工作用玻璃液体温度计温度修正值的测量不确定度分析

依据JJF1059－1999，利用二等水银湿度计标准装置，分析了工作用玻璃液体温度计温度修正值的测量不确定度。当温度测量点为20℃时，工作用玻璃液体温度计温度修正值的扩展不确定度为0.054℃，当温度测量点为95℃时，工作用玻璃液体温度计温度修正值的扩展不确定度为0.055℃。     

NMR chemical shifts in the low–pH form of a-chymotrypsin. A QM/MM and ONIOM–NMR study

 The relationship between hydrogen bonding and NMR chemical shifts in the catalytic triad of low-pH α-chymotrypsin is investigated by combined use of the effective fragment potential [(2001) J Phys Chem A 105:293] and ONIOM–NMR [(2000) Chem Phys Lett 317:589] methods. Our study shows that while the His57 N^δ1−H bond is stretched by a relatively modest amount (to about 1.060 ?) this lengthening, combined with the polarization due to the molecular environment, is sufficient to explain the experimentally observed chemical shifts of 18.2 ppm. Furthermore, the unusual down-field shift of H^ɛ1 (9.2 ppm) observed experimentally is reproduced and shown to be induced by interactions with the C=O group of Ser214 as previously postulated. The free-energy cost of moving H^δ1 from His57 to Asp102 is predicted to be 5.5 kcal/mol. Received: 26 September 2001 / Accepted: 6 September 2002 / Published online: 21 January 2003 Contribution to the Proceedings of the Symposium on Combined QM/MM Methods at the 222nd National Meeting of the American Chemical Society, 2001 Correspondence to: J. H. Jensen e-mail: jan-jensen@uiowa.edu Acknowledgements. This work was supported by a Research Innovation Award from the Research Corporation and a type G starter grant from the Petroleum Research Fund. The calculations were performed on IBM RS/6000 workstations obtained through a CRIF grant from the NSF (CHE-9974502) and on supercomputers at the National Center for Supercomputer Applications at Urbana-Champaign. The authors are indebted to Visvaldas Kairys for help with the CHARMM program, and to Daniel Quinn for many helpful discussions.     

Concentrated reverse micelles in a random graft block copolymer system: structure and in-situ synthesis of silver nanoparticles

The structure and rheological properties of a poly(dimethylsiloxane)-graft-poly(oxyethylene) copolymer at high concentrations in block-selective solvents were studied by small-angle X-ray scattering (SAXS) and rheometry. Analysis of SAXS data indicates that quasispherical, reverse micellar aggregates (with no ordered packing) are present in concentrated solutions of the copolymer in nonpolar solvents, and that upon addition of water, the size of such aggregates increases due to the solubilization inside the micellar cores. The viscosity of concentrated polymer solutions increases exponentially as water is added, and finally, viscoelastic, gel-like behavior is found in the vicinity of the phase separation limit. It was found that small silver nanoparticles with an average diameter of ≈3 nm can be synthesized inside the copolymer aggregates without the need of a reducing agent; namely, particles embedded in a viscoelastic matrix are obtained. The synthesis seems to follow first-order kinetics. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Palladium salicylaldimine complexes containing boronate esters

Reactions of salicylaldehydes with boronate ester derivatives of aniline have been examined. Addition of these Schiff base ligands to palladium acetate or Na₂PdCl₄ afforded novel boron-containing trans-bis(N-arylsalicylaldiminato) palladium complexes.Condensation of salicylaldehyde (2-HOC₆H₄C(O)H) with H₂NC₆H₄Bpin (pin=1,2-O₂C₂Me₄) afforded the boron-containing Schiff bases, 2-HOC₆H₄C(H)=NC₆H₄Bpin (1–3a). Similar reactivity with 2-hydroxy-5-nitrobenzaldehyde and 2-hydroxy-1-naphthaldehyde gave the corresponding Schiff bases (1-3b) and (1-3c), respectively. Reaction of Schiff bases (2) and (3) with palladium acetate or Na₂PdCl₄ afforded complexes of the type PdL₂ (4,5), where L=deprotonated Schiff base. The molecular structure of the nitro-salicylaldehyde 4-Bpin palladium complex (5b) was characterized by an X-ray diffraction study. All new palladium compounds have been characterized fully and tested for their antifungal activity against Aspergillus niger and Aspergillus flavus.     

