Potential vorticity and volume transport in the eastern North Atlantic from two long CTD sections     

Dr. Lothar Stramma 《Ocean Dynamics》1984,37(4):147-155

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Two distinct Miocene age ranges of basaltic rocks from the Rhön and Heldburg areas (Germany) based on Ar/Ar step heating data     

Michael Abratis  Jonas Mädler  Siegfried Hautmann  Romain Meyer  Lothar Viereck-Götte 《Chemie der Erde / Geochemistry》2007,67(2):133-150

New ⁴⁰Ar/³⁹Ar age data are determined for Cenozoic basaltic rocks from the Thuringian Rhön and Heldburg Gangschar (area also referred to as Grabfeld), integral parts of the Central European Volcanic Province. Applying the incremental heating technique on groundmass and plagioclase separates provided data which considerably specify our knowledge on the eruption ages in these volcanic fields and narrow down the duration of volcanic activity compared to earlier studies. All data but one outlier range between 20 and 14 Ma, being thus similar to those of the neighbouring Vogelsberg volcanic complex. The spectrum of ages is clearly divided into two distinct subsets: the Rhön ages are between 20 and 18 Ma, those of the Heldburg Gangschar are between 16 and 14 Ma. Thus, the present data clearly indicate a striking regional and temporal division of the Thuringian Miocene volcanism. The composition of the volcanic rocks in the two volcanic fields is remarkably diverse, ranging from tholeiitic basalts over alkali basalts and basanites to nephelinites. However, radiometric ages do not correlate with geochemical or petrological characteristics of the volcanics within each volcanic field, indicating that the different magma types erupted broadly contemporaneously.The outlier in age (29 Ma) is from a volcanic dyke of the NE Rhön area close to the NW end of the Thuringian Forest. However, more data are required to approve the significance of this age value, in particular since the rock showed isotopic age disturbance.  相似文献   

The geometry of the Archean, Paleo- and Neoproterozoic tectonics in the Southwest Cameroon     

Sbastien Owona  Joseph Mvondo Ondoa  Lothar Ratschbacher  Simon Pierre Mbola Ndzana  Flix M. Tchoua  Georges Emmanuel Ekodeck 《Comptes Rendus Geoscience》2011,343(4):312-322

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Integrated deep drilling,coring, downhole logging,and data management in the Chicxulub Scientific Drilling Project (CSDP), Mexico     

Lothar Wohlgemuth  Eckhard Bintakies  Jochem Kück  Ronald Conze  Ulrich Harms 《Meteoritics & planetary science》2004,39(6):791-797

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Discrete element simulation of geogrid-stabilised soil     

Michael Stahl  Heinz Konietzky  Lothar te Kamp  Hein Jas 《Acta Geotechnica》2014,9(6):1073-1084

A particle-based numerical simulation procedure is presented for the generation and calibration of geogrid-stabilised soil on the basis of experimental data. The paper describes how to simulate a biaxial geogrid depending on a specific particle and parallel bond model. Numerical and experimental pull-out tests have been performed to reproduce the pull-out force–strain behaviour of a biaxial geogrid specimen embedded in granular material under special consideration of the grain-size distribution, initial relative density, normal stress state as well as sample installation. Model analysis of soil mobilisation and geogrid deformation is presented to understand the significance of the interlocking effect as key mechanism for soil stabilisation. The procedure can be used for further investigations of the influence and effects of soil stabilisation depending on the significant properties of the interacting components (soils and geogrids).  相似文献   

GRAVITAS: general relativistic astrophysics via timing and spectroscopy     

Kirpal Nandra  Didier Barret  Andy Fabian  Lothar Strueder  Richard Willingale  Mike Watson  Peter Jonker  Hideyo Kunieda  Giovanni Miniutti  Christian Motch  Peter Predehl 《Experimental Astronomy》2012,34(2):445-462

GRAVITAS is an X-ray observatory, designed and optimised to address the ESA Cosmic Vision theme of ??Matter under extreme conditions??. It was submitted as a response to the call for M3 mission proposals. The concept centres around an X-ray telescope of unprecedented effective area, which will focus radiation emitted from close to the event horizon of black holes or the surface of neutron stars. To reveal the nature and behaviour of matter in the most extreme astrophysical environments, GRAVITAS targets a key feature in the X-ray spectra of compact objects: the iron K?? line at ~6.5?keV. The energy, profile, and variability of this emission line, and the properties of the surrounding continuum emission, shaped by General Relativity (GR) effects, provide a unique probe of gravity in its strong field limit. Among its prime targets are hundreds of supermassive black holes in bright Active Galactic Nuclei (AGN), which form the perfect laboratory to help understand the physical processes behind black hole growth. Accretion plays a fundamental role in the shaping of galaxies throughout cosmic time, via the process of feedback. Modest (~sub-arcmin) spatial resolution would deliver the necessary sensitivity to extend high quality X-ray spectroscopy of AGN to cosmologically-relevant distances. Closer to home, ultra-high count rate capabilities and sub-millisecond time resolution enable the study of GR effects and the equation of state of dense matter in the brightest X-ray binaries in our own Galaxy, using multiple probes, such as the broad iron line, the shape of the disk continuum emission, quasi-periodic oscillations, reverberation mapping, and X-ray burst oscillations. The enormous advance in spectral and timing capability compared to current or planned X-ray observatories would enable a vast array of additional scientific investigations, spanning the entire range of contemporary astrophysics from stars to distant galaxy clusters. Despite its breakthrough capabilities, all enabling technologies for GRAVITAS are already in a high state of readiness. It is based on ultra light-weight X-ray optics and a focal plane detector using silicon technology. The baseline launcher would be a Soyuz?CFregat to place GRAVITAS into a zero inclination, low-earth orbit, providing low and relatively stable background.  相似文献   

