Showing papers by "Université du Québec à Montréal published in 1995"

Incremental concept formation algorithms based on galois (concept) lattices

Abstract: The Galois (or concept) lattice produced from a binary relation has proved useful for many applications. Building the Galois lattice can be considered a conceptual clustering method because it results in a concept hierarchy. This article presents incremental algorithms for updating the Galois lattice and corresponding graph, resulting in an incremental concept formation method. Different strategies are considered based on a characterization of the modifications implied by such an update. Results of empirical tests are given in order to compare the performance of the incremental algorithms to three other batch algorithms. Surprisingly, when the total time for incremental generation is used, the simplest and less efficient variant of the incremental algorithms outperforms the batch algorithms in most cases. When only the incremental update time is used, the incremental algorithm outperforms all the batch algorithms. Empirical evidence shows that, on the average, the incremental update is done in time proportional to the number of instances previously treated. Although the worst case is exponential, when there is a fixed upper bound on the number of features related to an instance, which is usually the case in practical applications, the worst-case analysis of the algorithm also shows linear growth with respect to the number of instances.

Opening up Decision Making: The View from the Black Stool

Abstract: Set on its current course thirty years ago by Herbert Simon's notions of bounded rationality and sequential stages, the research literature of organizational decision making is claimed in this paper to have suffered from three major limitations labeled reification, dehumanization, and isolation. In particular, it has been stuck along a continuum between the cerebral rationality of the stage theories at one end and the apparent irrationality of the theory of organized anarchies at the other. This paper seeks to open up decision making in three respects. First, the concept of “decision” is opened up to the ambiguities that surround the relationship between commitment and action. Second, the decision maker is opened up to history and experience, to affect and inspiration, and especially to the critical role of insight in transcending the bounds of cerebral rationality. Third, the process of decision making is opened up to a host of dynamic linkages, so that isolated traces of single decisions come to be seen as interwoven networks of issues. The paper concludes with a plea to open up research itself to the development of richer theory on these important processes.

The impact of goal orientation on self‐regulation and performance among college students

Abstract: The first objective of this study was to examine whether a relationship exists between types of goal orientation, self-regulatory processes and school performance and the second was to examine how students' self-regulation and academic performance differ according to their profiles resulting from combining learning and performance goals orientation. A total of 702 college students (463 females and 239 males) was administered a questionnaire assessing their orientation toward learning and performance goals, and reported their self-regulatory strategies for studying. Results showed that both for males and females there exist systematic relations between learning goal and self-regulation and academic achievement. Relations were also found for performance goal, but for boys only. Results also showed that, among the four profiles of goal orientation, more self-regulatory strategies were reported and higher academic performance was achieved by students having high concern with both learning and performance goals than by the others. More girls were classified in this profile, but in each profile girls were found to report more self-regulatory strategies and to achieve higher academic performance than did boys. Overall, these findings are consistent with those of previous studies conducted with younger students. Although adhesion to learning goal has a positive impact on self-regulation both for girls and boys, for the latter adhesion to performance goal can also be helpful. In view of the role of goal orientation on self-regulation in academic activities, research is needed to identify and understand the nature of the determinants of both the adhesion to these profiles and the gender differences.

Self-Regulation and Academic Procrastination

Abstract: The role of autonomous self-regulation as a predictor of academic procrastination was assessed. French-Canadian students from a junior college (N = 498) completed the Academic Motivation Scale as well as an academic procrastination scale and other measures (anxiety, self-esteem, and depression) that have been found to be related to fear of failure. Correlation results indicated that students with intrinsic reasons for pursuing academic tasks procrastinated less than those with less autonomous reasons (external regulation and amotivation). Regression results indicated that the measures of depression, self-esteem, and anxiety accounted for 14% of the variance in academic procrastination, whereas the self-regulation variables accounted for 25%. These results support the notion that procrastination is a motivational problem that involves more than poor time management skills or trait laziness.

Archaean subduction inferred from seismic images of a mantle suture in the Superior Province

Abstract: PLATE tectonics provides the basis for the interpretation of most current terrestrial tectonic activity, and is widely accepted as having been active over much of the Earth's history1. Yet the timing of initiation of this process is subject to debate2–9. So far, the earliest seismic evidence for plate tectonics has come from a fossil mantle suture in the Svecofennian orogen (1.89 Gyr ago)10 and from inferred plate convergence, subduction and accretion in the Trans-Hudson orogen (1.91–1.79 Gyr ago)11. As yet, seismic data from Archaean areas have been able to demonstrate only the importance of compression in the construction of the continental crust12–15. Here we present seismic data from a collision zone in the Superior Province of Canada, involving the Abitibi granite–greenstone Subprovince and the plutonic, arc-related Opatica belt. We interpret dipping seismic reflections that extend 30km into the mantle as representing a relict 2.69-Gyr-old suture associated with subduction. Although crustal structure, lithospheric thicknesses and convergence rates may have differed from those seen today, these seismic data provide direct evidence that plate tectonics was active in late Archaean times, 800 Myr earlier than indicated by previous seismic reflection surveys.

