Li, Pulan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (p. 60-66). / Abstracts in English and Chinese. / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Overview of wavelength division multiplexed passive optical network (WDM-PON) and colorless optical network unit (ONU) --- p.1 / Chapter 1.2 --- Implementation of colorless ONU --- p.4 / Chapter 1.3 --- Rayleigh backscattering in WDM-PON --- p.6 / Chapter 1.4 --- Motivation of this thesis --- p.9 / Chapter 1.5 --- Outline of this thesis --- p.11 / Chapter Chapter 2 --- Previous works of remodulation for WDM-PON --- p.12 / Chapter 2.1 --- Introduction --- p.12 / Chapter 2.2 --- Devices utilized by colorless ONU in remodulation schemes --- p.13 / Chapter 2.2.1 --- Injection-locked Fabry-Perot laser diode at ONU --- p.13 / Chapter 2.2.2 --- Reflective semiconductor optical amplifier --- p.15 / Chapter 2.2.3 --- Reflective electro-absorption modulator and semiconductor optical amplifier (REAM-SOA) --- p.17 / Chapter 2.3 --- Modulation methods in remodulation schemes --- p.18 / Chapter 2.4 --- Summary --- p.23 / Chapter Chapter 3 --- A remodulation scheme based on time-interleaved DPSK modulation format --- p.25 / Chapter 3.1 --- Introduction --- p.25 / Chapter 3.2 --- Operation principle: time-interleaving technology for phase-modulated signal --- p.27 / Chapter 3.3 --- System architecture --- p.28 / Chapter 3.4 --- Experimental results and discussion --- p.31 / Chapter 3.5 --- Effect of timing misalignment on proposed remodulation scheme --- p.33 / Chapter 3.6 --- Summary --- p.35 / Chapter Chapter 4 --- Enhanced Tolerance to Rayleigh Backscattering in Remodulation Scheme Using Time-Interleaved DPSK Format --- p.37 / Chapter 4.1 --- Introduction --- p.37 / Chapter 4.2 --- Studies on Rayleigh backscattering suppression in optical domain --- p.39 / Chapter 4.2.1 --- RB suppression in carrier-distributed schemes --- p.39 / Chapter 4.2.2 --- RB suppression in remodulation schemes --- p.40 / Chapter 4.2 --- Experimental setup and results --- p.42 / Chapter 4.3 --- Discussion on RB suppression effect of the proposed scheme --- p.46 / Chapter 4.3.1 --- Theoretical study and simulation results --- p.46 / Chapter 4.3.2 --- Experimental demonstration of spectral relationship between signals and RB crosstalk --- p.49 / Chapter 4.4 --- Summary --- p.53 / Chapter Chapter 5 --- Conclusion and Future Works --- p.55 / Chapter 5.1 --- Conclusion of this thesis --- p.55 / Chapter 5.2 --- Future works --- p.57 / List of Publications --- p.59 / Bibliography --- p.60

Thesis (Master of Engineering in Electrical Engineering)--Cape Peninsula University of Technology, 2017. / This dissertation presents the development of a quadrature phase shift keying (QPSK) demodulator for nanosatellites that complies with both the limited resources associated with nanosatellites as well as the flexibility and configurability required for a software defined radio (SDR) platform. This research project is a component of a bigger project, which is to develop a high-speed receiver for nanosatellites, and aims to provide a practical solution to the need for communication technologies that support emerging nanosatellite applications, such as Earth observation and communications. The development of the QPSK demodulator follows an all-digital implementation approach. The main reason for selecting this approach is to have a system that is flexible and reconfigurable to comply with the SDR requirements. Another reason for selecting this approach is to comply with the low noise system, low power consumption as well as the small size and weight requirements associated with nanosatellites. The QPSK demodulator is implemented on an IGLOO2 Field Programmable Gate Array (FPGA), due to its robustness to radiation and high-speed capability. Initially, the techniques used to design each subsystem of the QPSK demodulator are selected. Then, algorithms to digitally implement the designed subsystems are produced. Thereafter, the code for the digital QPSK demodulator is written and verified in Matlab first. The simulation of the Matlab-based QPSK demodulator performs satisfactorily. Subsequently, the code to implement the QPSK demodulator on an FPGA (IGLOO2) has been written in Libero, using VHSIC Hardware Description Language (VHDL). The resulting FPGA-based QPSK demodulator has been emulated in Libero (an integration and development environment (IDE) for Microsemi FPGAs) using a test-bench as well as other analysis tools. The test-bench results are visualized using Modelsim. The results show that the demodulator can support data rates up to 13.25 Mbps if 16 samples-per-symbols are used, and up to 26.5 Mbps if 8 samples-per-symbols are used. It also has a very good bit-error-rate performance, which is simulated to be within a factor of 5 of the theoretical limit of QPSK modulation. Finally, the demodulator consumes less than 15 mW at the maximum operating speed. and has been coded to mitigate the effects of space radiation and noise contriution by the demodulator itself.

