Fifth graders from Snow Elementary School in Middletown toured Wesleyan’s astronomy, biology, chemistry, physics and scientific imaging departments on June 18, 2014. Students also visited the Joe Webb Peoples Museum and Collections in Exley Science Center.
Tag Archive for physics
by Olivia Drake •
Reinhold Blümel, the Charlotte Augusta Ayres Professor of Physics, and physics graduate student Yunseong Nam are the co-authors of “Robustness of the quantum Fourier transform with respect to static gate defects,” published in Physical Review A, Issue 89, in April 2014.
The quantum Fourier transform (QFT) is one of the most widely used quantum algorithms, ranging from its primary role in finding the periodicity hidden in a quantum state to its use in constructing a quantum adder.
by Mike Sembos •
The U.S. Air Force has taken a keen interest in the recent work of Tsampikos Kottos, the Douglas J. and Midge Bowen Bennet Associate Professor of Physics. Kottos, along with Graduate Research Assistant Eleana Makri, Hamidreza Ramezani Ph.D. ’13 (now a postdoc at U.C. Berkeley) and Dr. Ilya Vitebskiy (AFRL/Ohio), has come up with a theoretical way to build a more effective, reusable power limiter.
Generally speaking, the function of a power limiter is to protect a sensor — be it the human eye, an antenna, or other sensitive equipment — from high-intensity radiation, like that generated by high-power lasers.
Kottos, Makri, Ramezani and Vitebskiy published a paper titled “Non-Linear Localized Modes Give Rise to a Reflective Optical Limiter” [Phys. Rev. A 89, 031802(R) (2014)] that was highlighted in Washington, D.C. at the spring review meeting of the Air Force Office of Scientific Research (AFOSR) as one of the main research achievements in electromagnetics of 2014 that can potentially benefit the U.S. Air Force. Now, with the Air Force’s help, Kottos is taking the necessary steps to make the project become a reality.
Generally speaking, there are two categories of limiters — dynamic and passive. These new limiters are of the passive variety.
“Dynamic limiters are very slow,” explained Kottos. “They consist of many parts, and then these parts have to communicate with each other. So these are not very good. Passive limiters perform the limiting action — the filtering of the high power — based on the intrinsic properties of the materials.”
So, passive limiters are the way to go.
When striving to produce better passive limiter components, one can synthesize new materials (which Wes is not currently equipped to do on-site), or one can rely on existing materials and try to design or propose geometries that will improve the efficiency of existing materials.
Since the dawn of lasers in the 1960s, the standard filtering protection has been based on the use of what are called sacrificial limiters. When high-intensity light passes through a sacrificial limiter, the materials absorb the energy, heat up and melt, becoming opaque. The light is blocked and the sensor is protected, but the limiter is destroyed and must be swapped out like a burnt lightbulb. This is less than ideal, as it’s expensive and time-consuming to replace.
“We want to propose a clever limiter which is not going to sacrifice itself in order to save the sensor on the other side,” Kottos said. “What we are proposing is to create two stacks of alternate layers, A and B. This is what people usually call a Bragg mirror. Such a structure creates a frequency window for which light is completely reflected irrespective of its intensity. This solves one part of the problem but it creates another one. Namely, we want ‘non-harmful,’ low-intensity light to be transmitted. How can we achieve this? Well, the simple way is by creating a ‘bridge.’ But the bridge has to be clever. It must allow low intensity light to pass and block high intensity light. One way to do this is to make sure that the bridge will collapse if high intensity light goes through.”
Kottos’ new work involves placing a defect layer of dissipative nonlinearity (“the bridge”) in the middle of the Bragg mirror. The nonlinear properties of the materials increase dissipation for high light intensities. Strange as it sounds, losses (dissipation) can rescue the limiter (bridge) from high power light and reflect the energy into space.
“To understand this we need to think of how three oscillators coupled with springs — with the middle one having friction (the dissipation layer) — will behave when energy is pumped into the system. Say the left one is excited, displacing it from the equilibrium position. Then energy will move from the left one to the right one via the spring and then will continue to the third via the second spring that connects the last two together. Via this process, some energy will be turned to heat via the friction of the middle oscillator. Now let’s further increase the friction in the middle, which in optics is achieved via the dissipative nonlinear mechanism when incident power is increased. Obviously the process will be repeated, but now more energy will be radiated as heat since the friction in the middle is higher. But what will happen if the friction in the middle is huge, corresponding to high incident power in optics which will trigger high dissipative nonlinearities?”
