11 research outputs found

    The Land and Water Integration Decision Support System

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    Integration of data and component models describing habitat-based land use, non-point source pollutants transport, and water and soil quality forms the decision support development processes to assist policy makers in examining management options for dealing with the impacts of land use on water for agricultural issues in Canada. The land and water integration decision support system emphasizes on scale consistency, scenario gaming and testing, pollutant source tracing and optimal solutions. Examples of a watershed-based decision support system on water quality impact were presented as part of an assessment for the evaluation of best management practice options for future agricultural intensification scenario

    Phosphorus and Nitrogen Transport in the Binational Great Lakes Basin Estimated Using SPARROW Watershed Models

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    AbstractEutrophication problems in the Great Lakes are caused by excessive nutrient inputs (primarily phosphorus, P, and nitrogen, N) from various sources throughout its basin. In developing protection and restoration plans, it is important to know where and from what sources the nutrients originate. As part of a binational effort, Midcontinent SPARROW (SPAtially Referenced Regression On Watershed attributes) models were developed and used to estimate P and N loading from throughout the entire basin based on nutrient inputs similar to 2002; previous SPARROW models only estimated U.S. contributions. The new models have a higher resolution (~2‐km2 catchments) enabling improved descriptions of where nutrients originate and the sources at various spatial scales. The models were developed using harmonized geospatial datasets describing the stream network, nutrient sources, and environmental characteristics affecting P and N delivery. The models were calibrated using loads from sites estimated with ratio estimator and regression techniques and additional statistical approaches to reduce spatial correlation in the residuals and have all monitoring sites equally influence model development. SPARROW results, along with interlake transfers and direct atmospheric inputs, were used to quantify the entire P and N input to each lake and describe the importance of each nutrient source. Model results can be used to compare loading and yields from various tributaries and jurisdictions

    Sediment accumulation and retention in the littoral zone of lakes

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    Submerged macrophyte beds provide a secondary realm of accumulation in lakes. Particles otherwise destined to reside in the deep-water profundal zone are intercepted by nearshore macrophyte communities that attenuate wave and current energy. The microenvironment found inside submerged macrophyte beds can be substantially more quiescent than that of the open-water, allowing for fine particles to be deposited out of the water column. Together with larger, eroded inorganic sediments and coarse organic particles, these materials comprise the sediments underlying macrophyte communities.Thirty-four littoral sites were sampled in Lake Memphremagog (Quebec-Vermont) to quantify the role of morphometry (littoral slope and site exposure) and macrophyte beds (mean biomass and biomass density) on the accumulation of sediments. An established historical marker, stable Pb, was used to date the sediments (approx. 110 years) and calculate rates of accumulation (SARs). Identifiable stable Pb profiles were obtained at two-thirds of the sites confirming the utility and robustness of littoral sediment core analysis. Multiple regression analyses showed that macrophyte parameters were the best predictors of SARs. Macrophyte mean biomass and biomass density were clearly most important in predicting the volume (total SAR) and organic content (organic SAR) of the sediments (Rsp2=0.57rmto0.76R sp2=0.57 rm to 0.76, P<0.001P<0.001). The same macrophyte parameters, however, poorly predicted the bulk (mainly inorganic) accumulation of sediments. Biomass density was solely related to the long-term accumulation of stable Pb in the sediments supporting empirical models that credit growth form as an important factor explaining among species or among weedbed variability in sediment-plant tissue elemental concentrations. The quantification of SARs will benefit both lakewide modeling of nutrient and contaminant budgets, and the understanding of littoral succession and its contribution to lake ontogeny

    PROCEEDINGS OF THE British Pharmacological Society 15th-16th July, 1976 UNIVERSITY OF DUNDEE COMMUNICATIONS

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    Health-status outcomes with invasive or conservative care in coronary disease

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    BACKGROUND In the ISCHEMIA trial, an invasive strategy with angiographic assessment and revascularization did not reduce clinical events among patients with stable ischemic heart disease and moderate or severe ischemia. A secondary objective of the trial was to assess angina-related health status among these patients. METHODS We assessed angina-related symptoms, function, and quality of life with the Seattle Angina Questionnaire (SAQ) at randomization, at months 1.5, 3, and 6, and every 6 months thereafter in participants who had been randomly assigned to an invasive treatment strategy (2295 participants) or a conservative strategy (2322). Mixed-effects cumulative probability models within a Bayesian framework were used to estimate differences between the treatment groups. The primary outcome of this health-status analysis was the SAQ summary score (scores range from 0 to 100, with higher scores indicating better health status). All analyses were performed in the overall population and according to baseline angina frequency. RESULTS At baseline, 35% of patients reported having no angina in the previous month. SAQ summary scores increased in both treatment groups, with increases at 3, 12, and 36 months that were 4.1 points (95% credible interval, 3.2 to 5.0), 4.2 points (95% credible interval, 3.3 to 5.1), and 2.9 points (95% credible interval, 2.2 to 3.7) higher with the invasive strategy than with the conservative strategy. Differences were larger among participants who had more frequent angina at baseline (8.5 vs. 0.1 points at 3 months and 5.3 vs. 1.2 points at 36 months among participants with daily or weekly angina as compared with no angina). CONCLUSIONS In the overall trial population with moderate or severe ischemia, which included 35% of participants without angina at baseline, patients randomly assigned to the invasive strategy had greater improvement in angina-related health status than those assigned to the conservative strategy. The modest mean differences favoring the invasive strategy in the overall group reflected minimal differences among asymptomatic patients and larger differences among patients who had had angina at baseline

    Initial invasive or conservative strategy for stable coronary disease

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    BACKGROUND Among patients with stable coronary disease and moderate or severe ischemia, whether clinical outcomes are better in those who receive an invasive intervention plus medical therapy than in those who receive medical therapy alone is uncertain. METHODS We randomly assigned 5179 patients with moderate or severe ischemia to an initial invasive strategy (angiography and revascularization when feasible) and medical therapy or to an initial conservative strategy of medical therapy alone and angiography if medical therapy failed. The primary outcome was a composite of death from cardiovascular causes, myocardial infarction, or hospitalization for unstable angina, heart failure, or resuscitated cardiac arrest. A key secondary outcome was death from cardiovascular causes or myocardial infarction. RESULTS Over a median of 3.2 years, 318 primary outcome events occurred in the invasive-strategy group and 352 occurred in the conservative-strategy group. At 6 months, the cumulative event rate was 5.3% in the invasive-strategy group and 3.4% in the conservative-strategy group (difference, 1.9 percentage points; 95% confidence interval [CI], 0.8 to 3.0); at 5 years, the cumulative event rate was 16.4% and 18.2%, respectively (difference, 121.8 percentage points; 95% CI, 124.7 to 1.0). Results were similar with respect to the key secondary outcome. The incidence of the primary outcome was sensitive to the definition of myocardial infarction; a secondary analysis yielded more procedural myocardial infarctions of uncertain clinical importance. There were 145 deaths in the invasive-strategy group and 144 deaths in the conservative-strategy group (hazard ratio, 1.05; 95% CI, 0.83 to 1.32). CONCLUSIONS Among patients with stable coronary disease and moderate or severe ischemia, we did not find evidence that an initial invasive strategy, as compared with an initial conservative strategy, reduced the risk of ischemic cardiovascular events or death from any cause over a median of 3.2 years. The trial findings were sensitive to the definition of myocardial infarction that was used
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