McGill University Thèses et mémoires publiés en 1984

Weeds severely limit agricultural production in many Third World tropical countries where productivity is already marginal due to unfavourable environmental, biological, economic and social factors. Lack of both ecological and distributional information at the scale of the weed assemblage, and lack of detailed data on the life histories and responses of the constituent weedy species hinders development of cheap and effective weed management strategies not contingent on intensive use of herbicides. Plant geographers can contribute to the solution of tropical weed problems by investigating factors which mediate the dynamics of species: regional and local ranges. The research in this thesis …  Lire la suite

The primary grain in oat spikelets is larger than the secondary grain. Oat genotypes were grown to determine the effects of planting primary and secondary grains separately on vegetative and reproductive growth. Plants from primary seeds had higher yields than those from secondary seeds. The advantage was associated with earliness of heading. It was concluded that increased seed uniformity would be advantageous. Reductions in panicle size by removal of all primary grains and some secondary grains indicated that secondary grains have more growth potential than observed in untreated panicles. However, secondary grains in the treated panicles did not achieve weights …  Lire la suite

Hydrogen oxidation by Azospirillum brasilense Sp7 was studied in N(,2)-fixing and NH(,4)('+)-grown batch cultures. The K(,m) for H(,2) of O(,2)-dependent H('3)H oxidation in whole cells was 9 uM. The rates of H('3)H and H(,2) oxidation were very similar, indicating that the initial H(,2) activation step in the overall H(,2) oxidation reaction was not rate-limiting and that H('3)H oxidation was a valid measure of H(,2)-oxidation activity. Hydrogen-oxidation activity was inhibited irreversibly by air. In N-free cultures the O(,2) optima for O(,2)-dependent H(,2) oxidation, ranging from 0.5-1.25% O(,2) depending on the phase of growth, were significantly higher than those of C(,2)H(,2) reduction, …  Lire la suite

Some novel optical methods to study the structure of ordered latices have been developed. These methods, as well as the Bragg diffraction technique, have been used in rheo- and electro-optical studies of latex structure. In the rheo-optical studies, ordered latices were subjected to a simple shear field and a three-dimensional deformation of the structure was observed. The increase in spacing between parallel layers of particles is qualitatively explained by a proposed two-dimensional sliding layer model. In the electro-optical studies, ordered latices were subjected to an electric field and an asymmetrical particle distribution was found. The electric field effect was found …  Lire la suite

It is the purpose of this thesis to document, delineate and to some degree interpret the portion of Alexander Macdonell’s life which spans his birth in 1762 and his departure for Quebec City in 1804. Macdonell was forty-two when he arrived in Canada and of the years prior to his arrival, almost nothing is known, save for a few paragraphs contained in his memoirs. On the other hand, there is no lack of information concerning his behaviour and accomplishments, in particular the establishment of parishes and schools, after he began his ministry in Upper Canada. In presenting the details of …  Lire la suite

A model of faculty advising suggests that the tasks performed by faculty advisors are explained by three conceptual constructs differing in levels of complexity and type of skill. The three constructs identify a routine set of tasks termed Providing Information and two complex sets of tasks termed Developing Academic and Educational Goals, and Providing Personal Support. However, no empirical data exist to support this model. To test the model, a sample consisting of 481 University of Vermont undergraduate students rated their advisors on the three sets of items. The data were subjected to confirmatory factor analyses using maximum likelihood procedures …  Lire la suite

Eggs of many organisms contain a store of mRNA which supports protein synthesis during early embryonic development and various regions of the egg cytoplasm are not identical with respect to developmental potential. I investigated the extent to which sea urchin embryogenesis results from a progression of developmental events directed by the embryo, or an expression of a pre-formed maternal program. By the use of two-dimensional electrophoresis I demonstrated that cellular determination during embryonic development at the 16-cell stage is not accompanied by qualitative changes in the distribution within the embryo of abundantly-synthesized proteins, virtually all of which are coded by …  Lire la suite

This thesis is a study of the Canadian Free Church, an institution which played a considerable role in the social, political and religious life of mid-nineteenth-century Canada. The Free Church was characterized by its missionary zeal, theological orthodoxy, unity, financial solvency, and involvement in politics when it touched moral issues such as slavery, temperance, and sabbath breaking. Some important political and commercial leaders were attracted to it, including George Brown, Malcolm Cameron, Isaac Buchanan, and John Redpath. This church maintained a separate existence from 1844 when it was formed as a result of a secession from the Church of Scotland …  Lire la suite

