Intragranular deformation mechanisms in calcite deformed by high-pressure torsion at room temperature     

Schuster  Roman  Habler  Gerlinde  Schafler  Erhard  Abart  Rainer 《Mineralogy and Petrology》2020,114(2):105-118

Mineralogy and Petrology - Polycrystalline calcite was deformed to high strain at room-temperature and confining pressures of 1–4 GPa using high-pressure torsion. The high confining...  相似文献   

Mapping of a major paleodrainage system in eastern Libya using orbital imaging radar: The Kufrah River     

Philippe Paillou  Mathieu Schuster  Stephen Tooth  Tom Farr  Ake Rosenqvist  Sylvia Lopez  Jean-Marie Malezieux 《Earth and Planetary Science Letters》2009,277(3-4):327-333

Over the last few decades, remote sensing has revealed buried river channels in a number of regions worldwide, in many cases providing evidence of dramatic paleoenvironmental changes over Cenozoic time scales. Using orbital radar satellite imagery, we mapped a major paleodrainage system in eastern Libya, that could have linked the Kufrah Basin to the Mediterranean coast through the Sirt Basin, possibly as far back as the middle Miocene. Synthetic Aperture Radar images from the PALSAR sensor clearly reveal a 900 km-long river system, which starts with three main tributaries (north-eastern Tibesti, northern Uweinat and western Gilf Kebir/Abu Ras) that connect in the Kufrah oasis region. The river system then flows north through the Jebel Dalmah, and forms a large alluvial fan in the Sarir Dalmah. The sand dunes of the Calanscio Sand Sea prevent deep orbital radar penetration and preclude detailed reconstruction of any possible connection to the Mediterranean Sea, but a 300 km-long link to the Gulf of Sirt through the Wadi Sahabi paleochannel is likely. If this connection is confirmed, and its Miocene antiquity is established, then the Kufrah River, comparable in length to the Egyptian Nile, will have important implications for the understanding of the past environments and climates of northern Africa from the middle Miocene to the Holocene.  相似文献   

Chemicals in the Environment – the Need for a Clear Nomenclature: Parent Compounds,Metabolites, Transformation Products and Their Elimination     

Andreas Längin  Armin Schuster  Klaus Kümmerer 《洁净——土壤、空气、水》2008,36(4):349-350

  相似文献   

Hydrodynamics in Holocene Lake Mega-Chad     

Frédéric Bouchette  Mathieu Schuster  Claude Roquin  Patrick Marsaleix 《Quaternary Research》2010,73(2):226-236

Holocene Lake Mega-Chad (LMC) was the largest late Quaternary water-body in Africa. The development of this giant paleo-lake is related to a northward shift of the isohyetes interpreted as evidence for an enhanced Monsoon (African Humid Period). Numerous preserved coastal features have been described all around the LMC shore. Such features reveal the main paleo-hydrodynamical tendencies. In the context of a closed water-body like LMC, hydrodynamics are forced mainly by winds. We use a three-dimensional numerical model (SYMPHONIE) to simulate the mean hydrodynamics in LMC under both Harmattan-like (northeasterly trade winds) and Monsoon-like (southwesterly winds) forcings. The northern part of LMC displays coastal features, such as sand spits, that are consistent with the simulations forced by Harmattan-like winds. Geomorphic features related to Monsoon-driven hydrodynamics are not clearly expressed. They could have developed during the early stage of LMC but subsequently reworked. At the time of sand-spit building, Harmattan-like driven hydrodynamics prevailed and related coastal features were preferentially preserved in the sedimentary record.  相似文献   

Static elasticity of cordierite I: Effect of heavy ion irradiation on the compressibility of hydrous cordierite     

R. Miletich  K. S. Scheidl  M. Schmitt  A. P. Moissl  T. Pippinger  G. D. Gatta  B. Schuster  C. Trautmann 《Physics and Chemistry of Minerals》2014,41(8):579-591

