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Showing papers by "Université de Montréal published in 1988"


Journal ArticleDOI
TL;DR: In this article, the authors present a summary of recent work on a new methodology to test for the presence of a unit root in univariate time series models, which is quite general.

2,686 citations


Journal ArticleDOI
TL;DR: A maximal multistage 20 m shuttle run test was designed to determine the maximal aerobic power of schoolchildren, healthy adults attending fitness class and athletes performing in sports with frequent stops and starts, indicating that the same equation could be used keeping age constant at 18.
Abstract: A maximal multistage 20 m shuttle run test was designed to determine the maximal aerobic power of schoolchildren, healthy adults attending fitness class and athletes performing in sports with frequent stops and starts (e.g. basketball, fencing and so on). Subjects run back and forth on a 20 m course and must touch the 20 m line; at the same time a sound signal is emitted from a prerecorded tape. Frequency of the sound signals is increased 0.5 km h‐1 each minute from a starting speed of 8.5 km h‐1. When the subject can no longer follow the pace, the last stage number announced is used to predict maximal oxygen uptake (VO2max) (Y, ml kg‐1 min‐1) from the speed (X, km h‐1) corresponding to that stage (speed = 8 + 0.5 stage no.) and age (A, year): Y=31.025 + 3.238 X ‐ 3.248A + 0.1536.AX, r = 0.71 with 188 boys and girls aged 8–19 years. To obtain this regression, the test was performed individually. Right upon termination VO2 was measured with four 20 s samples and VO2max was estimated by retroextrap...

2,197 citations


Journal ArticleDOI
TL;DR: This article investigated the relationships of Porter's business strategies to the structures and environments of undiversified firms and showed that strategies must be matched with complementary strategies. But they did not consider the relationship between the two.
Abstract: This study investigated the relationships of Porter's business strategies to the structures and environments of undiversified firms. It was shown that strategies must be matched with complementary ...

1,223 citations


Journal ArticleDOI
TL;DR: It is compared empirically accuracy and speed of low-discrepancy sequence generators of Sobol' and Faure to find out which are more useful for multidimensional integration and global optimization.
Abstract: We compare empirically accuracy and speed of low-discrepancy sequence generators of Sobol' and Faure. These generators are useful for multidimensional integration and global optimization. We discuss our implementation of the Sobol' generator.

802 citations


01 Jan 1988
TL;DR: To deeply understand the lack of usefulness of the above cryptmystems in the case that messages are intended for (or are originating from) a group of people, let u s now nevertheless attempt to use these systems.
Abstract: Messages are frequently addressed to a group of people, e.g., board of directors. Conventional and public key systems (in the sense of Diffie and Hellman [4]) are not adapted when messages are intended for a group instead of for an individual. To deeply understand the lack of usefulness of the above cryptmystems in the case that messages are intended for (or are originating from) a group of people, let u s now nevertheless attempt to use these systems. When conventional and public key systems are used to protect privacy, the legitimate receiver(s) has (have) to know the secret key to decrypt. This means that, a first solution could be, to send the message to dl members of the group, e.g., using their public keys. A second is that the secret key is known to all membexs and that the message is sent only once. All other solutions using a conventional or public key system, are combinations of the above two solutions. We now explain briefly why these two obvious solutions are not adapted to security needs specific to the protection of information intended for groups.

418 citations


Journal ArticleDOI
TL;DR: A graph-theoretic framework for large scale transit networks and new insight into the equilibrium traffic assignment methodology is provided and computational techniques for shortest hyperpaths suggested.

