Effective interaction between active colloids and fluid interfaces induced by Marangoni flows

We show theoretically that near a fluid-fluid interface a single active colloidal particle generating, e.g., chemicals or a temperature gradient experiences an effective force of hydrodynamic origin. This force is due to the fluid flow driven by Marangoni stresses induced by the activity of the particle; it decays very slowly with the distance from the interface, and can be attractive or repulsive depending on how the activity modifies the surface tension. We show that, for typical systems, this interaction can dominate the dynamics of the particle as compared to Brownian motion, dispersion forces, or self-phoretic effects. In the attractive case, the interaction promotes the self-assembly of particles into a crystal-like monolayer at the interface.Comment: The manuscript proper and the supplementary information have been merged consecutively into a single PDF fil

Development and implementation of an HIV/AIDS trials management system: A geographical information systems approach

Introduction. Researchers, practitioners and policymakers make decisions at all levels – from local to international. Accessible, integrated and up-to-date evidence is essential for successful and responsive decision-making. A current trials register of randomised and clinically controlled trials of HIV/AIDS interventions can provide invaluable information to decision-making processes. Using the newly emerging geographical information systems (GIS) technology, we have developed a tool which assists such decisions. Objective. To demonstrate how the tool provides consistent, quantitative information in an accessible format, making it a key tool in evidence-based decision-making. Methods. We identified all HIV/AIDS trials in relation to publications for the period 1980 - 2007, using both electronic and manual search methods. To facilitate searching the trials register, studies were coded by using a comprehensive but user-friendly coding sheet. We captured the geographical co-ordinates for each trial and used the ArcGIS 9 mapping software to design and develop a geodatabase of trials. Results. The geodatabase delivered the complete requirements for a data-driven information system, featuring the following functions: (i) a clear display of the spatial distribution of HIV/AIDS trials around the world; (ii) identification of and access to information about any particular trial on a map; and (iii) a global resource of potential information on the safety and efficacy of prevention and treatment measures. Conclusions. The building of a functioning HIV/AIDS trials management system can provide policymakers, researchers and practitioners with accessible, integrated and up-to-date evidence that is essential to successful and dynamic decision-making. Southern African Journal of HIV Medicine Vol. 9 (2) 2008: pp. 58-6

Promoting and Supporting Effective Organizational Governance

Internal audit’s role in organizational governance has become increasingly important in the wake of the recent global financial crisis and the continuing spate of governance failures in both financial and public sectors throughout the world. Informed observers and commentators have asked initially, “Where were the external auditors?” then “Where was the audit committee?” and finally, “Where was internal audit in all this?” This report draws on survey responses from internal auditors in 166 countries to take stock of the current role of internal audit in the governance process and learn how internal audit can better position itself to contribute to effective organizational governance

Fast computations with the harmonic Poincaré-Steklov operators on nested refined meshes

In this paper we develop asymptotically optimal algorithms for fast computations with the discrete harmonic Poincar'e-Steklov operators in presence of nested mesh refinement. For both interior and exterior problems the matrix-vector multiplication for the finite element approximations to the Poincar'e-Steklov operators is shown to have a complexity of the order O(Nreflog3N) where Nref is the number of degrees of freedom on the polygonal boundary under consideration and N = 2-p0 · Nref, p0 ≥ 1, is the dimension of a finest quasi-uniform level. The corresponding memory needs are estimated by O(Nreflog2N). The approach is based on the multilevel interface solver (as in the case of quasi-uniform meshes, see [20]) applied to the Schur complement reduction onto the nested refined interface associated with nonmatching decomposition of a polygon by rectangular substructures

Does South Africa need a national clinical trials support unit?

ArticleThe original publication is available at http://www.samj.org.zaBackground. No national South African institution provides a coherent suite of support, available skills and training for clinicians wishing to conduct randomised controlled trials (RCTs) in the public sector. We report on a study to assess the need for establishing a national South African Clinical Trials Support Unit. Objectives. To determine the need for additional training and support for conduct of RCTs within South African institutions; identify challenges facing institutions conducting RCTs; and provide recommendations for enhancing trial conduct within South African public institutions. Design. Key informant interviews of senior decision-makers at institutions with a stake in the South African public sector clinical trials research environment. Results. Trial conduct in South Africa faces many challenges, including lack of dedicated funding, the burden on clinical load, and lengthy approval processes. Strengths include the high burden of disease and the prevalence of treatmentnaïve patients. Participants expressed a significant need for a national initiative to support and enhance the conduct of public sector RCTs. Research methods training and statistical support were viewed as key. There was a broad range of views regarding the structure and focus of such an initiative, but there was agreement that the national government should provide specific funding for this purpose. Conclusions. Stakeholders generally support the establishment of a national clinical trials support initiative. Consideration must be given to the sustainability of such an initiative, in terms of funding, staffing, expected research outputs and permanence of location.Publishers' versio

