301 |
Growing up with violent fathers: conversations with daughtersMtetwa, Thandazile Grace Nokukhanya 11 1900 (has links)
The effects of having witnessed their fathers’ violent behaviour impacts on daughters for a
long period afterwards, even in adulthood. This study explores this phenomenon by means of
literature review and interviews. The literature indicates that the effects of paternal violence is
linked to forced maturity, secrecy, pretending, self-blame, and negative impact on the
daughter’s relationships with both parents. A narrative approach was used to interview three
adult participants. The conversations were analysed using thematic analysis and hermeneutics.
Themes that emerged include avoidance, ambivalence towards the parents, aggression,
assertiveness, and over-responsibility. There is a tendency to avoid intense, emotionally-laden,
ambiguous and unpredictable situations through the use of interpersonal vigilance, an
emotionally strong poise, distancing, being agreeable and devoutness. Also, there is a fear of
becoming just like their abusive father. The psychological impact of being witness to a father’s
violent behaviours has long-lasting effects on daughters. / Psychology / M.A. (Clinical Psychology)
|
302 |
Étude de l'implication du Nerve Growth Factor et des Acid-Sensing Ion Channels dans l'hypersensibilité colique induite par le butyrate chez le ratMatricon, Julien 12 March 2010 (has links) (PDF)
Le syndrome de l'intestin irritable (SII) touche près de 10% de la population. Nous avons utilisé un modèle animal de SII induit par le butyrate développé au laboratoire afin de décortiquer les mécanismes de l'hypersensibilité colique (HSC) dans le SII. Le blocage du NGF par des anticorps anti-NGF prévient l'HSC induite par le butyrate, évaluée par le test de distension colorectale. Le NGF, quantifié par immunohistochimie (IHC), est surexprimé dans les ganglions rachidiens dorsaux (GRD) innervant le côlon des rats butyrate. Le blocage des canaux ASIC par amiloride prévient l'HSC induite par le butyrate. L'expression des ARNm ASIC1a et ASIC1b, évaluée par RT-PCR, est augmentée dans les GDR des rats butyrate. Cette augmentation est corrélée à une augmentation de l'expression de la protéine ASIC1A dans les neurones nociceptifs, quantifiée par IHC. Le blocage du NGF par des anticorps anti-NGF prévient la surexpression de ASIC1A dans les GRD. L'absence de variation d'expression du NGF et de ASIC1A au niveau colique suggère que ces moléciles ont une implication dans l'élément présynaptique plutôt que dans les terminaisons libres coliques. L'étude de l'expression spinale de la protéine Fos après stimulation des fibres coliques a montré que l'HSC induite par le butyrate est associée à une activation spécifique des segments thoraciques T10-T11-T12 de la moëlle épinière (MEp). Le blocage spinal du canal ASIC1A par la PcTx1 prévient l'HSC induite par le butyrate. L'expression de ASIC1a, évaluée par RT-PCR et Western blot, est augmentée dans la MEp des rats butyrate. Comme à la périphérie, l'expression de ASIC1a est modulée par le NGF puisque le blocage du NGF prévient la surexpression des ARNm et de la protéine ASIC1A dans la MEp des rats butyrate. En conclusion, ce travail de thèse suggère que le NGF et le canal ASIC1A jouent un rôle critique dans le développement de douleurs viscérales en contribuant à la fois à la sensibilisation périphérique et centrale.
|
303 |
The robot club : robots as agents to improve the social skills of young people on the autistic spectrumBlank, Sarah T. January 2010 (has links)
To better understand the difficulties and strengths associated with both high and low functioning individuals with an autistic spectrum disorder (ASD), the hyper-systemising theory has been proposed by Baron-Cohen and colleagues. It explains the social and communication difficulties in autism and Asperger syndrome (AS) by reference to delays and deficits in empathy, whilst explaining the areas of strength by reference to intact or even superior skill in systemising (Baron-Cohen, 2002). The evidence for hypersystemising alongside hypo-empathising in autism, suggests a corresponding desire to systemise the social world. Based on this theory, the use of technology in supporting the development of social and communication skills in children with an ASD is discussed. Technology and computers rely on strict, predictable systems made up of sets of rules that can be programmed, determined and understood. Use of such technology to assist in the development of social skills in an individual with an ASD utilises an existing area of strength and engages a person in an often existing area of interest and/or obsession. This thesis describes an exploratory study using non-humanoid robots with a group of young people with either high-functioning autism (HFA) or AS, which aimed to use robots as a focus of shared attention in a more naturally occurring and systemisable environment; thus promoting more implicit learning of social skills for this clinical group. Ten children attended the ‘robot club’ for eight sessions enabling a design using a series of single case studies pooled together for multiple and individual base line comparisons. The results indicate improvements as rated by parents and the young people themselves (although not by teachers), with some evidence of statistical and clinically significant changes, for example, in communication skills specifically and with general difficulties associated with autism. The results were found to be affected by total number of sessions attended, but not by age or academic functioning. Possible implications of the findings are presented in line with theory and for clinical practise. Limitations of the study are discussed and suggestions for future research made.
