The horizontal and vertical distributions of ozone and its precursors over North America during spring and summer are frequently determined by several factors: cloud convection, lightning NOx production, mixing depth, and long-range transport. The critical factors that contribute to the spatial distribution of air pollutants are studied using the Regional chEmical trAnsport Model (REAM) with diverse satellite measurements as well as in-situ surface and aircraft measurements. Surface and aircraft measurements show a large amount of reactive nitrogen tracers over the Antarctic plateau during summer. These enhanced measurements are investigated, and their photochemical impact is accessed by 1-D CTM and REAM.

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Depuis une vingtaine d'années, la qualité de la prévision de la trajectoire des cyclones tropicaux a fortement progressé mais peu d'améliorations ont été apportées à la prévision de l'intensité. Cette thèse s'intéresse aux changements d'intensité des cyclones tropicaux du sud-ouest de l'océan Indien sous l'angle original de l'activité électrique. Une première étude climatologique s'appuyant sur les données du réseau de détection d'éclairs World Wide Lightning Location Network (WWLLN) a permis de valider la qualité de ces données et de montrer que les cyclones tropicaux pouvaient être une source importante de production d'éclairs à l'échelle du bassin. À partir de ce résultat, une étude ciblée a été menée en considérant la spécificité du bassin et trois régions ont été définies (océan ouvert, région à proximité de la côte est de Madagascar et Canal du Mozambique). L'activité électrique des cyclones tropicaux dépend de la région où ils se trouvent ainsi que de leur stade d'intensité. Les éclairs semblent être un marqueur des phases d'intensification et d'affaiblissement dans certains situations. La troisième étape de cette thèse a consisté à simuler de manière idéalisée un cyclone tropical mature et a tenté d'expliquer les processus physiques à l'origine de l'activité électrique. Le modèle reproduit bien le comportement sporadique des éclairs habituellement observé. Des bilans montrent que ce cyclone présente trois phases caractéristiques, chacune associée à un comportement dynamique, microphysique et électrique différent. Enfin, une deuxième étude purement numérique a tenté d'identifier des estimateurs de l'activité électrique. Pour celà deux approches ont été adoptées : une étude globale et une étude par cellule. Dans les deux cas, les meilleurs estimateurs sont la masse totale de graupel, le volume d'updraft et le produit des flux des masses de glace précipitante et non précipitante.

<p><span style="font-size:12.0pt / line-height:150% / font-family: &quot / Times New Roman&quot / ,&quot / serif&quot / mso-bidi-font-family:&quot / Times New Roman&quot / mso-bidi-theme-font: minor-bidi / mso-bidi-font-weight:bold">The basic premise of this study was that when a learner is confronted with two contradictory explanations of the same phenomenon, there is cognitive dissonance in the learner as the learner tries to determine which of the two explanations is correct. An argumentation-based instructional intervention programme (ABIIP) was created for and used on and by the Grade 10 learners in order to attempt to ameliorate this cognitive conflict. </span><span style="font-size:12.0pt / line-height:150% / font-family: &quot / Times New Roman&quot / ,&quot / serif&quot / mso-bidi-font-family:&quot / Times New Roman&quot / mso-bidi-theme-font: minor-bidi">The purpose of this study was to determine the relative impact of that intervention programme on Grade 10 learners&rsquo / conceptions of lightning and thunder. The programme was designed to help learners to develop argumentative skills and use the acquired skills to negotiate and harmonise divergent and conflicting explanations of the nature of lightning and thunder that are propounded by different worldviews (Science and indigenous knowledge).</span><span style="font-size:12.0pt / line-height:150% / font-family: &quot / Times New Roman&quot / ,&quot / serif&quot / mso-bidi-font-family:&quot / Times New Roman&quot / mso-bidi-theme-font: minor-bidi">The research design was primarily a case study of 16 Grade 10 learners of the Xhosa ethnic group at a high school in the Eastern Cape Province of South Africa. The Xhosa people are a typical example of a people whose cultural values were undermined and whose voice was silenced by the colonisers and whose local knowledge has been repressed and replaced by forms of Western privileged knowledge and understandings but who remain, deeply and resolutely, steeped in their cultural values and practices, making them a classic example of a people who would battle to harmonise the indigenous and the scientific explanations of natural phenomena. The research instruments used were questionnaires which were administered to learners, educators, community leaders, indigenous knowledge holders and experts to solicit information on causes, dangers and prevention of lightning / individual and group activities as learners went through the lessons on both argumentation and on lightning / follow up interviews and discussions with learners individually or in groups to seek further clarification of the ideas the learners would have raised in their earlier responses to questionnaires or group discussions / guided and reflective essays by the learners to determine the learners&rsquo / levels of understanding of the major tenets of the two thought systems and the relationship between the two worldviews and to determine the qualitative gain, if any, that the learners got from the intervention programme / observation schedules used by the researcher during participant observation of group discussions and during the lessons on lightning / an achievement test on lightning / field notes used by the researcher for memoing observations and reflections as the research process proceeded / informal and serendipitous sources of information. <span style="font-size:12.0pt / line-height:150% / font-family: &quot / Times New Roman&quot / ,&quot / serif&quot / mso-bidi-font-family:&quot / Times New Roman&quot / mso-bidi-theme-font: minor-bidi">The collected data were analysed, mostly, qualitatively. Frequencies, percentages and t-test values were used to express and analyse quantitative data. Aspects of several analytical frameworks that included Toulmin&rsquo / s Argumentation Pattern (TAP) [and its modified versions such as that of Leitao (2000) and that of Osborne et al (2004)] and Contiguity Argumentation Theory (CAT) were used to attach meaning to the collected data and to address the research questions.</span></span></p>

