Ce travail concerne l'étude du phénomène de décharges partielles dans les matériaux isolants utilisés en électronique de puissance. En utilisant des méthodes de détection électrique et optique, le mécanisme de décharge partielle sur des substrats d'AlN dans l'huile silicone a été étudié sur un grand nombre d'échantillons. La variation de la nature du substrat (AlN, Al2O3 et composite verre/époxy) et du matériau d'encapsulation (huile silicone, huile de colza, huile minérale de transformateur, liquide d'imprégnant du condensateur Jarylec et Ugilec) met en évidence l'origine des décharges partielles de l'ensemble substrat - encapsulant. Les décharges partielles sur les substrats céramiques frittés ne dépendent pas du passivant, et se produisent dans le volume du substrat. L'évolution temporelle de la lumière émise dans les liquides en configuration pointe - plan et sur le substrat dans différents liquides montre que l'émission de lumière est un phénomène très complexe influencé par de nombreux paramètres : électroluminescence du solide, de l'encapsulant, décharges partielles, absorption des matériaux. Le phénomène d'électroluminescence du liquide est activé par une illumination extérieure. Les mesures de spectroscopie diélectrique haute tension n'apportent pas d'information supplémentaire sur le phénomène de décharges partielles, car les pertes correspondantes sont très faibles.

Habitat loss and fragmentation occur at unprecedented rates, especially in tropical countries where human activities have deforested or degraded around 80% of tropical rainforests. Tropical forest fragmentation is considered the main cause of extinction of tropical forest avifauna, yet the mechanisms by which fragmentation affects bird populations are poorly understood. The present study investigates the pattern of bird species distribution in a fragmented landscape in tropical southeastern Mexico and the relation of bird community and species distribution patterns to landscape and fragment characteristics. Area and isolation of forest fragments were the main determinant of species richness and abundance in fragments, especially for forest-dependent species. The significant effect of isolation on species persistence in forest fragments suggests that limitation of dispersal is one potential mechanism by which fragmentation affects species distribution in the landscape. To understand how fragmentation can affect bird dispersal in a fragmented landscape, the effect of open areas and corridors on movement patterns of forest birds was investigated. The evidence presented in this study supports the idea that bird movement is restricted by open areas, especially for forest-restricted birds. Forested corridors had a positive effect on movement rates of forest birds, potentially acting to preserve movement and dispersal processes, and ultimately species persistence, in heavily fragmented landscapes.

Accessibility is a key tenet of the Canadian health care system. As many older persons, age 60 years and older, are managing ongoing chronic health conditions as part of their everyday lives, issues of access to health services are particularly important. Vancouver has a substantial number of older Korean immigrants, yet little is known about their experience and perceptions about accessing Primary Health Care (PHC) services. This study explored issues related to PHC access by older (aged 60 years and older) Korean immigrants. This qualitative study employed purposive sampling and interpretive description methodology. Open-ended interview data and field notes were gathered from 10 older Korean immigrants (five male and five female) recruited in Vancouver from mid-October 2006 to April 2007. The findings revealed that older Korean immigrants have had difficulty gaining access to appropriate PHC services because of the shifts in their social positioning and other barriers which contributed to an inappropriate use of PHC services, delays in care and lack of continuity in PHC. Also, the data revealed a number of ways the PHC system is unresponsive to the health care needs of older Korean immigrants. This study offers insights that may assist health care professionals to understand the nature of the challenges older Korean immigrants face when seeking health care and how they seek to resolve them. The analysis proposes a number of interventions that respect the older Korean immigrants’ values and interventions that may improve their access to PHC.

