Showing papers by "Memorial University of Newfoundland published in 2004"

Collocation Methods for Volterra Integral and Related Functional Differential Equations

Abstract: Collocation based on piecewise polynomial approximation represents a powerful class of methods for the numerical solution of initial-value problems for functional differential and integral equations arising in a wide spectrum of applications, including biological and physical phenomena. The present book introduces the reader to the general principles underlying these methods and then describes in detail their convergence properties when applied to ordinary differential equations, functional equations with (Volterra type) memory terms, delay equations, and differential-algebraic and integral-algebraic equations. Each chapter starts with a self-contained introduction to the relevant theory of the class of equations under consideration. Numerous exercises and examples are supplied, along with extensive historical and bibliographical notes utilising the vast annotated reference list of over 1300 items. In sum, Hermann Brunner has written a treatise that can serve as an introduction for students, a guide for users, and a comprehensive resource for experts.

Efficacy of rehabilitative experience declines with time after focal ischemic brain injury.

Abstract: To maximize the effectiveness of rehabilitative therapies after stroke, it is critical to determine when the brain is most responsive (i.e., plastic) to sensorimotor experience after injury and to focus such efforts within this period. Here, we compared the efficacy of 5 weeks of enriched rehabilitation (ER) initiated at 5 d (ER5), ER14, or ER30 after focal ischemia, as judged by functional outcome and neuromorphological change. ER5 provided marked improvement in skilled forelimb reaching ability and ladder-rung- and narrow-beam-walking tasks and attenuated the stroke-induced reliance on the unaffected forepaw for postural support. ER14 provided improvement to a somewhat lesser extent, whereas recovery was diminished after ER30 such that motor function did not differ from ischemic animals exposed to social housing. To examine potential neural substrates of the improved function, we examined dendritic morphology in the undamaged motor cortex because our previous work (Biernaskie and Corbett, 2001) suggested that recovery was associated with enhanced dendritic growth in this region. ER5 increased the number of branches and complexity of layer V neurons compared with both social housing and control animals. Dendritic arbor after ER14 (although increased) and ER30 did not differ from those exposed to social housing. These data suggest that the poststroke brain displays heightened sensitivity to rehabilitative experience early after the stroke but declines with time. These findings have important implications for rehabilitation of stroke patients, many of whom experience considerable delays before therapy is initiated.

The decline and fate of an iron-induced subarctic phytoplankton bloom

Abstract: Iron supply has a key role in stimulating phytoplankton blooms in high-nitrate low-chlorophyll oceanic waters. However, the fate of the carbon fixed by these blooms, and how efficiently it is exported into the ocean's interior, remains largely unknown. Here we report on the decline and fate of an iron-stimulated diatom bloom in the Gulf of Alaska. The bloom terminated on day 18, following the depletion of iron and then silicic acid, after which mixed-layer particulate organic carbon (POC) concentrations declined over six days. Increased particulate silica export via sinking diatoms was recorded in sediment traps at depths between 50 and 125 m from day 21, yet increased POC export was not evident until day 24. Only a small proportion of the mixed-layer POC was intercepted by the traps, with more than half of the mixed-layer POC deficit attributable to bacterial remineralization and mesozooplankton grazing. The depletion of silicic acid and the inefficient transfer of iron-increased POC below the permanent thermocline have major implications both for the biogeochemical interpretation of times of greater iron supply in the geological past, and also for proposed geo-engineering schemes to increase oceanic carbon sequestration.

An acute bout of static stretching: effects on force and jumping performance.

Abstract: Static stretching (SS) is used pervasively throughout the exercise science and sporting communities as a fundamental element of the pre-exercise warm-up procedure. While SS has been proven effective to increase range of motion (ROM), its proposed benefits are questionable and relatively unsubstantiated. Moreover, in recent years researchers have demonstrated that pre-exercise SS may in fact be detrimental to subsequent performance due to impaired force and power output. Yet the practical application of these relatively recent findings is limited due to the prolonged SS protocols utilized. In addition, timelines associated with enhanced ROM and performance decrements have not been established. Thus, the objectives of this study were to determine if a typical SS routine decreased force, activation, and power while improving ROM. Secondly, the study attempted to compare the duration of the performance decrement to the duration of the augmented ROM.

