657 research outputs found

    The economic value of remote sensing of earth resources from space: An ERTS overview and the value of continuity of service. Volume 3: Intensive use of living resources: Agriculture. Part 1: Overview

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    Potential economic benefits obtainable from a state-of-the-art ERS system in the resource area of intensive use of living resources, agriculture, are studied. A spectrum of equal capability (cost saving), increased capability, and new capability benefits are quantified. These benefits are estimated via ECON developed models of the agricultural marketplace and include benefits of improved production and distribution of agricultural crops. It is shown that increased capability benefits and new capability benefits result from a reduction of losses due to disease and insect infestation given ERS's capability to distinguish crop vigor and from the improvement in world trade negotiations given ERS's worldwide surveying capability

    The Good, the Bad and the Lucky: CEO Pay and Skill

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    CEO compensation varies widely, even within industries. In this paper, we investigate whether differences in skill explain these differences in CEO pay. Using the idea that skilled CEOs should be more likely to continue prior good performance and more likely to reverse prior poor performance, we develop a new methodology to detect whether skill is related to pay. We find that highly paid CEOs are more skilled than their less well paid peers when pay is performancebased and when there is a large shareholder. This detected link between pay and skill is strong even when we examine industry-wide declines: highly paid CEOs are more likely to reverse the firm’s fortunes. We also examine CEO turnovers and show that the firm’s post-turnover performance is related to differences between the two CEO’s pay levels. These results highlight conditions where pay and skill are linked, and hence identify firms where high pay appears to have no justification

    On the Metabolism of β-Methionine-Methyl-C14

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    B-Amino-y-methyl-C14-thiobutyric acid (B-methionine-methyl -C14) fed in a single dose to rats caused a negligible activity of the carbon dioxide expired. Most of the activity was found in the urine due to the unchanged compound administered, as well as to its oxydation product B - amino- y - methyl - C14 - sulfoxibutyric acid (B-methionine sulfoxide). Choline and creatinine isolated from the body tissues and creatinine isolated from the urine showed a low activity. It is assumed therefore that under such conditions only a small fraction of B -methionine transfers its methyl group to the methyl acceptors

    Social-Ecological Change, Resilience, and Adaptive Capacity in the McKenzie River Valley, Oregon

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    This study explores perceptions of long-term residents regarding links between governance, landscape, and community change in the McKenzie River Valley (MRV) in western Oregon and provides a general assessment of factors affecting resilience and adaptive capacity. Residents interviewed indicated that dramatic changes driven by market competition, timber industry changes, increased regulation, and rural restructuring have occurred in both the landscape and community. The changes that have transpired have redefined the relationship between the community and the landscape, moving away from local dependence on timber harvests to an economy focused on tourism and other ecosystem services. In doing so the community has transitioned from one with a logging community identity to one that has begrudgingly become a retirement and vacation community. We found that the social-ecological system (SES) in the MRV is still in the midst of reorganization in the wake of the 1990s Timber Wars. As a result of low institutional capacity, the system is vulnerable to exogenous drivers of change. Using a modified version of Ostrom’s (2009) framework for SES analysis, this study recommends policymakers and policy entrepreneurs take three key steps to facilitate enhanced resilience and adaptive capacity: 1) support transboundary management strategies that transcend landownership classifications; 2) tighten system feedbacks to include more local influence; and 3) develop local multilayered institutions organized vertically and horizontally. Future research should explore the potential for collaborative forestry and stewardship contracting to enhance social-ecological resilience in this valley

    α-Elapitoxin-Aa2a, a long-chain snake α-neurotoxin with potent actions on muscle (α1)<inf>2</inf>βγδ nicotinic receptors, lacks the classical high affinity for neuronal α7 nicotinic receptors

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    In contrast to all classical long-chain α-neurotoxins possessing the critical fifth disulfide bond, α-elapitoxin-Aa2a (α-EPTX-Aa2a), a novel long-chain α-neurotoxin from the common death adder Acanthophis antarcticus, lacks affinity for neuronal α7-type nicotinic acetylcholine receptors (nAChRs) α-EPTX-Aa2a (8850 Da; 0.1-1 μM) caused a concentration-dependent inhibition of indirect twitches, and blocked contractures to cholinergic agonists in the isolated chick biventer cervicis nerve-muscle preparation, consistent with a postsynaptic curaremimetic mode of action. α-EPTX-Aa2a (1-10 nM) produced a potent pseudo-irreversible antagonism of chick muscle nAChRs, with an estimated pA2 value of 8.311 ± 0.031, which was not reversed by monovalent death adder antivenom. This is only 2.5-fold less potent than the prototypical long-chain α-neurotoxin, α-bungarotoxin. In contrast, α-EPTX-Aa2a produced complete, but weak, inhibition of 125I-α-bungarotoxin binding to rat hippocampal α7 nAChRs (pKI = 3.670), despite high sequence homology and similar mass to a wide range of long-chain α-neurotoxins. The mostly likely cause for the loss of α7 binding affinity is a leucine substitution, in loop II of α-EPTX-Aa2a, for the highly conserved Arg33 in long-chain α-neurotoxins. Arg 33 has been shown to be critical for both neuronal and muscle activity. Despite this substitution, α-EPTX-Aa2a retains high affinity for muscle (α1)2βγδ nAChRs. This is probably as a result of an Arg29 residue, previously shown to be critical for muscle (α1)2βγδ nAChR affinity, and highly conserved across all short-chain, but not long-chain, α-neurotoxins. α-EPTX-Aa2a therefore represents a novel atypical long-chain α-neurotoxin that includes a fifth disulfide but exhibits differential affinity for nAChR subtypes. Copyright © 2010 Published by Elsevier Inc. All rights reserved

