2,179 research outputs found

    Necessary and sufficient conditions of solution uniqueness in â„“1\ell_1 minimization

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    This paper shows that the solutions to various convex ℓ1\ell_1 minimization problems are \emph{unique} if and only if a common set of conditions are satisfied. This result applies broadly to the basis pursuit model, basis pursuit denoising model, Lasso model, as well as other ℓ1\ell_1 models that either minimize f(Ax−b)f(Ax-b) or impose the constraint f(Ax−b)≤σf(Ax-b)\leq\sigma, where ff is a strictly convex function. For these models, this paper proves that, given a solution x∗x^* and defining I=\supp(x^*) and s=\sign(x^*_I), x∗x^* is the unique solution if and only if AIA_I has full column rank and there exists yy such that AITy=sA_I^Ty=s and ∣aiTy∣∞<1|a_i^Ty|_\infty<1 for i∉Ii\not\in I. This condition is previously known to be sufficient for the basis pursuit model to have a unique solution supported on II. Indeed, it is also necessary, and applies to a variety of other ℓ1\ell_1 models. The paper also discusses ways to recognize unique solutions and verify the uniqueness conditions numerically.Comment: 6 pages; revised version; submitte

    Impact and cost-effectiveness of current and future tuberculosis diagnostics: the contribution of modelling.

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    The landscape of diagnostic testing for tuberculosis (TB) is changing rapidly, and stakeholders need urgent guidance on how to develop, deploy and optimize TB diagnostics in a way that maximizes impact and makes best use of available resources. When decisions must be made with only incomplete or preliminary data available, modelling is a useful tool for providing such guidance. Following a meeting of modelers and other key stakeholders organized by the TB Modelling and Analysis Consortium, we propose a conceptual framework for positioning models of TB diagnostics. We use that framework to describe modelling priorities in four key areas: Xpert(®) MTB/RIF scale-up, target product profiles for novel assays, drug susceptibility testing to support new drug regimens, and the improvement of future TB diagnostic models. If we are to maximize the impact and cost-effectiveness of TB diagnostics, these modelling priorities should figure prominently as targets for future research

    Temporal variations in quality of acute stroke care and outcomes in London hyperacute stroke units: a mixed-methods study

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    This is the final version. Available from the NIHR Journals Library via the DOI in this recordBackground Seven-day working in hospitals is a current priority of international health research and policy. Previous research has shown variability in delivering evidence-based clinical interventions across different times of the day and week. We aimed to identify factors influencing such variations in London hyperacute stroke units. Objectives To investigate variations in quality of acute stroke care and outcomes by day and time of admission in London hyperacute stroke units, and to identify factors influencing such variations. Design This was a prospective cohort study using anonymised patient-level data from the Sentinel Stroke National Audit Programme. Factors influencing variations in care and outcomes were studied through interview and observation data. Setting The setting was acute stroke services in London hyperacute stroke units. Participants A total of 7094 patients with a primary diagnosis of stroke took part. We interviewed hyperacute stroke unit staff (n = 76), including doctors, nurses, therapists and administrators, and 31 patients and carers. We also conducted non-participant observations of delivery of care at different times of the day and week (n = 45, ≈102 hours). Intervention Hub-and-spoke model for care of suspected acute stroke patients in London with performance standards was designed to deliver uniform access to high-quality hyperacute stroke unit care across the week. Main outcome measures Indicators of quality of acute stroke care, mortality at 3 days after admission, disability at the end of the inpatient spell and length of stay. Data sources Sentinel Stroke National Audit Programme data for all patients in London hyperacute stroke units with a primary diagnosis of stroke between 1 January and 31 December 2014, and nurse staffing data for all eight London hyperacute stroke units for the same period. Results We found no variation in quality of care by day and time of admission across the week in terms of stroke nursing assessment, brain scanning and thrombolysis in London hyperacute stroke units, nor in 3-day mortality nor disability at hospital discharge. Other quality-of-care measures significantly varied by day and time of admission. Quality of care was better if the nurse in charge was at a higher band and/or there were more nurses on duty. Staff deliver ‘front-door’ interventions consistently by taking on additional responsibilities out of hours, creating continuities between day and night, building trusting relationships and prioritising ‘front-door’ interventions. Limitations We were unable to measure long-term outcomes as our request to the Sentinel Stroke National Audit Programme, the Healthcare Quality Improvement Partnership and NHS Digital for Sentinel Stroke National Audit Programme data linked with patient mortality status was not fulfilled. Conclusions Organisational factors influence 24 hours a day, 7 days a week (24/7), provision of stroke care, creating temporal patterns of provision reflected in patient outcomes, including mortality, length of stay and functional independence. Future work Further research would help to explore 24/7 stroke systems in other contexts. We need a clearer understanding of variations by looking at absolute time intervals, rather than achievement of targets. Research is needed with longer-term mortality and modified Rankin Scale data, and a more meaningful range of outcomes.National Institute for Health Research (NIHR

