南海红树林内生真菌1356~#代谢产物的研究

从南海红树林内生真菌1356#分离出两种鞘胺醇(A,B)和三种环二肽(C,D,E)?它们的结构通过IR,MS,1D NMR和2D NMR谱推导出来?(3＇E,4E)-1-(-D-吡喃葡萄糖基-3-羟基-2-(2＇-羟基十八碳酰基)氨基-10-甲基-3＇,4,9-十八碳三烯(A)是一种新的鞘胺醇甙?     

Distribution of winter-spring snow over the Tibetan Plateau and its relationship with summer precipitation in Yangtze River

The distribution of winter-spring snow cover over the Tibetan Plateau(TP) and its relationship with summer precipitation in the middle and lower reaches of Yangtze River Valley(MLYRV) during 2003–2013 have been investigated with the moderate-resolution imaging spectrometer(MODIS) Terra data(MOD10A2) and precipitation observations. Results show that snow cover percentage(SCP) remains approximately 20% in winter and spring then tails off to below 5% with warmer temperature and snow melt in summer. The lower and highest percentages present a declining tendency while the middle SCP exhibits an opposite variation. The maximum value appears from the middle of October to March and the minimum emerges from July to August. The annual and winter-spring SCPs present a decreasing tendency. Snow cover is mainly situated in the periphery of the plateau and mountainous regions, and less snow in the interior of the plateau, basin and valley areas in view of snow cover frequency(SCF) over the TP. Whatever annual or winter-spring snow cover, they all have remarkable declining tendency during 2003–2013, and annual snow cover presents a decreasing trend in the interior of the TP and increasing trend in the periphery of the TP. The multi-year averaged eight-day SCP is negatively related to mean precipitation in the MLYRV. Spring SCP is negatively related to summer precipitation while winter SCP is positively related to summer precipitation in most parts of the MLYRV. Hence, the influence of winter snow cover on precipitation is much more significant than that in spring on the basis of correlation analysis. The oscillation of SCF from southeast to northwest over the TP corresponds well to the beginning, development and cessation of the rain belt in eastern China.     

Titan's stratospheric temperature asymmetry: a radiative origin?

During the 1981 Voyager encounter, Titan's stratosphere exhibited a large thermal asymmetry, with high northern latitudes being colder than comparable southern latitudes. Given the short radiative time constant, this asymmetry would not be expected at the season of the Voyager observations (spring equinox), if the infrared and solar opacity sources were distributed symmetrically. We have investigated the radiative budget of Titan's stratosphere, using two selections of Voyager IRIS spectra recorded at symmetric northern and southern latitudes. In the region 0.1-1 mbar, temperatures are 7 K colder at 50 degrees N than at 53 degrees S and the difference reaches approximately 13 K at 5 mbar. On the other hand, the northern region is strongly enriched in nitriles and hydrocarbons, and the haze optical depth derived from the continuum emission between 8 and 15 micrometers is twice as large as in the south. Cooling rate profiles have been computed at the two locations, using the gas and haze abundances derived from the IRIS measurements. We find that, despite lower temperatures, the cooling rate profiles in the pressure range 0.15-5 mbar are 20 to 40% larger in the north than in the south, because of the enhanced concentrations of infrared radiators. Because the northern hemisphere appears darker than the southern one in the Voyager images, enhanced solar heating is also expected to take place at 50 degrees N. Solar heating rate profiles have been calculated, with two different assumptions on the origin of the hemispheric asymmetry. In the most likely case where it results from a variation in the absorbance of the haze material, the heating rates are found to be 12-15% larger at the northern location than at the southern one, a smaller increase than that in the cooling rates. If the lower albedo in the north results from an increase in the particle number density, a 55 to 75% difference is found for the pressure range 0.15-5 mbar, thus larger than that calculated for the cooling rates. Considering the uncertainties in the haze model, dynamical heat transport may significantly contribute to the meridional temperature gradients observed in the stratosphere. On the other hand, the latitudinal variation in gas and haze composition may be sufficient to explain the entire temperature asymmetry observed, without invoking a lag in the thermal response of the atmosphere due to dynamical inertia.     

