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101.
Prions are the etiological agents of transmissible spongiform encephalopathies (TSSEs), a class of fatal neurodegenerative diseases affecting humans and other mammals. The pathogenic prion protein is a misfolded form of the host-encoded prion protein and represents the predominant, if not sole, component of the infectious agent. Environmental routes of TSE transmission areimplicated in epizootics of sheep scrapie and chronic wasting disease (CWD) of deer, elk, and moose. Soil represents a plausible environmental reservoir of scrapie and CWD agents, which can persist in the environment for years. Attachment to soil particles likely influences the persistence and infectivity of prions in the environment. Effective methods to inactivate TSE agents in soil are currently lacking, and the effects of natural degradation mechanisms on TSE infectivity are largely unknown. An improved understanding of the processes affecting the mobility, persistence, and bioaviailability of prions in soil is needed for the management of TSE-contaminated environments. 相似文献
102.
103.
This article discusses non-fiscal policy options to reduce energy demand and the resulting environmental impacts, and it reviews experiences with these options to date. Such policies include accelerating technology development and demonstration, stimulating product demand via procurement policies, applying efficiency standards to information-poor end-use sectors, and encouraging utility energy-efficiency programs. Efforts to implement such measures are underway in several industrialised countries and have begun in developing countries. Increasing energy efficiency is an important area for near-term carbon emission reductions, and a key strategy for cost-effective mitigation of global climate change. However, little of the energy-efficiency potential identified by technical studies will be realised in the absence of policies to reduce barriers to energy-efficiency investments. Performance standards can overcome the lack of information on the part of energy users, while technology procurement helps overcome the view of manufacturers that introducing efficient products is risky. The effects of these policy options on product markets are characterised, showing the synergy between different instruments and their potential to create and transform markets for energy-efficient products, systems and services. The existence of such energy-efficiency markets can stimulate new progress and innovation, providing the conditions in which the continuous process of technical improvement is significantly accelerated. Most policy analysis and discussions regarding climate-change mitigation have centred on various forms of carbon emission taxes and to some extent on tradable emission offsets or permits. This article concludes with an examination of why non-fiscal options are mostly absent from energy-economic models and climate-change policy studies, and we suggest approaches to include them more fully in energy-policy analysis and implementation. 相似文献
104.
Sex chromosome aneuploidy (SCA), when detected in amniocentesis, is usually an unexpected result of a test carried out for another purpose. For most SCAs, the prognosis is milder and less predictable than trisomy 21, and therefore parents are faced with a difficult decision regarding the option of pregnancy termination. While studies from Europe and the USA report a declining trend in termination rates for SCA, our local experience is different. During the period 1989–1998, we diagnosed 60 SCA (including mosaics) in 20 106 amniocenteses (0.29%) and 48 (80%) of these pregnancies were terminated, a significantly higher proportion than has been reported in Europe and the USA. The present study shows that the difference between our experience and others' may be related to differences in cultural norms and values. Thirty women were interviewed, of whom 23 terminated and seven continued the pregnancy. Interview analyses showed that the main reason behind the decision to terminate the pregnancy was associated with the parents' fear of non-specific abnormality of the child, and concerns about abnormal sexual development. Although genetic counseling practised in our center aims to be non-directive, 56% of the women reported that the counseling was either directive towards termination, or that they at least felt that the counselor's attitude was pro-termination. Most women (93%) reported themselves as having come to terms with their decision. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
105.
地下水铀污染的原位微生物还原与固定:在美国能源部田纳西橡树岭放射物污染现场的试验 总被引:4,自引:0,他引:4
吴唯民 Jack Carley David Watson 顾宝华 Scott Brooks Shelly D. Kelly Kenneth Kemner Joy D. van Nostran 吴力游 许玫英 周集中 罗剑 Erick Cardenas 黃家琪 Matthew W. Fields Terence L. Marsh James M. Tiedje Stefan J. Green Joel E. Kostk Peter K. Kitanidis Philip M. Jardine Craig S. Criddle 《环境科学学报》2011,31(3):449-459
总结了美国斯坦福大学和橡树岭国家实验室等在美国能源部田纳西州橡树岭综合试验基地进行的铀污染原位微生物修复阶段性试验结果.本试验利用微生物以乙醇为电子供体还原地下水和沉积物中的六价铀为不溶解的四价铀,使之原位固定化.随后通过加入溶解氧和硝酸盐来试验微生物还原后的地下水层中还原固定态铀的稳定性.通过预处理和长期间隔注入乙醇... 相似文献
106.
Snchez-Piero Joel Gmez-Meijide Paula Concha-Graa Estefana Moreda-Pieiro Jorge Muniategui-Lorenzo Soledad Lpez-Maha Purificacin 《Environmental Chemistry Letters》2022,20(1):49-57
Environmental Chemistry Letters - Polycyclic aromatic hydrocarbons (PAHs) in atmospheric particulate matter have adverse effects on human health, yet total PAH concentrations... 相似文献
107.