    Immunotherapy of lung cancer: An update

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    In Germany lung cancer is the leading cause of cancer-associated death in men. Surgery, chemotherapy and radiation may enhance survival of patients suffering from lung cancer but the enhancement is typically transient and mostly absent with advanced disease; eventually more than 90% of lung cancer patients will die of disease. New approaches to the treatment of lung cancer are urgently needed. Immunotherapy may represent one new approach with low toxicity and high specificity but implementation has been a challenge because of the poor antigenic characterization of these tumors and their ability to escape immune responses. Several different immunotherapeutic treatment strategies have been developed. This review examines the current state of development and recent advances with respect to non-specific immune stimulation, cellular immunotherapy ( specific and non-specific), therapeutic cancer vaccines and gene therapy for lung cancer. The focus is primarily placed on immunotherapeutic cancer treatments that are already in clinical trial or well progressed in preclinical studies. Although there seems to be a promising future for immunotherapy in lung cancer, presently there is not standard immunotherapy available for clinical routine

    The use of electrochemical sensors for monitoring urban air quality in low-cost, high-density networks

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    Measurements at appropriate spatial and temporal scales are essential for understanding and monitoring spatially heterogeneous environments with complex and highly variable emission sources, such as in urban areas. However, the costs and complexity of conventional air quality measurement methods means that measurement networks are generally extremely sparse. In this paper we show that miniature, low-cost electrochemical gas sensors, traditionally used for sensing at parts-per-million (ppm) mixing ratios can, when suitably configured and operated, be used for parts-per-billion (ppb) level studies for gases relevant to urban air quality. Sensor nodes, in this case consisting of multiple individual electrochemical sensors, can be low-cost and highly portable, thus allowing the deployment of scalable high-density air quality sensor networks at fine spatial and temporal scales, and in both static and mobile configurations.This work was supported by EPSRC (grant number EP/E002102/1) and the Department for Transport

    Tuberculosis

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    Asserts that despite progress in controlling tuberculosis (TB), the decline in incidence has been disappointing, pointing to the need for new strategies and more effective tools. HIV/AIDS is one factor that challenges effective control of TB, especially in Southern African countries. Three key elements are needed to achieve effective TB control and to meet the Sustainable Development Goals: (1) early and accurate diagnosis and drug-sensitivity testing, (2) patient access to and completion of effective treatment, and (3) prevention of progression from latent infection to disease. Prevention requires vaccination and screening of individual at high risk as well as interventions such as air disinfection and the use of masks and respirators in hospitals and other congregate settings. Recommendations stress the need to strengthen health systems in high-burden countries by emphasizing community-based care over hospital care; to improve information systems to ensure patient adherence and manage medication supply chains; and to invest in research to develop the necessary interventions. Fundamentally, current global TB control strategies must undergo revision and receive significant research funding
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