Colloidally separated samples from Allende residues: Noble gases,carbon and an ESCA-study     

Ulrich Ott  Johann Kronenbitter  Jose Flores  Sherwood Chang 《Geochimica et cosmochimica acta》1984,48(2):267-280

A non-colloidal fraction separated by physical means from an $\text{HF}\text{HCl}$-resistant residue of the Allende carbonaceous meteorite exhibits a ratio of isotopically “normal” (Q-type) xenon to “anomalous” xenon (X-type) that is ~4 times larger than usually observed. Coincidentally this fraction contains carbon that is isotopically heavier by ~10%. than bulk Allende residue samples. ESCA analyses of companion colloidal separates show that the major portion of the S contained in our $\text{HF}\text{HCl}$-residues is elemental rather than a sulfide. They also confirm earlier observations that no elementally distinct surface coating is present, in accord with the absence of a surface-sited sulfur-bearing gas carrier, and that the oxygen content is increased after etching with nitric acid. For these separates noble gas data coupled with the ESCA data for nitrogen and the isotopic data for carbon point to the existence of heterogeneities among the noble gas-, carbon- and nitrogen-bearing phases and, thus, preservation of discrete components from the variety of source regions (or production mechanisms, or both) sampled by the Allende parent body. In sharp contrast to the success of physical and chemical methods in yielding samples in which one of the major noble gas components predominates to an extraordinary degree over the other, carbon isotopic compositions that have been inferred for the respective carrier phases in these same samples are strongly contradictory. Mass and isotope balance considerations lead us to conclude that a major fraction of the carbonaceous matter in Allende is noble-gas-poor, a result that could be confirmed by direct isolation of a sample, the carbon in which is dominated by this variety; and for that reason no simple relationship is discernable yet between observed isotopic compositions and either major noble gas component. Similar ambiguities may exist for nitrogen. The possible relationship between carbon-rich phases in ureilites and carbonaceous chondrites is considered.  相似文献   

Photogeologische Untersuchungen über die Bruchtektonik im Toskanisch-Umbrischen Apennin     

Priv.-Doz. Dr. Johann Bodechtel 《International Journal of Earth Sciences》1969,59(1):265-278

Zusammenfassung Der toskanisch-umbrische Apennin zeigt einen großräumigen, ostvergenten Faltenbau mit intensiver Schuppentendenz zwischen faltungskompetenten und-inkompetenten Serien. Der Achsenplan ist einheitlich für die gesamte Toskana mit einer vorherrschenden NNW-SSE-Richtung. Jünger als die Faltung ist eine Bruchtektonik mit Blattverschiebungen in ac-Richtung und horstartige Heraushebungen in bc-Richtung, die eindeutig auf den, den Hauptfaltenachsen zuzuordnenden Kluftsystemen neu belebt wird. Diese Bruchtektonik war bis in subrezente Zeit wirksam, was die diesen Richtungen aufsitzenden Vulkane beweisen.

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The fold-tectonic of the Tuscan Apennines shows eastward inclination and intensively imbricated structure between competent and incompetent series. The axial plan, predominantly a NNW-SSE direction, is uniform for the whole Tuscany. The fault-tectonic, with strikeslip faults in the ac-direction and horst-like uplifts in the bc-direction, is younger than the fold-tectonic. These faults are reactivated joints, definitely belonging to the joint-sets of the mayor fold axes. These faults have been active until subrecent time, verified by the volcanoes, which are situated along these directions.

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Résumé L'Apennin toscan présente un plissement incliné vers l'est avec une imbrication intense de series compétentes et incompétentes. Le plan axial, d'une direction dominante NNW-SSE, est uniforme pour l'ensemble de la Toscane. Une tectonique de fractures avec des failles de décrochement dans la direction ac et des blocs surélevés dans la direction bc est plus récente que le plissement. Cette tectonique a été réactivée suivant le système de fractures du plissement principal. Elle a été active jusqu'à une époque subrécente, et s'est manifestée par des volcans situés le long de ces directions.

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- . , NNW-SSE. , , , . - , .

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Tracer experiment with sulfur hexafluoride to quantify the vertical transport in a meromictic pit lake     

Christoph von Rohden  Johann Ilmberger 《Aquatic Sciences - Research Across Boundaries》2001,63(4):417-431

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Addressing the coral reef crisis in developing countries   总被引：2，自引：0，他引：2  

Johann D. Bell  Blake D. Ratner  Ilona Stobutzki  Jamie Oliver 《Ocean & Coastal Management》2006,49(12):976-985

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Greenhouse-gas versus aerosol forcing and African climate response     

Heiko Paeth  Johann Feichter 《Climate Dynamics》2006,26(1):35-54

There are many indicators that human activity may change climate conditions all around the globe through emissions of greenhouse gases. In addition, aerosol particles are emitted from various natural and anthropogenic sources. One important source of aerosols arises from biomass burning, particularly in low latitudes where shifting cultivation and land degradation lead to enhanced aerosol burden. In this study the counteracting effects of greenhouse gases and aerosols on African climate are compared using climate model experiments with fully interactive aerosols from different sources. The consideration of aerosol emissions induces a remarkable decrease in short-wave solar irradiation near the surface, especially in winter and autumn in tropical West Africa and the Congo Basin where biomass burning is mainly prevailing. This directly leads to a modification of the surface energy budget with reduced sensible heat fluxes. As a consequence, temperature decreases, compensating the strong warming signal due to enhanced trace gas concentrations. While precipitation in tropical Africa is less sensitive to the greenhouse warming, it tends to decrease, if the effect of aerosols from biomass burning is taken into account. This is partly due to the local impact of enhanced aerosol burden and partly to modifications of the large-scale monsoon circulation in the lower troposphere, usually lagging behind the season with maximum aerosol emissions. In the model equilibrium experiments, the greenhouse gas impact on temperature stands out from internal variability at various time scales from daily to decadaland the same holds for precipitation under the additional aerosol forcing. Greenhouse gases and aerosols exhibit an opposite effect on daily temperature extremes, resulting in an compensation of the individual responses under the combined forcing. In terms of precipitation, daily extreme events tend to be reduced under aerosol forcing, particularly over the tropical Atlantic and the Congo basin. These results suggest that the simulation of the multiple aerosol effects from anthropogenic sources represents an important factor in tropical climate change, hence, requiring more attention in climate modelling attempts.  相似文献   

