Showing papers by "University of Calgary published in 1983"
TL;DR: In this paper, a semi-empirical model was formulated to correlate the experimental kinetic data, which revealed that the formation kinetics were dependent on the interfacial area, pressure, temperature and degree of supercooling.
611 citations
548 citations
TL;DR: The Peyer's patches of sheep have a number of important anatomical features and functional characteristics which are similar to tissues that have been classified as primary lymphoid organs and there was no evidence of any change in the rate of growth of the PP follicles at birth which could be related to the advent of the first antigens in the gut.
Abstract: The Peyer's patches (PP) of sheep have a number of important anatomical features and functional characteristics which are similar to tissues that have been classified as primary lymphoid organs. The prenatal maturation of PP occurs in the absence of any antigenic stimulus as immunogenic molecules are not normally encountered by the sheep fetus. Primordial PP were first detected in the small intestine of fetal sheep at about 60-days gestation; lymphoid follicles were present by 75-days gestation and vigorous lymphopoiesis was occurring in these follicles by 100 days. From 120-days gestation until birth, at about 150 days, the PP follicles were histologically mature and they had the greatest density of proliferating lymphoid cells found anywhere in the body. The total number of PP and their constituent follicles had developed before birth when there were 25-40 discrete PP in the jejunum and proximal ileum and one single continuous PP in the terminal ileum. There was no evidence of any change in the rate of growth of the PP follicles at birth which could be related to the advent of the first antigens in the gut. The total weight of PP tissue was greater than any other single lymphoid tissue by about 6 weeks after birth weighing around 120 g or about 1.2% of the body weight; about 50-60 g of the PP tissue was calculated to be lymphoid tissue. At this time the ileocecal PP (IPP) extended 2.5 m along the terminal ileum and accounted for about 90% of the total mass of PP. From about 12 weeks after birth the IPP began to involute and only a few PP follicles remained in this region of the intestine by 18 months of age. Follicles in PP in other parts of the small intestine remained and continued to produce lymphocytes throughout the life of the animal. PP contain a number of anatomically and functionally distinct lymphoid compartments that could play different roles in the body's immune defense. Explicit in most theories on the function of PP is the notion that antigenic stimulation is the cause of the lymphopoiesis in the follicles; our results do not support this view. Instead they suggest that the follicles in the PP of sheep may play a role similar to that played by the bursa of Fabricius in birds.
248 citations
TL;DR: In this paper, physically abusive and non-abusive mothers were observed interacting with their preschool aged children in both an unstructured play and a structured task situation, and the findings were discussed in terms of the abusive m...
Abstract: Physically abusive and non‐abusive mothers were observed interacting with their preschool aged children in both an unstructured play and a structured task situation. Mothers also completed several checklists describing their children and themselves. Abusive mothers perceived their children as having significantly more behavioral problems than non‐abusive mothers and although their ratings were about two standard deviations above the normative mean, there were no significant differences in the observed behaviors of abused versus non‐abused children. Abusive mothers were observed to be more directive and controlling of their children, but only for the more stressful task situation in which there were increased demands for performance placed on both mother and child. Abusive mothers reported higher levels of stress related to parenting than non‐abusive mothers, and these reports were correlated with their behavior during both the play and task situations. The findings were discussed in terms of the abusive m...
246 citations
TL;DR: In this article, a wind energy conversion scheme using an induction machine driven by a variable speed wind turbine is described, where a single value capacitor and a thyristor controlled inductor are employed for energy conversion.
Abstract: A wind energy conversion scheme using an induction machine driven by a variable speed wind turbine is described. Excitation control has been obtained by employing a single value capacitor and thyristor controlled inductor. Wind speed cube law is proposed to be followed in loading the induction machine for maximising energy conversion. Performance characteristics of the generation scheme have been evaluated over a wide speed range. Harmonic analysis of the proposed scheme shows that harmonic currents and their associated power loss is negligible.
209 citations
01 Oct 1983
TL;DR: This article reviewed various definitions of entrepreneurship employed by a number of theoretical economists since 1730 and found that three recurring themes emerge from their definitions, namely that entrepreneurship involves: uncertainty and risk, complementary managerial competence, and creative opportunism.
Abstract: This paper reviews various definitions of entrepreneurship employed by a number of theoretical economists since Richard Cantillon (circa 1730). Three recurring themes emerge from their definitions, namely that “entrepreneurship” involves: 1) uncertainty and risk, 2) complementary managerial competence, and 3) creative opportunism. The authors argue that modern definitions of entrepreneurship that exclude any of these three fundamental dimensions are basically incomplete.
