43 research outputs found

    Interwell relaxation times in p-Si/SiGe asymmetric quantum well structures: the role of interface roughness

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    We report the direct determination of nonradiative lifetimes in Si‚ąēSiGe asymmetric quantum well structures designed to access spatially indirect (diagonal) interwell transitions between heavy-hole ground states, at photon energies below the optical phonon energy. We show both experimentally and theoretically, using a six-band k‚ąôp model and a time-domain rate equation scheme, that, for the interface quality currently achievable experimentally (with an average step height ‚©ĺ1 √Ö), interface roughness will dominate all other scattering processes up to about 200 K. By comparing our results obtained for two different structures we deduce that in this regime both barrier and well widths play an important role in the determination of the carrier lifetime. Comparison with recently published experimental and theoretical data obtained for mid-infrared GaAs‚ąēAlxGa1‚ąíxAs multiple quantum well systems leads us to the conclusion that the dominant role of interface roughness scattering at low temperature is a general feature of a wide range of semiconductor heterostructures not limited to IV-IV material

    Developing a core outcome set for the health outcomes for children and adults with congenital oesophageal atresia and/or tracheo-oesophageal fistula: OCELOT task group study protocol

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    Introduction: Heterogeneity in reported outcomes of infants with oesophageal atresia (OA) with or without tracheo-oesophageal fistula (TOF) prevents effective data pooling. Core outcome sets (COS) have been developed for many conditions to standardise outcome reporting, facilitate meta-analysis and improve the relevance of research for patients and families. Our aim is to develop an internationally-agreed, comprehensive COS for OA-TOF, relevant from birth through to transition and adulthood. Methods and analysis: A long list of outcomes will be generated using (1) a systematic review of existing studies on OA-TOF and (2) qualitative research with children (patients), adults (patients) and families involving focus groups, semistructured interviews and self-reported outcome activity packs. A two-phase Delphi survey will then be completed by four key stakeholder groups: (1) patients (paediatric and adult); (2) families; (3) healthcare professionals; and (4) researchers. Phase I will include stakeholders individually rating the importance and relevance of each long-listed outcome using a 9-point Likert scale, with the option to suggest additional outcomes not already included. During phase II, stakeholders will review summarised results from phase I relative to their own initial score and then will be asked to rescore the outcome based on this information. Responses from phase II will be summarised using descriptive statistics and a predefined definition of consensus for inclusion or exclusion of outcomes. Following the Delphi process, stakeholder experts will be invited to review data at a consensus meeting and agree on a COS for OA-TOF. Ethics and dissemination: Ethical approval was sought through the Health Research Authority via the Integrated Research Application System, registration no. 297026. However, approval was deemed not to be required, so study sponsorship and oversight were provided by Alder Hey Children’s NHS Foundation Trust. The study has been prospectively registered with the COMET Initiative. The study will be published in an open access forum

    Increasing access to integrated ESKD care as part of Universal Health Coverage

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    The global nephrology community recognizes the need for a cohesive strategy to address the growing problem of end-stage kidney disease (ESKD). In March 2018, the International Society of Nephrology hosted a summit on integrated ESKD care, including 92 individuals from around the globe with diverse expertise and professional backgrounds. The attendees were from 41 countries, including 16 participants from 11 low- and lower-middle‚Äďincome countries. The purpose was to develop a strategic plan to improve worldwide access to integrated ESKD care, by identifying and prioritizing key activities across 8 themes: (i) estimates of ESKD burden and treatment coverage, (ii) advocacy, (iii) education and training/workforce, (iv) financing/funding models, (v) ethics, (vi) dialysis, (vii) transplantation, and (viii) conservative care. Action plans with prioritized lists of goals, activities, and key deliverables, and an overarching performance framework were developed for each theme. Examples of these key deliverables include improved data availability, integration of core registry measures and analysis to inform development of health care policy; a framework for advocacy; improved and continued stakeholder engagement; improved workforce training; equitable, efficient, and cost-effective funding models; greater understanding and greater application of ethical principles in practice and policy; definition and application of standards for safe and sustainable dialysis treatment and a set of measurable quality parameters; and integration of dialysis, transplantation, and comprehensive conservative care as ESKD treatment options within the context of overall health priorities. Intended users of the action plans include clinicians, patients and their families, scientists, industry partners, government decision makers, and advocacy organizations. Implementation of this integrated and comprehensive plan is intended to improve quality and access to care and thereby reduce serious health-related suffering of adults and children affected by ESKD worldwide

    Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

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    Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low‚Äďmiddle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‚Äėsingle-use‚Äô consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low‚Äďmiddle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high‚Äď and low‚Äďmiddle‚Äďincome countries

    The cleavage of DNA at phoshorothioate internucleotidic linkages by DNA gyrase

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    Titration microcalorimetry

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    Key features of an isothermal titration microcalorimeter (ITC) are described together with a general equation which forms the basis of the analysis of the calorimetric results. Recent applications of titration microcalorimetry to four subject areas concerned with the properties of aqueous solutions are reviewed. The four subjects covered are (i) pairwise enthalpic solute-solute interaction parameters in aqueous solution, (ii) deaggregation of micelles formed by ionic surfactants, (iii) protein-ligand interactions and (iv) adsorption of adsorbates on polymeric adsorbents.

    Titration microcalorimetry of mixed alkyltrimethylammonium bromide surfactant aqueous solutions

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    Enthalpograms recorded using a titration microcalorimeter are reported for mixtures of surfactants hexadecyltrimethylammonium bromide (CTAB) and tetradecyltrimethylammonium bromide (TTAB) in aqueous solutions at 298.2 K. The enthalpograms for each mixture show that the micellar phase comprises a mixture of the surfactants rather than separate domains comprising single surfactants. The enthalpograms are satisfactorily accounted for using the pseudo-phase model taking account of the non-ideal properties of the mixed micellar phase and of the mixed aqueous surfactant solutions. A quantitative treatment is described for the analysis of titration calorimetric results for mixed ionic surfactant systems. For the micellar phase a key parameter determining the critical micellar concentration (c.m.c.) is a generalised rational activity coefficient for the micellar phase. For the systems described here this parameter is less than unity indicating that surfactant-surfactant interactions stabilise the micellar phase, whereas a generalised Gibbs energy surfactant-surfactant interaction parameter for the aqueous phase is positive, opposing Debye-H√ľckel ionic-atmosphere stabilising effects although the corresponding enthalpic parameter is exothermic. As the total concentration of surfactant in the sample cell of the calorimeter increases during a given experiment, the calculated c.m.c. changes as a consequence of these interactions which are a function of composition. In general terms the c.m.c. and enthalpy of mixed micelle formation for the CTAB-TTAB mixture change smoothly between the corresponding properties of the two pure surfactants.