The influence of electronic word of mouth (eWOM) on consumers’ purchase intentions has long been known. However, the emergence of social media has brought a new perspective to eWOM through enabling users to communicate with their existing networks on the Internet. On social media, conversely to the other online platforms, users are able to exchange their opinions and experiences about products or services with familiar people, which refers to people who they already know such as friends and acquaintances. This new way of eWOM has the potential for greater impact on consumers. Therefore, the aim of this research is to examine the influence of eWOM in social media on consumers’ purchase intentions. To do so, the research in this thesis involved two major phases. In the first phase, in order to explore the determinants of eWOM information on social media which influences consumers’ purchase intentions, a theoretical model was developed based on the integration of Information Adoption Model (IAM) and related components of Theory of Reasoned Action (TRA). The new model, which is named as Information Acceptance Model (IACM), was validated through structural equation modelling (SEM) based on surveys of 384 social media users in the UK. The results have highlighted that quality, credibility, usefulness and adoption of information, needs of information and attitude towards information are the key factors for eWOM in social media which influence consumers’ purchase intentions. Furthermore, to provide better understanding of the influence of eWOM on social media, the second phase of this research was designed as a comparative study. To explore whether the eWOM between familiar people on social media or the eWOM between anonymous people on other online platforms was more influential on consumers’ purchase intentions, the data collected through survey was reanalysed with a different perspective; and a comparison was conducted based on multiple regression analysis. The results have revealed significant differences and found anonymous reviews to be more influential on consumers’ purchase intentions than friends’ recommendations on social media. However, since these results were contrary to expectations, 10 in-depth interviews were also administered to enlighten the insightful results found through the survey. The interview findings uncovered the survey results. Information quantity, information readiness, detailed information, and dedicated information were discovered as the factors which make online reviews superior than friends’ recommendations in terms of the influence of eWOM. This research contributes to theoretical implications through its validated model and found key dimensions. The research model, IACM, brings a new approach to information adoption by extending IAM and provides new insights to researchers who study Information Systems (IS). In addition, the model highlights the information adoption process as an antecedent of behavioural intention, which is a very important finding for the related literature. Future studies can build new models through considering this relationship between information adoption process and behavioural intention. Moreover, the second phase of this research provides new constructs for future studies through its qualitative findings. The findings reached through in-depth interviews, which explain why consumers prefer anonymous online reviews, can either be tested as components of new theories and models or they can be tested as inclusion of existing theories and models. Both types have potential to provide valuable results for the literature. On the other hand, in terms of practicality, this research provides marketers with a frame of reference to understand the influence of eWOM in social media on consumers’ purchase intentions. Both the contextual and the comparative studies in this research offer valuable insights for marketers; marketers thus can develop better strategies for marketing on social media.

El concentrador solar Fixed Mirror Solar Concentrator (FMSC) apareció en los años 70 con la finalidad de reducir costes en la producción de energía termoeléctrica. Este diseño consiste en un concentrador de reflector estacionario y foco móvil, presenta buena integrabilidad en cubiertas, y es capaz de alcanzar temperaturas entre 100 y 200ºC manteniendo una eficiencia aceptable. En esta tesis se expone una metodología para determinar el comportamiento del FMSC. Se ha desarrollado una herramienta de cálculo basada en el método de ray-tracing, que simula el trazado de los rayos solares en el sistema óptico. Con esta herramienta se ha analizado el comportamiento óptico y térmico del FMSC, y de la versión con espejos curvos Curved Slats Fixed Mirror Solar Concentrator (CSFMSC). Se ha realizado