Radiative recombination of holes in delta-p-doped gallium arsenide

Photoluminescence spectra of δ-p-doped GaAs structures of different doping levels are studied experimentally. It is found that set of PL bands observed in δ-p-doped samples recently is regularly broadened with doping concentration increase due to appearance of additional low-energy bands and their subsequent red shift at higher doping levels. A red shift of the bands and a change of their relative intensities were caused also by excitation laser intensity decrease and/or temperature increase. These results confirm our previous assumption that the bands are due to radiative recombination of spatially separated photoelectrons with holes occupying size-quantization levels of δ-layer potential well.     

Synthetic studies in the field of the porphyrins. synthesis of a mesoporphyrin and of a diacetyldeuteroporhyrin

A method is proposed for the synthesis of porphyrins based on the cyclization of a tetrapyrrole system with methyl and formyl groups at the ends of the molecule. The synthesis of mesoporphyrin IX and diacetyldeuteroporphyrin IX has been effected.     

Investigations in the field of complex lipids

Summary 1. The methyl ester of N-(N-carbobenzoyglycyl)-methoxyneuraminic acid has been synthesized by the carbodiimide method.2. Hydrogenation of the methyl ester of N-(N-carbobenzoxyglycyl)-methoxyneuraminic acid over Pb/BaSO₄ has given the methyl ester of N-glycyl-methoxyneuraminic acid.Khimiya Prirodnykh Soedinenii, Vol. 1, No. 4, pp. 241–244, 1965     

Synthesis of acetyltrialkylpyrroles from 2, 4-pentanediones

The condensation of isonitrosoacetylacetone with 3-alkyl-2,4-pentanediones and reduction with zinc in acetic acid gives-acetyltrialkylpyrroles. The analogous condensation of 3-alkyl-3-nitroso-2,4-pentanediones with acetylacetone leads to-acetyltrialkylpyrroles, and condensation with acetoacetic ester leads to-ethoxycarbonyltrialkylpyrroles. When the- and-acetyltrialkylpyrroles undergo salt formation, the oxygen of the carbonyl group is protonated.     

Synthetic studies in the field of the curare alkaloids

By oxidation and the identification of the oxidation products, it has been shown that the -[4-(2-alkoxy-5-alkoxycarbonylmethylphenoxy)-3-methoxyphenyl] ethylamides of 4-benzyloxyphenylacetic acid obtained previously and differing in their physicochemical properties are based on the same skeleton and differ only in their spatial configuration, since on Bischler-Napieralski cyclization they give isomeric dihydroisoquinoline compounds. The structure of the latter was established by oxidation to the isomeric acids 2,2-dimethoxy-3,4,5-tricarboxy(diphenyl ether) and 2,2-dimethoxy-4,5,5-tricarboxy-(diphenyl ether); the latter is identical with the compound obtained by the degradation of the methyl ester of natural tubocurarine. 1-(4Benzyloxybenzyl)-6-methoxy-7-(2-methoxy-5-methoxycarbonyl methylphenoxy)-N-methyl-1,2,3,4-tetrahydroisoquinoline and a compound isomeric with it have also been synthesized, and the former has been shown to be identical with a substance obtained by independent synthesis from the 4-benzyl ether of N-methylcoclaurine. During the synthesis of the latter it was shown that cyclization takes place unambiguously without the formation of isomeric compounds.For part XIII, see [2].     

New estimate in Vinogradov’s mean-value theorem

We refine the upper bound for the Vinogradov integral.