UF PHYSICS COLLOQUIUM SCHEDULE |
SPRING 2024 |
Colloquia begin at 3:00pm on Thursdays and are held in NPB 1002 unless otherwise noted. Contact: Imre Bartos (imrebartos@ufl.edu) Department of Physics Colloquium Committee: Imre Bartos (chair), Jeff Andrews, Rachel Houtz, Sergey Klimenko, Andrey Korytov,, Dominique Laroche, Konstantin Matchev, Tarek Saab, Yuta Takahashi |
January 11 (Thursday) |
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Speaker |
Zoe Zhu |
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Location |
NPB 1002 |
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Title |
Multiscale models for moiré materials |
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Abstract |
Manipulating the twist angle or lattice mismatch in stacks of multilayered two-dimensional (2D) materials, referred to as van der Waals (vdW) heterostructures, introduces a long-wavelength moiré potential that fundamentally alters the physical properties of the constituent materials. Following the initial discovery of superconductivity in single-twist moiré systems, forays into moiré of moiré vdW heterostructures, such as twisted trilayer graphene with two independent twist angles, have led to observations of novel correlated states. These complex multilayered heterostructures exhibit length scales that are generally orders of magnitude longer than the bilayer moiré length, and they are incommensurate even in the continuum limit. To overcome these computational challenges, we present an efficient and accurate multiscale framework based on first principles. Using this framework, we study the electronic structures, mechanical relaxation, and phonon properties of complex vdW heterostructures and help interpret experimental observations. |
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Host |
Xiaoguang Zhang |
January 18 (Thursday) |
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Speaker |
Guang Yue (University of Illinois Urbana-Champaign) |
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Location |
NPB 2205 |
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Title |
A Study on Quantum Devices and Quantum Materials |
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Abstract |
The Josephson junction device is a powerful tool to study physics. In this presentation the weak link Josephson junction and the topological insulator-based Josephson junction devices will be discussed. First, a superconducting quantum interference device made of weak link Josephson junctions can work directly in a high magnetic field which provides high sensitivity and spacial resolution on magnetic sample measurement. Such a device has been built into a spin resonance measurement setup to study quantum spin for quantum computing purposes. Second, the Majorana bound state physics are studied on the topological insulator-based Josephson junction devices. Evidence of the Majorana bound state is discussed together with methods to utilize such state for topological quantum computing. |
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Host |
Mark Meisel |
January 23 (Tuesday) (starting at 4pm!) |
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Speaker |
Jiabin Yu (Princeton) |
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Location |
NPB 2205 |
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Title |
Band geometry and topology in correlated quantum materials |
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Abstract |
Band geometry (or quantum geometry) and band topology describe, respectively, the local and global properties of Bloch electron wavefunctions in quantum materials. These concepts have already triggered a revolution in quantum materials based on single-particle physics, but their significance in interacting systems is much less explored. In this talk, I will discuss two recent advances in this direction for the two major interactions in solids: electron-phonon interaction and electron-electron Coulomb interaction. First, I will explain how quantum geometry contributes crucially to the electron-phonon interaction, potentially offering a new design principle for higher-temperature superconductors. Second, we show that band geometry/topology and band mixing are key to explaining various experimental puzzles centered around fractional Chern insulators (FCIs) recently observed in twisted MoTe2 and graphene-hBN superlattices. FCIs, the zero-field analogs of the fractional quantum Hall effect, are induced by the Coulomb interaction in fractionally filled, (nearly-)flat topological bands, and their discovery heralds the discovery of more exotic topologically ordered phases. These phases, and the diverse computational tools required to predict them, will be discussed. |
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Host |
Yuxuan Wang |
January 25 (Thursday 1pm!) |
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Speaker |
Kuate Defo (Princeton) |
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Location |
NPB 2205 |
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Title |
Investigating Color Centers in Wide-Bandgap Semiconductors Through First-Principles DFT |
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Abstract |
Density-Functional Theory (DFT) has seen tremendous improvements in the accuracy of its implementations since its first inception. The theory is characterized by the Nobel Prize-winning insight that the number density of electrons uniquely determines the ground-state properties of a system of atoms without the need to evaluate the many-body wavefunction for the electrons. In this talk, I will discuss another key insight that when coupled to DFT leads to exceptionally accurate predictions from first principles. The insight is that the Fermi level (the electronic chemical potential) is in some cases a manifestly local quantity rather than being uniform throughout a crystal sample as has been widely assumed in materials computations. This insight was used to accurately predict the measured values of electric fields probed using color centers in diamond to improve the functioning of semiconductor devices, leading to the selection of the work as an Editors’ Suggestion in Phys. Rev. B. The insight was also used to accurately determine timescales for charge-state decay of ionized color centers in diamond with applications in computation, communication, and sensing. In addition to the many opportunities offered by the treatment of the Fermi level as a local quantity in materials theory and computation, I will discuss the ability of DFT to characterize properties and phenomena such as the hyperfine interaction for group-IV impurity-vacancy color centers in diamond. |
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Host |
Xiaoguang Zhang |
January 25 (Thursday) |
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Speaker |
Hitoshi Murayama (Berkeley) |
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Location |
NPB 1002 |
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Title |
US Particle Physics for the Next Ten Years |
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Abstract |
The US particle physics community has gone through a long-range planning exercise for the next ten years. The Particle Physics Project Prioritization Panel (P5) issued a report with recommendations to Department of Energy and National Science Foundation. I discuss how the report defines its scientific scope, what the major initiatives are in the next ten years, derived from a long-term vision for the field. The report also recommends creating a balanced portfolio in the program for all sizes and time scales, domestic vs international, and different subfields. |