Understanding Student Motivation.

Abstract: Contemporary theories of academic motivation seek to explain students’ behaviours in academic settings. While each theory seems to possess its own constructs and unique explanations, these theories...

Effect of acute static stretching on force, balance, reaction time, and movement time.

Abstract: BEHM, D. G., A. BAMBURY, F. CAHILL, and K. POWER. Effect of Acute Static Stretching on Force, Balance, Reaction Time, and Movement Time. Med. Sci. Sports Exerc., Vol. 36, No. 8, pp. 1397–1402, 2004.Purpose:The purpose of the study was to investigate the effect of an acute bout of lower limb

Are natural microcosms useful model systems for ecology

Abstract: Several recent, high-impact ecological studies feature natural microcosms as tools for testing effects of fragmentation, metacommunity theory or links between biodiversity and ecosystem processes. These studies combine the microcosm advantages of small size, short generation times, contained structure and hierarchical spatial arrangement with advantages of field studies: natural environmental variance, 'openness' and realistic species combinations with shared evolutionary histories. This enables tests of theory pertaining to spatial and temporal dynamics, for example, the effects of neighboring communities on local diversity, or the effects of biodiversity on ecosystem function. Using examples, we comment on the position of natural microcosms in the roster of ecological research strategies and tools. We conclude that natural microcosms are as versatile as artificial microcosms, but as complex and biologically realistic as other natural systems. Research to date combined with inherent attributes of natural microcosms make them strong candidate model systems for ecology.

Substorm dependence of plasmaspheric hiss

Abstract: [1] We analyze wave and particle data from the CRRES satellite to determine the variability of plasmaspheric hiss (0.1 500 nT), with an average amplitude of 40 ± 1 pT observed in the region 2 15°) hiss is strongest during active conditions with an average amplitude of 47 ± 2 pT in the region 2 < L < 4 from 0800 to 1800 MLT but extending out beyond L = 6 from 1200 to 1500 MLT. Equatorial hiss at 600 Hz has minimum cyclotron resonant energies ranging from ∼20 keV at L = 6 to ∼1 MeV at L = 2, whereas midlatitude hiss at 600 Hz has minimum resonant energies ranging from ∼50 keV at L = 6 to ∼2 MeV at L = 2. The enhanced equatorial and midlatitude hiss emissions are associated with electron flux enhancements in the energy range of tens to hundreds of keV, suggesting that these electrons are the most likely source of plasmaspheric hiss. The enhanced levels of plasmaspheric hiss during substorm activity will lead to increased pitch-angle scattering of energetic electrons and may play an important role in relativistic electron dynamics during storms.

An epidemic model in a patchy environment.

Abstract: An epidemic model is proposed to describe the dynamics of disease spread among patches due to population dispersal. We establish a threshold above which the disease is uniformly persistent and below which disease-free equilibrium is locally attractive, and globally attractive when both susceptible and infective individuals in each patch have the same dispersal rate. Two examples are given to illustrate that the population dispersal plays an important role for the disease spread. The first one shows that the population dispersal can intensify the disease spread if the reproduction number for one patch is large, and can reduce the disease spread if the reproduction numbers for all patches are suitable and the population dispersal rate is strong. The second example indicates that a population dispersal results in the spread of the disease in all patches, even though the disease can not spread in each isolated patch.

Understanding Customer Trust in Agent-Mediated Electronic Commerce, Web-Mediated Electronic Commerce, and Traditional Commerce

Abstract: Customer trust is important in agent-mediated electronic commerce, web-mediated electronic commerce, and traditional commerce. However, the meaning of customer trust in these contexts has not been clearly defined or fully delineated. This paper proposes a new trust model that differentiates between cognitive trust and emotional trust, defines customer trust in each type of commerce as cognitive trust and emotional trust in the various entities (e.g., website, computer agent) that make up a commerce context, and then compares customer trust across the three types of commerce. We propose that, first, emotional trust merits research, particularly in e-commerce. Second, both awareness of the known and awareness of the unknown will be higher in e-commerce than in traditional commerce; this will lead to lower cognitive trust and emotional trust in e-commerce. Third, the key to increase customer trust in e-commerce is to design and develop technologies to reduce the distance between a customer and each entity, thereby increasing awareness of the known and decreasing awareness of the unknown. Fourth, cognitive trust and emotional trust fall along a continuum with potentially asymmetric effects on customer dependence on entities in e-commerce (e.g., computer agent adoption). Finally, future research on customer trust in e-commerce is outlined.

