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51.
This article explores the recent growth and current trends in outsourcing EHS services. More and more organizations are recognizing that outsourcing can cut costs, save time, improve staffing flexibility, and enhance the overall quality of EHS programs. © 2001 John Wiley & Sons, Inc.  相似文献   
52.
Sediment is an important pollutant for Lake Erie and its tributaries as a carrier of other substances and as a pollutant in its own right. Environmental managers have called for major reductions in sediment loadings in Lake Erie tributaries. In this study, 30-yr (1975-2005) datasets with daily resolution are analyzed to identify and interpret trends in sediment concentrations and loads in major US tributaries to Lake Erie. The Maumee and Sandusky Rivers in agricultural northwest Ohio show continual decreases throughout this period, but the River Raisin shows increases, especially in the last decade. The urban and forested Cuyahoga River shows little trend before 2000 but shows increases since then. The mostly forested Grand River shows strong decreases before 1995, little change thereafter until the early 2000s, and then increases. In most cases, the greatest decreases or smallest increases, depending on the river, are associated with summer and fall and with low flow conditions, whereas the smallest decreases or greatest increases are associated with the spring and with high flow conditions. Analysis of concentration-flow relationships indicates that these changes are not due to weather but reflect positive and negative anthropogenic influences. Sediment decreases in the northwestern Ohio tributaries seem to reflect the successful use of agricultural practices to reduce erosion and prevent sediment loss. Opportunities for further reductions in sediment loads and concentrations lie in better management of sediment losses during winter and spring.  相似文献   
53.
We documented valley and channel characteristics and wood loads in 19 reaches of forested headwater mountain streams in the Bighorn National Forest of northern Wyoming. Ten of these reaches were in the Upper Tongue River watershed, which has a history of management including timber harvest, tie floating, and road construction. Nine reaches were in the North Rock Creek watershed, which has little history of management activities. We used these data to test hypotheses that (i) valley geometry correlates with wood load, (ii) stream gradient correlates with wood load, and (iii) wood loads are significantly lower in managed watersheds than in otherwise similar unmanaged watersheds. Statistical analyses of the data support the first and third hypotheses. Stream reaches with steeper valley side slopes tend to have higher wood loads, and reaches in managed watersheds tend to have lower wood loads than reaches in unmanaged watersheds. Results do not support the second hypothesis. Shear stress correlated more strongly with wood load than did stream gradient, but statistical models with valley-scale variables had greater explanatory power than statistical models with channel-scale variables. Wood loads in stream reaches within managed watersheds in the Bighorn National Forest tend to be two to three times lower than wood loads in unmanaged watersheds.  相似文献   
54.
ABSTRACT: The ability to predict extreme floods is an important part of the planning process for any water project for which failure will be very costly. The length of a gage record available for use in estimating extreme flows is generally much shorter than the recurrence interval of the desired flows, resulting in estimates having a high degree of uncertainty. Maximum likelihood estimators of the parameters of the three parameter lognormal (3PLN) distribution, which make use of historical data, are presented. A Monte Carlo study of extreme flows estimated from samples drawn from three hypothetical 3PLN populations showed that inclusion of historical flows with the gage record reduced the bias and variance of extreme flow estimates. Asymptotic theory approximations of parameter variances and covariances calculated using the second and mixed partial derivatives of the log likelihood function agreed well with Monte Carlo results. First order approximations of the standard deviations of the extreme flow estimates did not agree with the Monte Carlo results. An alternative method for calculating those standard deviations, the “asymptotic simulation” method, is described. The standard deviations calculated by asymptotic simulation agree well with the Monte Carlo results.  相似文献   
55.
The benzene and toluene levels inside three homes with attached garages were measured for 12 consecutive weeks during the winter months in Fairbanks, Alaska (Latitude 64.5 degrees N). Results for air samples collected over 12 h for the homes showed indoor benzene mixing ratios ranging from 1.6 to 20.4 parts per billion of mixing ratio volume (ppbv), and toluene air mixing ratios ranging from 7.3 to 41.6 ppbv. A correlation between benzene and toluene levels in each home and similar regression lines suggested the same major emission source, car and small equipment gasoline, present in attached garages. In one home, there was a correlation between indoor benzene mixing ratios and the urinary biomarker, trans,trans-muconic acid. Inside, air mixing ratios of benzene and toluene decreased with decreasing outside temperature in all homes studied, even though homes were relatively tight to prevent heat loss during this period of low winter outdoor temperatures. It is suggested that buildup of these pollutants indoors is prevented by the influence of an increased indoor/outdoor temperature differential and an ensuing increase in home ventilation.  相似文献   
56.
