies the unexpected consequences of sub-second delays on fast-moving data systems

By Andrew Boryga
Special to UM News

johnson

Physicist Neil Johnson’s research appears in the journal Science.

CORAL GABLES. Fla. (March 7, 2017)—Professor Neil Johnson, a physicist at the University of Miami College of Arts and Sciences, is interested in complex networks. He studies how fast-moving packets of information spread and interact in large networks like stock markets and the human brain, and what makes the overall system then behave in ways that are unexpected.

He compares his research to understanding traffic. He wonders: How do traffic jams appear and why do they happen in the first place?

“It’s got to be more than just bad luck,” he said.

Johnson uses high-resolution data to analyze how extreme system behaviors sometimes surface that are not just freak accidents—like a sudden movement in the stock market or a seizure in the brain.

In a study published in the esteemed academic journal Science, Johnson used electronic stock exchange data to explore what happens when delays are added to parts of fast-moving networks that operate quicker than the blink of an eye.

The question is important, he says, because U.S. financial regulators recently decided to allow an exchange network to intentionally introduce a delay to their market in an effort to make the market fairer for participants.

Johnson said the idea is similar to adding a speed bump on a highway so that all cars—from the Ferraris to the Priuses—have the same delays. Except in the case of the stock market, the delay is 350 microseconds.

With one million microseconds in one second, you’d think that’s no big deal, right?

Johnson says that the data and analysis published in his paper prove otherwise.

“The fact is, there is still no scientific understanding of what the system-wide impact of such sub-second delays will be,” he said.

Returning to his traffic analogy, Johnson said the problem is that this lack of scientific understanding forces regulators to consider the impact, like speed bumps on a road.

Except, in that case, Johnson says, we are able to monitor traffic on the road and figure out whether the speed bumps work. Maybe we determine they need to be more spaced out, or that they make no change whatsoever. Point is, there is a way to stop and assess their impact.

But that is not the case with systems like the stock market that are moving a million times faster than the one second, or so, it typically takes a human to react.

“When things are moving that fast in a network system which is that complicated, there is no human intuition for how you should regulate the system,” said Johnson.

To illustrate this point, Johnson studied raw data from the major electronic exchanges in the New York City area, a global financial hub. What he found was interesting: Even without delays added by humans natural sub-second delays already exist in these systems that can become correlated in such a way that they cause unexpected and extreme system behaviors from time to time.

“If delays already happen and we add more delays, are we sure we know what will happen?” he asked. The answer, he said, is unclear.

What is clear is that if something were to go wrong, the system would be operating so fast that humans wouldn’t be able to pull the plug. This could be potentially disastrous and result in an avalanche effect that could crash a market, cause a drone to misfire, or even cause a driverless car to suddenly veer off course.

At the same time, there is a lot to be gained from an improved understanding of how such microscopic delays impact behaviors at the system level. For example, it may help shed light on understanding neurological disorders, given that the onset of consciousness occurs on the scale of thousands of microseconds. Indeed, recent studies have shown that children with autism are slower to integrate stimuli from different senses.

“You wouldn’t think 350 microseconds is a big deal, but it can be,” Johnson said.

Johnson’s study, “To slow or not? Challenges in subsecond networks,” appears in the February 24 edition of Science. The study is funded by the National Science Foundation and the Air Force Office of Scientific Research.

 

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Researchers Go High-Tech to Explore the Social World of Children


Psychology researchers will team up with physicists to monitor children’s real-time, movement-based interactions in preschool classrooms.

By Deserae E. del Campo
Special to UM News

children-social-networksCORAL GABLES, Fla. (October 12, 2016)— Remember your earliest friends from preschool? Researchers from the University of Miami want to know how those friendships form, and they plan to do just that through a grant from the National Science Foundation (NSF) and a nifty device that will track the movements of children at two UM centers in real time for four years.

“We know that early social experiences in the classroom impact later development and learning,” said Dr. Daniel Messinger, a psychology professor in the College of Arts and Sciences. “Yet, we really don’t know how those social networks form. The whole point of this project is to learn what kids are doing moment-to-moment, hour-to-hour, month-to-month, and year-to-year in the classroom.”

While child psychologists have observed classroom behavior in the past, research was always limited by the frequency and accuracy of the observations. Now, explains Messinger, researchers can harness technology to detect and record children’s movements throughout the day. Worn like a wristwatch, the data-tracking device gathers large amounts of data that UM researchers will analyze to ask how children’s social networks in early childhood change moment-to-moment and over several years.

