242 research outputs found
An enhanced classification of artificial ground
This report describes a detailed scheme for the mapping and recording of artificial ground. It presents codes and descriptions that underpin the entries in the British Geological Survey stratigraphical lexico
Interpretative modelling of a geological cross section from boreholes: sources of uncertainty and their quantification
We conducted a designed experiment to quantify sources of uncertainty in geologists' interpretations of a geological cross section. A group of 28 geologists participated in the experiment. Each interpreted borehole record included up to three Palaeogene bedrock units, including the target unit for the experiment: the London Clay. The set of boreholes was divided into batches from which validation boreholes had been withheld; as a result, we obtained 129 point comparisons between the interpreted elevation of the base of the London Clay and its observed elevation in a borehole not used for that particular interpretation. Analysis of the results showed good general agreement between the observed and interpreted elevations, with no evidence of systematic bias. Between-site variation of the interpretation error was spatially correlated, and the variance appeared to be stationary. The between-geologist component of variance was smaller overall, and depended on the distance to the nearest borehole. There was also evidence that the between-geologist variance depends on the degree of experience of the individual. We used the statistical model of interpretation error to compute confidence intervals for any one interpretation of the base of the London Clay on the cross section, and to provide uncertainty measures for decision support in a hypothetical route-planning process. The statistical model could also be used to quantify error propagation in a full 3-D geological model produced from interpreted cross sections
Model metadata report for Manchester and Salford, NW England
This report describes the creation of a 3D geological model of natural and artificial superficial
deposits in Manchester and Salford, NW England. The Manchester and Salford model forms part
of the Lower Mersey Corridor, NW England. The Lower Mersey Corridor includes models
within the region comprising:
Manchester-Salford
Warrington
Liverpool
Irlam
The location of the geological models is shown in Figure 1 and the spacing of cross-sections is
shown in Figure 2.
Figure 1 Location of Manchester and Salford 3D geological model and its relationship to
others in the Lower Mersey Corridor area of NW England.
The 3D models include natural and artificial superficial deposits. Cross-sections for Manchester
and Salford include schematic bedrock correlations for illustration only. Bedrock is not included
in the calculated mode
Integrated modelling of geoscience information to support sustainable urban planning
The provision of reliable and up-to-date geoscientific information for the urban
environment has assumed increasing importance in recent years as
legislative changes have forced developers, planning authorities and
regulators to consider more fully the implications and impact on the
environment of large-scale development initiatives. To comply with the
principles of sustainable development, developers are increasingly required to
demonstrate that proposals are based on the best possible scientific
information and analysis of risk. Nowhere is this more relevant than in the
context of urban regeneration, where planning policy guidance gives priority to
re-use of previously developed (brownfield) land. In England, brownfield sites
suitable for re-development cover an area equivalent to half the size of
London
3-D hydrogeological characterisation of the superficial deposits between Doncaster and Retford
A 3-D geological model of the area between Doncaster and Retford was created in order to
characterise the thickness and distribution of superficial deposits to allow hydrogeological
domains to be derived above the Sherwood Sandstone aquifer. The overarching aim of the study
was to use a domains approach, derived from the output of the 3-D model to assess potential
recharge to the Sherwood Sandstone aquifer. The results of the study are intended to help the
Environment Agency meet its regulatory requirements under the Water Framework Directive
and Catchment Abstraction Management Strategy (CAMS) and form part of its overall East
Midlands – Yorkshire Sherwood Sandstone Groundwater Study.
The 3-D model revealed a complex sequence of pre-glacial, glacial and post-glacial sediments
deposited on a rockhead surface that extends in paces to –26mOD as a result of deep incision
into the bedrock. These channels are orientated north-west, south-east or east-west. The
sequence of superficial deposits is generally less than 10m thick, increasing to 25m in places to
the east and southeast of the project area.
The area from Hatfield Moors in the north-east to Misson in the south-east is characterised by a
sequence of peat, variably underlain by Blown Sand, Glaciolacustrine silt and clay and “Older
River Gravel”. The Glaciolacustrine silt and clay is most thickly developed beneath Hatfield
Moors, but is laterally discontinuous. Elsewhere, to the west of the study area, the superficial
deposits comprise sand, gravel and till of limited extent and are generally less than 10m thick,
except in some fluvial valleys.
Seven hydrogeological domains were identified from the 3-D model and other published data
sources. The domains were defined in terms of the potential for recharge to occur either directly
into the Sherwood Sandstone or through the sequence of superficial deposits. Each of the units
making up the superficial deposits in the area was classified according to its inferred
hydrogeological properties.
A hydrogeological domains map produced via a series of GIS rules and queries using the digital
output from the model reveal that the potential for recharge is greatest in the western and central
parts of the project area, with only limited potential recharge occurring to the east
Vale of York 3-D borehole interpretation and cross-sections study
The Vale of York between Doncaster and Scunthorpe in the south and York and Bugthorpe in
the north is largely underlain by bedrock of the Sherwood Sandstone Group – one of the regions
principal aquifers. Significant superficial deposits of Quaternary age overlie the Sherwood
Sandstone. This study aims to investigate the nature of these superficial deposits with respect to
their relationship with the underlying aquifer.
The Vale of York project area represents a varied glaciated terrain, consisting of pro-glacial finegrained
sediments, coarser glaciofluvilal sediments and extensive glacial tills. These diverse
superficial units vary in thickness throughout the project area. The hydrogeological nature of the
natural superficial sequence is consequently highly variable. Units may be considered as
aquitards, while others may act as aquifers, providing a potential pathway to the underlying
sandstone. The classification of lithologies as aquifer or aquitard is described in detail in this
report.
