Sample positioning in neutron diffraction experiments using a multi-material fiducial marker

An alternative sample positioning method is reported for use in conjunction with sample positioning and experiment planning software systems deployed on some neutron diffraction strain scanners. In this approach, the spherical fiducial markers and location trackers used with optical metrology hardware are replaced with a specifically designed multi-material fiducial marker that requires one diffraction measurement. In a blind setting, the marker position can be determined within an accuracy of ±164 µm with respect to the instrument gauge volume. The scheme is based on a pre-determined relationship that links the diffracted peak intensity to the absolute positioning of the fiducial marker with respect to the instrument gauge volume. Two methods for establishing the linking relationship are presented, respectively based on fitting multi-dimensional quadratic functions and a cross-correlation artificial neural network

Should HIV be a notifiable disease? Old questions with some new arguments

KMHIV notification enters national debate regularly, often introduced by politicians and supported by many individual healthcare workers. We argue that its proponents advance confused or poorly informed rationales for making HIV notifiable. We present reasons why making HIV notifiable would be inappropriate in South Africa, why the public health benefits of a notification programme are not even likely, and why there are risks of public health and human rights harms

Enhanced Accessibility for People with Disabilities Living in Urban Areas

[Excerpt] People with disabilities constitute a significant proportion of the poor in developing countries. If internationally agreed targets on reducing poverty are to be reached, it is critical that specific measures be taken to reduce the societal discrimination and isolation that people with disabilities continue to face. Transport is an important enabler of strategies to fight poverty through enhancing access to education, employment, and social services. This project aims to further the understanding of the mobility and access issues experienced by people with disabilities in developing countries, and to identify specific steps that can be taken to start addressing problems. A major objective of the project is to compile a compendium of guidelines that can be used by government authorities, advocacy groups, and donor/loan agencies to improve the access of people with disabilities to transport and other services in urban areas

Descriptive analysis of World Health Organization-recommended second-line antiretroviral treatment: A retrospective cohort data analysis

Background. World Health Organization guidelines recommend that HIV patients who do not achieve viral suppression on efavirenz-based first-line antiretroviral therapy (ART) should be changed to a protease inhibitor (PI)-based regimen. In South Africa (SA), ~200 000 people are on second-line treatment, but little is known about these patients.Objectives. To describe second-line black African patients in a large urban area.Methods. A quantitative retrospective study of 825 second-line patients in central Johannesburg, SA (subdistrict F), was performed with data extracted from government databases. Demographic characteristics, treatment status and laboratory information were gathered, then analysed with CD4+ cell count, viral load (VL) and retention-in-care data as outcome variables.Results. The average recorded time to VL measurement after the switch to a PI-based ART regimen was 20 months, and 83.1% (570/686) of patients with a recent VL achieved viral suppression while on second-line treatment. The most recent median CD4+ cell count for the cohort was 286 cells/µL (interquartile range 160 - 478), which represented a 177 cells/µL increase from the baseline count at the start of first-line ART. Slightly less than three-quarters (72.4%) of the population remained active in care in the study clinics from initiation on first-line ART. Demographic characteristics such as being <25 years of age, male sex and geographical transfer (started initial treatment in a different region) independently predicted low CD4+ cell counts and virological failure on second-line treatment. Patients with virological failure were most likely (odds ratio (OR) 3.13, 95% confidence interval (CI) 1.50 - 6.56) to be lost to follow-up after the switch, while patients from Hillbrow Community Health Centre (OR 0.27, 95% CI 0.16 - 0.44), South Rand Hospital (OR 0.24, 95% CI 0.12 - 0.47) and Jeppe Clinic (OR 0.38, 95% CI 0.16 - 0.88), three larger sites, were most likely to remain active in care.Conclusions. VL suppression was high in patients on second-line treatment, but one-fifth of patients were lost to follow-up. Younger age, male sex and transfer from other treatment sites predicted poor treatment outcomes, highlighting opportunities for prioritisation of adherence interventions.

Theory of commensurable magnetic structures in holmium

The tendency for the period of the helically ordered moments in holmium to lock into values which are commensurable with the lattice is studied theoretically as a function of temperature and magnetic field. The commensurable effects are derived in the mean-field approximation from numerical calculations of the free energy of various commensurable structures, and the results are compared with the extensive experimental evidence collected during the last ten years on the magnetic structures in holmium. In general the stability of the different commensurable structures is found to be in accord with the experiments, except for the tau=5/18 structure observed a few degrees below T_N in a b-axis field. The trigonal coupling recently detected in holmium is found to be the interaction required to explain the increased stability of the tau=1/5 structure around 42 K, and of the tau=1/4 structure around 96 K, when a field is applied along the c-axis.Comment: REVTEX, 31 pages, 7 postscript figure

COVID-19 vaccines – less obfuscation, more transparency and action

Letter by Venter et al. on editorial  by Schoub (Dial down the rhetoric over COVID-19 vaccines. S Afr Med J 2021;111(6):522-523. https://doi.org/10.7196/SAMJ.2021.v111i6.15740)

Origin, diversification, and classification of the Australasian genus dracophyllum (richeeae, ericaceae)

The genus Dracophyllum Labill. (Ericaceae) has a fragmented distribution in Australasia, but reaches the greatest level of species richness and morphological diversity in New Zealand. We investigated evolutionary processes that contribute to this disparity in species richness by comparing DNA sequences from members of Dracophyllum, its close relatives Richea Labill. and Sphenotoma R. Br. ex Sweet (together constituting tribe Richeeae Crayn & Quinn), along with more distant relatives in the Ericaceae. We created complementary data sets for the chloroplast-encoded genes matK and rbcL. Parsimony, Bayesian, and maximum likelihood analyses were conducted to assess the robustness of our phylogenetic inferences. The results were largely congruent and, when analyzed in combination, provided greater resolution. In our analyses, tribe Richeeae formed a monophyletic group that diverged during the Eocene (at least 33.3 million years ago [Ma]) with a crown radiation during the Early Miocene (at least 16.5 Ma) that resulted in two disjunct lineages. This date corresponds roughly to the onset of aridification in central Australia. The southern Western Australian genus Sphenotoma formed an isolated evolutionary lineage, while Dracophyllum and Richea together formed a second lineage restricted to eastern Australia, Lord Howe Island, New Caledonia, and New Zealand. The relationships of the Tasmanian endemic, D. milliganii Hook. f., remain an enigma. It was ambiguously placed as sister to Sphenotoma or to the Dracophyllum Richea elude. We recovered two distinct lineages, traditionally recognized as Richea sect. Cystanthe (R. Br.) Benth. and Richea sect. Dracophylloides Benth., which were nested within Dracophyllum. The Lord Howe Island endemic, D. fitzgeraldii F. Muell., emerged as sister to an eastern Australian clade of Dracophyllum. Our evidence suggests that the New Caledonian and New Zealand species of Dracophyllum dispersed from Australia; we document two independent episodes of long-distance dispersal in the Late Miocene to Early Pliocene. Low levels of sequence divergence suggest a rapid and recent species radiation in these two island archipelagos largely within the last three to six million years. This radiation accompanied Pliocene uplift of the New Zealand Southern Alps and episodes of glaciation during the Pleistocene. Because Dracophyllum is paraphyletic and Richea is polyphyletic, the taxonomic circumscription of these genera requires revision