An Analysis of the Belousov-Zhabotinskii Reaction

In this survey paper, we begin with a brief history of the celebrated Belousov-Zhabotinskii (BZ) reaction. In particular, we consider the BZ reaction in a continuously stirred, closed vessel in the presence of a ferroin indicator. We examine the underlying chemical kinetics of the most significant reactions involved. This leads to the Oregonator model and an associated 3 x 3 system of nonlinear ordinary differential equations. We nondimensionalize this system and further reduce it to a 2 x 2 stiff system. Relaxation oscillations are expected and an analysis of the phase plane confirms this. Finally, we solve the system numerically for a certain set of system parameters and compare our computations with experimental results

The importance of self-efficacy and basic psychological needs in children’s physical activity: Measurement, prediction and intervention

The importance of physical activity in the overall health promotion and primary prevention of cardiovascular disease risk factors and metabolic diseases in children is well established. Nonetheless, interventions to increase physical activity among this population have been largely unsuccessful. The main objective of the research in this dissertation was to explore the suitability of self-efficacy and basic psychological needs for physical activity prediction and intervention in children. Item generation and psychometric evaluation of psychological questionnaires occurred in study 1 (Chapter 2). Using a prospective design, study 2 (Chapter 3) established task efficacy, barriers efficacy, competence, and autonomy as significant predictors of self-reported physical activity (R2 = 20.3%, p \u3c 0.05). Examining objective minutes in physical activity, autonomy accounted for 8% of the variance associated with moderate activity, while competence accounted for 9.4% of the variance associated with vigorous activity. Relatedness was unrelated to any physical activity outcome. In study 3 (Chapter 4), salient predictors from study 2 were targeted to increase physical activity in a sample of under-active children via a novel motivational interviewing inspired intervention protocol. The intervention significantly increased autonomy and competence but not physical activity. Overall findings provide initial construct validity and reliability evidence for the measures, and describe relationships between self-efficacy, psychological needs and physical activity in children. The brief intervention shows promise for affecting competence and autonomy, however, appears insufficient to increase physical activity

COORDNIATION OF CENTER OF MASS VELOCITY AND UPPER EXTREMITY KINEMATICS DURING BASKETBALL SHOTS FROM TWO DISTANCES

The purpose of this study was to analyze the coordination patterns for individual players when shooting from different distances. Seven experienced basketball players attempted at least 10 shots from 4.19 m and 6.02 m from the hoop. The coordination between the player’s center of mass vertical velocity, upper arm angular velocity, and forearm angular velocity were characterized using phase-plane analysis. Within player, coordination of center of mass vertical velocity and arm kinematics were found to be unique to each individual and comparable between shot distances, particularly during the shot preparation phase. Deviations in coordination patterns between shot distances were attributed to increases in center of mass vertical velocity at ground departure and ball release, consistent with the need for a greater ball velocity at release at further shot distances

