Showing papers by "University of Guelph published in 1992"
TL;DR: The present study provides a historical and theoretical context for the Fitts' law model, including an analysis of problems that have emerged through the systematic deviation of observations from predictions.
Abstract: According to Fitts' law, human movement can be modeled by analogy to the transmission of information. Fitts' popular model has been widely adopted in numerous research areas, including kinematics, human factors, and (recently) human-computer interaction (HCI). The present study provides a historical and theoretical context for the model, including an analysis of problems that have emerged through the systematic deviation of observations from predictions. Refinements to the model are described, including a formulation for the index of task difficulty that is claimed to be more theoretically sound than Fitts' original formulation. The model's utility in predicting the time to position a cursor and select a target is explored through a review of six Fitts' law studies employing devices such as the mouse, trackball, joystick, touchpad, helmet-mounted sight, and eye tracker. An analysis of the performance measures reveals tremendous inconsistencies, making across-study comparisons difficult. Sources of experimental variation are identified to reconcile these differences.
1,369 citations
TL;DR: The detection of 99.4% of Salmonella strains tested and the failure to specifically amplify DNA from non-Salmonellastrains confirm that the invA gene contains sequences unique to Salmoneella and demonstrate that this gene is a suitable PCR target, with potential diagnostic applications.
967 citations
TL;DR: There is now evidence that several growth factors, cell adhesion molecules and other molecules play important roles in the regulation of this minute organ.
961 citations
01 Jan 1992
777 citations
TL;DR: The measurements have identified that substantial angular and linear motions occur about and along each of the JCS axes during walking, and do not support the traditional view that the so-called 'screw home' mechanism of the knee joint operates during gait.
716 citations
01 Jun 1992
TL;DR: It is demonstrated that Fitts' law can break down and yield unrealistically low ratings for a task's index of difficulty (ID), and the Shannon formulation is shown to partially correct this problem.
Abstract: Fitts' law, a one-dimensional model of human movement, is commonly applied to two-dimensional target acquisition tasks on interactive computing systems. For rectangular targets, such as words, it is demonstrated that the model can break down and yield unrealistically low (even negative!) ratings for a task's index of difficulty (ID). The Shannon formulation is shown to partially correct this problem, since ID is always ≥ 0 bits. As well, two alternative interpretations “target width” are introduced that accommodate the two-dimensional nature of tasks. Results of an experiment are presented that show a significant improvement in the model's performance using the suggested changes.
600 citations
TL;DR: This review examines the toxicity and accumulation of germanium and silver in selected microbial species and resistance mechanisms to these biologically nonessential metals is discussed, with more emphasis placed on silver-resistant bacteria due to the knowledge available.
353 citations
TL;DR: Turn-of-month and pre-holiday effects on international markets were examined in this article, showing that the anomalies are not generated solely by American institutions, but originate from country-specific institutional practices.
Abstract: This study examines turn-of-month and pre-holiday effects on international markets. Turn-of-month effects are significant in Canada, the UK, Australia, Switzerland, and West Germany. Pre-holiday effects are significant in Canada, Japan, Hong Kong, and Australia. The absence of these effects in certain markets suggests that they originate from country-specific institutional practices. All countries exhibiting pre-holiday effects do so before local holidays; only Hong Kong does so before US holidays. This reinforces the conclusion that such anomalies are not generated solely by American institutions.
307 citations
TL;DR: The results indicate that Caf before exercise decreased muscle glycogenolysis by approximately 55% over the first 15 min of exercise at approximately 80% VO2max, indicating that a "spared glycogen" was available late in exercise and coincided with a prolonged time to exhaustion.
