A polimerização de monômeros vinílicos fotoiniciada por corantes foi estudada em diferentes meios (meio orgânico, ausência de solvente e meio hidrotrópico). A polimerização fotoiniciada do MMA pelo corante Vermelho Neutro na presença de trietilamina foi estudada com o objetivo de se determinar o mecanismo que leva à formação dos radicais iniciadores. Uma expressão para o rendimento de radicais livres foi deduzida a partir do mecanismo proposto, os valores experimentais para o equilíbrio e as constantes de reação para os estados fundamental, singlete e triplete do corante na presença de outras espécies e de trietilamina (co-iniciador) foram utilizadas para simular o comportamento do sistema de polimerização. A amina aromática 4-anisidina também foi utilizada como coiniciador. As cinéticas de fotopolimerização de monômeros multifuncionais foram acompanhadas com as técnicas de Fotocalorimetria Diferencial de Varredura (Foto-DSC) e Espectroscopia de Infravermelho por Transformada de Fourier em Tempo Real (RT-FTIR). Os iniciadores utilizados foram os corantes safranina e tioxantona. Os co-iniciadores usados foram as aminas TEA, TEOHA e EDB. Todos os sistemas foram estudados na ausência de solvente. Filmes poliméricos foram preparados para verificar a absorção de clorofórmio mediante a técnica de gravimetria. Tal estudo avaliou a relação entre a densidade de entrecruzamento dos polímeros e o fotoiniciador utilizado. Copolímeros de ESS e MMA ou HEMA foram preparados em meio hidrotrópico por polimerização fotoiniciada utilizando o corante catiônico safranina. A concentração de ESS utilizada foi de 0,5 M, pois nessa concentração há a formação de agregados de ESS, caracterizando o meio como hidrotrópico. As polimerizações dos monômeros MMA (hidrofóbico) e HEMA (hidrofílico) apresentaram comportamentos distintos frente ao meio hidrotrópico. / The photoinitiation of the polymerization of methyl methacrylate by the dye neutral red in the presence of thiethylamine was studied in order to determine the mechanism that leads to the formation of the initiating radicals. An expression for the yield of free radicals was deduced from the mechanism, and the experimental values for the equilibrium and reaction constants of the ground, singlet and triplet states of the dye in the presence of the other components of the formulation, were used to calculat the behaviour of the system when varying the concentration of the co-initiator triethylamine. The observed dependence fits closely the global polymerization rates obtained directly from polymerization kinetics studied by dilatometry. The amine 4-anisidine has also been used as co-initiator. The photoinitiated polymerization of multifunctional monomers was followed by real time infrared spectroscopy (RTIR) and by photo differential scanning calorimeter (Photo- DSC). Several parameters influence this kinetic such as temperature, photoinitiator concentration, light intensity, polymerizable function concentration, and material thickness. The initiators used in this study were the dyes safranine and thioxanthone. The co-initiators used were the amines TEA, TEOHA and EDB. The swelling of films of these copolymers were determined by chloroform absorption. A good inverse relationship was found between the swelling and the polymerization rates. Copolymers of styrenesulfonate and methyl methacrylate, or hydroxyethyl methacrylate, were prepared by photoinitiation polymerization using the cationic dye Safranine in hydrotropic medium. The reactions were be carried out at Stys concentrations higher than the MHC (minimum hydrotrope concentration) where the monomer forms aggregates.

