Search

Abstract: The issues of designing bone implants capable of creating an electrical stimulus for bone tissue regeneration under the influence of an external magnetic field are considered. A promising method for generating local electric fields is the use of magnetoelectric (multiferroid) micro- and nanoparticles that are polarized under the action of an external magnetic field and create electric fields comparable in amplitude to endogenous ones. Of practical interest are composite magnetoelectric particles consisting of a ferrimagnetic core and a piezoelectric shell brought into close mechanical contact. Modeling the magnetoelectric effect in a composite particle is carried out; composite particles with cobalt ferrite as a magnetostrictor are fabricated, and the issues of the chemical interaction of phases are discussed.

Abstract: Variants for the synthesis of aluminum acrylates, including substituted hydroxoacrylates, as well as an adduct of aluminum isopropylate with allylamine, were tested to develop a mixture that can be formed by photopolymerization, followed by annealing while maintaining the shape of the ceramic, for further use in molding using stereolithographic 3D printing. By photopolymerization of a polymer precursor based on an acrylate suspension of in situ synthesized alumoxane Al(OH)2(ООСН2СН=СН2), corundum ceramics of a given shape were prepared. The inhomogeneity of the polymer precursor does not prevent its use in technology. A significant percentage of weight loss during heat treatment of the polymer precursor suggests its possible use as a binder when filled with dispersed aluminum oxide powder. The highest shrinkage of a ceramic product occurs in the range of 200–400°C; it is necessary to develop a special program for heating up the product to the sintering temperature to minimize the consequences of severe shrinkage. When a molded product is heat treated in an inert atmosphere, the shrinkage is less than when annealed in air, since pyrolysis leaves behind a large amount of amorphous carbon. Annealing such ceramics with amorphous carbon in a nitrogen atmosphere is promising for carrying out the carbonitridization process in the preparation of aluminum nitride and oxynitride.

The mechanical characteristics are studied for macroporous composite implants on the basis of β‑Ca/PO4)2/polylactide and β-Ca/PO4)2/polycaprolactone obtained by means of thermal-extrusion 3D printing. The effect of the degree of filling exerted on the strength, Young’s modulus, and the characteristics of the material destruction is described for the polymer, as well as for the three-dimensional structure filled with phosphate cement.

Abstract: Thin films of Cd y Zn1 − y O and Mg x Zn1 − x O (y = 0−0.35, x = 0−0.45) ternary alloys have been grown by pulsed laser deposition onto sapphire substrates. The record solubility limits of Cd (y = 0.3) and Mg (x = 0.35) have been achieved in hexagonal zinc oxide. The mismatch of the lattice parameters a of Cd0.2Zn0.8O and Mg0.35Zn0.65O does not exceed 1%; in this case, the band gap discontinuity is 1.3 eV. The surface roughness of the films does not exceed 2.5 nm at x = 0−0.27 and y = 0−0.20.

Using pulsed laser deposition, we have grown n-ZnO/p-GaN, n-ZnO/i-ZnO/p-GaN and n-ZnO/n-Mg0.2Zn0.8O/i-Cd0.2Zn0.8O/p-GaN light-emitting diode (LED) heterostructures with peak emission wavelengths of 495, 382 and 465 nm and threshold current densities (used in electroluminescence measurements) of 1.35, 2, and 0.48 A cm-2, respectively. Because of the spatial carrier confinement, the n-ZnO/n-Mg0.2Zn0.8O/i-Cd0.2Zn0.8O/p-GaN double heterostructure LED offers a higher electroluminescence intensity and lower electroluminescence threshold in comparison with the n-ZnO/p-GaN and n-ZnO/i-ZnO/p-GaN LEDs.

The formation of laser-induced structures on the multicrystalline silicon surface has been investigated. Optimum performances of the surface structurization have been explored. A cardinal decrease in reflectance from modified surface has been discovered in a wide spectral range in comparison with the samples of chemically texturized monocrystalline silicon. The influence of subsequent chemical etching on the reflection spectra of the texturized samples surface has been analyzed.

A stereocontrolled racemic synthesis of conformationally restricted analogues 2a and 2b of a potent CGRP receptor antagonist 1 by novel functionalization of 2-substituted octahydropyrido[1,2-a]pyrazin-6-ones is described. The new diastereoselective LDA-promoted α-nitration of intermediate lactams established the required trans-configuration in the desired products.

A completely stereocontrolled approach to assembly of the major C1−C28 subunit of spongistatin 1 (altohyrtin A) is described. Key steps included the control of two asymmetric aldols by means of Fujita−Nagao (chiral N-acyl-1,3-thiazolidine-2-thione auxiliary) and Mukaiyama (BF3·OEt2-promoted enolsilane coupling) protocols in complex settings.

Mixed cationic Ca2+/Na+(Mg2+) polyphosphates, regarded as potential biocomposite fillers, were fabricated by solid-state reactions. Most of them demonstrated low solubility (assessed also by the Glasser and Jenkins approach) from 1 +- 0.2 g/L for Ca(PO3)2 to 5 +- 0.4 g/L for NaCa(PO3)3 and 50 +- 2 g/L for soluble phase of NaPO3. Liquid-state NMR of the soluble part of polyphosphates gave the degree of polymerization of their chains ranging from 10 to 30 for NaCa(PO3)3 and ca. 1000 monomeric units for NaPO3.

Using pulsed laser deposition, we have grown n-ZnO/p-GaN, n-ZnO/i-ZnO/p-GaN and n-ZnO/n-Mg0.2Zn0.8O/i-Cd0.2Zn0.8O/p-GaN light-emitting diode (LED) heterostructures with peak emission wavelengths of 495, 382 and 465 nm and threshold current densities (used in electroluminescence measurements) of 1.35, 2, and 0.48 A cm-2, respectively. Because of the spatial carrier confinement, the n-ZnO/n-Mg0.2Zn0.8O/i-Cd0.2Zn0.8O/p-GaN double heterostructure LED offers a higher electroluminescence intensity and lower electroluminescence threshold in comparison with the n-ZnO/p-GaN and n-ZnO/i-ZnO/p-GaN LEDs.

For Abstract see ChemInform Abstract in Full Text.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.