Investigations of group IVA transition metal mediated carbon-carbon bond forming reactions

Zirconocene aldehyde and ketone complexes were synthesized in high yield by treatment of zirconocene acyl complexes with trimethylaluminum or diisobutylaluminum hydride. These complexes, which are activated by dialkylaluminum chloride ligands, inserted unsaturated substrates such as alkynes, allenes, ethylene, nitriles, ketenes, aldehydes, ketones, lactones, and acid chlorides with moderate to high conversion. Insertion of aldehyde substrates yielded zirconocene diolate complexes with up to 20:1 (anti:syn) diastereoselectivity. The zirconocene diolates were hydrolyzed to afford unsymmetrical 1,2-diols in 40-80% isolated yield. Unsymmetrical ketones gave similar insertion yields with little or no diastereoselectivity. A high yielding one-pot method was developed that coupled carbonyl substrates with zirconocene aldehyde complexes that were derived from olefins by hydrozirconation and carbonylation. The zirconocene aldehyde complexes also inserted carbon monoxide and gave acyloins in 50% yield after hydrolysis.

The insertion reaction of aryl epoxides with the trimethylphoshine adduct of titanocene methylidene was examined. The resulting oxytitanacyclopentanes were carbonylated and oxidatively cleaved with dioxygen to afford y-lactones in moderate yields. Due to the instability and difficult isolation of titanocene methylidene trimethylphoshine adducts, a one-pot method involving the addition of catalytic amounts of trimethylphosphine to β,β-dimethyltitanacyclobutane was developed. A series of disubstituted aryl epoxides were examined which gave mixtures of diastereomeric insertion products. Based on these results, as well as earlier Hammett studies and labeling experiments, a biradical transition state intermediate is proposed. The method is limited to aryl substituted epoxide substrates with aliphatic examples showing no insertion reactivity.

The third study involved the use of magnesium chloride supported titanium catalysts for the Lewis acid catalyzed silyl group transfer condensation of enol silanes with aldehydes. The reaction resulted in silylated aldol products with as many as 140 catalytic turnovers before catalyst inactivation. Low diastereoselectivities favoring the anti-isomer were consistent with an open transition state involving a titanium atom bound to the catalyst surface. The catalysts were also used for the aldol group transfer polymerization of t-butyldimethylsilyloxy-1-ethene resulting in polymers with molecular weights of 5000-31,000 and molar mass dispersities of 1.5-2.8. Attempts to polymerize methylmethacrylate using GTP proved unsuccessful with these catalysts.

Modifying Bulk Metallic Glasses: Composites and Configurational States

Bulk metallic glasses (BMGs) maybe be considered to share some of the same inherent trade-offs as engineering ceramics. While BMGs typically exhibit high yield strengths, and while some have surprising fracture toughness, they exhibiting little to no tensile ductility, and fail in a brittle manner under uniaxial loading. Speaking broadly, there are two complimentary approaches to improving on these shortcomings: 1) create bulk metallic glass matrix composites (BMGMCs) and 2) improve the properties of a monolithic BMG. The structure of this thesis mirrors this division, with chapters 2-7 focusing on creating and processing amorphous metal matrix composites, and chapter 8 focusing on modifying the properties of a monolithic BGM by altering its configurational state through irradiation.

