"This study characterizes the image quality parameters of a clinical full-field digital mammography system at various x-ray spectral conditions. The energy of the incident x-ray beam, the spectral characteristics, and breast thickness impact the physical performance such as the detective quantum efficiency of the system, thereby affecting the overall performance. The modulation transfer function, noise power spectrum were measured without the anti-scatter grid, and the detective quantum efficiency was calculated for different incident x-ray conditions. Detective quantum efficiency was also calculated with the anti-scatter grid placed above the detector to study its impact. Results indicate a substantial drop in the detective quantum efficiency with the anti-scatter grid under certain conditions. It was also determined that detective quantum efficiency decreases as x-ray beam hardening is increased. A spatial frequency-dependent cascaded liner systems model was developed to predict the detective quantum efficiency of the system for different target-filter combinations. This theoretical model is based upon a serial cascade approach in which the system is conceptually divided into a number of discrete stages. Each stage represents a physical process having intrinsic signal and noise transfer properties. A match between the predicted data and the experimental detective quantum efficiency data confirmed the validity of the model. Contrast-detail performance, a widely used quality control tool to assess clinical imaging systems, for the clinical full-field digital mammography was studied using a commercially available CDMAM phantom to learn the effects of Joint Photographic Experts Group 2000 (JPEG2000) compression technique on detectability. A 4-alternative forced choice experiment was conducted. The images were compressed at three different compression ratios (10:1, 20:1 and 30:1). From the contrast-detail curves generated from the observer data at 50% and 75% threshold levels, it was concluded that uncompressed images exhibit lower (better) contrast-detail characteristics than compressed images but a certain limit to compression, without substantial loss of visual quality, can be used."

The aim of the present study was to investigate the link between ruminative processes and dysregulated behaviors. Accordingly, the emotional cascade model (Selby et al., 2008 / 2009) was tested in a sample of Turkish university students using structural equation modeling. The emotional cascade model posits that the link between emotional and behavioral dysregulation may be through emotional cascades, which are repetitive cycles of rumination and negative affect that result in an increased attention paid to the emotional stimuli and intensification of emotional distress. Dysregulated behaviors, such as non-suicidal self-injury, are used in order to break this cycle and distract the person from ruminative processes. In the first part of the study, a common measure of cognitive emotion regulation, namely The Cognitive Emotion Regulation Questionnaire (CERQ / Garnefski et al., 2001) was adapted into Turkish and its psychometric properties were investigated. Results suggested that the Turkish version of the CERQ is a reliable and valid meausure of cognitive coping. Next, a structural equation model was tested to assess the relationship between emotional cascades (as indicated by rumination, thought suppression, catastrophizing) and behavioral dysregulation (as indicated by binge eating, non-suicidal self-injury, excessive reassurance-seeking, and drinking to cope). The results showed that the emotional cascades are associated to behavioral dysregulation. This relationship, however, did not remain significant when the effect of current psychological distress on behavioral dysregulation was controlled for. The importance and possible implications of the present study was discussed.

Online social networks (OSNs) have become a powerful medium of communicating, sharing and disseminating information. Because of popularity and availability of OSNs throughout the world, the connected users can spread information faster and thus propagate influence over each other constantly. Due to such impact, a lot of applications on OSNs focused on picking an initial set of users (seeds) to infuse their message in the OSN. Due to huge size of the network, the main challenge in picking the initial set is to maximize the resultant influence over the users in the network. The optimization problem of finding out the most influential set of members in an OSN for maximization of influence is an NP-hard problem. In this paper, we propose using the Positive Influential Dominating Set (PIDS) algorithm for the initial seed. PIDS is a well-known algorithm which determines the influential backbone nodes in the networks. We implemented PIDS-based influence maximization by using different propagation models. We compared PIDS performance to that of the existing approaches based on greedy and random heuristics. The experimental results from extensive simulation on real-world network data sets show that PIDS gives better influence spread than greedy and random for both Independent Cascade Model and Linear Threshold Model of influence propagation. PIDS is also scalable to large networks and in all size ranges, it performs well in influence maximization.

