La fatigue induite par chargement cyclique est un mode d'endommagement majeur des métaux. Elle se caractérise par des effets environnementaux et de grandes dispersions de la durée de vie qui doivent être mieux comprises. Les matériaux analysés sont de type cfc : aluminium, cuivre, nickel et argent. Le comportement de marches naturellement créées en surface par le glissement cyclique de dislocations est examiné par simulations en dynamique moléculaire sous vide et sous environnement oxygène pour le cuivre et le nickel. Un phénomène de reconstruction est observé sur les marches en surface, qui peut induire une forte irréversibilité. Trois mécanismes de reconstruction des marches apparues en surface sont observés et décrits. L’irréversibilité de ces marches est ensuite analysé. Elles sont irréversibles pour des chargements expérimentaux, sauf arrivée de dislocations de signe opposé sur un plan de glissement directement voisin.Avec arrivée de dislocations sur des plans non voisins, l'irréversibilité s’accumule cycle par cycle et il est possible de reproduire l’apparition de fissures en surface dont la profondeur augmente graduellement.Un environnement oxygène modifie la surface (début d’oxydation) mais pas l’irréversibilité parce que l’oxygène n’a pas d'influence majeure sur les différents mécanismes liés à l’évolution du relief.Une estimation grossière de l'irréversibilité est faite pour des dislocations coin pures dans une bande de glissement persistante pour les matériaux dits ondulés. On obtient un facteur d’irréversibilité entre 0,5 et 0,75 pour le cuivre, sous vide et sous l’environnement oxygène, en accord avec des mesures récentes en microscopie à force atomique.La propagation de fissures est simulée en environnement inerte. Les fissures peuvent se propager à cause de l'irréversibilité des dislocations générées, liée à leurs interactions allant jusqu’à la création de jonctions. / Fatigue is one of the major damage mechanisms of metals. It is characterized by strong environmental effects and wide lifetime dispersions which must be better understood. Different face centred cubic metals, Al, Cu, Ni, and Ag are analyzed. The mechanical behaviour of surface steps naturally created by the glide of dislocations subjected to cyclic loading is examined using molecular dynamics simulations in vacuum and in air for Cu and Ni. An atomistic reconstruction phenomenon is observed at these surface steps which can induce strong irreversibility. Three different mechanisms of reconstruction are defined. Surface slip irreversibility under cyclic loading is analyzed. All surface steps are intrinsically irreversible under usual fatigue laboratory loading amplitude without the arrival of opposite sign dislocations on direct neighbor plane.With opposite sign dislocations on non direct neighbour planes, irreversibility cumulates cycle by cycle and a micro-notch is produced whose depth gradually increases.Oxygen environment affects the surface (first stage of oxidation) but does not lead to higher irreversibility as it has no major influence on the different mechanisms linked to surface relief evolution.A rough estimation of surface irreversibility is carried out for pure edge dislocations in persistent slip bands in so-called wavy materials. It gives an irreversibility fraction between 0.5 and 0.75 in copper in vacuum and in air, in agreement with recent atomic force microscopy measurements.Crack propagation mechanisms are simulated in inert environment. Cracks can propagate owing to the irreversibility of generated dislocations because of their mutual interactions up to the formation of dislocation junctions.

Dans cette thèse, nous proposons une analyse globale multi-échelles de la fatigue à faible nombre de cycles des matériaux à mémoire de forme (MMF). Dans un premier temps, une large campagne d’essais a été menée pour différents chargements thermomécaniques comprenant des tests de fatigue sous contrainte et déformation imposée et pour différentes fréquences de chargement. A partir des résultats des essais, un critère de fatigue, basé sur l’énergie de déformation, a été développé ; on montre que l’énergie de déformation est un paramètre pertinent pour prédire la fatigue des MMF en tenant compte du couplage thermomécanique et du type de chargement : contrainte ou déformation imposée. Ensuite, en prenant appui sur la répartition de l’énergie de l’hystérésis en dissipation et énergie stockée, on avance une interprétation physique du mécanisme de la fatigue des MMF. Dans la troisième partie, on propose une modélisation multi-échelles de l’initiation des fissures de fatigue dans les MMF à partir de la notion de plasticité de transformation (PlTr). Dans ce cadre, on montre que la fatigue de MMF est contrôlée par la (PlTr) et que la température maximale lors de la transformation de phase est le paramètre à retenir pour prédire la rupture par fatigue des MMF. Le modèle permet également de prédire le lieu d’initiation des premières fissures de fatigue. Enfin, un procédé – fondé sur l’«éducation» des MMF – permettant d’améliorer la résistance à la fatigue est proposé. / The thesis proposes a multi-scale comprehensive analysis of low cycle fatigue of shape memory alloys (SMAs). First, low cycle fatigue of SMAs is experimentally investigated; comprehensive tensile-tensile fatigue tests under both stress and strain controlled loadings at different frequencies are carried out and results are discussed. Second, a new strain energy-based fatigue criterion is developed; it is shown that the use of total strain energy is a relevant parameter to predict fatigue lifetime of SMAs for different thermomechanical conditions and under different types (strain-control or stress-control) loadings. A physical interpretation of the mechanism related to the low-cycle fatigue of SMAs is then provided based on the conversion of hysteresis work into dissipation and stored energy. Third, fatigue crack initiation during cyclic stress-induced phase transformation is modeled based on transformation induced plasticity (TRIP); it is shown that the maximum temperature during the cyclic loading is a relevant indicator of the fatigue of SMA. Furthermore, the effect of the macroscopic mechanical load on the the fatigue lifetime is addressed as well as the spatial location of crack initiation. Finally, a mechanical training process that allows enhancing resistance to low cycle fatigue of SMAs is proposed.

