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“ I am often amazed at how much more capability and enthusiasm for science there is among elementary school youngsters than among college students. ”
- Carl Sagan


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Physics Conference Room, SB B326
Coffee starts at 12:00 PM and talk starts at 12:15 PM
Aug '16
Klaus Ziegler  -  Monday, August 15, 2016
ABSTRACT: A spatially varying gap leads to the creation of edge states. These very robust states are associated with quantized currents, the foundation of the quantum Hall effect in electronic systems. Here we discuss a randomly distributed gap in photonic systems. Despite the presence of strong disorder, the behavior of photons is not characterized by conventional Anderson localization: Rather than confining the photons to an area of the size of the localization length, the random gap creates geometric states. This type of confinement can be understood as angular localization, where the photons of a local light source can propagate only along waveguides in certain directions. The directions are determined by the boundary of the spectrum. Thus, the system's properties on the shortest scales determine the behavior of the photon propagation on the largest scales.
Aug '16
Martin Moskovits  -  Tuesday, August 23, 2016
Sep '16
Stephen Holler  -  Monday, September 19, 2016
ABSTRACT: Light scattering from non-spherical particles and aggregates exhibit complex structure that is revealed only when observed in two angular dimensions. However, due to variations in shape, packing, and orientation of such aerosols, the structure of two-dimensional angular optical scattering (TAOS) patterns varies among particles. The spectral dependence of scattering contributes further to the observed complexity, but offers another facet to consider. By leveraging multispectral TAOS data from flowing aerosols, we have identified novel morphological descriptors that may be employed in multivariate statistical algorithms for “unknown" particle classification. While these descriptors provide a means for grouping particles as a class, they provide little information about particle orientation. For this, we implement digital holography, which can be recorded simultaneously with TAOS data on a single camera to enhance particle characterization. This talk will discuss the underlying principles behind the two strategies and their synergy for particle characterization.
Sep '16
Victor Gopar  -  Monday, September 26, 2016
ABSTRACT: Disorder effects on the transport of classical and matter waves (EM & electrons, for instance) have been widely investigated from fundamental and practical points of view. It is widely believed that the presence of disorder in 1D random media leads to an exponential spatial localization of waves, i.e., Anderson localization. We have recently proposed, however, a model of disorder that induces anomalous localization or delocalization of electrons in disordered quantum wires. Following that model, we provide experimental evidence demonstrating that anomalous localization of electromagnetic waves can be induced in microwave waveguides with dielectric slabs randomly placed: if the random spacing between the slabs follows a distribution with a power-law tail (Lévy-type distribution), unconventional properties in the microwave-transmission fluctuations take place revealing the presence of anomalous localization. We obtain both theoretical and experimental distributions of the transmission through random waveguides and show that only two parameters, both of them experimentally accessible, determined the complete transmission distribution.

Concerning matter waves (electrons), numerical simulations of disordered armchair graphene nanoribbons reveal the presence of anomalous electron localization, while the statistical properties of the conductance are also described by our model.

In this talk we will give some general and basic ideas of our theoretical framework (random-matrix theory) for describing wave transport phenomena in the presence of standard-Anderson and anomalous localizations.
Nov '16
Orly Levitan  -  Monday, November 7, 2016
Despite the fact that there are still abundant natural petroleum reserves (supplies will last for more than a century), significant carbon mitigation cannot be achieved without the development of environmentally sustainable and renewable fuels. Owing to their high productivity-to-biomass ratio, ease of cultivation, and ability to grow in saline water, algae have been considered as a leading biodiesel feedstock. To displace fossil fuels, however, algae must be grown at a scale that yields approximately 10 million barrels of oil per day – which would supply approximately 50% of the total U.S. consumption. For the last few decades, researchers have searched for the “sweet spot” between algae’s triacylglycerols (TAG) production and biomass accumulation to obtain a strain with increased lipid production that can be developed as a commercially viable algal feedstock for biofuel production. Diatoms, a unique algal taxon, naturally accumulate TAGs as storage components, which can be readily converted to biodiesel. In fact, lipids derived from fossil diatoms are a major component of the highest quality petroleum.  Therefore fast growing, lipid accumulating, diatoms can be an excellent platform for biodiesel production. For many years, studies have been performed to environmentally optimize diatoms’ lipid production and biomass accumulation, yet no economically sustainable strain has been reported. In my talk, I will present our unique, genetically modifies, strains generated from the model diatom Phaeodactylum tricornutum, that could be used as a test-case for economical sustainable biofuel production. These strains are characterized by high lipid yield, yet keep relatively fast growth rates and are more efficient in using solar energy for lipid production.
Nov '16
Sharon Loverde  -  Wednesday, November 9, 2016
Dec '16
Kazuhiko Uebayashi  -  Monday, December 5, 2016
ABSTRACT: Magnetic binary alloy, iron rhodium (FeRh), has attracted attention since 1938. It is known to exhibit a magnetic phase transition from a ferromagnetic to an antiferromagnetic state at 350 K. While its crystal structure remains unchanged at the transition, its volume undergoes a 1% increase. In this talk, we present our studies of several magnetic binary alloys related to FeRh: FePd, MnRh, MnPd, and FePt, using first-principles calculations based on the linear muffin-tin orbital approach. Our results, which agree with several experiments and calculations, suggest that our approach well describes the crystal and magnetic structures of these binary alloys in their ground states and the structures of the related pseudo-binary alloys. However, our treatment of the magnetic phase transition has thus far not incorporated the effects of temperature due to a limitation in our code. In order to take account of these thermal effects, we present an approach that combines first-principles and quantum field theoretical methods.