The charge distribution on interstellar grains—The effect of induced charge

A calculation of the equilibrium charge acquired by interstellar grains is given, which takes account of polarization charges that are induced in a grain by incident ions and electrons.Both metal and dielectric grains are considered and photoionization of the latter grains by UV radiation is taken into account where necessary. It is found that the inclusion of the polarization charges in the calculation is only important in gas clouds where the mean charge on a grain is low (<1e); that is, for HI regions and dense molecular clouds. In such clouds, the effect of the polarization charges is to increase the amount of negative charge acquired by a grain. A discussion is given concerning the validity of the classical electrostatic theory employed in the paper for small grains of radius 10^–6 cm, and some astrophysical consequences of the modification of the grain charge by polarization effects are considered.     

The evolution of massive close binaries

The results of evolutionary computations for massive binary systems (initial masses of the primary 10M ) with mass ratios between 0.3 and 0.8 are summarized and compared with observations in order to verify how far one can go with the conservative assumption of mass exchange. It is found that conservative mass exchange leads to acceptable first-order models of W-R and massive X-ray binaries. However, the comparison between this theory and observation reveals that for the observed systems (W-R and X-ray binaries) a preference exists for low intial mass ratios; moreover, the X-ray luminosities of the theoretical models are systematically too low, though this may be due to the adopted wind model. In addition, the influences of several parameters (distance between the components, chemical composition, primary mass, mass ratio and atmosphere) are examined. These parameters influence the remnant mass and any further evolution only marginally. Attention is also given to the effect on the system parameters of a supernova explosion of the remnant of the mass-losing component. For a large range of systems a disruption probability smaller than 25% is found.     

Hydrocarbons in surficial sediments from the Scotian Shelf

Surface sediments from 20 stations on the Scotian Shelf, collected on a transect from Halifax to Emerald Bank and around Sable Island, have been analyzed for hydrocarbon content and composition by gas chromatography and fluorescence spectrophotometry. Some samples were taken near abandoned exploratory drilling sites in the Sable Island area. Hydrocarbons appear to be mainly derived from biogenic terrestrial sources as evidenced by an inverse correlation of concentration with increasing distance from the mainland and a strong odd carbon preference in the n-alkanes. Contribution from petroleum sources, while minor, was most noticeable between Halifax and Emerald Bank. There is also evidence that the hydrocarbon composition at abandoned exploratory drilling sites has been slightly altered.     

Organic geochemistry of silicified wood,Petrified Forest National Park,Arizona

Lignin derivatives have been isolated for the first time from carbonaceous sections of the silicified (~90% SiO₂) conifer Araucarioxylon arizonicum. The products released by sequential high vacuum pyrolysis and identified by combined gas chromatography-mass spectrometry (GC-MS) include a wide variety of alkyl-substituted, phenolic and condensed aromatic compounds.Brauns spruce lignin was pyrolized and analyzed by GC-MS as a comparison for the fossil wood data. The primary pyrolyzates at the 300°C step were CO₂, H₂O, ethanol and propanol. The main product at 450°C was 4-methyl-2-methoxyphenol (methyl guaiacol), but at 600°C the pyrolyzates were similar both in product composition and in relative abundance to those from silicified wood. The results suggest that the fossil wood experienced a mild thermal event during which the ether bonds were ruptured and loss of oxygen occurred along with the rearrangement of the original wood into a highly stable polymer.     

Determination of the sources and circulation paths of thermal fluids: the Abano region,northern Italy

Water samples from natural springs and artesian wells in the Abano region of northern Italy are characterized by anomalous temperatures and compositions. Concentrations of major components and oxygen isotopes in samples of these fluids have been interpreted in the context of the regional geologic environment, circulation of groundwaters, and reactions between rocks and circulating groundwaters. These considerations define sourceregions and pathlines of the groundwaters.Circulation of fluids in the Abano region is interpreted to be the result of meteoric water infiltration into outcrops of Permian and Mesozoic aquifers in the pre-Alps, which lie north of the Abano region. These aquifers have southerly dips and, therefore, extend under the Abano region at depths between 0.5 and 2.5 km. This aquifer geometry is conducive to forced convection both of aqueous ions derived from the evaporate, limestone and dolomite bearing formations, and of thermal energy along flow paths which extend from the outcrops in the sourceregions to depths of 2 km below the Abano region and upward along high angle faults to thermal springs. Local variation in compositions of water samples is consistent with the mixing of local meteoric waters and formation fluids that were ultimately derived from Alpine sources.     

The opening of the Bay of Biscay - a review

The anticlockwise rotation of the Iberian Peninsula away from south Brittany during the Mesozoic has been demonstrated from palaeomagnetic data. Marine magnetic, seismic and gravity surveys have indicated that there is oceanic crust in the Bay of Biscay. Initial rifting began in the Triassic but the major part of the rotation of the Iberian Peninsula occurred during the Late Cretaceous. Two mechanisms for the opening of the Bay of Biscay have been proposed, firstly a simple anticlockwise rotation of the Iberian plate and secondly, a 350 km sinistral displacement of the Iberian plate along transform faults about a pole of rotation near Paris. Geological data, partly new, favours the first mechanism but with a pole of rotation approximately 100 km east of the west end of the Pyrenees rather than in the southeast corner of the Bay of Biscay. Geophysical data indicates a further small rotation of the Iberian Peninsula during the Late Eocene which resulted in the formation of the Pyrenees.