Tailoring the Mechanical Properties of Selective Laser Sintered Parts

The ~£1 million IMCRC-funded integrated project ‘Personalised Sports Footwear: From Elite to High Street’ is investigating the use of Rapid Manufacturing to produce personalised sports shoes, with the aim of enhancing performance, reducing injury, and providing improved functionality. Research has identified that, for sprinting, performance benefits can be achieved by tuning the bending stiffness of a shoe to the characteristics of an individual athlete. This paper presents research to date on several novel methods of influencing the mechanical properties of Selective Laser Sintered shoe soles, with a particular focus on stiffness.Mechanical Engineerin

Voltage controlled nuclear polarization switching in a single InGaAs quantum dot

Sharp threshold-like transitions between two stable nuclear spin polarizations are observed in optically pumped individual InGaAs self-assembled quantum dots embedded in a Schottky diode when the bias applied to the diode is tuned. The abrupt transitions lead to the switching of the Overhauser field in the dot by up to 3 Tesla. The bias-dependent photoluminescence measurements reveal the importance of the electron-tunneling-assisted nuclear spin pumping. We also find evidence for the resonant LO-phonon-mediated electron co-tunneling, the effect controlled by the applied bias and leading to the reduction of the nuclear spin pumping rate.Comment: 5 pages, 2 figures, submitted to Phys Rev

On the diffusion of lattice matched InGaAs/InP microstructures

Copyright (2003) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in F. Bollet et al., J. Appl. Phys. 93, 3881 (2003) and may be found at http://link.aip.org/link/?jap/93/388

Photoluminescence upconversion at GaAs/InGaP2 interfaces driven by a sequential two-photon absorption mechanism

This paper reports on the results of an investigation into the nature of photoluminescence upconversion at GaAs/InGaP2 interfaces. Using a dual-beam excitation experiment, we demonstrate that the upconversion in our sample proceeds via a sequential two-photon optical absorption mechanism. Measurements of photoluminescence and upconversion photoluminescence revealed evidence of the spatial localization of carriers in the InGaP2 material, arising from partial ordering of the InGaP2. We also observed the excitation of a two-dimensional electron gas at the GaAs/InGaP2 heterojunction that manifests as a high-energy shoulder in the GaAs photoluminescence spectrum. Furthermore, the results of upconversion photoluminescence excitation spectroscopy demonstrate that the photon energy onset of upconversion luminescence coincides with the energy of the two-dimensional electron gas at the GaAs/InGaP2 interface, suggesting that charge accumulation at the interface can play a crucial role in the upconversion process

Separation of river network–scale nitrogen removal among the main channel and two transient storage compartments

Transient storage (TS) zones are important areas of dissolved inorganic nitrogen (DIN) processing in rivers. We assessed sensitivities regarding the relative impact that the main channel (MC), surface TS (STS), and hyporheic TS (HTS) have on network denitrification using a model applied to the Ipswich River in Massachusetts, United States. STS and HTS connectivity and size were parameterized using the results of in situ solute tracer studies in first‐ through fifth‐order reaches. DIN removal was simulated in all compartments for every river grid cell using reactivity derived from Lotic Intersite Nitrogen Experiment (LINX2) studies, hydraulic characteristics, and simulated discharge. Model results suggest that although MC‐to‐STS connectivity is greater than MC‐to‐HTS connectivity at the reach scale, at basin scales, there is a high probability of water entering the HTS at some point along its flow path through the river network. Assuming our best empirical estimates of hydraulic parameters and reactivity, the MC, HTS, and STS removed approximately 38%, 21%, and 14% of total DIN inputs during a typical base flow period, respectively. There is considerable uncertainty in many of the parameters, particularly the estimates of reaction rates in the different compartments. Using sensitivity analyses, we found that the size of TS is more important for DIN removal processes than its connectivity with the MC when reactivity is low to moderate, whereas TS connectivity is more important when reaction rates are rapid. Our work suggests a network perspective is needed to understand how connectivity, residence times, and reactivity interact to influence DIN processing in hierarchical river systems

