A class of Sierpinski carpets with overlaps

Based on a scheme by Lau and Ngai, a sufficient and necessary condition for an IFS of contractive similitudes to satisfy the open set condition is given. A class of Sierpinski carpets with parameters (λ₁,λ₂) is then investigated.     

Bipolar copolymers comprised mesogen‐jacketed polymer containing oxadiazole units and PVK as host materials for electroluminescent devices

Nonconjugated bipolar transport polymers have been developed as host materials for electroluminescent devices by incorporating both electron‐transporting and hole‐transporting functionalities into copolymers. The random copolymer PCt‐nvk3‐7 containing mesogen‐jacketed segment of P‐Ct have been synthesized and characterized. The effect of mesogen‐jacketed segment content of these bipolar copolymers on device performance has been investigated. The results of polymer light‐emitting diodes (PLEDs) show that the jacketed content of copolymers has a significant effect on device performance: lowering charge transport and facilitating the hole‐electron recombination leads to much higher current efficiency. Applying these high triplet random copolymers as host, the maximum current efficiency of 0.70 cd/A and the maximum brightness of 1872.8 cd/m² was achieved for PCt‐nvk3‐7 with an orange‐emitting complex dopant. The results suggest that the bipolar copolymers PCt‐nvks can be good host polymers for electrophosphorescent devices. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7861–7867, 2008     

A new synthesis of alkynyl tellurides promoted by CsOH and 4(A°) MS

The mixture of cesium hydroxide and terminal alkynes in dry DMF in the presence of 4(A°), molecular sieves was stirred for 3.0 h at room temperature under N2, then aryltellurenyl bromide in THF was added, and the reaction mixture was stirred for 2.0 h. Alkynyl tellurides were obtained in about 90% yields by flash chromatography.     

Solvothermal synthesis of CdS nanowires using L-cysteine as sulfur source and their characterization

An effective solvothermal reaction route has been developed for large-scale synthesis of CdS nanowires. L-cysteine was used as both sulfur source and capping reagent. The nanowires obtained were characterized by XRD, SEM, TEM, HRTEM, UV-Vis and PL. On the basis of time-resolved experiments, a possible growth mechanism was proposed. FTIR analysis confirmed the formation of Cd-cysteine complex and peptide during the reaction. The mechanism was further supported by comparative experiments with other sulfur sources. Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users. PACS 81.05.Bx; 81.07.-b; 81.07.BC; 81.07.Vb; 81.10.Dn     

Orthorhombic B2CN crystal synthesized by high pressure and temperature

B_0.54C_0.28N_0.18 precursor powder with turbostratic structure was prepared by using melamine and boric acid. The precursor was transformed into orthorhombic B₂CN under definite high pressure and temperature conditions. The composition of the orthorhombic B₂CN powder is B_0.47C_0.23N_0.30. Its lattice parameters are a=0.4776 nm, b=0.4585 nm and c=0.3629 nm. A strong absorption band from 1088 to 1385 cm⁻¹ of orthorhombic B₂CN was observed by infrared measurement. In the photoluminescence (PL) spectrum of orthorhombic B₂CN powder measured at room temperature, a broad peak corresponding to its band-edge emission centers at 374 nm.     

有机酸在重铬酸钾铅烷发生体系中的作用

研究了铅烷发生体系有机酸的作用。结果显示：在Ｋ２Ｃｒ２Ｏ７－无机酸体系中氧化剂的还原产物Ｃｒ（Ⅲ）对铅烷的发生的抑制是单独使用Ｋ２Ｃｒ２Ｏ７效率不高的原因；体系中加入有机酸的主要作用是掩蔽Ｃｒ（Ⅲ），消除其抑制作用。     

Microscopic explosive boiling induced by a pulsed-laser irradiation

This paper presents an experimental study of microscopic explosive boiling introduced by a pulsed laser. The violent explosive boiling was observed in the liquid film, and the vapor bubbles together with liquid droplets were expelled from the platinum film. It is found that the apparent bubble nucleation temperature is a strong function of the heating rate. The pressure signal appears as continuous oscillation and is intensified as laser power density increases.     

Theoretical study of the performance for short channel carbon nanotube transistors with asymmetric contacts

We have simulated short channel carbon nanotube field-effect transistors with asymmetric source and drain contacts using a coupled mode space approach within the non-equilibrium Green's function framework. The simulated results show that the asymmetric conduction properties under positive and negative drain-to-source voltages are caused by the asymmetric Schottky barriers to carriers at the source and drain contacts. Under negative drain-to-source voltages, hole and electron conduction are dominated by thermionic emission and tunneling through the Schottky barrier, respectively, leading to the different subthreshold behaviors of the hole and electron conduction. With increasing channel length, short channel effects can be suppressed effectively and ON/OFF ratio can be improved.