Probing dynamics of a phase transition of two-dimensional nano-domains with STM imaging and manipulation

A reversible, temperature-driven structural surface phase transition of Pb/Si(1 1 1) nano-domains is studied with a variable-temperature scanning tunneling microscope (STM). Finite-size effects of the transition are clearly demonstrated. Most importantly, structural fluctuations in the low-temperature phase can be induced by the direct interaction between the tip atoms and the surface atoms. The structural changes reveal dynamics in the low-temperature phase. Amazingly, the largest size of the domains that can be manipulated decreases with decreasing sample temperature.     

采用真空管太阳能吸附集热器的制冷系统性能分析

为提高吸附集热器的性能，提出了一种真空管太阳能吸附集热器的设计方案，建立了相应的数学模型，对所设计吸附集热器的性能进行了分析，用传热方程对采用此集热器的吸附制冷系统进行了数值模拟计算，得到了吸附床内的温度分布规律，理论分析表明，系统的最高温度和性能均优于一般的吸附制冷系统，研究了一些关键参数变化对系统性能的影响，并在此基础上，提出了一些真空管优化设计的方案，为以后的实用化提供了理论依据。     

人脊髓灰质炎病毒感染诱发Vero细胞凋亡的研究

用人脊髓灰质炎病毒分别感染Ｖｅｒｏ细胞和稳定表达ｐ３５基因的Ｖｅｒｏ３５细胞，经细胞核ＤＡＰＩ染色，细胞ＤＮＡ琼脂糖电泳和ＴＤＴ生物素原位标记等方法证实病毒感染的细胞具有典型的凋亡细胞学特征和生物化学特征．实验结果表明人脊髓灰质炎病毒感染Ｖｅｒｏ细胞诱发的细胞死亡能被昆虫杆状病毒凋亡抑制基因ｐ３５抑制，为ＩＣＥ类蛋白水解酶途径的细胞凋亡．     

Submonolayer Au on Si(111) phase diagram

Based on a review of the current literature, a surface phase diagram is proposed for the submonolayer Au on Si(111) system. Kinetic considerations are reviewed and key surface phase diagram features such as the Θ < 0.4 ML metastable structure and the high temperature to Si(111)-(1 × 1)Au second order phase transition are discussed. Experiments to verify certain portions of the phase diagram are proposed.     

自动显微图像处理系统的研制

为实现病理切片的自动检测研制了一套显微图像处理系统。该系统由三目照相生物显微镜、ＣＣＤ摄像机和带图像处理卡的个人计算机组成。本文介绍显微镜的自动调焦、自动搜索及状态分析判断等系统驱动功能的原理和设计，最后给出该系统临床应用的部分结果     

Synthesis,hole mobility,and photovoltaic properties of two alternating poly[3‐(hex‐1‐enyl)thiophene‐co‐thiophene]s

Two alternating poly[3‐(hex‐1‐enyl)thiophene‐co‐thiophene]s, Pa (with 77% trans‐isomer and 23% cis‐isomer) and Pb (with 100% trans‐isomer), were synthesized by the coupling of 2,5‐dibromo‐3‐hex‐1‐enyl‐thiophene to 2,5‐bis(tributylstannyl)thiophene via a Stille reaction and compared with poly(3‐hexylthiophene‐co‐thiophene) ( P1 ) to study the effect of changing the carbon(α)–carbon(β) single bond into a carbon–carbon double bond on the properties of the polymers. From P1 to Pb and to Pa , the ultraviolet–visible absorption peaks of the polymers were slightly redshifted, and their electrochemical bandgaps decreased by 0.05–0.1 eV. X‐ray diffraction analysis indicated that Pa had a better lamellar structure than Pb . The hole mobilities of the three polymers, determined with the space‐charge‐limited current model, were 5.23 × 10^?6 ( P1 ), 2.34 × 10^?4 ( Pb ), and 7.02 × 10^?4 cm²/V s ( Pa ). The power conversion efficiencies (PCEs) of polymer solar cells based on the three polymers were 0.87 ( P1 ), 1.16 ( Pb ), and 1.70% ( Pa ). The increase in the hole mobility and PCE revealed the important effect of changing the carbon(α)–carbon(β) single bond into a carbon–carbon double bond on the properties of polythiophene derivatives containing 3‐alkylthiophene. The strategy used in this work enlarges the thinking to obtain novel, efficient donor polymers for optoelectronic applications. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 629–638, 2007     

Multiblock copolymers of poly(2,5‐benzophenone) and disulfonated poly(arylene ether sulfone) for proton‐exchange membranes. I. Synthesis and characterization

Nanophase‐separated, hydrophilic–hydrophobic multiblock copolymers are promising proton‐exchange‐membrane materials because of their ability to form various morphological structures that enhance transport. A series of poly(2,5‐benzophenone)‐activated, telechelic aryl fluoride oligomers with different block molecular weights were successfully synthesized by the Ni(0)‐catalyzed coupling of 2,5‐dichlorobenzophenone and the end‐capping agent 4‐chloro‐4′‐fluorobenzophenone. These telechelic oligomers (hydrophobic) were then copolymerized with phenoxide‐terminated, disulfonated poly(arylene ether sulfone)s (hydrophilic) by nucleophilic, aromatic substitution to form hydrophilic–hydrophobic multiblock copolymers. High‐molecular‐weight multiblock copolymers with number‐average block lengths ranging from 3000 to 10,000 g/mol were successfully synthesized. Two separate glass‐transition temperatures were observed via differential scanning calorimetry in the transparent multiblock copolymer films when each block length was longer than 6000 g/mol. Tapping‐mode atomic force microscopy also showed clear nanophase separation between the hydrophilic and hydrophobic domains and the influence of the block length as it increased from 6000 to 10,000 g/mol. Transparent and creasable films were solvent‐cast and exhibited moderate proton conductivity and low water uptake. These copolymers are promising candidates for high‐temperature proton‐exchange membranes in fuel cells, which will be reported separately in part II of this series. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 284–294, 2007     

一种硅原子簇边界处理方法

近年来,用量子化学—原子簇方法研究固体的电子性质,例对固体表面、体内杂质和缺陷、无序体系的电子结构等的研究越来越引起人们的重视。原子簇模型的基本思想是以有限大的原子团模拟无限大的体系。共价固体硅原子簇边界悬挂键的处理,对计算结果影响很大。边界饱和原子的选取,是原子簇方法中一个十分重要的问题。Tong曾用氢原子饱和边界,发现所计算的电子态密度结果中禁带较宽;张开     

Evidence for diffusion-limited kinetics during electromigration-induced step bunching on Si(1 1 1)

We have measured how the initial terrace width l₀ on vicinal Si(1 1 1) surfaces influences the rate of step bunching and the minimum terrace width within a bunch when direct-current heated at 940-1290 °C. A comparison of this data with analytic solutions and numerical simulations of the conventional “sharp-step” model give strong evidence that the kinetic length d is relatively small (d < ∼20 nm) in both temperature regime I (∼850-950 °C) and regime III (∼1200-1300 °C), in which step-down current is required for step bunching. This indicates that surface mass transport is diffusion-limited in both regimes I and III when l₀ > 20 nm, and hence that the adatom attachment- and terrace diffusion-hopping rates are of comparable magnitude. We also observe similar scaling with initial terrace width in temperature regime II (∼1040-1190 °C), in which step-up current is required for bunching, suggesting a similar step bunching mechanism in all three temperature regimes.