Showing papers by "University of Calgary published in 1991"

Development of an Instrument to Measure the Perceptions of Adopting an Information Technology Innovation

Abstract: This paper reports on the development of an instrument designed to measure the various perceptions that an individual may have of adopting an information technology IT innovation. This instrument is intended to be a tool for the study of the initial adoption and eventual diffusion of IT innovations within organizations. While the adoption of information technologies by individuals and organizations has been an area of substantial research interest since the early days of computerization, research efforts to date have led to mixed and inconclusive outcomes. The lack of a theoretical foundation for such research and inadequate definition and measurement of constructs have been identified as major causes for such outcomes. In a recent study examining the diffusion of new end-user IT, we decided to focus on measuring the potential adopters' perceptions of the technology. Measuring such perceptions has been termed a "classic issue" in the innovation diffusion literature, and a key to integrating the various findings of diffusion research. The perceptions of adopting were initially based on the five characteristics of innovations derived by Rogers 1983 from the diffusion of innovations literature, plus two developed specifically within this study. Of the existing scales for measuring these characteristics, very few had the requisite levels of validity and reliability. For this study, both newly created and existing items were placed in a common pool and subjected to four rounds of sorting by judges to establish which items should be in the various scales. The objective was to verify the convergent and discriminant validity of the scales by examining how the items were sorted into various construct categories. Analysis of inter-judge agreement about item placement identified both bad items as well as weaknesses in some of the constructs' original definitions. These were subsequently redefined. Scales for the resulting constructs were subjected to three separate field tests. Following the final test, the scales all demonstrated acceptable levels of reliability. Their validity was further checked using factor analysis, as well as conducting discriminant analysis comparing responses between adopters and nonadopters of the innovation. The result is a parsimonious, 38-item instrument comprising eight scales which provides a useful tool for the study of the initial adoption and diffusion of innovations. A short, 25 item, version of the instrument is also suggested.

An Attitude Approach to the Prediction of Entrepreneurship

Abstract: Attitude is presented as a better approach to the description of entrepreneurs than either personality characteristics or demographics. The development and validation of the Entrepreneurial Attitud...

Parents' differential socialization of boys and girls: A meta-analysis.

Abstract: A meta-analysis of 172 studies attempted to resolve the conflict between previous narrative reviews on whether parents make systematic differences in their rearing of boys and girls. Most effect sizes were found to be nonsignificant and small. In North American studies, the only socialization area o

The zero-frequency problem: estimating the probabilities of novel events in adaptive text compression

Abstract: Approaches to the zero-frequency problem in adaptive text compression are discussed. This problem relates to the estimation of the likelihood of a novel event occurring. Although several methods have been used, their suitability has been on empirical evaluation rather than a well-founded model. The authors propose the application of a Poisson process model of novelty. Its ability to predict novel tokens is evaluated, and it consistently outperforms existing methods. It is applied to a practical statistical coding scheme, where a slight modification is required to avoid divergence. The result is a well-founded zero-frequency model that explains observed differences in the performance of existing methods, and offers a small improvement in the coding efficiency of text compression over the best method previously known. >

Response of facial and rubrospinal neurons to axotomy: changes in mRNA expression for cytoskeletal proteins and GAP-43

Abstract: Neurons confined within the mammalian CNS usually do not regenerate after axonal injury, while axonal regeneration is the rule in the PNS. It has been hypothesized that this may be related to differences in the microenvironment of the PNS versus CNS and to differences in the neuronal response to injury. In order to test the latter hypothesis, we compared changes in gene expression after axotomy in two populations of neurons: rat facial motoneurons and rat rubrospinal neurons. In situ hybridization with cDNA probes for the medium and light neurofilament protein revealed a reduced mRNA content in both facial and rubrospinal neurons at all times investigated (i.e., 1, 2, and 3 weeks after axotomy). On the other hand, mRNAs for actin and tubulin were increased in both neuronal populations during the first week after axotomy. While this increase was sustained in facial motoneurons for several weeks, total tubulin mRNA and actin mRNA were decreased in rubrospinal neurons at 2 and 3 weeks after axotomy, coincident with their atrophy. The developmentally regulated T alpha 1 tubulin mRNA, which was previously shown to be reexpressed in facial motoneurons after axotomy, was elevated severalfold in axotomized rubrospinal neurons, and increased levels persisted in some rubrospinal neurons as late as 7 weeks after axotomy. Similarly, the developmentally regulated GAP-43 mRNA increased in both axotomized facial and rubrospinal neurons, and increased levels were sustained in some axotomized rubrospinal neurons for at least 7 weeks. The response of rubrospinal neurons to axotomy in the cervical spinal cord is, in the first week, qualitatively similar to the response of facial motoneurons. However, by 2 weeks after axotomy there is a generalized reduction in mRNA levels for all three cytoskeletal proteins that is associated with neuronal atrophy. During this period, mRNA levels for the two specific markers of the growth state, T alpha 1 tubulin and GAP-43, remain elevated. Thus, axotomy of rubrospinal neurons appears to set in motion two independent events. First, an axotomy signal initiates a cell-body reaction similar to that of PNS neurons, including increased mRNA levels for T alpha 1 tubulin and GAP-43. Later, a generalized cellular atrophy and decrease in mRNA levels occur without reversing the specific responses of T alpha 1 and GAP-43 to axotomy. We conclude that the failure of rubrospinal neurons to regenerate is not due to a failure to initiate gene-expression changes characteristic of regenerating peripheral neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Double blind, placebo controlled trial of metronidazole in Crohn's disease.

