High speed nonlinear optical components for next-generation optical communications

Electronic signal processing systems currently employed at core internet routers require huge amounts of power to operate and they may be unable to continue to satisfy consumer demand for more bandwidth without an inordinate increase in cost, size and/or energy consumption. Optical signal processing techniques may be deployed in next-generation optical networks for simple tasks such as wavelength conversion, demultiplexing and format conversion at high speed (≥100Gb.s-1) to alleviate the pressure on existing core router infrastructure. To implement optical signal processing functionalities, it is necessary to exploit the nonlinear optical properties of suitable materials such as III-V semiconductor compounds, silicon, periodically-poled lithium niobate (PPLN), highly nonlinear fibre (HNLF) or chalcogenide glasses. However, nonlinear optical (NLO) components such as semiconductor optical amplifiers (SOAs), electroabsorption modulators (EAMs) and silicon nanowires are the most promising candidates as all-optical switching elements vis-à-vis ease of integration, device footprint and energy consumption. This PhD thesis presents the amplitude and phase dynamics in a range of device configurations containing SOAs, EAMs and/or silicon nanowires to support the design of all optical switching elements for deployment in next-generation optical networks. Time-resolved pump-probe spectroscopy using pulses with a pulse width of 3ps from mode-locked laser sources was utilized to accurately measure the carrier dynamics in the device(s) under test. The research work into four main topics: (a) a long SOA, (b) the concatenated SOA-EAMSOA (CSES) configuration, (c) silicon nanowires embedded in SU8 polymer and (d) a custom epitaxy design EAM with fast carrier sweepout dynamics. The principal aim was to identify the optimum operation conditions for each of these NLO device configurations to enhance their switching capability and to assess their potential for various optical signal processing functionalities. All of the NLO device configurations investigated in this thesis are compact and suitable for monolithic and/or hybrid integration.

Health of the older worker in Ireland - occupational physical and psychosocial factors in the autumn of work life

Introduction: Worldwide, governments are striving to keep people in work to an older age. However, little is known about the effects of work on an older workforce. This thesis aims to investigate the importance of job characteristics to the antecedents and evolution of cardiovascular disease and functional limitations for the older worker (50+ years). Methods: Three studies were used in this thesis. The 5C (Cork Coronary Care Case- Control) Study investigated the association between job strain and a coronary event in males (n=208) 35-74 years old. The Mitchelstown Study examined the association between job characteristics and positive lifestyle behaviours and further, job characteristics and blood pressure for males and females 50-69 years (n=2,047). Finally, the Cork & Kerry Study investigated the physical effects of manual work and reported functional limitations/disabilities in a sample of 60-80 year olds (n=362). Results: Results from the 5C Study show a clear difference between younger (<50 years) and older (≥50 years) workers, with older workers who had a coronary event more likely to have high job strain and low job control. Data from the Mitchelstown Study showed workers with intermediate possibility for development or high quantitative demands (versus low) at work significantly more likely to have co-occurrence of positive lifestyle behaviours. Further, those who had high possibility for development were more likely to have high systolic blood pressure with no indication of recovery from this activation at night. Physically demanding work as reported by the participants of the Cork & Kerry Study was associated with functional limitations and activities of daily living disability for both the paid and unpaid worker. Discussion: The findings from this piece of work highlight the necessity to examine job characteristics and health outcomes in isolation for the over fifties. The challenge is to get this information into the workplace.

