Application of continuous-wave cavity ring-down spectroscopy to laminar flames

In this paper we describe the application of diode laser continuous-wave cavity ring-down spectroscopy (cw-CRDS) to in-situ flame diagnostics. Spectra of the P17e acetylene feature at 1535.4 nm were recorded in a premixed laminar ethylene/air flame. The overall absorption of the feature was measured to be ≈ 1.5×10−4 cm−1 a short distance above the reaction zone for a flame fuel equivalence ratio of 1.66, and the minimum detection limit (3σ) of the system was calculated to be1.2×10−5 cm−1. This demonstrates the potential of the technique for the measurement of weakly absorbing species in flames. Finally, we discuss the advantages and limitations of the cw-CRDS technique for flame measurements

High-repetition-rate combustion thermometry with two-line atomic fluorescence excited by diode lasers

We report on kilohertz-repetition-rate flame temperature measurements performed using blue diode lasers. Two-line atomic fluorescence was performed by using diode lasers emitting at around 410 and 451 nm to probe seeded atomic indium. At a repetition rate of 3.5 kHz our technique offers a precision of 1.5% at 2000 K in laminar methane/air flames. The spatial resolution is better than 150 mu m, while the setup is compact and easy to operate, at much lower cost than alternative techniques. By modeling the spectral overlap between the locked laser and the probed indium lines we avoid the need for any calibration of the measurements. We demonstrate the capability of the technique for time-resolved measurements in an acoustically perturbed flame. The technique is applicable in flames with a wide range of compositions including sooting flames

Scaling of glycine nucleation kinetics with shear rate and glass-liquid interfacial area

The scaling of the nucleation kinetics of glycine was investigated in supersaturated aqueous solutions under isothermal conditions. Induction times were measured in a Couette cell with a wide range of average shear rates γ_avg (25-250 s^-1) and a range of glass-liquid interfacial areas A (2.5-10 cm^2 per ml solution). The probability distributions of induction times were found to scale with shear rate and glass-liquid interfacial area, with the characteristic timescale (γ_avg.A)^-1. Primary nucleation rates and growth times to reach detection (estimated from the probability distributions) were both dependent on this timescale. In-situ dynamic light scattering revealed mesoscale clusters in the solutions that increased in size over time at rates which also depended on this timescale. The increase in size was thought to be due to the shear-enhanced aggregation or coalescence of mesoscale clusters leading to a higher number of larger mesoscale clusters, resulting in higher rates of primary nucleation

Freezing properties of alkenyl succinic anhydrides derived from linear isomerised olefins

Alkenyl succinic anhydrides are important specialty chemicals that are used in the paper, oilfield and fuel additives industries. In this paper we investigate the link between the physical properties of alkenyl succinic anhydrides and the identities of their linear alkyl olefin precursors. We describe a straightforward GC analysis of olefin isomer distributions and show that these correlate well with the freezing temperatures of the subsequent alkenyl succinic anhydride products. This allows the identification of olefin isomer profiles that are required to give the desired physical properties in the alkenyl succinic anhydrides; it also provides a method to predict the freezing temperatures of alkenyl succinic anhydrides synthesised from a particular supply of olefin

Temperature imaging in low pressure flames using diode laser two-line atomic fluorescence employing a novel indium seeding technique

The use of diode lasers for spatially resolved temperature imaging is demonstrated in low pressure premixed methane-air flames using two-line atomic fluorescence of seeded indium atoms. This work features the advantages of using compact diode lasers as the excitation sources with the benefits of two-dimensional planar imaging, which is normally only performed with high-power pulsed lasers. A versatile and reliable seeding technique with minimal impact on flame properties is used to introduce indium atoms into the combustion environment for a wide range of flame equivalence ratios. A spatial resolution of around 210 µm for this calibration free thermometry technique is achieved for three equivalence ratios at a pressure of 50 mbar in a laminar flat flame

Influence of controlled fluid shear on nucleation rates in glycine aqueous solutions

