Epidemiology of injuries among U18, U19, U21 and senior elite netball players.

Background: Despite a substantial body of literature on injuries among elite netball players in South Africa, no study reports on the timing and type of injuries and the reason for injuries. Objective: To determine the epidemiology of injuries in U18, U19, U21 and senior netball players in the Free State (FS), South Africa, over two consecutive netball seasons (2017/2018). Methods: An injury questionnaire was used to collect data on 96 eligible players. Results: A total of 48 injuries were reported. The profile of injuries revealed that 58% (n=28) of the injuries occurred during matches, 29% (n=14) during practice and 13% (n=6) during preseason training. Acute injuries accounted for 54% (n=26) of the total, while 46% (n=22) were overuse injuries. A third of all the injuries were re-injuries. The centre (C) position had the highest incidence of injuries in players (n=14; 29%). The ankle was the most frequently injured body part (n=18; 36%), followed by the lower leg and Achilles tendon (n=6; 13%) thus largely the ligaments and muscles. The overall incidence rate of injuries during match play was 33.9 injuries per 1 000 hours of match play. Conclusion: Preventative strategies should consist of ankle and lower leg strengthening and neuromuscular balance techniques. The focus should be on correct landing techniques, results of abrupt change of direction movements and short bursts of speed.

Physical and physiological profile of U18, U19, U21 and senior elite netball players.

Background: Physical and physiological profile data for elite netball players in South Africa and internationally are limited but are necessary for conditioning programme information. Objective: To determine the physical and physiological profiles of U18, U19, U21 and senior level elite netball players at provincial level in the Free State, South Africa. The information provided is by age group and playing position. The fitness of the players for South African and New Zealand netball is also given using the fitness normative data (norms). Methods: This cross-sectional, descriptive study consisted of 77 elite South African netball players. Anthropometric measurements were taken according to international standards. Fitness tests included the Star Execution Balance Test, standing broad jump, double- and single-leg vertical jump, Yo-Yo Intermittent Recovery Level 1(IR1) test, sprints over 5, 10 and 40 m, horizontal pull-ups and press-ups, the prone bridge test and anaerobic Octorepeater tests with 10 m and 20 m repeated shuttle sprints. In keeping with the descriptive nature of the study, descriptive statistics were calculated for numerical data by age group and playing position. Results: Players generally did not meet the accepted fitness standards in the following areas: press-ups (all age groups), horizontal pull-ups (senior and U21), standing broad jump (senior and U21), vertical squat jump (senior and U21), 5 m and 10 m sprints (senior and U21); anaerobic Octorepeater (senior players), and the aerobic Yo-Yo IR1 test (all age groups). Conclusion: Strength and conditioning coaches should develop training programmes to address fitness areas where players do not meet the international standards.

Noise-resistant pulse oximetry using a synthetic reference signal.

We describe a noise-resistant pulse oximetry algorithm suited to both signal reconstruction and oxygen saturation estimation. The algorithm first detects relatively clean signal sections from which the heart rate is estimated. The heart rate is used to construct a synthetic reference signal that matches an idealized pulse signal. An adaptive filter continuously processes the sensor signals, reconstructing signals in a linear subspace defined by the reference signal. A projective subspace algorithm is then applied to find the oxygenation level of the blood. We show that under specific circumstances this algorithm solves the sufficiency condition for signal reconstruction in linear saturation estimators. The core principle of using a frequency modulated synthetic reference signal can be applied to adaptive filtering of other physiological signals controlled by the heartbeat, such as blood pressure and electrocardiogram.

On a natural homotopy between linear and nonlinear single-layer networks.

In this paper we formulate a homotopy approach for solving for the weights of a network by smoothly transforming a linear single layer network into a nonlinear perceptron network. While other researchers have reported potentially useful numerical results based on heuristics related to this approach, the work presented here provides the first rigorous exposition of the deformation process. Results include a complete description of how the weights relate to the data space, a proof of the global convergence and validity of the method, and a rigorous formulation of the generalized orthogonality theorem to provide a geometric perspective of the solution process. This geometric interpretation clarifies conditions resulting in the appearance of local minima and infinite weights in network optimization procedures, and the similarities of and differences between optimizing the weights in a nonlinear network and optimizing the weights in a linear network. The results provide a strong theoretical foundation for quantifying performance bounds on finite neural networks and for constructing globally convergent optimization approaches on finite data sets.

On the uniqueness of weights in single-layer perceptrons.

In this paper the geometric formulation of the single layer perceptron weight optimization problem previously described by Coetzee et al. (1993, 1996) is combined with results from other researchers on nonconvex set projections to describe sufficient conditions for uniqueness of weight solutions. It is shown that the perceptron data surface is pseudoconvex and has infinite folding, allowing for the specification of a region of desired vectors having unique projections purely in terms of the local curvature of the data surface. No information is therefore required regarding the global curvature or size of the data surface. These results in principle allow for a posteriori evaluation of whether a weight solution is unique or globally optimal, and for a priori scaling of desired vector values to ensure uniqueness, through analysis of the input data. The practical applicability of these results from a numerical perspective is evaluated on some carefully chosen examples.

Malignant mesothelioma induced in baboons by inhalation of amosite asbestos.

Ten out of 12 South African baboons (Papio ursinus) survived exposure to amosite asbestos dust for periods ranging from 242 days to 898 days at an aerosol level ranging between 1,100 and 1,200 fibers per milliliter. After exposure, they were kept under observation until they died; the total residence time of amosite varied from 1.2-10.2 years. All underwent detailed postmortem necropsy examinations. All baboons had asbestosis. Five of the baboons developed malignant diffuse mesothelioma; three peritoneal, and two pleural with peritoneal invasion. These results indicate that amosite is highly carcinogenic. Since it is difficult to accomplish follow-up of persons exposed to amosite asbestos because of the geographic location of the amosite mines and mills in South Africa (a majority of the workers being migrant laborers from countries bordering on the Transvaal), it is therefore probable that cases of peritoneal mesothelioma have been missed. If human beings are likely to react to amosite as do baboons, epidemiological follow-up should include identification of abdominal as well as thoracic neoplasms.

[Subcutaneous fibrosarcoma in a lion (Panthera leo)]. / Subkutane fibrosarkoom in 'n leeu (Panthera leo).

A subcutaneous growth developed on the left side of a zoo lion. The growth enlarged over a period of 3 months. A diagnosis of fibrosarcoma was made on account of the history, clinical and histological examinations. The lion was killed 3 weeks after surgical removal of the tumour. The autopsy showed no evidence of metastases. A foreign body (wire) was discovered in the abdominal cavity but no association was found between the lesion caused by the wire and the malignancy.