La gestion de Phytophthora infestans, agent du mildiou de la pomme de terre, nécessite l’application d’une quinzaine de traitements par saison culturale. Pour réduire l’usage des fongicides, combiner résistance induite et résistance quantitative pourrait être une bonne stratégie. Elle nécessite cependant une meilleure connaissance des interactions entre les réponses physiologiques de Solanum tuberosum et l’écologie de P. infestans. Dans cet objectif, les réponses de défense induites chez la pomme de terre ont été confrontées aux traits d’histoire de vie et effecteurs de P. infestans. Quatre génotypes présentant différents niveaux de résistance ont été traités avec un filtrat de culture concentré (CCF) de P. infestans induisant la PAMP-triggered immunity (PTI). Des folioles détachées ont ensuite été inoculées avec des souches rapides ou lentes de P. infestans. Les expressions de 14 gènes de défense et de 6 effecteurs ont été analysée simultanément par qRT-PCR.Les symptômes de la maladie ont été mesurés classiquement ou par analyse d’images dans le visible et en fluorescence. Les résultats obtenus montrent que la réduction des symptômes après induction de la PTI est fonction du couple génotype-souche. En effet, l’efficacité des défenses induites par le CCF dépend des stratégies d’échappement (vitesse de croissance) ou d’adaptation (effecteurs) de P. infestans et du potentiel d’inductibilité du génotype (expression des protéines PR). Ainsi, pour optimiser l’utilisation de la résistante induite il serait nécessaire de sélectionner des génotypes inductibles et capables de modu / The management of Phytophthora infestans, responsible for potato late blight, requires the application of about 15 fungicide treatments per cropping season. To reduce the use of pesticides, combining induced resistance and quantitative resistance could be a positive strategy. However, this method requires a better understanding of the interactions between Solanum tuberosum physiological responses and P. infestans ecology. To this end, defense responses induced in potato have been opposed to the pathogen life history traits and effectors. Four potato genotypes with different resistance levels were treated with a concentrated culture filtrate (CCF) of P. infestans inducing PAMPtriggered immunity (PTI). Then, detached leaflets were inoculated with fast- or slow-growing strains of P. infestans.The expression of 14 defense genes and the expression of 6 effectors were analyzed simultaneously by qRT-PCR. Disease symptoms were measured either conventionally or by visible and fluorescence image analysis. The results obtained show that the reduction of symptoms after induction of PTI was specific to the genotype-strain pair. Indeed, the effectiveness of induced defenses by CCF depends on either the escape (growth rate) or adaptation (effectors) strategies of P. infestans and on the genotype inductibility potential (expression of PR proteins). Thus, to optimize the use of induced resistance, it would be necessary to breed inducible genotypes that are able to modulate strains growth rate.

La commande événementielle offre une alternative prometteuse à la commande périodique classique, qui est considérée comme peu économe vis-à-vis des ressources. Contrairement à la commande classique, la commande événementielle propose de passer d'une loi de commande en temps continu à une loi de commande numérique à travers un échantillonnage non-uniforme. Dans ce cas, une nouvelle valeur de la loi de commande n'est calculée que lorsque la réponse du système est inadmissible. En revanche, la valeur de la loi de commande est maintenue constante si la réponse est satisfaisante. Dans cette thèse, nous explorons des moyens de réduire le nombre de mise à jour de la loi de commande, et de rallonger les intervalles de temps entre les mises à jour.Dans le cas des systèmes linéaires, nous présentons un algorithme de stabilisation dans lequel nous relaxons les conditions de stabilité sur la fonction de Lyapunov du système. Pour induire moins d'échantillons, on requiert uniquement que cette fonction soit maintenue sous un seuil décroissant. Le calcul des paramètres optimaux du seuil est transformé en problème de valeurs propres généralisées. Ensuite, cette approche est étendue aux systèmes dits switched, et une version self-triggered est proposée. Nous traitons également le problème de suivi de trajectoire par une commande événementielle. Enfin, dans le cas du contrôle des systèmes non-linéaires, nous proposons d'utiliser une analyse de contraction des trajectoires, et ce à cause de la difficulté de trouver une fonction de Lyapunov pour ces systèmes. / Event-triggered control offers a promising alternative to the classical, resource-consuming, periodic control. It suggests to replace the periodic, high frequency sampling used in the continuous-to-discrete transformations of control signals with aperiodic sampling. A new value of the event-triggered control law is computed only when the system's response is unsatisfactory. The control value is kept constant otherwise. In this thesis, we explore ways to induce fewer updates, and to have longer intervals between two samples. We also seek to make the algorithms that we design more detailed, by describing how to choose or compute the optimal parameters.In the linear case, we present a stabilizing algorithm in which we relax the stability conditions on the system's Lyapunov function to produce fewer, sparser updates of the control law. Stability is ensured by maintaining the Lyapunov function below a certain decreasing threshold. The optimal threshold function is derived by solving a maximum generalized eigenvalue problem. This approach is then extended to switched linear systems. We also present a self-triggered version of this algorithm using Newton methods for optimization and root-finding. The reference tracking problem is treated in the event-triggered control framework as well. Finally, in the nonlinear case, due to the difficulty of finding a Lyapunov function, we explore the use of contraction analysis. This approach allows us to describe the nonlinear event-triggered control algorithm more thoroughly than if we had used Lyapunov techniques.