Digging supplementary buried channels: investigating the notch architecture within the CCD pixels on ESA's Gaia satellite

The European Space Agency (ESA) Gaia satellite has 106 CCD image sensors which will suffer from increased charge transfer inefficiency (CTI) as a result of radiation damage. To aid the mitigation at low signal levels, the CCD design includes Supplementary Buried Channels (SBCs, otherwise known as `notches') within each CCD column. We present the largest published sample of Gaia CCD SBC Full Well Capacity (FWC) laboratory measurements and simulations based on 13 devices. We find that Gaia CCDs manufactured post-2004 have SBCs with FWCs in the upper half of each CCD that are systematically smaller by two orders of magnitude (<50 electrons) compared to those manufactured pre-2004 (thousands of electrons). Gaia's faint star (13 < G < 20 mag) astrometric performance predictions by Prod'homme et al. and Holl et al. use pre-2004 SBC FWCs as inputs to their simulations. However, all the CCDs already integrated onto the satellite for the 2013 launch are post-2004. SBC FWC measurements are not available for one of our five post-2004 CCDs but the fact it meets Gaia's image location requirements suggests it has SBC FWCs similar to pre-2004. It is too late to measure the SBC FWCs onboard the satellite and it is not possible to theoretically predict them. Gaia's faint star astrometric performance predictions depend on knowledge of the onboard SBC FWCs but as these are currently unavailable, it is not known how representative of the whole focal plane the current predictions are. Therefore, we suggest Gaia's initial in-orbit calibrations should include measurement of the onboard SBC FWCs. We present a potential method to do this. Faint star astrometric performance predictions based on onboard SBC FWCs at the start of the mission would allow satellite operating conditions or CTI software mitigation to be further optimised to improve the scientific return of Gaia.Comment: Accepted for publication in MNRAS, 16 pages, 19 figure

Respiratory patient experience of measures to reduce risk of COVID-19: findings from a descriptive cross-sectional UK wide survey

Objectives: To assess the experience of people with long-term respiratory conditions regarding the impact of measures to reduce risk of COVID-19. Design: Analysis of data (n=9,515) from the Asthma UK and British Lung Foundation partnership COVID-19 survey collected online between 1st and 8th of April 2020. Setting: Community Participants: 9,515 people with self-reported long term respiratory conditions. 81% female, age ranges from <17 years to 80 and above, from all nations of the UK. Long term respiratory conditions reported included asthma (83%), Chronic Obstructive Pulmonary Disease (COPD) (10%), bronchiectasis (4%), Interstitial Lung Disease (ILD) (2%), and ‘other’ (<1%) (e.g. lung cancer and pulmonary endometriosis). Outcome measures: Study responses related to impacts on key elements of health care, as well as practical, psychological and social consequences related to the COVID-19 pandemic and social distancing measures. Results: 45% reported disruptions to care, including cancellations of appointments, investigations, pulmonary rehabilitation, treatment, and monitoring. Other practical impacts such as difficulty accessing healthcare services for other issues, and getting basic necessities such as food, were also common. 36% did not use online prescriptions and 54% had not accessed online inhaler technique videos. Psycho-social impacts including anxiety, loneliness and concerns about personal health and family were prevalent. 81% reported engaging in physical activity. Among the 11% who were smokers, 48% reported they were planning to quit smoking because of COVID-19. Conclusions: COVID-19 and related social distancing measures are having profound impacts on people with chronic respiratory conditions. Urgent adaptation and signposting of services is required to mitigate the negative health consequences of the COVID-19 response for this group

