Stabilization and characterization of colloidal gas aphron dispersions

Colloidal gas aphrons (CGAs) are finding increasing application in water processing, bioseparation, bubble-entrained floc flotation, separation of oil from sand, etc. This article proposes an effective method of encapsulation to stabilize the CGA bubbles with silicic sol solution for their characterization. The stabilized CGA bubbles can keep shapes and sizes for at least 12 h; even the bubbles smaller than 25 mum can also be stabilized and exist for very long times. Effects of concentration and pH of silicic sol solution on CGA stabilization were studied. The optimal ranges of concentration and pH of silicic sol solution are 0.15-0.25 mol/dm(3) and 7-10, respectively. The bubble distortion behavior in disturbance and size distribution of CGAs were examined by using the stabilization method and photographic techniques.     

Black fungus derived aerogel with double faced properties

Black fungus aerogel (BFA) exhibited interesting double-faced properties. Weexplored the diverse properties of each side of the black fungus in three aspects:water contact angle measurements, liquid selective absorption capacity and air pollutant adsorption abilities.     

Selective effect of guest molecule length and hydrogen bonding on the supramolecular host structure

A host supramolecular structure consisting of bis-(2,2':6',2' '-terpyridine)-4'-oxyhexadecane (BT-O-C16) is shown to respond to guest molecules in dramatic ways, as observed by using scanning tunneling microscopy (STM) on a highly oriented pyrolytic graphite surface under ambient conditions. It is observed that small linear molecules can be encapsulated within the host supramolecular lattice. The characteristics of the host structure were nearly unaffected by the encapsulated guest molecules of terphthalic acid (TPA) dimers, whereas appreciable changes in cavity dimension can be observed with azobenzene-4,4'-dicarboxylic acid. The STM study and density functional theory (DFT) analysis reveal that intermolecular hydrogen bonding interaction plays an essential role in forming the assembling structures. The difference in guest molecule length is considered the important cause for the different guest-host complexes.     

Reactions of magnesium formate on supports

Thermal decomposition of supported magnesium formate has been studied by gas chro-matography.The reaction paths of decomposition of supported magnesium formate depend on thenature of the supports.For Mg(HCO_2)_2/HZSM-5,the zeolite behaves as a dehydration catalyst togive CO and H_2O at lower temperatures;when the zeolite is modified by phosphorus,the methanationreaction will be partly restrained.In the case of Mg(HCO_2)_2/AC,strong adsorption of CO_2 leadsto the formation of the shoulder peak of CO_2 at higher temperatures,however,CH_4 disappears aftermodified by phosphorus.For Mg(HCO_2)_2/Al_2O_3,the dehydrogenation of HCO_2~- takes place on thesurface of Al_2O_3.The decomposition of Mg(HCO_2)_2 on SiO_2 in hydrogen yields two peaks of COand only one appears after modified by phosphorus.When Mg(HCO_2)_2 decomposes on MgO,the firstpeak of CO_2 arises from the reaction of surface Mg~(2+) with HCO_2~- from dissociated Mg(HCO_2)_2.     

Adsorption voltammetry of the scandium-alizarin red S complex onto a carbon paste electrode

For the first time, a new method is described for the determination of scandium based on the cathodic adsorptive stripping of the scandium-alizarin red S complex onto a carbon paste electrode. The second-order derivative linear scan voltammograms of the complex are recorded by use of model JP-303 polarographic analyzer from 0.0 to -1.0 V (versus SCE). Optimum conditions are found to be: an acetic acid (0.36 mol l(-1))-potassium biphthalate (0.064 mol l(-1)) buffer solution (pH 4.0) containing 2.0x10(-5) mol l(-1) alizarin red S, a preconcentration potential of 0.0 V, a preconcentration time of 60 s, a rest time of 10 s and a scan rate of 100 mV s(-1). The results show that the complex can be adsorbed on the surface of a carbon paste electrode, yielding one peak at -0.58 V, corresponding to the reduction of alizarin red S in the complex at the electrode. The detection limit is found to be 6.0x10(-10) mol l(-1) for 3 min of preconcentration time. The linear range is 1.0x10(-9) to 4.0x10(-7) mol l(-1). Application of the procedure to the determination of scandium in the ore samples gave good results.     

Preparation and Characterization of Nanoscopic Organic Semiconductor of Oxovanadium Phthalocyanine

Nanoscopic particles of oxovanadium phthalocyanine (VOPc, phase-II) with different particle sizes are prepared by aggregation of VOPc molecules in the presence of surfactants for the first time. A size effect in the region of nanoscale was observed in the UV-visible spectra. The photoconductivity of the nanoscopic VOPc is much higher than that of bulk VOPc. Copyright 1999 Academic Press.     

Organolithium-mediated diversification of peptide thiazoles

[Reaction: see text] We report a one-step, racemization-free method for the diversification of peptide thiazoles via direct lithiation of the thiazole ring. The method is compatible with N-Boc, N-trityl, carboxylic ester, and carboxamide protecting groups and has been used to directly functionalize the thiazole ring of cyclopeptide natural products.     

利用电荷迁移反应测定头孢羟氨苄

提出一种基于电荷迁移反应简便可靠地测定头孢羟氨苄的分光光度法。在甲醇－乙醇介质中，头孢羟氨苄与氯冉酸于５０℃反应１５ｍｉｎ能够形成稳定的１：１络合物，其λｍａｘ＝５２８ｎｍ，线性范围为２０￣４００ｍｇ／Ｌ。用拟定的方法测定原粉和胶囊，结果与药典法一致。对浓度１００ｍｇ／Ｌ的药物１０次测定相对标准偏差为１．４％，样品的标准加入回收率为９９．０％￣１００．８％。     

枸椽酸锗对小鼠免疫功能的影响

枸椽酸锗能明显提高小鼠血清溶血素抗体水平，增强二硝基氯苯（DNCB）致小鼠迟发型皮肤过敏反应。增加小鼠免疫器官胸腺和脾脏的重量，表明枸椽酸锗能增强小鼠体液免疫和细胞免疫水平。     

Asymmetric synthesis of syn-(2R,3S)-and anti-(2S,3S)-ethyl diamino-3-phenylpropanoates from N-(benzylidene)-p-toluenesulfinamide and glycine enolates

Addition of differentially N-protected glycine enolates to enantiopure sulfinimines affords syn- and anti-alpha,beta-diamino esters with high diastereoselectivities and good yields.