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Spherical single-roll dynamos at large magnetic Reynolds numbers
Henrik Latter,David Ivers
Physics , 2010, DOI: 10.1063/1.3453712
Abstract: This paper concerns kinematic helical dynamos in a spherical fluid body surrounded by an insulator. In particular, we examine their behaviour in the regime of large magnetic Reynolds number $\Rm$, for which dynamo action is usually concentrated upon a simple resonant stream-surface. The dynamo eigensolutions are computed numerically for two representative single-roll flows using a compact spherical harmonic decomposition and fourth-order finite-differences in radius. These solutions are then compared with the growth rates and eigenfunctions of the Gilbert and Ponty (2000) large $\Rm$ asymptotic theory. We find good agreement between the growth rates when $\Rm>10^4$, and between the eigenfunctions when $\Rm>10^5$.
Size-optimal Steiner points for Delaunay-refinement on curved surfaces
Darren Engwirda,David Ivers
Computer Science , 2015,
Abstract: An extension of the restricted Delaunay-refinement algorithm for surface mesh generation is described, where a new point-placement scheme is introduced to improve element quality in the presence of mesh size constraints. Specifically, it is shown that the use of off-centre Steiner points, positioned on the faces of the associated Voronoi diagram, typically leads to significant improvements in the shape- and size-quality of the resulting surface tessellations. The new algorithm can be viewed as a Frontal-Delaunay approach -- a hybridisation of conventional Delaunay-refinement and advancing-front techniques in which new vertices are positioned to satisfy both element size and shape constraints. The performance of the new scheme is investigated experimentally via a series of comparative studies that contrast its performance with that of a typical Delaunay-refinement technique. It is shown that the new method inherits many of the best features of classical Delaunay-refinement and advancing-front type methods, leading to the construction of smooth, high quality surface triangulations with bounded radius-edge ratios and convergence guarantees. Experiments are conducted using a range of complex benchmarks, verifying the robustness and practical performance of the proposed scheme.
Provider-initiated HIV testing in rural Haiti: low rate of missed opportunities for diagnosis of HIV in a primary care clinic
Louise C Ivers, Kenneth A Freedberg, Joia S Mukherjee
AIDS Research and Therapy , 2007, DOI: 10.1186/1742-6405-4-28
Abstract: Only 5–8% of individuals with Human Immunodeficiency Virus (HIV) infection globally are aware of their diagnosis [1]. In the developing world, early 'in-program' mortality has been prominent in a number of HIV treatment programs, often due to patients presenting late for care with already advanced disease [2]. In the ongoing effort to prevent new HIV infections and to treat those with established infection, emphasis must be placed on developing strategies to effectively identify and engage HIV-infected patients into care, with HIV testing as a critical step.Much of the HIV testing in the developing world is done through maternity clinics offering antiretroviral drugs for the prevention of maternal to child transmission of HIV or specialty voluntary counseling and testing (VCT) clinics to which people come desiring knowledge of their status. Studies from such settings in South Africa and C?te d'Ivoire have identified factors including 'fear of a positive HIV test', low levels of education and poor housing as associated with low uptake rates [3,4]. US and African studies have identified high rates of "missed opportunities" for making the diagnosis of HIV among primary care clinicians who did not offer HIV tests to their patients even if they had clinical syndromes associated with HIV infection or if they were from a high-risk sociodemographic group [5-10].In Haiti neither primary health care nor HIV VCT is widely available and the estimated HIV prevalence is estimated between 2.2 and 3.8% [11,12]. In the central plateau department, a 2005 Demographic and Health Survey reported the seroprevalence of HIV in 15–49 year olds as 1.6% [12]. In 2002, when the Global Fund to Fight AIDS, TB and Malaria called for applications, Partners In Health – a non-profit organization affiliated with Harvard Medical School – began a collaborative program with the Haiti Ministry of Health with the goal of improving access to primary care as an avenue to provide HIV prevention, testing and
Diabetes screening with hemoglobin A1c prior to a change in guideline recommendations: prevalence and patient characteristics
Michelle Greiver, Babak Aliarzadeh, Rahim Moineddin, Christopher Meaney, Noah Ivers
BMC Family Practice , 2011, DOI: 10.1186/1471-2296-12-91
Abstract: We conducted a retrospective study using data routinely collected in Electronic Medical Records. The participants were thirteen community-based family physicians in Toronto, Ontario. We calculated the proportion of non diabetic patients who had at least one Hbg A1c done in three years. We used logistic generalized estimating equation with year treated as a continuous variable to test for a non-zero slope in yearly Hbg A1c provision. We modelled screening using multivariable logistic regression.There were 11,792 non-diabetic adults. Of these, 1,678 (14.2%; 95%CI 13.6%-14.9%) had at least one Hgb A1c test done; this was higher for patients 45 years of age or older (20.2%; 95% CI 19.3% - 21.2%). The proportion of non-diabetic patients with an A1c test increased from 5.2% in 2007 to 8.8% in 2009 (p < 0.0001 for presence of slope). Factors associated