Novel waveguide configuration for convenient and sensitive fluorescence and Raman measurements of liquids over optical fibers

Fluorescence has been measured from a waveguide formed by a PTFE tube with an internal coating of a low-refractive-index amorphous fluoropolymer. The configuration is suited to taking measurements from liquids having a refractive index down to 1.32, including, in particular, aqueous solutions. The parameters which determine the optical collection efficiency have been mathematically modelled. We have produced waveguides up to 1m long, and with 0.955 mm and 0.445 mm internal radii, and measured a (fluorescence) collection enhancement factor of 3 from a 140 mm long, 0.955 mm internal radius waveguide. Work is continuing to increase the enhancement factor

Neuropsychological and psychiatric functioning in sheep farmers exposed to low levels of organophosphate pesticides

The aim of this thesis is to determine whether exposure to low levels of organophosphate pesticides (OPs) causes neuropsychological or psychiatric impairment. The thesis is arranged in three parts. Part 1 provides an introduction to neurotoxicology, the role of the psychologist, and the toxicity of OPs; Part 2 provides a historical review of the existing scientific evidence regarding the impact on human health of low level exposure to organophosphate pesticides. A major unresolved issue in the toxicity literature is whether repeated, low level exposure to OPs, in the absence of a history of acute toxicity, is harmful to human health. Part 3 presents the findings of a four year empirical study designed to address this issue. A cross-sectional study was undertaken in which the performance on neuropsychological tests of 127 sheep farmers with a history of low level exposure to organophosphate pesticides was compared with 78 nonexposed healthy volunteers (rural police workers) matched for age, gender, years in education and level of intelligence. Methodological weaknesses of earlier studies were addressed in the study design, such as inclusion of study participants who had retired on ill health grounds to take account of the ‘healthy worker effect’; exclusion of study participants with a history of acute poisoning and those with a psychiatric or medical history that might otherwise account for ill health; and exploration of factors that may render some individuals more vulnerable to the effects of OPs than others (e.g. genetic differences in the capacity to metabolise and detoxify OPs). In the final chapter the findings are summarised and discussed, the study design is critically appraised and the implications of the findings are listed along with recommendations for future research

Acute hypoxia reduces plasma myostatin independent of hypoxic dose

Background: Muscle atrophy is seen ~ 25 % of patients with cardiopulmonary disorders, such as chronic obstructive pulmonary disorder and chronic heart failure. Multiple hypotheses exist for this loss, including inactivity, inflammation, malnutrition and hypoxia. Healthy individuals exposed to chronic hypobaric hypoxia also show wasting, suggesting hypoxia alone is sufficient to induce atrophy. Myostatin regulates muscle mass and may underlie hypoxic-induced atrophy. Our previous work suggests a decrease in plasma myostatin and increase in muscle myostatin following 10 hours of exposure to 12 % O2. Aims: To establish the effect of hypoxic dose on plasma myostatin concentration. Concentration of plasma myostatin following two doses of normobaric hypoxia (10.7 % and 12.3 % O2) in a randomised, single-blinded crossover design (n = 8 lowlanders, n = 1 Sherpa), with plasma collected pre (0 hours), post (2 hours) and 2 hours following (4 hours) exposure. Results: An effect of time was noted, plasma myostatin decreased at 4 hours but not 2 hours relative to 0 hours (p = 0.01; 0 hours = 3.26 [0.408] ng.mL-1, 2 hours = 3.33, [0.426] ng.mL-1, 4 hours = 2.92, [0.342] ng.mL-1). No difference in plasma myostatin response was seen between hypoxic conditions (10.7 % vs. 12.3 % O2). Myostatin reduction in the Sherpa case study was similar to the lowlander cohort. Conclusions: Decreased myostatin peptide expression suggests hypoxia in isolation is sufficient to challenge muscle homeostasis, independent of confounding factors seen in chronic cardiopulmonary disorders, in a manner consistent with our previous work. Decreased myostatin peptide may represent flux towards peripheral muscle, or a reduction to protect muscle mass. Chronic adaption to hypoxia does not appear to protect against this response, however larger cohorts are needed to confirm this. Future work will examine tissue changes in parallel with systemic effects

Short-term isothermic heat acclimation elicits beneficial adaptations but medium-term elicits a more complete adaptation

