量子反应散射的动力学李代数方法

用动力学李代数方法描述了量子反应散射问题 .对共线交换反应A BC→AB C ,得到了含有主要动力学参数的反应跃迁几率的解析表达式 .计算了共线反应散射过程H H2 (n =0 )→H2 (n′ =0 ) H的反应跃迁几率 .结果表明 ,动力学李代数方法对计算反应几率是非常有效的 .     

分子间散射问题的李代数处理——关于AB+CD系统的振动-振动能量传递

采用半经典近似方法所给出的关于AB+CD散射系统的相互作用势,构造系统的一种动力学代数h_(15), 利用这种代数计算了在非反应情况下系统的跃迁几率及势能的统计平均值,并在群参量的一次近似下探讨了跃迁过程中的选择定则。     

分子间散射问题的李代数处理 关于AB+CD系统的振动-振动能量传递

采用半经典近似方法所给出的关于AB+CD散射系统的相互作用势, 构造系统的一种动力学代数h_(15), 利用这种代数计算了在非反应情况下系统的跃迁几率及势能的统计平均值, 并在群参量的一次近似下探讨了跃迁过程中的选择定则。     

NH_3-Ar转动激发的半经典理论计算

半经典方法以其优越于纯量子力学方法的特性特别适用于大分子散射的研究．将氨分子看作一个刚性转子，不考虑它的反演运动．体系的自由度用经典的作用量———角变量来描述，利用修正的ａｂｉｎｉｔｉｏ势在两种不同的能量条件下计算了ＮＨ３—Ａｒ散射体系转动激发的态－态跃迁的积分散射截面．计算结果与密耦合计算结果以及实验结果符合得较好，从而说明该半经典方法适用于ＮＨ３—Ａｒ散射体系．     

过渡金属复合氧化物电子组态与表面光伏响应的关系（Ⅰ）：M…

利用表面光电压谱及场诱导表面光电压谱研究了部分过渡金属复合氧化物的电子组态与其光伏响应的关系，结果表明，在过渡金属Ｍ（Ｍ＝Ｃｕ，Ｃｏ，Ｎｉ）铁酸盐系列样品中，开壳层的Ｃｕ和Ｃｏ的电荷转移跃迁具有双激发态的成分，其中含有较强的低能电子跃迁；与它们相比，闭壳层的Ｎｉ和铁酸盐的ＣＴ跃迁则需要较大的能量。     

过渡金属复合氧化物电子组态与表面光伏响应的关系(Ⅰ)──M(Ⅱ)铁酸盐(M=Cu,Co,Ni)的研究

利用表面光电压谱及场诱导表面光电压谱研究了部分过渡金属复合氧化物的电子组态与其光伏响应的关系.结果表明,在过渡金属M(M＝Cu,Co,Ni)铁酸盐系列样品中,开壳层的Cu(Ⅱ)(铁酸盐)和CO(Ⅱ)(铁酸盐)的电荷转移跃迁(CT)具有双激发态的成分,其中含有较强的低能电子跃迁;与它们相比,闭壳层的Ni(Ⅱ)铁酸盐的CT跃迁则需要较大的能量.三者的FISPS证实了它们具有不同的CT跃迁性质,为其催化反应机理研究提供了微观信息.     

含有金属-金属键的双核原子簇离子体系[Mo~2Sn]^2-(n=6~9)的电子结构与电子光谱

使用SCF-CI方法研究了含有Mo-Mo单键的原子簇离子体系[Mo~2Sn](n=6~9)的电子结构及电子光谱。讨论了随n增加, 配体S, S~2, S~4对Mo-Mo键序、原子电荷的影响及其变化规律。分析了原子簇离子中的d-d相互作用能级次序及Mo-Mo, Mo-S'~t等键的性质, CI计算得到的谱带波数及强度次序与实验符合。指认分析表明, 谱带的跃迁性质是有趣的, 如第一吸收带为成键轨道之间的跃迁σ~x^2-y^2→σ~x~2(n=6~8), 同时, 对电子跃迁的性质进行了分类, 对谱带的电荷转移性质也进行了讨论。     

丁酮分子3d态的共振增强多光子电离

酮类分子含有羰基,其价电子跃迁主要涉及ＣＯ成键π轨道,Ｏ原子的非键２ｐｙ轨道和ＣＯ反键π轨道,它们的能量顺序为π＜２ｐｙ＜π,里德堡态由最高占有轨道２ｐｙ(ｎ０)的一个孤对电子向各里德堡轨道跃迁产生［１］．ＶＵＶ吸收谱［１,２］和电子能谱［１,３］都显...     