387 citations


Journal ArticleDOI
01 Jan 1988-Infor
TL;DR: An efficient generalized permanent labelling algorithm is presented based on the definition of the concept of a generalized bucket and on a specific order of handling the labels to solve the shortest path problem with time windows.
Abstract: The shortest path problem with time windows (SPPTW) consists of finding the least cost route between a source and a sink in a network G = (N, A) while respecting specified time windows [ai, bi] at each visited node The duration dij of each arc is restricted to positive values while the cost Cij of each arc (i, j) Є A is unrestrictedThis article presents an efficient generalized permanent labelling algorithm to solve this problem This new algorithm is based on the definition of the concept of a generalized bucket and on a specific order of handling the labels The algorithm runs in pseudo-polynomial time Problems with up to 2500 nodes and 250,000 arcs have heen solved

369 citations


Journal ArticleDOI
TL;DR: This paper presents an in-depth study of the methodology for estimating or updating origin-to-destination trip matrices from traffic counts using a generic traffic assignment map.
Abstract: This paper presents an in-depth study of the methodology for estimating or updating origin-to-destination trip matrices from traffic counts. Following an analysis of the statistical foundation of the estimation and updating problems, various basic approaches are reviewed using a generic traffic assignment map. Computational issues related to specific assignment maps and estimation models for both road and transit networks are then discussed. Finally, additional insight into the relative performance of several estimators is provided by a set of test problems with varying input data.

363 citations


Journal ArticleDOI
TL;DR: Domenico Regoli and colleagues describe how new selective agonists developed have been successfully used in vitro to characterize the responses of peripheral organs to neurokinins, and in vivo to elucidate possible physiological roles of the neurokinin system.

347 citations


Journal ArticleDOI
TL;DR: The detection of this previously unsuspected stromal cell phenotype in non-malignant mammary tissues might help in characterizing the variant morphological aspects designated under the label “fibrocystic disease” and in understanding the biology of pre‐malignant or early malignant lesions of the breast.
Abstract: A mouse monoclonal antibody (MAb) recognizing α-smooth-muscle actin has been used to study smooth-muscle differentiation features in the stromal cells of desmoplastic reactions accompanying mammary tumors. We have studied, by the same immunohistochemical technique, a series of malignant and non-malignant human breast tissues. Cells composing the desmoplastic reaction were found to express α-smooth-muscle actin in all the 11 breast carcinomas examined, whereas no immunostain was demonstrated in the stromal cells of 7 breast tissue samples histologically defined as normal. Three of 9 cases of fibrocystic disease showed a minority of positively stained stromal cells, generally in association with epithelial hyperplasia. All the 7 cases of sclerosing adenosis, 3 of 4 cases of diffuse papillomatosis and all 3 intraductal papillomas exhibited a majority of immunoreactive stromal cells. Numerous stromal cells in 3 of 11 circumscribed fibroadenomas analyzed expressed low amounts of α-smooth-muscle actin. The factor(s) responsible for smooth-muscle differentiation in stromal cells are presently unknown, but the detection of this previously unsuspected stromal cell phenotype in non-malignant mammary tissues might help in characterizing the variant morphological aspects designated under the label “fibrocystic disease” and in understanding the biology of pre-malignant or early malignant lesions of the breast.

329 citations


Journal ArticleDOI
TL;DR: Evidence suggests that even short-latency, largely monosynaptic reflexes show a high degree of modulation during simple human motor activities such as walking and standing, and that the pattern of modulation can be specifically altered for the different functional requirements of each activity.

Journal ArticleDOI
TL;DR: In this paper, a series of LISREL analyses showed that aspects of the strategy-making process and the content of business strategies mediate between organizational context and structure, and that one dimension of context is the context of context.
Abstract: A series of LISREL analyses showed that aspects of the strategy-making process and the content of business strategies mediate between organizational context and structure. One dimension of context,...

