The isotopic compositions and concentrations of lead in some chondritic stone meteorites     

D. G. Hess  R. R. Marshall 《Geochimica et cosmochimica acta》1960,20(3-4):284-299

Microgram quantities of lead were volatilized from the chondrites Richardton, Holbrook, Beardsley and Plainview and purified for mass spectrometric analysis. Aliquots of approximately 1 μg were surface-ionized by use of the boric acid technique. The isotopic compositions found range from highly radiogenic lead in the case of Richardton to leads in the other three chondrites which are substantially less radiogenic than average lead in the crust of the earth. p]From our recent concentration determinations by the isotopic dilution method, it seems that the amount of lead in Beardsley is about 0·13 p.p.m. and that in Richardton about 0·06 p.p.m. The leads in these meteorites are consistent within a factor of approximately two with the lead-lead ages and the independently measured uranium and thorium concentrations. The lead—lead age for Richardton is the same as that found by (1955) for Nuevo Laredo, being 4·6 Æ. The lead concentration measured for Forest City is 0·09 p.p.m., while that for Holbrook is 0·28 p.p.m. Holbrook is quite anomalous in containing 2·5 times the amount of radiogenic lead that can be explained by the accumulation of decay products in situ with a primeval lead which had the isotopic composition of the lead from the troilite in the Canyon Diablo and Henbury iron meteorites. p]The total amount of lead on the surface of a meteorite appears to be comparable to the total amount inside. The isotopic composition of this surface lead indicates that it is principally terrestrial lead.  相似文献   

Structural and metamorphic evolution of the Camughera – Moncucco, Antrona and Monte Rosa units southwest of the Simplon line,Western Alps     

Lukas M. Keller  Maurus Hess  Bernhard Fügenschuh  Stefan M. Schmid 《Eclogae Geologicae Helvetiae》2005,98(1):19-49

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A method of characterizing the thermal relations in mountainous areas / the lower Beskid range in the Polish Carpathians as example     

M. Hess Dr.  T. Niedźwiedź Doc. Dr.  B. Obrębska-Starkelowa Doc. Dr. 《GeoJournal》1984,8(2):251-257

The method discussed in the present paper permits the determination in detail of the mesoclimatic conditions on the basis of standard data provided by a network of a measurement stations. The passage from the data available at certain points and obtained from meteorological stations to spatial conceptions leads along the determination of the relationships between the altitude, various forms of the relief, and the thermal indices of climate. Resulting from these data, the duration of the frostless period is a sensitive index in the scale of mesoclimate, besides all the other indices connected with the minimum air temperatures. The nomographs applied by the authors make it possible to construct detailed climatic maps, which — with the maps of other elements of the geographical environment — form a basis for the elaboration e.g. an agrocological map of habitats. Presented method of the evaluation of climate conditions can be applied to all mountain territories, in which a network of measurement stations enables the determination of the interdependencies between the chosen thermal parameters and the altitude, and the distinction of the impact of the convex and concave forms.  相似文献   

Polymer model of silicate melts     

Paul C Hess 《Geochimica et cosmochimica acta》1971

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Using Polar Coronal Hole Area Measurements to Determine the Solar Polar Magnetic Field Reversal in Solar Cycle 24     

N. Karna  S. A. Hess Webber  W. D. Pesnell 《Solar physics》2014,289(9):3381-3390

An analysis of solar polar coronal hole (PCH) areas since the launch of the Solar Dynamics Observatory (SDO) shows how the polar regions have evolved during Solar Cycle 24. We present PCH areas from mid-2010 through 2013 using data from the Atmospheric Imager Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) instruments onboard SDO. Our analysis shows that both the northern and southern PCH areas have decreased significantly in size since 2010. Linear fits to the areas derived from the magnetic-field properties indicate that, although the northern hemisphere went through polar-field reversal and reached solar-maximum conditions in mid-2012, the southern hemisphere had not reached solar-maximum conditions in the polar regions by the end of 2013. Our results show that solar-maximum conditions in each hemisphere, as measured by the area of the polar coronal holes and polar magnetic field, will be offset in time.  相似文献