Spectral characteristics for a spherically confined -1/r + br^2 potential

We consider the analytical properties of the eigenspectrum generated by a class of central potentials given by V(r) = -a/r + br^2, b>0. In particular, scaling, monotonicity, and energy bounds are discussed. The potential $V(r)$ is considered both in all space, and under the condition of spherical confinement inside an impenetrable spherical boundary of radius R. With the aid of the asymptotic iteration method, several exact analytic results are obtained which exhibit the parametric dependence of energy on a, b, and R, under certain constraints. More general spectral characteristics are identified by use of a combination of analytical properties and accurate numerical calculations of the energies, obtained by both the generalized pseudo-spectral method, and the asymptotic iteration method. The experimental significance of the results for both the free and confined potential V(r) cases are discussed.Comment: 16 pages, 4 figure

Water at an electrochemical interface - a simulation study

The results of molecular dynamics simulations of the properties of water in an aqueous ionic solution close to an interface with a model metallic electrode are described. In the simulations the electrode behaves as an ideally polarizable hydrophilic metal, supporting image charge interactions with charged species, and it is maintained at a constant electrical potential with respect to the solution so that the model is a textbook representation of an electrochemical interface through which no current is passing. We show how water is strongly attracted to and ordered at the electrode surface. This ordering is different to the structure that might be imagined from continuum models of electrode interfaces. Further, this ordering significantly affects the probability of ions reaching the surface. We describe the concomitant motion and configurations of the water and ions as functions of the electrode potential, and we analyze the length scales over which ionic atmospheres fluctuate. The statistics of these fluctuations depend upon surface structure and ionic strength. The fluctuations are large, sufficiently so that the mean ionic atmosphere is a poor descriptor of the aqueous environment near a metal surface. The importance of this finding for a description of electrochemical reactions is examined by calculating, directly from the simulation, Marcus free energy profiles for transfer of charge between the electrode and a redox species in the solution and comparing the results with the predictions of continuum theories. Significant departures from the electrochemical textbook descriptions of the phenomenon are found and their physical origins are characterized from the atomistic perspective of the simulations.Comment: 29 pages, 15 figure

Theoretical and computational study of high pressure structures in barium

Recent high pressure work has suggested that elemental barium forms a high pressure self-hosting structure (Ba IV) involving two `types' of barium atom. Uniquely among reported elemental structures it cannot be described by a single crystalline lattice, instead involving two interpenetrating incommensurate lattices. In this letter we report pseudopotential calculations demonstrating the stability and the potentially disordered nature of the `guest' structure. Using band structures and nearly-free electron theory we relate the appearance of Ba IV to an instability in the close-packed structure, demonstrate that it has a zero energy vibrational mode, and speculate about the structure's stability in other divalent elements.Comment: 4 pages and 5 figures. To appear in PR

Two-band second moment model and an interatomic potential for caesium

A semi-empirical formalism is presented for deriving interatomic potentials for materials such as caesium or cerium which exhibit volume collapse phase transitions. It is based on the Finnis-Sinclair second moment tight binding approach, but incorporates two independent bands on each atom. The potential is cast in a form suitable for large-scale molecular dynamics, the computational cost being the evaluation of short ranged pair potentials. Parameters for a model potential for caesium are derived and tested

Genetic Variation in the Perennial Ryegrass Fungal Endophyte \u3cem\u3eNeotyphodium Lolii\u3c/em\u3e

The common fungal endophytes (Neotyphodium species) of temperate pasture grasses are associated with improved tolerance to water and nutrient stress and resistance to insect pests, but are also the causal agents of animal toxicoses. Considerable variation exists among grass-endophyte associations for these beneficial and detrimental agronomic traits. The extent to which this variation may be attributed to the endophyte genotype, the host genotype or environmental interactions is currently unknown. The development of molecular genetic markers for endophytes based on simple sequence repeat (SSR) loci and the demonstration of the specific detection of endophytes in planta with these markers (van Zijll de Jong et al., 2005) allows efficient assessment of endophyte diversity in grass populations

The pulsating hot subdwarf Balloon 090100001: results of the 2005 multisite campaign

