Optical control of competing exchange interactions and coherent spin-charge coupling in two-orbital Mott insulators

In order to have a better understanding of ultrafast electrical control of exchange interactions in multi-orbital systems, we study a two-orbital Hubbard model at half filling under the action of a time-periodic electric field. Using suitable projection operators and a generalized time-dependent canonical transformation, we derive an effective Hamiltonian which describes two different regimes. First, for a wide range of non-resonant frequencies, we find a change of the bilinear Heisenberg exchange $J_{\textrm{ex}}$ that is analogous to the single-orbital case. Moreover we demonstrate that also the additional biquadratic exchange interaction $B_{\textrm{ex}}$ can be enhanced, reduced and even change sign depending on the electric field. Second, for special driving frequencies, we demonstrate a novel spin-charge coupling phenomenon enabling coherent transfer between spin and charge degrees of freedom of doubly ionized states. These results are confirmed by an exact time-evolution of the full two-orbital Mott-Hubbard Hamiltonian.Comment: 3 pages, 6 figure

The Heart of Whiteness: Interracial Marriage and White Masculinity in American Fiction, 1830-1905

Building on whiteness scholars’ notion that whiteness can be gained, my dissertation argues that a property in whiteness, and its attendant privileges, can be lost. By examining representations of interracial marriage in American literature between 1830 and 1905, I identify marriage across the color line as one of the primary modes through which white men can lose their privilege. Interracial marriage violates what I term the marriage contract, a tri-party agreement between man, woman, and nation that guaranteed democratic rights to white men and privileges to their dependents in return for white-white marriage. Men who violated this contract by marrying exogamously suffered the loss of their property in whiteness. Literary depictions of interracial marriage occur most frequently within a genre of fiction critics have termed “tragic mulatta” plots. While these plots have served as important sites for exploring black femininity in the nineteenth century, I call attention to the presence of the white male characters, or white suitors, who court the mulattas and play key roles in making the narrative tragedy possible. The white suitor faces his own tragedy as his involvement with a black lover leads to his identity crisis and subsequent loss of privilege. Antebellum and postbellum, black and white, egalitarian and racist authors alike shared an interest in how interracial marriage affects white masculinity. I conclude that this topic interested authors during the nineteenth century because the white suitor and his tragedy provided a proxy through which to contemplate the nation’s own identity crisis as it approached, survived, and recovered from a civil war that questioned the United States’ self-identification as “a white man’s country.

Critical Teaching Behaviors: What Does Good Teaching Look Like?

How can faculty and administrators identify and document evidence of “good” teaching? Defining “good” teaching as the implementation of evidence-based practices proven to foster success, we developed a Critical Teaching Behaviors framework consisting of six categories of observable behaviors: alignment, assessment, inclusive learning environment, student engagement, educational technology, and reflective practice. We will present an overview of the meta-analysis conducted to construct the framework, participants will then use the framework to reflect on their teaching practice before providing feedback on its design and usefulness in documenting effective teaching behaviors at their institutions

Changes in the Left Atrial-Esophageal Relationship with the Insertion of An Esophageal Protective Device: A Cadaveric Imaging Study

Background: Atrial fibrillation is the most common cardiac rhythm disorder in North America and is frequently treated by a minimally invasive procedure called catheter ablation. A rare, but often fatal complication of this procedure is development of an atrial-esophageal fistula (AEF) due to the proximity of the esophagus to the left atrium (LA) of the heart. Esophageal protective devices may potentially mitigate the risk of developing an AEF but their impact on the relationship between the esophagus and LA is unknown. This study will investigate the relevant anatomical changes that occur upon insertion of an esophageal protective device. Methods: 13 fresh cadaveric torsos were scanned with and without an esophageal protective device on the computed tomography (CT) modality. The width and anterior-posterior dimension of the esophagus were measured digitally and compared between pre- and post-device insertion scans. From the scans, 3D models of the LA and esophagus were created and used for a spatial analysis of their relationship. A heatmap was generated for each LA highlighting areas of close contact with the esophagus and how they changed post-device insertion. Results: Preliminary results have indicated the width and anterior-posterior dimension of the esophagus increase significantly with the insertion of the protective device (p \u3c 0.05). Further analysis of the esophagus-left atrial distance is still ongoing. Discussion: Data from this study will provide valuable insight on changes that could be made to the device design and potentially boost its clinical efficacy and prevent AEF formation

Nested recursions with ceiling function solutions

Consider a nested, non-homogeneous recursion R(n) defined by R(n) = \sum_{i=1}^k R(n-s_i-\sum_{j=1}^{p_i} R(n-a_ij)) + nu, with c initial conditions R(1) = xi_1 > 0,R(2)=xi_2 > 0, ..., R(c)=xi_c > 0, where the parameters are integers satisfying k > 0, p_i > 0 and a_ij > 0. We develop an algorithm to answer the following question: for an arbitrary rational number r/q, is there any set of values for k, p_i, s_i, a_ij and nu such that the ceiling function ceiling{rn/q} is the unique solution generated by R(n) with appropriate initial conditions? We apply this algorithm to explore those ceiling functions that appear as solutions to R(n). The pattern that emerges from this empirical investigation leads us to the following general result: every ceiling function of the form ceiling{n/q}$ is the solution of infinitely many such recursions. Further, the empirical evidence suggests that the converse conjecture is true: if ceiling{rn/q} is the solution generated by any recursion R(n) of the form above, then r=1. We also use our ceiling function methodology to derive the first known connection between the recursion R(n) and a natural generalization of Conway's recursion.Comment: Published in Journal of Difference Equations and Applications, 2010. 11 pages, 1 tabl