187 citations
TL;DR: Chromosomal analysis of 1000 spermatozoa from 33 normal men was performed using in vitro fertilization of zonafree golden hamster eggs and the majority (22/33) of structurally abnormal complements had a chromosome break.
Abstract: Chromosomal analysis of 1000 spermatozoa from 33 normal men was performed using in vitro fertilization of zona-free golden hamster eggs. The frequency of abnormal sperm complements was 8.5%: 5.2% were aneuploid and 3.3% had a structural chromosome abnormality. The frequencies of hyperhaploid (2.4%) and hypohaploid (2.7%) sperm complements were not significantly different and all chromosome groups were represented among the aneuploid complements. The majority (22/33) of structurally abnormal complements had a chromosome break. The percentages of X and Y-bearing sperm were 53.9% and 46.1%, which is significantly different from the expected one to one ratio.
183 citations
01 Dec 1983
TL;DR: In this article, it was shown that the conventional definition of BIBO stability for n-dimensional discrete systems is unnecessarily restrictive for most practical applications, and a new definition of practical-BIBO stability is introduced which is less restrictive, and more relevant for practical applications than the conventional one.
Abstract: It is shown that the conventional definition of BIBO stability for n-dimensional discrete systems is unnecessarily restrictive for most practical applications. The conventional definition permits the input signal to be unbounded in all n dimensions; however, in most practical applications the input signal is unbounded in, at most, one dimension. Based on this, a new definition of practical-BIBO stability is introduced which is less restrictive, and more relevant for practical applications than the conventional one. It is shown that the voltage transfer function of an n-D continuous network, consisting of a reactance 2-port terminated in a resistance, leads to practical-BIBO stable n-D digital filters after bilinear transformation. An example demonstrates the usefulness of the new definition.
177 citations
TL;DR: Glutamate and GABA did not alter receptive field size, although these amino acids did change the threshold and magnitude of the response to tactile stimulation, and no change in modality or submodality properties of any neuron was observed with any of the compounds tested.
160 citations
TL;DR: In vitro gallbladder contractility was studied in an animal model of cholesterol gallstones: Richardson ground squirrels fed either a trace or a 1% wt/wt cholesterol (test) diet to examine the effect of changes in bile lithogenicity on gallbladders muscle function.
128 citations
TL;DR: Results show that all ligaments healed by bridging scar formation rather than true ligament regeneration, which suggests much slower MCL healing than previously reported and probably, therefore, a longer period for potential treatment influence.
TL;DR: In this article, the authors observed hyperactive and normal boys interacting with their siblings in an unstructured play and mother-supervised task situation and found that negative behavior in the hyperactive child/sibling interaction was unrelated to either the sex or ordinal position (younger versus older) of the sibling.
Abstract: Forty‐six hyperactive and normal boys were observed while interacting with their siblings in an unstructured play and mother‐supervised task situation. Few behavioral differences were noted between identified hyperactive children and their reportedly non‐problem siblings with both showing equally high rates of negative behavior. Relative to normal siblings, hyperactive sibling dyads showed significantly higher levels of conflict. Negative behavior in the hyperactive‐child/sibling interaction was unrelated to either the sex or ordinal position (younger versus older) of the sibling. However, hyperactive sibling dyads which included a young hyperactive child showed more negative behavior during the supervised‐task situation relative to hyperactive sibling dyads which included an older hyperactive child. Maternal reports of stress and parenting self‐esteem were related to the hyperactive‐child/sibling interaction. The mothers of hyperactive siblings who interacted more during play reported higher levels of pa...
TL;DR: Cette recherche, faite sur des sujets anxieux ou non, montre que l'anxiete auto-evaluee est significativement plus elevee chez les pairs thangalaisant des symptomes somatiques.
Abstract: Cette recherche, faite sur des sujets anxieux ou non, montre que l'anxiete auto-evaluee est significativement plus elevee que l'anxiete evaluee par les pairs, ceci pour les sujets tres anxieux et presentant des symptomes somatiques
TL;DR: The existence of periodic orbits for Hamiltonian systems at low positive energies can be deduced from the existence of non-degenerate critical points of an averaged Hamiltonian on an associated reduced space as mentioned in this paper.