In recent years Ethernet has cought the attention of the real-time community. the main reason for this is that it has a high data troughput, 10Mbit/s and higher, and good EMI characteristics. As a protocol that might be used in real-time anvironments such as control systems for cars etc, it seems to fulfil the rquirements. TTEthernet is a TDMA extention to normal Ethnernet, designed to meet the hard deadlines required by real-time networks. This thesis describes how TTEthernet handles frames and the mathematical formulas to calculate shuffle delay of frames in such a network. Open problems related to TTEthernet are also discussed.

No description available.

Thesis (M.S. in E.A.S.)--School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 2004. Directed by James Gaherty. / Includes bibliographical references (leaves 38-42).

Aromatic peptide amphiphiles that self-assemble in response to a trigger, such as pH or enzymes, have the ability to support the culture of somatic cell types, in both two-dimensional (2D) and three-dimensional (3D) culture. Although a fully defined synthetic substrata is required for the successful clinical applications of Embryonic Stem (ES) cells hydrogels of SA aromatic peptide amphiphiles have not been investigated for this purpose. The aim of this investigation is to produce alkaline phosphatase (AP) triggered hydrogels as a substratum for ES cell culture. This SA trigger was chosen as it utilizes inherent biological processes, through the enhanced AP activity of ES cells, with SA occurring in otherwise constant conditions. We also sought to overcome the current inability to consistently control ES cell behaviour in vitro through two different routes that have previously been demonstrated to effect stem cell culture. Firstly, control of the hydrogels mechanical properties and secondly through the incorporation of biological function, principally through the addition of glycosaminoglycans (GAGs). Firstly AP triggered hydrogels of 9-fluorenylmethoxycarbonyl-Tyrosine-OH (Fmoc-Y-OH) were studied and compared with those formed by pH trigger. An unexpected relationship between AP concentration and molecular order was detected. It was observed that the hydrogels stiffness was controlled through the AP concentration; ideal for ES cell culture as Engler et al. (2006) has previously demonstrated the effect material stiffness had on the differentiation pathways chosen by mesenchymal stem cells. Differences between the SA trigger were detected with the hydrogels formed by pH trigger exhibiting significantly lower mechanical properties. This was attributed to the SA process and the disorder that arises from forming all of the hydrogelators instantaneously. The SA process of AP triggered Fmoc-Y-OH showed a 4 stage process. The first stage, dephosphorylation, occurred in a time and AP concentration dependent manner. The second stage transpired due to the spontaneous SA of Fmoc-Y-OH providing a temporary change in fluorenyl environment. The final stages, formation of chiral one dimensional (1D) fibres through proposed -β interactions and gelation through the entanglement of fibres are closely linked. Secondly we investigated AP triggered Fmoc-Phenylalanine-Tyrosine-OH (Fmoc-FY-OH) hydrogels in two distinct physiological environments. When formed in buffer (0.15M, pH 7) an optimum AP concentration was observed in terms of molecular interactions, -β interactions, which translated to the hydrogels mechanical properties. In these conditions helical fibres were imaged by AFM. The second medium for SA was KnockOUT™ DMEM, developed for ES cell culture. Although similarities in the molecular interactions were detected it appears the SA environment effects the structures formed with non-helical fibres imaged. GAGs were successfully incorporated into the hydrogels at biologically relevant levels at the extremes of sulphation. The sulphation patterns of the GAGs secreted by ES cells changes during differentiation and may provide a way to guide cell behaviour through growth factor binding. However the GAGs were not entrapped in the fibre network and leached out into solution limiting their ability to guide ES cell behaviour. Unfortunately both of the hydrogels produced in this study were deemed unsuitable as ES cell substrata due to their instability (Fmoc-Y-OH) or low biocompatibility (Fmoc-FY-OH). However we have demonstrated that it was possible for endogenous AP to trigger SA, indicating that in the future ES cells may be able to form their own substrata preventing the need for exogenous AP.