|
304 |
Contamination des solutions d’hyper-alimentation intraveineuses (HAIV) néonatales, effet de l’ascorbylperoxyde au foieCôté, François 12 1900 (has links)
Introduction : Chez les nouveau-nés prématurés, l’hyper-alimentation intraveineuse (HAIV) contribue à leur survie, mais elle est aussi une source importante de molécules oxydantes. L’absence d’une protection adéquate contre la lumière ambiante génère in vitro, via la photo-excitation de la riboflavine, du H2O2, des peroxydes organiques et un dérivé peroxydé de la vitamine C, l’ascorbylperoxyde (AscOOH). Plusieurs données du laboratoire associent l’infusion d’HAIV à des désordres lipidiques dans notre modèle animal. L’hypothèse est donc que l’AscOOH a un pouvoir oxydant et est responsable de certains des effets biologiques observés. Mes objectifs sont les suivants : 1) développer une méthode de dosage de l’AscOOH; 2) démontrer, à l’aide du modèle animal bien établi au laboratoire, des relations entre la concentration tissulaire de cette molécule et des paramètres métaboliques et l’état redox au foie et dans la circulation; et 3) confirmer l’effet physiologique de l’AscOOH dans un modèle cellulaire. Méthode : Différents étalons
internes potentiels ont été testés pour le dosage de l’AscOOH par spectrométrie de masse
après séparation sur HPLC (LC-MS). Les phases mobiles et conditions chromatographiques ont été optimisées. Pour l’objectif 2, des cobayes de 3 jours de vie (n=11) ont reçu par voie intraveineuse une dose d’AscOOH (entre 0 et 3,3mM). Les animaux ont été sacrifiés au 4e jour de traitement pour le prélèvement de tissus. Les concentrations tissulaires d’AscOOH ont été déterminées au LC-MS. La triglycéridémie et la cholestérolémie ont été mesurées à l’aide d’un kit commercial par spectrophotométrie. Le glutathion oxydé et réduit ont été mesurés par électrophorèse capillaire. Les relations linéaires obtenues sont exprimées par le ratio des carrés (r2), et traitées par ANOVA. Résultats : La validation du dosage de l’AscOOH par LC-MS a été réalisée. Chez les animaux, la concentration urinaire d’AscOOH par créatinine corrèle positivement avec la dose reçue, négativement avec la lipidémie, et
négativement avec le redox sanguin et érythrocytaire, indiquant un milieu moins oxydé.
Conclusion : La concentration urinaire d’AscOOH peut donc être un reflet de l’oxydation de l’HAIV en clinique. Nos données chez l’animal suggèrent une interaction de l’AscOOH avec le métabolisme hépatique produisant une chute de la concentration plasmatique de cholestérol et de triglycérides. Le modèle cellulaire n’a pas permis d’élucider le mécanisme moléculaire de l’action de l’AscOOH sur le métabolisme. / Introduction: Intravenous hyperalimentation (IVHA) often contributes to the survival of
preterm newborns, but it is also an important source of oxidizing molecules. The lack of
adequate protection from ambient light generates, in vitro, through the photo-excitation of
riboflavin, H2O2, organic peroxides and a peroxidated derivative of vitamin C:
ascorbylperoxide (AscOOH). Certain data from our laboratory linked the infusion of IVHA
to lipid disorders in our animal model. The hypothesis is that AscOOH is an oxidant that is responsible for some of the biological effects observed. My objectives are: 1) to develop a method for quantitation of AscOOH, 2) to demonstrate, using the guinea pig model used by our laboratory, relations between the tissue concentration of this molecule and metabolic and redox parameters in the liver and plasma, and 3) to confirm the physiological effect of AscOOH in a cell culture model. Method: Different promising internal standards were tested for AscOOH quantitation by mass spectrometry after HPLC separation (LC-MS). Mobile phases and chromatography conditions have been optimized. For objective #2, 3 days old guinea pig pups (n = 11) received an intravenous dose of AscOOH (between 0 and
3.3mM). Animals were sacrificed on the 4th day of treatment for tissue gathering. Tissues AscOOH concentrations were determined by LC-MS. The triglyceride and cholesterol levels were measured by spectrophotometry using a commercial kit. The oxidized and reduced glutathione were measured by capillary electrophoresis. The linear relations obtained are expressed by the square of the correlation coefficient (r2), and processed by ANOVA.