Networking protocols for long life wireless sensor networks

My original contribution to knowledge is the creation of a WSN system that further improves the functionality of existing technology, whilst achieving improved power consumption and reliability. This thesis concerns the development of industrially applicable wireless sensor networks that are low-power, reliable and latency aware. This work aims to improve upon the state of the art in networking protocols for low-rate multi-hop wireless sensor networks. Presented is an application-driven co-design approach to the development of such a system. Starting with the physical layer, hardware was designed to meet industry specified requirements. The end system required further investigation of communications protocols that could achieve the derived application-level system performance specifications. A CSMA/TDMA hybrid MAC protocol was developed, leveraging numerous techniques from the literature and novel optimisations. It extends the current art with respect to power consumption for radio duty-cycled applications, and reliability, in dense wireless sensor networks, whilst respecting latency bounds. Specifically, it provides 100% packet delivery for 11 concurrent senders transmitting towards a single radio duty cycled sink-node. This is representative of an order of magnitude improvement over the comparable art, considering MAC-only mechanisms. A novel latency-aware routing protocol was developed to exploit the developed hardware and MAC protocol. It is based on a new weighted objective function with multiple fail safe mechanisms to ensure extremely high reliability and robustness. The system was empirically evaluated on two hardware platforms. These are the application-specific custom 868 MHz node and the de facto community-standard TelosB. Extensive empirical comparative performance analyses were conducted against the relevant art to demonstrate the advances made. The resultant system is capable of exceeding 10-year battery life, and exhibits reliability performance in excess of 99.9%.

Child work and labour among orphaned and abandoned children in five low and middle income countries.

BACKGROUND: The care and protection of the estimated 143,000,000 orphaned and abandoned children (OAC) worldwide is of great importance to global policy makers and child service providers in low and middle income countries (LMICs), yet little is known about rates of child labour among OAC, what child and caregiver characteristics predict child engagement in work and labour, or when such work infers with schooling. This study examines rates and correlates of child labour among OAC and associations of child labour with schooling in a cohort of OAC in 5 LMICs. METHODS: The Positive Outcomes for Orphans (POFO) study employed a two-stage random sampling survey methodology to identify 1480 single and double orphans and children abandoned by both parents ages 6-12 living in family settings in five LMICs: Cambodia, Ethiopia, India, Kenya, and Tanzania. Regression models examined child and caregiver associations with: any work versus no work; and with working <21, 21-27, and 28+ hours during the past week, and child labour (UNICEF definition). RESULTS: The majority of OAC (60.7%) engaged in work during the past week, and of those who worked, 17.8% (10.5% of the total sample) worked 28 or more hours. More than one-fifth (21.9%; 13% of the total sample) met UNICEF's child labour definition. Female OAC and those in good health had increased odds of working. OAC living in rural areas, lower household wealth and caregivers not earning an income were associated with increased child labour. Child labour, but not working fewer than 28 hours per week, was associated with decreased school attendance. CONCLUSIONS: One in seven OAC in this study were reported to be engaged in child labour. Policy makers and social service providers need to pay close attention to the demands being placed on female OAC, particularly in rural areas and poor households with limited income sources. Programs to promote OAC school attendance may need to focus on the needs of families as well as the OAC.

Investigation and Development of a Fully 3D Tilt Capable Hybrid SPECT - CT System for Dedicated Breast Imaging

X-ray mammography has been the gold standard for breast imaging for decades, despite the significant limitations posed by the two dimensional (2D) image acquisitions. Difficulty in diagnosing lesions close to the chest wall and axilla, high amount of structural overlap and patient discomfort due to compression are only some of these limitations. To overcome these drawbacks, three dimensional (3D) breast imaging modalities have been developed including dual modality single photon emission computed tomography (SPECT) and computed tomography (CT) systems. This thesis focuses on the development and integration of the next generation of such a device for dedicated breast imaging. The goals of this dissertation work are to: [1] understand and characterize any effects of fully 3-D trajectories on reconstructed image scatter correction, absorbed dose and Hounsifeld Unit accuracy, and [2] design, develop and implement the fully flexible, third generation hybrid SPECT-CT system capable of traversing complex 3D orbits about a pendant breast volume, without interference from the other. Such a system would overcome artifacts resulting from incompletely sampled divergent cone beam imaging schemes and allow imaging closer to the chest wall, which other systems currently under research and development elsewhere cannot achieve.