The collection and analysis of this big data is possible through an interdisciplinary collaboration between the departments of psychology and physics in the College of Arts and Sciences.

“This is another exciting example of what the college has made possible through its support of complex systems science,” said physicist Neil Johnson. “I do not know of any other interdisciplinary project that involves psychology and physics working so closely together.”

The movement-tracking devices will be worn by children from the Debbie School at the UM Mailman Center for Child Development, which offers education services for children who are deaf and hard of hearing from birth through the second or third grade, and the Linda Ray Intervention Center, a Department of Psychology program that serves newborn to 3-year-old children who are developmentally delayed as a result of abuse, neglect, or prenatal exposure to drugs.

Dr. Lynne Katz, research associate professor and director of the Linda Ray Intervention Center, says the research will not only assist psychologists who study children’s behaviors, but help teachers understand the inner workings of how children play, who they play with, where they play, and where maximum learning and maximum language output occurs.

“At Linda Ray, we are going to see how we can best put this study into place,” adds Katz. “The children are very young and we need to get them comfortable with wearing the data-tracking devices.”

Kathleen Vergara, director of the Debbie School, said she is excited about the study and its focus on children with hearing loss at the school, which will “lead to the development of important interventions for this population.”

The study is expected to take four years to complete and will follow children from toddler to pre-kindergarten age.

 

 

 

 

 

 

 

 

 

 

 

 

 

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Study Suggests the Universe Was ‘Cooked’ Just Right

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Study Suggests the Universe Was ‘Cooked’ Just Right


By Marie Guma-Diaz
UM News

Quantum Goldilocks Effect

This complex structure illustrates the Goldilocks effect, the ‘just right’ structure that emerges when a system containing light and matter (like the universe), develops neither too fast nor too slow.

CORAL GABLES, Fla. (September 22, 2015) – Just as in the well-known children’s story of Goldilocks and the Three Bears, something good happens when things are done in moderation, rather than in extremes. Now, a new study has translated “not too hot or too cold, just right” to the quantum world and the generation of quantum entanglement – the binding within and between matter and light – and suggests that the universe started “neither too fast nor too slow.”

By studying a system that couples matter and light together, like the universe itself, researchers have now found that crossing a quantum phase transition at intermediate speeds generates the richest, most complex structure. Such structure resembles “defects” in an otherwise smooth and empty space. The findings are published in Physical Review, the American Physical Society’s main journal.

“Our findings suggest that the universe was ‘cooked’ at just the right speeds,” said Neil Johnson, professor of physics at the University of Miami’s College of Arts & Sciences and one of the authors of the study. “Our paper provides a simple model that can be realized in a lab on a chip, to explore how such defect structure develops as the speed of cooking changes.”

The big mystery concerning the origin of the universe is how the star clusters, planetary systems, galaxies, and other objects that we now see managed to evolve out of nothing. There is a widespread belief within the scientific community that the birth of structure in the universe lies in the crossing of a quantum phase transition and that the faster the transition is crossed, the more structure it generates. The current findings contradict that belief.

The study sheds new light on how to generate, control, and manipulate quantum entanglement, since the defects contain clusters of quantum entanglement of all sizes. The findings hold the key to a new generation of futuristic technologies—in particular, ultrafast quantum computing, ultrasafe quantum cryptography, high-precision quantum metrology, and even the quantum teleportation of information.

“Quantum entanglement is like the ‘bitcoin’ that funds the universe in terms of interactions and information,” Johnson said. “It is the magic sauce that connects together all objects in the universe, including light and matter.”

In the everyday world, a substance can undergo a phase transition at different temperatures; for example, water will turn to ice or steam when sufficiently cold or hot. But in the quantum world, the system can undergo a phase transition at absolute zero temperature, simply by changing the amount of interaction between the light and matter. This phase transition generates quantum entanglement in the process.

Johnson likes to compare the emergence of highly entangled light-matter structures, as the quantum phase transition is crossed, with the way lumps of porridge appear out of “nothing,” when you heat up milk and oats.

“If you cross the transition at the right speed (cook at right speed), the structures (lumps) that appear are far more complex – more ‘tasty’ – than when crossing fast or slow,” said Johnson. “Since it is a quantum phase transition that is being crossed, the structures that appear contain clumps of quantum entanglement.”

The results of the study, titled “Enhanced dynamic light-matter entanglement from driving neither too fast nor too slow,” are robust for a wide range of system sizes, and the effect is realizable using existing experimental setups under realistic conditions. O.L. Acevedo, from Universidad de los Andes, Colombia, is first author of the study. Other co-authors from Universidad de los Andes are L. Quiroga and F. J. Rodriguez.