The intuitive prediction is that friction-generated heat will burn the middle oscillator. But students in Kottos’ “Waves and Oscillations” course would predict that a huge friction will turn the middle oscillator into an immovable wall, neutralizing the friction and reflecting all the energy back without letting it pass to the third oscillator. And this is exactly the mechanism Kottos and co. are exploring, but in the optics realm.
“We knew this principle since centuries ago — it’s called impedance mismatching,” Kottos said. “The more you create an absorber, the more the energy that’s not absorbed but reflected back. I know that’s an oxymoron, but this is how it happens. The reason that we did not use this property up to now is rather psychological. In most cases we strive to ‘match’ things and we are used to this way of thinking. In this specific case we thought the other way around.”
The experimental realizations of these new theoretical optical limiters are currently being investigated at two U.S. labs. With time, the Wes group hopes to continue refining its proposal to further increase the limiters’ effectiveness. A further step down the road is to implement the same idea acoustically.
“I am hopeful that the experimental group of Professor Fred Ellis at Wes will be able to demonstrate the applicability of this idea in acoustics,” said Kottos. “Discussions along this line of research are in progress.”
by Olivia Drake •
Tsampikos Kottos, the Douglas J. and Midge Bowen Bennet Associate Professor of Physics, received a $575,000 grant from the U.S. Air Force Office of Scientific Research‘s Multidisciplinary University Research Program (MURI). MURI is a basic research program sponsored by the U.S. Department of Defense.
The award will support Kottos’ study on “PT-Summetric Optical Materials” through April 2017. During this time, Kottos will develop a theoretical framework for Parity-Time (PT) Symmetric Optics using mainly polymetric platforms. Additionally, efforts will be made towards identifying other platforms/areas where PT-Symmetric ideas can be applied. Kottos will be coordinating his research with faculty at the University of Central Florida, Rice University, Georgia Institute of Technology and University of Utah.
“We plan to explore a variety of opportunities provided by this reflection symmetry for a new generation of photonic materials, structures and devices that will exhibit novel optical properties and functionalities,” Kottos said. “We plan to pursue prospects in the areas of open quantum systems, plasmonics, and transformation optics. Our results may be also applicable to ultrasonics where stealth properties are often desired.”
The Air Force Office of Scientific Research granted six other awards to various academic institutions to perform multidisciplinary basic research. The AFOSR awards, totaling $67.5 million, are the result of the Fiscal Year 2013 competition conducted by AFOSR, the Army Research Office, and the Office of Naval Research under the Department of Defense’s MURI Program.
Hamidreza (Hamid) Ramezani Ph.D. ’13, recently won the Biruni Graduate Student Research Award. The award aims to promote and recognize outstanding research by a physics graduate student of Iranian heritage who is currently studying in one of the institutions of higher education in the United States, seeking originality, thoroughness, a teamwork spirit and ownership among the candidates. The honor comes with a cash award.
Before graduating with his Ph.D. from Wesleyan in November, Ramezani studied cosmology and gravitational physics while earning his master’s degree at the University of Tehran. He completed his bachelor study in solid state physics at Sahed University.
At Wesleyan, his mentor was Tsampikos Kottos, Douglas J. and Midge Bowen Bennet Associate Professor of Physics. Ramezani worked in the Wave Transport in Complex Systems lab and studied ways a macroscopic object is miniaturized. The lab’s objective is “to close the gap between the microscopic and macroscopic worlds and to develop models and theories that will help understand the interplay between quantum mechanics, interactions, and disorder, which dictate the dynamics on the mesoscopic scale.” More information on the lab and its research can be found on this website. Ramezani focused more specifically on the fundamental properties and application of complex optical systems with judicious balanced gain and loss.
Currently, Ramezani is a postdoctoral research assistant under Professor Xiang Zhang at the University of California – Berkeley. His interests are asymmetric transport phenomena in complex electronics, acoustics and photonics systems.
by Kate Carlisle •
Guy Geyer Marcus ’13 has won the Leroy Apker award for the American Physical Society, the highest prize offered in the United States for an undergraduate thesis in physics.
Marcus is the second Wesleyan student to win the prize in three years; Wade Hsu ’10 also claimed the prestigious award. In 2008, Gim Seng Ng ’08 was a finalist for the Apker.
“This achievement naturally highlights the quality and seriousness of our undergraduates and our undergraduate program,” said Physics Department Chair Brian Stewart.
Marcus’ Wesleyan advisor was Greg Voth, associate professor of physics.
Marcus is working toward a Ph.D in theoretical physics at Johns Hopkins University. His prizewinning thesis was titled: “Rotational Dynamics of Anisotropic Particles in Turbulence: Measurements of Lagrangian Vorticity and the Effects of Alignment with the Velocity Gradient.”
by Olivia Drake •
While technology at Wesleyan is growing by leaps and bounds, the computational capacity is growing by gigaFLOPS and now, teraFLOPS.