Avaliação de catalisadores à base de estanho visando à produção de biodiesel

Atualmente, existe um crescente interesse por fontes de energia renováveis e o desenvolvimento de novas tecnologias para a produção de biocombustíveis. O biodiesel é uma fonte alternativa de combustível bastante atrativa em relação ao diesel em decorrência de seus benefícios ambientais. A obtenção de biodiesel é geralmente realizada através de reações de transesterificação de óleos vegetais com álcool de cadeia curta. Entretanto, também se pode produzi-lo através da esterificação de ácidos graxos livres utilizando-se matérias-primas de baixa qualidade como rejeitos industriais, domésticos ou gorduras animais. O estudo de catalisadores que melhorem os resultados destas reações tem importante papel no desenvolvimento da produção de biodiesel. Normalmente, utilizam-se catalisadores básicos como o NaOH, nas reações de transesterificação. No entanto, o uso destes catalisadores causa impactos ambientais, além de promover a reação de saponificação quando a matéria-prima apresenta teores significativos de acidez, reduzindo o rendimento e dificultando a separação de fases. Este trabalho apresenta o estudo de catalisadores ácidos, à base de estanho, com ênfase especial no sulfato de estanho II, voltados para utilização na reação de esterificação de cargas contendo elevados teores em ácidos graxos. Avaliou-se a influência das variáveis: temperatura, concentração do catalisador, tipo de sistema reacional, quantidade de etanol, tipo de álcool, acidez, natureza dos ácidos graxos e temperatura de calcinação. Uma comparação entre os catalisadores, a questão da reutilização do catalisador e das mudanças proporcionadas pelo tratamento térmico ao qual foram submetidos também foram analisadas. Dentre os catalisadores estudados, os de sulfato de estanho mostraram maior atividade catalítica frente à reação estudada, os mais promissores sendo os calcinados até a temperatura de 500C. O principal motivo para os altos rendimentos encontrados foi associado ao comportamento pseudo-homogêneo do SnSO4, que se solubiliza, acidificando o meio reacional durante as reações de esterificação

Estudo de pirólise catalítica de biomassa em escala piloto para melhoramento da qualidade do bio-óleo

A pirólise rápida é um processo para conversão térmica de uma biomassa sólida em altos rendimentos de um produto líquido chamado de bio-óleo. Uma das alternativas para geração de um bio-óleo com menor teor de oxigênio é uso de catalisadores nos reatores de pirólise, ao invés de um inerte, num processo chamado de pirólise catalítica. O objetivo deste trabalho foi testar catalisadores comerciais, um ácido e outro básico, em uma unidade piloto de leito fluidizado circulante. O catalisador ácido utilizado foi o Ecat, proveniente de uma unidade industrial de craqueamento catalítico fluido (FCC), e como catalisador básico foi utilizado uma hidrotalcita. Os resultados foram comparados com testes utilizando um material inerte, no caso uma sílica. Uma unidade piloto de FCC do CENPES foi adaptada para realizar os testes de pirólise catalítica. Após fase de modificação e testes de condicionamento, foi comprovada a viabilidade na utilização da unidade piloto adaptada. Contudo, devido a limitações operacionais, maiores tempos de residência tiveram que ser aplicados no reator, configurando o processo como pirólise intermediária. Foram então realizados testes com os três materiais nas temperaturas de 450C e 550C. Os resultados mostraram que o aumento do tempo de residência dos vapores de pirólise teve um impacto significativo nos rendimentos dos produtos quando comparada com o perfil encontrado na literatura para pirólise rápida, pois devido ao incremento das reações secundárias, produziu maiores rendimentos de coque e água, e menores rendimentos de bio-óleo. O Ecat e a hidrotalcita se apresentaram mais efetivos em termos de desoxigenação. O primeiro apresentou maiores taxas de desoxigenação via desidratação e a hidrotalcita apresentou maior capacidade para descarboxilação. Contudo, o uso de Ecat e hidrotalcita não se mostrou adequado para uso em reatores de pirólise intermediária, pois acentuou ainda mais as reações secundárias, gerando um produto com alto teor de água e baixo teor de compostos orgânicos no bio-óleo, além de produzirem mais coque. À temperatura de 450C estes efeitos foram mais pronunciados. Em termos de caracterização química, a condição de pirólise intermediária apontou para a produção de bio-óleos com perfil fenólico, sendo a sílica o que proporcionou os melhores rendimentos, principalmente a temperatura de 550C, sendo superiores aos encontrados na literatura. Analisando as composições dos bio-óleos sob a ótica da produção de biocombustíveis, nenhum dos materiais testados apresentou rendimentos consideráveis em hidrocarbonetos. De maneira geral, a sílica foi o que proporcionou os melhores resultados em termos de rendimento e qualidade do bio-óleo. Sua menor área superficial e sua característica de inerte se mostraram mais adequados para o processo de pirólise intermediária, onde a contribuição das reações secundárias em fase gasosa é elevada em função do tempo de residência no reator

