Tag Archive for physics

Graduate Student Factor Studies Planet Formation Around a Young Star

Sam Factor, a graduate student in astronomy, at the Submillimeter Array, located on Mauna Kea in Hawai'i in March 2015.

Sam Factor, a graduate student in astronomy, at the Submillimeter Array, located on Mauna Kea in Hawai’i in March 2015.

#THISISWHY
In this News @ Wesleyan story, we speak with Sam Factor ’14, a graduate student in astronomy.

Q: Sam, congratulations on completing your master’s thesis in astronomy! We understand you took your first astronomy class in the fall of your senior year at Wesleyan. What was your undergraduate major and how did your late-developing interest in astronomy come about?

A: Thank you very much! As an undergrad, I majored in physics and computer science. During the fall of my senior year I took Introductory Astronomy (ASTR 155). I signed up for the course mainly because I wanted an interesting and relatively easy course to fill out my schedule. I had been interested in astronomy since I was very young, but had never taken a formal class. I absolutely loved the class and decided to apply to the BA/MA program.

Q: How and when did you decide to stay on at Wesleyan to pursue a master’s degree in astronomy?

A: I actually decided to apply to the BA/MA program only a few weeks before the application was due!

3 Students Receive Goldwater Honorable Mentions

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Wesleyan students Selin Kutlu ’16, Jacob “Jack” Lashner ’16 and Aaron Young ’16 have been chosen for honorable mention by the Barry Goldwater Scholarship and Excellence in Education Program for the 2015-2016 academic year. The award is presented annually to U.S. sophomores and juniors for excellence in mathematics, science and engineering. This year’s recipients were selected from a field of more than 1,200 students nominated by faculty from more than 420 colleges and universities nationwide. Less than half the students nominated each year are selected as a scholar or for honorable mention.

Kutlu

Selin Kutlu ’16

Kutlu, a molecular biology and biochemistry and neuroscience and behavior double major, is interested in understanding not only biological mechanisms at the cellular and molecular level, but also how these mechanisms can alter human health and behavior. Working with Manju Hingorani, professor of molecular biology and biochemistry, Kutlu combines her interest in both biochemistry and neuroscience through research on DNA mismatch repair, a process that corrects errors made during DNA replication. “These errors can cause mutations that can have deleterious effects on an organism’s health, including carcinogenesis and neurological disorders such as Huntington’s disease,” said Kutlu. Her career goal is to obtain an MA and PhD in molecular biology in order to teach at the university level and conduct biomedical research.

Petit Foundation Awards Grant to Green Street

Green Street

Green Street Director Sara MacSorley accepts a $12,500 grant from Dr. William Petit.

Wesleyan’s Green Street Teaching and Learning Center has received a $12,500 grant from the Petit Family Foundation to support the center’s Girls in Science Summer Camp. Green Street Director Sara MacSorley accepted the gift from Dr. William Petit.

The Green Street Girls in Science Summer Camp will take place August 3 – 7 and will be open to girls entering grades 4, 5, and 6. Erika Taylor, assistant professor of chemistry, assistant professor of environmental studies, Ruth Johnson, assistant professor of biology, and Christina Othon, assistant professor of physics, will participate in the five-day program, covering topics from biochemistry to physics and culminating in a science showcase to share projects with family and friends. The camp will be held at Green Street, but students will also spend time in teaching labs on Wesleyan’s campus.

Othon, Taylor Students Published in Physical Chemistry Letters

Christina Othon and Erika Taylor, along with physics graduate student Nimesh Shukla, Lee Chen ’15, Inha Cho ’15 and Erin Cohn ’15, are the co-authors of a paper titled “Sucralose Destabilization of Protein Structure” published in The Journal of Physical Chemistry Letters, March 2015. Othon is assistant professor of physics and was PI on the paper. Taylor is assistant professor of chemistry, assistant professor of environmental studies.

Sucralose is a commonly employed artificial sweetener that behaves very differently than its natural disaccharide counterpart, sucrose, in terms of its interaction with biomolecules. This research suggests that people may need to think about the impact of sucralose (a.k.a. Splenda) on their proteins.

