Digital predictions of complex cylinder packed columns

A digital computational approach has been developed to simulate realistic structures of packed beds. The underlying principle of the method is digitisation of the particles and packing space, enabling the generation of realistic structures. Previous publications [Caulkin, R., Fairweather, M., Jia, X., Gopinathan, N., & Williams, R.A. (2006). An investigation of packed columns using a digital packing algorithm. Computers & Chemical Engineering, 30, 1178–1188; Caulkin, R., Ahmad, A., Fairweather, M., Jia, X., & Williams, R. A. (2007). An investigation of sphere packed shell-side columns using a digital packing algorithm. Computers & Chemical Engineering, 31, 1715–1724] have demonstrated the ability of the code in predicting the packing of spheres. For cylindrical particles, however, the original, random walk-based code proved less effective at predicting bed structure. In response to this, the algorithm has been modified to make use of collisions to guide particle movement in a way which does not sacrifice the advantage of simulation speed. Results of both the original and modified code are presented, with bulk and local voidage values compared with data derived by experimental methods. The results demonstrate that collisions and their impact on packing structure cannot be disregarded if realistic packing structures are to be obtained

Evolving community response to tourism and change in Rotorua

The aim of this report is to outline how the Rotorua community experiences tourism and tourism development and how they have adapted to it. The objectives are to: give an historical account of the history of the development of tourism in Rotorua; give an account of broader community issues which influence the community's attitudes to tourism development in their town; record the perceptions that residents have of tourism and show how these have changed over time; describe how the host community copes with the type of tourism development that exists in the area; and suggest what factors might be important in influencing residents' perceptions of tourism and their adaptation to it. This report argues that the community in Rotorua is generally very accepting of tourism, and that tourism in the town is well managed due to the proactive role taken by the local Council in relation to tourism development and promotion. Local people see tourism as a source of stability at a time of great change. For local decision-makers, tourism is a means to address the problems of unemployment and poverty which appear to be increasing in the area

Adult triclabendazole-resistant Fasciola hepatica: morphological changes in the tegument and gut following in vivo treatment with artemether in the rat model

A study has been carried out to determine the morphological changes to the adult liver fluke, Fasciola hepatica after treatment in vivo with artemether. Rats were infected with the triclabendazole-resistant Sligo isolate of F. hepatica, dosed orally with artemether at a concentration of 200mg/kg and flukes recovered at 24, 48 and 72h post-treatment (p.t.). Surface changes were monitored by scanning electron microscopy and fine structural changes to the tegument and gut by transmission electron microscopy. Twenty-four hours p.t., the external surface showed minor disruption, in the form of mild swelling of the tegument. The tegumental syncytium and sub-tegumental tissues appeared relatively normal. Forty-eight and seventy-two hours p.t., disruption to the tegumental system increased, with isolated patches of surface blebbing and reduced production of secretory bodies by the tegumental cells being the main changes seen. The gastrodermal cells showed a relatively normal morphology 24h p.t. By 48h, large numbers of autophagic vacuoles and lipid droplets were present. Autophagy increased in magnitude by 72h p.t. and substantial disruption to the granular endoplasmic reticulum was observed. Results from this study show that flukes treated in vivo with artemether display progressive and time-dependent alterations to the tegument and gut. Disruption to the gut was consistently and substantially more severe than that to the tegument, suggesting that an oral route of uptake for this compound predominates. This is the first study providing ultrastructural information on the effect of an artemisinin compound against liver fluk

Electron microscopical study to assess the in vitro effects of the synthetic trioxolane OZ78 against the liver fluke, Fasciola hepatica

Adult Fasciola hepatica were incubated for 48 h in vitro in the synthetic peroxide, OZ78 at a concentration of 100 μg/ml and then prepared for scanning and transmission electron microscopy. There was limited disruption to the external fluke surface, with only slight swelling and blebbing of the interspinal tegument in the midbody and ventral tail regions. By contrast, significant disruption was observed to the ultrastructure of the tegument and subtegumental tissues. There was severe swelling of the basal infolds in the tegumental syncytium and the flooding spread internally to affect the subtegumental tissues. In the tegumental system, there was swelling of the cisternae of granular endoplasmic reticulum and of the mitochondria, with the latter showing signs of breaking down. Autophagic vacuoles and lipid droplets were present and the synthesis of tegumental secretory bodies was much reduced. The gastrodermal cells were severely affected, with swelling and degeneration of the mitochondria and the presence of autophagic vacuoles and lipid droplets. The granular endoplasmic reticulum was swollen and vesiculated and the cells contained few secretory bodies. Both the vitelline and testis follicles showed evidence of extensive cellular disruption and degeneration. This study confirms previous data indicating the potential flukicidal activity of OZ7