O destaque alcançado por um grupo significativo de cidades do interior do estado de São Paulo, que nas últimas décadas só foi mais reforçado pelo dinamismo econômico, evidenciou os aspectos que as projetam como pólos regionais. Nesse grupo de cidades ressalta-se a extrema urbanização, em muitas delas uma avançada conurbação com as vizinhas. Surgem aglomerações, que vão de 500 mil a mais de dois milhões de habitantes, formando uma rede de cidades que lideram o segundo maior mercado consumidor brasileiro. A atividade industrial crescente, a geração de empregos, o conseqüente crescimento demográfico e o espraiamento urbano, deram a essas cidades características de organização espacial muito própria e um sistema viário que não acompanhou esse crescimento, mais expressivo do que os das grandes capitais. Contudo, um elemento está presente em todas essas cidades e constitui um rico patrimônio histórico e, talvez, estratégico em seus futuros: a ferrovia. Nas dez maiores cidades do interior paulista, a presença marcante da velha estação e da linha férrea, que as cruzam e as dividem, são as heranças do processo de desmantelamento e total abandono da função ferroviária de transporte de passageiros de longo percurso. Quase sempre relegadas a funções acessórias no planejamento urbano, a ferrovia também esteve distante, encerrada entre seus muros, mantendo o diálogo com as cidades embaraçado ao longo do tempo. Essa pesquisa se propôs a fazer um levantamento geral desses patrimônios ferroviários, identificar suas interfaces atuais com o meio urbano, os novos agentes envolvidos na sua exploração e, principalmente, a visão e os usos pretendidos pelos municípios para as faixas ferroviárias e suas áreas lindeiras. Buscando amparo nas evoluções históricas, na análise de influências recíprocas e nas relações entre transporte e urbanismo, questiona-se a presença dos trilhos nessas áreas intensamente urbanizadas e são expostas as relações institucionais que devem ser consideradas para planejar e viabilizar o seu aproveitamento, seja pela implantação de novos equipamentos urbanos, pelo uso compartilhado de transportes ou mesmo pela sua erradicação. / A large number of relevant cities in the countryside of São Paulo state has recently faced a remarkable distinction brought by a high economical dinamism in these regional poles during the last decades. These cities already have extreme urbanization rates and they are getting aglomerated, creating new metropolitan areas, with a huge population that is responsible for Brazil´s second largest consuming market. The increasing industrial activity and the offers of new jobs have both stimulated the spreading of its urbanized areas that are not always followed by enough new transportation infra structures. However, one element is very present in any of these cities and it stands for rich historical assets: the old railway. Inside any medium size São Paulo´s city in, the prominent station and the rail tracks still divide the urban center, instersecting its streets and being source of many conflicts and accidents. Nowadays, those abandoned structures are the inheritahe of passenger rail transportation, which was completely dismantled after freight rail transports privatizations. Specially inside the cities, not only the railways were continualy limited to secondary functions in all urban planning process, but the urban transportation was never taken as a priority for rail administration either. This research aimed to build a general view of railway equipments and structures of ten cities, identify possible interfaces with their urban areas, identify the agents envolved in its exploitation and mainly identify what the local expectations to the railways are. The analysis was done based on historical evolution of railways and cities, by the influence of transportation infra structure on territories. Urbanism and public transport organization notions were considered as well, in order to identify the needs and ways on what kind of railway would contribute or would be more profitable in new urban functions.

Abstract Wireless sensor networks (WSNs) offer us a potential for greater awareness of our surroundings, collecting, measuring, and aggregating parameters beyond our current abilities, and provide an opportunity to enrich our experience through context-awareness. As a typical sensor node is small with limited processing power, memory, and energy resources, in particular, these WSNs must be very energy-efficient for practical deployment. Medium access control (MAC) protocols are central to the energy-efficiency objective of WSNs, as they directly control the most energy consuming part of a sensor node: communications over the shared medium. This thesis focuses on evaluating MAC protocols within the WSN domain by, firstly, surveying a representative number of MAC protocols and their features. Secondly, three novel MAC protocols are proposed, one for layered contention-based access, one for layered scheduled access, and one for cross-layer contention-based access. Thirdly, a novel energy consumption model is proposed, and fourthly, a holistic MAC protocol evaluation model is proposed that takes into account application emphasis on performance metrics. The MAC protocols are evaluated analytically. In addition, the layered contention-based MAC protocol has been implemented and measured, and the cross-layer contention-based protocol operating over an impulse radio-ultra wideband (IR-UWB) physical layer has been verified by simulations with relevant physical layer characteristics. The energy consumption evaluation model proposed is straightforward to modify for evaluating delay, and it can reuse state transition probabilities derived from throughput analysis. The holistic application-driven MAC protocol evaluation model uses a novel single compound metric that represents a MAC protocol's relative performance in a given application scenario. The evaluations have revealed several significant flaws in sensor MAC protocols that are adapted to sensor networking from ad hoc networks. Furthermore, it has been shown that, when taking sufficient details into account, single hop communications can outperform multi-hop communications in the energy perspective within the feasible transmission ranges provided by sensor nodes. The impulse radio physical layer introduces characteristics to MAC protocols that invalidate traditional techniques which model the physical layer in terms of simple collisions. Hence, these physical layer characteristics have been modelled and included in the analysis, which improves the level of agreements with simulated results.

The purpose of “The Digital Puppetmaster” is to provide a means of awareness and a suggestion of mindset for members of the digital age. The digital medium has come to define society and establish its existence as an increasingly omnipresent one. Fundamentally, the digital medium is a sandbox for creating worlds that transcend the limitations of real life. Given the unlimited potential of the digital medium, it becomes apparent that it is easy to show what people want to see and hide what they do not. I aim to bring to light and uncover the realities of the digital medium and how the larger powers that control it take advantage of society. Society at large perpetuates a dangerous mentality of blindly trusting technology and believing that it has their best intentions in mind. I make the case that the ones who control the digital world are the ones who created ground zero for this way of thinking.

Studies of small and medium-sized enterprises have provided evidence that CEOs of such firms can have a dominating influence on firm activities. Drawing on upper echelons theory, we analyze the influence of CEO personality (CEO internal locus of control), CEO ownership and CEO education on the evaluation of middle manager performance. In line with our expectations, we find evidence for a direct effect of CEO ownership (negative) and CEO education (positive) on the use of objective performance evaluations and for a direct effect of the CEO's internal locus of control on the use of subjective performance evaluations. Moreover, we provide evidence for a moderating role of both CEO ownership and education with respect to the influence of the CEO's locus of control on the use of subjective evaluations. We use a sample of 247 small and medium-sized manufacturing firms to test our hypotheses.