Des expériences pastorales en Afrique nous ont amené à constater qu’en plus du questionnement de certains prêtres sur leur identité, des plaintes récurrentes contre eux sont soulevées au sein de la société en rapport avec la mauvaise gestion des biens temporels de l’Église, l’esprit carriériste, le problème du tribalisme, la question des mœurs, l’oubli de la prière et l’abus de pouvoir. La question de l’identité sacerdotale, le problème de formation des candidats au sacerdoce ministériel et la mise en question de leur manière de collaborer aux réalités traditionnelles et de vivre leur immersion dans leurs communautés ont des répercussions sur le langage adapté pour véhiculer le message chrétien parmi les cultures et peuples africains de nos jours. Toutes ces questions mènent à un problème général : l’enjeu du modèle christologique. Le modèle proposé vient de Rome et met en valeur la culture européenne ; une fois transposé en Afrique, on constate un déphasage, ce qui justifie la problématique. Pour trouver une solution à la problématique du modèle christologique, il nous faudrait élaborer un modèle toujours christologique, mais qui soit en phase avec les réalités du contexte culturel africain. L’intérêt consiste à examiner les comportements des prêtres africains eux-mêmes et l’équilibre de leur ministère, à revoir leurs programmes et leurs structures dans les maisons de formation, dans le but de former des prêtres qui vivront leur ministère en harmonie avec les réalités culturelles africaines pour encourager la bonne collaboration entre les prêtres africains et leurs communautés. Les communautés ecclésiales de base trouveront dorénavant des prêtres africains qui sont bien intégrés dans leur culture. Dans le cadre de la discipline de la théologie, notre étude présente un nouveau concept ou modèle : la christologie du témoignage. Dans le contexte culturel d’Afrique, nous avons besoin d’une initiation christocentrique pour les prêtres africains et d’une théopraxis, en vue d’une nouvelle évangélisation en Afrique. Nous mettons en valeur des communautés africaines en présentant l’expérience d’immersion de J.-M. Ela et J.-A. Malula. L’exemplarité de leurs apprentissages auprès des peuples kirdi et kinois devient pertinente et s’avère même un modèle d’imitation du Christ en vue d’une christologie du témoignage pour les prêtres africains. / Our pastoral experiences in Africa have led us to observe that in addition to some priests questioning their identity, repeated complaints against them are raised within society regarding the mismanagement of the Church’s temporal goods, the careerist spirit, the tribalism problem, the morality issue, the forgetfulness of prayer and the abuse of power. The priestly identity question, the problem of the priesthood candidates’ formation and the way they interact with traditional realities and live their immersion in their communities affect the language adapted to convey the Christian message among African cultures and peoples today. All these questions lead to a general problem: the issue of the Christological model. The proposed model comes from Rome, and values the European culture; when transposed to Africa, it becomes apparent that there is a lack of relevance, which justifies the issue. In order to address the Christological model question, we would need to develop a model that is still Christological, but one that respects the African cultural context. The interest lies in examining how African priests themselves behave and balance their ministry, in reviewing the programs and structures offered in the houses of formation, in order to prepare priests who will live their ministry in phase with the African cultural realities and to encourage a good collaboration between African priests and their communities. The base ecclesial communities will then have well integrated African priests. Within the theological field framework, our study introduces a new concept or model: the Christology of witness. In Africa’s cultural context, we need a Christocentric initiation for African priests and a theopraxis allowing for a new evangelization of Africa. We showcase some African communities by presenting the immersion experience of J.-M. Ela and J.-A. Malula. The exemplarity of their learnings among the Kirdi and Kinshasa peoples becomes relevant, and even proves to be a model of imitation of Christ in order to develop a Christology of witness for African priests.

