Showing papers by "Université du Québec à Montréal published in 1993"

Free Lie Algebras

Abstract: Publisher Summary This chapter explores that the Lie algebra of Lie polynomials is the free Lie algebra. Lie polynomials appeared at the end of the 19th century and the beginning of the 20th century in the work of Campbell, Baker and Hausdorff on exponential mapping in a Lie group, which lead to the Campbell–Baker–Hausdorff formula. Around 1930, Witt showed that the Lie algebra of Lie polynomials is the free Lie algebra, and that its enveloping algebra is the associative algebra of noncommutative polynomials. The Poincare–Birkhoff–Witt theorem is proved, and shows that the free Lie algebra is related to the lower central series of a free group. The full linear group acts on Lie polynomials, and the symmetric group acts on those which are multilinear. The Lie representation of the symmetric group is induced from any faithful representation of a subgroup generated by a full cycle. Automorphism of a free Lie algebra are always tame, and are characterized by a Jacobian condition. The full linear group acts on Lie polynomials, and the symmetric group acts on those which are multilinear. The descent algebra is dual to the ring of quasi-symmetric functions which is, therefore, a free commutative algebra.

On the Assessment of Intrinsic, Extrinsic, and Amotivation in Education: Evidence on the Concurrent and Construct Validity of the Academic Motivation Scale:

Abstract: A new measure of motivation toward education has been developed in French, namely the "Echelle de Motivation en Education" (EME). The EME is based on the tenets of self-determination theory and is ...

Myoblast transfer in duchenne muscular dystrophy

Abstract: One biceps muscle of 8 patients with Duchenne muscular dystrophy was injected at 55 sites with a total of 55 million viable, purified, and contamination-free normal myoblasts (myoblast transfer). The other biceps of each patient was injected with a placebo to serve as a control. The procedure was blinded to the patients, parents, and investigators. Myoblasts derived from a biopsy specimen of the fathers were cultured and purified under strict conditions and carefully screened for microbial contamination. All patients received cyclophosphamide for immunosuppression for 6 or 12 months. No serious complications were observed after myoblast transfer, indicating that the procedure is safe. The overall therapeutic efficiency of myoblast transfer was poor as judged by the results in maximal voluntary force generation, dystrophin content of the muscle, magnetic resonance imaging of the muscle, and the lack of donor-derived DNA and dystrophin messenger RNA in the injected muscle. An improved efficiency of the take of myoblasts might be achieved by using younger cells and injecting the myoblasts with a myonecrotic agent (to increase the prevalence of regeneration) and a basal laminal fenestrating agent.

Persistent neuropsychological deficits and vigilance impairment in sleep apnea syndrome after treatment with continuous positive airways pressure (CPAP)

Abstract: The obstructive sleep apnea syndrome is characterized by nocturnal sleep disturbance, excessive daytime sleepiness and neuropsychological deficits in the areas of memory, attention, and executive tasks. In the present study, these clinical manifestations were assessed in apneic patients before and 6 months after treatment with nasally applied continuous positive airway pressure (CPAP). CPAP treatment was found to restore normal respiration during sleep and to normalize sleep organization. Daytime vigilance greatly improved with treatment but some degree of somnolence as compared to normal controls persisted. Similarly, most neuropsychological deficits normalized with treatment. The exception was for planning abilities and manual dexterity, two neuropsychological deficits that have been found to be highly correlated with the severity of nocturnal hypoxemia. These results raise the possibility that anoxic brain damage is a pathogenic factor in severe obstructive sleep apnea syndrome.

Decreasing frequency of forest fires in the southern boreal zone of Québec and its relation to global warming since the end of the 'Little Ice Age':

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 a climatically driven change in fire frequency since the warming that has followed the end of the 'Little Ice Age'. We present here evidence from fire and tree-ring chronologies that the post-'Little Ice Age' climate change has profoundly decreased the frequency of fires in the northwestern Quebec boreal forest. A 300-year fire history (AD 1688-1988) from the Lake Duparquet area (48°28' N, 79°17' W) shows an important decrease, starting 100 years ago, in the number and the extent of fires. This decrease in fire frequency is also associated with a long- term increase in the mean ring width of northern white cedar (Thuja occidentalis L.) in the same area. Agreement between the standardized tree-ring chronology and fire years, together with a negative correlation with a drought index reconstructed for the AD 1913-1987 period, shows that the decrease in fire frequ...

