Showing papers by "Université de Montréal published in 1986"

Metric and Euclidean properties of dissimilarity coefficients

Abstract: We assemble here properties of certain dissimilarity coefficients and are specially concerned with their metric and Euclidean status. No attempt is made to be exhaustive as far as coefficients are concerned, but certain mathematical results that we have found useful are presented and should help establish similar properties for other coefficients. The response to different types of data is investigated, leading to guidance on the choice of an appropriate coefficient.

Chief executive personality and corporate strategy and structure in small firms

Abstract: An empirical investigation of 97 firms was conducted to determine the relationships that three aspects of the chief executive's CEO's personality have with the strategies, structures, decision making methods and performance of their firms. CEO flexibility was associated with niche strategies, simple, informal structures, and intuitive, risk-embracing decision making. CEO need for achievement was related to broadly focussed, marketing-oriented strategies, formal and sophisticated structures, and proactive, analytical decision making. Executives with an internal locus of control pursued more product innovation, were more future oriented, and tailored their approaches to the circumstances facing their firms. The relationships between personality and organizational characteristics were found to be by far the strongest in small firms and also somewhat more significant in dynamic environments. Flexibility and locus of control related to corporate performance under certain conditions; need for achievement did not.

Porter's (1980) Generic Strategies and Performance: An Empirical Examination with American Data Part I: Testing Porter

Abstract: Porter's (1980) three generic strategies have received a great deal of attention recently in the literature on strategic management. In this, the first of two papers, we employ methods of taxonomy on the PIMS data base of consumer durable business units to determine whether Porter's differentiation, cost leadership and focus types occur with any degree of regularity. Then, in a sequel paper to appear in O.S. we examine whether the types differ among each other and between types not displaying differentiation or cost leadership in their growth and ROI performance.

Effects of a selective 5-HT reuptake blocker, citalopram, on the sensitivity of 5-HT autoreceptors: electrophysiological studies in the rat brain.

Abstract: Citalopram (CIT), is a selective serotonin (5-HT) reuptake blocker and a clinically effective antidepressant. The present electrophysiological studies were undertaken to investigate in vivo the acute and long-term effects of CIT administration on 5-HT neurotransmission. In a first series of experiments, a single dose of CIT (0.05–0.5 mg/kg) was administered intravenously to naive rats while recording the activity of a 5-HT-containing neuron in the nucleus raphe dorsalis. A dose-response relationship of the inhibitory effect of CIT on the firing activity of 5-HT neurons was obtained with an ED50 of 0.23±0.03 mg/kg. In a second series of experiments, rats were treated with CIT (20 mg/kg/day, i.p.) for 2, 7 and 14 days. In rats treated for 2 days, there was a marked reduction in the firing activity of 5-HT neurons in the nucleus raphe dorsalis; there was a partial recovery after 7 days and a complete recovery after 14 days of treatment. The response of 5-HT neurons to intravenously administered LSD was decreased in rats treated for 14 days with CIT, indicating a desensitization of the somatodendritic 5-HT autoreceptor. In a third series of experiments, carried out in rats treated with CIT (20 mg/kg/day, i.p.) for 14 days, the suppression of firing activity of CA3 hippocampal pyramidal neurons produced by microiontophoretically-applied 5-HT and by the electrical activation of the ascending 5-HT pathway was measured. Long-term treatment with CIT did not modify the responsiveness of these neurons to microiontophoretically-applied 5-HT; however, the effect of the electrical activation of the ascending 5-HT pathway on these same neurons was enhanced. To determine if 5-HT reuptake blockade could be responsible for this enhancement, CIT (1 mg/kg) was injected intravenously in naive rats while stimulating the ascending 5-HT pathway; it failed to modify the effectiveness of the stimulation. To assess the involvement of the 5-HT terminal autoreceptor, methiothepin, a 5-HT autoreceptor antagonist, was injected intravenously (1 mg/kg) in naive rats and in rats treated for 14 days with CIT while stimulating the ascending 5-HT pathway. Methiothepin enhanced the effect of the stimulation in naive rats but failed to do so in the CIT-treated rats. It is concluded that long-term CIT treatment enhances 5-HT neurotransmission by desensitizing both the somatodendritic and terminal 5-HT autoreceptors.