Magnetic source magnetic resonance imaging (msMRI) is an fMRI technique that has been under development for direct detection of neuronal magnetic fields to map brain activity and has been shown to be experimentally detectable using conventional means, but there is debate on the detection of the msMRI signal since it can be only a 0.2% change. Detection of its temporal characteristics has yet to be reported and may strengthen the case for msMRI detection. The temporal characteristics of the detected msMRI signal were examined in this work, but it was found that the sensitivity of conventional analysis techniques are low within the context of msMRI, preventing consistent msMRI signal detection and analysis of its temporal characteristics. Examination of blood oxygen level dependent (BOLD) contrast contamination and application of mean-shift clustering (MSC) to fMRI analysis were performed to look into the possibility of improving the low sensitivity. fMRI analysis is commonly performed with cross correlation analysis (CCA) and techniques based on the General Linear Model (GLM), but both CCA and GLM techniques typically perform calculations on a per-voxel basis and do not consider relationships neighboring voxels may have. MSC is a technique to consider for this purpose and shows improved activation detection for both simulated and real BOLD fMRI data. To consider the issue of BOLD contamination, the hemodynamic response over time was examined using repeated median nerve stimulation. On average, the results show the BOLD signal is not detectable after the second fMRI run. The results are consistent with previous hemodynamic habituation effect studies with other types of stimulation, but they do not completely agree with findings of evoked potential studies. Overall, this work shows that the low detection sensitivity may be able to be addressed with the purpose of furthering msMRI research.

The circadian system controls 24-hour cycles of behavior and physiology, such as rest-activity and feeding rhythms. The human circadian system synchronizes with, or entrains to, the light/dark cycle (sunrise/sunset) to promote activity and food consumption during the day and rest at night. However, strict work schedules and nighttime light exposure impair proper entrainment of the circadian system, resulting in chronic circadian misalignment. Numerous studies have shown that chronic circadian misalignment results in poor health. Therefore, therapeutic interventions that could shift circadian rhythms and alleviate circadian misalignment could broadly impact public health. Although light is the most salient time cue for the circadian system, several laboratory studies have shown that exercise can also entrain the internal circadian rhythm. However, these studies were performed in controlled laboratory conditions with physically-active participants. The purpose of this study was to determine whether timed exercise can phase advance (shift earlier) the internal circadian rhythm in sedentary subjects in free-living conditions. Fifty-two young, sedentary adults (16 male, 24.3±0.76 yrs) participated in the study. As a marker of the phase of the internal circadian rhythm, we measured salivary melatonin levels (dim light melatonin onset: DLMO) before and after 5 days of timed exercise. Participants were randomized to perform either morning (10h after DLMO) or evening (20h after DLMO) supervised exercise training for 5 consecutive days. We found that morning exercisers had a significantly greater phase advance than evening exercisers. Importantly, the morning exercisers had a 0.6h phase advance, which could theoretically better align their internal circadian rhythms with the light-dark cycle and with early-morning social obligations. In addition, we also found that baseline DLMO, a proxy for chronotype, influenced the effect of timed exercise. We found that for later chronotypes, both morning and evening exercise advanced the internal circadian rhythm. In contrast, earlier chronotypes had phase advances when they exercised in the morning, but phase delays when they exercised in the evening. Thus, late chronotypes, who experience the most severe circadian misalignment, may benefit from exercise in the morning or evening, but evening exercise may exacerbate circadian misalignment in early chronotypes. Together these results suggest that personalized exercise timing prescriptions based on chronotype could alleviate circadian misalignment in young adults.