Abstract: We examined the effects of a high-caffeine dose on endurance performance and muscle acetyl group metabolism during prolonged exercise. Eight subjects cycled to exhaustion at approximately 80% maximal oxygen uptake (VO2max) 1 h after ingestion of 9 mg/kg body wt dextrose (Pl) or caffeine (Caf). In the Pl trial, muscle biopsies were taken at rest (1 h postingestion) and at 15 min and exhaustion during exercise. The Caf trial followed the same protocol 1 wk later, with an additional biopsy at the time corresponding to Pl exhaustion. The subjects cycled significantly longer during the Caf trial (96.2 +/- 8.8 min) than in the Pl trial (75.8 +/- 4.8 min). Net glycogenolysis during the initial 15 min of cycling was reduced in the Caf vs. Pl trial (4.7 +/- 1.5 vs. 10.6 +/- 1.3 mmol.kg dry muscle-1.min-1; P less than 0.05). Muscle citrate concentration was increased at rest with Caf (0.59 +/- 0.07 vs. 0.37 +/- 0.05 mmol/kg dry muscle; P less than 0.05) but increased to similar values in both trials during cycling. Caf elevated the acetyl-CoA/CoA-SH ratio at rest (0.316 +/- 0.046 vs. 0.201 +/- 0.023; P less than 0.05) but had no effect on the increases in muscle acetyl-CoA and acetylcarnitine during exercise. The results indicate that Caf before exercise decreased muscle glycogenolysis by approximately 55% over the first 15 min of exercise at approximately 80% VO2max. This "spared glycogen" was available late in exercise and coincided with a prolonged time to exhaustion. Increased utilization of intramuscular triacylglycerol and/or extramuscular free fatty acids after caffeine ingestion may inhibit carbohydrate use at rest and early during exercise via elevations in muscle citrate and the acetyl-CoA/CoA-SH ratio. Muscle acetyl-CoA and acetylcarnitine were maintained above resting contents even at exhaustion when muscle glycogen was depleted.
306 citations
TL;DR: Fish that are fed always at the same time of day show typical pre-feeding activity and blood levels of some nutrients and hormones also show peaks or troughs at the time of feeding, but whether these are pre- feeding or post-prandial events is not clear.
Abstract: Although several studies have described effects of meal frequency and timing of meals on growth performance and body composition of different species of fishes, the mechanisms by which such variables influence the energy partitioning processes is not known. They may interact with the natural feeding rhythm of the fish, or with various behavioural and physiological parameters that exhibit ‘circadian-like’ patterns; however, in most cases, the endogenous character of such rhythms is not clear. The time of feeding, perse, can act as a Zeitgeber and override the effect of the light/dark alternation. Fish that are fed always at the same time of day show typical pre-feeding activity. Blood levels of some nutrients and hormones also show peaks or troughs at the time of feeding, but whether these are pre-feeding or post-prandial events is not clear. These results from fish are compared with similar studies with mammals. The existence and location of an endogenous multi-oscillator system is also discussed.
302 citations
TL;DR: Examination of allozyme gene frequencies in populations of eighteen aquatic invertebrate taxa at two sites in northern Canada suggests that gene frequency distributions are often not in equilibrium and that caution should be employed in attempts to infer gene flow from them in natural populations.
Abstract: The estimation of gene flow using gene frequency divergence information has become increasingly popular because of the difficulty involved in the direct determination of gene flow among populations. The present study examined allozyme gene frequencies in populations of eighteen aquatic invertebrate taxa at two sites in northern Canada. Gene frequencies at polymorpic loci were significantly different among 8–31 localized populations of all species at Igloolik and among 10–36 populations at Churchill confirming the generality of gene pool fragmentation in pond-dwelling organisms. Measures of gene flow estimated from gene frequency divergence, which assume that gene frequency distributions are at equilibrium, were inconsistent with the probable dispersal capacities of taxa. This provoked an examination of historical events as alternative explanations. Both theory and computer simulations demonstrated that when populations grow rapidly in size after founding from few individuals, the gene frequency divergence established during colonization is resistant to decay by gene exchange. Our work suggests that gene frequency distributions are often not in equilibrium and that caution should be employed in attempts to infer gene flow from them in natural populations.
TL;DR: It is demonstrated that BKME exposure affects reproduction by acting at multiple sites in the pituitary-gonadal axis by reducing responsiveness to the GtH analog human chorionic gonadotropin and to forskolin, a direct activator of adenylate cyclase.