un análisis paramétrico para conocer la influencia de los distintos parámetros en el modificador de ángulo (IAM), y para obtener los diseños óptimos a una temperatura de 200ºC para tres climas en diferentes latitudes. Se han comparado los valores teóricos obtenidos mediante ray-tracing con dos prototipos ensayados, obteniendo un buen ajuste en ambos casos. Los ensayos han sido utilizados para determinar la curva de rendimiento de uno de los prototipos. Se ha hecho uso del método propuesto en la norma EN-12975-2:2006, combinado con valores de IAM obtenidos mediante ray-tracing. Se prueba que esta combinación puede ser útil para obtener la curva de rendimiento de colectores complejos con un modelo biaxial para el IAM. / The Fixed Mirror Solar Concentrator (FMSC) appeared during the 70s with the aim of reducing costs in the production of electricity in solar thermal power plants. This design consists of a concentrator with fixed reflector and moving receiver, has a very good integrability into building roofs and can reach temperatures between 100 and 200ºC with an acceptable efficiency. In this Thesis a methodology is presented for the determination of the behaviour of the FMSC. A simulation tool based on the forward ray-tracing method has been developed. The optical and thermal behaviour of the FMSC and its curved mirror variation called the Curved Slats Fixed Mirror Solar Concentrator (CSFMSC), have been analyzed with this tool. A parametric analysis has been carried out in order to determine the influence of the different parameters on the Incidence Angle Modifier (IAM) and to determine the optimal designs at a temperature of 200ºC for three different climates at different latitudes. The theoretical values obtained from the ray-tracing code have been compared with two experimental prototypes. The experimental and numerical results obtained show a good fit. The efficiency curve of one of the prototypes has been determined from the experimental tests. The methodology proposed in the norm EN-12975-2:2006 has been used in combination with IAM values obtained by ray-tracing. It has been shown that this combination can be effectively used to obtain the efficiency curve of complex collectors with a bi-axial IAM model.

De nos jours, les liaisons par fibres optiques monomode ou multimodes équipent de plus en plus de bâtiments, de lieux et sites de transports publics (gares, aéroports, autoroutes, ports ou plateformes multimodales). Ceci est dû au débit important qu’offre la fibre optique et à son atténuation très faible sur de longues distances. Afin de gérer au mieux la transmission au sein de la fibre optique, les performances de divers codes à une dimension 1D OOC et PC et deux dimensions 2D-MWOOC sur les récepteurs conventionnels ont été étudiées. Cependant, les performances obtenues restent limitées lorsque le nombre d’utilisateurs croit significativement. En ne tenant pas compte du bruit causé par les composants du système, la dégradation des performances est principalement due aux interférences d’accès multiples (IAM). De ce fait, nous proposons dans le cadre de cette thèse d’optimiser les performances du récepteur PIC en ajoutant un facteur de compensation qui permet de réduire au mieux les interférences d’accès multiples. Ceci est étudié avec les codes optiques à deux dimensions 2D-PC/PC que nous générons. Des expérimentations sur un banc d’essai optique en laboratoire sont effectuées pour illustrer la mise en oeuvre de multiservices. Une validation de certains résultats théoriques est également menée sur un simulateur dédié. / Nowadays, public transport spaces (train stations, airports, highways, ports or multimodal platforms) and buildings are being more and more equipped by single mode or multimode optical fibers. The high throughput offered and the very low attenuation over long distances proposed by optical fiber are indeed very promising. For a better management of optical fiber transmissions, the performance of various one-dimensional 1D OOC and PC codes, and twodimensional2D- MWOOC codes on conventional receivers have been previously studied.These studies show that a good level of performance is only available to a restricted number of users. Assuming noiseless components in the system, the performance degradation is mainly due to multiple access interference (MAI). Therefore, we propose in this thesis to optimize the performance of PIC receivers by adding a compensation factor that can best reduce the MAI. This is studied with two-dimensional optical codes 2D-PC/PC that we have generated. Experiments on a laboratory test bench were made to implement multiple services. The theoretical studies and the channel optical transmission simulations were also validated by using a dedicated simulator tool.

