Ba3Yb(BO3)3 single crystals. Growth and spectroscopic characterization

We obtained Ba3Yb(BO3)3 single crystals by the flux method with solutions of the BaB2O4Na2OYb2O3 system. The evolution of the cell parameters with temperature shows a slope change at temperatures near 873 K, which may indicate a phase transition that is not observed by changes appearing in the x-ray powder patterns or by differential thermal analysis (DTA). The evolution of the diffraction patterns with the temperature shows incongruent melting at temperatures higher than 1473 K. DTA indicates that there is incongruent melting and this process is irreversible. Ba3Yb(BO3)3 has a wide transparency window from 247 to 3900 nm. We recorded optical absorption and emission spectra at room and low temperature, and we determined the splitting of Yb3+ ions. We used the reciprocity method to calculate the maximum emission cross section of 0.28 10-20 cm2 at 966 nm. The calculated lifetime of Yb3+ in Ba3Yb(BO3)3 is trad = 2.62 ms, while the measured lifetime is t = 3.80 ms.

Nitrogen incorporation effects in Fe(001) thin films

Nitrogen incorporates into Fe thin films during reactively sputtered TiN capping layer deposition. The influence that this nitrogen incorporation has both on the structure and magnetic properties is discussed for a series of Fe~001! thin films grown at different temperatures. A higher nitrogen content is accompanied by distortion in the Fe lattice and by reduction in the Fe magnetization saturation as well as in the effective anisotropy constant, K. The reduction of K brings as a consequence lowering in the coercive field with respect to equivalent Fe films with no nitrogen present.

Relaxation times of non-Markovian processes

We consider a general class of non-Markovian processes defined by stochastic differential equations with Ornstein-Uhlenbeck noise. We present a general formalism to evaluate relaxation times associated with correlation functions in the steady state. This formalism is a generalization of a previous approach for Markovian processes. The theoretical results are shown to be in satisfactory agreement both with experimental data for a cubic bistable system and also with a computer simulation of the Stratonovich model. We comment on the dynamical role of the non-Markovianicity in different situations.

Characterization of gravitational rock slope deformations at different spatial scales based on field, remote sensing and numerical approaches

