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Showing papers by "McGill University published in 1984"


Journal ArticleDOI
TL;DR: In this paper, the authors studied the flow of an idealized granular material consisting of uniform smooth, but nelastic, spherical particles using statistical methods analogous to those used in the kinetic theory of gases.
Abstract: The flow of an idealized granular material consisting of uniform smooth, but nelastic, spherical particles is studied using statistical methods analogous to those used in the kinetic theory of gases. Two theories are developed: one for the Couette flow of particles having arbitrary coefficients of restitution (inelastic particles) and a second for the general flow of particles with coefficients of restitution near 1 (slightly inelastic particles). The study of inelastic particles in Couette flow follows the method of Savage & Jeffrey (1981) and uses an ad hoc distribution function to describe the collisions between particles. The results of this first analysis are compared with other theories of granular flow, with the Chapman-Enskog dense-gas theory, and with experiments. The theory agrees moderately well with experimental data and it is found that the asymptotic analysis of Jenkins & Savage (1983), which was developed for slightly inelastic particles, surprisingly gives results similar to the first theory even for highly inelastic particles. Therefore the ‘nearly elastic’ approximation is pursued as a second theory using an approach that is closer to the established methods of Chapman-Enskog gas theory. The new approach which determines the collisional distribution functions by a rational approximation scheme, is applicable to general flowfields, not just simple shear. It incorporates kinetic as well as collisional contributions to the constitutive equations for stress and energy flux and is thus appropriate for dilute as well as dense concentrations of solids. When the collisional contributions are dominant, it predicts stresses similar to the first analysis for the simple shear case.

2,631 citations


Journal ArticleDOI
TL;DR: In this paper, a review of recent literature on the corporate life cycle disclosed five common stages: birth, growth, maturity, revival, and decline, and a sample of 161 periods of history from 36 firms were classified into the five life cycle stages using a few attributes deemed central to each.
Abstract: A review of recent literature on the corporate life cycle disclosed five common stages: birth, growth, maturity, revival, and decline. Theorists predicted that each stage would manifest integral complementarities among variables of environment "situation", strategy, structure and decision making methods; that organizational growth and increasing environmental complexity would cause each stage to exhibit certain significant differences from all other stages along these four classes of variables; and that organizations tend to move in a linear progression through the five stages, proceeding sequentially from birth to decline. These contentions were tested by this study. A sample of 161 periods of history from 36 firms were classified into the five life cycle stages using a few attributes deemed central to each. Analyses of variance were performed on 54 variables of strategy, structure, environment and decision making style. The results seemed to support the prevalence of complementarities among variables within each stage and the predicted inter-stage differences. They did not, however, show that organizations went through the stages in the same sequence.

1,337 citations


Journal ArticleDOI
TL;DR: In this paper, the role of the strain and strain rate gradients in raising the apparent torsion peak strain ep above the ep values obtained from homogeneous tension or compression testing is clarified.

917 citations


Journal ArticleDOI
TL;DR: This paper examined how irregularities in spelling or in the correspondence between spelling and sound influence two reading tasks, naming and lexical decision, and found that irregular spelling has separate effects on recognition.

664 citations


Journal ArticleDOI
TL;DR: The results indicate that only associative and semantic priming facilitate the decoding of a target; the other effects are postlexical.
Abstract: The context in which a word occurs could influence either the actual decoding of the word or a postrecognition judgment of the relatedness of word and context. In this research, we investigated the loci of contextual effects that occur in lexical priming, when prime and target words are related along different dimensions. Both lexical decision and naming tasks were used because previous research had suggested that they are differentially sensitive to postlexical processing. Semantic and associative priming occurred with both tasks. Other facilitative contextual effects, due to syntactic relations between words, backward associations, or changes in the proportion of related items, occurred only with the lexical decision task. The results indicate that only associative and semantic priming facilitate the decoding of a target; the other effects are postlexical. The results are related to the different demands of the naming and lexical decision tasks, and to current models of word recognition.