TL;DR: Investigation with steer calves fed corn silage diets found that supplemental chromium from high-Cr yeast increased serum immunoglobulin M and total Immunoglobulins in calves fed diets with soybean meal but had no effect in calves with urea-corn supplementation.
Abstract: The effects of supplemental chromium (Cr) from high-Cr yeast were investigated with steer calves fed corn silage diets. One hundred eight Charolais-crossed calves, weighing 245 kg after marketing and transport, were allotted to one of four treatments during the initial 28-d stress period: control, .4 ppm of Cr in the diet, long-acting injectable oxytetracycline (LAOTC), and Cr + LAOTC. Those fed Cr received 4 mg of Cr/d for the first 3 d sprinkled onto a small amount of hay over the silage. Chromium without LAOTC increased (P less than .05) ADG by 30% (.61 vs .79 kg/d) and ADG/DMI by 27% (.123 vs .156). Oxytetracycline alone increased (P less than .05) ADG by 30% and DMI by 15%. Chromium had no effect on morbidity. However, LAOTC tended (P less than .14) to reduce morbidity (26.0 vs 14.0%) after its administration. After d 28, steers were processed. Two weeks later, they were rerandomized within Cr groups to urea-corn vs soybean meal supplementation of corn silage during a 70-d growing period. Level of Cr was reduced to .2 ppm. Jugular blood was collected from eight steers on each treatment on two occasions. Chromium had no effect on ADG or ADG/DMI. However, Cr decreased (P less than .05) serum cortisol (75.0 vs 55.6 nmol/L). Furthermore, Cr increased (P less than .05) serum immunoglobulin M and total immunoglobulins in calves fed diets with soybean meal but had no effect in calves with urea-corn supplementation.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: It is demonstrated that the S layer acts as a template for fine-grain gypsum and calcite formation by providing discrete, regularly arranged nucleation sites for the critical initial events in the mineralization process.
Abstract: Cyanobacteria belonging to the Synechococcus group are ubiquitous inhabitants of diverse marine and freshwater environments. Through interactions with the soluble constituents of their aqueous habitats, they inevitably affect the chemistry of the waters they inhabit. Synechococcus strain GL24 was isolated from Fayetteville Green Lake, New York, where it has a demonstrated role in the formation of calcitic minerals. In order to understand the detailed interactions which lead to mineral formation by this organism, we have undertaken detailed ultrastructural studies of its cell surface and the initial events in mineral growth using a variety of electron microscopic and computer image enhancement techniques. Synechococcus strain GL24 has a hexagonally symmetrical S layer as its outermost cell surface component. The constituent protein(s) of this structure appears as a double band by sodium dodecyl sulfate-polyacrylamide gel electrophoresis with M(r)s of 104,000 and 109,000. We demonstrate that the S layer acts as a template for fine-grain gypsum and calcite formation by providing discrete, regularly arranged nucleation sites for the critical initial events in the mineralization process. To our knowledge, this is the first time that a bacterial S layer has been shown to have a role in mineral formation in a natural environment, and this report provides conclusive evidence for the specific involvement of bacterial surfaces in natural mineral formation processes.
TL;DR: This paper used an ordered series of five olfactory stimuli (A E and A > F) to demonstrate evidence of transitive inference in rats (Rattus norvegicus) and found that logical transitivity may reflect a form of spatial paralogic rather than formal deductions from a syllogistic-verbal system.
Abstract: Although Piagetian theory proposes that the ability to make transitive inferences is confined to humans above age 7, recent evidence has suggested that this logical ability may be more broad based. In nonverbal tests, transitive inference has been demonstrated in preschool children and 2 species of nonhuman primates. In these experiments, I demonstrate evidence of transitive inference in rats (Rattus norvegicus). I used an ordered series of 5 olfactory stimuli (A E and A > F). The possibility that logical transitivity may reflect a form of spatial paralogic rather than formal deductions from a syllogistic-verbal system is discussed.
TL;DR: It is argued that when genotypes of individuals can be identified for all individuals with observations on the trait, use of mixed-model procedures under an animal model treating single-Gene effects as fixed effects can provide unbiased estimates of single-gene effects and exact tests of associated hypotheses for pedigreed populations, even when selection is practiced.