We present the results of a multisite photometric campaign on the pulsating sdB star Balloon 090100001. The star is one of the two known hybrid hot subdwarfs with both long- and short-period oscillations. The campaign involved eight telescopes with three obtaining UBVR data, four B-band data, and one Stromgren uvby photometry. The campaign covered 48 nights, providing a temporal resolution of 0.36microHz with a detection threshold of about 0.2mmag in B-filter data. Balloon 090100001 has the richest pulsation spectrum of any known pulsating subdwarf B star and our analysis detected 114 frequencies including 97 independent and 17 combination ones. The strongest mode (f_1) in the 2.8mHz region is most likely radial while the remaining ones in this region form two nearly symmetric multiplets: a triplet and quintuplet, attributed to rotationally split \ell=1 and 2 modes, respectively. We find clear increases of splitting in both multiplets between the 2004 and 2005 observing campaigns, amounting to 15% on average. The observed splittings imply that the rotational rate in Bal09 depends on stellar latitude and is the fastest on the equator. We use a small grid of models to constrain the main mode (f_1), which most likely represents the radial fundamental pulsation. The groups of p-mode frequencies appear to lie in the vicinity of consecutive radial overtones, up to the third one. Despite the large number of g-mode frequencies observed, we failed to identify them, most likely because of the disruption of asymptotic behaviour by mode trapping. The observed frequencies were not, however, fully exploited in terms of seismic analysis which should be done in the future with a larger grid of reliable evolutionary models of hot subdwarfs.Comment: accepted for publication in MNRA

Quasi-classical trajectories study of Ne2Br2(B) vibrational predissociation: Kinetics and product distributions

The vibrational predissociation of the Ne2Br2(B) van der Waals complex has been investigated using the quasi-classical trajectory method (QCT), in the range of vibrational levels v' = 16-23. Extensive comparison is made with the most recent experimental observations [Pio et al., J. Chem. Phys. 133, 014305 (2010)], molecular dynamics with quantum transitions (MDQT) simulations [Miguel et al., Faraday Discuss. 118, 257 (2001)], and preliminary results from 24-dimensional Cartesian coupled coherent state (CCCS) calculations. A sequential mechanism is found to accurately describe the theoretical dynamical evolution of intermediate and final product populations, and both QCT and CCCS provide very good estimates for the dissociation lifetimes. The capabilities of QCT in the description of the fragmentation kinetics is analyzed in detail by using reduced-dimensionality models of the complexes and concepts from phase-space transport theory. The problem of fast decoupling of the different coherent states in CCCS simulations, resulting from the high dimensionality of phase space, is tackled using a re-expansion scheme. QCT ro-vibrational product state distributions are reported. Due to the weakness of the vdW couplings and the low density of vibrational states, QCT predicts a larger than observed propensity for \Delta v' = -1 and -2 channels for the respective dissociation of the first and second Ne atoms.Comment: 16 pages, 6 figures, 4 tables. Accepted for publication in J. Chem. Phy

Shifting microbial communities sustain multiyear iron reduction and methanogenesis in ferruginous sediment incubations

This is the peer reviewed version of the following article: Bray, MS, Wu, J, Reed, BC, et al. Shifting microbial communities sustain multiyear iron reduction and methanogenesis in ferruginous sediment incubations. Geobiology. 2017; 15: 678– 689. https://doi.org/10.1111/gbi.12239, which has been published in final form at https://doi.org/10.1111/gbi.12239. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited.Reactive Fe(III) minerals can influence methane (CH4) emissions by inhibiting microbial methanogenesis or by stimulating anaerobic CH4 oxidation. The balance between Fe(III) reduction, methanogenesis, and CH4 oxidation in ferruginous Archean and Paleoproterozoic oceans would have controlled CH4 fluxes to the atmosphere, thereby regulating the capacity for CH4 to warm the early Earth under the Faint Young Sun. We studied CH4 and Fe cycling in anoxic incubations of ferruginous sediment from the ancient ocean analogue Lake Matano, Indonesia, over three successive transfers (500 days in total). Iron reduction, methanogenesis, CH4 oxidation, and microbial taxonomy were monitored in treatments amended with ferrihydrite or goethite. After three dilutions, Fe(III) reduction persisted only in bottles with ferrihydrite. Enhanced CH4 production was observed in the presence of goethite, highlighting the potential for reactive Fe(III) oxides to inhibit methanogenesis. Supplementing the media with hydrogen, nickel and selenium did not stimulate methanogenesis. There was limited evidence for Fe(III)-dependent CH4 oxidation, although some incubations displayed CH4-stimulated Fe(III) reduction. 16S rRNA profiles continuously changed over the course of enrichment, with ultimate dominance of unclassified members of the order Desulfuromonadales in all treatments. Microbial diversity decreased markedly over the course of incubation, with subtle differences between ferrihydrite and goethite amendments. These results suggest that Fe(III) oxide mineralogy and availability of electron donors could have led to spatial separation of Fe(III)-reducing and methanogenic microbial communities in ferruginous marine sediments, potentially explaining the persistence of CH4 as a greenhouse gas throughout the first half of Earth history