589 citations


Journal ArticleDOI
TL;DR: Rhizopus arrhizus biomass was found to absorb a variety of different metal cations and anions but did not absorb alkali metal ions, and it is proposed that the uptake mechanism involves electrostatic attraction to positively charged functional groups.
Abstract: Rhizopus arrhizus biomass was found to absorb a variety of different metal cations and anions but did not absorb alkali metal ions. The amount of uptake of the cations was directly related to ionic radii of La3+, Mn2+, Cu2+, Zn2+, Cd2+, Ba2+, Hg2+, Pb2+, UO22+, and Ag+. The uptake of all the cations is consistent with absorption of the metals by sites in the biomass containing phosphate, carboxylate, and other functional groups. The uptake of the molybdate and vanadate anions was strongly pH dependent, and it is proposed that the uptake mechanism involves electrostatic attraction to positively charged functional groups.

518 citations


Journal ArticleDOI
TL;DR: The results suggest that faces have both component and configural properties and lend themselves to different processing strategies that are not mutually exclusive and can unfold simultaneously.
Abstract: The nature of the processes underlying face perception was examined in two different paradigms using the same set of stimuli varying on three dimensions of two values each. In a simultaneous matching task, both latencies and errors were found to decrease as the number of differences between stimuli increased. Regression analyses showed that the manipulated features interactively contributed to these variations when the faces were presented in their normal upright orientation, whereas no evidence of an interactive processing was found when the faces were inverted. A multidimensional scaling analysis of dissimilarity judgements between pairs of different upright faces revealed that the overall impression of a face was not simply the sum of subimpressions, and that a configuration typical of each face emerged from the relationship among their particular features, giving each face its individuality. The results suggest that faces have both component and configural properties and lend themselves to different processing strategies that are not mutually exclusive and can unfold simultaneously. Some implications of these results for current research on face perception and recognition are outlined.

499 citations


Journal ArticleDOI
C. Tome1, G.R. Canova1, U.F. Kocks1, N. Christodoulou1, John J. Jonas1 
TL;DR: In this article, the validity of using an equivalence criterion to describe the plastic properties of polycrystals at large strains is addressed from the point of view of the microscopic properties of the constituent grains.

497 citations


Journal ArticleDOI
Charles Taylor1
TL;DR: In traditional ethics, ordinary life is overshadowed by what are identified as higher activities for some, the citizen life for others as discussed by the authors, and in mediaeval Catholicism something like this overshadowing of ordinary lay life occurs relative to the dedicated life of priestly or monastic celibacy.
Abstract: In traditional ethics, ordinary life is overshadowed by what are identified as higher activities—contemplation for some, the citizen life for others. And in mediaeval Catholicism something like this overshadowing of ordinary lay life occurs relative to the dedicated life of priestly or monastic celibacy. Think for instance of the growth of the new understanding of the companionate marriage in the seventeenth-eighteenth centuries, the growing sense of the importance of emotional fulfillment in marriage—indeed the whole modern sense that one’s feelings are a key to the good life. The classical understanding of power turned on the notions of sovereignty and law. Much of early modern thought was taken up with definitions of sovereignty and legitimacy. The relation of domination within man, which is part of a stance of domination toward nature in general, cannot help engendering a domination of man by man.

481 citations


Journal ArticleDOI
01 Jan 1984-Nature
TL;DR: It is reported here that long spinal axons of primary sensory neurones are 100 times more likely to regenerate into peripheral nerve grafts if their peripheral axons are also cut.
Abstract: The success of peripheral and fetal neural tissue in promoting outgrowth of axons from the adult mammalian central nervous system has tended to focus attention on local interactions between extending axons and their environment. The contribution to axon regeneration of biochemical and morphological changes in injured neurones is more difficult to evaluate. We report here that long spinal axons of primary sensory neurones are 100 times more likely to regenerate into peripheral nerve grafts if their peripheral axons are also cut. Regenerative behaviour at the axon tip seems to be strongly influenced by inducible events in the nerve cell.

