Investigation of irradiated PA1010 containing heterogeneous nuclei

This paper deals with radiation effects on PA1010 containing heterogeneous nuclei (Nd2O3). With the help of DSC, WAXD and ESR techniques, the change in the crystallinity and the perfection of the crystal of irradiated PA1010 containing heterogeneous nuclei were studied. Copyright (C) 1996 Elsevier Science Ltd.

Orientation and electrocatalysis of riboflavin adsorbed on carbon substrate surfaces

Based on scanning tunnelling microscopy and electrochemical measurements, orientation and electrocatalytic function of riboflavin adsorbed on carbon substrates have been described for the first time. Scanning tunnelling micrographs show clearly that tip induction may result in an orientation change of the adsorbed riboflavin molecule on highly oriented pyrolytic graphite from the initially vertical orientation to the stable flat form. The adsorbed riboflavin as an effective mediator can accelerate the reduction of dioxygen which accepts two electrons from the reduced riboflavin to generate hydrogen peroxide. The rate constants of the electrocatalytic reaction in various pH solutions were determined using a rotating disc electrode modified with riboflavin. The pH effect and possible catalytic mechanism are discussed in detail.

Influence of the fold surface of the lamellae on radiation effects - Research on irradiated polyamide-1010 containing heterogeneous nuclei

Irradiated polyamide-1010 (PA1010) and PA1010 containing 0.5% (wt) heterogeneous nuclei were studied by ESR, WAXD, DSC and the determination of gel fractions. The fold surface of the lamellae plays an important role in the effects of radiation on crystalline PA1010. The results show that the direct radiation effects on both samples vary, while after being heated to 220 degrees C, the final radiation effects are identical, regardless of the difference in the amount of the fold surface of the lamellae. The post-radiation effects result predominantly from the fold surface.

A COMPARATIVE-STUDY ON STM IMAGING AND ELECTROCATALYTIC ACTIVITY OF DIFFERENT SURFACES MODIFIED WITH FLAVIN ADENINE-DINUCLEOTIDE

Flavin adenine dinucleotide (FAD) was modified onto the highly oriented pyrolytic graphite (hopg) and glassy carbon electrode (gee) surfaces with three methods, respectively. Corresponding image analysis for FAD-modified hopg surfaces has been performed by scanning tunnelling microscope (STM) for the first time. The molecular resolution STM image of FAD adsorbed on the freshly-cleaved hopg was obtained, the quantitative size determination suggests that the FAD molecules adsorb side lying on the substrate surface. The anodization treatment of hopg surface yields many pits, which were clearly observed under STM. These pits provide active sites on the hopg surface for modification and the treated hopg can strongly adsorb FAD molecules, the latter exhibiting an irregular cluster structure on such a surface. When FAD was electrochemically deposited on the substrate surface, a chain structure was successfully observed. The adsorbed FAD on anodized glassy carbon electrode (gee) surface can effectively catalyze the reduction of glucose oxidase, hemoglobin and myoglobin, with a large decrease in the overvoltage, whereas the deposited FAD film exhibits excellent electrocatalysis towards dioxygen reduction.

UNSTEADY DIFFUSION KINETICS OF ZIEGLER-NATTA HETEROGENEOUS CATALYST POLYMERIZATION .4. PREDICTION OF EXPERIMENTAL RESULTS OF PROPYLENE ETHYLENE 1-HEXADECENE TERPOLYMERIZATION

The prediction, based on unsteady diffusion kinetics, of the enhancement of reactivity and incorporation of 1-hexadecene in its copolymerization with propylene on adding a small amount of ethylene (increase from 5,2 mol-% to 10,8 mol-% when 2% of ethylene was added, and to 16,1 mol-% when 5% was added) was verified in the terpolymerization of propylene/1-hexadecene/ethylene on a commercial Solvay-type delta-TiCl3 catalyst. The catalyst efficiency was thus also increased. These augmentations originate from the increase in diffusion coefficient of 1-hexadecene at the catalyst surface when the PP crystallinity decreases on introduction of ethylene. Calculation based on unsteady diffusion kinetics showed that the order of diffusion coefficients ethylene > propylene > 1-hexadecene is reversed as the monomer concentration increases when the monomers are not at their equilibrium concentration. Sequence distribution as determined by means of C-13 NMR revealed a tendency of blocky structure rather than a Bernoullian one. The terpolymer compositions obtained by means of an IR method developed in this work conform rather well with the NMR results. Results in this work not only support the unsteady diffusion kinetics but also provide a new route to prepare olefinic copolymer rubbers with heterogeneous titanium catalysts.

