Showing papers by "University of Saskatchewan published in 1996"

Science Education: Border Crossing into the Subculture of Science

Abstract: (1996). Science Education: Border Crossing into the Subculture of Science. Studies in Science Education: Vol. 27, No. 1, pp. 1-52.

Web server workload characterization: the search for invariants

Abstract: The phenomenal growth in popularity of the World Wide Web (WWW, or the Web) has made WWW traffic the largest contributor to packet and byte traffic on the NSFNET backbone. This growth has triggered recent research aimed at reducing the volume of network traffic produced by Web clients and servers, by using caching, and reducing the latency for WWW users, by using improved protocols for Web interaction.Fundamental to the goal of improving WWW performance is an understanding of WWW workloads. This paper presents a workload characterization study for Internet Web servers. Six different data sets are used in this study: three from academic (i.e., university) environments, two from scientific research organizations, and one from a commercial Internet provider. These data sets represent three different orders of magnitude in server activity, and two different orders of magnitude in time duration, ranging from one week of activity to one year of activity.Throughout the study, emphasis is placed on finding workload invariants: observations that apply across all the data sets studied. Ten invariants are identified. These invariants are deemed important since they (potentially) represent universal truths for all Internet Web servers. The paper concludes with a discussion of caching and performance issues, using the invariants to suggest performance enhancements that seem most promising for Internet Web servers.

A full genome search in multiple sclerosis

Abstract: The aetiology of multiple sclerosis (MS) is uncertain. There is strong circumstantial evidence to indicate it is an autoimmune complex trait. Risks for first degree relatives are increased some 20 fold over the general population. Twin studies have shown monozygotic concordance rates of 25-30% compared to 4% for dizygotic twins and siblings. Studies of adoptees and half sibs show that familial risk is determined by genes, but environmental factors strongly influence observed geographic differences. Studies of candidate genes have been largely unrewarding. We report a genome search using 257 microsatellite markers with average spacing of 15.2 cM in 100 sibling pairs (Table 1, data set 1 - DS1). A locus of lambda>3 was excluded from 88% of the genome. Five loci with maximum lod scores (MLS) of >1 were identified on chromosomes 2, 3, 5, 11 and X. Two additional data sets containing 44 (Table 1, DS2) and 78 sib pairs (Table 1, DS3) respectively, were used to further evaluate the HLA region on 6p21 and a locus on chromosome 5 with an MLS of 4.24. Markers within 6p21 gave MLS of 0.65 (non-significant, NS). However, D6S461, just outside the HLA region, showed significant evidence for linkage disequilibrium by the transmission disequilibrium test (TDT), in all three data sets (for DS1 chi2 = 10.8, adjusted P < 0.01)(DS2 and DS3 chi2 = 10.9, P < 0.0005), suggesting a modest susceptibility locus in this region. On chromosome 5p results from all three data sets (222 sib pairs) yielded a multipoint MLS of 1.6. The results support genetic epidemiological evidence that several genes interact epistatically to determine heritable susceptibility.

A review of rapid prototyping technologies and systems

Abstract: Rapid Prototyping and Manufacturing (RP&M) technologies have emerged for quickly creating 3D products directly from computer-aided design systems. These technologies significantly improve the present prototyping practices in industry. This paper reviews the main technologies and applications of RP&M. The principles and the features of those RP&M technologies are presented. Some existing problems and research issues on these new technologies are introduced. We also include two current research and application examples in using rapid prototyping for further illustration.

Values and Organizational Structure

Abstract: Recent developments in organizational theory emphasize the need to examine the relationship between organizational values and structure. Values underpin organizational structure and give it meaning. Drawing on concepts of culture, institutional theory, and archetypes, this paper tests hypotheses on the value/structure relationship. The sample used for the study was a set of Canadian amateur sport organizations undergoing institutional change. This test shows that there is a fit between elite values and the nature of the institutionally prescribed organizational archetype.

A test system for teaching overall power system reliability assessment

Abstract: This paper presents the concept of overall power system reliability evaluation using an educational test system. The paper extends an existing test system by developing the necessary distribution and subtransmission networks. The extended test system has all the main facilities, such as generation, switching stations, transmission, sub-transmission and radial distribution networks found in a practical system. The test system, is however, sufficiently small that students can analyze it using hand calculations or by developing small computer programs to fully understand the reliability models and evaluation techniques. Overall power system reliability evaluation is concerned with providing acceptable customer service. This is an important concern in today's electric utility environment. This should therefore be an essential element in teaching power system reliability evaluation at either the graduate or undergraduate level, The extended test system presented in this paper and the concepts presented assist in satisfying this requirement.

