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CPLC Seminar: Simon Sponberg "Emergent Simplicity and Multiscale Mechanisms of Agile Animal Movement"

9/21/2018 7:41:47 AM CPLC Staff

The ability to move is a trait of all animals. Yet how do animals, including ourselves, get around in this complex and uncertain world with an ease and agility we find hard to recreate in engineered systems? Using an organismal physics approach my group explores the physical and physiological mechanisms that enable agile movement in living systems. I will discuss studies at three scales in animal movement. We first examine flight maneuvers as emergent dynamics from the underlying complex physiological systems. Using robophysical models of flowers, we probed how maneuverable, hovering hawk moths to adjust to light levels that vary by 7 orders of magnitude from early afternoon to late dusk. Using simple one-parameter models from control theory we discover the brain slows its visual processing to accomplish temporal summation in dim light – like increasing the exposure time on a camera. Perhaps more surprisingly the resulting dynamics are empirically linear, invariant under experimental scaling and superposition. This allows us to predict behavior to novel stimulus combinations. We next investigate the neural basis of these behaviors by recording a comprehensive motor program – all the electrical signals that the moth’s brain sends to it wings. The brains of small flapping insects are still complex, with 105-106 neurons, but we find that they control wingstroke dynamics with as little as 101 bits/wingstroke mostly through precise timing. Finally we explored how muscle’s macroscopic properties during locomotion are shaped by its unusual multiscale structure. High-speed x-ray diffraction through living muscles shows that muscle is active crystalline matter – the regular arrangement of actin and myosin filaments produces a lattice that dynamically changes spacing as a muscle contracts. As a result, muscle has a time-varying poisson ratio including an auxetic regime and these dynamics result in flow that assists the convective delivery of molecules. Moreover a single nanometer difference in muscle lattice spacing can account for how one muscle acts like a motor while another acts like a brake. We cannot yet emulate the motility seen in nature, nor derive behavior, but the emergent dynamics of animal locomotion is an exciting opportunity.

2/10/2014 Siv Schwink

Professor Mats Selen was recently appointed associate head for undergraduate programs at Physics Illinois. His predecessor, Professor Kevin Pitts, who held the position since August 2010, is now serving as the College of Engineering’s associate dean for undergraduate programs. Selen’s appointment was announced January 22 by Department Head and Professor Dale Van Harlingen, just hours after the College of Engineering had announced its appointment of Pitts.

Selen said he expects a straightforward transition into the new position.

“Kevin did a great job in this role and he has handed over a very smooth operation. We are working together to make the transition as seamless as possible for students, faculty, and staff,” comments Selen. “Kevin and I are in close communication as he makes his transition to associate dean. He isn’t far away—just down the road,”

Selen said he plans to maintain the undergraduate student advisory board Pitts initiated and to put his full support behind the department’s undergraduate student groups.

 “It will be important for me to maintain strong communications with students in our programs, to understand how we can best enhance their undergraduate experience and best support their career aspirations,” comments Selen. “It’s a reflection of the strength of our undergraduate programs that we have very robust engagement in our student groups, including the Society for Undergraduate Women in Physics, the Society of Physics Students, and the Physics Van. These organizations provide wonderful opportunities for our students to network with each other and with aspiring physicists at other universities, to take on leadership roles, and to serve the greater community through educational outreach activities.”

A leading expert in physics education research, Selen sets a high priority on further developing and improving teaching methods and retention rates in the department’s undergraduate courses.

“This is really a big priority in our undergraduate program. We teach a very large number of Engineering and Liberal Arts and Sciences students and we want to give all of our students what they need for their futures, so they can enjoy the benefits of a solid foundation in physics—they are the problem solvers and innovators of tomorrow. And with their diverse career goals, it’s hard to have a one-size-fits-all classroom experience.

“We are currently exploring ways to broaden our approach in our introductory courses, so an even greater number of students can be successful. This is really a question for all STEM subjects—how do you reach students who work extremely hard but still are struggling—those are the ones who often end up dropping out.”

Selen says he is also mindful of the department’s commitment to provide enriching research experiences for its undergraduate majors.

“Undergraduate research experience gives students a real edge when they are applying to postgraduate programs. It’s important that our degree holders not only have a solid foundation in physics, but that they also are competitive in terms of having up-to-date research skills.”

Van Harlingen notes, “Mats is a highly regarded and respected educator and has been a major force in the development of our introductory courses and a pioneer in our outreach activities.  I look forward to working with Mats in his new role as associate head to manage our expanding enrollments and develop innovative ways to provide an exceptional physics education and attractive career opportunities to our students.”