Events at Physics
Events During the Week of March 11th through March 18th, 2012
- Condensed Matter Theory Group Seminar
- Electroweak Phase Transition
- Time: 4:30 pm
- Place: 5310 Chamberlin
- Speaker: Michael Ramsey-Musolf, UW-Madison
- Chaos & Complex Systems Seminar
- Navigating oceans of consciousness with science and art
- Time: 12:05 pm
- Place: 4274 Chamberlin
- Speaker: Bernard Z. Friedlander, Department of Psychology, Emeritus, University of Hartford, West Hartford, CT
- Abstract: Human consciousness is the Moby Dick, the mysterious Great White Whale, the most elusive quarry for understanding, in the vast oceans of the world of nature. How do the complex systems of electrochemistry in billions of brain cells become transformed into our infinitely varied awareness of the sensations of touch, smell, taste, vision and hearing; into id, ego and superego; into memories, dreams and reflections; into our chaotic, grand, grandiose visions of science, art, religion, governance, trade, war and empire? Intersecting and divergent trajectories of progress and fashion in the realms of intellect both facilitate and impede efforts to comprehend this most complex of all challenges to human thought. In order to shrink zones of mystery and expand zones of solvable problems in decoding these unknowns, we must seek new ways to think about consciousness if we can ever hope to understand it. Navigating Oceans Of Consciousness With Science and Art presents a 12-Factor Trans-Darwinian Taxonomy of Consciousness that systematically links component elements of the phenomenon with a totality of the whole. This inclusiveness has been hitherto remotely within our sight and reach but beyond our grasp.
- Host: Sprott
- High Energy Seminar
- Observation of electron-antineutrino disappearance at Daya Bay
- Time: 3:00 pm
- Place: 4274 Chamberlin
- Speaker: Karsten M. Heeger, University of Wisconsin
- Abstract: The Daya Bay Reactor Neutrino Experiment has measured a non-zero value for the neutrino mixing angle theta13 with a significance of 5.2 standard deviations. Antineutrinos from six 2.9 GWth reactors were detected in six antineutrino detectors deployed in two near (flux-weighted baseline 470 m and 576 m) and one far (1648 m) underground experimental halls. With 55 days of data, 10416 (80376) electron antineutrino candidates were detected at the far hall (near halls). The ratio of the observed to expected number of antineutrinos at the far hall is R=0.940 +/- 0.011(stat) +/- 0.004(syst). A rate-only analysis finds sin^22theta13=0.092 +/- 0.016(stat) +/- 0.005(syst) in a three-neutrino framework.
- Host: Herndon
- Department Meeting
- Time: 12:15 pm
- Place: 5310 Chamberlin Hall
- R. G. Herb Condensed Matter Seminar
- Graphene: it’s all about the surface
- Time: 10:00 am
- Place: 5310 Chamberlin
- Speaker: Kirill Bolotin, Vanderbilt University
- Abstract: Every atom of graphene, a monolayer of graphite, belongs to the surface. Therefore, the environment of graphene -- the substrate onto which graphene is deposited and the coating on top of graphene -- intimately affects the properties of graphene. In this talk, we demonstrate that both mechanical and electrical properties of graphene can be greatly tuned by varying its environment.
First, we discuss ultraclean graphene devices suspended in vacuum. We achieve a carrier mobility in excess of 200,000 cm2/Vs in these devices and demonstrate previously inaccessible transport regimes, including ballistic transport and the fractional quantum Hall effect.
Second, we explore the electrical properties of graphene surrounded by liquid dielectrics. We find that the ions in liquids can cause strong scattering in graphene and demonstrate very large values for room temperature mobility (>60,000 cm2/Vs) in ion-free liquids with high dielectric permittivity.
Finally, we demonstrate that the environment of graphene affects its mechanical properties. We develop a novel technique to study the mechanical properties of graphene films attached to substrates by measuring the temperature-dependent deflection of a "bimetallic" cantilever composed of graphene and silicon nitride or gold layers. We demonstrate that the built-in strain, the substrate adhesion force and even the thermal expansion coefficient of graphene depend on the substrate under it.