Bedside reporting is one way to improve communication among the health care team. At the study site, at least 50% of bedside reporting was being conducted at the door of the patient's room instead of at the patient's bedside. The project question addressed whether a computer-based education and training video on bedside reporting and a standardized bedside reporting checklist would increase the rate of bedside shift-to-shift reporting among a medical surgical unit (MSU) to 100%. The project addressed the implementation of standardizing bedside reporting through education and training using Agency for Health Care Research and Quality's (AHRQ) Guide to patient and family engagement. The project also promoted use of a standardized tool to conduct bedside reporting and a surveillance tool to ensure bedside reporting was being conducted. Data was collected through surveys and surveillance. The data was tabulated for frequencies displayed in percentages. Post-implementation findings indicated that bedside reporting went from 0% to 86% during the 2-week surveillance period. MSU nursing staff improved their knowledge and skill on how to conduct bedside reporting, but their attitude did not change as they thought the practice of bedside reporting was not an effective use of their time. Findings may be used to increase involvement of patients and families in their inpatient health care.

Firefighters experience stressful job demands. Many of them work in shifts that can extend to 96-hour rotations. Firefighters also tend to suffer from poor sleep quality and psychological distress; however, there are conflicting findings on how these factors may relate to each other. The purpose of this quantitative survey study was to examine the relation between symptoms of depression, anxiety, posttraumatic stress disorder (PTSD), and alcohol abuse to shift duration in firefighters who work 24-hour shifts compared to those who work 48-hour shifts, with sleep quality as a mediating variable. The repair and restoration theory of sleep was the theoretical framework. One hundred forty-three adult firefighters employed in the midwestern region of the United States completed a demographic questionnaire, the Pittsburgh Sleep Quality Index, and the Psychiatric Diagnostic Screening Questionnaire using an online survey to help ensure anonymity. The results of a multivariate analysis of covariance indicated that anxiety [F (1, 140) = 4.042, p = .042; F (1, 140) = 4.521, p = .035] and alcohol abuse [F (1, 140) = 12.497, p = .001; F (1, 140) = 12.686, p =.001] were both significantly related to shift duration before and after controlling for sleep quality, with individuals in the longer shifts reporting more distress. PTSD was not significantly different between the groups; however, a trend emerged for longer shifts to be related to more distress after controlling for sleep quality. The findings of this research may be used to promote social change by improving the lives of firefighters and the communities they serve, as well as educating decision makers with information needed to address potential mental health burdens of shiftwork in this population.