A Dynamic Programming Solution of the Large-Scale Single-Vehicle Dial-A-Ride Problem with Time Windows

Abstract: SYNOPTIC ABSTRACTThe single-vehicle dial-a-ride problem with time window constraints for both pick-up and delivery locations, and precedence and capacity constraints, is solved using a forward dynamic programming algorithm. The total distance is minimized. The development of criteria for the elimination of infeasible states results in solution times which increase linearly with problem size.

Multicommodity, multimode freight transportation: A general modeling and algorithmic framework for the service network design problem

Abstract: We examine the freight transportation problem which occurs when the same authority controls and plans both the supply of transportation services (modes, routes, frequencies for the services and classification, consolidation, transfer policies for terminals) and the routing of freight. We present a general modeling framework, based on a network optimization model, which may be used to assist and enhance the tactical and strategic planning process for such a system. The problem is solved by means of an algorithm, described in some detail, based on decomposition and column generation principles. We also present detailed results on the behaviour and performance of the algorithm, as observed during experimentation with a specific rail application.

Some comments of Wolfe's `away step'

Abstract: We give a detailed proof, under slightly weaker conditions on the objective function, that a modified Frank-Wolfe algorithm based on Wolfe's ‘away step’ strategy can achieve geometric convergence, provided a strict complementarity assumption holds.

Network design problem with congestion effects: A case of bilevel programming

Abstract: Recently much attention has been focused on multilevel programming, a branch of mathematical programming that can be viewed either as a generalization of min-max problems or as a particular class of Stackelberg games with continuous variables The network design problem with continuous decision variables representing link capacities can be cast into such a framework We first give a formal description of the problem and then develop various suboptimal procedures to solve it Worst-case behaviour results concerning the heuristics, as well as numerical results on a small network, are presented

Applied physiology of swimming.

Abstract: Scientific research in swimming over the past 10 to 15 years has been oriented toward multiple aspects that relate to applied and basic physiology, metabolism, biochemistry, and endocrinology. This review considers recent findings on: 1) specific physical characteristics of swimmers; 2) the energetics of swimming; 3) the evaluation of aerobic fitness in swimming; and 4) some metabolic and hormonal aspects related to swimmers. Firstly, the age of finalists in Olympic swimming is not much different from that of the participants from other sports. They are taller and heavier than a reference population of the same age. The height bias in swimming may be the reason for lack of success from some Asian and African countries. Experimental data point toward greater leanness, particularly in female swimmers, than was seen 10 years ago. Overall, female swimmers present a range of 14 to 19% body fat whereas males are much lower (5 to 10%). Secondly, the relationship between O2 uptake and crawl swimming velocity (at training and competitive speeds) is thought to be linear. The energy cost varies between strokes with a dichotomy between the 2 symmetrical and the 2 asymmetrical strokes. Energy expenditure in swimming is represented by the sum of the cost of translational motion (drag) and maintenance of horizontal motion (gravity). The cost of the latter decreases as speed increases. Examination of the question of size-associated effects on the cost of swimming using Huxley's allometric equation (Y = axb) shows an almost direct relationship with passive drag. Expressing energy cost in litres of O2/m/kg is proposed as a better index of technical swimming ability than the traditional expression of VO2/distance in L/km. Thirdly, maximal direct conventional techniques used to evaluate maximal oxygen consumption (VO2 max) in swimming include free swimming, tethered swimming, and flume swimming. Despite the individual peculiarities of each method, with similar experimental conditions similar results for VO2 max will be found. Free swimming (unimpeded) using the backward extrapolation method will, however, lead to reliable and valid results obtained in a condition that is closer to the competitive situation than with a direct test. A maximal indirect field-test has been recently made available. This test can predict VO2 max with an acceptable accuracy (r = 0.877), and provides a mean to evaluate the functional maximal aerobic power in swimming which corresponds to the maximal aerobic swimming velocity.(ABSTRACT TRUNCATED AT 400 WORDS)

Self-efficacy, outcome, and attrition in a weight-reduction program.

