The effect of substrate concentration on biohydrogen production by using kinetic models

The effect of substrate concentration ranging from 0 to 300 g/L on fermentative hydrogen production by mixed cultures was investigated in batch tests using glucose as substrate. The experimental results showed that, at 35℃ and initial pH 7.0, during the fermentative hydrogen production, the hydrogen production potential and hydrogen production rate increased with increasing substrate concentration from 0 to 25 g/L. The maximal hydrogen production potential of 426.8 mL and maximal hydrogen pro-duction rate of 15.1 mL/h were obtained at the substrate concentration of 25 g/L. The maximal hydrogen yield and the maximal substrate degradation efficiency were respectively 384.3 mL/g glucose and 97.6%, at the substrate concentration of 2 g/L. The modified Logistic model could be used to describe the progress of cumulative hydrogen production in this study successfully. The Han-Levenspiel model could be used to describe the effect of substrate concentration on fermentative hydrogen production rate.     

Electrochemical behavior of phenol at acetylene black-dihexadecyl hydrogen phosphate composite modified glassy carbon electrode in the presence of cetyltrimethylammonium bromide

The electrochemical response of phenol at acetylene black (AB)-dihexadecyl hydrogen phosphate (DHP) composite modified glassy carbon electrode in the presence of cetyltrimethylammonium bromide (CTAB) was investigated. In this system, a sensitive oxidation peak at 0.62 V (SCE) was obtained. The electrode process and the influence of CTAB on the oxidation of phenol were explored by chronocoulometry and linear sweep voltammetry (LSV). Experimental conditions for the determination of phenol were optimized. In the range of 5.0 × 10⁻⁷ to 1.2 × 10⁻⁵ M, the phenol concentration was linear with the oxidation peak current and the detection limit was found to be 1.0 × 10⁻⁷ M for 3 min accumulation. The method was applied for the determination of phenol in lake water and the results were satisfactory. Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 2, pp. 222–229. The text was submitted by the authors in English.     

Ultrasensitive Voltammetric Detection of Trace Lead(II) and Cadmium(II) Using MWCNTs‐Nafion/Bismuth Composite Electrodes

Multiwall carbon nanotubes were dispersed in Nafion (MWCNTs‐NA) solution and used in combination with bismuth (MWCNTs‐NA/Bi) for fabricating composite sensors to determine trace Pb(II) and Cd(II) by differential pulse anodic stripping voltammetry (DPASV). The electrochemical properties of the MWCNTs‐NA/Bi composites film modified glassy carbon electrode (GCE) were evaluated. The synergistic effect of MWCNTs and bismuth composite film was obtained for Pb(II) and Cd(II) detection with improved sensitivity and reproducibility. Linear calibration curves ranged from 0.05 to 100 μg/L for Pb(II) and 0.08 to 100 μg/L for Cd(II). The determination limits (S/N=3) were 25 ng/L for Pb and 40 ng/L for Cd, which compared favorably with previously reported methods in the area of electrochemical Pb(II) and Cd(II) detection. The MWCNTs‐NA/Bi composite film electrodes were successfully applied to determine Pb(II) and Cd(II) in real sample, and the results of the present method agreed well with those of atomic absorption spectroscopy.     

“渐近非扩张映象不动点具误差的迭代逼近”的注记

本文在去掉条件"T在D上一致渐近正则"的情况下,在一致凸Banach空间中给出了几个渐近拟非扩张型映象和渐近非扩张型映象不动点的迭代逼近定理.这些定理推广和发展了最近一些文献的相关成果,并且改进了定理的证明方法.     

Unambiguous structural elucidation of base-modified purine nucleosides using NMR

A general and unambiguous approach has been developed for structural elucidation of modified purine nucleosides using NMR spectroscopy. Systematic assignment of proton and carbon signals of modified nucleosides was firmly established by COSY and the anomerism of the glycosidic linkage of synthetic nucleosides clearly elucidated by NOESY experiments. Characteristic properties of 15N-isotopic labelling at specific positions of nucleosides were also employed for structural studies. The reported approach is applicable to other modified nucleosides and nucleotides, as well as nucleobases.     

Second-order advantage from kinetic-spectroscopic data matrices in the presence of extreme spectral overlapping A multivariate curve resolution--alternating least-squares approach

Multivariate curve resolution coupled to alternating least-squares (MCR-ALS) has been employed to model kinetic-spectroscopic second-order data, with focus on the achievement of the important second-order advantage, under conditions of extreme spectral overlapping among sample components. A series of simulated examples shows that MCR-ALS can conveniently handle the studied analytical problem unlike other second-order multivariate calibration algorithms, provided matrix augmentation is implemented in the spectral mode instead of in the usual kinetic mode. The approach has also been applied to three experimental examples, which involve the determination of: (1) the antiparkinsonian carbidopa (analyte) in the presence of levodopa as a potential interferent, both reacting with cerium (IV) to produce the fluorescent species cerium (III) with different kinetics; (2) Fe(II) (analyte) in the presence of the interferent Zn(II), both catalyzing the oxidation of methyl orange with potassium bromate; and (3) tartrazine (analyte) in the presence of the interferent brilliant blue, both oxidized with potassium bromate, with the interferent leading to a product with an absorption spectrum very similar to tartrazine. The results indicate good analytical performance towards the analytes, despite the intense spectral overlapping and the presence of unexpected constituents in the test samples.     

Numerical analysis of the Gran methods. A comparative study

The paper concerns mainly the modified Gran methods, considered as extrapolative standard addition methods. Particularly, the approximation:

     

Rheological properties of asphalt/SBS/clay blends

The effect of the addition of clay as a third component in polymer modified asphalts has been investigated. After a preliminary investigation on the binary asphalt/clay and polymer/clay blends, the tertiary blends were prepared by adding the clay and polymer to the asphalt, either separately or in the form of a premixed master batch. Intercalated nanocomposites with comparable interlayer distances and glass transition temperatures were obtained in both cases. However, the results show that the mixing procedure significantly affected the final rheological properties. The master curves built in the linear viscoelastic range and represented in both the frequency and the temperature domains help to visualize and evaluate such differences.