Journal ArticleDOI
TL;DR: The most striking deviations from configurational randomness were observed at low nitrogen contents where more than two out of three silicon neighbors of a given nitrogen atom are monohydrogenated.
Abstract: The composition of hydrogenated silicon nitride films produced either by plasma-enhanced chemical-vapor deposition (PECVD) with 0.01\ensuremath{\le}[${\mathrm{NH}}_{3}$]/[${\mathrm{SiH}}_{4}$]\ensuremath{\le}20 in the 220--320-\ifmmode^\circ\else\textdegree\fi{}C temperature range or by low-pressure chemical-vapor deposition at 800 \ifmmode^\circ\else\textdegree\fi{}C was determined by elastic-recoil-detection techniques and compared with the relative and absolute atomic densities deduced from x-ray photoelectron spectroscopy and optical measurements in the infrared (ir) range. The [N]/[Si] ratio of PECVD samples followed a square-root dependence on [${\mathrm{NH}}_{3}$]/[${\mathrm{SiH}}_{4}$] over most of the gas-ratio range. We propose original calibrations of most of the ir-absorption bands observed in these samples over the 600--3600-${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ range, and we derived the experimental bond statistics by assuming complete valence satisfaction. In particular, the oscillator-strength factor of each of the six components of the SiH stretching peak was determined. The detailed statistics of all the hydrogenated configurations established for the first time in such a silicon-based ternary alloy are then compared to those expected to those expected for a random-bonded network. The most striking deviations from configurational randomness were observed at low nitrogen contents where more than two out of three silicon neighbors of a given nitrogen atom are monohydrogenated. Nitrogen atoms are found to have at least one monohydrogenated silicon nearest neighbor in all samples up to [N]/[Si]=1.1. The generality of such a second-neighbor correlation in hydrogenated III-IV amorphous alloys is also discussed.

Journal ArticleDOI
TL;DR: In this article, a forest succession following fire in a forest mosaic of northwestern Quebec has been studied in order to describe the successional pathways using communities of different ages and evaluate convergence of successional pathway and possible effect of fire suppression on the establishment of steady-state communities.
Abstract: Forest succession following fire in a forest mosaic of northwestern Quebec has been studied in order to: (1) describe the successional pathways using communities of different ages and (2) evaluate convergence of successional pathways and possible effect of fire suppression on the establishment of steady-state communities. As a first step, ordination and classification techniques were used in order to remove changes in forest composition which are related to abiotic conditions. Then, ordinations based on tree diameter distributions were used to study shifts in species composition in relation to time since the last fire.

Journal ArticleDOI
TL;DR: Observations support the hypothesis that RLS and PMS are two manifestations of the same central sensorimotor disorder.
Abstract: Six patients with restless legs syndrome (RLS) and periodic movements during sleep (PMS) received placebo or L-dopa in a double-blind study. We recorded patients for 36 consecutive hours in the sleep laboratory during a baseline investigation and at the end of each treatment period. Daily evening questionnaires and a suggested immobilization test (SIT) performed at bedtime on each recording night documented the effect of L-dopa in RLS. A nocturnal EMG recording of the anterior tibialis muscles revealed the effect of L-dopa on PMS. L-Dopa proved effective in treating both RLS and PMS. Although not present in every patient, leg movements recorded during the SIT exhibited a clear periodicity. These observations support the hypothesis that RLS and PMS are two manifestations of the same central sensorimotor disorder.

Journal ArticleDOI
TL;DR: It is demonstrated that chronic intermittent elemental diet effectively reverses growth arrest, while decreasing prednisone requirements and Crohn's disease activity index in pediatric Crohn't disease patients prior to puberty.

Journal ArticleDOI
TL;DR: The proposed algorithm speeds generation of truncated Poisson variates and the computation of expected terminal reward in continuous-time, uniformizable Markov chains and can be used to evaluate formulas involving Poisson probabilities.
Abstract: We propose an algorithm to compute the set of individual (nonnegligible) Poisson probabilities, rigorously bound truncation error, and guarantee no overflow or underflow. Work and space requirements are modest, both proportional to the square root of the Poisson parameter. Our algorithm appears numerically stable. We know no other algorithm with all these (good) features. Our algorithm speeds generation of truncated Poisson variates and the computation of expected terminal reward in continuous-time, uniformizable Markov chains. More generally, our algorithm can be used to evaluate formulas involving Poisson probabilities.

Journal ArticleDOI
TL;DR: A new way of controlling human face animation and synchronizing speech is proposed and a methodology for animating the face of synthetic actors based on three levels: the AMA-procedure level, the expression level and the script level.
Abstract: A new way of controlling human face animation and synchronizing speech is proposed. It is based on the concept of abstract muscle action procedure (AMA procedure). An AMA procedure is a specialized procedure which simulates the specific action of a face muscle. The paper describes the new technique and presents a methodology for animating the face of synthetic actors based on three levels: the AMA-procedure level, the expression level and the script level. The role of multiple tracks is also emphasized. Practical examples are also explained in detail, based on the film Rendez-vous a Montreal with the synthetic actors Marilyn Monroe and Humphrey Bogart

Journal ArticleDOI
TL;DR: In this article, a new approach to crew-pairing problems arising in the context of airline companies is proposed, in which the column generation subproblem is shown to be equivalent to a shortest path problem in an associated graph.