The nucleation of glycine was investigated in supersaturated aqueous solutions exposed to well-controlled fluid shear under isothermal conditions. Shear rates between 25 s-1 and 1000 s-1 were studied using Couette and capillary flow devices. Induction times were obtained from imaging, transmission and scattering measurements, or visual monitoring. Great care was taken to eliminate any seeding in order to avoid secondary nucleation preceding formation of first crystals through primary nucleation. The observed induction times of sheared solutions were considerably lower than those of unsheared solutions. Increasing the average shear rate was found to reduce the mean induction time through a power law relationship. A detailed statistical analysis showed that the number of experimental repetitions used was sufficient to obtain statistically significant trends for the system studied. Induction times appeared to closely follow a probability distribution based on a previously published model of Jiang and ter Horst. Using their model, where the induction time is related to the rate of formation of primary nuclei and the time it takes them to grow to the size where the secondary nucleation becomes significant, it was found that both the primary nucleation rate and the growth time were strongly dependent on the shear rate imposed

In-situ photoacoustic measurement of soot profiles in laminar flames using a high repetition-rate pulsed fibre laser

We present a photoacoustic technique for in situ sensing of particulates in reacting flows. The method is demonstrated by measuring soot distribution in laminar flat-flames. The excitation source is a high repetition-rate pulsed fibre laser. The resulting acoustic signals are measured using a uni-directional microphone and lock-in amplifier. Based on an Allan-Werle plot, the detection limit is estimated to be a soot volume fraction of 3 parts-per-billion. Fluence curves are presented, showing a plateau region similar to the behaviour typically observed for laser-induced incandescence. A dependence of the photoacoustic signal on pulse repetition rate is also demonstrated

Flash glucose monitoring with the FreeStyle Libre 2 compared with self-monitoring of blood glucose in suboptimally controlled type 1 diabetes: the FLASH-UK randomised controlled trial protocol.

INTRODUCTION: Optimising glycaemic control in type 1 diabetes (T1D) remains challenging. Flash glucose monitoring with FreeStyle Libre 2 (FSL2) is a novel alternative to the current standard of care self-monitoring of blood glucose (SMBG). No randomised controlled trials to date have explored the potential benefits of FSL2 in T1D. We aim to assess the impact of FSL2 in people with suboptimal glycaemic control T1D in comparison with SMBG. METHODS: This open-label, multicentre, randomised (via stochastic minimisation), parallel design study conducted at eight UK secondary and primary care centres will aim to recruit 180 people age ≥16 years with T1D for >1 year and glycated haemoglobin (HbA1c) 7.5%-11%. Eligible participants will be randomised to 24 weeks of FSL2 (intervention) or SMBG (control) periods, after 2-week of blinded sensor wear. Participants will be assessed virtually or in-person owing to the COVID-19 pandemic. HbA1c will be measured at baseline, 12 and 24 weeks (primary outcome). Participants will be contacted at 4 and 12 weeks for glucose optimisation. Control participants will wear a blinded sensor during the last 2 weeks. Psychosocial outcomes will be measured at baseline and 24 weeks. Secondary outcomes include sensor-based metrics, insulin doses, adverse events and self-report psychosocial measures. Utility, acceptability, expectations and experience of using FSL2 will be explored. Data on health service resource utilisation will be collected. ANALYSIS: Efficacy analyses will follow intention-to-treat principle. Outcomes will be analysed using analysis of covariance, adjusted for the baseline value of the corresponding outcome, minimisation factors and other known prognostic factors. Both within-trial and life-time economic evaluations, informed by modelling from the perspective of the National Health Service setting, will be performed. ETHICS: The study was approved by Greater Manchester West Research Ethics Committee (reference 19/NW/0081). Informed consent will be sought from all participants. TRIAL REGISTRATION NUMBER: NCT03815006. PROTOCOL VERSION: 4.0 dated 29 June 2020.Diabetes U

An exploratory randomised controlled trial of a premises-level intervention to reduce alcohol-related harm including violence in the United Kingdom

