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11.
Werner Lottermoser Karl Forcher Georg Amthauer Martin Kunz Thomas Armbruster 《Physics and Chemistry of Minerals》1997,24(1):2-6
Mössbauer measurements on neptunite (KNa2Li(Fe,Mn,Mg)2Ti2Si8O24) at 400?K reveal the distribution of Fe-ions on the crystallographic sites in agreement with neutron diffraction results published elsewhere. Even the previously postulated small amount of Fe-ions on the Ti(2) site has been detected, combined with a charge transfer which is in agreement with optical absorption investigations by other authors. A qualitative site occupation model is able to explain the different features of our observations. Single crystal Mössbauer measurements with the k-vector of incident γ-rays parallel to the crystallographic b-axis (space group Cc) of neptunite at different temperatures yield the angle β between the main component of the electric field gradient (EFG), V zz and b. This angle is in close accordance with a calculated value of β for the Fe(1) position from electron density maps. The latter also reveal an absolute value of V zz which is in satisfactory agreement with V zz derived from Mössbauer spectroscopy. 相似文献
12.
Karl Lumme 《Icarus》1975,24(4):483-491
The true shape of the Cassini division of Saturn's rings in red, yellow, green, and blue light has been derived from photographs of high quality, taking into account the correction due to the spreading of light. It is evident that the division is not completely dark. Its minimum brightness is about 20% of that of ring B and the width of the division 0″.44±0″.05. 相似文献
13.
Norbert Hertkorn Ronald Benner Philippe Schmitt-Kopplin Karl Kaiser John I. Hedges 《Geochimica et cosmochimica acta》2006,70(12):2990-3010
Refractory carboxyl-rich alicyclic molecules (CRAM) are characterized in marine dissolved organic matter (DOM) using nuclear magnetic resonance spectroscopy and ultrahigh resolution mass spectrometry. CRAM are distributed throughout the water column and are the most abundant components of deep ocean DOM ever characterized. CRAM are comprised of a complex mixture of carboxylated and fused alicyclic structures with a carboxyl-C:aliphatic-C ratio of 1:2 to 1:7. CRAM are expected to constitute a strong ligand for metal binding, and multiple coordination across cations could promote aggregation and marine gel formation thereby affecting CRAM reactivity and the bioavailability of nutrients and trace metals. It appears CRAM are ultimately derived from biomolecules with structural similarities to sterols and hopanoids. The occurrence of CRAM in freshwater and terrestrial environments seems likely, considering the global distribution of biomolecules and the similarities of biogeochemical processes among environments. 相似文献
14.
Ewald Lüschen Daniela Borrini Helmut Gebrande Bernd Lammerer Karl Millahn Franz Neubauer Rinaldo Nicolich TRANSALP Working Group 《Tectonophysics》2006,414(1-4):9
The TRANSALP consortium, comprising institutions from Italy, Austria and Germany, carried out deep seismic reflection measurements in the Eastern Alps between Munich and Venice in 1998, 1999 and 2001. In order to complement each other in resolution and depth range, the Vibroseis technique was combined with simultaneous explosive source measurements. Additionally, passive cross-line recording provided three-dimensional control and alternative north–south sections. Profits were obtained by the combination of the three methods in sectors or depths where one method alone was less successful.The TRANSALP sections clearly image a thin-skinned wedge of tectonic nappes at the northern Alpine front zone, unexpected graben or half-graben structures within the European basement, and, thick-skinned back-thrusting in the southern frontal zone beneath the Dolomite Mountains. A bi-vergent structure at crustal scale is directed from the Alpine axis to the external parts. The Tauern Window obviously forms the hanging wall ramp anticline above a southward dipping, deep reaching reflection pattern interpreted as a tectonic ramp along which the Penninic units of the Tauern Window have been up-thrusted.The upper crystalline crust appears generally transparent. The lower crust in the European domain is characterized by a 6–7 km thick laminated structure. On the Adriatic side the lower crust displays a much thicker or twofold reflective pattern. The crustal root at about 55 km depth is shifted around 50 km to the south with respect to the main Alpine crest. 相似文献
15.
