Characterization of polyphenol oxidase from plants

Polyphenol oxidase (PPO) which can mediate browning reaction is a bifunctional copper-containing enzyme encoded by plant nucleolus gene. It usually leads to excessive browning reaction which reduces the coercial profits of fruits and vegetables. In this paper, PPO genes and enzymes in plants are characterized systematically, and the latest progress is reviewed. Some clonings of PPOs genes are reported; the specific temporal and spatial expression pattern of PPOs genes is described; the model of the structure of the precursor form of catechol oxidase is introduced; the possible functions of PPOs in defending against pathogen, wounding, surrounding stress and other inducing factors are demonstrated; the induction and activation of latent PPOs in some plants is elucidated; the scheme of browning inhibition by L-cysteine is clarified; the mechanism of suicide inhibition of latent PPO and kinetic synergism are established. Furthermore, the area for future study is also discussed.     

Computer simulation for the precipitation process of Ni75Al7.5V17.5 alloy

The precipitation mechanism of Ni75Al7.5V17.5 alloy above the L12 instability line, between the L12 and D022 instability lines and below the D022 instability line are studied using microscopic phase-field kinetic equation. This paper is aimed at investigating the effect of temperature on precipitation mechanism and morphological evolution of the alloy. Our simulations demonstrate that the precipitation is a mixed mechanism of non-classical nucleation growth and spinodal decomposition above the L12 instability line. It needs certain thermal fluctuations for nucleation and the number of θ phases is small at this temperature. The precipitation mechanism of γ'phase is congruent ordering followed by spinodal decomposition, and θ phase is a mixed mechanism of non-classical nucleation growth and spinodal decomposition between the L12 and D022 instability lines. The mechanism below the D022 instability line is similar to that between the L12 and D022 instability lines. With the decrease of the temperature, ordering and phase separation becomes fast, the dimension of γ'phase becomes small, the shape transforms from equiaxed to block, the dimension of θ phase becomes large and the shape transforms from strip to circle.     

技术风险与对策研究

本文首先分析了技术风险的概念和特点及其发生的内在机制和各种模式 ,并通过探讨如何建立一套有效的技术风险评估体系 ,提出了技术风险的应对措施 ,以有效防范或减少技术风险。     

多回合组合双向拍卖交易机制研究

以组合双向拍卖分析为基础,建立了相关的数学模型,分别对单一回合和多个回合的组合双向拍卖交易机制进行了研究,证明多回合组合双向拍卖能更大地提高社会福利,也为进一步研究组合双向拍卖的市场效率、竞争均衡、竞标策略和计算机的模拟实验等问题提供了基础.     

规避道德风险的信贷风险决策合同模型分析

主要研究信贷市场中风险类型并合与风险类型非并合两种不同情形下道德风险的规避方法及信贷风险决策合同的设计.分析了贷前道德风险企业与贷后道德风险企业两种不同的拖欠还贷的特点,指出了在风险类型并合下,如果不采取激励相容机制,将使银行筛选有害银行利益的贷款合同.但如果银行对企业采取激励相容机制,则将有效抵御来自企业的道德风险.通过引入抵押率的概念来作为衡量道德风险的重要指标.研究结果表明,较大的抵押率使银行抵御道德风险的能力减弱,较小的抵押率使银行抵御道德风险的能力增强.通过模型证明了充足的抵押品能减少道德风险的产生,不充足的抵押品将有可能引发道德风险.     

论福建省中小企业的跨国经营策略与风险防范

跨国经营是我国企业在全球化的世界经济中求得生存和发展的必然选择.随着我国经济实力的不断增强,中小企业走出国门进行国际化经营的实践活动愈趋活跃,但总体来讲我国中小企业的跨国经营尚处于起步阶段.应在中小企业跨国经营理论的基础上,结合福建省中小企业的特点,对本省中小企业跨国经营策略的内容、思路、特色等进行深入研究,以期更好地引导实践.     

回溯推理与经济解释

皮尔士提出的回溯推理是根据事实尝试性地提出理论假说,应用演绎推理从前提推出一些结论,作出预言,然后,根据实验来验证.如果预言得到实验的证实,那么,我们可以在一定程度上接受这一假说,把它转化为理论.回溯推理是一类独立的逻辑推理形式,其特点在于作出最佳解释.最佳解释推理要求具备一致性、简单性、类比性等特点.回溯推理在经济解释和经济学方法论中比归纳和演绎更为适用.     

P2P文件共享系统中Peer的行为评价

以节点的行为评价是信任研究的基础为切入点,在严格遵循纯P2P系统信任机制建立的限制条件的基础上,综合运用表现序列和概率统计中即时估计、总体估计等数学理论知识,最终提出了对P2P共享文件系统中的Peer行为的一套评价预测方法.分析表明,该方法产生的误差在允许范围内.从而,能够为P2P系统准确、广泛、长时间的得到应用提供良好、完备的信任机制.     

世界男子100m跑运动项目发展及趋势分析

运用文献资料法和数理统计法,对当今男子100 m跑优秀运动员形态、最佳成绩年龄和技术特点进行比较,并结合100 m跑项目的技术特点,分析了世界男子100 m跑发展的趋势.研究结果表明100 m跑优秀运动员具有理想的身体形态、超人的专项素质、合理的技术特点和良好的心理素质,这些是创造优异成绩的保证.提高最大速度和速度耐力是未来100 m跑成绩突破的关键.     

Java多线程同步机制平台相关性浅析

Java多线程具有很大的平台相关性，导致了其同步机制的平台相关性。通过试验讨论了Java同步机制在不同平台下的成功实现和实现效率，并分析了这种平台相关性的原因和影响因素，对处理多线程同步机制的Java程序的跨平台性编写和执行具有借鉴意义。