Unlike mammals, plants do not have specific immune cells. However, plants can still recognize pathogens and defend themselves. They do that by recognizing microbial-associated molecular patterns (MAMPs) and secreted pathogen proteins, called effectors. MAMP-triggered immunity (MTI) relies on recognition of MAMPs by leucine-rich repeats (LRRs) pattern-recognition receptors (PRRs). The best-studied LRR PRR is Flagellin-Sensitive 2 (Fls2), the receptor of a 22-amino acid long epitope of bacterial flagellin, called flg22. In this project, alleles of FLS2 of different tomato cultivars were sequenced and compared to each other to get insight into natural selection acting on FLS2 and to identify residues important for ligand binding. This information may be used in the future to engineer Fls2 for improved ability to recognize flagellin. MTI can be suppressed by effectors secreted by bacteria into plant cells through the type III secretion system. On the other hand, plants are equipped with repertoires of resistance proteins, which can recognize some pathogen effectors. If a pathogen carries an effector that is recognized, effector-triggered immunity (ETI) is activated and the plant is resistant. Here, eggplant breeding lines were screened for their ability to activate ETI upon recognition of effectors of the soil borne pathogen Ralstonia solanacearum, a causative agent of bacterial wilt. Four effectors were found to trigger plant defenses in some of the lines. This is the first step in cloning the genes coding for the responsible resistance proteins. These genes may be used in the future for engineering tomato and potato for resistance to bacterial wilt. / Master of Science in Life Sciences

Narcolepsy is a neurological disorder characterized by a person’s inability to regulate sleep-wake cycles. Excessive daytime sleepiness and cataplexy are prominent symptoms of narcolepsy. Cataplexy is partial to full body muscle atonia usually brought on by the person with narcolepsy experiencing a positive emotion. Some features of cataplexy resemble those of REM sleep, including similar brain activity and muscle atonia. The neuronal circuit that produces cataplexy has yet to be determined. The similarities between REM sleep and cataplexy support the hypothesis that cataplexy is the result of the REM atonia pathways being activated. An emotion processing region, the central amygdala (CeA), projects to known REM regulatory regions and plays a role in cataplexy. GABAergic neurons of the CeA are sufficient and necessary to trigger cataplexy in mice and project to brainstem regions that regulate muscle tone. Cataplexy is often triggered in a social setting, such as when seeing an old friend or telling a joke. Oxytocin (OT) is involved in many social behaviors, making it a viable link between social stimuli and cataplexy. We hypothesized that oxytocin receptor (OTR) neurons of the CeA, a sub-population of GABAergic neurons, promote emotionally-triggered cataplexy. To determine the social phenotype of the narcolepsy mouse model, the orexin knock-out (OXKO) mouse, we used established behavioral assays of social interaction and social memory. To determine if social reunification influenced the amount of cataplexy, group-housed OXKO mice were isolated for a short time and reunited with their littermates. To determine if OTR neurons of the CeA were sufficient and necessary to promote socially-triggered cataplexy, we used chemogenetic technology known as Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) to selectively activate or inhibit these neurons. We injected adeno-associated viral vectors coding for either the excitatory hM3 Cre-dependent DREADD or the inhibitory hM4 Cre-dependent DREADD into the CeA of orexin knock-out mice crossed with OTR-Cre mice, allowing for expression of the DREADD exclusively in the OTR neurons of the CeA. After injection with either saline or clozapine-N-oxide (CNO) we put the mice through a behavioral assay to see if emotionally-triggered cataplexy increased or decreased following the activation or inhibition of OTR neurons of the CeA. The behavioral assays showed that acute social interactions in OXKO is normal, however they do have a social memory impairment. In addition, reunification promotes cataplexy in most OXKO mice. With the chemogenetic experiments, our number of mice is too low to report if OTR neurons of the CeA are sufficient and/or necessary for cataplexy at this time. / 2020-07-03T00:00:00Z

