Highly substituted poly(2,3‐diphenyl‐1,4‐phenylenevinylene) derivatives having bulky phenyl and fluorenyl pendant groups: Synthesis,characterization, and electro‐optical properties

Two series of poly(2,3‐diphenyl‐1,4‐phenylenevinylene) (DP‐PPV) derivatives containing multiple bulky substituents were synthesized. In the first series, two different groups were incorporated on C‐5,6 positions of the phenylene moiety to increase steric hindrance and to obtain blue‐shifted emissions. In the second series, bulky fluorenyl groups with two hexyl chains on the C‐9 position were introduced on two phenyl pendants to increase the solubility as well as steric hindrance to prevent close packing of the main chain. Polymers with high molecular weights and fine‐tuned electro‐optical properties were obtained by controlling the feed ratio of different monomers during polymerization. The maximum photoluminescent emissions of the thin films are located between 384 and 541 nm. Cyclic voltammetric analysis reveals that the band gaps of these light‐emitting materials are in the range from 2.4 to 3.3 eV. A double‐layer EL device with the configuration of ITO/PEDOT/P4/Ca/Al emitted pure green light with CIE′1931 at (0.24, 0.5). Using copolymer P6 as the emissive layer, the maximum luminescence and current efficiency were both improved when compared with the homopolymer P4. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6738–6749, 2006     

Co-C bond dissociation energy and reaction volume change of 2',5'-dideoxyadenosylcobalamin studied by laser-induced time-resolved photoacoustic calorimetry

Time resolved photoacoustic calorimetry (PAC) was applied to a study of the photolysis of a coenzyme B(12) analog 2',5'-dideoxyadenosylcobalamin, which lacks an -OH group at the 2' position of ribofuranose ring. In aqueous solution, we report for the first time the quantum yield Phi(d) (0.25+/-0.02), Co-C bond dissociation energy (BDE; 31.8+/-2.5 kcal mol(-1)) and reaction volume change deltaV(R) (6.5+/-0.5 ml mol(-1)) due to conformation changes of the corrin ring and its side chains accompanying the cleavage of the Co-C bond. These values for the analog are very similar to those for the natural cofactor. Based our results and previous studies, a possible explanation for the similarity in their structure and properties versus the large difference in their enzymatic activity is discussed.     

Effect of Thermal Processing on the Metabolic Components of Black Beans on Ultra-High-Performance Liquid Chromatography Coupled with High-Field Quadrupole-Orbitrap High-Resolution Mass Spectrometry

An ultra-high-performance liquid chromatography coupled with high-field quadrupole-orbitrap mass spectrometry (UHPLC-QE-MS) histological platform was used to analyze the effects of two thermal processing methods (cooking and steaming) on the nutritional metabolic components of black beans. Black beans had the most amino acids, followed by lipids and polyphenols, and more sugars. Multivariate statistical analysis indicated that heat processing significantly affected the metabolic component content in black beans, with effects varying among different components. Polyphenols, especially flavonoids and isoflavones, were highly susceptible. A total of 197 and 210 differential metabolites were identified in both raw black beans and cooked and steamed black beans, respectively. Cooking reduced the cumulative content of amino acids, lipids, polyphenols, sugars, and nucleosides, whereas steaming reduced amino acid and lipid content, slightly increased polyphenol content, and significantly increased sugar and nucleoside content. Our results indicated that metabolic components were better retained during steaming than cooking. Heat treatment had the greatest impact on amino acids, followed by polyphenols, fatty acids, sugars, and vitamins, indicating that cooking promotes the transformation of most substances and the synthesis of a few. The results of this study provide a basis for further research and development of nutritional products using black beans.     

含氧空位的氟掺杂二氧化锰助力稳定锌离子电池

将无机盐NH₄F加入到MnO₂的前驱体溶液中,通过高效、简单的一步水热法制备了具有氧缺陷的F掺杂α-MnO₂纳米棒(记为F-MnO₂)。氧空位和F掺杂对提高F-MnO₂的导电性、促进离子扩散、提高倍率性能起着至关重要的作用。另外,由于F掺杂,形成了F—Mn键,这可以有效地抑制放电产物中Mn³⁺的Jahn-Teller畸变,从而提高结构的稳定性。得益于这些协同效应,组装的Zn||F-MnO₂全电池在0.5 A·g^-1下,首圈放电比容量高达274 mAh·g^-1,且具有较长的循环寿命和优异的倍率性能。同时,通过循环伏安(CV)和恒流充放电(GCD)曲线证明了F-MnO₂的储能机制为H⁺和Zn²⁺的共嵌入/脱出过程。     

高温等离子体中固体弹丸消融过程的研究

本文求得了弹丸消融过程的自洽解析解。结果表明:Parks的弹丸消融理论需要修正;弹丸消融速率由消融物云和表面蒸发层共同控制;入射电子通过消融物云时慢化效应并不显著;消融物离开弹丸表面时一般呈部分电离态;聚变堆条件下,弹丸表面可能会出现激波。     

一组新型络合物晶体结构与光学性能的研究

研究了二氯三烯丙基硫脲合镉(ATCC),二氯三烯丙基硫脲合汞(ATMC)和二溴三烯丙基硫脲合镉(ATCB)三种晶体的结构特点.首次报道了ATMC和ATCB晶体的非线性光学系数及倍频性能;文中分析比较了三种晶体的非线性光学性能;讨论了晶体结构与性能的关系,为探索高效非线性光学新材料提供依据.     

煤粉燃烧过程碳烟生成的激光测量研究

燃煤锅炉生成的碳烟不仅会增强火焰辐射、影响燃烧外,还排放到大气环境中带来严重危害。为了进一步了解其生成机理从而更好地对其生成量及特性进行控制,对煤粉燃烧过程中颗粒周围碳烟的分布规律进行定量的研究十分必要。本文自行设计了注射式微量给粉装置,成功实现了0.1 g/h量级给粉率下的连续给粉,并通过改进多元扩散燃烧器和以及结合激光诱导白炽光(Laser Induced Incandescence)技术,首次实现了对单颗粒煤粉燃烧过程中碳烟分布的定量测量,发现对于70μm左右的煤粉颗粒,碳烟分布直径约为1 mm。此外还通过控制气氛,研究了含氧量对碳烟生成的影响,发现随着氧含量的上升,碳烟总浓度下降并且峰值出现更早的规律。     

微型同轴脉管制冷机最低制冷温度影响因素的实验研究

本文对微型同轴脉管制冷机最低制冷温度的影响因素进行了实验研究。试验结果表明:在其他运行参数不变的情况下,随着氢浓度的逐渐减少,最低制冷温度也逐渐降低,当氢的摩尔浓度小于20％时,其最低制冷温度和纯氦相差不大。不同的氢氦配比下,该脉管制冷机的最佳运转频率为16.7 Hz。随着系统平均压力的提高,最低制冷温度也随之下降,但变化幅度越来越小。     

Czochralski晶体生长中非定常热对流过程的数值模拟

本文应用有限控制体算法,采用中心差分格式处理具有Boussinesq近似的N-S方程的对流和扩散通量项,计算了无坩埚和籽晶旋转情况下CZ晶体生长中熔体的非定常自然对流。数值计算的结果得到了某些典型时刻的流场结构和温度分布情况。结合计算得到的CZ熔体总动能和总热能随时间变化的规律,分析了流场和温度场的不稳定变化过程。此外,计算结果还给出了在非稳定热对流影响下的晶-液界面热通量的变化。非定常计算的结果对于研究自然对流和CZ单晶生长,具有理论和实际意义。 关键词：