Journal ArticleDOI
TL;DR: Krecker's model (1939) which states that the abundance of invertebrates per unit macrophyte biomass varies with plant species and is higher on plants with finely dissected leaves than on Plants with broad leaves is tested.
Abstract: SUMMARY. 1. We tested Krecker's model (1939) which states that the abundance of invertebrates per unit macrophyte biomass varies with plant species and is higher on plants with finely dissected leaves than on plants with broad leaves. The abundance of invertebrates was measured in thirteen lacustrine macrophyte beds in southern Quebec, Canada. The model was tested for the total abundance of invertebrates and for the abundances of Chironomidae, Cladocera, Cyclopoida, Gastropoda, Hydracarina, Ostracoda and Trichoptera. 2. More epiphytic invertebrates were found on the dissected Myriophyllum spp. than on the broad-leaved Potamogeton amplifolius Tuckerm, P. robbinsii Oakes and Vallisneria americana Michx. (P<0.01). More invertebrates were also found on P. amplifolius than on P. robbinsii or V. americana (P<0.01). The total abundance of invertebrates was not systematically related to the degree of plant dissection. 3. The abundances of Chironomidae, Cladocera, Cyclopoida, Gastropoda, Hydracarina, Ostracoda and Trichoptera varied on different plant species (P<0.01). Contrary to Krecker's hypothesis, however, macrophytes with finely dissected leaves (Ceratophyllum demersum and Myriophyllum spp.) did not in general support more invertebrates per unit plant biomass than plants with large leaves (Potamogeton amplifolius, P. robbinsii and Vallisneria americana).

Journal ArticleDOI
TL;DR: Methods that can be used to explore the spatial structure of ecological data and to include spatial location as a variable in the study of relationships and models are described.
Abstract: Microbial ecologists often obtain data from sampling a piece of geographic space. These are likely to be spatially autocorrelated. Autocorrelation removes degrees of freedom from the usual tests of inferential statistics and can generate spurious correlations among variables, with the consequence that suspected causal relations may not hold. This paper describes methods that can be used to explore the spatial structure of ecological data and to include spatial location as a variable in the study of relationships and models. The relationship between environmental heterotrophic bacteria and phytoplankton, well established in aquatic environments, is re-examined in the Thau brackish lagoon (Mediterranean coast of France). It did not hold for the bacteria growing on bioMCrieux nutrient agar (BNA), which are presumably of continental origin; their spatial gradient can only partly be explained by the particulate organic carbon variable (POC) and not at all by phytoplankton biomass (CHL A), despite the existence of a spurious correlation between BNA and CHL A. The spatial gradient of abundance of heterotrophs growing on marine agar (MA), expected to bc mostly of marine origin, can be entirely explained by POC and CHL A. Different segments of the bacterial community, both reacting positively to variations ofthe particulate organic carbon, may follow partly, or not, variations of phytoplankton biomass. The mode of analysis developed here extends to many other spatially distributed processes in ecology and other fields.

Journal ArticleDOI
TL;DR: Occurrence of BaP adducts in the brain of three whales of this population coincides with the high incidence of tumours, which suggest an important role of industrial contaminants in the recent decrease ofThis population.

Journal ArticleDOI
TL;DR: It is suggested that the motor cortex plays a role in adjusting the flexor muscle activity to the requirements of the locomotor task.


