Interaction of positronium with dissolved oxygen in liquids.

The interaction of positronium (Ps) with molecular oxygen dissolved in liquids is experimentally investigated. Computer software has been developed for fitting the positron annihilation lifetime spectra in liquids using parameters with clear physical meaning: rate constants of the Ps chemical reactions, annihilation rate constants of the different positron states, probability of Ps formation in a quasi-free state, typical formation time of a Ps nanobubble. Such processing of the spectra allowed identification of the dominant interaction of the Ps atom with dissolved oxygen. It turns out to be mainly ortho-para-conversion (Ps → 1/4 p-Ps + 3/4 o-Ps), but not oxidation (Ps + O2→ e+ + O2-). Values of the reaction rate constants are obtained.

Mechanism of enhanced positronium formation in low-temperature polymers.

An enhanced positronium (Ps) formation in low-temperature polymers has been widely observed. The additional positronium formation is due to shallow trapped electrons in them. Positron annihilation lifetime spectroscopy was applied to investigate the Ps formation in a series of polymers, such as low-density polyethylene, ethylene-methyl methacrylate copolymers with various methyl methacrylate contents, and pure poly(methyl methacrylate) at low temperature. An analysis of the experimental data based on simple kinetic equations enables one to understand the Ps formation mechanism in polymers during low-temperature positron annihilation experiments as functions of the temperature and elapsed time. Good fittings of the experimental data were obtained. The fitting parameters seemed to show clear physical meanings.

State of the environment in the arrangement area of the enterprises for repairing and utilization of nuclear-powered submarines.

The influence of nuclear-powered utilization (disjunction) upon the state of health of the soil, vegetation and atmospheric air was studied. It was stated that the concentration of hazardous metals in the air of an industrial site did not exceed the permissible levels. In the residential area the cases of increased concentrations of manganese and chromium were noted. The major pollutants of vegetation are manganese, titanium, copper and nickel. The authors propose a complex of anthropogenic factors to be the cause of the environmental contamination by hard metals. The volume activity of radioactive aerosols in the studied site is confined to the local hum.

[Mechanism of the primary radiobiologic action]. / O mekhanizme pervichnogo radiobiologicheskogo deistviia.

Basing on the well-known high sensitivity of the biological processes to alteration of pH of a medium it is assumed that one of the major factors of primary biological effect of ionizing radiation is the increase of acidity in charged particle's tracks. This makes possible to understand the mechanism of protective action of various radioprotectors and the extremal experimental dependence of RBE vs LET has been explained. The position of corresponding maximum was estimated as approximately 10 eV/A in accord with experimental data.

[The radioprotective efficacy of karotinil under acute external and internal irradiation]. / Radiozashchitnaia éffektivnost' karotinila pri vneshnem i vnutrennem ostrom obluchenii.

Radioprotective, with respect to the whole body and reproductive system, geroprotective and anticarcinogenic properties of carotinyl after single acute external gamma-irradiation or exposure to tritium oxide have been revealed. It is concluded that the use of beta-carotene-containing substances is highly promising in preventing remote effects of chronic irradiation at low rates of absorbed doses, particularly the effects of incorporated radioactive substances.

[Paramagnetic form of ribonucleotide reductase in human tissues]. / Paramagnitnaia forma ribonukleotidreduktazy v tkaniakh cheloveka.

The paramagnetic form of ribonucleotide reductase was detected by ESR method in human cervix tissues, especially in tumor ones. The magnetic relaxation rate was proved to be slower for this form than for that in normal animal tissues having a high level of proliferative activity or in Ehrlich tumor cells studied before.

[Study of nonequilibrium states of cyanide complexes of hemoglobin and myoglobin by a low-temperature inhibition method]. / Issledovanie neravnovesnykh sostoianii tsanidnykh kompleksov gemoglobina metodom nizkotemperaturnogo ingibirovaniia.

Cyanide-ferrihemoglobin (myoglobin) interaction was studied by freeze-quenching technique and low-temperature ESR at various pH values. New ESR signals of these low-spin cyanide-protein complexes were recorded. These signals were interpreted as indication of the appearance of conformationally non-equilibrium states of these complexes. The relaxation to the equilibrium states of corresponding proteins takes about hundred milliseconds.