Abstract: The utility and validity of Bandura's self-efficacy construct was evaluated in a study involving 62 volunteer overweight women. Pretreatment, posttreatment, and follow-up assessments of self-efficacy and weight loss were obtained in the context of a behaviorally oriented weight-reduction program. It was predicted that (a) weight loss would be related to enhancement in personal efficacy, (b) posttreatment efficacy would be a significant and more accurate predictor of weight loss during follow-up intervals than posttreatment weight loss, and (c) self-efficacy would be related to attrition whereas weight loss would not. Results indicate a significant relationship between weight change and personal efficacy during the follow-up intervals. In accord with Bandura's theory, efficacy expectations predicted outcome during the 6-week and 6-month follow-up intervals, whereas posttreatment weight loss was unrelated to later outcome. In addition, completers had a substantially higher level of personal efficacy than dropouts over treatment and, to a lesser extent, over the follow-up period. Some procedural considerations regarding the assessment of personal efficacy are raised, and the relationship between the cognitively based constructs of goal choice and self-efficacy and task performance are discussed. Finally, given the nature and variability of weight-reduction efforts and the overall time span of the study, it is concluded that results attest to the validity and utility of the self-efficacy construct in predicting behavioral persistence and level of behavioral change.

Time-resolved spectroscopy of the visible emission band in strontium titanate

Abstract: The luminescence spectrum of ${\mathrm{SrTiO}}_{3}$ from 1.6 to 3.2 eV has been studied as a function of time elapsed after excitation. A broad emission band with maximum intensity at 2.44 eV can be observed. The shape of this band, including some fine structure, can be reproduced by the Huang-Rhys model for excitation-lattice interaction. A vibron energy \ensuremath{\Elzxh}\ensuremath{\Omega}=88 meV and a Huang-Rhys factor ${S}_{0}$\ensuremath{\simeq}6 are deduced. It is shown that those values are consistent with what is required for exciton self-trapping. The luminescence intensity has been followed for times between 100 ns and 10 ms. The decay curves indicate that two recombination processes are involved. We associate the first one with self-trapped excitons interacting with acoustic phonons and the second with the retarded formation of self-trapped excitons from localized electrons and holes. The emission appears to be quenched by a nonradiative recombination channel whose activation energy is 0.07 eV.

Porter's (1980) Generic Strategies and Performance: An Empirical Examination with American Data: Part II: Performance Implications

Abstract: In Part I of this paper, published in O.S. 7/1, we compared the strategic clusters that emerged from a taxonomy of consumer durable businesses to three strategies suggested by Porter (1980). We discovered clusters that pursued combinations of Porter's differentiation and cost leadership strategies, and also those that did not. The purpose of this paper is to compare the performance of these groups of clusters, discuss the differences in strategic behaviour among them that may explain performance, and elicit some normative implications.

Algorithm 647: Implementation and Relative Efficiency of Quasirandom Sequence Generators

Abstract: Whereas our recommendations in Section 3.4 for selecting generators of quasirandom sequences are consistent with our empirical results on accuracy and speed reported in Sections 3.1-3.3, the:y are based more on error bounds and theoretical running times discussed in Sections 1.1 and 1.2, respectively. Sections 1.3 and 1.4 point out why commonly used alternatives to quasirandom sequences are inferior. We describe implementations of the generators in Section 2, which could be skimmed on first reading. Section 4 lists important, suggestive, and nonsmooth applications.

Tailoring Benders decomposition for uncapacitated network design

Abstract: Because of its imbedded network flow structure, the generic network design problem is an attractive candidate for integer programming decomposition. This paper studies the application and acceleration of Benders decomposition for uncapacitated models from this problem class and illustrates the potential flexibility of the Benders solution strategy. In particular, it (i) shows that several lower bounding inequalities from the literature can be derived as Benders cuts; and (ii) introduces new Benders cuts for the network design problem.

