Variable mortality of Pyrenophora semeniperda--infected Bromus tectorum seeds has been referred to as a "race for survival", stating that seeds that germinate quickly are more likely to escape pathogen-caused mortality. Dormancy status is not the only variable determining outcomes within the Bromus-Pyrenophora pathosystem. Varying temperature and exposure to water may strongly influence germination outcomes of B. tectorum when in the presence of P. semeniperda. Low water potentials characteristic of semi-arid soils are often over-looked in the context of seed pathogens, and are ecologically relevant- especially for plant species that inhabit intermittently dry environments. To adequately characterize the Bromus tectorum-Pyrenophora semeniperda pathosystem, four studies were conducted to address the following questions: (1) do temperature, water potential, and dormancy status influence germination outcomes in the Bromus-Pyrenophora pathosystem, (2) do repeated wetting-drying scenarios influence germination outcomes of infected B. tectorum seeds following dehydration at low water potentials similar to those found in the field (i.e., -4 through -150 MPa), (3) can we accurately characterize the asexual life cycle of P. semeniperda on a dormant B. tectorum seed, determining when infection takes place, and what occurs during disease development in continuously hydrated conditions, and (4) how does disease development of P. semeniperda influence the B. tectorum seed embryo and endosperm. All studies were conducted using dormant and/or non-dormant B. tectorum seeds and an intermediate strain of P. semeniperda. Study one used varying temperatures (5-20°C), and five water potentials (0, -0.5, -1, -1.5, -2 MPa) (achieved using PEG 8000). Inoculated seeds were exposed to low water potentials at various temperatures for 7, 14, 21, or 28 days then re-hydrated for 28 days. In the second study, seeds were incubated at 20°C at four nominal water potentials (-4, -10, -40, or -150 MPa) following 8 or 24 hours of initial hydration. Seeds were dehydrated for 1, 7, 14, or 21 days, then re-hydrated. In study three, inoculated seeds were chemically fixed between days 0 and 21 and viewed with a scanning electron microscope. In the fourth study, infected seeds were frozen with liquid nitrogen following 3, 8, and 14 days of disease development, then cross sectioned longitudinally and laterally prior to chemical fixation. Results indicate that non-dormant seeds escape death by germinating rapidly under favorable conditions, that incubation at low water potentials greatly increases seed mortality, that -10 MPa is near the threshold for full pathogen activity, and at water potentials lower than -40 MPa, P. semeniperda may successfully survive severe dehydration if previous hydration resulting in infection has occurred. SEM images indicate that mycelia penetration occurs within 8-24 hours, and that mycelium may penetrate all opening in the seed (i.e., stomata, cracks). Development of P. semeniperda is shown to cause significant damage to the endosperm and embryo within 8 days. As starch is consumed, the endosperm collapses leaving a hollow middle. The embryo is more resilient, but gradually deforms and deteriorates.

In this project an experimental setup is designed to investigate the effect of intermittent load patterns in combination with moisture content on cellulose ageing. It is done by exposing groups of samples to different intermittent load patterns with varying frequency. A literature review is done on transformer insulation system and cellulose degradation. Various technical solutions to different aspects of the experimental design are reviewed. The final experimental setup is explained with the primary focus being on the hardware and programming of the controlling system. The controlling system consists of a Data Acquisition (DAQ) system from National Instruments and is programmed in LabVIEW. The controlling system is examined in two investigative tests where it performed satisfactorily. Three load patterns are developed. This project suggests how to prepare the samples and what direct- and indirect tests to apply to the insulation system for future analysis.Over the years, a considerable amount of scientific work has been devoted to understanding paper ageing in order to improve transformer diagnostics and investments for utility owners. However, transformer loading guidelines of today do not take intermittent load in combination with moisture content into account [1] [2]. Previous work suggests that the thermal models may be improved by looking into the effects of moisture content [3].The primary aim of the proposed experimental setup is to investigate whether an intermittent load pattern in combination with moisture content have a considerable detrimental effect on cellulose ageing. The intent is to contribute with new knowledge about transformer diagnostics and long-term possibly improve the current thermal models used for Dynamic Transformer Rating (DTR) which do not take this phenomenon into account. This would in particular benefit transformers with typically intermittent load patterns, e.g. a transformer connected to a wind farm or photovoltaic panels. Increasing renewable energy installations increase the need for developing the thermal models in the transformer loading guidelines to take unconventional load profiles into account. / I det här projektet utformas ett experiment för att undersöka inverkan av intermittenta lastmönster i kombination med fukthalt på åldrande av cellulosa. Detta görs genom att utsätta provgrupper för olika lastmönster med varierande frekvens. En litteraturgenomgång görs på transformatorisoleringssystem och nedbrytning av cellulosa. Olika tekniska lösningar för olika aspekter av experimentets design ses över. Den slutliga utformningen av experimentet förklaras med fokus på hårdvara och programmering av kontrollsystemet. Kontrollsystemet består av ett