[Radioprotective action of natural carotene-containing preparations: research on karotinil in white rats]. / Radiozashchitnoe deistvie prirodnykh karotinsoderzhashchikh preparatov: issledovanie karotinila na belykh krysakh.

Evidence was obtained that beta-carotene injected to rats subcutaneously or per os two times, 4 h and 19 h, before irradiation reduced their death rate from acute affection. The effect was almost invariable with the drug administered either before or after irradiation. The radioprotective efficacy of beta-carotene was attributed to its ability to scavenge active oxygen forms.

[Formation of intermediate products in the reaction of hemoglobin with cyanide]. / Obrazovanie promezhutochnykh produktov v reaktsii gemoglobina s tsianidom.

Interaction between methemoglobin and cyanide was studied by low temperature inhibition method in combination with ESR. A new, not earlier described in literature ESR signal of low spin cyanide complex of this protein was recorded.

[Effect of iodine-131 on the induction of osteosarcoma by strontium-90]. / O vliianii ioda-131 na osteosarkomogennuiu éffektivnost' strontsiia-90.

The paper submits the results of estimation of the osteosarcomogenic effectiveness of 90Sr in a combination with 131I incorporated prior to or after the administration of 90Sr. It was demonstrated that the incidence of osteosarcomas increased in rats received 131I a weak after the administration of 90Sr.

[Recovery processes in damage to rats by 252Cf]. / Vosstanovitel'nye protsessy pri porazhenii krys 252Cf.

The types of recovery processes were demonstrated in experiments on albino rats damaged with 252Cf. The frequency and the degree of manifestation of both pathological and recovery processes were function of radiation dose and time of its formation. The results obtained indicate that changes induced by the incorporation of 252Cf, within a wide range of doses, are compensated incompletely to be manifested later by sklerotic, hyperplastic and neoplastic processes.

[Reaction capacity of the nonequilibrium form of cytochrome c formed during reduction of the protein by radicals]. / Reaktsionnaia sposobnost' neravnovesnoi formy tsitokhroma c, obrazuiushcheisia pri vosstanovlenii belka radikalami.

It has been shown that during fast (< 1 ms) photosensitized by anthraquinone or benzophenone reduction of cytochrome c in 0.15 N NaOH water-glycerol solutions ferrocytochrome c in a nonequilibrium state with increased reactivity was formed. The rate constants for reactions of CO binding to nonequilibrium and equilibrium ferrocytochrome c are 2.10(4) M-1S-1 and 70 M-1S-1 correspondingly. Nonequilibrium cytochrome c is relaxed to corresponding equilibrium state with lambda = 4 S-1.

[Oligonucleotides and their analogs. II. Spectra of the circular dichroism of dinucleoside phosphate analogs containing 4-thiouracil]. / Oligonukleotidy i ikh analogi. II. Spektry krugovogo dikhroizma analogov dinukleozidfosfatov, soderzhashchikh 4-tiouratsil.

The dinucleoside phosphates analogues APpSU, SUPpA and UPpSU have been synthesised by direct thionation of DNP analogues, containing cytosine. The structure of compounds prepared was proved by UV- and PMR-spectra. The CD spectra of the DNP analogues were examined. It has been demonstrated that the "induced" dichroism contribution in the Cotton-effect of DNP was substantial in the case of stacking conformations and negligible for unstacking conformations.

[Chemical characteristics of conformationally-disequilibrium states of metal-containing proteins]. / Khimicheskie kharakteristiki konformatsionno-neravnovesnykh sostoianii metallosoderzhashchikh belkov.

Properties of conformation-out-equilibrium states of several iron containing proteins, for example, induced by fast changes of active site were investigated. It was shown that structure and chemical properties of out-of-equilbrium states can differ considerably from the equilibrium ones. Spectral characteristics and reactional ability of these molecules change in the way of slow (up to 10(-1)s) conformational relaxation, continuously approaching the equilibrium values.