Effect of humidity on the adsorption kinetics of lung surfactant at air-water interfaces

The in vitro adsorption kinetics of lung surfactant at air-water interfaces is affected by both the composition of the surfactant preparations and the conditions under which the assessment is conducted. Relevant experimental conditions are surfactant concentration, temperature, subphase pH, electrolyte concentration, humidity, and gas composition of the atmosphere exposed to the interface. The effect of humidity on the adsorption kinetics of a therapeutic lung surfactant preparation, bovine lipid extract surfactant (BLES), was studied by measuring the dynamic surface tension (DST). Axisymmetric drop shape analysis (ADSA) was used in conjunction with three different experimental methodologies, i.e., captive bubble (CB), pendant drop (PD), and constrained sessile drop (CSD), to measure the DST. The experimental results obtained from these three methodologies show that for 100% relative humidity (RH) at 37 degrees C the rate of adsorption of BLES at an air-water interface is substantially slower than for low humidity. It is also found that there is a difference in the rate of surface tension decrease measured from the PD and CB/CSD methods. These experimental results agree well with an adsorption model that considers the combined effects of entropic force, electrostatic interaction, and gravity. These findings have implications for the development and evaluation of new formulations for surfactant replacement therapy.     

在二甲基亚砜中电化学制备铈钴合金

利用循环伏安法和恒电位电解法研究了室温下在二甲基亚砜中铈钴合金膜的电化学制备.结果表明,二甲基亚砜中Ce(Ⅲ)在Pt电极上的还原反应为一步完全不可逆反应.控制沉积电位在-2.10V～2.30V,利用恒电位电解得到表面平滑,附着力好,铈含量为37wt%～45wt%的铈钴合金膜.     

Determination of trace elements in drinking tea by various analytical techniques

Tea has been one of the most popular simulating beverages which is both heavily produced and consumed in Taiwan. The determination of minor or trace elements in drinking tea and tea leaves is therefore important for estimating the daily intake of Taiwanese considered as a safety indicator. In order to accurately and precisely determine the concentrations of trace elements in samples, several analytical methods such as AAS, NAA and ICP-AES are suggested. This paper attempts to utilize all three methods to determine the concentrations of minor or trace elements in different types of tea leaves and the extracts percolated from them. The influence of fermentation processes on the concentration levels of minor or trace elements in tea samples is investigated. Because only free metal ions are bioavailable for the human body, it is necessary to determine their concentrations in drinking tea. The dissolution of trace elements in drinking tea is therefore studied by simulating the common Chinese style of tea percolation. Concentrations of thirteen elements including Zn, Mn, Ca, Cu, Ni, Al, K, Mg, Cd, Pb, Na, Co and Sc are determined.     

含铈不锈钢的抗菌性能

以00Cr18Ni9不锈钢成分为基础,添加0～5%的稀土元素铈（Ce）.利用电子探针分析了加铈（Ce）不锈钢中Ce的分布;用化学分析法测定了含铈不锈钢中铈（Ce）和碳（C）的含量;用X射线衍射方法测试了含铈（Ce）不锈钢中铈（Ce）的析出相成分;采用贴膜法测试了含Ce不锈钢对大肠杆菌ATCC 8099、金黄色葡萄球菌ATCC 6538的抗菌性能.结果表明： 含Ce不锈钢具有优异的抗菌性能,与含Cu抗菌不锈钢相比,含Ce不锈钢无需时效热处理就具有优异的抗菌性能.并讨论了含Ce不锈钢的抗菌机制.     

Laser-enhanced ionization and laser-induced atomic fluorescence as element-specific detection methods for gas chromatography. Application to organotin analysis

The applicability of (1R,2R)-1,3-diacetoxy-1-(4-nitrophenyl)-2-propyl isothiocyanate [(R,R)-DANI] as a recently developed chiral derivatizing agent for the enantioseparation of a series of β-blockers is described. The thiourea diastereomers formed were analyzed by reversed-phase high-performance liquid chromatography, mixtures of water and methanol or acetonitrile being used for elution. Conditions of derivatizations (temperature, reagent excess and reaction time) were optimized, and the effects of organic modifiers on the retention and separation were investigated; the diastereomers could readily be baseline separated with methanol-containing mobile phases with resolutions between 1.58 and 2.72.     

Synthesis of 2'-O-methoxyethylguanosine using a novel silicon-based protecting group

A short and efficient synthesis of 2'-O-methoxyethylguanosine (8) is described. Central to this strategy is the development of a novel silicon-based protecting group (MDPSCl(2), 2) used to protect the 3',5'-hydroxyl groups of the ribose. Silylation of guanosine with 2 proceeded with excellent regioselectivity and in 79% yield. Alkylation of the 2'-hydroxyl group of 6 proceeded with methoxyethyl bromide and NaHMDS and afforded compound 7 in 85% yield, without any noticeable cleavage of the silyl protecting group and without the need to protect the guanine base moiety. Finally, deprotection of 7 was achieved using TBAF and produced 8 in 97% yield.     

Simultaneous determination of sulfite, sulfate, and hydroxymethanesulfonate in atmospheric waters by ion-pair HPLC technique

A reversed-phase ion-pair HPLC with indirect photometric detection for the simultaneous determination of sulfite, sulfate, hydroxymethanesulfonate (HMS), and other inorganic anions in atmospheric water has been developed. Separations were accomplished in less than 10 min in a cetylpyridinium-coated C₁₈ column with 0.5 mM potassium hydrogen phthalate-0.015% triethanolamine-3% methanol at pH 7.9 as mobile phase. Quantitation was carried out by the peak area method, with detection limits in the pmol range. UV light absorption responses were linear over a wide concentration range from several hundred μmoles to the detection limits of each anion. The application of the method provides a rapid and efficient technique for the quantitative determination of sulfur and other inorganic species in atmospheric liquids.     

离聚体溶液

离聚体（ionomer）是指含离子基团低于15mol％的聚合物，这些离子基团能聚集成多重离子对[1]或离子簇[2-6]，使大分子链发生物理文联形成聚集体，导致性质起很大变化。例如常温下因物理交联而具有良好弹性，而高温时物理交联被破坏而具有流动性，所以离聚体能制成热塑性弹性体。由于物理交联存在，离聚体不能轻易溶于非极性溶剂中；由于离子含量低，又不易溶于水或其它强极性溶剂中．因此，尽管离聚体固体的研究和应用已有40多年的历史，但有关溶液研究的报导到70年代末才见发表[7-9]，近10年取得较大进展，其独特的粘度关系使人们考虑利用…     

Efficient synthesis of isoflavone analogues via a Suzuki coupling reaction

Analogues of 3-aryl-8-isobutyl-5,6,7-trihydroxy-2-methyl-4H-chromen-4-one were synthesized with high yields via the Suzuki coupling reaction of 3-iodo-8-isobutyl-5,6,7-trimethoxy-2-methyl-4H-chromen-4-one with different aryl boronic acids.