with significantly greater adjusted odds ratios of having the test done included increasing diastolic blood pressure, increasing fasting glucose, increasing body mass index, increasing age, as well as male gender and presence of hypertension, but not smoking status or LDL cholesterol. Patients living in the highest income quintile neighbourhoods had significantly lower odds ratios of having this test done than those in the lowest quintile (p < 0.001).A large and increasing proportion of the non-diabetic patients we studied have had an Hgb A1c for screening prior to guidelines recommending the test for this purpose. Several risk factors for cardiovascular disease or diabetes were associated with the provision of the Hgb A1c. Early uptake of the test may represent appropriate utilization.Diabetes is an increasingly prevalent condition in Canada, with serious effects on morbidity and mortality [1]. This condition can be present for up to seven years prior to diagnosis [2], leading to recommendations for periodic screening of asymptomatic individuals [1,3,4].Guideline recommendations regarding screening and diagnosis of diabetes
Morning quiet-time ionospheric current reversal at mid to high latitudes
R. Stening, T. Reztsova, D. Ivers, J. Turner,D. Winch
Annales Geophysicae (ANGEO) , 2005,
Abstract: The records of an array of magnetometers set up across the Australian mainland are examined. In addition to a well-defined current whorl corresponding to the ionospheric Sq current system, another system of eastward flowing currents is often found in the early morning. The system is most easily identified at observatories poleward of the focus of the Sq system, where a morning reversal from eastward to westward currents can be seen. The time of the reversal is usually later, sometimes up to 12h local noon, in June (Southern Winter) than in other seasons. There is some evidence of a similar current system at other longitudes and in the Northern Hemisphere. An important outcome of the study is that it enables identification of which features of a daily variation of the northward magnetic field ΔX relate to an Sq current whorl and which must be attributed to some other current system.
Translation of tobacco policy into practice in disadvantaged and marginalized subpopulations: a study of challenges and opportunities in remote Australian Indigenous communities
Robertson Jan A,Conigrave Katherine M,Ivers Rowena,Usher Kim
Health Research Policy and Systems , 2012, DOI: 10.1186/1478-4505-10-23
Abstract: Background In Australia generally, smoking prevalence more than halved after 1980 and recently commenced to decline among Australia's disadvantaged Indigenous peoples. However, in some remote Indigenous Australian communities in the Northern Territory (NT), extremely high rates of up to 83% have not changed over the past 25 years. The World Health Organisation has called for public health and political leadership to address a global tobacco epidemic. For Indigenous Australians, unprecedented policies aim to overcome disadvantage and close the 'health gap' with reducing tobacco use the top priority. This study identifies challenges and opportunities to implementing these important new tobacco initiatives in remote Indigenous communities. Methods: With little empirical evidence available, we interviewed 82 key stakeholders across the NT representing operational- and management-level service providers, local Indigenous and non-Indigenous participants to identify challenges and opportunities for translating new policies into successful tobacco interventions. Data were analysed using qualitative approaches to identify emergent themes. Results The 20 emergent themes were classified using counts of occasions each theme occurred in the transcribed data as challenge or opportunity. The 'smoke-free policies' theme occurred most frequently as opportunity but infrequently as challenge while 'health workforce capacity' occurred most frequently as challenge but less frequently as opportunity, suggesting that policy implementation is constrained by lack of a skilled workforce. 'Smoking cessation support' occurred frequently as opportunity but also frequently as challenge suggesting that support for individuals requires additional input and attention. Conclusions These results from interviews with local and operational-level participants indicate that current tobacco policies in Australia targeting Indigenous smoking are sound and comprehensive. However, for remote Indigenous Australian communities, local and operational-level participants' views point to an 'implementation gap'. Their views should be heard because they are in a position to provide practical recommendations for effective policy implementation faithful to its design, thereby translating sound policy into meaningful action. Some recommendations may also find a place in culturally diverse low- and middle-income countries. Key words: tobacco policy implementation, challenges, opportunities, remote Indigenous Australian communities.
Task-Shifting in HIV Care: A Case Study of Nurse-Centered Community-Based Care in Rural Haiti
Louise C. Ivers,Jean-Gregory Jerome,Kimberly A. Cullen,Wesler Lambert,Francesca Celletti,Badara Samb
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0019276
Abstract: At least 36 countries are suffering from severe shortages of healthcare workers and this crisis of human resources in developing countries is a major obstacle to scale-up of HIV care. We performed a case study to evaluate a health service delivery model where a task-shifting approach to HIV care had been undertaken with tasks shifted from doctors to nurses and community health workers in rural Haiti.