474 citations


Book ChapterDOI
TL;DR: In this article, the authors present a review of the classical papers of Bagnold and a discussion of the various modes and regimes of granular flow, such as vertical channels and inclined chutes.
Abstract: Publisher Summary This chapter discusses the mechanics of rapid granular flows. A “bulk solid” or “granular fluid” may be defined as an assembly of discrete solid components dispersed in a fluid, such that the solid constituents are in contact or near contact with their neighbors. Bulk solids comprise one member of a larger class of two-phase disperse systems made up of solids and fluids; dilute suspensions form another related member, which is more familiar to fluid mechanicists. The section II of this chapter presents a review of the classical papers of Bagnold and a discussion of the various modes and regimes of granular flow. A dimensional analysis provides a physical background to the detailed review of experimental and theoretical work that follows. Section III reviews flows in vertical channels and inclined chutes; it deals primarily with experimental observations of stress, velocity, and bulk-density fields. Laboratory devices and viscometric type experiments designed to determine the stress-strain-rate behavior are discussed in Section IV. Quasi-static testers, suspension viscometers, and high-shear-rate devices are described. Section V reviews theories for high-shear-rate granular flows. It includes continuum models as well as analytical and numerical microstructural models that consider the details of collisions between particles.

Proceedings ArticleDOI
02 Apr 1984
TL;DR: The class of data structures generated by this scheme includes a type of kd tree whose balance can be efficiently maintained, a multidimensional Btree which is simpler than previously proposed generalizations, and some previously reported data structures for range searching.
Abstract: By interleaving the bits of the binary representations of the attribute values in a tuple, an integer corresponding to the tuple is created. A set of these integers represents a relation. The usual ordering of these integers corresponds to an ordering of multidimensional data that allows the use of conventional file organizations, such as Btrees, in the efficient processing of multidimensional queries (e.g. range queries). The class of data structures generated by this scheme includes a type of kd tree whose balance can be efficiently maintained, a multidimensional Btree which is simpler than previously proposed generalizations, and some previously reported data structures for range searching. All of the data structures in this class also support the efficient implementation of the set operations.

Journal ArticleDOI
TL;DR: In this paper, the results obtained during rapid shearing of several dry, coarse, granular materials in an annular shear cell were described, and the main purpose of the tests was to obtain information that could be used to guide the theoretical development of constitutive equations suitable for the rapid flow of cohesionless bulk solids at low stress levels.
Abstract: Experimental results obtained during rapid shearing of several dry, coarse, granular materials in an annular shear cell are described. The main purpose of the tests was to obtain information that could be used to guide the theoretical development of constitutive equations suitable for the rapid flow of cohesionless bulk solids at low stress levels. The shear-cell apparatus consists of two concentric disk assemblies mounted on a fixed shaft. Granular material was contained in an annular trough in the bottom disk and capped by a lipped annular ring on the top disk. The bottom disk can be rotated at specified rates, while the top disk is loaded vertically and is restrained from rotating by a torque arm connected to a force transducer. The apparatus was thus designed to determine the shear and normal stresses as functions of solids volume fraction and shear rate.Tests were performed with spherical glass and polystyrene beads of nearly uniform diameters, spherical polystyrene beads having a bimodal size distribution and with angular particles of crushed walnut shells. The particles ranged from about ½ to 2 mm in size. At the lower concentrations and high shear rates the stresses are generated primarily by collisional transfer of momentum and energy. Under these conditions, both normal and shear stresses were found to be proportional to the particle density, and the squares of the shear rate and particle diameter. At higher concentrations and lower shear rates, dry friction between particles becomes increasingly important, and the stresses are proportional to the shear rate raised to a power less than two. All tests showed strong increases in stresses with increases in solids concentrations. The ratio of shear to normal stresses showed only a weak dependence upon shear rate, but it increased with decreasing concentration. At the very highest concentrations with narrow shear gaps, finite-particle-size effects became dominant and differences in stresses of as much as an order of magnitude were observed for the same shear rate and solids concentration.

Journal ArticleDOI
TL;DR: In patients with severe and persistent iron deficiency anemia who were found to have gastric antral vascular ectasia, endoscopic biopsy specimens showed dilatation of mucosal capillaries, with focal thrombosis and fibromuscular hyperplasia of the lamina propria.

Journal ArticleDOI
TL;DR: In this paper, the frontal lobe lesion was found to have specific cognitive deficits, such as a reduced output on fluency tasks, faulty regulation of behaviour of external cues, and impaired organization and monitoring of material to be remembered, and the subject's own responses.

