Plasmodium falciparum is responsible for the most virulent form of human malaria. The biology of the intra-erythrocytic stage of P. falciparum is the most well studied as it is this stage that marks the clinical manifestation of malaria. To establish a successful infection, P. falciparum brings about extensive remodeling of erythrocytes, its host compartment. The infected erythrocytes harbor several parasite induced membranous structures. Most importantly, pathogenesis related structures termed knobs, which impart cytoadherence, appear on the cell surface of the infected erythrocytes. For bringing about such eccentric renovations in its host compartment, the parasite exports 8% of its genome (~400 proteins) to various destinations in the host cell. Studies from our lab have shown that proteins belonging to heat shock protein40 (Hsp40) and heat shock protein70 (Hsp70) group of chaperones are also exported to the host compartment. We and others have implicated these chaperones in important processes such as protein trafficking and chaperoning assembly of parasitic proteins into the cytoadherent knobs. As detailed above, malaria parasite invests a lot of energy in exporting a large number of proteins including chaperones in the red blood cell to meet its pathogenic demands. In order to do so, it heavily relies on its secretory pathway. However, it is known that the parasite experiences a significant amount of oxidative stress on account of heme detoxification, its own metabolism and the immune system of the host. The parasite also effluxes large quantities of reduced thiols such as glutathione and homocysteine into the extracellular milieu indicative of redox perturbation. Additionally, the parasite lacks Peroxiredoxin IV, which otherwise localizes in the ER and carries out detoxification of peroxide generated as a result of oxidative protein folding. Together, these factors indicate that maintaining redox homeostasis is a challenging task for the parasite. It also implies that the ER, where the redox balance is even more critical as it requires oxidising environment for protein folding, is predisposed to stress. In light of this fact and the importance of secretory pathway in malaria pathogenesis, we decided to address the ways and mechanisms used by the parasite to tackle perturbations in its secretory pathway. Examination of a canonical unfolded protein response pathway in P. falciparum ER-stress is a condition arising whenever the load of unfolded proteins increases the folding capacity of the ER. However, eukaryotes have evolved a fairly well conserved homeostatic response pathway known as unfolded protein response (UPR) to tackle ER-stress. This signal transduction pathway is composed of three arms involving three ER-transmembrane signal transducers namely; IRE1, ATF6 and PERK. IRE1 brings about splicing of a bZIP transcription factor, XBP1/Hac1 and ATF6 becomes activated upon getting proteolytically cleaved in the Golgi. These transcription factors then migrate to the nucleus where they bind onto the ER-stress elements thereby, leading to the transcriptional up-regulation of the UPR targets such as ER chaperones and components of ER associated degradation (ERAD) pathway which rescue the function of the ER. PERK on the other hand brings about translational attenuation by phosphorylating eIF2α, thereby providing parasite the benefit of time to recover. We started our examination on UPR in Plasmodium by carrying out in silico analysis of the major components of UPR in the parasite by using Homo sapiens protein sequences as the query. We found that the parasite lacks the homologues of all the transcriptional regulators of canonical UPR. Only PERK component of the UPR was found to be present in the parasite. To rule out the existence of the canonical UPR in P. falciparum, we examined the status of UPR targets by subjecting the parasites to treatment with DTT. DTT perturbs the disulfide oxidation in the ER and thereby inhibits protein folding leading to ER-stress. Owing to the missing components of a canonical UPR, we did not find up-regulation of known UPR targets such as ER-chaperones including PfBiP, PfGrp94, PfPDI and ERAD marker Derlin1 at transcript as well as protein level. Owing to the presence of a PERK homologue, phosphorylation of eIF2α followed by attenuation of protein synthesis was observed upon subjecting the parasites to DTT mediated ER-stress. In the absence of a canonical UPR, the parasites were found to be hypersensitive to ER-stress in comparison to the mammalian counterpart. In the presence of DTT, the parasites showed perturbation in the redox homeostasis as indicated by increase in the levels of ROS. Next, we sought to examine if the parasites resorted to any alternate means of increasing the availability of chaperones in the ER. For this, we analysed the involvement of another Hsp70 family member, Hsp70-x which is homologous to BiP and which is known to traverse the ER while getting exported to the erythrocyte compartment. Interestingly, we found that upon exposure to ER-stress, the export of this protein is partially blocked and around 30% of the protein is retained in the ER. On the other hand, there was no effect on the trafficking of another exported chaperone KAHsp40. This indicates that the parasite possibly recruits this pool of retained Hsp70-x for the chaperoning of unfolded proteins in the ER. Global response to ER-stress in P. falciparum To dig deeper into the parasite specific strategies employed for dealing with ER-stress at a global level, we carried out high throughput transcriptomic and proteomic analysis upon subjecting the parasites to DTT