[Optimization approach to arterial hemodynamics in elastic capillaries].

The article considers a number of ways of optimizing arterial hemodynamics including finding of the best value of capillary resistance or coefficient of elasticity.

[Optimization approach to arterial hemodynamics on the systole stage].

With the help of a simple model of arterial hemodynamics as an example, the authors demonstrate it that dynamics of arterial pressure including the top and lower pressure values, systole-diastole length ratio, and coefficients of arterial and capillary elasticity can be obtained as an optimal solution of the problem of maintaining appropriate intensity of oxygen ingress in body tissues despite minimal "physiological" ability of the heart.

[Malignant transformation of left atrial myxoma]. / Malignizatsiia miksomy levogo predserdiia.

Malignant transformation of cardiac myxoma is poorly described in the literature. A case of diagnosis of cardiac angiofibroliposarcoma of the heart which developed after removal of the left atrial myxoma is described.

[A mathematical model of the changes in bone marrow cellularity in radiation exposures]. / Matematicheskaia model' izmenenii kletochnosti kostnogo mozga pri radiatsionnykh vozdeistviiakh.

The model is based on classical ideas about of hemopoiesis in normal conditions and under irradiation. It consists of only two equations characterizing stem and differentiated bone marrow cell dynamics. The systemic mechanisms of hemopoiesis regulation were roughly taken into account. The formulae suitable for calculations of equilibrium cell concentrations under prolonged irradiation were derived. The model was shown to be in agreement with experimental data on hemopoietic system changes under acute and prolonged irradiation of rodents and dogs. The model is intended for describing the extent of hemopoiesis disturbance under those modes of mammalian exposure when describing of general regularities is enough.

Radiation shielding estimates for manned Mars space flight.

In the analysis of the required radiation shielding protection of spacecraft during a Mars flight, specific effects of solar activity (SA) on the intensity of galactic and solar cosmic rays were taken into consideration. Three spaceflight periods were considered: (1) maximum SA; (2) minimum SA; and (3) intermediate SA, when intensities of both galactic and solar cosmic rays are moderately high. Scenarios of spaceflights utilizing liquid-propellant rocket engines, low- and intermediate-thrust nuclear electrojet engines, and nuclear rocket engines, all of which have been designed in the Soviet Union, are reviewed. Calculations were performed on the basis of a set of standards for radiation protection approved by the U.S.S.R. State Committee for Standards. It was found that the lowest estimated mass of a Mars spacecraft, including the radiation shielding mass, obtained using a combination of a liquid propellant engine with low and intermediate thrust nuclear electrojet engines, would be 500-550 metric tons.

[Radiation safety in space flights in the Intercosmos program]. / Problema radiatsionnoi bezopasnosti kosmicheskikh poletov v programme "Interkosmos".

This paper reviews the basic stages in the development of radiation safety of space flights within the framework of the Intercosmos program, including ground-based experiments on charged particle accelerators and gamma-emitters and actual flight studies onboard biosatellites and orbital stations. The paper also discusses norms and standards of radiation safety as related to flights of varying duration. It emphasizes the contribution made by Intercosmos cooperative projects into the development of space flight radiation safety parameters adopted as standards by the USSR Standardization Committee.

[Possible directions in improving the criteria of radiation safety for space flights]. / O vozmozhnykh napravleniiakh sovershenstvovaniia kriteriev radiatsionnoi bezopasnosti kosmicheskikh poletov.

This paper considers the possibility of characterizing space flight radiation safety, using a value which is integrated over the flight time, takes into account the radiation processes in an irradiated body and averages the probability of adverse radiobiological effects with respect to the distribution of solar proton flares of varying intensity. The proposed characteristic is compared with the current standards with reference to a hypothetic interplanetary flight.

Radiation: risk and protection in manned space flight.

Space radiation is the primary source of hazard for orbital and interplanetary space flight. Radiation levels for different space mission durations, have been established in order to determine the level of hazard. The risk of exceeding the established levels should not be more than 1%. Radiation environment models have been developed to estimate these values. It is possible to build spacecraft shielding based on the calculation of doses and the risk of exceeding these. By reviewing various calculated estimates of the risk, the radiation hazard and the efficiency of protective measures can be established for specific flights.

Results of cosmic radiation dose field measurements aboard the "Salyut-6" orbital station.

During the 3rd main expedition on board the "Salyut-6" orbital station in 1979 the integral characteristics of cosmic radiation were measured in various positions inside the manned modules (experiment "Integral"). Measurements were performed with thermoluminescent dosimeters, photographic films and solid state plastic detectors supplied for the experiment by specialists of the USSR, Bulgaria, Hungary, GDR and Romania. The dose gradient inside the manned modules of the station amounted to 70% for long intervals of time. During the experimental period the dose rate inside the station was 15 to 30 mrad per day. The mean flux of particles with Z > or = 6 and LET > or = 200 keV/micrometer was found to be 0.22 cm-2 or day-1.