Numerical simulations for the non-linear Molodensky problem     

Lothar Banz  Adrian Costea  Heiko Gimperlein  Ernst P. Stephan 《Studia Geophysica et Geodaetica》2014,58(4):489-504

We present a boundary element method to compute numerical approximations to the non-linear Molodensky problem, which reconstructs the surface of the Earth from the gravitational potential and the gravity vector. Our solution procedure solves a sequence of exterior oblique Robin problems and is based on a Nash-Hörmander iteration. We apply smoothing with the heat equation to overcome a loss of derivatives in the surface update. Numerical results show the error between the approximation and the exact solution in a model problem.  相似文献   

Tellurium speciation under hydrothermal conditions     

Pascal V. Grundler  Joël Brugger  Allan Pring  Paul G. Spry  William H. Casey  Lothar Helm  Weihua Liu  Stacey Borg  Barbara Etschmann 《Journal of Geochemical Exploration》2009

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The physico-chemical conditions of Turkwel Gorge Reservoir, a new man made lake in Northern Kenya     

Kiplagat Kotut  Stephen G. Njuguna  Francis M. Muthuri  Lothar Krienitz   《Limnologica》1999,29(4):377-392

Variations in some physical, chemical, and nutrient conditions were investigated at Turkwel Gorge Reservoir and its inflowing river, Suam between 1994 and 1995. Seasonal changes in inflow volume had the greatest impact on the reservoir and river conditions investigated. A wide fluctuation in inflow volume combined with a regulated outflow independent of season resulted in a draw down of over 10 m in each year. Flood inflows during the wet season resulted in the lowest values of Secchi depth (range, 0.09–2.16 m), electrical conductivity (EC, range = 140–200 mS cm⁻¹) and total alkalinity (TA, range = 75–111 mg l⁻¹) while the highest values were measured during the dry season. A functional relation between EC and TA (TA = 0.529 mg l⁻¹, EC: R² = 0.876) suggests a predominance of carbonates among the anions. Vertical profiles of temperature and dissolved oxygen (DO) revealed that the reservoir is monomictic with a wide variation in the depth of the daily mixed layer. High values of pH (range = 6.7–8.9) and DO (range = 4.9–9.2 mg l⁻¹) were associated with periods of peak phytoplankton photosynthesis while the lowest values followed reservoir mixing. Peak total nitrogen (TN, range = 119–526 μg l⁻¹) and total phosphorus (TP, range = 8.9–71.6 μg l⁻¹) levels during the wet season resulted from increased river loading. Values of dissolved reactive silica (DRS, range = 0.41–9.77 mg l⁻¹) showed a wet season decline which was related to diatom depletion during the wet season. Annual reservoir areal loading rates of 27.38, 10.90 and 408.5 mg m⁻² were computed for TN, TP and DRS respectively based on estimates of inflowing river loads in 1994.

At the inflowing river Suam, low levels of EC (range = 107–210 μS cm⁻¹) and TA (range = 62–125 mg l⁻¹) occurred during the wet season while the highest levels occurred shortly before the river dried up. The first flood water at the resumption of river inflow in March was characterized by very low levels of DO (range = 1.8–8.2 mg l⁻¹) and high levels of TN (range = 205–3354 μg l⁻¹) and TP (102–1259 μg l⁻¹). River pII (6.9–7.7) and DRs (range = 9.01–19.93 mg l⁻¹) varied irregularly throughout the year.  相似文献   

A fast tracking mirror for adaptive optics     

Thomas J. Kentischer  Andreas Bernert  Lothar Gantzert  Thomas Schelenz  Wolfgang Schmidt 《Astrophysics and Space Science》1996,239(2):213-219

A piezo driven tilt mirror was developed and built as one component of an image motion compensation system for a solar telescope. The bandwidth of the mirror with a diameter of 60 mm is about 1 kHz with negligible phase shift between input signal and mirror response up to 900 Hz. The tilt range is 1.6 mrad. Special care was taken to maintain the surface quality of the mirror to better than /15 after fixing it to the substrate.  相似文献