<b>Background</b><p></p> To assess the feasibility of a randomised controlled trial of a licensed premises intervention to reduce severe intoxication and disorder; to establish effect sizes and identify appropriate approaches to the development and maintenance of a rigorous research design and intervention implementation.<p></p> <b>Methods</b><p></p> An exploratory two-armed parallel randomised controlled trial with a nested process evaluation. An audit of risk factors and a tailored action plan for high risk premises, with three month follow up audit and feedback. Thirty-two premises that had experienced at least one assault in the year prior to the intervention were recruited, match paired and randomly allocated to control or intervention group. Police violence data and data from a street survey of study premises’ customers, including measures of breath alcohol concentration and surveyor rated customer intoxication, were used to assess effect sizes for a future definitive trial. A nested process evaluation explored implementation barriers and the fidelity of the intervention with key stakeholders and senior staff in intervention premises using semi-structured interviews.<p></p> <b>Results</b><p></p> The process evaluation indicated implementation barriers and low fidelity, with a reluctance to implement the intervention and to submit to a formal risk audit. Power calculations suggest the intervention effect on violence and subjective intoxication would be raised to significance with a study size of 517 premises.<p></p> <b>Conclusions</b><p></p> It is methodologically feasible to conduct randomised controlled trials where licensed premises are the unit of allocation. However, lack of enthusiasm in senior premises staff indicates the need for intervention enforcement, rather than voluntary agreements, and on-going strategies to promote sustainability

Osteoarthritis: 119. The Effectiveness of Exercise Therapy with and without Manual Therapy for Hip Osteoarthritis: A Multicentre Randomised Controlled Trial

Background: Current evidence indicates that exercise therapy (ET) has a short and medium-term benefit for hip osteoarthritis (OA), but evidence is inconclusive regarding the effect of manual therapy (MT). The primary aim of this randomised controlled trial was to determine the effectiveness of ET with and without MT on clinical outcomes for individuals with hip OA. A secondary aim was to ascertain the effect of an 8-week waiting period on outcomes. Methods: 131 men and women with hip OA recruited in four hospitals were initially randomised to one of three groups: ET (n = 45), a combination of ET and MT (n = 43) and wait-list control (n = 43). The two intervention groups underwent individualised ET or ET/MT for 8 weeks. Patients in the control group waited 8 weeks and were randomised to receive either ET or ET/MT after 9 week follow-up, and pooled with original treatment group data: ET (n = 66) and ET/ MT (n = 65). All participants were followed up at 9 and 18 weeks and the control group was reassessed at 27 weeks (18 weeks post-treatment) by the same blinded assessor. The primary outcome measure was the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Other outcomes included sit-to-stand, 50-foot walk test, pain severity, hip range of motion (ROM), anxiety, depression, quality of life (QOL), analgesic usage, physical activity, patient-perceived change and patient satisfaction. Intention-to-treat analysis was performed to determine within-group change and between-group differences for the three groups at baseline and 9 weeks, and the two treatment groups at baseline, 9 and 18 weeks. Results: Eight patients (6.1%) were lost to follow-up at 9 weeks and 19 (14.5%) were lost to follow-up by 18 weeks. Both ET (n = 66) and ET/MT groups (n = 65) showed significant within-group improvements in WOMAC, pain severity, sit-to-stand and HROM measures at 9 weeks, which were still evident at 18 weeks. There was no significant within-group change in anxiety, depression, QOL, analgesic usage, 50-foot walk test or physical activity. There was no significant difference between the two intervention groups for any of the outcomes. Regarding the results of the original ET, ET/MT and control group allocation, there was a significant improvement in one or both ET and ET/MT groups compared with the control group in the same outcomes, as well as patient perceived improvement at 9 weeks. There was no significant difference between the three groups in analgesic usage, WOMAC stiffness subscale, sit-to-stand and 50 foot walk tests, QOL and physical activity. There was an overall deterioration in anxiety and depression scores. Conclusions: The addition of MT to an 8 week programme of ET for hip OA resulted in similar improvements in pain, function and ROM at 9 and 18 weeks. The significant improvement which occurred in the same outcomes in the two treatment groups compared with a wait-list control of 8 weeks has implications for waiting list management Disclosure statement: The authors have declared no conflicts of interes