Bacterial transport in porous media: New aspects of the mathematical model

Transport of bacteria is an important aspect from scientific, industrial and environmental point of view. In this work, a one-dimensional mathematical model based on linear equilibrium adsorption of bacteria has been developed to predict bacterial transport through porous media. This model is more realistic than existing models because of its coupling both physicochemical and biological phenomena. Two important biological phenomena, the growth and decay of bacterial cells and chemotactic/chemotaxis of bacteria along with physicochemical properties have been adequately incorporated which are quite new aspects in our model. In agreement with experimental study by [D.K. Powelson, R.J. Simpson, C.P. Gerba, J. Environ. Qual. 19 (1990) 396], model simulations indicated that enhancement of breakthrough occurs due to increase in flow velocity, cell concentration, substrate concentration, respectively. It has also been found that chemo tactic has a significant effect on bacterial transport, especially under conditions of considerable substrate gradient and at low pore velocity. The importance of threshold concentration of captured cells (σ₀) on bacterial transport has also been identified which is also a new aspect in our model.     

蒸镀薄膜的分形生长行为

自Mandelbrot的分形几何学问世以来,分形理论的应用日趋广泛。在薄膜生长方面亦是如此。真空蒸镀薄膜的生长遵循着一定的规律。基本上是:(1)成核在此期间形成小的晶核,它们按统计规律分布(有一些例外)在基片表面上;(2)晶核生长并形成较大的岛这些岛通常具有小晶体(微晶)的形状;(3)岛(微晶)和岛(微晶)之间聚集并形成含有空沟道的许多连接着的网络;(4)沟道被填充,形成连续的薄膜。     

Influence of albumin adsorption on physico-chemical properties of alumina surfaces

The effect of albumin adsorption on neutral active aluminium oxide was investigated in the presence of polar and non-polar liquids. The adsorbed values were highest near the isoelectric point of albumin and varied in the range 5–10 and 3–11 mg g^–1 with phosphate buffer and potassium chloride respectively after 2 and 24 h. In the case of aluminium oxide the effect of albumin adsorption on total heterogeneity of adsorbents is not explicit. On the one hand, the modified samples showed decreasing surface area with increase of surface coverage with albumin. On the other hand, modifications under the same conditions but without albumin caused similar changes. These effects suggest the strong influence of medium pH on surface properties (due to surface polarization) and competitive co-adsorption of ions on the process. The volumetric fractal dimensions of the studied materials change in the range 2.25–2.32 for pure aluminium oxide and BSA modified from the phosphate solution. E _d,max values (desorption energy in the maximum of distribution function) diminish (in the range 40–45 kJ mol^–1) compared with pure aluminium oxide (E _d,max=52 kJ mol^–1) for water thermodesorption at modified surfaces to the increase of a number of active centers of hydrophobic character, and weakening of the adsorbent–adsorbate increases.     

铅铬黄粒子的微胶囊化及其表面形貌的表征

研究了铅铬黄粒子的微胶囊化及其机理；探讨了对粒子表面形貌的量化表征方法．结果表明，在油包水（Ｗ／Ｏ）乳液中对铅铬黄粒子进行无机微胶囊化是一提高其耐酸、碱性的有效方法．颜料粒子的表面形貌可用其表面分形维数（Ｄ）量化表征．     

小波分形分析重叠峰信号

用连续小波变换与分形理论相结合的小波分形峰位法对含噪重叠信号峰位置的提取进行了研究, 同时考察了信噪比和分离度对该法提取峰位置的影响; 结果表明 该法是一种提取含噪重叠信号中各单独峰峰位置的有效工具, 即使对于重叠程度和噪声干扰严重的信号也能得到较好的结果; 将其用于 Cd(Ⅱ )和 In(Ⅲ )重叠伏安信号的处理, 峰位置提取的相对误差小于± 1%; 该法具有准确、快捷、简便易行等特点, 发展前景广阔.     