mediated ER-stress. Microarray based gene expression profiling was carried out upon subjecting the parasites to DTT mediated ER-stress. We found that the parasite mounts a transcriptional response as indicated by up-regulation of 155 transcripts. In congruence with our biochemical analysis, we did not find up-regulation of ER chaperones as well as ERAD proteins. Functional grouping of the up-regulated genes revealed large number of hypothetical proteins in our list of differentially expressed genes. The genes encoding exported proteins represent yet another abundant class. In the course of examining the involvement of Plasmodium specific transcriptional regulators mediating response to DTT induced ER-stress, we identified 4 genes belonging to the family of AP2 transcription factors. AP2 (Apetela-2) are specific transcription factors which are possessed by apicomplexa and bring about regulation of developmental processes and stress response in plants. On comparing our list of up-regulated genes with the previously known targets of AP2 factors, we found that an entire cascade of AP2 factors is up-regulated upon DTT-mediated ER stress. Thus, AP2 factors appear to be the major stress response mediators as they are together responsible for the up-regulation of 60% of genes identified in this study. In addition, another striking observation made, was the up-regulation of a few sexual stage specific transcripts. 2D Gel electrophoresis and 2D-DIGE based Proteomic analysis indicated an up-regulation of secretory proteins and some components of vesicular trafficking and secretory machinery possibly to overcome the block in the functions of the secretory pathway. ER-stress triggers stage transition in P. falciparum Intrigued by the up-regulation of a few sexual stage specific genes, we were curious to examine if there was a functional significance of this observation. To this end, we decided to investigate the effect of ER-stress on induction of gametocytes, the only sexual stage found in humans. Indeed, we found a two fold induction in the numbers of gametocytes formed upon challenging the parasite with DTT mediated ER-stress. The induction of gametocytogenesis was also observed by using a clinical isolate of P. falciparum for the assay. The DTT treated cultures progressed through the gametocytogenesis pathway normally forming all the five morphologically distinct stages. Then we sought to examine if this phenomenon could be simulated in the physiological scenario as well. For this, we made use of a rodent model of malaria, P. berghei. Two different treatment regimes involving 1) direct injection of increasing concentration of DTT into P. berghei infected mice and 2) injection of DTT pretreated P. berghei infected erythrocytes into healthy mice were followed. In both cases, a significant increase in the gametocyte induction was observed. Having seen that Plasmodium undergoes gametocytogenesis upon exposure to ER-stress not only in in vitro cultures but also in in vivo scenario, we wanted to identify the players involved in the commitment to sexual stage. Recently, a transcription factor belonging to AP2 class of transcription factors, referred to as AP2-G has been implicated in committing the asexual parasites for transition to gametocyte stage. To examine the role of this factor in the phenotype observed by us, we looked at the effect of DTT on AP2-G. Interestingly, we found around 6 folds up-regulation in the expression of AP2-G levels under ER-stress. The downstream targets of AP2-G, many of which are the markers of gametocyte were also found to be up-regulated upon being exposed to DTT mediated ER-stress indicating the launch of a transcriptional program which together works in the direction of transition to gametocytes. Having seen that P. falciparum undergoes ametocytogenesis in response to DTT treatment both under in vitro and in vivo conditions, we sought to look for probable physiological analogue of DTT. Since glutathione is the major cellular redox buffer, critical for redox homeostasis, we quantitated the levels of both oxidized and reduced forms of this non protein thiol using Mass Spectrometric approach. We found that the levels of reduced forms of glutathione significantly increased upon treating the parasites with DTT. This indicates that the levels of glutathione could be one of the physiological triggers of gametocytogenesis. Conclusion In conclusion, our study analyses the ways and mechanisms employed by malaria parasite to cope with perturbations to its secretory pathway. We have established the absence of a canonical UPR in this parasite and our results suggest that Plasmodium has developed a three stage response to cope with ER stress: 1) an early adaptation to increase the local concentration of chaperones in the ER by partially blocking the export of a Hsp70 family member, 2) activation of gene expression cascade involving AP2 transcription factors and 3) a consequent switch to the transmissible sexual stage. Hence, our study throws light on a novel physiological adaptation utilised by malaria parasite to tackle stress to its secretory pathway. Gametocytogenesis, which can be transmitted to the mosquito vector, could hence serve as an effective means to escape ER-stress altogether. Importantly, while it is widely known that stress brings about switch towards sexual stages in P. falciparum, the molecular triggers involved in this process remain obscure in the field of malaria biology. Therefore, our findings also address this long standing question by providing the evidence of ER-stress being one such trigger required for switching to the transmissible sexual stages.

