Isotope and temperature effects in liquid water probed by x-ray absorption and resonant x-ray emission spectroscopy

High-resolution x-ray absorption and emission spectra of liquid water exhibit a strong isotope effect. Further, the emission spectra show a splitting of the 1b1 emission line, a weak temperature effect, and a pronounced excitation-energy dependence. They can be described as a superposition of two independent contributions. By comparing with gas phase, ice, and NaOH/NaOD, we propose that the two components are governed by the initial state hydrogen bonding configuration and ultrafast dissociation on the time scale of the O 1s core hole decay.     

Novel approach to 6-alkenyl-substituted pyridoxine derivatives based on the Heck reaction

A new synthetic approach to 6-alkenyl-substituted pyridoxine derivatives was developed based on the Heck reaction. The reaction, which was catalyzed using a mixture of Pd(OAc)₂, (o-Tol)₃P and Bu₃N as a base, led to seven new 6-alkenyl pyridoxine derivatives. When acrylic acid was used the products of decarboxylation and dimerization were formed.     

Correlation between the molecular structure and photoresponse in aliphatic self-assembled monolayers with azobenzene tailgroups

We have compared the structural and photoisomerization properties of self-assembled monolayers (SAMs) comprising either the trans or cis isomers of azobenzene terminated dithiolane with in-chain amide unit, viz., 4-(phenyldiazenyl)phenyl-4-(1,2-dithiolane-3-yl)-butylcarboxamide ( 1). These films were prepared on Au(111) from solutions of both isomers. Structure and composition of the SAMs were studied by X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy. The photoresponse of the films was monitored in real time by ellipsometry. SAMs fabricated from the trans isomer were found to be densely packed and highly ordered. These films did not show any discernible photoresponse upon irradiation with UV light, which, under favorable conditions, triggers the trans- cis isomerization. In contrast, films prepared from solutions containing predominantly the cis isomer were loosely packed and mostly disordered but exhibited reversible photoreactivity. The results confirm that steric effects, i.e., available free volume, play a dominant role for the photoresponse of aliphatic SAMs bearing the photoactive azobenzene group. The crystal structure of 1 ( trans isomer) exhibits a row-like aggregation of neighboring molecules by weak hydrogen bonds and can be taken as a model for the arrangement of 1 in the monolayer films. Further, in addition to the surface coordination behavior, we have also mimicked the chemisorption of the 1,2-dithiolane moiety onto the gold substrate in molecular coordination chemistry in oxidative addition reactions with the zero-valent platinum complex [Pt(PPh 3) 4].     

Electrical wiring of Pseudomonas putida and Pseudomonas fluorescens with osmium redox polymers

Two different flexible osmium redox polymers; poly(1-vinylimidazole)12-[Os-(4,4'-dimethyl-2,2'-di'pyridyl)2Cl2](2+/+) (osmium redox polymer I) and poly(vinylpyridine)-[Os-(N,N'-methylated-2,2'-biimidazole)3](2+/3+) (osmium redox polymer II) were investigated for their ability to efficiently "wire" Pseudomonas putida ATCC 126633 and Pseudomonas fluorescens (P. putida DSM 6521), which are well-known phenol degrading organisms, when entrapped onto cysteamine modified gold electrodes. The two Os-polymers differ in redox potential and the length of the side chains, where the Os(2+/3+)-functionalities are located. The bacterial cells were adapted to grow in the presence of phenol as the sole source of organic carbon. The performance of the redox polymers as mediators was investigated for making microbial sensors. The analytical characteristics of the microbial sensors were evaluated for determination of catechol, phenol and glucose as substrates in both batch analysis and flow analysis mode.     

The complete isomorphism class of an operator space

Suppose is an infinite-dimensional operator space and is a positive integer. We prove that for every there exists an operator space such that the formal identity map is a complete isomorphism, is an isometry, and . This provides a non-commutative counterpart to a recent result of W. Johnson and E. Odell.

     

Quantitative theory of living chain copolymerization covering anionic and free-radical mechanisms

Main results of our original general theory of a chain copolymerization are presented which enable the calculation of any statistical characteristic of a copolymer prepared. Outlined theoretical approach also permits one to find thermodynamic and scattering properties of solutions and melts of these copolymers.