The purpose of this study was to investigate the work of three administrators and their staffs as they attempted to solve the ill-structured problem of integrating students with fetal alcohol spectrum disorders (FASD) into their schools. A further purpose of the study was to investigate the role played by schools in influencing community responses that would enhance the post-school lives of students with FASD.<p>The study was conducted throughout one academic year and involved three schools in northern Canada. The use of Problem Based Methodology (PBM) permitted research to be conducted within the schools to generate solutions to the problem. By working with their staff, administrators were afforded opportunities to examine their theories in action and engage in double-loop learning as they searched for new theories of action and alternate constraint constructs.<p>The data for the study were derived from interviews with participating practitioners, parents, health professionals, and District Educational Authority (DEA) members. This permitted the gathering of spontaneous comments and general opinions to be turned into systemic records and detailed statements. The use of PBM determined that data selection involved a search for behaviours in classes of interest. Potential classes of interest were identified prior to the beginning of the study. By the use of a constraint structure, parameters were established for acceptable solutions that generated a theory of action for the ill-structured problem. The four criteria of explanatory accuracy, effectiveness, coherence and improvability were used in theory adjudication (Robinson 1993). Critical dialogue was used between the researcher and participants to collectively make decisions and solve problems through the exchange of the best possible information.<p>The study suggested implications for organizational theory that could better enable administrators and staff to address this ill-structured problem. The isolation and lack of resources oblige staff to create conditions conducive to inquiry and learning (Schon 1983). In the case of initial solutions the theories in action were similar, suggesting that assumptions surrounding the role of contextual factors caused by the heterogeneous nature of the schools are misleading. Prior to the study by Godel et al. (2000) lack of diagnosis diffused the urgency of the problem. Following the publication of the data from that study the lack of screening and diagnosis was a major challenge to stakeholders. Generation of data on the children with FASD in northern communities is essential to generate an organizational and professional focus.

The purpose is to isolate a natural compound, which shows a high activity against Candida albicans, from plant, Vincetoxicum stocksii. Bio-Assay, Thin layer Chromatography, Column Chromatography, TLC bio Assay, and other extraction techniques are used in order to isolate the active compound. First, bio assay technique is carried out on the crude gum. Next, several flash chromatography columns are carried out in order to isolate the target compound, which has a Rf value of ~0.53 in 10:1 DCM/methanol solvent mixture. The TLC bioassay technique is also carried out in order to confirm the hypothesis that the target compound is indeed active.

The variety of ways in which child abuse is currently defined hampers efforts to capture the prevalence of child abuse and seriously undermines research efforts. Professionals and researchers agree that the definition of child abuse is problematic and call for a concerted effort to address the problem. The goal of this study was to contribute to our understanding of child abuse by giving voice to individuals who labeled their childhood experiences as abusive. In-depth, unstructured interviews explored their childhood experiences, and the process by which they arrived at their decision to label these experiences as abusive. The categories and properties that emerged from the analysis of these narratives were tested against the narratives of individuals who shared similar childhood experiences but who did not label their experiences as abusive. I used the principles and methods of grounded theory to guide the collection, analysis and interpretation of the data. <p>As a result of the analysis, a theory was developed whereby child abuse is best described as a dynamic process that occurs in the interaction between a child and his or her parents as well as a child and his or her community. It is a struggle for control that begins with a parent's need for control that escalates over time into out-of-control behaviors as a child attempts to regain control through a variety of strategies that, over time, also become out of control. Stressors, both pre-existing and on-going, play a pivotal role in initiating and maintaining the child abuse process. Isolation, both social and psychological, is central to the experience of abuse and leads to the labeling of abuse. The experience of child abuse is one of being dehumanized or robbed of a sense of self. A discussion of this theory in relation to present models of abuse, the intergenerational transmission of abuse, interventions and directions forfuture research follows the presentation of the theory.

No description available.

