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No description available.

Aim The experiment proposed to study the effect of sustained visual attention in an effective visual field of 40 degrees, in cued and uncued conditions with different set-sizes. Methods The participants had a normal contrast and visual acuity with normal ocular/general health. The experiments were performed both for central (0 - 20degrees) and peripheral (>20 – 50 degrees) visual fields. The targets were presented with valid and invalid cued conditions in different set-sizes of 500, 1000 and 2000. The targets were Gabor gratings oriented at 90 or 180deg subtending a minimum angle of resolution (MAR) ranging from 1.5-10minarc at 25cm. The spatial frequency of the Gabor ranged from 1- 29cycles/degrees and contrast from 20-100%. The observer had to identify the Gabor with horizontal grating and register the response. The accuracy and the reaction times for the targets were evaluated. Results The central targets had lower reaction times and high accuracy compared to the peripheral targets. There was a significantly increasing eccentricity effect as the targets were displayed much peripherally. It was less with presentation of valid sustained cues but it was not eliminated. The diminishing contrast of the target had a significant increase in reaction times and reduced accuracy. The effect of increasing number of items in the display didn’t show any significant increase in reaction time, i.e. there was no “set-size effect” seen both central and peripheral targets. The valid cues improved the performance with lower reaction times, compared to the neutral cued conditions, in each of the different experiments and resulted in an improved accuracy in both the central and peripheral visual field. Conclusion Visual attention is affected by contrast, target size and spatial gratings. Reaction time is high and accuracy less for low contrast targets, high spatial frequency and larger set-size, except for set-size 2000 in the central field where it was seen that the reaction times were reduced. The effect is consistent in both central and peripheral visual fields. The set-size also has an effect on the reaction times and on accuracy. The effects are more pronounced in the peripheral visual field.

Aim The experiment proposed to study the effect of sustained visual attention in an effective visual field of 40 degrees, in cued and uncued conditions with different set-sizes. Methods The participants had a normal contrast and visual acuity with normal ocular/general health. The experiments were performed both for central (0 - 20degrees) and peripheral (>20 – 50 degrees) visual fields. The targets were presented with valid and invalid cued conditions in different set-sizes of 500, 1000 and 2000. The targets were Gabor gratings oriented at 90 or 180deg subtending a minimum angle of resolution (MAR) ranging from 1.5-10minarc at 25cm. The spatial frequency of the Gabor ranged from 1- 29cycles/degrees and contrast from 20-100%. The observer had to identify the Gabor with horizontal grating and register the response. The accuracy and the reaction times for the targets were evaluated. Results The central targets had lower reaction times and high accuracy compared to the peripheral targets. There was a significantly increasing eccentricity effect as the targets were displayed much peripherally. It was less with presentation of valid sustained cues but it was not eliminated. The diminishing contrast of the target had a significant increase in reaction times and reduced accuracy. The effect of increasing number of items in the display didn’t show any significant increase in reaction time, i.e. there was no “set-size effect” seen both central and peripheral targets. The valid cues improved the performance with lower reaction times, compared to the neutral cued conditions, in each of the different experiments and resulted in an improved accuracy in both the central and peripheral visual field. Conclusion Visual attention is affected by contrast, target size and spatial gratings. Reaction time is high and accuracy less for low contrast targets, high spatial frequency and larger set-size, except for set-size 2000 in the central field where it was seen that the reaction times were reduced. The effect is consistent in both central and peripheral visual fields. The set-size also has an effect on the reaction times and on accuracy. The effects are more pronounced in the peripheral visual field.

Methods are presented for the predication of the short-term and sustained load behaviour of reinforced concrete frames. These procedures are evaluated by an experimental program using a particular structure and loading configuration. The results of two short-term tests and one sustained load test are compared with the analytic predictions. The inadequacy of classical methods of structural analysis for sustained load problems is also discussed. It is concluded that the methods using small elements, numerical integration and successive iterations can provide accurate predictions of short-term and sustained load behaviour of reinforced concrete beams. / Thesis / Master of Engineering (ME)

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No description available.

The objective of this research was to evaluate the long-term performance of enhanced anaerobic bioremediation (EAB) at chlorinated solvent sites and the occurrence of sustained treatment following EAB. A database of groundwater concentration versus time records was compiled for 25 sites with at least three years of post-treatment data. The median post-treatment monitoring period for these sites was 5.2 years, with a maximum of 11.7 years. Long-term performance was evaluated based on concentration changes from before treatment to the final year of post-treatment monitoring. Results indicate that the median concentration reduction for all 25 sites was approximately 80%, just under 1 order of magnitude. Sustained treatment, where concentrations remain suppressed after ceasing active treatment, was evaluated using a lines-of-evidence approach including analysis of rebound, statistical concentration trends after treatment, and decay rates from before and after treatment. Results indicate that sustained treatment is occurring at a majority of the sites.

The allocation of attentional resources to a focal task can influence performance on that task, but within-person changes in allocation policy is typically understudied. This study investigates the off-task pull of emotional experiences and the competing on-task pull of goals. Emotional experience was manipulated using an ostracizing event and goals were experimenter-assigned. The results did not support the off-task pull of emotional experiences or the on-task pull of goals. Implications and directions for future research are discussed.

Executive functions are higher-order cognitive functions underlying self-regulation of behavior. That is, executive functions make it possible to resolve internal conflicts and behave according to future goals rather than acting on sudden impulses or going on automatic. Very similarly, the temperamental construct of effortful control is defined as being able to inhibit a dominant response, instead acting on a subdominant response. In children, poor executive functions and low levels of effortful control have both been associated with several negative outcomes, such as lower academic achievements and externalizing behavior problems. Although these self-regulatory functions seem to play a very important role in child development, little is still known about them during the first years of life. Furthering the knowledge of early executive functions and effortful control would likely increase the chances of early detection of risks of poor development. The present thesis aimed to investigate individual differences in executive functions and effortful control in infancy and toddlerhood, as well as the early development of, and the relation between, these two functions. The thesis further aimed to investigate the relationship between the self-regulatory functions and activity level, and the possibility of predicting toddlerhood self-regulatory functions with sustained attention in infancy. In Study I, individual differences in 10-month-olds’ rudimentary executive functions were found, and these were related to temperamental activity level. In Study II, individual differences in sustained attention in infancy were found to predict toddlerhood executive functions and effortful control. Both these self-regulatory functions improved significantly from infancy to toddlerhood although the individual stability was low. Executive functions and effortful control were related in toddlerhood but not in infancy. In Study III we replicated and extended the finding of a longitudinal relation between infant sustained attention and toddlerhood executive functions. In addition, partial support for the proposition that executive functions develop in a hierarchical fashion was found, with simple inhibition being predictive of more complex forms of working memory two years later. The results from the three studies combined contribute to a better understanding of the early development of the self-regulatory functions executive functions and effortful control.