Maintenance of EMG activity and loss of force output with instability.

Abstract: Swiss Balls used as a platform for training provide an unstable environment for force production The objective of this study was to measure differences in force output and electromyographic (EMG) activity of the pectoralis major, anterior deltoid, triceps, latissimus dorsi, and rectus abdominus for isometric and dynamic contractions under stable and unstable conditions Ten healthy male subjects performed a chest press while supported on a bench or a ball Unstable isometric maximum force output was 596% less than under stable conditions However, there were no significant differences in overall EMG activity between the stable and unstable protocols Greater EMG activity was detected with concentric vs eccentric or isometric contractions The decreased balance associated with resistance training on an unstable surface may force limb musculature to play a greater role in joint stability The diminished force output suggests that the overload stresses required for strength training necessitate the inclusion of resistance training on stable surfaces

Recognising and promoting collaboration in an online asynchronous discussion

Abstract: This paper reports on a study involving the identification and measurement of collaboration in an online asynchronous discussion (OAD). A conceptual framework served for the development of a model which conceptualises collaboration on a continuum of processes that move from social presence to production of an artefact. From this model, a preliminary instrument with six processes was developed. Through application of the instrument to an OAD, the instrument was further developed with indicators added for each process. Use of the instrument to analyse an OAD showed that it is effective for gaining insight into collaborative processes in which discussants in an OAD do or do not engage. Use of the instrument in other contexts would test and potentially strengthen its reliability and provide further insight into the collaborative processes in which individuals engage in OADs. Analysis of an OAD using the instrument revealed that participants engaged primarily in processes related to social presence and articulating individual perspectives, and did not reach a stage of sharing goals and producing shared artefacts. The results suggest that the higher-level processes related to collaboration in an OAD may need to be more explicitly and effectively promoted in order to counteract a tendency on the part of participants to remain at the level of individual rather than group or collaborative effort.

A Photo Elicitation Study of the Meanings of Outdoor Adventure Experiences

Abstract: This study explored the meanings of participating in college-based outdoor programs utilizing an innovative research methodology. Individual photo elicitation interviews were conducted with 14 part...

Cardiac plasticity in fishes: environmental influences and intraspecific differences

Abstract: Fish cardiac physiology and anatomy show a multiplicity of intraspecific modifications when exposed to prolonged changes in environmentally relevant parameters such as temperature, hypoxia and food availability, and when meeting the increased demands associated with training/increased activity and sexual maturation. Further, there is evidence that rearing fish under intensive aquaculture conditions significantly alters some, but not all, aspects of cardiac anatomy and physiology. This review focuses on the responses of cardiac physiology and anatomy to these challenges, highlighting where applicable, the importance of hyperplastic (i.e. the production of new cells) vs hypertrophic (the enlargement of existing cells) growth to the adaptive response of the heart. In addition, we summarize recent studies that have explored the relationship between the myocardial protection afforded by preconditioning and myocardial hypoxia tolerance. This latter research clearly demonstrates the capacity of the fish heart to adjust to short-term perturbations, and shows that it can be difficult to predict how short-term and long-term alterations in cardiac physiology will interact.

Laminar Forced Convection Heat Transfer in the Combined Entry Region of Non-Circular Ducts

Abstract: A new model for predicting Nusselt numbers in the combined entrance region of non-circular ducts and channels is developed. This model predicts both local and average Nusselt numbers and is valid for both isothermal and isoflux boundary conditions. The model is developed using the asymptotic results for convection from a flat plate, thermally developing flows in non-circular ducts, and fully developed flow in non-circular ducts. Through the use of a novel characteristic length scale, the square root of cross-sectional area, the effect of duct shape on Nusselt number is minimized. Comparisons are made with several existing models for the circular tube and parallel plate channel and with numerical data for several non-circular ducts

The role of medical education in the recruitment and retention of rural physicians.

