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DEC
11
Today
Chemistry Department Colloquium
"Structure, Interactions, and Electron-Transfer in Ionic Liquids"
Presented by Prof. Edward Castner, Jr., Dept. of Chemistry and Chemical Biology, Rutgers University
11 am, Hamilton Seminar Room, Bldg. 555
Wednesday, December 11, 2013, 11:00 am
Hosted by: Gregory Hall
I will discuss how the interplay between ionic liquid structure, transport properties and dynamics affects the outcomesof chemical reactions in these novel solvents. I will present results from recent high-energy X-ray studies of bulk ionic liquid structure, quantiatively compared with structures calculated by molecular dynamics simulation done in collaboration with Prof. Claudio Margulis (Univ. of Iowa). Nuclear Overhauser effect 2D-NMR studies are used to provide a complementary perspective on interactions between ions in the ionic liquids, and to study local solvation effects. I will introduce some of our most recent results on reactive electron-donating ionic liquids with cyanate anions, and on the preparation and characterization of ultrathin films of ionic liquids on SiO2/Si(111) and glassy carbon.
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DEC
11
Today
Joint HET/RIKEN/YITP Seminar
"Under the Lens of RPV: An Examination of the LHC Program"
Presented by Jared Evans, Rutgers University
2 pm, Small Seminar Room, Bldg. 510
Wednesday, December 11, 2013, 2:00 pm
Hosted by: Hooman Davoudiasl
R-parity violation is touted as a way to maintain a natural MSSM while evading LHC bounds. By systematically exploring simplified models motivated by the RPV MSSM, we can uncover gaps in the current array of searches performed by the Atlas and CMS collaborations. This talk reviews the details of RPV signatures relevant for colliders, and presents recast limits on naturalness-motivated topologies originating from pair-produced gluinos (in RPV and beyond), stops, and higgsinos. Many specific signatures which evade the current set of searches are discussed along with both extensions to existing searches and entirely new search strategies which together can fill many of these weak points in coverage.
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DEC
12
Thursday
Condensed-Matter Physics & Materials Science Seminar
"Dynamics of topological defects in ferromagnets"
Presented by Oleg Tchernyshyov, Johns Hopkins University
1:30 pm, ISB Bldg. 734, Seminar Room 201 (upstairs)
Thursday, December 12, 2013, 1:30 pm
Hosted by: Alexei Tsvelik
Topological defects are common in magnetic systems. Well-known examples are domain walls and vortices. I will outline a simple way to classify defects in the bulk and on the boundary of isotropic two- and three-dimensional ferromagnets and derive their classical equations of motion.
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DEC
18
Wednesday
Chemistry Department Colloquium
"Bio-Inspired Solar Fuel Production"
Presented by Professor J. Devens Gust, Arizona State University
11 am, Hamilton Seminar Room, Bldg. 555
Wednesday, December 18, 2013, 11:00 am
Hosted by: Dr. Javier Concepcion
Fossil fuels represent solar energy captured and stored in fuel by photosynthetic organisms. Photosynthesis can serve as inspiration for the design of artificial photosynthetic systems for production of hydrogen or other fuels. Photosynthetic antennas collect sunlight, transport excitation energy to reaction centers, and perform regulatory and photoprotective functions. Reaction centers are molecular-scale photovoltaics that convert excitation energy into electrochemical energy in the form of redox potential. Biological enzyme catalysts use the oxidation potential of reaction centers to oxidize water. The reduction potential of the reaction centers is employed by other catalysts to produce fuels. Living organisms have developed catalysts for production of carbohydrates, precursors of biodiesel, hydrogen gas, and other fuels. Following the photosynthetic paradigm, scientists are learning to design and construct artificial antennas that efficiently harvest light throughout the visible spectral region, transfer the excitation to artificial reaction centers, and regulate the artificial photosynthetic process. Artificial reaction centers use excitation energy from the antennas to carry out photoinduced electron transfer reactions that store a large fraction of the photon energy as redox potential. Catalysts that oxidize water and that produce hydrogen are being developed and functionally interfaced to reaction centers to create complete solar fuel production systems. Several examples of progress towards hydrogen production by artificial photosynthesis will be discussed.
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DEC
18
Wednesday
SANTA - Meet Santa, photo op, and reception! 5-7pm
"SANTA - Meet Santa, photo op, and reception! 5-7pm"
5 pm, Recreation Hall, Bldg. 317
Wednesday, December 18, 2013, 5:00 pm
Hosted by: Christine Carter
RSPVP required. Please call Ext. 5090 or email carter@bnl.gov to attend. Have your child's picture taken with Santa! Light refreshments will be served.
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DEC
19
Thursday
Condensed-Matter Physics & Materials Science Seminar
"Hidden Fermi Liquid, Scattering Rate Saturation, and Transport in Bad Metals"
Presented by Wenhu Xu, Rutgers University
1:30 pm, Bldg. 734, ISB Conf. Rm. 201 (upstairs)
Thursday, December 19, 2013, 1:30 pm
Hosted by: Alexei Tsvelik/Robert Konik
The spectral and transport properties of a doped Mott insulator are inves- tigated within dynamical mean-_eld theory. Canonical Fermi liquid behavior emerges only below a very low temperature scale TFL. Unexpectedly the quasi- particle scattering rate follows a quadratic energy (!) and temperature (T) dependence up to !; T _ TFL and crosses over to a saturating behavior when !; T & Tsat. Tsat is controlled by doping. We identify these quasiparticles as constituents of the hidden Fermi liquid. The non-Fermi-liquid transport above TFL is shown to be a result of the T-dependent quasiparticle renormalization Z. Furthermore, Z presents strong asymmetry near Fermi surface, giving rise to the kink structures in the energy dispersion of spectral functions. A Boltzmann formalism is derived for the charge and thermal transport properties in terms of the renormalized band structure and scattering rate of the hidden quasiparticles.
