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Quantitative Impact (quantitative + impact)
Selected AbstractsModelling approach to analyse the effects of nitrification inhibition on primary productionFUNCTIONAL ECOLOGY, Issue 1 2009S. Boudsocq Summary 1Wet tropical savannas have high grass productivity despite the fact that nitrogen is generally limiting for primary production and soil nutrient content is typically very low. Nitrogen recycling, and especially nitrification, is supposed to be a strong determinant of the balance between conservation and loss of nutrients at the ecosystem level. The important primary production observed in wet tropical savannas might be due to a tight nutrient cycling and the fact that some grass species inhibit soil nitrification. 2Using a general theoretical ecosystem model taking both nitrate and ammonium into account, we investigate analytically, using a four,compartment-differential-equation system the general conditions under which nitrification inhibition enhances primary production. We then estimate the quantitative impact of such a mechanism on the dynamics and budget of nitrogen in a well-documented ecosystem, the Lamto savanna (Ivory Coast). This ecosystem is dominated by the grass Hyparrhenia diplandra, which drastically reduces nitrification in the whole savanna except for a small zone. While this small zone supports a lower grass primary production, nitrification is higher, most likely due to the presence of another genotype of H. diplandra, which has no effect on nitrification processes. Ultimately, we test whether differences in nitrification fluxes can alone explain this variation in primary production. 3Model analysis shows that nitrification inhibition enhances primary production only if the recycling efficiency , that is, the fraction of nitrogen passing through a compartment that stays inside the ecosystem , of ammonium is higher than the recycling efficiency of nitrate. This condition probably manifests itself in most soils as ammonium is less mobile than nitrate and is not touched by denitrification. It also depends partially on the relative affinity of plants for ammonium or nitrate. The numerical predictions for this model in the Lamto savanna show that variations in nitrification inhibition capacity may explain observed differences in primary production. 4In conclusion we find that nitrification inhibition is a process which probably enhances ecosystem fertility in a sustainable way, particularly in situations of high nitrate leaching and denitrification fluxes. This mechanism could explain the ecological advantage exhibited by native African grasses over indigenous grasses in South-American pastures. [source] The role of permanent income and family structure in the determination of child health in CanadaHEALTH ECONOMICS, Issue 4 2001Lori J. Curtis Abstract We use data from the Ontario Child Health Study (OCHS) to provide the first Canadian estimates of how the empirical association between child health and both low-income and family status (lone-mother versus two-parent) changes when we re-estimate the model with pooled data. Two waves of data provide a better indication of the family's long-run level of economic resources than does one wave. Our measures of health status include categorical indicators and the health utility score derived from the Health Utilities Index Mark 2 (HUI2) system. Consistent with findings from other countries, we find that most outcomes are more strongly related to low-average income (in 1982 and 1986) than to low-current income in either year. Unlike some previous research, we find the quantitative impact of low-income on child health to be modest to large. Lone-mother status is negatively associated with most outcomes, but the lone-mother coefficients did not change significantly when we switched from low-current income to low-average income. This implies that the lone-mother coefficient in single cross-sections is not just a proxy for low-permanent income. Copyright © 2001 John Wiley & Sons, Ltd. [source] ASSESSING LAND USE IMPACTS ON WATER QUALITY USING MICROBIAL SOURCE TRACKING,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 6 2004Sharon C. Long ABSTRACT: A renewed emphasis on source water protection and watershed management has resulted from recent amendments and initiatives under the Safe Drinking Water Act and the Clean Water Act. Knowledge of the impact of land use choices on source water quality is critical for efforts to properly manage activities within a watershed. This study evaluated qualitative relationships between land use and source water quality and the quantitative impact of season and rainfall events on water quality parameters. High levels of specific conductance tended to be associated with dense residential development, while organic carbon was elevated at several forested sites. Turbidity was generally higher in more urbanized areas. Source tracking indicators were detected in samples where land use types would predict their presence. Coliform levels were statistically different at the 95 percent confidence levels for winter versus summer conditions and dry versus wet weather conditions. Other water quality parameters that varied with season were organic carbon, turbidity, dissolved oxygen, and specific conductance. These results indicate that land use management can be effective for mitigating impacts to a water body; however, year- round, comprehensive data are necessary to thoroughly evaluate the water quality at a particular site. [source] EXCHANGE RATE RISK AND EXPORT REVENUE IN TAIWANPACIFIC ECONOMIC REVIEW, Issue 2 2004Wen Shwo Fang Depreciation is found to stimulate export revenue in domestic currency, but the quantitative impact is small and any associated increase in exchange risk has a negative impact. Implications for economic policy are discussed. [source] The Role of Central Hypersensitivity in the Determination of Intradiscal Mechanical Hyperalgesia in Discogenic PainPAIN MEDICINE, Issue 5 2010Juerg Schliessbach PhD Abstract Objective., The primary aim of the present study was to investigate whether there is a