    Heat transfer measurements for Stirling machine cylinders

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    The primary purpose of this study was to measure the effects of inflow-produced heat turbulence on heat transfer in Stirling machine cylinders. A secondary purpose was to provide new experimental information on heat transfer in gas springs without inflow. The apparatus for the experiment consisted of a varying-volume piston-cylinder space connected to a fixed volume space by an orifice. The orifice size could be varied to adjust the level of inflow-produced turbulence, or the orifice plate could be removed completely so as to merge the two spaces into a single gas spring space. Speed, cycle mean pressure, overall volume ratio, and varying volume space clearance ratio could also be adjusted. Volume, pressure in both spaces, and local heat flux at two locations were measured. The pressure and volume measurements were used to calculate area averaged heat flux, heat transfer hysteresis loss, and other heat transfer-related effects. Experiments in the one space arrangement extended the range of previous gas spring tests to lower volume ratio and higher nondimensional speed. The tests corroborated previous results and showed that analytic models for heat transfer and loss based on volume ratio approaching 1 were valid for volume ratios ranging from 1 to 2, a range covering most gas springs in Stirling machines. Data from experiments in the two space arrangement were first analyzed based on lumping the two spaces together and examining total loss and averaged heat transfer as a function of overall nondimensional parameter. Heat transfer and loss were found to be significantly increased by inflow-produced turbulence. These increases could be modeled by appropriate adjustment of empirical coefficients in an existing semi-analytic model. An attempt was made to use an inverse, parameter optimization procedure to find the heat transfer in each of the two spaces. This procedure was successful in retrieving this information from simulated pressure-volume data with artificially generated noise, but it failed with the actual experimental data. This is evidence that the models used in the parameter optimization procedure (and to generate the simulated data) were not correct. Data from the surface heat flux sensors indicated that the primary shortcoming of these models was that they assumed turbulence levels to be constant over the cycle. Sensor data in the varying volume space showed a large increase in heat flux, probably due to turbulence, during the expansion stroke

    The Good, the Bad and the Lucky: CEO Pay and Skill

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    CEO compensation varies widely, even within industries. In this paper, we investigate whether differences in skill explain these differences in CEO pay. Using the idea that skilled CEOs should be more likely to continue prior good performance and more likely to reverse prior poor performance, we develop a new methodology to detect whether skill is related to pay. We find that highly paid CEOs are more skilled than their less well paid peers when pay is performancebased and when there is a large shareholder. This detected link between pay and skill is strong even when we examine industry-wide declines: highly paid CEOs are more likely to reverse the firm’s fortunes. We also examine CEO turnovers and show that the firm’s post-turnover performance is related to differences between the two CEO’s pay levels. These results highlight conditions where pay and skill are linked, and hence identify firms where high pay appears to have no justification

    Isotope Effects in the Photosensitized Dimerization of Pyrimidines

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    Many of the biological effects of ultraviolet radiation can be explained in terms of specific chemical and physical changes in the DNA. Correlations have been made between the survival of u. v. irradiated cells and the production of certain types of lesions in the DNA.1 The pyrimidines in the DNA are the most sensitive receptors of u. v. photons. Both in vitro and in vivo irradiation of DNA with u. v. light of wavelenghs shorter than 300 nm yield cyclobutyl pyrimidine dimeirs. Pyrimidines can also be dimerized with wavelengths longer than 300 nm in the presence of carbonyl compounds by means of energy tr:msfer.2,3,4,5 This pro_cess ~s known as molecular photosensitization and yields exclusively dimers without concomitant photohydration. Molecula.r photosensitization is of fundamental biologic importance, as wavelengths longer than 300 nm are .present in the sun spectrum on the earth\u27s surface

    Sociological and Human Developmental Explanations of Crime: Conflict or Consensus

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    This paper examines multidisciplinary correlates of delinquency in an attempt to integrate sociological and environmental theories of crime with human developmental and biological explanations of crime. Structural equation models are applied to assess links among biological, psychological, and environmental variables collected prospectively from birth through age 17 on a sample of 800 black children at high risk for learning and behavioral disorders. Results show that for both males and females, aggression and disciplinary problems in school during adolescence are the strongest predictors of repeat offense behavior. Whereas school achievement and family income and stability are also significant predictors of delinquency for males, early physical development is the next strongest predictor for females. Results indicate that some effects on delinquency also vary during different ages. It is suggested that behavioral and learning disorders have both sociological and developmental correlates and that adequate educational resources are necessary to ensure channels of legitimate opportunities for high-risk youths
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