TL;DR: It is argued that the phenomenon reflects a differential release of the two metabolites from the white muscle of the sole, La − being strictly retained in the muscle for gluconeogenesis in situ, and effects directly opposite those in trout.
Abstract: Chronically cannulated flathead sole were subjected to 10 min of either moderate or exhausting burst exercise and monitored over a 12 h recovery period. Acid-base disturbances were more severe after exhausting exercise, but ionic and haematological changes were the same in the two treatments. Most effects were qualitatively similar to those previously described in severely exercised rainbow trout (Turner, Wood & Clark, 1983). Specific differences are discussed and related to the different external environments sea water vs fresh water), exercise capabilities and ecologies of the two species. The most striking divergence occurred in lactate (La − ) and metabolic proton dynamics. Post-exercise La − levels in white muscle in sole were less than half those in trout but declined much more slowly. In contrast to the situation in trout, muscle [La − ] remained significantly elevated and large muscle to blood La − gradient persisted even after 12 h recovery. Blood [La − ] underwent only minimal elevation ( −1 ), and blood metabolic proton load (ΔH + m) greatly exceeded Δ;La − throughout the recovery period, effects directly opposite those in trout. This observed excess of ΔH + m over ΔLa − in the blood of exercised sole is probably not due to a preferential removal mechanism, because ΔH + m and ΔLa − disappeared from the blood at similar rates after an intra-arterial infusion of lactic acid in resting animals. It is therefore argued that the phenomenon reflects a differential release of the two metabolites from the white muscle of the sole, La − being strictly retained in the muscle for gluconeogenesis in situ .
TL;DR: It is demonstrated that there is a maternal store of histone and actin mRNA in the unfertilized egg but that this mRNA pool is reduced roughly 10-fold on an embryo basis by the mid-two-cell stage.
TL;DR: In this article, a technique for designing an optimal variable structure stabilizer is presented for improving the dynamic stability of power systems by increasing the damping torque of the synchronous machine in the system.
Abstract: A technique for designing an optimal variable structure stabilizer is presented for improving the dynamic stability of power systems by increasing the damping torque of the synchronous machine in the system. The proposed variable structure stabilizer is optimal in the sense of minimizing a quadratic performance index in the sliding mode operation. A characteristic feature of this paper is that a systematic approach based on the linear optimal control theory is developed for the selection of the switching hyperplane of the variable structure stabilizer. The dynamic responses following a step disturbance by digital simulation are obtained by means of three types of controllers: the conventional power system stabilizer, the linear optimal stabilizer and the optimal variable structure stabilizer. Simulation results show that the optimal variable structure stabilizer yields better system dynamic performance than the others in the sense of having larger damping in response to a step disturbance.
TL;DR: In this article, the retention times of double-bond gibberellin isomers were determined using gradient or isocratic elution with methanol-acetic acid 1%.
TL;DR: In this article, a multivariate analysis revealed that subjects trained in structured reminiscence showed significantly greater improvement on the dcpcndent measures than did those trained in unstructured remyniscence.
Abstract: One hundred and sixty:two depressed Caucasian elderly were treatment and control subjects for a therapeutic intervention designed to test the efficacy of structured and unstructured reminiscence training for subjects' depression. Pre-and posttreatment measures of depression, ego-strength and self-assessment ratings were obtained. Consistent with hypotheses, a multivariate analysis revealed that subjects trained in structured reminiscence showed significantly greater improvement on the dcpcndent measures than did subjects trained in unstructured reminiscence. Overall, subjects in both structured and unstructured reminiscence conditions reported more improvement than the no-treatment control subjects. Contents of subjects' reminiscence were factor-analysed for sex differences and yielded four factors with high factor loadings. Results of the factor analysis and the effects of the two forms of reminiscence training were discussed in terms of their implications for the treatment of depression in the elderly.
TL;DR: Forced oscillations of a two-degree-of-freedom autoparametric system with moderately high excitations were studied in this paper, and the approximate results obtained by the method of harmonic balance were found to be satisfactory by comparing with those obtained by numerical integration.
Abstract: Forced oscillations of a two degree-of-freedom autoparametric system are studied with moderately high excitations. The approximate results obtained by the method of harmonic balance are found to be satisfactory by comparing with those obtained by numerical integration. In the primary parametric instability zone, separate regions of stable and unstable harmonic solutions are obtained. In the regions of unstable harmonic solutions, depending on the forcing amplitude and frequency, the solutions may be amplitude modulated or completely nonperiodic. In the latter case the numerical integrations do not converge.