Investigating carbon materials for use as the electron emission source in a parallel electron-beam lithography system

A microelectronic parallel electron-beam lithography system using an array of field emitting microguns is currently being developed. This paper investigates the suitability of various carbon based materials for the electron source in this device, namely tetrahedrally bonded amorphous carbon (ta-C), nanoclustered carbon and carbon nanotubes. Ta-C was most easily integrated into a gated field emitter structure and various methods, such as plasma and heavy ion irradiation, were used to induce emission sites in the ta-C. However, the creation of such emission sites at desired locations appeared to be difficult/random in nature and thus the material was unsuitable for this application. In contrast, nanoclustered carbon material readily field emits with a high site density but the by-products from the deposition process create integration issues when using the material in a microelectronic gated structure. Carbon nanotubes are currently the most promising candidate for use as the emission source. We have developed a high yield and clean (amorphous carbon by-product free) PECVD process to deposit single free standing nanotubes at desired locations with exceptional uniformity in terms of nanotube height and diameter. Field emission from an array of nanotubes was also obtained. © 2001 Elsevier Science B.V.

高产小麦旗叶和芒细胞结构及其光合性能的研究

小麦旗叶的光合产物是其籽粒碳水化合物的主要来源，因此如何提高旗叶的光合能力从而提高小麦产量一直是小麦研究的热点。但是以往对高产小麦旗叶的研究主要集中在光合功能和生理生化指标等方面，很少涉及其结构与功能的联系，以及对亲本与子代的旗叶进行对比观察。本文以冬小麦亲本小偃54 、8602及其子代小偃81（高产品种）灌浆期的旗叶为材料，应用细胞离析法、组织切片和荧光显微技术等，对旗叶中叶肉细胞形态、叶绿体数目、叶片厚度、维管束数目和面积等进行了比较观察和测定，旨在探讨小麦旗叶结构与其光合效率的关系。研究结果表明，与亲本小偃54、8602相比，子代小偃81的叶片较厚，横切面内中央大维管束的周长与面积较大;高环数叶肉细胞所占比例、叶肉细胞的周长及其平面面积和细胞内叶绿体的数目等均大于亲本。由此可见，通过小麦品种的改良确实能使其旗叶的结构与光合细胞发生了明显的变化，从而为植物细胞结构和功能的密切关系提供了有力的证据;同时也为作物改良育种提供了又一种新的育种目标。 　　小麦非叶器官之一的芒，对其结构与光合特性关系的研究尚不够深入和广泛。本实验以具芒小麦高产耐旱品种京411籽粒不同发育时期的芒及旗叶为材料，对其叶绿体结构、放氧速率和磷酸烯醇式丙酮酸羧化酶(PEPCase EC 4.1.1.31)的活性进行了比较观察和测定。超微结构显示，从抽穗期开始，芒和旗叶中的叶绿体基粒及其垛叠度均有增加，之后由灌浆末期开始，叶绿体的膜系统开始逐渐解体。通过放氧速率的测定表明，在芒和旗叶中，光合速率在前几个时期呈上升趋势，随着器官的衰老逐渐下降，但是，旗叶放氧速率的下降比芒中更早。另外，芒的PEPCase活性在籽粒发育的整个过程中均高于旗叶，其中以籽粒干物质形成末期尤为显著。因此，芒对高产小麦籽粒的形成，特别是在干物质形成的后期起着更为重要的作用。 　　

Mapping the global flow of aluminum: from liquid aluminum to end-use goods.

Demand for aluminum in final products has increased 30-fold since 1950 to 45 million tonnes per year, with forecasts predicting this exceptional growth to continue so that demand will reach 2-3 times today's levels by 2050. Aluminum production uses 3.5% of global electricity and causes 1% of global CO2 emissions, while meeting a 50% cut in emissions by 2050 against growing demand would require at least a 75% reduction in CO2 emissions per tonne of aluminum produced--a challenging prospect. In this paper we trace the global flows of aluminum from liquid metal to final products, revealing for the first time a complete map of the aluminum system and providing a basis for future study of the emissions abatement potential of material efficiency. The resulting Sankey diagram also draws attention to two key issues. First, around half of all liquid aluminum (~39 Mt) produced each year never reaches a final product, and a detailed discussion of these high yield losses shows significant opportunities for improvement. Second, aluminum recycling, which avoids the high energy costs and emissions of electrolysis, requires signification "dilution" (~ 8 Mt) and "cascade" (~ 6 Mt) flows of higher aluminum grades to make up for the shortfall in scrap supply and to obtain the desired alloy mix, increasing the energy required for recycling.