The tectonic evolution of the Abitibi greenstone belt of Canada

Abstract: Based on structural, geochemical, sedimentological and geochronological studies, we have formulated a model for the evolution of the late Archaean Abitibi greenstone belt of the Superior Province of Canada. The southern volcanic zone (SVZ) of the belt is dominated by komatiitic to tholeiitic volcanic plateaux and large, bimodal, mafic-felsic volcanic centres. These volcanic rocks were erupted between approximately 2710 Ma and 2700 Ma in a series of rift basins formed as a result of wrench-fault tectonics.The SVZ superimposes an older volcanic terrane which is characterized in the northern volcanic zone (NVZ) of the Abitibi belt and is approximately 2720 Ma or older. The NVZ comprises basaltic to andesitic and dacitic subaqueous massive volcanics which are cored by comagmatic sill complexes and layered mafic-anorthositic plutonic complexes. These volcanics are overlain by felsic pyroclastic rocks that were comagmatic with the emplacement of tonalitic plutons at 2717 ±2 Ma.The tectonic model envisages the SVZ to have formed in a series of rift basins which dissected an earlier formed volcanic arc (the NVZ). Analogous rift environments have been postulated for the Hokuroko basin of Japan, the Taupo volcanic zone of New Zealand and the Sumatra and Nicaragua arcs. The difference between rift related ‘submergent’ volcanism in the SVZ and ‘emergent’ volcanism in the NVZ resulted in the contrasting metallogenic styles, the former being characterized by syngenetic massive sulphide deposits, whilst the latter was dominated by epigenetic ‘porphyry-type’ Cu(Au) deposits.

Negative Effects of Competition on Children's Intrinsic Motivation

Abstract: This study examined the effects of competition on intrinsic motivation. Subjects (N = 23) were randomly assigned to conditions of competition or intrinsic-mastery orientation. In the competition condition, subjects were instructed to perform an interesting activity with the explicit goal of “beating” other participants. In the intrinsic-mastery orientation condition, subjects were told to do as well as they could while looking for novel ways to perform the activity. Results showed that subjects in the competition condition displayed less subsequent intrinsic motivation than did mastery-oriented subjects. The present findings corroborate predictions based on cognitive evaluation theory (Deci & Ryan, 1985) that competition can have deleterious consequences on intrinsic motivation.

Is there a 'normal' profile of EMG activity in gait?

Abstract: The aim of the present study was to validate the notion that there is a normal profile for electromyographic (EMG) signals in gait. For eight subjects, surface electrodes were used to record signals over ten strides from the soleus, rectus femoris, biceps femoris, vastus medialis and tibialis anterior muscles. Analyses of EMG linear envelopes, normalised with respect to both time and amplitude, demonstrated that statistically significant differences exist in amplitude of activity across subjects for all muscles, and that within subjects the data were highly repeatable. More importantly, differences in profiles of activity were found especially for the rectus femoris muscle. It was also found that a given muscle from a given subject can present specific profiles, but usually these specificities are averaged out in the pooled between-subject data. Thus limits exist with the use or the notion of a normal profile of EMG for gait.

Nonlinear cost network models in transportation analysis

Abstract: The analysis of transportation phenomena by quantitative approaches naturally gives rise to network models that represent the spatial characteristics of the transport infrastructure. This paper surveys the nonlinear cost models that arise in transportation analysis and points out the principal methods used for their solution in practice. We discuss the network equilibrium problem, the problem of estimating an origin/destination matrix and certain concave cost network flow problems.

The treatment of the restless legs syndrome with clonazepam: a prospective controlled study.

Abstract: The effect of clonazepam on the restless legs syndrome was studied in a group of 6 patients. Following a drug-free period, 3 patients received clonazepam for 4 weeks followed by placebo for 4 weeks thereafter and 3 patients received the same medication and for the same length of time but in reverse order. The effectiveness of the medication was evaluated by means of a self-rating system in which patients assigned a score daily to the degree of discomfort experienced in the previous 24 hours. Three patients improved on clonazepam but 2 of these also improved on placebo. Clonazepam was not shown to be significantly more effective than placebo in the treatment of RLS.

Novel assay and pharmacokinetics of levamisole and p-hydroxylevamisole in human plasma and urine.

