50 resultados para Area and perimeter
Resumo:
Thecamoebians were examined from 71 surface sediment samples collected from 21 lakes and ponds in the Greater Toronto Area to (1) elucidate the controls on faunal distribution in modern lake environments; and (2) to consider the utility of thecamoebians in quantitative studies of water quality change. This area was chosen because it includes a high density of kettle and other lakes which are threatened by urban development and where water quality has deteriorated locally as a result of contaminant inputs, particularly nutrients. Fifty-eight samples yielded statistically significant thecamoebian populations. The most diverse faunas (highest Shannon Diversity Index values) were recorded in lakes beyond the limits of urban development, although the faunas of all lakes showed signs of sub-optimal conditions. The assemblages were divided into five clusters using Q-mode cluster analysis, supported by Detrended Correspondence Analysis. Canonical Correspondence Analysis (CCA) was used to examine species-environment relationships and to explain the observed clusterings. Twenty-four measured environmental variables were considered, including water property attributes (e.g., pH, conductivity, dissolved oxygen), substrate characteristics, sediment-based phosphorus (Olsen P) and 11 environmentally available metals. The thecamoebian assemblages showed a strong association with phosphorus, reflecting the eutrophic status of many of the lakes, and locally to elevated conductivity measurements, which appear to reflect road salt inputs associated with winter de-icing operations. Substrate characteristics, total organic carbon and metal contaminants (particularly Cu and Mg) also influenced the faunas of some samples. A series of partial CCAs show that of the measured variables, sedimentary phosphorus has the largest influence on assemblage distribution, explaining 6.98% (P < 0.002) of the total variance. A transfer function was developed for sedimentary phosphorus (Olsen P) using 58 samples from 15 of the studied lakes. The best performing model was based on weighted averaging with inverse deshrinking (WA Inv, r jack 2= 0.33, RMSEP = 102.65 ppm). This model was applied to a small modern thecamoebian dataset from a eutrophic lake in northern Ontario to predict phosphorus and performed satisfactorily. This preliminary study confirms that thecamoebians have considerable potential as quantitative water quality indicators in urbanising regions, particularly in areas influenced by nutrient inputs and road salts.
Resumo:
The modern stereologic method of vertical sections was applied to the retina as a means of generating unbiased estimates of three-dimensional structure. The method is illustrated with real data on the volume and surface area of the capillary basement membrane from the central retina of the rat. Novel methods of estimating the volume of retina sampled and of creating accurate vertical sections are described. The advantages of using stereologic methods to generate quantitative information on the three-dimensional structure of the retina are discussed and compared to those of previous quantitative methods that provide data on two-dimensional structure only.
Resumo:
This letter reports the statistical characterization and modeling of the indoor radio channel for a mobile wireless personal area network operating at 868 MHz. Line of sight (LOS) and non-LOS conditions were considered for three environments: anechoic chamber, open office area and hallway. Overall, the Nakagami-m cdf best described fading for bodyworn operation in 60% of all measured channels in anechoic chamber and open office area environments. The Nakagami distribution was also found to provide a good description of Rician distributed channels which predominated in the hallway. Multipath played an important role in channel statistics with the mean recorded m value being reduced from 7.8 in the anechoic chamber to 1.3 in both the open office area and hallway.
Resumo:
Using seven strategically placed, time-synchronized bodyworn receivers covering the head, upper front and back torso, and the limbs, we have investigated the effect of user state: stationary or mobile and local environment: anechoic chamber, open office area and hallway upon first and second order statistics for on-body fading channels. Three candidate models were considered: Nakagami, Rice and lognormal. Using maximum likelihood estimation and the Akaike information criterion it was established that the Nakagami-m distribution best described small-scale fading for the majority of on-body channels over all the measurement scenarios. When the user was stationary, Nakagami-m parameters were found to be much greater than 1, irrespective of local surroundings. For mobile channels, Nakagami-m parameters significantly decreased, with channels in the open office area and hallway experiencing the worst fading conditions.
Resumo:
One of the many results of the Global Financial Crisis was the insight that the financial sector is under-taxed compared to other industries. In light of the huge bailouts and continued subsidies for financial institutions that are characterized as too-big-to-fail demands came on the agenda to make finance pay for the mega-crisis it caused. The most prominent examples of such taxes are a Financial Transaction Tax (FTT) and a Financial Activities Tax (FAT). Possible effects of such taxes on the economic constitution and increasingly in particular on the European Single Market have been discussed controversially over the last decades already. Especially with the decision of eleven EU member states to adapt an FTT using the enhanced cooperation procedure a number of additional legal challenges for implementing such a tax have emerged. This paper analyzes how tax measures of indirectly regulating the financial industry differ, what legal challenges they pose, and what their overall contribution would be in making the financial system more stable and resilient. It also analyzes the legal arguments against enhanced cooperation in this area and the legal issues related to the British lawsuit against the Commission’s Directive proposal in the European Court of Justice on grounds of the extra-territoriality application of tax. The paper concludes that the feasibility of an FTT is legally sound and given the FTT’s advantages over a FAT the EU Directive should be implemented as a first step for a European-wide FTT. However, significant uncertainties about its implementation remain at this stage.