Journal ArticleDOI
TL;DR: A model of the structure of the handicap has been outlined illustrating how spontaneous adjustments can be in themselves sources of disadvantages.
Abstract: Hearing difficulties among noise-exposed workers were investigated by means of an interview. A group of 61 workers from a metal product plant had their hearing tested; 66% had abnormal hearing according to their age. Interviews on hearing problems and on their consequences were conducted at home with the spouses. The interviews were recorded and transcribed, and then treated according to a procedure that combines phenomenological and content analysis. The results were classified into hearing disabilities, disadvantages and adjustments. Listening and communication problems result in extra efforts, anxiety and stress, changes in social activities, isolation in groups and a negative self-image. These problems also affect others, especially the spouse, who take an active part in the spontaneous adjustment to disabilities. A model of the structure of the handicap has been outlined illustrating how spontaneous adjustments can be in themselves sources of disadvantages. Implications for rehabilitation services ar...

Journal ArticleDOI
TL;DR: It is argued that this patient's deficit is not central and not crucially syntactic (at least) at the level of knowledge but seems to disrupt specifically those (automatic?) processes responsible for both retrieval and production of free-standing grammatical morphemes whenever they have to be inserted into phrases and sentences.

Journal ArticleDOI
TL;DR: Results provide new information concerning those components of follicular fluid which may play a role in human sperm capacitation and provide further support for the concept that loss of cholesterol from the sperm plasma membrane is an important component of the capacitation process.
Abstract: The nature of cholesterol-binding proteins acting upon human spermatozoa during in vitro capacitation was determined by measuring the efflux of [3H]cholesterol and of [3H]cholesteryl sulfate from labeled spermatozoa. Efflux of [3H]sterols was stimulated when the labeled gametes were incubated in Ham's F-10 medium supplemented with female serum or follicular fluid. Upon centrifugation of capacitated spermatozoa and application of the supernatant to density-gradient ultracentrifugation for lipoprotein analysis, both [3H]cholesterol and [3H]cholesteryl sulfate were found to be carried by very-low-density lipoproteins (VLDL), low-density lipoproteins (VLDL), high-density lipoproteins (HDL), as well as the albumin fraction (d > 1.21) in serum. When the capacitation medium was supplemented with follicular fluid, the [3H]sterols were bound to HDL's and to the albumin fraction; when the latter fraction was analysed by molecular sieve chromatography, 60–70% of the radioactivity eluted in fractions with a mean molecular weight corresponding to that of human serum albumin. Sperm cholesterol efflux was also stimulated when serum or follicular fluid was added to a simplified medium (50 mM Tris-HCl, 0.56% NaCl, pH 7.8); efflux of [3H]cholesterol from labeled gametes progressed in a time-dependent manner, but was low in the absence of serum components. The [3H]cholesterol/cholesterol ratios were higher in the albumin and HDL fractions, indicating some degree of specificity of these sterol acceptors. It was observed that follicular fluid albumin has a [3H]sterol binding capacity that is 2—3-fold higher than that of serum albumin. Commercial human serum albumin also promoted sperm cholesterol efflux. These results provide new information concerning those components of follicular fluid which may play a role in human sperm capacitation and provide further support for the concept that loss of cholesterol from the sperm plasma membrane is an important component of the capacitation process.


Journal ArticleDOI
TL;DR: The analysis reported here provides, for the first time, an extensive phylogeny of the mitochondrial lineage and shows a high degree of similarity with those based on alternative data sets and/or generated by different techniques.
Abstract: Sequences of small subunit (SSU) and large subunit (LSU) ribosomal RNA genes from archaebacteria, eubacteria, and the nucleus, chloroplasts, and mitochondria of eukaryotes have been compared in order to identify the most conservative positions. Aligned sets of these positions for both SSU and LSU rRNA have been used to generate tree diagrams relating the source organisms/organelles. Branching patterns were evaluated using the statistical bootstrapping technique. The resulting SSU and LSU trees are remarkably congruent and show a high degree of similarity with those based on alternative data sets and/or generated by different techniques. In addition to providing insights into the evolution of prokaryotic and eukaryotic (nuclear) lineages, the analysis reported here provides, for the first time, an extensive phylogeny of the mitochondrial lineage.

Journal ArticleDOI
TL;DR: The ultrastructural features and synaptic relationships of dopamine (DA) axon terminals were examined in the prefrontal cortex of adult rat after immunocytochemical staining with a highly specific polyclonal antiserum directed against DA-glutaraldehyde-lysyl-protein conjugate.