Physics Colloquia

Physics Colloquium - Ronan Humphrey, UWM Physics
Presentation title and abstract will be announced when they are available.

Combining Quantum Master Equations with Linearized Semiclassical Methods to Simulate Electronic Energy & Charge Transfer Dynamics in Complex Molecular Systems
Professor Eitan Geva, Department of Chemistry
University of Michigan - Ann Arbor

Photo-induced electronic energy and charge transfer plays a key role in a variety of chemical, biological and technologically-important molecular systems. The simulation of the
underlying electronic dynamics is challenging due to its intrinsically quantum mechanical nature and the large number of coupled electronic and nuclear degrees of freedom involved. Quantum master equations provide a flexible and general-purpose framework for addressing this challenge.

Manifold-based Machine Learning for Scattering Data
Adam Opperman, PhD Candidate
University of Wisconsin-Milwaukee Department of Physics & Astronomy

Small Angle X-ray Scattering (SAXS) is a technique used to capture X-ray diffraction images of proteins in solution, mimicking biological conditions. These images provide insight into the overall shape and structure of the protein. By imaging the protein system at various times during a reaction, dubbed time-resolved SAXS (TR-SAXS), the evolution of the protein structure is observed. These measurements are commonly taken at X-ray Free Electron Laser (XFEL) facilities which generate X-rays with precision and high flux. The Compact X-ray Light Source (CXLS) and accompanying Compact X-ray Free Electron Laser (CXFEL) are under construction at Arizona State University. Due to the compact nature of the source in combination with the yet incomplete development, CXFEL has a reduced level of photon flux available compared to other XFELs. Due to this constraint, new analytical methods are needed to process TR-SAXS data.

Studying Magnetism with Resonant X-ray Scattering at Advanced Photon Source
Jong-Woo Kim, Physicists
Magnetic Material Group/Advanced Photon Source, Argonne National Laboratory

X-ray scattering at synchrotron facilities such as the Advanced Photon Source provides a powerful platform for investigating magnetic order with element and orbital specificity. In this colloquium, I will introduce the fundamentals of single-crystal X-ray diffraction and the principles of resonant elastic X-ray scattering (REXS), emphasizing how tuning to absorption edges enhances sensitivity to electronic and magnetic structures.

Constraining Common Envelope Evolution Simulations with Observations
Sarah Villanova Borges, PhD Candidate
University of Wisconsin-Milwaukee

Common Envelope Evolution (CEE) remains one of the biggest unresolved problems in binary stellar evolution, despite being the primary pathway for the formation of close binary systems. One of the main challenges in understanding CEE is its intrinsically multiscale and multiphysics nature, which makes it difficult to model with analytical or 1D models. 3D hydrodynamical simulations have therefore become essential tools for studying this phase. However, validating these simulations requires observational constraints, which are scarce. This lack of direct observations is another major obstacle in modeling CEE. One exception is luminous red novae, which is believed to correspond to CEE events that culminate in stellar mergers.

Gravitational Waves from Galactic Nuclei
Nicholas Stone, Assistant Professor
Department of Astronomy, University of Wisconsin-Madison

The discovery of GW150914 inaugurated the era of gravitational wave (GW) astronomy, opening a new window to study our Universe's compact objects and through which to test general relativity. Now, a decade later, the LIGO-Virgo-KAGRA (LVK) collaboration has seen hundreds of GW signals, overwhelmingly from mergers of binary stellar mass black holes. Despite the many successes of GW astronomy, a zeroth-order astrophysical question remains unanswered: what astrophysical environments produce the LVK binary black holes, and by what process are they assembled? Although many formation channels have been proposed, one uniquely testable solution is the "AGN channel:" a scenario in which individual black holes pair up and merge in the dissipative gaseous environment of an active galactic nucleus.

Novel Imaging Techniques for Studying Interactions of Membrane Receptors Among Themselves and with Downstream Signaling Partners
Thomas D. Killeen, PhD Candidate
University of Wisconsin-Milwaukee Department of Physics & Astronomy

Cells rely on complex signaling networks to sense and respond to environmental stimuli, but the bigger picture of how molecular assembly leads to robust cellular signaling is only beginning to emerge. A major challenge in characterizing cellular signaling is the ability to directly observe the dynamic interactions between membrane receptors and intracellular signaling partners in living cells. To address this challenge, this work presents the development of advanced fluorescence imaging and computational analysis tools designed to improve the precision and quantitative power of live-cell micro-spectroscopy for studying protein dynamics in real time.

This week's Physics Colloquium has been cancelled.

Superconductors Investigated by High-Energy Particle Irradiation
Dr. Kyuil Cho, Assistant Professor
Department of Physics, Hope College

Superconductor is a material that shows zero resistivity and Meissner effect below its critical temperature. This material has been used for various applications such as superconducting wires, medical device MRI, superconducting magnets for particle accelerators, quantum computing circuits, and many more. The superconductivity research group at Hope College conducts unique research on novel superconductors by using high energy particles. High energy particle irradiation is a useful method to generate homogeneous artificial defects on superconductors. By investigating how the defects affect the properties of superconductors, one can uncover the fundamental mechanism of superconductivity.

Titin-based Molecular Underpinnings of Skeletal and Cardiac Muscle Function
Jorge Alegre-Cebollada, PhD
Associate Professor & Group Leader, CNIC (Spanish National Center for Cardiovascular Research)

Titin is the largest protein in the human body. The function of the protein is not any smaller: it is critical for the contractile activity of muscles in the skeletal system and in the heart. In my presentation, I will introduce fundamental concepts that link titin nanomechanics with the macroscopic mechanical function of muscle. I will focus on our recent data demonstrating dysregulation of titin nanomechanics that can contribute to increased risk of heart failure in diabetic patients.