This thesis contains two main parts. The first part presents a database compiling 137 landslide-triggering earthquakes (LTEs) worldwide, with magnitudes greater than the minimum observed threshold for causing landslides (M4.5), for the period of 1998 -2009. Our data sources include a comprehensive review of the existing literature on earthquake-triggered landslides (ETLs), and also a USGS-based earthquake catalog (PAGER-CAT) that contains information on earthquake-triggered secondary events. Only 14 earthquakes out of the 137 seismic events induced significant numbers of landslides (>250). We compared the number of ETLs with the total number of earthquakes with M ≥ 4.5 (n=68,734) during the same period of time. The results show that only 0.2 % of ETLs and only 4.5% of earthquakes of M > 6 resulted in landslide. In addition, we compiled a database of 37 large-scale landslides, involving initial failure volumes of greater than 20 Mm3 that occurred worldwide between 1900 to 2010. The database contains large-scale earthquake-triggered (n ETLs=18) and non-earthquake-triggered landslides (n NETLs=20), i.e., ca. 50% of large-scale landslides were induced by seismic activity. Surprisingly, the volume-temporal frequency curves of ETLs and NETLs show almost identical slopes and intercepts. Thus, for a given volume, the annual frequency of ETLs is almost identical to that of NETLs in the 110 year period. In contrast to previous studies, this thesis found that the volume of the largest landslide triggered by a given landslide-triggering earthquake is not a function of earthquake magnitude. Peak ground motions (PGA, PGV, and PSA) were calculated for the 18 large-scale ETLs at the site of each occurrence and the resulting values show a correlation with the volume of landslides below the threshold of ca. 80 Mm3. Above this threshold, the relationship between peak ground motions and ETL volume shows complex and nonlinear behavior. The results suggest that 1) other special conditions are required for significant earthquake-triggered landslides to occur, and 2) that very large earthquake-triggered landslides (volume greater than 80 Mm3) result from complex progressive failure mechanisms initiated by seismic shaking (i.e., above this threshold volume, landslide volume is independent of PGA, PGV, and PSA). A detailed analysis of the two 1985 Nahanni earthquakes and the North Nahanni rockslide triggered by the first main shock is carried out in the second part of the study. The North Nahanni rockslide, Northwest Territories, Canada was triggered by the earthquake of M=6.6 on October 5th, 1985. The slide occurred in a Palaeozoic carbonate sequence along a thrust fault, which partly follows bedding and partly cuts across bedding. The sliding surface within the limestone consisted of two planes; the lower plane dipped at 20° while the upper plane dipped at 35°. Slope stability analysis is performed using discontinuum numerical modeling. Static slope stability analyses indicate that the sliding rock was marginally safe for the sliding surface friction angles of 24o or higher. Dynamic analyses of the co-seismic movements are conducted by applying a series of sinusoidal waves to the base of the model. The amplitudes of the October earthquake's seismic waves are estimated using strong motion data available from the second main shock. The results, from the dynamic analysis indicate that the slope becomes unstable for given seismic inputs at a specific range of friction angles (24o to 30o) for the sliding surface and the deformation behavior of the North Nahanni rock masses is dependent on the frequency of the seismic signals. Because the static slope stability analysis showed that the slope was close to instability prior to the seismic shaking, we suggest that the 1985 Nahanni earthquake operated as a trigger event that accelerated the occurrence of the slide. This finding supports our earlier results of the global scale study, which showed that the triggering event does not change the general trend of the frequency-volume distribution of landslides; however, it can accelerate the occurrence of slope failure.

Fractures make both opportunities and problems for exploration and production from hydrocarbon reservoirs. It is always difficult to predict how to optimally produce a fractured reservoir due to the complexity and heterogeneity of fluid flow paths. The following behavior is seen in fractured reservoirs: early water breakthroughs, reduced tertiary recovery efficiency due to channeling of injected gas or fluids, dynamic calculations of recoverable hydrocarbons that are much less than static mass balance and dramatic production changes due to changes in reservoir pressure as fractures close down as conduits. These problems often lead to reduced ultimate recoveries or higher production costs. Polymer gels, in particular in-situ gels that can be placed deep into the reservoir, have been widely used for improved conformance control. In this dissertation, we aim to block the high-permeability zones, fractures in particular, with the microgels to increase the sweep efficiency by diverting the waterflood water to the low permeability zones that still contain unswept oil. vii Polyacrylic acid microgels can swell a thousand fold as the pH of the surrounding solution changes, with an accompanying large increase in viscosity. This pH trigger is simpler than chemical cross-linking and thus offers operational advantages. The ability of pH-sensitive polymers to block high permeability fractures is studied by performing several coreflood and batch experiments. The effect of different rock and salt minerals, polymer concentration, polymer salinity, and temperature on polymer performance is studied in this dissertation. Polymer microgels show excellent consistency in the presence of various salt minerals and in contact with different rock minerals. The placement of microgels into the fractures lowered the overall core permeability in all cases. In addition, polymer microgels were stable after being in reservoir for a month with conditions at 58°C. Consequently, using pH-triggered polymers for conformance control and reducing the permeability of high permeability areas in fractured reservoirs merit further investigations. These polymers are inexpensive and are easy to prepare. The polymer concentration, salinity and shut-in time could be set according to the desired PRF value, injectivity, propagation distance and reservoir mineralogy. / text