An economic evaluation of rosuvastatin treatment in systolic heart failure: evidence from the CORONA trial

Aims: To estimate the cost-effectiveness of 10 mg rosuvastatin daily for older patients with systolic heart failure in the Controlled Rosuvastatin Multinational Study in Heart Failure (CORONA) trial. Methods and results: This within trial analysis of CORONA used major cardiovascular (CV) events as the outcome measure. Resource use was valued and the costs of hospitalizations, procedures, and statin use compared. Cost-effectiveness was estimated as cost per major CV event avoided. There were significantly fewer major CV events in the rosuvastatin group compared with the placebo group (1.04 vs. 1.20 per patient; difference 0.164; 95% CI: 0.075–0.254, P < 0.001). The average cost of CV hospitalizations and procedures was significantly lower for those receiving rosuvastatin (£1531 vs. £1769; difference £238; 95% CI: £73–403, P = 0.005); the additional cost of the statin resulted in significantly higher total costs for the rosuvastatin group (£1769 vs. £2072; difference £303; 95% CI: £138–468, P < 0.001). Overall, rosuvastatin was found to cost £1840 (95% CI: £562–6028) per major CV event avoided. Conclusion: This economic analysis showed that a significant reduction in major CV events with rosuvastatin led to significantly reduced costs of CV hospitalizations and procedures. The reduction in associated costs for major CV events was found to offset partially (by 44%) the cost of rosuvastatin treatment in patients with systolic heart failure

Genetic and Other Contributions to Alcohol Intake in Rhesus Macaques ( Macaca mulatta )

The etiology of alcoholism and alcohol abuse, like many other complex diseases, is heterogeneous and multifactorial. Numerous studies demonstrate a genetic contribution to variation in the expression of alcohol-related disorders in humans. Over the past decade, nonhuman primates have emerged as a valuable model for some aspects of human alcohol abuse because of their phylogenetic proximity to humans. Long-term, longitudinal studies of rhesus macaques ( Macaca mulatta ) have provided much insight into environmental influences, especially early life experiences, on alcohol consumption and behavior patterns that characterize alcohol intake later in life. It is not known, however, whether there is a genetic component as well to the variation seen in alcohol consumption in rhesus macaques. A significant genetic component to variation in alcohol consumption in rhesus macaques would show for the first time that like humans, for nonhuman primates additive genetic influences are important. Moreover, their use as a model for alcohol-related disorders in humans would have even greater relevance and utility for designing experiments incorporating the expanding molecular genetics field, and allow researchers to investigate the interaction among the known environmental influences and various genotypes. Methods : In this study, we investigate factors contributing to variation in alcohol consumption of 156 rhesus macaques collected over 10 years when subjects were adolescent in age, belonging to a single extended pedigree, with each cohort receiving identical early rearing backgrounds and subsequent treatments. To measure alcohol consumption each animal was provided unfettered simultaneous access both to an aspartame-sweetened 8.4% (v/v) alcohol-water solution, the aspartame-sweetened vehicle, and to water for 1 hour each day during the early afternoon between 13:00 and 15:00 in their home cages for a period of 5 to 7 weeks. We use multiple regression to identify factors that significantly affect alcohol consumption among these animals and a maximum likelihood program (ASReml) that, controlling for the significant factors, estimates the genetic contribution to the variance in alcohol consumption. Results : Multiple regression analysis identified test cohort and rearing environment as contributing to 57 and 2%, respectively, of the total variance in alcohol consumption. Of the remaining 41% of the variance about half (19.8%) was attributable to additive genetic effects using a maximum likelihood program. Conclusion : This study demonstrates that, as in humans, there are additive genetic factors that contribute to variation in alcohol consumption in rhesus macaques, with other nongenetic factors accounting for substantial portions of the variance in alcohol consumption, Our findings show the presence of an additive genetic component and suggest the potential utility of the nonhuman primate as a molecular genetics tool for understanding alcohol abuse and alcoholism.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66182/1/j.1530-0277.2006.00044.x.pd