De nos jours, les liaisons par fibres optiques monomode ou multimodes équipent de plus en plus de bâtiments, de lieux et sites de transports publics (gares, aéroports, autoroutes, ports ou plateformes multimodales). Ceci est dû au débit important qu'offre la fibre optique et à son atténuation très faible sur de longues distances. Afin de gérer au mieux la transmission au sein de la fibre optique, les performances de divers codes à une dimension 1D OOC et PC et deux dimensions 2D-MWOOC sur les récepteurs conventionnels ont été étudiées. Cependant, les performances obtenues restent limitées lorsque le nombre d'utilisateurs croit significativement. En ne tenant pas compte du bruit causé par les composants du système, la dégradation des performances est principalement due aux interférences d'accès multiples (IAM). De ce fait, nous proposons dans le cadre de cette thèse d'optimiser les performances du récepteur PIC en ajoutant un facteur de compensation qui permet de réduire au mieux les interférences d'accès multiples. Ceci est étudié avec les codes optiques à deux dimensions 2D-PC/PC que nous générons. Des expérimentations sur un banc d'essai optique en laboratoire sont effectuées pour illustrer la mise en oeuvre de multiservices. Une validation de certains résultats théoriques est également menée sur un simulateur dédié.

During mammalian fertilization, the exposure of the inner acrosomal membrane (IAM) after acrosomal exocytosis is essential for the secondary binding between sperm and zona pellucida (ZP) of the oocyte, a prerequisite for sperm penetration through the ZP. The identification of the sperm protein(s) responsible for secondary binding has posed a challenge for researchers. We were able to isolate a sperm head fraction in which the IAM was exposed. Attached to the IAM was an electon dense layer, which we termed the IAM extracellular coat (IAMC). The IAMC was also observable in acrosome reacted sperm. High salt extraction removed the IAMC including a prominent 38 kDa polypeptide, referred to as IAM38. Antibodies raised against IAM38 confirmed its presence in the IAMC of intact, sonicated, and acrosome-reacted sperm. Sequencing of IAM38 revealed it as the ortholog of porcine SP38, a protein that was found to bind specifically to ZP2 but whose intra-acrosomal location was not known. We showed that IAM38 occupied the leading edge of sperm contact with the zona pellucida during fertilization, and that secondary binding and fertilization were inhibited in vitro by antibodies directed against IAM38. As for the mechanism of secondary sperm-zona binding by IAM38, we provided evidence that the synthetic peptide derived from the ZP2-binding motif of IAM38 had a competitive inhibitory effect on both sperm-zona binding and fertilization while its mutant form was ineffective. In summary, our study provides a novel approach to obtain direct information on the peripheral and integral protein composition of the IAM and consolidates IAM38 as a genuine secondary sperm-zona binding protein. In addition, our investigation also provides an ultrastructural description of the origin, expression and assembly of IAM38 during spermatogenesis. It shows that IAM38 is originally secreted by the Golgi apparatus as part of the dense contents of the proacrosomic granules but later, during acrosome capping phase of spermiogenesis, is redistributed to the inner periphery of the acrosomal membrane. This relocation occurs at the time of acrosomal compaction, an obligatory structural change that fails to occur in Zpbp1-/- knockout mice, which do not express IAM38 and are infertile. / Thesis (Ph.D, Anatomy & Cell Biology) -- Queen's University, 2008-11-27 15:33:50.226

