Dynamics of dimensions in factor-space cosmology

For multi-dimensional cosmological models we investigate the dynamics of both, scales and dimensions. The classical equation of motions and the corresponding Wheeler-de Witt equation are set up generally and the qualitative behaviour of the system is discussed for some specific model with 2 factor spaces: A space M₁ with dynamical dimension, and a compact internal space M₂ of constant dimension. With a natural choice of some contraint, there exist a solution where M₁ expands as usual space while M₂ is shrinking down to unobservable scales.     

Potential applications of ERS-1 SAR data in near real-time

Summary Some important principles of remote sensing using synthetic aperture radar data (SAR data) from the first European Remote Sensing Satellite ERS-1 are explained. Examples illustrate the potential applications of satellite radar information. The possibility of using near-on-line processed remote information for operational purposes is discussed in particular.The satellite information used was received, processed and presented to the visitors of the exhibition which took place as part of the 1992 International Space Year (ISY) at the Bonn offices of the EEC. The BSH and DLR co-operated with DARA and TELEKOM. The intention was to familiarize a broader public with the potential of remote sensing and to stress the necessity of using space technology in combatting environmental problems.

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Zum Nutzungspotential von ERS-1-AAR-Daten in naher Echtzeit

Zusammenfassung Im vorliegenden Beitrag werden einige wichtige Grundlagen der Fernerkundung mit SAR-Daten des Ersten Europäischen Fernerkundungssatelliten ERS-1 erläutert und anhand einiger ausgewählter Beispiele Möglichkeiten der Nutzanwendung von Radar-Daten aufgezeigt. Dabei werden besonders die Möglichkeiten eines Nahe-Echtzeit-Einsatzes unter operationellen Gesichtspunkten aufgegriffen und diskutiert.Die verwendeten Daten wurden während einer Präsentation in der Vertretung der Kommission der Europäischen Gemeinschaft in Bonn anläßlich einer Veranstaltung zum Internationalen Weltraumjahr 1992 (ISY) von der BDDN-Fast-Delivery-Station des Bundesamts für Seeschiffahrt und Hydrographie (BSH) in Zusammenarbeit mit der Deutschen Forschungsanstalt für Luft- und Raumfahrt (DLR) und der TELEKOM aufgezeichnet, digital verarbeitet und den Besuchern der Ausstellung vorgestellt. Im Vordergrund stand, das Potential der Fernerkundung einer breiteren Öffentlichkeit zugänglich zu machen und die Notwendigkeit der Raumfahrt zur Erkundung unserer Umwelt zu bekräftigen.

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Le potentiel d'application des données ERS-1 SAR en utilisation presqueimmédiate

Résumé Des propriétés importantes du radar d'ouverture synthétique du premier satellite européen ERS-1 d'observation de la Terre sont présentées. Des exemples choisis illustrent les possibilités d'utilisation appliquée de l'information radar. La possibilité d'une exploitation en temps très légèrement différé sous des aspects opérationnels est démontrée.L'information du satellite ERS-1 a été reçue, traitée et archivée lors d'une présentation à la Commission de la Communauté Européene à Bonn. À l'occasion de la manifestation de l'année internationale de l'espace 1992 (ISY), avec le concours de l'Agence Maritime et Hydrographique Fédérale (BSH), en coopération avec le Centre Allemand de Recherches Aérospatiales (DLR) et les TELEKOM. Le but était de présenter au public les possibilités de la télédétection et de montrer la nécessité de l'usage de la technologie pour aider à résoudre les problèmes de l'environment.

     

Two Tephra Layers Bracketing Late Holocene Paleoecological Changes in Northern Germany

Paleoecological records from two Holocene peat bogs in northern Germany are linked by two microscopic volcanic ash layers, correlated by petrology and geochemistry to explosive volcanism on Iceland. The younger “Microlite tephra” cannot be correlated to any known eruption, while the older tephra layer is identified as a deposit of the Hekla 3 eruption. The tephra layers are dated by an age–depth regression of accelerator mass spectrometry ¹⁴C ages that have been calibrated and combined in probability distributions. This procedure gives an age of 730–664 cal yr B.C. for the “Microlite tephra” event and 1087–1006 cal yr B.C. for the Hekla 3 event. Accordingly, the tephra layers were deposited during the late Bronze Age. At this time, human settlement slowly increased pressure on the environment, as indicated by changes in woodland pollen composition at the two bogs. The tephra-marker horizons further show that the palynologically defined transition from the Subboreal to the Subatlantic Period is synchronous in the investigated area. However, the macroscopic visible marker in peat, the change from fibrous to sapric peat, the “Schwarztorf-Weißtorf-Kontakt,” is asynchronous. Bog vegetation did not immediately react in unison to a climatic change at this pollen zone boundary; instead, the timing of vegetation change depended on the location within the bog.     