Xenobiotics removal from polluted water by a multifunctional constructed wetland

Removal efficiencies on xenobiotics from polluted water in a twin-shaped constructed wetland consisting of a vertical flow chamber with the crop plant Colocasia esculenta L. Schott and a reverse vertical flow one with Ischaemum aristatum var. glaucum Honda, were assessed by chemical analysis and bioassays. After a four-month period of application, removal efficiencies of the applied pesticides parathion and omethoate were 100%, with no detectable parathion and omethoate in the effluent. For the applied herbicides, the decontamination was less efficient with removal efficiencies of 36% and 0% for 4-chloro-2-methyl-phenoxyacetic acid and dicamba, respectively. As shown by toxicity assay with duckweed Lemna minor L., growth retardation may occur if the water treated for herbicide removal is used in irrigation of sensitive cultivars in agriculture or horticulture. In contrast to I. aristatum var. glaucum Honda, the crop C esculenta L. Schott has a high yield in biomass production as a valuable source of renewable energy. (C) 2002 Elsevier Science Ltd. All rights reserved.

Al2O3 : Cr3+ nanotubes synthesized via homogenization precipitation followed by heat treatment

Cr3+-doped NH4Al(OH)(2)CO3 nanotubes, templated by surfactant assemblies, were successfully synthesized via the homogenization precipitation method, and various crystallographic phase Al2O3:Cr3+ nanotubes were also obtained by postannealing at different temperatures. The characteristic R-1, R-2 doublet line transitions of ruby can be observed in the high crystalline alpha-Al2O3 nanotubes calcined at temperatures higher than 1200 degrees C. The results also indicate that the formation mechanism of the tubular nanostructures should result from the self-rolling action of layered compound NH4Al(OH)(2)CO3 under the assistance of the surfactant soft-template. The convenient synthetic procedure, excellent reproducibility, clean reactions, high yield, and fine quality of products in this work make the present route attractive and significant. Aluminum oxide nanotubes with high specific surface area could be used as fabricating nanosized optical devices doped with different elements and stable catalyst supports of metal clusters.

高产抗旱优质谷子新品种辐谷7号的选育与推广利

利用400Gy 60Co γ射线处理87070谷子品系干种子,选育出辐谷7号新品种。该品种具有株型紧凑、茎秆矮、高产抗旱优质并且适应种植地区广等特点。2002年2月通过陕西省农作物品种审定委员会审定,截止2008年在黄土高原地区累计推广10.8万hm2。

The cost estimate for a novel cheap solar cell

The estimate for the lowest cost of SODL (silicon on defect layer) solar cell is made according to the price standard of present market. The estimate shows that the PV (photovoltaics) energy costs can be reduced from today's 25-30 cents/(kW h) to 7-8 cents/(kW h) which is comparable with the present cost of electricity generated by traditional energy sources such as fossil and petroleum fuels. The PV energy costs could be reduced to a value lower than 7-8 cents(kW h) by developing SODL technology. The SODL solar cell manufacture featuring simple processes is suitable to large scale automated assembly lines with high yield of large area cells. Some new ideas are suggested, favoring the further reduction in the cost of commercial solar cells.

