A preliminary investigation of spinal kinematics during sugar cane harvesting

The sugar cane industry forms a significant portion of the South African economy, and unlike many other countries the harvesting of sugar cane in South Africa remains manual in nature. The focus of the present study was therefore on the assessment of spinal kinematics (range of motion, velocities and accelerations in all three cardinal planes) during the harvesting process. Eight workers were recruited from the Illovo Esperanza farm in Kwa-zulu Natal as subjects for the study. The experimental protocol was conducted in situ and required subjects to cut the sugar cane using specially modified knives as they would under normal harvesting conditions. The motion performance was quantified using the lumbar motion monitor (LMM), a triaxial electrogoniometer. Results indicate that the harvesting of sugar cane places excessive demands on the spine. During cutting, subjects were required to maintain the spine in a high degree of flexion throughout the task which also demonstrated significant twisting and lateral bending. Of particular concern were the high lateral velocities (ranging between 50 and 90 m.s-1), as this is a key risk factor in the development of lower back pain. It is evident from these results that new techniques of harvesting sugar cane are essential to reduce the rate of injury within this industry

The consequences of goods perishing subsequent to a contract having been entered into for their sale

The thesis comprises three Parts, together with a preface and an addendum. Each of the Parts focuses upon one of the three inter-related concepts applicable where there is a post-contract perishing of goods. The concepts of "perishing", "risk" and "frustration" are separately analysed so as to identify their individual characteristics and in order that facets of their inter-relationship may emerge. Part One, which deals with the meaning of "perishing", is more descriptive in nature than the other two Parts, for, when considered in isolation, the issues raised in that Part are relatively straightforward. It is only when those same issues are re-considered, in the context of the concepts of risk and frustration, that their significance becomes apparent. In Part Two, an analysis is made of the meaning of "risk" and instances of the divisibility of risk are examined. Different views of the mishaps provided for by the statutory term "risk" are assessed and, as part of that exercise, the meaning of "perished" is re-appraised. An analysis is made, in Part Three, of the rules which provide for frustration of a contract of sale and for the consequences resulting from such frustration. An attempt is made to identify instances in which a contract of sale may be frustrated even though property, or risk, or, indeed, both property and risk, have passed to the buyer prior to the goods perishing. In the addendum to the thesis an opportunity is taken to re-examine the concepts of "perishing", "risk" and "frustration" in a context in which, the separate concepts having already been analysed and detailed statutory and common law provisions scrutinised, there is freedom to bring together strands which have emerged from the various Parts of the thesis. This opportunity is taken in an attempt to fix the relationship between the concepts

Metabolic responses to various combinations of gradient, load and marching speed

This study examined the metabolic cost of South African soldiers carrying loads under various conditions of gradient and marching speed. Thirty-two male soldiers participated in the study. Three speed and load combinations, 4, 5 and 6 km.h[superscript (-1)] carrying of 50, 35 and 20 kg respectively, were imposed, on each of three gradients: -10%, 0% and +10%; a total of nine experimental conditions. Subjects wore standardized military uniforms and breathed into a portable ergospirometer (Metamax) for the duration of each condition. Subjects were required to march for six minutes under each condition, and metabolic responses were monitored during the third and sixth minute of each condition. The metabolic responses to the three level marching conditions showed no significant differences. Marching uphill resulted in a significant increase in metabolic demands under all three speed and load onditions. Downhill marching elicited significant decreases only under the two lighter load conditions. Downhill marching with heavy loads appears to show no reduction in metabolic demands placed on soldiers

Random matrices, non-backtracking walks, and orthogonal polynomials

Several well-known results from the random matrix theory, such as Wigner's law and the Marchenko--Pastur law, can be interpreted (and proved) in terms of non-backtracking walks on a certain graph. Orthogonal polynomials with respect to the limiting spectral measure play a role in this approach.Comment: (more) minor change

Physical implications of prolonged sitting in a confined posture - a literature review

The main purpose of this review article was to highlight some of the physical consequences of sitting for prolonged periods in a confined setting. More specifically, the review relates this research to call centre work and where applicable comments on the limited literature relating specifically to ergonomics research within call centre settings. In particular the article explores the biomechanical stresses placed on the musculoskeletal system during prolonged sitting at a workstation, and the physiological consequences thereof. The paper then provides possible solutions to reduce the physical strain placed on these workers by looking at workstation design and work organisation emphasizing worker education and the promotion of worker well being

