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51.
应用11种限制性内酶BamHⅠ、BstEⅡ、EcoRⅠ、EcoRⅤ、HindⅢ、KpnⅠ、PstⅠ、SalⅠ、SstⅠ、XbaⅠaⅠ和XⅠⅠ和XhoⅠ分别将中国棉铃虫核多角体病毒(单粒包埋HaSNPV)湖北株基因组D组DNA酶切为10、12、22、21、13、6、6、40、6、21、6个片段,并求得基因组大小平均为1什什Mr≈79.1×106.以家委核多角体病毒BmNPV多角体基因为探针,利用Southern杂交技术将病毒多角体基因定位在SalⅠ4.2×103b左右的片段上.与棉铃虫核多角体病毒其它株系酶切图谱比较结果表明,本株病毒与上海等株系及美洲棉铃虫核多角体病毒HaSNPVElkar株系酶切图谱相似,它们之间的条带数和大小差异较小,而与已发现的所有多粒包埋型病毒HaSNPV酶切图主谱差异较大.据此认为HaSNPV和HaMNPV属于基因型不同的两类病毒,而HaSNPV不同分离株的同源性很高 相似文献
52.
Christian Damgaard 《Environmental and Ecological Statistics》2006,13(2):229-236
A methodology for estimating environmental thresholds of binary presence–absence data is presented where the level of the
threshold is parameterised. Presence–absence data is fitted to three complementary different models: an independent null-model,
a monotonically increasing or decreasing model, and an optimum model. The range of the three models is strictly between zero
and one and the models are therefore well suited for modelling presence probabilities. The results of the three models may
be combined by using Bayesian model selection methodologies. The proposed methodology is exemplified on observed binary presence–absence
data of Bauera rubioides along an elevation gradient.
Received: May 2005 / Revised: July 2005
An erratum to this article is available at. 相似文献
53.
54.
Mario Schirmer John W. Molson Emil O. Frind James F. Barker 《Journal of contaminant hydrology》2000,46(3-4)
Biodegradation of organic contaminants in groundwater is a microscale process which is often observed on scales of 100s of metres or larger. Unfortunately, there are no known equivalent parameters for characterizing the biodegradation process at the macroscale as there are, for example, in the case of hydrodynamic dispersion. Zero- and first-order degradation rates estimated at the laboratory scale by model fitting generally overpredict the rate of biodegradation when applied to the field scale because limited electron acceptor availability and microbial growth are not considered. On the other hand, field-estimated zero- and first-order rates are often not suitable for predicting plume development because they may oversimplify or neglect several key field scale processes, phenomena and characteristics. This study uses the numerical model BIO3D to link the laboratory and field scales by applying laboratory-derived Monod kinetic degradation parameters to simulate a dissolved gasoline field experiment at the Canadian Forces Base (CFB) Borden. All input parameters were derived from independent laboratory and field measurements or taken from the literature a priori to the simulations. The simulated results match the experimental results reasonably well without model calibration. A sensitivity analysis on the most uncertain input parameters showed only a minor influence on the simulation results. Furthermore, it is shown that the flow field, the amount of electron acceptor (oxygen) available, and the Monod kinetic parameters have a significant influence on the simulated results. It is concluded that laboratory-derived Monod kinetic parameters can adequately describe field scale degradation, provided all controlling factors are incorporated in the field scale model. These factors include advective–dispersive transport of multiple contaminants and electron acceptors and large-scale spatial heterogeneities. 相似文献
55.
本文在阐述景观格局指数空间尺度效应重要意义及3S技术特点的基础上,以四川省木里县梭罗沟金矿矿区为研究区,介绍了3S技术在不同空间尺度提取景观格局指数的技术要求、数据收集和工作流程,并对研究区不同空间尺度景观格局指数的提取结果进行了效应分析,将各景观格局指数随空间尺度表现出不同变化趋势划分为五种类型,确定了该研究区域景观格局分析的最适宜空间尺度为1.0 m~5.0 m。景观格局指数空间尺度效应分析研究,有利于揭示景观格局与尺度效应相互作用的机理,进而对景观格局的尺度推演的方向、过程进行模拟、预测、分析和评价等研究提供重要的科学参考,并对遥感数据和地理信息系统的正确使用具有重要的科学意义。 相似文献
56.
Modelling photochemical oxidant formation, transport, deposition and exposure of terrestrial ecosystems 总被引:1,自引:0,他引:1
Fowler D Cape JN Coyle M Smith RI Hjellbrekke AG Simpson D Derwent RG Johnson CE 《Environmental pollution (Barking, Essex : 1987)》1999,100(1-3):43-55
The chemical processes responsible for production of photochemical oxidants within the troposphere have been the subject of laboratory and field study throughout the last three decades. During the same period, models to simulate the atmospheric chemistry, transport and deposition of ozone (O(3)) from individual urban sources and from regions have been developed. The models differ greatly in the complexity of chemical schemes, in the underlying meteorology and in spatial and temporal resolution. Input information from land use, spatial and temporally disaggregated emission inventories and meteorology have all improved considerably in recent years and are not fully implemented in current models. The development of control strategies in both North America and Europe to close the gaps between current exceedances of environmental limits, guide values, critical levels or loads and full compliance with these limits provides the focus for policy makers and the support agencies for the research. The models represent the only method of testing a range of control options in advance of implementation. This paper describes currently applied models of photochemical oxidant production and transport at global and regional scales and their ability to simulate individual episodes as well as photochemical oxidant climatology. The success of current models in quantifying the exposure of terrestrial surfaces and the population to potentially damaging O(3) concentrations (and dose) is examined. The analysis shows the degree to which the underlying processes and their application within the models limit the quality of the model products. 相似文献
57.
