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371.
Scanning electron micrographs (SEM) demonstrate the growth of an epiphytic diatom and bacterial community on the surface of dialysis membranes incubated In situ, Narragansett Bay, Rhode Island (USA). A comparison is made between brushed and unbrushed tubes in summer, and unbrushed tubes in winter. Detrital deposition and epiphytic growth may decrease surface area and, by uptake and regeneration, influence nutrient flux through the membrane. 相似文献
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Annette L. Cowie Pete Smith Dale Johnson 《Mitigation and Adaptation Strategies for Global Change》2006,11(5-6):979-1002
Interest in bioenergy is growing across the Western world in response to mounting concerns about climate change. There is a risk of depletion of soil carbon stocks in biomass production systems, because a higher proportion of the organic matter and nutrients are removed from the site, compared with conventional agricultural and forestry systems. This paper reviews the factors that influence soil carbon dynamics in bioenergy systems, and utilises the model FullCAM to investigate the likely magnitude of soil carbon change where bioenergy systems replace conventional land uses. Environmental and management factors govern the magnitude and direction of change. Soil C losses are most likely where soil C is initially high, such as where improved pasture is converted to biomass production. Bioenergy systems are likely to enhance soil C where these replace conventional cropping, as intensively cropped soils are generally depleted in soil C. Measures that enhance soil C include maintenance of productivity through application of fertilisers, inclusion of legumes, and retention of nutrient-rich foliage on-site. Modelling results demonstrate that loss of soil carbon in bioenergy systems is associated with declines in the resistant plant matter and humified soil C pools. However, published experimental data and modelling results indicate that total soil C loss in bioenergy systems is generally small. Thus, although there may be some decline in soil carbon associated with biomass production, this is negligible in comparison with the contribution of bioenergy systems towards greenhouse mitigation through avoided fossil fuel emissions. 相似文献
375.
David R. Johnson MD Rachel A. Fisher Jenny J. Helwick Dennis L. Murray Maria J. Patterson Frances P. Downes 《黑龙江环境通报》1994,14(6):455-458
The association between gestational infection with human parvovirus (B19) and fetal loss has increased interest in this virus and demand for diagnostic testing. However, serological assays for B19 are not yet widely available. Maternal serum alpha-fetoprotein (MSAFP) testing is commonly used during the second trimester to screen for various fetal defects. We attempted to determine whether an elevated level of MSAFP would be an appropriate indication for B19-specific tests. Over a 26-month period, MSAFP tests were performed at Michigan State University for 21 392 women. Sera remaining after that testing were stored frozen. Of these, 22 case samples—from women with MSAFP levels greater than 3·0 multiples of the median (MOM) and pregnancies that ended in fetal loss—and 44 matched control samples—from women with MSAFP levels greater than 0·4 and less than 2·2 MOM and live births at term—were tested for B19 antibodies. None of the 66 samples was IgM positive, while 33 (50 per cent) were IgG positive. The presence of IgG was not significantly associated with case or control status (matched odds ratio=0·77, 95 per cent confidence interval 0·28–2·11). These findings are consistent with other studies indicating prior infection in approximately half of adults and suggest that elevated screening MSAFP levels, in the absence of other evidence of B19 infection, should not prompt B19-specific testing. 相似文献
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Sacral agenesis was diagnosed sonographically in the fetus of a diabetic mother and pancreatic agenesis was found additionally at autopsy. 相似文献
378.
R. Frank K. Johnson H. E. Braun C. G. Halliday J. Harvey 《Environmental monitoring and assessment》1991,16(2):137-150
Permethrin drift from two aerial applications at each of two sites in a potato growing area in Ontario were measured to a maximum distance of 61 m outside the treatment area. Droplet drift did not enter the adjacent surface water streams at either study site, since there was little or no wind on the four occasions. The concentration of the insecticide in soil as a result of drifting off site was significantly lower than the amount deposited on the treatment area. The spray drifting off-target was generally made up of droplets <100 m. Permethrin residues were detected in the water and sediment samples collected after treatment along the Bailey Creek and Beeton Creek; however, these levels did not cause lethal or sublethal effects to aquatic invertebrates and fish species. Based on the conditions and results of this study, it is concluded that a buffer zone of 65 m around sensitive and productive bodies of water would be effective and practical. 相似文献
379.
T L Johnson D W Keith 《Journal of the Air & Waste Management Association (1995)》2001,51(10):1452-1459
The decoupling of fossil-fueled electricity production from atmospheric CO2 emissions via CO2 capture and sequestration (CCS) is increasingly regarded as an important means of mitigating climate change at a reasonable cost. Engineering analyses of CO2 mitigation typically compare the cost of electricity for a base generation technology to that for a similar plant with CO2 capture and then compute the carbon emissions mitigated per unit of cost. It can be hard to interpret mitigation cost estimates from this plant-level approach when a consistent base technology cannot be identified. In addition, neither engineering analyses nor general equilibrium models can capture the economics of plant dispatch. A realistic assessment of the costs of carbon sequestration as an emissions abatement strategy in the electric sector therefore requires a systems-level analysis. We discuss various frameworks for computing mitigation costs and introduce a simplified model of electric sector planning. Results from a "bottom-up" engineering-economic analysis for a representative U.S. North American Electric Reliability Council (NERC) region illustrate how the penetration of CCS technologies and the dispatch of generating units vary with the price of carbon emissions and thereby determine the relationship between mitigation cost and emissions reduction. 相似文献
380.
The general solubility equation (GSE) proposed by Jain and Yalkowsky was used to estimate aqueous solubility of 1026 non-electrolytes. The only parameters used in the GSE are melting points (MP) and octanol-water partition coefficients (Kow). No fitted parameters and no training set are employed in the GSE. The experimental solubility values were taken from the AQUASOL dATAbASE. The average absolute error and the root-mean-square error in the solubility estimates are 0.38 and 0.53 log units, respectively. Thus, with an observed MP and calculated Kow; the users can obtain a reasonable estimation of the aqueous solubility of any organic non-electrolyte. 相似文献