Das Bestreben, den Aufbau, die Funktion sowie die Entwicklung des Immunsystems zu verstehen, steht schon lange Zeit im Zentrum des Interesses vieler Forschungsarbeiten, insbesondere um auf Grundlage der gewonnenen Erkenntnisse neue Behandlungsansätze für immunologisch relevante Krankheitsbilder zu entwickeln. Stillen könnte ein wichtiger Faktor sein, der bei der Entwicklung und Differenzierung von T-Zell-Subpopulationen und Zytokinmustern im Säuglings- und Kindesalter eine bedeutende Rolle spielt. Die Zielsetzung der hier vorgelegten Promotionsarbeit war es, den potentiellen Effekt des Faktors Stillen auf die Entwicklung, die Verteilung und die Differenzierung von Zell-populationen sowie die Expression von Zytokinen bei gesunden Kindern zu untersuchen. Dies geschah insbesondere im Hinblick auf einen möglicherweise vorhandenen Shift der relativen Verteilung der TH1- und TH2-Zytokinen, da in retrospektiven Kohortenstudien bereits gezeigt werden konnte, dass gestillte Kinder eine geringere Anfälligkeit gegenüber schwerwiegenden bakteriellen Infektionen (BACHRACH ET AL., 2003) sowie einer verminderten Inzidenz von Autoimmunerkrankungen (KOLETZKO ET AL., 1989; PISACANE ET AL., 1994) aufweisen. Die Studienkohorte bestand aus 196 gesunden Kindern im Alter zwischen 26 Tagen und 12 Jahren und 352 Tagen. Diese wurde in vier Altersgruppen unterteilt (<1, 1- <3, 3- <6 und 6-<13 Jahre) und mittels eines Fragebogens im Hinblick auf ein möglicherweise vorhandenes Bias bezüglich exogener Einflussfaktoren wie Impfungen, Nikotinexposition (FELESZKO ET AL., 2006) und allergische Erkrankungen in der Familie (HRDÝ ET AL., 2010), die in diesem Zusammenhang diskutiert werden, überprüft. Dabei zeigten sich keine signifikanten Unter-schiede zwischen den Gruppen. Alle immunologischen Parameter wurden in peripherem, heparinisiertem Blut ermittelt. Zunächst wurde mittels Durchflusszytometrie (FACS) eine Phänotypisierung, anhand von antikörpermarkierten Oberflächenantigenen der T-, B- und NK-Zellpopulationen („Immun-status“), durchgeführt. Des Weiteren wurden die mononuklearen Zellen des peripheren Blutes (PBMC) mittels PMA und Ionomycin stimuliert und die Zytokinsekretion durch Brefeldin blockiert. Durch FACS-Analyse wurde die nach 20-24 stündiger Anregung in der Kultur vorhandene intrazellulärer Zytokinexpression von IL2, IFNγ, TNFα, IL4, IL10, TGFβ und IL17 in den T-Zellpopulationen ermittelt. In einem zweiten Schritt wurde der Quotient aus IFNγ und IL4 berechnet, um das Verhältnis zwischen TH1 und TH2 zu analysieren. Das Datenmaterial zeigt die Entwicklung der T-Zell-Subpopulationen mit dem Alter. Junge Kinder zeigen eine durch regulatorische T-Zellen (Treg) bzw. TH0-Zellen vorherrschende TGFβ und IL2-Expression, während ältere Kinder das gesamte Repertoire an TH1 (IFNγ, TNFα) und TH2-Zytokinen (IL4), insbesondere durch T-Gedächtniszellen, exprimieren. Diese Ergebnisse bestätigten bereits zuvor beschriebene – vom Faktor Stillen unabhängige – altersabhängige Veränderungen der Zellpopulationen und der Zytokinexpression. Aus diesem Grund konnte von einer „normalen Verteilung“ der Studienkohorte ausgegangen werden. Zwischen gestillten und nicht-gestillten Kindern hat sich gezeigt, dass sich die Größe und das Verhältnis der übergeordneten Zellpopulationen (T-Helferzellen, zytotoxische T-Zellen) sowie die Reifung der T-Zellen (naive T-Zellen, T-Gedächtniszellen) bezogen auf das Alter nicht unterscheiden. Hingegen zeigt der Faktor Stillen in der Tat einen Einfluss auf die TH1/TH2-Balance. Bei gestillten Kindern lässt sich eine stärkere Gewichtung in Richtung der TH2-Zytokine feststellen (niedrigere IFNγ/IL4-Ratio), so dass davon auszugehen ist, dass Stillen einen so genannten TH2-Shift induziert. Dieses gegenüber nicht-gestillten Kindern „verschobene“ Gleichgewicht bleibt bis zur Altersgruppe der 6-13 Jährigen konstant. Gestillte Kinder haben zudem, im Vergleich zu Formula-ernährten Kindern, ein höheres Vermögen TH1-Zytokine wie TNFα und IFNγ zwischen dem dritten und sechsten Lebensjahr zu bilden. Diese Daten entsprechen nicht einem vorherrschenden TH2-Muster und einer Allergiedisposition, aber sie können die geringere Inzidenz von bakteriellen Infektionen im Vorschulalter (TH1-Antworten benötigt) und von TH1-vermittelten Autoimmunerkrankungen bei gestillten Kindern erklären. Aufgrund der Ergebnisse wird deutlich, dass Muttermilch einen bedeutenden Einfluss auf das Immunsystem hat. Insbesondere konnte gezeigt werden, dass der Einfluss der Muttermilchernährung über den eigentlichen Zeitraum des Stillens hinausreicht. Eine Prägung des Immunsystems durch die Muttermilch, während der frühen Kindheit, erscheint deshalb sehr wahrscheinlich. Diese Ergebnisse sollten