Rotationally-invariant mapping of scalar and orientational metrics of neuronal microstructure with diffusion MRI

We develop a general analytical and numerical framework for estimating intra- and extra-neurite water fractions and diffusion coefficients, as well as neurite orientational dispersion, in each imaging voxel. By employing a set of rotational invariants and their expansion in the powers of diffusion weighting, we analytically uncover the nontrivial topology of the parameter estimation landscape, showing that multiple branches of parameters describe the measurement almost equally well, with only one of them corresponding to the biophysical reality. A comprehensive acquisition shows that the branch choice varies across the brain. Our framework reveals hidden degeneracies in MRI parameter estimation for neuronal tissue, provides microstructural and orientational maps in the whole brain without constraints or priors, and connects modern biophysical modeling with clinical MRI.Comment: 25 pages, 12 figures, elsarticle two-colum

Contextualizing South Africa’s participation in the SITES 2006 module

The International Association for the Evaluation of Educational Achievement (IEA) initiated the Second International Technology in Education Study (SITES 2006) — a large-scale comparative survey on the use of Information and Communication Technologies (ICTs) in schools. The goal was to understand the pedagogical use of ICTs in schools in 22 education systems. We aim to contextualize South Africa’s participation in SITES 2006 on four levels: (i) the nature and structure of the South African education system, (ii) a review of South Africa’s participation in SITES 2006, (iii) ICT infrastructure, facilities and equipment, and (iv) teachers’ use of ICTs for teaching and learning. SITES 2006 administered three questionnaires to school principals, technology coordinators, and mathematics and science teachers. The final sample consisted of 666 mathematics and 622 science teachers. Although most education systems collected data via the internet, South Africa was the only country that used only a paper-and-pencil data collection strategy with an average return rate of 90%. South Africa scored low on most variables, e.g. ICT infrastructure, facilities, and equipment. A large percentage of South African teachers reported their ICT incompetence. South Africa’s inability to cross the boundaries of traditional learning towards the development of 21st century teaching and learning skills inhibits social and economic growth for the development of human capital.Keywords: developing context; e-Education; ICT in education; large-scale study; mathematics education; science education; SITES 2006; South Africa

Turbulence and wind speed profiles for simulating the TMT AO performances

The site testing campaign of the Thirty Meter Telescope gathered an extensive amount of turbulence profiles. This data is modeled to describe the statistical characteristics of each site and act as "standard atmospheres" for use in AO simulations

2.5 V 35 dBm IIP3 75 MHz sixth-order active RC filter

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Patients' experiences of transitioning between different renal replacement therapy modalities : a qualitative study

BACKGROUND: Different kidney replacement therapy modalities are available to manage end-stage kidney disease, such as home-based dialysis, in-center hemodialysis, and kidney transplantation. Although transitioning between modalities is common, data on how patients experience these transitions are scarce. This study explores patients' perspectives of transitioning from a home-based to an in-center modality. METHODS: Patients transitioning from peritoneal dialysis to in-center hemodialysis were purposively selected. Semi-structured interviews were performed, digitally recorded, and transcribed verbatim. Data analysis, consistent with Charmaz' constructivist approach of grounded theory was performed. RESULTS: Fifteen patients (10 males; mean age 62 years) participated. The conditions of the transitioning process impacted the participants' experiences, resulting in divergent experiences and associated emotions. Some participants experienced a loss of control due to the therapy-related changes. Some felt tied down and having lost independence, whereas others stated they regained control as they felt relieved from responsibility. This paradox of control was related to the patient having or not having (1) experienced a fit of hemodialysis with their personal lifestyle, (2) a frame of reference, (3) higher care requirements, (4) insight into the underlying reasons for transitioning, and (5) trust in the healthcare providers. CONCLUSIONS: Care teams need to offer opportunities to elicit patients' knowledge and fears, dispel myths, forge connections with other patients, and visit the dialysis unit before transition to alleviate anxiety. Interventions that facilitate a sense of control should be grounded in the meaning that the disorder has for the person and how it impacts their sense of self