Events at Physics

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Events During the Week of February 4th through February 11th, 2018

Monday, February 5th, 2018

Plasma Physics (Physics/ECE/NE 922) Seminar
Progress Toward Magnetic Confinement of Positron-Electron Plasma
Time: 12:00 pm
Place: 2241 Chamberlin Hall
Speaker: Dr. Matthew Stoneking, Lawrence University
Abstract: The hydrogen atom provides the simplest system and in some cases the most precise one for comparing theory and experiment in atomics physics. The field of plasma physics lacks an experimental counterpart, but there are efforts underway to produce a magnetically confined positron-electron plasma that promises to represent such a simplest plasma. Our approach is to utilize techniques from the non-neutral plasma community to trap and accumulate positrons prior to mixing them with electrons in a magnetic trap with good confinement properties. Ultimately we aim to use a levitated superconducting dipole configuration fueled by positrons from a reactor-based positron source and buffer-gas trap. This talk will provide an overview of progress toward this goal.
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Tuesday, February 6th, 2018

Chaos & Complex Systems Seminar
Prions and the environment
Time: 12:05 pm - 1:00 pm
Place: 4274 Chamberlin (Refreshments will be served)
Speaker: Joel Pedersen, UW Department of Soil Science
Abstract: Prions are the enigmatic etiological agents of transmissible spongiform encephalopathies (TSEs), a class of fatal neurodegenerative diseases affecting humans and other mammals. The pathogenic prion protein is a misfolded form of the host-encoded prion protein and represents the predominant, if not sole, component of the infectious agent. Environmental routes of TSE transmission are implicated in epizootics of sheep scrapie and chronic wasting disease of deer, elk, and moose. Soil is the most plausible candidate for preserving prion infectivity in the environment. We have investigated prion attachment to and detachment from inorganic and organic soil particle surfaces and examined the effect of association with specific soil constituents on disease transmission. Interaction of prions with some phyllosilicate mineral surfaces is remarkably strong. Interestingly, rather than diminishing bioavailability, attachment to such particles enhances disease transmission. This finding suggests an explanation for environmental disease transmission despite the presumably low levels of prions shed by infected animals. Our results to date suggest that prions released into many soil environments are preserved near the surface in a bioavailable form, likely perpetuating prion disease epizootics and exposing other species to the infectious agent. The high stability of prions observed in other contexts may contribute to their survival in the natural and engineered environments.
Host: Clint Sprott
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"Physics Today" Undergrad Colloquium (Physics 301)
Coral skeleton growth
Time: 1:20 pm - 2:10 pm
Place: 2241 Chamberlin Hall
Speaker: Pupa Gilbert, UW Madison Department of Physics
Host: Wesley Smith
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Wednesday, February 7th, 2018

No events scheduled

Thursday, February 8th, 2018

Astronomy Colloquium
Stellar Binaries: a Testbed for Planetary Formation and Dynamics
Time: 3:30 pm - 5:00 pm
Place: 4421 Sterling Hall, Coffee and cookies 3:30 PM, Talk Begins 3:45 PM
Speaker: Diego Munoz, Northwestern University
Abstract: Stellar binaries play an important role in the formation and evolution of planets. Planets and protoplanetary disks *within* binaries are subject to external perturbations that can alter the orbital and hydrodynamical evolution of these systems. Similarly, planets and protoplanetary disks *around* stellar binaries are expected to exhibit a distinct behavior from that of their single-star counterparts. Yet, observations suggest that binaries are able to form planets without much difficulty. In this talk, I will address different cases of planet formation and dynamics under the influence of additional stellar companions, spanning different stages of stellar evolution. I will discuss the hydrodynamics of circumbinary accretion, and argue that close-in T-Tauri stars provide a unique laboratory to explore the links between star and planet formation. I will describe what we have learned about the influence of external stellar companions on long-term planetary dynamics -- focusing on high-eccentricity migration -- and what puzzles still remain behind the origins of hot Jupiters. I will explain some of the mechanisms behind the dearth of transiting planets around the most compact main sequence (Solar mass) binaries, and how such planets could be in hiding. Finally, I will address the role of binaries in the post main sequence, presenting a hypothetical scenario in which binaries could contribute to the puzzling atmospheric pollution observed in nearly 30% of white dwarfs.
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Friday, February 9th, 2018

Physics Department Colloquium
The hunt for dark matter with neutrinos
Time: 3:30 pm
Place: 2241 Chamberlin Hall
Speaker: Carsten Rott, Sungkyunkwan University (SKKU)
Abstract: Dark Matter could be detected indirectly through the observation of neutrinos produced in self-annihilations or decays. Searches for such neutrino signals have resulted in stringent constraints on the dark matter self-annihilation cross section, lifetime, and the scattering cross section with matter. In recent years searches have significantly improved in sensitivity through new search methodologies, new detection channels, and through the availability of rich datasets from neutrino telescopes and detectors, like IceCube, ANTARES, Super-Kamiokande, etc. In this talk I will review recent experimental results and put them in context with respect to other direct and indirect dark matter searches. The prospects for discoveries at next generation neutrino detectors will be discussed.
Host: Albrecht Karle
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