An experiment was conducted to determine whether the water depth (above soil) and soil type would have any influence on the multispectral reflectances of paddy rice, and their calculated vegetation index values. The results showed that, when vegetation cover was low (below 600 grams of dry biomass per square meter), the near infrared (NIR) reflectances decreased very little with water depth. The same was true for red reflectances, but to a lesser degree. Overall the changes were not significant at 0.05 level of significance when the water depth was increased from 2.5 centimeters to 10 centimeters. When the vegetation cover became higher most NIR and red reflectances did not show a significant decrease with the increase of the water depth, and sometimes they even increased slightly up to a water depth of 6.4 cm. Nevertheless both rice cover and water depth as well as soils played an important role in the reflectance pattern in red and NIR bands. Some index values increased and some decreased depending on water depth and rice cover. Statistical analysis of the data showed that rice multispectral responses were mainly controlled by vegetation and minimally influenced by soil and water depths.

In the journey toward optimal spectrum usage, techniques and concepts such as Cognitive Radio and Dynamic Spectrum Access have enjoyed increasing attention in many research projects. Dynamic Spectrum Access introduces the need for real-time RF spectrum information in the form of Radio Environment Maps. This need motivates an investigation into a hybrid approach of sample measurements and spatial interpolation as opposed to using conventional propagation models. Conventional propagation models, both path-general and path-specific, require information of transmitters within the area of interest. Irregular Terrain Models such as the Longley-Rice model, further require topographic information in order to consider the effects of obstacles. The proposed spatial interpolation technique, kriging, requires no information regarding transmitters. Furthermore, Ordinary Kriging requires nothing other than measured samples whereas other kriging variants such as Universal Kriging and Regression Kriging can use additional information such as topographic data to aid in prediction accuracy. This dissertation investigates the performance of the three aforementioned kriging variants in producing Radio Environment Maps of received power. For practical and financial reasons, the received power measurement samples are generated using the Longley-Rice Irregular Terrain Model and are, therefore, simulated measurements. The experimental results indicate that kriging shows great promise as a tool to generate Radio Environment Maps. It is found that Ordinary Kriging produces the most accurate predictions of the three kriging methods and that prediction errors of less than 10 dB can be achieved even when using very low sampling densities. / MSc (Computer and Electronic Engineering), North-West University, Potchefstroom Campus, 2015

In the journey toward optimal spectrum usage, techniques and concepts such as Cognitive Radio and Dynamic Spectrum Access have enjoyed increasing attention in many research projects. Dynamic Spectrum Access introduces the need for real-time RF spectrum information in the form of Radio Environment Maps. This need motivates an investigation into a hybrid approach of sample measurements and spatial interpolation as opposed to using conventional propagation models. Conventional propagation models, both path-general and path-specific, require information of transmitters within the area of interest. Irregular Terrain Models such as the Longley-Rice model, further require topographic information in order to consider the effects of obstacles. The proposed spatial interpolation technique, kriging, requires no information regarding transmitters. Furthermore, Ordinary Kriging requires nothing other than measured samples whereas other kriging variants such as Universal Kriging and Regression Kriging can use additional information such as topographic data to aid in prediction accuracy. This dissertation investigates the performance of the three aforementioned kriging variants in producing Radio Environment Maps of received power. For practical and financial reasons, the received power measurement samples are generated using the Longley-Rice Irregular Terrain Model and are, therefore, simulated measurements. The experimental results indicate that kriging shows great promise as a tool to generate Radio Environment Maps. It is found that Ordinary Kriging produces the most accurate predictions of the three kriging methods and that prediction errors of less than 10 dB can be achieved even when using very low sampling densities. / MSc (Computer and Electronic Engineering), North-West University, Potchefstroom Campus, 2015