APPLICATIONS OF RAPID SCAN SPECTROELECTROCHEMISTRY - DETERMINATION OF HETEROGENEOUS ELECTRON-TRANSFER RATE-CONSTANT OF BILIVERDIN OXIDATION

The rapid scan spectrometer was used to determine the heterogeneous electron transfer rate parameters for the oxidation of Biliverdin in DMF by single potential step thin layer spectroelectrochemical techniques and yielded an average formal heterogeneous electron transfer rate constant K(s, h)0' = 2.45 (+/-0.12) x 10(-4) cm s-1, electrochemical transfer coefficient alpha = 0.694+/-0.008. The oxidation process of Biliverdin was also studied and the formal potential E0 = 0.637 V (vs. Ag/AgCl) was obtained.

SOME NEWER CONCEPTS OF ETHYLENE ALPHA-OLEFIN COPOLYMERIZATION ON HETEROGENEOUS ZIEGLER-NATTA CATALYSTS

Unsteady diffusion kinetic, recently advanced by this laboratory, is applied to the examination of some polymerization and molecular chain structure problems. Hitherto deemed "anomalous" phenomena, such as the faster rate of copolymerization of ethylene/alpha-olefin than the homopolymerization of ethylene and the enrichment in the incorporation of a higher alpha-olefin in its copolymerization with ethylene by a lower alpha-olefin, are reasonably explained by unsteady diffusion of monomers. Molecular chain structure of copolymers, such as compositional heterogeneity and its dependence on comonomer incorporation originates from the difference in diffusion coefficients of the monomers. A copolymer composition equation taking into consideration the unsteady diffusion was developed. In cases where simulated curves were compared with experimental curves, good agreements were found.

MARINE ORGANISMS ATTACHED TO SEAWEED SURFACES IN JIAOZHOU BAY, CHINA

Scanning electron microscopy of the surfaces of the seaweeds Laminaria japonica, haploid Porphyra yezoensis, Ulva pertusa and the diploid conchocelis of P. yezoensis and P. haitanensis revealed Vibrio and Micrococcus to be abundant on the surfaces of U. pertusa and P. yezoensis. Vibrio, Flavobacterium, Pseudomonas, Staphylococcus, Bacillus, Corynebacterium and other genera were isolated from the surfaces of L. japonica.

Isolation and identification of bacteria associated with the surfaces of several algal species

We conducted this study to assess the diversity of bacteria associated with the surfaces of algae based on 16S rDNA sequence analyses. Twelve strains of bacteria were obtained from the surfaces of the following four species of algae: Gracilaria textorii, Ulva pertusa, Laminaria japonica, and Polysiphonia urceolata. The isolated strains of bacteria can be divided into two groups: Halomonas and Vibrio, in physiology, biochemical characteristics and 16S rDNA sequence analyses. The phylogenetic tree constructed based on 16S rDNA sequences of the isolates shows four obvious clusters, Halomonas venusta, Vibrio tasmaniensis, Vibrio lentus, and Vibrio splendidus. Isolates from the surface of P. urceolata are more abundant and diverse, of which strains P9 and P28 have a 16S rDNA sequence very similar (97.5%-99.8%) to that of V. splendidus. On the contrary, the isolates from the surfaces of G textorii, U. pertusa and L. japonica are quite simple and distribute on different branches of the phylogenetic tree. In overall, the results of this study indicate that the genetic relationships among the isolates are quite close and display a certain level of host species specificity, and alga-associated bacteria species are algal species specific.

Characteristics of sulfide corrosion products on 316L stainless steel surfaces in the presence of sulfate-reducing bacteria

It has been found that microbial communities play a significant role in the corrosion process of steels exposed in aquatic and soil environments. Biomineralization influenced by microorganisms is believed to be responsible for the formation of corrosion products via complicated pathways of electron transfer between microbial cells and the metal. In this study, sulfide corrosion products were investigated for 316L stainless steel exposed to media with sulfate-reducing bacteria media for 7 weeks. The species of inorganic and organic sulfides in the passive film on the stainless steel were observed by epifluorescence microscope, environmental scanning electron microscope combined with energy dispersive spectroscopy and X-ray photoelectron spectroscopy. The transformation from metal oxides to metal sulfides influenced by sulfate-reducing bacteria is emphasized in this paper. (c) 2005 Elsevier B.V. All rights reserved.