Building and maintaining analysis-level class hierarchies using Galois Lattices

Abstract: Software reuse is one of the most advertised advantages of object-orientation. Inheritance, in all its forms, plays an important part in achieving greater reuse, at all stages of development. Class hierarchies start taking shape at the analysis level, where classes that share application-significant data and application-meaningful external behavior are grouped under more general classes. At the design level, such hierarchies are augmented with implementation classes, and possibly reorganized to take into account implementation factors such as performance or code reuse [22]. Getting the analysis-level hierarchy "right" is very important for the understandability and traceability of the models and the reusability of the resulting code [22]. In this paper, we propose a formal method that organizes a set of class interfaces into a lattice structure called Galois Lattice [10]. Such a lattice has several advantages including: 1) embodying protocol conformance, 2) supporting an incremental updating algorithm [9]), with applications for class hierarchy maintenance. We first present the basic method and illustrate its use through an example inspired from [3]. Next, we discuss extensions to the method to take into account richer class descriptions in general, and the specifics of OO analysis-level models. Finally, we discuss some of the research directions we are currently pursuing.

Working memory and the self-ordered pointing task: Further evidence of early prefrontal decline in normal aging

Abstract: Two major lines of investigation are currently clarifying the nature of the impairment of working memory associated with normal aging. Cognitive psychology has formulated the problem in terms such as the balance of impairment of encoding, retrieval, storage and/or attention, whereas neuropsychology has formulated the problem in terms such as the balance of frontal (executive) versus temporal (mnemonic) degeneration. The findings of this study support the contention that the primary impairment of working memory in early normal aging is an active attentional executive processing deficit. Specifically, on the Self-Ordered Pointing Task, there is significantly ineffective exploitation of top-down clustering strategy as a function of aging. On this task, self-organization of encoding and retrieval must occur simultaneously with ongoing responding. The finding cannot be explained as an impairment of encoding, retrieval, storage, or build-up and/or release of proactive interference, since indexes of these did not discriminate young-adult from middle-aged samples.

Predictors and indicators of work status after traumatic brain injury: A meta-analysis

Abstract: Heterogeneity of studies reporting data about predictive and indicative variables of return to work after traumatic brain injury led to a lack of clarity and reliability. A meta-analysis was performed to integrate and organise the results of studies reporting data about the relation between variables that are conceptually meaningful in rehabilitation and a dichotomous criteria of work status: employed or unemployed. The large quantity of variables were grouped chronologically according pre-, peri and post-traumatic phases. The results indicate that the highest and most reliable correlations were between unemployment and executive dysfunctions, emotional disturbances, deficits in activities of daily living, and less vocational rehabilitation services. Other variables, such as anosmia and post-coma activity level, show high correlations but are still to be corroborated.

Experimental comparison of navigation in a Galois lattice with conventional information retrieval methods

Abstract: A controlled experiment was conducted comparing information retrieval using a Galois lattice structure with two more conventional retrieval methods: navigating in a manually built hierarchical classification and Boolean querying with index terms. No significant performance difference was found between Boolean querying and the Galois lattice retrieval method for subject searching with the three measures used for the experiment: user searching time, recall and precision. However, hierarchical classification retrieval did show significantly lower recall compared to the other two methods. This experiment suggests that retrieval using a Galois lattice structure may be an attractive alternative since it combines a good performance for subject searching along with browsing potential.

Historical scientometrics? Mapping over 70 years of biological safety research with coword analysis

Abstract: This paper relates the results of a co-word analysis of over 70 years of biological safety literature. The database used in this project is theSonger Safety Bibliography (SSB) which lists around 17 000 references. The results show biological safety to be a very fragmented field, characterized by the existence of several relatively independent foci of interest, none of which has been able to structure the field into a tight network. Early periods of activity were marked by the construction of the basic tools of biological safety practices. Those tools became a robust package which, in more recent periods, was used routinely. While the safety problems related to recombinant DNA research have received much attention in the general press, they do not seem to occupy a prominent place within the biological safety literature, at least the one compiled in SSB.

Interactive Effects of Musical and Visual Cues on Time Perception: An Application to Waiting Lines in Banks:

Abstract: This study explores the interactive effects of musical and visual cues on time perception in a specific situation, that of waiting in a bank. Videotapes are employed to simulate the situation; a 2 ...

Complementary Aspects of Strawberry Pollination by Honey and IndigenQus Bees (Hymenoptera)

Abstract: The relative efficiency of two groups of insects that pollinate strawberries, Fragaria × ananassa Duch., was established by comparing the relative influence of the number and length of their visits to flowers, their foraging behavior, and the fertilization rates of the achenes during these visits. Honey bees, Apis mellifera L., were more efficient than indigenous pollinators (Hymenoptera: Andrenidae, Halictidae, and Megachilidae) when the frequency of visits was low. Average-sized apoids such as honey bees pivot at the top of the receptacle and pollinate the apical stigmata, whereas small apoids circle on the stamens and around the receptacle, pollinating mainly the basal stigmata. Data collected revealed that these two groups of pollinators playa complementary role in strawberry pollination.

