Ancient Chinese algorithm: The Ying Buzu Shu (method of surplus and deficiency) vs Newton iteration method

Air exploratory discussion of an ancient Chinese algorithm, the Ying Buzu Shu, in about 2nd century BC, known as the rule of double false position in the West is given. In addition to pointing out that the rule of double false position is actually a translation version of the ancient Chinese algorithm, a comparison with well-known Newton iteration method is also made. If derivative is introduced, the ancient Chinese algorithm reduces to the Newton method. A modification of the ancient Chinese algorithm is also proposed, and some of applications to nonlinear oscillators are illustrated.

Adsorption of His-tagged peptide to Ni, Cu and Au (100) surfaces: Molecular dynamics simulation

Molecular dynamics (MD) simulations are performed to study the interaction of His-tagged peptide with three different metal surfaces in explicit water. The equilibrium properties are analyzed by using pair correlation functions (PCF) to give an insight into the behavior of the peptide adsorption to metal surfaces in water solvent. The intermolecular interactions between peptide residues and the metal surfaces are evaluated. By pulling the peptide away from the peptide in the presence of solvent water, peeling forces are obtained and reveal the binding strength of peptide adsorption on nickel, copper and gold. From the analysis of the dynamics properties of the peptide interaction with the metal surfaces, it is shown that the affinity of peptide to Ni surface is the strongest, while on Cu and An the affinity is a little weaker. In MD simulations including metals, the His-tagged region interacts with the substrate to an extent greater than the other regions. The work presented here reveals various interactions between His-tagged peptide and Ni/Cu/Au surfaces. The interesting affinities and dynamical properties of the peptide are also derived. The results give predictions for the structure of His-tagged peptide adsorbing on three different metal surfaces and show the different affinities between them, which assist the understanding of how peptides behave on metal surfaces and of how designers select amino sequences in molecule devices design. (c) 2007 Elsevier Ltd. All rights reserved.

编写《钱学森手稿》和翻译《Story of Hsue-shen Tsien》解说词的体会

介绍笔者在编写《钱学森手稿》和翻译电视片《Story of Hsue-shen Tsien》英文解说词的体会,包括:1.钱学森在研究工作中所体现的科学精神;2.熟悉专业知识在科技翻译工作中的重要性等。

Molecular Mechanics Simulation of Recognition Identity of tRNA~(His/GUG)

本文选用经过实验验证的碱基序列 ,用简化的方式 ,构建了被水分子和镁离子修饰的核酸序列的分子模型 ,应用分子力学模拟方法对序列进行能量优化 ,对优化后序列的构象参数、成键状况和能量数据等进行了分析。对tRNAHHis GUG的识别特性作了初步的探索 ,得到了和实验结果相近的结论。此外 ,还从能力学的角度讨论了溶剂 -溶质 -溶剂相互作用形成的网状氢键网络对核酸结构稳定性的影响 ,探讨了非Crick_WatsonGU、UU配对的能力学特征并存在于被水分子和镁离子修饰的核酸序列中的GU、UU配对情况。

Room temperature mobility above 2100 cm2/Vs in Al0.3Ga0.7N/AIN/GaN heterostructures grown on sapphire substrates by MOCVD

Al0.3Ga0.7N/AlN/GaN HEMT structures with significantly high mobility have been grown by metalorganic chemical vapor deposition (MOCVD) on sapphire substrates. At room temperature (RT) a Hall mobility of 2104 cm(2)/Vs and a two-dimensional electron gas (2DEG) density of 1.1x10(13) cm(-2) are achieved, corresponding to a sheet resistance of 277.8 Omega/sq. The elimination of V-shaped defects were observed on Al0.3Ga0.7N/AlN/GaN HEMT structures and correlated with the increase of 2DEG mobility. (c) 2006 WILEY-VCH Verlag GmbH & Co KGaA, Weinheim.

Interaction Between Tripeptide Gly-Gly-His and Cu2+ Probed by Microcantilevers

Gly-Gly-His tripeptide modified microcantilever was developed by carbodiimide attachment of the Gly-Gly-His tripeptide onto a 3-mercaptopropionic acid(MPA) modified gold surface. The interaction of peptide with Cu2+ ion was studied. At a relative high concentration of Cu2+, the cantilever bent toward the gold side initially as the N atom of imidazole ring and carboxyl group in different peptide coordinate with Cu2+, which results in a tensile surface stress. And then the reversed deflection of microcantilever was observed, which implies that the peptide-Cu2+ complex are formed with conformation transition. In another case, i.e., at a relative low concentration Of Cu2+, only the process of conformation transition was observed due to the coordination mode can not be formed initially. The influences of pH and salt concentration of the test solution on the performance of the sensor were studied. The results show that the maximum deflection was obtained at pH 7 and the bonding Of Cu2+ to the Gly-Gly-His tripeptide was inhibited due to the formation Of CuClx2-x.

微悬臂梁检测三肽Gly-Gly-His与Cu~(2+)的相互作用过程

将三肽Gly-Gly-His(GGH)共价键合到MPA修饰的微悬臂梁表面,研究了肽与Cu2+的相互作用过程。研究发现,在Cu2+浓度较高时,Cu2+能快速与不同肽链上的羧基和咪唑环配位,并通过连锁反应诱导悬臂梁向镀金面偏转;而后肽链上的氮原子与Cu2+配位,同时构象发生变化,由直链转变成折叠状,进而增加链间的作用力使悬臂梁反向偏转;而Cu2+浓度低时不能实现连锁反应诱导悬臂梁表面快速的形成向内的拉力,直接通过构象变化推动悬臂梁反向偏转。考察了溶液pH值、Cl-浓度对GGH与Cu2+作用的影响,结果表明,在pH7.0的条件下GGH与Cu2+作用导致悬臂梁偏转最大。Cl-的存在会与Cu2+形成CuCl2x?x配合物不易与肽链结合。

Polyimide structure-property relationships - I. Polyimide properties vs dianhydride configuration

X-ray crystal structures of 2,2',3,3'-and 3,3',4,4'-biphenyltetracarboxylic dianhydride (2,2',3,3'- and 3,3',4,4'-BPDA) were determined. The dianhydride isomers have different symmetry caused by difference in two anhydride group positions and the dihedral angles between the two phenyl rings are 62.9 degrees for 2,2',3,3',-BPDA and 0 degrees for 3,3',4,4'-BPDA respectively. The polyimides from 2,2',3,3'-BPDA exhibit enhanced solubility, higher thermal stability, and higher glass transition temperature (T-g) compared with those from 3,3',4,4'-BPDA.

以Cyclo(L-Phe-L-His)催化的芳香氰醇不对称合成

以改进的方法合成了环状二肽(CycloL-Phe-L-His),它在苯甲醛和间苯氧基苯甲醛的不对称氰醇化反应中显示了高活性和高对映选择性。研究了各种反应条件对该催化剂活性和选择性的影响,考察了催化剂的回收使用,旋光稳定性和化学稳定性,探索了催化剂结构与性能间的关系。