Emergence of adaptable systems and evolution of a translation device

An over-all organizational framework for the origin of life is outlined and attemps for realization are given. Evolution can be described as a process resulting in an increase of “knowledge” where knowledge is the number of carriers of genetic information discarded, on the average, until the evolutionary state under consideration is reached. A model for the evolution of a translation device, a crucial event in the origin of life, is described in detail. Aggregates of short polynucleotide strands in a hairpin conformation play a major role in this model. Experimental evidence for the selectivity of aggregation supports the idea of aggregates as error filters. Chromatographic separation as selection process during chemical evolution supports the model of the early translation device leading to the origin of the genetic code.     

The infra-red background generated by pregalactic stars and their remnants

We examine whether the IR background reported by Matsumoto (1983) could have been generated by stars or black holes in the pregalactic era, z=10100.     

Results from the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Observatory

The Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory covers the high energy gamma ray energy range, approximately 30 MeV to 30 GeV, with a sensitivity considerably greater than earlier high energy gamma-ray satellites. Thus far, 4 pulsars have been detected and their properties measured, including in 3 cases the energy spectrum as a function of phase. The details of the galactic plane are being mapped and a spectra of the center region has been obtained in good agreement with that expected from cosmic ray interactions. The Magellanic clouds have been examined with the Large Magellanic Cloud having been detected at a level consistent with it having a cosmic ray density compatible with quasi-stable equilibrium. Sixteen Active Galactic Nuclei (AGN's) have been seen thus far with a high degree of certainty including 12 quasars and 4 BL Lac objects, but no Seyferts. Time variation has been detected in some of these AGN's.     

Composition of the Volatile Material in Halley's Coma from In Situ Measurements

The investigation of the volatile material in the coma of comets is a key to understanding the origin of cometary material, the physical and chemical conditions in the early solar system, the process of comet formation, and the changes that comets have undergone during the last 4.6 billion years. So far, in situ investigations of the volatile constituents have been confined to a single comet, namely P/Halley in 1986. Although, the Giotto mission gave only a few hours of data from the coma, it has yielded a surprising amount of new data and has advanced cometary science by a large step. In the present article the most important results of the measurements of the volatile material of Halley's comet are summarized and an overview of the identified molecules is given. Furthermore, a list of identified radicals and unstable molecules is presented for the first time. At least one of the radicals, namely CH₂, seems to be present as such in the cometary ice. As an outlook to the future we present a list of open questions concerning cometary volatiles and a short preview on the next generation of mass spectrometers that are being built for the International Rosetta Mission to explore the coma of Comet Wirtanen. This revised version was published online in June 2006 with corrections to the Cover Date.     

ETS-II Experiments Part III: Weather Radar System

The weather radar system used in conjunction with Earth-satellite propagation experiments for quantifying rainfall rate in a unit volume, determined by the beamwidth and the pulselength, is described. Firstly, methods for deriving rainfall rate per unit volume are stated in detail with special emphasis on calibration to determine unknown parameters associated with propagation losses in waveguides and the atmosphere. The calibration method is somewhat different from a conventional one but is useful for routine observation. Secondly, in addition to a simple explanation of the hardware of this radar system, the data modes, developed for measuring rainfall rate along the propagation path and radar reflectivity factor in the horizontal and vertical cross sections around the station are described. These data modes are effectively combined by the operational scanning modes for routine observation of propagation experiments, while each data mode can also be operated independently. Examples obtained by each data mode are also given.     

Rosette Constellations of Earth Satellites

Satellite constellations having rosette (flowerlike) orbital patterns are described which exhibit better worldwide coverage properties than constellations previously reported in U.S. literature. The best rosettes with 5-15 satellites are identified and evaluated relative to prior results. In most cases, the best results are obtained by placing one satellite in each of N separate planes and by using inclined rather than polar orbits. Coverage properties of these constellations are analyzed in terms of the largest possible great circle range between an observer anywhere on the Earth's surface and the nearest subsatellite point. When evaluated in this manner, coverage properties are invariant with deployment altitude. As deployment altitude is reduced, however, higher order constellations must be used to maintain a fixed minimum viewing angle. Coverage properties are also invariant with deployment orientation relative to Earth coordinates, although specific orientations can cause the satellite patterns to appear quasi-stationary. Thus these constellations offer a promising alternative to the use of geostationary satellites. Rosette constellations can also be used to guarantee multiple satellite visibility on a continuous worldwide basis. It is shown that 5, 7, 9, and 11 satellites are the minimum numbers required for single, double, triple, and quadruple visibility, respectively. Examples of rosette constellations which achieve these bounds are given.     

On the Derivation and Numerical Evaluation of the Weibull-Rician Distribution

The Weibull-Rician distribution and density functions are derived by a method based on conditional probability. The derivation is much simpler than the usual Rician approach, giving both the distribution and density as single integrals that are easy to evaluate numerically.     

Approximate qualitative spatial reasoning

Qualitative relations between spatial regions play an importantrole in the representation and manipulation of spatial knowledge.The RCC5 and RCC8 systems of relations,used in the Region-Connection Calculus, are of fundamentalimportance. These two systems deal with ideal regions havingprecisely determined location. However,in many practical examples of spatial reasoning,regions are represented by finite approximations rather than known precisely.Approximations may be given by describing how a regionrelates to cells forming a partition of the space underconsideration. Although the RCC5 and RCC8 systems have beengeneralized to ``egg-yolk' regions, in order to modelcertain types of vagueness, their extension to regionsapproximated in this way has not been discussed before.This paper presents two methods, the syntactic and the semantic, by which the RCC5 and RCC8 systemsmay be defined for approximate regions. The syntactic uses algebraicoperations on approximate regions which generalize operations on preciseregions. The semantic method makes use of the set of preciseregions which could be the intended interpretation of anapproximate region. Relationships between these two methods arediscussed in detail.alternative to navigation training with a map.