McGill University Theses and dissertations published in 1993

The structure of one member of a family of maize mitochondrial RNA replicons (or RNA plasmids), RNA b, has been characterized. It is shown that RNA b shares a 13 nucleotide sequence with the central conserved region of Cadang-Cadang viroid of coconuts which might be involved in substrate recognition by the RNA replicase during replication. RNA b likely was derived from a larger member in that family, RNA a, through co-linear deletions similar to those involved with the generation of the defective interfering (DI) elements associated with both animal and plant viruses. RNA b may represent a "selfish" RNA optimized …  Read more

Greatbatch, R. J. (Supervisor)  Read more

This thesis presents numerical studies of phase behavior for both thermotropic and lyotropic liquid crystals. The nature of the orientational transition in the Lebwohl-Lasher model for the nematic-isotropic phase transition is found to be weak first-order with the stability limits of the nematic and isotropic phases being extremely close to the equilibrium transition temperature. It is also found that the director fluctuations in the nematic phase correspond to fractional Brownian motion whereas the fluctuations in the isotropic phase follow ordinary Brownian motion. The Pink model is extended to give an accurate description of the main phase transition in lipid bilayers …  Read more

A novel and simple "constant-addition" technique was used to study calcite precipitation kinetics and the partitioning of REE between calcite overgrowths and their parent seawater solutions under steady state conditions. As a consequence of solute interactions in solution and at the growing mineral surface, the calcite precipitation mechanism in seawater is complex. It is dominated by the following reversible overall reaction: $ rm Ca sp{2+}+CO sbsp{3}{2-} rightleftharpoons CaCO sb3.$ A kinetic expression is proposed which describes the precipitation rate according to this reaction. A partial reaction order of 3 with respect to CO$ sb3 sp{2-}$ is obtained. REE have a …  Read more

Carcinoembryonic antigen (CEA), an immunoglobulin (Ig) superfamily member, functions as an adhesion molecule in vitro. This thesis reports that nonspecific cross-reacting antigen (NCA), a CEA family member, can mediate Ca$ sp{++}$-independent, homotypic intercellular adhesion in vitro. Heterotypic adhesion studies demonstrate that CEA can cross-interact with NCA; however, neither NCA nor CEA can interact with other Ig superfamily members such as neural cell adhesion molecule (NCAM) and myelin-associated glycoprotein. This specificity was used to investigate the mechanism of CEA-CEA binding using CEA truncated and CEA/NCAM chimeric constructs. A novel model has been proposed in which double reciprocal interactions between the V-like …  Read more

Mammalian striate and circumstriate cortical neurons have long been understood as coding spatially localized retinal luminance variations, providing a basis for computing motion, stereopsis, and contours from the retinal image. However, such perceptual attributes do not always correspond to the retinal luminance variations in natural vision. Recordings from area 17 and 18 neurons revealed a specialized nonlinear processing stream that responded to stimulus attributes having no corresponding luminance variations. This nonlinear stream acts in parallel to the conventional luminance processing of single cortical neurons. The two streams were consistent in their preference for orientation and direction of motion, but distinct …  Read more

The hydrolysis of iron(III) from sulphate bearing aqueous solutions was investigated to significantly improve the neutralization of acidic mineral effluents. Both theoretical and experimental studies were undertaken. A literature review and a thermodynamic analysis of the Fe(III)-SO$ sb4$-H$ sb2$O system were performed. The thermodynamic analysis determined that Fe(III)-sulphato complexes dominate in the acidic pH range (pH $<$ 4) while at neutral to mild alkaline pH range Fe(OH)$ sb3 sp circ sb{ rm (aq)}$ is the dominant species. It was found that a relationship exists between the precipitation pH and the sulphate content of the precipitate (17% at pH 3, 7-9% …  Read more

This study investigates the phenomenon of a communal Jewish organization, the National Budgeting Conference (NBC). In essence, the NBC is in charge of allocating money to national organizations through contributions collected from each local community. This unique arrangement doesn't exist in other Jewish communities around the globe; the common procedure is that every local federation allocates money for the local needs. The objective of this dissertation is to follow the activities of the NBC from a strategic management point of view. So far, almost the entire body of literature on Jewish organizations stem from a political science and an ethnicity …  Read more

The normal lung with its air-filled alveoli is designed primarily to function in gas-exchange. Pulmonary edema, particularly in its alveolar flooding phase, is life-threatening because it interferes with this gas-exchange function. An important safety factor against alveolar flooding is the pulmonary interstitium that has a high compliance to accommodate edema fluid. We tested the hypothesis that if we decreased the compliance of the interstitium by experimental fibrosis, lung edema would be redistributed from the interstitium and predominantly flood alveoli. To study this, severe left lung fibrosis was produced in six dogs with radiation and bleomycin. Twenty-four months later, hydrostatic edema …  Read more

We prove a completeness result for the equivalence of proofs in the positive fragment (T, $ Lambda, rightarrow$) of intuitionistic propositional logic with respect to sets. We also show that proofs in the full intuitionistic propositional logic factor through interpolants--in this way we prove a stronger interpolation property than the usual one which gives only the existence of interpolants. Translating that to categorical terms, we give a representation theroem for free Cartesian closed categories (Theorem 3.16) in the category of sets and we show that pushouts of biCartesian closed categories have the interpolation property (Theorem 4.47).  Read more