Working Within Constraints: Managing African Savannas for Animal Production and Biodiversity

The mean density of livestock biomass on African rangelands now greatly exceeds that of indigenous large herbivores, although livestock cannot fully substitute for wildlife with respect to co-evolved ecosystem processes involving herbivory. The dominance of livestock in semi-arid rangelands is largely due to water provision, which uncouples livestock population dynamics from the rainfall-driven trajectories followed by indigenous ungulate species in wildlife areas. Ecological sustainability cannot be achieved with a few exotic species maintained at unprecedented biomass densities in savanna ecosystems, which are evolutionarily adapted for species-rich communities of ungulates of a wise range of sizes. Integrating wildlife and livestock in multi-species animal production systems offers a partial solution. Community-based ecotourism can effectively augment pastoralism in semi-arid rangelands but, as rainfall increases, the opportunity costs become too high. Direct payment approaches show promise for offsetting opportunity costs, although major obstacles remain in the form of political corruption and obstructive practices by national governments

Browsing lawns? Responses of Acacia nigrescens to ungulate browsing in an African savanna

We measured browsing-induced responses of Acacia trees to investigate browsing lawns as an analogy to grazing lawns in a semiarid eutrophic African savanna. During the two-year field study, we measured plant tolerance, resistance, and phenological traits, while comparing variation in leaf nitrogen and specific leaf area (SLA) across stands of Acacia nigrescens, Miller, that had experienced markedly different histories of attack from large herbivores. Trees in heavily browsed stands developed (1) tolerance traits such as high regrowth abilities in shoots and leaves, high annual branch growth rates, extensive tree branching and evidence of internal N translocation, and (2) resistance traits such as close thorn spacing. However, phenological escape responses were weak even in heavily browsed stands. Overall, browsing strongly affected plant morpho-functional traits and decreased both the number of trees carrying pods and the number of pods per tree in heavily browsed stands. Hence, there is experimental evidence that tolerance and resistance traits may occur simultaneously at heavily browsed sites, but this comes at the expense of reproductive success. Such tolerance and resistance traits may coexist if browsers trigger and maintain a positive feedback loop in which trees are continually investing in regrowth (tolerance), and if the plant\u27s physical defenses (resistance) are not nutritionally costly and are long-lived. Our results confirm that chronic browsing by ungulates can maintain A. nigrescens trees in a hedged state that is analogous to a grazing lawn. Further research is needed to fully understand the long-term effects of chronic browsing on reproduction within such tree populations, as well as the overall effects on nutrient cycling at the ecosystem level

Integration of inverter constraints in geometrical quantification of the optimal solution to an MPC controller

Published Conference ProceedingsThis paper considers a model predictive controller with reference tracking that manipulates the integer switch positions of a power converter. It can be shown that the optimal switch position can be computed without solving an optimization problem. Specifically, in a new coordinate system, the optimization problem can be solved offline, leading to a polyhedral partition of the solution space. The optimal switch position can then be found using a binary search tree. This concept is exemplified for a three-level single-phase converter with an RL load

Improving the effectiveness of interventions to balance conservation and development: a conceptual framework

There are numerous case studies around the world describing integrated conservation and development projects (ICDPs). Recently some localized syntheses have been published that use sophisticated statistics to identify patterns and causal linkages, but no attempt has yet been made to draw together lessons from across the globe. This paper is an attempt to provide a framework for such an analysis. A set of lessons is proposed for improving the prospects of ICDPs by giving consideration to each of the five capitals: natural, social, human, built, and financial. The language of ICDPs has been adopted by development agencies of all persuasions. There is now some urgency to identify the characteristics of the environment and the community in which success is most likely. This paper is intended as a step in that direction

Orthopaedic referrals using a smartphone app: Uptake, response times and outcome

Background. It is well established that South Africa (SA) suffers an immense burden of violence and injuries. The responsibility of providing care for these injuries falls mainly on public health services, resulting in overloading of the health system. Prior to a recent intervention, the large burden had been exacerbated by limitations in the traditional referral system that highlighted the need for a better referral system. Vula’s smartphone app was introduced at Tygerberg Hospital in August 2016. This study evaluated the uptake, response times and outcomes using this app.Objectives. The main objectives of the study were to describe: (i) the number of referrals; (ii) referral response times; (iii) referring facilities; and (iv) referral outcomes. Secondary objectives were to: (i) evaluate whether the referral outcome pathway was appropriate; and (ii) assess professional conduct and evidence of upskilling.Methods. This retrospective, descriptive study investigated Vula app referrals to the Division of Orthopaedic Surgery at Tygerberg Hospital between 1 August 2016 and 31 March 2017. Vula was advertised to key facilities in the hospital’s referral network. All referrals to the division during the study period were systematically included in the analysis of operational outcomes, although some were excluded from the subsequent referral outcome analysis. Operational outcomes included the number of referrals, referring facilities and referral response times. Referral outcome analysis included the clinical diagnosis, referral pathway, whether the referral was used for upskilling and whether it was conducted in a professional manner.Results. A total of 2 275 referrals from 39 different facilities were received during the study period from 238 individual users; 50% of referrals received a response within 11 minutes, while a small percentage received no response. Clinical and demographic characteristics of 1 985 patients included in the referral outcome analysis indicated that the majority of trauma and emergency referrals involved males, with closed fractures being the most frequent clinical presentation. Although the most common referral outcome was immediate transfer, one-third of the patients were treated at the referring hospital with advice only.Conclusions. The large volume of orthopaedic referrals received through the Vula app suggests that Vula represents a successful alternative to traditional referral methods. Referrals managed by advice only could suggest that Vula facilitates some relief for the overburdened trauma services. Future research could further explore Vula’s role in strengthening the public health system, including interventions for high-volume referral areas and upskilling of referring health workers.