Purpose To investigate the effects of 60 min daily, short-term (STHA) and medium-term (MTHA) isothermic heat acclimation (HA) on the physiological and perceptual responses to exercise heat stress. Methods Sixteen, ultra-endurance runners (female = 3) visited the laboratory on 13 occasions. A 45 min sub-maximal (40% Wmax) cycling heat stress test (HST) was completed in the heat (40 °C, 50% relative humidity) on the first (HSTPRE), seventh (HSTSTHA) and thirteenth (HSTMTHA) visit. Participants completed 5 consecutive days of a 60 min isothermic HA protocol (target Tre 38.5 °C) between HSTPRE and HSTSTHA and 5 more between HSTSTHA and HSTMTHA. Heart rate (HR), rectal (Tre), skin (Tsk) and mean body temperature (Tbody), perceived exertion (RPE), thermal comfort (TC) and sensation (TS) were recorded every 5 min. During HSTs, cortisol was measured pre and post and expired air was collected at 15, 30 and 45 min. Results At rest, Tre and Tbody were lower in HSTSTHA and HSTMTHA compared to HSTPRE, but resting HR was not different between trials. Mean exercising Tre, Tsk, Tbody, and HR were lower in both HSTSTHA and HSTMTHA compared to HSTPRE. There were no differences between HSTSTHA and HSTMTHA. Perceptual measurements were lowered by HA and further reduced during HSTMTHA. Conclusion A 60 min a day isothermic STHA was successful at reducing physiological and perceptual strain experienced when exercising in the heat; however, MTHA offered a more complete adaptation

Yb:YAG planar waveguide lasers grown by pulsed laser deposition: 70% slope efficiencies at 16 W of output power

We present our recent advances in the use of pulsed laser deposition (PLD) to fabricate active gain elements for use as amplifiers and laser oscillators. Record output powers exceeding 16 W and slope efficiencies of 70% are reported for optimized epitaxial growth of Yb(7.5%):YAG on to YAG substrates. We show for the first time that the performance of PLD material can meet or even exceed that of materials grown by more established methods such as the Czochralski technique. Details of fabrication, characterization and laser performance are presented in addition to outlining expected future improvements

Comparative study of rare-earth doped sesquioxides grown by pulsed laser deposition and their performance as planar waveguide lasers

The sesquioxides yttria, scandia and lutetia have been identified as promising host materials for high power lasers due to their excellent thermal properties, their ability to incorporate RE-ions and their resulting spectroscopic properties [1]. However, the melting points of these materials exceed 2400°C and are therefore problematic to grow from the melt. Pulsed laser deposition (PLD) is an alternative method of growing thin crystalline films of these materials, avoiding the requirement for such high temperature growth

Better living with non-memory led dementia: Protocol for a feasibility randomised controlled trial of a web-based caregiver educational programme

Background Non-memory-led dementias such as posterior cortical atrophy (PCA), primary progressive aphasia (PPA) and behavioural variant frontotemporal dementia (bvFTD) are low prevalent and often affect individuals under the age of 65. Tailored educational and support resources for caregivers of people living with these dementia phenotypes are scarce and unevenly distributed geographically. Web-based educational programmes are emerging as promising alternatives to improve caregiver self-efficacy and well-being. Here, we present the protocol of a study aiming to assess the feasibility of a co-produced online educational programme for caregivers of people living PCA, PPA and bvFTD: the Better Living with Non-memory-led Dementia programme. Methods A randomised controlled feasibility trial will be conducted on a sample of 30 caregivers of people living with PCA, PPA and bvFTD. Participants will be recruited among members of the support organisation Rare Dementia Support (based at UCL in the UK). The intervention group will be given access to an 8-week co-produced web-based educational programme consisting of 6 modules addressing education about PCA, PPA and bvFTD and support strategies for the person with dementia and for the caregiver. The control group will receive treatment as usual (TAU). Feasibility will be measured through feasibility of recruitment, clinical measurement tools and acceptability. Clinical measures will be used to assess preliminary efficacy and data on completion rates, missing data and variability used to decide on measures to be included in a full-scale trial. Allocation ratio will be 2:1 (intervention:control) stratified by diagnosis. Feasibility of recruitment and acceptability will be assessed. Clinical measures will be administered at baseline and 8-week and 3-month post-randomisation. The control group will be offered access to the intervention at the completion of data collection. Participants will be unblinded, and all measures will be self-reported online. Discussion Online-delivered educational programmes show potential for improving care competency of caregivers and may contribute to overcoming geographical inequalities in local provision of support services. This pilot study will inform a fully powered international trial to determine the effectiveness of Better Living with Non-memory-led Dementia. Trial registration This trial has been registered prospectively on the Clinical Trials Registry on 1st September 2022, registration number NCT05525377