手性催化剂脯氨酸在不对称合成中的应用进展

针对脯氨酸作为一种结构简单而且含量丰富的小分子手性催化剂在多种不对称催化反应中表现出的非常好的催化性能,综述了近年来脯氨酸在Aldol反应、Mannich反应、Michael反应及其他不对称合成反应中的应用,展望了脯氨酸的应用前景。     

探讨有机催化的不对称Michael加成反应

在现今的科研领域中,针对有机催化的不对称合成反应是主要的研究热点,不对称Michele加成反应是大量手性合成子以及药物中间体的合成的重要方式。现今已有催化Michale加成反应的有机催化剂主要有脯氨酸及其衍生物、手性咪唑啉酮以及金鸡纳碱衍生物等。文章对多种有机催化剂在催化不对称Michael加成反应中的使用、不对称诱导反应的作用机制、催化剂分子结构、作用反应条件对催化活性以及不对称诱导作用的影响等方面进行了综述,期望为后续研究带来一定的参考。     

新型脯氨酸类催化剂在不对称Aldol反应中的应用

新型脯氨酸类催化剂能够有效的催化不对称Aldol反应,通过文献得知其催化产物具有高产率,高对映选择性的特点。本文综述了四种无论是在制备工艺还是反应条件方面都比较完善的新型脯氨酸类催化剂,并从结构特性和在Aldol反应中实际应用等方面展开介绍。     

有机小分子催化的不对称直接Aldol反应研究新进展

对近些年来L脯氨酸(LProline)等6类有机小分子催化剂催化不对称直接Aldol反应的特点、实用范围及结果作了详细介绍,认为该领域具有广阔的发展前景。     

L-脯氨酸催化的不对称直接Aldol反应

着重介绍了L-脯氨酸催化不对称直接Aldol反应的特点及反应类型,认为L-脯氨酸及其类似物催化的不对称直接Aldol反应不仅具有理论上的研究价值而且具有潜在的工业化前景。     

环氧乙烷水合制备乙二醇非均相催化剂研究进展

乙二醇作为一种重要的石化原材料,主要用于PET行业。目前国内乙二醇的生产仍以石油气路线为主,包含两段工艺,所用催化剂种类繁多。文章介绍了近年来环氧乙烷催化水合非均相催化剂的研究进展情况,并基于现有研究,对各类催化剂的改进方向进行了展望。特别地,针对分子筛催化剂在乙烯环氧化和EO水合反应中优异的催化性能,提出了应用乙烯氧化水合直接制备MEG反应的分子筛催化剂的改进措施。     

高性能双原子层纳米金催化剂

以常态形式存在的金元素是惰性的 ,但呈纳米形态时就会表现出卓越的催化性能。自几年前日本科学家发现纳米金原子簇团负载在二氧化钛(TiO2 )等金属氧化物上会对某些反应表现出较高的催化活性之后 ,科学家们一直对金元素作为CO和丙烯氧化以及其他反应的潜在催化剂进行探索。现在美国TexasA&M大学的科学家们透露了一项研究结果 ,认为具有双原子层结构的纳米金元素是CO催化氧化的关键性因素 ,对于开发具有更高活性的工业应用催化剂具有重要意义。该研究探讨了有关的催化反应机理 ,研究了金属催化剂粒子的薄层和形状、金属氧化态以及与氧化…     

丙烯酸甲酯的合成

可膨胀石墨作为密封材料已广泛应用于各个领域，但将其作为酯化反应催化剂的研究并不多。酯化反应多采用浓硫酸催化，但副反应多，设备腐蚀严重。近年来，人们在寻找对设备腐蚀小的酯化反应催化剂方面进行了大量的研究工作，如阳离子交换树脂、三相相转移、稀土硫酸盐等。对于催化丙烯酸甲酯的合成，可膨胀石墨与其它催化剂相比，具有催化活性高、反应时间短、收率高、且对设备无腐蚀、不污染环境、易分离及再生处理简单等特点。     

一种新型核磁共振成像方法可优化加氢反应工艺

许多工业技术都依赖催化加氢反应过程。能确定催化剂床层中的活性点有助于优化这些反应工艺。当气相反应物料通过一台微型反应器时，采用一种新型的核磁共振（NMR）成像方法就可以使研究者们判断出加氢反应发生的具体位置。这种方法可作为催化剂开发以及微型反应器表征的一种工具。     

氯苯胺催化加氢反应探讨

本文主要探讨分析氯苯胺催化加氢反应,通过采用尿素沉积-沉淀方法制备Pt-Au/TiO2催化剂,观察改性后的Pt-Au/TiO2催化性能、温度对反应的影响及反应时间对Pt-Au/TiO2催化性能的影响。从实验结果中可得知加入少量的Pt会极大的提高Pt-Au/TiO2催化剂的活性,在50℃、1.0MPa氢气条件下反应时间为1h。因此用0.5%Au//TiO20.02作为催化剂,其中最佳反应条件为50℃、1.0MPa氢气及反应1h。     