The effects of background music on consumers' desire to affiliate in buyer‐seller interactions

Abstract: The effect of music-induced pleasure and arousal on consumers' desire to affiliate in buyer-seller interactions were investigated in the context of bank services. Background music was manipulated using classical music extracts pretested to vary in pleasure (low, moderate, and high) and arousal (low, moderate, and high) according to the Affect Grid (Russell, Weiss, & Mendelsohn, 1989). Independent and interactive effects of music-induced pleasure and arousal on consumers' desire to affiliate were found. Higher desire to affiliate was associated with more pleasure and more arousal; pleasure had a stronger positive impact under low and high arousal than under a moderate level, and arousal had a stronger effect under low and high pleasure compared to moderate level. Theoretical and practical implications of the results are provided. © 1995 John Wiley & Sons, Inc.

Constraints on Pb closure temperature in titanite based on rocks from the Ungava orogen, Canada: Implications for U-Pb geochronology and P-T-t path determinations

Abstract: On the basis of multiequilibrium metamorphic pressure-temperature ( P-T ) estimates, we have determined that 660–700 °;C is a reasonable minimum estimate of the closure T of Pb diffusion in titanite, a temperature significantly higher than previously suggested. Activity-corrected reactions that produce titanite define narrow T stability fields (≈40 °;C) that correspond closely to metamorphic P-T determinations derived for coronitic garnet-clinopyroxene-hornblende samples. Growth of titanite, occurring between 1789 and 1814 Ma in the underthrust Archean basement of the Paleoproterozoic Ungava orogen (northern Quebec), is associated with retrograde metamorphism during underthrusting of the Archean basement (Approx.)1 b.y. after formation of the original granulitic assemblages.

Immunolocalization of freezing‐tolerance‐associated proteins in the cytoplasm and nucleoplasm of wheat crown tissues

Abstract: A protein family associated with the development of freezing tolerance in wheat has been identified. This protein family is Gramineae-specific and coordinately regulated by low temperature. Antibodies directed against the 50 kDa (WCS120) protein recognize at least 5 members of this family. Using these antibodies, the cellular content and location of this protein family was determined in cold-acclimated wheat seedlings. Western analyses of subcellular fractions indicated the presence of all members of the family in the cytosolic and purified nuclear fractions. These proteins accumulated to 0.9% of soluble proteins after 21 days of cold acclimation in winter wheat. This represents a cellular concentration of 1.34 microM. Immunohistochemical localization showed that these proteins are highly expressed in the vascular transition zone. No detectable expression was found in mature xylem, in the shoot apical meristem or lateral root primordia. This differential tissue expression suggests that the sensitive cells near the regions where water tends to freeze first require a higher amount of these proteins. This observation is consistent with the fact that regrowth after freezing stress is highly dependent on the viability of this region of the crown. Electron microscopy analysis using immunogold labelling showed that these proteins are present in the cytoplasm and in the nucleoplasm. They are not found in cell walls or other organelles. In vitro cryoprotective assays indicated that the WCS120 protein (PD50 of 10 micrograms ml-1 or 0.2 microM) are as effective as BSA and sucrose (at 250 mM) against freezing denaturation of lactate dehydrogenase. These results suggest that this protein family may be involved in a general mechanism of protection in the soluble fraction of the cell. Their presence in the nucleoplasm may also suggest a possible protective function of the transcriptional machinery. The high hydrophilicity, the abundance and stability of these proteins to boiling suggest that they may provide a particular micro-environment needed for cell survival in the sensitive vascular transition zone during freezing stress.

Possible mechanisms of action of environmental contaminants on St. Lawrence beluga whales (Delphinapterus leucas).

