GaAsN-on-GaAs MBE using a DC plasma source

A new dc plasma source for MBE growth of GaAsN layers is suggested. The efficiency of nitrogen incorporation, crystal perfection, surface morphology, and luminescent properties of the epilayers vs. operation conditions of the source are studied.     

Synthesis and structure of azido-and amino-substituted dibenzoxazepinones

1,3-Dinitro[b, f][1,4]dibenzoxazepin-11(10H)-one enters nucleophilic substitution reactions with N-nucleophiles, azide ion preferably replacing the nitro group in position 3, whereas amines the one in position 1. Structures of the substitution products were confirmed by X-ray diffraction and ¹H NMR NOE spectroscopy. The selectivity observed in the reaction with amines was supposed to be caused by the stabilization of the intermediate σ-complex with the NH…O intramolecular hydrogen bond. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2018–2022, October, 2007.     

Unusual structure of a biphenyl fragment: the important role of weak interactions

1,5‐Bis([1,1′‐biphenyl]‐4‐yl)‐5‐hydroxy‐3‐methylheptane‐1,6‐dione, C₃₂H₃₀O₃, was investigated by X‐ray analysis, quantum chemical calculations and AIM (atoms in molecules) analysis. It was shown that four intramolecular C—H…π forces are established between the two biphenyl fragments. C—H…π interactions lead to a bending of the biphenyl part. The energy of the intramolecular interactions was estimated and the exclusive role of the moment of force was established.     

Dynamics of 5-Aminolevulinic Acid-Induced Accumulation of Protoporphyrin IX in Three Cell Lines of Different Origin

Technical Physics - The dynamics of synthesis and accumulation of protoporphyrin IX induced by 5-aminolevulinic acid (5-ALA) was studied using confocal fluorescence microscopy in three established...     

Mass spectrometry in the study of extracellular enzymes produced by filamentous fungi

The use of MALDI-TOF and other types of mass spectrometry for the identification and investigation of extracellular enzymes (carbohydrases, proteinases, esterases, etc.) produced by filamentous fungi belonging to the genera Aspergillus, Trichoderma, Penicilium, Chrysosporium, etc. is discussed. The method of mass spectrometric peptide fingerprinting combined with the use of Internet software for on line data analysis (MASCOT, Aldente, FindPept, FindMod, GlycoMod) allows the fast and reliable identification of both individual enzymes and the components of crude multienzyme preparations without their fractionation. The method was also applied to the discrimination of the fungal genes encoding enzymes with similar substrate specificity. Other enzyme-based applications of mass spectrometry, such as the revelation of the presence or absence of structural domains in the molecules of carbohydrases, the detection of posttranslational and artificial modifications in the enzymes, and the use of tandem mass spectrometry for de novo peptide sequencing are described.     

Preparation of oxygen-containing organic products from bed-oxidized brown coal by ozonation

The possibility of modifying the functional composition of humic acids by gas-phase ozonation of bed-oxidized brown coal was examined. About 90% of the organic matter of brown coal was converted to low-molecular-weight soluble oxygen-containing products by stepwise liquid-phase ozonation (in chloroform and acetic acid).     

Lattices of Order-Convex Sets of Forests

We give a characterization of the class Co(F)\mathbf{Co}(\mathcal{F}) [Co(F_n)\mathrm{\mathbf{Co}}(\mathcal{F}_n), n < ω, respectively] of lattices isomorphic to convexity lattices of posets which are forests [forests of length at most n, respectively], as well as of the class Co(L)\mathbf{Co}(\mathcal{L}) of lattices isomorphic to convexity lattices of linearly ordered posets. This characterization yields that the class of finite members from Co(F)\mathbf{Co}(\mathcal{F}) [from Co(F_n)\mathbf{Co}(\mathcal{F}_n), n < ω, or from Co(L)\mathbf{Co}(\mathcal{L})] is finitely axiomatizable within the class of finite lattices.