The dependence of x-ray scatter radiation on object shape, size, material composition and the CT acquisition trajectory, was investigated with a well-established beam stop array (BSA) scatter correction method. While the 2D scatter to primary ratio (SPR) was the main metric used to characterize total system scatter, a new metric called ‘normalized scatter contribution’ was developed to compare the results of scatter correction on 3D reconstructed volumes. Scatter estimation studies were undertaken with a sinusoidal saddle (±15° polar tilt) orbit and a traditional circular (AZOR) orbit. Clinical studies to acquire data for scatter correction were used to evaluate the 2D SPR on a small set of patients scanned with the AZOR orbit. Clinical SPR results showed clear dependence of scatter on breast composition and glandular tissue distribution, otherwise consistent with the overall phantom-based size and density measurements. Additionally, SPR dependence was also observed on the acquisition trajectory where 2D scatter increased with an increase in the polar tilt angle of the system.

The dose delivered by any imaging system is of primary importance from the patient’s point of view, and therefore trajectory related differences in the dose distribution in a target volume were evaluated. Monte Carlo simulations as well as physical measurements using radiochromic film were undertaken using saddle and AZOR orbits. Results illustrated that both orbits deliver comparable dose to the target volume, and only slightly differ in distribution within the volume. Simulations and measurements showed similar results, and all measured dose values were within the standard screening mammography-specific, 6 mGy dose limit, which is used as a benchmark for dose comparisons.

Hounsfield Units (HU) are used clinically in differentiating tissue types in a reconstructed CT image, and therefore the HU accuracy of a system is very important, especially when using non-traditional trajectories. Uniform phantoms filled with various uniform density fluids were used to investigate differences in HU accuracy between saddle and AZOR orbits. Results illustrate the considerably better performance of the saddle orbit, especially close to the chest and nipple region of what would clinically be a pedant breast volume. The AZOR orbit causes shading artifacts near the nipple, due to insufficient sampling, rendering a major portion of the scanned phantom unusable, whereas the saddle orbit performs exceptionally well and provides a tighter distribution of HU values in reconstructed volumes.

Finally, the third generation, fully-suspended SPECT-CT system was designed in and developed in our lab. A novel mechanical method using a linear motor was developed for tilting the CT system. A new x-ray source and a custom made 40 x 30 cm2 detector were integrated on to this system. The SPECT system was nested, in the center of the gantry, orthogonal to the CT source-detector pair. The SPECT system tilts on a goniometer, and the newly developed CT tilting mechanism allows ±15° maximum polar tilting of the CT system. The entire gantry is mounted on a rotation stage, allowing complex arbitrary trajectories for each system, without interference from the other, while having a common field of view. This hybrid system shows potential to be used clinically as a diagnostic tool for dedicated breast imaging.

Revising Justice: Punitory Thought and Action in the Work of Atwood, Jordan, and Oates

*Designated as an exemplary master's project for 2015-16*

Analysis of the utility of QuantiFERON-TB gold in tube and measurement of IFNgamma release by peripheral mononuclear cells in response to different mycobacterium antigen in the work-up of patients with uveitis.

Evaluation Studies

A model to predict the life of pneumatic conveyor bends

A new approach to the prediction of bend lifetime in pneumatic conveyors, subject to erosive wear is described. Mathematical modelling is exploited. Commercial Computational Fluid Dynamics (CFD) software is used for the prediction of air flow and particle tracks, and custom code for the modelling of bend erosion and lifetime prediction. The custom code uses a toroidal geometry, and employs a range of empirical data rather than trying to fit classical erosion models to a particular circumstance. The data used was obtained relatively quickly and easily from a gas-blast erosion tester. A full-scale pneumatic conveying rig was used to validate a sample of the bend lifetime predictions, and the results suggest accuracy of within ±65%, using calibration methods. Finally, the work is distilled into user-friendly interactive software that will make erosion lifetime predictions for a wide range of bends under varying conveying conditions. This could be a valuable tool for the pneumatic conveyor design or maintenance engineer.

[Conference report] Magic and mathematics: The life and work of John Dee. National Maritime Museum, Greenwich, 13-14 June 2003

Tony Mann provides a report of a two-day meeting "Magic and mathematics: The life and work of John Dee" held from 13-14 June 2003 at the National Maritime Museum, Greenwich.