Abstract: Studies involving the effects of single genes on quantitative traits may involve closed populations, selection may be practiced, and the quantitative trait of concern may also be influenced by background genes that are inherited in a polygenic manner. It is shown analytically that analysis of such data by ordinary least squares, the usual method of analysis, can lead to finding an excess of spurious significant effects of single genes, when no effect exists, for both randomly and directionally selected populations and can lead to bias in estimates of single-gene effects when selection has been practiced. The bias depends on heritability of the polygenic effects on the trait, selection intensity, mode of inheritance, magnitude of gene effect, gene frequency, and data structure. It is argued that when genotypes of individuals can be identified for all individuals with observations on the trait, use of mixed-model procedures under an animal model treating single-gene effects as fixed effects can provide unbiased estimates of single-gene effects and exact tests of associated hypotheses for pedigreed populations, even when selection is practiced. Results are illustrated through computer simulation.
TL;DR: In this paper, the authors study the microeconomic forces that influence real wages and find that the real wage is an increasing function of past profitability in the employer's industry, and a decreasing function of the level of unemployment in the region.
Abstract: The microeconomic forces that influence real wages are not fully understood. This paper studies pay determination using data on approximately 600 labour contracts. It finds that the real wage is an increasing function of past profitability in the employer''s industry, and a decreasing function of the level of unemployment in the employer''s region. These results are consistent with rent-sharing theories.
TL;DR: One hundred and fifteen dogs with neoplasms of the lower urinary tract (bladder and/or urethra) were retrospectively evaluated at five referral institutions participating in ongoing studies by the Veterinary Cooperative Oncology Group.
Abstract: One hundred and fifteen dogs with neoplasms of the lower urinary tract (bladder and/or urethra) were retrospectively evaluated at five referral institutions participating in ongoing studies by the Veterinary Cooperative Oncology Group. Most tumors were malignant (97%) and of epithelial origin (97%). Lower urinary tract tumors were more common in older dogs weighing greater than 10 kg. The following significant (P less than 0.05) statistical associations were found using the University of Guelph hospital population as control; there was no sex predisposition although the female:male ratio was 1.95:1. Neutered dogs were predisposed as were Airedale Terriers, Beagles, and Scottish Terriers, whereas German Shepherds were significantly under-represented among dogs with lower urinary tract tumors. These statistical associations should be interpreted cautiously because of possible demographic differences in hospital populations among the University of Guelph and other cooperating institutions. There were no significant correlations between age, gender, weight, breed, response to therapy, and survival time. Clinical signs were indicative of lower urinary tract disease and included hematuria, stranguria, and pollakiuria. The laboratory data were nonspecific except for urinalysis test results. Hematuria and inflammatory urinary sediments were most commonly reported; neoplastic cells were identified in the urine sediment of 30% of dogs with lower urinary tract tumors. Contrast cystography was a useful noninvasive diagnostic method since 96% of the dogs had a mass or filling defect in the lower urinary tract demonstrated by this technique.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: Cattle embryos produced by in vitro maturation and fertilization of oocytes, and culture with bovine oviductal epithelial cells showed significant increases in the metabolism of glucose and glutamine, presumably reflecting the increased energy demands of Na(+)-K+ ATPase necessary for formation and maintenance of the blastocoel.
Abstract: The metabolism of radiolabelled glucose and glutamine was measured in individual cattle embryos produced by in vitro maturation and fertilization of oocytes, and culture with bovine oviductal epithelial cells. Metabolism of glucose through the pentose-phosphate pathway increased almost 15 times and the total metabolism of glucose 30 times, during development from the two-cell to the expanded blastocyst stage. The first marked increase in glucose metabolism did not occur until between the eight- and 16-cell stages, the time of activation of the embryonic genome. Conversely, the metabolism of glutamine was high in two- and four-cell embryos and then decreased to reach a minimum at the compacted morula to blastocyst stage, possibly because of degradation of maternally derived enzymes. Blastocyst expansion was accompanied by significant increases in the metabolism of glucose and glutamine, presumably reflecting the increased energy demands of Na(+)-K+ ATPase necessary for formation and maintenance of the blastocoel.