A Motivational Model of Leisure Participation in the Elderly

Abstract: We developed a motivational model of leisure participation to examine the factors that may encourage involvement by the elderly in leisure activities. This model posits that opportunities and constraints determine motivation to participate, which in turn predicts satisfaction. Satisfaction is expected to lead to participation. In a study testing the proposed model, 102 elderly Canadians answered a questionnaire assessing the variables in the model. As predicted, results of a path analysis supported the proposed motivational model and accounted for 32% of the variance in the elderly' leisure participation. These results are discussed in the light of self-determination theory (Deci & Ryan, 1985).

Bubble Convection Experiments with a Semi-implicit Formulation of the Euler Equations

Abstract: Atmospheric models based on the Euler equations exist and are used occasionally to carry out numerical experiments. Such a model is used here to simulate the motion of warm bubbles in a dry isentropic atmosphere. For the time integration, this model uses a scheme that is semi-Lagrangian and semi-implicit. It is the stability and the efficiency of this integration scheme that is examined in the context of an isentropic vertical stratification. Some results are presented and are compared with the results generated by similar experiments reported in the scientific literature.

Bisimulation and open maps

Abstract: An abstract definition of bisimulation is presented. It allows a uniform definition of bisimulation across a range of different models for parallel computation presented as categories. As examples, transition systems, synchronization trees, transition systems with independence (an abstraction from Petri nets), and labeled event structures are considered. On transition systems, the abstract definition readily specialises to Milner's (1989) strong bisimulation. On event structures, it explains and leads to a revision of the history-preserving bisimulation of Rabinovitch and Traktenbrot (1988), and Goltz and van Glabeek (1989). A tie-up with open maps in a (pre)topos brings to light a promising new model, presheaves on categories of pomsets, into which the usual category of labeled event structures embeds fully and faithfully. As an indication of its promise, this new presheaf model has refinement operators, though further work is required to justify their appropriateness and understand their relation to previous attempts. >

Pullout and bond of glass-fibre rods embedded in concrete and cement grout

Abstract: Consideration is being given to replacing steel rebars with glass-fibre rods in some specific areas, particularly those in which premature failure due to corrosion has been observed. This paper presents the results of an experimental study of pullout behaviour and bond characteristics of glass-fibre rods embedded in normal and high-strength concretes and in cement grout. The results of the study show that glass-fibre rod bond strength is about 12 MPa and the optimal anchored length approximately 10 times the rod diameter. The average modification factor of top-cast reinforcement was found to be equal to 1.23 and 1.18 for normal and high-strength concrete, respectively. Other considerations, such as bond slip, are also discussed in the paper. Comparisons with steel reinforcement are made whenever appropriate.

Expert knowledge and decision-making in controversy contexts

Abstract: There was a time when the mobilization of experts was a taken-for-prated. unproblematic aspect of decision-making processes. That confidence has vanished. Ascertaining the significance of expertise now requires a reconsideration of the dynamics of controversies. The current view still assimilates conlroversy to the medieval exercise of the disputatio in which two parties argue one against the other. A non-reductionist view is needed to take fully into account the diversity of worlds of relevance involved in the dynamics of any public controversy. Only then is it possible to understand how decision making is predicated upon associations of worlds of relevance, and how expertise is actually a collective learning process which sets the boundary conditions for the efficacy of individual experts.

Stochastic differential equations with fractional Brownian motion input

Abstract: Kolmogorov-Levy-Mandelbrot (t − s)2a -fractional Brownian motion (FBM) appears to be quite relevant for modelling long range memory stochastic systems, and the problem of defining stochastic differential equations subject to such a noise is considered. The Liouville fractional derivative and the self-similarity property of FBM are recalled and then, via detailed calculation, the main statistical characteristics of FBM are derived. First-order stochastic differential equations with FBM are considered via path integrals and a corresponding mean squares approach to non-linear filtering is described. Lastly, a new modelling via stochastic differential equations of fractional order is suggested.

Trichothecene mycotoxins in the dust of ventilation systems in office buildings.

Abstract: Analysis of trichothecene mycotoxins in dust samples from ventilation systems of office buildings was applied as a rapid and inexpensive method for the detection of mycotoxins. Dust samples from three different office spaces of the Montreal urban area, reportedly affected by the “sick buildings syndrome”, were analysed by thin-layer chromatography (TLC). Positive colour reaction on TLC plates with 4-(p-nitrobenzyl) pyridine, specific for the 12,13-epoxy group in the trichothecene nucleus, was obtained for the extracts of 0.5- to 50-g dust samples. The dust samples contained at least four trichothecenes: T-2 toxin, diacetoxyscirpenol, roridine A and T-2 tetraol. The results were confirmed by high-performance liquid chromatography analysis. Screening of dust samples from air ventilation systems of reportedly affected buildings provided direct evidence of trichothecene mycotoxins, with the detection limit estimated as 0.4-4 ng/mg dust. Thus, the dust sample analysis is suggested as a rapid technique for detecting the presence of mycotoxins in the dust of ventilation systems.