Addition reactions of nitrones on the reconstructed C(100)-2 x 1 surfaces

In this paper, the reactions of nitrone, N-methyl nitrone, N-phenyl nitrone and their hydroxylamine tautomers (vinyl-hydroxylamine, N-methyl-vinyl-hydroxylamine and N-phenyl-vinyl-hydroxylamine) on the reconstructed C(100)-2 x 1 surface have been investigated using hybrid density functional theory (B3LYP), Moller-Plesset second-order perturbation (MP2) and multi-configuration complete-active-space self-consistent-field (CASSCF) methods. The calculations showed that all the nitrones can react with the surface "dimer" via facile 1.3-dipolar cycloaddition with small activation barriers (less than 12.0 kJ/mol at B3LYP/6-31g(d) level). The [2+2] cycloaddition of hydroxylamine tautomers on the C(100) surface follows a diradical mechanism. Hydroxylamine tautomers first form diradical intermediates with the reconstructed C(I 00)-2 x I surface by overcoming a large activation barrier of 50-60 kJ/mol (B3LYP), then generate [2+2] cycloaddition products via diradical transition states with negligible activation barriers. The surface reactions result in hydroxyl or amino-terminated diamond surfaces, which offers new opportunity for further modifications. (C) 2007 Elsevier B.V. All rights reserved.

地震波模拟：非规则网格离散的数值解法、吸收边界及其实际应用

This dissertation presents a series of irregular-grid based numerical technique for modeling seismic wave propagation in heterogeneous media. The study involves the generation of the irregular numerical mesh corresponding to the irregular grid scheme, the discretized version of motion equations under the unstructured mesh, and irregular-grid absorbing boundary conditions. The resulting numerical technique has been used in generating the synthetic data sets on the realistic complex geologic models that can examine the migration schemes. The motion equation discretization and modeling are based on Grid Method. The key idea is to use the integral equilibrium principle to replace the operator at each grid in Finite Difference scheme and variational formulation in Finite Element Method. The irregular grids of complex geologic model is generated by the Paving Method, which allow varying grid spacing according to meshing constraints. The grids have great quality at domain boundaries and contain equal quantities of nodes at interfaces, which avoids the interpolation of parameters and variables. The irregular grid absorbing boundary conditions is developed by extending the Perfectly Matched Layer method to the rotated local coordinates. The splitted PML equations of the first-order system is derived by using integral equilibrium principle. The proposed scheme can build PML boundary of arbitrary geometry in the computational domain, avoiding the special treatment at corners in a standard PML method and saving considerable memory and computation cost. The numerical implementation demonstrates the desired qualities of irregular grid based modeling technique. In particular, (1) smaller memory requirements and computational time are needed by changing the grid spacing according to local velocity; (2) Arbitrary surfaces and interface topographies are described accurately, thus removing the artificial reflection resulting from the stair approximation of the curved or dipping interfaces; (3) computational domain is significantly reduced by flexibly building the curved artificial boundaries using the irregular-grid absorbing boundary conditions. The proposed irregular grid approach is apply to reverse time migration as the extrapolation algorithm. It can discretize the smoothed velocity model by irregular grid of variable scale, which contributes to reduce the computation cost. The topography. It can also handle data set of arbitrary topography and no field correction is needed.

Heterogeneous asymmetric hydrogenation of ethyl pyruvate on chirally modified Pt/Al2O3 catalyst with fixed-bed reactor

The enantioselective hydrogenation of ethyl pyruvate on the cinchonidine modified Pt/Al2O3 catalyst was investigated using a high-pressure reaction system with a fixed-bed reactor for the purpose to produce the,chiral product without separating the catalyst from the reaction system. The reaction was also investigated in a batch reactor for comparison. About 60% e. e. and 90% e. e. were obtained with the fixed-bed reactor and the batch reactor respectively, demonstrating the possibility for the heterogeneous asymmetric hydrogenation in the fixed-bed reactor. Some adsorbed chiral modifier, cinchonidine, can be slowly removed from the surface of Pt/Al2O3 under the continuous flow reaction, as a result, the e, e, values drops with the reaction time in the fixed-bed reactor. The enantio-selectivity is higher in the fixed-bed reactor, but lower in the batch reactor when ethanol was used as solvent than that when acetic acid as solvent. CO was used as molecular probe to characterize the adsorption of cinchonidine an the catalyst surface by IR spectroscopy, A red shift observed in IR spectra of coadsorbed CO with cinchonidine suggests that the cinchonidine adsorption is mainly through the pi -interaction with platinum surface and donating electron to the platinum surface.