Regional and local contributions to ambient non-methane volatile organic compounds at a polluted rural/coastal site in Pearl River Delta, China

Identification of major sources of airborne pollutants and their contribution to pollutant loadings are critical in developing effective pollution control and mitigation strategies. In this study, a comprehensive dataset of non-methane volatile organic compounds (NMVOCs) collected from August 2001 to December 2002 at a polluted rural/coastal site in the Pearl River Delta (PRD) is analyzed to assess the relative contributions of major pollution sources to ambient NMVOC mixing ratios. A unique approach based on emission ratios of individual chemical species was used to classify the bulk air samples in order to apportion regional and local source contributions to the measured mixing ratios. The collected air samples fell into four major groups, including air masses from the inner PRD region and Hong Kong (HK) urban area. To estimate the source apportionment of NMVOCs, a principal component analysis/absolute principal component scores receptor model was applied to the classified data points. The results indicate that the regional and local source contributions to ambient NMVOC levels at the site were significantly different due to the differences in local versus regional energy use and industrial activities. For air masses originating from HK, vehicular emissions accounted for approximately 39% of the total NMVOC levels, followed by industrial emissions (35%), gasoline evaporation (14%) and commercial/domestic liquefied petroleum gas/natural gas use (12%). By contrast, for air masses originating from the PRD the industrial emissions accounted for 43% of the total NMVOC burden, followed by vehicular emissions (32%) and biomass burning (25%). In particular, the higher regional contribution of biomass burning found in this study as compared to existing emission inventories suggests that further efforts are necessary to refine the emission inventories of NMVOCs in the PRD region. © 2006 Elsevier Ltd. All rights reserved

Causes of severe visual impairment and blindness in Bangladesh: a study of 1935 children.

OBJECTIVE: To identify the anatomical site and underlying aetiology of severe visual impairment and blindness (SVI/BL) in children in Bangladesh. DESIGN: A national case series. METHODS: Children were recruited from all 64 districts in Bangladesh through multiple sources. Causes were determined and categorised using standard World Health Organization methods. RESULTS: 1935 SVI/BL children were recruited. The median age was 132 months, and boys accounted for 63.1% of the sample. The main site of abnormality was lens (32.5%), mainly unoperated cataract, followed by corneal pathology (26.6%) and disorders of the whole eye (13.1%). Lens-related blindness was the leading cause in boys (37.0%) compared with corneal blindness in girls (29.8%). In 593 children, visual loss was due to childhood factors, over 75% being attributed to vitamin A deficiency. Overall 1338 children (69.2%) had avoidable causes. Only 2% of the country's estimated SVI/BL children have access to education and rehabilitation services. CONCLUSIONS: This is the first large-scale study of SVI/BL children in Bangladesh over two-thirds of whom had avoidable causes. Strategies for control are discussed

Relationship of trabecular and cortical bone to circulating total homocysteine and C-reactive protein in postmenopausal women

Homocysteine (Hcy) and C-reactive protein (CRP) are established risk factors for atherosclerotic cardiovascular disease and are emerging as novel risk factors for osteoporosis. The primary purpose of this study was to determine whether total Hcy and CRP concentrations are associated with trabecular and/or cortical bone mineral content (BMC) or bone mineral density (BMD) in postmenopausal women. The secondary objective was to determine the body composition and nutritional status indices (dietary and circulating) and key biologic factors related to total Hcy and CRP. The tertiary purpose of this study was to examine changes in total Hcy and CRP over one year. We enrolled healthy postmenopausal women (N=242) as part of a randomized, double-blind, placebo-controlled multi-center clinical trial designed to examine the effect of two doses of soy isoflavones on bone loss over three years in early postmenopausal women. This study assessed volumetric BMD at the distal tibia and femur (1/3 site) using peripheral quantitative computed tomography (pQCT) in a subset of women (N=184 for distal tibia; N=237 for 1/3 femur site). Total Hcy and CRP did not contribute to the variability in trabecular BMC of the distal tibia or cortical BMC of the 1/3 femur site using pQCT. Approximately 22% of the variability in trabecular BMC was accounted for by weight, hemoglobin, serum uric acid, and blood glucose. Study site, weight, and age accounted for about 14% of the variability in cortical BMC. The overall variability (19%; p[less than or equal to]0.0001) in total Hcy was accounted for by serum vitamin B₁₂ and creatinine; the overall variability (28%; p[less than or equal to]0.0001) in CRP was accounted for by serum iron, overall percent body fat, serum uric acid, triglycerides, and white blood cell count. Total Hcy and CRP increased, while serum vitamin B₁₂, serum folate, and intracellular folate decreased over a one year period. Total Hcy and CRP were not related to trabecular or cortical bone, but this may be because these women were healthy and non-osteoporotic. Since hemoglobin was a significant contributor to trabecular BMC, while iron was a significant contributor to CRP, it is possible that inflammation may mediate the relationship between iron and trabecular BMC

Dynamical model of DNA-protein interaction: effect of protein charge distribution and mechanical properties

The mechanical model based on beads and springs, which we recently proposed to study non-specific DNA-protein interactions [J. Chem. Phys. 130, 015103 (2009)], was improved by describing proteins as sets of interconnected beads instead of single beads. In this paper, we first compare the results obtained with the updated model with those of the original one and then use it to investigate several aspects of the dynamics of DNA sampling, which could not be accounted for by the original model. These aspects include the effect on the speed of DNA sampling of the regularity and/or randomness of the protein charge distribution, the charge and location of the search site, and the shape and deformability of the protein. We also discuss the efficiency of facilitated diffusion, that is, the extent to which the combination of 1D sliding along the DNA and 3D diffusion in the cell can lead to faster sampling than pure 3D diffusion of the protein.Comment: accepted in JC

Modeling Site Specific Heterogeneity in an On-Site Stratified Random Sample of Recreational Demand

Using estimation of demand for the George Washington/Jefferson National Forest as a case study, it is shown that in a stratified/clustered on-site sample, latent heterogeneity needs to be accounted for twice: first to account for dispersion in the data caused by unobservability of the process that results in low and high frequency visitors in the population, and second to capture unobservable heterogeneity among individuals surveyed at different sites according to a stratified random sample (site specific effects). It is shown that both of the parameters capturing latent heterogeneity are statistically significant. It is therefore claimed in this paper, that the model accounting for site-specific effects is superior to the model without such effects. Goodness of fit statistics show that our empirical model is superior to models that do not account for latent heterogeneity for the second time. The price coefficient for the travel cost variable changes across model resulting in differences in consumer surplus measures. The expected mean also changes across different models. This information is of importance to the USDA Forest Service for the purpose of consumer surplus calculations and projections for budget allocation and resource utilization.Recreational Demand models, Clustering, Subject-specific effects, Truncated Stratified Negative Binomial Model, Overdispersion, Environmental Economics and Policy,

Results of a Conference Site Selection and Recreational Amenities Survey Mailed to Southeastern Meeting Planners

This study was designed to determine the influence that the presence of recreational amenities has on a meeting planner\u27s convention site selection process. A total of 459 surveys were mailed in October of 1988 to meeting planners from Georgia, Florida and South Carolina. The 161 returns received accounted for a 35% response rate