Single-photon metrology with superconducting nanowire single-photon detectors

Single-photon sources and detectors underpin the development of quantum photonic technologies. This thesis presents research into single-photon devices with a focus on telecom wavelengths. A two-channel superconducting nanowire single-photon detector (SNSPD) system was constructed and characterised. It provides free-running single-photon detection at telecom wavelengths with low dark counts and timing jitter below 90 ps FWHM. The system detection e ciency at 1310 nm is 1 % with a 1 kHz dark count rate, which was competitive when the SNSPD was built in 2009. In this work, the low timing jitter of the SNSPD was bene cial to the development of a two-photon interference experiment. Experiments were carried out with single-photon sources based on self-assembled InAs/GaAs quantum dots in micropillar cavities. Preliminary measurements of the second-order correlation function gave g(²)(τ=0) = 0.12 ± 0.04 with above-band excitation and g(²)( τ = 0) = 0:07 ± 0:05 with near-resonant excitation. These values agree with recent papers reporting improved measurements with near-resonant excitation. Irreparable damage to the sample prevented further investigation. This thesis also presents the design, construction and characterisation of a highresolution single-photon spectrometer for telecom wavelengths. The instrument, a scanning Fabry-Perot interferometer, was optimised for the characterisation of quantum photonic sources. It has a spectral resolution of 550 MHz and a free spectral range of (119.0 ± 0.4) GHz

Using Microbial Indicators to Assess Soil Ecosystem Restoration

Soil microbial communities play a crucial role in maintaining ecosystem health and sustainable integrity. The objective of this study was to determine the progress of ecosystem recovery in soils under a federal conservation reserve program (CRP) by examining several key microbial community-related soil health indicators. Three adjacent soil ecosystems were evaluated, including conventional crop production, undisturbed (>20 years post tillage), and marginal land that was formally cultivated and has been under CRP for five years. The latter two ecosystems contained mixed perennial vegetation, whereas the former was cultivated with winter wheat, Triticum aestivum L for at least 20 years. Soils were taken from these three ecosystems at two different locations twice a year for two consecutive years. Five replicate samples were taken from each ecosystem at each location during each sampling event. Soils were evaluated for water-stable aggregation and composition and structure of the soil microbial communities using fatty acid methyl ester analysis. Roots isolated from soils were evaluated for arbuscular mycorrhizal intraradical colonization. Results show that AMF abundance was high in CRP plots compared to both Wheat and Native systems. Microbial indicators suggest that the level of disturbance and nutritional stress remained significantly higher in CRP than Native plots during the 1st and 3rd samplings, indicating less resistance against heat or drought stress. Total microbial abundance and geometric mean diameter, which were highly correlated with each other, were found to be significantly lower in CRP than Native systems. Soil organic carbon and total nitrogen in CRP was not significantly different from the wheat fields, suggesting a much greater amount of time would be needed to reach pre-cultivation levels. Because of significant differences between the two Native plots at different locations, using this study's selected indicators for soil ecosystem recovery, we were able to ascertain based on a combined value for measured indicators that the CRP at one location had recovered approximately 50% compared to the Native system, but that the other only recovered about 10% after 5-6 years in the program. The Native plot at the former location was possibly more degraded before being abandoned, or was less disturbed than the latter. Because a typical contract with the CRP typically lasts 10-15 years, more time may be required for full recovery of the soil properties measured in this study than what is currently allotted.Department of Plant and Soil Science

Emerging Optical Methods for Endoscopic Barrett’s Surveillance

Barrett’s oesophagus is an acquired metaplastic condition that predisposes patients to the development of oesophageal adenocarcinoma, prompting the use of surveillance regimes to detect early malignancy for endoscopic therapy with curative intent. The currently accepted surveillance regime uses white light endoscopy together with random biopsies, but suffers poor sensitivity and discards information from numerous light-tissue interactions that could be exploited to probe structural, functional and molecular changes in the tissue. Advanced optical methods are now emerging that are exquisitely sensitive to these changes and hold significant potential to improve surveillance of Barrett’s oesophagus if they can be applied endoscopically. The next decade will see some of these exciting new methods applied to Barrett’s surveillance in new device architectures for the first time, potentially leading to a longawaited improvement of the standard of care

Nitrotyrosine Density of Rabbit Urinary Bladder Muscle and Mucosa Measured via Western Blotting and 96-Well Plate Analysis

Purpose. Nitrotyrosine was quantitated in rabbit bladder muscle and mucosa using two analytical systems: Western blotting analyses and a 96-well plate quantitative analysis kit. Materials and Methods. Rabbit bladder muscle and mucosa were obtained from control rabbits. For the Western analysis, the samples were loaded into a SDS page gel and then transferred to a PVDF membrane. The optical density was measured using a Kodak Scanner. Using the 96-well plate, the samples and standards were loaded, incubated with primary and secondary antibody, washed and vacuumed with 10x wash buffer three times between each incubation period. Stop buffer was added to the plate and the results were quantified via the plate reader. Results. For both muscle and mucosa tissue, the optical density readings were linear with tissue concentration; the concentration of nitrotyrosine in the mucosa was significantly higher than in the muscle. However, whereas the Western blot analysis is based on relative optical densities, the 96-well plate kit provides a truly quantitative analysis. Discussion. Mucosa tissue displayed a higher density of nitrotyrosine than did detrusor muscle tissue. This may well be due to the significantly higher metabolic activity of the mucosa compared to the muscle

The Management and Creation of Knowledge: Do Wikis Help?

