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71.
Cultures of a chorion biopsy taken from a pregnancy at risk of Bloom's syndrome revealed the high sister chromatid exchange frequency diagnostic of this rare disorder. To obtain the result, cultures were grown under standard conditions, with the addition of 10μM 5′;-bromodeoxyuridine for the final 48 h of incubation. This result demonstrates the feasibility of early prenatal diagnosis of Bloom's syndrome. 相似文献
72.
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74.
Davies Wykes Megan S. Hogg Charlie Partridge Jamie Hughes Graham O. 《Environmental Fluid Mechanics》2019,19(4):819-831
The mixing efficiency of a plume in a filling box and an emptying-filling box is calculated for both transient and steady states. The mixing efficiency of a plume in a filling box in an asymptotic state is 1/2, independent of the details of this state or how the plume is modelled. The mixing efficiency of a plume in an emptying-filling box in steady state is \(1 - \xi \), where \(\xi = h/H\), the depth of the ambient layer h normalised by the height of the box H. A deeper mixed layer therefore corresponds to a higher mixing efficiency. These results shed light on the interpretation of mixing efficiencies of open and closed systems.
相似文献75.
A newly constructed coastal revetment at Colhuw Beach in the Glamorgan Heritage Coast, Wales, UK, was analysed using a recently
developed environmental risk assessment package (ERA). Conflict with Heritage Coast conservation objectives is apparent and
the act of building such a structure is questioned for a location where maintenance ofnatural beauty is an axiom of the coastal management philosophy. The likelyhood of revetment related environmental consequences of
significant magnitude was analysed using estimated probability values derived from Bayesian theory. The damaging impact of
the structure on the natural environment is out of all proportion to the level of storm protection afforded to the site. Analyses,
such as carried out via ERA, would have shown planners, engineers and environmentalists, the inadequacies of such an investment
and management strategy. The ERA approach can help to introduce greater clarity and consistency into decision making processes. 相似文献
76.
A newly constructed coastal revetment at Colhuw Beach in the Glamorgan Heritage Coast, Wales, UK, was analysed using a recently
developed environmental risk assessment package (ERA). Conflict with Heritage Coast conservation objectives is apparent and
the act of building such a structure is questioned for a location where maintenance ofnatural beauty is an axiom of the coastal management philosophy. The likelyhood of revetment related environmental consequences of
significant magnitude was analysed using estimated probability values derived from Bavesian theory. The damaging impact of
the structure on the natural environment is out of all proportion to the level of storm protection afforded to the site. Analyses,
such as carried out via ERA, would have shown planners, engineers and environmentalists, the inadequacies of such an investment
and management strategy. The ERA approach can help to introduce greater clarity and consistency into decision making processes. 相似文献
77.
78.
The current range of ecological habitats occupied by a species reflects a combination of the ecological tolerance of the species, dispersal limitation, and competition. Whether the current distribution of a species accurately reflects its niche has important consequences for the role of ecological niche modeling in predicting changes in species ranges as the result of biological invasions and climate change. We employed a detailed data set of species occurrence and spatial variation in biotic and abiotic attributes to model the niche of a native California annual plant, Collinsia sparsiflora. We tested the robustness of our model for both the realized and fundamental niche by planting seeds collected from four populations, representing two ecotypes, into plots that fully represented the five-dimensional niche space described by our model. The model successfully predicted which habitats allowed for C. sparsiflora persistence, but only for one of the two source ecotypes. Our results show that substantial niche divergence has occurred in our sample of four study populations, illustrating the importance of adequately sampling and describing within-species variation in niche modeling. 相似文献
79.
Peter W. Abrahams Trevor D. Davies Timothy D. Jickells Martyn Tranter 《Environmental monitoring and assessment》1993,27(3):159-174
This paper records the concentrations of major and trace elements determined from snow samples collected during a comprehensive survey undertaken in the Scottish Highlands during the winter and spring period of 1987. The configuration of calculated back-trajectories allowed the samples to be categorized into one of five geographical sectors. Discriminant analysis was used to check the validity of these calculations, to isolate potentially deviant samples, and to predict the possible source of one sample whose back-trajectory could not be computed with confidence. Limitations of the statistical method are discussed, but we conclude that the technique justifies more use by environmental scientists involved in the evaluation of data. 相似文献
80.
An investigation was carried out to establish the physical, mechanical and chemical characteristics of a non-standard (unprocessed) pulverised fuel ash (PFA) and waste tyres from a former landfill site at the Power Station Hill near Church Village, South Wales, United Kingdom. Investigations are on-going to establish the suitability of the fly ash and/or tyres in road construction (embankment and pavement) and also in concrete to be used in the construction of the proposed highway. This paper reports on concrete-based construction where concrete blends (using various levels of PFA as partial replacement for Portland cement (PC), and shredded waste tyres (chips 15-20mm) as aggregate replacement) were subjected to unconfined compressive strength tests to establish performance, hence, optimising mix designs. Strength development up to 180 days for the concrete made with PC-PFA blends as binders (PC-PFA concrete), with and without aggregate replacement with tyre chips, is reported. The binary PC-PFA concrete does not have good early strength but tends to improve at longer curing periods. The low early strength observed means that PC-PFA concrete cannot be used for structures, hence, only as low to medium strength applications such as blinding, low-strength foundations, crash barriers, noise reduction barriers, cycle paths, footpaths and material for pipe bedding. 相似文献