Food assistance is associated with improved body mass index, food security and attendance at clinic in an HIV program in central Haiti: a prospective observational cohort study
Louise C Ivers, Yuchiao Chang, J Gregory Jerome, Kenneth A Freedberg
AIDS Research and Therapy , 2010, DOI: 10.1186/1742-6405-7-33
Abstract: Adults with HIV infection were eligible for monthly food rations if they had any one of: tuberculosis, body mass index (BMI) <18.5kg/m2, CD4 cell count <350/mm3 (in the prior 3 months) or severe socio-economic conditions. A total of 600 individuals (300 eligible and 300 ineligible for food assistance) were interviewed before rations were distributed, at 6 months and at 12 months. Data collected included demographics, BMI and food insecurity score (range 0 - 20).At 6- and 12-month time-points, 488 and 340 subjects were eligible for analysis. Multivariable analysis demonstrated that at 6 months, food security significantly improved in those who received food assistance versus who did not (-3.55 vs -0.16; P < 0.0001); BMI decreased significantly less in the food assistance group than in the non-food group (-0.20 vs -0.66; P = 0.020). At 12 months, food assistance was associated with improved food security (-3.49 vs -1.89, P = 0.011) and BMI (0.22 vs -0.67, P = 0.036). Food assistance was associated with improved adherence to monthly clinic visits at both 6 (P < 0.001) and 12 months (P = 0.033).Food assistance was associated with improved food security, increased BMI, and improved adherence to clinic visits at 6 and 12 months among people living with HIV in Haiti and should be part of routine care where HIV and food insecurity overlap.Food insecurity and undernutrition are increasingly recognized as factors that are important in the health and livelihoods of individuals living with HIV infection in poor settings [1,2]. HIV infection has long been associated with wasting syndrome and being underweight with HIV is predictive of a poor prognosis, even in people receiving antiretroviral therapy (ART) [1,3-5]. Food insecurity--meaning lack of access to food of sufficient quality and quantity to perform usual daily activities--contributes to a negative cycle of events that often worsens the effect of HIV infection on ability to work, attend school, contribute to family liveli
A randomized trial to evaluate the effectiveness of an individual, education-based safe transport program for drivers aged 75 years and older
Lisa Keay, Kristy Coxon, Julie Brown, Elizabeth Clarke, Soufiane Boufous, Anita Bundy, Serigne Lo, Rebecca Ivers
BMC Public Health , 2013, DOI: 10.1186/1471-2458-13-106
Abstract: A randomised trial will be conducted, involving 380 drivers aged 75 years and older, resident in urban and semi-rural areas of North-West Sydney. The intervention is an education program based on the Knowledge Enhances Your Safety (KEYS) program, adapted for the Australian context. Driving experience will be measured objectively using an in-vehicle monitoring device which includes a global positioning system (GPS) to assess driving exposure and an accelerometer to detect rapid deceleration events. Participation will be assessed using the Keele Assessment of Participation (KAP). Data will be analysed on an intention-to-treat basis; the primary outcomes include driving exposure, rapid deceleration events and scores for KAP. Secondary outcomes include self-reported measures of driving, socialisation, uptake of alternative forms of transport, depressive symptoms and mood. A detailed process evaluation will be conducted, including examination of the delivery of the program and uptake of alternative forms of transport. A subgroup analysis is planned for drivers with reduced function as characterized by established cut-off scores on the Drivesafe assessment tool.This randomised trial is powered to provide an objective assessment of the efficacy of an individually tailored education and alternative transportation program to promote safety of older drivers but maintain mobility. Trial registration: Australian New Zealand Clinical Trials Registry ACTRN12612000543886.Older people are a large and growing sector of the driving population. Concerns over safety of older drivers have been raised due to increased crash involvement and vulnerability to crash injury [1-3]. Crash involvement per mile driven and likelihood for driver responsibility begins to increase from age 65 [4] and by age 85 likelihood of crash involvement is approximately 2.5 times higher than that of the younger drivers [5]. However, concerns over safety need to be tempered by the fact that driving is an importan
Childhood and adult mortality from unintentional falls in India
Jagnoor,Jagnoor; Suraweera,Wilson; Keay,Lisa; Ivers,Rebecca Q; Thakur,JS; Gururaj,Gopalkrishna; Jha,Prabhat; ,;
Bulletin of the World Health Organization , 2011, DOI: 10.1590/S0042-96862011001000012
Abstract: objective: to estimate fall-related mortality by type of fall in india. methods: the authors analysed unintentional injury data from the ongoing million death study from 2001-2003 using verbal autopsy and coding of all deaths in accordance with the international statistical classification of diseases and related health problems, tenth revision, in a nationally representative sample of 1.1 million homes throughout the country. findings: falls accounted for 25% (2003/8023) of all deaths from unintentional injury and were the second leading cause of such deaths. an estimated 160 000 fall-related deaths occurred in india in 2005; of these, nearly 20 000 were in children aged 0-14 years. the unintentional-fall-related mortality rate (mr) per 100 000 population was 14.5 (99% confidence interval, ci: 13.7-15.4). rates were similar for males and females at 14.9 (99% ci: 13.7-16.0) and 14.2 (99% ci: 13.1-15.4) per 100 000 population, respectively. people aged 70 years or older had the highest mortality rate from unintentional falls (mr: 271.2; 99% ci: 249.0-293.5), and the rate was higher among women (mr: 281; 99% ci: 249.7-311.3). falls on the same level were the most common among older adults, whereas falls from heights were more common in younger age groups. conclusion: in india, unintentional falls are a major public health problem that disproportionately affects older women and children. the contexts in which these falls occur and the resulting morbidity and disability need to be better understood. in india there is an urgent need to develop, test and implement interventions aimed at preventing falls.
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