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No. of bitstreams: 1 danielgustavomesquitadasilva.pdf: 3042917 bytes, checksum: 06395c899324e2d8dfd65fdbf105d471 (MD5) Previous issue date: 2018-06-19 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Valores precisos de Secção de Choque Total (SCT) para o espalhamento de elétrons por álcoois primários, como metanol, etanol, 1-propanol e 1- butanol, são muito importantes em muitas áreas aplicadas, uma vez que refletem a reatividade do alvo molecular no processo de colisão, como função da energia dos elétrons. Esses valores são muito úteis, por exemplo, quando se quer modelar a combustão do álcool no processo de ignição por centelha dentro de um motor de combustão interna. Através dessa modelagem, podemos melhorar o desempenho de veículos motorizados e de todas as tecnologias que utilizam atualmente combustíveis fósseis. Medidas de SCT absoluta para espalhamento de elétrons por moléculas do 1-propanol foram realizadas neste trabalho, para energias de impacto de 40 a 500 eV. Esses dados foram obtidos utilizando um novo aparelho desenvolvido neste trabalho, baseado na atenuação de um feixe de elétrons colimado através de uma célula gasosa que contém as moléculas a serem estudadas, a uma pressão e temperatura conhecidas. Este aparelho é constituído de um canhão de elétrons, uma célula gasosa, um analisador de energia de elétrons composto de um sistema de lentes eletrostáticas desaceleradoras seguido por um analisador cilíndrico dispersivo 127° (ACD 127°) e um coletor de Faraday. O aparelho está instalado dentro de uma câmara de vácuo coberta por 5 camadas de mu-metal, para blindagem de campos magnéticos espúrios, sendo diferencialmente bombeada através de duas bombas turbomoleculares; uma com velocidade de bombeamento de 80 l/s, para bombear a câmara do canhão de elétrons, a fim de evitar mudanças nas características de emissão do filamento quando o gás é introduzido na câmara; e a outra, com uma velocidade de bombeamento de 600 l/s, para bombear a célula de espalhamento e a região do analisador. O aparelho desenvolvido mostrou excelente desempenho, quando os dados de SCT por ele produzidos foram comparados com dados da literatura para os gases Ar, He, N2. Nossos dados experimentais de SCT para o 1-propanol, pelo melhor de nosso conhecimento, são os primeiros da literatura. Eles foram comparados com os resultados teóricos produzidos pelo Modelo do Átomo Independente Regra da Aditividade Revisada mais contribuições de interferências (MAIRAR+I), sendo verificada uma boa concordância. / Precise values of the Total Cross Section (TCS) for electron scattering by primary alcohols such as methanol, ethanol, 1-propanol and 1-butanol, are very important in many applied areas, given that the TCS reflects the reactivity of a molecular target in the collision processes as a function of the electron energy. These values are very useful, for instance, when modeling alcohol combustion through a spark ignition process within an internal combustion engines. Through this modeling we can improve the performance of motor vehicles, and all technologies currently utilizing fossil fuels. Absolute Total Cross Section (ATCS) measurements for electron scattering from 1-propanol molecules were obtained in this work, for impact energies from 40 to 500 eV. These data were obtained using a new apparatus developed in this work, which is based on the measurement of the attenuation of a collimated electron beam through a gas cell containing the molecules to be studied at a given pressure and temperature. This new apparatus consists of an electron gun, a gas cell, an electron energy analyzer composed of an array of decelerating electrostatic lenses, a cylindrical dispersive 127° analyzer (CDA 127°), and a Faraday cup. The apparatus is housed inside a vacuum chamber covered by 5 layers of mu-metal, for shielding against spurious magnetic fields, and differentially pumped through two turbomolecular pumps; one with a pumping speed of 80 l/s, for pumping the electron gun chamber in order to avoid changes in the electron emitting filament characteristics when gas is introduced into the chamber; and the other, with 600 l/s pumping speed, for pumping the scattering cell and analyzer region. The developed apparatus showed excellent performance when comparing our TCS data produced with it, with data from literature for the gases Ar, He, N2. Our TCS measurements for 1-propanol, to the best of our knowledge, are the first in the literature. These experimental measurements were compared with calculated TCS using the Independent-Atom Model with Screening Corrected Additivity Rule and Interference (IAM-SCAR+I) approach with the level of agreement between them being typically found to be very good.

