27 research outputs found

    Current density inhomogeneity throughout the thickness of superconducting films and its effect on their irreversible magnetic properties

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    We calculate the distribution of the current density jj in superconducting films along the direction of an external field applied perpendicular to the film plane. Our analysis reveals that in the presence of bulk pinning jj is inhomogeneous on a length scale of order the inter vortex distance. This inhomogeneity is significantly enhanced in the presence of surface pinning. We introduce new critical state model, which takes into account the current density variations throughout the film thickness, and show how these variations give rise to the experimentally observed thickness dependence of % j and magnetic relaxation rate.Comment: RevTex, 9 PS figures. To appear in Phys. Rev.

    Étude ethnobotanique et floristique de quelques plantes médicinales commercialisées à Kinshasa, République Démocratique du Congo

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    According to the WHO, more than 80% of the population in Africa resort to traditional medicine to solve primary health problem. In the present study, an ethnobotanical survey was carried out according to a stratified probabilistic sampling plan in five markets of the district of Mont-Amba, in Kinshasa city. The ethnobotanical data collected were then supplemented by information concerning plant ecological types. 47 species belonging 44 genera and 29 families were inventoried in the medicinal flora of the District of Mont-Amba. These plant species are used in treating 41 diseases but only the treatment of poison (toxicological hepatitis), sexual weakness, malaria and tooth decay received an informant consensus factor ? 50%. According to the value of agreement use, only the following eight plant species are of interest: Aframomum melegueta, Garcinia kola, Gladiolus gregarius, Gongronema latifolium, Heinsia crinita, Morinda morindoides, Quassia africana and Sarcocephalus latifolius. It is thus desirable that studies should be carried out on these eight plant species in order to collect scientific data for guiding future research on the phytochemistry and the bioactivity which will lead to the domestication of raw materials for the development of improved plant-based medicines. Also, the creation of a botanical garden of medicinal plants will be able to contribute to the safeguard of the medically active plants, the diffusion of knowledge, medical and pharmaceutical experiences and sociocultural exchanges. Keywords: Ethno-botanical survey, medicinal plant species, sustainable management, conservation, Democratic Republic of the CongoSelon l’OMS, plus de 80% de la population africaine recourt à la médecine traditionnelle pour résoudre le problème de santé primaire. Dans la présente étude, une enquête ethnobotanique a été menée selon un plan d’échantillonnage stratifié probabiliste dans cinq marchés du district de Mont-Amba. Les données ethnobotaniques recueillies ont ensuite été complétées par des informations concernant les types écologiques. 47 espèces appartenant 44 genres et 29 familles ont été inventoriées dans la flore médicinale du District de Mont-Amba à Kinshasa. Ces plantes traitent 41 maladies, cependant seuls les traitements du poison (hépatite toxicologique), de la faiblesse sexuelle, du paludisme et de la carie dentaire ont un facteur de consensus informateur ? 50 %. En recourant à la valeur d’accord d’utilisation, seules huit plantes se dégagent du lot, notamment Aframomum melegueta, Garcinia kola, Gladiolus gregarius, Gongronema latifolium, Heinsia crinita, Morinda morindoides, Quassia africana et Sarcocephalus latifolius. Il est donc souhaitable que des études soient réalisées sur ces huit plantes en vue de recueillir les données scientifiques pouvant orienter les recherches pharmaco-biologiques et phytochimiques futures et susceptibles de conduire à la domestication des matières premières pour la fabrication de médicaments traditionnels améliorés. Aussi, la création d’un jardin botanique de plantes médicinales pourra contribuer à la sauvegarde des espèces bioactives, à la diffusion et à l’échange des connaissances et des expériences médico-pharmaceutiques et socio-culturelles. Mots-cléfs: Enquête ethnobotanique, Plantes médicinales, Gestion durable, Conservation, République démocratique du Cong

    Ethnobotanical and floristic study of some medicinal plant species sold in Kinshasa city, Democratic Republic of Congo