Journal ArticleDOI
TL;DR: A new solution to the image segmentation problem that is based on the design of a rule-based expert system that dynamically alters the processing strategy is presented.
Abstract: A major problem in robotic vision is the segmentation of images of natural scenes in order to understand their content. This paper presents a new solution to the image segmentation problem that is based on the design of a rule-based expert system. General knowledge about low level properties of processes employ the rules to segment the image into uniform regions and connected lines. In addition to the knowledge rules, a set of control rules are also employed. These include metarules that embody inferences about the order in which the knowledge rules are matched. They also incorporate focus of attention rules that determine the path of processing within the image. Furthermore, an additional set of higher level rules dynamically alters the processing strategy. This paper discusses the structure and content of the knowledge and control rules for image segmentation.

Journal ArticleDOI
TL;DR: In this paper, a conceptual model is developed to assist multinational corporation managers in selecting appropriate control systems and determining the extent of delegation to be provided to subsidiary managers, and the authors suggest directions for future research.
Abstract: The paper has 2 major objectives: first, to identify control and delegation issues confronting multinational corporation managers; second, to develop a conceptual model to assist multinational corporation managers in selecting appropriate control systems and determining the extent of delegation to be provided to subsidiary managers. Finally, the paper suggests directions for future research.

Journal ArticleDOI
Elliot Block1
TL;DR: Samples of blood plasma showed that cows consuming the anionic diet maintained calcium and phosphorus through parturition, whereas cows consume the cationic diet decreased in these minerals around calving, and hydroxyproline was higher for cowsconsuming the anionics during the peripartal period.

Journal ArticleDOI
TL;DR: Patients' perceptions of increased intrusiveness, and their perceptions of limited control over eleven life dimensions, each correlated significantly and uniquely with increased negative and decreased positive mood, suggesting that each of these two factors contributes importantly and independently to patients' distress.
Abstract: The emotional impact of the intrusiveness of illness and patients' reduced control over several aspects of life were examined in the context of end-stage renal disease. A sample of thirty-five hemo...

Journal ArticleDOI
TL;DR: Multiple regression analysis of published zooplankton filtering and feeding rates yielded separate regression equations for cladocerans, marine Calanoid copepods, and all zoopLankton, which suggest possible mechanisms of feeding limitation and provide a heuristic framework for the design of experimental analyses of zoopalankton feeding in marine and freshwater systems.
Abstract: Multiple regression analysis of published zooplankton filtering and feeding rates yielded separate regression equations for cladocerans, marine Calanoid copepods, and all zooplankton. Ingestion rate was found to increase significantly with animal size, food concentration, and temperature. Filtering rate also increased with animal size and temperature, but declined as food concentration increased. The analysis suggests a difference in particle size preference between cladocerans and copepods. Experimental conditions such as crowding and duration also significantly affected filtering and feeding rates. The regression models allow examination of differences and similarities among zooplankton taxa, functional response, particle size selection, energy allocation, and threshold food concentration. The statistical models describe suspension feeding more precisely than either average literature values or verbal descriptions of trend. The results also suggest possible mechanisms of feeding limitation and provide a heuristic framework for the design of experimental analyses of zooplankton feeding in marine and freshwater systems.

Journal ArticleDOI
TL;DR: Under the conditions of these experiments, the distance from cell body to injury appeared to be an important determinant of axonal regeneration, and there was no obvious example of a fibre tract in the lateral spinal columns from which axons failed to regenerate nor fromWhich axons regenerated exceptionally well.
Abstract: To investigate regeneration of long spinal axons, the right lateral column of the rat spinal cord was cut at high cervical, low cervical, midthoracic or lumbar level, and one end of an autologous sciatic nerve segment was grafted to the spinal cord at the site of incision. Three to six months after operation, the origin of axons in the grafts was traced retrogradely with horseradish peroxidase injected into the grafts and, in some cases, anterogradely with radioautography of tritiated amino acids injected into the brainstem. Axons from each of the major lateral spinal tracts arising in the brainstem as well as axons ascending from the lower spinal cord succeeded in growing into low cervical grafts. However, long descending axons rarely regenerated after midthoracic or lumbar injury; axons ascending from lumbar segments of the spinal cord usually failed to enter high cervical grafts. Differences in axonal regrowth at the four segmental levels were not simply attributable to dwindling of axonal number in fibre tracts. Axonal regeneration from Clarke's column or the red nucleus was observed only with lesions causing atrophy of many neurons. There was no obvious example of a fibre tract in the lateral spinal columns from which axons failed to regenerate nor from which axons regenerated exceptionally well. Under the conditions of these experiments, the distance from cell body to injury appeared to be an important determinant of axonal regeneration.