TL;DR: In this paper, the authors studied the problem of gravitationally induced spacetime collapse in the framework of quantum cosmology and found that whether quantum collapse occurs is effectively predetermined, on the classical level, by the choice of time.
Abstract: The problem of gravitationally induced spacetime collapse is studied in the framework of quantum cosmology. We find that whether quantum collapse occurs is effectively predetermined, on the classical level, by the choice of time. The crucial distinction is between "fast" and "slow" times, that is, between times which give rise to complete or incomplete classical evolution, respectively. We conjecture that unitary slow-time quantum dynamics is always nonsingular, while unitary fast-time quantum dynamics inevitably leads to collapse. These contentions are supported by an analysis of the dust-filled Friedmann-Robertson-Walker universes in two choices of time: a cosmic time defined by the velocity potential for the dust and an intrinsic time linked to the expansion. Indeed, these quantum models avoid the classical singularity in the slow matter-time gauge but collapse in the fast geometric-time gauge. We also investigate the qualitatively different forms---unitary and contractive---that the slow-time quantum evolution may take and explore their implications regarding quantum singularity avoidance. One surprising result is that, contrary to widespread belief, this phenomenon does not depend upon the choice of boundary conditions.
TL;DR: The ability of three homologous peptides, ovine corticotropin-releasing factor, sauvagine and urotensin I, to release ACTH was examined in vitro and in vivo, suggesting that all three peptides evolved from a common mammalian precursor that possessed high hypophysiotropic potency.
TL;DR: The effect of VIP was not inhibited by phentolamine or propranolol, suggesting that its action was not elicited by interaction with α‐ or β‐adrenergic receptors, and receptors for VIP were distinct from those for isoproterenol, prostaglandin E1, and 2‐chloroadenosine.
Abstract: Adenylate cyclase in microvessels isolated from rat cerebral cortex was stimulated by guanine nucleotides, catecholamines, prostaglandin E1, prostaglandin E2, and 2-chloroadenosine. Catecholamine stimulation was mediated by interaction with beta-adrenergic receptors. The order of relative potency was: isoproterenol greater than epinephrine greater than norepinephrine. Activation of microvessel adenylate cyclase by prostaglandins E1 and E2 as well as by 2-chloroadenosine was dose related. Twenty-two peptides were tested for possible effects on the microvessel adenylate cyclase. Only vasoactive intestinal polypeptide (VIP) was stimulatory. No inhibitory action was observed. Activation by VIP required guanosine triphosphate and was dose dependent from 10 nM to 1 microM (ED50 = 0.1 microM). At 30 degrees C, stimulation of adenylate cyclase by the peptide increased linearly with time for up to 15 min. The effect of VIP was not inhibited by phentolamine or propranolol, suggesting that its action was not elicited by interaction with alpha- or beta-adrenergic receptors. Activation achieved by VIP and isoproterenol, prostaglandin E1, or 2-chloroadenosine was the sum of the individual stimulations, suggesting that receptors for VIP were distinct from those for isoproterenol, prostaglandin E1, and 2-chloroadenosine.
TL;DR: It is concluded that the rate of axon regeneration can be influenced by the environment through which the regenerating axons grow.
Abstract: The rate of regeneration of rat sciatic nerve sensory axons was measured using the pinch-reflex test method, and confirmed by studying the transport of labelled protein into the regenerating axons. For nerves receiving a single test crush lesion the rate was 4.02 +/- 0.03 (SE) mm/day. For nerves with a conditioning lesion made at the knee seven days prior to the test lesion at the hip the rate was 5.73 +/- 0.06 mm/day, and for nerves where both conditioning and test lesions were made at the same site (hip or knee) but separated by seven days, the rate was 6.76 +/- 0.04 mm/day, a 68% increase over the normal rate, showing that pre-degeneration of the nerve distal to the site of the test lesion increases the rate of regeneration. It is concluded that the rate of axon regeneration can be influenced by the environment through which the regenerating axons grow.
Journal Article•
TL;DR: In this article, microprobe study of minerals in rocks of the blueschist facies from the Black Butte and Ball Rock areas of the South Fork Mountain Schist, Northern California Coast Ranges, is the basis for analysis of reactions and phase relations among lawsonite, pumpellyite, epidote and associated minerals.
