The shape parameter of Liposomes and DNA-lipid complexes determined by viscometry utilizing small sample volumes

A minicapillary viscometer utilizing <0.5 ml of sample at a volume fraction of <0.1% is described. The calculated a/b of DPPC/DPPG multilamellar liposome was 1.14 as prolate ellipsoids and a/b of dioleoylpropyltrimethyl ammonium methylsulfate-DNA complex at a charge ratio of 4: 1 (+/-) was 3.7 as prolate ellipsoids or 4.9 as oblate ellipsoids. The deviation of shape from perfect sphere is thus expressed quantitatively in more than two significant figures. In these measurement, the necessary amount of DNA is <0.5 mg.

多环芳烃降解菌ZL5分离鉴定及其降解质粒

通过选择性富集培养 ,从辽河油田石油污染土壤中分离到一株多环芳烃 (PAHs)降解菌ZL5 .它能以菲和芘为唯一碳源生长 ,但是不能利用萘 .16SrDNA核苷酸序列分析结果表明 ,ZL5属于变形细菌α亚类中的鞘氨醇单胞菌属 .该菌株含有一个大小约为 6 0kb的质粒 .丝裂霉素C消除实验表明 ,随着质粒的丢失 ,菌株利用菲和芘的能力也丧失 .用电转化和氯化铷转化法分别将菌株ZL5的质粒导入大肠杆菌JM10 9和DH5α中 ,随着质粒的获得 ,这些转化子获得了降解菲和芘的能力 .本研究结果表明 ,鞘氨醇单胞菌ZL5降解PAHs的功能和质粒有关 .图 4参 16

An alternative approach to ascertain the rate-determining steps of TiO2 photoelectrocatalytic reaction by electrochemical impedance spectroscopy

In an attempt to ascertain the rate-determining steps (RDS) of TiO2 photoelectrocatalytic (PEC) reaction, the PEC oxidation of sulfosalicylic acid (SSA) solution in a TiO2-coated electrode reactor system was monitored by applying the electrochemical impedance spectroscopy (EIS) method. In the meantime, an EIS mathematical model was first established to theoretically simulate the PEC reaction. Based on the EIS model, the theoretical simulation indicates three typical reactions in a PEC oxidation process, which include the charge-transfer-dominated reaction, both the charge-transfer- and adsorption-dominated reaction, and the adsorption-dominated reaction. The experimental results of EIS measurement showed that there was only one arc/semicircle on the EIS plane display when the external bias applied was below 200 mV (vs SCE) in the SSA PEC degradation whereas there were two arcs/semicircles when the externally applied bias exceeded 200 mV (vs SCE). The experimental results have a good agreement with the model simulation. The EIS method in this study provides an easier way to determine the RDS in a PEC oxidation process, which would be helpful to better control the reaction in practice.

Synthesis and spectroscopic study of mesoporous aluminum methylphosphonate foam templated by dibutyl methylphosphonate

New types of templates and novel interactive mechanisms between template and framework are very important for creating porous materials. In this work, by using neutral dibutyl methylphosphonate as a template, an inorganic-organic hybrid mesoporous material, aluminum methylphosphonate, was prepared. The as-synthesized material was studied by P-31 magnetic angle spinning nuclear magnetic resonance (MAS NMR), Al-27 MAS NMR, C-13 CP/MAS, FT-IR spectroscopy, thermogravimetry (TG), differential thermal analysis (DTA), and transmission electron microscopy. After thermal treatment at 673 K and 10 mmHg for 2 h, hybrid mesoporous foam was obtained. The transformation process was investigated by FT-IR. TG-DTA results indicate that the methyl group bonded to the framework keeps intact up to 792 K under air and 823 K under nitrogen. The characterization results from nitrogen gas adsorption-desorption measurements show that the BET surface area and the Barrett-Joyner-Halenda desorption cumulative pore volume of the foam are 90 m(2) g(-1) and 0.32 cm(3) g(-1) respectively. (C) 2003 Elsevier Inc. All rights reserved.

耕地土壤交换性镁含量的空间变异性特征

利用地统计学和地理信息系统相结合的方法研究了沈阳市郊耕地土壤(0～20cm)交换性镁含量的空间变异性特征 ,绘制了交换性镁含量的空间分布图。结果表明 :土壤交换性镁含量符合正态分布 ,变异函数的最佳理论模型为球状模型 ,交换性镁含量具有中等的空间相关性(C0 与C0+C比值为55.0 %) ,但空间自相关距离较大(73.1km) ,影响其空间变异的结构性因子主要是成土母质、河流走向以及土壤类型。

Improvement of Pt catalyst for soot oxidation using mixed oxide as a support

Catalytic activity of Pt catalysts for soot oxidation was studied using temperature programmed reactions. The activity of Pt loaded over TiO2-SiO2 (Pt/TiO2-SiO2) showed higher activity than other Pt/MOx systems (MOx = TiO2, ZrO2, SiO2, Al2O3. TiO2-ZrO2. TiO2-Al2O3, ZrO2-SiO2, ZrO2-Al2O3, SiO2-Al2O3). The activity was highest when the molar ratio of TiO2/(TiO2 + SiO2) ranged from 0.4 to 0.7. The effect of pretreatment with a gas containing low SO2 concentrations on the activity was compared for Pt/SiO2, Pt/TiO2 and Pt/TiO2-SiO2. In the case of Pt/TiO2-SiO2, the activity was markedly promoted by the pretreatment whereas no variation in the activity was observed for Pt/SiO2. The difference in the behavior towards the SO, pretreatment was attributed to property difference in the supports for sulfate accumulation. The high activity of Pt/TiO2-SiO2 was also confirmed under practical conditions with a diesel engine exhaust using a catalyst-supported diesel particulate filter (DPF). (C) 2003 Elsevier Science B.V. All rights reserved.