Watch Othon explain associated research in this video. She speaks around the 34 minute mark.

Wesleyan Physics Lab, U.S. Air Force Partner on Groundbreaking Research

Graduate student Eleana Makri and Tsampikos Kottos, the Douglas J. and Midge Bowen Bennet Associate Professor of Physics, work on reflective optical limiter research Feb. 3. (Photo by Hannah Norman '16)

Graduate student Eleana Makri and Tsampikos Kottos, the Douglas J. and Midge Bowen Bennet Associate Professor of Physics, work on reflective optical limiter research Feb. 3. (Photo by Hannah Norman ’16)

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Graduate student Eleana Makri and Tsampikos Kottos, the Douglas J. and Midge Bowen Bennet Associate Professor of Physics, work on reflective optical limiter research Feb. 3. (Photo by Hannah Norman '16)

Makri and Kottos review their power limiter research.

For many years, pilots in the Air Force, scientists conducting research with high-powered lasers, and others have struggled to protect their eyes and sensitive equipment from being damaged by intense laser pulses. In many cases, this was achieved by intense power filters, which offered protection, but self-destructed. Now they have a solution, which provides protection without damaging the filters themselves, thanks to a research collaboration between the Air Force Research Laboratory (AFRL) and a team of researchers in Wesleyan’s Physics Department.

The research, led by Tsampikos Kottos, the Douglas J. and Midge Bowen Bennet Associate Professor of Physics, is included in the just-released U.S. Air Force Office of Scientific Research 2014 Technical Strategic Plan. The document is published on the Air Force Research Laboratory (AFRL) webpage.

Previous attempts at a solution focused on creating gradually darkening sunglasses to protect the wearer’s eyes when s/he steps into bright sunlight, but return quickly to their normal state when indoors. However, no version could darken quickly enough to protect the wearer from short laser pulses.

As described in the Technical Strategic Plan,

Huwel, Morgan Investigate Dynamics of Laser-Induced Sparks in Helium

Lutz Huwel, professor of physics, and Thomas Morgan, the Foss Professor of Physics, are the co-authors of an article titled “Investigating the dynamics of laser induced sparks in atmospheric helium using Rayleigh and Thomson scattering,” published in the Journal of Applied Physics, Volume 117 in January 2015.

The paper describes the use of two laser systems to prepare and study a helium plasma, and draws on an extensive international collaboration. The electron density and temperature of the plasma are measure as a function of time and space with high precision. The work has important impact in the area of laser induced breakdown spectroscopy and to the spectral line shape scientific community.

Makri’s Power Limiter Research Noted in Scientific Reports Article

Makri used a power limiter consisting of a nonlinear lossy layer embedded in two mirror layers. This setup provides a resonant transmission of a low intensity light and nearly total reflectivity of a high-intensity light.

Makri used a power limiter consisting of a nonlinear lossy layer embedded in two mirror layers. This setup provides a resonant transmission of a low intensity light and nearly total reflectivity of a high-intensity light.

A study co-authored by Graduate Research Assistant Eleana Makri and two other Wesleyan researchers is a topic of a Oct. 20 article published in Scientific Reports.

Due to the ultrahigh-speed and ultrawide-band brought by adopting photons as information carriers, photonic integration has been a long-term pursuit for researchers, which can break the performance bottleneck incurred in modern semiconductor-based electronic integrated circuits. The article states that “recently, Makri theoretically proposed the concept of reflective power limiter based on nonlinear localized modes, where a nonlinear layer was sandwiched by two reflective mirrors, thus increased the device complexity.”

The report is based on Makri’s study, titled “Non-Linear Localized Modes Give Rise to a Reflective Optical Limiter” published in March 2014. The paper is co-authored by Tsampikos Kottos, the Douglas J. and Midge Bowen Bennet Associate Professor of Physics; Hamidreza Ramezani Ph.D. ’13 (now a postdoc at U.C. Berkeley) and Ilya Vitebskiy (Sensors Directorate at the Air Force Research Laboratory, Ohio).

