Electrical characterization of deep levels created by bombarding nitrogen-doped 4HSiC with alpha-particle irradiation

Deep-level transient spectroscopy (DLTS) and Laplace-DLTS were used to investigate the effect of alpha-particle irradiation on the electrical properties of nitrogen-doped 4H-SiC. The samples were bombarded with alpha-particles at room temperature (300 K) using an americium-241 (241Am) radionuclide source. DLTS revealed the presence of four deep levels in the as-grown samples, E0.09, E0.11, E0.16 and E0.65. After irradiation with a fluence of 4.1 × 1010 alpha-particles-cm–2, DLTS measurements indicated the presence of two new deep levels, E0.39 and E0.62 with energy level, EC – 0.39 eV and EC –0.62 eV, with an apparent capture cross sections of 2×10–16 and 2×10–14 cm2, respectively. Furthermore, irradiation with fluence of 8.9×1010 alpha-particles-cm–2 resulted in disappearance of shallow defects due to a lowering of the Fermi level. These defects - minutes. Defects, E0.39 and E0.42 with close emission rates were attributed to silicon or carbon vacancy and could only be separated by using high resolution Laplace-DLTS. The DLTS peaks at EC – (0.55-0.70) eV (known as Z1/Z2) were attributed to an isolated carbon vacancy (VC).This work is based on the research supported in part by the National Research Foundation (NRF) of South African (Grant specific unique reference number (UID) 78838).http://www.elsevier.com/locate/nimb2017-03-31hb2016Physic

Electrical characterization of 5.4 MeV alpha-particle irradiated 4H-SiC with low doping density

Nickel Schottky diodes were fabricated on 4H-SiC. The diodes had excellent current rectification with about ten orders of magnitude between 50 V and +2 V. The ideality factor was obtained as 1.05 which signifies the dominance of the thermionic emission process in charge transport across the barrier. Deep level transient spectroscopy revealed the presence of four deep level defects in the 30–350 K temperature range. The diodes were then irradiated with 5.4 MeV alpha particles up to fluence of 2.6 1010 cm 2. Current–voltage and capacitance–voltage measurements revealed degraded diode characteristics after irradiation. DLTS revealed the presence of three more energy levels with activation enthalpies of 0.42 eV, 0.62 eV and 0.76 eV below the conduction band. These levels were however only realized after annealing the irradiated sample at 200 C and they annealed out at 400 C. The defect depth concentration was determined for some of the observed defects.National Research Foundation (NRF) of South Africa.http://www.elsevier.com/locate/nimb2016-09-30hb201

Electrical characterization of electron irradiated and annealed lowly-doped 4H-SiC

Please read abstract in the article.The University of Pretoria; Postdoctoral Fellowship Program of the University of Pretoria and the National Research Foundation (NRF) of South Africa.http://www.elsevier.com/locate/nimb2018-10-15hj2017Physic

Electrical characterization of high energy electron irradiated Ni/4H-SiC Schottky barrier diodes

The effect of high energy electron (HEE) irradiation on Ni/4H-SiC Schottky barrier diodes was evaluated by current-voltage (I-V) and capacitance-voltage (C-V) measurements at room temperature. Electron irradiation was achieved by using a radioactive strontium source with peak emission energy of 2.3 MeV. Irradiation was performed in fluence steps of 4.9 × 1013 cm–2 until a total fluence of 5.4 × 1014 cm–2 was reached. The Schottky barrier height determined from (I-V) measurements was not significantly changed by irradiation while that obtained from (C-V) measurements increased with irradiation. The ideality factor was obtained before irradiation as 1.05 and this value did not significantly change as a result of irradiation. The series resistance increased from 47 Ω before irradiation to 74 Ω after a total electron fluence of 5.4 × 1014 cm–2. The net donor concentration decreased with increasing irradiation fluence from 4.6 × 1014 cm–3 to 3.0 × 1014 cm–3 from which the carrier removal rate was calculated to be 0.37 cm–1.National Research Foundation (NRF) of South Africahttp://link.springer.com/journal/116642017-08-31hb2016Physic

Social-ecological, motivational and volitional factors for initiating and maintaining physical activity in the context of HIV

