921 resultados para Concentration, spatial autocorrelation, local Gini index, Moran and Geary indices, neighbourhood


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The spatial patterns of diffuse, primitive, classic and compact beta-amyloid (Abeta) deposits were studied in the medial temporal lobe in 14 elderly, non-demented patients (ND) and in nine patients with Alzheimer’s disease (AD). In both patient groups, Abeta deposits were clustered and in a number of tissues, a regular periodicity of Abeta deposit clusters was observed parallel to the tissue boundary. The primitive deposit clusters were significantly larger in the AD cases but there were no differences in the sizes of the diffuse and classic deposit clusters between patient groups. In AD, the relationship between Abeta deposit cluster size and density in the tissue was non-linear. This suggested that cluster size increased with increasing Abeta deposit density in some tissues while in others, Abeta deposit density was high but contained within smaller clusters. It was concluded that the formation of large clusters of primitive deposits could be a factor in the development of AD.

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This paper considers whether there has been a shift in the balance between equity and efficiency in respect of decentralised public policy in England since the election of the Conservative / Liberal Democrat coalition in 2010. Drawing on the literature on policy decentralisation and fiscal federalism from both Political Science and Economics, reasons are discussed why a trade-off between equity and efficiency might be expected. The context of English local government then outlined, and consideration is then given to four areas of policy: business rate localisation, the ‘New Homes Bonus’, council tax benefit and social housing, and regional economic development. In each case, some shift in the balance away from concern with equity towards one with efficiency is discerned: whether or not this is desirable will prove a matter of political and moral, as well as scientific judgement.

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This paper introduces a method for the analysis of regional linguistic variation. The method identifies individual and common patterns of spatial clustering in a set of linguistic variables measured over a set of locations based on a combination of three statistical techniques: spatial autocorrelation, factor analysis, and cluster analysis. To demonstrate how to apply this method, it is used to analyze regional variation in the values of 40 continuously measured, high-frequency lexical alternation variables in a 26-million-word corpus of letters to the editor representing 206 cities from across the United States.

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This research focuses on two groups of local companies; namely, high-growth local companies and other local companies, to examine and compare the influence of utilising governmental initiatives, servicing foreign MNCs and internationalisation on their strategic planning process. The theme of this thesis argues that the approach of an organisation towards strategic planning is not only determined by the internal influences; namely, its firm size and the planning behaviour and attitude of an entrepreneur, as revealed in the literature, but it can also be affected by external influences. The theoretical contribution of this research determines this unique situation in Singapore, and tests the robustness of the conventional models of planning in smaller companies. As a result of the external influences, this study reveals that local companies are more likely to undertake a much more formal strategic planning than the conventional Western literature and models would indicate. High-growth local companies, in comparison, however, had undertaken a more formal and rigorous strategic planning process than other local companies.

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The thesis compares two contrasting strategies employed with the aim of combating particular forms of racism within contemporary Britain. Both are assessed as political strategies in their own right and placed within the broader context of reformist and revolutionary political traditions. The sociology of social movements is examined critically, as are Marxist and post-Marxist writings on the role of human agency within social structures and on the nature of social movements. The history of the Anti Nazi League (ANL) in the late 1970s and its opposition to the National Front is considered as an example of anti-racist social movement based on the Trotskyist model of the United Front. The degree to which the Anti Nazi League corresponded to such a model is analysed as are the potential broader applications for such a strategy. The strategy with which the ANL is compared is the development of anti-racist and equal opportunities policies within local government in the 1980s, primarily by Labour-controlled local authorities. The theory of the local state and the political phenomenon of municipal socialism are discussed, specifically the role of various groups operating in and around local authorities in the formation and implementation of anti-racist policy and practice. Following this general discussion, two case studies in each of the areas of local authority housing, education and employment are explored to consider in depth the problems of specific anti-racist policies. In summation the efficacy of the two strategies are considered as parts of wider political currents in tandem with their declared specific objectives.