Role engineering, a critical task in role-based access control systems, is the process of identifying a complete set of roles that accurately reflect the structure of an organization. Role mining, a data-driven approach, utilizes data mining techniques on user-permission assignments represented as binary data to automatically derive these roles. However, relying solely on data-driven methods often leads to the generation of a large set of roles lacking interpretability. To address this limitation, this thesis presents a role mining algorithm, whose results can be viewed as an initial step in the role engineering process, in order to streamline the task of defining semantically meaningful roles, where human analysis is an inevitable post-processing step. The algorithm is based on hierarchical clustering analysis, and its main objective is identifying a sufficiently small set of roles that cover as large a proportion of the user-permission assignments as possible. To evaluate the performance of the algorithm, multiple real-world data sets representing diverse access control scenarios are utilized. The evaluation focuses on comparing various binary similarity measures, with the goal of determining the most suitable characteristics of a binary similarity measure to be used for role mining. The evaluation of different binary similarity measures provides insights into their effectiveness in achieving accurate role definitions to be used as a foundation for constructing meaningful roles. Ultimately, this research contributes to the advancement of role mining methodologies, facilitating improved access control systems that align with organizational needs and enhance security and efficiency. / Role engineering går ut på att identifiera en komplett uppsättning roller som återspeglar strukturen i en organisation och är en viktig uppgift när organisationer övergår till rollbaserad åtkomstkontroll. Role mining är en datadriven metod som använder data mining-tekniker på användarnas behörighetstilldelningar för att automatiskt härleda dessa roller. Dessa tilldelningar kan representeras som binär data. Att enbart förlita sig på datadrivna metoder leder dock ofta till att en stor uppsättning svårtolkade roller genereras. För att adressera denna begränsning har en role mining-algoritm utvecklas i det här arbetet. Genom att applicera algoritmen på den binära tilldelningsdatan kan de erhållna resultaten betraktas som ett inledande steg i role engineering-processen. Syftet är att effektivisera arbetet med att definiera semantiskt meningsfulla roller, där mänsklig analys är en oundviklig fas. Algoritmen är baserad på hierarkisk klustring och har som huvudsyfte att identifiera en lagom stor uppsättning roller som täcker så stor del av behörighetstilldelningarna som möjligt. För att utvärdera algoritmens prestanda appliceras den på flertalet datamängder insamlade från varierande verkliga åtkomstkontrollsystem. Utvärderingen fokuserar på att jämföra olika binära likhetsmått med målet att bestämma de mest lämpliga egenskaperna för ett binärt likhetsmått som ska användas för role mining. Utvärderingen av olika binära likhetsmått ger insikter i deras effektivitet att uppnå korrekta rolldefinitioner som kan användas som grund för att konstruera meningsfulla roller. Denna forskning bidrar till framsteg inom role mining och syftar till att underlätta övergången till rollbaserad åtkomstkontroll samt förbättra metoderna för att identifiera roller som överensstämmer med organisationsbehov och förbättrar säkerhet och effektivitet.

Para um composto químico exercer seu efeito bioativo é necessário que ele atravesse várias barreiras biológicas até alcançar seu sitio de ação. Propriedades farmacocinéticas insatisfatórias (como absorção, distribuição, metabolismo e excreção) são reconhecidamente as principais causas na descontinuidade de pesquisas na busca por novos fármacos. Neste trabalho, modelos biofísicos foram utilizados para o estudo de absorção de uma série de flavonóides naturais com atividade tripanossomicida. O coeficiente cromatográfico de partição, kw, foi determinado através da cromatografia líquida de alta eficiência em fase reversa, RP-HPLC, utilizando-se de colunas cromatográficas empacotadas com constituintes básicos da membrana biológica (fosfatidilcolina e colesterol). Os resultados obtidos demonstraram que nas colunas compostas por fosfatidilcolina a retenção de flavonóides hidroxilados é determinada por interações secundárias, além da partição, e no caso da coluna de colesterol, a partição é o principal mecanismo que rege a retenção. Uma série de descritores físico-químicos foi gerada pelos campos moleculares de interações (MIFs) entre os flavonóides naturais e algumas sondas químicas virtuais, utilizando o programa GRID. Os descritores físico-químicos gerados foram correlacionados com os log kw por análise dos mínimos múltiplos parciais (PLS), utilizando o programa VolSurf, com a finalidade de gerar um modelo quantitativo entre estrutura e propriedade (QSPR) para esta classe de compostos. O modelo produzido por este estudo, ao utilizar os dados de partição em colesterol, log