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41.
The predatory pliosaurs were among the largest creatures ever to inhabit the oceans, some reaching gigantic proportions greater
than 15 m in length. Fossils of this subclade of plesiosaurs are known from sediments all over the world, ranging in age from
the Hettangian (approximately 198 Myr) to the Turonian (approximately 92 Myr). However, due to a lack of detailed studies
and because only incomplete specimens are usually reported, pliosaur evolution remains poorly understood. In this paper, we
describe the three dimensionally preserved skull of the giant Jurassic pliosaur Rhomaleosaurus cramptoni. The first phylogenetic analysis dedicated to in-group relationships of pliosaurs allows us to hypothesise a number of well-supported
lineages that correlate with marine biogeography and the palaeoecology of these reptiles. Rhomaleosaurids comprised a short-lived
and early diverging lineage within pliosaurs, whose open-water top-predator niche was filled by other pliosaur taxa by the
mid-late Jurassic.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
42.
Wendy Kenyon Gareth Edwards-Jones 《Journal of Environmental Planning and Management》1998,41(4):463-475
Although contingent valuation is widely discussed in the literature as a technique for environmental valuation, it is well recognized that a number of problems are associated with its use. This paper seeks to address two of these problems: the difficulty of externally verifying the results of a CV study; and the choice of an appropriate level of information to provide to respondents. Four sites were evaluated, first by expert ecologists and then by the general public using the CV method. In conducting the CV, six different categories of information were presented to different groups of respondents to test which was most appropriate.The results show that, given an information set consisting of photographic,textual and ecological data, respondents to a CV study were able to rank the four sites in the same order as ecological experts. This may be seen as a form of external verification to the results of the contingent valuation. 相似文献
43.
This article argues that climate change, seen as a socially constructed anticipation of natural disasters and a future-risk that plays out in present politics, is enabling the emergence of new modes of governance in cities of the global south. The article focuses on the process by which the city of Esmeraldas, Ecuador, developed a Climate Change Adaptation and Mitigation Strategy. Within the context of climate change adaptation, Esmeraldas mobilised new discourses, stakeholders, and planning mechanisms to address pre-existing urban planning and development limitations. This discursively enabled the municipality's ongoing governance project by leveraging resources, creating consensus, and informing practice. Climate change adaptation thus became an important mechanism for engaging with local priorities, particularly those of the most vulnerable populations, and for bridging the gap between the formal world of policymaking and the reality of life in the city, which is more often structured by informality. 相似文献
44.
45.
Stef Bokhorst Jarle W. Bjerke Hans Tømmervik Catherine Preece Gareth K. Phoenix 《Ambio》2012,41(3):246-255
Winter climate and snow cover are the important drivers of plant community development in polar regions. However, the impacts of changing winter climate and associated changes in snow regime have received much less attention than changes during summer. Here, we synthesize the results from studies on the impacts of extreme winter weather events on polar heathland and lichen communities. Dwarf shrubs, mosses and soil arthropods were negatively impacted by extreme warming events while lichens showed variable responses to changes in extreme winter weather events. Snow mould formation underneath the snow may contribute to spatial heterogeneity in plant growth, arthropod communities and carbon cycling. Winter snow cover and depth will drive the reported impacts of winter climate change and add to spatial patterns in vegetation heterogeneity. The challenges ahead lie in obtaining better predictions on the snow patterns across the landscape and how these will be altered due to winter climate change. 相似文献
46.
Gwyther CL Jones DL Golyshin PN Edwards-Jones G Williams AP 《Waste management (New York, N.Y.)》2012,32(5):933-938
The EU Animal By-Products Regulations generated the need for novel methods of storage and disposal of dead livestock. Bioreduction prior to rendering or incineration has been proposed as a practical and potentially cost-effective method; however, its biosecurity characteristics need to be elucidated. To address this, Salmonella enterica (serovars Senftenberg and Poona), Enterococcus faecalis, Campylobacter jejuni, Campylobacter coli and a lux-marked strain of Escherichia coli O157 were inoculated into laboratory-scale bioreduction vessels containing sheep carcass constituents. Numbers of all pathogens and the metabolic activity of E. coli O157 decreased significantly within the liquor waste over time, and only E. faecalis remained detectable after 3months. Only very low numbers of Salmonella spp. and E. faecalis were detected in bioaerosols, and only at initial stages of the trial. These results further indicate that bioreduction represents a suitable method of storing and reducing the volume of livestock carcasses prior to ultimate disposal. 相似文献
47.
