The Transient response of heat exchangers

The transient response of heat exchangers to a change in inlet temperature of one of the fluids is of much interest in industrial practice. Due to the complexity of the problem, no generally accepted solutions exist. This thesis presents an extensive survey of major solutions available in literature and identifies the ranges of parameters for which solutions are not available. A commercially available thermal network solver software package (Thermonet) will be used to model the transient response of heat exchangers. The software package will be verified using five existing solutions found in literature. The software package will be utilized to generate transient solutions for a counterflow heat exchanger covering a wide range of parameters useful in engineering practice. The results are presented in tabular form. Important parametric influences are discussed and effects of process and geometrical variables on the transient performance is evaluated

Intraindividual variability is a fundamental phenomenon of aging: Evidence from an 8-year longitudinal study across young, middle and older adulthood

Moment-to-moment intraindividual variability (IIV) in cognitive speed is a sensitive behavioural indicator of the integrity of the aging brain and brain damage, but little information is known about how IIV changes from being relatively low in young adulthood to substantially higher in older adulthood. We evaluated possible age group, sex, and task differences in IIV across adulthood using a large, neurologically normal, population-based sample evaluated thrice over 8 years. Multilevel modeling controlling for education, diabetes, hypertension, and anxiety and depressive symptoms showed expected age group differences in baseline IIV across the adult lifespan. Increase in IIV was not found until older adulthood on simple tasks, but was apparent even in the 40s on a more complex task. Females were more variable than males, but only at baseline. IIV in cognitive speed is a fundamental behavioural characteristic associated with growing older, even among healthy adults

Pseudo-Stereo Audio Processor

Due to both technical and resource limitations, non-professional audio production must often record with a single microphone, creating a mono audio signal. Even some originally multi-channel audio files often combine the separate channels into a single channel to save memory. However, this channel limitation makes any music held within the audio duller during listening. The Pseudo-Stereo Audio Processor remedies this situation, introducing a quadrature phase shift onto a given single-channel audio signal, producing multiple phase shifted output signals. These separate fixed-phase output signals are then recombined to produce a variable phase difference, emulated two-channel version of the input signal, allowing for an easy post-production sound quality enhancement of a single-channel signal that independent or small-scale audio recording studios could utilize. Further, this method of quadrature filtering produces completely decorrelated output signals using a Hilbert Transform, creating unique auditory effects useful in certain aspects of psychoacoustic research much harder to obtain through other means

Changes in hedgerows in Britain between 1984 and 1990

1. This report summarises the results of work on changes in hedgerows which was commissioned by the Directorate of Rural Affairs, DOE, as part of the analysis of data collected during 'Countryside Survey 1990'. 2. The primary purpose of the report is to present data on change, and to provide descriptions of the methods used to obtain them. Discussion of results, and especially their relevance to countryside policy matters, is minimal although a short comment section is included to cover research and methodological aspects

Gait and cognition: mapping the global and discrete relationships in ageing and neurodegenerative disease

Recent research highlights the association of gait and cognition in older adults but a stronger understanding is needed to discern coincident pathophysiology, patterns of change, examine underlying mechanisms and aid diagnosis. This structured review mapped associations and predictors of gait and cognition in older adults with and without cognitive impairment, and Parkinson's disease. Fifty papers out of an initial yield of 22,128 were reviewed and a model of gait guided analysis and interpretation. Associations were dominated by the pace domain of gait; the most frequently studied domain. In older adults pace was identified as a predictor for cognitive decline. Where comprehensive measurement of gait was conducted, more specific pathological patterns of association were evident highlighting the importance of this approach. This review confirmed a robust association between gait and cognition and argues for a selective, comprehensive measurement approach. Results suggest gait may be a surrogate marker of cognitive impairment and cognitive decline. Understanding the specific nature of this relationship is essential for refinement of diagnostics and development of novel therapies

Inconsistency in serial choice decision and motor reaction times dissociate in younger and older adults

Intraindividual variability (inconsistency) in reaction time (RT) latencies was investigated in a group of younger (M = 25.46 years) and older (M = 69.29 years) men. Both groups performed 300 trials in 2-, 4-, and 8-choice RT conditions where RTs for decision and motor components of the task were recorded separately. A dissociation was evident in that inconsistency was greater in older adults for decision RTs when task demands relating to the number of choices and fatigue arising from time-on-task were high. For younger persons, a weak trend toward greater inconsistency in motor RTs was evident. The results are consistent with accounts suggesting that inconsistency in neurobiological mechanisms increases with age, and that attentional lapses or fluctuations in executive control contribute to RT inconsistency