Rock slope instabilities such as rock slides, rock avalanche or deep-seated gravitational slope deformations are widespread in Alpine valleys. These phenomena represent at the same time a main factor that control the mountain belts erosion and also a significant natural hazard that creates important losses to the mountain communities. However, the potential geometrical and dynamic connections linking outcrop and slope-scale instabilities are often unknown. A more detailed definition of the potential links will be essential to improve the comprehension of the destabilization processes and to dispose of a more complete hazard characterization of the rock instabilities at different spatial scales. In order to propose an integrated approach in the study of the rock slope instabilities, three main themes were analysed in this PhD thesis: (1) the inventory and the spatial distribution of rock slope deformations at regional scale and their influence on the landscape evolution, (2) the influence of brittle and ductile tectonic structures on rock slope instabilities development and (3) the characterization of hazard posed by potential rock slope instabilities through the development of conceptual instability models. To prose and integrated approach for the analyses of these topics, several techniques were adopted. In particular, high resolution digital elevation models revealed to be fundamental tools that were employed during the different stages of the rock slope instability assessment. A special attention was spent in the application of digital elevation model for detailed geometrical modelling of past and potential instabilities and for the rock slope monitoring at different spatial scales. Detailed field analyses and numerical models were performed to complete and verify the remote sensing approach. In the first part of this thesis, large slope instabilities in Rhone valley (Switzerland) were mapped in order to dispose of a first overview of tectonic and climatic factors influencing their distribution and their characteristics. Our analyses demonstrate the key influence of neotectonic activity and the glacial conditioning on the spatial distribution of the rock slope deformations. Besides, the volumes of rock instabilities identified along the main Rhone valley, were then used to propose the first estimate of the postglacial denudation and filling of the Rhone valley associated to large gravitational movements. In the second part of the thesis, detailed structural analyses of the Frank slide and the Sierre rock avalanche were performed to characterize the influence of brittle and ductile tectonic structures on the geometry and on the failure mechanism of large instabilities. Our observations indicated that the geometric characteristics and the variation of the rock mass quality associated to ductile tectonic structures, that are often ignored landslide study, represent important factors that can drastically influence the extension and the failure mechanism of rock slope instabilities. In the last part of the thesis, the failure mechanisms and the hazard associated to five potential instabilities were analysed in detail. These case studies clearly highlighted the importance to incorporate different analyses and monitoring techniques to dispose of reliable and hazard scenarios. This information associated to the development of a conceptual instability model represents the primary data for an integrated risk management of rock slope instabilities. - Les mouvements de versant tels que les chutes de blocs, les éboulements ou encore les phénomènes plus lents comme les déformations gravitaires profondes de versant représentent des manifestations courantes en régions montagneuses. Les mouvements de versant sont à la fois un des facteurs principaux contrôlant la destruction progressive des chaines orogéniques mais aussi un danger naturel concret qui peut provoquer des dommages importants. Pourtant, les phénomènes gravitaires sont rarement analysés dans leur globalité et les rapports géométriques et mécaniques qui lient les instabilités à l'échelle du versant aux instabilités locales restent encore mal définis. Une meilleure caractérisation de ces liens pourrait pourtant représenter un apport substantiel dans la compréhension des processus de déstabilisation des versants et améliorer la caractérisation des dangers gravitaires à toutes les échelles spatiales. Dans le but de proposer un approche plus globale à la problématique des mouvements gravitaires, ce travail de thèse propose trois axes de recherche principaux: (1) l'inventaire et l'analyse de la distribution spatiale des grandes instabilités rocheuses à l'échelle régionale, (2) l'analyse des structures tectoniques cassantes et ductiles en relation avec les mécanismes de rupture des grandes instabilités rocheuses et (3) la caractérisation des aléas rocheux par une approche multidisciplinaire visant à développer un modèle conceptuel de l'instabilité et une meilleure appréciation du danger . Pour analyser les différentes problématiques traitées dans cette thèse, différentes techniques ont été utilisées. En particulier, le modèle numérique de terrain s'est révélé être un outil indispensable pour la majorité des analyses effectuées, en partant de l'identification de l'instabilité jusqu'au suivi des mouvements. Les analyses de terrain et des modélisations numériques ont ensuite permis de compléter les informations issues du modèle numérique de terrain. Dans la première partie de cette thèse, les mouvements gravitaires rocheux dans la vallée du Rhône (Suisse) ont été cartographiés pour étudier leur répartition en fonction des variables géologiques et morphologiques régionales. En particulier, les analyses ont mis en évidence l'influence de l'activité néotectonique et des phases glaciaires sur la distribution des zones à forte densité d'instabilités rocheuses. Les volumes des instabilités rocheuses identifiées le long de la vallée principale ont été ensuite utilisés pour estimer le taux de dénudations postglaciaire et le remplissage de la vallée du Rhône lié aux grands mouvements gravitaires. Dans la deuxième partie, l'étude de l'agencement structural des avalanches rocheuses de Sierre (Suisse) et de Frank (Canada) a permis de mieux caractériser l'influence passive des structures tectoniques sur la géométrie des instabilités. En particulier, les structures issues d'une tectonique ductile, souvent ignorées dans l'étude des instabilités gravitaires, ont été identifiées comme des structures très importantes qui contrôlent les mécanismes de rupture des instabilités à différentes échelles. Dans la dernière partie de la thèse, cinq instabilités rocheuses différentes ont été étudiées par une approche multidisciplinaire visant à mieux caractériser l'aléa et à développer un modèle conceptuel trois dimensionnel de ces instabilités. A l'aide de ces analyses on a pu mettre en évidence la nécessité d'incorporer différentes techniques d'analyses et de surveillance pour une gestion plus objective du risque associée aux grandes instabilités rocheuses.