A price worth paying?: Women and work – choice, constraint or satisficing

Purpose – Are women held back or holding back? Do women choose their jobs/careers or are they structurally or normatively constrained? The purpose of this paper is to shed fresh light on these questions and contribute to an on-going debate that has essentially focused on the extent to which part-time work is women’s choice, the role of structural and organisational constraints and the role of men in excluding women. Design/methodology/approach – The paper uses data from interviews with 80 working women – both full-time and part-time – performing diverse work roles in a range of organisations in the south east of England. Findings – It was found that many women do not make strategic job choices, rather they often ‘‘fall into’’ jobs that happen to be available to them. Some would not have aspired to their present jobs without male encouragement; many report incidents of male exclusion; and virtually all either know or suspect that they are paid less than comparable men. Those working reduced hours enjoy that facility, yet they are aware that reduced hours and senior roles are seen as incompatible. In short, they recognise both the positive and negative aspects of their jobs, whether they work full or part-time, whether they work in male-dominated or female-dominated occupations, and whatever their position in the organisational hierarchy. Accordingly, the paper argues that the concept of ‘‘satisficing’’, i.e. a decision which is good enough but not optimal, is a more appropriate way to view women’s working lives than are either choice or constraint theories. Originality/value – There is an ongoing, and often polarised, debate between those who maintain that women choose whether to give preference to work or home/family and others who maintain that women, far from being self-determining actors, are constrained structurally and normatively. Rather than supporting these choice or constraint theories, this paper argues that ‘‘satisficing’’ is a more appropriate and nuanced concept to explain women’s working lives.

'Bowing from the heart': an investigation into discourses of professionalism and the work of caring for students in further education

Since their incorporation in 1993, further education (FE) colleges in England have been responsible for their own staffing and, faced with funding constraints as well as recruitment and retention targets, some have introduced a new category of staff referred to here as 'learning support workers' (LSWs). Though their employment conditions and specific duties vary considerably, LSWs' work often includes providing individual care for students. In this small-scale study, using semi-structured interviews, the perceptions of some teachers and LSWs about the nature of their relationships with each other and with students are investigated. The study is set broadly in the context of debates about the impact of public sector reform on FE colleges and teachers. A discourse analysis approach is adopted in discussion of the data. The authors conclude that although they are differently positioned in relation to traditional discourses of professionalism, both teachers and LSWs are perceived to be carrying out what Hochschild termed 'emotional labour'. The contradictory nature of emotional labour is also highlighted. Some of the implications of employing a new group of workers in FE are discussed.

The interprofessional practitioner: changing professional identity in social work

Twenty years ago the first joint training programme in learning disability nursing and social work was established as a collaborative project to develop practitioners able to work holistically with people with learning disabilities. Since then a number of programmes have continued this work and more recently the approach has developed in the mental health specialism. These programmes have changed the nature of singular social work education and created a new region of knowledge (Bernstein, 2000) for those who have experienced them. What began as a radical experiment in interprofessional education has been sustained by a strong commitment to the belief that the practitioners who qualify from such programmes are well equipped to support people with learning disabilities in changing and multi-professional services. As with much interprofessional education, however, there is an ongoing need to build an evidence base linking such education with successful outcomes in practice. This paper presents and explores the outcomes of a doctoral research study aimed at evaluating the impact of joint training in learning disability nursing and social work on the professional identity, skills and working practices of practitioners who undertook it. The research was undertaken with almost fifty jointly trained practitioners and involved a national survey followed by semi-structured interviews. The results suggest that practitioners who experience the dual socialisation inherent in this type of training found both gains and losses in the process. They appear to emerge, however, with a confidence, resilience and breadth of knowledge which were part of the early vision for this transformative approach to professional training. Bernstein B. (2000). Pedagogy, Symbolic Control and Identity. Theory, Research, Critique. Revised Edition. Lanham: Rowman and Littlefield (USA).