Preface     

A. Colin de Verdiére 《Surveys in Geophysics》2001,22(3):177-177

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Distorted Froude‐scaled flume analysis of large woody debris     

Nicholas P. Wallerstein  Carlos V. Alonso  Sean J. Bennett  Colin R. Thorne 《地球表面变化过程与地形》2001,26(12):1265-1283

This paper presents the results of a movable‐boundary, distorted, Froude‐scaled hydraulic model based on Abiaca Creek, a sand‐bedded channel in northern Mississippi. The model was used to examine the geomorphic and hydraulic impact of simplified large woody debris (LWD) elements. The theory of physical scale models is discussed and the method used to construct the LWD test channel is developed. The channel model had bed and banks moulded from 0·8 mm sand, and flow conditions were just below the threshold of motion so that any sediment transport and channel adjustment were the result of the debris element. Dimensions and positions of LWD elements were determined using a debris jam classification model. Elements were attached to a dynamometer to measure element drag forces, and channel adjustment was determined through detailed topographic surveys. The fluid drag force on the elements decreased asymptotically over time as the channel boundary eroded around the elements due to locally increased boundary shear stress. Total time for geomorphic adjustment computed for the prototype channel at the Q₂ discharge (discharge occurring once every two years on average) was as short as 45 hours. The size, depth and position of scour holes, bank erosion and bars created by flow acceleration past the elements were found to be related to element length and position within the channel cross‐section. Morphologies created by each debris element in the model channel were comparable with similar jams observed in the prototype channel. Published in 2001 John Wiley & Sons, Ltd.  相似文献   

Geochronological constraints on the evolution of the Periadriatic Fault System (Alps)     

Wolfgang Müller  Giacomo Prosser  Neil S. Mancktelow  Igor M. Villa  Simon P. Kelley  Giulio Viola  Felix Oberli 《International Journal of Earth Sciences》2001,90(3):623-653

Fault rocks from various segments of the Periadriatic fault system (PAF; Alps) have been directly dated using texturally controlled Rb-Sr microsampling dating applied to mylonites, and both stepwise-heating and laser-ablation ⁴⁰Ar/³⁹Ar dating applied to pseudotachylytes. The new fault ages place better constraints on tectonic models proposed for the PAF, particularly in its central sector. Along the North Giudicarie fault, Oligocene (E)SE-directed thrusting (29-32 Ma) is currently best explained as accommodation across a cogenetic restraining bend within the Oligocene dextral Tonale-Pustertal fault system. In this case, the limited jump in metamorphic grade observed across the North Giudicarie fault restricts the dextral displacement along the kinematically linked Tonale fault to ~30 km. Dextral displacement between the Tonale and Pustertal faults cannot be transferred via the Peio fault because of both Late Cretaceous fault ages (74-67 Ma) and sinistral transtensive fault kinematics. In combination with other pseudotachylyte ages (62-58 Ma), widespread Late Cretaceous-Paleocene extension is established within the Austroalpine unit, coeval with sedimentation of Gosau Group sediments. Early Miocene pseudotachylyte ages (22-16 Ma) from the Tonale, Pustertal, Jaufen and Passeier faults argue for a period of enhanced fault activity contemporaneous with lateral extrusion of the Eastern Alps. This event coincides with exhumation of the Penninic units and contemporaneous sedimentation within fault-bound basins.  相似文献   

Quantification of mineral matter in the Argonne Premium Coals using interactive Rietveld-based X-ray diffraction     

Colin R. Ward  John C. Taylor  C. E. Matulis  L. S. Dale 《International Journal of Coal Geology》2001,46(2-4)

The mineral matter in the eight reference North American coal samples of the Argonne Premium Coal series has been investigated on a quantitative basis using X-ray diffraction (XRD) techniques. X-ray diffraction data obtained from electronic low-temperature (oxygen–plasma) ash (LTA) residues, from ashes produced by heating the coals in air at 370°C, and also from the raw coals themselves, were evaluated using an interactive data processing system ( ™) based on Rietveld interpretation methods. The results from the three types of material (LTA, 370°C ash and raw coal) were compared for each sample. This allowed the components present in the raw coals in crystalline form to be recognised separately from mineral artifacts produced, particularly in the low-rank coals, from interaction of organically associated elements (Ca, S, etc.) during the two ashing processes.After the allowance for the production of any artifacts, the quantitative mineral assemblages identified from XRD of the raw coals were found to be consistent, even for coals having a relatively low ash percentage (around 5%), with the results obtained from the respective mineral concentrates prepared by the ashing methods. The effects of heating the coal to 370°C could also be distinguished, relative to the raw coal or the LTA, through changes in components such as pyrite and the clay minerals.Although some areas of uncertainty exist, particularly with magnesium in the low-rank coals, the calculated chemical compositions of the coal ash derived from the mineral mixtures identified for each coal were also found to be consistent with the results of direct chemical analysis of the respective coal ash materials.  相似文献   