TL;DR: Herd sensitivity can be increased by using a test that is less than 100% specific, and herd apparent prevalence increases directly with the number of animals tested, but the herd positive predictive value decreases.
TL;DR: Induction of prolific shoot formation in Phaseolus vulgaris L. cv.
Abstract: Induction of prolific shoot formation in Phaseolus vulgaris L. cv. Kinghorn Wax was achieved by germinating mature seeds and growing seedlings on a medium supplemented with 10 μM thidiazuron (TDZ), a substituted phenylurea, or 80 μM N6-benzylaminopurine (BAP). Culture for 7 d in the presence of 10 μM TDZ was sufficient to induce maximal shoot formation, whereas a continuous presence of BAP was required for the induction and development of shoots. The differentiation of adventitious shoots occurred within four weeks of seed culture, from tissues in the regions of axillary buds on the cotyledonary node and also areas surrounding the shoot apex of the intact seedling. The number of shoots regenerated from intact seedlings was significantly higher than that obtained with expiants. Regenerated shoots developed into flowering plants. Similar results were obtained in six other bean cultivars.
TL;DR: In this paper, the contribution of radiation use efficiency (RUE, g dry matter MJ −1 ) to the difference in dry matter accumulation between an old and a new maize (Zea mays L.) hybrid was investigated.
Abstract: Differences in dry matter accumulation among crop cultivars can be attributed to differences in either the absorptance of incident photosynthetically active radiation (PAR) and/or the conversion of absorbed PAR into dry matter. This study was conducted to quantity the contribution of radiation use efficiency (RUE, g dry matter MJ −1 ) to the difference in dry matter accumulation between an old and a new maize (Zea mays L.) hybrid. An old (Pride 5) and a new (Pioneer 3902) maize hybrid were grown during 1989 and 1990 at the Elora Research Station, Ontario, on a London loam (Aquic Hapludalf) soil that had been tile drained (...)
TL;DR: In this article, the authors showed that the use of N6-benzylaminopurine in combination with indole-3-acetic acid was sufficient for inducing embryogenesis.
Abstract: Somatic embryogenesis was induced in hypocotyl explants of geranium (Pelargonium × hortorum) cultured on media supplemented with various concentrations of N-phenyl-N′-1,2,3-thiadiazol-5-ylurea (thidiazuron). In less than 2 weeks, somatic embryos were observed in treatments containing levels of thidiazuron (TDZ) ranging from 0.2 to 1.0 micromolar. The use of N6-benzylaminopurine in combination with indole-3-acetic acid also evoked embryogenesis, but the efficiency of somatic embryo production was significantly lower than that obtained with TDZ. Hypocotyl culture for only 2 days on TDZ-supplemented medium before transfer to a basal medium was sufficient for inducing somatic embryogenesis. This distinction between the induction and expression of embryogenesis may provide an experimental system for studying the developmental biology of somatic embryogenesis. Substitution of the auxin-cytokinin requirement for the induction of somatic embryogenesis by TDZ suggests the possibility of a novel mode of its action by modulation of endogenous growth regulators.
TL;DR: These metabolic and dietary changes are linked to the emergence of hunting and gathering, the evolution of the human pattern of prolonged development, and the coexistence and competition with the robust australopithecines.
Abstract: A bioenergetics model is developed to examine changes in metabolic requirements over the course of human evolution. Data on (1) body size and resting metabolism, (2) brain size and metabolism, (3) activity budgets, and (4) foraging patterns for humans and other anthropoids are used to evaluate ecological correlates of variation in diet and energy expenditure. Analyses of variation in these extant species provide a framework for estimating (1) resting metabolic requirements, (2) brain metabolic needs, and (3) total energy requirements in fossil hominids. Anthropoid primates spend about 8% of resting metabolism to maintain their brains, a significantly larger proportion than in other mammals (3-4%), but still significantly less than 20-25% in humans. Total energy expenditure among anthropoids is positively correlated with day range and dietary quality. Human foragers fit this pattern, having high levels of energy expenditure, large foraging ranges, and a high quality diet. Within the fossil record, it appears that both total energy expenditure (TEE) and energy required by the brain increased substantially with the emergence of Homo erectus. For H. erectus, the percentage of resting metabolism used by the brain falls beyond the nonhuman primate range and approaches the modern human range. Additionally, TEE is 35-55% greater than in the australopithecines. The high total metabolic needs and the large proportion of energy required by the brain imply that important dietary changes occurred with H. erectus. These metabolic and dietary changes are linked to (1) the emergence of hunting and gathering, (2) the evolution of the human pattern of prolonged development, and (3) the coexistence and competition with the robust australopithecines.
