No description available.

Le noyau d'une cellule est hétérogène par sa structure et son activité et beaucoup de ses composants interagissent de façon dynamique. Lors de l'étude de processus cellulaires comme la réponse au stress thermique, des expériences classiques de spectroscopie de corrélation de fluorescence (FCS), qui sont habituellement limitées à un seul volume d'observation, n'apportent que des résultats partiels à cause des informations spatiales manquantes. Ce mémoire de thèse présente une nouvelle technique de FCS multi-confocale (mFCS) qui permet des mesures FCS simultanées à différents endroits d'une cellule. La technique est basée sur l'emploi d'un modulateur spatial de lumière pour la création de plusieurs volumes d'observations distincts et d'une caméra ''electron-multiplying'' CCD (EMCCD) pour la détection en parallèle. La résolution spatiale ainsi que la sensibilité du système mFCS sont proches de celles d'un système FCS classique et en utilisant un mode d'acquisition particulier une résolution temporelle de $14mu s$ a pu être atteinte. La technique mFCS est appliquée à l'étude de la réponse cellulaire au stress thermique en observant le facteur de transcription heat shock factor 1 (HSF1), qui est un régulateur clé de la réponse au stress thermique. Des mesures mFCS dans des cellules vivantes révèlent des changements dans la dynamique de HSF1 pendant le choc thermique. Ces changements concernent l'affinité ainsi que l'homogénéité spatiale des interactions avec l'ADN. En outre, nous avons également évalué les performances d'une caméra CMOS-SPAD et testé le dispositif en tant que capteur alternatif pour la mFCS en cellules vivantes.

La spectroscopie de corrélation de fluctuation a été utilisée pour étudier la réponse optique, en solution, de molécules et de billes d'or nanométriques individuelles, fonctionnalisées ou non, en vue du développement de nouvelles sondes biochimiques. Les expériences réalisées s'appuient sur un système de microscopie confocale et/ou biphotonique optimisé pour la détection de faibles signaux. Plusieurs procédés de filtrage du signal de fluorescence et d'algorithmes de calcul de la corrélation ont permis une analyse détaillée des signaux acquis. A travers un modèle original, je montre qu'il faut tenir compte de la réponse impulsionnelle tensorielle du microscope lors de l'ajustement des courbes de corrélation de particules ayant un diagramme d'émission anisotrope. Je me suis intéressé à trois types de nanosondes différentes. J'ai montré que l'on peut caractériser efficacement des sondes calciques comme l'Oregon Green Bapta 5N par spectroscopie de corrélation de fluctuations tout en pointant les limites de la méthode. J'ai ensuite mis en évidence et caractérisé une anisotropie inattendue de l'absorption à deux photons et de l'émission de photoluminescence de nanosphères d'or. Son interprétation montre l'importance du rôle des états de surface et de celui des ligands et de leur dynamique. J'ai aussi caractérisé des nanosondes formées de particule d'or fonctionnalisées avec des chromophores. Une technique originale s'appuyant sur la nature hybride de la sonde, m'a permis de démontrer l'hétérogénéité de ces systèmes, la formation d'agrégats de fluorophores et la très forte annihilation de la fluorescence des chromophores liés aux particules d'or.

For years social workers have been involved in the investigation of child abuse cases, which includes the sexual abuse of children. The forensic social worker primarily engages with the investigation of child sexual abuse allegations and their involvement begins when a criminal case of alleged child sexual abuse is registered with the police. The core function of forensic social workers is to objectively assist the South African Police Service (SAPS) and the judicial system during the investigation of crimes against children, which includes cases of alleged sexual abuse of babies. The aim of this study was to determine the role of the forensic social worker in cases of sexual abuse of babies in the Boland. A qualitative research procedure was followed and data was gathered through in-depth interviews with three state prosecutors working in regional courts in Worcester, Ceres and Paarl. In-depth interviews were also conducted with three SAPS forensic social workers in these areas. The results of the investigation were summarised according to certain themes. The results of the study indicate that the successful prosecution and conviction of offenders of the sexual abuse of babies are limited, because a baby is unable to deliver testimony. The crucial role of the qualified forensic social worker in the investigation of these cases was highlighted in the study. The participants found the thorough investigation of collateral sources and the interpretation of information gathered by forensic social workers of great value. As an expert witness the forensic social worker can therefore play a prominent role in the conviction of offenders of sexual abuse of babies. / Thesis (MA (SW (Forensic))--North-West University, Potchefstroom Campus, 2013