Abstract: A double blind study compared the efficacy of metronidazole in two doses (20 mg/kg, 10 mg/kg) with placebo in patients with Crohn's disease One hundred and five patients participated but only 56 completed the 16 week study -21 were withdrawn for deterioration of symptoms, 17 for adverse experiences, and 11 for protocol violation Significant improvement in disease activity as measured by the Crohn's disease activity index (metronidazole 20 mg/kg, 97 units; metronidazole 10 mg/kg, 67 units; placebo -1 unit, p = 0002) and serum orosomucoid (metronidazole 20 mg/kg/day, 49; 10 mg/kg/day, 38; placebo, -9, p = 0001)) were detected Changes in C reactive protein concentrations did not achieve significance when all three groups were considered but were significant when all metronidazole treated patients were grouped and compared with the placebo treated patients (08 v -09, p less than 005) Although patients receiving metronidazole 20 mg/kg/day had a greater improvement in disease activity than those receiving 10 mg/kg/day (difference 30 units (95% confidence intervals -27-87), the small sample size may have precluded the detection of statistical significance Preliminary analysis suggests that metronidazole was more effective in patients with disease confined to the large intestine or affecting both small and large bowel than in those with small bowel disease only There were no differences in remission rates between metronidazole and placebo treated patients We conclude that metronidazole warrants further assessment in the treatment of patients with active Crohn's disease

Vertebrate protamine genes and the histone-to-protamine replacement reaction.

Abstract: Publisher Summary This chapter discusses Bloch's classes Type 1 (“true” protamines) and Type 2 (“stable” protamines), for which substantial molecular information is now available. Protamines are defined as having a cysteine-plus-arginine composition of 45–80 mol% and a serine plus- threonine content of 10–25 mol%. However, it should be mentioned that an additional class of sperm protamines found in the sperm nuclei of certain flat fish in the order Pleuronectiformes. These protamines are rich in arginine and serine, but are very large (80,000–200,000 daltons) compared to the typical true and stable protamines ranging from 5000 to 10,000 Da. In addition, the fact that distinctive amino acids, such as threonine or valine, present in chicken protamine polypeptides, are conserved in position in the amino acid sequence of quail only if the sequence redetermined by Oliva and Dixon is considered, makes the probability of different allelic variants in chicken much less likely.

Engineering a Bacillus subtilis expression-secretion system with a strain deficient in six extracellular proteases.

Abstract: We describe the development of an expression-secretion system in Bacillus subtilis to improve the quality and quantity of the secreted foreign proteins. This system consists of a strain (WB600) deficient in six extracellular proteases and a set of sacB-based expression vectors. With the inactivation of all six chromosomal genes encoding neutral protease A, subtilisin, extracellular protease, metalloprotease, bacillopeptidase F, and neutral protease B, WB600 showed only 0.32% of the wild-type extracellular protease activity. No residual protease activity could be detected when WB600 was cultured in the presence of 2 mM phenylmethylsulfonyl fluoride. By using TEM beta-lactamase as a model, we showed that WB600 can significantly improve the stability of the secreted enzyme. To further increase the production level we constructed an expression cassette carrying sacY, a sacB-specific regulatory gene. This gene was placed under the control of a strong, constitutively expressed promoter, P43. With this cassette in the expression vector, an 18-fold enhancement in beta-lactamase production was observed. An artificial operon, P43-sacY-degQ, was also constructed. However, only a partial additive enhancement effect (24-fold enhancement) was observed. Although degQ can stimulate the production of beta-lactamase in the system, its ability to increase the residual extracellular protease activity from WB600 limits its application. The use of the P43-sacY cassette and WB600 would be a better combination for producing intact foreign proteins in high yield.

