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71.
72.
D. Heath Jones Mike A. Read Will Saunders Matthew Colless Tom Jarrett Quentin A. Parker Anthony P. Fairall † Thomas Mauch Elaine M. Sadler Fred G. Watson Donna Burton Lachlan A. Campbell Paul Cass Scott M. Croom John Dawe † Kristin Fiegert Leela Frankcombe Malcolm Hartley John Huchra Dionne James Emma Kirby Ofer Lahav John Lucey Gary A. Mamon Lesa Moore Bruce A. Peterson Sayuri Prior Dominique Proust Ken Russell Vicky Safouris Ken-ichi Wakamatsu Eduard Westra Mary Williams 《Monthly notices of the Royal Astronomical Society》2009,399(2):683-698
We report the final redshift release of the 6dF Galaxy Survey (6dFGS), a combined redshift and peculiar velocity survey over the southern sky (| b | > 10°) . Its 136 304 spectra have yielded 110 256 new extragalactic redshifts and a new catalogue of 125 071 galaxies making near-complete samples with ( K , H , J , r F , b J ) ≤ (12.65, 12.95, 13.75, 15.60, 16.75) . The median redshift of the survey is 0.053. Survey data, including images, spectra, photometry and redshifts, are available through an online data base. We describe changes to the information in the data base since earlier interim data releases. Future releases will include velocity dispersions, distances and peculiar velocities for the brightest early-type galaxies, comprising about 10 per cent of the sample. Here we provide redshift maps of the southern local Universe with z ≤ 0.1 , showing nearby large-scale structures in hitherto unseen detail. A number of regions known previously to have a paucity of galaxies are confirmed as significantly underdense regions. The URL of the 6dFGS data base is http://www-wfau.roe.ac.uk/6dFGS . 相似文献
73.
An intense environmental dispute surrounds the maize-fields of Mexico. Mexican maize traditional varieties (or ‘landraces’) constitute a global genetic resource that may well be critical to future agricultural development and corn breeding. Many environmentalists, farmers, and consumers in Mexico are therefore concerned that their maize landraces may have been ‘contaminated’ by imported transgenic maize, grown in the USA. The criticisms of this transgenic technology are complex and call into question the nature of the boundary between political and ecological (i.e. scientific) disputes. Our paper surveys these criticisms, and this political-scientific boundary, in a three-part analysis. First, we turn to Gramsci’s notes on science from his eleventh prison notebook to rethink the political ecology of transgenic maize, i.e., the way the ecological analysis of transgenic introgression is treated as politics. Second, we present the multiple criticisms of transgenic maize as scalar phenomena. Third, we review the recent scientific literature on transgene introgression to evaluate recent calls for the ‘decontamination’ of Mexican maize. Our reading illustrates two dilemmas facing the group that occupies the hegemonic subject-position in this dispute, ecological scientists. First, the popular desire to ‘decontaminate’ Mexican maize exceeds their capacities (due to complications involved with sampling). Second, although the political debate surrounding ‘contaminated’ Mexican maize exceeds science, the boundary between the dispute’s scientific and parascientific elements cannot be adjudicated scientifically. In other words, the boundary between science and politics is porous. Thus in two respects the dispute is ecological, yet beyond the capacity of this science to resolve. Yet, following Gramsci, these findings should not lead us to see science as mere ideology, or apolitical, or encourage a retreat into metaphysics. Rather it points to the need for a social transformation that sees science as “humanity forging its methods of research … in other words, culture, the conception of the world.” By exploring the dilemmas of decontamination, the dispute over transgene introgression in Mexican maize-fields provides an opportunity to elaborate upon Gramsci’s neglected insights into the politics of science. 相似文献
74.
Joyce Maschinski Michael S. Ross Hong Liu Joe O��Brien Eric J. von Wettberg Kristin E. Haskins 《Climatic change》2011,107(1-2):147-167
Low-elevation islands face threats from sea level rise (SLR) and increased storm intensity. Evidence of endangered species?? population declines and shifts in vegetation communities are already underway in the Florida Keys. SLR predictions indicate large areas of these habitats may be eliminated in the next century. Using the Florida Keys as a model system, we present a process for evaluating conservation options for rare and endemic taxa. Considering species characteristics and habitat, we assess central issues that influence conservation options. We contrast traditional and controversial options for two animal and two plant species giving special emphasis to perceptions of ecological risk and safety from SLR and suggest courses of action. Multiple strategies will be required to spread extinction risk and will be effective for different time periods. Global climate change presents an uncertain, perhaps no-analog future that will challenge land managers and practitioners to re-evaluate equilibrium-state-conceived laws and policies not only for these taxa, but for many facing similar threats. To embrace conservation in a changing world will require a new dialogue that includes controversial ideas, a review of existing laws and policies, and preparation for the oncoming change. 相似文献
75.
Homogeneous, nonrotating flow over a backward-facing rounded step is simulated using the 2D vertical version of two general
circulation models, a z-coordinate model—the Massachusetts Institute of Technology general circulation model (MITgcm)—and a σ-coordinate model—the Bergen Ocean Model (BOM). The backward-facing step is a well-known testcase since it is geometrically
simple but still embodies important flow characteristics such as separation point, reattachment length, and recirculation
of the flow. The study compares the core of the two models and uses constant eddy viscosities and diffusivities. The Reynolds
numbers ranges from 2·102 to 2·106. The results correspond with previously published results having a relatively stationary separation point and a fluctuating
reattachment length due to downslope propagating eddies released from the reattachment zone for Reynolds numbers higher than
or equal to 2 · 104. For Reynolds number within the laminar regime, the flow is stationary. The discrepancies between the models increase by
enhancing Reynolds numbers. The σ-coordinate model experiences a reduction in eddy sizes with increasing resolution and Reynolds numbers in correspondence
with published experiments, while the size of the eddies are independent of the Reynolds number using the MITgcm. Due to mixing
generated by the staircase topography, the z-coordinate model gives a better convergence of the separation point and reattachment length compared with the BOM; however,
this conclusion might change with the inclusion of a relevant turbulence scheme. 相似文献
76.