selbstverständlich durch weiterreichende Studien, die eventuell vorhandene weitere Störgrößen wie genetische Prädispositionen oder auch Umwelttoxine einschließen, verifiziert werden. Zudem wäre es von Interesse welche in der Muttermilch enthaltene Stoffe zu diesem TH2-Shift beitragen oder ob es sich bei den Einflussfaktoren vielmehr um in der Muttermilch nicht enthaltene Stoffe handelt, die in Formula-Nahrung enthalten sind, wie zum Beispiel Kuhmilchantigene. Schlussendlich bleibt festzuhalten, dass Muttermilch erwiesene positive Vorteile mit sich bringt, wie geringere Infektionsraten (Atemwegsinfektionen, Otitis media) und eine Risiko-verminderung für bestimmte Erkrankungen (Diabetes mellitus Typ1, Morbus Crohn, Multiple Sklerose) im späteren Leben. Die Ergebnisse dieser Arbeit können bestätigen, dass das Stillen mit Muttermilch tatsächlich einen Einfluss auf die Entwicklung des individuellen Immunsystems hat, der auch nach dem Abstillen weiter anhält. Eine wichtige Rolle kann diese Erkenntnis bei der Beratung werdender Mütter spielen, gerade in Hinblick auf ein gegebenenfalls erhöhtes endogenes familiäres Risiko für beispielsweise Autoimmunerkrankungen. Folgearbeiten sind sicher wünschenswert, um den pathophysiologischen Hintergrund dieser beobachteten Daten besser zu verstehen. / The aspiration to understand the construction, the function as well as the development of the immune system is for a long time in the centre of the interest of many research projects, in particular to develop new attempts of treatment for immunological relevant clinical pictures on basis of the won knowledge. Breast-feeding could be an important factor which plays an important role by the development and differentiation of T-cell subsets and cytokine profiles in infancy and childhood. The objective of the doctorate work presented here was to examine the potential effect of the factor breast-feeding for the development, the distribution and the differentiation of cell populations as well as the expression of cytokines with healthy children. This happened in particular in view of a possibly available Shift of the relative distribution of the TH1 and TH2 cytokines, because in retrospective cohort studies could be already demonstrated, that breastfed children show a lower susceptibility for serious bacterial infections (BACHRACH ET AL.,2003) as well as a decreased incidence of autoimmune illnesses (KOLETZKO ET AL.,1989; PISACANE ET AL.,1994). The study cohort existed of 196 healthy children at the age between 26 days and 12 years and 352 days. This was divided into four age groups (<1, 1-<3, 3-<6 and 6-<13 years) and by means of a questionnaire in view of a possibly available Bias with regard to exogenous factors of influence like vaccinations, nicotine exposition (FELESZKO ET AL.,2006) and allergic illnesses in the family (HRDÝ ET AL.,2010) which are discussed in this connection, checks. Besides, no significant differences appeared between the groups. All immunological parametres were determined in peripheral, heparinised blood. First a phenotype determination, on the basis of antibody-marked surface antigens of the T-, B- and NK-cell populations ("immune status"), was carried out by means of flow cytometry (FACS). Besides the mononuclear cells of the peripheral blood (PBMC) were stimulated by means of PMA and Ionomycin and the cytokine secretion was blocked by Brefeldin. By FACS analysis the cytokin expression of IL2, IFN γ, TNF α, IL4, IL10, TGF β and IL17 in the T-cell subpopulations was determined. In the second step the quotient from IFN γ and IL4 was calculated to analyse the relation between TH1 and TH2. The data material shows the development of the T-cell subsets with the age. Young children show one by regulatory T-cells (Treg) or TH0-cells prevailing TGF β and IL2 expression, while older children can produce the whole repertoire of TH1-(IFN γ, TNF α) and TH2-cytokines (IL4), in particular by memory T-cells. These results already confirmed before described – from the factor breast-feeding independent – changes of the cell populations and the cytokine production dependent on age. That's why could be gone out from a „normal distribution“ of the study cohort. Between breastfed and non-breastfed infants has appeared that the size and the relation of the higher cell populations (T-helper cells, zytotoxic T-cells) as well as the maturation of the T- cells (naive T-cells, memory T-cells) did refer to the age make no distinction. Indeed, however, breastfeeding shows an influence on the TH1/TH2-balance. Breastfed children show a stronger weighting in the direction of the TH2-Zytokine (lower IFN γ/IL4-Ratio), so that is to be assumed from the fact that