system för datainsamling från National Instruments och programmeras i LabVIEW. Kontrollsystemet utvärderas i två undersökande test där det förfor på ett tillfredsställande sätt. Tre lastmönster till experimentet har tagits fram. Det här projektet föreslår hur man förbereder proverna och vilka direkta och indirekta test som kan göras för framtida analyser.Under åren har en betydande mängd vetenskapligt arbete ägnats åt att förstå pappersåldring för att förbättra transformatordiagnostik och investeringsunderlaget för nätägare. De industriella standarderna tar dock inte hänsyn till intermittent belastning i kombination med fukthalt [1] [2]. Tidigare arbete föreslår att de termiska modellerna möjligen kan förbättras genom att undersöka effekterna av fukthalt [3].Det huvudsakliga målet med den föreslagna experimentella uppställningen är att undersöka huruvida ett intermittent belastningsmönster i kombination med fukthalt har en betydande inverkan på pappersåldrandet. Föresatsen är att bidra med ny kunskap om transformatordiagnostik och för att om möjligt långsiktigt förbättra de nuvarande termiska modellerna som används till dynamiska lastbarhetsmodeller för transformatorer. Detta skulle särskilt gynna transformatorer med typiskt intermittenta belastningsmönster, t ex en transformator ansluten till en vindkraftpark eller solcellspaneler. Ökande antal av anläggningar för förnybar energi ökar behovet av att utveckla de termiska modellerna för att ta hänsyn till okonventionella lastprofiler.

As we move deep into nanometer regime of CMOS VLSI (45nm node and below), the device noise margin gets sharply eroded because of continuous lowering of device threshold voltage together with ever increasing rate of signal transitions driven by the consistent demand for higher performance. Sharp erosion of device noise margin vastly increases the likelihood of intermittent failures (also known as parametric failures) during device operation as opposed to permanent failures caused by physical defects introduced during manufacturing process. The major sources of intermittent failures are capacitive crosstalk between neighbor interconnects, abnormal drop in power supply voltage (also known as droop), localized thermal gradient, and soft errors caused by impact of high energy particles on semiconductor surface. In nanometer technology, these intermittent failures largely outnumber the permanent failures caused by physical defects. Therefore, it is of paramount importance to come up with efficient test generation and test application methods to accurately detect and characterize these classes of failures. Soft error rate (SER) is an important design metric used in semiconductor industry and represented by number of such errors encountered per Billion hours of device operation, known as Failure-In-Time (FIT) rate. Soft errors are rare events. Traditional techniques for SER characterization involve testing multiple devices in parallel, or testing the device while keeping it in a high energy neutron bombardment chamber to artificially accelerate the occurrence of single events. Motivated by the fact that measurement of SER incurs high time and cost overhead, in this thesis, we propose a two step approach: hii a new filtering technique based on amplitude of the noise pulse, which significantly reduces the set of soft error susceptible nodes to be considered for a given design; followed by hiii an Integer Linear Program (ILP)-based pattern generation technique that accelerates the SER characterization process by 1-2 orders of magnitude compared to the current state-of-the-art. During test application, it is important to distinguish between an intermittent failure and a permanent failure. Motivated by the fact that most of the intermittent failures are temporally sparse in nature, we present a novel design-for-testability (DFT) architecture which facilitates application of the same test vector twice in a row. The underlying assumption here is that a soft fail will not manifest its effect in two consecutive test cycles whereas the error caused by a physical defect will produce an identically corrupt output signature in both test cycles. Therefore, comparing the output signature for two consecutive applications of the same test vector will accurately distinguish between a soft fail and a hard fail. We show application of this DFT technique in measuring soft error rate as well as other circuit marginality related parametric failures, such as thermal hot-spot induced delay failures. A major contribution of this thesis lies on investigating the effect of multiple sources of noise acting together in exacerbating the noise effect even further. The existing literature on signal integrity verification and test falls short of taking the combined noise effects into account. We particularly focus on capacitive crosstalk on long signal nets. A typical long net is capacitively coupled with multiple aggressors and also tend to have multiple fanout gates. Gate leakage current that originates in fanout receivers, flows backward and terminates in the driver causing a shift in driver output voltage. This effect becomes more prominent as gate oxide is scaled more aggressively. In this thesis, we first present a dynamic simulation-based study to establish the significance of the problem, followed by proposing an automatic test pattern generation (ATPG) solution which uses 0-1 Integer Linear Program (ILP) to maximize the cumulative voltage noise at a given victim net due to crosstalk and gate leakage loading in conjunction with propagating the fault effect to an observation point. Pattern pairs generated by this technique are useful for both manufacturing test application as well as signal integrity verification for nanometer designs. This research opens up a new direction for studying nanometer noise effects and motivates us to extend the study to other noise sources in tandem including voltage drop and temperature effects.