An ADI extrapolated Crank-Nicolson orthogonal spline collocation method for nonlinear reaction-diffusion systems: a computational study

An alternating direction implicit (ADI) orthogonal spline collocation (OSC) method is described for the approximate solution of a class of nonlinear reaction-diffusion systems. Its efficacy is demonstrated on the solution of well-known examples of such systems, specifically the Brusselator, Gray-Scott, Gierer-Meinhardt and Schnakenberg models, and comparisons are made with other numerical techniques considered in the literature. The new ADI method is based on an extrapolated Crank-Nicolson OSC method and is algebraically linear. It is efficient, requiring at each time level only $O({\cal N})$ operations where ${\cal N}$ is the number of unknowns. Moreover,it is shown to produce approximations which are of optimal global accuracy in various norms, and to possess superconvergence properties

Almost Block Diagonal Linear Systems: Sequential and Parallel Solution Techniques, and Applications

Almost block diagonal (ABD) linear systems arise in a variety of contexts, specifically in numerical methods for two-point boundary value problems for ordinary differential equations and in related partial differential equation problems. The stable, efficient sequential solution of ABDs has received much attention over the last fifteen years and the parallel solution more recently. We survey the fields of application with emphasis on how ABDs and bordered ABDs (BABDs) arise. We outline most known direct solution techniques, both sequential and parallel, and discuss the comparative efficiency of the parallel methods. Finally, we examine parallel iterative methods for solving BABD systems. Copyright (C) 2000 John Wiley & Sons, Ltd

Assessment of iron bioavailability from different bread making processes using an in vitro intestinal cell model

Myo-inositol hexakisphosphate (IP6), is the main iron chelator in cereals and bread. The aim of this study was to investigate the effect of three commercial baking processes (sourdough, conventional yeast and Chorleywood Bread Making Process (CBP)) on the IP6 content of wholemeal bread, its impact on iron uptake in Caco-2 cells and the predicted bioavailability of iron from these breads with added iron, simulating a mixed-meal. The sourdough process fully degraded IP6 whilst the CBP and conventional processes reduced it by 75% compared with wholemeal flour. The iron released in solution after a simulated digestion was 8-fold higher in sourdough bread than with others but no difference in cellular iron uptake was observed. Additionally, when iron was added to the different breads digestions only sourdough bread elicited a significant ferritin response in Caco-2 cells (4.8-fold compared to the other breads) suggesting that sourdough bread could contribute towards improved iron nutrition

Dietary Iron bioavailability: A simple model that can be used to derive country-specific dietary reference values for adult men and women

Background: Reference intakes for iron are derived from physiological requirements, with an assumed value for dietary iron absorption. A new approach to estimate iron bioavailability, calculated from iron intake, status, and requirements was used to set European dietary reference values, but the values obtained cannot be used for low- and middle-income countries where diets are very different. Objective: We aimed to test the feasibility of using the model developed from United Kingdom and Irish data to derive a value for dietary iron bioavailability in an African country, using data collected from women of child-bearing age in Benin. We also compared the effect of using estimates of iron losses made in the 1960s with more recent data for whole body iron losses. Methods: Dietary iron intake and serum ferritin (SF), together with physiological requirements of iron, were entered into the predictive model to estimate percentage iron absorption from the diet at different levels of iron status. Results: The results obtained from the 2 different methods for calculating physiological iron requirements were similar, except at low SF concentrations. At a SF value of 30 µg/L predicted iron absorption from the African maize-based diet was 6%, compared with 18% from a Western diet, and it remained low until the SF fell below 25 µg/L. Conclusions: We used the model to estimate percentage dietary iron absorption in 30 Beninese women. The predicted values agreed with results from earlier single meal isotope studies; therefore, we conclude that the model has potential for estimating dietary iron bioavailability in men and nonpregnant women consuming different diets in other countries