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The biofilm-associated protein (Bap) of Staphylococcus aureus is a high molecular weight cell-wallanchored protein involved in biofilm formation, first described in bovine mastitis strains from Spain. So far, studies regarding Bap were mainly based on the Spanish strain V329 and its mutants, but no information on the genetic variability of bap-positive Staph. aureus strains is yet available in the literature. The present study investigated the molecular characteristics of 8 bap-positive Staph. aureus strains from subclinical bovine mastitis, isolated in 5 herds; somatic cell counts (SCC) of milk samples were also registered. Strains were characterised using MLST, SPA typing and microarray and the results were compared with V329. All isolates from this study and V329 were assigned to ST126, t605, but some molecular differences were observed. Only herd A and B strains harboured the genes for β-lactams resistance; the leukocidin D/E gene, a type I site-specific deoxyribonuclease subunit, 3rd locus gene and serin-protease A and B were carried by all strains, but not by V329, while serin-protease E was absent in V329 and in another isolate. Four isolates and V329 harboured the fibronectin-binding protein B gene. SCC showed the highest value in the milk sample affected by the only strain carrying all the virulence factors considered. Potential large variability of virulence was evidenced among V329 and all bap-positive Staph. aureus strains considered: the carriage of fnb could enhance the accumulation of biofilm, but the lack of lukD/E and splA, B or E might decrease the invasiveness of strain.

Self-consolidating concrete (SCC) is an emerging technology that utilizes flowable concrete that eliminates the need for consolidation. The advantages of SCC lie in a remarkable reduction of the casting time, facilitating the casting of congested and complex structural elements, possibility to reduce labor demand, elimination of mechanical vibrations and noise, improvement of surface appearance, producing a better and premium concrete product. The research focussed on capturing existing knowledge and making recommendations for current practice. An experimental program was undertaken at the Université de Sherbrooke to evaluate the lateral pressure developed by SCC mixtures. A portable devise (UofS2 pressure column) for measuring and predicting lateral pressure and its rate of decay of SCC was developed and validated. The UofS2 pressure column is cast with 0.5 m high fresh concrete and air pressure is introduced from the top to simulate casting depth up to 13 m. Then, develop and implement test method for field evaluation of relevant plastic and thixotropic properties of SCC that affect formwork pressure were done. Portable vane (PV) test based on the hand-held vane test method used to determine the undrained shear strength property of clay soil was the first setup as well as the inclined plane (IP) test. The IP device involves slumping a small concrete cylinder on a horizontal plate and then lifting up the plate at different durations of rest until the slumped sample starts to move. Identifying role of material constituents, mix design, concrete placement characteristics (casting rate, waiting periods between lifts, and casting depth), temperature, and formwork characteristics that have major influence on formwork pressure exerted by SCC were evaluated in laboratory and validated by actual field measurements. Relating the maximum lateral pressure and its rate of decay to the plastic properties of SCC were established. In the analytical part of the research, effective ways to reduce lateral pressure by developing formulation expertise and practical guidelines to lower lateral pressure of SCC were proposed. Various design equations as well as chart diagrams to predict formwork pressure that can be exerted by SCC on column and wall elements were derived and reported. In general, the results obtained show that measured lateral pressure is lower than corresponding hydrostatic pressure. The study has shown that lateral pressure exerted by SCC is closely related to the structural build-up at rest (or thixotropy) of SCC. The latter can be controlled using different mixture proportionings, material constituents, and chemical admixtures. SCC mixture with a high rate of structural build-up at rest can develop low lateral pressure on formwork. Increased rate of structural build-up at rest can be ensured by incorporating a greater volume of coarse aggregate, lower paste volume, and/or lower sand-to-total aggregate ratio. Incorporating coarse aggregate of larger maximum size could also increase the thixotropy and hence reduce the lateral pressure. This can also be achieved by reducing the workability of SCC using less HRWRA concentration. Indeed, all mixture factors have been replaced by measuring the rate of structural build-up at rest (or thixotropy) using the developed portable vane and inclined plane field-oriented test as well as the modified Tattersall MK-III concrete rheometer. On the other hand, increasing or maintaining the concrete temperature at a certain level plays an important role to reduce the lateral pressure. The higher concrete temperature can accelerate the heat of hydration of cement with water and increase the internal friction leading to higher thixotropy. Controlling the placement rate has a great impact on the resultant lateral pressure of SCC. The lateral pressure can be reduced by slowing down the casting rate, as concrete has more time to build-up. However, this can slow down the rate of construction. The casting rate should be optimized to yield a cost effective formwork system. Pausing the continuous casting by a waiting period can reduce the exerted lateral pressure. The research investigation could accelerate the acceptance and implementation of SCC technology in cast-in-place applications, which is the preponderate business of the ready mixed concrete suppliers. The research findings could also contribute to the removal of some of the major barriers hindering the acceptance of SCC in cast-in-place applications and provide the industry with much needed guidelines on formwork pressure.--Résumé abrégé par UMI.

In vitro micropropagation of saffron (Crocus sativus L.) by using direct and indirect organogenesis was the aim of this study. Also, the effect of plant growth regulators on growth parameters, such as corm production, sprouting time and germination ratio were investigated in ex vitro conditions. For in vitro regeneration of saffron, the effects of 2,4-D (2,4-dichlorophenoxyacetic acid) and BAP (6-benzylaminopurine) were tested initially. It was observed that 0,25 mg/L 2,4-D and 1 mg/L BAP combination was superior for indirect organogenesis while 1 mg/L 2,4-D and 1 mg/L BAP combination was favorable for direct organogenesis. During the improvement of direct organogenesis experiments, BAP (1 mg/L) without 2,4-D stimulated further shoot development. For adventitious corm and root induction, NAA (naphthaleneacetic acid) and BAP combinations were tested. Although a few corm formations were achieved, root development was not observed with these treatments. Further experiments with the culture medium supplemented with 1 mg/L IBA (indole-3-butyric acid) and 5% sucrose was effective on obtaining contractile root formation and increasing corm number. As a result, the overall efficiency was calculated as 59.26% for contractile root formation, 35.19% for corm formation and 100% for shoot development. In ex vitro studies, 50 mg/L IAA (indole-3-acetic acid) , 50 mg/L kinetin and 200 mg/L GA3 (gibberellic acid) were used. These applications were not as efficient as expected on assessed growth parameters.