Abstract: A small isolated population of beluga whales (Delphinapterus leucas) that are highly contaminated by pollutants, mostly of industrial origin, resides in the St. Lawrence estuary, Quebec, Canada. Overhunting in the first half of the century was the probable cause for this population to dwindle from several thousand animals to the current estimate of 500. The failure of the population to recover might be due to contamination by organochlorine compounds, which are known to lead to reproductive failure and immunosuppression in domestic and laboratory animals and seals. Functional and morphological changes have been demonstrated in thyroid gland and adrenal cortex in many species exposed to organochlorinated compounds, including seals. Morphological lesions, although different, were also found in belugas. Functional evaluation of thyroid and adrenal glands of contaminated (St. Lawrence) versus much less contaminated (Arctic) belugas is currently under way. Necropsy of St. Lawrence belugas showed numerous severe and disseminated infections with rather mildly pathogenic bacteria, which suggests immunosuppression. Organochlorine compounds and other contaminants found in beluga whales cause immunosuppression in a variety of animal species including seals. Thirty-seven percent of all the tumors reported in cetaceans were observed in St. Lawrence beluga whales. This could be explained by two different mechanisms: high exposure to environmental carcinogens and suppression of immunosurveillance against tumors. Overall, St. Lawrence belugas might well represent the risk associated with long-term exposure to pollutants present in their environment and might be a good model to predict health problems that could emerge in highly exposed human populations over time.

Endocrine and metabolic dysfunction in yellow perch, Perca flavescens, exposed to organic contaminants and heavy metals in the St. Lawrence River

Abstract: The endocrine and biochemical responses to the acute stress of capture and handling were investigated in sexually mature and in immature male and female yellow perch, Perca flavescens, from a site contaminated by organic contaminants (PAHs and PCBs) and heavy metals (Hg, Cd, As, and Zn) and from a reference site in the St. Lawrence River. Following a standardized capture and handling stress, fish from the contaminated site did not exhibit the expected physiological stress response observed in fish from the reference site. Blood cortisol and thyroxine levels were lower, and liver glycogen stores were greater in mature males and females, as well as in the immature fish from the contaminated site, compared to the reference site. Fish from the contaminated site also had smaller gonads and lower condition factor. The impaired ability to elevate blood cortisol in response to an acute stress may be used as a biomarker of toxic stress in health assessment of feral fish from polluted environments.

Geochemistry of Mercury in Pristine and Flooded Ferralitic Soils of a Tropical Rain Forest in French Guiana, South America

Abstract: In ferralitic soils of the dense Guianese forest, mercury (Hg) concentrations of the surface horizons varied from 122 to 318 ng/g d.w. The behaviour and accumulation of Hg is not related to the accumulation of organic matter but to the penetration of humic substances and the progressive adsorption onto iron (Fe) oxy-hydroxydes in the mineral horizons. The flooding of such soils with the creation of a small reservoir has lead to a release of 20% of the Hg initially present. This observation is related to the reduction of the Fe oxy-hydroxydes and to the migration of the organo-metallic complexes to the water column. Although physico-chemical conditions are appropriate for bacterial methylation, methyl Hg (MeHg) levels of these soils are very low. The process regulating MeHg production and its possible loss from the soil are unknown.

Predicting the Effects of Climate Change on Fire Frequency in the Southeastern Canadian Boreal Forest

Abstract: Although an increasing frequency of forest fires has been suggested as a consequence of global warming, there are no empirical data that have shown climatically driven increases in fire frequency since the warming that has followed the end of the “Little Ice Age” (~1850). In fact, a 300-year fire history (AD 1688–1988) from the Lac Duparquet area (48°28'N, 79°17'W) shows a significant decrease both in the number and extent of fires starting 100 years ago during a period of warming. To explore this relationship between climatic change and fire frequency we used daily data from the Canadian Atmospheric Environment Service’s General Circulation Model to calculate components of the Canadian Forest Fire Weather Index (FWI) System for the 1×CO2 and 2xCO2 scenarios. The average FWI over much of eastern Canada, including the Lac Duparquet region, decreased under the 2×CO2 simulation, whereas FWI increased dramatically over western Canada. According to these results, fire frequency would decrease over the southeastern boreal forest which is in agreement with the empirical data from the fire history. Our results stress the importance of large regional variability and call into question previous generalisations suggesting universal increases in the rate of disturbance with climate warming.

Motivation and Gambling Involvement

Abstract: It is argued that motivation is a key determinant of gambling involvement. The hypothesis–that participants who exhibit a high self-determined motivational profile (i.e., engage in gambling for fun and have a sense of choice) will report a higher degree of involvement–was supported in a study conducted in Canada, with 245 gamblers who bet on horses. Also, the male participants were more involved in gambling than the female participants were.

Factors That Influence the Next Generation's Decision to Take Over the Family Farm:

Abstract: The survival of family farms is threatened by rapid change, intense international competition, and a resulting reduction of interest in perpetuating the family farm. What influences the next generation to pursue family farming, in spite of the difficulties? Do these factors differ between men and women? An in-depth, descriptive, and exploratory study of thirty next generation family farm members indicates specific factors critical to their decision to pursue the family farm succession. The findings are depicted in a framework that portrays these factors of influence and the effect they have on the succession decision of the next generation. Implications for practice and future research are also presented.