Abstract: In many countries the sustainability of rural healthcare systems is being challenged by a shortage of rural physicians and difficulties in recruiting and retaining physicians in rural practice. There are numerous factors that influence efforts in rural physician recruitment and retention, many of which are beyond the scope of the academic medical centre and medical education. Nevertheless, there are strategies that medical schools can adopt to contribute to efforts to recruit and retain physicians in rural communities. Rural student recruitment, admissions policies, rural-oriented medical curriculum, rural practice learning experiences, faculty values and attitudes, and advanced procedural skills training are areas which the medical school has direct control of and which have been shown to influence the likelihood of medical students entering rural primary care practice. The purpose of this paper is to elaborate on some of the key strategies that have been identified in the literature.

Polyphenolics extracts from legume seeds: correlations between total antioxidant activity, total phenolics content, tannins content and astringency

Abstract: Extracts of polyphenolic compounds were obtained from seeds of faba bean, broad bean, adzuki bean, red bean, pea, red lentil and green lentil using 80% (v/v) acetone. The total antioxidant activity (TAA) of extracts was determined and their astringency (Sensation Astringency Indices – SAI) investigated using the sensory scaling method. The content of tannins in extracts was expressed as absorbance values at 500 and 550 nm after color developed with vanillin/HCl reagent and after n-butanol-HCl hydrolysis, respectively. A statistically significant correlation was found between the TAA values and total phenolics (P = 0.01), TAA and tannins determined by vanillin method (P = 0.05), TAA and tannins determined after n-butanol-HCl hydrolysis (P = 0.05), SAI values and tannins determined with vanillin method (P = 0.10), SAI values and tannins determined after n-butanol-HCl hydrolysis (P = 0.05), SAI values and total phenolics (P = 0.01), total phenolics and tannin content determined by vanillin method (P = 0.01), total phenolics and tannin content determined after n-butanol-HCl hydrolysis (P = 0.05), tannins determined with vanillin method and tannins determined after n-butanol hydrolysis (P = 0.02).

Integrated inherent safety index (I2SI): A tool for inherent safety evaluation

Abstract: Inherent safety is a proactive approach for loss prevention and risk management. Considering the lifetime costs of a process and its operation, an inherent safety approach can lead to a cost-optimal option. Inherent safety may be achieved at any stage of process design; however, its application at the early stages of process design yields the best results. Despite being an attractive and cost-effective approach, the inherent safety methodology is not widely used. Many reasons have been attributed to this lack of widespread use; the nonavailability of systematic tools for the application of inherent safety principles is perhaps the most important reason. This paper presents a conceptual framework of an integrated inherent safety index (I2SI). It is called an integrated index because the procedure, when fully developed, is intended to consider the life cycle of the process with economic evaluation and hazard potential identification for each option. The I2SI is composed of subindices which account for hazard potential, inherent safety potential, and add-on control requirements. An application of the I2SI is also discussed. © 2004 American Institute of Chemical Engineers Process Saf Prog 23: 136–148, 2004

Community health psychology: promoting analysis and action for social change.

Abstract: Community health psychology is concerned with the theory and method of working with communities to combat disease and to promote health. This introductory article outlines key assumptions and debates underlying this area of research and practice-in the interests of framing the papers in this special edition of the Journal of Health Psychology. Attention is given to the value of emphasizing the community level of analysis and action; the role of collective action in improving health; psycho-social mediatiors between community participation and health; and the potential role of partnerships in creating 'healthy communities'. A distinction is made between 'accommodationist' and 'critical' perspectives, and the authors consider whether or not significant social change can come from community-level action.

Amino acid metabolism in the Zucker diabetic fatty rat: effects of insulin resistance and of type 2 diabetes.

Abstract: We investigated amino acid metabolism in the Zucker diabetic fatty (ZDF Gmi fa/fa) rat during the prediabetic insulin-resistant stage and the frank type 2 diabetic stage. Amino acids were measured ...