Bacterial resistance to antibiotics: the role of biofilms.

Abstract: Bacteria adhere to natural and synthetic, medically important surfaces within an extracellular polymer generically termed the glycocalyx This quasi-structure is a biofilm The enhanced antibiotic resistance of biofilm bacteria, relative to floating (planktonic) bacteria, encourages the establishment of chronic bacterial infections Resistance mechanisms include the hinderance of antibiotic diffusion by the glycocalyx, the physiology of the bacteria and the environment conditions of the niche in which the biofilm resides

Shortening of muscle fibres during stretch of the active cat medial gastrocnemius muscle: the role of tendon compliance

Abstract: 1. The length of muscle fibres in the medial gastrocnemius (MG) muscle of the anaesthetized cat was measured using ultrasound techniques. During the course of 'isometric' contractions, the muscle fibres shortened by stretching the compliant tendons, until the muscle fibres could no longer produce enough force to stretch the tendons further. At optimal muscle length (Lo) the maximal shortening of muscle fibres was 28%. 2. At muscle lengths much longer than Lo, 'isometric' contractions produced a slow shortening of the muscle fibres as the tendons were stretched and this resulted in a slow rise in tension. This phenomenon, usually referred to as 'creep', is due to low power at long muscle fibre length. This study shows that the series compliance present in the tendons is the major contributor to 'creep' in the cat MG muscle. As the tendons stretched during the course of the contraction, the average sarcomere length became shorter providing greater filament overlap and increasing power. 3. Slow to medium speed stretches applied shortly after the onset of contraction, as occurs in cat MG during walking and trotting, were entirely taken up in the tendons and the muscle fibres actually shortened throughout the imposed muscle stretch. 4. When early stretches were applied at muscle lengths longer than Lo, stretch of the muscle resulted in a peak force that was less than if the stretch had not been applied. This was the reverse of the situation for stretches at lengths less than Lo. When stretch was applied after attaining peak force, the force was greatly enhanced and the muscle fibres were also stretched. 5. Using the same techniques in a freely walking cat, the muscle fibres shortened by 1.0 +/- 0.3 mm during the stance phase of the step-cycle when the muscle was being stretched, in 198 consecutive step-cycles. 6. The tendons act as a mechanical buffer to protect muscle fibres from damage during eccentric contractions. 7. Since stretches of the MG muscle are not faithfully imposed on the muscle fibres, studies of muscle spindle function during locomotion need to take into consideration these effects of tendon compliance. The dominant view, when the foot lands on the ground during normal locomotion, is that muscle spindles are stretched along with the muscle resulting in reflex enhancement of contractile force. This study shows that the muscle fibres do not stretch under these circumstances, except at high speeds of locomotion when the stretch rate is also high.

Strategic Bridging: The Collaboration between Environmentalists and Business in the Marketing of Green Products

Abstract: A case of interorganizational collaboration in Canada involving a retail grocery chain and several environmental groups is analyzed. In this case, one environmental group attempted to act as a brid...

Imaging of synaptically evoked intrinsic optical signals in hippocampal slices

Abstract: Imaging analysis techniques were used to examine changes in the intrinsic optical properties in hippocampal brain slices that occurred during synaptic activity evoked by Schaffer collateral stimulation in CA1. Repetitive synaptic activity was associated with an increase in light transmission in the synaptic region in stratum radiatum. The effect was seen at wavelengths of light between 450 and 800 nm but was of greater amplitude at longer wavelengths. Blocking synaptic transmission with either Ca(2+)-free EGTA perfusate or kynurenic acid (an excitatory amino acid antagonist) blocked the optical signal, indicating that it resulted from postsynaptic activation of the cells and was not due to presynaptic fiber volleys or transmitter release alone. Because the optical changes were blocked by reducing extracellular Cl- (by replacement with gluconate) or by furosemide (an anion transport inhibitor), increased Cl- transport (conceivably Na-K- 2Cl cotransport) may generate these signals possibly by causing cellular swelling and thereby less light scattering. These optical changes were not blocked, however, by bicarbonate-free solution, indicating that bicarbonate transport may not be involved. Changes in the intrinsic optical signal could be related to glial swelling due to K+ released during neuronal activity because high-K(+)-induced swelling of cultured astrocytes is blocked by furosemide and low-Cl- solution. Intrinsic optical signals of neuronal tissue should be considered when voltage- or ion-sensitive dyes are used.