No description available.

Thesis (PhD (Botany and Zoology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The use of organophosphate pesticides is still an integral part of commercial farming activities and these substances have been implicated as a major source of environmental contamination in South Africa. Evidence exists that many non target animals in and around agricultural areas are at risk of being affected due to the mobile nature of pesticides and the intermittent nature of pesticide application. The extent to which non-target animals are affected by exposure to two organophosphates (azinphos-methyl and chlorpyrifos) was investigated through monitoring selected biomarker responses and life cycle effects under laboratory conditions in two selected test species. A representative species from both the aquatic and terrestrial environment was used as these two compartments of the environment are inevitably linked due to the mobility of pesticides from the area of application to surrounding areas. The earthworm Eisenia fetida was used as test organism in the terrestrial environment while the fish Oreochromis mossambicus served as representative of the aquatic environment. Juvenile life stages of both species were subjected to standard acute toxicity tests which showed that for both species, juvenile life stages were more sensitive to both pesticides than adults. It was also illustrated that azinphos-methyl is more toxic than chlorpyrifos to both species. Both test species were also subjected to an intermittent exposure regime in order to assess the effects of repeated pesticide application on biomarker, life-cycle and behaviour responses. The results indicated that for similar exposure regimes, azinphos-methyl was more toxic to E. fetida than chlorpyrifos and detrimentally affected all endpoints investigated. The present study suggests that exposure concentration may have a more pronounced effect in inducing a toxic response than exposure interval, irrespective of the pesticide used. In addition to this, E. fetida was unable to avoid the presence of these pesticides in soil, even at concentrations as high as 50% of the LC50 value, indicating that the presence of pesticides in the soil pose a realistic threat to earthworms and other soil dwelling organisms. Biomarker responses, morphological effects and feeding behaviour was assessed for O. mossambicus and similar to the terrestrial toxicity experiments, there was evidence to suggest that in the case of an intermittent exposure scenario, azinphos-methyl was more hazardous than chlorpyrifos to this species. For the majority of endpoints that were investigated, it appeared that exposure interval played a more important role in inducing an effect than exposure concentration. At a shorter exposure interval, the majority of endpoints showed no difference between higher and lower exposure concentrations, while at a longer exposure interval the effects of exposure concentration became evident. In addition, feeding behaviour was affected by pesticide exposure in a dose-dependent manner. The present study yielded important results that improve the understanding of biological impacts of pesticide pollution on the environment. This can aid in optimising farming practices such as pesticide application not only in terms of eradicating the pest organisms, but also in terms of mitigating the environmental effects associated with large-scale pesticide use, thereby ensuring sustained biodiversity in these areas. / AFRIKAANSE OPSOMMING: Die gebruik van organofosfaat plaagdoders is ‘n integrale deel van kommersiële landbou aktiwiteite maar hierdie middels is ook ‘n prominente bron van omgewingsbesoedeling in Suid-Afrika. Daar is bewys dat verskeie nie-teiken diere in en om landbouareas geaffekteer word weens die nie-statiese aard van plaagdoders in die omgewing, sowel as die herhalende aard van plaagdodertoediening. Die graad waartoe nie-teiken diere geaffekteer word deur die plaagdoders azinphos-metiel en chlorpyrifos is ondersoek deur die monitering van verskeie biomerkerresponse en lewenssiklus-effekte in geselekteerde toetsspesies binne ‘n beheerde laboratoriumomgewing. ‘n Verteenwoordigende spesie van beide die akwatiese en die terrestriële omgewing is gebruik aangesien hierdie twee dele van die omgewing onlosmaaklik verbind is weens die beweging van plaagdoders vanaf die area van toediening na omringende areas. Die erdwurm Eisenia fetida is gekies as toetsorganisme vir die terrestriële omgewing en die varswatervis Oreochromis mossambicus het gedien as verteenwoordigende spesie vir die akwatiese omgewing. Onvolwasse diere van beide spesies is onderwerp aan standaard akute toksisiteitstoetse en daar is gevind dat, vir beide spesies, onvolwasse diere meer sensitief vir die betrokke plaagdoders is as volwasse diere. Dit is ook gevind dat azinphosmetiel giftiger is as chlorpyrifos vir beide spesies. Beide toetsspesies is ook onderwerp aan ‘n chroniese blootstellingsregime om die effek van herhaalde plaagdodertoediening op biomerker-, lewenssiklus- en gedragsresponse te ondersoek. Die resultate van die herhaalde blootstelling het aangedui dat vir soortgelyke blootstellingsregimes, azinphos-metiel giftiger is as chlorpyrifos vir E. fetida en dat beide middels alle eindpunte wat ondersoek is, nadelig affekteer. Die huidige studie toon ook bewyse dat blootstellingskonsentrasie ‘n meer prominente effek as blootstellingsinterval kan hê in die teweegbringing van ‘n toksiese respons. Verder was E. fetida nie in staat om die teenwoordigheid van die plaagdoders in grond te vermy nie, self nie by konsentrasies so hoog as 50% van die LC50 waarde nie. Laasgenoemde resultaat dui dus aan dat die aanwesigheid van plaagdoders in die grondomgewing ‘n realisitese bedreiging inhou vir erdwurms en ander grondorganismes. Soortgelyk aan die terrestriële toksisiteitseksperimente, was daar getuienis vir die verhoogde toksisiteit van azinphos-metiel relatief tot chlorpyrifos vir O. mossambicus. Dit blyk dat blootstellingsinterval ‘n meer prominente rol as blootstellingskonsentrasie speel in die teweegbringing van effekte vir die meerderheid van die eindpunte wat ondersoek is. In die geval van ‘n korter blootstellingsinterval het die meerderheid van eindpunte wat ondersoek is geen verskille getoon tussen ‘n hoër en ‘n laer konsentrasie nie, terwyl met ‘n langer blootstellingsinterval daar ‘n aanduiding was dat blootstellingskonsentrasie ‘n meer prominente rol gespeel het. Verder is gevind dat voedingsgedrag in O. mossambicus geaffekteer is op ‘n konsentrasie verwante manier. Die huidige studie toon resultate wat ‘n belangrike bydrae kan lewer tot die begrip van die biologiese impakte van organofosfaat plaagdoders op die omgewing. Die resultate kan gebruik word vir die optimisering van boerderypraktyke soos plaagdodertoediening, sodat laasgenoemde effektief is vir die beheer van pes-organismes, maar ook die impakte van grootskaalse plaagdodertoediening kan minimaliseer en sodoende die biodiversiteit binne hierdie areas sal beskerm.

