968 resultados para (Ag.) W. Sm.


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利用白钨矿对金属矿床进行了Sm-Nd同位素定年. 研究结果表明, 湘西沃溪Au-Sb-W床中白钨矿的Sm, Nd含量较高, Sm/Nd值较大. 在147Sm/144Nd-143Nd/144Nd图解中, 浸染状白钨矿样品呈良好的线性分布, 其对应的等时线年龄为402±6 Ma, εNd(t)值为−30.7. 该矿两个石英样品的40Ar-39Ar年龄谱均呈“马鞍型”, 样品的最小视年龄、坪年龄和等时线年龄基本一致, 其最小视年龄(420±20和414±19 Ma)与白钨矿的Sm-Nd同位素数据相当吻合. 白钨矿的Sm-Nd年龄和石英Ar-Ar年龄均表明沃溪矿床形成于加里东晚期, 这与湖南雪峰山地区的构造演化和一些金锑钨矿床的同位素年代数据相吻合. 白钨矿的初始εNd值异常低, 远低于湖南元古宇地层的相应值, 成矿流体中的Nd很可能来自下伏的更老的陆壳基底. 对该矿成矿时间的厘定和对其成矿物源的制约为进一步认识其矿床成因奠定了基础.

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Thesis (doctoral)--Universite de Lausanne.

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The investigation of the species composition and ecology of diatoms of modern bottom sediments in water bodies of arctic polygonal tundra in three subregions of North Yakutiya has been carried out. As a result, 161 taxons of diatoms were determined; the determinant role of the depth, conductivity, pH of the water, and geographic latitude in their distribution was confirmed, and two complexes of species with respect to the leading abiotic factors were distinguished. The diatoms of the first complex prefer shallow water bodies of high latitudes with neutral and slightly alkaline water and relatively high conductivity. The second complex is confined to the water bodies of lower latitudes with small conductivity, as well as neutral and slightly acidic water.

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Ice-wedge polygon (IWP) mires in the Arctic and Subarctic are extremely vulnerable to climatic and environmental change. We present the results of a multidisciplinary paleoenvironmental study on IWPs in the northern Yukon, Canada. High-resolution laboratory analyses were carried out on a permafrost core and the overlying seasonally thawed (active) layer, from a low-centered IWP located in a drained lake basin on Herschel Island. In relation to 14 Accelerator Mass Spectrometry (AMS) radiocarbon dates spanning the last 5000 years, we report sedimentary data including grain size distribution and biogeochemical parameters (organic carbon, nitrogen, C/N ratio, d13C), stable water isotopes (d18O, dD), as well as fossil pollen, plant macrofossil and diatom assemblages. Three sediment units (SUs) correspond to the main stages of deposition (1) in a thermokarst lake (SU1: 4950 to 3950 cal yrs BP), (2) during transition from lacustrine to palustrine conditions after lake drainage (SU2: 3950 to 3120 cal yrs BP), and (3) in palustrine conditions in the IWP field that developed after drainage (SU3: 3120 cal yrs BP to AD 2012). The lacustrine phase (pre 3950 cal yrs BP) is characterized by planktonic-benthic and pioneer diatoms species indicating circumneutral waters, and very few plant macrofossils. The pollen record has captured a regional signal of relatively stable vegetation composition and climate for the lacustrine stage of the record until 3950 cal yrs BP. Palustrine conditions with benthic and acidophilic species characterize the peaty shallow-water environments of the low-centered IWP. The transition from lacustrine to palustrine conditions was accompanied by acidification and rapid revegetation of the lake bottom within about 100 years. Since the palustrine phase we consider the pollen record as a local vegetation proxy dominated by the plant communities growing in the IWP. Ice-wedge cracking in water-saturated sediments started immediately after lake drainage at about 3950 cal yrs BP and led to the formation of an IWP mire. Permafrost aggradation through downward closed-system freezing of the lake talik is indicated by the stable water isotope record. The originally submerged IWP center underwent gradual drying during the past 2000 years. This study highlights the sensitivity of permafrost landscapes to climate and environmental change throughout the Holocene.

