Breast-feeding and weaning practices in Venda, 1990

A stratified randOlll cluster survey, using a structured interview schedule, was performed to determine the prevalence, frequency and duration of breast-feeding alllong Venda mothers as well as the foods that Venda children commonly ate in their first 2 years of life. Nearly all children under 2 years old were being breast-fed and virtually all of these were fed on demand. Approximately 60% of infants under 3 months of age and virtually all others under 2 years old received supplementary foods daily. A further 30% ofinfants under the age of 3 months were given supplementary water daily. Forty per cent of infants under 3 months old and virtually all in the other age groups were given carbohydrates daily. Protein foods, vitamin mineral and high-energy sources were given less frequently. Only 12% in the 6 - 11-month age group and 21% in the 12 - 23-111onth age group received a balanced diet daily. A significant proportion of children in all age groups received only carbohydrates over and above breast-milk. Traditional xnixes were infrequently given. More research is needed to assess actual breast-milk production by mothers whose children are being fed supplelllentary foods. The effect of socio-economic status on weaning practices and that of weaning practices on nutritional status need to be investigated. Food supplelllentation and nutrition education progralllllles need to be intensified

Giant proximity exchange and valley splitting in TMDC/hBN/(Co, Ni) heterostructures

We investigate the proximity-induced exchange coupling in transition-metal dichalcogenides (TMDCs), originating from spin injector geometries composed of hexagonal boron-nitride (hBN) and ferromagnetic (FM) cobalt (Co) or nickel (Ni), from first-principles. We employ a minimal tight-binding Hamiltonian that captures the low energy bands of the TMDCs around K and K' valleys, to extract orbital, spin-orbit, and exchange parameters. The TMDC/hBN/FM heterostructure calculations show that due to the hBN buffer layer, the band structure of the TMDC is preserved, with an additional proximity-induced exchange splitting in the bands. We extract proximity exchange parameters in the 1-10 meV range, depending on the FM. The combination of proximity-induced exchange and intrinsic spin-orbit coupling (SOC) of the TMDCs, leads to a valley polarization, translating into magnetic exchange fields of tens of Tesla. The extracted parameters are useful for subsequent exciton calculations of TMDCs in the presence of a hBN/FM spin injector. Our calculated absorption spectra show a large splitting of the first exciton peak; in the case of MoS$_2$/hBN/Co we find a value of about 8 meV, corresponding to about 50 Tesla external magnetic field in bare TMDCs. The reason lies in the band structure, where a hybridization with Co $d$ orbitals causes a giant valence band exchange splitting of more than 10 meV. Structures with Ni do not show any $d$ level hybridization features, but still sizeable proximity exchange and exciton peak splittings of around 2 meV are present in the TMDCs

Simulation of Malaria Transmission among Households in a Thai Village using Remotely Sensed Parameters

We have used discrete-event simulation to model the malaria transmission in a Thailand village with approximately 700 residents. Specifically, we model the detailed interactions among the vector life cycle, sporogonic cycle and human infection cycle under the explicit influences of selected extrinsic and intrinsic factors. Some of the meteorological and environmental parameters used in the simulation are derived from Tropical Rainfall Measuring Mission and the Ikonos satellite data. Parameters used in the simulations reflect the realistic condition of the village, including the locations and sizes of the households, ages and estimated immunity of the residents, presence of farm animals, and locations of larval habitats. Larval habitats include the actual locations where larvae were collected and the probable locations based on satellite data. The output of the simulation includes the individual infection status and the quantities normally observed in field studies, such as mosquito biting rates, sporozoite infection rates, gametocyte prevalence and incidence. Simulated transmission under homogeneous environmental condition was compared with that predicted by a SEIR model. Sensitivity of the output with respect to some extrinsic and intrinsic factors was investigated. Results were compared with mosquito vector and human malaria data acquired over 4.5 years (June 1999 - January 2004) in Kong Mong Tha, a remote village in Kanchanaburi Province, western Thailand. The simulation method is useful for testing transmission hypotheses, estimating the efficacy of insecticide applications, assessing the impacts of nonimmune immigrants, and predicting the effects of socioeconomic, environmental and climatic changes

Is adrenal suppression in asthmatic children reversible? A case series

CITATION: Zollner, E. W. 2018. Is adrenal suppression in asthmatic children reversible? A case series. South African Medical Journal, 108(6):502-505, doi:10.7196/SAMJ.2018.v108i6.13031.The original publication is available at http://www.samj.org.zaBackground. Six hypocortisolaemic asthmatic children on steroids given at physiological doses were identified during a previous study. Objectives. To establish whether hypothalamic-pituitary-adrenal axis suppression (HPAS) could be reversed in hypocortisolaemic asthmatic children treated with steroids without sacrificing asthma control. Methods. In this case series, treatment of six hypocortisolaemic patients was modified by introducing steroid-sparing asthma medications. Serum cortisol and repeat overnight metyrapone tests (ONMTPTs) were done until HPAS was reversed in all patients. A retrospective folder review was performed and the following data were extracted: body mass index standard deviation score (BMI SDS), adherence, daily steroid type and dose, treatment modification, serum cortisol, final ONMTPT result and time taken to achieve normalisation. Results. The median serum cortisol level recovered to 311 nmol/L after 0.9 years (median). The ONMTPT normalised within 3.3 years (median). Steroid load decreased from 9.2 to 5.0 hydrocortisone equivalent mg/m2/d (medians), while asthma score improved from 1.42 to 0.85 (medians). Poor adherence was noted in two children before and four after treatment modification. BMI SDS decreased from –0.08 to –0.16 (medians). Conclusions. Hypocortisolaemia and HPAS could be reversed in asthmatic children treated with physiological doses of steroids by reducing steroid load by 40% and supplementing therapy with steroid-sparing medication. Poor adherence may have either contributed to or retarded HPA recovery. Simultaneously, asthma control improved. Confirmation by a prospective study would be ideal, but may not be feasible.http://www.samj.org.za/index.php/samj/article/view/12307Publisher's versio