Not to be confused with the prehistoric pterodactyl’s beach footwear, a teraFLOP is a term used in high-performance computing to quantify the rate at which computer systems can perform arithmetic operations. TeraFLOPs can perform one trillion operations per second (S), and for scientists at Wesleyan, this means calculations can be done up to 50 times faster with the new computing cluster, installed during the summer 2013.
“The new cluster has been revolutionary in my own work,” said Francis Starr, professor of physics. “I used to run calculations that would take a month or even a year to compute, and my patience would run out. Now, I can get results in two or three days.”
In 2006, Wesleyan’s computing cluster came in around 0.5 teraflops. In the 2010 at 1.5 teraflops, and the newest cluster has a theoretical capacity of 25 to 75 teraflops, depending on the application.
“By way of comparison, my Mac laptop comes in around 0.02 teraflops, so I would need 3,500 laptops to achieve the same compute power! I think I will need a bigger backpack,” Starr said.
The new technology also is “green.” While the new machine is 100 times more powerful than the 2006 cluster, it requires half the the electrical power to operate and less cooling power to run the hardware.
The new cluster is currently used by faculty and students in chemistry, computer science, physics, biology, the social sciences and the Quantitative Analysis Center. Henk Meij, unix systems group manager and a senior consultant for the QAC, manages the facility’s operation and offers support and maintenance for any software issues. He also offers training and teaches faculty and students how to submit jobs to the scheduling system.
“Anyone on campus who needs a fast computation, ITS offers this tremendous resource which can be very beneficial to your research,” Meij said. “We can now solve real world problems in a matter of days.”
The newest cluster cost $125,000,
by Olivia Drake •
Q: Coady, what are you majoring in and why did you choose Wesleyan?
A: I’m double majoring in astronomy and physics. I had actually never been to Wesleyan before applying, but I had heard very good things from friends, and its reputation for being unconventional was very appealing to me. The clincher though was the very generous financial aid that the university offered me, without which I definitely would not be here.
Q: Tell us about your efforts with the Long Lane Organic Farm. Why did you decide to become a student-farmer?
A: After coming to Wesleyan, I fell in with a group of people who really got me thinking about the state of food production and consumption in this country. Industrial farming and a disconnect between what we eat and how it is produced is hurting our well-being, and I think that the best way to remedy that is to educate myself and others on growing our own food in a more responsible and sustainable way.
Q: What is your role with the farm this summer? Please describe a day “down on the farm.”
A: We don’t really have set roles, although I often choose to participate in or initiate various building projects, like planning and building our irrigation system. Our day begins at 7 a.m. with a morning meeting at the farm. There, all the people who are working that day discuss plans for work, like whether or not we should companion plant radishes with the squash. We try to be horizontally organized and make decisions only with 100 percent consensus, so that everyone can have a say in what we’re doing, and can suggest new ideas if they want. We work until 11, and then have a midday break, during which we eat lunch, run errands and do other work for the farm that can be done in the field, like emails and budget spreadsheets. At 3 p.m., we return to the farm and review what was accomplished in the morning, and then finish up whatever wasn’t quite done by lunch. At 7 we close up the shed and gates, and then return home for dinner. Nine of us live in the same house, and so whoever takes the afternoon off cooks dinner for the house.
Q: Who else is working on the farm this summer? Are you looking for new recruits?
A: Laura Cohen ’14, Kate Enright ’15, Ben Guilmette ’15, Josh Krugman ’14, Maggie Masselli ’16, Anna Redgrave ’16, Rebecca Sokol ’15, Hailey Sowden ’15 and Cat Walsh ’16 are all living in Middletown to work on the farm this summer. Whoever wants to help is a farmer, and we’re always looking for new people, from Wesleyan or from Middletown at large.
Q: Where are you from? Did you have any farming background or is this all new to you?
A: I’m from Wadsworth, Ill., which is about an hour north of Chicago and 15 minutes west of Lake Michigan. Most of the surrounding area is cornfields, but even so I didn’t get involved in farming until coming to Wesleyan.
Q: What does the farm do with the produce that you grow?
A: We give a lot of it to Bon Appetít, the campus dining service, so that they can serve it in the dining hall. Another large portion we take to the North End Farmers’ Market in Middletown. Anything we bring to the market and don’t sell is then donated to the Amazing Grace food pantry. We also have a new program this year with families in the area called the Middletown Food Project. We have the families over to the farm and teach the children about various aspects of farming and producing food, and also send everyone home with a bag of produce they harvest themselves. And we eat some of it ourselves, of course.