Regional variations in action potentials and transient outward current in myocytes isolated from rabbit left ventricle.

Abstract: 1. Regional variations in the shape of early repolarization of the action potential have been correlated to differences in transient outward K+ current, I(t), in myocytes isolated from the epicardial surface, the endocardial trabeculae and the papillary muscles of rabbit left ventricles. Temperature was 35 degrees C during whole-cell, and 22-23 degrees C during cell-attached experiments. 2. Membrane resting potentials were very similar regionally. At 0.1 Hz stimulation the action potential plateau amplitude in papillary muscle cells was significantly higher (104.7 mV) than in epicardial cells (96.47 mV). Exposure to 4-aminopyridine or increases in the rate of stimulation from 0.1 Hz to 3.3 Hz increased plateau height and diminished the initial notch on repolarization. These effects were correlated to the magnitude of I(t) in these cells. At low rates of stimulation I(t) caused a 'spike and dome' morphology of the action potential. 3. Voltage clamp experiments confirmed a higher current density of I(t) in epicardial cells (7.66 pA/pF at +20 mV) than in endocardial (6.45 pA/pF) or papillary muscle cells (3.69 pA/pF). I(t) at 35 degrees C was faster and larger than previously reported and individual currents inactivated almost completely during 100 ms pulses to plateau potentials. No differences in the kinetics or voltage dependence of whole-cell currents were found. Thus, the half-inactivation potential was -37.8 mV in cells from all three regions. 4. Cell-attached recordings from endocardial and epicardial cells showed very similar single-channel amplitudes, burst open probabilities and ensemble averages. The peak channel open probability soon after the start of depolarizing voltage clamp pulses did not change between cell types (P approximately 0.8). The slope conductance of I(t) channels was 13.0 pS with an intercept near the resting potential of the cell. 5. We conclude that regional variations in the shape of initial repolarization in cells from rabbit left ventricle are caused by variations in the magnitude of the transient outward K+ current, I(t). Epicardial cells have the largest, and papillary muscle cells the smallest I(t). The differences are not explained by alterations in the whole-cell kinetics or single-channel kinetics and conductance. The most likely explanation for variations in whole-cell current density is therefore a decrease in channel density in endocardium and papillary muscle compared with epicardial tissue. We estimate the density of I(t) channels per cell to be 1495 (one per 3-4 micron2) in epicardium, 1175 (one per 4-5 micron2) in endocardium, and 875 (one per 6 micron2) in papillary muscle cells.

Mobility Versus Density-Limited Predator--Prey Dynamics on Different Spatial Scales

Abstract: We investigate the dynamics of a predator-prey model that explicitly accounts for the spatial position and the movement behaviour of individual prey and predators, and does not assume the law of mass action. We show that limited individual mobility greatly reduces fluctuations in total density, although average densities and vital rates are virtually unaffected. We analyse the dynamics of patterns in the spatial distribution of prey and predator, which are generated by the model, and show that population dynamic observations at different spatial scales depend on the characteristic scale imposed by the individual biology.

The covariant phase space of asymptotically flat gravitational fields

Abstract: Publisher Summary This chapter discusses the covariant phase space of asymptotically flat gravitational fields and covariant constructions for field theories. In the case of general relativity, boundary conditions play a critical role and must be adjusted carefully for the symplectic structure to be finite and for the framework to be well-defined. The chapter presents a new application: the derivation of the expression of energy-momentum of an isolated gravitating system at null infinity. This derivation makes a crucial use of the covariant construction and cannot be carried out within the familiar, 3+1 phase space frameworks. The chapter presents a summarization of the basic ideas of the covariant procedure and the general framework for field theories on a background space-time. It reviews the covariant Hamiltonian description of gravitational fields in general relativity, which are asymptotically flat at spatial infinity. The chapter shows that the ADM 4-momentum is the generator of the asymptotic translation group, which arises from the boundary conditions. The chapter also discusses space-times that are asymptotically flat at null infinity.

Critical Thinking and Adult Education: A Conceptual Model for Developing Critical Thinking in Adult Learners.

Abstract: While critical thinking has been intimately associated with adult education, there is not always a consensus as to its meaning and how to develop it in adult learners. After analysing the concept of critical thinking, a model is suggested consisting of five phases, which attempts to incorporate aspects of problem solving and creative thinking. Next, the development of critical thinking and the central role it plays in adult education are explored. It is concluded that issues surrounding the development of critical thinking may be an important key to developing an understanding of the field of adult education.