Doctor of Philosophy / Department of Plant Pathology / Frank F. White / Plants have evolved sophisticated mechanisms to protect against microbial invaders of which resistance (R) genes are an important component. R genes mediate specific recognition of pathogens possessing cognate avirulence (avr) gene products, which leads to the induction of plant defense responses and the arrest of pathogen ingress. In contrast to numerous examples of R gene–avr interactions, the susceptible interaction is less well examined. Recent studies on rice and wheat indicate that host resistance to pathogens also involves genetic variability in dominant traits for susceptibility. Xanthomonas oryzae pv.oryzae (Xoo) causes bacterial blight disease in rice, a serious threat in the major rice growing regions of Asia. The pathogenicity of Xoo depends on the translocation of a cocktail of effector proteins into rice cells by a type III secretion system. The family of transcription activator like (TAL) effectors is the one of the most intriguing due to their eukaryotic features and function as major virulence determinants. The specificity of TAL effectors is determined by the nearly identical repeat units at the center of each protein. The major virulence determinant of the strain PXO99A is PthXo1, which hijacks the transcription of the host susceptibility (S) gene Os8N3, an allele of recessive resistance gene xa13. The strains that overcome xa13-mediated resistance harbor alternate major TAL effectors including PthXo2, PthXo3 and AvrXa7. Alternate effectors do not induce Os8N3. This study identified the alternate S gene Os11N3, which is dependent on the effectors AvrXa7 and PthXo3. The effectors bind to specific elements in the proximal promoter regions of the respective S genes and act as transcriptional activators. Our results indicate that rice–Xoo interactions involve gene-for-gene susceptibility to bacterial blight in addition to gene-for-gene resistance.

Appressorium-mediated plant infection is a common strategy used by many plant pathogenic fungi. Understanding the underlying genetic network that controls cellular differentiation of appressorium is therefore pivotal to design durable resistance strategies for these devastating pathogens. This thesis describes four published studies, which investigate the role of septin GTPases in infection and the role of secretion during plant tissue invasion by the rice blast pathogen Magnaporthe oryzae. Appressorium development involves a series of morphogenetic changes that are tightly regulated by cell cycle checkpoints. Entry into mitosis allows differentiation of an appressorium, while penetration peg emergence appears to require progression through subsequent cell cycle checkpoints and cytokinesis. The studies presented here show that symmetry-breaking events that occur during appressorium differentiation are mediated by scaffold proteins, named septins. Septin GTPases recruit actomyosin ring components during septation and define the site of cytokinesis. They also recruit a toroidal cortical F-actin network to the appressorium pore that provides cortical rigidity to facilitate plant infection. Septins act as diffusion barriers for proteins that mediate membrane curvature necessary for penetration peg formation. Repolarization of the F-actin cytoskeleton at the appressorium pore is essential for plant penetration and is controlled by cell polarity regulators, such as Cdc42 and Chm1. Septin-mediated plant infection is regulated by NADPH oxidase (Nox) dependent generation of reactive oxygen species (ROS). The Nox2/NoxR complex is essential for septin organization at the appressorium pore. Septins are therefore key determinants of appressorium repolarization. I also report an investigation of fungal secretory processes during tissue invasion and present evidence that distinct pathways are involved in effector secretion by Magnaporthe oryzae. A BrefeldinA-sensitive pathway is necessary for secretion of apoplastic effectors, such as Bas4 and Slp1, while a BrefeldinA-insensitive pathway is necessary for secretion of effectors destined for delivery to rice cells.