Investigating the impact of invasive Asian carp on river otter diet and the native fish communities of Indiana

Invasive Asian carp (i.e., bighead and silver carp, Hypophthalmic molitric and hypophalmichthy nobilis), threaten native fish populations in Midwestern United States freshwater ecosystems. These species are primarily planktivorous, experience rapid growth rates, and have enhanced predator avoidance traits resulting in a competitive advantage over native fish species. The success of Asian carp may also threaten higher-level predators by altering prey availability, potentially causing a change in predator behavior and diet. Since the coinciding river otter (Lontra canadensis) reintroduction and Asian carp invasion in Indiana’s waterways in 1995, no studies have investigated the impact of Asian carp on higher- level predators. Our objective is to determine the role of Asian carp in the diet of a top predator in Indiana’s waterways, the North American river otter. To determine the impact of Asian carp in otter diet, we will be conducting diet analyses through two methods: gross fecal analysis and stable isotope analysis. We will compare otter diet in a carp-invaded watershed to the otter diet in a carp-free watershed. We are collecting scat at 2 different locations along the carp-invaded Tippecanoe River: Prophetstown State Park, YMCA Camp Tecumseh and 2 different locations in non-carp invaded waterways: Chain’O Lakes State Park and Pigeon River Fish and Wildlife Area. We hypothesize that river otters will select against invasive Asian carp in preference for native species, with which they have coevolved. This result would indicate an increase in predation pressure upon already reduced native fish populations, as well as a reduction in fitness of the predator from limited prey availability. If otters do prefer Asian carp, they may serve as an effective bio control for Asian carp while also creating a positive public perception of otters

Low-scaling GW algorithm applied to twisted transition-metal dichalcogenide heterobilayers

The $GW$ method is widely used for calculating the electronic band structure of materials. The high computational cost of $GW$ algorithms prohibits their application to many systems of interest. We present a periodic, low-scaling and highly efficient $GW$ algorithm that benefits from the locality of the Gaussian basis and the polarizability. The algorithm enables $G_0W_0$ calculations on a MoSe$_2$/WS$_2$ bilayer with 984 atoms per unit cell, in 42 hours using 1536 cores. This is four orders of magnitude faster than a plane-wave $G_0W_0$ algorithm, allowing for unprecedented computational studies of electronic excitations at the nanoscale

Simulation and optimisation of terahertz emission from InGaAs and InP photoconductive switches

We simulate the terahertz emission from laterally-biased InGaAs and InP using a three-dimensional carrier dynamics model in order to optimise the semiconductor material. Incident pump-pulse parameters of current Ti:Sapphire and Er:fibre lasers are chosen, and the simulation models the semiconductor's bandstructure using parabolic Gamma, L and X valleys, and heavy holes. The emitted terahertz radiation is propagated within the semiconductor and into free space using a model based on the Drude-Lorentz dielectric function. As the InGaAs alloy approaches InAs an increase in the emitted power is observed, and this is attributed to a greater electron mobility. Additionally, low-temperature grown and ion-implanted InGaAs are modelled using a finite carrier trapping time. At sub-picosecond trapping times the terahertz bandwidth is found to increase significantly at the cost of a reduced emission power.Comment: 9 pages, 7 figure

Full real-space analysis of a dodecagonal quasicrystal

The atomically resolved real-space structure of a long-range-ordered dodecagonal quasicrystal is determined based on scanning tunnelling microscopy. For the BaTiO3-derived oxide quasicrystal which spontaneously forms on a Pt(111) surface, 8100 atomic positions have been determined and are compared with an ideal Niizeki–Gähler tiling. Although the Niizeki–Gähler tiling has a complex three-element structure, the abundance of the triangle, square and rhomb tiling elements in the experimental data closely resembles the ideal frequencies. Similarly, the frequencies of all possible next-neighbour tiling combinations are, within the experimental uncertainty, identical to the ideal tiling. The angular and orientational distributions of all individual tiling elements show the characteristics of the dodecagonal quasicrystal. In contrast, the analysis of the orientation of characteristic and more complex tiling combinations indicates the partial decomposition of the quasicrystal into small patches with locally reduced symmetry. These, however, preserve the long-range quasicrystal coherence. The symmetry reduction from dodecagonal to sixfold is assigned to local interaction with the threefold substrate. It leads to atomic flips which preserve the number of quasicrystal tiling elements

Strain-tunable orbital, spin-orbit, and optical properties of monolayer transition-metal dichalcogenides

When considering transition-metal dichalcogenides (TMDCs) in van der Waals heterostructures for periodic ab initio calculations, usually, lattice mismatch is present, and the TMDC needs to be strained. In this study we provide a systematic assessment of biaxial strain effects on the orbital, spin-orbit, and optical properties of the monolayer TMDCs using ab initio calculations. We complement our analysis with a minimal tight-binding Hamiltonian that captures the low-energy bands of the TMDCs around the K and K' valleys. We find characteristic trends of the orbital and spin-orbit parameters as a function of the biaxial strain. Specifically, the orbital gap decreases linearly, while the valence (conduction) band spin splitting increases (decreases) nonlinearly in magnitude when the lattice constant increases. Furthermore, employing the Bethe-Salpeter equation and the extracted parameters, we show the evolution of several exciton peaks, with biaxial strain, on different dielectric surroundings, which are particularly useful for interpreting experiments studying strain-tunable optical spectra of TMDCs