461 research outputs found
The Banach Algebras AC(σ) and BV(σ)
The spaces BV(σ) and AC(σ) were introduced as part of a program to find a general theory which covers both well-bounded operators and trigonometrically well-bounded operators acting on a Banach space. Since their initial appearance it has become clear that the definitions could be simplified somewhat. In this paper we give a self-contained exposition of the main properties of these spaces using this simplified approach
Approximation in AC(σ)
For a nonempty compact subset σ in the plane, the space AC(σ) is the closure of the space of complex polynomials in two real variables under a particular variation norm. In the classical setting, AC[0, 1] contains several other useful dense subsets, such as continuous piecewise linear functions, C1 functions and Lipschitz functions. In this paper, we examine analogues of these results in this more general setting
The challenge of overdiagnosis begins with its definition
Overdiagnosis means different things to different people. S M Carter and colleagues argue that we should use a broad term such as too much medicine for advocacy and develop precise, case by case definitions of overdiagnosis for research and clinical purposes The implicit social contract underpinning healthcare is that it will reduce illness and preventable death and improve quality of life. But sometimes these promises are not delivered. Sometimes health services take people who don’t need intervention, subject them to tests, label them as sick or at risk, provide unnecessary treatments, tell them to live differently, or insist on monitoring them regularly.1 These interventions don’t improve things for people; they produce complications or illness, reduce quality of life, or even cause premature death. Active health intervention is not always a good thing: it can be “too much medicine,” or produce what is often called overdiagnosis. Although the concept of overdiagnosis has been described in the literature for nearly 50 years in relation to cancer screening,2 3 it was Welch and colleagues’ 2011 book, Overdiagnosed: Making People Sick in the Pursuit of Health, that popularised the term.4 Overdiagnosis is now an acknowledged problem for patients, clinicians, researchers, and policymakers; it is discussed in journals5 6 7 and at specialist conferences8 and addressed through policy and practice initiatives.9 10 11 There is, however, no formal, agreed definition of overdiagnosis. Rather, the word has become a banner under which disparate people with similar general concerns can unite. This vagueness and breadth allows the appearance of unity but does not serve the more exacting demands of research and healthcare. Here we examine the meanings of overdiagnosis more closely and discuss related challenges for healthcare professionals, patients, and researchers. If overdiagnosis is to be understood and mitigated, the broad concept should be subdivided into different problems and its ethical dimensions better acknowledged.NHMR
On the Quantization of the Chern-Simons Fields Theory on Curved Space-Times: the Coulomb Gauge Approach
We consider here the Chern-Simons field theory with gauge group SU(N) in the
presence of a gravitational background that describes a two-dimensional
expanding ``universe". Two special cases are treated here in detail: the
spatially flat {\it Robertson-Walker} space-time and the conformally static
space-times having a general closed and orientable Riemann surface as spatial
section. The propagator and the vertices are explicitely computed at the lowest
order in perturbation theory imposing the Coulomb gauge fixing.Comment: 15 pp., Preprint LMU-TPW 93-5, (Plain TeX + Harvmac
The benefits and harms of receiving a polycystic ovary syndrome diagnosis: a qualitative study of women's experiences
Study Question: What are the benefits and harms of receiving a polycystic ovary syndrome (PCOS) diagnosis in a community sample of women, including impact on psychosocial wellbeing, lifestyle choices and behaviour? Summary Answer: Although some women benefit considerably from the diagnosis, such as through increased awareness and reassurance, women with minimal symptoms may experience more harm than benefit, including long-lasting anxiety and altered life plans. What Is Known Already: Disease labels can validate symptoms and play a vital role in understanding and coping with illness; however, they can also cause harm by evoking illness schemas about severity and permanence. Regarding PCOS, the diagnostic criteria have expanded over time to include women with milder phenotypes (such as those without signs of androgen excess). This has occurred despite