新疆策勒棉花节水与特高产栽培技术

该文通过田间观测研究，查明了绿洲棉花需水耗水规律，建立了高产棉田节水和高效用水技术体系.通过对密植条件下棉花生态适应性的研究，创立了双株双层立体栽培模式和相应配套技术，使皮棉产量达到了3,859.5kg.hm<'-2>，比普通棉田产量翻了一番，也创造了皮棉单产的世界纪录.试验结果表明，普通棉田传统灌溉量高达770.0mm，水分利用效率仅为0.10kg.m<'-3>，而研究得出的普通栽培模式的优化灌溉定额仅为362.3mm，其优化分配方案为播种期90.0mm、苗期51.0mm、蕾期76.5mm、花铃期85.1mm、吐絮期59.6mm，水分利用效率达到0.22kg.m<'-3>.特高产栽培模式的水分利用效率高达0.50kg.m<'-3>.连续三年的高产实践证明，该高产模式不仅具有在不降低皮棉品质的前提下保证高产的先进性，而且还具有良好的可重现性.“双株双层”结构的形成是棉花特高产栽培技术的核心.由选用良种、蹲苗密植、化控塑型、植保防病、配方施肥和节水灌溉等配套技术组成的技术体系是实现棉花特高产的关键.

硫手性有机小分子催化剂的设计、合成及其在不对称亚胺氢转移还原中的应用

过去十多年，世界手性药物市场需求迅速增长，手性制药工业的发展壮大，已经引起了各国政府、学术界，特别是企业界的高度重视。手性药物中含有大量的手性胺单元，因此研究高效构建手性胺结构单元的方法具有重要的意义和实用价值，而亚胺的不对称还原是合成手性胺最便捷的方法。 手性有机小分子路易斯碱催化三氯氢硅不对称还原亚胺是最近几年才发展起来的一类新的亚胺不对称还原方法。尽管在对映选择性和底物适用范围等方面已经获得了突破性的进展，但是，高性能的路易斯碱催化剂仅局限于N-甲酰氨基酸酰胺一种类型，而且其底物适用范围和催化活性仍不够理想。因此，发展新型催化剂很有必要。 手性硫氧化物作为手性诱导剂的应用已经有数十年的时间，广泛应用在不对称合成及天然产物的全合成中。理论上，硫氧结构单元也可以作为路易斯碱，对硅烷类试剂进行活化，而且硫氧键还有碳氧键难以比拟的先天优势，硫原子自带手性特征，在反应过程中，手性中心离反应位点更近，因此，从手性硫氧化合物出发，极有可能开发出新的高效手性路易斯碱催化剂。最近，Kobayashi和Khiar在亚胺的不对称烯丙基化反应中用手性亚砜活化烯丙基三氯硅烷，获得了较好的ee值，但反应中手性亚砜的用量都需要化学计量以上，因此还不能算做真正意义上的催化剂，进一步的文献调研也未见真正意义上的硫手性有机小分子催化剂。 本文首次成功将硫手性亚磺酰胺衍生物应用于催化三氯氢硅对亚胺的不对称还原，在经过对亚磺酰胺衍生物的多次结构优化，开发出了合成容易，催化活性和立体选择性都很优良，并且有着前所未有的底物普适性的新型手性路易斯碱催化剂。 我们首先尝试将商品化的20mol%叔丁基亚磺酰胺和对甲基亚磺酰胺直接用作催化剂催化三氯氢硅对亚胺的不对称还原，尽管仅获得中等的收率和很低的对映选择性，但证明我们的设计思路是可行的。在此基础上，我们以叔丁基亚磺酰胺为原料和基本骨架，设计合成了一系列的亚磺酰胺类催化剂，通过对催化剂的结构改造，发现当催化剂中存在较强酸性的酚羟基时，催化效果得到大幅提高。随着对催化剂的进一步结构优化，我们找到了一个结构简单，催化效果还不错的催化剂，经过反应条件优化以后，催化反应的收率最高能达到98%，对映选择性最高达93%，并且这个催化剂的底物适应范围比之前报道的催化剂都要广泛。针对酚羟基在催化剂中的重要作用，我们进行了仔细的机理研究后发现，在催化反应中，催化剂极有可能是通过双分子机理去活化三氯氢硅从而实现不对称催化的，而酚羟基的作用就是通过分子间氢键促进双分子催化剂与三氯氢硅的络合。受此启发，我们设计了一系列具有双齿结构的催化剂，通过对双齿催化剂的结构优化，最终筛选出了一个结构更加简单，但催化效果更好的双齿催化剂。10mol%该催化剂催化亚胺还原最高获得95%的收率和96%的ee值。这一结果也进一步验证了我们先前对催化剂机理的推测。 随后，我们还尝试将这些催化剂用于二级胺和芳香酮的直接还原胺化反应中，虽然能获得不错的收率，但对映选择性却很差，我们对反应条件进行了仔细的摸索，仍然没有获得突破。但这些实验为进一步研究二级胺和酮的不对称直接还原胺化反应奠定了良好的基础。 In the past decade, the rapid growth of the global chiral drug market and the significant development of the chiral pharmaceutical industry have attracted a great deal of attention from government, academia and enterprises. Chiral amine is an important structural motif of chiral drugs. Therefore, development of methods for the construction of this motif is of great importance. Catalytic enantioselective reduction of imines represents one of the most straightforward and efficient methods for the preparation of chiral amines. The chiral Lewis base organocatalysts promoted asymmetric reduction of imines by HSiCl3 has recently achieved significant advancements. Although big breakthroughs have been made in terms of substrate generality and enantioselectivity, the highly effective catalysts are limited to N-formyl amino acid amides, of which the efficiency and substrate scope remain unsatisfactory. Therefore, development of novel organocatalysts for this transformation is in great demand. Chiral sulfoxides have been well established as efficient and versatile stereocontrollers and have been extensively used in asymmetric synthesis and total synthesis of natural products. The S=O structural motif of sulfoxide could also behave as Lewis base activator for cholorsilane reagents, which, moreover, could be even better than caboxamide considering