No description available.

Auditorische Transduktion beschreibt die Umwandlung von Schall in elektrische Signale in Rezeptorzellen. Dies geschieht durch eine Kette biophysikalischer Prozesse: mechanische Ankopplung der Schallwelle, Öffnung von mechanosensitiven Ionenkanälen in den Rezeptorzellen, Ansammlung des Membranpotentials und Auslösung von Aktionspotentialen. In dieser Arbeit wird die damit verbundene Signalverarbeitung am Beispiel der Rezeptorzellen im Ohr von Heuschrecken untersucht. Die Transduktion wird dazu als Kaskade einzelner funktioneller Module beschrieben. Es wird gezeigt, wie derartige Module aus der Beobachtung der System-Antwort, hier der Aktionspotentiale im auditorischen Nerv, mit Hilfe der Iso-Antwort-Methode charakterisiert werden können. Dabei werden im Experiment unterschiedliche akustische Reize ermittelt, die die gleiche System-Antwort liefern. In drei aufeinander aufbauenden experimentellen Untersuchungen führt dies zu folgenden Ergebnissen: 1) Für stationäre Signale wird die Feuerrate der Rezeptorzellen durch die Energie der Trommelfell-Schwingung reguliert. 2) Die auditorische Transduktion lässt sich durch eine Kaskade aus zwei linearen Filtern und zwei nicht-linearen Transformationen (LNLN-Kaskade) beschreiben. Die involvierten Prozesse agieren im sub-Millisekunden-Bereich und können mit der beschriebenen Methode - trotz der auf etwa eine Millisekunde beschränkten Präzision der Aktionspotentiale - mit einer Genauigkeit von ca. 10 Mikrosekunden vermessen werden. 3) Die Adaptation der Feuerrate enthält neben einem dominierenden rückgekoppelten Prozess, der durch die Feuerrate selbst gesteuert wird, auch eine Komponente, die direkt durch das Eingangssignal, die Schallintensität, ausgelöst wird und mechanischer Natur ist. Die Ergebnisse spiegeln die hohen Anforderungen an das zeitliche Auflösungsvermögen im Ohr wider. Die verwendete Methodik ist jedoch auch auf viele andere systemtheoretische Untersuchungen biophysikalischen Kaskaden anwendbar. / Auditory transduction describes the conversion of sound into electrical signals in receptor cells. A sequence of biophysical processes is involved: the mechanical coupling of the sound-pressure wave, the opening of mechanosensory ion channels in the receptor cells, the accumulation of membrane potential and the generation of action potentials. In this work, the signal processing in receptor cells is investigated. The ears of grasshoppers serve as a model system, and transduction is described as a cascade of functional modules. It is shown how such modules can be characterized by the iso-response method from observations of the system''s response. To this end, different acoustic stimuli are determined experimentally that trigger the same response. In three consecutive experimental investigations, this approach leads to the following results: 1) For stationary signals, the firing rate of the receptor neurons is governed by the energy of the ear-drum vibrations. 2) Auditory transduction can be described by a cascade that consists of two linear filters and two nonlinear transformations (LNLN cascade). The processes involved act on sub-millisecond time scales and can be analyzed by the described method with a resolution of around 10 microseconds - despite the limited precision of the action potentials near one millisecond. 3) Spike-frequency adaptation is governed by a feedback process, which is governed by the firing rate, but also contains a feedforward component triggered by the system''s input, the sound intensity. This component is of mechanical origin. The results reflect the high demands for temporal resolution in the ear. The applied method, however, can also be used for a large range of further system-theoretical investigations of biophyical cascades.