James L. Crowley Mark D. Schmitz Samuel A. Bowring Michael L. Williams Karl E. Karlstrom 《Contributions to Mineralogy and Petrology》2006,151(3):313-330
Zircon from lower crustal xenoliths erupted in the Navajo volcanic field was analyzed for U–Pb and Lu–Hf isotopic compositions
to characterize the lower crust beneath the Colorado Plateau and to determine whether it was affected by ∼1.4 Ga granitic
magmatism and metamorphism that profoundly affected the exposed middle crust of southwestern Laurentia. Igneous zircon in
felsic xenoliths crystallized at 1.73 and 1.65 Ga, and igneous zircon in mafic xenoliths crystallized at 1.43 Ga. Most igneous
zircon has unradiogenic initial Hf isotopic compositions (ɛHf=+4.1–+7.8) and 1.7–1.6 Ga depleted mantle model ages, consistent with 1.7–1.6 Ga felsic protoliths being derived from “juvenile”
Proterozoic crust and 1.4 Ga mafic protoliths having interacted with older crust. Metamorphic zircon grew in four pulses between
1.42 and 1.36 Ga, at least one of which was at granulite facies. Significant variability within and between xenoliths in
metamorphic zircon initial Hf isotopic compositions (ɛHf=−0.7 to +13.6) indicates growth from different aged sources with diverse time-integrated Lu/Hf ratios. These results show
a strong link between 1.4 Ga mafic magmatism and granulite facies metamorphism in the lower crust and granitic magmatism and
metamorphism in the exposed middle crust. 相似文献
16.
Potential of High-Resolution Satellite Data in the Context of Vulnerability of Buildings 总被引:1,自引:2,他引:1
High-resolution space-borne remote sensing data are investigated for their potential to extract relevant parameters for a
vulnerability analysis of buildings in European countries. For an evaluation of large earthquake scenarios, the number of
parameters in models for vulnerability is reduced to a minimum of relevant information such as the type of building (age,
material, number of storeys) and the geological and spatial context. Building-related parameters can be derived from remote
sensing data either directly (e.g. height) or indirectly based on the recognition of the urban structure type in which the
buildings are located. With the potential of a fully- or semi-automatic inventory of the buildings and their parameters, high-resolution
satellite data and techniques for their processing are a useful supporting tool for the assessment of vulnerability. 相似文献
17.
Based on Coastal Zone Color Scanner data from November 1978 through December 1981, the seasonal cycle of phytoplankton pigment
in the upper part of the euphotic zone is established for the offshore Laccadive Sea. Year-round, the pigment content is low
and the seasonal range is small, following the pattern of the nutrient-poor Arabian Sea to the west. Apparently, indigenous
phytoplankton blooms are absent. July and August, however, were poorly studied because of cloud cover. Interannual differences
during the northeast monsoon and the spring intermonsoon periods are minor. The abundant phytoplankton caused by the upwelling
off India during the southwest monsoon remains essentially restricted to the shelf, but there are occasional large, zonal
outbreaks into the Laccadive Sea, as well as others advected to the south of India. Visual inspection of the raw CZCS scenes
for June through November 1982–1985, with almost no data until August or even September, shows such outbreaks of pigment-rich
water to be common. Inspection of monthly SeaWiFS images for 1997 through part of 2001 confirms the absence of indigenous
phytoplankton blooms. 相似文献
18.
Studies evaluating the reproductive pattern of Mytilus edulis L. were conducted in western and eastern Iceland at two sites at about the same latitude but with different temperature regimes. Mussels were sampled once or sometimes twice a month during two years in Breidifjördur, western Iceland and one year at Mjoifjördur, eastern Iceland. Gonad development was monitored by microscopic observation of thin sections of the gonads. The initiation of gonad development was observed in January in Breidifjördur while in Mjoifjördur some of the animals started developing gonads in October, a month before spawning was over in the population. Spawning started in late June or July, peaked in August and continued until November at both sites. Nutrient reserve stores seemed to be limited and used for initiation of gonad development in winter but were not sufficient for maturation of the gonads. The main growth of the gonads occured in spring in conjunction with phytoplankton blooming and renewal of food resources. 相似文献
19.
Edward A. Parson Robert W. Corell Eric J. Barron Virginia Burkett Anthony Janetos Linda Joyce Thomas R. Karl Michael C. MacCracken Jerry Melillo M. Granger Morgan David S. Schimel Thomas Wilbanks 《Climatic change》2003,57(1-2):9-42
Based on the experience of the U.S. National Assessment, we propose a program of research and analysis to advance capability for assessment of climate impacts, vulnerabilities, and adaptation options. We identify specific priorities for scientific research on the responses of ecological and socioeconomic systems to climate and other stresses; for improvement in the climatic inputs to impact assessments; and for further development of assessment methods to improve their practical utility to decision-makers. Finally, we propose a new institutional model for assessment, based principally on regional efforts that integrate observations, research, data, applications, and assessment on climate and linked environmental-change issues. The proposed program will require effective collaboration between scientists, resource managers, and other stakeholders, all of whose expertise is needed to define and prioritize key regional issues, characterize relevant uncertainties, and assess potential responses. While both scientifically and organizationally challenging, such an integrated program holds the best promise of advancing our capacity to manage resources and the economy adaptively under a changing climate. 相似文献
20.
John F. Bratton John Karl Böhlke Frank T. Manheim David E. Krantz 《Ground water》2004,42(7):1021-1034