Over the last two decades, implementation of membrane bioreactors (MBRs) has increased due to their superior effluent quality and low plant footprint. However, they are still viewed as a high-cost option, both with regards to capital and operating expenditure (capex and opex). The present thesis extends the understanding of the impact of design and operational parameters of membrane bioreactors on energy demand, and ultimately whole life cost. A simple heuristic aeration model based on a general algorithm for flux vs. aeration shows the benefits of adjusting the membrane aeration intensity to the hydraulic load. It is experimentally demonstrated that a lower aeration demand is required for sustainable operation when comparing 10:30 to continuous aeration, with associated energy savings of up to 75%, without being penalised in terms of the fouling rate. The applicability of activated sludge modelling (ASM) to MBRs is verified on a community-scale MBR, resulting in accurate predictions of the dynamic nutrient profile. Lastly, a methodology is proposed to optimise the energy consumption by linking the biological model with empirical correlations for energy demand, taking into account of the impact of high MLSS concentrations on oxygen transfer. The determining factors for costing of MBRs differ significantly depending on the size of the plant. Operational cost reduction in small MBRs relies on process robustness with minimal manual intervention to suppress labour costs, while energy consumption, mainly for aeration, is the major contributor to opex for a large MBR. A cost sensitivity analysis shows that other main factors influencing the cost of a large MBR, both in terms of capex and opex, are membrane costs and replacement interval, future trends in energy prices, sustainable flux, and the average plant utilisation which depends on the amount of contingency built in to cope with changes in the feed flow.

The potential to track changes in training status and fitness levels of especially team sport participants by making use of more time efficient and accessible methods such as heart rate variability (HRV) and heart rate recovery (HRR) cannot be overlooked and needs to be considered. However, studies that have investigated this aspect in team sport participants are scarce. It is against this background that the main objectives of this study were firstly, to determine the relationships between HRV and HRR as well as the fitness levels of a cohort of university-level rugby players. The second objective was to determine the validity of the BioForce Heart Rate Variability System to determine the HRV of a cohort of university-level rugby players. Twenty-four university-level rugby players (age: 20.1 ± 0.41 years; body stature: 182.7 ± 6.2 cm; body mass: 89.7 ± 12.7 kg) of a South African university’s Rugby Institute participated in the first part of the study. During the test day players’ fasting baseline HRV (baseline HRV) values were taken. This was followed by the measurement of the post-breakfast HRV (Pre-Yo-Yo IR1 HRV). Players were then required to perform the Yo-Yo Intermittent Recovery Test Level 1 (Yo-Yo IR1) while they were fitted with a portable Cosmed K4b2 gas analyser apparatus and a Fix Polar Heart Rate Transmitter Belt. After completion of the test, HRR was taken on 1 and 3 minutes and followed by the measurement of HRV (Post-Yo-Yo IR1 HRV). For the second part of the study a group of twenty u/21 university-level rugby players (age: 20.06 ± 0.40 years; body stature: 181.8 ± 5.5 cm; body mass: 91.1 ± 10.7 kg) of a South African university’s Rugby Institute were recruited to participate in this study. HRV was measured simultaneously by the Actiheart monitor system as well as the BioForce Heart Rate Variability System over three times periods: during the morning in a fasting state just after players had woken up (baseline); in the morning just after the players ate breakfast (pre-anaerobic); after completion of a high-intensity anaerobic training session (post-anaerobic) and after completion of a 20 min recovery session (post-recovery). Significant correlations (p ≤ 0.05) were found between Pre-Yo-Yo IR1 HRV and heart rate (HR) at the respiratory compensation point (RCP-HR (bpm)) (r = -0.468) as well as oxygen uptake at the RCP (RCP- 2max VO (% of 2max VO )) (r = 0.476), respectively. A forward stepwise regression analysis showed that HR at ventilatory threshold 1 (VT1-HR (bpm)) contributed significantly (p ≤ 0.05) to the post-Yo-Yo IR1 HRV with a variance of 39.8%. Final Yo-Yo IR1 level also contributed significantly (p ≤ 0.05) to 3 minute post-Yo-Yo IR1 HRR with a variance of 16.5%. For the second part of the study the majority of significant relationships (p < 0.05) between the Actiheart and Bioforce obtained HRV results were observed for the post-recovery period (Mean RR, SDNN, RMSSD and Peak LF power), followed by the pre-anaerobic period (Mean R-R and SDNN) and the baseline period (LF:HF ratio). No significant relationships were observed between the HRV results of the two apparatuses during the post-anaerobic period. In conclusion, HRV and HRR may have the potential to act as affordable and easy measurement tools of team sport participants’ fitness levels. However, the study results suggested that the BioForce Heart Rate Variability System that is used to obtain team sport participants’ HRV is especially valid to determine HRV after recovery periods that follow hard training sessions. The results do however cast a shadow of doubt over the accuracy of this apparatus when used directly after hard training sessions. / MSc (Sport Science), North-West University, Potchefstroom Campus, 2014