Detrital,metamorphic and metasomatic tourmaline in high-pressure metasediments from Syros (Greece): intra-grain boron isotope patterns determined by secondary-ion mass spectrometry

The boron isotopic composition of zoned tourmaline in two metasediments from the island of Syros, determined by secondary-ion mass spectrometry (SIMS), reflects the sedimentary and metamorphic record of the rocks. Tourmaline from a silicate-bearing marble contains small (≤20 μm) detrital cores with highly variable δ ¹¹B values (−10.7 to +3.6‰), pointing to a heterogeneous protolith derived from multiple sources. The sedimentary B isotopic record survived the entire metamorphic cycle with peak temperatures of ∼500°C. Prograde to peak metamorphic rims are homogeneous and similar among all analysed grains (δ ¹¹B ≈ +0.9‰). The varying δ ¹¹B values of detrital cores in the siliceous marble demonstrate that in situ B isotope analysis of tourmaline by SIMS is a potentially powerful tool for provenance studies not only in sediments but also in metasediments. A meta-tuffitic blueschist bears abundant tourmaline with dravitic cores of detrital or authigenic origin (δ ¹¹B ≈ −3.3‰), and prograde to peak metamorphic overgrowth zones (−1.6‰). Fe-rich rims, formed during influx of B-bearing fluids under retrograde conditions, show strongly increasing δ ¹¹B values (up to +7.7‰) towards the margins of the grains. The δ ¹¹B values of metamorphic tourmaline from Syros, formed in mixed terrigenous–marine sediments, reflect the B signal blended from these two different sources, and was probably not altered by dehydration during subduction.     

Influence of the enzyme dissimilatory sulfite reductase on stable isotope fractionation during sulfate reduction

The stable isotopes of sulfate are often used as a tool to assess bacterial sulfate reduction on the macro scale. However, the mechanisms of stable isotope fractionation of sulfur and oxygen at the enzymatic level are not yet fully understood. In batch experiments with water enriched in ¹⁸O we investigated the effect of different nitrite concentrations on sulfur isotope fractionation by Desulfovibrio desulfuricans.With increasing nitrite concentrations, we found sulfur isotope enrichment factors ranging from −11.2 ± 1.8‰ to −22.5 ± 3.2‰. Furthermore, the δ¹⁸O values in the remaining sulfate increased from approximately 50-120‰ when ¹⁸O-enriched water was supplied. Since ¹⁸O-exchange with ambient water does not take place in sulfate, but rather in intermediates of the sulfate reduction pathway (e.g. ), we suggest that nitrite affects the steady-state concentration and the extent of reoxidation of the metabolic intermediate sulfite to sulfate during sulfate reduction. Given that nitrite is known to inhibit the production of the enzyme dissimilatory sulfite reductase, our results suggest that the activity of the dissimilatory sulfite reductase regulates the kinetic isotope fractionation of sulfur and oxygen during bacterial sulfate reduction. Our novel results also imply that isotope fractionation during bacterial sulfate reduction strongly depends on the cell internal enzymatic regulation rather than on the physico-chemical features of the individual enzymes.     

Early Thermal and Structural Evolution of Small Bodies in the Trans-Neptunian Zone

Early evolution of trans-Neptunian objects,commonly known as Kuiper Belt objects (KBOs),is the result of heating due to radioactive decay, the most important sourcebeing ²⁶Al. Several studiesare reviewed, dealing with the long-termevolution of KBO models, calculatedby means of 1-D numerical codesthat solve the heat and mass balanceequations on a fixed spherically symmetric grid. It is shown that, depending on parameters, the interior may reachquite high temperatures. The modelsthus suggest that KBOs are likely to lose the ices of very volatile species during early evolution; ices of less volatile species are retained in the cold subsurface layer. As the initially amorphous ice isshown to crystallize in the interior, some objects may also lose part of the volatiles trapped in amorphous ice. Generally, the outer layers are far less affected than the inner part, resulting in a stratified composition and altered porosity distribution. It is further shown that the thermal evolution of KBOs cannot be treated separately from their accretional evolution, as the processes occur in parallel. A systematic attempt to calculate accretion and thermal evolution simultaneously is presented, based on a numerical moving grid scheme. The accretion rate is obtained from the solution of the coupled coagulation equations for gravitationally interacting planetesimals. The effect of planetesimal velocities on the accretion scheme is included by a simplified equipartition argument. The time dependent accretion rates serve as input for the numerical solution of the heat transport equation for growing bodies mainly heated by radioactive decay of ²⁶Al, allowing for phase transitions. Calculations carried out over the parameter space [heliocentric distance; final radius; ice fraction] lead to conclusions regarding the structure of KBOs, such as melt fraction, or extent of crystalline ice region.     

