羊鲍(Haliotis ovina)和耳鲍(H.asinina)MtDNA COⅠ和COⅡ基因片段序列的比较研究     

黎中宝 《海洋与湖沼》2008,39(2):168-173

采用基因测序的方法,对我国海南产的羊鲍和耳鲍两个自然种群的COⅠ和COⅡ基因片段进行了PCR扩增和测序。结果表明,羊鲍和耳鲍COⅠ基因片段的核苷酸序列均为193bp,4种碱基组成非常相似,且其A T的含量也非常相似,分别为45.08%和45.60%。羊鲍和耳鲍COⅠ基因片段的核苷酸序列之间有29bp的差异,其中有8处发生碱基颠换,21处发生碱基转换,差异为15.03%,同源性为84.97%;羊鲍和耳鲍COⅡ基因片段的核苷酸序列均为157bp,羊鲍和耳鲍4种碱基组成差异较大,且其A T的含量也不同,分别为59.24%和55.41%。羊鲍和耳鲍COⅡ基因片段的核苷酸序列之间有19bp的差异,其中3处发生碱基颠换,16处发生碱基转换,达到12.10%的差异,同源性为87.90%。分子变异分析表明羊鲍和耳鲍物种间的变异组成为0.50,变异百分数为100.00,羊鲍和耳鲍物种间的遗传分化显著(FST=1,P<0.001)。  相似文献   

The signatures of voids — I. Numerical model     

Sharon L. Vadas 《Monthly notices of the Royal Astronomical Society》1998,299(1):277-284

In this paper, we describe the ray-tracing code used to calculate the signatures of quasi-linear voids in front of, and on, the last scattering surface. The spherically symmetric, general relativistic, Lagrangian fluid equations are integrated in time along with the geodesic equations. The voids are partially filled and are surrounded by either cold dark matter or interacting fluid with a small amount of pressure. In order to obtain accurate results using smaller arrays, a non-uniform grid is employed.  相似文献   

A comparison of the vegetation response to rainfall in the Sahel and East Africa,using normalized difference vegetation index from NOAA AVHRR   总被引：1，自引：0，他引：1  

Sharon E. Nicholson  Michael L. Davenport  Ada R. Malo 《Climatic change》1990,17(2-3):209-241

This article presents the results of a study of the relationship between rainfall and Normalized Difference Vegetation Index (NDVI) in East Africa and the Sahel. Monthly data for the years 1982 to 1985 have been analyzed. We have evaluated NDVI-rainfall relationships by vegetation type, using the major formations described by White (1983). In the article, a comparison of the differential response of vegetation growth to rainfall in the two study regions is emphasized. The most important conclusions of our research are as follows:

1. The spatial patterns of annually-integrated NDVI closely reflect mean annual rainfall.
2. There is a good relationship between rainfall variations and NDVI on seasonal and interannual time scales for areas where mean annual rainfall ranges from approximately 200 to 1200 mm.
3. In most cases, NDVI is best correlated with the rainfall total for the concurrent plus two antecedent months; the correlation is better in the Sahel than in East Africa.
4. The ratios of NDVI to rainfall are considerably higher in East Africa than in the Sahel.
5. Mean annually-integrated NDVI is linearly related to mean annual rainfall in the Sahel. In East Africa the relationship is approximately log-linear; above some threshold value of rainfall, NDVI values level off and vary minimally with rainfall.

Two possible explanations of this last conclusion are suggested: above this threshold, rainfall is no longer the limiting factor in vegetation growth and/or NDVI is not a good indicator of vegetation growth. The latter is a likely possibility since NDVI directly reflects photosynthetic activity and becomes a poor indicator of biomass (i.e., growth) as high canopy densities are reached. The NDVI-rainfall relationship for East Africa is markedly similar to the relationship between NDVI and Leaf Area Index demonstrated by Sellers (1985) and Asrar et al. (1984).  相似文献   

Remediation of DNAPL source zones with granular iron: laboratory and field tests   总被引：2，自引：0，他引：2  

Wadley SL  Gillham RW  Gui L 《Ground water》2005,43(1):9-18

Degradation of dissolved chlorinated solvents using granular iron is an established in situ technology. This paper reports on investigations into mixing iron and bentonite with contaminated soil for in situ containment and degradation of dense nonaqueous phase liquid source zones. In the laboratory, hypovials containing soil, water, bentonite, iron, and free-phase trichloroethene (TCE) were assembled. Periodic measurement of TCE, chloride, and degradation products showed progressive degradation of TCE to nondetectable levels. Subsequently, a demonstration was conducted at Canadian Forces Base Borden near Alliston, Ontario, Canada, where, in 1991, a portion of the surficial aquifer was isolated and free-phase tetrachloroethene (PCE) was introduced. Using a drill rig equipped with large-diameter mixing blades, three mixed zones were prepared containing 0%, 5%, and 10% granular iron by volume. The bentonite was added to serve as a lubricant to facilitate injection of the iron and to isolate the contaminated zone. Analysis of core samples showed reasonably uniform distributions of iron through the mixed zones. Monitoring over a 13-month period following installation showed, relative to the control, a decline in PCE concentrations to virtually nondetectable values. Reaction rates in the laboratory tests were similar to those reported in the literature, while the rate in the field test was substantially lower. The lower rate may be a consequence of mass transfer limitations under the static conditions of the field test. Results indicate that mixing iron and bentonite into source zones may be an effective means of source-zone remediation, with the particular advantage of being relatively immune to effects of geologic heterogeneity.  相似文献   

