Geospatial analysis between the environment and past incidences of West Nile virus in bird specimens in Ontario,Canada     

Benita Y. Tam  Ian Martin  Leonard J. S. Tsuji 《GeoJournal》2014,79(6):805-817

Over recent years, the prevalence of the West Nile virus (WNV) in Canada has greatly increased due to various factors including changes in feeding behavior among WNV vectors. To understand whether changes in climate are a significant factor, the association between the environment and cases of WNV-infected bird specimens from 2009 to 2012 in Ontario, Canada, was examined using SAS and Quantum Geographic Information Systems (QGIS). Through a generalized linear mixed analysis, monthly totals of cooling degree days (CDD) and a two-way interaction between maximum temperature (Tmax) and precipitation were significantly positively associated to past incidences of WNV; while Tmax, precipitation, and a two-way interaction between CDD and precipitation were significantly negatively associated to past incidences of WNV. With the effects of increased warming, locations at higher latitudes in Canada may soon be at risk to WNV, as a positive case of WNV in a bird specimen was found close to the near north of Ontario in 2012.  相似文献   

Shear strength of lunar soil from oceanus procellarum     

Leonard D. Jaffe 《Earth, Moon, and Planets》1973,8(1-2):58-72

Soil from the scoop of Surveyor 3, returned to Earth by Apollo 12 astronauts, has been tested in a miniature shear box at five bulk densities, from 0.99 to 1.87 g cm^–3. Cohesion increased with bulk density from 3 × 10^–2 to 3 × 10^–1 N cm^–2; internal friction angle increased from 13° to 56°. Shear stress vs normal stress data fit a logarithmic relationship better than a linear one, at normal stresses of 3 × 10^–3 to 3 x 10⁰ N cm^–2. Results of these tests, in air, show no systematic differences from those for tests made elsewhere in vacuum and nitrogen. Results agree with those obtained in remotely controlled lunar surface operations with Surveyor 3 and other spacecraft provided that the bulk density was slightly underestimated for the on-surface measurements.Paper dedicated to Prof. Harold C. Urey on the occasion of his 80th birthday on 29 April 1973.This work represents one phase of research conducted at the Jet Propulsion Laboratory, California Institute of Technology, for the National Aeronautics and Space Administration, under Contract NAS 7-100.  相似文献   

Microtopography,water storage and flow patterns in a fine‐textured soil under agricultural use     

Christina Bogner  Mohammadreza Mirzaei  Stéphane Ruy  Bernd Huwe 《水文研究》2013,27(12):1797-1806

Agricultural use of soils implies tillage and often compaction and therefore influences processes on soil surface and affects infiltration of water into the subsoil. Although many studies on soil surface processes or flow patterns in soils exist, works relating both are rare in literature. We did two tracer experiments with Brilliant Blue FCF on a tilled and compacted plot and a non‐tilled one to investigate water storage on the soil surface during simulated rainfall and changes of soil microtopography, to analyse the associated flow patterns in the soil and to relate both to tillage and compaction. Our results show that storage was larger on the tilled and compacted plot than on the non‐tilled one. After tillage, transport processes above the plough pan were partly disconnected from those underneath because macropores were disrupted and buried by the tillage operation. However, preferential flow along cracks occurred on both plots and the macropores buried below the tillage pan still functioned as preferential flow paths. Therefore, we conclude that the studied soil is susceptible to deep vertical solute propagation at dry conditions when cracks are open, irrespective of tillage and compaction. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Till‐forming processes beneath parts of the Cordilleran Ice Sheet,British Columbia,Canada: macroscale and microscale evidence and a new statistical technique for analysing microstructure data     

Christina M. Neudorf  Tracy A. Brennand  Olav B. Lian 《Boreas: An International Journal of Quaternary Research》2013,42(4):848-875