Effects of cationic micelles on fluorescence of indole and indolecarboxylic acids. Analytical determinations

The effect of cationic micelles of benzyldimethylhexadecylammonium chloride and hexadecyltrimethylammonium bromide on the fluorescence spectra of indole and its carboxylic derivatives were determined. The larger solute-micelle binding constants were provided by benzyldimethylhexadecylammonium chloride, ranging from 0.10·10⁵ and 2.15·10⁵ M ^–1 for indole-5-carboxylic and indole-2-carboxylic acid, respectively. The determination of indole-4-carboxylic acid with a detection limit of 1.0 ng ml^–1, in the presence of the 3-and 5-substituted derivatives, shows the analytical potential of the synchronous spectrofluorimetry combined with the enhancement effects caused by micellar media.     

Cs2.5H0.5PW12O40 catalyzed diastereoselective synthesis of β-amino ketones via three component Mannich-type reaction in water

A series of insoluble salts of Keggin heteropoly compounds were prepared and used as catalysts for the Mannich-type reaction of benzaldehyde, aniline, and cyclohexanone in water. Among them, Cs_2.5H_0.5PW₁₂O₄₀ showed excellent catalytic activity. Effects of surfactant, catalyst loading and temperature were studied to introduce the best reaction condition. The optimized reaction conditions were extended to Mannich reaction of various aldehydes, ketones, and amines in water. This rapid procedure afforded structurally divers β-amino ketones with major anti diastereoselectivity. Additionally, four new compounds were reported. The catalyst was recovered and reused for subsequent runs.     

Spectrofluorimetry in organized media coupled to second-order multivariate calibration for the determination of galantamine in the presence of uncalibrated interferences

The present article describes the spectrofluorimetric determination of galantamine, a widely used acetylcholinesterase inhibitor, through excitation-emission fluorescence matrices and second-order calibration. With the purpose of enhancing the fluorescence intensity of this substance, the effect of different organized assemblies was evaluated. Although the interaction of galantamine with different cyclodextrins is weak, it was corroborated that the fluorescence intensity of this pharmaceutical in the presence of α-cyclodextrin is increased by a twofold factor. Among the studied micellar media, the anionic surfactant sodium dodecyl sulfate produced the largest signals for the compound of interest (sixfold enhancement), and was selected as auxiliary reagent for the subsequent determinations. The developed approach enabled the determination of galantamine at the ng mL⁻¹ level without the necessity of applying separation steps, and in the presence of uncalibrated interferences. The applied second-order chemometric tools were parallel factor analysis (PARAFAC), unfolded partial least-squares coupled to residual bilinearization (U-PLS/RBL), and multidimensional partial least-squares coupled to residual bilinearization (N-PLS/RBL). The ability of U-PLS/RBL to successfully overcome spectral interference problems is demonstrated. The quality of the proposed method was established with the determination of galantamine in both artificial and natural water samples.     

Sequential injection fluorimetric determination of Sn in juices of canned fruits

The present work describes the development of a fast and robust sequential injection fluorimetric procedure for the determination of Sn in juices of canned fruits. The developed automatic methodology is based on the complexation of Sn with 8-hydroxyquinoline-5-sulfonic acid (HQSA) to form a fluorimetric product (λ_exc = 354 nm; λ_em = 510 nm). The influence of dimethylsulfoxide (DMSO) and cetylpyridinium bromide (CPB) on the sensitivity of the fluorimetric determination was evaluated.Linear calibration plots were obtained for Sn concentrations between 1 and 10 mg L⁻¹, with a detection limit of 0.38 mg L⁻¹. In each analytical cycle 0.006 mg of HQSA and 0.47 mg of CPB were consumed and 1.5 mL of effluent was generated.The developed methodology was applied to the determination of Sn in juices of canned fruits and the results complied with those furnished by an electrothermal atomic absorption spectrometry comparison procedure, with relative deviations lower than 5.2%.The automatic procedure exhibited good precision (R.S.D. < 1.4%) and the sampling rate was about 70 determinations per hour.