The role of shoreland development and commercial cranberry farming in a lake in Wisconsin,USA     

Paul J.?GarrisonEmail author  Sharon A.?Fitzgerald 《Journal of Paleolimnology》2005,33(2):169-188

Musky Bay in Lac Courte Oreilles, Wisconsin, USA, is currently eutrophic. This large, shallow bay of an oligotrophic lake possesses the densest aquatic plant growth and a floating algal mat. Paleoecological reconstructions encompassing the last 130 years, were based on multiproxy analyses of sediment cores from three coring sites, two within the bay and one in the lake itself. These data were compared to historical records of the construction and expansion of two commercial cranberry bogs and shoreline residential homes to identify temporal and causal relations of eutrophication. The proxies investigated included: minor and trace elements; biogenic silica; and the diatom community. Post-depositional diagenesis of organic carbon, nitrogen, and phosphorus in the upper 30 cm of the core obscured records of historical ambient nutrient concentrations in the bay obviating their usefulness for this purpose. In contrast, calcium, magnesium, and potassium concentration profiles appeared to reflect runoff of soil amendments applied to the cranberry bogs and aerial fertilizer spraying over the eastern bog adjacent to Musky Bay. The increase in aluminum content since about 1930 coincided with the historical trend in shoreland development and construction of the original commercial cranberry farm. The biogenic silica profile recorded a steady increase of nutrients to Musky Bay over the last several decades. Stratigraphic changes in the diatom community indicated that nutrient input began to increase in the 1940s and accelerated in the mid-1990s with the onset of a noxious floating algal mat. The diatom community indicates the bay has possessed a significant macrophyte community for at least the last 200 years, but increased nutrient input was manifested by a change in the composition, and an increase in the density of the epiphytic diatom community. Cranberry farming appeared to be the major source of nutrients because the diatom community changes occurred prior to the significant increase in residential housing.  相似文献   

Limited infaunal response to experimental trawling in previously untrawled areas   总被引：2，自引：2，他引：2  

Drabsch  Sharon L.; Tanner  Jason E.; Connell  Sean D. 《ICES Journal of Marine Science》2001,58(6):1261-1271

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Striving for equivalency across the Alberta,British Columbia,Ontario and Québec carbon pricing systems: the Pan-Canadian carbon pricing benchmark     

Sharon Mascher 《Climate Policy》2018,18(8):1012-1027

The Pan-Canadian Framework on Clean Growth and Climate Change is designed to put Canada on track to meet its Paris commitments. A key pillar of the plan is the introduction of a pan-Canadian carbon price by the end of 2018. However, four Canadian provinces, nearly 85% of the Canadian economy and population, have already implemented carbon pricing systems. British Columbia (BC) has a carbon tax. Alberta is transitioning from an output-based allocation system for industrial emitters to a hybrid system combining a carbon levy and refined output-based system. Québec and Ontario have implemented cap-and-trade systems, linked to California. Recognizing these existing systems, rather than impose a single carbon pricing mechanism, the Pan-Canadian Approach to Carbon Pricing gives provinces and territories the flexibility to adopt a carbon tax, a hybrid system, or a cap-and-trade system. To address concerns relating to ‘fairness’ and equivalency of carbon price, a federal carbon pricing benchmark establishes criteria relating to minimum ‘common scope’ and ‘increases in stringency’ that provincial and territorial carbon pricing systems must meet. This article explores the design features of the existing Alberta, BC, Ontario and Québec carbon pricing systems, and considers how the benchmark affects stringency and addresses equivalency of carbon price across these different systems.

Key policy insights

• Canada is taking advantage of its federal structure of government to introduce a minimum pan-Canadian carbon price of $10/tCO₂e in 2018, rising by $10/year to $50/tCO₂e in 2022.

• Rather than imposing a uniform pricing mechanism, the Canadian federal government is recognizing existing subnational carbon pricing mechanisms with very different design features – BC’s carbon tax, Québec and Ontario’s cap-and-trade systems, and Alberta’s hybrid system – to deliver the pan-Canadian carbon price.

• In order to deliver a minimum level of increasing stringency and to address issues of equivalency of carbon price across sub-national jurisdictions, the federal government is in the early stages of implementing a federal carbon-pricing benchmark.

