Showing papers by "University of Calgary published in 1985"

Personal Practical Knowledge: A Study of Teachers' Classroom Images

Abstract: Teachers develop and use a special kind of knowledge. This knowledge is neither theoretical, in the sense of theories of learning, teaching, and curriculum, nor merely practical, in the sense of knowing children. If either of these were the essential ingredient of what teachers know, then it would be easy to see that others have a better knowledge of both; academics with better knowledge of the theoretical and parents and others with better knowledge of the practical. A teacher's special knowledge is composed of both kinds of knowledge, blended by the personal background and characteristics of the teacher and expressed by her in particular situations.The idea of “image” is one form of personal practical knowledge, the name given to this special practical knowledge of teachers (Clandinin, 1985; Connelly and Dienes, 1982). In this article I show how one teacher's image of the “classroom as home” embodies her personal and professional experience and how, in turn, the image is expressed in her classro...

Patterns of mortality and age at first reproduction in natural populations of mammals.

Abstract: There is great variation in the age at which females of different mammalian species first breed. Recent comparative analyses have focused on the relationship between age at first reproduction and body size, but differences in patterns of mortality experienced by natural populations are expected to have major effects on selection for age at first reproduction. Here we show that the age at which females first reproduce is strongly correlated with expectation of life at birth, after the effects of body size have been removed, within and among species of mammals living in natural populations.

Systems of Numeration

Abstract: (1985). Systems of Numeration. The American Mathematical Monthly: Vol. 92, No. 2, pp. 105-114.

Phenomena of Bacterial Adhesion

Abstract: When we use direct microscopic techniques to examine bacteria growing in natural and pathogenic ecosystems, we are forcibly struck by the profound differences between these organisms and cells within derived in vitro laboratory cultures. The development of a series of new techniques for the stabilization and visualization of bacterial surface structures has intensified these differences because, as we come to understand bacterial surface structures more fully, we see that they comprise a very complex and fluid interface with the environment which the bacterium must maintain in order to survive amid the ubiquitous antibacterial agents and factors in nature.

Information technology assessment and adoption: a field study

Abstract: This article presents the results of a field study examining the strategies and mechanisms used by major companies for identifying, assessing, and adopting new information technology. The principle finding is the identification of several generic models which reveal the driving forces for new technology adoption. The article also describes phases in the adoption process, organizational roles, and information gathering mechanisms. This new line of research in MIS parallels and builds upon technology transfer research and marketing studies in the area of organizational buying behavior. The purpose of this work is to assist organizations with the challenge of coping with rapidly changing information technology.

Tyrosine and Phenylalanine Ammonia Lyase Activities during Shoot Initiation in Tobacco Callus Cultures.

Abstract: Both phenylalanine ammonia lyase and tyrosine ammonia lyase were detected in tobacco (Nicotiana tabacum L. Wisconsin 38) callus. The enzymes were separated from each other by Sephadex G-200 column chromatography. Increased activity of tyrosine ammonia lyase was observed during culture of tobacco callus under shoot-forming conditions, while activity of phenylalanine ammonia lyase increased during culture under non-organ-forming conditions. Confirmation of these findings was obtained by examining the incorporation of [14C]tyrosine and [14C]phenylalanine into p-coumarate and trans-cinnamate, respectively.

Optimal Server Location on a Network Operating as an M/G/1 Queue

Abstract: This paper extends Hakimi's one-median problem by embedding it in a general queueing context. Demands for service arise solely on the nodes of a network G and occur in time as a Poisson process. A single mobile server resides at a facility located on G. The server, when available, is dispatched immediately to any demand that occurs. When a demand finds the server busy with a previous demand, it is either rejected Model 1 or entered into a queue that is depleted in a first-come, first-served manner Model 2. Service time for each demand comprises travel time to the scene, on-scene time, travel time back to the facility and possibly additional off-scene time. One desires to locate the facility on G so as to minimize average cost of response, which is either a weighted sum of mean travel time and cost of rejection Model 1, or the sum of mean queueing delay and mean travel time. For Model 1, one finds that the optimal location reduces to Hakimi's familiar nodal result. For Model 2, nonlinearities in the objective function can yield an optimal solution that is either at a node or on a link. Properties of the objective function for Model 2 are utilized to develop efficient finite-step procedures for finding the optimal location. Certain interesting properties of the optimal location as a function of demand rate are also developed.

