The Soil Taxonomy definition for the brittle, compact subsoil horizons known as fragipans is vague and processes responsible for fragipan formation are poorly understood. Ambiguities in the fragipan definition have resulted in a lack of consistency in the interpretation of fragipan characteristics. These ambiguities may be attributed to difficulties encountered in establishing a precise definition broad enough to encompass the wide range of fragipan soils known to occur. This study approaches the problems of defining and identifying fragipans from a geographic perspective; emphasizing distribution of fragipan soils in the United States, and interpretation of fragipan characteristics across this range. A series of maps based on data gathered from county soil surveys are presented to estimate the areal distribution of fragipan soils in the United States and explore the regional variability of several fragipan characteristics. This study demonstrates that a "universal" definition of fragipans may not be realistic. / Master of Science

This is a qualitative study of women whose children are or have been enrolled in a Head Start program in the midwest. Head Start is an educational program designed to provide a wide range of services to disadvantaged children and their families. Part of the program’s goals is to encourage parental participation in order to provide low-income parents a possibility of enriching their lives and empowering themselves through education. Using symbolic interaction as the initial theoretical perspective, I examine the experiences of mothers and how their involvement in the Head Start program has impacted their lives. Through interviews and observation, I investigate how Head Start as a formal organization designed to be part of the solution to the officially defined social problem of poverty affects the lives of Head Start mothers. As a former Head Start mother, I use my experiences as the starting point for the study. From the mothers' accounts of their experiences with Head Start, I found several factors which may lead to changes in self-concepts and personal empowerment. The women identified "mother" as a very important self. Head Start is able to provide an arena where the women can see their self as mother in a positive light. Parental involvement in the program is both expected and appreciated. The mothers indicated that through their work as volunteers, they feel important and needed for the program's operation and feel good about the things they do in Head Start. Among the factors identified which may lead to changes in self, empowerment, and self-concepts were the Federal mandate calling for maximum feasible participation of the parents, the transformation of clients into volunteers, the appreciation and encouragement shown to the mothers, the acknowledgement of the parents as primary educators of their children, and their peer relationship with the Head Start staff. Through participation in various Head Start activities, the women reported positive changes in their "selves." / Ph. D.

Tableau d’honneur de la Faculté des études supérieures et postdoctorales, 2012-2013. / L'avancement technologique des sources de rayonnement laser est tel qu'il permet désormais l'observation résolue en temps des phénomènes se déroulant dans les atomes et les molécules sous l'effet de champs intenses et de très courte durée [1, 2]. La complexité croissante de ces expériences et des processus auxquels elles s'intéressent suscite plusieurs questions à propos de la dynamique multiélectronique de ces systèmes. Par exemple, dans un travail récent portant sur la molécule de CO₂ [3], une technique d'imagerie moléculaire exploitant les interférences dans le signal d'émission des harmoniques élevées a été proposée. Ces interférences qui dépendent fortement de la géométrie moléculaire sont également influencées par divers effets multiélectroniques déterminant l'importance relative des différentes voies d'ionisation possibles de la molécule sondée rendant difficile leur interprétation. Il est donc très important de développer des modèles théoriques suffisamment précis pour pouvoir s'adresser à de telles interrogations. La compréhension du déroulement de ces processus permet d'avoir une meilleure emprise sur ceux-ci et de tirer une juste part de ce type d'expérience. Ainsi, nos développements méthodologiques récents s'inscrivent dans cette ambition de dévoiler la nature des effets multiélectroniques sur la dynamique des molécules polyélectroniques dirigées par un champ laser intense. Le développement complet de ce schéma général multi-configurationnel à champ autocohérent dépendant du temps (TDMCSCF) [4, 5] sera présenté et illustré avec quelques résultats préliminaires obtenus pour des systèmes simples. Finalement, on discutera de quelques applications utiles de l'étude de la dynamique électronique, telle que l'imagerie moléculaire dynamique.