Journal ArticleDOI
TL;DR: The kinetic data suggest that planktonic bacteria are unlikely to be limited by phosphorus in situ and are consistent with the hypothesis that the bacteria should be markedly superior competitors at natural phosphate concentrations.
Abstract: Extant physiological and in situ data provide contradictory answers to the question of whether the bacterioplankton can outcompete the phytoplankton for phosphorus at natural concentrations. Two phytoplankton species and three bacterial spccics isolated from the epilimnion of Lake Memphremagog, Quebec, were grown in phosphorus-limited continuous cultures and their abilities to take up and retain phosphorus compared. The algae showed orthophosphate uptake kinetics comparable to those reported elsewhere. In contrast, the specific orthophosphate uptake rates (i.c. uptake per unit cell P) by the bacteria were variable, but much higher than the algal rates at the low P concentrations characteristic of natural waters. Algal and bacterial alkaline phosphatase activities were similar and provided no evidence that the algae could utilize organic P more efficiently than the bacteria. The bacteria showed some tendency to excrete P more readily than the algae but mixed culture experiments indicated that excretion did little to alter the long term partitioning of phosphorus between the algae and the bacteria. The kinetic data suggest that planktonic bacteria are unlikely to be limited by phosphorus in situ. Furthermore, our results are consistent with the hypothesis that the bacteria should bc markedly superior competitors at natural phosphate concentrations.

Journal ArticleDOI
TL;DR: In this paper, two models are given to predict internal phosphorus load (L;,,) in anoxic lakes, i.e., the difference between the observed phosphorus retention and that predicted (Rpred) by a formula that adequately describes phosphorus retention in oxic lakes.
Abstract: Lakes with anoxic hypolimnia (anoxic lakes) have significantly lower values for phosphorus retention than do lakes with aerobic hypolimnia (oxic lakes). This difference may reflect an increased internal phosphorus load from the anoxic hypolimnia. Two models are given to predict internal phosphorus load (L;,,) in such lakes. The first predicts internal load as the difference between the observed phosphorus retention in anoxic lakes and that predicted (Rpred) by a formula that adequately describes phosphorus retention in oxic lakes. The second predicts internal load as the product of an average rate of phosphorus release from anoxic sediments, the surface area of the anoxic sediment, and the period of anoxia. Predictions of the first model compare favorably with 17 observed values of internal load; further data are required to test the second model. These models suggest that mean phosphorus concentration (TP) in anoxic lakes can be predicted in two ways. One can use whole-lake phosphorus budget models which implicilly incorporate internal phosphorus load, because they include a measurement of phosphorus retention. Alternatively, a term to account for the internal load can be added to current models based on external load (L,,,) and predicted retention (I&J, where

Journal ArticleDOI
Ronald Melzack1
01 Aug 1984-Pain
TL;DR: My recent work supports John Bonica's contention that most women suffer severe pain during labor, and wrote the 2‐vol set Principles and Practice of Obstetric Analgesia and Anesthesia, which is an acknowledged modern medical classic.
Abstract: We are all familiar with John Bonica's magnificent contributions to the management and understanding of acute and chronic pain. But some people are not aware that John is also a world authority on obstetrical anesthesia. He developed a special interest in obstetrical problems early in his career, after his wife Emma had a near-disastrous experience with improperly administered ether anesthesia during the birth of their first child. He worked hard at acquiring skill and expertise in administering epidural analgesia, and subsequently organized the first 24-h medical anesthesia service for obstetrics in the United States. After two decades of experience, he wrote the 2-vol set Principles and Practice of Obstetric Analgesia and Anesthesia [4] which is an acknowledged modern medical classic. Every aspect of childbirth is addressed with the same thoughtfulness, insight and meticulous detail that are characteristic of John's books and papers on chronic pain. John has repeatedly argued [5,6] that labor is often extremely painful and that severe, prolonged pain can be dangerous to women with cardiovascular problems and to the fetus whose oxygen supply may be at risk during protracted, complicated deliveries. My recent work supports John's contention that most women suffer severe pain during labor.

