Cheyne-Stokes respiration is a distinct breathing pattern consisting of periods of hyperpnea followed by apneas, with unknown etiology. One in two patients with congestive heart failure suffer from this condition. Researchers hypothesize that key factors in CSR are the fluid shift from the standing to supine position and the differences between genders. A mathematical model of the cardio-respiratory system was constructed using parameter values from real data. Hopf bifurcation analysis was used to determine regions of stable versus oscillatory breathing patterns. In the model, Cheyne-Stokes respiration is more likely to occur while in the supine position and males are more likely to develop Cheyne-Stokes than females. These findings, which are in agreement with clinical experience, suggest that both gender and fluid shift contribute to the pathogenesis of Cheyne-Stokes respiration, and that physical quantities such as blood volumes and neural feedback may be sufficient to explain the observations of CSR. / Department of Mathematics and Statistics

Background: Long-term night shift work has been associated with multiple cancer sites, including breast, prostate, colon and endometrial. The mechanism for this effect is hypothesized to include the hormone melatonin; where increased light at night exposure during shift work reduces melatonin production and decreased melatonin levels are associated with increased cancer risk. In addition, physical activity has been shown to reduce cancer risk and existing laboratory studies indicate it has the potential to influence melatonin levels. Methods: A cross-sectional study of light intensity exposure, physical activity and melatonin levels was conducted among 61 rotating shift nurses at Kingston General Hospital. Light intensity exposure was measured using a light intensity data logger and melatonin concentrations were measured from urine and saliva samples, collected over a 24-hour period. Physical activity was assessed from a study questionnaire and one-day diary. Results: A statistically significant inverse association between light exposure and urinary melatonin levels was observed; however, the relationship was no longer significant when stratified by shift group. Analysis of salivary melatonin levels demonstrated that circadian rhythms of melatonin production in night workers were not altered in timing, such that peak melatonin production occurred at night. No association between light exposure and the magnitude of salivary melatonin variation was observed. The relationship between recent physical activity and melatonin differed by shift group, with a positive association seen among day workers, while an inverse relationship was seen among night workers. There was no association between usual physical activity and melatonin in either shift group. Finally, no significant correlation was observed between sleep duration and melatonin among either day or night workers. Conclusions: While this study demonstrated an inverse relationship between light intensity and melatonin, the comparison of functional time points between day and night workers meant that differences in urinary melatonin levels between shift groups could be attributed to differences in the time of day when urine samples were collected. No consistent relationship between recent or usual physical activity and melatonin levels was observed in either shift group. Sleep duration was not correlated with urinary melatonin levels, suggesting it cannot be used as a proxy for melatonin production. / Thesis (Master, Community Health & Epidemiology) -- Queen's University, 2008-06-26 08:39:21.645

Background: In 2007, the International Agency for Research on Cancer (IARC) classified long-term shift work as a probable human carcinogen; however, the mechanism through which shift work potentially increases cancer risk is not known. One hypothesis is that diminished melatonin production may be involved, possibly as a result of exposure to light during night work. Experimental studies suggest a link between melatonin and peptides in the insulin-like growth factor (IGF) family, also implicated in carcinogenesis. This research aimed to describe the distributions of circulating concentrations of insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding protein-3 (IGFBP-3) and their associations with urinary melatonin as possible intermediates in the pathway between work at night and breast cancer. Methods: A cross-sectional study was conducted among 85 premenopausal nurses working a rotating shift pattern of two 12-hour days, two 12-hour nights, and five days off. Once during both the summer and winter seasons, melatonin metabolites were measured in urine samples and circulating concentrations of IGF-I and IGFBP-3 were determined from serum samples. Weight and height were measured by the study coordinator, while a questionnaire and study diaries were used to collect all other covariate information. Predictors of IGF levels were identified using multivariate mixed effects modeling and relationships between melatonin and the IGFs were investigated using Spearman’s rank correlation and multivariate mixed effects modeling. Results: Both age (β = -3.6, p < 0.0001) and current OC use (β = -40.8, p = 0.003) were associated with decreases in circulating IGF-I, while levels of IGF-I were increased in the winter months (β = 26.3, p = 0.02). A positive relationship between recent alcohol consumption and serum IGFBP-3 was also suggested (β = 197.8, p = 0.05). Neither Spearman’s rank correlations nor mixed effects modeling indicated that urinary melatonin was a determinant of serum IGFs. Conclusions: Age, season, and current OC use were observed to predict circulating IGF-I, while recent alcohol consumption was a determinant of IGFBP-3 levels. A relationship between melatonin and IGFs, theorized as a component of the mechanism linking shift work and cancer, was not supported by the results of this project. / Thesis (Master, Community Health & Epidemiology) -- Queen's University, 2012-05-30 15:29:31.253