South Africa, notwithstanding her comprehensive legislation, has disturbingly high figures of child sexual violence. These crimes and the low conviction rates should put any role-player within the field of sexual violence to shame. Concerns are raised that, unless trained professionals deal with child sexual abuse victims, we will fail to protect children from abuse and fail in our quest for justice. The South African police, in its efforts to prioritize crimes against women and children, employed forensic social workers. This article presents the results of an explorative study of the role and responsibilities of the forensic social worker in the SAPS. Data was collected from three groups of participants (forensic social workers, state prosecutors and police investigating officers) according to a mixed method approach. Both qualitative (semi-structured interviews) and quantitative (statistical data) methods were therefore employed. The forensic process is designed to answer a question of relevance to the legal system, which makes the role of the forensic social worker very specific. If roleplayers in the field of child sexual offences, however, are not entirely familiar with what forensic social work entails, it could not only complicate matters for the forensic social workers, but it could also mean that their services are not used optimally and effectively. The findings of the study indicate that forensic social workers make a valuable contribution to the successful investigation of child sexual offences; however, in the absence of adequate continuous trainin training, supervision and consultation, they could fail in providing a proficient service. / Thesis (MSW (Forensic Practice))--North-West University, Potchefstroom Campus, 2013.

For years social workers have been involved in the investigation of child abuse cases, which includes the sexual abuse of children. The forensic social worker primarily engages with the investigation of child sexual abuse allegations and their involvement begins when a criminal case of alleged child sexual abuse is registered with the police. The core function of forensic social workers is to objectively assist the South African Police Service (SAPS) and the judicial system during the investigation of crimes against children, which includes cases of alleged sexual abuse of babies. The aim of this study was to determine the role of the forensic social worker in cases of sexual abuse of babies in the Boland. A qualitative research procedure was followed and data was gathered through in-depth interviews with three state prosecutors working in regional courts in Worcester, Ceres and Paarl. In-depth interviews were also conducted with three SAPS forensic social workers in these areas. The results of the investigation were summarised according to certain themes. The results of the study indicate that the successful prosecution and conviction of offenders of the sexual abuse of babies are limited, because a baby is unable to deliver testimony. The crucial role of the qualified forensic social worker in the investigation of these cases was highlighted in the study. The participants found the thorough investigation of collateral sources and the interpretation of information gathered by forensic social workers of great value. As an expert witness the forensic social worker can therefore play a prominent role in the conviction of offenders of sexual abuse of babies. / Thesis (MA (SW (Forensic))--North-West University, Potchefstroom Campus, 2013

South Africa, notwithstanding her comprehensive legislation, has disturbingly high figures of child sexual violence. These crimes and the low conviction rates should put any role-player within the field of sexual violence to shame. Concerns are raised that, unless trained professionals deal with child sexual abuse victims, we will fail to protect children from abuse and fail in our quest for justice. The South African police, in its efforts to prioritize crimes against women and children, employed forensic social workers. This article presents the results of an explorative study of the role and responsibilities of the forensic social worker in the SAPS. Data was collected from three groups of participants (forensic social workers, state prosecutors and police investigating officers) according to a mixed method approach. Both qualitative (semi-structured interviews) and quantitative (statistical data) methods were therefore employed. The forensic process is designed to answer a question of relevance to the legal system, which makes the role of the forensic social worker very specific. If roleplayers in the field of child sexual offences, however, are not entirely familiar with what forensic social work entails, it could not only complicate matters for the forensic social workers, but it could also mean that their services are not used optimally and effectively. The findings of the study indicate that forensic social workers make a valuable contribution to the successful investigation of child sexual offences; however, in the absence of adequate continuous trainin training, supervision and consultation, they could fail in providing a proficient service. / Thesis (MSW (Forensic Practice))--North-West University, Potchefstroom Campus, 2013.

