退化问题中Bland规则的改进

Bland规则是退化问题中避免循环的一种方法，本给出了Bland规则的两种改进形式，并从理论上证明了规则Ⅲ为有限规则，另外，还对一个退化问题给出了相应于不同规则的解法。     

Synthesis of a pericosine analogue with a bicyclo[2.2.2]octene skeleton

A new analogue of the antitumor pericosines possessing a bicyclo[2.2.2]octene skeleton has been synthesized from methyl gallate using oxidative dearomatization and regio- and diastereoselective Diels-Alder reaction as the key steps.     

Aqueous RAFT Synthesis of Low Molecular Weight Anionic Polymers for Determination of Structure/Binding Interactions with Gliadin

Gliadin, a component of gluten and a known epitope, is implicated in celiac disease (CeD) and results in an inflammatory response in CeD patients when consumed. Acrylamide‐based polyelectrolytes are employed as models to determine the effect of molecular weight and pendent group on non‐covalent interaction modes with gliadin in vitro. Poly(sodium 2‐acrylamido‐2‐methylpropane sulfonate) and poly(sodium 3‐methylpropyl‐3‐butanoate) are synthesized via aqueous reversible addition fragmentation chain transfer (aRAFT) polymerization and characterized by gel permeation chromatography‐multiangle laser light scattering. The polymer/gliadin blends are examined via circular dichroism, zeta potential measurements, 8‐anilinonaphthalene‐1‐sulfonic acid fluorescence spectroscopy, and dynamic light scattering. Acrylamide polymers containing strong anionic pendent groups have a profound effect on gliadin secondary structure and solution behavior below the isoelectric point, while polymers containing hydrophobic character only have a minor impact. The polymers have little effect on gliadin secondary structure and solution behavior at the isoelectric point.     

投资项目的期权评价与最优投资规则

本文介绍了不确定环境下的投资项目的期权评价方法和最优投资规则，研究了单期项目和连续投资项目的投资决策问题，探讨了实物期权评价方法与传统的净现值评价方法中最优投资规则的差异，并对影响最优投资规则的差异因素进行了敏感性分析，得出了直观而有实用价值的结论。     

α‐Cyanobenzyl dithioester reversible addition–fragmentation chain‐transfer agents for controlled radical polymerizations

A series of new reversible addition–fragmentation chain transfer (RAFT) agents with cyanobenzyl R groups were synthesized. In comparison with other dithioester RAFT agents, these new RAFT agents were odorless or low‐odor, and this made them much easier to handle. The kinetics of methyl methacrylate radical polymerizations mediated by these RAFT agents were investigated. The polymerizations proceeded in a controlled way, the first‐order kinetics evolved in a linear fashion with time, the molecular weights increased linearly with the conversions, and the polydispersities were very narrow (～1.1). A poly[(methyl methacrylate)‐block‐polystyrene] block copolymer was prepared (number‐average molecular weight = 42,600, polydispersity index = 1.21) from a poly(methyl methacrylate) macro‐RAFT agent. These new RAFT agents also showed excellent control over the radical polymerization of styrenics and acrylates. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1535–1543, 2005     

Υ三胶子碎裂粒子产率的普适质量关系

发现Υ→3g三胶子碎裂的末态强子多重数满足与e⁺e^－→q₀q₀事例相同的普适质量关系,表明胶子、夸克碎裂成强子时有相同的规律性.不需引入任何其它假定,就自然解释了Υ→3g三胶子碎裂末态重子多重数增高的重要特征.     

中、高能电子被SO2分子散射的微分截面、动量转移截面及弹性积分截面

在考虑分子内成键原子间的电子云重叠效应的基础上, 提出了一种能够准确计算“中、高能电子-分子”散射的微分截面、动量转移截面及弹性积分截面的修正势方法. 利用可加性规则、使用Hartree-Fock波函数并采用被这一方法修正过的复光学势, 在100—1000eV内对电子被SO₂分子散射的微分截面、动量转移截面及弹性积分截面进行了计算, 并将计算结果与实验及其他理论结果进行比较. 结果表明, 利用这一修正过的复光学势及可加性规则获得的微分截面比利用未修正的复光学势及可加性规则得到的结果准 关键词： 可加性规则 微分截面 动量转移截面 电子散射     

高电荷态离子引起的富勒烯禹子的碎裂

离子在与富勒烯的相互作用过程中会导致C60分子的激发。处于低激发态的C60^r＋离子通过发射中性C2分子或带电的轻团簇碎片Cn^＋等非对称碎裂方式来耗散激发能，但如果激发能很高，笼形的C60^r＋离子可能会彻底崩溃，而发生多重碎裂。C60^r＋离子的碎裂过程与其电荷态r及分裂势垒密切相关。低电荷态的C60^r＋（r≤3）离子蒸发一个C2分子需要克服10．3eV左右的势垒。随着电荷态的升高，发射带电的Cn^＋会变得越来越容易，并逐渐过渡到多重碎裂过程。另一方面，C60^r＋离子的碎裂机制还与激发方式有关，在直接正碰过程中，将C60分子当作固体薄靶来处理，通过分析不同价态的C60^r＋离子的碎片谱，发现母核的初始电荷态决定碎裂方式，由此获得一个可以表征激发能大小的可观测量——发射电子个数。     

Rings, towers, cages of ZnO

Theoretical electronic structure studies on (ZnO)_n (n= 2–18, 21) have been carried out to show that the transition from an elementary ZnO molecule to the bulk wurtzite ZnO proceeds via hollow rings, towers, and cages. Our first principles electronic structure calculations carried out within a gradient corrected density functional framework show that small Zn_nO_n (n=2–7) clusters form single, highly stable rings. Zn₃O₃ and the symmetric cage Zn₁₂O₁₂ are shown to be particularly stable clusters. Among larger clusters, the most stable are oblong cages, Zn₁₅O₁₅, Zn₁₈O₁₈, and Zn₂₁O₂₁, which are reminiscent of nanotubes.     

Changing the fragmentation pattern of molecules in helium nanodroplets by co-embedding with water

Individual amino acid molecules embedded in helium nanodroplets fragment extensively when the beam is ionized by electron bombardment. However, we find that when glycine and tryptophan are picked up right after, or right before, a small amount of water, the mass spectra become significantly altered. For glycine, the detected ions consist almost entirely of intact protonated amino acids, with or without a few water molecules attached. In other words, the presence of water exerts a striking “buffering” effect on the ionization-induced fragmentation. For tryptophan the effect is weaker but also present. In both cases, the hydroxyl group lost upon ionization overwhelmingly comes from the water partner (in strong contrast to the situation observed when amino acids are picked up by neat water clusters). A complementary experiment involving DCl molecules co-embedded with water shows that in this case Cl and/or DCl invariably leave the droplet upon ionization. The observed patterns may be steered by the analytes' dipole moments or by solvation effects.