Population genetics of the eastern oyster in Chesapeake Bay

The eastern oyster, Crassostrea virginica, plays an important role in the ecology of Chesapeake Bay. Its large population size, long larval dispersal stage and potential for high variance in reproductive success is representative of many marine invertebrates. Nevertheless, many important aspects of the oyster's biology remain unclear. I investigated how migration, natural selection, and effective population size have shaped the evolution of Chesapeake oysters. First, I examined aspects of genetic connectivity among oysters from rivers throughout the Bay. A correlation between geographic and genetic distance indicated that oyster larval dispersal tends to be local and that migration between Bay tributaries is rare over an ecological time scale. This result contributes to a growing body of literature indicating that larval dispersal is not passive. Next, I showed that a pattern of non-neutral mitochondrial evolution previously observed in different oyster populations also existed in Chesapeake Bay C. virginica. Tests of selection indicated that the pattern, in which there is an excess of high frequency and low frequency haplotypes and a deficit of intermediate frequency haplotypes, was the result of positive selection on the genome. Demographic explanations appear unlikely to account for the mitochondrial haplotype pattern because nuclear loci exhibited neutral patterns of sequence evolution. Estimates of effective population size were several orders of magnitude smaller than census size, indicating that there was variance in reproductive success (sweepstakes reproduction). Nevertheless sweepstakes reproduction was not so severe that individual cohorts of juvenile oysters exhibited reduced levels of variation compared to the adult population. Finally I evaluated the risks associated with a supplementation program in which hatchery-raised oysters bred for disease tolerance were released into wild oyster populations. The results indicated that following supplementation, the wild effective population size remained large despite the danger of severe genetic bottlenecks. Increased hatchery effective population is suggested to prevent future harm to the wild population

Molecular Basis of Inward Rectification: Polyamine Interaction Sites Located by Combined Channel and Ligand Mutagenesis

Polyamines cause inward rectification of (Kir) K+ channels, but the mechanism is controversial. We employed scanning mutagenesis of Kir6.2, and a structural series of blocking diamines, to combinatorially examine the role of both channel and blocker charges. We find that introduced glutamates at any pore-facing residue in the inner cavity, up to and including the entrance to the selectivity filter, can confer strong rectification. As these negative charges are moved higher (toward the selectivity filter), or lower (toward the cytoplasm), they preferentially enhance the potency of block by shorter, or longer, diamines, respectively. MTSEA+ modification of engineered cysteines in the inner cavity reduces rectification, but modification below the inner cavity slows spermine entry and exit, without changing steady-state rectification. The data provide a coherent explanation of classical strong rectification as the result of polyamine block in the inner cavity and selectivity filter

On the construction of model Hamiltonians for adiabatic quantum computation and its application to finding low energy conformations of lattice protein models

In this report, we explore the use of a quantum optimization algorithm for obtaining low energy conformations of protein models. We discuss mappings between protein models and optimization variables, which are in turn mapped to a system of coupled quantum bits. General strategies are given for constructing Hamiltonians to be used to solve optimization problems of physical/chemical/biological interest via quantum computation by adiabatic evolution. As an example, we implement the Hamiltonian corresponding to the Hydrophobic-Polar (HP) model for protein folding. Furthermore, we present an approach to reduce the resulting Hamiltonian to two-body terms gearing towards an experimental realization.Comment: 35 pages, 8 figure

Map of the late Quaternary active Kern Canyon and Breckenridge faults, southern Sierra Nevada, California

Surface traces of the Quaternary active Kern Canyon and Breckenridge faults were mapped via aerial reconnaissance, analysis of light detection and ranging (LiDAR) elevation data, review and interpretation of aerial photography, field reconnaissance, and detailed field mapping. This effort specifically targeted evidence of late Quaternary surface deformation and, combined with separate paleoseismic investigations, identified and characterized the North Kern Canyon, South Kern Canyon, and Lake Isabella sections of the Kern Canyon fault and the Breckenridge fault. The mapping presented here provides definitive evidence for previously unrecognized Holocene and late Pleistocene east-down displacement along the Kern Canyon and Breckenridge faults. Our results indicate that much of the Kern Canyon fault has undergone Quaternary reactivation to accommodate internal deformation of the otherwise rigid Sierra Nevada block. This deformation reflects ongoing, seismogenic crustal thinning in the southern Sierra Nevada, and highlights the effects of localized tectonic forces operating in this part of the Sierra Nevada