This paper presents the first integrated macroscale and microscale examination of subglacial till associated with the last‐glacial (Fraser Glaciation) Cordilleran Ice Sheet (CIS). A new statistical approach to quantifying till micromorphology (multivariate hierarchical cluster analysis for compositional data) is also described and implemented. Till macrostructures, macrofabrics and microstructures support previous assertions that primary till in this region formed through a combination of lodgement and deformation processes in a temperate subglacial environment. Macroscale observations suggest that subglacial environments below the CIS were probably influenced by topography, whereby poor drainage of the substrate in topographically constricted areas, or on slopes adverse to the ice‐flow direction at glacial maximum, facilitated ductile deformation of the glacier bed. Microscale observations suggest that subglacial till below the CIS experienced both ductile and brittle deformation, including grain rotation and squeeze flow of sediment between grains under moist conditions, and microshearing, grain stacking and grain fracturing under well‐drained conditions. Macroscale observations suggest that ductile deformation events were probably followed by brittle deformation events as the substrate subsequently drained. The prevalence of ductile‐type microstructures in most till exposures investigated in this study suggests that ductile deformation signatures can be preserved at the microscale after brittle deformation events that result in larger‐scale fractures and shear structures. It is likely that microscale ductile deformation can also occur within distributed shear zones during lodgement processes. Cluster analysis of microstructure data and qualitative observations made from thin sections suggest that the relative frequency of countable microstructures in this till is influenced by topography in relation to ice‐flow direction (bed drainage conditions) as well as by the frequency and distribution of voids in the till matrix and skeletal grain shapes.  相似文献   

PM2.5 co-benefits of climate change legislation part 2: California governor’s executive order S-3-05 applied to the transportation sector     

Michael J. Kleeman  Christina Zapata  John Stilley  Mark Hixson 《Climatic change》2013,117(1-2):399-414

California Governor’s Executive Order (CGEO) S-3-05 requires that California greenhouse gas (GHG) emissions be reduced to 80 % below 1990 levels by the year 2050. Meeting this target will require drastic changes in transportation technology, fuel, and behavior which will reduce criteria pollutant emissions as well as GHG emissions. The improvement to local air quality caused by the reduced criteria pollutant emissions must be calculated to fully evaluate the overall benefits and costs of CGEO S-3-05. In the present study, seven different transportation scenarios that move towards the goals of CGEO S-3-05 in the transportation sector were examined to determine how they would affect future airborne particulate matter (PM_2.5) concentrations in California: (1) hydrogen fuel cells, (2) electric vehicles, (3) high efficiency vehicles, (4) public mass transit, (5) biofuels, (6) biofuels + hybrid electric vehicles, and (7) hydrogen fuel cells + electric vehicles. The air quality implications of each scenario were evaluated using a chemical transport model applied during a wintertime stagnation episode representing future climate in California. Scenarios (6) and (7) reduced population-weighted PM_2.5 mass concentrations by ~9 % and PM_2.5 elemental carbon (EC) concentrations by ~30 % relative to base-case predictions.  相似文献   

10Be content in clasts from fallout suevitic breccia in drill cores from the Bosumtwi impact crater,Ghana: Clues to preimpact target distribution     

Anna Losiak  Eva Maria Wild  Leonard Michlmayr  Christian Koeberl 《Meteoritics & planetary science》2014,49(3):394-411

Rocks from drill cores LB‐07A (crater fill) and LB‐08A (central uplift) into the Bosumtwi impact crater, Ghana, were analyzed for the presence of the cosmogenic radionuclide ¹⁰Be. The aim of the study was to determine the extent to which target rocks of various depths were mixed during the formation of the crater‐filling breccia, and also to detect meteoric water infiltration within the impactite layer. ¹⁰Be abundances above background were found in two (out of 24) samples from the LB‐07A core, and in none of five samples from the LB‐08A core. After excluding other possible explanations for an elevated ¹⁰Be signal, we conclude that it is most probably due to a preimpact origin of those clasts from target rocks close to the surface. Our results suggest that in‐crater breccias were well mixed during the impact cratering process. In addition, the lack of a ¹⁰Be signal within the rocks located very close to the lake sediment–impactite boundary suggests that infiltration of meteoric water below the postimpact crater floor was limited. This may suggest that the infiltration of the meteoric water within the crater takes place not through the aerial pore‐space, but rather through a localized system of fractures.  相似文献   