Capillary electrochromatographic separation of enantiomers on chemically bonded type of cellulose derivative chiral stationary phases with a positively charged spacer

Positively charged chiral stationary phases (CSPs) were prepared for capillary electrochromatography (CEC) separation of enantiomers by chemically immobilizing cellulose derivatives onto diethylenetriaminopropylated silica (DEAPS) with tolylene-2,4-diisocyanate (TDI) as a spacer reagent. Anodic electroosmotic mobility was observed in both nonaqueous and aqueous mobile phases due to the positively charged amines on the surface of the prepared CSPs. For comparison, the traditionally used 3-aminopropyl silica (APS) was also adopted as the base material instead of DEAPS to prepare CSP. It was observed that the EOF on the DEAPS-based CSP was 18%-60% higher than that on the APS-based CSP under nonaqueous mobile phase conditions. Separation of enantiomers in CEC was performed on the positively charged CSPs with the nonaqueous mobile phases of pure ethanol or mixture of hexane-alcohol and the aqueous phases of acetonitrile-water or 95% ethanol. Fast separation of enantiomers was achieved on the newly prepared CSPs.

光合细菌及其在化工有机废水处理方面的应用

光合细菌作为一类古老的细菌类群 ,已经在众多领域得到应用。利用光合细菌处理有机废水具有处理有机负荷高、占地面积小、便于管理、能耗低、投资费用少、菌体可以回收利用等优点 ,已经引起人们的重视。对光合细菌在处理化工有机废水方面的研究和应用进行了综述 ,指出光合细菌处理法的优缺点和发展趋势 ,认为光合细菌在有机废水处理方面的应用前景广阔

Synthesis of covalently bonded cellulose derivative chiral stationary phases with a bifunctional reagent of 3-(triethoxysilyl)propyl isocyanate

A bifunctional reagent of 3-(triethoxysilyl)propyl isocyanate (TEPI) was initially adopted as a spacer reagent to prepare the bonded types of chiral stationary phases (CSPs) with cellulose derivatives. The silica-based CSPs were chemically prepared with non-regioselective and regioselective approaches and their chiral resolving capabilities were evaluated in terms of HPLC resolution of test enantiomers. It was observed that the chiral recognition capabilities of the non-regioselectively prepared CSPs were influenced by the amount of TEPI used. And also, the regioselectively prepared CSP generally showed a slightly higher resolution power than the non-regioselectively prepared CSP, while the non-regioselective procedures were highly advantageous to rapid preparation. In addition, chiral recognition of the prepared CSPs was affected by the properties of the used silica matrices. (C) 2003 Elsevier B.V. All rights reserved.

Determination of 1-phenyl-3-methyl-5-pyrazolone-labeled carbohydrates by liquid chromatography and micellar electrokinetic chromatography

In this paper, the method for the derivatization of carbohydrates with 1-phenyl-3-methyl-5-pyrazolone (PMP) was simplified. One-third of the derivatization time was saved. Five monosaccharide derivatives have been well separated by MEKC and HPLC under optimized conditions. Good reproducibility could be obtained with relative standard deviation (RSD) values of the migration times within 5.0 and 2.3%, respectively. Furthermore, the developed methods have been successfully applied to the analysis of carbohydrates in Aloe powder and food. These methods are quite useful for routine analysis of monosaccharides and oligosaccharides in real samples. (C) 2003 Elsevier B.V. All rights reserved.

景观生态学的学科前沿与发展战略

根据美国景观生态学 2 0 0 1年年会关于景观生态学的关键议题和研究领域特别专题的讨论 ,综合 1 6位国际知名专家所发表的关于深化理论、整合协调和方法改进等方面的意见 ,深入论述了景观生态学的 6项关键议题和 1 0个优先研究领域。包括通过景观镶嵌体的生态流 ,土地利用和土地覆被变化的过程、机制 ,非线性动态和景观复杂性 ,尺度转换方法论的发展 ,景观指标与生态过程 ,人类活动与景观生态 ,景观格局的优化 ,景观保育与可持续性 ,资料获取与准确性评价。并对构建中国景观生态学的理论框架提出了初步的想法 ,即发展以格局——过程关系为中心的生态空间理论 ,以人类活动有序化为中心的景观生态建设理论 ,以发挥景观多重价值为中心的景观规划理论。

林带空间配置与布局优化研究

农田防护林 (林带 )的空间配置与布局是影响防护林结构和防护效益发挥并持续的关键因素 .为达到农田防护林防护效益最大并持续的经营目标 ,在保证林分多样性和稳定性的条件下 ,林带必须具有空间上布局的合理性和时间上的连续性 .经过多年防护林营林研究实践 ,在对 1 992年于辽宁省昌图县双井子乡设计营造的试验示范林带调查的基础上 ,对农田防护林单条林带方向的设置、带内树木的空间搭配方式、树种组成形式 ,多条林带或林网的带间距离以及大面积或区域防护林体系的空间景观布局等进行了综合研究 .结果表明 ,单条林带和林网走向都应以垂直主害风作为设计的原则 ;林带内树木的空间搭配以”品”字型为佳 ,在不同树种混交的同一条林带中 ,可利用”边行优势”将生长相对缓慢的树种配置于边行 ,生长相对迅速的树种配置于内行 ;多条林带或林网空间配置参数———带间距离的设计应以林带达到初始防护成熟龄时的树高作为成林高 ,以林带结构变化规律和降低害风比例作为林带设计关键参数 ;区域防护林体系的空间布局应以景观生态学原理为基础 ,对林网体系进行评价与调控