Body size influences virtually all aspects of the autecology of material flow by organisms. Thus, size classes may be considered as alternatives to grouping by trophic level, function or taxonomy to describe the structure and function of communities. The general intent of this thesis is to assess the role of body size in the dynamics of radiophosphorus in the freshwater plankton. To calculate a priori estimates of the fluxes of phosphorus through size classes of plankton, the rates of assimilation and excretion of laboratory cultures of algae and cladocerans were measured, and regressed on body mass (W). In both groups, …  Lire la suite

Maturation and aging-associated changes in membrane transport of sheep reticulocytes of the high-K('+) and low-K('+) genotypes were studied. The results indicate that during short term (less than 10 days) in vitro maturation, there is a progressive decrease in ouabain-sensitive Na('+),-K('+)-pump activity (('86)Rb('+) uptake in low-K('+) cells) and Na('+)-ATPase activity (high-K('+) cells). However, during long term (several weeks) in vivo maturation in which HbC was used as a marker of newly formed reticulocytes, kinetic changes, as well as a decline in total activity, were observed. The effect of metabolic depletion on the maturation-associated loss of two membrane transport functions was also …  Lire la suite

Graph-monoids are introduced as algebraic objects which correspond to congruences over graphs. Varieties are defined, and a one-to-one correspondence between varieties of graph-monoids and varieties of graph-congruences is demonstrated. This is viewed as a generalization of the known correspondence between monoid varieties and congruence varieties. Some classification and effective characterizations of graph-monoid varieties are obtained. These are used to decide membership in the wreath product of certain monoids varieties and the variety of definite semigroups.  Lire la suite

The uptake, metabolism and releasability of ethyl-analogues of homocholine were studied in rat brain and cat superior cervical ganglion. Results from these experiments further describe the specificities of the processes of uptake and acetylation for choline and of storage and release for acetylcholine in the mammalian nervous system. Specificity at the level of the transport mechanism into synaptic vesicles in mammalian brain tissue was identified with acetyldiethylhomocholine, a poor substrate for vesicular compartmentation. This property of the analogue was exploited to study the site of origin of released transmitter from brain slices. When tissue was incubated with ('3)H choline and …  Lire la suite

Two characteristics prevail in the works of Natalia Ginzburg: the tendency towards reduction and the tendency towards repetition. Reduction and repetition resemble each other; they are analogous, complementary; both are efficient and dramatic means to express a reality which is partial and incomplete and to underline the inherent obscure suffering which results from that reality. Although Natalia Ginzburg does not belong to any of the various literary trends (and, in particular, not to neo-realism which coincides chronologically with the beginning of her career), she interprets a sorry and limited world and bears sensitive witness to its loneliness, to its "male …  Lire la suite

When high yield chemimechanical sulphite pulp fibres were suspended in water, both lignin and carbohydrate were leached out of the pulp. The rate of leaching fitted a theory developed previously for the diffusion of macromolecules through the water-swollen fibre wall. The average intrafibre diffusion coefficients for lignin and carbohydrate were several orders of magnitude lower than the free diffusion of these macromolecules in solution. Leaching over a long period indicated a polydispersity of diffusion coefficients. This was related to an increase with time in the molecular weights of macromolecules removed from the fibre. Although the rate of leaching increased markedly …  Lire la suite

Variability in the clinical course of multiple sclerosis is one of its most interesting and yet discouraging features. Research into patient and disease characteristics which might predict future disease course has produced conflicting results. This thesis presents an original approach in which the course of the disease is described by the movement of patients through well defined disease states. Two probabilistic models: the semi-Markov and the stochastic survival model are proposed to evaluate the effect of prognostic factors on transitions from state to state. The feasibility and applicability of both models is evaluated using data on the course of multiple …  Lire la suite

Misra, A. K. (Supervisor)  Lire la suite

Economic exploitation of mineral resources, especially in underdeveloped mountainous areas, requires evaluating potential base-metal deposits over a large area of mineralization. Sophisticated techniques of potential field data processing are needed for this purpose, including reliable methods for regional-residual separation, continuation of potential fields and accurate computation of magnetic field in various rock materials. For the regional-residual separation problem, it is shown that the finite element method can be useful in conjunction with the generalized linear inverse approach, to produce improved regional and residual gravity maps compared to traditional methods. Then the generalized linear inverse method is applied to downward continuation …  Lire la suite