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元素在矿物中的扩散作用,对其在地质体中的配布有着重要影响,被越来越多的用来解决地球化学动力学方面的问题。稀土元素(REE)能反映重要的地球化学信息,作为地球化学的示踪剂被广泛应用于探讨各类岩石成因和矿床成因。因此,查明REE在矿物中的扩散行为对于地学研究具有重要意义。 前人对元素(如O、Ar等)在不同矿物中扩散行为的理论研究,大多采用的是矿物晶格单独制约扩散速率的模型,由于稀土元素的离子半径各不相同,用此类模型来探讨其在不同矿物中的扩散行为是不合适的。为了寻求获取矿物中稀土元素扩散参数的简捷途径,本博士论文通过对前人关于矿物中REE扩散作用研究的实验结果进行分析归纳,探讨了扩散体系不同因素对扩散行为的控制规律。在此基础上,使用多元统计分析方法建立了预测REE在不同矿物中扩散参数的多变量模型,由此模型计算的1atm、无水环境下REE的扩散参数与实验测定结果在实验误差范围内相当吻合。与前人的模型相比,多变量模型能更全面地反映扩散体系各因素对扩散速率的制约。 此外,为了检验白钨矿Sm-Nd同位素定年方法的可靠性,本论文从不同角度进行了研究: (一) 理论验证 矿物内部的微量元素信息能否有效保存,在很大程度上取决于其扩散速率,因此本文从扩散动力学角度对白钨矿Sm-Nd同位素体系的封闭性进行了探讨。通过理论计算并结合实验模拟验证的方式获得了白钨矿中SmNd的扩散参数,得出在1atm、无水环境下SmNd的扩散方程为: Nd:D=4.00exp(-438kJmol-1/RT)cm2/s SmD=1.85exp(-427kJmol-1/RT)cm2/s 借助这些扩散数据,对白钨矿中Sm-Nd信息受扩散作用的影响程度做了分析。结果表明,在大多数地质环境下,SmNd在白钨矿晶体中的扩散速率很低,同位素体系容易保持封闭不受热力学作用的影响。 (二) 地质验证 以湘西沃溪Au-Sb-W床为研究对象,通过对不同矿体的白钨矿进行Sm-Nd同位素年龄测定,将其结果与其它同位素方法得到的年龄数据以及野外地质关系、区域构造演化等进行了对比。结果表明,沃溪Au-Sb-W床的白钨矿Sm-Nd年龄结果与Ar-Ar年龄是一致的,与野外地质关系及区域构造演化特征等也相当吻合。 通过本论文的工作,得出以下主要成果和认识: (1)首次建立了适合于计算REE在不同矿物中扩散参数的理论模型,为研究矿物中REE的扩散行为提供了可靠的理论方法。 (2)首次获得了白钨矿中Sm-Nd的扩散参数,探讨了白钨矿中REE的扩散性质,并建立了1atm、无水环境下SmNd在此矿物中的扩散方程。 (3)通过扩散动力学研究,得出白钨矿中Sm-Nd同位素体系的封闭性较为理想,为评价Sm-Nd同位素方法是否适合于制约白钨矿的成矿年龄提供了理论依据。 (4)通过不同同位素定年结果的比较以及与野外地质关系、区域构造演化等的对比,得出白钨矿Sm-Nd同位素年龄结果是真实有效的,从矿床学角度为评价该同位素定年方法的可靠性提供了实践证据。

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Knowledge of the elements present in house dusts is important in understanding potential health effects on humans. In this study, dust samples collected from 10 houses in south-east Queensland have been analysed by scanning electron microscopy and X-ray microanalysis to measure the inorganic element compositions and to investigate the form of heavy metals in the dusts. The overall analytical results were then used to discriminate between different localities using chemometric techniques. The relative amounts of elements, particularly of Si, Ca, and Fe, varied between size fractions and between different locations for the same size fraction. By analysing individual small particles, many other constituents were identified including Ti, Cr, Mn, Ni, Cu, Zn, Ba, Ag, W, Au, Hg, Pb, Bi, La and Ce. The heavy metals were mostly concentrated in small particles in the smaller size fractions, which allowed detection by particle analysis, though their average concentrations were very low.

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Fruiting hybrids are reported for the first time between the genera Citrus L. and Citropsis (Engl.) Swing. & M.Kell. Conventional hybridization using the recently described species Citrus wakonai P.I.Forst. & M.W.Sm. and Citropsis gabunensis (Engl.) Swing. & M.Kell. resulted in high rates of fruit set and seed formation. Although seed were only half normal size, over 90% germinated without the need for embryo rescue techniques. Plant losses were high during the first few months but after six months, the 327 surviving hybrids were potted on. These grew vigorously on their own roots and 35 of them flowered within two years of sowing. Plants flowered continuously but all were pollen-sterile and ovaries abscised shortly after petal fall. However, at 25 months, two newly flowering hybrids began setting fruit. The development, identification, morphology, breeding efficiency, and future implications of this unique germplasm are described.