No description available.

Christian Spirituality, Church History and Missiology / D.Th. (Missiology)

With the growth of Pentecostalism over the last few decades, conservative values and punitive sanctions related to the sexual behavior of adolescents and unmarried youth began to play an important and systematic role in Pentecostal and renewed Protestant churches as well as in charismatic Catholic communities. Simultaneously, religion has become an important and highly present factor in the lives of many adolescents and youth in Brazil. In terms of attempting to attract this age group, these churches and communities, stand out, as they have used their resources to create a space for this segment of the population to participate in a religious environment. Youth groups, dating groups, trade courses, lectures, aid work in poor communities, confirmation and other activities such as retreats and religious trips, have been frequently observed in these churches and charismatic communities. In this dissertation, I examine the associations between religious involvement and sexual initiation in Brazil. More specifically, I investigate (1) whether religious denomination and religiosity are associated with age at premarital first sexual intercourse, (2) whether these associations have changed over the last three decades, (3) how different churches and religious leaders address sexual behavior issues, and (4) the mechanisms through which religion can influence adolescents’ sexual behavior in Brazil. These research questions are assessed by employing multiple data sources and methodologies including three Demographic and Health Surveys carried out in Brazil in 1986, 1996, and 2006 and event history analysis, as well as in-depth interview data and participant observation among different religious groups and affiliations by attending several Catholic masses, Protestant religious services, youth groups, Sunday schools, and religious talks/lectures. Quantitative and qualitative findings of this dissertation show that adolescents and youth from Pentecostal churches and communities seem more likely to delay or abstain from premarital sexual initiation when compared to traditional Catholics. I conclude by suggesting that the dissemination of conservative norms and sanctions as well as the availability of greater space for youth to maintain close relationships with these churches have helped create mechanisms through which religion can directly and indirectly influence the lives and sexual behavior of young people in Brazil. / text

Conversion of aspartate and asparagine residues to isoaspartate is a prevalent covalent protein modification in cells. The accumulation of these altered residues can lead to the loss of protein function and the consequent loss of cellular function. The L-ISOASPARTATE METHYLTRANSFERASE (EC 2.1.1.77) (PIMT) iteratively methylates abnormal isoaspartyl residues leading to conversion to L-aspartate, thereby mitigating the injurious effects of aging. Arabidopsis thaliana is unique among eukaryotes studied to date in that it possesses two genes (At3g48330 (PIMT1) and At5g50240 (PIMT2)) encoding PIMT. The PIMT2 gene exhibits a complex transcriptional control involving different transcriptional initiation sites and 5'- and 3'- alternative splice site selection in the first intron. Varying the transcriptional initiation site results in alternative targeting of the PIMT2 proteins thus produced to: 1) the nucleus, or 2) the cytoplasm, while PIMT1 is cytosolic. Inclusion of a 51 nucleotide 5 alternatively spliced sequence with or without a nine nucleotide 3 alternatively spliced sequence dramatically alteres the subcellular protein localization from the cytoplasm and around the chloroplast to inside the chloroplast. All recombinant PIMT2 isoform tested exhibit PIMT activity, although solubility varied among them. Multiplex RT-PCR was used to establish PIMT1 and PIMT2 transcript presence and abundance, relative to -TUBULIN, in various tissues and under a variety of stresses imposed on seeds and seedlings. PIMT1 transcript is constitutively present but can increase, along with PIMT2, in developing seeds presumably in response to increasing endogenous ABA. Transcript from PIMT2 also increases in establishing seedlings due to exogenous ABA application or applied stress presumably through an ABA-dependent pathway. Furthermore, Cleaved Amplified Polymorphic Sequence analysis of the PIMT2 amplicons has shown that the ratio among the splicing variants alters upon ABA application, implicating a role for the spliceosome or differential RNA stability in orchestrating the plant's response to stress. T-DNA insertional mutants of both genes were isolated but no obvious phenotype has been identified. The double mutant has been generated and will be evaluated.