Les bétons autoplaçants (BAP) constituent une nouvelle génération de béton avec un fort potentiel d’utilisation compte-tenu de la facilité de leur mise en œuvre dans les chantiers de construction. Leur production révèle cependant plus de difficultés par rapport à celle des bétons ordinaires, principalement liée à leur caractère très sensible à la variation de composition. En particulier, la variation du dosage en eau influe fortement sur la régularité de la fabrication des BAP. Cette variation est à l'origine de la connaissance insuffisante de l'eau apportée par les granulats. D'autre part, la formulation des BAP prévoit l'utilisation d'un volume élevé d'éléments fins ainsi que d'une forte proportion en adjuvants dans la composition de ces bétons. Cela conduit à des temps de malaxage plus longs que ceux des bétons ordinaires, diminue la productivité et augmente le coût de production. Le travail présenté dans ce mémoire vise à proposer des méthodes de contrôle pour améliorer la régularité et la productivité des BAP dans les centrales à béton prêt à l'emploi.Dans un premier temps, l'outil traditionnel du contrôle en ligne de l'humidité du béton - le wattmètre a été calibré suivant une procédure de simplifiée et réalisable en centrale à béton. En utilisant cette méthode de calibration, la stabilisation de la puissance consommée par le malaxeur, en milieu industriel, est validée comme un indicateur fiable de la teneur en eau des BAP. En parallèle, un critère objectif de stabilisation de la puissance a été proposé afin de définir quantitativement le temps de stabilisation de la puissance. Ce dernier est considéré comme un temps de malaxage suffisant pour décider la fin du malaxage en vue d’une augmentation de la productivité.Dans un second temps, nous avons étudié, à l'échelle de laboratoire, l'influence du temps de malaxage sur l'ouvrabilité d'une formule de BAP dont les gâchées sont différenciées seulement par leur dosage en eau. Cette étape a permis de montrer que le temps de stabilisation de la puissance de malaxage est comparable et proportionnel au temps nécessaire pour obtenir l'ouvrabilité optimale du BAP.Enfin, nous avons traité un cas particulier des BAP fluides dans une plage de dosage en eau élevé sur laquelle la méthode traditionnelle de mesure d'humidité par le wattmètre devient insuffisamment sensible. Une nouvelle exploitation du signal wattmétrique a été proposée en construisant un modèle de lissage des courbes de puissance. La validation expérimentale sur un malaxeur de laboratoire permet de montrer qu'il est possible d'améliorer la sensibilité du wattmètre à l'aide du paramètre "temps caractéristique" tiré du modèle. / Self-compacting concrete (SCC) is a new generation of concrete with a great potential thank to their ease of placement in construction sites. However, as compared to ordinary concrete, it is more difficult to produce SCC; sensitivity to the variation of the composition dosage often gets cited. In particular, changes in concrete water content strongly influence the SCC production regularity. The primary source of uncertainty in concrete water content stems from poor knowledge of aggregate moisture. On the other hand, the use of a high amount of fines together with a high dosage of superplasticizer results in a long mixing time of SCC, which decreases productivity and increases the cost of production. The aim of this work is then to propose methods to improve the SCC production regularity and productivity.At first, the traditional online mixer measurement - wattmeter was calibrated through use of a simple calibration procedure in a concrete plant. By using this calibration method, the stabilization of mixing power is confirmed as a reliable online indication of SCC water content in an industrial environment. In parallel, a stabilisation criterion of power curves was proposed to quantitatively define the stabilization time. This time is considered as a sufficient mixing time to stop mixing for an increase in productivity.Secondly, we studied at the laboratory scale, the influence of the mixing time on the workability of a SCC mix design with batches in which only the water content was varied. The result has shown that the stabilization time is comparable and proportional to the time required to obtain the optimum workability of SCC.Finally, we treated a case of SCC mixtures over a range of high water content in which the traditional processing of mixing power is not able to distinguish the water proportioning difference from water over dosage in SCC. A new wattmeter signal processing was proposed through using a mathematical model to fit the power consumption curve of the mixer. The experimental validation in a laboratory mixer can show that it is possible to improve the precision of wattmeter thanks to the use of the parameter "characteristic time" from the model

in English The apoplastic barriers of the root (endodermis and exodermis) represent an important regulatory mechanism for the uptake of water and nutrients from the environment, ensuring its selectivity. In addition, both layers respond to stress factors by altering its rate and degree of cell wall modification, which affects the transport properties of the root and represents adaptive plants to high heterogeneity of the soil environment. Apoplastic barriers also respond to the availability of mineral nutrients. This issue has recently been intensively studied and a number of ambiguities persist. Interestingly, the deficiency of some mineral nutrients stimulates the differentiation of barriers, while the deficiency of other mineral nutrients delays the differentiation. In addition, different plant species react differently to the deficiency of the same element. Another interesting aspect is the fact that the reaction of the endodermis and exodermis is localized and takes place mainly in that part of the root system which is directly exposed to the stress factor. This phenomenon has been observed with cadmium toxicity, but more recently with local nutrient deficiencies (nitrogen and potassium) in Zea mays. This diploma thesis deals with the functional significance of localized enhancing or delaying...

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