Cost of breast preservation surgery for cancer

CITATION: Smit, B. J., Liebenberg, T. J. & Du Toit, D. F. 1992. Cost of breast preservation surgery for cancer. South African Medical Journal, 82:481.The original publication is available at http://www.samj.org.za[No abstract available]Publisher’s versio

A systematic review and meta-analysis of longitudinal studies of the antecedents and consequences of wellbeing among university students

Background and objectives: Wellbeing among university students is associated with better academic outcomes and diminished harm from mental illness. This study systematically reviews and meta-analyses longitudinal studies of the antecedents and consequences of wellbeing within this population, providing an overview which establishes a ‘natural history’ of wellbeing to form a background for intervention and policy. Method: This study was a systematic review and meta-analysis of the peer-reviewed literature, based on a broad range of search terms across four journal databases in psychology, medicine and education. Studies were organised by the domain of their study variables (i.e., Self, Relationships, or Institutional Context) and variables relating to wellbeing were extracted. The incremental effect of study variables measured at baseline upon prospective wellbeing was calculated with semipartial correlation coefficients which controlled for baseline wellbeing. Meta-regressions were used to examine the effect of follow-up interval on effect sizes. Results: Sixty-two longitudinal studies of university student cohorts were identified. In 57 studies, wellbeing was an outcome variable. Meta-analyses showed that effects were moderated by measurement interval between baseline and follow-up, becoming weaker with longer intervals, and that this was not an artifact of the measurement instrument. The study factors with the strongest positive effect sizes after controlling for baseline wellbeing were authenticity, self-esteem, self-support for autonomy, emotional repair, and ability to regulate distress and despondency; relationship commitment and group memberships; self-identification with the university and time pressure. Study factors with the strongest negative effect sizes were uncertainty regarding university, materialism, a belief in social complexity, depression, and stress. In five studies, wellbeing was an antecedent, showing positive associations with educational outcomes. Conclusion: This review identified several antecedents of student wellbeing which could be targeted for interventions. These included self-relationship, emotion regulation, and interventions to decrease mental illness. Universities might also make it easier to establish and maintain groups (e.g., study cohorts, interest groups). Many variables which affect wellbeing are not amenable to study with experimental methods, but their study and use in wellbeing interventions should not be neglected. Because the antecedents of wellbeing are numerous and diverse, further research in the area should take advantage of research methods which maximise the variety of data collected and minimise respondent burden, such as passively collected and linked data

Fitness and body composition profiling of elite junior South African rugby players

Objective. The aim of this study was to describe the body composition, strength and speed characteristics of elite junior South African rugby players. Design. Cross-sectional. Setting. Field study. Subjects. Rugby players (16 and 18 years old, N = 174) selected for the South African Rugby Union National Green Squad. Outcome measures. Body composition, 10 m and 40 m speed, agility, 1RM bench press, underhand pull-ups, push-ups, multistage shuttle run. Results. The under-16 players were on average shorter (175.6 ± 5.7 v. 179.2 ± 6.7 cm), weighed less (76.5 ± 8.2 v. 84.8 ± 8.3 kg) had less upper body absolute strength (77.1 ± 11.8 kg v. 95.3 ± 16.7 kg) and muscular endurance (41 ± 12 v. 52 ± 15 push-ups) and aerobic fitness (87.1 ± 19.4 v. 93.5 ± 15.3 shuttles) than the under-18 players. There were no differences in body fat, sprinting speed (10 m and 40 m) or agility between the two age groups. There were differences between playing positions, with the props having the most body fat, strongest upper bodies, slowest sprinting speed, least agility and lowest aerobic capacity compared with players in the other positions. Conclusion. This study provides data for elite junior rugby players and can be used to monitor the progression of players after intervention while also assisting with talent identification for the different playing positions. South African Journal of Sports Medicine Vol. 18 (2) 2006: pp. 38-4

Fitness and body composition profiling of elite junior South African rugby players

Objective. The aim of this study was to describe the body composition, strength and speed characteristics of elite junior South African rugby players. Design. Cross-sectional. Setting. Field study. Subjects. Rugby players (16 and 18 years old, N = 174) selected for the South African Rugby Union National Green Squad. Outcome measures. Body composition, 10 m and 40 m speed, agility, 1RM bench press, underhand pull-ups, push-ups, multistage shuttle run. Results. The under-16 players were on average shorter (175.6 ± 5.7 v. 179.2 ± 6.7 cm), weighed less (76.5 ± 8.2 v. 84.8 ± 8.3 kg) had less upper body absolute strength (77.1 ± 11.8 kg v. 95.3 ± 16.7 kg) and muscular endurance (41 ± 12 v. 52 ± 15 push-ups) and aerobic fitness (87.1 ± 19.4 v. 93.5 ± 15.3 shuttles) than the under-18 players. There were no differences in body fat, sprinting speed (10 m and 40 m) or agility between the two age groups. There were differences between playing positions, with the props having the most body fat, strongest upper bodies, slowest sprinting speed, least agility and lowest aerobic capacity compared with players in the other positions. Conclusion. This study provides data for elite junior rugby players and can be used to monitor the progression of players after intervention while also assisting with talent identification for the different playing positions