Intranasal administration of the synthetic polypeptide from the C-terminus of the circumsporozoite protein of Plasmodium berghei with the modified heat-labile toxin of Escherichia coli (LTK63) induces a complete protection against malaria challenge.

Needle-free procedures are very attractive ways to deliver vaccines because they diminish the risk of contamination and may reduce local reactions, pain or pain fear especially in young children with a consequence of increasing the vaccination coverage for the whole population. For this purpose, the possible development of a mucosal malaria vaccine was investigated. Intranasal immunization was performed in BALB/c mice using a well-studied Plasmodium berghei model antigen derived from the circumsporozoite protein with the modified heat-labile toxin of Escherichia coli (LTK63), which is devoid of any enzymatic activity compared to the wild type form. Here, we show that intranasal administration of the two compounds activates the T and B cell immune response locally and systemically. In addition, a total protection of mice is obtained upon a challenge with live sporozoites.

Relaxation times in a bistable system with parametric, white noise: Theory and experiment

We consider the effects of external, multiplicative white noise on the relaxation time of a general representation of a bistable system from the points of view provided by two, quite different, theoretical approaches: the classical Stratonovich decoupling of correlations and the new method due to Jung and Risken. Experimental results, obtained from a bistable electronic circuit, are compared to the theoretical predictions. We show that the phenomenon of critical slowing down appears as a function of the noise parameters, thereby providing a correct characterization of a noise-induced transition.

Spatial weights : constructing weight-compatible exchange matrices from proximity matrices

Exchange matrices represent spatial weights as symmetric probability distributions on pairs of regions, whose margins yield regional weights, generally well-specified and known in most contexts. This contribution proposes a mechanism for constructing exchange matrices, derived from quite general symmetric proximity matrices, in such a way that the margin of the exchange matrix coincides with the regional weights. Exchange matrices generate in turn diffusive squared Euclidean dissimilarities, measuring spatial remoteness between pairs of regions. Unweighted and weighted spatial frameworks are reviewed and compared, regarding in particular their impact on permutation and normal tests of spatial autocorrelation. Applications include tests of spatial autocorrelation with diagonal weights, factorial visualization of the network of regions, multivariate generalizations of Moran's I, as well as "landscape clustering", aimed at creating regional aggregates both spatially contiguous and endowed with similar features.

Fra��ões de carbono em topossequências de solos sob eucalipto com diferentes históricos de uso

No Brasil, boa parte dos plantios florestais tem sido realizada em solos que apresentam algum grau de degrada��ão física, química ou biológica. A proteção ao solo fornecida pelas árvores, em função da deposição de serapilheira, constitui um dos processos de recupera��ão de áreas degradadas, e, como a matéria orgânica está relacionada com muitos dos atributos físicos, químicos e biológicos do solo, ela se caracteriza como um fator-chave na manutenção da qualidade ambiental de sistemas florestais. Assim, objetivou-se neste trabalho caracterizar fra��ões da matéria orgânica em solos sob cultivo mínimo de eucalipto com diferentes históricos de uso e posições na paisagem. O estudo foi realizado em três hortos florestais (HFs): Terra Dura, Canafístula e Sanga das Pedras, cultivados com eucalipto no Estado do Rio Grande do Sul. Os solos foram amostrados nas profundidades de 0-5, 5-20 e 20-40 cm. Na profundidade de 0-5 cm, a maioria dos Argissolos dos HFs estudados apresentou teores de carbono orgânico (CO) superiores aos de matas nativas adjacentes. Nas áreas cultivadas, há maior armazenamento de CO no HF Canafístula, sendo notados, em geral, menores teores de CO no terço inferior da encosta em rela��ão às outras posições das topossequências avaliadas. O índice de humifica��ão, em geral, é maior nas áreas de mata em compara��ão às áreas cultivadas; contudo, ele varia em função da profundidade do solo, da posição amostrada na topossequência e do HF avaliado. Nas profundidades de 0-5 e 5-20 cm, a abundância natural de 13C dos HFs é similar à das áreas de mata nativa, porém há maior teor de 13C na camada mais profunda dos solos cultivados, o que sinaliza para a contribuição à matéria orgânica do solo (MOS) de C oriundo das pastagens que antecederam o eucalipto.