To investigate the hydrogeological nature of the superficial sequence, six east-west and three
north-south lithostratigraphical cross-sections were constructed. A range of geoscientific
information was considered, including existing geological mapping and over 3000 fully
attributed and coded boreholes. The cross-sections show a subdivision of the superficial
sequence into lithostratigraphical units. Each unit is described in detail in this report.
In addition, a series of thematic maps were generated from the lithological component of the
digital borehole data. Total superficial aquifer and superficial aquitard maps show how the
lithological nature of the superficial sequence varies across the area. Rockhead elevation and
superficial thickness maps indicate where the sandstone aquifer outcrops at the ground surface.
In summary, four main lithostratigraphical units overlie the Sherwood Sandstone Group aquifer
in the project area: a basal sequence of glaciofluvial sand and gravel (interpreted as a superficial
aquifer), glaciolacustrine laminated silt & clay (aquitard), glacial till comprising sandy gravelly
clay (aquitard), and a cover sequence of fluvial and aeolian sand, clay and peat (aquifer /
aquitard). The correlations illustrate that in certain areas, superficial deposits are thin or absent
and that in these areas the Sherwood Sandstone aquifer comes directly to ground surface
Energy radiation of moving cracks
The energy radiated by moving cracks in a discrete background is analyzed.
The energy flow through a given surface is expressed in terms of a generalized
Poynting vector. The velocity of the crack is determined by the radiation by
the crack tip. The radiation becomes more isotropic as the crack velocity
approaches the instability threshold.Comment: 7 pages, embedded figure
Lubricating Bacteria Model for Branching growth of Bacterial Colonies
Various bacterial strains (e.g. strains belonging to the genera Bacillus,
Paenibacillus, Serratia and Salmonella) exhibit colonial branching patterns
during growth on poor semi-solid substrates. These patterns reflect the
bacterial cooperative self-organization. Central part of the cooperation is the
collective formation of lubricant on top of the agar which enables the bacteria
to swim. Hence it provides the colony means to advance towards the food. One
method of modeling the colonial development is via coupled reaction-diffusion
equations which describe the time evolution of the bacterial density and the
concentrations of the relevant chemical fields. This idea has been pursued by a
number of groups. Here we present an additional model which specifically
includes an evolution equation for the lubricant excreted by the bacteria. We
show that when the diffusion of the fluid is governed by nonlinear diffusion
coefficient branching patterns evolves. We study the effect of the rates of
emission and decomposition of the lubricant fluid on the observed patterns. The
results are compared with experimental observations. We also include fields of
chemotactic agents and food chemotaxis and conclude that these features are
needed in order to explain the observations.Comment: 1 latex file, 16 jpeg files, submitted to Phys. Rev.
Clastic Polygonal Networks Around Lyot Crater, Mars: Possible Formation Mechanisms From Morphometric Analysis
Polygonal networks of patterned ground are a common feature in cold-climate environments. They can form through the thermal contraction of ice-cemented sediment (i.e. formed from fractures), or the freezing and thawing of ground ice (i.e. formed by patterns of clasts, or ground deformation). The characteristics of these landforms provide information about environmental conditions. Analogous polygonal forms have been observed on Mars leading to inferences about environmental conditions. We have identified clastic polygonal features located around Lyot crater, Mars (50°N, 30°E). These polygons are unusually large (> 100 m diameter) compared to terrestrial clastic polygons, and contain very large clasts, some of which are up to 15 metres in diameter. The polygons are distributed in a wide arc around the eastern side of Lyot crater, at a consistent distance from the crater rim. Using high-resolution imaging data, we digitised these features to extract morphological information. These data are compared to existing terrestrial and Martian polygon data to look for similarities and differences and to inform hypotheses concerning possible formation mechanisms. Our results show the clastic polygons do not have any morphometric features that indicate they are similar to terrestrial sorted, clastic polygons formed by freeze-thaw processes. They are too large, do not show the expected variation in form with slope, and have clasts that do not scale in size with polygon diameter. However, the clastic networks are similar in network morphology to thermal contraction cracks, and there is a potential direct Martian analogue in a sub-type of thermal contraction polygons located in Utopia Planitia. Based upon our observations, we reject the hypothesis that polygons located around Lyot formed as freeze-thaw polygons and instead an alternative mechanism is put forward: they result from the infilling of earlier thermal contraction cracks by wind-blown material, which then became compressed and/or cemented resulting in a resistant fill. Erosion then leads to preservation of these polygons in positive relief, while later weathering results in the fracturing of the fill material to form angular clasts. These results suggest that there was an extensive area of ice-rich terrain, the extent of which is linked to ejecta from Lyot crater
Faking like a woman? Towards an interpretative theorization of sexual pleasure.
This article explores the possibility of developing a feminist approach to gendered and sexual embodiment which is rooted in the pragmatist/interactionist tradition derived from G.H. Mead, but which in turn develops this perspective by inflecting it through more recent feminist thinking. In so doing we seek to rebalance some of the rather abstract work on gender and embodiment by focusing on an instance of 'heterosexual' everyday/night life - the production of the female orgasm. Through engaging with feminist and interactionist work, we develop an approach to embodied sexual pleasure that emphasizes the sociality of sexual practices and of reflexive sexual selves. We argue that sexual practices and experiences must be understood in social context, taking account of the situatedness of sex as well as wider socio-cultural processes the production of sexual desire and sexual pleasure (or their non-production) always entails interpretive, interactional processes
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