The effect of ion beam irradiations on the elastic properties of hydrous cordierite was investigated by means of Raman and X-ray diffraction experiments. Oriented single crystals were exposed to swift heavy ions (Au, Bi) of various specific energies (10.0–11.1 MeV/u and 80 MeV/u), applying fluences up to 5 × 10¹³ ions/cm². The determination of unit-cell constants yields a volume strain of 3.4 × 10^?3 up to the maximum fluence, which corresponds to a compression of non-irradiated cordierite at ~480 ± 10 MPa. The unit-cell contraction is anisotropic (e ₁ = 1.4 ± 0.1 × 10^?3, e ₂ = 1.5 ± 0.1 × 10^?3, and e ₃ = 7 ± 1 × 10^?4) with the c-axis to shrink only half as much as the axes within the ab-plane. The lattice elasticity for irradiated cordierite (? = 1 × 10¹² ions/cm²) was determined from single-crystal XRD measurements in the diamond anvil cell. The fitted third-order Birch–Murnaghan equation-of-state parameters of irradiated cordierite (V ₀ = 1548.41 ± 0.16 Å³, K ₀ = 117.1 ± 1.1 GPa, ?K/?P = ?0.6 ± 0.3) reveal a 10–11 % higher compressibility compared to non-irradiated cordierite. While the higher compressibility is attributed to the previously reported irradiation-induced loss of extra-framework H₂O, the anomalous elasticity as expressed by elastic softening (β _a ^?1 , β _b ^?1 , β _c ^?1  = 397 ± 9, 395 ± 28, 308 ± 11 GPa, ?(β ^?1)/?P = ?4.5 ± 2.7, ?6.6 ± 8.4, ?5.4 ± 3.0) appears to be related to the framework stability and to be independent of the water content in the channels and thus of the ion beam exposure.  相似文献   

Das Entwässerungsverhalten von Klärschlamm in Gegenwart von Polyelektrolyten     

Ch. Schuster  J. Ktz  W.-M. Kulicke  S. Parker  N. Bhm  W. Jaeger 《洁净——土壤、空气、水》1997,25(1):27-33

Dewatering Behaviour of Sludge in the Presence of Polyelectrolytes Interactions of sludge particles with well defined synthetic polyelectrolytes of different charge, molecular mass, and molecular geometry were investigated by means of zeta- and streaming potential measurements and polyelectrolyte titrations. Different mechanisms of flocculation were discussed with regard to the dewatering behaviour of the sludge. In dependence on the flocculation procedure (cationic monoflocculation, anionic-cationic, and cationicanionic dual flocculation) as well as on the chain length and branching of the polyelectrolytes used, different mechanisms of sludge dewatering were discussed: Polyanions are not adsorbed on the sludge particles and lead to a decline of the dewatering results. Linear short chain polycations result in a flocculation after surface charge neutralization of the particles according to a patch mechanism. Long chain linear polycations cause a bridging of the particles leading to a flocculation without charge neutralization of the aggregates formed. With branched polycations, a flocculation according to a patch mechanism is observed. These polycations form sludge particle aggregates which are surface charge neutralized at the flocculation point. In anionic-cationic dual flocculations using long chain polycations, an inclusion flocculation due to polyanion-polycation complex formation is the predominating mechanism. The cationic-anionic dual flocculation with complete covering of the particles with polycations in the first step can be discussed by a patch mechanism quite similar to an anionic monoflocculation of cationic particles. By knowing the mechanism of interaction for a given flocculation agent, an optimal sludge dewatering procedure can be predicted.  相似文献   

Metallicity and absolute magnitude calibrations for UBV photometry     

Y. Karata&#;  W. J. Schuster 《Monthly notices of the Royal Astronomical Society》2006,371(4):1793-1812

  相似文献   

The Gaia spectrophotometric standard stars survey: II. Instrumental effects of six ground‐based observing campaigns     

