Modelling South African grain farmers’ preferences to adopt derivative contracts using discrete choice models

This paper applies a discrete choice model to determine specific characteristics that influence South African grain farmers’ preferences to hedge against uncertainties. This is the first empirical study on South African grain producers’ preferences to adopt derivative contracting and is based on the survey data of Grain South Africa for 2006. With the application of separate binary logit models for each major grain commodity, this paper establishes that different grain farmers are significantly heterogeneous. The results also show that grain farmers’ preferences to adopt derivative contracting are mostly influenced by the farmers’ prediction of daily grain prices and trends, farm size and various geographic characteristics. From a policy perspective it has been indicated that food and income insecurity will be reduced if farmers can adopt derivative contracting at large scale since it will enable the producers to produce staple food on a continuous basis at a relatively profitable level.Discrete choice models, micro-analysis of farmers, agricultural markets and marketing,

A competence assessment tool that links thinking operations with knowledge types

Background. Although there is a need for a greater number of nurses to meet the demands for universal health coverage, these trained nurses should also be competent. However, assessment of nurses’ competence remains a challenge, as the available instruments do not focus on identifying the knowledge level that is lacking.Objectives. To report on the development and reliability of an instrument that can be used to assess undergraduate student nurses’ competence.Methods. A methodological research design was used. The authors extracted items from existing competence assessment instruments, inductively analysed the items and categorised them into themes. The extracted items were used to draft a new instrument. Review by an expert panel strengthened the content and face validity of the instrument. Twenty assessors used the developed assessment instrument to assess 15 student nurses’ competence via video footage.Results. The Cronbach alpha coefficient of 0.90 and intraclass correlation coefficient of 0.85 indicate that the instrument is reliable and comparable with other instruments that assess competence.Conclusions. Nurse educators can use the developed instrument to assess the competence of a student and identify the type of  knowledge that is lacking. The student, in collaboration with the educator, can then plan specific remedial action

A new approach to evaluate gamma-ray measurements

Misunderstandings about the term random samples its implications may easily arise. Conditions under which the phases, obtained from arrival times, do not form a random sample and the dangers involved are discussed. Watson's U sup 2 test for uniformity is recommended for light curves with duty cycles larger than 10%. Under certain conditions, non-parametric density estimation may be used to determine estimates of the true light curve and its parameters

Moderate malnutrition in children aged five years and younger in South Africa: are wasting or stunting being treated?

Objectives: The objective of the study was to describe wasting and stunting in children aged 12-60 months, admitted to targeted supplementary feeding programmes for the treatment of moderate acute malnutrition (MAM) in South Africa.Design: A cross-sectional, descriptive study was performed.Subjects and setting: Children with MAM, managed as outpatients at primary healthcare facilities in three provinces, were included in the study conducted between September 2012 and August 2013.Outcome measures: Weight, height and mid-upper-arm circumference (MUAC) measurements were collected to classify the children as moderately or severely stunted or wasted.Results: Of the total sample (n = 225), 13% (n = 30) were diagnosed as wasted, 58% (n = 131) as stunted, and 21% (n = 47) as both wasted and stunted. MUAC was significantly associated with wasting. However, an association was not found between MUAC and stunting. Of the sample, 32% (n = 72) presented with severe stunting, and 29% (n = 65) with moderate wasting. Food insecurity was associated with wasting, but not with stunting.Conclusion: A low weight-for-age z-score resulted more from stunting than from wasting in this study. Severe stunting presented as a greater health concern than moderate wasting. Without scrutinising wasting and stunting, healthcare professionals may remain unaware of the drivers of underweight for age in children treated at South African primary healthcare facilities. Following this study’s outcomes, the sensitivity of MUAC in screening for moderate malnutrition in South African settings with a high prevalence of stunting is questionable. It is recommended that current nutritional interventions are revisited to explore the efficacy of treating children with wasting, stunting or both.Keywords: malnutrition, children, wasting, stunting, treatmen