- Host: Vavilov
- Astronomy Colloquium
- "New Results on Gas Flows In and Out of Galaxies"
- Time: 3:30 pm
- Place: 4421 Sterling Hall
- Speaker: Alice Shapley, UCLA
- Abstract: Over the last several years, there has been growing consensus in the theoretical literature about the process of galaxy growth through cold gas accretion. Both analytic calculations and numerical simulations suggest that high-redshift galaxies primarily grow by smoothly accreting cold gas from the surrounding intergalactic medium (IGM). Furthermore, simulations indicate that gas is accreted in collimated cool streams containing both smooth gas and small galaxies. While recent theoretical work has identified the importance of cold accretion, spectroscopic observations have much more consistently indicated the existence of large-scale outflows from star-forming galaxies at high redshift. Resolving the apparent disconnect between simulations and observations and identifying observational signatures of infalling gas are crucial for testing the theoretical paradigm of cold accretion. Here we present new evidence for the smoking gun of cool gas accreting onto star-forming galaxies at high redshift (z~1-3), using spectroscopy of both HI and heavy elements. We also describe new insights into the properties of outflowing gas around galaxies, which will provide important constraints on models for star-formation feedback.
- Host: Prof Snezana Stanirmirovic
- Cosmology Journal Club
- An Informal discussion about a broad variety of arXiv papers related to Cosmology
- Time: 12:00 pm
- Place: 5242 Chamberlin Hall
- Abstract: Please visit the following link for more details:
Please feel free to bring your lunch!
If you have questions or comments about this journal club, would like to propose a topic or volunteer to introduce a paper, please email Le Zhang (firstname.lastname@example.org)
- Host: Peter Timbie
- Physics Department Colloquium
- Kelvin, Pascal, and mollusk shells
- Time: 3:30 pm
- Place: 2241 Chamberlin Hall (coffee at 4:30 pm)
- Speaker: Pupa Gilbert, University of Wisconsin-Madison
- Abstract: NacreaEuro"or mother-of-pearlaEuro"the tough, iridescent biomineral lining the inner side of some mollusk shells, is composed of aragonite (CaCO3) tablet layers alternating with organic sheets. New Polarization-dependent Imaging Contrast (PIC) maps revealed that nacre tablets are not co-oriented, but have a broad distribution of angular orientations, as shown by the Gilbert group (1) and subsequently by many others. The angle spread is the full-width of this distribution, and was found to vary across different species, and different shell growth environments. Most interestingly, we found strong correlation between nacre tablet angle spread and environmental temperature (2), and this has far-reaching consequences: nacre angle spread could be used as a thermometer. Analysis of one shell with well-established stable oxygen isotope analysis and PIC-mapping validates the nacre thermometer in one modern shell. Once validated on more shells, modern and ancient, nacre-paleothermometry could be established as the first entirely-physical, as opposed to chemical, proxy for temperature (3). But the implications of this finding are more profound: if T is the temperature at which the nacre formed and AS is the measured angle spread, then the equation T=26.826+0.051 AS links environment and bio-structure. This equation suggests that one could predict a biological structure based on the environment in which the organism forms it.
1. RA Metzler, M Abrecht, RM Olabisi, D Ariosa, CJ Johnson, BH Frazer, SN Coppersmith, PUPA Gilbert. Architecture of columnar nacre, and implications for its formation mechanism. Phys. Rev. Lett. 98, 268102, 2007.
2. IC Olson, R Kozdon, JW Valley, PUPA Gilbert. Mollusk shell nacre ultrastructure correlates with environmental temperature and pressure. J Am Chem Soc in press, 2012.
3. IC Olson, PUPA Gilbert. Nacre as a temperature proxy. RSC Faraday Discussions submitted, 2012.
- Host: Department