Contaminant exposure and effects in Baltic ringed and grey seals as assessed by biomarkers

The Baltic Sea ecosystem has suffered from a heavy pollutant load for more than three decades. Persistent organic pollutants (POPs) and heavy metals have been of most concern due to their persistence and toxic properties. Ringed seals (Phoca hispida baltica) and grey seals (Halichoerus grypus) living in the Baltic Sea have been suffering from pathological impairments, including reproductive disturbances, which have resulted in a depressed reproductive capacity. We investigated several biochemical parameters as potential biomarkers for exposure to and effects of the contaminant load in the Baltic seals. Seals from less polluted areas were used as reference material in terms of the pollution load. In both Baltic seal populations, the levels of some biochemical parameters diverged from those in the reference seals, and some of these showed a clear correlation with the individual contaminant load. Of the potential bioindicators, we propose cytochrome P4501A activity and vitamin E levels, in blubber or plasma, as exposure biomarkers for polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT) in both species. The arylhydrocarbon receptor-mediated chemical-activated luciferase gene expression (CALUX) response reflects the whole PCB and DDT burden in ringed seals. Retinyl palmitate (vitamin A) levels showed a negative correlation with the individual POP load, and is proposed as potential effect biomarkers for the depletion of the vitamin A stores. As the nutritional levels of both vitamin A and E have an impact on the vitamin levels in the seals, more information on the dietary vitamin levels is needed before any conclusions can be drawn. As the relationship between biochemical parameters and contaminants varied between the two species, species-specific characteristics has to be considered when monitoring the health status and possible toxic effects of the contaminant load in ringed and grey seals.     

贫岩浆陆缘从裂谷到海底扩张的演化

伊比利亚西部—纽芬兰共轭陆缘大约于１３３Ｍａ前开始经历早白垩世最后的裂谷和海底扩张期。阿尔卑斯特提斯陆缘在晚三叠世／早侏罗世经历了最后的裂谷期 ,形成了利古里亚—皮埃蒙特海 ,该海区海底扩张导致的岩浆活动开始于１６０～１６５Ｍａ之前。伊比利亚西部和阿尔卑斯这两个贫岩浆陆缘的特征是深水带与陆缘平行分布 ,明显表示出了陆缘演化阶段的顺序为 :低角度挤离断层将薄陆壳切割成陆块 ,剥露出陆下的地幔 ,镁铁质熔融物向海洋方向增加最后与洋壳溶为一体。笔者在提出解释这种现象之前 ,先根据两个陆缘区的种种迹象对各个地带分别加…     

作为自组织格局的滩角

对海滩冲流带内的流与泥沙输运的计算机模拟表明，一个将局部流加速与沿岸水面梯度结合的模型足以形成均匀间距的滩角。模拟的滩角特征以及其形成的条件与观测的自然滩角状况吻合良好。模型中的自组织机制与一个巳被接受的孤立波模型不同，在孤立波模型中沿岸孤立波产生规则的淤积模式从而形成滩角。由于这两个模型给出类似的预测，目前所具有的观测数据不足以将它们分开。     

Geographic and temporal variations of sulfate aerosols over the Pacific Ocean

To investigate the life cycle of marine sulfate aerosols, chemicophysical characteristics of marine aerosolswere measured during five cruises in the Pacific Ocean. Dimethyl sulfide concentrations in seawater and in the air were also measured. The geographic variation of sulfate-aerosol concentrations was studied in relation to biogenic and anthropogenic sources,transport with air trajectories, and chemical transformations in the atmosphere. The highest concentrations were found near Asian and American ports, indicating anthropogenic pollution is the major sulfate aerosols source. Higher concentrations were observed in the upwelling regions than in the oligotrophic areas. Along the coastal regions, both mass and number concentrations of sulfate aerosols depended on wind direction and wind speed, and land-breeze and sea-breeze oscillations; no clear diurnal variation was detected. In pelagic areas, along the equator, the concentrations of small sulfate particles showed a maximum in the afternoon and the m     

Mafic Dyke Records of Paleoproterozoic Mantle Plume Activity in the Karelian Craton: U-Pb Baddeleyite/Zircon Geochronology and Sr-Nd Isotopic Data

正Mafic dykes preserved important information on mantle melting regimes in the early Earth history.Despite the fact that a large volume of geochronological data for mafic dykes was recently received,several important issues     

Mafic, Ultramafic and Carbonatitic Dykes in the Southern Siberian Craton with Age of ca 1 Ga: Remnants of a New Large Igneous Province?

正Virtual absence of igneous complexes with ages between1.8 Ga and 0.8 Ga in southern part of the Siberian Craton allowed to Galdkochub et al.(2010)to formulate a hypothesis of long magmatic quiescence.Most reliable