Simultaneous comparisons of treatments at multiple time points: combined marginal models versus joint modeling

We discuss several aspects of multiple inference in longitudinal settings, focusing on many-to-one and all-pairwise comparisons of (a) treatment groups simultaneously at several points in time, or (b) time points simultaneously for several treatments. We assume a continuous endpoint that is measured repeatedly over time and contrast two basic modeling strategies: fitting a joint model across all occasions (with random effects and/or some residual covariance structure to account for heteroscedasticity and serial dependence), and a novel approach combining a set of simple marginal, i.e. occasion-specific models. Upon parameter and covariance estimation with either modeling approach, we employ a variant of multiple contrast tests that acknowledges correlation between time points and test statistics. This method provides simultaneous confidence intervals and adjusted p-values for elementary hypotheses as well as a global test decision. We compare via simulation the powers of multiple contrast tests based on a joint model and multiple marginal models, respectively, and quantify the benefit of incorporating longitudinal correlation, i.e. the advantage over Bonferroni. Practical application is illustrated with data from a clinical trial on bradykinin receptor antagonism

The role of the transaction assurance, perceived cost and the perceived innovation in the decision to continue using mobile money services among small business owners

The motive of this study is to assess the role of the perceived transaction assurance, perceived transaction cost, and anticipated future innovations to predict the intention to continue using mobile money services. Currently, many models on the intention to continue using the technology are based on frameworks for general technology adoption. This study acknowledges the value of these frameworks, but extended the analysis to include the perceived transaction assurance and the perceived innovation upon testing. Other variables included in the study are as follows: the influence of the customer support, the ease of correcting mistakes, and the comfortability with transaction steps. Moreover, this study draws its relevance from the literature, where models on the intention to use the technology provided the basis for conceptualization. Furthermore, the study adopted the survey strategy, where a closed-end questionnaire was used to extract data from 110 small business owners. Additionally, the study adopted the ordinal regression model in making decisions about relationships proposed through different hypotheses. Generally, the perceived transaction assurance and the perceived innovative future significantly predict the intention to continue using mobile money services among small business owners

Graduateness of computing students in a Sub-Saharan African context

This paper surveys graduate attributes as is required of students in Computer Science and Information Systems disciplines in Africa in general and in South Africa in particular. Graduate attributes as envisioned by students and employers internationally are discussed complemented by an international, liberal education perspective to indicate the importance of graduate attributes from both of these groups’ perspective. This discussion is followed by insights specific to computing disciplines in Sub-Saharan African countries. An overview of the graduate attributes required by the South African National Qualifications Framework and the South African Qualifications Authority is compared to the attributes suggested by the Association for Computing Machinery for Computing syllabi. It is felt that this may help African and in particular South African computing departments to self-assess their programmes in terms of international standards

Factors determining the perceived relevance of social commerce in the African context

Background: This study determined factors influencing the perceived relevance of social commerce in the African context, in which Tanzania was chosen as a case for study. The motivation comes from the recent trend in which different service vendors take social networks as a platform for their business display, in conjunction with the use of mobile money and other online financial services in business facilitation. Objectives: The study determines factors influencing the perceived relevance of social commerce in the African context. Methods: The study used the survey strategy in its operationalisation. Only social media subscribers based in Tanzania formed the study population. It used the literature to identify the knowledge gap, followed by hypotheses formulation. Advanced quantitative models were used for testing the hypotheses. Results: Collectively, the following variables have a significant impact on the perceived relevance of social commerce: the effectiveness of order delivery, the perceived vendor’s response to queries, the perceived quality of online display, the perceived shopping convenience, the perceived rejection of returned goods and the perceived convenience of returning goods. Conclusion: Social-media-based commerce provides useful platforms to subscribers and vendors of different services. The approval rate is a good predictor of the future increase in the number of users across Africa, and Tanzania in particular

Building capacity and developing human capital: an exploration of curriculum development in ICT programmes at South African universities

