Effect of substrate orientation on growth rate and doping level of vapour grown GaAs. Interval (111)A—(100)—(111)B

The effect of the substrate orientation and the supersaturation on the growth rate and doping level of vapor grown GaAs is considered. Experimental results are discussed in terms of crystal growth theory developed by BURTON , CABRERA , FRANK and CHERNOV (BCFCh). It is shown that the main predictions of theory are in agreement with the experimental results. At the same time experimental results, on the whole, are more complicated than predicted by simple crystal growth model. It can be concluded that the BCFCh-theory is applicable for analysing the growth rate and doping level anisotropy for vapor grown crystals.     

Host-Guest Systems on the Surface of Functionalized Superparamagnetic Iron Oxide Nanoparticles (SPIONs) Utilizing Hamilton Receptors and Cyanurate Derivative Molecules

The study of hydrogen bonding interactions at the level of functionalized nanoparticles remains highly challenging and poorly explored area. In this work, superparamagnetic iron oxide nanoparticles (SPIONs) were orthogonally functionalized using receptors bearing multiple hydrogen bonding motifs. Pristine SPIONs were modified by wet chemical processes with Hamilton receptors (hosts), or cyanurate-guest molecules linked to phosphonic acid moieties for monolayer functionalization. The modified surfaces were fully characterized and the number of attached ligands on the surface were determined. The host-guest interactions on the interface of modified SPIONs were investigated by using UV-Vis spectroscopic titrations. Functionalized SPIONs demonstrated two to three magnitudes stronger binding affinities as compared to the related molecular interactions in solution due to synergistic effects on complex surface environment. Higher supramolecular binding ratios of host-guest interactions on the modified surface were emerged. These studies provide fundamental insights into supramolecular complexations on the surface at solid-liquid interface systems with applications in engineered nanomaterials, nano-sensing devices, and drug delivery systems.     

Synthesis and structure of hydrazones obtained by the reaction of 2-[6-methyl-2,4-dioxo-1-(thietan-3-yl)-1,2,3,4-tetrahydropyrimidin-3-yl]acetic acide hydrazide with β-dicarbonyl compounds

Reaction of 2-[6-methyl-2,4-dioxo-1-(thietan-3-yl)-1,2,3,4-tetrahydropyrimidin-3-yl]acetic acid hydrazide with β-dicarbonyl compounds proceeds regioselectively; the structure of the formed hydrazones is governed by the structure of the β-dicarbonyl reaction component. The reaction with acetyl- and propionylacetone afforded 3-[2-(5-alkyl-3-methyl-1H-pyrazol-1-yl)-2-oxoethyl]-6-methyl-1-(thietan-3-yl)pyrimidin-2,4(1H,3H)-diones, with aroylacetones, 5-hydroxypyrazoline derivatives which are present in DMSO solutions in E′ conformation with respect to the amide bond. The condensation products with acetoacetic acid derivatives have a linear structure and consist of mixtures of E,Z- and E′,Z′-isomers owing to the geometric and conformational isomerism.     

Antituberculosis activity of glycosides from <Emphasis Type="Italic">Stevia rebaudiana</Emphasis> and hybrid compounds of steviolbioside and pyridinecarboxylic acid hydrazides

Stevioside and steviolbioside, glycosides from Stevia rebaudiana Bertoni, in addition to hybrid compounds synthesized from steviolbioside and the antituberculosis drug isoniazid and its isomer nicotinic acid hydrazide exhibited moderate antituberculosis activity against M. tuberculosis strain H₃₇R_V in vitro (MIC = 7.5, 3.75, 5, and 10 μg/mL, respectively).     

Synthesis and antimicrobial activity of several bis-quaternized ammonium derivatives of the diterpenoid isosteviol

Previously unreported bis-quaternized ammonium derivatives of the diterpenoid isosteviol (16-oxo-entbeyeran-19-oic acid) were synthesized. The compound in which the two quaternized N atoms were joined by a dodecamethylene spacer had the greatest antimicrobial activity and was comparable in activity with ciprofloxacin and clotrimazole.     

Two-loop calculations for the propagators of gluonic currents

We calculate two-loop corrections to the propagators of gluonic currents$j_{PG}=\alpha G_{\mu v}^a{\overline{G}}_{\mu v}$ and j_SG = (β(α)/α)G_μν². The results of the calculations are used for finding the connection between the characteristic scales of quark and gluon worlds in perturbative QCD and for an estimate of the mass of the first radial excitation of the η′ meson [we obtain (m_η′)¹ = 1.55GeV].     

Estimate of the Degree of the Spin Polarization of a Ferromagnet from Data on the Superconductor/Ferromagnet Proximity Effect

The superconductor/ferromagnet proximity effect in the Pb/Co₂Cr_1–xFe _x Al bilayer systems has been studied. Thin films of the Heusler alloy Co₂Cr_1–xFe _x Al have been prepared at different substrate temperatures. It has been established using Andreev spectroscopy of point contacts that the degree of spin polarization of conduction electrons in the Heusler alloy is on the order of 30 and 70% for the films prepared at a substrate temperature of 300 and 600 K, respectively. It has been found that the dependence of the superconducting transition temperature on the thickness of the Pb layer at a fixed thickness of the Heusler layer is determined by the degree of spin polarization of the conduction band in the ferromagnetic layer.