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This thesis describes an investigation into a Local Authority's desire to use its airport to aid regional economic growth. Short studies on air freight. the impact of an airport on the local economy, incoming tourism. and the factors influencing airlines in their use of airports, show that this desire is valid. but only in so far as the airport enables air services to be provided. A survey of airlines. conducted to remedy some deficiencies in the documented knowledge on airline decision-making criteria. indicates that there is cause for concern about the methods used to develop air services. A comparison with the West German network suggests that Birmingham is underprovided with international scheduled flights, and reinforces the survey conclusion that an airport authority must become actively involved in the development of air services. Participation in the licence applications of two airlines to use Birmingham Airport confirms the need for involvement but without showing the extent of the influence which an airport authority may exert. The conclusion is reached that in order to fulfill its development potential, an airport must be marketed to both the general public and the air transport industry. There is also a need for a national air services plan.

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The aim of this work was to investigate human contrast perception at various contrast levels ranging from detection threshold to suprathreshold levels by using psychophysical techniques. The work consists of two major parts. The first part deals with contrast matching, and the second part deals with contrast discrimination. Contrast matching technique was used to determine when the perceived contrasts of different stimuli were equal. The effects of spatial frequency, stimulus area, image complexity and chromatic contrast on contrast detection thresholds and matches were studied. These factors influenced detection thresholds and perceived contrast at low contrast levels. However, at suprathreshold contrast levels perceived contrast became directly proportional to the physical contrast of the stimulus and almost independent of factors affecting detection thresholds. Contrast discrimination was studied by measuring contrast increment thresholds which indicate the smallest detectable contrast difference. The effects of stimulus area, external spatial image noise and retinal illuminance were studied. The above factors affected contrast detection thresholds and increment thresholds measured at low contrast levels. At high contrast levels, contrast increment thresholds became very similar so that the effect of these factors decreased. Human contrast perception was modelled by regarding the visual system as a simple image processing system. A visual signal is first low-pass filtered by the ocular optics. This is followed by spatial high-pass filtering by the neural visual pathways, and addition of internal neural noise. Detection is mediated by a local matched filter which is a weighted replica of the stimulus whose sampling efficiency decreases with increasing stimulus area and complexity. According to the model, the signals to be compared in a contrast matching task are first transferred through the early image processing stages mentioned above. Then they are filtered by a restoring transfer function which compensates for the low-level filtering and limited spatial integration at high contrast levels. Perceived contrasts of the stimuli are equal when the restored responses to the stimuli are equal. According to the model, the signals to be discriminated in a contrast discrimination task first go through the early image processing stages, after which signal dependent noise is added to the matched filter responses. The decision made by the human brain is based on the comparison between the responses of the matched filters to the stimuli, and the accuracy of the decision is limited by pre- and post-filter noises. The model for human contrast perception could accurately describe the results of contrast matching and discrimination in various conditions.

