4,989 Works

Thermische Evolution und Habitabilität erdähnlicher Exoplaneten

Christine Bounama
In der vorliegenden Arbeit werden Methoden der Erdsystemanalyse auf die Untersuchung der Habitabilität terrestrischer Exoplaneten angewandt. Mit Hilfe eines parametrisierten Konvektionsmodells für die Erde wird die thermische Evolution von terrestrischen Planeten berechnet. Bei zunehmender Leuchtkraft des Zentralsterns wird über den globalen Karbonat-Silikat-Kreislauf das planetare Klima stabilisiert. Für eine photosynthetisch-aktive Biosphäre, die in einem bestimmten Temperaturbereich bei hinreichender CO2-Konzentration existieren kann, wird eine Überlebenspanne abgeschätzt. Der Abstandsbereich um einen Stern, in dem eine solche Biosphäre produktiv...

A Numerical Model of Tracer Transport in a Non-isothermal Two-Phase Flow System for CO2 Geological Storage Characterization

Fuguo Tong, Auli Niemi, Zhibing Yang, Fritjof Fagerlund, Tobias Licha & Martin Sauter

Airborne Thermal Data Identifies Groundwater Discharge at the North-Western Coast of the Dead Sea

Ulf Mallast, Friedhelm Schwonke, Richard Gloaguen, Stefan Geyer, Martin Sauter & Christian Siebert
A qualitative and quantitative monitoring of groundwater discharge was conducted based on an airborne thermal campaign undertaken along the north-western coast of the Dead Sea in January 2011 to contribute to the relatively scarce information on groundwater discharge to date in the region. The application of airborne thermal data exploits thermal contrasts that exist between discharging groundwater and background sea surface temperatures of the Dead Sea. Using these contrasts, 72 discharge sites were identified from...

Comments on \"Decontamination of solutions containing EDTA using metallic iron\"

Chicgoua Noubactep
This letter presents an improved discussion of the data provided in a recent article on EDTA removal from aqueous solutions using elemental iron (Fe0) by O. Gyliene and his co-workers. It is shown that the authors have furnished a brilliant validation of the concept that dissolved contaminants are primary removed in Fe0/H2O systems by adsorption onto iron corrosion products and co-precipitation with iron corrosion products. It is reiterated that contaminant removal and contaminant reduction should...

Archaea in past and present geobiochemical processes and elemental cycles.

Michael Hoppert, Martin Krüger, Joachim Reitner & Charles Cockell
For a long time, Archaea have been considered as an ancient prokaryotic group comprising specialists restricted to narrow ecological niches. This opinion might have been supported by the characteristics of the first well-investigated isolates, being strictly anaerobic (methanogens), halophilic (haloarchaea), or thermophilic (various groups). This is, however, just the tip of the iceberg. Archaea are abundant in all ecosystems. Representatives of the whole domain span the widest range of ecological adaptations from psychrophilic to hyperthermophilic....

Ecological and biogeochemical change in an early Paleogene peat-forming environment: Linking biomarkers and palynology

Gordon N. Inglis, Margaret E. Collinson, Walter Riegel, Volker Wilde, Brittany E. Robson, Olaf K. Lenz & Richard D. Pancost
Sphagnum moss is the dominant plant type inmodern boreal and (sub)arctic ombrotrophic bogs and is of particular interest due to its sensitivity to climate and its important role in wetland biogeochemistry. Here we reconstruct the occurrence of Sphagnum moss – and associated biogeochemical change – within a thermally immature, early Paleogene (~55 Ma) lignite from Schöningen, NW Germany using a high-resolution, multi-proxy approach. Changes in the abundance of Sphagnum-type spores and the C23/C31 n-alkane ratio...

Distribution and timing of Holocene and late Pleistocene glacier fluctuations in western Mongolia

Frank Lehmkuhl, Michael Klinge, Henrik Rother & Daniela Hülle
Despite being a key location for paleoglaciological research in north-central Asia, with the largest number of modern and Pleistocene glaciers, and in the transition zone between the humid Russian Altai and dry Gobi Altai, little is known about the precise extent and timing of Holocene and late Pleistocene glaciations in western Mongolia. Here we present detailed information on the distribution of modern and late Holocene glaciers, and new results addressing the geomorphological differentiation and numerical...