Analysis of factors affecting the choice of route of pedestrians

Abstract: Pedestrians as compared to vehicular traffic enjoy a high degree freedom of movement even in heavily congested areas. Consequently, there are more alternative links available to pedestrians between a given origin‐destination (O‐D) pair. This paper describes a study done by the University of Calgary to evaluate the factors affecting the choice of route on intra‐CBD trips or trips within the Central Business District (CBD). An origin destination survey conducted in downtown Calgary, Alberta enabled the identification of the most significant factors influencing the choice. These factors were analyzed in relation to the physical characteristics of the location, personal characteristics of the trip maker and the type of the trip. It appears that most people chose the shortest link and factors such as the level of congestion, safety or visual attractions were only secondary. This suggests that the length should be made a major consideration when planning and designing pedestrian links.

Intra-oral air mercury released from dental amalgam

Abstract: Intra-oral air was analyzed for mercury (Hg) vapor concentration in 46 subjects, 35 of whom had dental amalgam restorations. Measurements were made with a Jerome Hg detector both before and ten min after chewing stimulation. Subjects with dental amalgams had unstimulated Hg vapor concentrations that were nine times greater than basal levels in control subjects with no amalgams. Chewing stimulation in subjects with amalgams increased their Hg concentration six-fold over unstimulated Hg levels, or a 54-fold increase over levels observed in control subjects. Concentrations of Hg measured in intra-oral air larger than those reported in expired air were attributed to the rate and direction of air passage across amalgam surfaces. There were significant correlations between Hg vapor released into intra-oral air after chewing stimulation and the numbers and types of amalgam restorations. It is concluded that intraoral air is a reliable physiological indicator of Hg released from dental amalgam that may reflect a major source of chronic Hg exposure.

Biomechanics, Load Analysis and Sports Injuries in the Lower Extremities

Abstract: The study of sports injuries has grown with the increase in importance of sport as a leisure-time activity. The origin of many sports injuries is assumed to be mechanical, with the forces and/or stresses acting on one element of the human locomotor system exceeding the critical limits. This article presents some biomechanical considerations on the mechanical aspect of the aetiology, reduction and treatment of sport injuries with special emphasis on the lower extremities. Forces acting on the locomotor system have a magnitude, a point of application and a direction. Both magnitude and geometry (point of application and direction) are important in load analysis. However, the geometrical aspect of externally acting forces is an extremely important aspect, especially with respect to reduction of load in practical situations. Load analysis is usually performed with force transducers and optical instruments in order to quantify magnitude and geometry. Two possible approaches to load analysis are discussed. One approach works with the critical limits of biomaterials. This approach shows that the local stresses for cartilage, tendon and bone are in the order of 10 to 20% of the critical limit for normal daily activities, such as walking. The second approach deals with strategies to reduce load, assuming that it is usually too high in sports activities. The nature of playing surfaces and shoes are revealed as important possibilities for load reduction.

Serial Measurements of Intra-oral Air Mercury: Estimation of Daily Dose from Dental Amalgam

Abstract: Serial measurements of Hg concentration in intra-oral air were made during and after chewing stimulation in 35 subjects with occlusal amalgam restorations. Hg concentrations remained elevated during 30 min of continuous chewing and declined slowly over 90 min after cessation of chewing. By curve-fitting and integration analysis of data during these time periods (including corrections for respiratory volume, retention rate of inspired Hg, oral-to-nasal breathing ratios, and consumption of three meals and three snacks per day), we calculated that all subjects received an average daily Hg dose of approximately 20 μg. Subjects with 12 or more occlusal amalgam surfaces were estimated to receive a daily Hg dose of 29 μg, whereas in subjects with four or fewer occlusal amalgam surfaces, the dose was 8 μg. These Hg dosages from dental amalgam were as much as 18-fold the allowable daily limits established by some countries for Hg exposure from all sources in the environment. The results demonstrate that the amount...

Bacterial fouling in a model core system.

