Thallium as an Additive Modifying the Selectivity of Pd/SiO2 Catalysts

Catalytic properties of palladium and bimetallic palladium–thallium catalysts supported on SiO₂ in the reaction of glucose oxidation to gluconic acid were studied. Catalysts modified with thallium showed better selectivity and activity than palladium catalysts. XRD studies proved the presence of intermetallic interactions, which probably increase the selectivity of Pd–Tl/SiO₂ catalysts. Particular attention was paid to the losses of thallium and palladium from the catalysts during the catalytic reaction.     

PHOTOCHEMICAL BINDING OF PHENOTHIAZINES ON BIOLOGICAL MEMBRANE PROTEINS

Abstract— The photobinding of phenothiazine derivatives (chlorpromazine, fluphenazine, promazine and promethazine) was studied on four different types of biological membranes (microsomes, myelin and synaptosomes from rat brain as well as human erythrocytes). The photoreaction was performed by ultraviolet irradiation of the tritiated compounds in their long wavelength absorption band (313 nm) and bound photoproducts were analysed by autoradiography of the proteins separated by polyacrylamide gel electrophoresis. The specificity of binding is low, however, a 34000 dalton band is intensely labeled on synaptic membranes with chlorpromazine and fluphenazine. All the phenothiazines bind on erythrocyte membrane proteins and specially on band 4.2 and on a peptide located before actin on the electrophoresis gel. These results show the generality of the phenothiazine photobinding on membrane proteins. These photobinding properties can be used for the identification and localization of some of these proteins.     

Study of the complexation of Cu(II) by fulvic acids extracted from a sewage sludge and its compost

 The complexation of Cu(II) by two samples of fulvic acids (FA) extracted from the raw sewage sludge (RsFA) of a waste water processing plant and from the composted sludge (CsFA) obtained upon aerobical digestion was studied at pH 6.0. Synchronous molecular fluorescence spectroscopy was used to monitor the association of FA with Cu(II) and a self-modelling mixture analysis method (SIMPLISMA) was used to preprocess the spectral data to calculate the number of components with different quenching profiles as function of the Cu(II) concentration and their spectra. The stability constants and a rough estimation of the binding site concentrations were obtained by a Stern-Volmer analysis, by a non-linear least-square method and by a linear procedure. The analysis of the SyF spectra allowed the identification of two binding sites for both samples. The logarithm of the conditional stability constant corresponding to the 1:1 complex formed between the stronger binding site and Cu(II) is about 4 for both samples. Received: 22 April 1996 / Revised: 5 August 1996 / Accepted: 7 August 1996     

Empirical relation between permittivity $$(\varepsilon)$$ and viscosity $$(\eta)$$ of polar and non-polar liquids

An empirical relation is proposed wherein the inverse of the permittivity of a pure liquid is described as a linear function of the inverse of the viscosity. It also provides a simple method of calculating the permittivity of a solid at the freezing temperature.     

The use of the CNDO method in spectroscopy: VII. Changes in dipole moment upon excitation

The results of the calculations of changes in dipole moment upon excitation of some organic molecules are discussed in connection with recent high resolution spectroscopic measurements of the same quantities. Calculations are reported for several substituted benzenes, several azines, and for formaldehyde, propynal, formyl fluoride, difluorodiazirine and azulene. The calculations were carried out within the CNDO/S parametrization scheme.     

A spectroscopic study of hydrogen bond formation by silatranes and their analogues

The IR absorption shifts of OH and OD stretching vibrations upon interaction of silatranes XSi(OCH(CH₃)CH₂)₃N and their monocyclic analogues of the type R₂(OCHR′CH₂)₂NR$?with phenol and deuteromethanol, respectively, were measured. In the systems involving silatranes these values are higher than in systems with the corresponding ethoxysilanes. The equilibrium constants and thermodynamic parameters of the interaction of the compounds studied with phenol in n-heptane were measured by electronic spectroscopy. The interaction of phenol with the compounds studied shows two lines correlating with the thermodynamic parameters ΔH - f(ΔS). One of the lines is plotted by alkoxysilanes, cyclic and acyclic ethers. The second line corresponds to the compounds having a O-C-C-N group. This enables a conclusion to be drawn that in a non-polar medium the basic centre of silatranes and their monocyclic analogues is different from the oxygen in ethers and alkoxysilanes.     

Nested Partitions Method for Stochastic Optimization

The nested partitions (NP) method is a recently proposed new alternative for global optimization. Primarily aimed at problems with large but finite feasible regions, the method employs a global sampling strategy that is continuously adapted via a partitioning of the feasible region. In this paper we adapt the original NP method to stochastic optimization where the performance is estimated using simulation. We prove asymptotic convergence of the new method and present a numerical example to illustrate its potential.