Phase and structural transitions in vicinal water on protein surfaces by means of the DSC

This paper presents investigations of phase and structural transitions occurring in water adsorbed on the surface of bovine serum albumin (BSA) and on the so-called intelligentrs or smart silica gel surface covered with a chemically bonded BSA phase. Cyclic changes of heat flow (HF) were observed in the samples studied during cooling and heating of the measuring cell of the differential scanning calorimetry (DSC) apparatus. These cyclic changes reflect structural transitions occurring in the water adsorbed on the surface at subambient and elevated temperatures. This is connected with cyclic changes (decay and reproduction) of ice-like structures existing in the adsorbed water layers. On the basis of quantitative investigations it appears that, depending on the direction of the cooling or heating process of the samples studied, the number of ice-like water structures in the surface film increases or decreases. It has been stated that the observed fluctuations occur spontaneously and suddenly in the whole volume of adsorbed water in different and not regular temperature ranges, especially at the paradoxical effect temperatures.Support from the Research Council (Dr. R. K. Gilpin and Dr. M. Jaroniec) of Kent State University (Ohio, USA) is acknowledged. The author thanks Dr. V. Tittlebach for providing the samples of pure BSA and silica gel with chemically, bonded BSA phase.     

Characterization of self‐assembled phenyl and benzyl isothiocyanate thin films on Au surfaces

Structures of self‐assembled monolayers (SAMs) prepared from benzyl isothiocyanate (BZIT) and phenyl isothiocyanate (PHIT) were comparatively investigated by means of surface enhanced Raman scattering (SERS) on gold nanoparticle surfaces. Both the molecules are assumed to have upright geometries binding via the sulfur atom, from the SERS spectral features. The broad and split bands at ～2100 cm^?1 could be ascribed to the combination band ν_9a + ν₁₂ of the phenyl ring vibrations through a Fermi‐resonance interaction with the ν₃(NCS) band in the neat‐liquid state. Such broad bands became quite symmetric upon adsorption on Au. UV‐vis absorbance spectroscopy and cyclic voltammetry (CV) were used to compare the kinetics of the formation of SAMs on gold. Our results suggest that BZIT should have a relatively faster self‐assembly than PHIT, as indicated from signal decrease in the CV graph, which suggests a more vertical stance for BZIT in line with Raman measurements. Copyright © 2006 John Wiley & Sons, Ltd.     

氧原子在Pt(s)-[n(111)×(100)]型台阶面上的吸附和振动

应用原子和表面簇合物相互作用的5-参数Morse势(简称5-MP)方法系统地研究了氧-铂台阶面体系.理论结果表明:在Pt(s)-[n(111)×(100)]型台阶面上，氧原子吸附在台阶下的四重位，对应稳定吸附态β2；平台上靠近四重位的三重吸附态被湮灭，其它三重位对应吸附态β1；而且平台的长度对四重吸附态有影响.     

The topology of energy hypersurfaces IV. Generator sets for the fundamental group of reaction mechanisms and the complete set of reaction paths

A countable set of distinguished fundamental reaction mechanisms on a potential surface serves as the set of generators for the fundamental group of reaction mechanisms. The effects of a change in the upper limit for energy on such groups are described with the aid of a lower semilattice, introduced into the family of all fundamental groups of reaction mechanisms, supported by the given potential energy surface. The algebraic structure of all reaction paths is described with the aid of groupoids and various subgroupoids and semigroups derived from them.     

Model studies in heterogeneous catalysis at the microscopic level: from the structure and composition of surfaces to reaction kinetics

Heterogeneous catalysis is one of the fields of modern technology, in which a characterization of structural and chemical properties of solid surfaces at the microscopic level is of enormous importance. For a long time, such insights have been precluded by the complexity of most catalytically active materials. Recently, substantial progress has been made, however, toward a microscopic-level understanding of complex catalyst surfaces. We discuss the driving factors for these advancements, which are based on the development of new well-defined model systems as well as on advances in experimental technology and theory. Scrutinizing the example of planar model catalysts, we identify the process of linking structural and chemical information to microscopic reaction kinetics as a particular challenging aspect of today’s work. We review the kinetic effects which may have an influence on the reaction kinetics on complex surfaces. As an example how structural and kinetic information can be correlated at the microscopic level we discuss the case of surface oxidation and oxygen induced restructuring of Pd nanoparticles as studied by molecular beam methods.     