Imaging distribution patterns of magnetic minerals by a novel high-T_c-SQUID-based field distribution measuring system: application to Permian sediments     

Norbert Nowaczyk  Horst-Ulrich Worm  rea Knecht  & Johann Hinken 《Geophysical Journal International》1998,132(3):721-724

A newly developed field distribution measuring system based on a high- T _c SQUID has been employed in the study of magnetic mineral distribution in several Permian sedimentary rocks. The instrument consists of a small, 1.4×1.4 mm sized YBaCu-oxide SQUID magnetic field sensor that is operated in a thin-walled dewar, so that the sample's surface, at room temperature, can be scanned at a distance of only ∼1.5 mm. The samples were subjected to a saturation remanence perpendicular to the surface and the scanning measurements in zero field reveal that the magnetization might be carried by only a small part of a sample, in one case associated with secondary oxide phases. High-resolution magnetic scans can aid in the interpretation of the magnetic remanence acquisition process.  相似文献   

Upper bathyal trace fossils document palaeoclimate changes     

Johann Hohenegger  Peter Pervesler  Alfred Uchman  Michael Wagreich 《地学学报》2009,21(3):229-236

Marine trace fossils were investigated in a 102-m cored section that covers −14.379 to −14.142 Ma (Middle Miocene). Long-term climate trends are perfectly reflected by changing trace fossil communities of the upper bathyal (−200 to −300 m). The community structure is expressed in abundance of taxa based on probabilities of time concordance between the deposition of the sediment and the time, when the traces were produced. Changes in community structure precisely parallel the increasing δ¹³C isotopes during the Middle Miocene climate transition and perfectly mirror oscillations in solar insolation in both amplitudes and phase. Furthermore, the density stratification of the seawater caused by wind-induced currents is reflected in trace fossil communities. Additionally, the dependence of ichnotaxa abundance from threshold values in the sedimentation rate could be demonstrated.  相似文献   

Transforming management of tropical coastal seas to cope with challenges of the 21st century     

Peter F. Sale  Tundi Agardy  Cameron H. Ainsworth  Blake E. Feist  Johann D. Bell  Patrick Christie  Ove Hoegh-Guldberg  Peter J. Mumby  David A. Feary  Megan I. Saunders  Tim M. Daw  Simon J. Foale  Phillip S. Levin  Kenyon C. Lindeman  Kai Lorenzen  Robert S. Pomeroy  Edward H. Allison  R.H. Bradbury  Jennifer Corrin  Alasdair J. Edwards  David O. Obura  Yvonne J. Sadovy de Mitcheson  Melita A. Samoilys  Charles R.C. Sheppard 《Marine pollution bulletin》2014

Over 1.3 billion people live on tropical coasts, primarily in developing countries. Many depend on adjacent coastal seas for food, and livelihoods. We show how trends in demography and in several local and global anthropogenic stressors are progressively degrading capacity of coastal waters to sustain these people. Far more effective approaches to environmental management are needed if the loss in provision of ecosystem goods and services is to be stemmed. We propose expanded use of marine spatial planning as a framework for more effective, pragmatic management based on ocean zones to accommodate conflicting uses. This would force the holistic, regional-scale reconciliation of food security, livelihoods, and conservation that is needed. Transforming how countries manage coastal resources will require major change in policy and politics, implemented with sufficient flexibility to accommodate societal variations. Achieving this change is a major challenge – one that affects the lives of one fifth of humanity.  相似文献   

Neues über den Basalt von Kollnitz im Lavanttal Kärnten     

Erich Johann Zirkl  O. Braitsch  F. Hofer  Erentraud Kahler 《Mineralogy and Petrology》1962,8(1):96-139

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Possibilities and Limitations of Interdisciplinary, User-oriented Research: Experiences from the German Research Network Natural Disasters     

Bruno Merz  Jana Friedrich  Markus Disse  Jochen Schwarz  Johann G. Goldammer  Jochen Wächter 《Natural Hazards》2006,38(1-2):3-20

The German Research Network for Natural Disasters (DFNK) linked 15 partners with scientific expertise in the field of natural hazards. Main objectives were the development and provision of the scientific fundamentals for an advanced risk management of important natural disasters in Germany, i.e., floods, earthquakes, storms and wildland fires. This included risk analyses, the development of information systems for supporting disaster management, and recommendations for risk reduction measures. This paper gives an overview of DFNK and summarises its experiences concerning multidisciplinarity and user-orientation. It illustrates the concept of risk chains, causally linking the different processes from hazard to risk. The step from hazard to risk requires interdisciplinary research teams. The experiences show that integrative concepts allow results not achievable with mono-disciplinary approaches. Integrative approaches pave the way to harmonised safety considerations taking into account the different hazards in a region within a common framework. User-orientation, policy advice and development of operational tools are key issues of disaster research. The experiences of DFNK illustrate the limitations of a research network in bridging the gap between research and application within rather short-term projects. Successful cooperation with users could be established by those activities where, at the beginning of the project, a user was identified who had a strong interest in solving an urgent problem.  相似文献