A systems dynamics model was developed to assess the planetary boundary for P supply in relation to use by human society. It is concluded that present day use rates and poor recycling rates of P are unsustainable at timescales beyond 100+ a. The predictions made suggest that P will become a scarce and expensive material in the future. The study shows clearly that market mechanisms alone will not be able to secure an efficient use before a large part of the resource will have been allowed to dissipate into the natural environment. It is suggested that population size management and effective recycling measures must be planned long term to avoid unpleasant consequences of hunger and necessary corrections imposed on society by mass balance and thermodynamics. 相似文献
77.
Donald P. Hauber Kristin Saltonstall David A. White Craig S. Hood 《Estuaries and Coasts》2011,34(4):851-862
Multiple introductions are believed to play an important role in increasing genetic diversity and adaptability of invasive
species, but there are few well-documented examples. The common reed, Phragmites australis, has dramatically increased in tidal wetlands throughout the USA in the past century due primarily to the introduction of
a Eurasian lineage. In the Mississippi River “Balize” delta, P. australis is the dominant vegetation where monotypic stands of an introduced form blanket the outer marshes. The delta’s interior marshes,
on the other hand, are more vegetatively diverse, serving as important waterfowl foraging habitat. Recent encroachment by
various phenotypic forms of P. australis into the interior marshes led to this study examining genetic variation in these stands. Our results revealed four chloroplast
DNA haplotypes that also segregate based on microsatellite variation. Three of these are closely related and introduced, but
differ relative to time and likely mode of introduction. The “Delta” type (haplotype M1), which is unique to the region and
the most common lineage, displays considerable microsatellite diversity. The Eurasian introduced lineage of P. australis (haplotype M), which is invasive elsewhere in North America, is increasing its distribution in the delta. A novel haplotype,
AD, was also identified which is phenotypically and genetically similar to haplotype M. Despite the close relatedness, we
found no evidence for inter-haplotype gene exchange at the nuclear level, suggesting that intraspecific hybridization is not
a contributing factor to these invasions. The site provides a unique opportunity for researchers to understand the dynamics
of multiple P. australis invasions. 相似文献
78.
Kristin Stock Vera Karasova Anne Robertson Guillaume Roger Mark Small Mohamed Bishr Jens Ortmann Tim Stojanovic Femke Reitsma Lukasz Korczynski Boyan Brodaric Zoe Gardner 《Transactions in GIS》2013,17(4):612-639
Current approaches to the discovery of scientific resources (publications, data sets and web services) are dominated by keyword search. These approaches do not allow scientists to search on the deeper semantics of scientific resources, or to discover resources on the basis of the scientific approaches taken. This article evaluates a user interface that allows users to discover scientific resources through structured knowledge in the form of ontologies describing the domain and the scientific knowledge inherent within the scientific resource, and also through informal user tags. These combined capabilities provide scientists with new and powerful options for resource discovery. A qualitative user evaluation explored how scientists felt about the approach for resource discovery in the context of their scientific work. The study showed that marine scientists were enthusiastic about the capabilities of such an approach and appreciated the ability to browse the visual structure of the knowledge and query on scientific method but, overall, preferred the use of tags over ontologies. The exploratory nature of the user study was used to identify future directions for such improvements. 相似文献
79.
Kristin M. Stock Rob Atkinson Chris Higgins Mark Small Andrew Woolf Keiran Millard 《International journal of geographical information science》2013,27(2):231-252
The use of a semantically rich registry containing a Feature Type Catalogue (FTC) to represent the semantics of geographic feature types including operations, attributes and relationships between feature types is required to realise the benefits of Spatial Data Infrastructures (SDIs). Specifically, such information provides a more complete representation of the semantics of the concepts used in the SDI, and enables advanced navigation, discovery and utilisation of discovered resources. The presented approach creates an FTC implementation in which attributes, associations and operations for a given feature type are encapsulated within the FTC, and these conceptual representations are separated from the implementation aspects of the web services that may realise the operations in the FTC. This differs from previous approaches that combine the implementation and conceptual aspects of behaviour in a web service ontology, but separate the behavioural aspects from the static aspects of the semantics of the concept or feature type. These principles are demonstrated by the implementation of such a registry using open standards. The ebXML Registry Information Model (ebRIM) was used to incorporate the FTC described in ISO 19110 by extending the Open Geospatial Consortium ebRIM Profile for the Web Catalogue Service (CSW) and adding a number of stored queries to allow the FTC component of the standards‐compliant registry to be interrogated. The registry was populated with feature types from the marine domain, incorporating objects that conform to both the object and field views of the world. The implemented registry demonstrates the benefits of inheritance of feature type operations, attributes and associations, the ability to navigate around the FTC and the advantages of separating the conceptual from the implementation aspects of the FTC. Further work is required to formalise the model and include axioms to allow enhanced semantic expressiveness and the development of reasoning capabilities. 相似文献
80.