铁合金厂回收的硅微粉在不同温度下晶相结构的研究

铁合金厂冶炼过程产生的大量硅微粉烟尘, 可以作为耐火材料和窑具材料的结合剂, 活性剂和矿化剂, 可促进耐火材料固相反应和烧结, 有利于晶型的转变, 提高耐火材料的高温性能。硅微粉在高于或等于1100 ℃不析晶。1200和1300 ℃析晶规律是:首先α-石英转变为α-方石英, 然后转变为α-鳞石英。在1400～1450 ℃首先析出卡片号为290085的石英变体, 然后转变为α-方石英。 而常规转化过程是α-方石英很难形成α-鳞石英, 而且不形成290085的变体, 因此其转化规律与常规不同。在液相存在情况下, 少量α-方石英转变为α-鳞石英, 不同温度下析晶结构探讨为实际生产提供适宜的升温曲线。     

Comparison of line search minimization algorithms for exploring topography of multidimensional potential energy surfaces: Mg+Arn case

The most robust numerical algorithms for unconstrained optimization that involve a line search are tested in the problem of locating stable structures and transition states of atomic microclusters. Specifically, the popular quenching technique is compared with conjugate gradient and variable metric algorithms in the Mg⁺Ar_n clusters. It is found that the variable metric method BFGS combined with an approximate line minimization routine is the most efficient, and it shows global convergence properties. This technique is applied to find a few hundred stationary points of Mg⁺Ar₁₂ and to locate isomerization paths between the two most stable icosahedral structures found for Mg⁺Ar₁₂. The latter correspond to a solvated and a nonsolvated ion, respectively. © 1997 John Wiley & Sons, Inc. J Comput Chem 18 :1011–1022, 1997     

The development of conductive composite surfaces by a diffusion-limited in situ polymerization of pyrrole in sulfonated polystyrene ionomers

Electrically conductive composite surfaces were prepared by a diffusion-controlled in situ polymerization of pyrrole in the surface layer of sulfonated polystyrene ionomer films. Premolded films of the ionomer sulfonic acid derivatives were sequentially immersed in aqueous solutions of pyrrole and FeCl₃, and polymerization occurred only where both the monomer and the oxidant were present. The penetration of the polypyrrole (PPy) into the film was controlled by varying the immersion time in the monomer solution. The amount of PPy produced depended on the immersion time of the film in the monomer and the degree of sulfonation of the ionomer. Surface conductivities of 10⁻⁴-10⁻¹ S/cm were achieved with PPy concentrations from 2 to 22 wt % and composite layers as thin as 15 μm. Intermolecular interactions occurred between PPy and the ionomer by proton transfer. Incorporation of PPy also increased the tensile strength of the ionomer film, significantly increased its modulus above T_g, and inhibited melt flow. © 1997 John Wiley & Sons, Inc.     

Monte-Carlo model for the hydrogenation of alkenes on metal catalyst

A Monte-Carlo model for the simulation of alkene hydrogenation on metallic catalysts has been developed and implemented in Fortran language. We describe the model employed for ethylene hydrogenation on platinum and show the flow chart of the program. Computational characteristics such as number of necessary calculations to reach steady state, running times on different platforms, and effect of the size of the catalyst matrix, are presented. Good correlation between simulated and experimental data was observed. A subroutine allows for visual observation of the reaction. This approach is very useful for obtaining a personal impression of the important factors governing the reaction. By using this example the advantages of Monte-Carlo simulation to test the level of understanding of catalytic phenomena are discussed. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 396–403, 1998