An on-line relay coordination algorithm for adaptive protection using linear programming technique

Abstract: An adaptive system for protecting a distribution network should determine and implement relay settings that are most appropriate for the prevailing state of the power system. This paper presents a technique for determining coordinated relay settings. The technique uses the Simplex two-phase method; Phase I determines whether the constraints selected for illustrating the conditionality between primary and back up relays are feasible, and Phase II finds the optimal relay settings. A looped distribution system, protected by directional overcurrent relays, was used for testing the technique. The tests were conducted in a laboratory environment; some results from those tests are reported in the paper.

Optimal switching device placement in radial distribution systems

Abstract: This paper presents a new formulation for power system sectionalizing device placement taking into consideration outage, maintenance and investments costs. The formulation of sectionalizing switches is a combinatorial constrained optimization problem with a nonlinear, nondifferentiable objective function. A solution methodology based on the optimization technique of simulated annealing, is proposed to determine: (i) the number of sectionalizing switches; and (ii) the locations of the switches. The proposed solution methodology can offer a global optimal solution for the sectionalizing device placement problem which includes the reliability, investment and maintenance costs.

A sequential simulation technique for adequacy evaluation of generating systems including wind energy

Abstract: A wind energy conversion system (WECS) has a different impact on the reliability performance of a generating system than does a conventional energy conversion system. This is due to the variation of wind speeds and the dependencies associated with the power output of each wind turbine generator (WTG) in a wind farm. In this paper, a sequential Monte Carlo simulation technique is proposed for adequacy evaluation of a generating system including WECS. The method is based on an hourly random simulation to mimic the operation of a generating system, taking into account the auto-correlation and fluctuating characteristics of wind speeds, the random failure of generating units and other recognized dependencies. The hourly wind speeds are simulated utilizing autoregressive and moving average time series models that are established based on the F-criterion. A small reliability test system designated as the RBTS is used to illustrate the proposed method.

Bone Densitometry in Canadian Children 8–17 Years of Age

Abstract: Normative bone mineral density (BMD) and bone mineral content (BMC) values for the total body (TB), proximal femur (PF), and antero-posterior lumbar spine (LS) were obtained from a large cross-sectional sample of children and adolescents who were 8–17 years of age. There were 977 scans for the TB, 892 for the PF, and 666 for the LS; bone mineral values were obtained using a HOLOGIC QDR 2000 in array mode. Data are presented for the subregions of the PF (femoral neck, trochanter, intertrochanter, and the total region) and for the LS (L1–L4 and L3). Female and male values for the FN, LS (L1–L4), and the TB were compared across age groups using a two-way ANOVA. In addition, we compared the 17-year-old female values to a separate sample of young adult women (age 21). At all these sites, BMC and BMD increased significantly with age. There was no gender difference in TB BMC until age 14 or in TB BMD until age 16, when male values were significantly greater. Females had significantly greater LS BMC at ages 12 and 13, but by age 17 the male values were significantly greater. Females had significantly greater LS BMD across all age groups, however. Males had significantly greater FN BMC and BMD across all age groups. There were no significant differences in BMC or BMD at any sites between the 17- and 21-year-old women.

Thermal cracking of canola oil: reaction products in the presence and absence of steam

Abstract: The product distribution obtained from the thermal cracking of canola oil was studied at atmospheric pressure in a fixed-bed reactor in the temperature range 300−500 °C and gas hourly space velocity (GHSV) in the range 3.3−640 h-1 over inert materials and in the presence and absence of steam. Results showed that canola oil conversions were high (54−100 wt %) and depended strongly on the operating variables. Products essentially consisted of C4 and C5 hydrocarbons, aromatic and C6+ aliphatic hydrocarbons, and C2-C4 olefins, as well as a diesel-like fuel fraction and hydrogen. GC−MS analyses showed that product distribution as well as the lengths of the carbon chain of hydrocarbons and oxygenated hydrocarbons depended strongly not only on the cracking temperature and space velocity but also on whether cracking was conducted in the presence or absence of steam. On the other hand, cracking over inert materials showed that both conversion and product distribution were completely independent of morphology of th...