The essay represents the projector principle, on which, as the essay’s author believes, the narration of The Summer Lightning and Other Stories by Olive Senior is based. The projector principle illustrates the idea that little details and images in the text serve big purposes, for example, reflect the emotional state of the characters or how the characters construct their identity. The literary analysis of the present essay aims at exploring a complicated identity construction in the context of Jamaica with its half-lost indigenous and half-remained colonial legacies through the identity construction of adolescent Jamaican protagonists of the short stories.

To diversify their genetic material, allowing adaptation to environmental disturbances and colonization of new ecological niches, bacteria use various evolutionary processes, including the acquisition of new genetic material by horizontal transfer mechanisms such as conjugation, transduction and transformation. Electrotransformation mediated by lightningrelated electrical phenomena may constitute an additional gene transfer mechanism occurring in nature. The presence in clouds of bacteria capable of forming ice nuclei that lead to precipitations and are involved in the triggering of lightning, such as the global phytopathogen Pseudomonas syringae, led us to postulate that natural electrotransformation in clouds may affect bacteria, by contributing to increase their adaptive potential. We first determined if the ice nucleator bacterium P. syringae could survive when in clouds and acquire exogenous genetic material through lightning shock-simulating in vitro electroporation. In comparison to two other bacteria, P. syringae appears to be best adapted for survival and for genetic electrotransformation under these conditions, which suggests that this bacterium would be able to survive and evolve whilst being transported in clouds. Secondly, we evaluated the impact of lightning shock-simulating in vitro electroporation on the survival, the electrotransformation potential and the diversity of bacteria collected from rain samples. These isolates better resisted lightning than the laboratory strains and some were able to electrotransform exogenous DNA. The rain bacteria we isolated were of different origins and were representative of life modes of the various sources of bacterial emissions on Earth. Our study suggests that bacteria aerosolized from diverse terrestrial ecosystems can spread to new habitats through clouds whilst also being able to acquire new genetic material via lightning-based electrotransformation, thereby potentially enhancing their genetic diversity. The final part of our work consisted of evaluating whether electrotransformation could be applied to the engineering of indigenous soil bacteria in order to develop a tool for the bioremediation of lindane, a once widely used pesticide. Optimized experiments revealed that both natural and electrotransformation contributed to the incorporation of a plasmid harboring a gene encoding the first lindane dechlorination steps by indigenous soil bacteria. In conclusion, we showed that natural electrotransformation mediated by electrical discharges such as those occurring in clouds or reaching soils can be involved in the horizontal gene transfer process among bacteria and, considering the importance of lightning worldwide, may play a role in the adaptation and evolution of these organisms.

Depuis une vingtaine d'années, la qualité de la prévision de la trajectoire des cyclones tropicaux a fortement progressé mais peu d'améliorations ont été apportées à la prévision de l'intensité. Cette thèse s'intéresse aux changements d'intensité des cyclones tropicaux du sud-ouest de l'océan Indien sous l'angle original de l'activité électrique.Une première étude climatologique s'appuyant sur les données du réseau de détection d'éclairs World Wide Lightning Location Network (WWLLN) a permis de valider la qualité de ces données et de montrer que les cyclones tropicaux pouvaient être une source importante de production d'éclairs à l'échelle du bassin. À partir de ce résultat, une étude ciblée a été menée en considérant la spécificité du bassin et trois régions ont été définis (océan ouvert, région à proximité de la côte est de Madagascar et Canal du Mozambique). L'activité électrique des cyclones tropicaux dépend de la région où ils se trouvent ainsi que de leur stade d'intensité. Les éclairs semblent être un marqueur des phases d'intensification et d'affaiblissement dans certains situations. La troisième étape de cette thèse a consisté à simuler de manière idéalisée un cyclone tropical mature et a tenté d'expliquer les processus physiques à l'origine de l'activité électrique. Le modèle reproduit bien le comportement sporadique des éclairs habituellement observé. Des bilans montrent que ce cyclone présente trois phases caractéristiques, chacune associée à un comportement dynamique, microphysique et électrique différent. Enfin, une deuxième étude purement numérique a tenté d'identifier des estimateurs de l'activité électrique. Pourcelà deux approches ont été adoptées : une étude globale et une étude par cellule. Dans les deux cas, les meilleurs estimateurs sont la masse totale de graupel, le volume d'updraft et le produit des flux des masses de glace précipitante et non précipitante.