The variety of ways in which child abuse is currently defined hampers efforts to capture the prevalence of child abuse and seriously undermines research efforts. Professionals and researchers agree that the definition of child abuse is problematic and call for a concerted effort to address the problem. The goal of this study was to contribute to our understanding of child abuse by giving voice to individuals who labeled their childhood experiences as abusive. In-depth, unstructured interviews explored their childhood experiences, and the process by which they arrived at their decision to label these experiences as abusive. The categories and properties that emerged from the analysis of these narratives were tested against the narratives of individuals who shared similar childhood experiences but who did not label their experiences as abusive. I used the principles and methods of grounded theory to guide the collection, analysis and interpretation of the data. <p>As a result of the analysis, a theory was developed whereby child abuse is best described as a dynamic process that occurs in the interaction between a child and his or her parents as well as a child and his or her community. It is a struggle for control that begins with a parent's need for control that escalates over time into out-of-control behaviors as a child attempts to regain control through a variety of strategies that, over time, also become out of control. Stressors, both pre-existing and on-going, play a pivotal role in initiating and maintaining the child abuse process. Isolation, both social and psychological, is central to the experience of abuse and leads to the labeling of abuse. The experience of child abuse is one of being dehumanized or robbed of a sense of self. A discussion of this theory in relation to present models of abuse, the intergenerational transmission of abuse, interventions and directions forfuture research follows the presentation of the theory.

Pollen contamination is a severe problem in production breeding programs since it reduces the expected gain. In an attempt to solve this problem Skogforsk created an isolation experiment in the advanced Scots pine (Pinus sylvestris) seed orchard Västerhus in Västerbotten, Sweden. This experiment involves covering blocks of trees with a tent during the pollination period so that they only can mate with each other inside. To evaluate the effects of this tent treatment one tree from inside a tent with supplementary mass pollination (SMP) and one tree from the open control were chosen for this study. 48 seeds from each tree were sampled and genotypes at 9 microsatellite (SSR) loci. The likelihood and exclusion methods for paternity assignment were used to establish the fathers to these seeds. The results showed 0% contamination inside the tent and 4-8% outside in the control. The number of fathers contributed to the fertilization of the 48 seeds was 9 inside and 15 outside. The selfing rate was unexpectedly high, 10% inside the tent and 19% outside. The mating system inside the tent need to be further evaluated to fully understand what other effect the treatment has on the future progeny.

Oil from flaxseed (Linum usitatisssimum L.) contains hydrophobic cyclic peptides or cyclolinopeptides (CLs) comprising eight or nine amino acids. These bioactive compounds have potential therapeutic applications and may be used as scaffolds for increased utility. Two steps were undertaken to increase the potential utility of these compounds. Initially multigram quantities of flax CLs were highly enriched from flax oil. Subsequently new synthetic procedures were developed for modification of the CLs through the methionine group (Met). Finally, the utility of the modified CLs was tested in a number of applications. CLs were recovered from a crude oil extract that contain five CLs (CLA, CLC, CLE, CLJ and CLK). Oxidation of this mixture reduced the complexity of the mix to just three CLA, CLJ and CLK. CLJ and CLK were enriched then characterized by NMR and MS-MS methods. CLs containing methionine sulfoxide groups (Mso), CLC and CLE were isolated from crude mixture then selectively reduced to afford Met containing analogs: CLB and CLE'. The Met of modified CLs was used as a point for attachment of tags and couplers for various applications. Cyclic peptide modification through Met groups has not been reported previously. Synthetic methods were devised to introduce activating functional groups such as -CN, -COOH, -OH and -NH2 to the sulfur atom of Met. The modified CL conjugates were characterized using spectrometric techniques including 1D and 2D NMR spectrometry, as well as mass spectrometry. After activation the CLs were covalently linked to molecules or materials of interest including fluorescence tags (coumarin), affinity chromatography media and bovine serum albumin (BSA) for production of polyclonal antibodies. Fluorescence studies were performed in methanol, ethanol, dimethylformamide and acetonitrile to study the solvent effect. CLs attached to solid affinity matrix showed specific binding to apolipoprotein A1 after incubation with chicken serum. These CLs also act as hapten and have been used to couple BSA to produce polyclonal antibodies. Met modification was a satisfactory approach to produce a range of useful peptide products where more conventional methods of molecule attachment are not available.