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丁香属隶属于木犀科,分布于东南欧和东亚至喜马拉雅地区,我国是丁香属的现代分布中心。《中国植物志》(61卷,1992)记录了我国野生丁香种类16种;《Flora of China》(15卷,1996)记录了中国原产丁香种类16种,并认为全世界大约有20种。丁香属属下分类等级划分分歧较大,很多种的划分也存在争议。花叶丁香、四川丁香等种类是根据栽培植物描述的,没有指定模式标本,给分类处理带来了一定困难。另外,丁香属很多分类群的性状变异非常复杂,仅根据有限的标本很难做出合理的分类处理。本研究通过广泛查阅文献和标本,同时进行野外居群取样和性状观察,对各类群的性状在居群内和居群间的变异进行统计学分析,判断其分类价值,并运用多变量分析的方法,为各类群的合理划分提供依据。结合性状分析和地理分布等证据,做出分类处理。 作者查阅了国内外16个标本馆的近2000份标本,其中模式标本约70份。对我国12个省市的40余个居群进行了取样和观察,采集标本500余份,涉及了《中国植物志》61卷收录的除了藏南丁香以外的所有类群。通过对9个复合体的40余个性状在居群内和居群间的变异进行统计分析,发现叶片类型、叶柄长度、花序着生类型、花冠大小、花丝长度、花药颜色在不同类群间差异明显,可以用作划分种的依据;叶片形状、叶片毛被、花序轴毛被、花冠管形状等性状在有些复合体内的居群间呈现连续的变异,只能用作种下等级(亚种)的划分;叶片大小、花序轴形状、花药着生在花冠的位置、蒴果是否被皮孔等性状在不同复合体的居群间呈现间断或连续的变异,视不同情况可以用作种间或种下等级的划分依据,或作种内变异处理;而叶脉、花色、花萼齿裂、花冠裂片形状等性状在居群间差异不大,不适合用作分类依据。 在性状分析和多变量分析的基础上,本文将丁香属划分为2组2系12种13亚种,其中短花冠管组有1种3亚种;长花冠管组的顶生花序系有5种5亚种,侧生花序系有6种5亚种,并指定了各组和系的模式种;编制了属下各组、系、种和亚种划分的检索表,对12种13亚种进行了形态描述、标本引证,给出了地理分布图和生境,并提出了分类处理依据。文中对巧玲花、皱叶丁香、红丁香和云南丁香等复合体内的一些分类群进行了归并,做出4个新组合:S. pubescens ‘Meyer’、S. villosa subsp. wolfii、S. yunnanensis subsp. sweginzowii和S. yunnanensis subsp. tomentella,处理了11个新异名(S. fauriei H. Lév.、S. julianae C. K. Schneid.、S. meyeri var. spontanea M. C. Chang、S. pinetorum W. W. Sm.、S. wardii W. W. Sm.、S. oblata var. donaldii R. B. Clark et J. L. Fiala、S. afghanica C. K. Schneid.、S. protolaciniata P. S. Green et M. C. Chang、S. tibetica P. Y. Bai、S. reflexa C. K. Schneid. 、S. wilsonii C. K. Schneid.)。作者指定了3种4亚种(S. reticulata subsp. reticulata、 S. reticulata subsp. amurensis、S. pubescens subsp. microphylla、S. oblata subsp. dilatata的后选模式,并对其它10个名称指定了后选模式。文中还提出了分类处理原则,对我国丁 香属的分布及各地方植物志的记载进行了评述,并对丁香属的分布格局提出了作者的看法。 作者还对13个分类群的16号材料进行了染色体观察,发现除了毛丁香有染色体2n=48外,其它均为2n=46,其中朝阳丁香的染色体数目为首次报道。对小叶巧玲花不同异名(包括小叶蓝丁香、小叶巧玲花与小叶蓝丁香的杂交种)的材料进行染色体观察时,发现它们之间差异很小,进一步佐证了作者将其合并的合理性。另外野生的花叶丁香(华丁香)与栽培的花叶丁香在染色体数目上也无差异,支持了作者认为二者为同物异名的观点。

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Electronic Kαl x-ray isotope shifts have been measured for Sn 116-124, Sm 148-154, W 182-184, W 184-186, and W 182-186 using a curved crystal Cauchois spectrometer. The analysis of the measurements has included the electrostatic volume effect, screening by the transition electron as well as the non-transition electrons, normal and specific mass shifts, dynamical nuclear qudrupole polarization, and a radiative correction effect of the electron magnetic moment in the nuclear charge radii are obtained. Where other experimental data are available, the agreement with the present measurements is satisfactory. Comparisons with several nuclear model predictions yield only partial agreement.

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Signatur des Originals: S 36/G01729

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Signatur des Originals: S 36/G01739

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With: Mašinkář / Jan Nep. Nürnberger. W Praze : Tisk Jar. Pospíšila, 1846 -- Weselý šwec, aneb Proměněné ženy / Jan Nep. Štěpánek. W Praze : Nákl. Wclawa Špinky, 1841.