Extraordinarily high leaf selenium to sulfur ratios define ‘se-accumulator’ plants

Background and Aims: Selenium (Se) and sulfur (S) exhibit similar chemical properties. In flowering plants (angiosperms) selenate and sulfate are acquired and assimilated by common transport and metabolic pathways. It is hypothesized that most angiosperm species show little or no discrimination in the accumulation of Se and S in leaves when their roots are supplied a mixture of selenate and sulfate, but some, termed Se-accumulator plants, selectively accumulate Se in preference to S under these conditions. Methods: This paper surveys Se and S accumulation in leaves of 39 angiosperm species, chosen to represent the range of plant Se accumulation phenotypes, grown hydroponically under identical conditions. Results: The data show that, when supplied a mixture of selenate and sulfate: (1) plant species differ in both their leaf Se ([Se]leaf) and leaf S ([S]leaf) concentrations; (2) most angiosperms show little discrimination for the accumulation of Se and S in their leaves and, in non-accumulator plants, [Se]leaf and [S]leaf are highly correlated; (3) [Se]leaf in Se-accumulator plants is significantly greater than in other angiosperms, but [S]leaf, although high, is within the range expected for angiosperms in general; and (4) the Se/S quotient in leaves of Se-accumulator plants is significantly higher than in leaves of other angiosperms. Conclusion: The traits of extraordinarily high [Se]leaf and leaf Se/S quotients define the distinct elemental composition of Se-accumulator plants

Optimizing baryon acoustic oscillation surveys – I. Testing the concordance ΛCDM cosmology

We optimize the design of future spectroscopic redshift surveys for constraining the dark energy via precision measurements of the baryon acoustic oscillations (BAO), with particular emphasis on the design of the Wide-Field Multi-Object Spectrograph (WFMOS). We develop a model that predicts the number density of possible target galaxies as a function of exposure time and redshift. We use this number counts model together with fitting formulae for the accuracy of the BAO measurements to determine the effectiveness of different surveys and instrument designs. We search through the available survey parameter space to find the optimal survey with respect to the dark energy equation-of-state parameters according to the Dark Energy Task Force Figure-of-Merit, including predictions of future measurements from the Planck satellite. We optimize the survey to test the LambdaCDM model, assuming that galaxies are pre-selected using photometric redshifts to have a constant number density with redshift, and using a non-linear cut-off for the matter power spectrum that evolves with redshift. We find that line-emission galaxies are strongly preferred as targets over continuum emission galaxies. The optimal survey covers a redshift range 0.8 < z < 1.4, over the widest possible area (6000 sq. degs from 1500 hours observing time). The most efficient number of fibres for the spectrograph is 2,000, and the survey performance continues to improve with the addition of extra fibres until a plateau is reached at 10,000 fibres. The optimal point in the survey parameter space is not highly peaked and is not significantly affected by including constraints from upcoming supernovae surveys and other BAO experiments.Comment: 15 pages, 9 figure

First fringes with an integrated-optics beam combiner at 10 um - A new step towards instrument miniaturization for mid-infrared interferometry

Observations at mas-resolution scales and high dynamic range hold a central place in achieving, for instance, the spectroscopic characterization of exo-Earths or the detailed mapping of their protoplanetary disc birthplace. Ground or space-based multi-aperture infrared interferometry is a promising technique to tackle these goals. But significant efforts still need to be undertaken to achieve a simplification of these instruments if we want to combine the light from a large number of telescopes. Integrated-optics appears as an alternative to the current conventional designs, especially if its use can be extended to a higher number of astronomical bands. This article reports for the first time the experimental demonstration of the feasibility of an integrated-optics approach to mid-infrared beam combination for single-mode stellar interferometry. We have fabricated a 2-telescope beam combiner prototype integrated on a substrate of chalcogenide glasses, a material transparent from 1 to 14 um. We have developed laboratory tools to characterize the modal properties and the interferometric capabilities of our device. We obtain fringes at 10 um and measure a mean contrast V=0.981 \pm 0.001 with high repeatability over one week and high stability over 5h. We show experimentally - as well as on the basis of modeling considerations - that the component has a single-mode behavior at this wavelength, which is essential to achieve high-accuracy interferometry. From previous studies, the propagation losses are estimated to 0.5 dB/cm for such components. We also discuss possible issues that may impact the interferometric contrast. The IO beam combiner performs well at 10. We also anticipate the requirement of a better matching between the numerical apertures of the component and the (de)coupling optics to optimize the total throughput. The next step foreseen is the achievement of wide-band interferograms.Comment: Accepted in A&A; 7 pages; 7 figure