RISE: a fast-readout imager for exoplanet transit timing

By the precise timing of the low amplitude (0.005 - 0.02 magnitude) transits of exoplanets around their parent star it should be possible to infer the presence of other planetary bodies in the system down to Earth-like masses. We describe the design and construction of RISE, a fast-readout frame transfer camera for the Liverpool Telescope designed to carry out this experiment. The results of our commissioning tests are described as well as the data reduction procedure necessary. We present light curves of two objects, showing that the desired timing and photometric accuracy can be obtained providing that autoguiding is used to keep the target on the same detector pixel for the entire (typically 4 hour) observing run.Comment: Published in PROC SPIE, vol 7014, 70416

The effects of load and gradient on hand force responses during dynamic pushing and pulling tasks

The limited attention afforded to push/pull activities and the motion phases (initial, sustained and ending) characteristic of these tasks has prompted a research focus in this area. The present study examined biomechanical responses in the form of hand forces during dynamic submaximal trolley pushing and pulling. Participants pushed/pulled loads of 100, 200 and 300 kg on the level (determining impact of load) or pushed 100 kg along a 12° ramp (uphill and downhill- determining impact of gradient). During level exertions significant differences (p<0.05) in hand forces occurred between loads of 100 and 200 kg, and 100 and 300 kg for initial and sustained forces but not ending forces. Values were similar for pushing and pulling at respective loads and motion phases. Strong correlations indicate that initial forces can be used to accurately estimate sustained and ending forces. Importantly, correct technique is essential in force reduction. Forces were highest during uphill initial and sustained phases and the downhill sustained phase. For the initial phase, the forces were highest during uphill pushing (86.5 ± 25.73 N); for the sustained phase, there was no difference between uphill and downhill forces but level forces were significantly lower (18.19 ± 8.09 N) than either of the other two conditions; for the ending phase, the highest forces were produced during downhill pushing (-53.34 ± 13.65N). As sustained forces equaled or exceeded initial forces for uphill and downhill efforts, consideration of sustained forces may be appropriate in determining the inherent potential risk of graded pushing

Enhancing military efficiency : a South African perspective

While extensive military research has been conducted in developed countries, very little work has been done on soldiers in industrially developing countries (IDCs). Although many aspects of marching are similar around the globe, the challenges facing soldiers in IDCs, and in particular South Africa, are unique. Since the 1990’s South Africa has seen a considerable shift in the morphological and cultural make-up of the South African National Defence Force (SANDF). The result is a mix of soldiers from a variety of ethnic backgrounds. Ethnic differences may ultimately impact performance particularly as research has postulated that Blacks and Whites may differ in body composition and body proportions. It is highly probable then that the universal recommendations of optimal marching speeds, load masses and gradients need to be modified to accommodate the diversity of soldiers which currently comprise the SANDF

Nucleosynthesis in Outflows from the Inner Regions of Collapsars

We consider nucleosynthesis in outflows originating from the inner regions of viscous accretion disks formed after the collapse of a rotating massive star. We show that wind-like outflows driven by viscous and neutrino heating can efficiently synthesize Fe-group elements moving at near-relativistic velocities. The mass of 56Ni synthesized and the asymptotic velocities attained in our calculations are in accord with those inferred from observations of SN1998bw and SN2003dh. These steady wind-like outflows are generally proton rich, characterized by only modest entropies, and consequently synthesize essentially nothing heavier than the Fe-group elements. We also discuss bubble-like outflows resulting from rapid energy deposition in localized regions near or in the accretion disk. These intermittent ejecta emerge with low electron fraction and are a promising site for the synthesis of the A=130 r-process peak elements.Comment: 35 pages, 6 figures, added discussion of the influence of nuclear recombination on wind dynamics, to appear in Ap

On the Influence of Ionic Strength on Radium and Strontium Sorption to Sandy Loam Soils

Models which can estimate environmental transport of radioactive contaminants in natural and engineered systems are required to 1) deploy effective remediation strategies for contaminated sites, 2) design waste repositories for future waste streams, and 3) ensure protection of human and environmental health in all cases. These models require accurate transport parameters in order to correctly predict how these contaminants will move in the subsurface. This work aimed to determine more accurately the distribution coefficients for radium and strontium sorption to Savannah River Site (SRS) soils. Radium and strontium sorption to the soils was found to be highly dependent upon ionic strength due to competition for ion exchange sites. Radium distribution coefficients (Kd) for the clayey soil were determined to be 185.1 ± 25.63 L kg-1 and 30.35 ± 0.66 L kg-1 for ionic strengths of 0.02M and 0.1M as NaCl which is the approximate ionic strength of groundwater at the SRS. Radium distribution coefficients for the sandy soil were determined to be 24.95 ± 2.97 L kg-1 and 9.05 ± 0.36 L kg-1 for ionic strengths of 0.02M and 0.1M as NaCl. Sorption of Ra2+ was generally greater than Sr2+, consistent with the frequent use of higher distribution coefficients for Ra in performance assessments