Results: The validation of the LC-MS method for AscOOH quantification has been achieved.
In animals, the concentration of urinary AscOOH by creatinine correlates positively with the dose received, negatively with blood lipids, and negatively with blood and erythrocyte redox, indicating a less oxidized environment. Conclusion: The urinary AscOOH
concentration may be a good indicator of the oxidation state of clinical IVHA. Our data in
animals suggest an interaction between AscOOH and liver metabolism producing a drop in
plasma concentration of cholesterol and triglycerides. The cell model was not able to
clarify the molecular mechanism of AscOOH action on metabolism.
|
305 |
Hyperlokální média v České republice / Hyperlocal media in Czech republicMiksová, Veronika January 2011 (has links)
This thesis deals with one of the fresh trend in media production which caught attention of both scholars and laic public. It concerns phenomenon of hyper local media. Theoretical base of this work lies in appropriation of "locality"as a distinctive attribute in terms of globalization processes. It operates with such terms as spatio- temporal changes, localization, globalization, human and place, authority and social integrity trying to contextualize these terms with media studies. Further it attempts to enlighten what are hyper local media, where can we find its roots in the field of journalism, how do they work and which advantages and disadvantages they have. Research part of the thesis studies particular Czech hyper local project of PPF Investment Company combining case study and quantitative content analysis. Main intention is to find out whether the concept of hyper local journalism is sustainable in Czech media landscape (and under which conditions) and whether it has got working business model. We are also interested in its ability of capturing and keeping new audience and delivering the different content in comparison with another available and comparable media. Keywords hyper local media - Naše adresa - PPF Media - Futuroom - locality - globalization - local and regional press -...
|
306 |
超競爭下之商業生態系統-以行動支付為例 / The Business Ecosystem under Hypercompetition: the Cases of Mobile Payment劉品佳 Unknown Date (has links)
本研究運用質性研究方法,加以個案研究方式,對於第三方支付模式和實體信用卡虛擬化之非第三方支付模式進行個案分析,以探討在超競爭下,行動支付業者如何透過競爭以及合作策略,形成行動支付生態系統發展模式。本研究所得結論如下:
一、中國和肯亞等開發中國家之金融體系尚不發達,交易雙方出現信任缺口,銀行服務並不健全,金融資源分配不均,因此透過破壞傳統支付體系架構,發揮網路外部性之雙邊市場效應,打造出第三方支付模式之行動支付生態系統,以達到普惠金融發展目標。
二、歐美日等已開發國家之金融體系已臻健全,金融匯兌服務普及,金融監理重視市場公平與金融穩定,因此未破壞傳統支付體系架構,而是透過跨產業競合方式修改現有支付面前端程序,型塑出實體信用卡虛擬化支付模式之行動支付生態系統,以達到優化金融服務目標。
綜合上述結論,可歸納出二項管理意涵:第一項為在金融服務普及率較低的體系,傾向於發展填補信任缺口之第三方支付模式,而在金融服務普及率較高的體系,則傾向於發展提高安全性之實體信用卡虛擬化支付模式。第二項為企業藉由競合策略,既爭取價值也創造價值,其中爭取價值的本質是競爭,而創造價值的本質則是合作,以達到雙贏。
台灣傳統金融服務與超商密集度高,客戶需求被高度重視及滿足,銀行、超商與第三方支付業者形成跨產業競合關係,發展出多元支付方式,因此建構使用單一裝置即可提供多元支付功能之行動支付平台,可做為台灣行動支付生態系統健全發展之解決方案。具體建議為尋求跨產業競合,金融監管持開放態度,培訓金融科技人才,加強資訊安全,以建構完善的行動支付生態系統。 / In the view of hyper-competition, sustainable competitive advantage does not exist, and only by constant innovation in order to obtain a series of short-term competitive advantage. However, business ecosystem could clarify the competition and cooperation relationship between businesses. In this study, qualitative research and case study methodologies are used to find the adoptable mobile payment ecosystem.
