Elastic constants for wood by an ultrasonic method

Summary Ultrasonic measurements were carried out on cubic specimens of six species (pine, spruce, douglas-fir, oak, beech, tulip-tree). An orthotropic model of wave propagation was used to interpret these measurements and compute estimates of the elastic compliances. In order to calculate the off-diagonal stiffness terms, velocities were computed on samples with faces at an angle to the principal directions. The elastic compliance matrix was calculated by inverting the stiffness matrix.We thank François Thiercelin, Centre National de Recherches Forestières Nancy, for useful suggestions and assistance in processing the data     

On the origin of growth stresses in trees

Summary The mechanics of growth stress generation in a tissue of developing wood cells is studied by means of a continuum-mechanical model which assumes that the stresses which accumulate in the cells are induced by growth strains in the newly formed cell wall increments as they are laid down. The feasibility of the model is examined by using cell parameters both anatomical and physical to predict the variation of growth stresses with microfibril angle. In particular the measured change from tensile to compressive stresses with increasing microfibril angle for conifers is compared with the results predicted by the model.     

Opportunities for value chain research in sugar industries

In agriculture, value chain research provides a capacity to increase efficiencies, business integration, responsiveness and ultimately market competitiveness. In sugar, such research has expanded rapidly over the past two decades, and has been motivated by low world sugar prices and rising costs of production. In this paper, we highlight the future opportunities in value chain research to achieve more profitable and sustainable sugar industries in different countries. We do this by: (a) conducting an extensive review of value chain research in sugar; (b) assessing the change resulting from chain research using case studies in the Australian and South African sugar industries; highlighting challenges to value chain research; and (c) considering opportunities and methodologies used in other industries. The paper makes several conclusions and recommendations. In particular we show that value chain opportunities require more than just a technical solution, and need collective participation from across the chain, and usually evolutionary change management. Also, we show that whilst value chain thinking and research in sugar has targeted to achieving a lean system, there are potentially greater benefits in developing an agile chain. From a modelling perspective, we highlight the future prospects of multi-agent approaches to accommodating complexities of addressing value chain opportunities in sugar. While the focus of this paper is on sugar value chains, much of the information is relevant to chains of other agricultural commodities.     

A comparison of enterotomies through the antimesenteric band and the sacculation of the small (descending) colon of ponies

Three pairs of longitudinal enterotomies were performed in the small colon of 10 ponies. Each pair consisted of one enterotomy through the antimesenteric band and one through the sacculation. The ponies were destroyed 96 h after surgery. The enterotomies in the two sites were compared for: speed of surgery, adhesions, bursting wall tension, neovascularisation by micro-angiography, and histological reaction. Enterotomies made through the antimesenteric band were superior because they were quicker to perform, stronger, more accurately apposed, and had less inflammation than those made through the sacculation.     

Jejunojejunal intussusception associated with a transmural adenocarcinoma in an aged cow

After 3 days of intestinal obstruction, a proximal jejunojejunal intussusception was resected during surgery in an adult Holstein cow. A transmural adenocarcinoma was found at the proximal margin of the intussusception. The cow recovered well from surgery and produced milk and embryos to expectation. During the seventh month after surgery, the cow developed pneumonia and, therefore, was euthanatized. Disseminated abdominal and thoracic neoplasia was observed at necropsy.