South Africa has witnessed radical policy reforms since the advent of the new democratic dispensation in 1994. As provincial, district and local practitioners developed responses to those new national education policies, implementation issues were revealed in all their complexity. Policy implementation became one of the most difficult challenges South Africa had to contend with. It necessitated the development of the capacity of the state and its people to implement policy. The complexities of the people development environment in South Africa create a range of challenges for development. The lack of multi-level empirical data on training effects continues to exacerbate this state of affairs. This context requires that comprehensive assessment mechanisms be put in place for training programmes aimed at the realisation of policy goals. The broad purpose of this inquiry, therefore, is to determine the impact of an education management development training intervention as it passes through different levels of the education system in South Africa - national, provincial, district and local. The following key questions guided this investigation. Firstly, how do stakeholder understandings of “education management development” transfer from one level to another in a cascade model of training? And secondly, what is the operational impact of an education management development-training programme at the different levels (i.e., province, district and school) of the education system? Questionnaires, free attitude interviews and observations were used as key data collection instruments. Data was analysed using a combination of quantitative and qualitative strategies for making sense of the training information. Data was interpreted against the backdrop of the literature on the “transfer of training”, and these findings are represented in the last three chapters of this thesis. This research generated four major findings, with a variety of subsidiary findings, which deepen our insights into policy implementation as it relates to education management development in South Africa. Some of the major findings of this study are that: a) The organisers did not in the first place conduct the baseline study on training needs and secondly, they did not take into consideration the organisational requirements of the anticipated training. This anomaly could ultimately compromise the outcomes of this intervention. b) The policy deployment processes of the North West Department of Education (of ensuring that the governmental policies for quality, cost and service delivery are understood from the highest to the lowest level of the organisation) are fraught with problems that undermined basic understandings of the Education Management Development training programme which was conducted between 1998 – 2000. c) Successful policy implementation depends crucially on resource allocation and, in the case of the Education Management Development Training Programme, the nature and magnitude of allocated resources e.g., transport provision could not guarantee positive training results; and d) The overly rationalistic view adopted by the trainers of the Education Management development-training programme did not take into account the complex contexts within which change unfolds. Resultantly, the changing of the roles of facilitators could not be planned-for in advance. The significance of this study is that it identifies the barriers to learning in training events, and sheds new light on the transfer of training problem that continues to undermine organisational change and human resource development. Some of the unique findings of the study can be found in the fact that the Expert Trainers could only recall a few intentions of the EMD modular training. The District Facilitators displayed limited knowledge of the disciplinary procedures in their areas of operation and there was limited conceptualisation of the EMD by the principals of schools. / Thesis (PhD (Education Policy Studies))--University of Pretoria, 2005. / Education Management and Policy Studies / unrestricted

No description available.

Outcomes Based Education (OBE), has been, since its inception, fraught with problems. OBE in its very nature is complex. To fully embrace this method and ensure its success, schools must be able to make the necessary paradigm shift. This can only be achieved when schools receive relevant and empowering training, support and development. In other words, organisational development must be the key words. The aim of this study is to explore the impact of organisational development interventions on the implementation of OBE. The case study method was employed where it was realised that schools that received organisational development interventions, together with Outcomes Based Education, were able to implement this method with greater understanding, skill, and confidence. The investigation recommends an organisational development design that could be used instead of the cascade model, and provides suggestions on what can be done to ensure a more successful implementation process. / Educational Studies / M. Ed (Education Management)

