910 research outputs found
Evidence for life in the isotopic analysis of surface sulphates in the Haughton impact structure, and potential applications on Mars
No full textThe analysis of sulphur isotopic compositions in three sets of surface sulphate samples from the soil zone in the Haughton impact structure shows that they are distinct. They include surface gypsum crusts remobilized from the pre-impact gypsum bedrock (mean δ<sup>34</sup>S +31‰), efflorescent copiapite and fibroferrite associated with hydrothermal marcasite (mean δ<sup>34</sup>S −37‰), and gypsum-iron oxide crusts representing weathering of pyritic crater-fill sediments (mean δ<sup>34</sup>S +7‰). Their different compositions reflect different histories of sulphur cycling. Two of the three sulphates have isotopically light (low δ<sup>34</sup>S) compositions compared with the gypsum bedrock (mean δ<sup>34</sup>S +31‰), reflecting derivation by weathering of sulphides (three sets of pyrite/marcasite samples with mean δ<sup>34</sup>S of −41, −20 and −8‰), which had in turn been precipitated by microbial sulphate reduction. Thus, even in the absence of the parent sulphides due to surface oxidation, evidence of life would be preserved. This indicates that on Mars, where surface oxidation may rule out sampling of sulphides during robotic exploration, but where sulphates are widespread, sulphur isotope analysis is a valuable tool that could be sensitive to any near-surface microbial activity. Other causes of sulphur isotopic fractionation on the surface of Mars are feasible, but any anomalous fractionation would indicate the desirability of further analysis
Short length-scale variability of hybrid event beds and its applied significance
No full textHybrid event beds (HEBs) are a type of deep-water sediment gravity flow deposit that generally comprise a basal clean sandstone overlain by a variety of muddier and less-permeable sandy facies. They are thought to be emplaced by combinations of turbidity currents, transitional flows and debris flows, all as part of the same transport event. To date, a number of studies have highlighted the common presence of HEBs mainly in the outer and marginal parts of deep-water systems where they replace beds composed dominantly of clean sand up-dip and/or axially over scales of km to 10s km. In addition to these broad patterns, important yet poorly understood short-length facies changes (over metres to 100s m) occur, modifying the overall texture and reservoir characteristics at or beneath typical spacing of production wells. The nature and origin of the short length-scale transitions is here addressed in four well-exposed HEB-prone outcrops: the Cretaceous-Paleocene Gottero Sandstone and the Miocene Cilento Flysch, both in Italy, the Carboniferous Mam Tor Sandstone in northern England, and the Carboniferous basal Ross Sandstone Formation, Western Ireland. A series of detailed correlation panels show marked lateral variations in internal bed make-up for most of the hybrid event beds studied. This variability typically involves lateral changes in the proportions of the cleaner basal sandstone and the overlying muddy sandstone division that occur without substantial change in the overall event bed thickness. The variability is inferred to reflect the complex fingering between the up-dip sandstone-dominated part of the event bed and the down-dip linked debrite due to internal erosion (ploughing) of the debrite into the basal clean sand. Where the upper part of the bed is dominated by large mudstone rafts, these may have foundered into liquefied sand and been injected and partly fragmented by the sand intrusions. The variable thickness and continuity of the basal clean sandstones have important implications for reservoir characterisation; significant variability in bed character at interwell scale can be anticipated. Rugose contacts between the intra-bed facies divisions may impact on drainage and sweep efficiency during hydrocarbon production
Corporate city?: partnership, participation, and partition in urban development in Leeds
No full textedited by Graham Haughton and Colin C. Williams.xiv, 313 p. : ill., maps ; 23 cm
Household enterprises in Vietnam : survival, growth, and living standards
No full textIn Vietnam almost a quarter of adults worked in nonfarm household enterprises in 1998. Based on household panel data from the Vietnam Living Standards Surveys of 1993 and 1998, the authors find some evidence that operating an enterprise leads to greater affluence. The data show that nonfarm household enterprises are most likely to be operated by urban households, by those with moderately good education, and by the children of proprietors. The authors were able to construct a panel of nonfarm household enterprises; 39 percent of enterprises operating in 1993 were still in business in 1998. Those in the (more affluent) south of the country were less likely to survive, as were smaller and younger businesses. A pattern emerges from the data. In poor areas the lack of education, credit, and effective demand limits the development of nonfarm household enterprises. In rich areas there is the attraction of wage labor. Nonfarm household enterprises are thus most important in the period of transition, when agriculture is declining in importance but before the formal sector becomes established. The authors expect these enterprises to continue to play a modest supporting role in fostering economic growth in Vietnam.Public Health Promotion,Housing&Human Habitats,Banks&Banking Reform,Municipal Financial Management,Microfinance,Banks&Banking Reform,Municipal Financial Management,Small and Medium Size Enterprises,Private Participation in Infrastructure,Microfinance
Drilling Subsurface Ice at the Haughton Crater Analog Site
