Bias-Enhanced Formation of Metastable and Multiphase Boron Nitride Coating in Microwave Plasma Chemical Vapor Deposition

Boron nitride (BN) is primarily a synthetically produced advanced ceramic material. It is isoelectronic to carbon and, like carbon, can exist as several polymorphic modifications. Microwave plasma chemical vapor deposition (MPCVD) of metastable wurtzite boron nitride is reported for the first time and found to be facilitated by the application of direct current (DC) bias to the substrate. The applied negative DC bias was found to yield a higher content of sp3 bonded BN in both cubic and metastable wurtzite structural forms. This is confirmed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Nano-indentation measurements reveal an average coating hardness of 25 GPa with some measurements as high as 31 GPa, consistent with a substantial fraction of sp3 bonding mixed with the hexagonal sp2 bonded BN phase.

Resolvable polymorphism in an intergrowth of two modifications of tris(diethyldithiocarbamato)antimony

Tris(diethyldithiocarbamato-κS)antimony(III), [Sb(C5H10NS2)3], is tentatively presumed to comprise a triclinic and a monoclinic polymorph intergrown into each other. The geometry in the triclinic phase is a ψ-capped octahedron and that in the monoclinic phase is a ψ-pentagonal bipyramid. The study also identifies the polyhedral symbols for a reported pair of polymorphs of another SbIII coordination compound, as well as for those of published polymorphic modifications of other BiIII and PbII coordination compounds; the symbols in the pair differ in most of these examples. When differentiating related structures of such classes of coordination compounds, lone-pair stereochemistry may be another informative variable, as stereochemical activity is not always apparent from bond distances and angles only.

Interaction in the systems Y2O3−Ln2O3 (Ln=Tb–Lu)

Based on the analysis of literature data from experimentally constructed phase diagrams of Y2O3 − Ln2O3 systems (Ln = Tb − Lu), as well as temperatures of polymorphic transformations of rare earth oxides (REE), tentative phase diagrams of Y2O3 − Ln2O3 systems (Ln = Tb − Lu) were constructed in wide intervals of temperatures and concentrations. Prediction of the binary phase diagrams structure of yttria − yttrium subgroup lanthanides systems was carried out on the basis of three principles: 1. Since double systems are formed by lanthanide oxides of one (yttrium) subgroup, it is very likely that in such systems continuous solid solutions will be formed between the components. 2. Intermediate binary phases are not formed in these systems. 3. The formation of continuous solid solutions occurs with a decrease in the temperatures of phase transformations in the solid state to a minimum shifted towards a lower transformation temperature of the system component. The forecast of the Y2O3 – Ln2O3 systems phase diagrams structure, where Ln = Tb – Lu, indicates the complete solubility of the components in the liquid and solid states. Binary compounds in the considered systems are not predicted. Phase transformations in the solid solutions on the basis of polymorphic modifications X, H, A, B and C of lanthanide oxides cascade at high temperatures by the peritectoid mechanism. Below 1850 °C regions of solid solutions with cubic C-structure of REE oxides are formed in the whole range of concentrations in the systems. Key words: REE oxides, yttria, polymorphs of REE oxides, phase diagram.

Solvatomorph and polymorph screening of clopamide drug and its copper(ii) complex crystals

The anhydrate and hemihydrate structures of the marketed drug, clopamide, are described the first time. Structural landscape of its copper complexes is presented: three polymorphic modifications and an isostructural series of its alcohol clathrates.

ELECTROANALYSIS IN POSTGENOMIC ERA: RESULTS AND PERSPECTIVES

A method for electroanalysis of the catalytic activity of polymorphic modifications of cytochrome P450 2C9, 2C9 * 2 and 2C9 * 3 has been developed. A study of the mechanisms of interaction of DNA with drugs was carried out.

Investigation of pharmacokinetics of N-(4-trifluoromethylphenyl)-4-methyl-2.2-dioxo-1H-2λ6.1-benzothiazine-3-carboxamide various crystalline modifications in vivo

The phenomenon of polymorphism, inherent in many biologically active substances, including drugs, is an extremely serious problem that requires close attention and comprehensive study. Various crystalline modifications of biologically active compounds, as well as excipients can dramatically change the biopharmaceutical properties and pharmacological characteristics of already known drugs. The bioactive compound N-(4-trifluoromethylphenyl)-4-methyl-2.2-dioxo-1H-2λ6.1-benzothiazine-3-carboxamide was obtained by bioisosterical substitution in the molecule of known non-steroidal anti-inflammatory drugs of the oxycam group in the form of three polymorphic modifications of the crystal. sticks (form A), plates (form B) and blocks (form C) with varying degrees of analgesic and anti-inflammatory effects. The aim of the study was to investigate the pharmacokinetic profile of these polymorphic forms of benzothiazine-3-carboxamide derivative by their oral administration in vivo. The concentration of compounds in the blood of mice was determined by HPLC and the main pharmacokinetic parameters were calculated. It was found that the polymorphic form in the form of plates (form B), in particular, having the largest surface area of crystals, has differences mainly at the stage of absorption with corresponding changes in absorption values, maximum concentration and time of its achievement, has the highest bioavailability and rapid elimination which correlates with the most optimal pharmacological and toxicological characteristics of this compound in comparison with other crystalline forms. This makes it possible to recommend the most active and safe polymorphic form of the compound (form B) for in-depth preclinical study and possible clinical trials as an analgesic and anti-inflammatory agent.