Some dielectric and spectroscopic studies on hydrogen bonding

Dielectric relaxation studies were carried out principally on some hydroxy compounds (e.g., phenols) and some carboxylic acids in polystyrene (PS) matrices and, in some cases, in compressed solids (CS). The hydroxy compounds in PS showed at least one absorption each corresponding to the molecular relaxation. In CS and, in some cases, in PS, a second absorption process due to the O-H group relaxation was observed in some of these compounds. The relaxation parameters as well as the Eyring activation parameters for both the molecular relaxation and group relaxation were found to be significantly influenced by hydrogen bonding in several cases. In general, carboxylic acids showed two families of absorptions. The common absorption process observed for all the acid molecules was attributed to the 0-H group relaxation in cyclic acid dimers which has to be preceded by the breakage of hydrogen bonds in the cyclic structures. The other absorption process for a number of the acid molecules was attributed to the molecular relaxation and/or segmental motion. In case of ester molecules a common process due to O-R group reorientation was observed

Assessing the cumulative impact of wildland fires and seismic line disturbance on peatlands in northern Alberta

This thesis examined the impact of wildland fires and seismic line fragmentation on peatlands in northern Alberta. The objectives were to determine if wildland fires alter regeneration trajectories of conifer vs deciduous species and lead towards the regeneration of woody vegetation adjacent to seismic lines. Multi-spectral lidar data were collected for a boreal peatland chronosequence of 5, 18, 30, and 38 years since fire (YSF) and were compared with areas that had not burned to quantify changes in the post-fire distribution of shrubs and trees. The results illustrated that there was high shrub regeneration in peatlands up to and including 38 YSF and trees tended to grow above shrubs by 18 YSF. Wildland fires promoted woody vegetation regeneration adjacent to seismic lines with taller deciduous trees and conifers found in mature post-fire peatlands (30 to 38 YSF). However, fens were more vulnerable to seismic line fragmentation and had less post-fire regeneration compared to bogs

Identifying Conifer Tree vs. Deciduous Shrub and Tree Regeneration Trajectories in a Space-for-Time Boreal Peatland Fire Chronosequence Using Multispectral Lidar

Wildland fires and anthropogenic disturbances can cause changes in vegetation species composition and structure in boreal peatlands. These could potentially alter regeneration trajectories following severe fire or through cumulative impacts of climate-mediated drying, fire, and/or anthropogenic disturbance. We used lidar-derived point cloud metrics, and site-specific locational attributes to assess trajectories of post-disturbance vegetation regeneration in boreal peatlands south of Fort McMurray, Alberta, Canada using a space-for-time-chronosequence. The objectives were to (a) develop methods to identify conifer trees vs. deciduous shrubs and trees using multi-spectral lidar data, (b) quantify the proportional coverage of shrubs and trees to determine environmental conditions driving shrub regeneration, and (c) determine the spatial variations in shrub and tree heights as an indicator of cumulative growth since the fire. The results show that the use of lidar-derived structural metrics predicted areas of deciduous shrub establishment (92% accuracy) and classification of deciduous and conifer trees (71% accuracy). Burned bogs and fens were more prone to shrub regeneration up to and including 38 years after the fire. The transition from deciduous to conifer trees occurred approximately 30 years post-fire. These results improve the understanding of environmental conditions that are sensitive to disturbance and impacts of disturbance on northern peatlands within a changing climate

Kisah Quaid-I-Azam Ali jinnah/ Enayetullah

52 hal.: ill.; 21 cm