中性Ⅱ配体稀土有机配合物Sm(η~6(CH_3)_2C_6H_4)(η~2AlCl_4)_3的合成及晶体结构

中性Π配体过渡金属,特别是钛的有机配合物的合成和结构已有较深入的研究。但是含中性Π配体的稀土有机配合物的合成研究刚刚开始。1986年,Cotton等人报道了第一个这种类型的配合物Sm(η~6C_6Me_6)(η~2AlCl_4)_3。研究中性π配体稀土有机配合物的合成、结构及性能,对于揭示f元素的成

η~6-芳烃稀土有机配合物的合成、结构及性能研究——Ⅱ.Sm(η~6-CH_3C_6H_5)(η~2-AlCl_4)_3的合成及晶体结构

在前报中,从对η~6-苯钐配合物Sm(η~6-C_6H_5)(η~2-AlCl_4)_3的晶体结构测定,得到配合物中Sm-C键平均键长为2.92 ,这一结果,与Cotton报道的Sm(η~6-C_6Me_6)(η~6-AICI_4)_3中的Sm-C键平均键长(2.89 )相比,明显地增大了。可见,配体芳烃与相应的稀土有机配合物的结构有着密切的关系。为了进一步了解苯环上甲基取代数目对这类配合物结构的影响规律,我们以甲苯为配体,研究了η~6-甲苯钐有机配合物的合成及晶体结构。

Modeling trophic positions of the alpine meadow ecosystem combining stable carbon and nitrogen isotope ratios

Stable carbon and nitrogen isotope ratios of single tissues or whole bodies were analyzed to establish trophic positions of main consumers living at the alpine meadow ecosystem in the Tibetan Plateau. The results demonstrated that delta C-13 and delta N-15 values of vertebrates showed great variations and ranged from -26.83 to -22.51 parts per thousand and from 2.33 to 8.44 parts per thousand, respectively. Plateau pika, root vole, plateau hare, infants of rodents and hatchlings of passerine bird species had the lowest delta C-13 and delta N-15 values. delta C-13 and delta N-15 values of omnivorous and insectivorous birds and amphibians showed intermediate. Carnivorous species, steppe polecat and Upland buzzard, and omnivorous Robin accentor and White wagtail possessed extremely higher VC and delta N-15 values. Omnivorous birds captured in earlier year had significantly less negative delta C-13 and greater delta N-15 values than those captured later. Based on steady angular enrichment between trophic levels, an "alpha and vector model" combing delta C-13 and delta N-15 values was introduced to reveal trophic positions, the results indicated that Tibetan sheep, Tibetan yak, plateau pika, root vole, plateau hare, infants of small rodents showed the lowest trophic positions (TP 1.81-2.38). While omnivorous and insectivorous birds, their hatchlings and amphibians showed intermediate trophic positions (TP 2.06-2.89), carnivorous species steppe polecat and Upland buzzard, migrant birds possessed extremely higher trophic positions (TP 2.89-3.05). The isotopic investigation of organisms and the introduced "alpha and vector model" successfully demonstrated the same trophic positions and diet prediction of consumers as nitrogen enrichment model at the alpine meadow ecosystem. Besides of this information, the "alpha and vector model" can also be incorporated into multiple isotope signatures to infer trophic relationships. This angular enrichment model has the potential to address basic ecological questions, such as trophic structure, trophic dynamics, and energy flow in other terrestrial ecosystems of properly handled. (C) 2005 Elsevier B.V. All rights reserved.

