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81.
82.
The heliocentric radial distribution of the flux of hyperbolic cosmic dust particles, as measured by the Pioneer 8 and 9 spacecraft, is closely related to the radial variation of the spatial density of source or “parent” meteoroids. Within the limits of the experimental and theoretical uncertainties the spatial density of parent meteoroids, as deduced from the hyperbolic cosmic dust data, is found to be increasing with increasing heliocentric distance in the neighborhood of one a.u. Other recent experimental evidence confirms this result. The new results also suggest that the ratio of the areal density of submicron sized craters to the areal density of millimeter sized craters will be less on the north-south faces of lunar rocks than on the east-west faces of the same rocks. The changeinratio is not as large as previously thought, however. Finally it is noted that the solar system is not presently contributing significant amounts of dust to the interstellar medium though it may once have done so.  相似文献   
83.
Herbert Frey 《Icarus》1975,25(3):439-446
It may be possible to understand the apparent intermittent nature of the post-eclipse brightenings and nonbrightenings of Io in terms of a nonuniform distribution of blue reflectors grouped in the hemisphere centered at 0° longitude. The dimensions required for such blue mirrors are consistent with very large craters. The high blue albedo of water frost and other ices makes these materials likely candidates for the reflectors.  相似文献   
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Eighteen short cores were analyzed for major and trace metals (Al, Fe, Ca, Mg, Mn, Si, K, Ti, Pb, Zn, Cu, Ni, Cr), 210Pb, 137Cs, and other sediment characteristics, so as to describe the chronology of pollution and calculate metal concentration factors and fluxes. Substantial evidence was found that trace metal profiles are influenced by anthropogenic sources and by changes in sediment composition. Only Zn presents concentrations (up to 13.1 μmol g) and concentration factors (1.3 to 13.2) that can be attributed to heavy contamination. Pb, Cu and Ni, in this order, are less significant. The areal distribution of concentrations and inventories reflects the importance of direct sources, in particular the industrial area of Porto Marghera and the Dese river. The inventories of excess metals, above pre-industrial levels, were determined for each core and the three different parts of the study area, the amounts of Zn accumulated in sediments are 11.0 Mmol, 5.1 Mmol and 0.37 Mmol in the Campalto, S. Erasmo, and Palude di Cona areas, respectively. Ruxes were also calculated and compared with those suggested for the atmospheric delivery by Cochran et al. [(1995)b. Atmospheric fluxes of heavy metal contaminants to the Venice Lagoon, Rapp. Comm. Int. Mer Médit., 34, 136.], the atmospheric contribution is predominant or significant in many cases, especially at sites far from the major local inputs. Concentrations and fluxes show a significant increase in the anthropogenic metal supply starting from the second decade of this century, with maximum inputs in the period between the (1930)s and the (1970)s. At some stations a decrease in heavy metal contamination of surficial sediments was found and this could be ascribed to a reduced input of pollutants in recent years.  相似文献   
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New coring data have been acquired along the western Gulf of Lions showing anomalous concentrations of methane (up to 95,700 ppm) off the Rhône prodelta and the head of the southern canyons Lacaze-Duthiers and Cap de Creus. Sediment cores were acquired with box and kasten cores during 2004–2005 on several EuroSTRATAFORM cruises. Anomalous methane concentrations are discussed and integrated with organic carbon data. Sampled sites include locations where previous surveys identified acoustic anomalies in high-resolution seismic profiles, which may be related to the presence of gas. Interpretation of the collected data has enabled us to discuss the nature of shallow gas along the Gulf of Lions, and its association with recent sedimentary dynamics. The Rhône prodelta flood deposits deliver significant amounts of terrigenous organic matter that can be rapidly buried, effectively removing this organic matter from aerobic oxidation and biological uptake, and leading to the potential for methanogenesis with burial. Away from the flood-related sediments off the Rhône delta, the organic matter is being reworked and remineralized on its way along the western coast of the Gulf of Lions, with the result that the recent deposits in the canyon contain little reactive carbon. In the southernmost canyons, Lacaze-Duthiers and Cap de Creus, the gas analyses show relatively little shallow gas in the core samples. Samples with anomalous gas (up to 5,000 ppm methane) are limited to local areas where the samples also show higher amounts of organic matter. The anomalous samples at the head of the southern canyons may be related to methanogenesis of recent drape or of older sidewall canyon infills.  相似文献   
89.
1 IntroductionSecretion is a basic function of all living organ-isms. In fish, like in mammals, neurotransmitters,hormones, enzymes and other macromolecules aresecreted in several neuronal, neuroendocrine and ex-ocrine organs and tissues located in brain,…  相似文献   
90.
The time dependence of the ordering and disordering of Al and Si in sanidine is described within the framework of the kinetic rate laws developed in papers I and II of this series. It was found that the relevant order parameter Q t is homogeneous and non-conserved. The rate law is:
  相似文献   
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