Can Simple Postural Instructions Modify Running Forms in Recreational Runners

Purpose/Hypothesis: Recent research suggests that alteration of trunk angle and foot strike pattern during running may result in beneficial changes that prevent running related injuries due to reduction in vertical ground reaction forces (vGRF). For example, running form emphasizing a forward trunk lean and a midfoot or forefoot strike pattern has been shown to be effective in reducing knee stress and the risks of other impact-related running injuries. In clinical practice however, it is currently unknown if simple postural cues given to runners can elicit motor learning that leads to modification of running form. The purpose of this study was to analyze the biomechanical changes in the running form of recreational runners after being instructed to run with a forward trunk lean and a forefoot strike pattern over a 4-week training period. Methods: Eighteen runners, 11 females and 7 males, mean age 28.5±6.10 years, mean body mass index= 23.18 kg/m2, that run at least five miles per week and are injury free at the time of the study participated. During a 4-week training period, the runners received the following simple postural instructions: 1) lean your trunk forward and 2) land on the front part of your foot. The runners were asked to focus on these postural cues whenever they ran on their own during the 5-week study period. Participants were assessed at the following time points: prior to training (PRE), immediately after receiving the instructions (iPST), at 2 weeks (2WK) and 4 weeks (4WK), and 7-10 days after the conclusion of training (RET). Assessment consisted of an initial running trial on a treadmill during which trunk angle and peak vertical ground reaction force (vGRF) in stance phase were assessed using a 3D motion capture system and a force plate-instrumented treadmill. The runners were assessed at their self-selected running speed and a predetermined speed of 2.5 m/s during which three 20-second trials were collected for each speed. One-way repeated measures ANOVA tests were used to compare the changes in trunk angle and peak vGRF over time. Results: There was a significant increase in forward trunk angle during running immediately after receiving the instructions for both running speeds (PRE vs. iPST, self-selected speed: 6.69º vs. 9.76º, p=0.001; 2.5m/s: 6.78º vs. 9.14º, p=0.005). When compared toPRE, there was a significant increase in trunk flexion angle at 4WK (PRE vs. 4WK, self-selected running speed: 6.69º vs. 9.94º, p=0.031; 2.5 m/s: 6.78º vs. 10.05º, p=0.002). When compared to PRE, there was a significant increase in trunk flexion angle at RET at 2.5 m/s speed (PRE vs. RET: 6.78º vs. 9.99º, p=0.044), however there was no significant increase in trunk flexion angle at RET for the self-selected speed (PRE vs. RET: 6.69º vs. 9.45º, p=0.111). There was no significant change in vGRF over the course of the training for the self-selected and 2.5 m/s speeds (p=0.644 and 0.187, respectively). Conclusions: Based on our findings, we conclude that simple postural instructions and training over 4 weeks can induce changes in trunk angle during running in recreational runners. However, vGRF may not significantly change after alteration of trunk posture. Clinical Relevance: This study demonstrated that simple postural instructions can induce short- and mid-term changes in running form in recreational runners

THE CONTRIBUTION OF BODY CENTER OF MASS VELOCITY TO BASKETBALL BALL RELEASE VELOCITY ACROSS SHOT DISTANCES

This study investigated the contribution of the body center of mass velocity to basketball ball velocity at release when taking shots from different distances from the hoop. Seven basketball players with ten years of experience performed at least ten shots from progressively greater distances: close (\u3c 2.5 m), medium (4.57 m, free throw line), and long (6.02 m, American high school three-point line). As the distance from the hoop increases, the ball velocity required at release increases. Our hypothesis was that an increase in the shot distance would increase the contribution of the body center of mass velocity to ball velocity at release was hypothesized. Kinematics of the ball were recorded using video. Reaction forces generated by each leg were measured using two force plates and used to determine the velocity of the body center of mass during the shooting motion. The results indicate that the percent contribution of the body center of mass velocity to ball velocity at release increased, and the arm contribution decreased with an increase in shot distance. Releasing the ball earlier in the body center of mass trajectory before the apex resulted in a greater percent body contribution of the center of mass vertical velocity to ball vertical velocity

The effects of sustained attention, workload and task-related fatigue on physiological measures and performance during a tracking task