A case example of near-surface correction for multicomponent VSPS     

Xinwu Zeng  Colin MacBeth 《Geophysical Prospecting》1996,44(5):889-910

A deterministic near-surface correction procedure is developed for multicomponent VSP data, shot using directional sources and recorded using three-component receivers. The method is capable of removing unwanted effects of acquisition such as unequal source strengths or misorientations, but may also remove near-surface multiples and anisotropy. This is of considerable benefit for obtaining accurate and consistent estimates of subsurface anisotropy from different source combinations. Application of the technique is illustrated using a dataset from the Romashkino reservoir in Russia, where three or four different directional sources are used at the same source locations. The technique corrects for the large discrepancies which exist between the estimates obtained using different source combinations. Application of the technique to three wells in the survey region reveals a nearly isotropic subsurface, except for a few isolated zones of moderate to high (2 to 8%) anisotropy which lie close to the expected depth for the reservoir. Although there is no significant correlation with the production figures for each well, the qS1 polarization azimuth within the reservoir does vary at each well location, suggesting that this may be a more sensitive indicator of reservoir Drocess.  相似文献   

Biotransformation at 10° C of Di-n-Butyl Phthalate in Subsurface Microcosms     

Christian Chauret  William E. Inniss  Colin I. Mayfield 《Ground water》1996,34(5):791-794

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Storm solute behaviour in a montane Mediterranean forested catchment     

Anna vila  Josep Piol  Ferran Rod  Colin Neal 《Journal of Hydrology》1992,140(1-4):143-161

The results of an extensive study of streamwater chemistry during stormflow events, for a montane Mediterranean area, are presented. Four groups of variables are identified as having contrasting behaviour: alkalinity and pH; nitrate and potassium; sulphate and chloride; sodium, calcium and magnesium. The results show a complex pattern of response to flow that can be broadly linked to: (1) antecedent hydrological conditions; (2) rainfall intensity; (3) supplies of water from chemically distinct areas within the catchment. However, comparisons between this study and a parallel one which examined the composition of waters within the catchment, show that it is presently impossible to quantify the relative supplies from each part of the catchment. The findings are reviewed in relation to analogous studies within a European setting and in relation to modelling initiatives.  相似文献   

Environmental management in Antarctica Instruments and institutions     

Colin M. Harris  Janice Meadows 《Marine pollution bulletin》1992,25(9-12):239-249

Instruments and institutions for environmental management in Antarctica have evolved from beginnings in the Antarctic Treaty, with subsequent introduction of the Convention for the Conservation of Antarctic Seals, the Convention on the Conservation of Antarctic Marine Living Resources, and recommendations made at Treaty meetings. The Protocol on Environmental Protection to the Antarctic Treaty will improve existing provisions for environmental management in Antarctica. When it enters into force the Protocol will apply to all activities in the Treaty area: it provides rules for environmental impact assessment, conservation of fauna and flora, disposal of wastes, prevention of marine pollution and specially protected and managed areas. The Protocol's Committee for Environmental Protection will facilitate discussion and advice on environmental management. Management of information is a vital part of ensuring measures are effective. The Protocol should be ratified quickly to improve the basis for environmental protection, but the test will be whether and how it is implemented in practice.  相似文献   

High Resolution Radio Observations of Luminous IR Galaxies     

Colin J. Lonsdale 《Astrophysics and Space Science》1999,266(1-2):119-124

High resolution radio observations provide a unique tool for investigation ofultraluminous infrared galaxies, due to the combination of high angularresolution and source transparency available at centimeter wavelengths. Thetypical angular size of the IR emitting region in the most luminous systems isof order 0.1 arcsec, while dust absorption appears to obscure this region fromdirect view at wavelengths shorter than 100 microns. Radio observationswith VLBI and MERLIN are revealing compact radio structures indicative of bothstarburst and AGN activity in these systems. Additional observations arerequired to clarify relationships between radio structures and the energygeneration mechanisms, and to realize the full potential of radio interferometryfor ULIRG studies.  相似文献   

Survivorship and growth of Fucus gardneri after transplant to an acid mine drainage-polluted area     

Marsden AD  DeWreede RE  Levings CD 《Marine pollution bulletin》2003,46(1):65-73

Acid mine drainage (AMD) from an abandoned copper mine at Britannia Beach, British Columbia, Canada, enters the marine environment through Britannia Creek. The surrounding intertidal zone is devoid of rockweed, Fucus gardneri Silva, a seaweed that dominates nearby shores. Rockweed plants were transplanted to the intertidal zone near Britannia Creek and monitored for changes in percent cover, survivorship, growth rate and Cu content. Autumn and winter transplants to within 100 m of Britannia Creek resulted in negative growth rates and high mortality within 57 days of exposure to AMD, with Cu levels in rockweed surpassing 2,300 ppm in dry tissue. Summer transplants to sites 300-700 m from Britannia Creek showed no consistent differences between AMD-exposed rockweed and control plants, possibly because the plants were stressed by desiccation. The results are consistent with ecological effects observed in other studies, and provide strong evidence for the role of AMD in excluding rockweed from the shores near Britannia Creek.  相似文献