Fluorescence Study of Chiral β‐Ketoiminate‐Based Newly Synthesized Boron Hybrid Polymers

Two novel chiral β‐ketoiminate‐based boron hybrid polymers, P‐1 and P‐2, are synthesized from a chiral β‐ketoiminate‐based boron hybrid complex ( M‐1 ), with 1,4‐dioctyl‐2,5‐diethynyl­benzene ( M‐2 ) and 3,6‐diethynyl‐9‐octyl‐9H‐carbazole ( M‐3 ), respectively, via a Pd‐catalyzed Sonogashira coupling reaction. The resulting polymers P‐1 and P‐2 show strong fluorescence emission centered at 525 nm and 534 nm with large Stokes’ shifts and high quantum yields. Most importantly, compared with the circularly polarized luminescence (CPL) dissymmetry factor (g_lum = +0.042) of chiral small model molecules, P‐1 and P‐2 can exhibit a large g_lum as high as +0.105 and +0.349 in CH₂Cl₂ solution, which can be attributed to the amplification effect of CPL arising from the conjugated polymer structure.

     

Simultaneously Enhanced Thermal Conductivity and Breakdown Performance of Micro/Nano-BN Co-Doped Epoxy Composites

Micro/nano- BN co-doped epoxy composites were prepared and their thermal conductivity, breakdown strength at power frequency and voltage endurance time under high frequency bipolar square wave voltage were investigated. The thermal conductivity and breakdown performance were enhanced simultaneously in the composite with a loading concentration of 20 wt% BN at a micro/nano proportion of 95/5. The breakdown strength of 132 kV/mm at power frequency, the thermal conductivity of 0.81 W·m⁻¹·K⁻¹ and voltage endurance time of 166 s were obtained in the composites, which were approximately 28%, 286% and 349% higher than that of pristine epoxy resin. It is proposed that thermal conductive pathways are mainly constructed by micro-BN, leading to improved thermal conductivity and voltage endurance time. A model was introduced to illustrate the enhancement of the breakdown strength. The epoxy composites with high thermal conductivity and excellent breakdown performance could be feasible for insulating materials in high-frequency devices.     

饮水硼对大鼠肾上腺组织结构的影响

目的研究饮水添加不同水平硼对大鼠肾上腺的平均质量、器官指数及微细结构的影响。方法选用192只(28±2)天清洁级SD大鼠,分为对照组和40、80、160、320和640mg/L硼染毒组,每组32只,雌雄各半,染毒组饮水添加硼酸,对照组饮用蒸馏水,试验期60天。分别于试验的第30天和60天每组随机取鼠16只,雌雄各8只,解剖取肾上腺称重并取材,石蜡切片,HE染色及嗜铬细胞特染,显微观察与摄影。结果试验30天各染毒组雄鼠的肾上腺平均质量均显著或极显著低于对照组(P<0.05或P<0.01);试验60天640mg/L染毒组雄鼠的肾上腺器官指数显著高于对照组(P<0.05)。40mg/L染毒组肾上腺组织结构较对照组有明显改善,髓质细胞内嗜铬颗粒明显增多;80～640mg/L染毒组肾上腺可见不同程度病理组织学变化,病变程度随硼添加量增大而趋于严重;比较观察发现,肾上腺髓质细胞的损伤先于皮质出现,雄鼠的病变较雌鼠明显。结论饮水添加硼40mg/L对大鼠肾上腺的组织结构有较明显改善作用;添加80～640mg/L硼对肾上腺组织结构则有不同程度损伤,甚至有明显毒性作用。     

无石棉摩阻材料的研究——Ⅰ.玻璃纤维增强摩阻材料

本文选用热分解温度为461℃,700℃时残留物为63%的硼改性酚醛(P树脂)与丁腈橡胶共混后作为基体,以玻璃纤维作增强剂。对该体系制成的摩阻材料进行了配方、制备工艺及复合机理等较系统的研究。结果表明,在33%基体含量中,丁腈橡胶占4～7%时具有良好的增韧性及其它综合性能。含21%玻璃纤维的无石棉摩阻材料离合器片,其性能已符合国家标准,可以进行扩大生产。     

Effect of Boron Doping on the Interlayer Spacing of Graphite

Boron-doped graphite was prepared by the heat treatment of coke using B₄C powder as a graphitization catalyst to investigate the effects of the substitutional boron atoms on the interlayer spacing of graphite. Boron atoms can be successfully incorporated into the lattice of graphite by heat treatment, resulting in a reduction in the interlayer spacing of graphite to a value close to that of ideal graphite (0.3354 nm). With an increase in the catalyst mass ratio, the content of substituted boron in the samples increased significantly, causing a decrease in the interlayer spacing of the boron-doped graphite. Density functional theory calculations suggested that the effects of the substitutional boron atoms on the interlayer spacing of the graphite may be attributed to the transfer of Π electrons between layers, the increase in the electrostatic surface potential of the carbon layer due to the electron-deficient nature of boron atoms, and Poisson contraction along the c-axis.     