G. Altavilla  S. Marinoni  E. Pancino  S. Galleti  S. Ragaini  M. Bellazzini  G. Cocozza  A. Bragaglia  J. M. Carrasco  A. Castro  L. Di Fabrizio  L. Federici  F. Figueras  M. Gebran  C. Jordi  E. Masana  W. Schuster  G. Valentini  H. Voss 《Astronomische Nachrichten》2015,336(6):515-529

The Gaia SpectroPhotometric Standard Stars (SPSS) survey started in 2006, was awarded almost 450 observing nights and accumulated almost 100000 raw data frames with both photometric and spectroscopic observations. Such large observational effort requires careful, homogeneous, and automatic data reduction and quality control procedures. In this paper, we quantitatively evaluate instrumental effects that might have a significant (i.e., ≥1 %) impact on the Gaia SPSS flux calibration. The measurements involve six different instruments, monitored over the eight years of observations dedicated to the Gaia flux standards campaigns: DOLORES@TNG in La Palma, EFOSC2@NTT and ROSS@REM in La Silla, CAFOS@2.2m in Calar Alto, BFOSC@Cassini in Loiano, and LaRuca@1.5m in San Pedro Mártir. We examine and quantitatively evaluate the following effects: CCD linearity and shutter times, calibration frames stability, lamp flexures, second order contamination, light polarization, and fringing. We present methods to correct for the relevant effects which can be applied to a wide range of observational projects at similar instruments. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Forced regressive deposits of a deglaciation sequence: Example from the Late Quaternary succession in the Lake Saint‐Jean basin (Québec,Canada)          下载免费PDF全文

Alexis Nutz  Jean‐François Ghienne  Mathieu Schuster  Pierre Dietrich  Claude Roquin  Murray B. Hay  Frédéric Bouchette  Pierre A. Cousineau 《Sedimentology》2015,62(6):1573-1610

Differentiating between forced regressive deposits from deglacial periods in high latitude domains and forced regressive deposits from the onset of glacial periods in low latitude domains is fundamental for the accurate interpretation of glacial cycles within the geological record and then for the reconstruction of palaeogeography and palaeo‐climate. A forced regressive deglacial sequence is documented from the Lake Saint‐Jean basin (Québec, Canada). In this area, the Late Pleistocene to Holocene sediments have recorded the Laurentide ice sheet retreat accompanied by the invasion of marine waters (Laflamme Gulf) from ca 12·9 cal kyr bp . Subsequently, fluvio‐deltaic and coastal prograding wedges were deposited; they followed the base‐level fall due to glacio‐isostatic rebound. This succession, representing a transition from glacial to post‐glacial periods within a previously glaciated area, was investigated through recent mapping, preserved landforms, facies analysis, and new optical stimulated luminescence and radiocarbon dates. Three basin‐scale geological sections share a common lower part made of isolated ice‐contact fan deposits overlying bedrock. Throughout the entire basin, ice‐contact fans are capped by glacimarine muds. Above, fluvial and coastal prograding systems were deposited and evolved through four steps: (i) deltaic systems progressively increased in width; (ii) coastal influence on sedimentation increased; (iii) hydrographic drainage systems became more organised; and (iv) deltas graded from steep (Gilbert delta) to low‐angle foresets (mouth‐bar delta). Deposited during the base‐level fall from glacio‐isostatic rebound, the complete succession has been designated as a single falling stage system tract referred to as a deglacial falling stage system tract. It is representative of a deglaciation sequence in areas previously covered by ice during glacial periods (i.e. medium to high latitude domains). Diagnostic criteria are provided to identify such a deglacial falling stage system tract in the geological record, which may aid identification of previously unknown glacial cycles.  相似文献   

Reply to comment on ‘Characterization of surface and ground water δ18O seasonal variation and its use for estimating groundwater residence times’ by R. E. Criss and W. E. Winston     

Michael M. Reddy  Paul Schuster  Carol Kendall  Micaela B. Reddy 《水文研究》2006,20(16):3573-3578

  相似文献