极大似然估计法及其在混合酸电位滴定中的应用

本文提出了以氢离子活度为测量值的混合酸滴定的计算公式;介绍了一种非线性模型参数估计方法--极大似然估计法(MLE),并用于混合酸的滴定计算,获得了比最小二乘估计法(LS)更为满意的结果;用蒙特卡罗方法对MLE和LS的结果作了研究。     

毛细管微乳液电动色谱和胶束电动色谱分离冰毒及其麻黄碱杂质的比较

通过毛细管微乳液电动色谱10 m in内同时分离了安非他明、甲基安非他明、4,5-亚甲基二氧基安非他明(MDA)和3-甲氧基-4,5-亚甲基二氧基安非他明(MDMA)4种苯丙胺类毒品及其麻黄碱、伪麻黄碱、甲基麻黄碱、甲基伪麻黄碱、去甲麻黄碱等麻黄生物碱杂质。比较了毛细管微乳液电动色谱和丁醇改进的胶束电动色谱模式对分离的影响,发现正丁醇是影响分离的最主要因素。本方法具有很好的重复性和稳定性,可实现对冰毒及其麻黄生物碱杂质的快速分析和鉴定,相对保留时间和相对峰面积的RSD分别小于1.3%和5.0%,可用于冰毒的实际来源推断。     

Altitudinal trends of leaf δ13C follow different patterns across a mountainous terrain in north China characterized by a temperate semi‐humid climate

Many studies have documented that the δ¹³C values of plants increase with altitude both on a global scale and locally in humid climates, while in semi‐arid areas the opposite trend has been found. The study reported herein was conducted in a mountainous area of China characterized by a temperate semi‐humid climate. The δ¹³C values of C₃ species do not exhibit a consistent variation along an altitudinal gradient and the observations suggest that the pattern of increasing δ¹³C with altitude cannot be generalized. In the study area, in addition to environmental factors such as changing air pressure and light, the interaction between temperature and plant water balance determines the δ¹³C‐altitude variations in C₃ plants. The δ¹³C of the leaves of C₄ plants is found to increase with altitude with a mean gradient of 0.9‰/km. The altitudinal trend of C₄ plants is attributed to the combined influences of water availability and other factors rather than temperature. Copyright © 2010 John Wiley & Sons, Ltd.     

分形理论在摩擦学研究中的应用

采用尺度独立的分形参数可使粗糙表面和磨屑形貌的表征简单明了，并使表征具有唯一性，易于识别；基于分形参数所建立的摩擦学研究模型的预测结果可望不受测量仪器分辨率和取样长度的影响，因而比传统的基于统计分析的模型更为合理和有效。综述了分形几何在粗糙表面的表征，接触，磨损预测和摩擦温度分布以及磨屑定量分析等方面的应用现状和发展，指出了用分形理论研究摩擦学问题时应注意的着重点。     

A Novel in Situ Oxidization-Sulfidation Growth Route via self-Purification Process to β-In2S3 Dendrites

A novel in situ oxidization-sulfidation growth route via a self-purification process has been developed to synthesize β-In₂S₃ dendrites. To our best knowledge, this is the first example to prepare dendrites of III-VI compounds, which are expected to show particular physical properties. The X-ray analysis (EDXA), X-ray photoelectron spectra (XPS), Raman spectrum and optical properties of β-In₂S₃ dendrites have also been investigated. It is found that the product is pure In₂S₃ and shows the strong quantum confinement of the excitonic transition expected for the In₂S₃ dendrites.     

Simultaneous LC–UV–MS–MS Analysis of Nine Pivotal Metabolites in Human Serum: Application to Studies of Impaired Glucose Tolerance

A rapid, sensitive, and selective LC–UV–MS–MS method for simultaneous quantification of uric acid, creatinine, xanthine, creatine, hypoxanthine, adenosine, inosine, thymidine, and uridine in serum from patients with impaired glucose tolerance (IGT) has been developed and validated. After precipitation of protein in the serum with methanol samples were evaporated with a stream of nitrogen then reconstituted with aqueous ammonia (0.002 mol L^?1). Chromatographic separation was performed on a C₁₈ column with methanol–buffer (8 mmol L^?1 ammonium acetate adjusted to pH 6.1 with glacial acetic acid) as mobile phase at a flow rate of 0.8 mL min^?1. UV and MS–MS detection were used to quantify the metabolites on the basis of different concentrations and detector response. Linearity was excellent, with r ² no <0.998. Recovery, and intra-day and inter-day relative standard deviation (RSD) were >85, <10, and <10%, respectively. This reliable bioanalytical method enables evaluation of the levels of purines and pyrimidines in serum for IGT studies and diagnosis.     

Study on Interactions of Phenolic Acid-Like Drug Candidates with Bovine Serum Albumin by Capillary Electrophoresis and Fluorescence Spectroscopy

The interactions of the phenolic acids cinnamic acid (CNA), ferulic acid (FA), caffeic acid (CA) and chlorogenic acid (CLA) with bovine serum albumin (BSA) were investigated and compared using affinity capillary electrophoresis (ACE) and the fluorescence quenching methods. ACE gives binding constants (K _b) and thermodynamic parameters. The thermodynamic parameters show that each of four phenolic acids bind to BSA mainly by hydrogen bonds, electrostatic and hydrophobic interactions. The fluorescence quenching method provided quenching constant K _sv, binding site number n and K _b. The fluorescence results indicate that BSA fluorescence quenching is mainly a static quenching process. The binding constants (K _b) of CNA, FA, CA and CLA were from 2.52×10⁴ to 7.90×10⁴ L⋅mol⁻¹ from ACE experiments and 1.19×10⁴ to 5.21×10⁴ L⋅mol⁻¹ from fluorescence, their increase corresponded to the increase in the number of hydroxyl groups. These results imply that molecular structure and the number of hydroxyl groups of phenolic acids play act key roles in the affinity of natural phenolic acids towards BSA.     

Structure–activity relationships of eight <Emphasis Type="Italic">ent</Emphasis>-kaurene diterpenoids from three <Emphasis Type="Italic">Isodon</Emphasis> plants

Eight ent-kaurene diterpenoids were isolated from three Isodon plants, Isodon excisoides (Sun ex C. H. Hu) C. Y. Wu et H. W. Li, Isodon weisiensis C. Y. Wu, and Isodon racemosa (Hemsl.) Hara. Their cytotoxicities were tested by SRB assay against four human tumor cell lines, HepG2, Tb, HO-8910 and SGC-7901. The DNA damage degrees on their Hep G2 cells were evaluated by Comet assay. The results showed that ent-kaurene diterpenoids were selectively toxic against these four tumor cell lines. Weisiensic C had the lowest cytotoxicity against four cell lines and degree of DNA damage on the Hep G2 cell line. Leukamenin E and Glaucocalyxin A had similar IC₅₀ values and also induced a similar degree of DNA damage. The cytotoxicity and degree of DNA damage of eight ent-kaurene diterpenoids on Hep G2 was in the order Leukamenin E > Glaucocalyxin A > Wangzaozin A > Kamebanin > Macrocalyxin D > Weisiensin B > Excisanin K > Weisiensic C. The structure–activity relationships indicated that there was some correlation between the substituents and their structures of ent-kaurene diterpenoids and their activities on Hep G2 cells.     

甘氨酸间硝基苯甲酸晶体比热容的测定——差示扫描量热法(DSC)

论述用DSC及比热软件测量甘氨酸间硝基苯甲酸(G.mNBA)晶体比热容的方法。以蓝宝石为标样,测量G.mNBA晶体的比热容,其相对平均偏差在0.08%～0.47%之间。