Relationship of soil microbial biomass and activity with fertilization practice and crop yield of three ultisols

Abstract: The relationships of crop yield with soil factors such as microbial biomass (Cmic), basal respiration, microbial biomass-to-organic C (Cmic.:Corg) ratio, and metabolic quotient (qCO2) were investigated in three long-term field experiments in Alabama. On all three sites soybean (Glycine max L.) yield was significantly correlated with Cmic: (r = 0.77). On the Auburn and Brewton sites, there were positive correlations of Cmic with the yields of sorghum, rye and corn. Only in a few cases, soil nutrient contents (N, P. K) were significantly correlated with Cmic. The Cmk:Corg ratio increased with crop yield. The data suggest that part of the variability of Cmic and the Cmk:Corg ratio which to a great entent are determined by the climatic conditions at a certain site, may be explained with differences in crop yield. These may in turn be caused by mineral fertilization. No relationship was found between basal respiration and soybean yield. However, the qCO2 was negatively correlated with soybean yield (r = − 0.78) on all sites. This has important implications on agriculture: if more C is lost by respiration at less C input, more care must be taken to maintain organic C contents.

Gray level thresholding in badly illuminated images

Abstract: The thresholding method involves first locating objects in an image by using the intensity gradient, then noting the levels that correspond to the objects in various areas of the image, and finally using these levels as initial guesses at a threshold. This method is capable of thresholding images that have been produced in the context of variable illumination. The thresholding method, called the local intensity gradient (LIG) method, was implemented in C using a Sun4 host running UNIX. The LIG method was compared against iterative selection (IS), gray level histograms (GLHs) and two correlation based algorithms on a dozen sample images under three different illumination effects. Overall, the LIG method, while it takes significantly longer, properly thresholds a larger set of images than does any other method examined over the sample images tested. >

Synaptic organization of starburst amacrine cells in rabbit retina: analysis of serial thin sections by electron microscopy and graphic reconstruction.

Abstract: The synaptic organization of starburst amacrine cells was studied by electron microscopy of individual or overlapping pairs of Golgi-impregnated cells. Both type a and type b cells were analyzed, the former with normally placed somata and dendritic branching in sublamina a, and the latter with somata displaced to the ganglion cell layer and branching in sublamina b. Starburst amacrine cells were thin-sectioned horizontally, tangential to the retinal surface, and electron micrographs of each section in a series were taken en montage. Cell bodies and dendritic trees were reconstructed graphically from sets of photographic montages representing the serial sections. Synaptic inputs from cone bipolar cells and amacrine cells are distributed sparsely and irregularly all along the dendritic tree. Sites of termination include the synaptic boutons of starburst amacrine cells, which lie at the perimeter of the dendritic tree in the "distal dendritic zone." In central retina, bipolar cell input is associated with very small dendritic spines near the cell body in the "proximal dendritic zone." The proximal dendrites of type a and type b cells generally lie in planes or "strata" of the inner plexiform layer (IPL), near the margins of the IPL. The boutons and varicosities of starburst amacrine cells, distributed int he distal dendritic zone, lie in the "starburst substrata," which occupy a narrow middle region in each of the two sublaminae, a and b, in rabbit retina. As a consequence of differences in stratification, proximal and distal dendritic zones are potentially subject to different types of input. Type b starburst amacrines do not receive inputs from rod bipolar terminals, which lie mainly in the inner marginal zone of the IPL (stratum 5), but type a cells receive some input from the lobular presynaptic appendages of rod amacrine cells in sublamina a, at the border of strata 1 and 2. There is good correspondence between boutons or varicosities and synaptic outputs of starburst amacrine cells, but not all boutons gave ultrastructural evidence of presynaptic junctions. The boutons and varicosities may be both pre- and postsynaptic. They are postsynaptic to cone bipolar cell and amacrine cell terminals, and presynaptic primarily to ganglion cell dendrites. In two pairs of type b starburst amacrine cells with overlapping dendritic fields, close apposition of synaptic boutons was observed, raising the possibility of synaptic contact between them. The density of the Golgi-impregnation and other technical factors prevented definite resolution of this question. No unimpregnated profiles, obviously amacrine in origin, were found postsynaptic to the impregnated starburst boutons.(ABSTRACT TRUNCATED AT 400 WORDS)