During the past few years, a worldwide interest and unanimous consensus has arisen on personal communication services (PCS), where satellites can play a crucial role in a global scenario for the provision of PCS's all over the world. While for maritime and aeronautical communication services, the mature technologies of geostationary earth orbit (GEO) satellite systems seem the most suitable for present and future enhanced systems, other orbital configuration such as low earth orbit (LEO) and medium earth orbit (MEO) are being considered for the provision of satellite personal communication services to hand-held mobile terminals. One of the main objectives of personal communication services is the capability to provide personal (or continuous) mobility, communication anytime, anywhere. In general, satellite systems can provide a limited capacity with respect to terrestrial networks, nevertheless they are particularly suited in order to cover large terrestrial areas offering a scarce amount of traffic. The problem of radio frequency management for mobile applications has been addressed by World Administrative Radio Conference (WARC-92). One of the most relevant decisions taken at WARC-92 was to allocate the radio determination satellite system (RDSS) 1610-1626.5 MHz (L-Band) and 2483.5-2500 MHz (S-Band) slots to LEO satellite services on a worldwide, primary basis. This enables "big LEO's" to have a reasonable amount of spectram (i.e. capacity) to serve a substantial number of subscribers. However, the available amount of spectrum at L-band and S-band out of WARC-92 appears hardly sufficient to permit several systems to operate. Hence, to enable all the systems to operate and fulfil the capacity demand, S-PCNs need to share the limited available frequency spectrum. In this thesis we have proposed and evaluated a new fully overlapped band sharing scheme for mobile satellite systems operating in a land mobile satellite channel environment. The results show that the mobile satellite systems can share the limited available bandwidth. However, the overall system capacity of the MSS has been reduced due to excess intersystem interference. In order to reduce the excess inter-system interference a new enhanced overlapped band sharing protocol is proposed. The performance of this optimised band sharing scheme outperforms the conventional band segmentation scheme. Thus, achieving superior overall system capacity.

Le financement des PME dans un contexte d’asymétries d’information et de rationnement / Financing Small and medium enterprises in a context of information asymmetries and rationing

Since Namibia’s independence in 1990, various changes were introduced to the Namibian Income Tax Act. None of these changes were specifically targeting small and medium enterprises although the majority of entities in Namibia can be classified as small and medium enterprises. Recognising the contribution made by small and medium enterprises, Government recently indicated that tax reform for small and medium enterprises should be treated as a priority. Differentiated tax treatment is applied in the United Kingdom and South Africa and aims to reduce the tax burden. Although previous studies have been carried out on differentiated tax treatment for small and medium enterprises, none of these studies were done from a Namibian perspective. The aim of this study is to analyse literature on taxation for small and medium enterprises in the United Kingdom and South Africa to recognize the advantages and disadvantages of tax policies aimed at the small and medium enterprises sector. The study also compared tax policies for small and medium enterprises in the United Kingdom and South Africa to recommend possible implementation for the Namibian tax system. Namibia should learn from these countries and apply the best practices. The study reached the conclusion that tax reform in Namibia for the small and medium enterprises sector is desperately needed and recommends that tax policies aiming at reducing the tax compliance burden should receive preference over those reducing the tax rate burden. This research may serve as the starting point for revised tax policies and legislation specifically aiming at small and medium enterprises. / Dissertation (MCom)--University of Pretoria, 2014. / Taxation / unrestricted

Magister Educationis - MEd / This study explores the effect of English as medium of instruction in Geography teaching in Grade 11. It focuses on classroom interaction where both the teachers and learners have limited proficiency in the language of instruction. It reflects on the challenges experienced by Afrikaans speaking teachers in mediating Geography lessons to isiXhosa speaking learners in Grade 11 at one secondary school in the Western Cape.

Cosmological simulations suggest a strong correlation between high optical-depth Lya absorbers, which arise from the intergalactic medium, and 3D mass overdensities on scales of 10-30 h(-1) comoving Mpc. By examining the absorption spectra of similar to 80,000 QSO sight lines over a volume of 0.1 Gpc(3) in the Sloan Digital Sky Survey III (SDSS-III), we have identified an extreme overdensity, BOSS1441, which contains a rare group of strong Lya absorbers at z = 2.32 +/- 0.02. This absorber group is associated with six QSOs at the same redshift on a 30 comoving Mpc scale. Using Mayall/MOSAIC narrowband and broadband imaging, we detect Lya emitters (LAEs) down to 0.7 x L-Ly alpha ' * a and reveal a large-scale structure of LAEs in this field. Our follow-up LBT observations have spectroscopically confirmed 20 galaxies in the density peak. We show that BOSS1441 has an LAE overdensity of 10.8 +/- 2.6 on a 15 comoving Mpc scale, which could collapse to a massive cluster with M greater than or similar to 10(15) M-circle dot at z similar to 0. This overdensity is among the most massive large-scale structures at z similar to 2 discovered to date.