物理学与生物学相融合——让不同风格的学科相互沟通

分子生物学家注重冗长的实验数据,而物理学家则习惯于把复杂的系统归结为可有助于了解其全部意义的几个基本原理中。但把这两个学科结合起来并非一件容易的事——     

Energetic landscape of alpha-lytic protease optimizes longevity through kinetic stability.

During the evolution of proteins the pressure to optimize biological activity is moderated by a need for efficient folding. For most proteins, this is accomplished through spontaneous folding to a thermodynamically stable and active native state. However, in the extracellular bacterial alpha-lytic protease (alphaLP) these two processes have become decoupled. The native state of alphaLP is thermodynamically unstable, and when denatured, requires millennia (t1/2 approximately 1,800 years) to refold. Folding is made possible by an attached folding catalyst, the pro-region, which is degraded on completion of folding, leaving alphaLP trapped in its native state by a large kinetic unfolding barrier (t1/2 approximately 1.2 years). alphaLP faces two very different folding landscapes: one in the presence of the pro-region controlling folding, and one in its absence restricting unfolding. Here we demonstrate that this separation of folding and unfolding pathways has removed constraints placed on the folding of thermodynamically stable proteins, and allowed the evolution of a native state having markedly reduced dynamic fluctuations. This, in turn, has led to a significant extension of the functional lifetime of alphaLP by the optimal suppression of proteolytic sensitivity.     

Observation of conformation-specific pathways in the photodissociation of 1-iodopropane ions.

Many molecules can rotate freely around single bonds and thereby interconvert between different conformations, such as gauche and anti 1,2-disubstituted ethane, a classic example of conformational isomerism. Even though rotation occurs rapidly at room temperature, the product selectivity seen in some reactions has been explained by conformation-dependent reaction mechanisms: if reactant molecules differing only in their conformation are located at different positions on the reaction path, they may undergo different reactions. But a direct verification of this effect is difficult, because the energy barrier separating conformational isomers is so low that under ambient conditions reactants with more than one conformation will be present. But by using temperatures low enough to suppress the interconversion between different conformations, gauche-1-iodopropane ions and anti-1-iodopropane ions have been selectively generated. Here we show that the kinetic energy released during the photodissociation of 1-iodopropane ions depends strongly on the conformation of the ions. Thermodynamic arguments and ab initio calculations indicate that this difference in kinetic energy release results from differences in the reaction mechanism, with gauche-1-iodopropane ions forming 2-propyl ions and anti-1-iodopropane ions forming protonated cyclopropane ions. These findings suggest that the well-known concept of conformation selection forms the basis of a simple scheme for reaction control, thus providing in some cases an attractive alternative for more involved schemes that utilize the phase and pulse shape of laser beams to control chemical reactions.     

在线WOM内容和效果的关系:产品知识和相关的影响

以证明在线口传内容对口传效果的影响及收信者的特性的作用为目的。通过已有的研究,把口传内容划分为商品信息和个人经验,把口传效果划分为口传受用和口传行为。以大学生为对象,对MP3购买活动和相关在线口传活动进行了268个问卷调查,并用SPSS 10.0统计法进行了分析。研究结果表明:第一,口传信息的受用度使商品资讯更高,口传行为使个人体验资讯更为受用。第二,商品资讯和个人体验对口传内容的效果(口传受用,口传行为)决定于收信者的产品知识,即对在线的口传内容和口传信息受用的关系有调节作用,而且,对口传行为的影响也有调节效果。最后,关联度变数如先前所设的口传内容和口传效果的关系,对它们的关系有调节作用。     

Efficient and power-awareness query over sensor networks

Sensor networks consisted of low-cost, low-power, multifunctional miniature sensor devices have played an important role in our daily life. Light and humidity monitoring, seismic and animal activity detection, environment and habitat monitoring are the most common applications. However, due to the limited power supply, ordinary query methods and algorithms can not be applied on sensor networks. Queries over sensor networks should be power-aware to guarantee the maximum power savings. The minimal power consumption by avoiding the expensive communication of the redundant sensor nodes is concentrated on. A lot of work have been done to reduce the participated nodes, but none of them have considered the overlapping minimum bounded rectangle (MBR) of sensors which make them impossible to reach the optimization solution. The proposed OMSI-tree and OMR algorithm can efficiently solve this problem by executing a given query only on the sensors involved. Experiments show that there is an obvious improvement compared with TinyDB and other spatial index, adopting the proposed schema and algorithm.     

Applying Petri-Net-Based Reduction Approach for Verifying the Correctness of Workflow Models

0 IntroductionTobadaseyd’s o nintfhoer mflaotiwonof s ywsotrekmss t hhraovueg hbe tehne doervgealnoipzead-tion rather than based ontasks .Duetothistrend,work-flowand business process technology has been applied tovarious applications such as ERP, groupwares , E-mar-ketplaces , E-business etc . When business processes areapplied to these applications ,business processes are de-fined by process designers and business process instancesare executed by workflowengines or workflow manage-ment sys…     

线性搜索方法的改进

线性搜索是最优化计算中最普遍应用的方法，文中对Ｆｌｅｔｃｈｅｒ线性搜索方法作了改进，它具有减少梯度值计算次数的特点，并用数值结果表明了方法的有效性。