Background: Shift work has recently been identified as a breast cancer risk factor, where meta-analysis has indicated an approximately 50% increased risk among long-term shift workers. However, additional studies with more comprehensive methods of shift work exposure assessment are needed to capture the diversity of shift patterns. The hypothesized mechanism for this relationship involves chronodisruption (altered circadian rhythms), where increased exposure to light at night during night shifts may decrease production of the cancer-protective hormone melatonin. Further, coordination of circadian rhythms, including melatonin production, is governed by the interactions of a set of central clock genes. Recent studies have suggested that variants in clock genes are associated with cancer risk at multiple sites, including breast cancer, although few studies have considered potential interactions with shift work. Methods: This thesis examined relationships of both shift work and clock gene polymorphisms (and their interactions) with breast cancer risk in a case-control study of 1,142 cases and 1,178 controls. The association between light exposure and melatonin production was also investigated in a longitudinal biomarker study conducted among 123 nurses working a two-day, two-night rotating shift pattern. Results: In the case-control study, an association between breast cancer and ≥30 years of shift work (OR = 2.20, 95%CI = 1.13 – 4.28) was detected, although no relationship with short (0 – 14 years) or medium (15 – 29 years) term shift work was observed. As well, variants in 14 clock-related genes were not associated with breast cancer and there were no apparent interactions with shift work history. In the biomarker study, both peak melatonin levels and daily change in melatonin levels were similar when nurses were working their day and night shifts. Further, on the night shift, a slight inverse relationship between light and change in melatonin was observed (p = 0.04). Conclusions: Taken together, these results contribute to the understanding of both the association between shift work and breast cancer, and the biologic mechanisms underlying this relationship. Since shift work is required for many occupations, understanding the mechanisms through which it impacts breast cancer is important to the development of healthy workplace policy. / Thesis (Ph.D, Community Health & Epidemiology) -- Queen's University, 2012-09-26 20:59:40.209

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SAMMANFATTNING Bakgrund Att arbeta skift har visat sig vara en stressfaktor som påverkar både sömn och hälsa negativt och inom sjukvården kan även patientsäkerheten äventyras om personalen är utmattad på grund av sömnbrist. Syfte Syfte med denna litteraturstudie var att beskriva vilka faktorer som påverkar sömnen och kan medföra sömnstörningar, samt vilka preventiva åtgärder som kan leda till förbättrad sömn hos skiftarbetande vårdspersonal. Metod Resultatet bygger på tio vetenskapliga artiklar publicerade under åren 2007-2013. Dessa söktes genom databaserna Cinahl, PsykINFO och PubMed. Resultat I analysen av artiklarna framkom att skiftarbete som inkräktar på normala sömntider har en uppenbart skadlig effekt på sömnen med svårigheter att somna och sömnighet under både arbetstid och ledighet. Utmärkande var att stigande ålder och låg stresströskel (hardiness) ökade risken för sömnstörningar. Att ges möjlighet till tupplur under nattpass var en viktig åtgärd för att förebygga trötthet och främja hälsan hos skiftarbetande vårdpersonal. Slutsats Eftersom skiftarbete i sig har en uppenbart skadlig effekt på sömnen så är det av största vikt att ge vårdpersonalen bästa möjliga förutsättningar för att bibehålla sin hälsa på sikt. Förutom att planera för bra skiftscheman med schemalagd rast samt möjlighet att sova på nattpassen, bör man ta hänsyn till vårdpersonalens ålder och stresstålighet (hardiness). / ABSTRACT Background Working shift has been shown to be a stressor that impacts both sleep and health negatively and within the healthcare also the patient safety could be affected if the personnel are fatigued due to sleep deprivation. Aim The aim of the literature review was to describe which factors that influences sleep and can lead to insomnia, and which preventive actions that could lead to improved sleep among shift working healthcare personnel. Methods The analysis included then scientific articles (between year 2007-2013). The literature was sought from the databases Cinahl, PsykINFO och PubMed. Result The result showed that shift work that interfere with normal sleep times has an obvious harmful effect on sleep with difficulty falling asleep, and sleepiness during working time as well as leisure time. Significant was that age and low hardiness increased the risk for insomnia. To be able to take a nap during the nightshift was an important action to prevent sleepiness and promote health among shift working healthcare personnel. Conclusion Due to the fact that shift work in itself has an obvious harmful effect on sleep, it is of great importance to ensure the best possible conditions to retain health within the health care personnel in the long term. Beside planning for good shift systems, including night brake with possibility to take a nap, it is important to take age and hardiness into consideration.