Effect of h-BN Support on Photoluminescence of ZnO Nanoparticles: Experimental and Theoretical Insight

Herein we report a simple and easily scalable method for fabricating ZnO/h-BN composites with tunable photoluminescence (PL) characteristics. The h-BN support significantly enhances the ultraviolet (UV) emission of ZnO nanoparticles (NPs), which is explained by the ZnO/h-BN interaction and the change in the electronic structure of the ZnO surface. When h-BN NPs are replaced with h-BN microparticles, the PL in the UV region increases, which is accompanied by a decrease in visible light emission. The dependence of the PL properties of ZnO NPs on the thickness of h-BN carriers, observed for the first time, is explained by a change in the dielectric constant of the support. A quantum chemical analysis of the influence of the h-BN thickness on the electron density redistribution at the wZnO/h-BN interface and on the optical properties of the wZnO/h-BN composites was carried out. Density functional theory (DFT) calculations show the appearance of hybridization at the h-BN/wZnO interface and an increase in the intensity of absorption peaks with an increase in the number of h-BN layers. The obtained results open new possibilities for controlling the properties of ZnO/h-BN heterostructures for various optical applications.     

Dry Sliding Wear Studies on Sillimanite and B4C Reinforced Aluminium Hybrid Composites Fabricated by Vacuum Assisted Stir Casting Process

This paper presents the results of studies to understand the influence of hybridisation on mechanical and tribological behaviour as well as dry sliding wear of aluminium metal matrix composites. Sillimanite and boron carbide (B₄C) were used as primary and secondary reinforcements and pure aluminium was used as the matrix material. The composite was fabricated by using a vacuum assisted stir casting process. Different research instruments were used, including a scanning electron microscope with EDX spectrometer, a surface measurement device, a thermal image analyser, as well as a tribotester. The results show that tensile, impact strength and hardness of the hybridised composites are superior (a step ahead) than unreinforced and primary composites. The wear behaviour of the fabricated specimens was tested for the dry sliding wear behaviour under the load range of 10–50 N with the steps of 20 N for the sliding velocities 0.75, 1.5 and 2.25 m/s over a distance of 1000 m. The wear rate increased with load and decreased as the wt.% of reinforcement increased. The wear rate of the composite with 10 wt.% Al₂SiO₅ was approximately 44% lower than that of the composite with 5 wt.% Al₂SiO₅. The same dependence was noted for hybrid composite (5 wt.% Al₂SiO₅ + 5 wt.% B₄C)—the wear rate was approximately 50.8% lower than that of the composite with 5 wt.% Al₂SiO₅ under the same test condition. The friction coefficient decreased as the weight percentage of the reinforcement (Al₂SiO₅ and B₄C) increased due to the uniform distribution of the reinforcement on the surface of the composites. The main wear mechanism of the studied materials was abrasion wear. The wear mechanism of the composite had tribochemical type. It involved the oxidation and transfer of the material, which formed protective tribolayers ensuring an additional sliding process. The mechanism that played the main role in the wear process of the composites was a combination of abrasive, adhesive and oxidative wear.     

冰硼合剂声门下间隙冲洗对机械通气患者的影响

目的：探讨运用冰硼合剂间隙声门下冲洗护理呼吸机辅助通气患者的临床价值。方法将我院重症监护室2011年5月～2013年2月共62例行气管切开机械通气患者随机分成两组,在常规护理的同时,实验组运用中药冰硼合剂每6h一次进行声门下冲洗且低负压持续吸引;对照组运用生理盐水每6h一次进行声门下冲洗且低负压持续吸引。观察两组气管切开病人呼吸机相关性肺炎（VAP）发生率、抗生素使用天数、低氧血症发生率。结果实验组气管切开呼吸机相关性肺炎（VAP）发生率、抗生素使用天数、低氧血症发生率均较对照组下降,三项指标均显示有统计学差异（P＜0．05）。结论呼吸机辅助通气患者使用中药冰硼合剂定时进行声门下冲洗护理,具有较高的临床价值,可以提高护理质量。     

Quantitative Analysis of Mercaptoundecahydrododecaborate by Fourier Transform Infrared Spectroscopy

Mercaptoundecahydrododecaborate (BSH) is an important agent in boron neutron capture therapy (BNCT) of various cancers. A simple and rapid analytical method for the measurement of mercaptoundecahydrododecaborate in aqueous solution and in urine by Fourier transform infrared spectroscopy has been developed. A thin-pathlength sampling apparatus was used to minimize the strong absorption of water. The subtraction of water absorbance from sample spectra resolved a B-H band at 2493 cm^–1. The quantitative measurement of BSH concentration was carried out by integrating the B-H band above baseline in the range of 2534-2440 cm^–1. The lower limit of measuring the concentration of sodium BSH (Na₂B₁₂H₁₁SH) in our experiment was 10 µg/ml (about 5 ppm of boron). This method measures the hydroborate (B-H) concentration instead of total boron and, thus, may be utilized to measure the BSH concentration in in vivo samples for metabolic studies.