The same study was also 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. Read more about this study in this past News @ Wesleyan article.

Read the full Scientific Report article, titled “Chip-integrated optical power limiter based on an all-passive micro-ring resonator,” online here.

Kottos, Basiri Author Paper Published in Physical Review

Data by Tsampikos Kottos and Ali Basiri.

Tsampikos Kottos and Ali Basiri, a Ph.D. student in physics, are co-authors of a paper titled “Light localization induced by a random imaginary refractive index,” published in Physical Review A 90, on Oct. 13, 2014. Kottos is the Douglas J. and Midge Bowen Bennet Associate Professor of Physics.

In the paper, the authors show the emergence of light localization in arrays of coupled optical waveguides with randomness.

 

 

 

Hanakata ’14 Finalist for American Physical Society’s Apker Award

Paul Hanakata '14

Paul Hanakata ’14

Paul Hanakata ’14 was named a finalist for the American Physical Society’s prestigious Leroy Apker Award, the highest prize offered in the United States for an undergraduate thesis in physics. He will compete to win the award this month.

The Apker Award was created to recognize outstanding achievements in physics by undergraduate students, and thereby provide encouragement to young physicists who have demonstrated great potential for future scientific accomplishment.

At Wesleyan, Hanakata received high honors for his Wesleyan thesis titled, “Cooperative Dynamics in Supported Polymer Films,” under his advisor, Francis Starr, professor of physics and director of the College of Integrative Sciences.

In recognition of his exceptional research accomplishments,

Wesleyan Faculty Teach Fifth Graders about Physics, Biology, Chemistry, Astronomy

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.

Brian Northrop, assistant professor of chemistry, used the reversible hydration and dehydration of cobalt(II) chloride to demonstrate Le Chatelier's principle and create color-changing "humidity sensors." Pieces of filter paper were saturated with a solution of cobalt(II) in water, which turned the paper pink. Warming the paper with a blow dryer evaporated the water and turned the paper blue by re-forming cobalt(II) chloride.

Brian Northrop, assistant professor of chemistry, used the reversible hydration and dehydration of cobalt(II) chloride to demonstrate Le Chatelier’s principle and create color-changing “humidity sensors.” Pieces of filter paper were saturated with a solution of cobalt(II) in water, which turned the paper pink. Warming the paper with a blow dryer evaporated the water and turned the paper blue by re-forming cobalt(II) chloride.

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Research student Jesse Mangiardi ’15 Mangiardi ’15 demonstrated how to change the chemical composition — and color — of a penny. First he submerged a copper penny in a solution containing zinc mixed with a base, which coated the penny in zinc and made it appear silver. Next, he heated the zinc-coated penny with a blow torch which caused the zinc and copper to react and form brass, and turned a penny bright gold.

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The students took a few silver and gold pennies back with them to Snow School.

Blümel, Nam Published in Physical Review A

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.

Physics’ Kottos Develops an Innovative Power Limiter

Tsampikos Kottos, the Douglas J. and Midge Bowen Bennet Associate Professor of Physics is developing a power limiter which may protect the human eye from radiation.

Tsampikos Kottos, the Douglas J. and Midge Bowen Bennet Associate Professor of Physics, is developing a reusable power limiter that will protect sensors from radiation without being destroyed in the process.

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.

Tsampikos Kottos is working with Professor of Physics Fred Ellis on a sensor experiment.

Tsampikos Kottos is working with Professor of Physics Fred Ellis on a related acoustical experiment.

“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.

A power limiter consisting of a non-linear lossy layer (blue layer) embedded in a Bragg grating (white and orange layers) allows for (a) a transmission of a low intensity beam while (b) it completely reflects a high intensity beam without any absorption.

A power limiter consisting of a non-linear lossy layer (blue layer) embedded in a Bragg grating (white and orange layers) allows for (a) a transmission of a low intensity beam while (b) it completely reflects a high intensity beam without any absorption.

“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.”