Reduction in long-term disability in patients with rheumatoid arthritis by disease-modifying antirheumatic drug–based treatment strategies

Abstract: Objective. Therapeutic strategies for rheumatoid arthritis (RA) have been evolving from the traditional “pyramid” approach toward one based upon early and sustained use of disease-modifying antirheumatic drugs (DMARDs), in the hope of improving long-term health outcomes. However, few data to have been presented to document the effects of this approach. We sought to directly assess associations between consistent DMARD use and long-term functional outcomes. Methods. We studied 2,888 RA patients who were followed up prospectively for up to 20 years (average 9 years) at 8 databank centers. The independent variable was the proportion of patient encounters that resulted in treatment with ⩾1 DMARD (hydroxychloroquine, sulfasalazine, auranofin, intramuscular gold, D-penicillamine, methotrexate, and/or azathioprine). The dependent variable was each patient's last recorded Disability Index value from the Health Assessment Questionnaire (HAQ). Results. Increased DMARD use was strongly associated with better long-term Disability Index values (P < 0.0001). The association was strengthened when restricted to more seriously affected (rheumatoid factor (RF)–positive) patients. The magnitude of the effect, unadjusted, was a difference of 0.53 HAQ Disability units (scale 0–3) between 100% DMARD use and 0%. Correlation coefficients ranged up to 0.26. Effects were similar for all disease duration periods (0–4, 5–9, 10–14, 15–19, and 20+ years). “Control” correlations, with variables computed to represent the proportion of time in which patients were taking either nonsteroidal antiinflammatory drugs or prednisone, failed to show positive associations. A multiple linear regression model, which controlled for age, disease duration, sex, RF positivity, proportion of visits under a prednisone regimen, and initial disability level, included the proportion of time in which patients were taking DMARDs (P < 0.0001), with a model R2 of 0.54. These results were obtained despite an adverse selection bias in which more severely affected individuals were given DMARDs more frequently, and despite absence of data on drug use early in the disease course of many patients. Thus, these results, which suggest up to a 30% reduction in longterm disability with consistent DMARD use, are most likely conservative. Conclusion. An association between consistent DMARD use and improvement in long-term functional outcomes in RA is supported by these data.

Dynamics of Organic Phosphorus in Soils under Natural and Agricultural Ecosystems

Abstract: Publisher Summary This chapter focuses on the short and long-term dynamics of organic phosphorus (P) in various terrestrial ecosystems and discusses the role of organic P in the soil–plant system. The organic P compounds found in plants and microbes undergo selective stabilization, degradation, and modification in soils. The biochemical compounds present in soil show the sources of organic P and the transformation processes that are active in soil. Research centered on the efforts to chemically characterize soil organic P relies on the solubilization/extraction of organic P followed by complex analyses for nucleotides, inositols, and lipids. The chapter also discusses the experimental methods that are used for the study of organic P in soil, and the associated problems. The complex, interactive nature of the various factors and processes that influence organic P cycling in soil requires the development and refinement of appropriate simulation models, especially over the short-term.

Communities on the edge: an economic geography of resource-dependent communities in canada

Abstract: Our impressions of Canadian resource-dependent communities are often still influenced by the classic works of Innis, Robinson, Lucas, Siemens, and others. Although this research has proven to be valuable, it has also established several generalizations regarding these settings, including the perceptions that community labour forces and economic structures are relatively homogenous, that nonresource sectors play an insignificant role in the communities, and that these communities are found primarily in isolated northern regions. These generalizations are now beginning to be questioned, given the rapid economic and social changes taking place in these communities and the recent theoretical and empirical contributions of geographers and other social scientists. This paper summarizes this classic research, then challenges these generalizations by discussing recent applications of the concepts of economic restructuring and labour-market segmentation theory to the context of resource-dependent communities. To further illustrate these characteristics, the paper then presents an empirical analysis of 220 Canadian resource-dependent communities across six resource sectors, focusing specifically on their labour-market characteristics and the relationship between resource dependence and spatial isolation. Nos impressions des communautes mono-industrielles canadiennes specialisees dans la production des ressources sont souvent encore influencees, entre autres, par les etudes classiques de Innis, Robinson, Lucas, et Siemens. Bien que cette recherche ait prouve sa valeur, elle a aussi servi aetablir plusieurs generalisations concernant ces milieux, incluant les notions que la main d'oeuvre et les structures economiques de ces communautes sont relativement homogenes, que les secteurs non-relies a l'exploration des ressources n'y jouent qu'un role peu significatif, et que ces communautes se retrouventsurtout dans les regions isolees du nord. Ces generalisations sont maintenant soumises a une remise en question, compte tenu des changements economiques et sociaux rapides dont ces communautes font l'objet et des recentes contributions theoriques et empiriques de geographes et d'autres chercheurs en sciences sociales. Cet article resume cette recherche classique et conteste ces generalisations en commentant les recentes applications du concept de restructuration economique etde la theorie de la segmentation du marche d'emploi associes au contexte des communautes dependentes de l'extraction de ressources. Afin d'illustrer ces caracteristiques, l'article presente une analyse empirique portant sur 220 communautes canadiennes et sur six secteurs de ressources, etse concentre plus specifiquement sur les caracteristiques de leur marche de la main-d'oeuvre et sur les liens existant entre la condition de dependance a une ressource et l'isolation spatiale.

