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排序方式: 共有218条查询结果,搜索用时 15 毫秒
51.
Elisa Doné Leonardo Gucciardo Tim Van Mieghem Jacques Jani Mieke Cannie Dominique Van Schoubroeck Roland Devlieger Luc De Catte Philipp Klaritsch Steffi Mayer Veronika Beck Anne Debeer Eduardo Gratacos Kypros Nicolaides Jan Deprest 《黑龙江环境通报》2008,28(7):581-591
Congenital diaphragmatic hernia (CDH) can be associated with genetic or structural anomalies with poor prognosis. In isolated cases, survival is dependent on the degree of lung hypoplasia and liver position. Cases should be referred in utero to tertiary care centers familiar with this condition both for prediction of outcome as well as timed delivery. The best validated prognostic indicator is the lung area to head circumference ratio. Ultrasound is used to measure the lung area of the index case, which is then expressed as a proportion of what is expected normally (observed/expected LHR). When O/E LHR is < 25% survival chances are < 15%. Prenatal intervention, aiming to stimulate lung growth, can be achieved by temporary fetal endoscopic tracheal occlusion (FETO). A balloon is percutaneously inserted into the trachea at 26–28 weeks, and reversal of occlusion is planned at 34 weeks. Growing experience has demonstrated the feasibility and safety of the technique with a survival rate of about 50%. The lung response to, and outcome after FETO, is dependent on pre-existing lung size as well gestational age at birth. Early data show that FETO does not increase morbidity in survivors, when compared to historical controls. Several trials are currently under design. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
52.
Plant responses to abiotic stress can alter their response to biotic stress. We examined changes in the activity of several
defense proteins in response to powdery mildew infection of garlic mustard (Alliaria petiolata) in the greenhouse and in the field. Second, we examined the effects of water limitation on the same defense protein responses,
as well as on total soluble protein and glucose concentration, plant growth, and powdery mildew disease development. Similar
increases in the activity of peroxidase, chitinase, and β-1-3-glucanase were observed in leaves of plants with substantial
powdery mildew disease in both greenhouse- and field-grown plants. In the greenhouse, activities of chitinase and peroxidase
as well as total soluble protein and glucose concentrations generally increased with the degree of water limitation. In turn,
leaf growth and powdery mildew symptom development decreased as the degree of water limitation increased. This study revealed
that plant chemical responses to water limitation and powdery mildew disease can overlap to a large extent, which, in addition
to changing microenvironmental conditions and other indicators of plant quality, may underlie the ability of water limitation
to inhibit powdery mildew disease symptom development in this wild plant pathosystem. 相似文献
53.
J. M. Don MacElroy 《Ambio》2016,45(1):5-14
In this paper, a brief overview is presented of natural gas as a fuel resource with subsequent carbon capture and re-use as a means to facilitate reduction and eventual elimination of man-made carbon emissions. A particular focus is shale gas and, to a lesser extent, methane hydrates, with the former believed to provide the most reasonable alternative as a transitional fuel toward a low-carbon future. An emphasis is placed on the gradual elimination of fossil resource usage as a fuel over the coming 35 to 85 years and its eventual replacement with renewable resources and nuclear power. Furthermore, it is proposed that synthesis of chemical feedstocks from recycled carbon dioxide and hydrogen-rich materials should be undertaken for specific applications in the transport sector which require access to high energy density fuels. To achieve the latter, carbon dioxide capture is imperative and possible synthetic routes for chemical feedstock production are briefly reviewed. 相似文献
54.
Atmospheric concentrations are reported for the main component of the brominated flame retardant decaBDE (BDE-209) in air samples collected from Southern Ontario for the period January 23-June 06, 2002. Levels ranged from below detection to 105pgm(-3) with virtually all of BDE-209 being trapped by the filter and thus deduced to be sorbed to aerosol particles. Thus, it is likely that the long-range atmospheric transport (LRAT) of BDE-209 is controlled by the transport characteristics of the aerosols. This conclusion that BDE-209 does not have the same potential for LRAT as other more volatile PBDEs is subject to possible complications arising from the uncertainties about the LRAT potential of aerosols. 相似文献
55.
Mackay D Foster KL Patwa Z Webster E 《Environmental science and pollution research international》2006,13(1):2-8
- DOI: http://dx.doi.org/10.1065/espr2006.01.002
Background Davide Calamari and his colleagues were among the first to appreciate that vegetation could play a key role in determining
the fate and effects of organic contaminants. They conducted pioneering experiments to investigate the uptake of contaminants
by plants from the atmosphere and they sought to model the observed phenomena. In the nearly two decades since there has been
a marked increase in understanding of these phenomena as a result of both experimental and modelling studies.