M. Díaz-Jaramillo N. Sandoval R. Barra P. Gillet C. Valdovinos 《Chemistry and Ecology》2013,29(4):308-319
Reproductive and population-level responses are ecologically relevant diagnostic tools for revealing the cost of long-term tolerance to contaminants. Spatial density distribution, seasonal density, biomass, size frequency histograms and oocytes stages in Perinereis gualpensis (Polychaeta: Nereididae) from a highly anthropogenically impacted estuary (Lenga, south-central Chile) were compared with low-polluted estuaries (Tubul and Raqui). Spatial distribution showed that the highest P. gualpensis abundances occur in the central (middle) estuarine area, establishing them as suitable zones for comparisons of estuaries. Middle areas also showed differences among estuaries in terms of population and reproductive responses. Mature stage oocytes and juvenile recruitment limited to certain seasons and low adult survival led to significant low densities and biomasses in Lenga individuals (p?.05). Conversely, high densities and biomass, continuous recruitment and mature oocyte occurrence were observed in Tubul–Raqui estuaries. These results reflected population and reproductive differences among high- and low-polluted estuaries, suggesting that chronic pollution status in Lenga estuary is a factor to be considered when evaluating these responses. 相似文献
108.
Abstract A series of mesocosms was exposed to a suite of light treatments and nutrient enrichment in order to generate algal communities of varying biomass. the influence of this biomass on the speciation of copper (II) was studied. Distribution coefficients ( Kd,Lkg?1) were relatively high (log Kd = 5 to 7), indicative of robust trace metal sequestration, and were likely controlled by the particulate organic carbon content (foc). Differences in Kd over time and among treatments were significant, as was the relationship between Kd and foc. Fluorescence quenching was used to determine binding capacities ( Lt , M) and their associated binding constants ( Kcond ,M?1) in order to model the solid phase copper speciation. the Kcond ranged between 2.1 and 5.2 × 1012M?1, indicating a very strong copper-ligand complex, and was higher in mesocosms that received more light. the light Lt increased over time, dramatically after the nutrient enrichment, but did not vary systematically among light treatments. Lt ranged from 7.2 × 10? 7 to 4.9 × 10? 5 M. the large magnitudes of Kd , Kcond and Lt ensured that greater than 97% of total copper in the mesocosms was complexed by organic matter. the total copper concentration ([Cu]T, M) needed to reach a target dissolved copper concentration of 10?12.5 M (pCu = 12.5) was determined for each mesocosm over time. [Cu]T was between 8.02 × 10?5 and 3.41 × 10?2 M, and increased over time. the [Cu]T normalized to the target pCu (Effective Dose Ratio, EDR) increased directly with increases in algal biomass, indicating a direct link between system productivity and copper exposure. Approximately 45% of the variance in EDR was explained by variance in total biomass, while the residual variance in EDR was due likely to differences in the strengths of particle associations and magnitude of binding capacities. 相似文献
109.
Alan Cuthbertson Janek Laanearu Magda Carr Joel Sommeria Samuel Viboud 《Environmental Fluid Mechanics》2018,18(1):27-57
Results are presented from a series of large-scale experiments investigating the internal and near-bed dynamics of bi-directional stratified flows with a net-barotropic component across a submerged, trapezoidal, sill obstruction. High-resolution velocity and density profiles are obtained in the vicinity of the obstruction to observe internal-flow dynamics under a range of parametric forcing conditions (i.e. variable saline and fresh water volume fluxes; density differences; sill obstruction submergence depths). Detailed synoptic velocity fields are measured across the sill crest using 2D particle image velocimetry, while the density structure of the two-layer exchange flows is measured using micro-conductivity probes at several sill locations. These measurements are designed to aid qualitative and quantitative interpretation of the internal-flow processes associated with the lower saline intrusion layer blockage conditions, and indicate that the primary mechanism for this blockage is mass exchange from the saline intrusion layer due to significant interfacial mixing and entrainment under dominant, net-barotropic, flow conditions in the upper freshwater layer. This interfacial mixing is quantified by considering both the isopycnal separation of vertically-sorted density profiles across the sill, as well as calculation of corresponding Thorpe overturning length scales. Analysis of the synoptic velocity fields and density profiles also indicates that the net exchange flow conditions remain subcritical (G < 1) across the sill for all parametric conditions tested. An analytical two-layer exchange flow model is then developed to include frictional and entrainment effects, both of which are needed to account for turbulent stresses and saline entrainment into the upper freshwater layer. The experimental results are used to validate two key model parameters: (1) the internal-flow head loss associated with boundary friction and interfacial shear; and (2) the mass exchange from the lower saline layer into the upper fresh layer due to entrainment. 相似文献
110.
About bridges and bonds: community responses to the 2000 floods in Mabalane district, Mozambique 总被引:1,自引:0,他引:1
Massive floods hit Mozambique in 2000.1 Many of the affected regions benefited from external aid. This paper investigates how the floods impacted on two communities in the interior of the Limpopo Valley, which did not receive significant assistance during the event and in the immediate aftermath. Drawing on the livelihood approach, it focuses on the role of two types of local resources: knowledge and social capital. The paper shows that the scale of the 2000 floods surpassed the response capacity of these resources and looks at how wealth and gender influenced access by households to the local support mechanisms that enhance survival and recovery. It appears that the floods mainly affected wealthier households, as these more frequently lost houses and cattle. The paper points to the importance of ploughs and cattle for local support mechanisms, which, in turn, most likely reduced the capacities of communities to recover from the disaster. 相似文献