Iron-binding ligands in the Southern California Current System : mechanistic studies

© The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Frontiers in Marine Science 3 (2016): 27, doi:10.3389/fmars.2016.00027.The distributions of dissolved iron and organic iron-binding ligands were examined in water column profiles and deckboard incubation experiments in the southern California Current System (sCCS) along a transition from coastal to semi-oligotrophic waters. Analysis of the iron-binding ligand pool by competitive ligand exchange-adsorptive cathodic stripping voltammetry (CLE-ACSV) using multiple analytical windows (MAWs) revealed three classes of iron-binding ligands present throughout the water column (L1−L3), whose distributions closely matched those of dissolved iron and nitrate. Despite significant biogeochemical gradients, ligand profiles were similar between stations, with surface minima in strong ligands (L1 and L2), and relatively constant concentrations of weaker ligands (L3) down to 500 m. A phytoplankton grow-out incubation, initiated from an iron-limited water mass, showed dynamic temporal cycling of iron-binding ligands. A biological iron model was able to capture the patterns of the strong ligands in the grow-out incubation relatively well with only the microbial community as a biological source. An experiment focused on remineralization of particulate organic matter showed production of both strong and weak iron-binding ligands by the heterotrophic community, supporting a mechanism for in-situ production of both strong and weak iron-binding ligands in the subsurface water column. Photochemical experiments showed a variable influence of sunlight on the degradation of natural iron-binding ligands, providing some evidence to explain differences in surface ligand concentrations between stations. Patterns in ligand distributions between profiles and in the incubation experiments were primarily related to macronutrient concentrations, suggesting microbial remineralization processes might dominate on longer time-scales over short-term changes associated with photochemistry or phytoplankton growth.RB, KB, and MC were supported by NSF OCE #10-2667 for the CCE-LTER program. MJ was funded by NSF ANT grant 0948378 and Harbor Branch Oceanographic Institute Foundation

Prospects For Identifying Dark Matter With CoGeNT

It has previously been shown that the excess of events reported by the CoGeNT collaboration could be generated by elastically scattering dark matter particles with a mass of approximately 5-15 GeV. This mass range is very similar to that required to generate the annual modulation observed by DAMA/LIBRA and the gamma rays from the region surrounding the Galactic Center identified within the data of the Fermi Gamma Ray Space Telescope. To confidently conclude that CoGeNT's excess is the result of dark matter, however, further data will likely be needed. In this paper, we make projections for the first full year of CoGeNT data, and for its planned upgrade. Not only will this body of data more accurately constrain the spectrum of nuclear recoil events, and corresponding dark matter parameter space, but will also make it possible to identify seasonal variations in the rate. In particular, if the CoGeNT excess is the product of dark matter, then one year of CoGeNT data will likely reveal an annual modulation with a significance of 2-3$\sigma$. The planned CoGeNT upgrade will not only detect such an annual modulation with high significance, but will be capable of measuring the energy spectrum of the modulation amplitude. These measurements will be essential to irrefutably confirming a dark matter origin of these events.Comment: 6 pages, 6 figure

Pseudomonas aeruginosa isolates from dental units waterlines can be divided in two distinct groups, including one displaying phenotypes similar to isolates from cystic fibrosis patients.

Pseudomonas aeruginosa displays broad genetic diversity, giving it an astonishing capacity to adapt to a variety of environments and to infect a wide range of hosts. While many P. aeruginosa isolates of various origins have been analyzed, isolates from cystic fibrosis (CF) patients have received the most attention. Less is known about the genetic and phenotypic diversity of P. aeruginosa isolates that colonize other environments where flourishing biofilms can be found. In the present study, 29 P. aeruginosa isolates from dental unit waterlines and CF patients were collected and their genetic and phenotypes profiles were compared to determine whether environmental and clinical isolates are related. The isolates were first classified using the random amplified polymorphic DNA method. This made it possible to distribute the isolates into one clinical cluster and two environmental clusters. The isolates in the environmental cluster that were genetically closer to the clinical cluster also displayed phenotypes similar to the clinical isolates. The isolates from the second environmental cluster displayed opposite phenotypes, particularly an increased capacity to form biofilms. The isolates in this cluster were also the only ones harboring genes that encoded specific epimerases involved in the synthesis of lipopolysaccharides, which could explain their increased ability to form biofilms. In conclusion, the isolates from the dental unit waterlines could be distributed into two clusters, with some of the environmental isolates resembled the clinical isolates. Keywords: Pseudomonas aeruginosa, cluster, RAPD, elastase, biofilm, Dictyostelium discoideum, cell lysi

Nonequilibrium Magnons from Hot Electrons in Antiferromagnetic Systems

We describe a \emph{nonthermal} magnon activation mechanism in antiferromagnetic (AFM) systems via locally equilibrated \emph{spin-unpolarized} hot electrons excited by an ultrafast intense laser pulse. We employ a quantum kinetic equation that takes into account a direct electron-magnon scattering channel in either bulk AFM metal or at the interface of the AFM/normal-metal heterostructure. The mechanism is responsible for the nonequilibrium population of AFM magnon modes on a subnanosecond timescale, which are formed shortly after the local thermalization of hot electrons by Coulomb interactions. Nonequilibrium magnon populations can be additionally manipulated by applying an external magnetic field. Our work paves the way toward spin dynamics control in AFM systems via the ultrafast manipulation of out-of-equilibrium magnon excitations.Comment: 5.5 pages, 3 figures, Supplemental Material available as ancillary fil