No description available.

La spectroscopie de fluorescence de molécule individuelle a révolutionné le domaine des sciences biophysiques, en permettant la visualisation des interactions moléculaires dynamiques et des caractéristiques nanoscopiques avec une haute résolution spatio-temporelle. Le contrôle des réactions enzymatiques et l'étude de la dynamique de diffusion de molécules individuelles permet de comprendre l'influence et le contrôle de ces entités nanoscopiques sur plusieurs processus biophysiques. La nanophotonique basée sur la plasmonique offre des nouvelles opportunités de suivi d'évènements à molécule unique, puisque il est possible de confiner des champs électromagnétiques dans les hotspots à nano-échelle, à dimensions spatiales comparables à une molécule unique. Dans ce projet de thèse, nous explorons plusieurs plateformes de nanoantennas photoniques avec des hotspots, et nous avons démontré les applications dans l'amélioration de la spectroscopie de fluorescence de molécule individuelle. En utilisant la fluorescence burst analysis, l'analyse de fluctuations temporelle de fluorescence,TCSPC, nous quantifions les facteurs d'amélioration de fluorescence, les volumes de détection de nanoantennas; ainsi, nous discutons l'accélération de fluorescence photo dynamique. En alternative aux structures plasmoniques, des antennes diélectriques basées sur les dimères en silicone ont aussi démontré d'améliorer la détection de fluorescence à molécule unique, pour des concentrations micro molaires physiologiquement pertinentes. En outre, nous explorons des systèmes planaires antennas in box pour l'investigation de la dynamique de diffusion de la PE et de la SM dans les membranes des cellules vivantes. / Single-molecule fluorescence spectroscopy has revolutionized the field of biophysical sciences by enabling visualization of dynamic molecular interactions and nanoscopic features with high spatiotemporal resolution. Monitoring enzymatic reactions and studying diffusion dynamics of individual molecules help us understand how these nanoscopic entities influence and control various biochemical processes. Nanophotonic antennas can efficiently localize electromagnetic radiation into nanoscale spatial dimensions comparable to single bio-molecules. These confined illumination hotspots there by offer the opportunity to follow single-molecule events at physiological expression levels. In this thesis, we explore various photonic nanoantenna platforms and demonstrate their application in enhanced single-molecule fluorescence detection. Using fluorescence burst analysis, fluorescence correlation spectroscopy (FCS), time-correlated TCSPC measurements, and near field simulations, we quantify nanoantenna detection volumes, fluorescence enhancement factors and discuss the fluorescence photodynamic accelerations mediated by optical antennas. Further, using resonant planar antenna-in-box devices we investigate the diffusion dynamics of phosphoethanolamine and sphingomyelin on the plasma membrane of living cells and discuss the results in the context of lipid rafts. Together with cholesterol depletion experiments, we provide evidence of cholesterol-induced nanodomain partitioning within less than 10~nm diameters and characteristic times being ~100 microseconds.

Mesoscopic structures in liquids have an impact on the diffusion dynamics of the constituting molecules. Smectic 8CB liquid crystals on silicon wafers show the formation of mesoscopic structures on the μm scale at a film thickness of 200 nm. Depending on the kind of substrate (thermally grown or native SiOx), we observed the formation of focal conic domains (FCDs) and a new type of terraced holes, respectively. Dynamics are described via single perylene diimide tracer molecule tracking of translational diffusion and in the case of FCDs by a combination of translation and rotation detected via fluorescence correlation spectroscopy. Tailoring perylene diimide molecules such that the optical transition dipole moment follows the liquid crystal director allows mapping out FCDs and investigating the dynamics within a single FCD.