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171.
Occurrence and distribution of vibrios in fishes and shellfishes in coastal waters of Hong Kong 总被引:1,自引:0,他引:1
Xu Huaishu Li Jun Phyllis Brayton Norman Y. S. Woo David Swartz Zhang Shuting Rita R. Colwell 《海洋学报(英文版)》1998,17(4):545-553
INTRODUCTIONTheoccurrenceanddistributionofhalophilicvibriosinthecoastalwatersofHongKonghasbeenrePorted(Chanetal.,l986).Theresultsshowedthatvibrioswerepresentduringthesum-mermonthsinHongKongcoastalwatersatconcentrationsof9oto67ooind./cm3,accountingo.4l%~4o%ofthetotalbacterialPOpulationofthe48isolatesexaminedindetail.Theyob-servedV.Paraheamolyticus,V.harvha,V.vulnfficus,V.camPbelliandV.fiuvialis.Becausemanyofthevibri0species,includingsome0ftheisolatesbyChanetal.(1986)fromHongKongwate… 相似文献
172.
Fertilizers and liming agents are generally used to achieve optimal economic yields. However, several negative effects of long‐term annual fertilization of nitrogen (N) in particular have been observed, such as reduced cation exchange capacity and decreased base saturation, which may stimulate accelerated leaching loss of other nutrients. Equilibrium‐tension lysimeters installed at a depth of 1.4 m were used to evaluate leaching of soil‐solution ionic constituents from a tallgrass prairie restoration and optimally and deficiently N‐fertilized, no‐tillage (NT) and chisel‐plowed (CP) maize (Zea mays L.) agroecosystems on Plano silt loam soil (fine‐silty, mixed, superactive, mesic Typic Argiudoll). This study was conducted in south‐central Wisconsin, USA during a 1‐year period of above‐normal precipitation between January 2000 and January 2001. The loss of soluble constituents added to agroecosystems to maintain adequate soil fertility and pH, such as N, phosphorus, potassium, calcium, and magnesium, was generally numerically smaller from the natural prairie 25 years after conversion from cultivated agriculture than from optimally and deficiently N‐fertilized, NT and CP maize agroecosystems, though the differences were not significant. Tillage and fertilizer N‐rate generally did not significantly affect drainage, ionic concentrations, or their leaching losses in the maize agroecosystems, though all parameters evaluated tended to be numerically smaller in the deficiently than optimally N‐fertilized maize agroecosystems. Nitrate‐N leaching losses were generally significantly positively correlated with leaching losses of K, Ca, Mg, and Na in the maize agroecosystems, but not for the prairie, indicating that nitrate‐N leaching plays a significant role in the concomitant loss of cations to maintain soil‐solution charge balance in N‐fertilized maize agroecosystems in a temperate environment. 相似文献
173.
Given the direction cosines a i ′ = (a 1 i , a 2 i , a 3 i )corresponding to a set of pspherically projected fabric poles, an initial estimate x′ = (x1, x2, x3, x4)for the angular radius x4,and direction cosines of the center of the least-squares small circle which minimizes the sum of the squares of the angular residuals $$r = \sum\limits_p {\left[ {x_4 - \cos ^{ - 1} \left( {a_1^i x_1 + a_2^i x_2 + a_3^i x_3 } \right)} \right]} ^2 $$ can be iteratively improved by taking xj+1 = xj + Δxwhere xj is the value of xat the jth iteration and $$\Delta x = - H_j^{ - 1} \left[ {q_j + x_j \left( {x'_j H_j^{ - 1} x_j } \right)\left( {q_j - x'_j H_j^{ - 1} q_j } \right)} \right],$$ where As an initial approximation for xwe have found it convenient to ignore the fact that the data are constrained to lie on the surface of the reference sphere and to use the parameters of a least-squares plane through the given poles. Generalization of this approach to fitting variously constrained great and small circles is easily made. The relative merits of differently constrained fits to the same data can be tested approximately if it is assumed that the errors in the location of the poles are isotropic and normally distributed. It is thus possible to statistically assess the relative significance of conflicting structural models which predict different geometrical patterns of fabric elements. 相似文献
174.
The Canadian Centre for Climate Modelling and Analysis atmospheric general circulation model (AGCM4) is used to study the
role of shallow convection in the hydrologic and energy cycles of the atmosphere. Sensitivity tests with AGCM4 show a marked
effect of the parameterization of shallow convection in the model. In particular, including the parameterization of shallow
convection produces considerably enhanced vertical mixing and decreased stratiform cloud amounts in the lower subtropical
atmosphere over the oceans. The differences in simulated stratiform cloud amounts are associated with a change in the globally
averaged outgoing shortwave radiative flux at the top of the atmosphere of about 11 W m−2. Additionally, precipitation rates are considerably reduced for stratiform clouds and enhanced for convective clouds in the
subtropics, if the parameterization of shallow convection is included in the model. Additional tests show that the simulated
responses in cloud amounts and precipitation to the treatment of shallow convection are robust. Additional simulations with
modified closures for deep convection and other changes to the treatment of convection in the model still lead to similar
responses of the model results. 相似文献
175.
J.W. Norman 《Journal of Structural Geology》1984,6(6):737-747
Examples are given of circular features over 100 km diameter on the Earth's surface. It is suggested that some of these are the eroded remains of the effects of very large impacts after a brittle crust had developed. Some of the tectonic effects of major impact events are reviewed using experimental evidence and established ground examples, and the resulting geological patterns to be anticipated are described. Such past events may have had a widespread influence on our present geology, and speculative suggestions are made of the types of existing phenomena that could be attributed to this cause in some local cases of such features as regional metamorphism, cratons, island arcs, arcuate ophiolites and greenstone belts, large rotational movements, thermal anomalies, introduction of new materials to our planet, biological and magnetic effects. 相似文献
176.