The Suitability of Pozzolan as Admixing Aggregate for Fe0-Based Filters

Arnaud Ndé-Tchoupé, Suzanne Makota, Achille Nassi, Rui Hu & Chicgoua Noubactep
Continuous gravity-fed column experiments using the methylene blue (MB) discoloration method were performed to characterize the suitability of a pozzolan (PZ) specimen as alternative admixing aggregate for metallic iron filters (Fe0-filters). Investigated systems were: (i) pure sand, (ii) pure PZ, (iii) pure Fe0, (iv) Fe0/sand, (v) Fe0/PZ, and (vi) Fe0/sand/PZ. The volumetric proportion of Fe0 was 25%. The volumetric proportions of the Fe0/sand/PZ system was 25/45/30. The initial MB concentration was 2.0 mg L􀀀1, 6.0...

The fossil record of the Haplosclerid excavating sponge Aka de Laubenfels

Joachim Reitner & H. Keupp

Tracing the oxygen isotope composition of the upper Earth's atmosphere using cosmic spherules

Andreas Pack, Andres Höweling, Dominik C. Hezel, Maren T. Stefanak, Anne-Katrin Beck, Stefan T. M. Peters, Sukanya Sengupta, Daniel Herwartz & Luigi Folco
Molten I-type cosmic spherules formed by heating, oxidation and melting of extraterrestrial Fe,Ni metal alloys. The entire oxygen in these spherules sources from the atmosphere. Therefore, I-type cosmic spherules are suitable tracers for the isotopic composition of the upper atmosphere at altitudes between 80 and 115 km. Here we present data on I-type cosmic spherules collected in Antarctica. Their composition is compared with the composition of tropospheric O2. Our data suggest that the Earth's atmospheric...

Improving the sustainability of granular iron/pumice systems for water treatment.

Stefania Bilardi, Paolo S. Calabrò, Sabine Caré, Nicola Moraci & Chicgoua Noubactep
Metallic iron (Fe(0)) is currently used in subsurface and above-ground water filtration systems on a pragmatic basis. Recent theoretical studies have indicated that, to be sustainable, such systems should not contain more than 60% Fe(0) (vol/vol). The prediction was already validated in a Fe(0)/sand system using methylene blue as an operational tracer. The present work is the first attempt to experimentally verify the new concept using pumice particles. A well-characterized pumice sample is used as...

Comparison of Random Forest, k-Nearest Neighbor, and Support Vector Machine Classifiers for Land Cover Classification Using Sentinel-2 Imagery.

Phan Thanh Noi & Martin Kappas
In previous classification studies, three non-parametric classifiers, Random Forest (RF), k-Nearest Neighbor (kNN), and Support Vector Machine (SVM), were reported as the foremost classifiers at producing high accuracies. However, only a few studies have compared the performances of these classifiers with different training sample sizes for the same remote sensing images, particularly the Sentinel-2 Multispectral Imager (MSI). In this study, we examined and compared the performances of the RF, kNN, and SVM classifiers for land...

Testing the Suitability of Zerovalent Iron Materials for Reactive Walls

Chicgoua Noubactep, Günther Meinrath, Peter Dietrich, Martin Sauter & Broder J. Merkel
Zerovalent iron (ZVI) has been proposed as reactive material in permeable in situ walls for contaminated groundwater. An economically feasible ZVI-based reactive wall requires cheap but efficient iron materials. From an uranium treatability study and results of iron dissolution in 0.002 M EDTA by five selected ZVI materials, it is shown that current research and field implementation is not based on a rational selection of application-specific iron metal sources. An experimental procedure is proposed which...

Höhenverluste von Moorböden – eine Herausforderung für Wasserwirtschaft und Landnutzung

Michael Trepel
Abstract: Drained peat soils subside and lose height. This vicious circle of peat use was managed in the past with regularly draining activities for sustaining intensive land use. This approach will not work so easily in the future, because the hydrological and physical limits of drainage are often reached. This contribution presents in the first part more accurate approaches for predicting subsidence rates of peat soils than the widely used rule of thumb values. Recent...

Climate effects on vegetation vitality at the treeline of boreal forests of Mongolia

Michael Klinge, Choimaa Dulamsuren, Stefan Erasmi, Dirk Nikolaus Karger & Markus Hauck
In northern Mongolia, at the southern boundary of the Siberian boreal forest belt, the distribution of steppe and forest is generally linked to climate and topography, making this region highly sensitive to climate change and human impact. Detailed investigations on the limiting parameters of forest and steppe in different biomes provide necessary information for paleoenvironmental reconstruction and prognosis of potential landscape change. In this study, remote sensing data and gridded climate data were analyzed in...