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This article examines the role that qualitative methods can play in the study of children's racial attitudes and behaviour. It does this by discussing a number of examples taken from a qualitative, ethnographic study of five- and six-year-old children in an English multi-ethnic, inner-city primary school. The examples are used to highlight the limitations of research that relies solely on quantitative methods and the potential that qualitative methods have for addressing these limitations. Within this context the article contrasts the strengths and weaknesses of qualitative and quantitative methods in the study of children's racial attitudes and identities. The article concludes by arguing that a much more integrated multi-method approach is needed in this area and sets out some of the most effective ways this could be achieved.
Resumo:
Potential explanatory variables often co-vary in studies of species richness. Where topography varies within a survey it is difficult to separate area and habitat-diversity effects. Topographically complex surfaces may contain more species due to increased habitat diversity or as a result of increased area per se. Fractal geometry can be used to adjust species richness estimates to control for increases in area on complex surfaces. Application of fractal techniques to a survey of rocky shores demonstrated an unambiguous area-independent effect of topography on species richness in the Isle of Man. In contrast, variation in species richness in south-west England reflected surface availability alone. Multivariate tests and variation in limpet abundances also demonstrated regional variation in the area-independent effects of topography. Community composition did not vary with increasing surface complexity in south-west England. These results suggest large-scale gradients in the effects of heterogeneity on community processes or demography.
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Much of the interest in promoting sustainable development in planning for the city-region focuses on the apparently inexorable rise in the demand for car travel and the contribution that certain urban forms and land-use relationships can make to reducing energy consumption. Within this context, policy prescription has increasingly favoured a compact city approach with increasing urban residential densities to address the physical separation of daily activities and the resultant dependency on the private car. This paper aims to outline and evaluate recent efforts to integrate land use and transport policy in the Belfast Metropolitan Area in Northern Ireland. Although considerable progress has been made, this paper underlines the extent of existing car dependency in the metropolitan area and prevailing negative attitudes to public transport, and argues that although there is a rhetorical support for the principles of sustainability and the practice of land-use/transportation integration, this is combined with a selective reluctance to embrace local changes in residential environment or in lifestyle preferences which might facilitate such principles.
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This article reports the findings of a mixed-method evaluation of a pilot educational programme undertaken with 6-7 year olds in a sample of primary schools in England with the aim of increasing their awareness of and respect for diversity through theatre, workshops and related teacher-led classroom activities. The qualitative feedback from the teachers involved was extremely positive and encouraging and an analysis of the actual impact of the pilot programme on the children’s attitudes and awareness, using an experimental design, demonstrated some positive effects. In particular, the programme was found to increase the children’s general awareness of diversity and their ability to recognise instances of exclusion. While not a planned objective of the pilot programme, the evaluation also examined whether it had any effects on the children’s attitudes to specific differences, in this particular case racial differences. Interestingly, however, no evidence was found of any change in the children’s racial attitudes. With this in mind the article suggests that there is a need to distinguish between the general and specific effects of such educational programmes. The article considers the implications of this for future work in the area and also stresses the need to undertake more thorough and rigorous evaluations of such initiatives.
Resumo:
We investigate the influence of tube-tube interactions in ropes of (10,10) carbon nanotubes, and find that these effects induce a pseudogap in the density of state (DOS) of the rope of width 0.1 eV at the Fermi level. In an isolated (n,n) carbon nanotube there are two bands that cross in a linear fashion at the Fermi level, making the nanotube metallic with a DOS that is constant in a 1.5 eV wide window around the Fermi energy. The presence of the neighbouring tubes causes these two bands to repel, opening up a band gap that can be as large as 0.3 eV. The small dispersion in the plane perpendicular to the rope smears out this gap for a rope with a large cross-sectional area, and we see a pseudogap at the Fermi energy in the DOS where the DOS falls to one third of its value for the isolated tube. This phenomenon should affect many properties of the behavior of ropes of (n,n) nanotubes, which should display a more semimetallic character than expected in transport and doping experiments, with the existence of both hole and electron carriers leading to qualitatively different thermopower and Hall-effect behaviors from those expected for a normal metal. Band repulsion like this can be expected to occur for any tube perturbed by a sufficiently strong interaction, for example, from contact with a surface or with other tubes.
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This paper describes the results of a review of the housing content of UK General Election 2001 manifestos. Housing policy was of little importance during the election campaign. The main British political parties had, essentially, a shared housing agenda - to promote and facilitate home ownership, support area and community regeneration, tackle homelessness, improve the private rented sector, and prevent building on greenfield sites. Many issues of importance to housing specialists received little or no attention, most notably that of low demand. Some policy variations within the UK were evident, for example in attitudes towards greenfield development, home ownership and stock transfer. The paper concludes that differences in housing policy are emerging within the UK as part of a new politics of devolution and that the days of a single housing policy approach for the UK are over.
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Matrix algorithms are important in many types of applications including image and signal processing. A close examination of the algorithms used in these, and related, applications reveals that many of the fundamental actions involve matrix algorithms such as matrix multiplication. This paper presents an investigation into the design and implementation of different matrix algorithms such as matrix operations, matrix transforms and matrix decompositions using a novel custom coprocessor system for MATrix algorithms based on Reconfigurable Computing (RCMAT). The proposed RCMAT architectures are scalable, modular and require less area and time complexity with reduced latency when compared with existing structures.