The third-party payment would fill the trust gap between the parties. Therefore, developing countries should adopt third party mobile payment ecosystem, in order to achieve financial inclusion. The non-third party payment would improve the security of cardholder transactions and reduce the risk of banking. Therefore, developed countries should adopt non-third party mobile payment ecosystem, in order to optimize financial services.
The above conclusions can be summarized as two management implications: First, low penetration of financial services tends to develop third-party payment, and high penetration of financial services tends to develop non-third party payment. Second, business co-opetition strategy has the nature of value creation and value capture to achieve win-win situation.
Taiwan’s financial service-intensive, customer needs are met, banks, stores can be formed with the third-party payment industry co-opetition relations, the development of a diverse payment methods, and therefore the construction using a single device to provide pluralistic payment function of mobile payment platform, will be suitable for robust development of Taiwan’s mobile payment ecosystem. Suggestions include cross-industry co-opetition, open-minded financial supervision, training financial technology professionals, and strengthen information security.
|
307 |
[en] TWO-DIMENSIONAL SIMULATION OF DEBRIS FLOW USING DISTINCT ELEMENT METHOD / [es] SIMULACIÓN BIDIMENSIONAL DE FLUJOS DE DETRITOS COM EL USO DEL MÉTODO DE ELEMENTOS DISCRETOS / [pt] SIMULAÇÃO BIDIMENSIONAL DE CORRIDAS DE DETRITOS USANDO O MÉTODO DE ELEMENTOS DISCRETOSLUIS ALONSO SALAS ALVARADO 13 December 2006 (has links)
[pt] Apresenta-se neste trabalho uma ferramenta numérica
programada que
permite a simulação bidimensional de corridas de detritos
usando o Método de
Elementos Discretos (DEM) desenvolvido por Cundall em
1979, cuja
metodologia resolve as equações do movimento
simultaneamente de cada
elemento mediante a técnica numérica de Relaxação Dinâmica
(MRD) por se
tratar de um problema transiente. Esta metologia parte da
existência do
programa SAND desenvolvido na PUC (2002) para uma
simulação da produção
de areia em poços de petróleo sob fluxo bifásico. Dois
aspectos novos
incorporados neste tipo de análise são a representação
gráfica de anteparos
mediante segmentação de curvas spline cúbicas e o uso da
metodologia de
Munjiza na detecção de contatos com os propósitos de
implementar o uso de
paramentos irregulares próximos à curva real do terreno e
diminuir o tempo de
execusão do programa, respectivamente. Com diversos
exemplos de
paramentos e variando os parâmetros de entrada do modelo
numérico é
avaliada a idoneidade da ferramenta criada para simular os
principais
mecanismos físicos característicos do movimento deste tipo
de fenômeno. Além
disso, são descritas em detalhe as principais feições e
terminologias usadas na
classificação e identificação das corridas de detritos e
fenômenos similares, pois
estas são usualmente confundidas nas literaturas
existentes e entre os
profissionais das áreas da Geologia, Geografia e Geotecnia. / [en] A programed numerical tool that allows two-dimensional
simulation of
debris flows is presented in this dissertation. Cundall´s
Distinct Element Method
(DEM) is used to this purpose, which was developed in
1979. Following this
methodology, motion equations are simultaneilly solved by
the numerical method
of Dynamic Relaxation (MRD) for each distinct particle.
This method is used in
order to the transient behavior of this particular
problem. The numerical modeling
is based on the SAND program, developed at PUC (2002) for
a numerical
application on sand production for petroleum extraction
process considering
biphasic flow motion. Two new features incorporated in
this kind of analyses are
the graphical representation of walls with cubic spline
curves segmentation and
the implementation of the Munjiza´s method for contact
detection. They attemp to
implement irregular curves that are closely to represent
real sliding surface and to
decrease the total program executation time respectively.