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Host |
Andrey Korytov |
January 31 (Wednesday) |
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Speaker |
Yinong Zhou (UC Irvine) |
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Location |
NPB 2205 |
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Title |
Quantum Phases in Topological and Chiral Materials |
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Abstract |
Topological and chiral quantum materials exhibit intriguing electronic, magnetic, and optical properties, holding great promise to shape future electronic and spintronic technologies. In this talk, I will show three different approaches to manipulate quantum phases, based on physics models and density functional theory (DFT) calculations. First, exotic electronic band structures are realized through atomic lattice design, as exemplified by the design of perfectly flat bands based on the line graph theorem. The completely quenched electronic kinetic energy in a flat band magnifies any finite electron-electron interaction, leading to a range of exotic quantum phases, such as ferromagnetism, superconductivity, and Mott insulating state. Specifically, I will present a system with two flat bands of opposite chirality that induces a giant circular dichroism effect and transitions from a flat-band material to a Mott insulator through orbital design. Secondly, topological states are manipulated by applying an external field, which can be either an electric, magnetic, or strain field. As an example, I will demonstrate a physical mechanism to remotely control the topological corner states in a higher-order topological insulator. Thirdly, structural chirality engenders a chiral-induced spin selectivity effect, which enables the harnessing of electron spin to open promising opportunities in spintronics and quantum technologies. Especially, I will showcase the realization of higher-dimensional spin selectivity in chiral crystals for controlling phase transition and spin-flipping processes. |
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Host |
Xiaoguang Zhang |
February 1 (Thursday) |
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Speaker |
Sumitabha Brahmachari, Center for Theoretical Biological Physics, Rice University |
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Location |
NPB 1002 |
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Title |
Physical modeling of chromosomes across species: mec anistic insights and biological consequences of emergent structural features
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Abstract |
Chromosomes are long polymers of DNA that are folded into a tiny nucleus by a concerted activity of various proteins. Quantitative understanding of the mechanistic link between protein activity, chromosome architecture, and biological function is nascent but imperative to comprehend how the DNA code governs cellular life. Establishing these links will steer biological research and yield fruitful discoveries in the physics of active polymers. In this talk, I will focus on a physical simulation framework that incorporates genomic data and furnishes mechanistic insights into regulating chromosome structure. I will discuss how this framework has been crucial in rationalizing our observations, linking the activity of specific proteins to conserved architectural features of chromosomes across species spanning the tree of life. We find that the species-wide diversity of structures emerges from a competition between three kinds of generalized forces, where the balance between these forces depends on the relative abundance of specific proteins and is a predictor of the structure. Using this framework, we further explore the elusive link between chromosome structure and crucial biological functionality like segregation or replicated DNA. The developed framework is an essential stride towards a cohesive, physics-based understanding of the chromosome architecture and its implications for cellular life. |
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Host |
BingKan Xue |
February 7 (Wednesday!) |
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Speaker |
Arkajit Mandal (Columbia University) |
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Location |
NPB 2205 |
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Title |
Quantum Dynamics of Light and Matter between Two Mirrors |
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Abstract |
Placing molecules and materials between mirrors (or inside optical cavities) can enable the generation of exciting new chemical and physical phenomena in a highly controllable manner. In this talk, I will share a few of our theoretical works that demonstrate how photons can play the roles of a catalyst, a solvent, a quantum degree of freedom, beyond their usual role as a source of energy, to modify the chemical and physical properties of molecules and materials that are coupled to quantized radiation. First, I will discuss how quantum light-matter interactions can be utilized to modify the photochemistry of molecules and how a single photon can act as a catalyst to initiate multiple chemical reactions, leading to a quantum yield of more than one. Second, I will share our theoretical work that investigates how coupling molecular vibrations to vacuum radiation inside optical cavities can suppress or enhance the cleavage of specific chemical bonds, as seen in several recent experiments. I will share our theories that reveal that photons can act like solvents to enhance or suppress ground-state chemical kinetics. Next, I will show that quantum light-matter interactions can modify exciton-phonon interactions and can lead to the suppression of phonon-mediated decoherence. This enables fast ballistic transport in materials that are coupled to cavity radiation. I will share experimental results from our collaborators that confirm our theoretical predictions. Finally, I will share our theoretical framework, the quasi-diabatic propagation scheme, that allows for performing on-the-fly ab-initio quantum dynamics simulations, enabling us to investigate a wide range of problems, from photochemistry to polariton chemistry and beyond. |
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Host |
Amlan Biswas |
February 8 (Thursday) |
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Speaker |
Gabriel Birzu (Stanford University) |
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Location |
NPB 1002 |
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Title |
Do bacteria form species? Long term evolution leads to frequent
hybridization in a natural microbial community |
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Abstract |
Genetic sequencing of natural bacterial populations often reveals
distinct genomic clusters, which are usually interpreted as distinct
species. At the same time, recent studies have shown extensive
recombination across a wide range of genetic divergences, raising the
question of how clusters can be maintained over time. Previous studies
have shown that ecological separation can emerge within
highly-recombining bacterial populations. However, whether this
mechanism can prevent the hybridization and merging of distinct clusters
is not known. Here, I show that thermophilic cyanobacteria from the
Yellowstone National Park form a rare natural experiment to address this
question. By analyzed a large collection of single-cell genomes, I
demonstrate that despite their different ecologies, continual
hybridization and natural selection have gradually eroded the genetic