- Goal. In this study we briefly review our current understanding of chemical partitioning between foliage and air. A model
in both fugacity and concentration format is described, based on that of Tolls and McLachlan (1994), in which the leaf is
treated as consisting of two layers, a waxy cuticle with an underlying 'reservoir' layer, the cuticle being surrounded by
an air boundary layer and containing stomata that provide direct access from the air to the 'reservoir'. The model quantifies
the dynamic penetration of a defined chemical into a defined leaf as a function of time.
Main Features The model is applied for illustrative purposes to a hypothetical but typical leaf for a set of illustrative chemicals to
demonstrate the effect of changes in physical-chemical properties and leaf characteristics.
Discussion The results are compared qualitatively with a variety of field and laboratory studies of foliage uptake and clearance of
chemicals.
Conclusion It is concluded that the model yields results that are generally consistent with observations. It is suggested that with
appropriate parameterisation and validation, the model can contribute to an improved understanding of the process of foliage
uptake from the atmosphere and to the development of an improved predictive capability. 相似文献
56.
57.
58.
Anwar Battikhi Don Kirkham 《Journal of the American Water Resources Association》1979,15(4):1004-1015
ABSTRACT: A mathematical solution based on porous media flow is developed for solute travel time to a well as affected by a leak around the upper part of the casing. Consider a well of radius 0.2 meters (m) penetrating, fully, a semiconfined aquifer of thickness 6 m with impermeable casing length of 4.5 m, and screened casing length 1.5 m. Around the upper 1.5 m of the impermeable casing length, there is a highly permeable region (a leak). The radius of influence of the well is 10 m. The porous flow medium has a hydraulic conductivity of 10 m/day and a porosity of 0.25. Between the water table and the water level in the well, there is a steady state pumped down head difference of 0.3 m. Solute travel time from a point at the bottom of the leak to the well is 2.33 days. If the leak is sealed (grouted), the travel time is 6.24 days. Examples of six different geometries are given. Laboratory studies verify the theory. The computations should be useful in the design and protection of water wells from solutes, such as from agriculture, industry, strip mines, or sanitary landfills. 相似文献
59.
In this paper, we focus on the issues related to development densities that emerged from our study of sprawl and development issues in three regions of British Columbia, Canada. We chose to focus on this aspect of the Smart Growth agenda because, while many of its other elements enjoy wide support across social interests, the goal of achieving a higher density urban fabric is highly controversial. We proceeded by collecting data on development densities and 13 indicators of community sustainability in 26 municipalities. The results suggest that the density of communities is associated with efficiencies in infrastructure and with reduced automobile dependence, with the ecological and economic implications which flow from that. However, it does not necessarily correlate with greater affordability of housing or more access to green space. In fact, if anything, we discovered a negative relationship between housing affordability and green space per capita and higher land-use densities. In a second stage of the research, we conducted a qualitative analysis of a subset of six municipalities and identified key policy issues for moving ahead with the Smart Growth agenda. The paper concludes with a discussion of the policy issues that emerged from these case studies. 相似文献
60.
Michael J. Manfredo Tara L. Teel Andrew W. Don Carlos Leeann Sullivan Alan D. Bright Alia M. Dietsch Jeremy Bruskotter David Fulton 《Conservation biology》2020,34(6):1549-1559
We introduced a multilevel model of value shift to describe the changing social context of wildlife conservation. Our model depicts how cultural-level processes driven by modernization (e.g., increased wealth, education, and urbanization) affect changes in individual-level cognition that prompt a shift from domination to mutualism wildlife values. Domination values promote beliefs that wildlife should be used primarily to benefit humans, whereas mutualism values adopt a view that wildlife are part of one's social network and worthy of care and compassion. Such shifts create emergent effects (e.g., new interest groups) and challenges to wildlife management organizations (e.g., increased conflict) and dramatically alter the sociopolitical context of conservation decisions. Although this model is likely applicable to many modernized countries, we tested it with data from a 2017–2018 nationwide survey (mail and email panel) of 43,949 residents in the United States. We conducted hierarchical linear modeling and correlational analysis to examine relationships. Modernization variables had strong state-level effects on domination and mutualism. Higher levels of education, income, and urbanization were associated with higher percentages of mutualists and lower percentages of traditionalists, who have strong domination values. Values affected attitudes toward wildlife management challenges; for example, states with higher proportions of mutualists were less supportive of lethal control of wolves (Canis lupus) and had lower percentages of active hunters, who represent the traditional clientele of state wildlife agencies in the United States. We contend that agencies will need to embrace new strategies to engage and represent a growing segment of the public with mutualism values. Our model merits testing for application in other countries. 相似文献