BIMODAL WHOLE-1 MOUNT IMAGING OF TENDON USING CONFOCAL MICROSCOPY AND X-RAY MICRO-COMPUTED TOMOGRAPHY

BACKGROUND:3-dimensional imaging modalities for optically dense connective tissues such as tendons are limited and typically have a single imaging methodological endpoint. Here, we have developed a bimodal procedure utilising fluorescence-based confocal microscopy and x-ray micro-computed tomography for the imaging of adult tendons to visualise and analyse extracellular sub-structure and cellular composition in small and large animal species. RESULTS: Using fluorescent immunolabelling and optical clearing, we visualised the expression of the novel cross-species marker of tendon basement membrane, laminin-α4 in 3D throughout whole rat Achilles tendons and equine superficial digital flexor tendon 5 mm segments. This revealed a complex network of laminin-α4 within the tendon core that predominantly localises to the interfascicular matrix compartment. Furthermore, we implemented a chemical drying process capable of creating contrast densities enabling visualisation and quantification of both fascicular and interfascicular matrix volume and thickness by x-ray micro-computed tomography. We also demonstrated that both modalities can be combined using reverse clarification of fluorescently labelled tissues prior to chemical drying to enable bimodal imaging of a single sample. CONCLUSIONS: Whole-mount imaging of tendon allowed us to identify the presence of an extensive network of laminin-α4 within tendon, the complexity of which cannot be appreciated using traditional 2D imaging techniques. Creating contrast for x-ray micro-computed tomography imaging of tendon using chemical drying is not only simple and rapid, but also markedly improves on previously published methods. Combining these methods provides the ability to gain spatio-temporal information and quantify tendon substructures to elucidate the relationship between morphology and function

Photoluminescence spectroscopy of bandgap reduction in dilute InNAs alloys

Photoluminescence (PL) has been observed from dilute InNxAs1–x epilayers grown by molecular-beam epitaxy. The PL spectra unambiguously show band gap reduction with increasing N content. The variation of the PL spectra with temperature is indicative of carrier detrapping from localized to extended states as the temperature is increased. The redshift of the free exciton PL peak with increasing N content and temperature is reproduced by the band anticrossing model, implemented via a (5×5) k·p Hamiltonian

Moving singing for lung health online in response to COVID-19: experience from a randomised controlled trial

Introduction Singing for Lung Health (SLH) is a popular arts-in-health activity for people with long-term respiratory conditions. Participants report biopsychosocial benefits, however research on impact is limited. The ‘SHIELD trial’, a randomised controlled, single (assessor) blind, trial of 12 weeks SLH vs usual care for people with Chronic Obstructive Pulmonary Disease (COPD) (n=120) was set-up to help to address this. The first group (n=18, 9 singing and 9 controls) started face-to-face (5 sessions) before changing to online delivery (7 sessions) due to COVID-19 related physical distancing measures. As such, the experience of this group is here reported as a pilot study to inform further research in this area. Methods We conducted semi-structured interviews and thematic analysis regarding barriers, facilitators and key considerations for transitioning from face-to-face to online delivery. Pilot quantitative outcomes include attendance, pre and post measures of quality of life and disease impact (SF-36, CAT score), breathlessness (MRC breathlessness scale, Dyspnoea-12), depression (PHQ9), anxiety (GAD-7), balance confidence (ABC scale) and physical activity (clinical visit PROactive physical activity in COPD tool, combining subjective rating and actigraphy). Results Attendance was 69% overall, (90% of the face-to-face sessions, 53% online sessions). Analysis of semi-structured interviews identified three themes regarding participation in SLH delivered face-to-face and online, these where 1) perceived benefits; 2) digital barriers (online); 3) digital facilitators (online). Findings were summarised into key considerations for optimising transitioning singing groups from face-to-face to online delivery. Pilot quantitative data suggested possible improvements in depression (treatment effect -4.78 PHQ9 points, p< 0.05, MCID 5) and balance confidence (treatment effect +17.21 ABC Scale points, p=0.04, MCID 14.2). Discussion This study identifies key considerations regarding the adaptation of SLH from face-to-face to online delivery. Pilot data suggest online group singing for people with COPD may deliver benefits related to reducing depression and improved balance confidence