Q: What other extracurricular activities are you involved with at Wesleyan?
A: I tutor other students in General Physics II, and also have a job at the Star and Crescent, helping the head chef prep and serve the meals. This past spring I was in the Spring Dance performance, and I plan on auditioning for other dances in the future.
Q: As a rising junior, do you know what your post-Wesleyan plans might be?
A: After Wesleyan I hope to get my Ph.D. in astrophysics, though I haven’t given much thought about a particular institution to attend. After that I plan on applying to NASA in order to be an astronaut. I know it sounds farfetched, especially given the current state of NASA, but I believe strongly in the scientific and societal benefits of manned space exploration, and also have a great personal passion for science, space and discovery.
by Olivia Drake •
by Cynthia Rockwell •
Jack DiSciacca ’07 is first author on a paper that appeared in the April issue of Physical Review Letters, a premier journal for physics. Now a Ph.D candidate at Harvard, DiSciacca earned his undergraduate degree with high honors; Foss Professor of Physics Tom Morgan was his advisor. The published paper, “One Particle Measurement of the Anti-Proton Magnetic Moment,” details DiSciacca’s research on the antiproton, which is an antimatter particle.
Morgan explains, “DiSciacca spent the last six months at CERN [the European Organization for Nuclear Research], at the same accelerator facility where physicists recently discovered the Higgs boson to measure the magnetic moment of the antiproton (how much spinning current this anti-matter particle possesses).”
DiSciacca’s work is significant because it offers experimental confirmation of a key theory in physics known as CPT – charge, parity, time invariance. His findings were cited for their importance in Physics Viewpoints, where Eric Hudson and David Salzberg from the University of California in Los Angeles wrote: “Specifically, Jack DiSciacca of Harvard University and his colleagues present the most precise measurement to date of the antiproton magnetic moment … As reported in Physical Review Letters, the results match data on the proton, thus extending CPT’s shatterproof status for the time being.”
Morgan also notes that DiSciacca recently visited his class to give a presentation on his work, which DiSciacca says was “really a discussion, with lots of questions and more of a dialog than a typical presentation.” He was pleased with the engaged quality of the students’ remarks and describes Wesleyan as “a spectacular place to do physics. You won’t find more committed teachers anywhere,” with an atmosphere that is relaxed and friendly, as well as highly academic. The professors, he says, are truly accessible.
As for his current work, DiSciacca says, “The process of making the antiproton measurement was quite interesting and also demanding. We had about six months to move almost everything we used at Harvard to Switzerland, install the experiment and make the measurement using a single antiproton. The goal was to make a measurement before the December 2012 start of an extended upgrade phase at CERN, where there would be no antiprotons for another year and a half. One interesting part of this process is the story of moving the experiment to Switzerland. We went from having an experiment that fits in a room at Harvard, to working in a Home Depot-sized building with many other experiments in close proximity.”
“Our experiment is rather tall, about my height, and it’s quite delicate. So, to secure it safely for the plane ride over, we found that it would exceed the height limit of planes leaving Boston. As a result, we had it trucked to JFK, flown to Paris on a larger plane, and then trucked from Paris to CERN. The fact that it arrived in one piece, without any broken components, continues to amaze me.”
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by Olivia Drake •
Francis Starr, associate professor of physics, received a $100,000 grant from the American Chemical Petroleum Fund for his work examining the properties of extremely thin polymer films. These systems have important applications ranging from nano-electronics to artificial tissues. The work will be supported through August 2014.
by Olivia Drake •
Greg Voth, associate professor of physics, received a grant worth $300,000 from the National Science Foundation’s Material Research division to support his study on “Rod Dynamics in Turbulence: Simultaneous 3D measurements of Anisotropic Particles and Velocity Fields” through May 31, 2015.
In a wide range of natural and industrial situations, turbulent flows carry particulate material. For example, clouds are turbulent flows containing water droplets and ice crystals. Papermaking uses turbulent suspensions of fibers. If the particles are spheres, there are a variety of tools available for measuring their motion. But usually the particles are not spheres, and the movement and rotations of non-spherical particles have never before been measured as they are carried by a turbulent flow. Voth’s project will develop experimental tools to make these measurements. Particle rotations are of particular interest because their statistics are expected to be similar in all turbulent flows, and measurements can be compared with theoretical predictions for the universal properties of turbulence. This work seeks to establish a clear understanding of the fundamental characteristics of non-spherical particle motion in laboratory turbulent flows that can be used to understand more complex applications such as icy clouds and papermaking. Education and research training are central to this project, which will support the mentoring of undergraduates, graduate students, and a postdoctoral scientist, as well as training K-12 educators in physical science.