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    According to the WHO, more than 80% of the population in Africa resort to traditional medicine to solve primary health problem. In the present study, an ethnobotanical survey was carried out according to a stratified probabilistic sampling plan in five markets of the district of Mont-Amba, in Kinshasa city. The ethnobotanical data collected were then supplemented by information concerning plant ecological types. 47 species belonging 44 genera and 29 families were inventoried in the medicinal flora of the District of Mont-Amba. These plant species are used in treating 41 diseases but only the treatment of poison (toxicological hepatitis), sexual weakness, malaria and tooth decay received an informant consensus factor ? 50%. According to the value of agreement use, only the following eight plant species are of interest: Aframomum melegueta, Garcinia kola, Gladiolus gregarius, Gongronema latifolium, Heinsia crinita, Morinda morindoides, Quassia africana and Sarcocephalus latifolius. It is thus desirable that studies should be carried out on these eight plant species in order to collect scientific data for guiding future research on the phytochemistry and the bioactivity which will lead to the domestication of raw materials for the development of improved plant-based medicines. Also, the creation of a botanical garden of medicinal plants will be able to contribute to the safeguard of the medically active plants, the diffusion of knowledge, medical and pharmaceutical experiences and sociocultural exchanges

    Applications of Porous Silicon Thin Films in Solar Cells and Biosensors

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    An overview of the applications of porous silicon (PS) thin films, as antireflection coatings (ARC) in silicon solar cells and transducers in biosensors, is presented. The reflectance spectra of PS films have been compared with other conventional ARCs (such as SiNx, TiO2/MgF2 and ZnS), and optimal PS ARC with minimum reflectance has been obtained. The implementation of PS into an industrially compatible screen-printed (SP) solar cell by both the electrochemical etching (ECE) and chemical etching (CE) methods are reviewed. Porous silicon films, formed via ECE for short anodization times, on textured n+ emitter of c-Si solar cell having SP front and back contacts, lead to improvements in the performance of solar cells and demonstrate their viability in industrial applications

    Forestland tenure systems in Tanzania: an overview of policy changes in relation to forest management

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    INA fagrapport 14 Institutt for naturforvaltning Universitetet for miljø- og biovitenskap 2009ummary Zahabu, E., Eid, T., Kajembe, G. C., Mbwambo, L., Mongo, C., Sangeda, A.Z., Malimbwi, R. E., Katani, J.Z., Kashaigili, J.J. and Luoga, E.J. 2009. Forestland tenure systems in Tanzania: an overview of policy changes in relation to forest management [Eiendomsforholdene for skogarealer i Tanzania: en oversikt over policyendringer i skogforvaltningen]. INA-fagrapport no. 14, 24 pp. A review of the role of forestland tenure systems in Tanzania, and how different forestland tenure approaches and reforms have influenced forest management is presented. The complexity of land reforms and processes that have taken place in Tanzania during the pre-colonial, colonial and post-independence periods is discussed. The pre-colonial period, though not much is written, was characterised by forest management through traditional institutions, low population and low forest resources exploitation. Colonial governments undermined the role of local traditions in managing the forests related to for example burial areas and springs. They also established forest reserves and in some areas cleared indigenous forests to establish tea, coffee and exotic fruit and timber plantations. Different land reforms that were geared towards sustainable development occurred after independence, forests depletion continued, however. Currently, it is observed that there coexists state, village, private and collective rights on forests without clear ownership. This is greatly linked to the ongoing deforestation and forest degradation in the country. In this situation, sustainable forestland use may be attained through establishing an enabling environment that allows effective local communities’ participation in forest management. Sustainable management, however, always presupposes effective control of harvesting and other activities to secure the carrying capacity of forests and woodlands, whether it is undertaken by central authorities or local people. Studies on forestland tenures and rights, and the impact of changes in tenures and rights on forest resources and rural livelihoods are therefore important. Such studies are required for the provision of facts for the establishment of proper future policy means that aim at reducing forest degradation and improving livelihoods in Tanzania
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