We present the observations, reduction and preliminary analysis of a sample of 45 mid-to-high redshift galaxy clusters imaged with the Spitzer Space Telescope's MIPS camera at 24 ~m and selected from the Red Sequence Cluster Survey. The purpose of the data set is motivated by a broad review of studies into the evolutionary trends of galaxy clusters and their constituent galaxy populations, focusing specifically on recent results that indicate clusters are environmental drivers of dusty starburst and active galactic nuclei activity. To accommodate the large amount of data in hand, we have constructed an extensive data reduction pipeline for the MIPS data and describe its development and output in detail. Using the resulting catalogues for introductory analysis, we find strong evidence for an excess luminous infrared galaxy population in galaxy clusters at high redshift and discuss the implications of this discovery in terms of cluster evolution and motivate future work.

Problem: Many individuals with chronic illnesses such as stroke and ongoing activity limitations report self-perceived health related quality of life (HRQL) that is similar to that of healthy individuals. This phenomenon is termed response shift (RS). RS describes how people change: internal standards in assessing HRQL (recalibration), values (reprioritization), or how they define HRQL (reconceptualization), after an event such as stroke. Changes in HRQL post stroke may be inaccurate if RS is not taken into account. Increased knowledge of RS may affect the way in which HRQL measures are used, both clinically and in research. The overall objective was to assess RS in construct specific HRQL models post stroke: physical function, mental health, and participation. Methods: Data were analysed from the longitudinal study “Understanding Quality of Life Post-Stroke: A Study of Individuals and their Caregivers”. Six-hundred and seventy- eight persons with stroke at 1, 3, 6, and 12 months post stroke participated. Generic and stroke specific HRQL measures were collected. Descriptive analysis was completed with SAS, and identification of RS utilized structural equation modeling with LISREL. Results: Mean age of participants was 67 years (SD 14.8), and 45% were female. RS was identified in mental health using a framework which was developed for identifying RS statistically with multiple time points. RS was also identified in physical function where it had not been expected, possibly due to the self perceived nature of the response options. The effect size of change in physical function was affected by the presence of RS. The timing of RS in mental health and physical function was primarily around the 12 month time period, and predominantly recalibration RS. RS was also identified in participation. Conclusions: The framework that was developed was useful in identifying RS and incorporated important issues such as multiple testing and validation of the model. The presence of RS affects measurement of HRQL constructs post stroke; recalibration RS can be measured clinically with specific methods to account for RS. RS should also be measured in research studies to ensure accurate measurement of change. Future research should evaluate additional models in stroke and other populations.

Sustainability has become a buzz word of our time, although our developed world community is still coming to terms with what the word really means. Universities and polytechnics in Aotearoa New Zealand will have to change in many ways before sustainability can be considered to occupy a meaningful place in the tertiary education sector. However the change process that sees an organisation moving towards sustainability is complex, and agency for change can be considered on many different levels including the individual identities of staff and students, the identity of managers, and the programme and wider organisational identities constructed by the communities that comprise them. This qualitative research explores education for sustainability within the context of outdoor education using the Bachelor of Adventure Recreation and Outdoor Education (BRecEd) at the Christchurch Polytechnic Institute of Technology (CPIT) (the programme into which the author teaches) as a case study. Participatory action research forms the overarching methodology for a multiple method approach to data collection. The research leans heavily on the lived experiences of staff and students within the programme, is woven with my own reflections, and incorporates many examples of students’ work. The weaving together of these experiences grounds the research and helps bring theory to life. The research reveals the complexity of change towards more sustainable ways of practising outdoor education in an organisational setting. It explores the tensions that are encountered and mechanisms that have allowed for staff and students to engage in education for sustainability in a more meaningful way. The key themes of the research explore the intersection of identity construction processes and change agency, and it is argued these processes are inseparable for those concerned with organisational change towards sustainability.

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