Paper [I] Using a unique and highly detailed data set on energy consumption at the appliance-level for 200 Swedish households, seemingly unrelated regression (SUR)-based end-use specific load curves are estimated. The estimated load curves are then used to explore possible restrictions on load shifting (e.g. the office hours schedule) as well as the cost implications of different load shift patterns. The cost implications of shifting load from "expensive" to "cheap" hours, using the Nord Pool spot prices as a proxy for a dynamic price, are computed to be very small; roughly 2-4% reduction in total daily costs from shifting load up to five hours ahead, indicating small incentives for households (and retailers) to adopt dynamic pricing of electricity. Paper [II] Using a detailed data set on appliance-level electricity consumption at the hourly level, we provide the first estimates of hourly and end-use-specific income elasticities for electricity. Such estimates are informative about how consumption patterns in general, and peak demand in particular, will develop as households’ income changes. We find that the income elasticities are highest during peak hours for kitchen and lighting, with point estimates of roughly 0.4, but insignificant for space heating. Paper [III] In this paper, I estimate the price elasticity of electricity as a function of the choice between fixed-price and variable-price contracts. Further, assuming that households have imperfect information about electricity prices and usage, I explore how media coverage of electricity prices affects electricity demand, both by augmenting price responsiveness and as a direct effect of media coverage on electricity demand, independent of prices. I also address the endogeneity of the choice of electricity contract. The parameters in the model are estimated using unique and detailed Swedish panel data on monthly household-level electricity consumption. I find that price elasticities range between −0.025 and −0.07 at the mean level of media coverage, depending on contract choice, and that households with monthly variation in electricity prices respond more to prices when there is extensive media coverage of electricity prices. When media coverage is high, for example 840 news articles per month (which corresponds to the mean plus two standard deviations), the price elasticity is −0.12, or 1.7 times the elasticity at the mean media coverage. Similarly, media coverage is also found to have a direct effect on electricity demand. Paper [IV] I explore how households switch between fixed-price and variable-price electricity contracts in response to variations in price and temperature, conditional on previous contract choice. Using panel data with roughly 54000 Swedish households, a dynamic probit model is estimated. The results suggest that the choice of contract exhibits substantial state dependence, with an estimated marginal effect of previous contractchoiceof0.96, andthattheeffectofvariationinpricesandtemperatureonthechoice of electricity contract is small. Further, the state dependence and price responsiveness are similar across housing types, income levels and other dimensions. A plausible explanation of these results is that transaction costs are larger than the relatively small cost savings from switching between contracts.

La vallée de la Komadougou Yobé constitue un site privilégié de recharge de l'aquifère quaternaire du bassin du lac Tchad. Depuis les années 1980, le développement des cultures de rente (p. ex. poivron) a conduit à un doublement des surfaces irriguées (1995-2005) dans sa partie aval. Afin de quantifier la recharge supplémentaire induite, une modélisation des flux hydriques verticaux dans la zone non-saturée (0-8 m) a été engagée. La première étape, objet de ce travail de thèse, consiste à décrire l'organisation spatiale et les propriétés hydrodynamiques des corps sédimentaires constitutifs de l'alluvium.Des forages à travers les formations superficielles mettent en évidence des alternances sable-sable argileux dans la totalité de la zone non-saturée, conséquence des migrations du lit mineur de la Komadougou Yobé. Le calcul de la corrélation entre les forages indique une forte analogie avec les hétérogénéités identifiées en surface à partir de données de télédétection (Landsat 7 binarisée). Ces données sont donc utilisées pour l'apprentissage de statistiques multipoints représentatives des hétérogénéités et un modèle géologique 3D de l'alluvium est généré via l'algorithme snesim.Des suivis neutroniques de l'humidité le long de plusieurs profils caractéristiques des différentes unités sédimentaires associées à ce modèle sont réalisés pour des conditions de flux contrôlées en surface. A partir de simulations numériques 1D, des jeux de paramètres hydrodynamiques permettant de reproduire les humidités mesurées sont déterminés par une approche de type Monte-Carlo. Des