Urban social vulnerability assessment with physical proxies and spatial metrics derived from air- and spaceborne imagery and GIS data 总被引:2,自引:0,他引:2
Risk management in urban planning is of increasing importance to mitigate the growing amount of damage and the increasing
number of casualties caused by natural disasters. Risk assessment to support management requires knowledge about present and
future hazards, elements at risk and different types of vulnerability. This article deals with the assessment of social vulnerability
(SV). In the past this has frequently been neglected due to lack of data and assessment difficulties. Existing approaches
for SV assessment, primarily based on community-based methods or on census data, have limited efficiency and transferability.
In this article a new method based on contextual analysis of image and GIS data is presented. An approach based on proxy variables
that were derived from high-resolution optical and laser scanning data was applied, in combination with elevation information
and existing hazard data. Object-oriented image analysis was applied for the definition and estimation of those variables,
focusing on SV indicators with physical characteristics. A reference Social Vulnerability Index (SVI) was created from census
data available for the study area on a neighbourhood level and tested for parts of Tegucigalpa, Honduras. For the evaluation
of the proxy-variables, a stepwise regression model to select the best explanatory variables for changes in the SVI was applied.
Eight out of 47 variables explained almost 60% of the variance, whereby the slope position and the proportion of built-up
area in a neighbourhood were found to be the most valuable proxies. This work shows that contextual segmentation-based analysis
of geospatial data can substantially aid in SV assessment and, when combined with field-based information, leads to optimization
in terms of assessment frequency and cost. 相似文献
177.
Michelle A Ramsay Richard P.J Swannell Warren A Shipton Norman C Duke Russell T Hill 《Marine pollution bulletin》2000,41(7-12):413-419
Bioremediation was conducted in the field on a mature Rhizophora stylosa mangrove stand on land to be reclaimed near Fisherman’s Landing Wharf, Gladstone Australia. Gippsland crude oil was added to six large plots (>40 m2) and three plots were left untreated as controls. Bioremediation was used to treat three oiled plots and the remaining three were maintained as oiled only plots. The bioremediation strategy consisted of actively aerating the sediment and adding a slow-release fertilizer in order to promote oil biodegradation by indigenous micro-organisms. Oil addition stimulated the numbers of alkane-degrading bacteria slightly to levels of 104–105/g sediment. Bioremediation of the oiled sediment had a marked effect on the alkane-degrading population, increasing the population size by three orders of magnitude from 105 to 108 cells/g of sediment. An effect of bioremediation on the growth of aromatic-degraders was detected with numbers of aromatic-degraders increasing from 104 to 106 cells/g of sediment. Active aeration and nutrient addition significantly stimulated the growth of hydrocarbon-degraders in oiled mangrove sediment in the field. 相似文献
178.
Steven?J.?SmithEmail author Allison?M.?Thomson Norman?J.?Rosenberg R.?Cesar?Izaurralde Robert?A.?Brown Tom?M.?L.?Wigley 《Climatic change》2005,69(1):7-25
As carbon dioxide and other greenhouse gases accumulate in the atmosphere and contribute to rising global temperatures, it is important to examine how derivative changes in climate may affect natural and managed ecosystems. In this series of papers, we study the impacts of climate change on agriculture, water resources and natural ecosystems in the conterminous United States using twelve scenarios derived from General Circulation Model (GCM) projections to drive biophysical impact models. These scenarios are described in this paper. The scenarios are first put into the context of recent work on climate-change by the IPCC for the 21st century and span two levels of global-mean temperature change and three sets of spatial patterns of change derived from GCM results. In addition, the effect of either the presence or absence of a CO2 fertilization effect on vegetation is examined by using two levels of atmospheric CO2 concentration as a proxy variable. Results from three GCM experiments were used to produce different regional patterns of climate change. The three regional patterns for the conterminous United States range from: an increase in temperature above the global-mean level along with a significant decline in precipitation; temperature increases in line with the global-mean with an average increase in precipitation; and, with a sulfate aerosol effect added to in the same model, temperature increases that are lower than the global-mean. The resulting set of scenarios span a wide range of potential climate changes and allows examination of the relative importance of global-mean temperature change, regional climate patterns, aerosol cooling, and CO2 fertilization effects. 相似文献
179.
Esther C. Peters Philip A. Meyers Paul P. Yevich Norman J. Blake 《Marine pollution bulletin》1981,12(10):333-339
Colonies of the shallow-water Caribbean coral Manicina areolata incorporated petroleum hydrocarbons into their tissues during exposure to water accommodated fractions of No. 2 fuel oil for three months. This contamination was not removed after depuration periods of up to two weeks. Although these corals remained alive, evidence of pathological responses was found which included impaired development of reproductive tissues, degeneration and loss of symbiotic zooxanthellae, and atrophy of mucous secretory cells and muscle bundles. 相似文献
180.
Norman J. Hyne 《Environmental Geology》1978,2(5):279-287
The bottom sediments of two reservoirs, one with significant river sediment input and one without, were analyzed for organic
matter content. Lake Texoma sediments average 1.0% organic carbon, of which 0.26% organic carbon is deposited by the river
sediments of the Red and Washita River deltas. In Fort Gibson reservoir, where there is minimal river sediment input, the
organic carbon averages 1.2% and is deposited with a strong correlation to water depth (+0.9). There is a significant difference
between the C/N ratio of Lake Texoma sediments (11.5) and Fort Gibson sediments (9.6). The higher C/N ratio is suggested to
be a result of the larger input of terrestrial plant debris (with a high original C/N ratio) by the rivers draining into Lake
Texoma and the relatively high resistance of the lignin material in the plant debris to decomposition in the reservoir sediments. 相似文献