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The main aim of this work was two fold, firstly to investigate the effect of a highly reactive comonomer, divinylbenzene (DVB), on the extent of melt grafting of glycidyl methacrylate (GMA) on ethylene-propylene rubber (EPR) using 2,5-dimethyl-2,5-bis-(tert-butyl peroxy) hexane (Trigon ox 101, Tl 01) as a free radical initiator, and to compare the results with a conventional grafting of the same monomer on EPR. To achieve this, the effect of processing conditions and chemical composition including the concentration of peroxide, GMA and DVB on the extent of grafting was investigated. The presence of the comonomer (DVB) in the grafting process resulted in a significant increase in the extent of the grafting using only a small concentration of peroxide. It was also found that the extent of grafting increased drastically with increasing the DVB concentration. Interestingly, in the comonomer system, the extent of the undesired side reaction, normally the homopolymerisation of GMA (polyGMA) was shown to have reduced tremendously and in most cases the level of polyGMA was immeasurable in the samples. Compared to a conventional EPR-g-GMACONV (in the absence of a comonomer), the presence of the comonomer DVB in the grafting system was shown to result in more branching and crosslinking (shown from an increase in melt flow index (MFI) and torque values) and this was paralleled by an increase in DVB concentration. In contrast, the extent of grafting in conventional system increased with increasing the peroxide concentration but the level of grafting was much lower than in the case of DVB. Homopolymerisation of GMA and excessive crosslinking of EPR became dominant at high peroxide concentration and this. reflects that the side reactions were favorable in the conventional grafting system. The second aim was to examine the effect of the in-situ functionalised EPR when used as a compatibiliser for binary blends. It was found that blending PET with functionalised EPR (ƒ-EPR) gave a significant improvement in terms of blend morphology as well as mechanical properties. The results showed clearly that, blending PET with ƒ-EPRDVB (prepared with DVB) was much more effective compared to the corresponding PET/ƒ-EPRCONV (without DVB) blends in which ƒ-EPRDVB having optimum grafting level of 2.1 wt% gave the most pronounced effect on the morphology and mechanical properties. On the other hand, blends of PET/ƒ-EPRDVB containing high GMA/DVB ratio was found to be unfavorable hence exhibited lower tensile properties and showed unfavorable morphology. The presence of high polyGMA concentration in ƒ-EPRCONV was found to create damaging effect on its morphology, hence resulting in reduced tensile properties (e.g. low elongation at break). However, the use of commercial terpolymers based on ethylene-methacrylate-glycidyl methacrylate (EM-GMA)or a copolymer of ethylene-glycidyl methacrylate (E-GMA) containing various GMA levels as compatibilisers in PET/EPR blends was found to be more efficient compared to PET/EPR/ƒ-EPR blends with the former blends showing finer morphology and high elongation at break. The high efficiency of the terpolymers or copolymers in compatibilising the PET/EPR blends is suggested to be partly, higher GMA content compared to the amount in ƒ-EPR and due to its low viscosity.

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In this letter, we present a standard linear cavity fiber laser incorporating a microchannel for refractive index (RI) and temperature sensing. The microchannel of ~6µm width created by femtosecond laser aided chemical etching provides an access to the external liquid; therefore, the laser cavity loss changes with the liquids of different RIs. Thus, at a fixed pump power, the output laser power will vary with the change of RI in the microchannel. The results show that the proposed sensing system has a linear response to both the surrounding medium RI and temperature. The RI sensitivity of the laser system is on the order of 10-3, while the temperature sensitivity is about 0.02 C. Both sensitivities could be further enhanced by employing a more sensitive photodetector and using higher pump power.

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In order to gain a greater understanding of firms' 'environmental behaviour' this paper explores the factors that influence firms' emissions intensities and provides the first analysis of the determinants of firm level carbon dioxide (CO2) emissions. Focussing on Japan, the paper also examines whether firms' CO2 emissions are influenced by the emissions of neighbouring firms and other possible sources of spatial correlation. Results suggest that size, the capital-labour ratio, R&D expenditure, the extent of exports and concern for public profile are the key determinants of CO2 emissions. Local lobbying pressure, as captured by regional community characteristics, does not appear to play a role, however emissions are found to be spatially correlated. This raises implications for the manner in which the environmental performance of firms is modelled in future. © 2013 Elsevier Inc.

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Thus far, achieving net biodiversity gains through major urban developments has been neither common nor straightforward - despite the presence of incentives, regulatory contexts, and ubiquitous practical guidance tools. A diverse set of obstructions, occurring within different spatial, temporal and actor hierarchies, are experienced by practitioners and render the realisation of maximised biodiversity, a rarity. This research aims to illuminate why this is so, and what needs to be changed to rectify the situation. To determine meaningful findings and conclusions, capable of assisting applied contexts and accommodating a diverse range of influences, a ‘systems approach’ was adopted. This approach led to the use of a multi-strategy research methodology, to identify the key obstructions and solutions to protecting and enhancing biodiversity - incorporating the following methods: action research, a questionnaire to local government ecologists, interviews and personal communications with leading players, and literature reviews. Nevertheless, ‘case studies’ are the predominant research method, the focus being a ‘nested’ case study looking at strategic issues of the largest regeneration area in Europe ‘the Thames Gateway’, and the largest individual mixeduse mega-development in the UK (at the time of planning consent) ‘Eastern Quarry 2’ - set within the Gateway. A further key case study, focussing on the Central Riverside development in Sheffield, identifies the merits of competition and partnership. The nested cases, theories and findings show that the strategic scale - generally relating to governance and prioritisation - impacts heavily upon individual development sites. It also enables the identification of various processes, mechanisms and issues at play on the individual development sites, which primarily relate to project management, planning processes, skills and transdisciplinary working, innovative urban biodiversity design capabilities, incentives, organisational cultures, and socio-ecological resilience. From these findings a way forward is mapped, spanning aspects from strategic governance to detailed project management.