breast-feeding induces a so-called TH2-Shift. These towards non-breastfed children "postponed" balance remains up to the age group of the 6-13 year-old steady. Besides, breastfed children have a higher ability, in comparison to Formula-fed children, to produce TH1-Zytokine like TNF α and IFN γ between the third and sixth year of life. These data do not correspond to a prevailing TH2 pattern and an allergy arrangement, but they can explain the lower incidence of bacterial infections in the pre-school age (TH1-answers needed) and from TH1-provided auto immune illnesses with breastfed children. On account of the results becomes clear that breastmilk has an important influence on the immune system. In particular it could be shown that the influence of breastmilk stretches beyond the real period of the breast-feeding. Therefore, an imprinting of the immune system by breastmilk, during the early childhood, seems very likely. These results should be verified of course by the handing on studies which enclose, perhaps, available other sturgeon dimensions like genetic prearrangements or also environmental toxins. Besides, it would be of interest which ingredients of breastmilk to this TH2-Shift contribute or whether it concerns with the factors of influence rather materials not contained in the mother's milk which are included in Formula food, as for example cow's milk antigens. Finally remains to stick that mother's milk brings proved positive advantages with itself, how lower infection rates (breath way infections, Otitis media) and a risk decrease for certain illnesses (diabetes mellitus Typ1, Morbus Crohn, multiple sclerosis) in the later life. The results of this work can confirm that the breast-feeding with mother's milk really has an influence on the development of the individual immune system. An important role can play this knowledge with the consultation of mothers, just in view of an endogenous informal risk raised if necessary for example auto immune illnesses. Subsequent works are surely desirable to understand the pathophysiological background of these observed data better.

Shiftwork, particularly that involving night work and/or transmeridian flight, forces a mismatch between the sleep/wake cycle and the endogenous circadian timing system. Specifically, shiftworkers are often required to sleep at a phase in the circadian cycle when they would usually be active, and to work at a phase in the circadian cycle when they would usually be asleep. The current thesis describes a series of five studies designed to examine the disruption and adaptation associated with shiftwork, with an emphasis on night work and, to a lesser extent, transmeridian flight. The first study (Chapter 3), conducted in the field, was designed to examine the effects of break duration and time of break onset on the amount of sleep that shiftworkers obtain between consecutive work periods, and to consider the role that pineal production of melatonin may play in this process, through its regulation of sleep. Not surprisingly, total sleep time (TST) increased with break duration for breaks that began at similar times of day. Importantly though, TST was greater for breaks that occurred during the night-time than for breaks that occurred during the daytime. These results indicated that the minimum-length break requirements contained in prescriptive duty hours regulations might not necessarily protect shiftworkers from being exposed to unacceptable levels of fatigue. In addition, there was a temporal relationship between the circadian rhythms of sleep duration, sleep quality, and 6-sulphatoxymelatonin excretion, such that sleep was longer and of better quality when melatonin production was relatively high. This data did not prove a causal link, but it did provide further indication that melatonin may be involved in the regulation of sleep. The aim of the second study (Chapter 4) was to examine the effects of time of day, shift duration, and prior sleep length on self-assessed alertness and neurobehavioural performance of shiftworkers in a real work setting. Cosinor regression models fitted to the data indicated that time of day had a significant effect on alertness and performance, with both reaching nadirs in the early morning. Indeed, the cosinor regression lines of best fit explained more than 90% of the within-subjects variability in both the alertness and performance measures. In addition, alertness declined as shift duration increased and rose as prior sleep length increased, and there was a decline in performance across work periods that was greater for extended shifts. However, the results indicated that time of day was the most important determinant of