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This Week at Physics

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Events During the Week of February 13th through February 20th, 2011

Sunday, February 13th, 2011

Wonders of Physics
Annual show
Time: 1:00 pm
Place: 2103 Chamberlin
Speaker: Clint Sprott
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Wonders of Physics
Annual show
Time: 4:00 pm
Place: 2103 Chamberlin
Speaker: Clint Sprott
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Monday, February 14th, 2011

Special Seminar
Microbial Interaction Networks in Soil and in Silico
Time: 9:00 am
Place: Forum room, Wisconsin Institutes of Discovery
Speaker: Kalin H. Vetsigian, Harvard University
Abstract: Soil harbors a huge number of microbial species interacting through secretion of antibiotics and other chemicals. What patterns of species interactions allow for this astonishing biodiversity to be sustained, and how do these interactions evolve? I used a combined experimental-theoretical approach to tackle these questions. Focusing on bacteria from the genus Streptomyces, known for their diverse secondary metabolism and production of antibiotics, I isolated 64 natural strains from several individual grains of soil and systematically measured all pairwise interactions among them. Quantitative measurements on such scale were never possible before. They were enabled by a novel experimental platform based on robotic handling, a unique self-built scanner array and automatic image analysis. This unique platform allowed the simultaneous capturing of ~15,000 time-lapse movies of growing colonies of each isolate on media conditioned by each of the other isolates. The data revealed a rich network of strong negative (inhibitory) and positive (stimulating) interactions. Analysis of this network and the phylogeny of the isolates, together with mathematical modeling of microbial communities, revealed that: 1) The network of interactions has three special properties: "balance", "bi-modality", and "reciprocity"; 2) The interaction network is fast evolving; 3) Mathematical modeling explains how rapid evolution gives rise to the three special properties through an interplay between ecology and evolution. These properties are not a result of stable co-existence, but rather of continuous evolutionary turnover of strains with different production and resistance capabilities.
Host: Pupa Gilbert
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Plasma Physics (Physics/ECE/NE 922) Seminar
“Turbulent Mixing: Problems, Concepts, Solutions”
Time: 12:05 pm
Place: 2241 Chamberlin Hall
Speaker: Snezhana Abarzhi, University of Chicago
Abstract: Turbulent mixing plays an important role in a broad variety of plasma systems, spanning astrophysical to atomistic scales and low to high energy densities. Examples include inertial confinement fusion, Z-pinches, core-collapse supernovae, thermonuclear stellar flashes, magneto-convection, ionospheric plasmas, and light-material interaction. Theoretical description of non-equilibrium mixing transports is a challenging problem due to singular aspects of the governing (Euler or Navier-Stokes) equations. Furthermore these processes are statistically unsteady and their fluctuating quantities are essentially time-dependent and non-Gaussian.

We developed a novel theoretical concept, the rate of momentum loss, and applied it to describe the transports of mass, momentum and energy in turbulent mixing flow and to capture its anisotropic and inhomogeneous character. It was shown that invariant, scaling and spectral properties of unsteady turbulent mixing differ substantially from those of isotropic and homogeneous turbulence. Time- and
scale-invariance of the rate of momentum loss leads to non-dissipative momentum transfer, to and power-law
scale-dependencies of the velocity and Reynolds number and to non-Kolmogorov spectra. Turbulent mixing exhibits more order compared to isotropic turbulence, and its viscous and dissipation scales are finite and set by flow acceleration. We suggested how to describe the random character of the statistically unsteady turbulent flow and showed that the rate of momentum loss is the statistic invariant and a robust
diagnostic parameter for either sustained or time-dependent acceleration. Some criteria are outlined for the estimate of the fidelity and information capacity of the experimental and numerical data sets.
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Tuesday, February 15th, 2011

Chaos & Complex Systems Seminar
"How I Stopped Worrying and Learned to Love Global Warming"
Time: 12:00 pm
Place: 4274 Chamberlin Hall
Speaker: Jim Blair, Milton and Edgewood College
Abstract: Warmers vs. Skeptics: who are the skeptics?
What are we doing about Climate Change?
What would we do if we were serious?
The sunny side of Climate Change.
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High Energy Seminar
Long and Longer Baseline Neutrino Oscillations: Searching for Symmetry Violation
Time: 3:00 pm
Place: 4274 Chamberlin
Speaker: Roger Wendell, Duke University
Abstract: Massive neutrinos are one of the first clues that the Standard Model of particle physics is not a complete description of nature. Exactly how far beyond the Standard Model they are though, is a topic of continuing study. At present, evidence for their mass in the form of flavor oscillations has been observed in several sources and has established a global picture of oscillations in two primary regimes. Existing data can be described in large part by mixing between two active neutrinos, dependent upon the ratio of the neutrino flight length (baseline) to its energy, L/E. The presence of the third neutrino, however, may bridge these two regimes through the as-yet-unmeasured mixing angle, $ heta_{13}$. If $ heta_{13}$ is found to be non-zero, the door to a measurement of CP violation using neutrinos will be opened. In this talk I will discuss the physics of very long baseline ($sim$10,000~km) neutrino oscillations including searches for $ heta_{13}$ at Super-Kamiokande. I will also discuss on-going searches for $ heta_{13}$ at the T2K long baseline ($sim$300~km) experiment and prospects for a future measurement of CP violation.
Host: Karsten Heeger
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Wednesday, February 16th, 2011

Department Meeting
Time: 12:15 pm
Place: 5310 Chamberlin Hall
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Thursday, February 17th, 2011