Shock wave-boundary layer interactions (SWBLIs) have been studied ex-tensively due to their practical importance in the design of high speed ve-hicles. These interactions, especially the ones leading to shock induced separation are typically unsteady in nature and can lead to large fluctuating pressure and thermal loads on the structure. The resulting shock oscil-lations are generally composed of high-frequency small-scale oscillations and low-frequency large-scale oscillations, the source of the later being a subject of intense recent debate. Motivated by these debates, we study in the present work, the SWBLI at a compression ramp and on a forward-facing step (FFS) at a Mach number of 2.5. In the case of compression ramps, a few ramp angles are studied ranging from small (10 degree) ramp angle to relatively large values of up to 28 degrees. The FFS configuration, which consists of a 90 degree step of height h, may be thought of as an extreme case of the compression ramp geometry, with the main geometri-cal parameter here being (h/δ), where δis the thickness of the oncoming boundary layer. This configuration is less studied and has some inherent advantages for experimentally studying SWBLI as the size of the separa-tion bubble is large. In the present experimental study, we use high-speed schlieren, unsteady wall pressure measurements, surface oil flow visualiza-tion, and detailed particle image velocimetry (PIV) measurements in two orthogonal planes to help understand the features of SWBLI in the com-pression ramp geometry and the forward-facing step case. The SWBLI at a compression ramp has been more widely studied, and our measurements show the general features that have been seen in earlier studies. The upstream boundary layer is found to separate close to the ramp corner forming a separation bubble. The streamwise length of the separa-tion bubble is found to increase with the ramp angle, with a consequent shift of the shock foot further upstream. At very small ramp angles up to 10 degrees, there is no evidence of separation, while at large ramp angles of 28 degrees, the separation bubble extends upstream to about 3.5δ(δ=boundary layer thickness). In all cases, the separation bubble is however very small in the wall normal direction, typically known to be about 0.1δ, and hence is difficult to directly measure in experiments using PIV. Shock foot measurements using PIV show that the shock has a spanwise ripple, which seems directly related to the high-and low-speed streaks in the in-coming boundary layer as recently shown by Ganapathisubramani et al. (2007). The forward-facing step configuration may be thought of as an extreme case of the compression ramp geometry, with a ramp angle of 90 degrees. This configuration has not been extensively studied, and is experimentally convenient due to the large separation bubbles formed ahead of the step. In the present work, extensive measurements of the mean and unsteady flow around this configuration have been done, especially for the case of h/δ=2, where his the step height. Pressure measurements in this case, show clear low-frequency motions of the shock at non-dimensional frequencies of about fh/U∞≈ 0.02. In this case, PIV measurements show the pres-ence of a large mean separation bubble extending to about 4hupstream and about 1hvertically. Instantaneous PIV measurements have been done in both cross-stream (streamwise and wall-normal plane) and in the span-wise (streamwise-spanwise) plane. Instantaneous cross-stream PIV mea-surements show significant variations of the shock location and angle, be-sides large variations in the recirculation region (or separation bubble), this being determined as the area having streamwise velocities less than zero. From a large set of individual PIV instantaneous fields, we can estimate the correlation of the measured shock location to both downstream effects like the area of the recirculation region, and upstream effects like the presence of high-/low-speed streaks in the oncoming boundary layer. We find that the shock location measured from data outside the boundary layer is more highly correlated to downstream effects as measured through the recircu-lation area compared to upstream effects in the boundary layer. However, we find that the shock foot within the boundary layer has ripples in the spanwise direction which are well correlated to the presence of high-/low-speed streaks in the incoming boundary layer. These spanwise ripples are however found to be small (less than one h) compared to the highly three-dimensional shape of the recirculation region with spanwise variation of the order of 3 step heights. In summary, the study shows that the separated region ahead of the step is highly three-dimensional. The shock foot within the boundary layer is found to have ripples that are well correlated to fluctuations in the in-coming boundary layer. However, we find that the large-scale nearly two-dimensional shock motions outside the boundary layer are not well cor-related to the fluctuations in the boundary layer, but are instead well cor-related with the spanwise-averaged separation bubble extent. Hence, the present results suggest that for the forward-facing step configuration, it is the downstream effect caused by the separation bubble that leads to the observed low-frequency shock motions.