含有金属-金属键的双核原子簇离子体系[Mo~2Sn]^2-(n=6~9)的电子结构与电子光谱

使用SCF-CI方法研究了含有Mo—Mo单键的原子簇离子体系[Mo_2Sn]~(2-)(n=6～9)的电子结构及电子光谱。讨论了随n增加,配体S,S_2,S_4对Mo—Mo键序、原子电荷的影响及其变化规律。分析了原子簇离子中的d-d相互作用能级次序及Mo—Mo,Mo—S′_t等键的性质,CI计算得到的谱带波数及强度次序与实验符合。指认分析表明,谱带的跃迁性质是有趣的,如第一吸收带为成键轨道之间的跃迁σ_(x~2-y~2)→π_(xz)(n=6～8),同时,对电子跃迁的性质进行了分类,对谱带的电荷转移性质也进行了讨论。     

面向有机光电材料的电子激发态结构与过程的计算方法

共轭聚合物与有机分子材料中的电子激发结构与过程决定了材料的光电功能：根据Kasha规则,低能级激发态的排序决定能否发光;最低激发态至基态的辐射跃迁与无辐射跃迁之间的竞争决定了发光效率,后者主要由非绝热耦合（声子作用）决定;电荷激发态载体的传输由电子分布与振动耦合或杂质和无序的散射弛豫过程决定．本文针对有机功能材料的发光性能,介绍两种理论方法的研究进展,即可用于计算共轭聚合物激发态结构的量子化学密度矩阵重整化群方法和计算发光效率的多模耦合无辐射跃迁速率方法．这些方法被应用于有机功能材料的性能预测和分子设计中．     

Bacterial cellulose films with controlled microstructure–mechanical property relationships

Bacterial cellulose (BC) films with different porosities have been developed in order to obtain improved mechanical properties. After 13 days of incubation of Gluconobacter xylinum bacteria in static culture, BC pellicles have been set. BC films have been compression molded after water dispersion of BC pellicles and filtration by applying different pressures (10, 50, and 100 MPa) to obtain films with different porosities. Tensile behavior has been analyzed in order to discuss the microstructure–property relationships. Compression pressure has been found as an important parameter to control the final mechanical properties of BC films where slightly enhanced tensile strength and deformation at break are obtained increasing mold compression pressure, while modulus also increases following a nearly linear dependence upon film porosity. This behavior is related to the higher densification by increasing mold compression pressure that reduces the interfibrillar space, thus increasing the possibility of interfibrillar bonding zones. Network theories have been applied to relate film elastic properties with individual nanofiber properties.     

Penetration behaviour of alkylbetainate chlorides into lipid monolayers

In this paper, the penetration behaviour of the alkylbetainate chloride surfactants (C(n)BC, n=10-16) into lipid monolayers of dipalmitoylphosphatidylserine (DPPS), dipalmitoylphosphatidic acid (DPPA), dipalmitoylphosphatidylethanolamine (DPPE), palmitoyoleoylphosphatidylcholine (POPC) and cholesterol (CHOL) is investigated using the Langmuir trough technique. The penetration of C(n)BC is followed by measurement of the surface pressure increase (Δπ) at a constant surface area after the injection of C(n)BC into the aqueous phase, underneath the lipid monolayer previously spread at the air-water interface at 25°C and at different initial surface pressures (π(i)). The influence of both the lipid head group and the surfactant hydrocarbon chain length on the effectiveness of C(n)BC penetration into these monolayers is discussed. The results have shown that C(n)BC adsorb at the air-water interface giving evidence of their surface-active properties. The adsorption kinetics of C16BC into different lipid monolayers are lipid head charge and lipid head volume-dependent. The magnitude of the surface pressure increase (Δπ) arises in the following order: DPPA>DPPS?CHOL≈DPPE>POPC. C(n)BC penetration into negatively-charged (DPPS and DPPA) monolayers does not seem to depend on surfactant alkyl-chain length compared to uncharged (CHOL) and zwitterionic (DPPE and POPC) monolayers for which Δπ increases with a larger alkyl-chain length. Electrostatic interactions are mainly involved in the affinity of C(n)BC with monolayers but the hydrophobic effect plays also a role.     