Rheumatoid arthritis (RA) is a progressive autoimmune disorder of joints that is associated with high health care costs and yet lacks guidance on how early to initiate biologic disease-modifying antirheumatic drugs (DMARDs), a class of medications that is the major cost driver in RA management. The main purpose of this study was to examine patient socio-demographics, medication use patterns, and clinical characteristics associated with initiation of biologic DMARDs. This was a retrospective study using Texas Medicaid prescription and medical claims database during the study period of July 1, 2003 – December 31, 2010. Patients (18 – 63 years) with an RA diagnosis (ICD-9-CM code 714.xx), no non-biologic DMARD or biologic DMARD use during the pre-index period, and a minimum of 2 prescription claims for the same non-biologic DMARD during the post-index period were included in the study. The primary study outcomes were time to initiation of biologic DMARDs and likelihood of initiating biologic DMARDs. There was a total of 2,714 subjects included in the study. The majority had claims for pain medications (92.4%), glucocorticoids (64.9%), and non-biologic DMARD monotherapy (86.4%); while 24.3% initiated on biologic DMARDs and 58.9% had a Charlson Comorbidity Index (CCI) score=1. Compared to time to initiation (days) of biologic DMARDs for methotrexate (539.7±276.9) users, it was longer for sulfasalazine (670.2±167.8) and hydroxychloroquine (680.2±158.7) users and similar to leflunomide users (541.6±286.5; p<0.0001). There were no significant differences in time to initiation between non-biologic DMARD mono vs. dual therapy. Younger age, glucocorticoid use, methotrexate user (vs. sulfasalazine, hydroxychloroquine users), and non-biologic DMARD monotherapy user (vs. dual therapy user) were significantly associated with higher likelihood to initiate biologic DMARDs. In conclusion, age, glucocorticoid use, non-biologic DMARD type and therapy were significant factors associated with initiation of biologic DMARDs. Healthcare providers and Texas Medicaid should recognize these potential driving factors and take efforts to achieve optimal therapy for RA patients through thorough RA medication evaluation, well-structured RA monitoring programs, and patient education. / text

<p>Initiation is the first step in protein biosynthesis representing a fundamental event in cell life which determines fidelity, efficiency and regulation of gene expression. In addition to the ribosome and mRNA, three protein factors IF1, IF2 and IF3 are involved in the initiation of translation in prokaryotes. Several minor functions have been attributed to the smallest of these factors, IF1. However, the main function of IF1 remains to be elucidated.</p><p>In order to investigate the role of this protein in the initiation process we have mutated the corresponding gene infA. Using a high-copy plasmid and site-directed mutagenesis, the six arginine residues of IF1 were separately altered to leucine or aspartate. Another set of plasmid-encoded IF1 mutants with a cold-sensitive phenotype was collected using localized random mutagenesis. This strategy was followed by deletion of the chromosomal infA gene. All variants with a mutated infA gene on a plasmid and a deletion of the chromosomal infA copy were viable, except for an R65D alteration. Several of the mutated infA genes were successfully recombined into the chromosome thereby replacing the wild-type allele. Some of these mutants displayed reduced growth rates and a partial cold-sensitive phenotype.</p><p>The influence of the leucine group of mutants in IF1 on the expression of two reporter genes with different initiation and/or +2 codons has been investigated. Our results do not indicate any involvement of IF1 in recognition of the +2 codon immediately following the start codon, thus representing the A-site. In addition, this group of mutants has no changed efficiency of decoding at the near-cognate initiation codons UUG and GUG. However, one cold-sensitive IF1 mutant shows a general overexpression of both reporter genes, in particular at low temperatures. Overall, the results do not support the hypothesis that IF1 could possess codon discriminatory functions while blocking the A-site of the ribosome.</p><p>In this study we also identify that IF1 has RNA chaperone activity both in vitro and in vivo. The chaperone assays are based on splicing of the group I intron in the thymidylate synthase gene (td) from phage T4. Some of the IF1 mutant variants are more active as RNA chaperones than the wild-type. Both wild-type IF1 and mutant variants bind with high affinity to RNA in a band-shift assay. It is suggested that the RNA chaperone activity of IF1 contributes to RNA rearrangements during the early phase of translation initiation.</p>

<p>SIP is receiving much attention these days and it seems to be the most promising candidate as a signaling protocol for the current and future IP telephony services. Realizing this, there is the obvious need to provide a certain level of quality comparable to the traditional telephone service signalling system. Thus, we identified the major costs of SIP, which were found to be delay and security. This thesis discusses the costs of SIP, the solutions for the major costs, and the development of a low cost SIP application. The literature review of the components used to develop such a service is discussed, the networks in which the SIP is used are outlined, and some SIP applications and services previously designed are discussed. A simulation environment is then designed and implemented for the instant messaging service for wireless devices. This environment simulates the average delay in LAN and WLAN in different scenarios, to analyze in which scenario the system has the lowest costs and delay constraints.</p>