Asymmetric rivalry between strategic groups: response,speed of response and ex ante vs. ex post competitive interaction in the spanish bank deposit market

The objective of this study is to examine asymmetric rivalry between strategic groups in a given industry. Two research hypotheses argue for the existence of asymmetric rivalry in the sense that strategic groups of small companies have a greater degree of response but a slower speed of response to the actions of strategic groups of large companies, than vice versa. To test this, we use an ex post approach that examines the news releases published on the strategic actions and reactions of firms. A third hypothesis compares ex ante competitive expectations with ex post asymmetric rivalry between strategic groups. To test this, we compare ex post news on actions/reactions with an ex ante approach that estimates conjectural variations. The empirical application carried out on bank deposits in the Spanish market defines strategic groups in terms of size due to the historical and institutional conditions of the industry (deregulatory change). The results obtained show that rivalry patterns between strategic groups in terms of company size can be predicted as asymmetric in the sense that smaller bank strategic groups have a greater degree of response (Stackelberg ‘leader–follower’ competitive interaction), and a slower speed of response to the actions of larger bank strategic groups than is found the other way around. Moreover, ex ante expectations of aggressiveness on the part of larger strategic groups characterize greater ex post reactions from the smaller‐size strategic groups. Therefore, the size distribution of strategic groups is valuable to research on complex industries with deregulation changes. Copyright © 2005 John Wiley & Sons, Ltd.     

Determinants of capital structure of australian trading banks

Using pooled time series/cross section data of Australian trading banks over the 1967–1988 period, this study examines the determinants of bank capital ratios. Little evidence is found to support the tax benefit/bankruptcy cost trade-off, whereas evidence is broadly consistent with the predictions of Myers' pecking order theory in the presence of transactions costs and asymmetric information. Institutional factors, including bank deregulation and type of bank, are also significant determinants of capital management of Australian trading banks.The author is from the University of New South Wales, Kensington, N.S.W. Thanks are due to Neil Esho, Paul Gatward, Warren Hogan, Michael Skully and two anonymous referees for helpful comments on earlier drafts of this paper.     

戴尔：最熟悉的陌生人

只过了5年,戴尔,这家1984年诞生于美国德克萨斯州、靠直销模式卖电脑起家、曾在21世纪初连续4年占据全球PC业头把交椅、目前年收入超过600亿美元的明星企业,几乎已经＂面目全非＂。戴尔用一种典型的戴尔速度,迅速改变了人们对它的惯性认知。戴尔公司的创始人、     

Effects of asymmetric information on airport congestion management mechanisms

We study and compare three different mechanisms for capacity (slot) allocation in a congested airport when airlines have one-dimensional private information: direct allocation of slots, differentiated tolls and slot auctions. With perfect information, direct allocation is a first best policy which can be implemented through Pigouvian taxes or slot auctions; the mechanisms are equivalent in terms of social welfare. With the introduction of asymmetric information this equivalence is lost: direct allocation is always ex-post inefficient and, in some cases, tolls and subsequent quantity delegation is a better alternative social welfare wise. Auctions may be superior or inferior to tolls. We further show that naïve application of Pigouvian tolls is sub-optimal when imperfect information exists.     

环境规制与企业自主创新--基于波特假设的企业竞争优势构建

传统的假设认为,环境规制必然会导致企业的成本增加。本文在Robert模型中引入了技术系数,模型表明环境规制在给一些企业带来直接费用的同时,也会激发一些创新,可以部分或全部地抵消这些费用成本。这暗合了迈克尔.波特的观点——环境规制能使受规制的企业受益。企业内生的技术变化会使波特假设变得可行,而外生的环境政策如果产生与波特假设一致的效果,则该政策不一定最佳。海尔通过自主创新,实现了从遵守标准到制定标准,其产品成功地进入了欧美市场,表明全球经济一体化背景下,发展中国家的企业要应对发达国家实施的技术壁垒,只有通过自主创新,才能实现竞争优势。     

Modelling Mortgage Terminations in Turbulent Times

Techniques used to predict mortgage defaults during a relatively stable period proved less successful during the turbulent financial cycle of the early 1980s. An alternative specification of the relationship between defaults, homeowner equity, and interest-rate movements better captures the effect of interest rates on default probability. Results confirm the powerful effect of equity on mortgage defaults and the strong, but asymmetric, influence of interest rates on both defaults and prepayments. The new specification allows direct measurement of the interest-rate effect on defaults, distinguishing the effect when rates rise or fall.     

The R&D Effectiveness Index: A Metric for Product Development Performance

Measuring the overall success of product development efforts has been frustrating because there is no generally recognized metric to measure effectiveness. The R&D Effectiveness Index is introduced to address this need. It measures effectiveness by comparing the profit from new products to the investment in new product development. The article provides the details for calculating the index along with alternative interpretations. Michael McGrath and Michael Romeri report that this index was validated through a study of 45 electronic systems companies. They found a strong relationship between the R&D Effectiveness Index and other performance factors and believe that the R&D Effectiveness Index can be used to compare performance, measure improvement, and evaluate business units. Its application is illustrated in a case study.