Informing investment to reduce inequalities: a modelling approach

Background: Reducing health inequalities is an important policy objective but there is limited quantitative information about the impact of specific interventions. Objectives: To provide estimates of the impact of a range of interventions on health and health inequalities. Materials and methods: Literature reviews were conducted to identify the best evidence linking interventions to mortality and hospital admissions. We examined interventions across the determinants of health: a ‘living wage’; changes to benefits, taxation and employment; active travel; tobacco taxation; smoking cessation, alcohol brief interventions, and weight management services. A model was developed to estimate mortality and years of life lost (YLL) in intervention and comparison populations over a 20-year time period following interventions delivered only in the first year. We estimated changes in inequalities using the relative index of inequality (RII). Results: Introduction of a ‘living wage’ generated the largest beneficial health impact, with modest reductions in health inequalities. Benefits increases had modest positive impacts on health and health inequalities. Income tax increases had negative impacts on population health but reduced inequalities, while council tax increases worsened both health and health inequalities. Active travel increases had minimally positive effects on population health but widened health inequalities. Increases in employment reduced inequalities only when targeted to the most deprived groups. Tobacco taxation had modestly positive impacts on health but little impact on health inequalities. Alcohol brief interventions had modestly positive impacts on health and health inequalities only when strongly socially targeted, while smoking cessation and weight-reduction programmes had minimal impacts on health and health inequalities even when socially targeted. Conclusions: Interventions have markedly different effects on mortality, hospitalisations and inequalities. The most effective (and likely cost-effective) interventions for reducing inequalities were regulatory and tax options. Interventions focused on individual agency were much less likely to impact on inequalities, even when targeted at the most deprived communities

Watershed Management on Range and Forest Lands Proceedings of the Fifth Workshop of the United States/Australia Rangelands Panel

Preface: The U.S.-Australia Cooperative Rangeland Science Program In October 1968 the governments of the United States and Australia entered into an agreement for the purpose of facilitating close cooperative activities between the scientific communities of the two countries. The joint communique issued at that time designated the U.S. National Science Foundation and the Australian Commonwealth Department of Education and Science as the coordinating agencies. Both countries were to encourage binational teamwork in research, interchanges of scientists, joint seminars, and exchanges of information. A United States-Australia Rangeland Panel was established in December 1969 to further cooperation between the two countries in the rangeland sciences. The present panel includes the following

A connection between star formation activity and cosmic rays in the starburst galaxy M 82

Although Galactic cosmic rays (protons and nuclei) are widely believed to be dominantly accelerated by the winds and supernovae of massive stars, definitive evidence of this origin remains elusive nearly a century after their discovery [1]. The active regions of starburst galaxies have exceptionally high rates of star formation, and their large size, more than 50 times the diameter of similar Galactic regions, uniquely enables reliable calorimetric measurements of their potentially high cosmic-ray density [2]. The cosmic rays produced in the formation, life, and death of their massive stars are expected to eventually produce diffuse gamma-ray emission via their interactions with interstellar gas and radiation. M 82, the prototype small starburst galaxy, is predicted to be the brightest starburst galaxy in gamma rays [3, 4]. Here we report the detection of >700 GeV gamma rays from M 82. From these data we determine a cosmic-ray density of 250 eV cm-3 in the starburst core of M 82, or about 500 times the average Galactic density. This result strongly supports that cosmic-ray acceleration is tied to star formation activity, and that supernovae and massive-star winds are the dominant accelerators.Comment: 18 pages, 4 figures; published in Nature; Version is prior to Nature's in-house style editing (differences are minimal

Discovery of Very High-Energy Gamma-Ray Radiation from the BL Lac 1ES 0806+524

The high-frequency-peaked BL-Lacertae object \objectname{1ES 0806+524}, at redshift z=0.138, was observed in the very-high-energy (VHE) gamma-ray regime by VERITAS between November 2006 and April 2008. These data encompass the two-, and three-telescope commissioning phases, as well as observations with the full four-telescope array. \objectname{1ES 0806+524} is detected with a statistical significance of 6.3 standard deviations from 245 excess events. Little or no measurable variability on monthly time scales is found. The photon spectrum for the period November 2007 to April 2008 can be characterized by a power law with photon index $3.6 \pm 1.0_{\mathrm{stat}} \pm 0.3_{\mathrm{sys}}$ between $\sim$300 GeV and $\sim$700 GeV. The integral flux above 300 GeV is $(2.2\pm0.5_{\mathrm{stat}}\pm0.4_{\mathrm{sys}})\times10^{-12}\:\mathrm{cm}^{2}\:\mathrm{s}^{-1}$ which corresponds to 1.8% of the Crab Nebula flux. Non contemporaneous multiwavelength observations are combined with the VHE data to produce a broadband spectral energy distribution that can be reasonably described using a synchrotron-self Compton model.Comment: 14 pages, 4 figures, accepted to APJ