No full textOver a decade of evolutionary development of integrated automated drilling and sample handling at the terrestrial polar Mars analog site at Haughton Crater has made it possible to propose missions that could sample 1-2m into rocks and ice on Mars. The eventual search for biomarkers and signs of past or extant life in Mars polar regions will require sample acquisition there below the desiccated and irradiated surface. Drilling and drill tests at the Haughton Crater site since 1998 have also shown a retreat downward of the active-layer boundary in annual measurements
Aftermath : legacies and memories of war in Europe
No full textFocusing on three of the defining moments of the twentieth century - the end of the two World Wars and the collapse of the Iron Curtain - this volume presents a rich collection of authoritative essays, covering a wide range of thematic, regional, temporal and methodological perspectives. By re-examining the traumatic legacies of the century’s three major conflicts, the volume illuminates a number of recurrent yet differentiated ideas concerning memorialisation, mythologisation, mobilisation, commemoration and confrontation, reconstruction and representation in the aftermath of conflict. The post-conflict relationship between the living and the dead, the contestation of memories and legacies of war in cultural and political discourses, and the significance of generations are key threads binding the collection together. While not claiming to be the definitive study of so vast a subject, the collection nevertheless presents a series of enlightening historical and cultural perspectives from leading scholars in the field, and it pushes back the boundaries of the burgeoning field of the study of legacies and memories of war. Bringing together historians, literary scholars, political scientists and cultural studies experts to discuss the legacies and memories of war in Europe (1918-1945-1989), the collection makes an important contribution to the ongoing interdisciplinary conversation regarding the interwoven legacies of twentieth-century Europe’s three major conflicts
Further Geophysical Studies of the Haughton Impact Structure
No full textThe approximately 23 Ma Haughton impact structure, located at 75 deg 23 min N, 89 deg 39 min W in the Canadian Arctic, on Devon Island, Nunavut, Canada is a well-preserved impact structure with an original rim diameter estimated at about 23 - 24 km. Past studies, in the 1980s, did an initial survey of the Haughton structure, looking at its surface units, exposures, map surface geology, topographic and initial surveys of gravity and magnetic fields in profiles across the impact structure. A topological outer ring and the lack of a well-defined central peak was cited as evidence that Haughton was a multi-ring structure. However other authors consider it more likely that the Haughton structure is a central-peak basin with simply a limited extent, and/or full peak features having been removed through glaciations and subsequent years. The impact structure is located in approximately 2 km thickness of carbonate material on top of a gneissic basement. The impact structure itself can be described in terms of uplifted and moved blocks of altered gneissic and carbonate material with areas in the center of the crater covered with impact carbonate melts and/or reworked impact breccias. Additional information is included in the original extended abstract
The European ultrasonic planetary core drill: preliminary results from field trials at the Haughton Mars Project
No full textThis paper presents the findings of a recent field trip by the Ultrasonic Planetary Core Drill team to the Mars analog site at the Haughton Mars Project. Results of this trip are compared to results obtained drilling permafrost simulant in the lab
Towards a classification of hybrid event beds
No full textHybrid event beds (HEBs) are a type of deep-water sediment gravity flow deposit comprising a basal clean (H1) and/or banded (H2) sandstone overlain by a muddier sandy facies (H3) emplaced during the same transport event. They generally have a tabular geometry but an internal complexity in terms of relative thickness and texture of the component divisions. HEBs are increasingly recognised in outcrop and in hydrocarbon reservoirs, requiring an improved understanding of their textural make-up, association, context and impact on reservoir properties.
Although HEBs share the described common characters that allow them to be differentiated from ‘classic’ turbidites, observations from a range of sedimentary basins show great variability in their sedimentological character. The texture of the relatively mud-rich H3 division and the size and shape of substrate clasts within it are key feature for classification and process interpretation. Two important and recurring bed associations are identified: (1) a range of commonly thick beds in which the H3 division can include very large substrate slabs and blocks, evidence of extensive autoinjection and clast break-up, and dense mudclast concentrations, all set in a sandstone with elevated interstitial clay. This association typically is found in outer fan and confined sheet systems in a downdip position. (2) beds in which H3 divisions are characterised by high levels of dispersed clay, floating mudstone clasts and matrices that are enriched in hydraulically-fractionated components (mica, organic matter, clay flocs). Beds with thin H3 divisions typically pass down-dip to those in which H3 is expanded. This association is found in fan lobe successions where it can alternate with turbidites. The two associations are interpreted to reflect different modes of flow transformation. In the first case, the rafts and chaotic textures are related to local substrate delamination processes that culminated in the formation of a linked cohesive debris flow because of intense internal shearing and clast disaggregation. The second association formed by mud entrainment at channel mouths, proximal lobe locations or flow expansion points and developed through progressive longitudinal flow transformation and rapid deceleration and may include deposition from transitional flows
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