Abstract: We have used a sintered glass bead core to simulate the spaces and surfaces of reservoir rock in studies of the bacterial plugging phenomenon that affects waterflood oil recovery operations. The passage of pure or mixed natural populations of bacteria through this solid matrix was initially seen to promote the formation of adherent bacterial microcolonies on available surfaces. Bacteria within these microcolonies produced huge amounts of exopolysaccharides and coalesced to form a confluent plugging biofilm that eventually caused a >99% decrease in core permeability. Aerobic bacteria developed a plugging biofilm on the inlet face of the core, facultative anaerobes plugged throughout the core, and dead bacteria did not effectively plug the narrow (33-μm) spaces of this solid matrix because they neither adhered extensively to surfaces nor produced the extensive exopolysaccharides characteristic of living cells. The presence of particles in the water used in these experiments rapidly decreased the core permeability because they became trapped in the developing biofilm and accelerated the plugging of pore spaces. Once established, cells within the bacterial biofilm could be killed by treatment with a biocide (isothiazalone), but their essentially inert carbohydrate biofilm matrix persisted and continued to plug the pore spaces, whereas treatment with 5% sodium hypochlorite killed the bacteria, dissolved the exopolysaccharide biofilm matrix, and restored permeability to these plugged glass bead cores.

Algorithms for limited-view computed tomography: an annotated bibliography and a challenge.

Abstract: In many applications of computed tomography, it may not be possible to acquire projection data at all angles, as required by the most commonly used algorithm of convolution backprojection. In such a limited-data situation, we face an ill-posed problem in attempting to reconstruct an image from an incomplete set of projections. Many techniques have been proposed to tackle this situation, employing diverse theories such as signal recovery, image restoration, constrained deconvolution, and constrained optimization, as well as novel schemes such as iterative object-dependent algorithms incorporating a priori knowledge and use of multispectral radiation. We present an overview of such techniques and offer a challenge to all readers to reconstruct images from a set of limited-view data provided here.

Adaptive personalized interfaces—A question of viability

Abstract: It is widely accepted that interfaces between computers and users should differ to accommodate individual, or group, needs. One method of ‘personalizing’ an interface is to have the system form a limited model of the user and employ it to fashion the dialogue to his needs. Unfortunately, little is known about the effect of adaptation on the man–machine interface. Although obvious advantages accrue from ‘personalized’ interfaces, there are also obvious disadvantages to presenting users with a changing, adapting and perhaps apparently inconsistent interface. The goal of this work is to determine the viability of an adaptive interface through a human–factor pilot study of a simple, specially designed, interactive computer system. The system uses menu–driven selection to retrieve entries from a large ordered telephone directory. This simple task has several advantages: it is a realistic application area for interactive computers; plausible adaptive modelling methods exist and have been studied theore...

Long-term morbidity of infants with bronchopulmonary dysplasia.

Abstract: Bronchopulmonary dysplasia occurred in 179 infants discharged from a regional neonatal intensive care unit between 1975 and 1982. Perinatal and outcome factors were compared for these study infants and a group of 112 controls matched for birth weight category and year of birth. There were multiple differences between study infants and controls in demographic, diagnostic, and therapeutic items, all of which were categorized as pulmonary items occurring before and after the development of bronchopulmonary dysplasia, and nonpulmonary items. The postdischarge death rate was 11.2% in infants and 0.9% in control infants (P less than .001). Ongoing morbidity was most marked in the areas of health history, physical examination, growth, and vision. Neurodevelopmental abnormalities and hearing abnormalities occurred slightly more frequently in study infants than in controls but not significantly so. Major developmental abnormalities were less frequent in this population than has been the case in other follow-up studies in this area. This group of infants requires close postdischarge observation because ongoing morbidity and postdischarge mortality, part of which may be preventable, are frequent.

Isotope composition of sulphates generated by bacterial and abiological oxidation

Abstract: Oxygen isotope compositions of secondary sulphates provide a potentially powerful tool for elucidating mechanisms of sulphur oxidation. Such studies should reveal the consequences of various anthropogenic sulphur contributions to the environment, including gaseous emissions, aqueous solutions and elemental sulphur dust. At mining sites, metal sulphides may be oxidized in situ, giving rise to acid mine waters. The environment can receive these compounds from natural sources also, for example volcanoes, sulphurous springs and sour-gas seeps. There are many fundamental questions concerning the specific oxidation reactions and associated kinetics. In principle, isotope data from appropriate experiments can be used to address such questions. In the case of acid mine drainage, the approach of Taylor et al.1 is noteworthy. Here we present a critical examination of their results and suggest a novel method of determining the kinetic isotope effects identified with the incorporation of O2 and H2O-oxygen by SO42−.