Sport and exercise can have several health benefits for people living with HIV. These benefits can be achieved through different types of physical activity, adapting to disease progression, motivation and social-ecological options. However, physical activity levels and adherence to exercise are generally low in people living with HIV. At the same time, high drop-out rates in intervention studies are prevalent; even though they often entail more favourable conditions than interventions in the natural settings. Thus, in the framework of an intervention study, the present study aims to explore social-ecological, motivational and volitional correlates of South African women living with HIV with regard to physical activity and participation in a sport and exercise health promotion programme. The qualitative data was produced in the framework of a non-randomised pre-post intervention study that evaluated structure, processes and outcomes of a 10-week sport and exercise programme. All 25 participants of the programme were included in this analysis, independent of compliance. Data was produced through questionnaires, participatory group discussions, body image pictures, research diaries and individual semi-structured interviews. All participants lived in a low socioeconomic, disadvantaged setting. Hence, the psychological correlates are contextualised and social-ecological influences on perception and behaviour are discussed. The results show the importance of considering social-cultural and environmental influences on individual motives, perceptions and expectancies, the fear of disclosure and stigmatisation, sport and exercise-specific group dynamics and self-supporting processes. Opportunities and strategies to augment physical activity and participation in sport and exercise programmes in the context of HIV are discussed.Scopu

Fusarium: more than a node or a foot-shaped basal cell

Recent publications have argued that there are potentially serious consequences for researchers in recognising distinct genera in the terminal fusarioid clade of the family Nectriaceae. Thus, an alternate hypothesis, namely a very broad concept of the genus Fusarium was proposed. In doing so, however, a significant body of data that supports distinct genera in Nectriaceae based on morphology, biology, and phylogeny is disregarded. A DNA phylogeny based on 19 orthologous protein-coding genes was presented to support a very broad concept of Fusarium at the F1 node in Nectriaceae. Here, we demonstrate that re-analyses of this dataset show that all 19 genes support the F3 node that represents Fusarium sensu stricto as defined by F. sambucinum (sexual morph synonym Gibberella pulicaris). The backbone of the phylogeny is resolved by the concatenated alignment, but only six of the 19 genes fully support the F1 node, representing the broad circumscription of Fusarium. Furthermore, a re-analysis of the concatenated dataset revealed alternate topologies in different phylogenetic algorithms, highlighting the deep divergence and unresolved placement of various Nectriaceae lineages proposed as members of Fusarium. Species of Fusarium s. str. are characterised by Gibberella sexual morphs, asexual morphs with thin- or thick-walled macroconidia that have variously shaped apical and basal cells, and trichothecene mycotoxin production, which separates them from other fusarioid genera. Here we show that the Wollenweber concept of Fusarium presently accounts for 20 segregate genera with clear-cut synapomorphic traits, and that fusarioid macroconidia represent a character that has been gained or lost multiple times throughout Nectriaceae. Thus, the very broad circumscription of Fusarium is blurry and without apparent synapomorphies, and does not include all genera with fusarium-like macroconidia, which are spread throughout Nectriaceae (e.g., Cosmosporella, Macroconia, Microcera). In this study four new genera are introduced, along with 18 new species and 16 new combinations. These names convey information about relationships, morphology, and ecological preference that would otherwise be lost in a broader definition of Fusarium. To assist users to correctly identify fusarioid genera and species, we introduce a new online identification database, Fusarioid-ID, accessible at www.fusarium.org. The database comprises partial sequences from multiple genes commonly used to identify fusarioid taxa (act1, CaM, his3, rpb1, rpb2, tef1, tub2, ITS, and LSU). In this paper, we also present a nomenclator of names that have been introduced in Fusarium up to January 2021 as well as their current status, types, and diagnostic DNA barcode data. In this study, researchers from 46 countries, representing taxonomists, plant pathologists, medical mycologists, quarantine officials, regulatory agencies, and students, strongly support the application and use of a more precisely delimited Fusarium (= Gibberella) concept to accommodate taxa from the robust monophyletic node F3 on the basis of a well-defined and unique combination of morphological and biochemical features. This F3 node includes, among others, species of the F. fujikuroi, F. incarnatum-equiseti, F. oxysporum, and F. sambucinum species complexes, but not species of Bisifusarium [F. dimerum species complex (SC)], Cyanonectria (F. buxicola SC), Geejayessia (F. staphyleae SC), Neocosmospora (F. solani SC) or Rectifusarium (F. ventricosum SC). The present study represents the first step to generating a new online monograph of Fusarium and allied fusarioid genera (www.fusarium.org)

Attitudes and perceived impact of antiretroviral therapy on sexual risk behaviour among young people in Kahe, Moshi Rural District, Tanzania

