Nanocrystals grown in amorphous Cr and CrNi thin films

The structure of vacuum annealed amorphous sputtered Cr and CrNi (55:45) thin films has been studied by transmission electron microscopy (TEM) and electron diffraction (TED). The thin films with thicknesses ranging from 150 to 600 Å were annealed while still on their alkali halide substrates under high vacuum at temperatures ranging from 200 to 370°C. The TEM and TED data permitted to establish the annealing conditions (temperature, duration), which lead to the nucleation and growth of nanosized crystals in the Cr and CrNi icosahedral glasses.     

Human topoisomerase I poisoning: docking protoberberines into a structure-based binding site model

Summary Using the X-ray crystal structure of the human topoisomerase I (top1) – DNA cleavable complex and the Sybyl software package, we have developed a general model for the ternary cleavable complex formed with four protoberberine alkaloids differing in the substitution on the terminal phenyl rings and covering a broad range of the top1-poisoning activities. This model has the drug intercalated with its planar chromophore between the −1 and +1 base pairs flanking the cleavage site, with the nonplanar portion pointing into the minor groove. The ternary complexes were geometry-optimized and relative interaction energies, computed by using the Tripos force field, were found to rank in correct order the biological potency of the compounds; in addition, the model is also consistent with the top1-poisoning inactivity of berberine, a major prototype of the protoberberine alkaloids. The model might serve as a rational basis for elaboration of the most active compound as a lead structure, in order to develop more potent top1 poisons as next generation anti-cancer drugs.     

Calculation of the information content of retrieval procedures applied to mass spectral data bases

A procedure has been developed for estimating the information content of retrieval systems with binary-coded mass spectra, as well as mass spectra coded by other methods, from the statistical properties of a reference file. For a reference file, binary-coded with a threshold of 1% of the intensity of the base peak, this results typically in an estimated information content of about 50 bits for 200 selected $\text{m}\text{z}$ values. It is shown that, because of errors occurring in the binary-coded spectra, the actual information content is only about 12 bits. This explains the poor performance observed for retrieval systems with binary-coded mass spectra.     

Introduction of a planar chirality onto steroid substrates: synthesis of (S) and (R)-2′-formylcymantrenyl-17α-ethynylestradiols using (S) and (R)-1-formyl-2-iodo-cymantrenes

We report the synthesis and characterisation of (S) and (R)-2′-formylcymantrenyl-17α-ethynylestradiol synthesized using the Sonogashira cross-coupling reaction between optically pure (S) and (R) 1-formyl-2-iodo cymantrenes and ethynylestradiol. (S) and (R) 1-formyl-2-iodo cymantrenes were obtained from the same precursor: (2R,4R)-4-(methoxymethyl)-2-cymantrenyl-1,3-dioxane.     

Influence of Coriolis coupling on inelastic scattering of deuterons

Influence of Coriolis coupling on excitation of some Nilsson states in¹⁵⁵Gd,¹⁵⁷Gd and¹⁶⁷Er by inelastic scattering of 12·1 MeV deuterons is analysed. Expanded Nilsson potential with hexadecapolar deformation is used for the model calculations. Theoretical values of reduced transition probability,B(E2) are compared with experimental ones.     

Preparation and basic physical properties of BiTeI single crystals

A modified Bridgman method is described, which makes it possible to prepare homogeneous BiTeI crystals using excess iodine. At room temperature the values of the electrical conductivity of the crystals range around 2000 ^–1 cm^–1, the Hall constant value about 0·09 cm^–3 coul^–1, the Seebeck coefficient about 50 V K^–1. In connection with the assumption of super-stoichiometric iodine content we expect there exist point defects in the crystals, where Te atoms are replaced with I atoms, which gives rise to electric conductivity. On the basis of the temperature dependence of the electron mobility one can suppose a mixed mechanism of the scattering of the free carriers by the acoustic branch of lattice vibrations and by ionized impurities.     

Catalyst selectivity in thiophene hydrodesulfurization: Effect of H2S and aging

The distribution of hydrodesulfurization (HDS) products of thiophene was compared on 9 different catalysts at different degrees of sulfidation and at aging in H₂/thiophene mixtures. The main products of HDS were C₄ and C_l-C₃ hydrocarbons. The effect of sulfur uptake on the productsmin distribution was similar for Co and Ni promoted, and reverse to that on Pd and Pt promoted samples. The effect of aging was similar for all samples. This revised version was published online in August 2006 with corrections to the Cover Date.     

Comparison of the acid strength of solid catalysts

The catalytic activity of some solid acidic catalysts was tested in the depolymerization of paraldehyde. It was found that the activities of sulfonated ion exchange resin and mounted phosphotungstic acid strongly exceed the activity of silica-alumina and other oxide catalysts. By means of Brönsted relationship, the differences in H_O of the surfaces were estimated.

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