Für die Menschen zählen Gewitter mit Donner und Blitz zu den ältesten bekannten Phänomenen der Natur. Die Tatsache, dass Blitze dennoch bis heute nicht abschließend erforscht sind, liegt in dem äußerst komplexen, schnellen und stochastischen Verhalten der Blitzentladung begründet. Der Autor befasste sich in Rahmen dieser Arbeit u.a. mit der Entwicklung eines modernen Messsystems, durch das die Erfassung von sowohl elektrischen als auch optischen Parametern der im Nanosekundenbereich ablaufenden Prozesse der Entladungen möglich wurde. Es handelt sich um technisch anspruchsvolle Messungen von hohen Stoßspannungen und schwachen Vorentladungsströmen in einem großen Frequenzbereich. Außerdem gelang es durch eine geschickte Synchronisation, die Entladungsprozesse präzise und erstmalig in einer Fotosequenz aufzunehmen. Auf Grundlage der Messergebnisse konnte der Entladungsprozess in mehrere Phasen der Vorentladung unterteilt und beschrieben werden. Vor allem beweisen die Messergebnisse die Existenz einer kanalartigen Vorentladung, die nicht zwingend zu einem Durchschlag führt. Dieser Mechanismus, der bei langsam ansteigenden Spannungen als stabile Leaderentladung benannt und mit Thermoionisation gekennzeichnet ist, war bei Blitzstoßspannungen bisher umstritten. / The breakdown behavior of long air gaps by Lightning Voltages has been investigated and the results of a new measurement system are reported. A series of up to eight photos (made by a high-speed camera) have recorded the expansion of discharge activities during the breakdown process. The pre-discharge current and voltage have been measured as well. The modern measurement techniques have made possible the synchronization of the photos with the current and voltage measurements in nanosecond-ranges. The combination of the measured current, voltage, and photos can precisely explain the breakdown process. The experiments have been carried out with the lightning impulses up to 2.4 MV and the air gaps up to 4 m. Despite of such high voltages, the experimental system has been verified to be appropriate for measuring the pre-discharge current in mA-ranges.

Lightning-caused forest fires are one of the major natural disturbances in Ontario managed boreal forests. Survival of these forests with fires for centuries shows that such disturbances are integral to the boreal ecosystem and its ecological functioning. Characterizing the fire regimes defined by fire ignition frequency, fire sizes and their spatial distribution patterns etc. thus can help to improve our understanding of the boreal forest dynamics and provide guidance for management practices attempting to maintain biodiversity and achieve sustainability. In this thesis the lightning-caused fire ignitions data for four ecoregions in Ontario managed boreal forests (3E, 3W, 3S and 4S) for 1960–2009 were analyzed using pattern analysis and density estimation to determine the spatial nature of fire ignitions. These fire ignition spatial patterns were further used (as weighted ignition scenario) to simulate forest fire regimes in the study area. Fire regimes were also simulated using spatially unweighted ignitions (unweighted ignition scenario). Non-spatial (total number of fires, total burn area, number of fires by size classes, annual burn fraction) and spatial (spatial burn probability) indicators of the simulated fire regimes under both ignition scenarios were compared to test the null hypothesis that modeled forest fire regime is not affected by the spatial patterns of input fire ignitions. All data analysis were performed for individual ecoregions. Spatial pattern of ignitions were analyzed using the nearest neighbour index and Ripley’s K-function. Ignition densities were estimated using the adaptive kernel density estimation method and the fire regimes were simulated using BFOLDS (Boreal Forests Landscape Dynamics Simulator). Results showed that lightning-caused fire ignitions are clustered in all ecoregions. Fire ignition density also varied spatially within ecoregions. Overall fire ignition density was highest in the northwestern ecoregion (4S) and lowest in the eastern ecoregion (3E), which corresponds to the combined gradient of effective humidity and temperature in Ontario. For each ecoregion, comparison of non-spatial simulated fire regime indicators showed statistically non-significant differences between unweighted and weighted ignitions. The spatial burn probability however captured clear spatial differences between unweighted and weighted ignitions. Spatial differences in spatial burn probability between both ignition scenarios were more prominent in ecoregions of high fire occurrence. Results of the weighted ignition scenario closely followed the spatial patterns of the estimated fire ignition density in the study area. Based on these results this thesis rejects the null hypothesis and emphasizes that ignition patterns must be considered in simulating fire regime in Ontario boreal forests.

Thèse(D.Eng.)-- Université du Québec à Chicoutimi, 2002. / Document électronique également accessible en format PDF. CaQCU