Michel Jules Dreyfus-Len 《Ecological modelling》1999,120(2-3)
A model to mimic the search behaviour of fishermen is built with two neural networks to cope with two separate decision-making processes in fishing activities. One neural network deals with decisions to stay or move to new fishing grounds and the other is constructed for the purpose of finding prey within the fishing areas. Some similarities with the behaviour of real fishermen are found: concentrated local search once a prey has been located to increase the probability of remaining near a prey patch and the straightforward movement to other fishing grounds. The artificial fisherman prefers areas near the port when conditions in different fishing grounds are similar or when there is high uncertainty in its world. In the latter case a reluctance to navigate to other areas is observed. The artificial fisherman selects areas with higher concentration of prey, even if they are far from the port of departure, unless a high uncertainty is related to the fishing ground. Connected areas are preferred and followed in orderly fashion if a higher catch is expected. The observed behaviour of the artificial fisherman in uncertain scenarios can be described as a risk-averse attitude. The approach seems appropriate for an individual-based modelling of fishery systems, focusing on the learning and adaptive characteristics of fishermen and on interactions that take place at a fine scale. 相似文献
58.
Uncertainty,complexity and controversy in dolphin threat management: A role for post-normal science?
Managing fishing threats to populations of endemic, threatened Hector’s and Māui dolphins around New Zealand is a complex and controversial issue, underpinned by uncertain scientific knowledge. As such, it can be argued that it falls into the realm of post-normal science, which advocates transparency about uncertainties and stakeholder peer review of knowledge feeding into decision-making. This paper focuses on selected examples of modelling and risk assessment research relating to Hector’s and Māui dolphin threat management. It explores how knowledge is developed, shared and utilised by decision-makers, finding that uncertain scientific knowledge may be shared in ways that make it appear more certain, with some of the subjectivities involved in knowledge production hidden from view. Interviews with stakeholders illustrate how some stakeholders are aware of the subjectivities involved when uncertain knowledge underpins decision-making, so a lack of transparency may be leading to erosion of social trust in decisions made. This in turn can lead to a lack of support for dolphin conservation measures from key stakeholders such as the commercial fishing industry. The paper concludes that while moves towards increasing transparency and stakeholder involvement are apparent, a deeper embrace of post-normal science approaches to knowledge production and dissemination would contribute to effective dolphin threat management in New Zealand. 相似文献
59.
Zhu Dajian 《中国人口.资源与环境(英文版)》2008,6(4):3-8
Circular economy has become one of China's important strategies to realize scientific development and build ecological civilization at present. As in China circular economy was put forward as a new economic pattern, the international community generally holds that this is an innovative move for China's economy to realize leap-forward development and hopes to learn more about the theory, policy and practice relating to China's circular economy. This article introduces and comments on the necessity to develop circular economy in China, implications and characteristics of China's circular economy, and China's main practices and policies to promote it at present. 相似文献
60.
Environmental Control and Limnological Impacts of a Large Recurrent Spring Bloom in Lake Washington,USA 总被引:3,自引:1,他引:2
A series of statistical analyses were used to identify temporal and spatial patterns in the phytoplankton and nutrient dynamics
of Lake Washington, an mesotrophic lake in Washington State (USA). These analyses were based on fortnightly or monthly samples
of water temperature, Secchi transparency, ammonium (NH4), nitrate (NO3), inorganic phosphorus (IP), total nitrogen (TN), total phosphorus (TP), dissolved oxygen (DO), pH and chlorophyll a (chl a) collected during 1995–2000 from 12 stations. Lake Washington has a very consistent and pronounced annual spring diatom bloom
which occurs from March to May. During this bloom, epilimnetic chl a concentrations peak on average at 10 μg/L, which is 3 times higher than chl a concentrations typically seen during summer stratified conditions. The spring bloom on average comprised 62% diatoms, 21%
chlorophytes and 8% cyanobacteria. During summer stratification, diatoms comprised 26% of the phytoplankton community, chlorophytes
37% and cyanobacteria 25%. Cryptophytes comprised approximately 8% of the community throughout the year. Overall, 6 phytoplankton
genera (i.e., Aulacoseira, Fragilaria, Cryptomonas, Asterionella, Stephanodiscus, and Ankistrodesmus) cumulatively accounted for over 50% of the community. These analyses also suggest that the phytoplankton community strongly
influences the seasonality of NO3, IP, DO, pH and water clarity. According to a MANOVA, seasonal fluctuations explained 40% of the total variability for the
major parameters, spatial heterogeneity explained 10% of variability, and the seasonal-spatial interaction explained 10% of
variability. Distinctive patterns were identified between offshore and inshore sampling stations. The results of our analyses
also suggest that spatial variability was substantial, but much smaller than temporal variability. 相似文献