Le schéma d'allumage par choc pour la fusion par confinement inertiel utilise une impulsion laser intense à la fin d'une phase d'assemblage de combustible. Les paramètres clefs de ce schéma sont la génération d'une haute pression d'ablation, l'amplification de la pression du choc généré par un facteur supérieur à cent et le couplage du choc avec le point chaud de la cible. Dans cette thèse, de nouveaux modèles semi-analytiques sont développés afin de décrire le choc d'allumage depuis sa génération jusqu'à l'allumage du combustible. Tout d'abord, un choc sphérique convergent dans le coeur pré-chauffé de la cible est décrit. Le modèle est obtenu par perturbation de la solution auto-semblable de Guderley en tenant compte du nombre de Mach du choc élevé mais fini. La correction d'ordre un tient compte de l'effet de la force du choc. Un critère d'allumage analytique est exprimé en fonction de la densité surfacique du point chaud et de la pression du choc d'allumage. Le seuil d'allumage est plus élevé pour un nombre de Mach faible. Il est montré que la pression minimale du choc, lorsqu'il entre dans le coeur de la cible, est de 20Gbar. La dynamique du choc dans la coquille en implosion est ensuite analysée. Le choc se propage dans un milieu non inertiel avec un fort gradient de pression et une augmentation temporelle générale de la pression. La pression du choc est amplifiée plus encore durant la collision avec une onde de choc divergente provenant de la phase d'assemblage. Les modèles analytiques développés permettent une description de la pression et de la force du choc dans une simulation typique de l'allumage par choc. Il est démontré que, dans le cas d'une cible HiPER, une pression initiale du choc de l'ordre de 300 Mbar dans la zone d'ablation est nécessaire. Il est proposé une analyse des expériences sur la génération de chocs forts avec l'installation laser OMEGA. Il est montré qu'une pression du choc proche de 300Mbar est atteinte près de la zone d'ablation avec une intensité laser absorbée de l'ordre de 2 X 10(15) W.cm-2 et une longueur d'onde de 351 nm. Cette valeur de la pression est deux fois plus importante que la valeur attendue en considérant une absorption collisionnelle de l'énergie laser. Cette importante différence est expliquée par la contribution d'électrons supra-thermiques générés durant l'interaction laser/plasma dans la couronne. Les modèles analytiques proposés permettent une optimisation de l'allumage par choc lorsque les paramètres de la phase d'assemblage, sont pris en compte. Les diverses approches analytiques, numériques et expérimentales sont cohérentes entre-elles. / The shock ignition concept in inertial confinement fusion uses an intense power spike at the end of an assembly laser pulse. the key feature of shock ignition are the generation of a high ablation pressure, the shock pressure amplification by at least a factor of a hundred in the cold fuel shell and the shock coupling to the hot-spot. in this theses, new semi-analytical hydrodynamic models are developed to describe the ignitor shock from its generation up to the moment of fuel ignition. A model is developed to describe a spherical concerging shock wave in a pre-heated hotspot. The self-similar solution developed by Guderley is perturbed over the shock Mach number Ms >>1. The first order correction accounts for the effects of the shock strength. An analytical ignition criterion is defined in terms of the shock strength ans th hot-spot areal density. The ignition threshold is higher when the initial Mach number of the shock is lower. A minimal shock pressure of 20 Gbar is needed when it enters the hot-spot. The shock dynamics in the imploding shell is the analyzed. The shock is propagating into a non inertial medium with a high radial pressure gradient and an averall pressure increase with time. The collision with a returning shock coming from the assembly phase enhances further the ignitor shock pressure. The analytica theory allows to des cribe the shock pressure and strength evolution in a typical shock ignition implosion. It is demonstrated that, in the case of the HiPER target design, a generation shock pressure near the ablation zone on the order of 300-400 Mbar is needed. An analysis of experiments on the strong shock generation performed on the OMEGA laser facility is presented. It is sown that a shock presssure close to 300 Mbar near the ablation zone has been reached with an absorbed laser intensity up to 2 x 10(15) W:cm-2 and a laser wavelength of 351 nm. This value is two times higher than the one expected from collisional laser absorption only. That significant pressure enhancement is explained by contribution of hot-electrons generated by non-linear laser/plasma interaction in the corona. The proposed analytical models allow to optimize the shock ignition scheme, including the inuence of the implosion parameters. Analytical, numerical and experimental results are mutualy consistent.