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DEC
19
Thursday
Particle Physics Seminar
"Photoproduction of K* from proton and Pre-shower calorimeter construction at CLAS"
Presented by Wei Tang, Jefferson Lab
3 pm, Small Seminar Room, Bldg. 510
Thursday, December 19, 2013, 3:00 pm
Hosted by: Elizabeth Worcester/Xin Qian
The first high statistics cross sections for the reactions and were measured using the CLAS detector at photon energies between threshold and 3.9 GeV at the Thomas Jefferson National Accelerator Facility (Jefferson Lab). Differential cross sections are presented over the full range of center of mass angles, and then fitted to Legendre polynomials to extract the total cross section. Results for the final states are compared with two different calculations in an isobar and a Regge model, respectively. A Pre-shower calorimeter (PCAL) was recently constructed at Hall-B Jefferson Lab. The PCAL is a part of the upgraded CLAS12 detector. The PCAL consists of 6 identical modules, and each module is a lead-scintillator sandwich with three stereo readout planes. The PCAL is used to reconstruct the energy of high energy showering particles and to separate high-energy and photons. It is critical for several experiments and overall will benefit all future measurement. In this talk I will present the analysis of the photoproduction, as well as the construction process of the PCAL.
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DEC
20
Friday
Particle Physics Seminar
"The T2K Experiment"
Presented by Patrick de Perio, University of Toronto
11 am, Small Seminar Room, Bldg. 510
Friday, December 20, 2013, 11:00 am
Hosted by: Elizabeth Worcester
I will describe the recent T2K neutrino oscillation, νe appearance and νμ disappearance measurements, outlining the principal components of the experiment including the neutrino beamline, near detector (ND280) and far detector, Super-Kamiokande (SK). My main contributions will be highlighted: a novel proton beam monitor, neutrino interaction and detector MC development including the modeling of pion (hadronic) interactions, the ND280 constraint on the SK event rate prediction, and a new SK event reconstruction algorithm.
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JAN
29
Wednesday
Condensed-Matter Physics & Materials Science Seminar
"The Kondo effect from an STM perspective:Comparison between metals and insulators"
Presented by Steffen Wirth, Max-Planck-Institute for Chemical Physics of Solids Dresden, Germany
1:30 pm, ISB Bldg. 734, Conf. Room 201 (upstairs)
Wednesday, January 29, 2014, 1:30 pm
Hosted by: Meigan Aronson
Hybridization is a fundamental concept in strongly correlated electron physics. In heavy fermion metals, it may result in the generation of low-energy scales that can give rise to quantum criticality and unconventional superconductivity. We discuss the effects of hybridization and of the Kondo interaction as probed by tunneling and magnetotransport studies, and focus on the heavy fermion metal YbRh2Si2 and the intermediate valence insulator SmB6. We investigated YbRh2Si2 and its doped counterparts Yb(Rh1��'xMx)2Si2. Hints toward the existence of a quantum critical point are discussed in terms of an antiferromagnetic instability and the Kondo break-down of the heavy quasiparticles [1,2]. Recent Scanning Tunneling Microscopy (STM) and Spectroscopy (STS) studies identified a hybridization-induced gap-like feature of the tunneling conductance as well as crystal field excitations [3]. Here we focus on the evolution of the signatures of the Kondo lattice. While the Kondo lattice starts forming already at the single-ion Kondo temperature it dominates the material properties only at much lower temperatures. These findings by STS are augmented by band structure calculations and additional measurements [4,5]. Hybridization also plays a decisive role in the low temperature properties of the intermediate valence system SmB6. The hybridization gap, inter-multiplet transitions and possible crystal field excitations are observed by STS. The temperature evolution of these spectra again points toward the Kondo effect being at play. STS conducted on non-reconstructed surfaces gave results in excellent agreement with expectations for a Fano resonance. The impact of surface properties and reconstructions is discussed, also in relation to the recent proposal of a topologicall
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FEB
4
Tuesday
Nuclear Physics Seminar
"THE PROTON'S FLUCTUATING WAISTLINE"
Presented by Berndt Mueller, Brookhaven National Laboratory
11 am, Small Seminar Room, Bldg. 510
Tuesday, February 4, 2014, 11:00 am
Hosted by: Anne Sickles
As any ground state quantum system, the proton wave function is a coherent superposition of many different configurations, in particular, configurations of different geometric cross section. At high energy, time dilatation freezes the time scale associated with these fluctuations and lets a fast proton collide with another object (proton or nucleus) in a randomly chosen, apparently incoherent configuration. High-multiplicity events in proton-proton or proton-nucleus collisions may originate from large-size fluctuations of the nucleon shape. I discuss two of simple models of such proton shape fluctuations. A "fat" proton with a size of 3 fm occurs with observable frequency. In light of this result, collective flow behavior in the ensuing nuclear interaction seems plausible. I will discuss the implications of these models on the parton structure of the proton.