limited investigation of the benefits and harms of the diagnosis and has increased the number of women diagnosed. Study Design, Size, Duration: Semi-structured interviews were conducted face-to-face or by telephone with 26 participants from April-July 2018 to explore women's experiences with the diagnosis, including the benefits and harms of receiving the diagnosis and the impact on their life. Participants/Materials, Setting, Methods: In total, 26 women in the community self-reporting a diagnosis of PCOS (reporting mild to severe symptoms) made by a medical doctor, aged 18-45 years and living in Australia were recruited through social media. Data were analysed thematically using Framework analysis. Main Results and the Role of Chance: The study identified a range of both positive and negative effects of a PCOS diagnosis in the immediate, short and long-term, which were influenced by symptom severity, expectations and experience. For women with previously unexplained and bothersome symptoms, it was a relief to receive a diagnosis, and this resulted in an increased understanding about the importance of a healthy lifestyle. By contrast, women with milder symptoms often reported feeling shocked and overwhelmed by the diagnosis, consequently experiencing anxiety about the associated long-term risks. The majority of women, regardless of symptom severity, experienced prolonged worry and anxiety about infertility, resulting for some in risk taking with contraception, unintended pregnancies, pressure to conceive early or altered life plans. With time, many women developed positive coping strategies and perceived the diagnosis to be valuable, including those who felt they had experienced minimal benefit or even harm. Limitations, Reasons for Caution: PCOS diagnosis was self-reported and the sample was highly educated. Wider Implications of the Findings: Fear of infertility was salient for many women, underscoring the need for accurate information, counselling and reassurance of fertility potential. Given the risk of significant consequences, health professionals should use a tailored approach to PCOS diagnosis to increase the benefits of appropriate and timely diagnosis for women affected by significant symptoms, while reducing the harms of unnecessarily labelling healthy women for whom the benefits of a diagnosis are small.T. Copp, J. Hersch, D.M. Muscat, K.J. McCaffery, J. Doust, A. Dokras, B.W. Mol, and J. Janse
Clinicians' perspectives on diagnosing polycystic ovary syndrome in Australia: a qualitative study
STUDY QUESTION: What are clinicians' views about the diagnosis of polycystic ovary syndrome (PCOS), and how do they handle any complexities and uncertainties in practice?SUMMARY ANSWER: Clinicians have to navigate many areas of complexity and uncertainty regarding the diagnosis of PCOS, related to the diagnostic criteria, limitations in current evidence and misconceptions surrounding diagnosis, and expressed concern about the risk and consequences of both under- and overdiagnosis.WHAT IS KNOWN ALREADY: PCOS is a complex, heterogeneous condition with many areas of uncertainty, raising concerns about both underdiagnosis and overdiagnosis. Quantitative studies with clinicians have found considerable variation in diagnostic criteria used and care provided, as well as a lack of awareness around the breadth of PCOS features and poor uptake of recommended screening for metabolic complications. Clinicians' views about the uncertainties and complexities of diagnosing PCOS have not been explored.STUDY DESIGN, SIZE, DURATION: Semi-structured telephone interviews were conducted with clinicians from September 2017 to July 2018 to explore their perceptions about the diagnosis of PCOS, including how they handle any complexities and uncertainties in practice.PARTICIPANTS/MATERIALS, SETTING, METHODS: A group of 36 clinicians (15 general practitioners, 10 gynaecologists and 11 endocrinologists) currently practicing in Australia, were recruited through advertising via professional organisations, contacting a random sample of endocrine and gynaecology teams across Australia and snowballing. Transcribed audio-recordings were analysed thematically using Framework analysis.MAIN RESULTS AND THE ROLE OF CHANCE: Clinicians expressed a range of uncertainties and complexities regarding the diagnosis of PCOS, which were organised into three areas: (i) establishing diagnosis (e.g. lack of standardisation regarding diagnostic cut-offs, risk of misdiagnosis), (ii) factors influencing the diagnostic process (e.g. awareness of limitations in evidence and consideration of the benefits and harms) and (iii) strategies for handling challenges and uncertainties (e.g. using caution and communication of uncertainties). Clinicians also varied in their concerns regarding under- and overdiagnosis. Overall, most felt the diagnosis was beneficial for women provided that it was the correct diagnosis and time was taken to assess patient expectations and dispel misconceptions, particularly concerning fertility.LIMITATIONS, REASONS FOR CAUTION: There is possible selection bias, as clinicians who are more knowledgeable about PCOS may have been more likely to participate. Clinicians' views may also differ in other countries.WIDER IMPLICATIONS OF THE FINDINGS: These findings underscore the vital need to first consider PCOS a diagnosis of exclusion and use caution before giving a diagnosis in order to reduce misdiagnosis, as suggested by clinicians in our study. Until there is greater standardisation of diagnostic criteria, more transparent conversations with women may help them understand the uncertainties surrounding the criteria and limitations in the evidence. Additionally, clinicians emphasised the importance of education and reassurance to minimise the potential harmful impact of the diagnosis and improve patient-centred outcomes
The Stability of Gauss Model Having One-Prey and Two-Predators
The study of the dynamics of predator-prey interactions can be recognized as a major issue in mathematical biology. In the present paper, some Gauss predator-prey models in which three ecologically interacting species have been considered and the behavior of their solutions in the stability aspect have been investigated. The main aim of this paper is to consider the local and
global stability properties of the equilibrium points for represented systems. Finally, stability of some examples of Gauss model with one prey and two predators is discussed
Early invasive versus conservative strategies for unstable angina & non-ST-elevation myocardial infarction in the stent era (Review)
BACKGROUND: In patients with unstable angina and non-ST-elevation myocardial infarction (UA/NSTEMI) two strategies are possible: a routine invasive strategy where all patients undergo coronary angiography shortly after admission and, if indicated, coronary revascularization; or a conservative strategy where medical therapy alone is used initially with selection of patients for angiography based on clinical symptoms or investigational evidence of persistent myocardial ischemia. OBJECTIVES: To determine the benefits of an invasive compared to a conservative strategy for treating UA/NSTEMI in the stent era. SEARCH STRATEGY: The Cochrane Central Register of Controlled Trials (Issue 3 2005), MEDLINE and EMBASE were searched from 1996 to September 2005 with no language restrictions. SELECTION CRITERIA: Included studies were prospective trials comparing invasive with conservative strategies in UA/NSTEMI. DATA COLLECTION AND ANALYSIS: We identified 5 studies (7818 participants). Using intention-to-treat analysis with random effects models, summary estimates of relative risk (95% confidence interval [CI]) were determined for primary end-points of all-cause death, fatal and non-fatal myocardial infarction; all-cause death or non-fatal myocardial infarction; and refractory angina. Further analysis of included studies was undertaken based on whether glycoprotein IIb/IIIa receptor antagonists were used routinely. Heterogeneity was assessed using chi-square and variance (I(2)) methods. MAIN RESULTS: In the all-study analysis, mortality during initial hospitalization showed a trend to hazard with an invasive strategy; relative risk 1.59 (95% CI 0.96 to 2.64). Mortality and myocardial infarction assessed at 2-5 years in two trials were significantly decreased by an invasive strategy with relative risk of 0.75 (95% CI 0.62 to 0.92) and 0.75 (95% CI 0.61 to 0.91) respectively. The composite end-point of death or non-fatal myocardial infarction was significantly decreased by an invasive strategy at several time points after initial hospitalization. The incidence of early
Early (Days 1–4) post-treatment serum hCG level changes predict single-dose methotrexate treatment success in tubal ectopic pregnancy
Acknowledgements S.C.M. was supported by the South-East Scotland Academic Foundation Programme. Medical Research Council (MRC) Centre grants to the Centre for Reproductive Health (CRH) (G1002033 and MR/N022556/1) are also gratefully acknowledged. Funding This project was supported by funding from the Efficacy and Mechanism Evaluation programme, a Medical Research Council and National Institute for Health Research partnership (grant reference number 14/150/03).Peer reviewedPublisher PD
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