BOCAIUVA—A SILICATE-INCLUSION BEARING IRON METEORITE RELATED TO THE EAGLE-STATION PALLASITES

Bocaiuva is a unique meteorite consisting of major metal having a high Ge/Ga ratio and minor (～ 50 mg/g) silicates. The silicates are generally chondritic and consist of major olivine (Fa.7.7) and orthopyroxene (Fs7.6) and minor plagioclase (Ab49, An49) and clinopyroxene (Fs4.5, Wo42). The low alkali content of the silicates is the only property inconsistent with a chondritic composition. Based on metal composition Bocaiuva seems distantly related to certain iron meteorites having similar Ge contents and similar Ge/Ga ratios, but detailed comparison with six such irons shows none to be closely related to Bocaiuva. Perhaps most closely related is Cold Bay, a member of the Eagle-Station trio of pallasites, but its composition is too different to suggest formation on the same parent body. Oxygen-isotope data show that Bocaiuva silicates are closely related to those in the Eagle-Station pallasites and to the CO and CV chondrites. The composition and texture of the Bocaiuva metal-silicate assembly indicate mixing in an impact event. We suggest that the Eagle-Station pallasites were also formed by impact heating rather than by a long-lived internal heat source.     

Variation of the geomagnetic field in Costa Rica during the total solar eclipse of July 11, 1991

Ground measurements of the geomagnetic field, during the total solar eclipse of July 11, 1991, were carried out at three sites in Costa Rica located within the eclipse's path of totality. Near totality, there was a significant change in the total intensity,F. Its normal decrease in the afternoon hours was interrupted during a period of about 45 min, in whichF varied very little. This was due mainly to a small variation in horizontal intensity,H, during such a period. The departure ofF from normal lasted about 100 min; its maximum departure was near 10 nT and occurred about 38 min after totality, The declination,D, also experienced a small change (about 2.3 min) during the total period of the eclipse. The vertical intensity,Z, and the inclination,I, did not show significant changes.     

Determination of pteridines and flavins in seawater by reverse-phase,high-performance liquid chromatography with fluorometric detection

Methods are described for routine analyses of individual pteridines and flavins from marine waters at picomolar concentrations. Samples were concentrated by adsorption on bonded-phase, C₁₈ silica and Florisil Sep-Pak extraction columns connected in series. Sample extracts derived from Sep-Pak eluates were analysed by reverse-phase liquid chromatography with fluorometric detection. These methods proved sensitive for the quantitative identification of pterin, xanthopterin, isoxanthopterin, 6-biopterin, pterin-6-carboxylic acid, 6-hydroxymethylpterin, riboflavin, riboflavin-5′-phosphate, lumiflavin and lumichrome in reef waters at Davies Reef, Great Barrier Reef, Australia.Preliminary experiments were conducted to test the application of these methods to the measurement of pterin and flavin excretion from several reef-dwelling, benthic organisms. Results from these experiments suggest that the benthic community contributes these compounds to the coral reef environment.     

Superluminal velocity and deviation from Newton's inverse square law

Starting from the theory of gravitation in flat space-time of Petry (1981), the gravitational field of a static spherically-symmetric body is studied. Petry (1982) has shown that this field in the exterior of the body depends on a parameter which is fixed by the interior solution, i.e., it depends on the density of matter, the pressure, the equation of state, etc. If this parameter is small, the results for the well-known effects, i.e., redshift, deflection of light, perihelion shift, and radar time-delay, agree with those of general relativity. In this paper, we study these effects for larger values of this parameter. Furthermore, for sufficiently large positive values of the parameter, in the neighbourhood of the body the radial velocity of light can exceed several times the vacuum light-velocity. Therefore, the components of such an object can move away with velocities a few times greater than that of light in agreement with the observed superluminal velocities in extragalactic objects.     

Friedrich Wilhelm Bessel (1784–1846)

May I first express my warmest thanks to the organizers of the Conference for having invited me to present a brief bibliographic report on the great astronomer F. W. Bessel. You have given me a welcome opportunity to express an appreciation of Bessel's work which has marked the beginning of research on the motion of stars and which was pioneer work on astrometric binaries and on the determination of stellar distances. Bessel has established the first celestial coordinate system which approximates an inertial system, and my colleagues and I at Heidelberg in establishing an improved fundamental reference system, the FK5, have had to review again some of Bessel's pioneer contributions to this field, and such contributions shall be mentioned later. My talk shall be divided into the following parts: (1) Bessel's course of life and family; (2) Education in astronomy in Bremen; (3) Fundamenta Astronomiae; (4) Fundamental observations at the Königsberg Observatory (or according to S. Newcomb (1906): the German School of Astrometry); (5) 61 Cygni; (6) Bibliography of Bessel's original works.Communication presented at the International Conference on Astrometric Binaries, held on 13–15 June, 1984, at the Remeis-Sternwarte Bamberg, Germany, to commemorate the 200th anniversary of the birth of Friedrich Wilhelm Bessel (1784–1846).     

A numerical simulation of the Martian polar cap breeze

A mathematical model for the Martian polar cap breeze was constructed in part from work previously done by others on the terrestrial sea breeze. With this model a numerical simulation corresponding to the Southern Hemisphere winter season was made. The results obtained with the proposed model show that the Martian polar cap breeze is a well defined system with some similarities to the terrestrial sea breeze. At the time of maximum intensity, the largest values of vertical velocities are about 10 cm/s and occur at heights between 850–1250 m. The largest values of horizontal velocities are about 15 m/s. A polar cap breeze front is clearly discernible in the results. The rate of advance of this front is at an average of about 10 km/h.