727 research outputs found

    "Cost Effective Conservation Planning: Twenty Lessons from Economics"

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    Economists advocate that the billions of public dollars spent on conservation should be allocated to achieve the largest possible social benefit. This is what we term “cost-effective conservation”-- a process that incorporates both benefits and costs that are measured with money. This controversial proposition has been poorly understood and not implemented by conservation planners. Drawing from evidence from the largest conservation programs in the United States, this paper seeks to improve the communication between economists and planners and overcome resistance to cost-effective conservation by addressing the open questions that likely drive skepticism among non-economists and by identifying best practices for project selection. We first delineate project-selection strategies and compare them to optimization. Then we synthesize the body of established research findings from economics into 20 practical lessons. Based on theory, policy considerations, and empirical evidence, these lessons illustrate the potential gains from improving practices related to cost-effective selection and also address how to overcome landowner-incentive challenges that face programs.conservation planning, cost-effectiveness, nonmarket valuation, benefit cost targeting, optimization, prioritization

    Inelastic quantum transport: the self-consistent Born approximation and correlated electron-ion dynamics

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    A dynamical method for inelastic transport simulations in nanostructures is compared with a steady-state method based on non-equilibrium Green's functions. A simplified form of the dynamical method produces, in the steady state in the weak-coupling limit, effective self-energies analogous to those in the Born Approximation due to electron-phonon coupling. The two methods are then compared numerically on a resonant system consisting of a linear trimer weakly embedded between metal electrodes. This system exhibits enhanced heating at high biases and long phonon equilibration times. Despite the differences in their formulation, the static and dynamical methods capture local current-induced heating and inelastic corrections to the current with good agreement over a wide range of conditions, except in the limit of very high vibrational excitations, where differences begin to emerge.Comment: 12 pages, 7 figure

    A discrete time-dependent method for metastable atoms in intense fields

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    The full-dimensional time-dependent Schrodinger equation for the electronic dynamics of single-electron systems in intense external fields is solved directly using a discrete method. Our approach combines the finite-difference and Lagrange mesh methods. The method is applied to calculate the quasienergies and ionization probabilities of atomic and molecular systems in intense static and dynamic electric fields. The gauge invariance and accuracy of the method is established. Applications to multiphoton ionization of positronium and hydrogen atoms and molecules are presented. At very high intensity above saturation threshold, we extend the method using a scaling technique to estimate the quasienergies of metastable states of the hydrogen molecular ion. The results are in good agreement with recent experiments.Comment: 10 pages, 9 figure, 4 table

    On the Whitehead spectrum of the circle

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    The seminal work of Waldhausen, Farrell and Jones, Igusa, and Weiss and Williams shows that the homotopy groups in low degrees of the space of homeomorphisms of a closed Riemannian manifold of negative sectional curvature can be expressed as a functor of the fundamental group of the manifold. To determine this functor, however, it remains to determine the homotopy groups of the topological Whitehead spectrum of the circle. The cyclotomic trace of B okstedt, Hsiang, and Madsen and a theorem of Dundas, in turn, lead to an expression for these homotopy groups in terms of the equivariant homotopy groups of the homotopy fiber of the map from the topological Hochschild T-spectrum of the sphere spectrum to that of the ring of integers induced by the Hurewicz map. We evaluate the latter homotopy groups, and hence, the homotopy groups of the topological Whitehead spectrum of the circle in low degrees. The result extends earlier work by Anderson and Hsiang and by Igusa and complements recent work by Grunewald, Klein, and Macko.Comment: 52 page

    Water induced sediment levitation enhances downslope transport on Mars

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    On Mars, locally warm surface temperatures (~293 K) occur, leading to the possibility of (transient) liquid water on the surface. However, water exposed to the martian atmosphere will boil, and the sediment transport capacity of such unstable water is not well understood. Here, we present laboratory studies of a newly recognized transport mechanism: “levitation” of saturated sediment bodies on a cushion of vapor released by boiling. Sediment transport where this mechanism is active is about nine times greater than without this effect, reducing the amount of water required to transport comparable sediment volumes by nearly an order of magnitude. Our calculations show that the effect of levitation could persist up to ~48 times longer under reduced martian gravity. Sediment levitation must therefore be considered when evaluating the formation of recent and present-day martian mass wasting features, as much less water may be required to form such features than previously thought

    Wide Hybridization in Legumes at ICRISAT

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    Attempts were made to cross Cajanus cajan with Atylosia species, and to investigate causes of, and develop techniques to overcome, intergeneric incompatibility. Pods formed following some interspecific hybridizations contained shriveled seeds, and hybrid embryos were cultured. Seeds were obtained from some interspecific crosses with chickpea. Hormone treatment at pollination was used to produce hybrid embryos from crosses between A. hypogaea and distantly related tetraploid wild species. Ovule and embryo culture was used to produce hybrid callus and shoots, but effective roots were not induced. Hybrid shoots were grafted onto groundnut seedlings. Compatible diploid wild species were used as sources of resistance, and a number of high-yielding, disease-resistant lines were produced following ploidy and genome manipulations

    Cancer mortality 1981-2016 and contribution of specific cancers to current socioeconomic inequalities in all cancer mortality: a population-based study

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    Background: In many high-income countries cancer mortality rates have declined, however, socioeconomic inequalities in cancer mortality have widened over time with those in the most deprived areas bearing the greatest burden. Less is known about the contribution of specific cancers to inequalities in total cancer mortality. Methods: Using high-quality routinely collected population and mortality records we examine long-term trends in cancer mortality rates in Scotland by age group, sex, and area deprivation. We use the decomposed slope and relative indices of inequality to identify the specific cancers that contribute most to absolute and relative inequalities, respectively, in total cancer mortality. Results: Cancer mortality rates fell by 24 % for males and 10 % for females over the last 35 years; declining across all age groups except females aged 75+ where rates rose by 14 %. Lung cancer remains the most common cause of cancer death. Mortality rates of lung cancer have more than halved for males since 1981, while rates among females have almost doubled over the same period. Conclusion: Current relative inequalities in total cancer mortality are dominated by inequalities in lung cancer mortality, but with contributions from other cancer sites including liver, and head and neck (males); and breast (females), stomach and cervical (younger females). An understanding of which cancer sites contribute most to inequalities in total cancer mortality is crucial for improving cancer health and care, and for reducing preventable cancer deaths
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