relationship between central hypersensitivity (assessed by pressure pain thresholds of uninjured tissues) and intradiscal pain threshold during discography. The secondary aim was to test the hypothesis that peripheral noxious stimulation dynamically modulates central hypersensitivity. Patients., Twenty-four patients with positive provocation discography were tested for central hypersensitivity by pressure algometry before and after the intervention with assessments of pressure pain detection and tolerance thresholds. Intradiscal pain threshold was assessed by measuring intradiscal pressure at the moment of pain provocation during discography. Correlation analyses between intradiscal pain threshold and pressure algometry were made. For the secondary aim, pressure algometry data before and after discography were compared. Results., Significant correlation with intradiscal pain threshold was found for pressure pain detection threshold at the toe (regression coefficient: 0.03, P = 0.05) and pressure pain tolerance thresholds at the nonpainful point at the back (0.02, P = 0.024). Tolerance threshold at the toe was a significant predictor for intradiscal pain threshold only in multiple linear regression (0.036, P = 0.027). Detection as well as tolerance thresholds significantly decreased after discography at the painful and the nonpainful point at the back, but not at the toe. Conclusions., Central hypersensitivity may influence intradiscal pain threshold, but with a modest quantitative impact. The diagnostic value of provocation discography is therefore not substantially impaired. Regional, but not generalized central hypersensitivity is dynamically modulated by ongoing peripheral nociceptive input. [source] How does photorespiration modulate leaf amino acid contents?PLANT CELL & ENVIRONMENT, Issue 7 2002A dual approach through modelling, metabolite analysis Abstract The aim of this work was to establish the quantitative impact of photorespiration on leaf amino acid contents. Attached leaves of wheat and potato were incubated for 30,40 min under defined conditions in which net CO2 uptake (A) was manipulated by irradiance, ambient CO2 or ambient O2. The incubated portion of the leaf was sampled by a rapid-quench method and photorespiratory flux (vo) was modelled from the measured rate of net CO2 uptake. In both wheat and potato, the ratio between glycine and serine showed a strong positive correlation with vo. Aspartate and alanine correlated negatively with vo but glutamate and glutamine showed less clear relationships. In potato, glutamate and glutamine did not correlate clearly with either A or vo. In wheat, glutamine showed a general increase with A but no relationship with vo, whereas 2-oxoglutarate contents correlated positively with vo and negatively with A. As a result, glutamine : glutamate and glutamine : 2-oxoglutarate increased with net CO2 uptake in wheat, observations that are attributed primarily to imperfect and variable coupling between the supply of NH3 in primary nitrogen assimilation and the associated delivery of 2-oxoglutarate to the chloroplast. A simple theoretical analysis is used to illustrate the potentially marked impact of primary nitrogen assimilation on leaf glutamine, even against a background of high rates of photorespiratory ammonia recycling. [source] Veterinary Drug Usage and Antimicrobial Resistance in Bacteria of Animal OriginBASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 4 2005Frank M. Aarestrup There are large variations in the amounts of antimicrobial agents used to produce the same amount of meat among the different European countries, which leaves room for considerable reductions in some countries. The emergence of resistant bacteria and resistance genes due to the use of antimicrobial agents are well documented. In Denmark it has been possible to reduce the usage of antimicrobial agents for food animals significantly and in general decreases in resistance have followed. Guidelines for prudent use of antimicrobial agents may help to slow down the selection for resistance and should be based on knowledge regarding the normal susceptibility patterns of the causative agents and take into account the potential problems for human health. Current knowledge regarding the occurrence of antimicrobial resistance in food animals, the quantitative impact of the use of different antimicrobial agents on selection of resistance and the most appropriate treatment regimes to limit the development of resistance is incomplete. Programmes monitoring the occurrence and development of resistance and consumption of antimicrobial agents are strongly desirable, as is research into the most appropriate ways to use antimicrobial agents in veterinary medicine. [source] Weight loss predicts mortality after recurrent oral cavity and oropharyngeal carcinomas,CANCER, Issue 3 2002Thao V. Nguyen B.S.E. Abstract BACKGROUND The prognosis of patients with recurrent tumors of the head and neck generally is considered poor. Better prediction of outcomes can help physicians counsel patients about the merits of additional treatment. The TNM system, which was created for patients with primary tumors, may not provide optimal information. Anatomic staging systems traditionally have ignored symptom-based variables, such as weight loss, despite their known prognostic value. The objectives of this study were 1) to measure the prognostic impact of weight loss, 2) to evaluate the prognostic value of the TNM staging system, and 3) to create a practical staging system capable of predicting survival after patients develop recurrent tumors of the oral cavity and oropharynx. METHODS A retrospective chart review was used to identify an inception cohort of patients seeking treatment for recurrent, persistent, and second primary tumors of the oral cavity and oropharynx at the University of Washington. The primary outcome variable was 1-year survival. RESULTS The 1-year survival rate for the cohort (n = 97 patients) was 38%, with a median survival of 0.7 years. Multivariate analysis (Cox regression) identified weight loss, previous radiation to the head and neck, and