There is a growing consensus on the potential for information and communications technologies (ICTs) to support socio-economic development in sub-Saharan Africa (SSA). Universities as providers of higher education are critical to developing SSA countries by, amongst others, empowering the region to develop appropriate ICT solutions for local challenges. The purpose of this paper is to describe and discuss how contextual realities influence the development of ICT programme curricula at public universities in South Africa, a developing country in SSA, in order to meet the demand for ICT skills. After a brief discussion of the factors that influence the content and delivery in education systems an overview of the South African public higher education context is provided. Against this background the content and delivery of ICT programme offerings and the rationale behind the programmes at four South African public universities are presented in case study format and concludes with a discussion of the case studies. The paper may be of value to academic departments as examples of how other departments are responding and adjusting their offerings, to government departments and policy makers by engendering a better understanding of the impact of policy on programme development and to industry by illustrating the diverse stakeholders in higher education and academia’s responsiveness to these diverse requirements

Aligning African Computing Disciplines' Graduate Attributes with International Standards

This paper explores graduate attributes as is required of students in Computer Science and Information Systems disciplines in Africa in general and in South Africa in particular. Graduate attributes as envisioned by students and employers internationally are discussed to indicate the importance of graduate attributes from both of these groups’ perspective. This discussion is followed by insights specific to computing disciplines in Sub-Saharan African countries. An overview of the graduate attributes required by the South African National Qualifications Framework and the South African Qualifications Authority is compared to the attributes suggested by the Association for Computing Machinery for computing syllabi. It is felt that this may help African and in particular South African computing departments to self-assess their programmes in terms of international standards

Magnitude and Kinetics of CD8+ T Cell Activation during Hyperacute HIV Infection Impact Viral Set Point

CD8[superscript +] T cells contribute to the control of HIV, but it is not clear whether initial immune responses modulate the viral set point. We screened high-risk uninfected women twice a week for plasma HIV RNA and identified 12 hyperacute infections. Onset of viremia elicited a massive HIV-specific CD8[superscript +] T cell response, with limited bystander activation of non-HIV memory CD8[superscript +] T cells. HIV-specific CD8[superscript +] T cells secreted little interferon-γ, underwent rapid apoptosis, and failed to upregulate the interleukin-7 receptor, known to be important for T cell survival. The rapidity to peak CD8[superscript +] T cell activation and the absolute magnitude of activation induced by the exponential rise in viremia were inversely correlated with set point viremia. These data indicate that rapid, high magnitude HIV-induced CD8[superscript +] T cell responses are crucial for subsequent immune control of acute infection, which has important implications for HIV vaccine design.Bill & Melinda Gates FoundationCollaboration for AIDS Vaccine DiscoveryWitten Family FoundationDan and Marjorie SullivanUrsula BrunnerGary and Loren CohenMark and Lisa Schwartz Foundation,International AIDS Vaccine Initiative (UKZNRSA1001)National Institute of Allergy and Infectious Diseases (U.S.) (R37AI067073)Center for AIDS Research (P30 AI060354

Preparing the COROT space mission: incidence and characterisation of pulsation in the Lower Instability Strip

By pursuing the goal to find new variables in the COROT field-of-view we characterised a sample of stars located in the lower part of the instability strip. Our sample is composed of stars belonging to the disk population in the solar neighbourhood. We found that 23% of the stars display multiperiodic light variability up to few mmag of amplitude. uvbyBeta photometry fixed most of the variables in the middle of the instability strip and high-resolution spectroscopy established that they have vsin i>100 km/s. The comparison with delta Sct stars in the whole Galaxy shows slightly different features, i.e., most delta Sct stars have a 0.05-mag redder (b-y)_0 index and lower vsin i values. Additional investigation in the open cluster NGC 6633 confirms the same incidence of variability, i.e., around 20%. The wide variety of pulsational behaviours of delta Sct stars (including unusual objects such as a variable beyond the blue edge or a rapidly rotating high-amplitude pulsator) makes them very powerful asteroseismic tools to be used by COROT. Being quite common among bright stars, delta Sct stars are suitable targets for optical observations from space.Comment: 9 pages, 9 figures Accepted for publication in Astronomy & Astrophysics, Main Journa