densités de probabilité intégrant l'incertitude sur les mesures sont obtenues pour les paramètres de Mualem - van Genuchten décrivant les courbes de rétention et de conductivité hydraulique des sédiments.Une procédure 1D-distribuée est utilisée pour simuler les écoulements non-saturés verticaux au sein de plusieurs réalisations du modèle géologique et pour différents jeux de paramètres hydrodynamiques probables. La recharge diffuse calculée se montre particulièrement sensible au paramètre de pression d'entrée d'air attribué aux dépôts superficiels, siège des principales interactions sol-plante-atmosphère, ainsi qu'aux contrastes verticaux de conductivité hydraulique. / The downstream part of the Komadugu Yobe River is an important recharge area for the Lake Chad Quaternary aquifer. Since the 1980s, cash crop development (e.g. sweet pepper) has led to the doubling (1995-2005) of irrigated surfaces in the vicinity of the river. A modeling approach of vertical water fluxes through the vadose zone (0-8 m) was designed to quantify the related increase in groundwater recharge. The first step, which is the main topic of this PhD thesis, consisted in describing both spatial arrangement and hydrodynamic properties of the sedimentary bodies that make up the alluvium.Boreholes in surficial deposits highlighted sandy to clayey alternations within the whole unsaturated zone; this was interpreted as the result of frequent migrations of the River channel. Spatial correlation between bore logs showed strong similarities with heterogeneities depicted on ground by means of remote sensing data (binarized Landsat 7 image). This data were therefore used to train multiple-point statistics representative of heterogeneities, and a 3D geological model was generated through the snesim algorithm.For each representative sedimentary unit, soil moisture under controlled hydraulic surface conditions was monitored by vertical neutron probe soundings. Using 1D numerical simulations, different data sets of hydrodynamic properties that reproduced moisture measurements were determined by a Monte-Carlo approach. Probability density functions including measurement uncertainties were deduced for the Mualem - van Genuchten parameters which describe both retention and hydraulic conductivity curves.A 1D-distributed procedure was applied for modeling vertical flows in the unsaturated zone within several geological model realizations with different probable sets of hydrodynamics parameters. The simulated diffuse recharge was shown to be particularly sensitive to two main parameters: air-entry pressure linked to superficial deposits, where soil-plant-atmosphere interactions do occur, and vertical hydraulic conductivity contrasts within the alluvium.

Alcoholism is a persistent substance abuse disorder that is associated with negative health, social, and economic outcomes. Treatment strategies for alcohol use disorders are limited, and only three drugs have been approved by the FDA for treatment. Although behavioral therapy and drug combination strategies improve abstinence outcomes, the majority of those in treatment will not achieve long-term abstinence. Therefore, better treatment strategies are needed. While much progress has been made toward understanding the neurobiology of alcoholism, this knowledge has not been effectively translated into treatment strategies. Animal models of alcohol drinking have been crucial to this research effort, but until recently there have been few procedures that effectively model alcoholism by producing binge-like drinking, withdrawal, and relapse behavior. In the last five years the intermittent alcohol access (IAA) model, which uses repeated cycles of scheduled alcohol deprivation and reinstatement to elevate drinking, has been established as such a procedure, with substantial evidence that escalation of drinking produced by IAA is mediated by similar mechanisms as in human alcoholics, which include transcriptional regulation that alters functioning of mesolimbocortical reward pathways. The IAA model. The studies reported herein characterize changes in gene expression in mesolimbocortical brain regions associated with development of maladaptive binge-like alcohol drinking due to scheduled abstinence, particularly in the nucleus accumbens, which regulates motivated behavior. Furthermore the IAA model is characterized with regard to effectiveness in 2 ethanol-preferring C57BL/6 inbred mouse strains, and the influence of concurrent access to multiple alcohol concentrations is examined. Finally, the potential of naltrexone and novel mu-opioid receptor-selective antagonist NAQ to modulate alcohol drinking under continuous access and intermittent access procedures is reported. Microarray analysis is used to analyze the transcriptome in prefrontal cortex, nucleus accumbens, and ventral midbrain of C57BL/6NCrl mice after alcohol deprivation, and to identify differentially expressed genes and gene co-expression networks in C57BL/6J mice during continuous access, as well as after six cycles of IAA. Differentially expressed genes, network hub genes, and regulation mechanisms represent high priority targets for further study in binge-like drinking behavior, with the goal of translating this knowledge to treatment strategies for alcoholism.