Journal ArticleDOI
TL;DR: In this paper, the theory of Sarason is applied to the determination of the optimal weighted sensitivity function and an upper bound on its norm, and the problem of achieving small sensitivity over a specified frequency band is studied.
Abstract: This paper deals with the design of feedback controllers which minimize the H^{\infty} -norm of the sensitivity function, suitably weighted. This approach to the theory of feedback design was introduced by Zames [1] and developed by Zames and Francis [2]. In this paper the theory of Sarason [3] is applied to the determination of the optimal weighted sensitivity function and an upper bound on its norm. The problem of achieving small sensitivity over a specified frequency band is studied, and the effect of nonminimum phase is elucidated. Finally, a method is introduced for handling plant poles and zeros on the imaginary axis.

Journal ArticleDOI
01 Nov 1984-Peptides
TL;DR: Visualization of [125I]ANF binding sites in rat brain by an autoradiographic technique demonstrated that these sites are highly localized in areas such as the olfactory bulb, subfornical organ, area postrema and nucleus tractus solitarius.

Journal ArticleDOI
TL;DR: An economic comparison demonstrated that this biosurfactant could be produced significantly more cheaply than any of the previously reported microbial surfactants.
Abstract: Two types of carbon sources—carbohydrate and vegetable oil—are necessary to obtain large yields of biosurfactant from Torulopsis bombicola ATCC 22214. Most of the surfactant is produced in the late exponential phase of growth. It is possible to grow the yeast on a single carbon source and then add the other type of substrate, after the exponential growth phase, and cause a burst of surfactant production. This product is a mixture of glycolipids. The maximum yield is 70 g liter−1, or 35% of the weight of the substrate used. An economic comparison demonstrated that this biosurfactant could be produced significantly more cheaply than any of the previously reported microbial surfactants.

Journal ArticleDOI
TL;DR: In this paper, the results of the relaxed constraints (RC) theory and of the full constraints (FC) classical theory (Taylor/Bishop and Hill) were compared with those of experiments, and the RC results correspond far better to the experimental textures, which tend towards a unique end orientation.

Book ChapterDOI
TL;DR: In this article, the problem of designing, for a linear multivariable plant, a feedback controller which minimizes the H ∞ -norm of a weighted sensitivity matrix is treated.
Abstract: This paper treats the problem of designing, for a linear multivariable plant, a feedback controller which minimizes the H^{\infty} -norm of a weighted sensitivity matrix. There exists a family of optimal improper feedbacks. This family is determined by application of a theory of Ball and Helton. A method for computing optimal feedbacks is described in detail and a numerical example is included. It is shown that an optimal improper feedback can be approximated by a proper one under certain conditions on the weighting matrices.

Journal ArticleDOI
TL;DR: In this article, the authors derived a model of organization life cycles in three steps: (1) considering relationships of power distribution inside an organization with that around it, a typology of six configurations of organization power is produced; (2) considering intrinsic forces that work within each of these configurations to destroy it, the likely transitions between these configurations are identified; and (3) stringing these transitions together in sequences over time as organizations survive and develop, the model is developed.
Abstract: This paper derives a model of organization life cycles in three steps: (1) by considering relationships of power distribution inside an organization with that around it, a typology of six configurations of organization power is produced; (2) by considering intrinsic forces that work within each of these configurations to destroy it, the likely transitions between these configurations are identified; and (3) by stringing these transitions together in sequences over time as organizations survive and develop, the model is developed. Some implications of such a model in a society of large organizations are addressed briefly in conclusion.