Global behavior of the equatorial anomaly since 1999 and effects on GPS signals

Tools to generate VTEC maps were developed. These maps have been used to study the global behavior of the equatorial anomaly since 1999 up to now, and its effects on GPS signal. The VTEC data for any place around the world is based on IONEX data. In this way, a quick annual behavior of the VTEC may be analyzed, and also compared to the VTEC behavior for different places and different years. Based on these data an electron density model taking into account radial as well latitudinal and longitudinal gradients were developed. This model was incorporated in a 3D ray-tracing program. Using this program it was possible to compare the STEC conversion to the VTEC. As expected the results show that the lower the elevation angles of the Satellite Vehicle, the greater the error in the VTEC estimation.     

Monitoring of biologically effective UV irradiance at El Arenosillo (INTA), Andalucia, in Spain.

Biological UV (ultraviolet) dosimetry was applied using the biofilm-technique (DLR patent) to determine the UV levels weighted of biologically weighted UV radiation at the INTA Sounding Station of El Arenosillo at Huelva, Spain (37 degrees 06'N, 6 degrees 44'W, 50 m a s 1=above sea level) on 2 days in 1997 [correction of 1977] (April 1, and May 5). Exposure periods were calculated for clear sky days using a radiative transfer model for erythemal doses to reach 1.3 to 1.5 MED (minimal erythemal dose). Reliability of the radiative transfer model was demonstrated by the doses registered by a Yankee-UV biometer for the same exposure periods as used for the biosensor. This work presents the methodology employed (biofilm-technique utilized [correction of utiliced], calculation of exposing periods with radiative transfer model, etc) and the results obtained with the Yankee biometer and the biofilm. At noon, the ratio of biofilm measurements (Ieff, W/m2=biological effective irradiance, in W/m2) to the UV Biometer data (in MED/h) was 3-4.     

Production of hydrocarbons and nitriles by electrical processes in Titan's atmosphere.

Although lightning has not been observed in Titan's atmosphere, the presence of methane rain in the troposphere suggests the possibility of electrical activity in the form of corona and/or lightning discharges. Here we examine the chemical effects of these electrical processes on a Titan simulated atmosphere composed of CH4 in N2 at various mixing ratios. Corona discharges were simulated in two different experimental arrays. For the detection of reactive intermediates we used a mass spectrometer to study the main positive ions arising by bombarding low-energy electrons from a hot filament into low-pressure methane. The final stable products, generated by applying a high voltage in a coaxial reactor with either positive or negative polarity, were separated and detected by gas chromatography-Fourier transform infrared spectroscopy and electron impact mass spectrometry (GC-FTIR-MS). Lightning discharges were simulated by a hot and dense plasma generated by a Nd-YAG laser and the final products were separated and detected by GC-FTIR-MS. Corona discharges produce linear and branched hydrocarbons as well as nitriles whereas lightning discharges generate mainly unsaturated hydrocarbons and nitriles. Lightning discharges are about 2 orders of magnitude more efficient in product formation than corona discharges.     

Geometric problem solving with strings and pins

Humans solve spatial and abstract problems more easily if these can be visualized and/or physically manipulated. We analyze the domain of geometric problem solving from a cognitive perspective and identify several levels of domain abstraction that interact in the problem solving process. We discuss the roles of physical manifestations of spatial configurations, their manipulation, and their perception for understanding problem solving processes. We propose an extension of the classical problem solving repertoire of constructive geometry to approach certain problems more directly than under the compass-and-straightedge paradigm. Specifically, we introduce strings and pins as helpful metaphors for a generalization of the constructive geometry approach. We present classical problems from spatial problem solving to illustrate the ‘strings and pins’ paradigm. Three case studies are discussed: strings-and-pins solutions to (i) the ellipse construction problem; (ii) the shortest path problem; and (iii) the angle trisection problem. Comparisons to formal solutions are drawn. Differences and similarities between the compass-and-straightedge paradigm and the strings-and-pins paradigm are analyzed. Features and limitations of constructive and depictive geometry as well as implications for computational approaches are discussed. The strings-and-pins domain is shown to be more general and less restrictive than the compass-and-straightedge domain.     

Microphysics of Cosmic Plasmas: Background, Motivation and Objectives

With the maturing of space plasma research in the solar system, a more general approach to plasma physics in general, applied to cosmic plasmas, has become appropriate. There are both similarities and important differences in describing the phenomenology of space plasmas on scales from the Earth’s magnetosphere to galactic and inter-galactic scales. However, there are important aspects in common, related to the microphysics of plasma processes. This introduction to a coordinated collection of papers that address the several aspects of the microphysics of cosmic plasmas that have unifying themes sets out the scope and ambition of the broad sweep of topics covered in the volume, together with an enumeration of the detailed objectives of the coverage.     

Spirulina acceptability trials in rats. A study for the "MELISSA" life-support system.

Groups of five rats were fed for sixteen weeks a slightly deficient diet, supplemented with 0-40% of a dried preparation of the blue-green alga Spirulina as a protein source. Control groups were fed a normal rat diet. No significant differences between groups were found in food intake, growth rate or carbon dioxide production. All animals remained apparently healthy, and had similar organ weights. The study suggests that Spirulina may be used as a protein source in rat diets.