Hydrogen absorption in bulk BC3: a first-principles study

We have performed first-principles calculations for H absorption, H2 dissociation, and H diffusion in bulk BC3, a graphitelike layered structure. We show that in bulk BC3, H2 can dissociatively (and exothermically) absorb at low coverages. Several low-energy pathways have been computed for the dissociation process. The dissociation barriers are on the order of 0.2 eV or less. This presents a striking contrast to the situation in pure graphite and also on monolayer BC3(0001), where H2 dissociative absorption is considerably more difficult. Hydrogen absorption at high coverages has also been investigated; we find that the absorption enthalpy becomes moderately more exothermic at higher coverages. The calculated range of H binding energies is close to the desired value for reversible hydrogen storage.     

Thermodynamics and Kinetics of Bacterial Cellulose Adsorbing Persistent Pollutant from Aqueous Solutions

The adsorption capability of bacterial cellulose(BC) for anionic dye acid fuchsine was studied. Meanwhile, the processes of the adsorption were investignted and fitted by adsorption isotherm models, adsorption thermodynamics and adsorption kinetics models, respectively. The changes of BC before and after adsorbing acid fuchsine were investigated via scanning electron microscopy(SEM) and Fourier transform infrared spectroscopy(FTIR) to further explain the adsorption mechanism. The results show that acid fuchsine could be effectively adsorbed by BC. The adsorption process was fitted well by Langmuir equation and the pseudo-second order kinetics, indicating that the adsorption process was monolayer molecule adsorption with the main action of chemical adsorption. The adsorption process was spontaneous and endothermic. Glucuronic acid groups and hydroxyl groups were responsible for the adsorption of acid fuchsine on BC.     

塔克拉玛干沙漠黑碳气溶胶的特性及来源

长期监测并采集塔克拉玛干沙漠腹地的大气颗粒物及黑碳气溶胶样品.在塔克拉玛干沙漠腹地,沙尘气溶胶中的黑碳在PM10中的年平均含量高达1.14%,这说明在人迹罕至的塔克拉玛干沙漠地区,其上空的沙尘气溶胶也已经受到人为活动的影响.黑碳气溶胶具有明显的季节变化和日变化,冬季最高,平均达2261.7ngm-3,依次为冬季春季秋季夏季.黑碳气溶胶日变化特征与城市地区恰好相反,夜间高于白天,午夜0:00～2:00出现峰值,而在上午8:00～11:00出现低值.非沙尘暴期间黑碳对PM10的贡献是沙尘暴时期的11倍.塔里木盆地周边绿洲带人为活动,尤其是新疆南北部地区跨越春秋冬三季的居民采暖所产生的黑碳经由局地、区域或长途传输是塔克拉玛干沙漠腹地黑碳气溶胶的主要来源,也是沙漠黑碳气溶胶具有明显的季节特征和日变化的主要原因.随着沙尘气溶胶的长途传输,沙漠每年大约输出6.3×104吨黑碳气溶胶,这势必会对全球的气候与环境变化产生一定影响.     

Benzalkonium chloride and sulfamethoxazole adsorption onto natural clinoptilolite: effect of time, ionic strength, pH and temperature

The influence of different physical factors on the adsorption of the cationic surfactant benzalkonium chloride (BC) and the model drug sulfamethoxazole by a purified natural clinoptilolite (NZ) has been studied in order to employ zeolite-surfactant-drug composites as drug deliverer. It has been demonstrated that the adsorption of BC and sulfamethoxazole onto NZ depends of the time, the temperature, the ionic strength and the pH of the aqueous medium. The optimal conditions for the preparation of the zeolite-surfactant and zeolite-surfactant-drug composite materials are established. The results of the composite characterization support the presence of BC and sulfamethoxazole, as well as the structural stability of NZ during the treatments performed. The release experiments in acid medium demonstrate that the adsorption of sulfamethoxazole is reversible. It is also confirmed that the drug release profile corresponds to a diffusion or zero-order mechanism as a function of the compression pressure.     