Evaluation and legal assessment of certified seafood

This study presents a legal review of international treaties to derive sound definitions of overfishing. It examines seafood stocks that were certified by the Marine Stewardship Council (MSC) or Friend of the Sea (FOS). Stock size and fishing pressure were compared with the internationally agreed reference points which both organizations have accepted. No suitable status information was found for 11% (MSC) to 53% (FOS) of the certified stocks. For the stocks with available status information, 19% (FOS) to 31% (MSC) had overfished stock sizes and were subject to ongoing overfishing. An analysis of legal implications of certification of overfished stocks suggests that a certifying body cannot be held liable for a violation of internationally agreed standards unless the domestic law of its home country so regulates. States may ban the import of fish products from overfished stocks, but only in very specific cases. Possible causes for the certification of overfished stocks are discussed and recommendations are given on how the certifiers could improve their performance. The study concludes that it is still reasonable to buy certified seafood, because the percentage of moderately exploited, healthy stocks is 3–4 times higher in certified than in non-certified seafood.     

Cosmogenic nuclides in the Košice meteorite: Experimental investigations and Monte Carlo simulations

Results of nondestructive gamma‐ray analyses of cosmogenic radionuclides (⁷Be, ²²Na, ²⁶Al, ⁴⁶Sc, ⁴⁸V, ⁵⁴Mn, ⁵⁶Co, ⁵⁷Co, ⁵⁸Co, and ⁶⁰Co) in 19 fragments of the Ko?ice meteorite are presented and discussed. The activities varied mainly with position of fragments in the meteoroid body, and with fluxes of cosmic‐ray particles in the space affecting radionuclides with different half‐lives. Monte Carlo simulations of the production rates of ⁶⁰Co and ²⁶Al compared with experimental data indicate that the pre‐atmospheric radius of the meteoroid was 50 ± 5 cm. In two Ko?ice fragments, He, Ne, and Ar concentrations and isotopic compositions were also analyzed. The noble‐gas cosmic‐ray exposure age of the Ko?ice meteorite is 5–7 Myr, consistent with the conspicuous peak (or doublet peak) in the exposure age histogram of H chondrites. One sample likely contains traces of implanted solar wind Ne, suggesting that Ko?ice is a regolith breccia. The agreement between the simulated and observed ²⁶Al activities indicate that the meteoroid was mostly irradiated by a long‐term average flux of galactic cosmic rays of 4.8 particles cm^?2 s^?1, whereas the short‐lived radionuclide activities are more consistent with a flux of 7.0 protons cm^?2 s^?1 as a result of the low solar modulation of the galactic cosmic rays during the last few years before the meteorite fall.     

Geographic distribution of the diapycnal component of thermohaline circulations in coupled climate models

Data archives from four global coupled ocean–atmosphere models are used to construct maps of diapycnal mass flux through selected isopycnal surfaces in the model oceans. The maps illustrate location and strength of the up and downwelling limbs of thermohaline-forced overturning loops whose stability in the face of rising atmospheric carbon dioxide (CO₂) concentrations is of major concern in century-scale climate prediction. The up and downwelling limbs simulated by the four models for present-day greenhouse gas concentrations are compared with observational estimates. Predicted changes in the overturning brought about by gradually rising atmospheric CO₂ content are compared model-to-model. While all four models predict some decline in the rate of Atlantic overturning during CO₂-induced global warming, the geographic layout of the overturning circulations in each model is found to be insensitive to the changing climate.     

石英ESR测年信号衰退特征研究进展

电子自旋共振(ESR)测年法是第四纪地质年代学的重要测试方法之一,其测年范围广,特别是对于20万年至百万年尺度的第四纪样品有着重要意义.准确测量古剂量是影响ESR测年法精度和可信度的重要因素之一,而掌握ESR信号衰退特征及机制是获得准确、可信古剂量的重要前提.ESR测年法适用的地质样品种类较多,如热液石英脉、地质断层泥、水系沉积物等,不同样品的ESR信号衰退特征和机制有较大差异.近年来,国内外学者针对不同地质样品中石英ESR信号的衰退特征和机制深入开展了一系列的实验室模拟和野外观测研究,取得了诸多新认识.回顾了近年来在石英ESR信号衰退特征领域取得的进展,特别是水系沉积物石英ESR信号的衰退特征,并展望了这一领域的未来工作重点.