TL;DR: Evidence is presented that bovine male embryos generally develop to more advanced stages than do females during the first 8 days after insemination in vitro, which suggest that sex‐related gene expression affects the development of embryos soon after activation of the embryonic genome and well before gonadal differentiation.
Abstract: The classical concept of sex determination in mammals is that a Y chromosomal gene controls the development of the indifferent gonad into a testis. Subsequent divergence of sexual phenotypes is secondary to this gonadal determination. The most likely candidate gene is SRY (sex-determining region Y) in humans, and Sry in mouse. However, several lines of evidence indicate that sexual dimorphism occurs even before the indifferent gonad appears. Here we present evidence that bovine male embryos generally develop to more advanced stages than do females during the first 8 days after insemination in vitro. Corresponding relationships between both cell numbers and mitotic indices and sex were also seen. Although it is not clear whether this phenomenon involves factors originating before or after fertilization, these findings suggest that sex-related gene expression affects the development of embryos soon after activation of the embryonic genome and well before gonadal differentiation.
Proceedings Article•
01 Sep 1992TL;DR: In this article, the prediction of human-computer interfaces using Fitts' law is reviewed and techniques for model building are summarized and three refinements to improve the theoretical and empirical accuracy of the law are presented.
Abstract: The prediction of movement time in human-computer interfaces as undertaken using Fitts' law is reviewed. Techniques for model building are summarized and three refinements to improve the theoretical and empirical accuracy of the law are presented. Refinements include (1) the Shannon formulation for the index of task difficulty, (2) new interpretations of “target width'' for two- and three-dimensional tasks, and (3) a technique for normalizing error rates across experimental factors. Finally, a detailed application example is developed showing the potential of Fitts' law to predict and compare the performance of user interfaces before designs are finalized.
TL;DR: An understanding of the mechanisms of production and elimination of oxygen radicals in embryos may lead to significant improvements in the success of embryo culture and the practical techniques which depend on it.
TL;DR: In vitro bioassays using goldfish revealed that GtH I and GTH II share the same spectrum of biological activities causing stimulation of ovarian and testicular steroidogenesis and induction of oocyte final maturation.
TL;DR: This review examines specific elements critical in experiments designed to estimate nutrient requirements for vitamins, proteins, amino acids, essential fatty acids, and minerals in fish feed.
TL;DR: Analysis of the predicted amino acid sequence demonstrated that the extracellular receptor domain is highly homologous to S-locus glycoproteins, whereas the cytoplasmic kinase domain contains conserved amino acids present in serine/threonine kinases.
Abstract: An S-receptor kinase (SRK) cDNA, SRK-910, from the active S-locus in a self-incompatible Brassica napus W1 line has been isolated and characterized. The SRK-910 gene is predominantly expressed in pistils and segregates with the W1 self-incompatibility phenotype in an F2 population derived from a cross between the self-incompatible W1 line and a self-compatible Westar line. Analysis of the predicted amino acid sequence demonstrated that the extracellular receptor domain is highly homologous to S-locus glycoproteins, whereas the cytoplasmic kinase domain contains conserved amino acids present in serine/threonine kinases. An SRK-910 kinase protein fusion was produced in Escherichia coli and found to contain kinase activity. Phosphoamino acid analysis confirmed that only serine and threonine residues were phosphorylated. Thus, the SRK-910 gene encodes a functional serine/threonine receptor kinase.