The effects of microgravity on induced mutation in Escherichia coli and Saccharomyces cerevisiae.

We examined whether microgravity influences the induced-mutation frequencies through in vivo experiments during space flight aboard the space shuttle Discovery (STS-91). We prepared dried samples of repair-deficient strains and parental strains of Escherichia (E.) coli and Saccharomyces (S.) cerevisiae given DNA damage treatment. After culture in space, we measured the induced-mutation frequencies and SOS-responses under microgravity. The experimental findings indicate that almost the same induced-mutation frequencies and SOS-responses of space samples were observed in both strains compared with the ground control samples. It is suggested that microgravity might not influence induced-mutation frequencies and SOS-responses at the stages of DNA replication and/or DNA repair. In addition, we developed a new experimental apparatus for space experiments to culture and freeze stocks of E. coli and S. cerevisiae cells.     

Collisions in space: A retrospective overview of ISAS studies

A chronological review of studies in ISAS concerning collisions in space is presented. The collision probability in space with artificial orbiting bodies was estimated, and a Space Traffic Control System was proposed, in 1971. The design of a space station for safety against collision hazards was discussed in 1972. A trajectory optimization technique for low-thrust multiple rendezvous mission in order ti sweep space debris around the earth was developed in 1977. In 1984, the collision probability was reestimated using space bedris data accumulated for more than a decade. Several experimental projects in ISAS, such as hypervelocity impact experiments using a railgun system, sampling and measuring of alumina particles in exhaust plume of solid-propellant propellant rocket motors, and a result of analysis on the behavior of such alumina particles in orbit are also introduced.     

绿色制造中的干切削技术

冷却润滑液的存储、使用以及废弃处理需要专门的物流系统,因而费用很高;冷却润滑液处理不当会对人的健康以及环境造成危害;工件经过湿加工后必须进行清洁处理,这都费时费力,同时增加了对系统的要求.基于上述原因,近年来干切削技术受到广泛关注.     

Changes in chromatin and nucleic acids in rat tissues after two-week spaceflight

The quantitative changes in nucleic acids and chromatin breakdown were followed in blood, thymus and spleen in rats after 14 day flights on board the biosatellites Cosmos-1887 and Cosmos-2044. Quantitative nucleic acid changes within 8-11 h after landing were only mild, most statistically non-significant. An analysis at 48 h after landing showed a marked decrease in a total content of DNA and RNA in spleen and thymus. Within 8-11 h after landing, the symptoms of chromatin breakdown were found as is seen in an increased concentration of its fragments-polydeoxyribonucleotides. The obtained results show that a partial adaptation to microgravity occurs up to flight day 14 in lymphoid organs. Adaptation is accompanied with a reappearing of the sensitive cells. Their chromatin breaks down, then, in a final phase of flight due to hypergravity stress manifesting itself by a temporary increase in polydeoxyribonucleotide concentration several hours after landing. The results are discussed in relation to the changes in chosen parameters after shorter or more prolonged flights.     

A technique of analyzing critical forces and moments for isotropic rods of arbitrary cross-section in the general case of their complex resistance

The derivation of parametric equations for a limiting surface in the space of internal forces and moments that act in the rod cross-sections, using the basic concepts of plasticity theory and conventional hypotheses of the rod theory, is presented. The plastic properties of rod material are described by the Mises criterion. A case of small displacements and strains under static simple loading is considered. The results of solving a number of problems of constructing limiting curves in the planes of internal forces and moments are given.     

Periodic components in Cyg X-3

Hard X-ray observations of Cyg X-3 in the energy range 20–100 keV were made with a Balloon-borne telescope using two large area proportional counters. The source was seen with a total significance of 20.

A 121 s periodicity was seen during Fourier analysis of the data. The phenomenon can be interpreted as due to transient pulsation since no other peak was seen in our data. Quasi-periodic oscillation in the range 0.06–20 mHz have been observed from Cyg X-3 at lower energies. Interestingly, most of the reported periods are multiple of the present measurements. The observed pulsation at high energies indicate the occasional unstable behaviour of the inner parts of the accretion disk connected with the basic rotation period of the compact object.

The 4.8^h modulation, characteristic of the orbital period of the binary system was seen in the data, with a broad maximum between the phase 0.3 to 0.7.     

Experiments with injection of powerful plasma jet into the ionosphere

This paper describes two rocket experiments “Aelita” with high power lithium plasma injection. The results of onboard magnetometer, massspectrometer, photometer, plasma, corpuscular and ground radar measurements are given. Dynamics and structure of plasma formation are discussed.