O Presente trabalho propôs o estudo de reações fotonucleares e fotoprodução de pions em energias intermediárias e altas usando o modelo de cascata intranuclear MCMC para a fase rápida de reação e outro algoritmo de Monte Carlo para descrever o processo de decaimento do núcleo composto via evaporação de partículas e fissão nuclear. Dentre as principais inovações implementadas no MCMC, podemos citar: i) a inclusão detalhada do canal do quase-dêuteron no intervalo 20 < Eg < 140 MeV; ii) o desenvolvimento inédito e rigoroso de um mecanismo de bloqueio de Pauli não-estocástico, avaliando as excitações partícula-buraco em tempo real na fase de pré-equilíbrio; iii) a incorporação de um critério energético de parada para a cascata; iv) a utilização de distribuições de momento apropriadas para núcleos leves (Modelo de Camadas), v) a inclusão de canais de fotoprodução do pi^0 na região da Delta (1232) e em altas energias 4,0 < Eg < 6,0 GeV e ângulos frontais e, vi) a metodologia inédita para avaliar as interações de estado final de mésons e ressonâncias com o núcleo via cenário de espalhamentos múltiplos. O mecanismo do quase-dêuteron reproduz satisfatoriamente as seções de choque totais de fotoabsorção e as multiplicidades médias de nêutrons emitidos em núcleos pesados, interpretando qualitativamente as seções de choque para os canais de eletrodesintegração (e,xnyp) do 232Th. A contribuição de um possível processo de fotoabsorção por poucos corpos no 232Th é analisada via canal de fotofissão. Os cálculos das distribuições angulares na fotoprodução incoerente do pi^0 para o 12C e 208Pb em energias intermediárias estão em ótimo acordo com dados experimentais obtidos no Microtron de Mainz (MAMI). Os resultados para as seções de choque das distribuições angulares do pi^0 em altas energias servirão como referência na Colaboração PrimEx no Jefferson Laboratory Facility, propiciando a separação da parte incoerente das demais contribuições nucleares e eletromagnéticas e auxiliando na determinação precisa da meia-vida do decaimento radiativo pi^0 --> GG. / Photonuclear reactions and pion photoproduction at intermediate and high energies have been studied using the multicollisional intranuclear cascade model (MCMC) for the rapid reaction step and another Monte Carlo algorithm to describe the de-excitation of the compound nucleus via particle evaporation and nuclear fission. The new features of the MCMC are: i) the detailed inclusion of the quasideuteron channel in the range 20 < Eg < 140 MeV; ii) the development of a rigorous and completely new non stochastic Pauli blocking mechanism, taking into account particle - hole excitations during the pre-equilibrium stage; iii) the incorporation of an energetic criterion to stop de cascade; iv) the employment of an appropriate momentum distribution for light nuclei (Shell Model); v) the inclusion of pi^0 photoproduction channels in the Delta (1232) region and at high energies 4.0 < Eg < 6.0 GeV and forward angles, and vi) the new methodology to evaluate the pion-nucleus and Delta - nucleus Final State Interactions via a multiple scattering scenario. The quasideuteron mechanism reproduces the total photoabsorption cross sections and neutron multiplicities in heavy nuclei, giving a qualitative interpretation for the cross sections of the electrodisintegration channels (e,xnyp) from 232Th. The contribution of a possible few body photoabsorption process in 232Th is evaluated via fission channel. The calculations of the pi^0 angular distributions for incoherent production at intermediate energies for 12C and 208Pb are in excellent agreement with the experimental data of the Mainz Microtron (MAMI). The results of the pi^0 angular distributions at higher energies will be reference for the PrimEx Collaboration at the Jefferson Laboratory Facility, propitiating the separation of the incoherent part from the remaining nuclear and electromagnetic contributions and helping to perform a high precision measurement of the pi^0 to gamma-gamma radiactive decay width.