Over-the-counter and prescription medicine misuse in Cape Town - findings from specialist treatment centres

Objective. To provide community-level public health surveillance information on over-the-counter (OTC) and prescription medicine misuse.Methods. A retrospective study of OTC and prescription medicine misuse among 9 063 patients from 23 specialist substance abuse treatment centres in Cape Town, South Africa, between 1998 and 2000.                       Results. OTC and prescription medicine misuse places a burden on health and social services in South Africa. This is evidenced through the constant demand for treatment for OTC/prescription medicine misuse. Benzodiazepines are the class of medicines for which users most often receive treatment, followed by analgesics. Analgesic misuse is most often accounted for by the use of codeine-containing medicines, many of which are available over the counter. Patients using OTC/prescription medicines as their primary drug of abuse are significantly more likely to be female, and aged over 40 years. In contrast, patients using OTC/prescription medicine as an additional drug of abuse tend to be male and over 40 years of age.Conclusions. This study points to the need to develop primary health care protocols for detection, management and referral of patients misusing OTC/prescription drugs and the need to debate the re-scheduling of codeine as a prescription-only substance. The study also points to the need for further community-based research on the nature and extent of OTC/prescription drug misuse among the general population

Adolescent experiences in a vaccine trial: A pilot study

Little is known about how adolescents experience clinical trials. We assessed  the experiences of South African adolescent participants in a clinical trial,  employing semi-structured interviews to gather qualitative data on the  experiences and effects of trial participation. Despite misunderstanding certain concepts regarding assent and trial processes subsequent to  enrolment, participants reported positive experiences overall. Subjects’ motivations for participation included: an ability to help others; receipt of healthcare; and free blood screening. Participants expressed fears associated with trial procedures, such as phlebotomy; however, these apprehensionsdiminished as the trial progressed. We found that conducting qualitative research within a trial site is feasible, and can provide insight into the uptake and acceptability of interventions.S Afr Med J 2011;101:884-886

Hydrological heterogeneity and the plant colonization of recently deglaciated terrain

Climate change accelerates glacier retreat, leading to extensive exposure of sediment to light and ecological succession. Succession has traditionally been studied as a chronosequence, where vegetation development is directly correlated with time since glacier retreat or distance from the retreating glacier margin. More recent work has challenged this model, arguing that succession seems to be mainly influenced by heterogeneous conditions at the local scale. The aim of this study was to identify the factors influencing the local-scale establishment of plant communities following glacier recession. Vascular plants and their cover were inventoried in 100 plots (1 m2) for a thirty-year-old alluvial plain in front of the Otemma glacier (Swiss Alps). Depth to water table, distance to the glacial main river and to the nearest channel, sediment size, moss, lichen, and biological soil crust cover were measured. Results showed that proglacial margins develop hydrological heterogeneity over a small scale, reflected in the four observed plant communities. These range from the dry Sempervivum-dominated community, on gravel-rich sediments with a deep water table, to the Trifolium-dominated community, close to secondary channels, with the highest plant cover and species richness and incorporating grassland species. Heterogeneity in water availability exerted a critical control on vegetation development

Auditing Organizational Governance: Internal Audit Has An Integral Role to Play in Improving the Organization\u27s Strategic Performance

Organizational governance is a broad concept that ensures superior strategy formulation, development, and execution in ways that balance performance, conformance, and accountability. It includes systems, controls, and associated processes that promote ethics and values, performance and accountability, and risk communication and coordination among the board, external and internal auditors, and management in meeting and exceeding stakeholder expectations. Internal audit’s role in organizational governance has always been recognized and valued, but it has become increasingly important in the wake of governance failures in financial and public sectors throughout the world. As a result, more and more boards as well as executive management are turning to internal audit for assurance on governance effectiveness, culture, and strategy implementation