The African Climate as Predicted by the IAP Grid-Point Nine-Layer Atmospheric General Circulation Model (IAP-9L-AGCM)   总被引：4，自引：3，他引：4  

Chineke Theo Chidiezie  Bi Xunqiang  Wang Huijun  Xue Feng 《大气科学进展》1997,14(3):409-416

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Intercomparison of Two Hydroxyl Radical Measurement Techniques at the Atmosphere Simulation Chamber SAPHIR     

Eric Schlosser  Birger Bohn  Theo Brauers  Hans-Peter Dorn  Hendrik Fuchs  Rolf Häseler  Andreas Hofzumahaus  Frank Holland  Franz Rohrer  Lutz Olaf Rupp  Manfred Siese  Ralf Tillmann  Andreas Wahner 《Journal of Atmospheric Chemistry》2007,56(2):187-205

At the atmosphere simulation chamber SAPHIR in Jülich both Laser-Induced Fluorescence Spectroscopy (LIF) and Long-Path Differential Optical Laser Absorption Spectroscopy (DOAS) are operational for the detection of OH radicals at tropospheric levels. The two different spectroscopic techniques were compared within the controlled environment of SAPHIR based on all simultaneous measurements acquired in 2003 (13 days). Hydroxyl radicals were scavenged by added CO during four of these days in order to experimentally check the calculated precisions at the detection limit. LIF measurements have a higher precision (σ= 0.88×10⁶ cm^–3) and better time resolution (Δt = 60 s), but the DOAS method (σ= 1.24×10⁶ cm^–3, Δt = 135 s) is regarded as primary standard for comparisons because of its good accuracy. A high correlation coefficient of r = 0.95 was found for the whole data set highlighting the advantage of using a simulation chamber. The data set consists of two groups. The first one includes 3 days, where the LIF measurements yield (1 – 2) ×10⁶ cm^–3 higher OH concentrations than observed by the DOAS instrument. The experimental conditions during these days are characterized by increased NO_x concentration and a small dynamic range in OH. Excellent agreement is found within the other group of 6 days. The regression to the combined data of this large group yields unity slope without a significant offset.  相似文献   

The role of antelope trampling on scarp erosion in a hyper-arid environment, Skeleton Coast, Namibia     

Jan Boelhouwers  Theo Scheepers 《Journal of Arid Environments》2004,58(4):9

The role of animal trampling in a hyper-arid environment is evaluated. Field observations on fluvial terraces of the Uniab fan in Namibia suggest that animal impact on level surfaces with gravel armouring is minimal. However, animal trampling along tracks across scarp slopes results in scarp recess and initiate cutback development. With continued growth ephemeral fluvial processes become more dominant and obscure the animal impact. Animal trampling effects are pronounced in hyper-arid environments due to the low rates of other slope processes. However, it is argued that large herd migration may have contributed significantly to cutback development in other environments, especially in Africa, but may be very difficult to substantiate by landform analysis.  相似文献   

Paleomagnetic studies combined with fission-track datings on the western arc of Sulawesi, east Indonesia     

Sadao Sasajima  Susumu Nishimura  Kimio Hirooka  Yoichiro Otofuji  Theo Van Leeuwen  Fred Hehuwat 《Tectonophysics》1980,64(1-2)

Paleomagnetic studies in conjunction with fission-track dating on the western arc of Sulawesi yield important evidence bearing on the tectonic history of the area. During the Paleogene to Early Miocene time interval the paleomagnetic pole for southwestern Sulawesi was situated at 36.5°E 44.8°N. This pole position is significantly different from that in the time interval Middle Miocene to Recent, which is consistent with the north pole of the axial geocentric dipole. This fact suggests that subsequent to the Paleogene to Early Miocene period, possibly 19–13 m.y. B.P., a major tectonic event occurred which caused about 40 degrees of anticlockwise rotation of the area. It is suggested by the present work that the postulated collision followed by welding of eastern Sulawesi with western Sulawesi during the Pliocene (Katili, 1978) may be the tectonic event mentioned above. In addition, our data does not support the hypothesis that western Sulawesi has been derived from the dispersal of Gondwanaland.  相似文献   

The geography of containerization: half a century of revolution,adaptation and diffusion   总被引：1，自引：0，他引：1  

Jean-Paul Rodrigue  Theo Notteboom 《GeoJournal》2009,74(1):1-5

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Late Carboniferous foreland basin formation and Early Carboniferous stretching in Northwestern Europe: inferences from quantitative subsidence analyses in the Netherlands     

