Journal Articles
Published Research
The following is a summary of journal publications by Associate Professor Knowles. Click on the references below for further details.
Journal Articles
2008
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Nelson, E. A., Palombo, E. A., & Knowles, S. R. (2008). Comparison of evaporation techniques for the preparation of salivary cortisol for analysis by liquid chromatography-electrospray tandem mass spectrometry. Clinical Biochemistry. Clinical Biochemistry, 41(16-17), 1413-1416.
Objective: Compare evaporation techniques in the work-up procedure of saliva samples for cortisol analysis by a previously validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method.
Design and methods: Samples were evaporated using freeze drying, centrifugal concentration, and nitrogen flow and analyzed by LC-MS/MS.
Results: Cortisol concentrations detected using each technique did not significantly differ. Factors other than the recovery of cortisol were evaluated.
Conclusions: Evaporation using freeze drying/centrifugal concentration is an automated process, reducing overall processing time for analysis of numerous samples.
URL: https://www.ncbi.nlm.nih.gov/pubmed/?term=18789315
Goldsworthy, B., & Knowles, S. (2008). Caregiving for Parkinson’s Disease Patients: An Exploration of a Stress-Appraisal Model for Quality of Life and Burden. Journal of Gerontology: Psychological sciences, 63, 372-376.
Extending the 2002 stress-appraisal model of Chappell and Reid, we examined the relationships between caregiver stressors (e.g., cognitive impairment and functional dependency of the recipient), appraisal (informal hours of caregiving), and protective factors (e.g., social support, self-esteem, and quality of the caregiver-recipient relationship) associated with the burden and quality of life of Parkinson’s disease caregivers. There were 136 caregivers (M = 64.59 years) who completed an online survey. Using structural equation modeling, we found that the extended stress-appraisal model of Chappell and Reid provided a good fit to the data (chi2 = 67.87, df = 55, p >.05; chi2/df = 1.23, Comparative Fit Index = 0.98, Root Mean Square Error of Approximation = 0.04). This study provides an important contribution to a growing field of research that applies theoretical models to investigate the stressors, appraisals, and protective factors that impact caregiver well-being.
URL: https://www.ncbi.nlm.nih.gov/pubmed/?term=19092040
Tucker, P., & Knowles, S. (2008). Review of studies that have used the Standard Shiftwork Index: Evidence for the underlying model of shiftwork and health. Applied Ergonomics, 39, 550-564.
The Standard Shiftwork Index (SSI) provides shiftwork researchers with a standardised battery for assessing the impact of shiftwork on psychological and physiological well-being. We review the published SSI literature and evaluate the extent to which the results of these publications support the model underpinning the SSI. A total of 70 SSI publications were identified, of which 41 were selected. The 41 studies were published between 1993 and 2006 and had a combined total of 21,420 respondents. The analysis indicated support for parts of the SSI model, particularly in relation to the impact of shift systems design on individual well-being, as well as the role of individual factors (e.g., personality, coping style). However, evidential support for the model as a whole is incomplete. The findings of the reviewed studies are summarised and methodological limitations are discussed.
URL: https://www.ncbi.nlm.nih.gov/pubmed/?term=18348885
Knowles, S.R., Nelson, E.A., & Palombo, E.A. (2008). Investigating the role of perceived stress on bacterial flora activity and salivary cortisol secretion: a possible mechanism underlying susceptibility to illness. Biological Psychology, 77, 132-137.
This study examined the impact of academic stress on salivary cortisol concentrations and lactic acid bacteria activity. Whole, unstimulated saliva samples and faecal samples were collected from 23 healthy undergraduate students (23.0+/-6.8 years; range 18-44) over two 1-week periods: during the beginning of semester (low-stress baseline condition) and during the first week of exams (high-stress condition). Students also completed a series of questionnaires measuring perceived levels of stress, gastrointestinal symptoms, and nutritional intake. Significant findings indicated that faecal lactic acid bacterial levels were lower during the high-stress condition. Paralleling this, students rated perceived levels of stress as being greater during the exam period compared to the baseline condition. The findings from this study have provided further insight into the link between stress and gastrointestinal flora activity in humans.
URL: https://www.ncbi.nlm.nih.gov/pubmed/?term=18023961