The role of acceptance and job control in mental health, job satisfaction, and work performance

Acceptance, the willingness to experience thoughts, feelings and physiological sensations without having to control them or let them determine one's actions, is a major individual determinant of mental health and behavioral effectiveness in a more recent theory of psychopathology. This 2-wave panel study examined the ability of acceptance also to explain mental health, job satisfaction, and performance in the work domain. The authors hypothesized that acceptance would predict these 3 outcomes 1 year later in a sample of customer service center workers in the United Kingdom (N = 412). Results indicated that acceptance predicted mental health and an objective measure of performance over and above job control, negative affectivity, and locus of control. These beneficial effects of having more job control were enhanced when people had higher levels of acceptance. The authors discuss the theoretical and practical relevance of this individual characteristic to occupational health and performance

Job control mediates change in a work reorganization: intervention for stress reduction

This longitudinal, quasi-experiment tested whether a work reorganization intervention can improve stress-related outcomes by increasing people's job control. To this end, the authors used a participative action research (PAR) intervention that had the goal of reorganizing work to increase the extent to which people had discretion and choice in their work. Results indicated that the PAR intervention significantly improved people's mental health, sickness absence rates, and self-rated performance at a 1-year follow-up. Consistent with occupational health psychology theories, increase in job control served as the mechanism, or mediator, by which these improvements occurred. Discussion focuses on the need to understand the mechanisms by which work reorgnization interventions affect change

Cognitive Deficits Are Associated with Frontal and Temporal Lobe White Matter Lesions in Middle-Aged Adults Living in the Community

BACKGROUND The association between brain white matter lesions and cognitive impairment in old age is well established. However, little is known about this association in midlife. As this information will inform policy for early preventative healthcare initiatives, we investigated non-periventricular frontal, temporal, parietal and occipital lobe white matter hyperintensities (WMH) in relation to cognitive function in 428 (232 women) community-dwelling adults aged 44 to 48 years. RESULTS Frontal white matter lesions were significantly associated with greater intraindividual RT variability in women, while temporal WMH were associated with face recognition deficits in men. Parietal and occipital lobe lesions were unrelated to cognitive performance. These findings did not differ when education and a range of health variables, including vascular risk factors, were taken into account. CONCLUSION Gender differences in WMH-cognition associations are discussed, and we conclude that small vessel disease is present in midlife and has functional consequences which are generally not recognized. Preventative strategies should, therefore, begin early in life.David Bunce's collaboration in this work was supported by the Leverhulme Trust and the British Academy. The study was funded by NHMRC of Australia Unit Grant No. 973302, Program Grant No. 179805, NHMRC project grant No. 157125, grants from the Australian Rotary Health Research Fund and the Australian Brewers Foundation. Nicolas Cherbuin is funded by NHMRC Research Fellowship No. 471501. Kaarin Anstey is funded by NHMRC Research Fellowship No. 366756. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript

Aerobic Fitness and Intraindividual Reaction Time Variability in Middle and Old Age.

Objective: To examine whether aerobic fitness moderated age differences in within-person reaction time variability (WP RT variability) and given conceptual linkage involving the frontal cortex, whether effects were mediated by executive function. Method: Aerobic fitness (estimated VO2max) and WP RT variability were investigated in 225 healthy, community-dwelling adults aged 50-90 years (M = 63.83) across 4 cognitive domains; psychomotor performance, executive function, visual search, and recognition. Results: Significant Age × Aerobic fitness interactions were found in relation to WP variability in 3 cognitive domains: psychomotor performance (4-choice RT), executive function (Flanker and Stroop arrows), and immediate recognition. Lower aerobic fitness was associated with greater RT variability, and this effect increased with age. Additionally, some of these effects were mediated by executive function. Discussion: The findings suggest that aerobic fitness moderated the association between age and intraindividual RT variability, and that executive function selectively mediated that association. It is possible that aerobic fitness helps attenuate the neurobiological decline that contributes to cognitive deficits in old age and that WP variability is a measure that may be particularly sensitive to this effect