Henk Kombrink  Karen A. Leever‡  Jan-Diederik van Wees†  ‡  Frank van Bergen†  Petra David†  Theo E. Wong 《Basin Research》2008,20(3):377-395

The large thickness of Upper Carboniferous strata found in the Netherlands suggests that the area was subject to long-term subsidence. However, the mechanisms responsible for subsidence are not quantified and are poorly known. In the area north of the London Brabant Massif, onshore United Kingdom, subsidence during the Namurian–Westphalian B has been explained by Dinantian rifting, followed by thermal subsidence. In contrast, south and east of the Netherlands, along the southern margin of the Northwest European Carboniferous Basin, flexural subsidence caused the development of a foreland basin. It has been proposed that foreland flexure due to Variscan orogenic loading was also responsible for Late Carboniferous subsidence in the Netherlands. In the first part of this paper, we present a series of modelling results in which the geometry and location of the Variscan foreland basin was calculated on the basis of kinematic reconstructions of the Variscan thrust system. Although several uncertainties exist, it is concluded that most subsidence calculated from well data in the Netherlands cannot be explained by flexural subsidence alone. Therefore, we investigated whether a Dinantian rifting event could adequately explain the observed subsidence by inverse modelling. The results show that if only a Dinantian rifting event is assumed, such as is found in the United Kingdom, a very high palaeowater depth at the end of the Dinantian is required to accommodate the Namurian–Westphalian B sedimentary sequence. To better explain the observed subsidence curves, we propose (1) an additional stretching event during the Namurian and (2) a model incorporating an extra dynamic component, which might well explain the very high wavelength of the observed subsidence compared with the wavelength of the predicted flexural foreland basin.  相似文献   

Variability of residual fluxes of suspended sediment in a multiple tidal-inlet system: the Dutch Wadden Sea     

Maximiliano Sassi  Matias Duran-Matute  Thijs van Kessel  Theo Gerkema 《Ocean Dynamics》2015,65(9-10):1321-1333

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A review of the synthesis and characterisation of pillared clays and related porous materials for cracking of vegetable oils to produce biofuels     

J. Theo Kloprogge  Loc V. Duong  Ray L. Frost 《Environmental Geology》2005,47(7):967-981

This paper presents an overview of the modification of clay minerals by propping apart the clay layers with an inorganic complex. This expanded material is converted into a permanent two-dimensional structure, known as pillared clay or shortly PILC, by thermal treatment. The resulting material exhibits a two-dimensional porous structure with acidic properties comparable to that of zeolites. Synthetic as well as natural smectites serve as precursors for the synthesis of Al, Zr, Ti, Fe, Cr, Ga, V, Si and other pillared clays as well as mixed Fe/Al, Ga/Al, Si/Al, Zr/Al and other mixed metal pillared clays. Biofuels form an interesting renewable energy source, where these porous, catalytically active materials can play an important role in the conversion of vegetable oils, such as canola oil, into biodiesel. Transesterification of vegetable oil is currently the method of choice for conversion to biofuel. The second part of this review focuses on the catalysts and cracking reaction conditions used for the production of biofuel. A distinction has been made in three different vegetable oils as starting materials: canola oil, palm oil and sunflower oil.  相似文献   

Toxic metal adsorption in the triassic sandstone aquifer of the English Midlands     

Theo Mimides  John William Lloyd 《Environmental Geology》1987,10(3):135-140

Laboratory experimental results show that adsorption can be an important mechanism in taking up heavy metals contained in groundwaters in the sandstones. The adsorption can be described in terms of Freundlich isotherms and can be simply modeled mathematically. The adsorption function has been integrated into a mass balance equation, and tested using a laboratory sand tank model and in a small field study. The results show that the transport-adsorption models are not easily applied in the field because of hydrogeological complications.  相似文献   

The scarp lands of Saudi Arabia     

Randolf Rausch  Theo Simon  Hussain Al Ajmi  Heiko Dirks 《Arabian Journal of Geosciences》2014,7(6):2437-2450

In central Saudi Arabia, the combination of rock types and sedimentary bedding created a unique scarp landscape. The escarpments were formed during Late Miocene through Early Quaternary times. At present, cuesta formation and migration are restricted to the actual escarpments as a consequence of negligible sediment removal. The plains between the escarpments are sealed through periodically active fluvial processes and through eolian sedimentation. In this publication, the major escarpments of central Saudi Arabia are described. The interactions between tectonics, climate, and morphogenesis which created this unique landscape are reviewed.  相似文献