A Avaliação de Ciclo de Vida (ACV) é um método estruturado, compreensivo e padronizado a nível internacional que quantifica informações sobre emissões, recursos consumidos e impactos ambientais potenciais de produtos através do seu ciclo de vida. Uma das fases do estudo, a Avaliação de Impacto do Ciclo de Vida (AICV), refere-se ao processo quantitativo e/ou qualitativo aplicado na avaliação dos impactos associados ao inventário do ciclo de vida. Dentre os impactos ambientais abordados na AICV estão aqueles relacionados ao uso da terra, sendo avaliados segundo duas vertentes: impactos sobre a biodiversidade e impactos sobre Serviços Ecossistêmicos. A modelagem dos impactos dos serviços ecossistêmicos na ACV ainda apresenta limitações e alguns erros conceituais como, por exemplo, não avaliar de fato os benefícios fornecidos ao homem. Além disso, um dos grandes desafios na ACV refere-se à diferenciação espacial nos procedimentos metodológicos de AICV, sobretudo para impactos devido ao uso da terra. Assim, o principal objetivo desde estudo é discutir a inserção do conceito de serviços ecossistêmicos na ACV e obter fatores de caracterização de impactos em serviços ecossistêmicos relacionados ao solo para a AICV, aplicáveis de maneira regionalizada para o Brasil. A revisão de literatura e comparação do mecanismo ambiental para os impactos do uso da terra na AICV com o modelo em cascata de serviços ecossistêmicos possibilitou o desenvolvimento de um novo modelo conceitual para serviços ecossistêmicos relacionados solo. Cada uma das etapas do modelo de cascata foi alinhada à terminologia da ACV para coincidir com os níveis de modelagem de ponto intermediário e de danos ao mesmo tempo considerando os principais processos, funções, serviços, benefícios e valores relacionados ao solo. Além disso, foram calculados fatores de caracterização para impactos aos serviços ecossistêmicos relacionados à fertilidade do solo através da aplicação de um modelo de caracterização de AICV espacialmente diferenciado. O procedimento metodológico envolveu (i) a definição do mecanismo ambiental, tendo como indicador o teor de Carbono Orgânico do Solo (COS), (ii) a definição da Vegetação Natural Potencial como situação de referência e (iii) a definição das unidades biogeográficas de análise denominadas Associação Solo-Vegetação (ASV). Com base nestes parâmetros, foram calculados os estoques de COS para 32 classes diferentes de uso da terra e os estoques de COS para as situações referência, necessários para o cálculo dos impactos resultantes do uso da terra. Foram calculados e disponibilizados mais de três mil fatores de caracterização aos usuários de ACV, aplicáveis em 32 classes diferentes de uso da terra para 74 unidades biogeográficas (ASV). Além desses, foram obtidos fatores de caracterização também para as 27 unidades federativas do país, que apesar de estarem agregados em divisões políticas, levam em consideração dados regionais de COS. Por fim, os resultados e discussões deste trabalho contribuem na integração de dois campos de estudo e podem auxiliar ao melhor entendimento do sistema de produtos, não apenas focando em danos ambientais, mas também possibilitando a identificação de impactos positivos e agregação de valor. / Life Cycle Assessment (LCA) is a structured, comprehensive and standardized method at international level that quantifies information on emissions, resources consumed and potential environmental impacts of products through their life cycle. One of it phases, the Life Cycle Impact Assessment (LCIA), refers to the quantitative and/or qualitative process applied in assessing the impacts associated with the life cycle inventory. Among the environmental impacts addressed in LCIA are those related to land use, being evaluated according to two pathways: impacts on biodiversity and impacts on ecosystem services. The ecosystem services impact modelling on LCA still presents limitations and some conceptual errors, such as not actually evaluating the benefits provided to humans. In addition, one of the major challenges in LCA relates to the spatial differentiation in LCIA methodological procedures, especially for impacts due to land use. Thus, the main goal of the present study is to discuss the ecosystem services concept integration in LCA and obtain characterization factors of soil-related ecosystem services impacts, regionally applicable to Brazil. The literature review and the LCA environmental mechanism of land use impacts and the cascade model of ecosystem services comparison allowed the development of a new conceptual model for soil-related ecosystem services. Each one of these steps in the cascade model was aligned with the LCA\'s terminology to match the midpoint and endpoint modelling levels while considering the key processes, functions, services, benefits, and values related to the soil. In addition, characterization factors for ecosystem services related to soil fertility were calculated applying a spatially differentiated characterization model. The methodological procedure involved the (i) environmental mechanism definition, establishing the Soil Organic Carbon content (SOC) as an indicator, (ii) the definition of Potential Natural Vegetation as a reference situation and (iii) the definition of the biogeographic analysis units denominated Soil Vegetation Association (SVA). Based on these parameters, SOC stocks were calculated for 32 different land use classes and SOC stocks for reference situations allowing the calculation of impacts resulting from land use. More than two thousand characterization factors were calculated, being available to LCA users, applicable in 32 different land use classes to 74 biogeographic units (SVA). In addition, characterization factors were also obtained for the 27 Brazilian federative units, which, although aggregated in political divisions, consider SOC regional data. Finally, the results and discussions of this study contribute to the integration of two scientific domains and help to better understand the product system, not only focusing on environmental damages, but also enabling the identification of positive impacts and value aggregation.