39 research outputs found

    Badly approximable points on manifolds

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    Addressing a problem of Davenport we show that any finite intersection of the sets of weighted badly approximable points on any analytic nondegenerate manifold in has full dimension. This also extends Schmidt's conjecture on badly approximable points to arbitrary dimensions

    Continued fractions and irrationality exponents for modified engel and pierce series

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    An Engel series is a sum of reciprocals of a non-decreasing sequence (xn) of positive integers, which is such that each term is divisible by the previous one, and a Pierce series is an alternating sum of the reciprocals of a sequence with the same property. Given an arbitrary rational number, we show that there is a family of Engel series which when added to it produces a transcendental number ? whose continued fraction expansion is determined explicitly by the corresponding sequence (xn), where the latter is generated by a certain nonlinear recurrence of second order. We also present an analogous result for a rational number with a Pierce series added to or subtracted from it. In both situations (a rational number combined with either an Engel or a Pierce series), the irrationality exponent is bounded below by (3 + ?5)/2, and we further identify infinite families of transcendental numbers ? whose irrationality exponent can be computed precisely. In addition, we construct the continued fraction expansion for an arbitrary rational number added to an Engel series with the stronger property that x2j divides xj+1 for all j

    Research-policy partnerships - experiences of the Mental Health and Poverty Project in Ghana, South Africa, Uganda and Zambia

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    Background: Partnerships are increasingly common in conducting research. However, there is little published evidence about processes in research-policy partnerships in different contexts. This paper contributes to filling this gap by analysing experiences of research-policy partnerships between Ministries of Health and research organisations for the implementation of the Mental Health and Poverty Project in Ghana, South Africa, Uganda and Zambia. Methods: A conceptual framework for understanding and assessing research-policy partnerships was developed and guided this study. The data collection methods for this qualitative study included semi-structured interviews with Ministry of Health Partners (MOHPs) and Research Partners (RPs) in each country. Results: The term partnership was perceived by the partners as a collaboration involving mutually-agreed goals and objectives. The principles of trust, openness, equality and mutual respect were identified as constituting the core of partnerships. The MOHPs and RPs had clearly defined roles, with the MOHPs largely providing political support and RPs leading the research agenda. Different influences affected partnerships. At the individual level, personal relationships and ability to compromise within partnerships were seen as important. At the organisational level, the main influences included the degree of formalisation of roles and responsibilities and the internal structures and procedures affecting decision-making. At the contextual level, political environment and the degree of health system decentralisation affected partnerships. Conclusions: Several lessons can be learned from these experiences. Taking account of influences on the partnership at individual, organisation and contextual/system levels can increase its effectiveness. A common understanding of mutually-agreed goals and objectives of the partnership is essential. It is important to give attention to the processes of initiating and maintaining partnerships, based on clear roles, responsibilities and commitment of parties at different levels. Although partnerships are often established for a specific purpose, such as carrying out a particular project, the effects of partnership go beyond a particular initiative

    HIV infection and sexual risk among men who have sex with men and women (MSMW): A systematic review and meta-analysis

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    Objectives: To estimate the number of men who have sex with men and women who are HIV-positive in the United States, and to compare HIV prevalence rates between men who have sex with men and women, men who have sex with men only, and men who have sex with women exclusively. Methods: Following PRISMA guidelines, we conducted a systematic review and meta-analysis of reports referencing HIV prevalence and men who have sex with men and women. We searched PubMed and Ovid PsycINFO for peer-reviewed, U.S.-based articles reporting on HIV prevalence among men who have sex with men and women. We conducted event rate, effect size, moderation and sensitivity analyses. Results: We estimate that 1.0% of U.S. males are bisexually-behaving, and that 121,800 bisexually-behaving men are HIV-positive. Men who have sex with men and women are less than half as likely to be HIV-positive as men who have sex with men only (16.9% vs. 33.3%; OR = 0.41, 95% CI: 0.31, 0.54), but more than five times as likely to be HIV-positive as men who have sex with women exclusively (18.3% vs. 3.5%; OR = 5.71, 95% CI: 3.47, 9.39). They are less likely to engage in unprotected receptive anal intercourse than men who have sex with men only (15.9% vs. 35.0%; OR = 0.36, 95% CI: 0.28, 0.46). Men who have sex with men and women in samples with high racial/ethnic minority proportions had significantly higher HIV prevalence than their counterparts in low racial/ethnic minority samples. Conclusions: This represents the first meta-analysis of HIV prevalence in the U.S. between men who have sex with men and women and men who have sex with men only. Data collection, research, and HIV prevention and care delivery specifically tailored to men who have sex with men and women are necessary to better quantify and ameliorate this population's HIV burden. © 2014 Friedman et al

    Lessons from the removal of lead from gasoline for controlling other environmental pollutants: A case study from New Zealand

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    <p>Abstract</p> <p>Background</p> <p>It took over two decades to achieve the removal of leaded gasoline in this country. This was despite international evidence and original research conducted in New Zealand on the harm to child cognitive function and behaviour from lead exposure.</p> <p>Objective</p> <p>To identify lessons from the New Zealand experience of removing leaded gasoline that are potentially relevant to the control of other environmental pollutants.</p> <p>Discussion</p> <p>From the available documentation, we suggest a number of reasons for the slow policy response to the leaded gasoline hazard. These include: (1) industry power in the form of successful lobbying by the lead additive supplier, Associated Octel; (2) the absence of the precautionary principle as part of risk management policy; and (3) weak policymaking machinery that included: (a) the poor use of health research evidence (from both NZ and internationally), as well as limited use of expertise in academic and non-governmental organisations; (b) lack of personnel competent in addressing technically complex issues; and (c) diffusion of responsibility among government agencies.</p> <p>Conclusion</p> <p>There is a need for a stronger precautionary approach by policymakers when considering environmental pollutants. Politicians, officials and health workers need to strengthen policymaking processes and effectively counter the industry tactics used to delay regulatory responses.</p

    Why we need easy access to all data from all clinical trials and how to accomplish it

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    International calls for registering all trials involving humans and for sharing the results, and sometimes also the raw data and the trial protocols, have increased in recent years. Such calls have come, for example, from the Organization for Economic Cooperation and Development (OECD), the World Health Organization (WHO), the US National Institutes of Heath, the US Congress, the European Commission, the European ombudsman, journal editors, The Cochrane Collaboration, and several funders, for example the UK Medical Research Council, the Wellcome Trust, the Bill and Melinda Gates Foundation and the Hewlett Foundation
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