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Lateral Extent (lateral + extent)
Selected AbstractsStable carbon isotope signature of ancient maize agriculture in the soils of Motul de San José, GuatemalaGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 3 2007Elizabeth A. Webb Soil profiles collected from a 2.5-km transect radiating from the Maya center of Motul de San José were analyzed for the stable carbon-isotope composition of their soil organic matter. The residues of maize (Zea mays), the only C4 plant known to have been cultivated in this area by the ancient Maya, impart a carbon-isotope signature to the underlying soil organic matter reservoir that is distinct from that produced by the native C3 forest vegetation. The varying turnover rates of the humic acid and humin fractions of the soil organic matter allowed us to distinguish between the presence of modern and ancient maize residues in these soils, and to delineate the lateral extent of maize cultivation at this ancient Maya site. The strongest isotopic evidence of maize residues is preserved in the soils surrounding the peripheral settlement of Chäkokot and at one locality within the urban center of Motul de San José. © 2007 Wiley Periodicals, Inc. [source] Glacial Sediment Causing Regional-Scale Elevated Arsenic in Drinking WaterGROUND WATER, Issue 6 2005Melinda L. Erickson In the upper Midwest, USA, elevated arsenic concentrations in public drinking water systems are associated with the lateral extent of northwest provenance late Wisconsin-aged drift. Twelve percent of public water systems located within the footprint of this drift (212 of 1764) exceed 10 ,g/L arsenic, which is the U.S. EPA's drinking water standard. Outside of the footprint, only 2.4% of public water systems (52 of 2182) exceed 10 ,g/L arsenic. Both glacial drift aquifers and shallow bedrock aquifers overlain by northwest provenance late Wisconsin-aged sediment are affected by arsenic contamination. Evidence suggests that the distinct physical characteristics of northwest provenance late Wisconsin-aged drift,its fine-grained matrix and entrained organic carbon that fosters biological activity,cause the geochemical conditions necessary to mobilize arsenic via reductive mechanisms such as reductive desorption and reductive dissolution of metal oxides. This study highlights an important and often unrecognized phenomenon: high-arsenic sediment is not necessary to cause arsenic-impacted ground water,when "impacted" is now defined as >10 ,g/L. This analysis also demonstrates the scientific and economic value of using existing large but imperfect statewide data sets to observe and characterize regional-scale environmental problems. [source] Drawdown and Stream Depletion Produced by Pumping in the Vicinity of a Partially Penetrating StreamGROUND WATER, Issue 5 2001James J. Butler Jr. Commonly used analytical approaches for estimation of pumping-induced drawdown and stream depletion are based on a series of idealistic assumptions about the stream-aquifer system. A new solution has been developed for estimation of drawdown and stream depletion under conditions that are more representative of those in natural systems (finite width stream of shallow penetration adjoining an aquifer of limited lateral extent). This solution shows that the conventional assumption of a fully penetrating stream will lead to a significant overestimation of stream depletion (> 100%) in many practical applications. The degree of overestimation will depend on the value of the stream leakance parameter and the distance from the pumping well to the stream. Although leakance will increase with stream width, a very wide stream will not necessarily be well represented by a model of a fully penetrating stream. The impact of lateral boundaries depends upon the distance from the pumping well to the stream and the stream leakance parameter. In most cases, aquifer width must be on the order of hundreds of stream widths before the assumption of a laterally infinite aquifer is appropriate for stream-depletion calculations. An important assumption underlying this solution is that stream-channel penetration is negligible relative to aquifer thickness. However, an approximate extension to the case of nonnegligible penetration provides reasonable results for the range of relative penetrations found in most natural systems (up to 85%). Since this solution allows consideration of a much wider range of conditions than existing analytical approaches, it could prove to be a valuable new tool for water management design and water rights adjudication purposes. [source] RESERVOIR POTENTIAL OF A LACUSTRINE MIXED CARBONATE / SILICICLASTIC GAS RESERVOIR: THE LOWER TRIASSIC ROGENSTEIN IN THE NETHERLANDSJOURNAL OF PETROLEUM GEOLOGY, Issue 1 2008D. Palermo The Lower Triassic Rogenstein Member of the Buntsandstein Formation produces gas at the De Wijk and Wanneperveen fields, NE Netherlands and consists mainly of claystones with intercalated oolitic limestone beds. The excellent reservoir properties of the oolites (,= 20-30%; k = 5-4000 mD) are predominantly controlled by depositional facies. Oolitic limestones are interpreted as the storm and wave deposits of a shallow, desert lake located in the Central European Buntsandstein Basin. The vertical sequence of lithofacies in the Rogenstein Member indicates cyclic changes of relative lake level. The reservoir rock is vertically arranged in a three-fold hierarchy of cycles, recognised both in cores and wireline logs. These cycles are a key to understanding the distribution of reservoir facies, and are used as the basis for a high-resolution sequence stratigraphic correlation of the reservoir units. Slight regional-scale thickness variations of the Rogenstein Member (in the order of tens of metres) are interpreted as the effects of differential subsidence associated with the inherited Palaeozoic structural framework. The depositional basin can be subdivided into subtle palaeo-highs and -lows which controlled facies distribution during Rogenstein deposition. Oolitic limestones show their greatest lateral