The Type IIn supernova 1994W: evidence for the explosive ejection of a circumstellar envelope     

Nikolai N. Chugai  Sergei I. Blinnikov  Robert J. Cumming  Peter Lundqvist  Angela Bragaglia  Alexei V. Filippenko  Douglas C. Leonard  Thomas Matheson  Jesper Sollerman 《Monthly notices of the Royal Astronomical Society》2004,352(4):1213-1231

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Hydrogeologic controls on summer stream temperatures in the McKenzie River basin,Oregon     

Christina Tague  Michael Farrell  Gordon Grant  Sarah Lewis  Serge Rey 《水文研究》2007,21(24):3288-3300

Stream temperature is a complex function of energy inputs including solar radiation and latent and sensible heat transfer. In streams where groundwater inputs are significant, energy input through advection can also be an important control on stream temperature. For an individual stream reach, models of stream temperature can take advantage of direct measurement or estimation of these energy inputs for a given river channel environment. Understanding spatial patterns of stream temperature at a landscape scale requires predicting how this environment varies through space, and under different atmospheric conditions. At the landscape scale, air temperature is often used as a surrogate for the dominant controls on stream temperature. In this study we show that, in regions where groundwater inputs are key controls and the degree of groundwater input varies in space, air temperature alone is unlikely to explain within-landscape stream temperature patterns. We illustrate how a geologic template can offer insight into landscape-scale patterns of stream temperature and its predictability from air temperature relationships. We focus on variation in stream temperature within headwater streams within the McKenzie River basin in western Oregon. In this region, as in other areas of the Pacific Northwest, fish sensitivity to summer stream temperatures continues to be a pressing environmental issue. We show that, within the McKenzie, streams which are sourced from deeper groundwater reservoirs versus shallow subsurface flow systems have distinct summer temperature regimes. Groundwater streams are colder, less variable and less sensitive to air temperature variation. We use these results from the western Oregon Cascade hydroclimatic regime to illustrate a conceptual framework for developing regional-scale indicators of stream temperature variation that considers the underlying geologic controls on spatial variation, and the relative roles played by energy and water inputs. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

INTELLECTUAL COHERENCE AND THE FOUNDATIONS OF GEOGRAPHY     

Leonard Guelke 《The Professional geographer》1989,41(2):123-130

The discipline of geography needs a more clearly defined academic purpose if it is to retain and enhance its position as an essential university subject. The discipline lacks the intellectual coherence it once achieved on the basis of environmental determinism. Geographers could re-establish a coherent intellectual foundation for geography by adopting a historical-intellectual mode of enquiry focusing on human thought and ideas and re-emphasizing the central importance of the human-environment relationship as the foundation of the discipline. An understanding of human activity in the environment in relation to ideas could provide a clearer focus for the discipline of geography and give it a stronger intellectual identity.  相似文献   

Delgada Fan: Preliminary interpretation of channel development     

William R. Normark  Christina E. Gutmacher 《Geo-Marine Letters》1984,3(2-4):79-83

The Delgada Fan, an irregularly shaped turbidite deposit extending more than 350 km offshore from northern California, consists of two large leveed-valley units each fed by a separate complex of coalescing submarine canyons and slope gullies. Although the leveed-valley units head within 25 km of each other, both appear to have developed independently during fan growth. The larger southern leveed-valley system has not developed middle-fan distributary channels and appears to illustrate a period of progressive valley abandonment. Although the lower-fan area is underlain by sandy sediments, little sand has been recovered in piston cores from the leveed-valley unit. Margin setting represents fan and/or source area  相似文献