(Aryloxy)aryl Semicarbazones and Related Compounds: A Novel Class of Anticonvulsant Agents Possessing High Activity in the Maximal Electroshock Screen

Abstract: A number of (aryloxy)aryl semicarbazones and related compounds were synthesized and evaluated for anticonvulsant activities. After intraperitoneal injection to mice, the semicarbazones were examined in the maximal electroshock (MES), subcutaneous pentylenetetrazole (scPTZ), and neurotoxicity (NT) screens. The results indicated that greater protection was obtained in the MES test than the scPTZ screen. Quantitation of approximately one-third of the compounds revealed an average protection index (PI, i.e. TD50/ED50) of approximately 9. After oral administration to rats, a number of compounds displayed significant potencies in the MES screen (ED50 of 1−5 mg/kg) accompanied by very high protection indices. In fact over half the compounds had PI figures of greater than 100, and two were in excess of 300. The compounds were essentially inactive in the scPTZ and NT screens after oral administration to rats. Various compounds displayed greater potencies and PI figures in the mouse intraperitoneal and rat oral scr...

Semantic ambiguity effects in word identification

Abstract: The influence of semantic ambiguity on word identification processes was explored in a series of word naming and lexical-decision experiments. There was no reliable ambiguity effect in 2 naming experiments, although an ambiguity advantage in lexical decision was obtained when orthographically legal nonwords were used. No ambiguity effect was found in iexical decision when orthographically illegal nonwords were used, implying a semantic locus for the ambiguity advantage. These results were simulated by using a distributed memory model that also produces the ambiguity disadvantage in gaze duration that has been obtained with a reading comprehension task. Ambiguity effects in the model arise from the model's attempt to activate multiple meanings of an ambiguous word in response to presentation of that word's orthographic pattern. Reasons for discrepancies in empirical results and implications for distributed memory models are considered. Any comprehensive theory of mental representation and process must accommodate the complex means by which concepts are communicated through language. Through the course of history, humans have developed tools of communication that facilitate the relaying of ideas and concepts, such as a writing system or orthography. This mapping of concepts to orthography is not entirely one to one, however, resulting in some words that correspond to multiple concepts, which are known as semantically ambiguous words. When reading text, the context provided by preceding words and sentences provides a means of disambiguating such words. As a result, we may not even notice the ambiguity in words that we are reading in context. If, on the other hand, semantically ambiguous words are presented in isolation, their alternative meanings are readily accessible, and thus their ambiguous nature is noticed. In the research reported in this article, we compare performance on semantically ambiguous words with that of semantically unambiguous words in isolated word identification tasks and describe simulations of the empirical effects within the framework of a distributed memory architecture (Masson, 1995). The effect of semantic ambiguity on isolated word identification has usually been determined by comparing performance on unambiguous words (which are associated with only one

Amantadine treatment is an independent predictor of improved survival in Parkinson's disease

Abstract: Amantadine has been used for more than 20 years in the symptomatic treatment of Parkinson's disease (PD). Several recent discoveries suggest that amantadine could also have a neuroprotective effect in PD. We studied survival in all parkinsonism (including PD and other parkinsonian syndromes) patients attending a single clinic, employing standard survival curves and a Cox regression model, to identify independent predictive variables for survival (while taking into account factors potentially associated with both outcome and treatment selection). Amantadine-treated patients (n = 250) were similar to the patients not treated with amantadine (n = 586) in terms of age, gender, type of parkinsonism, Hoehn and Yahr stage and dementia status at initial neurological visit. Amantadine use was an independent predictor of improved survival (p < 0.01). Improved survival was also associated with a higher 10-year expected survival (based on age, gender, and birth year), absence of dementia, type of parkinsonism = PD, and low Hoehn and Yahr stage (I or II) at initial neurologic visit (all p < 0.01); these additional factors occurred in statistically similar proportions in the groups that were and were not treated with amantadine. The association of improved survival with amantadine use may stem from symptomatic benefit or may reflect a "neuroprotective" effect, mediated through N-methyl-D-aspartate (NMDA) receptor antagonism, dopamine uptake blockade activity, or other mechanisms. Our preliminary findings suggest that a prospective, controlled, randomized trial of amantadine's effects on PD progression is warranted.