The C₄ photosynthetic cycle acts to concentrate CO₂ around the enzyme Rubisco. By doing so, C₄ photosynthesis leads to increased radiation, water and nitrogen use efficiencies. As such, C₄ photosynthesis is the most productive form of photosynthesis known. Because it enables such high levels of productivity there are large international efforts to introduce C₄ photosynthesis into non-C₄ crop species such as rice. Kranz anatomy is a characteristic leaf cellular arrangement of concentric rings of bundle sheath and mesophyll cells around closely spaced veins and is crucial to C₄ photosynthesis in almost all known examples. Despite the fact that Kranz has evolved on over 60 times independently little is known about the genetic regulation of Kranz development, as attempts to elucidate Kranz regulators using conventional mutagenesis screens have provided few insights. However, the advent of next generation DNA sequencing technologies has enabled the interrogation of genetic networks at a previously unprecedented scale. The work in this thesis describes a genome-wide transcriptomic analysis of leaf development in maize, a C₄ species, that develops both Kranz-type and non-Kranz-type leaves. Detailed bioinformatics analyses identified candidate regulators of both Kranz development and additional aspects of maize leaf development. Three of the identified Kranz candidates were functionally characterised in both C₄ and non-C₄ species. Furthermore, expression and phylogenetic analyses of GOLDEN2-LIKE (GLK) genes, a small transcription factor family previously implicated in C₄ development in maize, were extended to determine the generality of GLK function in C₄ evolution.

No description available.

This dissertation explores the relationship between gender, war, and media constructions of both. Using the theoretical frameworks of the social constructions of gender and the gendered constructions of the public sphere, I have analyzed how Time magazine portrayed Condoleezza Rice and Hillary Clinton in discussions of war. Time represents mainstream mediated coverage in this case. Rice and Clinton represent women outside the normal boundaries of femininity. First, they were participants in the public sphere, which is largely male-dominated in our society. Second, both women were involved in discussions of war and foreign policy. Their participation in this area of the public sphere is a contradiction to how society expects women to act during war time. The most interesting conclusion is the way the women are linked back to the private sphere through their relationships with men. These representations align with historical theoretical definitions of the public sphere, which favor male participation and often disregard female participation. / text