extent and thickest development in the Middle Rogenstein during large-scale maximum flooding. Potential reservoir rocks (decimetre to metres thick) are present in the NE Netherlands, in particular in the Lauwerszee Trough and the Lower Saxony Basin, where abundant gas shows of 200 - 4000 ppm CH4 have been recorded. Preserved primary porosity is interpreted to be a result of rapid burial in subtle depositional palaeo-lows in this area. The thickest, amalgamated oolite intervals (tens of metres thick) occur in the eastern part of the Central Netherlands Basin. Because of poor reservoir properties, other areas appear to be less promising in terms of Rogenstein exploration potential. [source] Histopathological study of the spreading neoplastic cells in cervical glands and surface epithelia in cervical intra-epithelial neoplasia and microinvasive squamous cell carcinoma: Ki-67 immunostaining is a useful marker for pathological diagnosis from the gland involvement sitePATHOLOGY INTERNATIONAL, Issue 8 2006Miki Kimura The purpose of the present study was to clarify the spreading status of neoplastic cells in the cervical glands and surface epithelia in cervical intra-epithelial neoplasia (CIN) and microinvasive squamous cell carcinoma (MiSCC), and to evaluate the diagnostic usefulness of Ki-67 immunostaining from the gland involvement (GI) site. Cervical conization samples from 120 patients, including 110 with CIN (CIN1, n = 2; CIN2, n = 21; CIN3, n = 87) and 10 patients with MiSCC, was examined using HE and Ki-67 immunostaining. The linear extent, lateral extent in the surface epithelia and depth of GI were significantly increased from CIN1 to MiSCC. A significant correlation was found between the linear extent and lateral extent, between the linear extent and depth, and between the lateral extent and depth. These results indicated that the size of the surface epithelial lesion and the depth in CIN gradually increased in accordance with the grade of CIN, and that GI became deeper according to the increase in the size of the surface epithelial lesion. The Ki-67 labeling index in the GI site gradually increased from CIN1 to MiSCC, which indicated that Ki-67 immunostaining is a useful marker for the pathological diagnosis of CIN from the GI site. [source] Morphological and electrical changes in TiO2 memristive devices induced by electroforming and switchingPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 1-2 2010Ruth Münstermann Abstract Combining delamination technique with conductive AFM, we have been able to reveal spatially resolved morphology and conductance changes in TiO2 memristive junctions after electroforming and switching. Being able to distinguish between effects caused by electroforming and switching, respectively, we could demonstrate that electroforming results in the creation of localized conductance channels induced by oxygen evolution while subsequent resistive switching causes an additional conducting structure next to the forming spot. We observe that the lateral extent of this structure depends on the number of switching cycles indicating an ongoing breaking of existing and creation of neighbouring current channels during subsequent switching. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Stratigraphic and structural expression of the lateral growth of thrust fault-propagation folds: results and implications from kinematic modellingBASIN RESEARCH, Issue 2 2003Kate A. Cooper In order to better understand the development of thrust fault-related folds, a 3D forward numerical model has been developed to investigate the effects that lateral slip distribution and propagation rate have on the fold geometry of pre- and syn-tectonic strata. We consider a fault-propagation fold in which the fault propagates upwards from a basal decollement and along-strike normal to transport direction. Over a 1 Ma runtime, the fault reaches a maximum length of 10 km and accumulates a maximum displacement of 1 km. Deformation ahead of the propagating fault tip is modelled using trishear kinematics while backlimb deformation is modelled using kink-band migration. The applicability of two different lateral slip distributions, namely linear-taper and block-taper, are firstly tested using a constant lateral propagation rate. A block-taper slip distribution replicates the geometry of natural fold-thrusts better and is then used to test the sensitivity of thrust-fold morphology to varied propagation rates in a set of fault-propagation folds that have identical final displacement to length (Dmax/Lmax) ratios. Two stratigraphic settings are considered: a model in which background sedimentation rates are high and no topography develops, and a model in which a topographic high develops above the growing fold and local erosion, transport and deposition occur. If the lateral propagation rate is rapid (or geologically instantaneous), the fault tips quickly become pinned as the fault reaches its maximum lateral extent (10 km), after which displacement accumulates. In both stratigraphic settings, this leads to strike-parallel rotation of the syn-tectonic strata near the fault tips; high sedimentation rates relative to rates of uplift result in along-strike thinning over the structural high, while low sedimentation rates result in pinchout against it. In contrast, slower lateral propagation rates (i.e. up to one order of magnitude greater than slip rate) lead to the development of along-strike growth triangles when sedimentation rates are high, whereas when sedimentation rates are low, offflap geometries result. Overall we find that the most rapid lateral propagation rates produce the most realistic geometries. In both settings, time-equivalent units display both nongrowth and growth stratal geometries along-strike and the transition from growth to nongrowth has the potential to delineate the time of fault/fold growth at a given location. This work highlights the importance of lateral fault-propagation and fault tip pinning on fault and fold growth in three dimensions and the complex syn-tectonic geometries that can result. [source] | ||||||||||