TNM stage of the recurrent tumor as factors that had a substantial impact on mortality. A second multivariate technique called conjunctive consolidation was used to determine the relative quantitative impact of each variable on survival and to develop a clinical staging system. Weight loss and previous radiation had the greatest influence, and the use of just these two variables resulted in a three-tiered staging system with 1-year survival rates of 62% (16 of 26 patients), 44% (18 of 41 patients), and 10% (3 of 30 patients). In contrast, the TNM staging system produced survival rates of 60% (patients with Stage I disease), 67% (patients with Stage II disease), 32% (patients with Stage III disease), and 32% (patients with Stage IV disease). CONCLUSIONS The authors found substantial variation in survival after patients developed recurrent tumors of the oral cavity and oropharynx. Two readily available clinical variables,weight loss and previous radiation,were combined to create a clinically practical staging scheme with more prognostic power than the TNM staging system. Until molecular markers can reliably used be to predict outcomes, greater attention needs to be given to the utility of simple, inexpensive, and surprisingly powerful clinical variables. Cancer 2002;95:553,62. © 2002 American Cancer Society. DOI 10.1002/cncr.10711 [source] Life Cycle Attribute AssessmentJOURNAL OF INDUSTRIAL ECOLOGY, Issue 4 2009Case Study of Quebec Greenhouse Tomatoes Summary Practitioners of life cycle assessment (LCA) have recently turned their attention to social issues in the supply chain. The United Nations life cycle initiative's social LCA task force has completed its guidelines for social life cycle assessment of products, and awareness of managing upstream corporate social responsibility (CSR) issues has risen due to the growing popularity of LCA. This article explores one approach to assessing social issues in the supply chain,life cycle attribute assessment (LCAA). The approach was originally proposed by Gregory Norris in 2006, and we present here a case study. LCAA builds on the theoretical structure of environmental LCA to construct a supply chain model. Instead of calculating quantitative impacts, however, it asks the question "What percentage of my supply chain has attribute X?" X may represent a certification from a CSR body or a self-defined attribute, such as "is locally produced." We believe LCAA may serve as an aid to discussions of how current and popular CSR indicators may be integrated into a supply chain model. The case study demonstrates the structure of LCAA, which is very similar to that of traditional environmental LCA. A labor hours data set was developed as a satellite matrix to determine number of worker hours in a greenhouse tomato supply. Data from the Quebec tomato producer were used to analyze how the company performed on eight sample LCAA indicators, and conclusions were drawn about where the company should focus CSR efforts. [source] Water Resources Modeling of the Ganges-Brahmaputra-Meghna River Basins Using Satellite Remote Sensing Data,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 6 2009Bushra Nishat Nishat, Bushra and S.M. Mahbubur Rahman, 2009. Water Resources Modeling of the Ganges-Brahmaputra-Meghna River Basins Using Satellite Remote Sensing Data. Journal of the American Water Resources Association (JAWRA) 45(6):1313-1327. Abstract:, Large-scale water resources modeling can provide useful insights on future water availability scenarios for downstream nations in anticipation of proposed upstream water resources projects in large international river basins (IRBs). However, model set up can be challenging due to the large amounts of data requirement on both static states (soils, vegetation, topography, drainage network, etc.) and dynamic variables (rainfall, streamflow, soil moisture, evapotranspiration, etc.) over the basin from multiple nations and data collection agencies. Under such circumstances, satellite remote sensing provides a more pragmatic and convenient alternative because of the vantage of space and easy availability from a single data platform. In this paper, we demonstrate a modeling effort to set up a water resources management model, MIKE BASIN, over the Ganges, Brahmaputra, and Meghna (GBM) river basins. The model is set up with the objective of providing Bangladesh, the lowermost riparian nation in the GBM basins, a framework for assessing proposed water diversion scenarios in the upstream transboundary regions of India and deriving quantitative impacts on water availability. Using an array of satellite remote sensing data on topography, vegetation, and rainfall from the transboundary regions, we demonstrate that it is possible to calibrate MIKE BASIN to a satisfactory level and predict streamflow in the Ganges and Brahmaputra rivers at the entry points of Bangladesh at relevant scales of water resources management. Simulated runoff for the Ganges and Brahmaputra rivers follow the trends in the rated discharge for the calibration period. However, monthly flow volume differs from the actual rated flow by (,) 8% to (+) 20% in the Ganges basin, by (,) 15 to (+) 12% in the Brahmaputra basin, and by (,) 15 to (+) 19% in the Meghna basin. Our large-scale modeling initiative is generic enough for other downstream nations in IRBs to adopt for their own modeling needs. [source] Impact Of Tariff Reduction On Structural Employment In China: A Computable General Equilibrium AnalysisPACIFIC ECONOMIC REVIEW, Issue 2 2000Dianqing Xu The paper studies the effect of tariff reduction on employment in China. Using a computable general equilibrium (CGE) analysis, a model simulates the structural adjustment in the Chinese economy as a result of tariff cuts and predicts their quantitative impacts on structural unemployment during the adjustment period. It is concluded that the structural unemployment in China caused by tariff reduction is not as serious as some have claimed. The technique of study on structural unemployment can be extended to other countries to analyze the impact of trade reform. [source] | |||||||||||||