Dynamic nuclear polarization and ESR hole burning in As doped silicon.

We present an experimental study of the Dynamic Nuclear Polarization (DNP) of 29Si nuclei in silicon crystals of natural abundance doped with As in the temperature range 0.1-1 K and in a strong magnetic field of 4.6 T. This ensures a very high degree of electron spin polarization, extremely slow nuclear relaxation and optimal conditions for realization of Overhauser and resolved solid effects. We found that the solid effect DNP leads to the appearance of a pattern of holes and peaks in the ESR line, separated by the super-hyperfine interaction between the donor electron and 29Si nuclei closest to the donor. On the contrary, the Overhauser effect DNP mainly affects the remote 29Si nuclei having the weakest interaction with the donor electron. This leads to the appearance of a very narrow (≈3 mG wide) hole in the ESR line. We studied relaxation of the holes after burning, which is caused by the nuclear spin diffusion. Analyzing the dynamics of the hole in the spectrum with a simple one-dimensional diffusion model leads to a value of the diffusion coefficient D = 8(3) × 10-9 G2 s-1. Our data indicate that the spin diffusion is not completely prevented even in the frozen core near the donors. The emergence of the narrow hole after the Overhauser DNP may be explained by a partial "softening" of the frozen core caused by decoupling of the donor electron and remote 29Si nuclei.

Quadrupole shift of nuclear magnetic resonance of donors in silicon at low magnetic field.

Shifts from the expected nuclear magnetic resonance frequencies of antimony and bismuth donors in silicon of greater than a megahertz are observed in electrically detected magnetic resonance spectra. Defects created by ion implantation of the donors are discussed as the source of effective electric field gradients generating these shifts via quadrupole interaction with the nuclear spins. The experimental results are modeled quantitatively by molecular orbital theory for a coupled pair consisting of a donor and a spin-dependent recombination readout center.

[Variability in mitochondrial DNA in Russian inhabitants from Krasnodar Krai, Belgorod and the lower Novgorod region]. / Izmenchivost' mitokhondrial'noi DNK v populiatsiiakh russkogo naseleniia Krasnodarskogo kraia, Belgorodskoi i Nizhegorodskoi oblastei.

Mitochondrial DNA (mtDNA) polymorphism was examined in three Russian populations from the European part of Russia (Krasnodar Krai, Belgorod, and Nizhnii Novgorod oblast). This analysis revealed that mitochondrial gene pool of Russians was represented by the mtDNA types belonging to groups H, V, pre-V, HV*, J, T, U, K, I, W, and X. The major groups (average frequency over 5%) were H, V, J, T, and U. Mongoloid admixture in Russians, constituting only 1%, was revealed in the form of mtDNA types of groups C and D. Analysis of the frequency distribution of the mtDNA type groups indicated the absence of genetic differences between the Russian populations studied.

[Studies of in vitro and in vivo derived 1,2-diazetine and nitronylnitroxide as donors and acceptors of nitric oxide]. / Issledovaniia in vitro i in vivo proizvodnykh 1,2-diazetina i nitronilnitroksida v kachestve donorov i aktseptorov oksida azota.

The series of nitronylnitroxyl radicals (NNR) were studied as paramagnetic scavengers of nitric oxide. These radicals react with NO with rate constants of (0.6-1.1).10(4) M-1.sec-1 forming stable iminonitroxyl radicals. They can be used to assay nitric oxide in solutions by EPR spectroscopy; the sensitivity of the method is 1 microM for the detection of NO concentration and 0.3 nM/sec for the measurements of the rates of NO generation for 1 h in 0.2 ml sample. To overcome fast reduction of the radicals in biological samples, charged NNR was incorporated into the inner volume of large unilamellar phosphatidylcholine liposomes thus decreasing the rates of NNR reduction about 1000-fold. The method was used for the NO synthase activity assay in rat cerebellum cytosol. NNR was used to study the kinetics of the decomposition of 3,4-dihydro-1,2-diazete 1,2-dioxides (DD). Several DD derivatives at 5-80 microM concentrations are very effective vasodilators in perfused rat tail artery. Intraperitoneal injection of several DD (40-200 micrograms/kg weight). in hereditary hypertensive rats (ISIAH-strain) significantly (by 30%) decreased systolic arterial blood pressure whereas similar effect of trinitroglycerin was detected at significantly higher dose (900 micrograms/kg weight).

[Characteristics of the autonomic nervous system tests during group psychotherapy of patients with opioid dependence at the stage of induction of remission]. / Osobennosti vegetativnykh testov pri gruppovoi psikhoterapii bo'lnykh opiinoi narkomaniei v stadii formirovaniia remissii.

The time-course of changes in vegetative tests was studied in 47 men suffering from stage II opium dependence. The patients' age ranged from 18 to 28 years, with the dependence standing amounting to 1-10 years. Use was made of cardiointervalography to define the vegetative tone, as well as of the vagal and adrenaline tests to explore vegetative responsiveness. The orthostatic test was employed for studying vegetative maintenance of the activity. A group of patients (n = 22) was distinguished, with a positive attitude towards treatment and experienced in group psychotherapy, as was a group of patients (n = 25) with a negative attitude towards therapy and treated with medicaments. The results of the use of the vegetative tests indicate the normalization of the vegetative nervous system in the patients group with a positive attitude towards treatment and experienced in group psychotherapy and allow the conclusion about a greater efficacy of group psychotherapy as compared to the drug treatment in the management of patients suffering from opium dependence.