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31.
Douglas A. Simons Paola Amico Dietrich Baade Sam Barden Randall Campbell Gert Finger Kirk Gilmore Roland Gredel Paul Hickson Steve Howell Norbert Hubin Andreas Kaufer Ralf Kohley Philip MacQueen Sergej Markelov Mike Merrill Satoshi Miyazaki Hidehiko Nakaya Darragh O'Donoghue Tino Oliva Andrea Richichi Derrick Salmon Ricardo Schmidt Hongjun Su Simon Tulloch Maria Luisa García Vargas R. Mark Wagner Olivier Wiecha Binxun Ye 《Experimental Astronomy》2005,19(1-3):15-44
Results of a survey of instrumentation and detector systems, either currently deployed or planned for use at telescopes larger than 3.5 m, in ground based observatories world-wide, are presented. This survey revealed a number of instrumentation design trends at optical, near, and mid-infrared wavelengths. Some of the most prominent trends include the development of vastly larger optical detector systems (> 109 pixels) than anything built to date, and the frequent use of mosaics of near-infrared detectors – something that was quite rare only a decade ago in astronomy. Some future science applications for detectors are then explored, in an attempt to build a bridge between current detectors and what will be needed to support the research ambitions of astronomers in the future. 相似文献
32.
Richard Dame Norbert Dankers Theo Prins Henk Jongsma Aad Smaal 《Estuaries and Coasts》1991,14(2):130-138
The uptake and release of materials by intertidal mussel beds were directly measured in two cultivated Dutch estuaries. Generally, chlorophylla, seston, and particulate organic carbon were taken up, while ammonium, orthophosphate, and silicate were released. The observed rates were higher than values computed from organismic observations and similar to those observed for intertidal oyster reefs in South Carolina. Specific estuarine material turnover rates varied from 1 week to 38 weeks when calculated with mussel bed fluxes. The fastest turnover rates were for chlorophylla and ammonium. These results support the idea that dense assemblages of bivalves are major components in the recycling of nutrients in estuaries. 相似文献
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34.
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
35.
Florian Einsiedl Norbert Hertkorn Moritz Frommberger Boris P. Koch 《Geochimica et cosmochimica acta》2007,71(22):5474-5482
The study of molecular transformation processes of dissolved organic carbon (DOC) in the environment significantly contributes to a better understanding of the global biogeochemical organic matter cycle. In an oxic karst groundwater system, in which the most powerful abiotic DOC degradative reactions, photodegradation and metal-mediated redox chemistry, are at best marginal contributors, a near complete turnover of fulvic acids (FAs) has been observed within decades (∼60 years). Depletion of oxygen for a very extensive range of aliphatic and aromatic carbon chemical environments has been confirmed as well as the formation of novel classes of compounds, suggesting a major contribution from biotic processes. From these results we infer that FAs must be perceived as a rather active participant in the global carbon cycle. Molecular-level alterations of such magnitude and rapidity on such short-time scales ought to be considered as widespread in the processing of “refractory” DOC in the environment. 相似文献
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37.
N. Morgenstern 《Pure and Applied Geophysics》1962,52(1):104-114
Summary It is shown that hydraulic fracture pressures are related to the stresses in the formation and the strength of the rock composing it. Using the Coulomb-Mohr failure criterion and the principle of effective stress, expressions can be obtained relating these factors. The theory indicates that in areas characterized by thrust faulting, the fractures will be inclined horizontally whereas in areas subject to normal faulting stress conditions, they will be more vertical. The analysis of some field data gives reasonable results. 相似文献
38.
Icy surfaces like the polar caps of Mars, comets, Edgeworth-Kuiper belt objects or the surface areas of many moons in the outer Solar System behave different than rock and soil surfaces when irradiated by solar light. The latter ones absorb and reflect incoming solar radiation immediately at the surface. In contrast, ices are partially transparent in the visible spectral range and opaque in the infrared. Due to this fact it is possible for the solar radiation to reach a certain depth and increase the temperature of the sub-surface layers directly. This internal temperature rise is called “solid-state greenhouse effect,” in analogy to the classical greenhouse effect in an atmosphere. It may play an important role in the energy balance of various icy bodies in the Solar System. Within the scope of a project conducted at the Space Research Institute of the Austrian Academy of Sciences in Graz the solid-state greenhouse effect was investigated experimentally and theoretically. A number of experiments with diverse materials, focussing mainly on layered samples with a surface cover consisting of transparent H2O-ice, were performed. The samples were irradiated under cryo-vacuum conditions by a solar simulator. The temperature distributions inside the samples were measured and compared with the results of numerical model calculations. We found that the predicted sub-surface temperature maximum is very clearly measurable in glass beads samples with various particle size distributions, but can also be detected in transparent compact surface ice layers. However, in the latter case it is less distinct than originally expected. Measuring the effect by laboratory methods turned out to be a difficult task due to the shallow depth where the temperature maximum occurs. 相似文献
39.
Norbert Schartel 《Astronomische Nachrichten》2010,331(2):139-139
40.
Kevin R. Chamberlain Axel K. Schmitt Susan M. Swapp T. Mark Harrison Norbert Swoboda-Colberg Wouter Bleeker Tony D. Peterson Charles W. Jefferson Andrei K. Khudoley 《Precambrian Research》2010
An in situ U–Pb SIMS (IN-SIMS) method to date micro-baddeleyite crystals as small as 3 μm is presented with results from three samples that span a variety of ages and geologic settings. The method complements ID-TIMS geochronology by extending the range of dateable crystals to sizes smaller than can be recovered by physical separation. X-ray mapping and BSE imaging are used to locate target grains in thin section, followed by SIMS analysis on a CAMECA ims 1270, using the field aperture in the transfer column to screen out ions from host phases. Internal age precisions for the method are anticipated to range from 0.1% for Precambrian rocks to 3–7% for Phanerozoic rocks. Results establish a 2689 ± 5 Ma age for mafic dikes in the Wyoming craton, USA, a 1540 ± 30 Ma age for a subaerial lava flow from the Thelon Basin of northern Canada, and a 457 ± 34 Ma age for mafic dikes in the platform sequence of southeastern Siberia. The method is ideal for relatively non-destructive dating of small samples such as extraterrestrial rocks and precious terrestrial samples. 相似文献