We consider population dynamics and sustainable use and development of fishery resources in Moree, a small-scale fishing and coastal community of 20,000 people in the Central Region of Ghana near Cape Coast. Moree suggests that relationships between population dynamics and fishery resources are more complex than the concept of Malthusian overfishing implies. Reasons include changing biophysical characteristics of the upwelling system along the coast of West Africa; qualitative as well as quantitative changes in fishing activity throughout the year; the market nature of fishing activity and nonlocal demands for fish; regular fishery migration; and institutions regulating fishery resource access at home and at migration destinations. Population and resource relationships in Moree may be the effects of fishery resource and economic changes on migration rather than population pressure on fishery resources. Fisheries management policies must take into account processes that lie beyond the influence of local fishermen.  相似文献   
57.
Studying the effects of pollution on the reproductive performance of birds in the natural environment is of increasing importance due to the need to monitor environmental quality biologically. In this study we investigated the reproductive success and the quality of blue tits in four study sites (at 0.1, 1, 2.5 and 4 km from a metallurgic smelter) located within a heavy metal pollution gradient during three consecutive years. At the two sites closest to the pollution source, a significantly higher proportion of females had egg laying interruptions, and the interruptions also lasted longer (although not significantly). Although the hatching success differed significantly among sites, these differences could not be related to differences in pollution levels. Other important breeding parameters such as the start of egg laying, the clutch size and the breeding success did not differ significantly among sites. Our results suggest that exposure to heavy metal pollution did not influence blue tit reproduction in an important way.  相似文献   
58.
Cross-cultural differences exist in prenatal diagnosis and abortion for fetal anomaly, stemming from variations in laws, reimbursement policies, litigation, physicians' decision-making authority, and attitudes toward the prevention of handicaps. The first part of this paper discusses such differences in France and the U.S. The second part describes a survey of practising obstetricians in Paris, designed to assess (1) their attitudes toward pregnancy termination for various conditions, (2) their concern about fetal viability, (3) their desire for diagnostic certainty before justifying a late abortion, and (4) their perceived role in such decision-making. Among the 64.8 per cent (N = 217) who responded, the majority supported third-trimester termination (TTT) for diseases such as spina bifida, trisomy 21 , microcephaly, and Duchenne muscular dystrophy; 30–59 per cent supported TTT for cystic fibrosis and sickle cell disease; and 22–29 per cent supported TTT for haemophilia, tetralogy of Fallot, limb amputation, and Turner and Klinefelter syndromes. Obstetricians who approved of abortion across trimesters were less concerned with the certainty of diagnosis than its severity, more likely to think that abortion ought to be the parents' choice, but more likely to report making a recommendation to the parents about whether to abort a fetus. Such permissive abortion attitudes might imply more permissive prenatal diagnosis and abortion practice among Parisian obstetricians, which might lead to increased migration of patients from other E.C. countries. Cross-cultural variation in obstetric practice suggests that an international registry of pregnancies terminated for medical reasons, enabling further study of this issue, would be valuable.  相似文献   
59.
60.
Interactions between fleshy fruited plants and frugivores are crucial for the structuring and functioning of biotic communities, particularly in tropical forests where both groups are diverse and play different roles in network organization. However, it remains poorly understood how different groups of frugivore species and fruit traits contribute to network structure. We recorded interactions among 28 plant species and three groups of frugivores (birds, bats, and non-flying mammals) in a seasonal forest in Mexico to determine which species contribute more to network structure and evaluate the importance of each species. We also determined whether fruit abundance, water content, morphology traits, and fruiting phenology are related to network parameters: the number of interactions, species contribution to nestedness, and species strength. We found that plants did not depend on a single group of frugivores, but rather on one species of each group: the bird Pitangus sulphuratus, the bat Sturnira parvidens, and the non-flying mammal Procyon lotor. The abundance, size, and water content of the fruits were significantly related to the contribution to nestedness, number of interactions, and species strength index of plant species. Tree species and birds contributed mainly to the nested structure of the network. We show that the structure of plant-frugivore networks in this seasonal forest is non-random and that fruit traits (i.e., abundance, phenology, size, and water content) are important factors shaping plant-frugivore networks. Identification of the key species and their traits that maintain the complex structure of species interactions is therefore fundamental for the integral conservation of tropical forests.  相似文献   
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