that the sulfur atom is chiral and thus the chirality center is closer to the reaction center. There exist great potentials that highly effective novel Lewis base organocatalysts could be developed starting from S-chiral sulfoxides. Recently, several S-chiral sulfoxides were reported by Kobayashi and Khiar to be used as Lewis base catalyst to activate allyltrichlorosilanes in asymmetric allylations and good enantioselectivities were obtained. However, these S-chiral sulfoxides were all used at a more than stoichiometric amount and were thus not authentically catalytic. A careful literature survey further revealed that there has been so far no S-chiral organocatalyst available. In this study, we, for the first time, successfully used S-chiral sulfinamides as Lewis base organocatalysts for the asymmetric reduction of ketimines by HSiCl3. After several rounds of structural optimization, we developed the first example of highly effective S-chiral organocatalysts, which promoted the asymmetric reduction of ketimines with trichlorosilane in high yield and excellent enantioselectivity with unprecedented substrate spectrum. In our initial practice, we examined 20mol% of the commercially available (R)-tert-butanesulfinamide and (S)-toluenesulfinamide as the catalyst in the hydrosilylation of ketimine. Although the product was only furnished in moderate yield and low ee, these results demonstrated that our strategy of catalyst design is on the right way. Next, starting from chiral tert-butanesulfinamide, we prepared a series of tert-butanesulfinamide derivatives via simple reductive amination and examined their catalytic efficiencies in the reduction of ketimine. We found that the catalyst bearing a phenolic hydroxyl group exhibited good reactivity and enantioselectivity. On the basis of which, we obtained a structurally simple and highly effective novel organocatalyst, affording the product in 98% yield and 93% ee under optimal reaction conditions. After careful exploration on the role of phenolic hydroxyl group in the catalyst, we speculated that two molecules of the catalyst be involved in the course of reaction, of which the assembly around the silicon center is facilitated by the intermolecular hydrogen bonding through the phenolic hydroxyl groups. Thus, we incorporated two units of sulfonamide into one molecular and prepared a new type of bissulfinamides organocatalysts and examined their catalytic efficiencies in the reduction of ketimine. After optimizing the structure of these catalysts, we finally obtained a novel organocatalyst which has even simpler molecular structure but showed better efficacies, 10mol% of which afforded up to 97% yield and 96% ee under optimal reaction conditions. These results further proved our speculation about the catalytic mechanism. We also examined the newly developed S-chiral organocatalysts in direct asymmetric reductive amination of secondary amines with aromatic ketone. The product was furnished in good yield but in low ee. No better results could be obtained despite our intense opimization efforts. Nevertheless, these experiments laid excellent foundations for eventual success.