Chez le riz, la céréale modèle, le système racinaire est principalement constitué de racines issues de la tige, nommées racines coronaires (RC). Peu de gènes contrôlant le développement des RC sont connus, parmi eux CROWN ROOTLESS1 (CRL1) code une protéine à domaine AS2/LOB (ASL/LBD), qui est probablement un facteur de transcription. Le gène CRL1 est nécessaire à l'initiation des primordia de RC, il est directement activé par l'auxine et est situé en amont du réseau de gènes contrôlant le programme de différentiation des RC. Afin de mieux connaître les processus génétiques impliqués dans l'initiation des RC, l!objectif principal de cette thèse est de comprendre la fonction moléculaire de la protéine CRL1 en validant sa fonction de facteur de transcription et en identifiant ses gènes cibles. L'interaction de la protéine CRL1 avec l!ADN a été montrée in vitro et une expérience de SELEX a permis d'identifier sa séquence de fixation à l!ADN : CACA(A/C)C (CRL1-box). Des expériences en levure ont permis de montrer que CRL1 est un activateur de la transcription. Une comparaison entre le sauvage et le mutant crl1, ainsi que l'élaboration d!un système inductible à la dexaméthasone permettant d'activer l'expression de CRL1 dans le fond génétique mutant crl1, ont été utilisés pour identifier des gènes cibles précoces de CRL1 grâce à des analyse de transcriptome. 277 gènes sont activés dès quatre heures après induction de CRL1, les deux tiers contiennent au moins une CRL1-box dans leur promoteur et peuvent donc être des cibles directes de CRL1. CRL1 induit l'expression d!un ensemble de gènes permettant la mise en place des processus de régulation de l'information génétique, de division, de croissance et de différenciation cellulaires nécessaires à la création d'un méristème de racine coronaire organisé et fonctionnel. Parmi eux, QHB code un facteur de transcription clé nécessaire au maintien des cellules souches des méristèmes racinaires. Ce résultat établit pour la première fois un lien moléculaire entre la signalisation de l!auxine et des gènes impliqués dans la mise en place ou le maintien des cellules souches lors de la formation d!un nouveau méristème racinaire au cours du développement post-embryonnaire. Par ailleurs, une étude histologique a permis de révéler que les RC sont issues d!une couche de péricycle dans la tige, un tissu équivalent en termes de localisation et de potentiel rhizogène au péricycle de la racine à partir duquel sont initiées les racines latérales. Les données acquises suggèrent de fortes similarités dans les processus cellulaires et génétiques de la différentiation des méristèmes racinaires au cours du développement post-embryonnaire chez les monocotylédones et les dicotylédones. La découverte de gènes spécifiques au développement de racines issues de la tige ouvre une voie importante vers la compréhension du déterminisme génétique de l!architecture du système racinaire chez les céréales et offre un nouveau potentiel de ressources génétiques pour l!amélioration variétale. / In rice, the model cereal, the root system is mainly composed of stem-derived roots, named crown roots (CR). Very few genes that control the root system development are known, among them CROWN ROOTLESS1 (CRL1) encodes an AS2/LOB-domain protein that is a putative transcription factor (TF). CRL1 is necessary for CR primordium initiation, it is directly activated by auxin and is situated upstream of the gene regulatory network that control the CR differentiation programme. To better known the genetic processes involved in CR initiation, the main objective of this thesis is to understand the molecular function of the CRL1 protein by validating its function of TF and by identifying its target genes. The interaction of CRL1 with DNA was shown in vitro and a consensus CRL1 DNA-binding motif was identified with a SELEX method : CACA(A/C)C named CRL1-box. A yeast assay showed that CRL1 is a transcriptional activator. A comparison between wild type and c rl1 mutant, and the development of a dexamethasone inducible system to ectopically express CRL1 in the crl1 background, were used to identify CRL1 early target genes by transcript profiling. 277 genes were induced from four hours following CRL1 activation, the two-thirds possess at least one CRL1-box and may be CRL1 direct target genes. CRL1 activates the expression of a broad range of genes that allow to orientate genome expression and to initiate cell division, growth and differentiation mechanisms required for the building of an organized and functional CR meristem. Among these genes, QHB encodes a key TF required for the maintenance of root meristem stem cells. This result evidences for the first time a molecular link between auxin signalling and major genes involved in stem cell patterning and maintenance in the formation of a new root meristem during post-embryonic development. Otherwise, an histological study showed that CR are derived from a shoot pericycle, a tissue equivalent to the root pericycle, from which lateral roots develop, in terms of location and rhizogenic potential. All these data suggest strong similarities between monocots and dicots in cellular and genetic mechanisms that control root meristem differentiation during post-embryonic development. The identification of genes specifically involved in stem-derived root development pave the way towards the understanding of the genetic control of root system architecture in cereals and offer a new potential of genetic resources for plant breeding.

This essay discusses the differences in depiction of vampires between Stephenie Meyer’s Twilight (2005) and Bram Stoker’s Dracula (1897). By using examples from the novels, the essay exemplifies how genre, narration, and readership affect the description of vampires within the two novels. The essay bases its discussion on genre on the premise that the vampire genre is in fact a genre to itself, but one with a broad variation. Furthermore, the essay briefly discusses the shift within the vampire genre, where vampires during the last centuries have gone from dangerous and scary to appealing and romantic. A connection is made between the shift within the vampire genre and Anne Rice’s vampire fiction. The discussion on genre shows how the romance, fantasy, and horror genres affect the depiction of vampires. / Denna uppsats diskuterar hur vampyrer i verken Twilight (Meyer, 2005) och Dracula (Stoker, 1897) skildras på olika sätt. Skillnader i beskrivningarna illustreras med hjälp av exempel från de båda böckerna och berör genre, berättarperspektiv och läsarkrets. Diskussionen i uppsatsen baseras på att vampyrgenren är en egen genre med många olika beskrivningar av vampyren. Uppsatsen berör även förändringen i genren och lyfter kort hur vampyren från början tolkas som farlig och skrämmande för att sedan framstå som attraktiv och romantisk. En koppling görs också mellan förändringen i vampyrgenren och Anne Rices vampyrnoveller. Vidare i diskussionen kring genre berörs även hur genrerna romantik, fantasy och skräck påverkar skildringen av vampyrerna i de nämnda verken.