differences between clusters. These results suggest that ecological
barriers cannot by themselves maintain genomic clusters over long
evolutionary times and highlight the importance of spatial dynamics for
maintaining microbial diversity. |
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Host |
BingKan Xue |
February 15 (Thursday) |
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Speaker |
RESERVED |
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Location |
NPB 1002 |
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Title |
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Abstract |
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Host |
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February 22 (Thursday) |
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Speaker |
Junxin Chen (MIT) |
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Location |
NPB 1002 |
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Title |
Preparing Macroscopic Quantum Mechanical Oscillators by Measurement |
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Abstract |
Macroscopic mechanical oscillators prepared in quantum states are valuable resources to explore the boundary between the typically microscopic quantum world and the typically macroscopic classical world. This topic points to new physics beyond the current framework of quantum mechanics. Measurement in the quantum regime not only allows acquiring information of a physical observable at an unprecedented level, but also shapes the state of the system under measurement. In this talk, I will introduce my works demonstrating measurement-based preparation of macroscopic mechanical oscillators into their quantum ground states, and the ongoing work of preparing a macroscopic system into a quantum squeezed state. These works pave the way to studying macroscopic quantum systems.
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Host |
Paul Fulda |
February 29 (Thursday) |
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Speaker |
RESERVED |
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Location |
NPB 1002 |
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Title |
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Abstract |
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Host |
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March 7 (Thursday) |
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Speaker |
Chang Long |
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Location |
ZOOM |
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Title |
Life After Grad School: Exploring the Transition from Physics to Quantitative Finance |
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Abstract |
Many physics Ph.D. students often contemplate their career paths after passing the qualifier exam: should we pursue an academic position or explore opportunities in industry? For those who consider the latter, questions arise about what industry and role best aligns their skill sets? In this talk, I will draw from my own experiences as a grad student to help provide insights and benchmarks to help you navigate these questions in the world of finance. I will first introduce general concepts of the finance job market and what goes on in building finance and investments model by using principles from physics and math in a commercial bank, investment bank and an asset management company. In addition, I will reflect on my background, preparation, and the challenges I faced when seeking a job in the finance industry, about 7 years ago. This will include an introduction to where to find positions, how to read job descriptions, and what unique skill sets we have in Physics that can give us a competitive edge in the job market. I will preface that I do not claim to be an expert of job placement agent, but I will give my opinion on job market trends and other tips based on my experiences and observations. |
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Host |
Physics Graduate Community |
March 21 (Thursday) |
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Speaker |
Lam Hui (Columbia) |
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Location |
NPB 1002 |
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Title |
Wave dark matter |
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Abstract |
We will discuss the possibility that dark matter is composed of sufficiently light particles that it effectively behaves as a collection of waves. We will review the particle physics motivations and the rich wave phenomenology, and discuss the implications for astronomical observations and experimental detection. |
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Host |
Wei Xue |
March 28 (Thursday) |
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Speaker |
Paul Steinhardt (Princeton) |
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Location |
NPB 1002 |
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Title |
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Abstract |
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Host |
BingKan Xue |
April 4 (Thursday) |
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Speaker |
Joe LaVeigne |
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Location |
NPB 1002 |
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Title |
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Abstract |
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Host |
Physics Graduate Community |
April 11 (Thursday) |
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Speaker |
Patrick Brady (UW Milwaukee) |
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Location |
NPB 1002 |
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Title |
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Abstract |
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Host |
Imre Bartos |
FALL 2024 |
September 19 (Thursday) |
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Speaker |
Steve Taylor (Vanderbilt) |
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Location |
NPB 1002 |
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Title |
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Abstract |
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Host |
Jeff Dror |
September 26 (Thursday) |
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Location |
NPB 1002 |
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October 10 (Thursday) |
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Location |
NPB 1002 |
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October 24 (Thursday) |
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Speaker |
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Location |
NPB 1002 |
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October 31 (Thursday) |
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Location |
NPB 1002 |
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November 7 (Thursday) |
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Location |
NPB 1002 |
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November 28 (Thursday) |
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Location |
NPB 1002 |
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December 5 (Thursday) |
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Speaker |
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Location |
NPB 1002 |
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December 12 (Thursday) |
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Speaker |
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NPB 1002 |
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