subjective alertness and neurobehavioural performance. Consequently, the fatigue associated with night work can never be eliminated, only minimised through the application of risk management strategies. The aim of the third study (Chapter 5) was to quantify the effects of fatigue on performance in a simulated work environment, i.e. a rail simulator, and to compare them with the effects of alcohol intoxication. Reaction time (RT) performance on a visual psychomotor vigilance task (PVT) was also assessed. Rather than cause a general decline in performance as was hypothesised, fatigue impaired some safety and efficiency measures (i.e. number and duration of extreme speed violations increased, average speed reduced, brake use increased), but not others (i.e. fuel use, inter-train forces, and minor and moderate speed violations were unaffected). The reduction in safety and consequent increase in risk due to fatigue reached levels equivalent to those associated with moderate levels of alcohol intoxication (i.e. -05?-10%). The results indicated that fatigue caused participants to disengage from operating the simulator such that safety was traded off, not necessarily deliberately, against some aspects of efficiency. RT performance on the PVT was also significantly impaired by fatigue, similar to the magnitude of impairment associated with moderate levels of alcohol intoxication (i.e. -05?-10%). However, the PVT results could not predict the complex relationship between simulator safety and efficiency measures. This indicated that the effects of fatigue on performance in the workplace cannot necessarily be derived on the basis of simple performance measures such as RT. The fourth study (Chapter 6), conducted in the laboratory, was designed to assess adaptation to a simulated night work schedule using salivary dim light melatonin onset (DLMO) as the circadian phase marker. Participants worked seven consecutive simulated 8-hour night shifts (i.e. 23:00?07:00h). This resulted in a mean total phase delay in DLMO of 5.5 hours, equivalent to an average delay of 0.8 hours per day. In addition, baseline DLMO was significantly correlated with mean wake time over the previous seven days. These results indicated that partial circadian adaptation occurred in response to the simulated night work schedule, and that baseline DLMO was reliably predicted by the mean wake up time for the preceding week. The radioimmunoassay used proved to be a sensitive measure of melatonin concentration in saliva for the determination of DLMO, and thus provides an alternative phase marker to core body temperature. The last study (Chapter 7) was designed to examine the adaptation of a RAAF aircrew to several small time zone transitions using salivary melatonin onset as the marker of circadian phase. In addition, the effects of the aircrew?s work schedule on their sleep/wake patterns and subjective alertness were assessed. During the first six days of a routine surveillance patrol (SURPAT), the aircrew travelled eastward and melatonin onset occurred progressively earlier (i.e. phase advanced). During the second six days of the SURPAT, the aircrew travelled westward but melatonin onset did not significantly shift. Night-time sleep duration was shorter prior to work days than prior to rest days, and subjective alertness was not significantly affected by either the duration of night-time sleep prior to work, or the duration of flight. The melatonin onset results indicated that participants? body clocks adapted well to several small time zone transitions when initially travelling eastward, but did not adapt to a similar pattern of time zone transitions when subsequently travelling westward. This was contrary to expectations based on studies of single acute time zone transitions, which indicate that adaptation to westward flight is more rapid than adaptation to eastward flight. Taken together, the results of these five studies confirm that shiftwork provides a considerable source of disruption to shiftworkers? sleep/wake patterns. Whilst this disruption to shiftworkers? sleep may impair subjective alertness, the greatest influence on alertness and performance is exerted by time of day. Furthermore, the combined effects of sleep disruption and time of day may result in a level of performance impairment in a simulated work environment similar to that associated with moderate levels of alcohol intoxication. Finally, night work and transmeridian flight provide a source of circadian disruption, the adaptation to which can be assessed in both laboratory and field settings by examining changes in the timing of nocturnal melatonin onset. / thesis (PhD)--University of South Australia, 2001.