Automatic structuring of knowledge bases by conceptual clustering

Abstract: An important structuring mechanism for knowledge bases is building an inheritance hierarchy of classes based on the content of their knowledge objects. This hierarchy facilitates group-related processing tasks such as answering set queries, discriminating between objects, finding similarities among objects, etc. Building this hierarchy is a difficult task for the knowledge engineer. Conceptual clustering may be used to automate or assist the engineer in the creation of such a classification structure. This article introduces a new conceptual clustering method which addresses the problem of clustering large amounts of structured objects. The conditions under which the method is applicable are discussed. >

The handling of objects other than boxes: univariate analysis of handling techniques in a large transport company.

Abstract: The purpose of this study, carried out on handlers in the distribution centre of a large transport company, was to identify the techniques used for handling objects other than boxes. Thirty-one workers, with experience varying from one month to 17 years, were each filmed during one shift. A grid with 36 variables allowed the successive operations to be described: the type of grip, the nature and the direction of the efforts by the upper limbs, the use of the back and the lower limbs, and the displacement of the object. Nine hundred and forty-four handlings carried out in 3217 distinct movements were analysed. These observations revealed the complexity of the handling techniques and the tendency to favour some of them. Seventy-nine per cent of the handlings observed included pre-transfer and/or post-placement phases in addition to the transfer itself. Essentially horizontal phases (pulling, pushing) are more frequent than essentially vertical ones (lifting, lowering); asymmetry is generalized, whether it involves the back position (torsion), the direction and the type of effort, the position of the hands on the object, etc. More than half of the efforts are used to move an object resting on a surface (sliding, pivoting, turning, rolling); resistive efforts downwards (e.g., lowering) are avoided in favour of 'throwing' or 'dropping'.

How large must surface inhomogeneities be before they influence the convective boundary layer structure? A case study

Abstract: A high-resolution large-eddy simulation model has been used to investigate the effect of scale in surface inhomogeneities on the turbulence structure of the convective boundary layer (CBL). Surface heat fluxes were varied sinusoidally in two dimensions with wavelengths of 250, 500 and 1000 m, corresponding to about 0.27 zi, 0.55 zi and 1.1zi (zi is the boundary layer depth). the geostrophic wind speed was 1 ms−1. Horizontally-averaged statistics of the CBL above surface heat-flux inhomogeneities of different two-dimensional scales were compared. the phase-average method was used to study the horizontal variation of turbulence and the mean circulation in the CBL. Results from horizontally-averaged statistics show that surface inhomogeneities of small horizontal extent (x < zi, influence the horizontally-averaged variances, covariances and third moments. the surface heterogeneities of larger scales produce more vigorous energy transport in the CBL and larger temperature variances near the ground than do those of smaller scales. There is more entrainment over the region of high heat flux than over the region of low heat flux. the magnitude of entrainment and the mean circulation both increase with increasing scale of heterogeneities present at the ground. The effects on the turbulence structure of the two-dimensional surface inhomogeneities differ from those in the one-dimensional case reported by Hadfield et al. (1991, 1992). the most pronounced difference occurs when the scale of the surface heterogeneities is comparable to the height of the boundary layer; the v-variance is larger than the u-variance in the boundary layer. Although the scope of this case-study is restricted to a limited number of typical scenarios, it does provide evidence in support of the fact that even small-scale inhomogeneities in the surface thermal forcing can modify the CBL structure very differently than could an equivalent but uniform field. the sensitivity of the CBL turbulence structure to surface thermal perturbations with scales smaller than the boundary layer depth is also discussed.

Immunotoxicity of heavy metals in relation to Great Lakes.

Abstract: Heavy metals including mercury, lead, and cadmium are present throughout the ecosystem and are detectable in small amounts in the Great Lakes water and fish. The main route of exposure of humans to these metals is via the ingestion of contaminated food, especially fish. Extensive experimental investigations indicated that heavy metals alter a number of parameters of the host's immune system and lead to increased susceptibility to infections, autoimmune diseases, and allergic manifestations. The existing limited epidemiologic data and data derived from in vitro systems in which human peripheral blood leukocytes were used suggested that the human immune system may also be at increased risk following exposure to these metals. The magnitude of the risk that the presence of such metals in the Great Lakes may pose to the human immune system, and consequently to their health, is not known. In this review, the available data with respect to potential adverse effects of heavy metals on the immune system of humans and experimental animals are discussed, and additional data requirements are suggested.

The occurrence of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) in Canada

Abstract: In a study on the population dynamics of the predators of insect pests in apple orchards of Quebec, three specimens of the Asian coccinellid Harmonia axyridis were found. This is the first occurrence of this species in Canada