The molecular systematics and phylogeography of the widespread North American meadow vole (Microtus pennsylvanicus)

The climatic and environmental fluctuations of the Quaternary played an integral role in geographic distribution and genetic structure within many organisms today. Understanding how these historical biogeographic events may have partitioned genetic variation throughout the landscape is critical to forecasting the implications of modern climate change and how animals will respond to projected climate shifts. Through geographic and taxonomically comprehensive sampling, we used multi-locus and species delimitation analyses along with niche modeling methods to investigate the evolutionary and biogeographic history of the meadow vole, Microtus pennsylvanicus. The findings of this study highlight the vulnerability and importance that special consideration and conservational strategies be taken to preserve peripheral populations that harbor unique characteristics. The dynamic evolutionary and geographic history of the meadow vole furthers our understanding of the important role Quaternary climatic oscillations played in the diversification and geographic distribution of organisms today

High Field de Haas - van Alphen Studies of the Fermi Surfaces of LaMIn5_{5} (M = Co, Rh, Ir)

We report measurements of the de Haas - van Alphen effect on a series of compounds, LaMIn$_{5}$ (M = Co, Rh, Ir). The results show that each of the Co and Ir Fermi surfaces (FSs) exhibit some portions that are two dimensional and some portions that are three dimensional. The most two dimensional character is exhibited in LaCoIn$_{5}$, less two dimensional behavior is seen in LaIrIn$_{5}$, no part of Fermi surface of LaRhIn$_{5}$ is found to have a two dimensional character. Thus the two dimensionality of portions of the FSs is largely determined by the d character of the energy bands while all of the effective masses remain $\leq$ 1.2. This fact has implications for the causes of the heavy fermion nature of superconductivity and magnetism in the Ce-based compounds having the similar composition and structure. All of the measurements were performed at the National High Magnetic Field Laboratory using either cantilever magnetometry or field modulation methods.Comment: 10 pages, 4 figure

Air Bubble Curtain Anchoring

To prevent salp (jellyfish) from entering Diablo Canyon Power Plant’s intake pipes, and ultimately having the plant shut down as a result, an air bubble curtain is anchored along the ocean floor for the duration of the salp swarm to create a barrier that prevents the salp and other debris from entering the intake. The curtain consists of four large air compressors connected to four parallel pipes with holes strategically drilled at various places along the length of the pipe. When the air compressors are turned on, a torrent of bubbles are shot out from the pipes which create a current which deters the salp from floating into the intake. As the ocean floor shifts with the current and tide, the pipes becomes unlevel and do not produce an adequate barrier of bubbles across the length of the pipe. To improve the bubble curtain, our team was tasked with creating a self-leveling anchor system to work with the existing air bubble curtain pipes. Over the course of the last academic year, we designed, built, and tested a model sized prototype of an anchoring concept that would keep the bubble curtain pipes level. The final design suspends the bubble curtain pipes from buoys. The concept uses the surface of the water to remain level, while a long tether to a ground anchor keeps it from floating freely. Through testing, we determined this design stays level independent of change in floor elevation. However, the effectiveness is dependent on the tide, and works best at low tide and in water with a low tide greater than 20 feet. We recommend designing this system for deeper sections of the intake bay, and implementing it to allow a constant upward slope in the bubble pipe. Before building a complete system, we recommend constructing and testing a partial system to insure it behaves as expected and withstands full-scale ocean conditions

Power of Bayesian and heuristic tests to detect cross-species introgression with reference to gene flow in the Tamias quadrivittatus group of North American chipmunks

In the past two decades genomic data have been widely used to detect historical gene flow between species in a variety of plants and animals. The Tamias quadrivittatus group of North America chipmunks, which originated through a series of rapid speciation events, are known to undergo massive amounts of mitochondrial introgression. Yet in a recent analysis of targeted nuclear loci from the group, no evidence for cross-species introgression was detected, indicating widespread cytonuclear discordance. The study used the heuristic method HyDe to detect gene flow, which may suffer from low power. Here we use the Bayesian method implemented in the program bpp to reanalyze these data. We develop a Bayesian test of introgression, calculating the Bayes factor via the Savage-Dickey density ratio using the Markov chain Monte Carlo (MCMC) sample under the model of introgression. We take a stepwise approach to constructing an introgression model by adding introgression events onto a well-supported binary species tree. The analysis detected robust evidence for multiple ancient introgression events affecting the nuclear genome, with introgression probabilities reaching 63%. We estimate population parameters and highlight the fact that species divergence times may be seriously underestimated if ancient cross-species gene flow is ignored in the analysis. We examine the assumptions and performance of HyDe, and demonstrate that it lacks power if gene flow occurs between sister lineages or if the mode of gene flow does not match the assumed hybrid speciation model with symmetrical population sizes. Our analyses highlight the power of likelihood-based inference of cross-species gene flow using genomic sequence data

The Fermi surface of CeCoIn5: dHvA

Measurements of the de Haas - van Alphen effect in the normal state of the heavy Fermion superconductor CeCoIn5 have been carried out using a torque cantilever at temperatures ranging from 20 to 500 mK and in fields up to 18 tesla. Angular dependent measurements of the extremal Fermi surface areas reveal a more extreme two dimensional sheet than is found in either CeRhIn5 or CeIrIn5. The effective masses of the measured frequencies range from 9 to 20 m*/m0.Comment: 4 pages, 2 figures, submitted to PRB Rapid

Space construction system analysis. Part 2: Platform definition

The top level system requirements are summarized and the accompanying conceptual design for an engineering and technology verification platform (ETVP) system is presented. An encompassing statement of the system objectives which drive the system requirements is presented and the major mission and subsystem requirements are described with emphasis on the advanced communications technology mission payload. The platform design is defined and used as a reference configuration for an end to space construction analyses. The preferred construction methods and processes, the important interactions between the platform design and the construction system design and operation, and the technology development efforts required to support the design and space construction of the ETVP are outlined

Anomalous Superconducting Properties and Field Induced Magnetism in CeCoIn5

In the heavy fermion superconductor CeCoIn5 (Tc=2.3K) the critical field is large, anisotropic and displays hysteresis. The magnitude of the critical-field anisotropy in the a-c plane can be as large as 70 kOe and depends on orientation. Critical field measurements in the (110) plane suggest 2D superconductivity, whereas conventional effective mass anisotropy is observed in the (100) plane. Two distinct field-induced magnetic phases are observed: Ha appears deep in the superconducting phase, while Hb intersects Hc2 at T=1.4 K and extends well above Tc. These observations suggest the possible realization of a direct transition from ferromagnetism to Fulde-Ferrel-Larkin-Ovchinnikov superconductivity in CeCoIn5.Comment: 4 pages, 3 figure