A Visit to the Battlefield

This piece was transcribed and edited by Michael J. Birkner and Richard E. Winslow. With fighting concluded at Gettysburg on July 3, 1863, the enormous task of burying the dead, treating the wounded, and rehabilitating the town began in earnest. Although Gettysburg looked and smelled worse than it ever had or ever would again, thousands of people arrived on the battlefield in the days and weeks following General Robert E. Lee\u27s retreat. Some came to minister to the sick and reclaim the bodies of neighbors and loved ones; others scavenged souvenirs of the battle. Of the many visits to the battlefield in July 1863, few have been more affectingly described than the account of Joseph H. Foster of Portsmouth, New Hampshire. In the document reprinted below, of a speech Foster delivered at the Unitarian Sabbath School in Portsmouth on July 26, 1863, he describes a brief trip to Gettysburg from which he had just returned. His objective in going to Gettysburg was straightforward: he wanted to locate the body of his neighbor and friend Henry L. Richards and bring it back to New Hampshire for a proper interment. [excerpt

Color Breaking Baryogenesis

We propose a scenario that generates the observed baryon asymmetry of the Universe through a multi--step phase transition in which SU(3) color symmetry is first broken and then restored. A spontaneous violation of $B-L$ conservation leads to a contribution to the baryon asymmetry that becomes negligible in the final phase. The baryon asymmetry is therefore produced exclusively through the electroweak mechanism in the intermediate phase. We illustrate this scenario with a simple model that reproduces the observed baryon asymmetry. We discuss how future electric dipole moment and collider searches may probe this scenario, though future EDM searches would require an improved sensitivity of several orders of magnitude.Comment: Updated to comply with referees suggestions and mirror published versio

TeV Lepton Number Violation: From Neutrinoless Double Beta Decay to the LHC

We analyze the sensitivity of next-generation tonne-scale neutrinoless double $\beta$-decay ($0\nu\beta\beta$) experiments and searches for same-sign di-electrons plus jets at the Large Hadron Collider to TeV scale lepton number violating interactions. Taking into account previously unaccounted for physics and detector backgrounds at the LHC, renormalization group evolution, and long-range contributions to $0\nu\beta\beta$ nuclear matrix elements, we find that the reach of tonne-scale $0\nu\beta\beta$ generally exceeds that of the LHC. However, for a range of heavy particle masses near the TeV scale, the high luminosity LHC and tonne-scale $0\nu\beta\beta$ may provide complementary probes.Comment: 5 pages, 3 figure

Nanodiscs: A novel approach to the study of the Methionine ABC Transporter System

Membrane transporter proteins play the vital role of moving compounds in and out of the cell and are essential for all living organisms. ATP Binding Cassette (ABC) family transporters function both as importers and exporters in prokaryotes. MetNI is an E. coli Type I ABC transporter responsible for the uptake of methionine into the cytosol from the cell periplasmic space through the cell membrane to maintain intracellular methionine pools. ABC transporters, like other membrane proteins, are most often mechanistically and structurally studied in vitro, solubilized by detergents. However, detergent micelles may affect the conformational changes of membrane proteins relative to those in a native membrane lipid environment, altering transport and ATPase hydrolysis activities. The goal of this research project was to test a promising alternative to liposomal reconstitution of MetNI for preserving native activities. This system, termed “nanodiscs,” is a well-established biochemical tool for membrane proteins consisting of a nanoscale discoidal bilayer of polar lipids encircled by an amphipathic scaffold of apolipoprotein ApoA1 proteins. In this work, the MetNI transporter was purified and successfully reconstituted into two different MSP phospholipid bilayer nanodisc systems (MSP1D1 and MSP1E3D1), confirmed by size exclusion chromatography, native gel electrophoresis, and co-immunoprecipitation. Stabilization of a more native MetNI structure following nanodisc reconstitution was evaluated by the level of basal ATP hydrolysis when compared with purified MetNI solubilized by detergent. Surprisingly, the KM and Vmax of ATP hydrolysis were similar for both forms of MetNI, indicating the presence of basal, futile ATP hydrolysis in both types. Futile ATP hydrolysis was also observed for a mutant MetNI form which lacks methionine substrate inhibition of ATP hydrolysis, MetNI N295A. Additionally, binding of purified substrate binding protein (SBP) to the detergent-solubilized and nanodisc-reconstituted MetNI transporter, was demonstrated by fluorescence anisotropy. Future functional assays performed on completely reconstituted MetNI-SBP complexes in lipid nanodiscs could reveal critical insights into the lipid and structural requirements for native transporter activit