Extended duration and irregularly planned overnight shifts are becoming frequent features of current working time arrangements. However, there is great concern about the detrimental effect that these shifts are likely to have on the sleep, performance and fatigue levels of workers. To date, the empirical evidence regarding the effects of extended and irregular overnight shifts is sparse and workers have rarely been followed up longer term to assess possible changes over time. Because these types of overnight shifts are being introduced into transport settings such as aviation and shipping where safe and productive operations are paramount, there is a real imperative to examine and trial workplace-based methods aimed at counteracting night shift related fatigue and performance deficits. Taking short duration naps on the nightshift at work is one potential countermeasure that has shown promise in the laboratory but has yet to be examined in any real-world setting under conditions of extended duration or irregular night work. This thesis takes up these issues in a series of four empirical workplace-based studies. The impact of the introduction of regularly planned 12 h day and overnight shifts was examined on three occasions via questionnaire in a group of aircraft maintenance engineers, once before the change, and twice after the change from 8 h shifts. The results showed that high levels of acute fatigue on the 12 h night shifts and high chronic fatigue levels were common, and were strongly associated with poor overall job performance, poor safety of job performance, and longer recovery times, effects that persisted over time. Of major concern was the finding that over half of the engineers reported having nodded off while driving home from their extended overnight shifts. The impact of irregularly planned 8 h overnight shifts worked by cargo handlers in a shipping container terminal was also examined via self-report questionnaire. The findings revealed significant detrimental impacts on sleep, fatigue levels and performance at work. High fatigue levels were strongly associated with poor self-rated performance output and safety of performance at work on the overnight shifts. The primary focus of this thesis was to evaluate the effect of a scheduled 20 min nap opportunity taken in these two fully operational workplaces during the night shift on sleep, performance and alertness. Sleep was achieved by 50 to 59% of workers. Speed of performance in 24 male aircraft maintenance engineers on a vigilance task was significantly faster at the end of a 12 h overnight shift that had contained sleep during the nap compared to the control condition. There was no such effect of the nap on the performance of 22 cargo handlers working impromptu 8 h shifts in a shipping container terminal. However, the duration of sleep obtained by the 8 h workers was shorter in comparison and was likely to have been undermined by the high noise levels around the nap facility and time pressures related to the organisation of work. Actigraphy data recorded from all subjects showed that subsequent daytime sleep was not disrupted by the night shift nap opportunity. Overall, the most interesting findings were that simply being tired and presented with a sleep opportunity during the night shift did not guarantee either sleep, or recovery but that sleep, as opposed to rest, was necessary for the benefits to performance to be fully realised. These findings have shown for the first time that management of fatigue associated with extended duration night work can be achieved in some instances by the use of a short duration nap taken in the workplace on the night shift. However, operationalizing in-situ napping on the night shift has a range of organisational influences that must be considered for the potential of such a strategy to be fully harnessed.

Research into the quality of life of nurses working at night has received scant attention to date. Apart from studies relating to changes in circadian rhythms of night nurses, very few other aspects of the complex adaptive process have been given serious consideration. Yet, knowledge of that adaptive process is a prerequisite for the selection of staff, and for the design of an appropriate educational programme and staff development strategy. This study looks first at methods of describing the quality of life in general, in order to aim at criteria for evaluation which do not impose the conventional position that day work is proper work. In the light of these criteria, preconceptions and limitations which surround shift work in general are identified and discussed. Night nurses as a group are then subjected to a more intensive examination, including a theoretical review; a survey of a population of one-hundred and sixty-one night nurses and selected interviews; and an account of a pilot study of a potential curriculum. Results of the survey indicate that nurses who show a preference for night work and who selfselect these hours on a permanent basis are more likely to derive challenge from and express greater satisfaction with their work, than those on alternative day and night shifts. Further, there is a stable population of workers who choose night work above all other options as a source of personal satisfaction, freedom and challenge. In the light of these findings, recommendations are made as to the selection, education and development of hospital night staff.