Wikis are frequently cited in Higher Education research as appropriate and powerful web spaces which provide opportunities to capture, discuss, and review individual, group, project or organisational activities. These activities, in turn, offer possibilities for knowledge development by utilising wiki collaborative active spaces. The chapter uses selected case studies examples to illustrate the use of wikis to support online community based tasks, project development/process, collaborative materials development and various student and peer supported activities. A key focus of the chapter centres on evaluating the effectiveness (or otherwise) of wikis to create online communities to support knowledge management (development, retention and transfer). See Choy & Ng (2007), Lamb (2004), Elgort (2008), Raman et al. (2005). By way of contextualising the studies, a variety of uses of wikis in higher education are reviewed as part of this chapter. See, for example, Lamb, (2004) Choy, & Ng, (2007), Doolan, (2006) Jones P. (2007) Raman, et al. (2005) Grierson, et al.,, (2004). Creation of knowledge sentence + refs? The chapter concludes with a review of the emergent themes arising and lessons learned from the case studies. This leads into a series of recommendations relating to the effective establishment, design, management and support and use of wikis to support knowledge creation and collaborative enterprise

Associations between physical activity and stress levels in medical doctors working in New Zealand and Australia during initial COVID-19 restrictions

In 2020, the world was gripped by the COVID-19 pandemic which put an unprecedented strain on health care workers. The aim of this study was to assess the effects of the Australian and New Zealand lockdowns on physical activity, depression, and anxiety in medical doctors. We hypothesized that during stressful times such as the COVID-19 pandemic lockdown, physical activity would have a positive effect on the mental health of medical doctors. Convenience sampling (using mass emailing via professional networks including medical associations) and snowball sampling were used during the early period of COVID-19 government mandated restrictions (25 March to 27 April 2020) in New Zealand and Australia. All registered medical doctors working in New Zealand and Australia were eligible to participate in the survey. The short survey collected information demographics, levels of physical activity and mental health using the International Physical Activity Questionnaire: Short Form and the Depression, Anxiety and Stress Scale-42. Of 469 participants who completed the survey, over 81% met the recommended physical activity levels (150 minutes of at least moderate-intensity physical activity/week). Physically inactive New Zealand and Australian medical doctors reported significantly higher depression (p = 0.006), anxiety (p = 0.008) and stress (p = 0.002) scores compared to their active counterparts. This study demonstrated that less physical activity was associated with higher anxiety and depression in medical doctors. A key recommendation from this study is to incorporate greater access to physical activity in healthcare settings for medical doctors

A roadmap for the clinical implementation of optical-imaging biomarkers

Clinical workflows for the non-invasive detection and characterization of disease states could benefit from optical-imaging biomarkers. In this Perspective, we discuss opportunities and challenges towards the clinical implementation of optical-imaging biomarkers for the early detection of cancer by analysing two case studies: the assessment of skin lesions in primary care, and the surveillance of patients with Barrett’s oesophagus in specialist care. We stress the importance of technical and biological validations and clinical-utility assessments, and the need to address implementation bottlenecks. In addition, we define a translational roadmap for the widespread clinical implementation of optical imaging-technologies

Integrating cognition in the laboratory with cognition in the real world: the time cognition takes, task fidelity, and finding tasks when they are mixed together

It is now possible for real-life activities, unfolding over their natural range of temporal and spatial scales, to become the primary targets of cognitive studies. Movement toward this type of research will require an integrated methodological approach currently uncommon in the field. When executed hand in hand with thorough and ecologically valid empirical description, properly developed laboratory tasks can serve as model systems to capture the essentials of a targeted real-life activity. When integrated together, data from these two kinds of studies can facilitate causal analysis and modeling of the mental and neural processes that govern that activity, enabling a fuller account than either method can provide on its own. The resulting account, situated in the activity’s natural environmental, social, and motivational context, can then enable effective and efficient development of interventions to support and improve the activity as it actually unfolds in real time. We believe that such an integrated multi-level research program should be common rather than rare and is necessary to achieve scientifically and societally important goals. The time is right to finally abandon the boundaries that separate the laboratory from the outside world

Implementing social prescribing in primary care in areas of high socioeconomic deprivation:process evaluation of the ‘Deep End’ community links worker programme

Background: Social prescribing involving primary care-based ‘link workers’ is a key UK health policy which aims to reduce health inequalities. However, the process of implementation of the link worker approach has received little attention despite this being central to desired impact and outcomes. Aim: Our objective was to explore the implementation process of such an approach in practice. Design and Setting: Qualitative process evaluation of the ‘Deep End’ Links Worker Programme (LWP) over a two-year period, in seven general practices in deprived areas of Glasgow. Methods: We used thematic analysis to identify the extent of LWP integration in each practice and key factors associated with implementation. Analysis was informed by Normalisation Process Theory. Results: Only three of the seven practices fully integrated the LWP into routine practice within two years, based on NPT constructs of coherence, cognitive participation, and collective action. Compared to ‘Partially Integrated Practices’, ‘Fully Integrated Practices’ had better shared understanding of the programme among staff, higher staff engagement with LWP, and were implementing all aspects of LWP at patient, practice and community levels of intervention. Successful implementation was associated with GP buy-in, collaborative leadership, good team dynamics, link worker support, and the absence of competing innovations. Conclusions: Even in a well-resourced government funded programme, the majority of practices involved had not fully integrated the LWP within the first two years. Implementing social prescribing and link workers within primary care at scale is unlikely to be a ‘quick fix’ for mitigating health inequalities in deprived areas