80 research outputs found
Stellar Reaction Rates for ^(28)Si
Stellar rates for the reactions ^(27)Al(p,-y)^(28)Si and ^(24)Mg(É,-y)^(28)Si have been calculated from new cross- section data for these reactions. The contributions to the interaction rates, (Ïv)_(py) and (Ïv)_(ay), and to the
corresponding photodisintegration rates, λ_(yp) and λ_(ya), from the excited states of ^(27)Al, ^(24)Mg, and ^(28)Si are
discussed. The calculated interaction rates, N_A(Ïv), are listed for temperatures from 0.1 X 10^9Âș to 5.0 X 10^9° K; two- and four-parameter fits are given for N_A(Ïv) as a function of temperature
Capture of alpha Particles by Isospin-Symmetric Nuclei
The reaction rates for alpha capture processes on self-conjugate nuclei in
the mass range A=20-40 have been investigated. The rates were calculated using
the statistical model code NON-SMOKER taking into account isospin suppression
rules. These theoretical predictions are compared with rates derived from the
available experimental data about the alpha capture reactions taking also into
account additional experimental information from different reaction channels
populating the alpha unbound states of the self-conjugate compound nuclei.Comment: 29 pages including 7 figures; figures are revised in the new version;
accepted for publication in Nuclear Physics
Ecological forecastingâ21st century science for 21st century management
Natural resource managers are coping with rapid changes in both environmental conditions and ecosystems. Enabled by recent advances in data collection and assimilation, short-term ecological forecasting may be a powerful tool to help resource managers anticipate impending near-term changes in ecosystem conditions or dynamics. Managers may use the information in forecasts to minimize the adverse effects of ecological stressors and optimize the effectiveness of management actions. To explore the potential for ecological forecasting to enhance natural resource management, the U.S. Geological Survey (USGS) convened a workshop titled "Building Capacity for Applied Short-Term Ecological Forecasting" on May 29â31, 2019, with participants from several Federal agencies, including the Bureau of Land Management, the U.S. Fish and Wildlife Service, the National Park Service, and the National Oceanic and Atmospheric Administration as well as all mission areas within the USGS.
Participants broadly agreed that short-term ecological forecastingâon the order of days to years into the futureâhas tremendous potential to improve the quality and timeliness of information available to guide resource management decisions. Participants considered how ecological forecasting could directly affect their agency missions and specified numerous critical tools for addressing natural resource management concerns in the 21st century that could be enhanced by ecological forecasting. Given this breadth of possible applications for forecast products, participants developed a repeatable framework for evaluating potential value of a forecast product for enhancing resource management. Applying that process to a large list of forecast ideas that were developed in a brainstorming session, participants identified a small set of promising forecast products that illustrate the value of ecological forecasting for informing resource management. Workshop outcomes also include insights about important likely obstacles and next steps. In particular, reliable production and delivery of operational ecological forecasts will require a sustained commitment by research agencies, in partnership with resource management agencies, to maintain and improve forecasting tools and capabilities.https://pubs.er.usgs.gov/publication/ofr2020107
Construction, assembly and testing of the ATLAS hadronic end-cap calorimeter
The construction and assembly of the four wheels of the ATLAS hadronic end-cap calorimeter and their insertion into the two end-cap cryostats are described. The results of the qualification tests prior to installation of the two cryostats in the ATLAS experimental cavern are reviewed
Assessing the role of bed sediments in the persistence of red mud pollution in a shallow lake (Kinghorn Loch, UK)
Red mud is a by-product of alumina production. Little is known about the long-term fate of red mud constituents in fresh waters or of the processes regulating recovery of fresh waters following pollution control. In 1983, red mud leachate was diverted away from Kinghorn Loch, UK, after many years of polluting this shallow and monomictic lake. We hypothesised that the redox-sensitive constituents of red mud leachate, phosphorus (P), arsenic (As) and vanadium (V), would persist in the Kinghorn Loch for many years following pollution control as a result of cycling between the lake bed sediment and the overlying water column. To test this hypothesis, we conducted a 12-month field campaign in Kinghorn Loch between May 2012 and April 2013 to quantify the seasonal cycling of P, As, and V in relation to environmental conditions (e.g., dissolved oxygen (DO) concentration, pH, redox chemistry and temperature) in the lake surface and bottom waters. To confirm the mechanisms for P, As and V release, a sediment core incubation experiment was conducted using lake sediment sampled in July 2012, in which DO concentrations were manipulated to create either oxic or anoxic conditions similar to the bed conditions found in the lake. The effects on P, As, and V concentrations and species in the water column were measured daily over an eight-day incubation period.
Phosphate (PO4-P) and dissolved As concentrations were significantly higher in the bottom waters (75.9 ± 30.2 ÎŒg Lâ1 and 23.5 ± 1.83 ÎŒg Lâ1, respectively) than in the surface waters (12.9 ± 1.50 ÎŒg Lâ1 and 14.1 ± 2.20 ÎŒg Lâ1, respectively) in Kinghorn Loch. Sediment release of As and P under anoxic conditions was confirmed by the incubation experiment and by the significant negative correlations between DO and P and As concentrations in the bottom waters of the lake. In contrast, the highest dissolved V concentrations occurred in the bottom waters of Kinghorn Loch under oxic conditions (15.0 ± 3.35 ÎŒg Lâ1), with the release from the bed sediment apparently being controlled by a combination of competitive ion concentrations, pH and redox conditions
Consistent Indicators and Methods and a Scalable Sample Design to Meet Assessment, Inventory, and Monitoring Information Needs Across Scales
Seventy-Five Years of Vegetation Treatments on Public Rangelands in the Great Basin of North America
Land treatments occurring over millions of hectares of public rangelands in the Great Basin over the last 75 years represent one of the largest vegetation manipulation and restoration efforts in the world. The ability to use legacy data from land treatments in adaptive management and ecological research has improved with the creation of the Land Treatment Digital Library (LTDL), a spatially explicit database of land treatments conducted by the U.S. Bureau of Land Management. The LTDL contains information on over 9,000 confirmed land treatments in the Great Basin, composed of seedings (58%), vegetation control treatments (24%), and other types of vegetation or soil manipulations (18%). The potential application of land treatment legacy data for adaptive management or for retrospective analyses of effects of land management actions on physical, hydrological, and ecological patterns and processes is considerable and just beginning to be realized. © 2016The Rangelands archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information
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Observation of the 16. 7 MeV D-T fusion gamma using a gas Cerenkov detector
A measurement of the 16.7 MeV gamma production in a D-T fusion plasma was performed, using a four channel carbon dioxide gas Cerenkov detector system to measure the Cerenkov light generated by the gamma conversion electrons produced in a thin aluminum foil. 4 refs., 7 figs
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