Abstract: Microprobe study of minerals in rocks of the blueschist facies from the Black Butte and Ball Rock areas of the South Fork Mountain Schist, Northern California Coast Ranges, is the basis in this report for analysis of reactions and phase relations among lawsonite, pumpellyite, epidote and associated minerals. Observed assemblages are intermediate in a progression from those observed elsewhere in high P-low T schists of the Franciscan (e.9., Panoche Pass) where lawsonite is present in nearly all lithologies, to the relatively low Phigh T assemblages of the Shuksan blueschist (Washington) where epidote is ubiquitous. Two successive reactions in this sequence, in order of increasing temperature, are: (l) lawsonite + Na-amphibole : epidote + quartz + albite + chlorite + HzO; (2) Na-amphibole + pumpellyite + quartz : epidote + Ca-amphibole + albite + chlorite + H2O. The pressure of metamorphism for the Black Butte and Ball Rock areas is estimated from the jadeite content of pyroxene and from the stability of aragonite to have been approximately 7 kbar; temperature estimates are not tightly constrained by mineral equilibria but are suggested to be in the range of 250 to 300"C.
TL;DR: In this article, three related proposals are made for accelerating the familiar successive substitution procedure for phase equilibrium flash calculations, based on the observation that successive substitution can be regarded as a method of steep descent for free energy minimization.
Abstract: Three related proposals are made for accelerating the familiar successive substitution procedure for phase equilibrium flash calculations. Basic to the development of the acceleration procedures is the observation that successive substitution can be regarded as a method of steep descent for free energy minimization. Acceleration is obtained by choosing an optimal step length. Results show a significant decrease in the number of iterations required for convergence, even in difficult problems near the mixture critical point.
On propose trois methodes pour accelerer le procede iteratif habituel de calcul des equilibres de phase pour la distillation-eclair. Le developpement de ces methodes est base sur l'observation que les iterations peuvent e'tre considerees comme une methode de gradient maximum pour la recherche du minimum d'energie libre.
On obtient l'acceleration en choisissant une longueur optimale pour l'increment. Les resultats obtenus indiquent une diminution du nombre d'iterations requis pour atteindre la convergence, me'me pour les problemes les plus delicats au voisinage du point critique du melange.
TL;DR: In this article, the authors study two special cases in which mathematical simplifications occur and find that the reflection and transmission coefficients approach constant (complex) values independent of the incidence angle, and that there is almost no ray bending (refraction) upon transmission of the incident wave through the boundary.
Abstract: In the general problem of plane wave reflection and transmission at a boundary separating two linear viscoelastic media, the mathematical formulas for the reflection and transmission coefficients, the transmission angle, the attenuation vector, etc., are not easily interpretable because they cannot easily be expressed in terms of the basic input parameters ( Q , incidence angle, etc.). To gain further insight, we study two special cases in which mathematical simplifications occur. No low-loss approximations are involved. In the first case, the incident wave is homogeneous, and the Q values of the two layers are equal, and we find, among other things, that the reflection and transmission coefficients are the same as the ones for perfect elasticity (they do not involve complex velocities, etc., and are independent of Q ). In the second special case, the degree of inhomogeneity of the incident wave approaches its upper limit, and we find that the reflection and transmission coefficients approach constant (complex) values independent of the incidence angle, and that there is almost no ray-bending (refraction) upon transmission of the incident wave through the boundary.
TL;DR: In this article, the combustion characteristics of the two fuels and their respective performance in both spark ignition and compression ignition engines are compared and the relative operational safety aspects of these two fuels are evaluated.
Abstract: The paper reviews the combustion characteristics of the two fuels and sets out to consider their respective performance in both spark ignition and compression ignition engines Results of comparative tests involving spark ignition engines over a wide range of operating conditions are presented and discussed Some of the performance characteristics considered are those relating to power output, efficiency, tendency to knock, cyclic variations, optimum spark requirements and exhaust emissions Similarly, some of the performance characteristics in compression ignition engines considered include power output, efficiency, tendency towards knock and autoignition, exhaust emissions and low operational temperature problems Finally, the relative operational safety aspects of the two fuels are evaluated It is then suggested that in this regard, methane has some excellent physical, chemical and combustion characteristics that makes it a particularly safe fuel
TL;DR: In this paper, a bilinear isoparametric finite element concept is used for the numerical analysis of multilayered plates, which allows for transverse shear and normal strains in each layer, thus extending the analysis to very thick plates and laminates.