Changes in the forest floor of Canadian southern boreal forest after disturbance

Abstract: . The concentrations and contents of organic matter and nutrients in organic deposits on the forest floor were estimated along a 231-yr chronosequence following fire at the southern limit of the boreal forest in eastern Canada. The sampling design was stratified to take into account the variability related to the presence of the principal tree species as well as to the presence of large gaps created by a recent spruce budworm (Choristoneura fumiferana) outbreak. The forest floor showed a steady accumulation of organic matter and total nutrients with time-since-fire and a 50 % decrease in the concentrations of available P and K, but not N (as determined by aerobic incubation). The increase in forest-floor weight was accompanied by an increased storage of available N, Ca and Mg. The availability of N and Ca was more strongly affected by tree species and gaps than by time-since-fire. A high N-availability was observed under Betula papyrifera and in gaps, while high a Ca-availability was found near Populus tremuloides and Thuja occidentalis. In old sites, the forest floor of gaps, created by a recent spruce budworm outbreak, had a necromass similar to that of a young forest, but the low concentrations of available P and K of an old forest.

A leaf-specific gene stimulated by light during wheat acclimation to low temperature

Abstract: We report here the identification and characterization of a new leaf-specific light-stimulated gene induced during cold acclimation of wheat. Sequence analysis revealed that the gene encodes a protein of 19 kDa with a pI of 8.8. This is a novel protein with a particular charge distribution. The C-terminal half has a high propensity to form an α-helix and contains all the acidic amino acids with a net negative charge of -7. On the other hand, the N-terminal half is rich in proline, lysine and arginine with a net positive charge of +10. These properties are commonly found in several transcription factors. The protein is also rich in alanine (21%), is hydrophilic but not boiling soluble in contrast to other alanine-rich proteins. During low temperature exposure, the corresponding mRNA accumulates rapidly in the leaf and remains at a constant level in two tolerant cultivars used. However, is a less tolerant cultivar, the mRNA level declines despite maintaining the plants at 4°C. Southern blot analysis indicates that the differential expression in the less tolerant genotype is not due to a different genomic organization or gene copy number. The mRNA was specifically localized in leaf tissues and increased several-fold during the greening at 4°C. Furthermore, this gene is not induced in callus cultures acclimated in the absence or presence of light. This suggests that the full expression of this gene is dependent on organized leaf tissue. The expression of this gene was not affected by ABA, drought, heat shock, salinity, wounding or anaerobiosis, demonstrating that it is specifically induced by low temperature. The Wcs19 mRNA is preferentially expressed in tolerant Gramineae species.

Search behavior of dogs ( Canis familiaris ) in invisible displacement problems

Abstract: Gagnon and Dore (1992) showed that domestic dogs are able to solve a Piagetian object permanence task called the invisible displacement problem. A toy is hidden in a container which is moved behind a screen where the toy is removed and left. Dogs make more errors in these problems than they do in visible displacement tests, in which the object is hidden directly behind the target screen. In Experiment 1, we examined components of the standard procedure of invisible displacements that may make encoding or retention of the hiding location more difficult than it is in visible displacements. In Experiment 2, we compared dogs’ performances in visible and invisible displacement problems when delays of 0, 10, and 20 sec were introduced between the object’s final disappearance and the subject’s release. The results revealed that dogs’ poorer performance in invisible displacement tests is related to the complex sequence of events that have to be encoded or remembered as well as to a difficulty in representing the position change that is signaled, but not directly perceived.

The relative importance of biological and chemical processes in the release of phosphorus from a highly organic sediment

Abstract: Bacteria can play an important role in the process of anaerobic phosphorus release: they can act as a direct source of orthophosphates, or as a catalyst of iron hydroxyde reduction. We studied their influence on phosphorus release from highly organic sediments of a Canadian shield lake. Phosphorus and iron release were measured under aerobic and anaerobic conditions, with or without sterilization, and at different pH. We measured also the abundance and activity of bacteria in sediments. The increased P release after sterilization can be explained by cell lysis. Compared to sterilization, changing oxygen concentrations or acidification had little or no effect on P release. In these sediments, phosphorus and iron movements were independent. Most of the total dissolved iron seemed to be linked to humic acids, but not phosphorus.