Molecular Electronic Tuning of Photosensitizers to Enhance Photodynamic Therapy: Synthetic Dicyanobacteriochlorins as a Case Study

Photophysical, photostability, electrochemical and molecular‐orbital characteristics are analyzed for a set of stable dicyanobacteriochlorins that are promising photosensitizers for photodynamic therapy (PDT). The bacteriochlorins are the parent compound (BC), dicyano derivative (NC)₂BC and corresponding zinc (NC)₂BC‐Zn and palladium chelate (NC)₂BC‐Pd. The order of PDT activity against HeLa human cancer cells in vitro is (NC)₂BC‐Pd > (NC)₂BC > (NC)₂BC‐Zn ≈ BC. The near‐infrared absorption feature of each dicyanobacteriochlorin is bathochromically shifted 35–50 nm (748–763 nm) from that for BC (713 nm). Intersystem crossing to the PDT‐active triplet excited state is essentially quantitative for (NC)₂BC‐Pd. Phosphorescence from (NC)₂BC‐Pd occurs at 1122 nm (1.1 eV). This value and the measured ground‐state redox potentials fix the triplet excited‐state redox properties, which underpin PDT activity via Type‐1 (electron transfer) pathways. A perhaps counterintuitive (but readily explicable) result is that of the three dicyanobacteriochlorins, the photosensitizer with the shortest triplet lifetime (7 μs), (NC)₂BC‐Pd has the highest activity. Photostabilities of the dicyanobacteriochlorins and other bacteriochlorins studied recently are investigated and discussed in terms of four phenomena: aggregation, reduction, oxidation and chemical reaction. Collectively, the results and analysis provide fundamental insights concerning the molecular design of PDT agents.     

Pressure-induced order transition in nanodot-forming diblock copolymers at the air/water interface

Understanding and controlling the processes in block copolymer (BC) monolayers at the air/water interface during surface area compression is a key issue for producing ultrathin films of predetermined morphology with well-defined order and known dimensions. Langmuir isotherms of nanodot-forming BC monolayers generally display a plateau indicative of a 2D phase transition, which has been the subject of various interpretations in the literature. Here, based on investigations of Langmuir-Blodgett and Langmuir-Schaefer nanodot films of PS-P4VP mixed with 3-n-pentadecylphenol (PDP), we show by atomic force microscopy (AFM) that it involves a change in nanodot packing order (from quasi-hexagonal to quasi-square), argued to be a general phenomenon for nanodot BC monolayers. It is accompanied by system-specific conformational changes (as discussed in previous literature), which, in the present case, implicate PDP alkyl chain ordering, as deduced previously from in situ infrared data and indirectly supported here by AFM imaging.     

Antioxidant activity of β-carotene compounds in different in vitro assays

β-Carotene (BC) is the most abundant carotenoid in human diet, almost solely as(all-E)-isomer. Significant amounts of (Z)-isomers of BC are present in processed food as well as in mammalian tissues. Differences are described for the activity of various BC isomers in forming retinal and protecting against cancer and cardiovascular diseases. Eccentric cleavage of BC leads to degradation products such as carotenals. A variety of negative consequences were published for the non-vitamin A active BC metabolites, such as inducing the carcinogenesis of benzo[a]pyrene, impairing mitochondrial function, or increasing CYP activity. To increase the knowledge on the antioxidant activity, a variety of BC isomers and metabolites were tested in various in vitro assays. In the present study, no ferric reducing activity (FRAP assay) was observed for the BC isomers. Between the major BC isomers (all-E, 9Z, and 13Z) no significant differences in bleaching the ABTS●+ (αTEAC assay) or in scavenging peroxyl radicals (ROO●) generated by thermal degradation of AAPH (using a chemiluminescence assay) were detected.However, the (15Z)-isomer was less active, maybe due to its low stability. The degradation to β-apo-carotenoids increased FRAP activity and ROO● scavenging activity compared to the parent molecule. Dependence on chain length and character of the terminal function was determined in αTEAC assay with following order of increasing activity: β-apo-8'-carotenal < β-apo-8'-carotenoic acid ethyl ester < 6'-methyl-β-apo-6'-carotene-6'-one (citranaxanthin). The results indicate that BC does not lose its antioxidant activity by degradation to long chain breakdown products.