The chromatic number of the product of two 4-chromatic graphs is 4

Abstract: For any graphG and numbern≧1 two functionsf, g fromV(G) into {1, 2, ...,n} are adjacent if for all edges (a, b) ofG, f(a) ≠g(b). The graph of all such functions is the colouring graph ℒ(G) ofG. We establish first that χ(G)=n+1 implies χ(ℒ(G))=n iff χ(G ×H)=n+1 for all graphsH with χ(H)≧n+1. Then we will prove that indeed for all 4-chromatic graphsG χ(ℒ(G))=3 which establishes Hedetniemi’s [3] conjecture for 4-chromatic graphs.

WAMDII: wide-angle Michelson Doppler imaging interferometer for Spacelab

Abstract: A wide-angle Michelson Doppler imaging interferometer (WAMDII) is described that is intended to measure upper atmospheric winds and temperatures from naturally occurring visible region emissions, using Spacelab as a platform. It is an achromatic field-widened instrument, with good thermal stability, that employs four quarterwave phase-stepped images to generate full images of velocity, temperature, and emission rate. For an apparent emission rate of 5 kR and binning into 85 × 105 pixels, the required exposure time is 1 sec. The concept and underlying principles are described, along with some fabrication details for the prototype instrument. The results of laboratory tests and field measurements using auroral emissions are described and discussed.

Antibiotic resistance of Pseudomonas aeruginosa colonizing a urinary catheter in vitro.

Abstract: A modified Robbins Device was used to establish coherent biofilms of Pseudomonas aeruginosa on the surface of catheter material in an artificial urine milieu and the ability of an antibiotic to penetrate the biofilm and kill the enclosed bacteria was assessed. The Pseudomonas aeruginosa strain used had been isolated from a patient with urinary tract infection. Although planktonic (floating) cells of the Pseudomonas aeruginosa strain were inhibited by less than 1 mg/l of tobramycin and killed by 50 mg/l, contact with 1,000 mg/l of tobramycin for 12 h failed to kill all the sessile (adherent) bacteria in the biofilms on the surface of the catheter material. Surviving sessile bacteria recovered directly from the exposure to 1,000 mg/l of tobramycin were inhibited by 0.4 mg/l of this agent when tested as dispersed planktonic cells by standard MIC methods. It is suggested that growth within thick adherent biofilms confers upon cells of Pseudomonas aeruginosa a large measure of resistance to aminoglycosides and other antibiotics that may help to explain the frequent failure of antibiotic chemotherapy in catheter-associated urinary tract infections.

Free piston Stirling engines

Abstract: Consider a free-piston engine of the type shown in Figure 1.12 and again in Figure 2.1. It consists essentially of three components, a heavy piston, a lightweight displacer and a cylinder sealed at the top end and which may be open or closed at the bottom. A displacer rod of appreciable diameter passes through the piston. The displacer and displacer rod are hollow thin wall shells. They may be open at the lower end so their interior is in fact part of the ‘bounce space’, the part of the cylinder below the piston. Alternatively, they may be closed and may or may not be provided with a small orifice to allow the interior to be charged to the mean cycle pressure. The ‘working space’ is above the piston and is divided into, a) the compression space above the piston and below the displacer, and b) the expansion space above the displacer. There is a long, thin annulus between the displacer and cylinder wall and this serves as the regenerative heat exchanger for working fluid passing between the hot expansion space and the cold compression space. Some form of heating is provided for the expansion space and some form of cooling in the compression space.

The amino acid sequence of human sperm protamine P1

Abstract: Human sperm protamines have been extracted from spermatozoa pooled from several donors, converted to their S-pyridylethylated derivatives and resolved into two major components, P1 and PI, by Bio-Rex 70 chromatography. Protamine P1 was further purified by Bio-Gel P-10 chromatography and sequenced directly on a gas phase protein sequencer for 43 residues. To complete the sequence, P1 was cleaved at methionine 36 and the C-terminal tetradecapeptide was purified by h.p.i.c , and sequenced completely. The 50 residue sequence is: 10 20 30 40 ARYRC CRSQS RSRYY RQRQR SRRRR RRSCQ TRRRA MRCCR 50 PRYRP RCRRH. This sequence has a calculated molecular weight of 6674 and is homologous with four other published mammalian protamine sequences.