Subterranean Loss and Gain of Water in Mountain Lake, Virginia: A Hydrologic Model

Mountain Lake, Virginia is a small, unique, oligotrophic, subalpine ecosystem in the southern Appalachians. Previous studies have disclosed that this lake has manifested periodic prolonged low water levels during the several thousand years of its existence. The most recent low water level occurred during the drought years of 1999-2002. Measurements of lake level, precipitation, and other meteorological data including calculated evapotranspiration in the lake basin from 2/19/02 to 8/31/03 have enabled estimation of net subterranean water losses presumably through cracks between Clinch sandstone boulders and/or the recently discovered deep hole at the northwest end of Mountain Lake. These net losses reflect the balance between total losses and any gains from springs and boulder cracks not quantified in this study. Scuba divers have documented the existence of these cracks and the deep hole. Subterranean net water losses of about 0.04-0.05 m3/s (634-792 gpm) apparently occur year-round

Phenylalanine as a hydroxyl radical-specific probe in pyrite slurries

The abundant iron sulfide mineral pyrite has been shown to catalytically produce hydrogen peroxide (H2O2) and hydroxyl radical (.OH) in slurries of oxygenated water. Understanding the formation and fate of these reactive oxygen species is important to biological and ecological systems as exposure can lead to deleterious health effects, but also environmental engineering during the optimization of remediation approaches for possible treatment of contaminated waste streams. This study presents the use of the amino acid phenylalanine (Phe) to monitor the kinetics of pyrite-induced .OH formation through rates of hydroxylation forming three isomers of tyrosine (Tyr) - ortho-, meta-, and para-Tyr. Results indicate that about 50% of the Phe loss results in Tyr formation, and that these products further react with .OH at rates comparable to Phe. The overall loss of Phe appeared to be pseudo first-order in [Phe] as a function of time, but for the first time it is shown that initial rates were much less than first-order as a function of initial substrate concentration, [Phe]o. These results can be rationalized by considering that the effective concentration of .OH in solution is lower at a higher level of reactant and that an increasing fraction of .OH is consumed by Phe-degradation products as a function of time. A simplified first-order model was created to describe Phe loss in pyrite slurries which incorporates the [Phe]o, a first-order dependence on pyrite surface area, the assumption that all Phe degradation products compete equally for the limited supply of highly reactive .OH, and a flux that is related to the release of H2O2 from the pyrite surface (a result of the incomplete reduction of oxygen at the pyrite surface). An empirically derived rate constant, Kpyr, was introduced to describe a variable .OH-reactivity for different batches of pyrite. Both the simplified first-order kinetic model, and a more detailed numerical simulation, yielded results that compare well to the observed kinetic data describing the effects of variations in concentrations of both initial Phe and pyrite. This work supports the use of Phe as a useful probe to assess the formation of .OH in the presence of pyrite, and its possible utility for similar applications with other minerals

Temporal patterns of radial growth in declining Austrocedrus chilensis forests in Northern Patagonia: The use of tree-rings as an indicator of forest decline

Using dendrochronology, combined with tree- and stand-level information, we reconstructed the temporal dynamics of ‘mal del ciprés’, a widespread decline of Austrocedrus chilensis forests in Argentina. We developed 12 new site-specific ring-width chronologies representing the growth of trees with no external (crown) or internal (radial growth) symptoms of decline. By comparing the ring-width series of individual trees with these reference chronologies, we detected reduced radial growth, likely due to ‘mal del ciprés’, in 301 symptomatic and dead overstory trees out of 1082 sampled trees. Radial growth decline also occurred in 67 living trees with asymptomatic crowns providing evidence that radial growth decline can be an early indicator of ‘mal del ciprés’. The length of the radial growth decline averaged 27 years for all trees and was 29 and 22 years for living symptomatic and dead overstory trees, respectively; the maximum decline length was 80 years. At the site level, the onset of radial growth decline ranged from the early 1920s to the 1960s, preceding dates reported in historical records. By 1979, P75% of trees per site exhibited radial growth decline. We conclude that decline in radial growth precedes crown symptoms in at least some A. chilensis trees in forests with ‘mal del ciprés’. Reduced radial growth prior to external crown symptoms implies that water uptake had been reduced, possibly because of root damage from Phyophthora or drought or their interactions. It also suggests salvage harvests that aim to eradicate trees with crown symptoms and facilitate growth of residual trees may not be the most effective management response to ‘mal del ciprés’.Fil: Amoroso, Mariano Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Daniels, Lori D.. University of British Columbia; CanadáFil: Larson, Bruce C.. University of British Columbia; Canad

