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Quantitative Models (quantitative + models)
Selected AbstractsPredicting the impacts of an introduced species from its invasion history: an empirical approach applied to zebra mussel invasionsFRESHWATER BIOLOGY, Issue 6 2003Anthony Ricciardi SUMMARY 1.,Quantitative models of impact are lacking for the vast majority of known invasive species, particularly in aquatic ecosystems. Consequently, managers lack predictive tools to help them prioritise invasion threats and decide where they can most effectively allocate limited resources. Predictive tools would also enhance the accuracy of water quality assessments, so that impacts caused by an invader are not erroneously attributed to other anthropogenic stressors. 2.,The invasion history of a species is a valuable guide for predicting the consequences of its introduction into a new environment. Regression analysis of data from multiple invaded sites can generate empirical models of impact, as is shown here for the zebra mussel Dreissena polymorpha. Dreissena's impacts on benthic invertebrate abundance and diversity follow predictable patterns that are robust across a range of habitat types and geographic regions. Similar empirical models could be developed for other invaders with a documented invasion history. 3.,Because an invader's impact is correlated with its abundance, a surrogate model may be generated (when impact data are unavailable) by relating the invader's abundance to environmental variables. Such a model could help anticipate which habitats will be most affected by invasion. Lack of precision should not be a deterrent to developing predictive models where none exist. Crude predictions can be refined as additional data become available. Empirical modelling is a highly informative and inexpensive, but underused, approach in the management of aquatic invasive species. [source] The Role of Amoeboid Protists and the Microbial Community in Moss-Rich Terrestrial Ecosystems: Biogeochemical Implications for the Carbon Budget and Carbon Cycle, Especially at Higher Latitudes,THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 3 2008O. ROGER ANDERSON ABSTRACT. Moss-rich terrestrial communities are widely distributed in low- and high-latitude environments, covering vast surface areas in the boreal forests and tundra. The microbial biota in these organic-rich communities may contribute substantially to the carbon budget of terrestrial communities and the carbon cycle on a global scale. Recent research is reported on the carbon content of microbial communities in some temperate and high-latitude moss communities. The total carbon content and potential respiratory carbon dioxide (CO2) efflux is reported for bacteria, microflagellates, naked amoebae, and testate amoebae within sampling sites at a northeastern forest and the tundra at Toolik, Alaska. Quantitative models of the predicted total CO2 efflux from the microbes, based on microscopic observations and enumeration of the microbiota in samples from the research sites, are described and predictions are compared with published field-based data of CO2 efflux. The significance of the predictions for climate change and global warming are discussed. [source] A Comparison of Arbitration Procedures for Risk-Averse Disputants,DECISION SCIENCES, Issue 4 2004Michael J. Armstrong ABSTRACT We propose an arbitration model framework that generalizes many previous quantitative models of final offer arbitration, conventional arbitration, and some proposed alternatives to them. Our model allows the two disputants to be risk averse and assumes that the issue(s) in dispute can be summarized by a single quantifiable value. We compare the performance of the different arbitration procedures by analyzing the gap between the disputants' equilibrium offers and the width of the contract zone that these offers imply. Our results suggest that final offer arbitration should give results superior to those of conventional arbitration. [source] Polyphase evolution and reaction sequence of compositional domains in metabasalt: a model based on local chemical equilibrium and metamorphic differentiationGEOLOGICAL JOURNAL, Issue 3-4 2000T. M. Toóth Abstract Eclogitic garnet amphibolite samples from the Southern Steep Belt of the Central Alps show evidence of several stages of metamorphic evolution and exhumation. A method for unravelling this evolution is presented and applied to these samples. It involves a combination of detailed petrographic analysis and microchemical characterization with quantitative models of the thermodynamically stable phase relations for specific compositional domains of each sample. Preserved mineral relics and textural evidence are compared to model predictions to identify the important irreversible reactions. The interpretation of the exhumation history is thus based on the consistency of a wide spectrum of observations with predicted phase diagrams, leading to robust reconstruction of a pressure,temperature (P,T) path even where the mineralogical relics in samples are insufficient, due to retrogression, to warrant application of multi-equilibrium thermobarometric techniques. The formation of compositionally different domains in the metabasalt samples studied is attributed to prograde growth of porphyroblasts (e.g. garnet, plagioclase, zoisite) in the matrix, implying substantial metamorphic differentiation at the scale of a few millimetres. Chemical interaction among different domains during the subsequent P,T evolution is shown to have been very limited. This led to different reaction sequences during exhumation, in which relics preserved in different domains reflect a range of continually changing P,T conditions. For samples from a single outcrop, we deduce a Barrovian prograde path to eclogite facies (23,±,3,kbar, 750,±,50°C), followed by (rapid) decompression to 8,±,1,kbar and 675,±,25°C, and a final heating phase at similar pressures reaching 750,±,40°C. This evolution is attributed to the Alpine cycle involving subduction,collision and slab breakoff,extrusion of tectonic fragments that make up the Southern Steep Belt of the Central Alps. Copyright © 2000 John Wiley & Sons, Ltd. [source] Establishing quantitative in-line analysis of multiple solid-state transformations during dehydrationJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 11 2008Karin Kogermann Abstract The aim of the study was to conduct quantitative solid phase analysis of piroxicam (PRX) and carbamazepine (CBZ) during isothermal dehydration in situ, and additionally exploit the constructed quantitative models to analyze the solid-state forms in-line during fluidized bed drying. Vibrational spectroscopy (near-infrared (NIR), Raman) was employed for monitoring the dehydration and the quantitative model was based on partial least squares (PLS) regression. PLS quantification was confirmed experimentally using isothermal thermogravimetric analysis (TGA) and X-ray powder diffractometry (XRPD). To appraise the quality of quantitative models several model parameters were evaluated. The hot-stage spectroscopy quantification results were found to be in reasonable agreement with TGA and XRPD results. Quantification of PRX forms showed complementary results with both spectroscopic techniques. The solid-state forms observed during CBZ dihydrate dehydration were quantified with Raman spectroscopy, but NIR spectroscopy failed to differentiate between the anhydrous solid-state forms of CBZ. In addition to in situ dehydration quantification, Raman spectroscopy in combination with PLS regression enabled in-line analysis of the solid-state transformations of CBZ during dehydration in a fluidized bed dryer. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:4983,4999, 2008 [source] MULTISCALE INFLUENCES ON PHYSICAL AND CHEMICAL STREAM CONDITIONS ACROSS BLUE RIDGE LANDSCAPES,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 5 2002Mark C. Scott ABSTRACT: Streams integrate biogeochemical processes operating at broad to local spatial scales and long term to short term time scales. Humans have extensively altered those processes in North America, with serious consequences for aquatic ecosystems. We collected data on Upper Tennessee River tributaries in North Carolina to: (1) compare landuse and landscape geomorphology with respect to their ability to explain variation in water quality, sedimentation measures, and large woody debris; (2) determine if landscape change over time contributed significantly to explaining present stream conditions; and (3) assess the importance of spatial scale in examining landuse influences on streams. Stream variables were related to both landuse and landscape geomorphology. Forest cover accounted for the most variation in nearly all models, supporting predictions of nutrient enrichment, thermal pollution, and sedimentation caused by landscape disturbance. Legacy effects from past catchment disturbance were apparent in sedimentation measures. Nitrogen and phosphorus concentrations, as well as stream temperature, were lower where riparian buffers had reforested. Models of stream physicochemistry fit better when predictors were catchment wide rather than more localized (i.e., within 2 km of a site). Cumulative impacts to streams due to changes in landuse must be managed from a watershed perspective with quantitative models that integrate across scales. [source] Quantitative description of loss of clinical benefit following withdrawal of levodopa,carbidopa and bromocriptine in early Parkinson's diseaseMOVEMENT DISORDERS, Issue 5 2002Robert A. Hauser MD Abstract In Parkinson's disease, effects of medications on the progression of the underlying disease can be assessed clinically by evaluating patients at baseline prior to treatment and at endpoint following medication washout. With this design, it is critical to employ a washout of sufficient duration to ensure elimination of all symptomatic effects. To assess the time course of resolution of symptomatic effects, we evaluated 31 patients with early Parkinson's disease for 2 weeks following discontinuation of levodopa,carbidopa and bromocriptine after 14 months of treatment. Patients had previously been randomly assigned to treatment with selegiline or placebo, and these had been discontinued 2 months earlier. Data from 20 patients with a clear washout of clinical benefit were used to investigate quantitative models describing the time course of total (Activities of Daily Living + motor) Unified Parkinson's Disease Rating Scale score change. The mean half-life of loss of clinical benefit was 7.9 days (95% confidence interval, 2.2,30.4 days). This indicates that a washout period of 32 days (4 half-lives) may be required to eliminate approximately 90% of the long-term symptomatic effects of levodopa,carbidopa and bromocriptine following their withdrawal from patients with early Parkinson's disease. © 2002 Movement Disorder Society [source] Very high efficiency solar cell modulesPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 1 2009Allen Barnett Abstract The Very High Efficiency Solar Cell (VHESC) program is developing integrated optical system,PV modules for portable applications that operate at greater than 50% efficiency. We are integrating the optical design with the solar cell design, and have entered previously unoccupied design space. Our approach is driven by proven quantitative models for the solar cell design, the optical design, and the integration of these designs. Optical systems efficiency with an optical efficiency of 93% and solar cell device results under ideal dichroic splitting optics summing to 42·7,±,2·5% are described. Copyright © 2008 John Wiley & Sons, Ltd. [source] | |||||||||||||