No description available.

The particular study case in this thesis is the shock test performed on the LISA Pathfinder satellite conducted in a laboratory environment on a dedicated test bed: Vega Shock Test Apparatus (VESTA). This test is considered fully representative to study shock levels produced by fairing jettisoning event at Vega Launcher Vehicle, which induces high shock loads towards the satellite. In the frame of this thesis, some transient response analyses have been conducted in MSC Nastran, and a shock simulation tool for the VESTA test configuration has been developed. The simulation tool is based on Nastran Direct Transient Response Analysis solver (SOL 109), and is representative of the upper composite of Vega with the LISA Pathfinder coupled to it. Post-processing routines of transient response signals were conducted in Dynaworks which served to calculate Shock Response Spectra (SRS). The simulation tool is a model of forcing function parameters for transient analysis which adequately correlates with the shock real test data, in order to understand how the effect of shock generated by the launcher is seen in the satellite and its sub-systems. Since available computation resources are limited the parameters for analysis were optimised for computation time, file size, memory capacity,  and model complexity. The forcing function represents a release of the HSS clamp band which is responsible for fairing jettisoning, thus the parameters which were studied are mostly concerning the modelling of this event. Among many investigated, those which visibly improved SRS correlation are radial forcing function shape, implementation of axial impulse, clamp band loading geometry and refined loading scheme. Integration time step duration and analysis duration were also studied and found to improve correlation.  From each analysis, the qualifying shock environment was then derived by linear scaling in proportion of the applied preload, and considering a qualification margin of 3dB. Consecutive tracking of structural responses along shock propagation path exposed gradual changes in responses pattern and revealed an important property that a breathing mode (n = 0) at the base of a conical Adapter translates into an axial input to the spacecraft. The parametrisation itself was based on responses registered at interfaces located in near-field (where the clamp band is located and forcing function is applied) and medium-field with respect to the shock event location. Following shock propagation path, the final step was the analysis of shock responses inside the satellite located in a far-field region, which still revealed a very good correlation of results. Thus, it can be said that parametrisation process was adequate, and the developed shock simulation tool can be qualified. However, due to the nature of shock, the tool cannot fully replace VESTA laboratory test, but can support shock assessment process and preparation to such test. In the last part of the thesis, the implementation of some finite element model improvements is investigated. Majority of the panels in spacecraft interior exhibited shock over-prediction due to finite element model limitation. Equipment units modelled as lump masses rigidly attached with RBE2 elements to the panel surface are a source of such local over-predictions. Thus, some of the units were remodelled and transient responses were reinvestigated. It was found that remodelling with either solid elements, or lump mass connected to RBE3 element and reinforced by RBE2 element, can significantly improve local transient responses. This conclusion is in line with conclusions found in ECSS Shock Handbook.

The response of submerged structures subject to loading by underwater blast waves is governed by complex interactions between the moving or deforming structure and the surrounding fluid and these phenomena need to be thoroughly understood in order to design structural components against underwater blast. This thesis has addressed the response of simple structural systems to blast loading in shallow or deep water environment. Analytical models have been developed to examine the one-dimensional response of both water-backed and air-backed submerged rigid plates, supported by linear springs and loaded by underwater shock waves. Cavitation phenomena as well as the effect of initial static fluid pressure are explicitly included in the models and their predictions were found in excellent agreement with detailed FE simulations. Then, a novel experimental apparatus has been developed, to reproduce controlled blast loading in initially pressurised liquids. It consists of a transparent water shock tube and allows observing the structural response as well as the propagation of cavitation fronts initiated by fluid-structure interaction in a blast event. This experimental technique was then employed to explore the one-dimensional response of monolithic plates, sandwich panels and double-walled structures subject to loading by underwater shock waves. The performed experiments provide great visual insight into the cavitation process and the experimental measurements were found to be in good agreement with analytical predictions and dynamic FE results. Finally, underwater blast loading of circular elastic plates has been investigated by theoretically modelling the main phenomena of dynamic plate deformation and fluid-structure interaction. In addition, underwater shock experiments have been performed on circular composite plates and the obtained measurements were found in good correlation with the corresponding analytical predictions. The validated analytical models were then used to determine the optimal designs of circular elastic plates which maximise the resistance to underwater blast.