Consistência hidrológica de modelos digitais de eleva��ão (MDE) para definição da rede de drenagem na sub-bacia do horto florestal Terra Dura, Eldorado do Sul, RS

O desenvolvimento da erosão hídrica ocorre em resposta ao modo como a água se move através e sobre uma determinada paisagem. O modelo digital de eleva��ão (MDE) deve, portanto, ser o mais preciso possível, uma vez que constitui a base para a análise do relevo. Este trabalho teve como objetivo definir um modelo digital de eleva��ão hidrologicamente consistente (MDEHC) e o método de direção de fluxo mais adequado para a definição da rede de drenagem na sub-bacia do horto florestal Terra Dura, município de Eldorado do Sul, RS. Foram testados os modelos gerados com os interpoladores Topogrid e redes triangulares irregulares (Triangulated Irregular Network -TIN) linear (TIN L) e TIN natural neighbor (TIN NN). A qualidade em rela��ão às análises hidrológicas foi avaliada por meio da compara��ão das curvas de nível geradas pelos modelos testados com as curvas originais da sub-bacia (escala 1:10.000); da avalia��ão da quantidade de áreas planas; e da compara��ão da drenagem gerada pelos modelos a partir dos métodos de direção de fluxo Deterministic (D8) e Deterministic infinity (D∞ ou D infinito) com a drenagem original. Entre os modelos avaliados, o Topogrid apresentou maior consistência hidrológica, verificada na melhor continuidade das curvas de nível (menos arestas) e maior detalhamento da área de drenagem e divisores, acarretando menor quantidade de áreas planas e caminhos de fluxo mais detalhados, independentemente do método de direção de fluxo utilizado. Em rela��ão à rede de drenagem, o método distribuído D∞ obteve melhor desempenho na descrição dos caminhos de fluxo, comparado ao método de direção única D8. O MDEHC Topogrid associado ao método D∞ proporcionou a identifica��ão mais precisa dos caminhos preferenciais do fluxo que formam a rede de drenagem.

Transparency ratio in γ A -> η' A ' and the in-medium η ' width

The photoproduction of η′η′-mesons off different nuclei has been measured with the CBELSA/TAPS detector system for incident photon energies between 15002200 MeV. The transparency ratio has been deduced and compared to theoretical calculations describing the propagation of η′η′-mesons in nuclei. The comparison indicates a width of the η′η′-meson of the order of Γ=1525 MeVΓ=1525 MeV at ρ=ρ0ρ=ρ0 for an average momentum pη′=1050 MeV/cpη′=1050 MeV/c, at which the η′η′-meson is produced in the nuclear rest frame. The inelastic η′Nη′N cross section is estimated to be 310 mb. Parameterizing the photoproduction cross section of η′η′-mesons by σ(A)=σ0A��σ(A)=σ0A��, a value of α=0.84±0.03α=0.84±0.03 has been deduced.

Drogues illégales et santé publique, stratégie de la Confédération : étude menée dans le cadre de l'évaluation globale du ProMeDro, 4ème phase 1999-2003

[Table des matières] 1. Méthodologie. 1.1. Questions d'évaluation. 1.2. Collecte de l'information. 1.3. Validation. 1. 4. Analyse. 1.5. Utilité. 2. Planification de l'intervention en 2000, par domaine. 2.1. Clé de lecture des théories d'action. 2. 2. Les domaines de : la prévention, des thérapies et traitements, de la réduction des risques, de la formation, de la coordination, Campagne, migration et santé, de l'épidémiologie, de la recherche, de l'évaluation. 3. Evolution de la stratégie entre 1998 et 2000. 4. Théories d'action en 1998. 5. Dimensions de la théorie d'action globale 2000.