Free antiretroviral therapy (ART) has been provided through the public health system in Tanzania since 2004. The success of national ART roll out programme is premised upon collaborative efforts of health systems, communities and policy environment. However, community perceptions of ART and its implications on sexual behaviours and HIV/AIDS prevention remain largely unknown. Drawing on focus group discussions with young people, this paper examines perception about ART and the potential impact of antiretroviral therapy on risk sexual behaviour in rural Tanzania. Participants included a purposively selected sample of males and females aged 14-24 years. Results show that young people were both optimistic and concerned regarding availability of ART. Positive attitudes toward ART were associated with public health significance of therapy in managing opportunistic infections and extending lives of HIV infected persons. However, the positive outcomes of therapy were considered to be short lived, unsustainable and potentially threatening to the sexual health and wellbeing of HIV negative members in the community. ART was considered to empower infected persons to intentionally spread HIV to uninfected individuals in the community through deliberate unprotected sexual activities. The study highlights the significance of reinforcing HIV prevention while underscoring the need to provide appropriate information and increasing access to ART in rural areas of Tanzania. In conclusion, creating a therapy friendly atmosphere through information delivery is crucial in promoting social acceptability of antiretroviral therapy among youths. Efforts to improve access to antiretroviral drugs should re-emphasize prevention counselling to minimize sexual transmission of HI

Attitudes and perceived impact of antiretroviral therapy on sexual risk behaviour among young people in Kahe, Moshi Rural District, Tanzania

Free antiretroviral therapy (ART) has been provided through the public health system in Tanzania since 2004. The success of national ART roll out programme is premised upon collaborative efforts of health systems, communities and policy environment. However, community perceptions of ART and its implications on sexual behaviours and HIV/AIDS prevention remain largely unknown. Drawing on focus group discussions with young people, this paper examines perception about ART and the potential impact of antiretroviral therapy on risk sexual behaviour in rural Tanzania. Participants included a purposively selected sample of males and females aged 14-24 years. Results show that young people were both optimistic and concerned regarding availability of ART. Positive attitudes toward ART were associated with public health significance of therapy in managing opportunistic infections and extending lives of HIV infected persons. However, the positive outcomes of therapy were considered to be short lived, unsustainable and potentially threatening to the sexual health and wellbeing of HIV negative members in the community. ART was considered to empower infected persons to intentionally spread HIV to uninfected individuals in the community through deliberate unprotected sexual activities. The study highlights the significance of reinforcing HIV prevention while underscoring the need to provide appropriate information and increasing access to ART in rural areas of Tanzania. In conclusion, creating a therapy friendly atmosphere through information delivery is crucial in promoting social acceptability of antiretroviral therapy among youths. Efforts to improve access to antiretroviral drugs should re-emphasize prevention counselling to minimize sexual transmission of HI

Toward Precision and Reproducibility of Diffusion Tensor Imaging: A Multicenter Diffusion Phantom and Traveling Volunteer Study

Background and purposePrecision medicine is an approach to disease diagnosis, treatment, and prevention that relies on quantitative biomarkers that minimize the variability of individual patient measurements. The aim of this study was to assess the intersite variability after harmonization of a high-angular-resolution 3T diffusion tensor imaging protocol across 13 scanners at the 11 academic medical centers participating in the Transforming Research and Clinical Knowledge in Traumatic Brain Injury multisite study.Materials and methodsDiffusion MR imaging was acquired from a novel isotropic diffusion phantom developed at the National Institute of Standards and Technology and from the brain of a traveling volunteer on thirteen 3T MR imaging scanners representing 3 major vendors (GE Healthcare, Philips Healthcare, and Siemens). Means of the DTI parameters and their coefficients of variation across scanners were calculated for each DTI metric and white matter tract.ResultsFor the National Institute of Standards and Technology diffusion phantom, the coefficients of variation of the apparent diffusion coefficient across the 13 scanners was <3.8% for a range of diffusivities from 0.4 to 1.1 × 10-6 mm2/s. For the volunteer, the coefficients of variations across scanners of the 4 primary DTI metrics, each averaged over the entire white matter skeleton, were all <5%. In individual white matter tracts, large central pathways showed good reproducibility with the coefficients of variation consistently below 5%. However, smaller tracts showed more variability, with the coefficients of variation of some DTI metrics reaching 10%.ConclusionsThe results suggest the feasibility of standardizing DTI across 3T scanners from different MR imaging vendors in a large-scale neuroimaging research study