Abstract: A new gas chromatographic method was developed for the quantification of levamisole in human plasma and urine, using a nitrogen-phosphorus flame ionization detector. The adsorption of the drug onto glass was prevented by treating the glassware with a siliconizing agent. The sensitivity of the assay was 10 ng ml-1 and as low as 2 ng ml-1 can be detected in plasma. The urinary metabolite p-hydroxylevamisole was analysed by high performance liquid chromatography with ultraviolet detection. The sensitivity of this assay was 0.50 micrograms ml-1. Plasma and urinary concentrations of levamisole were determined in 10 healthy volunteers including seven men and three women following the administration of a single 150 mg dose of levamisole. Levamisole was rapidly absorbed (tmax 1.5 h), giving a peak plasma concentration of 716.7 +/- 217.5 ng ml-1. The plasma elimination half-life of levamisole was 5.6 +/- 2.5 h. Only 3.2 +/- 2.9 per cent of the oral dose was recovered as unchanged drug in the urine, suggesting the importance of clearance of levamisole by routes other than the kidney, and most probably by hepatic metabolism. The urinary concentrations of p-hydroxylevamisole were determined before and after hydrolysis of the urine samples with beta-glucuronidase, and the level of conjugation of the metabolite with glucuronic acid was then estimated. Cumulative recovery of the metabolite accounted for 1.6 +/- 1.1 per cent and 12.4 +/- 5.5 per cent of the oral dose of levamisole before and after hydrolysis, respectively, indicating that p-hydroxylation is a relatively important route of metabolism of levamisole, and that the p-hydroxylated metabolite is excreted mainly in conjugation with glucuronic acid. Except for the absorption rate of levamisole which is approximately twice as rapid in women as in men, there is no marked difference in the pharmacokinetics of levamisole between healthy men and women.

Minimal clones i: the five types

Abstract: Publisher Summary A composition closed set of finitary operations on a fixed universe A containing all projections is a clone. The clones, ordered by inclusion, form an algebraic lattice L . This chapter presents special and extreme clones. For A finite, the coatoms of L , called maximal clones, are important for primality and are fully known. On the other hand, the atoms of L , called minimal clones, have received scant attention and are fully known only for |A| ≦ 3. This is surprising because, contrary to the maximal clones, their study falls more in the traditional fold of universal algebra. For example, every nontrivial operation of a minimal clone generates a variety whose nontrivial members generate minimal clones. Typically, minimal clones are relatively small in the sense of the proportion of their n -ary operations among all n -ary operations and therefore could provide good example of algebras with few polynomials. A minimal clone may satisfy many equations and therefore, minimal clones may lead to interesting albeit particular varieties.

Associations between several sites of cancer and nine organic dusts: results from an hypothesis-generating case-control study in montreal, 1979–1983

Abstract: A multi-cancer site, multi-factor case-control study was undertaken to generate hypotheses about possible occupational carcinogens. Probing interviews were carried out with over 2,000 subjects. All incident cases of 19 sites of cancer in males aged 35-70 and resident in Montreal were eligible. The interview was designed to obtain detailed lifetime job histories, and information on potential confounders. Each job history was reviewed by a team of chemists who translated it into a history of occupational exposures. These occupational exposures were then analyzed as potential risk factors in relation to the sites of cancer included. For each site of cancer analyzed as a case series, controls were selected from among the other cancer sites in the study. This report concerns the associations between sites of cancer for which there were over 100 cases processed (stomach; colorectal, also analyzed by subsites; lung; prostate; bladder; kidney; non-Hodgkin's lymphoma) and nine organic dusts (wood; paper; grain; flour; fabrics; cotton; wool; synthetics; fur). All site-exposure combinations were investigated. The ones that provided the most interesting leads were lung-wood dust (odds ratio (OR) = 1.5), stomach-wood dust (OR = 1.5), colorectal-synthetic fiber (OR = 1.5), bladder-synthetic fiber (OR = 1.8), non-Hodgkin's lymphoma-cotton dust (OR = 1.9), colon-grain dust (OR = 2.6), prostate-grain dust (OR = 2.2), and prostate-paper dust (OR = 2.0). Only the associations with wood dust, synthetic fibers and cotton dust showed some evidence of "dose-response" with duration of exposure. Because it is such a common exposure and appears to increase lung and stomach cancer risks, wood dust may be responsible for a great deal of occupational cancer.