Effect of spatial spin modulation on the relaxation and NMR frequencies of 57Fe nuclei in a ferroelectric antiferromagnet BiFeO3

The ⁵⁷Fe NMR spectra of the ⁵⁷Fe-enriched (95.43%) ceramics of a ferroelectric antiferromagnet BiFeO₃ with a spatially modulated magnetic structure have been studied. It is established that a cycloidal spin modulation in BiFeO₃ causes a spatial modulation of the spin-spin relaxation rate along the magnetic cycloid period and results in inhomogeneous broadening of the local NMR lineshape. It is also found that the local magnetic moments of Fe ions in various parts of the cycloid depend differently on the temperature, which is indicative of a difference in the spin wave excitation. The observed phenomena can be explained in terms of the Shul-Nakamura indirect nuclear interaction which becomes effective at high concentrations of the magnetoactive nuclei and low temperatures. Similarity of the obtained experimental results to the regularities of NMR in the Bloch walls is discussed.     

Affinity chromatography of pepsin using pepstatin fragments as ligands of specific sorbents

Summary 1. Specific sorbents for the affinity chromatography of pepsin on hexamethylenediamine-Sepharose using valine peptides differing by the acyl groups and configurations of the valine residue have been synthesized.2. The sorbents investigated are effective in the purification of pepsin with a low specific activity when 30–40 mg of protein is deposited on 1 ml of resin, a fourfold purification of the enzyme being achieved.M. V. Lomonosov Moscow State University. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 387–392, May–June, 1977.     

Substitution of 3H-furan-2-ones in amination and hydroamination reactions

The amination and hydroatnination of 5-alkyl-3H-furan-2-ones and their 3-benzylidene- and 3 formyl-derivatives were studied. The characteristics of the reactions, the requirements for the nature of the nucleophilic reagents, and the reaction conditions leading to the destruction of the furan ring and recyclization to pyrrolidinone and pyrrolinone structures are indicated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 349–352, March, 1994.     

Excitons bound at oxygen centers in zinc selenide

Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 67–72, November, 1989.