Mesoscale models are needed to predict the effect of changes to the microstructure of plastic-bonded explosives on their shock initiation and detonation behaviour. This thesis describes the considerable progress that has been made towards a mesoscale model for two HMX-based explosives PBX9501 and EDC37. In common with previous work in the literature, the model is implemented in hydrocodes that have been designed for shock physics and detonation modelling. Two relevant physics effects, heat conduction and Arrhenius chemistry, are added to a one-dimensional Lagrangian hydrocode and correction factors are identified to improve total energy conservation. Material models are constructed for the HMX crystals and polymer binders in the explosives, and are validated by comparison to Hugoniot data, Pop-plot data and detonation wave profiles. One and two-dimensional simulations of PBX9501 and EDC37 microstructures are used to investigate the response of the bulk explosive to shock loading. The sensitivity of calculated temperature distributions to uncertainties in the material properties data is determined, and a thermodynamic explanation is given for time-independent features in temperature profiles. Hotspots are widely accepted as being responsible for shock initiation in plastic-bonded explosives. It is demonstrated that, although shock heating of crystals and binder is responsible for temperature localisation, it is not a feasible hotspot mechanism in PBX9501 and EDC37 because the temperatures generated are too low to cause significant chemical reaction in the required timescales. Critical hotspot criteria derived for HMX and the binders compare favourably to earlier studies. The speed of reaction propagation from hotspots into the surrounding explosive is validated by comparison to flame propagation data, and the temperature of the gaseous reaction products is identified as being responsible for negative pressure dependence. Hotspot size, separation and temperature requirements are identified which can be used to eliminate candidate mechanisms in future.

Les plantes n'échappent pas à leur lieu de vie, elles doivent en permanence adapter leurs processus physiologiques pour répondre aux variations de leurs conditions environnementales. Durant ma thèse, j'ai étudié deux stress affectant le développement des plantes, les stress thermique (HS) et oxydant (OS), en ciblant des éléments clé de ces phénomènes (les protéines de choc thermique Hsp et Thiorédoxines TRX) afin d'apporter des éléments de réponse quant à l'interconnexion de ces stress et leur importance pour la plante.En utilisant le riz et le soja comme modèles, je montre que le HS suit une « signature Ca2+ » en provoquant une entrée de calcium de l'apoplaste vers le cytosol, assurant ainsi une rigidité à la paroi cellulaire et une cascade de signaux. J'identifie aussi une Pectine Methylesterase nécessaire au remodelage de la paroi cellulaire et à l'intégrité de la membrane. J'ai aussi recherché comment la plante perçoit les changements de température et transmet ce signal vers des effecteurs. Par des analyses d'expression de gènes, je montre qu'une CaM bien spécifique coordonne la réponse au HS, qui se traduit par l'expression spécifique de certaines petites Hsp nucléaires et cytosoliques.Je réalise enfin une étude moléculaire de TDX, une TRX suspectée d'agir dans la réponse au HS. Je montre que TDX interagit avec des Hsp70 de type cytosoliques/nucléaires de façon redox dépendante, que les stress HS et OS induisent une relocalisation nucléaire de TDX. Je montre enfin que TDX est essentielle pour la thermotolérance acquise et la transduction du signal oxydant. Ces résultats sont discutés et des modèles de transduction des signaux entre HS et OS sont proposés. / While being unable to escape their lands, plants are continuously submitted to the modifications of their environment, and need to adjust proper physiological processes in response to various stimuli. During this work, I devoted my studies on two major stresses affecting plant development, heat shock (HS) and oxidative stresses (OS), focusing on key elements in these pathways (HS chaperons and HS-related thioredoxins) in order to bring news elements of knowledge and interconnexion of these pathways.Using rice and soybean as mono- and dicotyledonous plant systems, I show how HS leads to calcium release from plant cell apoplast to the cytosol in a typical calcium signature, conferring cell wall rigidity and enhancing HS signaling pathway. I also identify Pectin Methylesterase as required in this pathway for cell wall remodeling and plasma membrane integrity. I further investigate how plant sense temperature increases and how they transmit the HS signal to downstream elements. Using systematic analyses of Calmodulin (CaM) and small heat shock protein (sHsp) gene expression, I identify one CaM as a coordinator of HS response, which I characterize as involving specific cytosolic/nuclear isoforms of the sHsp family.I latter perform the molecular analysis of TDX, a Thioredoxin suspected to be involved in heat shock response. I show that TDX interacts with cytosolic/nuclear members of the Hsp70 family in a redox dependent manner, both HS and OS inducing its nuclear relocation, and that TDX is required for both acquired thermotolerance and OS signaling.I finally discuss the data brought by this work and propose models with cross-talks between HS and oxidative stress signaling.

