1,544 research outputs found

    THE USE OF BIOPHYSICAL AND EXPECTED PAYOFF PROBABILITY SIMULATION MODELING IN THE ECONOMIC ASSESSMENT OF BRUSH MANAGEMENT ALTERNATIVES

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    Woody plant encroachment restricts forage production and capacity to produce grazing livestock. Biophysical plant growth simulation and economic simulation were used to evaluate a prescribed burning range management technique. Modeling systems incorporated management practices and costs, historical climate data, vegetation and soil inventories, livestock production data, and historical regional livestock prices. The process compared baseline non-treatment return estimates to expected change in livestock returns resulting from prescribed burning. Stochastic analyses of production and price variability produced estimates of greater net returns resulting from use of prescribed burning relative to the baseline.biophysical simulation, prescribed burning, range management, simulation, Land Economics/Use,

    Chemical Weed and Brush Control: Suggestions for Rangeland

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    34 pp.,2 tables, 3 chartsMillions of acres of Texas rangeland support an excessive cover of woody plants and forbs. This publication lists herbicides to use for controlling brush and weeds on rangeland. It can help in developing a brush management program that gives optimum benefits to livestock and wildlife. See B-1466A for a 2007 update of information in this publication. A copy of B-1466A is included with each orde

    Barriers to international experiential participation.

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    Abstract Does "preflection," as proposed by Jones and Bjelland (2004

    The coordination of cell growth during fission yeast mating requires Ras1-GTP hydrolysis

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    The spatial and temporal control of polarity is fundamental to the survival of all organisms. Cells define their polarity using highly conserved mechanisms that frequently rely upon the action of small GTPases, such as Ras and Cdc42. Schizosaccharomyces pombe is an ideal system with which to study the control of cell polarity since it grows from defined tips using Cdc42-mediated actin remodeling. Here we have investigated the importance of Ras1-GTPase activity for the coordination of polarized cell growth during fission yeast mating. Following pheromone stimulation, Ras1 regulates both a MAPK cascade and the activity of Cdc42 to enable uni-directional cell growth towards a potential mating partner. Like all GTPases, when bound to GTP, Ras1 adopts an active conformation returning to an inactive state upon GTP-hydrolysis, a process accelerated through interaction with negative regulators such as GAPs. Here we show that, at low levels of pheromone stimulation, loss of negative regulation of Ras1 increases signal transduction via the MAPK cascade. However, at the higher concentrations observed during mating, hyperactive Ras1 mutations promote cell death. We demonstrate that these cells die due to their failure to coordinate active Cdc42 into a single growth zone resulting in disorganized actin deposition and unsustainable elongation from multiple tips. These results provide a striking demonstration that the deactivation stage of Ras signaling is fundamentally important in modulating cell polarity

    Ozone and PM(2.5) Exposure and Acute Pulmonary Health Effects: A Study of Hikers in the Great Smoky Mountains National Park

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    To address the lack of research on the pulmonary health effects of ozone and fine particulate matter (≤ 2.5 μm in aerodynamic diameter; PM(2.5)) on individuals who recreate in the Great Smoky Mountains National Park (USA) and to replicate a study performed at Mt. Washington, New Hampshire (USA), we conducted an observational study of adult (18–82 years of age) day hikers of the Charlies Bunion trail during 71 days of fall 2002 and summer 2003. Volunteer hikers performed pre- and posthike pulmonary function tests (spirometry), and we continuously monitored ambient O(3), PM(2.5), temperature, and relative humidity at the trailhead. Of the 817 hikers who participated, 354 (43%) met inclusion criteria (nonsmokers and no use of bronchodilators within 48 hr) and gave acceptable and reproducible spirometry. For these 354 hikers, we calculated the posthike percentage change in forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV(1)), FVC/FEV(1), peak expiratory flow, and mean flow rate between 25 and 75% of the FVC and regressed each separately against pollutant (O(3) or PM(2.5)) concentration, adjusting for age, sex, hours hiked, smoking status (former vs. never), history of asthma or wheeze symptoms, hike load, reaching the summit, and mean daily temperature. O(3) and PM(2.5) concentrations measured during the study were below the current federal standards, and we found no significant associations of acute changes in pulmonary function with either pollutant. These findings are contrasted with those in the Mt. Washington study to examine the hypothesis that pulmonary health effects are associated with exposure to O(3) and PM(2.5) in healthy adults engaged in moderate exercise
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