Gareth K. Phoenix Jonathan R. Leake David J. Read J. Philip Grime John A. Lee 《Water, Air, & Soil Pollution: Focus》2005,4(6):159-167
Semi-natural calcareous and acidic grasslands are known to be sensitive to increased atmospheric N deposition. However, the fate of pollutant N within these systems is unknown. This paper reports on the first studies to determine the fate of added N within a calcareous and an acidic grassland subject to long-term simulated enhanced N deposition. Intact soil/turf cores were removed from field plots treated for six years with enhanced N deposition (ambient +0, +35 and +140 kg N ha?1 year?1). Cores were inserted into lysimeters and output fluxes of N were monitored in detail. Complete N budgets—calculated from the N flux data—showed considerable accumulation of N within the treated grasslands, up to 76% and 38% of pollutant N in the calcareous and acidic grasslands respectively. In the second study, the short-term (21 day) fate of pollutant N was determined by tracing 15N labelled ammonium nitrate (+35 kg N ha?1 year?1) though the acidic and calcareous lysimeters into plant, soil and leachate pools. Up to 91% and 59% of 15N was recovered in soils and vegetation of the calcareous and acidic grasslands respectively, with negligible amounts recovered in soil extractable ammonium and nitrate (<0.3%) and in leachate (<0.02%). This rapid short-term immobilisation of pollutant N supports the long-term accumulation of the element calculated from the N flux study. 相似文献
48.
Gareth K. Phoenix Jonathan R. Leake David J. Read J. Philip Grime John A. Lee 《Water, Air, & Soil Pollution: Focus》2004,4(6):159-167
Semi-natural calcareous and acidic grasslands are known to be sensitive to increased atmospheric N deposition. However, the fate of pollutant N within these systems is unknown. This paper reports on the first studies to determine the fate of added N within a calcareous and an acidic grassland subject to long-term simulated enhanced N deposition. Intact soil/turf cores were removed from field plots treated for six years with enhanced N deposition (ambient +0, +35 and +140 kg N ha–1 year–1). Cores were inserted into lysimeters and output fluxes of N were monitored in detail. Complete N budgets—calculated from the N flux data—showed considerable accumulation of N within the treated grasslands, up to 76% and 38% of pollutant N in the calcareous and acidic grasslands respectively. In the second study, the short-term (21 day) fate of pollutant N was determined by tracing 15N labelled ammonium nitrate (+35 kg N ha–1 year–1) though the acidic and calcareous lysimeters into plant, soil and leachate pools. Up to 91% and 59% of 15N was recovered in soils and vegetation of the calcareous and acidic grasslands respectively, with negligible amounts recovered in soil extractable ammonium and nitrate (<0.3%) and in leachate (<0.02%). This rapid short-term immobilisation of pollutant N supports the long-term accumulation of the element calculated from the N flux study. 相似文献
49.
George Yu. Sofronov Gareth E. Evans Jonathan M. Keith Dirk P. Kroese 《Environmental Modeling and Assessment》2009,14(5):577-584
The genomes of complex organisms, including the human genome, are highly structured. This structure takes the form of segmental
patterns of variation in various properties and may be caused by the division of genomes into regions of distinct function,
by the contingent evolutionary processes that gave rise to genomes, or by a combination of both. Whatever the cause, identifying
the change-points between segments is potentially important, as a means of discovering the functional components of a genome,
understanding the evolutionary processes involved, and fully describing genomic architecture. One property of genomes that
is known to display a segmental pattern of variation is GC content. The GC content of a portion of DNA is the proportion of
GC pairs that it contains. Sharp changes in GC content can be observed in human and other genomes. Such change-points may
be the boundaries of functional elements or may play a structural role. We model genome sequences as a multiple change-point
process, that is, a process in which sequential data are separated into segments by an unknown number of change-points, with
each segment supposed to have been generated by a different process. We consider a Sequential Importance Sampling approach
to change-point modeling using Monte Carlo simulation to find estimates of change-points as well as parameters of the process
on each segment. Numerical experiments illustrate the effectiveness of the approach. We obtain estimates for the locations
of change-points in artificially generated sequences and compare the accuracy of these estimates to those obtained via Markov
chain Monte Carlo and a well-known method, IsoFinder. We also provide examples with real data sets to illustrate the usefulness
of this method. 相似文献
50.