PVC/PBD-b-PMMA共混体系相容性的研究

采用ＤＭＡ和ＴＥＭ系统研究了聚丁二烯－聚甲基丙烯酸甲酯的嵌段共聚物（ＰＢＤ－ｂ－ＰＭＭＡ）与聚氯乙烯（ＰＶＣ）共混体系的相容性问题。结果表明：ＰＶＣ／ＰＢＤ－ｂ－ＰＭＭＡ共混体系具有部分相溶性。相容的程度与共混体系的组成、组分聚合物的分子量以及共聚物中ＰＢＤ和ＰＭＭＡ嵌段的比例密切相关。     

云南几次中强地震热红外异常特征对比研究

云南省位于多个地块交界处，构造活动活跃且地震活动频发。利用中国静止气象卫星风云二号系列相当黑体温度TBB数据，应用小波变换和相对傅氏功率谱的时频相对功率谱方法（T-F RPS），提取并分析了云南省2008年至今发生的5.5级以上地震热红外异常信息，且对比分析了特征周期、特征幅值、异常形态、异常演化过程等参数。结果表明：（1）该系列地震热红外异常信息易于用时频相对功率谱方法（T-F RPS）提取识别，且异常特征具有"出现-扩大-减小-消失"的规律；（2）异常特征周期和持续时间也具有一定的规律性；（3）异常沿着断层延展，震中位于异常边缘一侧或者异常区域交汇地带，发震时刻多位于相对功率谱幅值下降阶段；（4）震级与相对功率谱峰值有一定的相关性，震级高，峰值也较高；（5）地震类型与异常面积有一定的相关性，双震型地震异常面积较大。此外，讨论了地震热红外异常与构造活动、气候状况、天气情况和季节等因素的关系。     

共聚高分子混合物的分子热力学模型

以硬球链流体的分子热力学模型为基础 ,引入方阱位能相互作用的贡献 ,建立了共聚高分子混合物的分子热力学模型 .模型中具有物理意义的链节参数 (链节数、链节直径和链节间的相互作用能 )由纯物质的pVT关系拟合得到 ,而用来校正交叉作用能和交叉碰撞直径的可调参数需由液液平衡的实验数据回归得到 .采用了相对简单的处理方法来确定这些可调参数 .对所选共聚高分子混合物的共存曲线、互溶窗和互溶图等相行为的关联结果令人满意 .     

The self-organization properties of <Emphasis Type="Italic">n</Emphasis>-dodecylammonium α-glutamate/<Emphasis Type="Italic">n</Emphasis>-C<Subscript>5</Subscript>H<Subscript>11</Subscript>OH/water system

A biocompatible surfactant-n-dodecylammonium α-glutamate (GDA) with biodegradable and biocompatible properties was synthesized, and the phase behavior and the structural properties of GDA/n-pentanol/water system was studied by small-angle X-ray diffraction, electron spin resonance, and freeze-fracture transmission electron microscopy (FF-TEM). In the ternary phase diagram of GDA/n-pentanol/water system, there exist three isotropic regions—O/W, bicontinuous, and W/O structures, and two anisotropic regions—hexagonal liquid crystal (HEX), and lamellar liquid crystal (LLC) regions. UV irradiation causes the decrease in the interlayer space, d, of lamellar liquid crystal and in the radius, r, of column aggregates of hexagonal liquid crystal, but it has little effect on the structure of O/W and W/O microemulsions.     

Immobilization and direct electrochemistry of cytochrome <Emphasis Type="BoldItalic">c</Emphasis> at a single-walled carbon nanotube-modified electrode

A single-walled carbon nanotube (SWNT)-modified electrode was fabricated and characterized by SEM and ac impedance techniques. The direct electrochemistry of cytochrome c (Cyt c), which was adsorbed on the surface of the SWNT, was studied by cyclic voltammetry. The results from cyclic voltammetry and infrared spectroscopy indicated that Cyt c remained in its original structure and did not undergo structural change after its immobilization on the SWNT. Further results demonstrated that the SWNT had promotional effects on the direct electron transfer of Cyt c and also indicated that the immobilized Cyt c retained its electrocatalytic activity to the reduction of H₂O₂. This modified electrode might be used in development of new biosensors and the biofuel cells.