Food insecurity among students at the University of the Free State, South Africa

Objective: The objective of this study was to investigate food insecurity in students in a developing country with high national food insecurity.Design: This was a cross-sectional survey.Subjects and setting: Registered students at the University of the Free State were invited to participate. Thirty-one thousand and fourteen students were enrolled in 2013. One thousand, four hundred and sixteen students completed a self-administered web-based questionnaire.Outcome measures: Food insecurity was assessed using a one-item measure, i.e. the Australian National Nutrition Survey, and a 10-item measure, i.e. the United States Department of Agriculture Community Food Security Assessment Toolkit. Associations of food insecurity with biographical attributes, food procurement measures and coping strategies were determined using the chi-square test and multivariate logistic regression analysis.Results: The prevalence of food insecurity according to the one-item measure was 65%. Using the 10-item measure, 60% of the students experienced food insecurity “with hunger”, and 26% food insecurity “without hunger”. The highest prevalence of food insecurity was in black and coloured, undergraduate, first-generation and male students, as well as in students who were unmarried, unemployed and those relying on loans or bursaries. Using the regression model, the strongest significant predictors of food insecurity were race, gender, being a first-generation student, not having enough food money, having borrowed food money from parents, having asked for food and having sold belongings to obtain food.Conclusion: Severe food insecurity in students may be contributing to the high attrition rates experienced by universities in South Africa. Urgent intervention is required, as not having access to enough nutritionally adequate and safe food could be one of the reasons why more than 50% of South African university students never graduate.Keywords: food insecurity, students, University of the Free State, South Afric

Microwave radar cross sections and Doppler velocities measured in the surf zone

Author Posting. © American Geophysical Union, 2005. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 110 (2005): C12024, doi:10.1029/2005JC003022.The relationship between microwave imaging radar measurements of fluid velocities in the surf zone and shoaling, breaking, and broken waves is studied with field observations. Normalized radar cross section (NRCS) and Doppler velocity are estimated from microwave measurements at near-grazing angles, and in situ fluid velocities are measured with acoustic Doppler velocimeters (ADVs). Joint histograms of radar cross section and Doppler velocity cluster into identifiable distributions. The NRCS values from pixels with large NRCS and high Doppler velocities (>2 m/s) decrease with decreasing bore height to the shoreline, similar to scattering from a cylinder with decreasing radius. The Doppler velocities associated with these regions in the histograms agree well with theoretical wave phase velocities. Radar and ADV measurements of fluid velocities between bore crests have similarly shaped energy density spectra for frequencies above about 0.1 Hz, but energy levels from the radar are an order of magnitude higher than those of the ADV data. Instantaneous interbore Doppler velocities are correlated with ADV measured fluid velocities but are offset by 0.8 m/s. This offset may be due to Bragg wave phase velocities, wind drift, range and azimuth sidelobes, the finite spatial resolution of the radar, and differences between mean flows measured at the surface with radar and flows measured below the surface with ADVs. Shoaling and breaking waves measured through radar grating lobes significantly affect both the Doppler velocities near the edges of the images and the scattering from the rear faces of waves, causing large Doppler velocities to be observed in these regions.This work was funded by the ONR Coastal Geosciences Program

Soft X-ray seeding studies for the SLAC Linac Coherent Light Source II

We present the results from studies of soft X-ray seeding options for the LCLS-II X-ray free electron laser (FEL) at SLAC. The LCLS-II will use superconducting accelerator technology to produce X-ray pulses at up to 1 MHz repetition rate using 4 GeV electron beams. If properly seeded, these pulses will be nearly fully coherent, and highly stable in photon energy, bandwidth, and intensity, thus enabling unique experiments with intense high-resolution soft X-rays. Given the expected electron beam parameters from start to end simulations and predicted FEL performance, our studies reveal echo enabled harmonic generation (EEHG) and soft X-ray self-seeding (SXRSS) as promising and complementary seeding methods. We find that SXRSS has the advantage of simplicity and will deliver 5-35 times higher spectral brightness than EEHG in the 1-2 nm range, but lacks some of the potential for phase-stable multipulse and multicolor FEL operations enabled by external laser seeding with EEHG

Calculation of the Coherent Synchrotron Radiation Impedance from a Wiggler

Most studies of Coherent Synchrotron Radiation (CSR) have only considered the radiation from independent dipole magnets. However, in the damping rings of future linear colliders, a large fraction of the radiation power will be emitted in damping wigglers. In this paper, the longitudinal wakefield and impedance due to CSR in a wiggler are derived in the limit of a large wiggler parameter $K$. After an appropriate scaling, the results can be expressed in terms of universal functions, which are independent of $K$. Analytical asymptotic results are obtained for the wakefield in the limit of large and small distances, and for the impedance in the limit of small and high frequencies.Comment: 10 pages, 8 figure