Identifications of emission lines in the EUV solar spectrum

Conclusions During the past three years there have been significant extensions of the solar data available. Over most of the solar spectrum between 1 – 2200 the new or improved observations have led to interesting problems in line identifications. The identifications have in turn led to new methods of determining the physical conditions in the solar atmosphere, eg electron density determinations from the Hei like ion intercombination line to forbidden line ratio (Gabriel and Jordan, 1969b). The majority of the strong lines have now been identified, either by theoretical considerations or from the extensive laboratory data which have recently become available. However, weak lines may also aid the understanding of the chromosphere and corona and work on the identifications of all remaining features observed must continue.     

Mollusc-microbe mutualisms extend the potential for life in hypersaline systems

Metazoans in extreme environments have evolved mutualisms with microbes that extend the physical and chemical capabilities of both partners. Some of the best examples are bivalve molluscs in evaporite and hypersaline settings. Mollusc tissue is developmentally and evolutionarily amenable to housing vast numbers of symbiotic microbes. Documented benefits to the host are nutritional. Multiple postulated benefits to the microbes are related to optimizing metabolic performance at interfaces, where heterogeneity and steep gradients that cannot be negotiated by microbes can be spanned by larger metazoan hosts. A small cockle, Fragum erugatum, and its photosymbiotic microbes provide a remarkable example of a mutualistic partnership in the hypersaline reaches of Shark Bay, Western Australia. Lucinid bivalves and their endosymbiotic chemolithotrophic bacteria provide examples in which hosts span oxic/anoxic interfaces on behalf of their symbionts at sites of seafloor venting. Multiple lines of evidence underscore the antiquity of mutualisms and suggest that they may have played a significant role in life's first experiments above the prokaryotic grade of complexity. The study of metazoan-microbe mutualisms and their signatures in extreme environments in the geologic record will provide a significant augmentation to microbial models in paleobiology and astrobiology. There are strong potential links between mutualisms and the early history of life on Earth, the persistence of life in extreme environments at times of global crisis and mass extinction, and the possibilities for life elsewhere in the universe.     

Embraer 170/190的维修市场前景

随着北美地区Embraer 170/190双发喷气机机队规模的扩大,各类MRO供应商开始扩展其维修能力,以满足此类机型日益增长的维修需求.     

Space insurance : Comments from an observer

The space insurance industry has suffered serious financual setbacks in recent years. These setbacks, amounting to a net cash outflow of hundreds of millions of dollars, have resulted in substantial increases in insurance rates and the withdrawal of a number of firms from the launch insurance market. After two decades of commerial space activity a number of questions may be raised: What has been learned from the experience to date? What are the causes of the poor performance of the space insurance industry? What can be done to improve performance? What are the likely prospects of the insurance industry and the likely impacts on the communications satellite industry? In order to answer these questions several examples are considered and analytic approaches discussed. The implications of mission modes, failure/recovery paths and multiple correlated payloads are considered, and analytic approaches based upon computer simulation techniques are described which are required to understand the complex insurance environment and the setting of policies and rate structures.     

Ethological analysis of a polar team in the French Antarctic station Dumont d'Urville as simulation of space teams for future interplanetary missions

This new ethological study focuses on the co-adaptation of the crew's spatial behavior to social isolation in a polar base thus simulating long-term living and working of a space team. The method consisted in drawing the subjects' position (n=13) on an observation map at the midday and evening meals at the Dumont d'Urville French station in Antarctica, daily during the summer campaigns and weekly during the winter-over of the TA46 mission. Quantitative data are presented in geocentric (positions), allocentric (distances) and egocentric (orientations) analyses with an emphasis on three adaptative periods (first 3 months, intermediary 2 months and last 3 months of isolation). Results show a large space occupancy during the first week after arrival and the last week before departure from the polar base, and a team-members' grouping during the winter-over. On the over-all time, the inter-individual distances increase. The social orientations are higher at the beginning than at the end of the mission. Discussion underlies the pertinent use of such ethological indicators collected from polar stations as predictors of well-being and optimal-working of the future orbital and planetary stations users.