The idoneousness of
the programed numerical tool for the representation of the
most caracteristic
phisical mechanisms of these kind of flows is tested using
several curves
configurations as variation on the inicial parametrics
values of the numerical
model. Moreover, main features and associated
terminologies for identification
and classification of debris flows and similar events are
largely described here
because of the usual confusion in the use of them within
scientific literatures and
professional communications between technician of Geology,
Geography and
Geotechnical Engineering. / [es] En este trabajo se disponibiliza una herramienta numérica
para la
simulación bidimensional de flujos de detritos usando el
Método de Elementos
Discretos (DEM) creado por Cundall en 1979, donde las
ecuaciones del
movimiento para cada elemento son resueltas
simultáneamente con la técnica
numérica de Relajación Dinámica (MRD) debido al
comportamiento transiente
del fenómeno. La herramienta se basa en el programa SAND
desarrollado en la
PUC (2002) para la simulación de producción de arena en la
extracción de
petróleo en pozos considerando condiciones de flujo
bifásico. Dos nuevos
aspectos se introducen en este tipo de análises: la
representación gráfica de
paredes mediante la segmentación de curvas splina cúbicas
y el uso de la
metodologia de Munjiza en la detección de contactos. Ambos
son
implementados con la intención de hacer uso de paredes
irregulares próximas a
la forma real de la curva del terreno y de disminuir el
tiempo de ejecución del
programa respectivamente. Mediante varios ejemplos con
diferentes superficies
y con variación en los valores de los parámetros de
entrada del modelo numérico
fue posible evaluar la idoneidad de la herramienta aquí
creada para simular los
principales mecanismos físicos característicos del
movimiento de este tipo de
fenómenos. Además, se describen detalladamente las
principales características
e terminologías utilizadas en la identificación y
clasificación de los flujos de
detritos y fenómenos similares, pues estos son motivos de
confusión en la
literatura existente y entre los profesionales de las
ramas de Geología, Geografía
y Geotecnia.
|
308 |
Approche bayésienne pour la localisation de sources en imagerie acoustique / Bayesian approach in acoustic source localization and imagingChu, Ning 22 November 2013 (has links)
L’imagerie acoustique est une technique performante pour la localisation et la reconstruction de puissance des sources acoustiques en utilisant des mesures limitées au réseau des microphones. Elle est largement utilisée pour évaluer l’influence acoustique dans l’industrie automobile et aéronautique. Les méthodes d’imagerie acoustique impliquent souvent un modèle direct de propagation acoustique et l’inversion de ce modèle direct. Cependant, cette inversion provoque généralement un problème inverse mal-posé. Par conséquent, les méthodes classiques ne permettent d’obtenir de manière satisfaisante ni une haute résolution spatiale, ni une dynamique large de la puissance acoustique. Dans cette thèse, nous avons tout d’abord nous avons créé un modèle direct discret de la puissance acoustique qui devient alors à la fois linéaire et déterminé pour les puissances acoustiques. Et nous ajoutons les erreurs de mesures que nous décomposons en trois parties : le bruit de fond du réseau de capteurs, l’incertitude du modèle causée par les propagations à multi-trajets et les erreurs d’approximation de la modélisation. Pour la résolution du problème inverse, nous avons tout d’abord proposé une approche d’hyper-résolution en utilisant une contrainte de parcimonie, de sorte que nous pouvons obtenir une plus haute résolution spatiale robuste à aux erreurs de mesures à condition que le paramètre de parcimonie soit estimé attentivement. Ensuite, afin d’obtenir une dynamique large et une plus forte robustesse aux bruits, nous avons proposé une approche basée sur une inférence bayésienne avec un a priori parcimonieux. Toutes les variables et paramètres inconnus peuvent être estimées par l’estimation du maximum a posteriori conjoint (JMAP). Toutefois, le JMAP souffrant d’une optimisation non-quadratique d’importants coûts de calcul, nous avons cherché des solutions d’accélération algorithmique: une approximation du modèle direct en utilisant une convolution 2D avec un noyau invariant. Grâce à ce modèle, nos approches peuvent être parallélisées sur des Graphics Processing Unit (GPU) . Par ailleurs, nous