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We re-analysed visuo-spatial perspective taking data from Kessler and Thomson (2010) plus a previously unpublished pilot with respect to individual- and sex differences in embodied processing (defined as body-posture congruence effects). We found that so-called 'systemisers' (males/low-social-skills) showed weaker embodiment than so-called 'embodiers' (females/high-social-skills). We conclude that 'systemisers' either have difficulties with embodied processing or, alternatively, they have a strategic advantage in selecting different mechanisms or the appropriate level of embodiment. In contrast, 'embodiers' have an advantageous strategy of "deep" embodied processing reflecting their urge to empathise or, alternatively, less flexibility in fine-tuning the involvement of bodily representations. © 2012 Copyright Taylor and Francis Group, LLC.

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This paper analyses the context and use of risk management in local authorities in England and Australia. The basic structures of risk management were found to be common across all four local authorities in both countries. However, substantial differences were found in the national context in which risk management was used. The national context in each country was compared, and a large and small local authority in each country was used for illustrative purposes. The research findings were tested against institutional, contingency, resource dependence, and political perspectives. The research finding is that each theory was necessary but not sufficient and a pluralist approach was formulated to explain the similarities and differences in risk management in local authorities across two countries.

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We have studied a series of samples of bovine serum albumin (BSA) solutions with protein concentration, c, ranging from 2 to 500 mg/mL and ionic strength, I, from 0 to 2 M by small-angle X-ray scattering (SAXS). The scattering intensity distribution was compared to simulations using an oblate ellipsoid form factor with radii of 17 x 42 x 42 A, combined with either a screened Coulomb, repulsive structure factor, S-SC(q), or an attractive square-well structure factor, S-SW(q). At pH = 7, BSA is negatively charged. At low ionic strength, I <0.3 M, the total interaction exhibits a decrease of the repulsive interaction when compared to the salt-free solution, as the net surface charge is screened, and the data can be fitted by assuming an ellipsoid form factor and screened Coulomb interaction. At moderate ionic strength (0.3-0.5 M), the interaction is rather weak, and a hard-sphere structure factor has been used to simulate the data with a higher volume fraction. Upon further increase of the ionic strength (I >= 1.0 M), the overall interaction potential was dominated by an additional attractive potential, and the data could be successfully fitted by an ellipsoid form factor and a square-well potential model. The fit parameters, well depth and well width, indicate that the attractive potential caused by a high salt concentration is weak and long-ranged. Although the long-range, attractive potential dominated the protein interaction, no gelation or precipitation was observed in any of the samples. This is explained by the increase of a short-range, repulsive interaction between protein molecules by forming a hydration layer with increasing salt concentration. The competition between long-range, attractive and short-range, repulsive interactions accounted for the stability of concentrated BSA solution at high ionic strength.

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The local image representation produced by early stages of visual analysis is uninformative regarding spatially extensive textures and surfaces. We know little about the cortical algorithm used to combine local information over space, and still less about the area over which it can operate. But such operations are vital to support perception of real-world objects and scenes. Here, we deploy a novel reverse-correlation technique to measure the extent of spatial pooling for target regions of different areas placed either in the central visual field, or more peripherally. Stimuli were large arrays of micropatterns, with their contrasts perturbed individually on an interval-by-interval basis. By comparing trial-by-trial observer responses with the predictions of computational models, we show that substantial regions (up to 13 carrier cycles) of a stimulus can be monitored in parallel by summing contrast over area. This summing strategy is very different from the more widely assumed signal selection strategy (a MAX operation), and suggests that neural mechanisms representing extensive visual textures can be recruited by attention. We also demonstrate that template resolution is much less precise in the parafovea than in the fovea, consistent with recent accounts of crowding. © 2014 The Authors.