An Outpatient Hospital-based Exercise Training Program for Patients With Cirrhotic Liver Disease Awaiting Transplantation: A Feasibility Trial

Background: Time spent on the waiting list prior to liver transplantation (LT) provides an opportunity to optimise recipient fitness through prehabilitation; potentially reducing the physiological impact of major surgery. We assessed the feasibility and effectiveness of a six-week exercise programme in patients with cirrhotic liver disease awaiting LT. / Methods: This single centre, prospective cohort, feasibility study, enrolled patients awaiting LT to a six week period of thrice weekly, supervised exercise on a static bike. Cardiopulmonary exercise testing (CPET) was used to objectively assess cardiopulmonary fitness at baseline and after six weeks of exercise. A follow-up CPET was performed at 12 weeks. CPET-derived measures were used to guide prescription of the training programme. A non-randomised control cohort of LT patients were selected to match the exercise group based on specific demographic data. Allocation to study arms was primarily based on the distance participants lived from the hospital where training occurred. Both groups received structured nutritional advice. / Results: The exercise programme was feasible, with 9/16 (56%) patients completing the full programme of six weeks. Peak oxygen consumption (VO2peak) in the exercise group rose from a mean (SD) of 16.2 (± 3.4) ml/kg/min at baseline to 18.5 (±4.6) ml/kg/min at week 6 (p=0.02). In the control group VO2peak decreased from a mean (SD) of 19.0 (± 6.1) ml/kg/min to 17.1 (±6.0) at week 6 (p=0.03). / Conclusion: We have demonstrated that it is feasible to engage patients awaiting LT in an intensive aerobic exercise programme with a signal of improvement in fitness being detected

Low-density series expansions for directed percolation I: A new efficient algorithm with applications to the square lattice

A new algorithm for the derivation of low-density series for percolation on directed lattices is introduced and applied to the square lattice bond and site problems. Numerical evidence shows that the computational complexity grows exponentially, but with a growth factor \lambda < \protect{\sqrt[8]{2}}, which is much smaller than the growth factor \lambda = \protect{\sqrt[4]{2}} of the previous best algorithm. For bond (site) percolation on the directed square lattice the series has been extended to order 171 (158). Analysis of the series yields sharper estimates of the critical points and exponents.Comment: 20 pages, 8 figures (3 of them > 1Mb

Structured decision making as a conceptual framework to identify thresholds for conservation and management

Threshold and their relevance to conservation have become a major topic of discussion in the ecological literature. Unfortunately, in many cases the lack of a clear conceptual framework for thinking about thresholds in terms of a structured decision making process. The purpose of this framework is to promote a logical and transparent process for making informed decisions for conservation. Specification of such a framework leads naturally to consideration of definitions and roles of different kinds of thresholds in the process. We distinguish among three categories of thresholds. Ecological thresholds are values of system state variables at which small changes bring about substantial changes in system dynamics. Utility thresholds are components of management objectives (determined by human values) and are values of state or performance variables at which small changes yield substantial changes in the value of the management outcome. Decision thresholds are values of system state variables at which small changes prompt changes in management actions in order to reach specified management objectives. The approach that we present focuses directly on the objectives of management, with an aim to providing decisions that are optimal with respect to those objectives. This approach clearly distinguishes the components of the decision process that are inherently subjective (management objectives, potential management actions) from those that are more objectives (system models, estimates of system state). Optimization based on these components then leads to decision matrices specifying optimal actions to be taken at various values of system state variables. Values of state variables separating different actions in such matrices are viewed as decision thresholds. Utility thresholds are included i the objectives component, and ecological thresholds may be embedded in models projecting consequences of management actions. Decision threshold are determined by the above-listed components of a structured decision thresholds inherited from them. These dynamic decision thresholds can then be determined using adaptive management. We provide numerical examples (that are based on patch occupancy models) of structured decision processes that include all three kinds of thresholds