kwCol, apresentou elevada consistência interna, com bom poder de correlação (R2 = 0, 97) e predição (Q2 = 0,86) para a partição destas moléculas / In order to a chemical compound exert its bioactive effect it is necessary that it crosses some biological barriers until reaching its site of action. Unfavorable pharmacokinetics properties (absorption, distribution, metabolism and excretion) are admittedly one of the main causes in the discontinuity of research in the search for new drugs. In this work, biophysics models were used for the study of absorption of a series of natural flavonoids with trypanocide activity. The chromatographic retention indices (log kw) were determined on immobilized artificial membranes columns (IAM.PC.DD, IAM.PC.DD2, Cholesteryl 10-Undecetonoato) obtained by the extrapolation method. The results demonstrated that in the composed columns for fosfatidilcolina the retention of hydroxil flavonoids is determined by secondary interactions, beyond the partition. In the case of the retention for the cholesterol column, the partition is the main mechanism that drives the retention. A series of physico-chemical descriptors were generated by the molecular interaction fields (MIF) between the flavonoids and some virtual chemical probes, using the program GRID. The descriptors were correlated with log kw by the partial least squares regression (PLS), using the VolSurf program, with the purpose to generate a quantitative model between the structure and the retention (QSRR) for this compounds class. The model produced for this study, when using the data of partition in cholesterol, log kwCol, presented high internal consistency, with good correlation power (R2 = 0, 97) and prediction (Q2 = 0,86) for the partition of these molecules

Para um composto químico exercer seu efeito bioativo é necessário que ele atravesse várias barreiras biológicas até alcançar seu sitio de ação. Propriedades farmacocinéticas insatisfatórias (como absorção, distribuição, metabolismo e excreção) são reconhecidamente as principais causas na descontinuidade de pesquisas na busca por novos fármacos. Neste trabalho, modelos biofísicos foram utilizados para o estudo de absorção de uma série de flavonóides naturais com atividade tripanossomicida. O coeficiente cromatográfico de partição, kw, foi determinado através da cromatografia líquida de alta eficiência em fase reversa, RP-HPLC, utilizando-se de colunas cromatográficas empacotadas com constituintes básicos da membrana biológica (fosfatidilcolina e colesterol). Os resultados obtidos demonstraram que nas colunas compostas por fosfatidilcolina a retenção de flavonóides hidroxilados é determinada por interações secundárias, além da partição, e no caso da coluna de colesterol, a partição é o principal mecanismo que rege a retenção. Uma série de descritores físico-químicos foi gerada pelos campos moleculares de interações (MIFs) entre os flavonóides naturais e algumas sondas químicas virtuais, utilizando o programa GRID. Os descritores físico-químicos gerados foram correlacionados com os log kw por análise dos mínimos múltiplos parciais (PLS), utilizando o programa VolSurf, com a finalidade de gerar um modelo quantitativo entre estrutura e propriedade (QSPR) para esta classe de compostos. O modelo produzido por este estudo, ao utilizar os dados de partição em colesterol, log kwCol, apresentou elevada consistência interna, com bom poder de correlação (R2 = 0, 97) e predição (Q2 = 0,86) para a partição destas moléculas / In order to a chemical compound exert its bioactive effect it is necessary that it crosses some biological barriers until reaching its site of action. Unfavorable pharmacokinetics properties (absorption, distribution, metabolism and excretion) are admittedly one of the main causes in the discontinuity of research in the search for new drugs. In this work, biophysics models were used for the study of absorption of a series of natural flavonoids with trypanocide activity. The chromatographic retention indices (log kw) were determined on immobilized artificial membranes columns (IAM.PC.DD, IAM.PC.DD2, Cholesteryl 10-Undecetonoato) obtained by the extrapolation method. The results demonstrated that in the composed columns for fosfatidilcolina the retention of hydroxil flavonoids is determined by secondary interactions, beyond the partition. In the case of the retention for the cholesterol column, the partition is the main mechanism that drives the retention. A series of physico-chemical descriptors were generated by the molecular interaction fields (MIF) between the flavonoids and some virtual chemical probes, using the program GRID. The descriptors were correlated with log kw by the partial least squares regression (PLS), using the VolSurf program, with the purpose to generate a quantitative model between the structure and the retention (QSRR) for this compounds class. The model produced for this study, when using the data of partition in cholesterol, log kwCol, presented high internal consistency, with good correlation power (R2 = 0, 97) and prediction (Q2 = 0,86) for the partition of these molecules

No description available.