FS Sonne Fahrtbericht/Cruise report SO177

Erwin Suess

Snowmobile impacts on snowpack physical and mechanical properties

Steven R. Fassnacht, Jared T. Heath, Niah B. H. Venable & Kelly J. Elder
Snowmobile use is a popular form of winter recreation in Colorado, particularly on public lands. To examine the effects of differing levels of use on snowpack properties, experiments were performed at two different areas, Rabbit Ears Pass near Steamboat Springs and at Fraser Experimental Forest near Fraser, Colorado USA. Differences between no use and varying degrees of snowmobile use (low, medium and high) on shallow (the operational standard of 30 cm) and deeper snowpacks (120...

Teleseismic tomographic images of the Central Andes at 21°S and 25.5°S

Benjamin S. Heit

Regional geoid determination

Alexander N. Marchenko

Atmospheric CO2 fertilization effects on biomass yields of 10 crops in northern Germany

Jan F. Degener
The quality and quantity of the influence that atmospheric CO2 has on crop growth is still a matter of debate. This study's aim is to estimate if [CO2] will have an effect on biomass yields at all, to quantify and spatially locate the effects and to explore if an elevated photosynthesis rate or water-use-efficiency is predominantly responsible. This study uses a numerical carbon-based crop model (BioSTAR) to estimate biomass yields within the administrative boundaries of...

A new interpretation of the sedimentary cover in the western Siljan Ring area, central Sweden, based on seismic data

Christopher Juhlin, Erik Sturkell, Jan Ove R. Ebbestad, Oliver Lehnert, Anette E.S. Högström & Guido Meinhold
Two new reflection seismic profiles over the Paleozoic successions of the western part of the Siljan Ring impact structure show a contrasting seismic signature. The more southerly c. 10 km long Mora profile reveals a highly disturbed structure, with only a few kilometers of relatively horizontally layered structures observed. However, interpretations of refracted arrivals in the data, that can be correlated to reflections, indicate the Silurian clastic rocks to be about 200 m thick in...

The structural record of mid crustal stress and pore fluid pressure changes related to the earthquake cycle

Jens-Alexander Nüchter
Die Gefüge diskordanter Quarzgänge in der hochdruck/niedertemperaturmetamorphen Styra-Ochieinheit in süd Evia / Griechenland gewähren Einblick in kurzzeitige (auf dem geologischen Zeitmaßstab) und episodische Deformation in einem Krustenabschnitt direkt unterhalb des langzeit Spröd-Duktilüberganges. Die Gefüge zeigen sprödes Versagen gefolgt von duktiler Verformung des Gesteins bei zunächst hohen, aber abnehmenden Spannungen und Strainraten. Der finite Strain ist niedrig. Die Entstehung der Gefüge wird durch Rissausbreitung während des koseismischen Spannungsaufbaus gefolgt von duktiler Deformation des Nebengesteins begleitet von...

The optical properties and quantum chemical calculations of thienyl and furyl derivatives of pyrene.

Krzysztof R. Idzik, Piotr J. Cywiński, Wojciech Kuznik, Jaroslaw Frydel, Tobias Licha & Tomasz Ratajczyk
A detailed electrochemical, photophysical and theoretical study is presented for various new thienyl and furyl derivatives of pyrene. Their optical properties are described based on UV-VIS absorption and both steady-state and time-resolved fluorescence spectroscopy. DFT and TDDFT calculations are also presented to support experimental data. The calculations results show that HOMO-LUMO orbitals are delocalized uniformly between aromatic core and aryl substituents. Good electrochemical stability of thienyl and furyl hybrids of pyrene confirm their potential application...

The Sail-Backed Reptile Ctenosauriscus from the Latest Early Triassic of Germany and the Timing and Biogeography of the Early Archosaur Radiation

Richard J. Butler, Stephen L. Brusatte, Mike Reich, Sterling J. Nesbitt, Rainer R. Schoch & Jahn J. Hornung
Background Archosaurs (birds, crocodilians and their extinct relatives including dinosaurs) dominated Mesozoic continental ecosystems from the Late Triassic onwards, and still form a major component of modern ecosystems (>10,000 species). The earliest diverse archosaur faunal assemblages are known from the Middle Triassic (c. 244 Ma), implying that the archosaur radiation began in the Early Triassic (252.3–247.2 Ma). Understanding of this radiation is currently limited by the poor early fossil record of the group in terms...

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