The Gotschlich procedure for the production of carbohydrate antigens from the supernatant fluids of cultures of Neisseria meningitidis groups A and C was modified. Steps involving digestion with nucleases and gel filtration through Sephadex G-50 were added, the number of extractions was greatly reduced, and high-speed centrifugations were eliminated. The antigens thus obtained appeared to be entirely comparable to those described by Gotschlich et al. in physical, chemical, and antigenic properties. A slight degree of protection of mice was repeatedly demonstrated with extraordinarily large doses of antigen (50 azg/mouse), but not with smaller doses. Toxicity of the antigens for laboratory animals was very slight. Gotschlich, Liu, and Artenstein (6) recently isolated group-specific polysaccharide antigens of high molecular weight from group A and group C Neisseria meningitidis. The toxicity of these polysaccharides for the mouse, guinea pig, or rabbit was shown to be insignificant, and no adverse reactions were produced in man (4, 5). These polysaccharides did not elicit antibodies in labora
NASA maintains and operates a global network of Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR), and Global Navigation Satellite System ground stations as part of the NASA Space Geodesy Program. The NASA Space Geodesy Network (NSGN) provides the geodetic products that support Earth observations and the related science requirements as outlined by the US National Research Council (NRC in Precise geodetic infrastructure: national requirements for a shared resource, National Academies Press, Washington, 2010. http://nap.edu/12954, Thriving on our changing planet: a decadal strategy for Earth observation from space, National Academies Press, Washington, 2018. http://nap.edu/24938). The Global Geodetic Observing System (GGOS) and the NRC have set an ambitious goal of improving the Terrestrial Reference Frame to have an accuracy of 1 mm and stability of 0.1 mm per year, an order of magnitude beyond current capabilities. NASA and its partners within GGOS are addressing this challenge by planning and implementing modern geodetic stations colocated at existing and new sites around the world. In 2013, NASA demonstrated the performance of its next-generation systems at the prototype next-generation core site at NASA's Goddard Geophysical and Astronomical Observatory in Greenbelt, Maryland. Implementation of a new broadband VLBI station in Hawaii was completed in 2016. NASA is currently implementing new VLBI and SLR stations in Texas and is planning the replacement of its other aging domestic and international legacy stations. In this article, we describe critical gaps in the current global network and discuss how the new NSGN will expand the global geodetic coverage and ultimately improve the geodetic products. We also describe the characteristics of a modern NSGN site and the capabilities of the next-generation NASA SLR and VLBI systems. Finally, we outline the plans for efficiently operating the NSGN by centralizing and automating the operations of the new geodetic stations.
This paper describes a technique for the collection and analysis of observational data using a specially configured stereo tape recorder and a dual-channel amplifier-recorder for a paper printout. The technique has been used to compare trainer operations to real-life operations, and in field studies to evaluate console designs, activity rates, and percentage of time devoted to various activities.
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