Revised estimates and projections of international migration : 1980-2000

This report reviews the World Bank's latest international migration statistics for every country in the world for each five year period from 1980 - 2000. The estimates and projections of net international migration during this period will be used as input statistics for the forthcoming edition of the World Population Projections. In the early 1980s, net international migration to all receiving countries totaled more than 1.2 million persons a year. The author assumes this figure to gradually decrease to fewer than 900,000 persons a year in the period 1995 - 2000. The current male dominance of international migration flows is also expected to decrease. He also assumes that the importance of the United States as a prime destination of immigrants will increase substantially in the 1990s. Mexico is by far the largest net exporter of international migrants.Human Migrations&Resettlements,Voluntary and Involuntary Resettlement,Health Monitoring&Evaluation,International Migration,Gender and Social Development

NASA/MSFC FY88 Global Scale Atmospheric Processes Research Program Review

Interest in environmental issues and the magnitude of the environmental changes continues. One way to gain more understanding of the atmosphere is to make measurements on a global scale from space. The Earth Observation System is a series of new sensors to measure globally atmospheric parameters. Analysis of satellite data by developing algorithms to interpret the radiance information improves the understanding and also defines requirements for these sensors. One measure of knowledge of the atmosphere lies in the ability to predict its behavior. Use of numerical and experimental models provides a better understanding of these processes. These efforts are described in the context of satellite data analysis and fundamental studies of atmospheric dynamics which examine selected processes important to the global circulation

Improved ion beam tools for ultraprecision figure correction of curved aluminum mirror surfaces

Aluminum mirrors offer great potential for satisfying the increasing demand in high-performance optical components for visible and ultraviolet applications. Ion beam figuring is an established finishing technology and in particular a promising technique for direct aluminum figure error correction. For the machining of strongly curved or arbitrarily shaped surfaces as well as the correction of low-to-mid spatial frequency figure errors, the usage of a high-performance ion beam source with low tool width is mandatory. For that reason, two different concepts of ion beam generation with high ion current density and narrow beam width are discussed. (1) A concave ion beam extraction grid system is used for apertureless constriction of ion beams in the low millimeter range. An oxygen ion beam with a full-width at half-maximum (FWHM) of 4.0 mm with an ion current density of 29.8  mA  /  cm2 was achieved. (2) For even smaller ion beams, a conic aperture design with a submillimeter-sized exit opening was tested. A nitrogen ion beam with an FWHM down to 0.62 mm with an ion current density of 4.6  mA  /  cm2 was obtained. In situ ion current density mapping is performed by scanning Faraday probe measurements. Special interest is set on the data evaluation for submillimeter ion beam analysis