Despite extensive research into the concept of mental fatigue there is as yet no “gold standard” definition or measurement technique available. Because of this a large amount of fatigue-related errors are still seen in the workplace. The complexity of the problem lies with the inability to directly measure mental processes as well as the various endogenous and exogenous factors that interact to produce the experienced fatigue. Fatigue has been divided into sleep-related and task-related fatigue; however the task-related aspect is evident both during normal waking hours as well as during periods of sleep deprivation, therefore this aspect is considered important in the understanding of fatigue in general. The concept of task-related fatigue has further been divided into active and passive fatigue states; however differentiation between the two requires careful consideration. Various physiological measures have been employed in an attempt to gain a better understanding of the mechanisms involved in the generation of fatigue, however often studies have produced dissociating results. The current study considered the task-related fatigue elicited by a tracking task requiring sustained attention, in order to evaluate the usefulness of various cardiovascular and oculomotor measures as indicators of fatigue. A secondary aim was to determine whether the behavioural and physiological parameter responses could be used to infer the type of fatigue incurred (i.e. an active versus passive fatigue state) as well as the energetical mechanisms involved during task performance. A simple driving simulator task was used as the main tracking task, requiring constant attention and concentration. This task was performed for approximately two hours. Three experimental groups (consisting of 14 subjects each) were used: a control group that performed the tracking task only, a group that performed a five minute auditory memory span task concurrently with the driving task after every 20 minutes of pure driving, and a group that performed a visual choice reaction task for five minutes following every 20 minute driving period. The secondary tasks were employed in order to evaluate the extent of resource allocation as well as arousal level. Performance measures included various driving performance parameters, as well as secondary task performance. Physiological measures included heart rate frequency (HR) and various time- and frequency-domain heart rate variability (HRV)parameters, pupil dilation, blink frequency and duration, fixations, and saccadic parameters as well as critical flicker fusion frequency (CFFF). The Borg CR-10 scale was used to evaluate subjective fatigue during the task, and the NASA-TLX was completed following the task. A decline in driving performance over time was supplemented by measures such as HR, HRV and pupil dilation indicating an increase in parasympathetic activity (or a reduction in arousal). An increase in blink frequency was considered as a sign of withdrawal of attentional resources over time. Longer and faster saccades were also evident over time, coupled with shorter fixations. With regards to the secondary task influence, the choice RT task did not affect any behavioural or physiological parameters, thereby contesting the active fatigue theory of resource depletion, as well as implying that the increase in demand for the same resources used by the primary task was insufficient to affect the state of the subjects. The increased load elicited by the memory span task improved driving performance and increased measures of HR, HRV, pupil dilation and blink frequency. Some of these measures produced opposite effects to what was expected; an attempt to explain the dissociation of the various physiological parameters was expressed in terms of arousal, effort and resource theories. Overall, the results indicate that the fatigue and/or reduced arousal accompanying a monotonous sustained attention task can, to some degree, be alleviated through intermittent performance of a secondary task engaging mental resources other than the ones used for the primary task. The degree to which such a task is beneficial, however, requires careful consideration as while an immediate increase in arousal and primary task performance is noted, the impact of the task on general attentional resources may be detrimental in the case of reacting should an emergency situation occur

Comparison of Bayesian Credible Intervals to Frequentist Confidence Intervals

Frequentist confidence intervals were compared with Bayesian credible intervals under a variety of scenarios to determine when Bayesian credible intervals outperform frequentist confidence intervals. Results indicated that Bayesian interval estimation frequently produces results with precision greater than or equal to the frequentist method

Microbial Communities in a High Arctic Polar Desert Landscape

The High Arctic is dominated by polar desert habitats whose microbial communities are poorly understood. In this study, we used next generation sequencing to describe the α- and β-diversity of microbial communities in polar desert soils from the Kongsfjorden region of Svalbard. Ten phyla dominated the soils and accounted for 95% of all sequences, with the Proteobacteria, Actinobacteria, and Chloroflexi being the major lineages. In contrast to previous investigations of Arctic soils, relative Acidobacterial abundances were found to be very low as were the Archaea throughout the Kongsfjorden polar desert landscape. Lower Acidobacterial abundances were attributed to characteristic circumneutral soil pHs in this region, which has resulted from the weathering of underlying carbonate bedrock. In addition, we compared previously measured geochemical conditions as possible controls on soil microbial communities. Phosphorus, pH, nitrogen, and calcium levels all significantly correlated with β-diversity, indicating landscape-scale lithological control of available nutrients, which in turn, significantly influenced soil community composition. In addition, soil phosphorus and pH significantly correlated with α-diversity, particularly with the Shannon diversity and Chao 1 richness indices