R. G. Herb Condensed Matter Seminar
Topological Insulators With Point Group Symmetry
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Andrei Bernevig, Princeton University
Abstract: We analyze several insulators that fall outside the current classification of topological insulators. We show that the topological nature of a state is not based on whether it supports gapless edge modes, and that a new concept, the entanglement spectrum, is required to classify insulators. We show that topological insulators with inversion symmetry can support many of the interesting effects that their time reversal counterparts exhibit: theta vacuum, E dot B effect, monopole image, etc. At the same time they do not exhibit gapless edge modes when an edge/surface is placed on the material. We also provide for a gauge-invariant way to calculate topological invariants which has so far been absent in the literature. Experimental consequences will also be discussed.
Host: Andrey Chubukov & Maxim Vavilov
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NPAC (Nuclear/Particle/Astro/Cosmo) Forum
Supernova Burst Studies in DUSEL Detectors
Time: 4:00 pm
Place: 4274 Chamberlin Hall
Speaker: Alex Friedland, LANL
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Friday, February 18th, 2011

High Energy Seminar
New Spectacles for Spectacular Discoveries
Time: 11:00 am
Place: 4274 Chamberlin Hall
Speaker: Prof. Daniel Ferenc, University of California Davis
Abstract: IceCube and SuperKamiokande are huge, but we need significantly larger experiments in the future.Who will make the PMTs, how, and when? Who will pay for them? It is high time to introduce a new technology. I will describe ABALONE, a vacuum photosensor concept that is simplified to the bones, and mass-producible at a low cost.
Host: Teresa Montaruli
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Physics Department Colloquium
Fay Ajzenberg-Selove Colloquium
Regular and Irregular Polyhedra in Multi-Component Crystalline Shells
Time: 4:00 pm
Place: 2241 Chamberlin Hall (coffee at 3:30 pm)
Speaker: Monica Olvera de la Cruz, Northwestern University, Department of Materials Science and Engineering
Abstract: The captivating charm of uniform convex polyhedra such as Platonic and Archimedean solids has beguiled scientist, philosophers, and artists for millenia. In our modern era, it is incorporated in the revolutionary Descartes' geometrization of nature, and still reflects the common practice of introducing esthetic elements in physical sciences. While mathematicians have rigorously captured the "morphological essence" of such highly regular polytopes by classifying and formalizing their symmetries and isometries, the search of such structures in the realm of nature has been rather elusive. Icosahedral shapes, among all Platonic polyhedrals, have been identified in molecular elastic shells such as large viral shells or fullerenes. We demonstrate that other geometries, including some Archimedean polyhedrals, arise spontaneously in shells formed by more than one component. We study the buckling of an elastic shell with two coexisting elastic components, at different relative concentrations. By using theoretical arguments and numerical simulations we find various polyhedra and n-gonal hosohedra shapes. Our work explains the principles to design various hallow polyhedra and the existence of the regular and irregular polyhedra shells recently observed in organelles. Our analysis suggests that these polyhedral shapes are ubiquitous in cellular shells and in closed elastic membranes made of various proteins. We provide experimental evidence of the spontaneous buckling phenomena in shells made of mixtures of cationic and anionic amphiphiles, where electrostatics drives their co-assembly, and orders the assembly into faceted ionic structures.
Host: Gilbert
Poster: http://www.physics.wisc.edu/twap/posters/2011/2093.pdf
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Saturday, February 19th, 2011

4th Annual Physics Fair
Time: 11:00 am
Place: Chamberlin Hall
Abstract: Please join the UW-Madison Department of Physics for the 4th annual Physics Fair from 11am-4pm on the Saturday, the 19th of February, 2011 in Chamberlin Hall at 1150, University Ave.. This open house will be a great opportunity to learn about the research and teaching that are a part of our department. The fair will feature hands-on demonstrations, laboratory tours, activities for kids and families, a public lecture and informal conversations with scientists. The Ingersoll Physics Museum will be open, and we will have exhibits representing research groups in the department as well as displays on more general physics topics. Visit http://uw.physics.wisc.edu/~wonders/PhysicsFair.html for more details.
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Wonders of Physics
Annual show
Time: 1:00 pm
Place: 2103 Chamberlin
Speaker: Clint Sprott
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Special Physics Talk
The Physics of Color
Time: 2:30 pm
Place: 2241 Chamberlin
Speaker: Pupa Gilbert, UW Department of Physics
Abstract: The color we see depends on physical as well as physiological parameters. During this talk Pupa will do several experiments, and you will experience and see the results for yourself. Whether you are an artist, a scientist, or simply have a curious mind, you will find this interesting: it will change all you already knew about color, primary colors, how color mixing works on a computer screen (additive) or in a color printer, a paint shop, or an artist's palette (subtractive), and how artists in the past have used color mixing, some more successfully than others.
Poster: http://www.physics.wisc.edu/twap/posters/2011/2124.pdf
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Wonders of Physics
Annual show
Time: 4:00 pm
Place: 2103 Chamberlin
Speaker: Clint Sprott
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Wonders of Physics
Annual show
Time: 7:00 pm
Place: 2103 Chamberlin
Speaker: Clint Sprott
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Sunday, February 20th, 2011

Wonders of Physics
annual show
Time: 1:00 pm
Place: 2103 Chamberlin
Speaker: Clint Sprott
Add this event to your calendar

Wonders of Physics
Annual show
Time: 4:00 pm
Place: 2103 Chamberlin
Speaker: Clint Sprott
Add this event to your calendar

"This Week at Physics" poster: http://www.physics.wisc.edu/twap/posters/2011/2011-02-14.pdf

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