High-Throughput Cultivation of Bacterioplankton from the Gulf of Mexico and Genomics of the First Cultured LD12 Representative

Cultivation of microorganisms facilitates characterization of metabolism, interspecies dependencies, virus-host interactions, and other information necessary to resolve the functions and distribution of individual taxa. However, the metabolic and physiological capacities for the majority of microbes remains unresolved because of the lack of cultivated representatives for many groups limits our ability to test cultivation-independent observations. The Northern Gulf of Mexico offers a diversity of ecosystems under the continuous threat from natural and anthropogenic disturbances, yet little is known about its native bacterioplankton community. This dissertation sought to use high-throughput cultivation over three-years at six sites to isolate important coastal bacteria to uncover their role in biogeochemical cycling and ecosystem health. During the seventeen experiments, 7820 wells were inoculated, resulting in 328 repeatedly transferable cultivars. Isolates were placed into 49 monophyletic groups based on 16SR rRNA gene sequences, and represent multiple novel Species and Genera, including the first reported cultures of the SAR11 LD12 Alphaproteobacteria, OM241 Gammaproteobacteria, and acIV Actinobacteria clades. Cultivars also contribute to the expansion of cultured diversity of numerous cosmopolitan bacterioplankton such as SAR11 subclade IIIa and SAR116 Alphaproteobacteria, and BAL58, MWH-UniP1, and OM43 Betaproteobacteria. Physiological and genomic characterization of the first cultivated LD12 representative, Candidatus Fonsibacter ubiquis strain LSUCC0530, yielded novel insights into the potential metabolic capacity related to sulfur, ecotype differentiation based on temperature, as well as key gene losses associated with osmoregulation that provide a concise hypothesis for the evolution of salinity tolerance in SAR11. Comparison between the success of isolation and the relative abundance of the cultivar in the source water revealed that relative abundance was a good predictor of cultivation success for some frequently cultured clades, while it was unreliable for rarely cultivated clades such as SAR11 subclades IIIa, LD12 Alphaproteobacteria, acIV Actinobacteria, and HIMB59-type Alphaproteobacteria. We hypothesize that taxon-specific variations in dormancy and/or phenotypic variation rates among populations may affect the cultivation reliability of that clade rather than the isolation medium alone. The insights from this dissertation provide a new look at the complexity of cultivation even when providing an organism with its nutritional requirements while showcasing the importance of cultivation for answering ecological questions like the evolution of salinity tolerance

Stop-Catalyzed Baryogenesis Beyond the MSSM

Non-minimal supersymmetric models that predict a tree-level Higgs mass above the Minimal Supersymmetric Standard Model (MSSM) bound are well motivated by naturalness considerations. Indirect constraints on the stop sector parameters of such models are significantly relaxed compared to the MSSM; in particular, both stops can have weak-scale masses. We revisit the stop-catalyzed electroweak baryogenesis (EWB) scenario in this context. We find that the LHC measurements of the Higgs boson production and decay rates already rule out the possibility of stop-catalyzed EWB. We also introduce a gauge-invariant analysis framework that may generalize to other scenarios in which interactions outside the gauge sector drive the electroweak phase transition.Comment: 9 pages, 3 figures. v2: Minor changes. Added appendix with the details of the higgs couplings fit. References adde

UNDERSTANDING OF LOW REYNOLDS NUMBER AERODYNAMICS AND DESIGN OF MICRO ROTARY-WING AIR VEHICLES

The goal of the present research is to understand aerodynamics at low Reynolds numbers and synthesize rules towards the development of hovering micro rotary-wing air vehicles (MRAVs). This entailed the rigorous study of airfoil characteristics at low Reynolds numbers through available experimental results as well as the use of an unsteady Reynolds-Averaged Navier-Stokes solver. A systematic, experimental, variation of parameters approach with physical rotors was carried out to design and develop a micro air vehicle-scale rotor which maximizes the hover Figure of Merit. The insights gained in low Reynolds number aerodynamics have been utilized in the systematic design of a high endurance micro-quadrotor. Based on available characteristics, the physical relations governing electric propulsion system and structural weights have been derived towards a sizing methodology for small-scale rotary-wing vehicles