• The lessons learned from the Canadian experience will be relevant to harmonizing carbon pricing systems across both other federal jurisdictions and countries.

  相似文献   

Spatial variations of Pb,As, and Cu in surface snow along the transect from the Zhongshan Station to Dome A,East Antarctica     

Xing Xing Jiang  Shu Gui Hou  Yuan Sheng Li  Hong Xi Pang  Rong Hua  Mayewski Paul  Sneed Sharon  Chun Lei An  HANDley Michael  Ke Liu  Wang Bin Zhang 《寒旱区科学》2018,10(3):219-231

The spatial distributions of lead, arsenic, and copper(Pb, As, and Cu, respectively) in surface snow along the transect from the Zhongshan Station to Dome A, East Antarctica, are presented. The mean concentrations of Pb, As, and Cu are1.04±1.56 pg/g, 0.39±0.08 pg/g, and 11.2±14.4 pg/g, respectively. It is estimated that anthropogenic contributions are dominant for Pb, As, and Cu. Spatially, Pb concentrations show an exponentially decreasing trend from the coast inland, while a moderate decreasing trend is observed for Cu concentrations in the coastal area(below 2,000 m above sea level(a.s.l.)).In the intermediate area(2,000–3,000 m a.s.l.), the concentrations and enrichment factors of all these elements show high variability due to the complicated characteristics of climate and environment. On the inland plateau(above 3,000 m a.s.l.),the high concentrations of As and Pb are induced by high deposition efficiency, the existence of polar stratospheric precipitation, and the different fraction deposition to East Antarctica. The extremely high concentrations with maximum values of9.59 pg/g and 69.9 pg/g for Pb and Cu, respectively, are suggested to result mainly from local human activities at the station. Our results suggest that source, transport pathway, and deposition pattern, rather than distance from the coast or altitude, lead to the spatial distributions of Pb, As, and Cu; and it is further confirmed by spatial variations of the three metals deposited over the whole continent of Antarctica.  相似文献   

A pulse in the delivery of ice-rafted debris at site 704 in the southeast Atlantic during glacial Termination V     

Sharon L. Kanfoush 《Marine Geophysical Researches》2016,37(1):37-48

Termination V, the transition from glacial marine isotope stage 12 to interglacial stage 11–425 ka, is the largest deglaciation of the late Pleistocene and culminated with temperatures potentially warmer than present. Coastal geomorphic and stratigraphic evidence provides estimates of a sea-level high-stand 20 m above present at the time (Hearty et al. in Geology 27(4):375–378, 1999). Such sea-level rise would require disintegration of the Greenland Ice Sheet and West Antarctic Ice Sheet as well as part of the East Antarctic Ice Sheet (Raynaud et al. in Earth’s climate and orbital eccentricity: the marine isotope stage 11 question. Geophysical monograph 137. American Geophysical Union, Washington, 2003). Lithic fragments in deep-sea sediments >150 μm at Site 704 in the South Atlantic Ocean were quantified. A large multipronged peak in concentration of this ice-rafted debris consisting of clear minerals, rose-colored transparent minerals, and ash punctuates glacial Termination V. It coincides with a brief two-pronged 1 ‰ reversal to heavier isotopic values from ~2.4 to ~3.4 ‰ at ~416 ka interpreted to reflect cooling resulting from influx of a large number of icebergs. The peak in ice-rafted debris also coincides with a 1 ‰ decrease in carbon isotopic ratios interrupting the ~2 ‰ increase in carbon isotope values across the entirety of Termination V. This is interpreted to reflect a reduction or shutdown in North Atlantic Deep Water formation and attendant Circumpolar Deep Water upwelling at the site and is also consistent with a shift in storage of carbon and carbonate from the deep sea to continental shelves resulting from a dramatic sea-level high-stand. Consequently, the lithic record at Site 704 lends support for the upper end of sea-level estimates based upon land-based evidence that requires a substantial contribution from the East Antarctic Ice Sheet. However, caution is warranted as differences with lithic records from Site 1089, 1090 and 1094 suggest sea-surface temperatures may have also affected lithic concentration through controls on iceberg trajectories and decay.  相似文献   

Spatial reconstruction of semi-quantitative precipitation fields over Africa during the nineteenth century from documentary evidence and gauge data     

Sharon E. Nicholson  Douglas Klotter  Amin K. Dezfuli 《Quaternary Research》2012,78(1):13-23

The article presents a newly created precipitation data set for the African continent and describes the methodology used in its creation. It is based on a combination of proxy data and rain gauge records. The data set is semi-quantitative, with a “wetness” index of ? 3 to + 3 to describe the quality of the rainy season. It covers the period AD 1801 to 1900 and includes data for 90 geographical regions of the continent. The results underscore a multi-decadal period of aridity early in the nineteenth century.  相似文献