L'interaction entre une onde de choc plane et un nuage de gouttes d'eau homogène, monodisperse est étudiée dans un tube à choc. Les influences de la fraction volumique d'eau, αd(1 %, 0.3 % et 0.1%), rapport du volume d'eau sur le volume du nuage, de la hauteur du nuage Hd (70 cm, 40 cm et 15 cm), du diamètre des gouttes φd (250 µm et 500 µm ) et du nombre de Mach M (1.3 et 1.5) sont étudiées pour des fractions volumiques inférieures au pour cent. Lors de cette interaction, la pression en paroi du tube à choc est mesurée et la visualisation du nuage est obtenue par une méthode ombroscopique directe. Une évolution temporelle caractéristique de la pression induite par la propagation d'une onde de choc dans un tel milieu, est mise en évidence. Cette allure, diffère significativement de celle obtenue avec un nuage constitué de particules solides: la fragmentation des gouttes en est responsable. Une zone où la pression diminue directement après le pic de pression est alors observée aux stations de mesure localisées dans le nuage. L'atténuation de la surpression est mise en évidence: elle peut atteindre 80% du pic de pression mesuré sans nuage. Dans la partie numérique de ce travail, deux modèles de fragmentation sont implémentés, comparés et validés dans un code de calcul monodimensionel, instationnaire, Eulérien appliqué aux écoulements dilués (αd<1 %). On montre que la formulation du taux de production des gouttes selon le taux d'accroissement soit de leur nombre, soit de leur diamètre doit être utilisée respectivement soit avec, soit sans la prise en compte l'étape de déformation de la fragmentation. / The interaction between a planar shock wave and an both homogeneous and monodispersed droplet water cloud is studied in a shock tube. The effects of the water volume fraction αd (1% %, 0.3 % et 0.1%), ratio between the volume of water and the volume of the cloud, the height of the two-phase medium Hd (70 cm, 40 cm et 15 cm), the droplets diameters φd (250 µm et 500 µm ) and the Mach number M (1.3 et 1.5) are studied for a volume fraction smaller than one per cent. During this interaction, the pressure is measured and the visualization of the cloud is obtained by direct shadowgraphy. A characteristic temporal evolution of the pressure induced by the propagation of the shock wave in such a mixture is highlighted. This behavior differs significatively from the one obtained with a solid particles cloud : the droplet atomization is responsible of this change. A zone where the pressure decreases directly after the pressure peak is observed at different stations located into the water cloud. The mitiagtion of the overpressure is shown: it can reach 80%of the pressure peak measured without cloud. In the numerical part, two fragmentation models are added, compared and validated in a comptutational, one dimensional, instationnary, Eulerien code in the case of dilute flows (αd<1 %). We show that the formulation of the production rate of droplets defined by the number of droplets growth, or the diameter droplet growth, must be used, respectively, with and without taking into account the deformation stage of the droplet breakup. Thus, the numerical results are in good agrement with those obtained experimentally.

Sucrose fading was used to initiate self-administration of ethanol on an FR4 schedule in male Fischer 344 rats. Rats showed low response rates for ethanol alone. After administration of liquid diet containing ethanol, ethanol intake increased over levels prior to administration of the liquid diet. In situ hybridization compared mRNA for the inducible or constitutive 70 kD heat shock proteins in ethanol and nonethanol rats. Both inducible and constitutive mRNAs were found in nonethanol and ethanol tissues. In peripheral organs, radiolableling was higher in ethanol tissue. In brain regions, nonethanol tissues showed higher radiolabeling.