avons affiné notre modèle statistique sur 2 aspects : prise en compte de la non stationarité spatiale des erreurs de mesures et la définition d’une loi a priori pour les puissances renforçant la parcimonie en loi de Students-t. Enfin, nous ont poussé à mettre en place une Approximation Variationnelle Bayésienne (VBA). Cette approche permet non seulement d’obtenir toutes les estimations des inconnues, mais aussi de fournir des intervalles de confiance grâce aux paramètres cachés utilisés par les lois de Students-t. Pour conclure, nos approches ont été comparées avec des méthodes de l’état-de-l’art sur des données simulées, réelles (provenant d’essais en soufflerie chez Renault S2A) et hybrides. / Acoustic imaging is an advanced technique for acoustic source localization and power reconstruction using limited measurements at microphone sensor array. This technique can provide meaningful insights into performances, properties and mechanisms of acoustic sources. It has been widely used for evaluating the acoustic influence in automobile and aircraft industries. Acoustic imaging methods often involve in two aspects: a forward model of acoustic signal (power) propagation, and its inverse solution. However, the inversion usually causes a very ill-posed inverse problem, whose solution is not unique and is quite sensitive to measurement errors. Therefore, classical methods cannot easily obtain high spatial resolutions between two close sources, nor achieve wide dynamic range of acoustic source powers. In this thesis, we firstly build up a discrete forward model of acoustic signal propagation. This signal model is a linear but under-determined system of equations linking the measured data and unknown source signals. Based on this signal model, we set up a discrete forward model of acoustic power propagation. This power model is both linear and determined for source powers. In the forward models, we consider the measurement errors to be mainly composed of background noises at sensor array, model uncertainty caused by multi-path propagation, as well as model approximating errors. For the inverse problem of the acoustic power model, we firstly propose a robust super-resolution approach with the sparsity constraint, so that we can obtain very high spatial resolution in strong measurement errors. But the sparsity parameter should be carefully estimated for effective performance. Then for the acoustic imaging with large dynamic range and robustness, we propose a robust Bayesian inference approach with a sparsity enforcing prior: the double exponential law. This sparse prior can better embody the sparsity characteristic of source distribution than the sparsity constraint. All the unknown variables and parameters can be alternatively estimated by the Joint Maximum A Posterior (JMAP) estimation. However, this JMAP suffers a non-quadratic optimization and causes huge computational cost. So that we improve two following aspects: In order to accelerate the JMAP estimation, we investigate an invariant 2D convolution operator to approximate acoustic power propagation model. Owing to this invariant convolution model, our approaches can be parallelly implemented by the Graphics Processing Unit (GPU). Furthermore, we consider that measurement errors are spatially variant (non-stationary) at different sensors. In this more practical case, the distribution of measurement errors can be more accurately modeled by Students-t law which can express the variant variances by hidden parameters. Moreover, the sparsity enforcing distribution can be more conveniently described by the Student's-t law which can be decomposed into multivariate Gaussian and Gamma laws. However, the JMAP estimation risks to obtain so many unknown variables and hidden parameters. Therefore, we apply the Variational Bayesian Approximation (VBA) to overcome the JMAP drawbacks. One of the fabulous advantages of VBA is that it can not only achieve the parameter estimations, but also offer the confidential interval of interested parameters thanks to hidden parameters used in Students-t priors. To conclude, proposed approaches are validated by simulations, real data from wind tunnel experiments of Renault S2A, as well as the hybrid data. Compared with some typical state-of-the-art methods, the main advantages of proposed approaches are robust to measurement errors, super spatial resolutions, wide dynamic range and no need for source number nor Signal to Noise Ration (SNR) beforehand.