塔里木盆地奥陶系不整合面岩溶作用特征与油气储层研究

Based on the principle and methods of carbonate sedimentology and reservoir geology, and guided by the theories of carbonate reservoir geology, the palaeokarst of Ordovician carbonate rocks in Tarim Basin has been comprehensively studied with multiple methods from different branches of geology. It is indicated that the features and distribution of palaeokarstification have developed in Ordovician carbonates. The controlling of karstification to Ordovician carbonate reservoirs has been discussed. Regional distribution of carbonate reservoirs controlled by karstification has been predicted within this basin. The main consents and conclusions of the this dissertation is as follows: Nine key indicators to the recognition of palaeokarst are proposed in terms of careful observation upon the well cores, lithological and geochemical analyses, and drilling and logging responses to the karst caves and fractures. The time and environment of cave filling are documented from careful research of lithofacies, mineralogy, and geochemistry of the physical and chemical fillings within karst caves. The caves in Ordovician carbonates were filled in Early Carboniferous in Lunnan area. The muddy filling in upper caves was deposited under subaerial fresh-water setting, while the muddy filling in lower caves was formed in the mixed water body of fresh-water and dominated sea water. Although most chemical fillings are suggested being precipated in the burial diagenetic environment after karstification but mineralogic and geochemical characteristics of some chemical fillings indicates they formed in meteoric environment during the karstification. It is obvious that the palaeokarst has been zoned in vertical profile. It can be divided into four units from top to bottom: surface karst, vadose karst, phreatic and tranquil flow zones. Between two types of limestone karst and dolostone karst are firstly differentiated in Tarim Basin, based on the comparison of features of each karst zone in limestone and dolostone regions. In Tabei area, the lowest depth of karstification is approximately 300 m below the Upper Ordovician unconformity interface, while the bottom depth of karstification in Tazhong area ranges commonly from 300 to 400 m, in rare cases may be up to 750 m below the upper Ordovician unconformity interface. In Lunnan and Tazhong areas, the palaeokarst morphology and the surface hydrosystem are firstly reconstructed based on the top of carboniferous "Shuangfeng limestone bed (Double-Peaks limestone)" as basal. According to the palaeomorphologic feature, karst topography can be divided into three units: karst upland, karst slope, and karst valley. Vadose zone was well developed in karst upland, and it can be found in a quite depth. Both vadose and phreatic zones were well developed in karst slope and upstream valley. In downstream valley, the karstification is not strong, the vadose and phreatic zones are thin in thickness. In Tazhong and Yingmaili areas, karstification is also developed in relict carbonate palaeo-hills which existed as isolated blocks admits clastic strata.

热察绥地区过去300年土地利用覆被变化

The historical land use and land cover changes is one of the key issues in LUCC research. However, the achievement of China in this field doesn't match her position in the world yet. And the reliability of the quantitive records in Chinese historical literature, the basic data for historical land use research, has been doubted. This research focuses on Re-Cha-Sui, a typical area for the farming-pastoral region in the north of China, to make a detailed case study in this field. Based on a deep mining and calibration on the data from massive historical documents and land-use surveys, the author gives a detailed analysis on the administrative region evolution, historical population dynamics, reclamation policy, and the land statistic system. According to textual researches, parallel validation and physical geographical analysis, a unified land use series for recent 300 years, which founded on the results of modern land-use surveys, is constructed. And the thematic maps on the cultivation index for different counties in several temporal sections are plotted. Based on the endeavor above, the dynamic of forest and steppe is reconstructed as well. The temporal-spatial patterns of land use/land cover changes in the area is analyzed. And the influence of different driving forces are discussed. The main conclusions of the research are as followed: 1. The quantitive records in literatures on Re-Cha-Sui area are reflection of real amounts of croplands. It is practical to reconstruct a result comparable with the modern land-use surveys, based of a deep mining and considerate validation on historical documents. The unexceptional negative attitude towards the numerical records in historical documents is unnecessary. 2. In recent 300 years, 3 climax of reclamation appeared in Re-Cha-Sui area and altered the pure pastoral area into a farming-pastoral region. The interval were respectively the early time till mid time of the Qing dynasty, the end of the Qing dynasty till early time of the Republic of China(ROC), and the time after A.D. 1949. After the first expansion, the area of cropland in this region reached 2.0 million ha. Among them, Guisui area, which was most densely cultivated, had a cultivation index over 30%, which is similar with modern situation. The second expansion covered broader area, and the amount of cropland reached 3.5 million ha. The increase of farming area after 1949 is due to the recultivation of abandoned farmland. The current area of cropland in this region is 5.6 million ha. In the southern area where the land was reclaimed early, the amount on of the cropland has some fluctuation in 300 years. While in the new reclaimed area in the north, the area of cropland has kept the trend of increasing. 3. Due to the different natural conditions, most forests in Re-Cha-Sui area distribute in the mountain area of North Hebei province, and the upland of West Liaoning province, especially the former, which has a forest coverage near 70%. However, most of these forests were destroyed before the end of the Qing dynasty. In 1949, the natural forest near Chengde was nearly cleared up. They were partly renewed after 1949 due to plantation. 4. In the steppe zone such as northern Rehe, Suiyuan and Chahar, the area of steppe has a negative correlation with that of cropland. With the expansion of cropland, the percentage of steppe has shrunk from over 80% to 53%. In the mountain area of North Hebei province, steppe expanded with the shrinkage of forest, though cropland was expanding. The percentage once reached 60%, and then fell with the renew of forest. However, in the upland of West Liaoning province, the steppe shrink slowly from original 50% to current 26%, with the expansion of cropland. 5. The land use and land cover change in Re-Cha-Sui area in recent 300 years is driven by various factors, including human dimensions such as population, policy of the government, disorder of the society, cultural tradition, and natural factors such as climate change and natural disasters. Among them, pressure from surplus population is the basic driving force.