“Understanding quantum entanglement in light-matter systems is arguably the fundamental problem in physics,” Johnson said.

The current paper opens up a novel line of investigation in this area. In addition, it provides a unique opportunity to design and build new nanostructure systems that harness and manipulate quantum entanglement effects. The researchers are now looking at specifying the precise conditions that experimentalists will need in order to see the enhanced quantum entanglement effect that they predict.

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Network and Complexity Scientists Paint Big Picture of Cultural History

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Network and Complexity Scientists Paint Big Picture of Cultural History


By Marie Diaz-Guma
and Annette Gallagher
UM News

 

The visualization of birth-death network dynamics offers a meta-narrative of cultural history: Europe 0-2012 CE. [Final still of Movie S1 in Schich et al.] Copyright: Ma

The visualization of birth-death network dynamics offers a meta-narrative of cultural history of Europe from 0 to 2012 CE. Copyright: Maximilian Schich & Mauro Martino, 2014

CORAL GABLES, Fla. (July 31, 2014)—Quantifying and transforming the history of culture into visual representation isn’t easy. There are thousands of individual stories, across thousands of years, to consider, and some historical conditions are nearly impossible to measure.

Addressing this challenge, Maximilian Schich, associate professor of arts and technology at the University of Texas at Dallas, assembled a team of network and complexity scientists, including University of Miami physicist Chaoming Song, to create and quantify a big picture of European and North American cultural history.

Schich and his fellow researchers reconstructed the migration and mobility patterns of more than 150,000 notable individuals over a time span of 2,000 years. By connecting the birth and death locations of each individual and drawing and animating lines between the two locations, Schich and his team have made progress in our understanding of large-scale cultural dynamics.

Their research is detailed in the article “Historical Patterns in Cultural History,” published August 1 in the journal Science. Another eminent journal, Nature, produced a video about the findings.

Song, an assistant professor in UM’s Department of Physics in the College of Arts and Sciences, is a co-author of the study. A statistical physicist, Song’s research lies in the intersection of statistical physics, network science, biological science, and computational social science, broadly exploring patterns behind petabytes of data. Song’s role in the project was primarily data analysis and model development.

“My research approach is mainly based on statistical physics, a sub-branch of physics that helps to understand the connections between macroscopic phenomena and microscopic details,” Song said.

“The study draws a surprisingly comprehensive picture of European and North American cultural interaction that can’t be otherwise achieved without consulting vast amounts of literature or combing discrete datasets,” Schich said. “This study functions like a macro-scope, where quantitative and qualitative inquiries complement each other.”

Schich and his colleagues collected the birth and death data from three databases to track migration networks within and out of Europe and North America, revealing a pattern of geographical birth sources and death attractors.

“The resulting network of locations provides a macroscopic perspective of cultural history, which helps us retrace cultural narratives of Europe and North America using large-scale visualization and quantitative dynamical tools, and to derive historical trends of cultural centers beyond the scope of specific events or narrow time intervals,” says Song.

Other findings show that despite the dependence of the arts on money, cultural centers and economic centers do not always coincide, and that the population size of a location does not necessarily point to its cultural attractiveness. In addition, the median physical distance between birth and death locations changed very little, on average, between the 14th and 21st centuries, from about 214 kilometers (133 miles) to about 382 km (237 miles), respectively.

The topic of art and cultural history is an uncommon topic for papers in journals such as Science.

“A large amount of multidisciplinary expertise was necessary to arrive at the results we found,” Schich said. “The paper relies on the fields of art history, complex networks, complexity science, computational sociology, human mobility, information design, physics, and some inspiration from systems biology.”

“There is an increasing realization that systems across different disciplines often share similar structural and dynamic properties,” said Song. “Such similarities offer new perspectives and unique opportunities for physicists to apply their methodologies on a much broader set of phenomena.”

Researchers involved in the study came from the groups of Dirk Helbing at the ETH Zurich, Swiss Federal Institute of Technology and Albert-László Barabási at Northeastern University. Current affiliations of the team include the following institutions: Central European University in Budapest; Harvard Medical School; IBM Research; Indiana University; Ludwig-Maximilians-University in Munich; and the University of Miami. Data was collected from Freebase.com, the Allgemeines Künstlerlexikon, the Getty Union List of Artist Names, and the Winckelmann Corpus.

The research was funded by the German Research Foundation, the European Research Council, and UT Dallas.

 

 

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