|
309 |
Não linearidades de segunda e terceira ordem de sistemas moleculares ramificados / Second and third order nonlinearities of branched molecular systemsRodriguez, Ruben Dario Fonseca 26 October 2016 (has links)
Compostos orgânicos constituem uma classe interessante de materiais para aplicações em óptica por apresentarem boa processabilidade, relativa facilidade para integração em dispositivos e, principalmente, pela possibilidade de otimização de suas propriedades ópticas através da engenharia molecular. Várias estratégias têm sido empregadas para sintetizar moléculas orgânicas, que exibam singificativos efeitos ópticos não lineares. Nesta direção, nos últimos anos moléculas multi-ramificadas vêm sendo produzidas com o objetivo de intensificar efeitos não lineares, já que estas podem exibir um forte efeito cooperativo entre seus ramos. Nesta tese estudamos a relação da absorção de dois fótons (A2F) e da primeira hiperpolarizabilidade com a estrutura molecular, para um conjunto de nove derivados de trifenilamina com diferentes grupos aceitadores de elétrons arranjadas em geometrias dipolar, quadrupolar e octopolar. O processo A2F foi estudados através da técnica de Varredura-Z, enquanto que a primeira hiperpolarizabilidade foi caracterizada pela técnica de espelhamento hiper Rayleigh. Os dados experimentais para a absorção de dois fótons revelaram espectros bem definidos, com valores razoáveis de seção de choque na região do visível e infravermelho próximo. Observamos ainda um engrandecimento para a seção de choque de A2F para as moléculas quadrupolares. Os resultados obtidos para a primeira hiperpolarizabilidade (β) mostraram que moléculas quadrupolares apresentam maior β do que as dipolares e octopolares, portanto, nossos resultados permitem concluir que o acoplamento eletrônico entre os ramos contribuem fortemente para a seção de choque por A2F e β nas moléculas quadrupolares, não sendo este processo relevante nas moléculas octopolares. Todos os resultados foram interpretados por meio de estudos teóricos empregando a teoria do funcional da densidade (DFT). / Organic compounds constitute an interesting class of materials for optical applications due to their excellent processability, easy integration into devices and, mainly, the possibility of optimizing its optical properties through molecular engineering. Several strategies have been employed to synthesize organic molecules, which exhibit significant nonlinear optical effects. In this direction, in the last few years multi-branched molecules have been obtained aiming at intensifying nonlinear optical effects, since they may exhibit a strong cooperative effect among their branches. On this thesis we have studied the relationship of two-photon absorption (2PA) and first hyperpolarizability with the molecular structure of a group of nine triphenylamine derivatives attached to distinct electron acceptor groups arranged in dipole, quadrupole and octopolar geometries. The 2PA process was studied by Z-scan technique, while the first hyperpolarizability was characterized by the hyper-Rayleigh scattering technique. The experimental data for two-photon absorption revealed well-defined spectra with reasonable cross section magnitude in the visible and near infrared range. We also observed an enhancement of the 2PA cross-section for the quadrupolar molecules in comparison to the dipolar and octopolar ones. The results obtained for the first hyperpolarizability (β) shown that the quadrupolar molecules present higher β than the dipolar and octopolar, suggesting that the electronic coupling between the branches strongly contribute to the 2PA cross-section and β in quadrupolar molecules, being not relevant in the octopolar molecules. All results were interpreted through theoretical studies based on the density functional theory (DFT).
|
310 |
Propriedades ópticas não-lineares de oligômeros de anilina / Nonlinear optical properties of aniline oligomersFranzen, Paulo Licênio 29 October 2002 (has links)
Apresentamos os resultados do estudo das não-linearidades ópticas de origem eletrônica de duas moléculas da classe dos oligômeros de anilina: o dímero e o tetrâmero. Foram medidas quatro concentrações de tetrâmero, puras e também dopadas em 33 e 100%; uma de dímero pura e outra dopada em 100%. As soluções foram preparadas usando dimetil-sulfóxido (DMSO) como solvente e a dopagem foi realizada com ácido clorídrico. As amostras foram caracterizadas por medidas de absorção linear e fluorescência antes das medidas não-lineares. Obtivemos os valores da primeira hiperpolarizabilidade (?) para todas as amostras, o índice de refração não-linear (n2) do tetrâmero dopado e não dopado, e a absorção não-linear em função da intensidade e da concentração do tetrâmero. As medidas foram realizadas através das técnicas de Varredura-Z, absorção não-linear e espalhamento Hiper-Rayleigh. Os resultados foram interpretados em termos da comparação entre diferentes estados de dopagem e da variação da seção de choque do estado fundamental para o primeiro excitado. / We report on the study of electronic optical non linearities in two aniline oligomers: dimer and the tetramer. Four tetramer concentrations were measured, pure and also 33 and 100% doped; one of dimer non doped another 100% doped. The solutions were prepared using dimethyl sulfoxide (DMSO) as solvent and the doping was performed with hydrochloric acid. The samples were characterized by measurements of linear absorption and fluorescence. We obtained the values of the first hyperpolarizability (?) for all samples, the non linear index of refraction (n2) for non doped and doped tetramer, and the non linear absorption in function of intensity and concentration of the tetramer. The measurements were accomplished through the techniques of Z-Scan, non linear absorption and Hyper-Rayleigh Scattering. The results were interpreted in terms of the comparison among different doping states and of the variation of cross-section for the transition from ground to the first excited states.
|
Page generated in 0.0189 seconds