Spatiotemporal rainfall forecasting models for agricultural management

The main aim of the current PhD thesis is to develop forecast systems for Australia over medium time scales such as weekly, monthly, seasonal and annual for Agricultural planning. Common data driven algorithms in hydrology and climate studies including statistical methods, Artificial Intelligent (AI), machine learning and data mining techniques are sought to improve the rainfall prediction using historical data from land and oceans. First, spatiotemporal monthly rainfall forecasting is developed for south-eastern and eastern Australia using climatic and non-climatic variables. To improve model performance, climate regionalization and regionalization of the climate drivers are considered as initial steps for Neural Network model. The outcome of this study indicates that climate regionalization can improve performance of space-time prediction model for monthly rainfall in eastern and south-eastern Australia. The second part of the study investigates the stability and reliability of the lagged relationship between climate drivers and leading modes of seasonal rainfall in south-eastern Australia. Strength and polarity of correlation between climatic indices and leading mode of seasonal rainfall vary in different seasons and over time. This suggests using suitable lagged climatic indices rather than fixed climatic indices for each season leads to better rainfall predictions. Finally, annual rainfall, using Gene Expression Programming (GEP) method, significant predictors that were identified are Geographic Information System (GIS) variables, long-term mean and median annual rainfall, seasonal rainfall, previous annual rainfall and lagged climatic indices. The results indicate that the best predictors for modelling Australian annual rainfall in space-time are climatology (median and mean of rainfall) in comparison with GIS variables

Additives Increasing the Bone-Forming Potential around Calcium Phosphate Cements : Statin, Strontium and Silicon

More than one million people worldwide receive some kind of bone graft each year. Grafts are often needed following bone tumour removal or traumatic fractures to fill voids in the bone and to aid in the healing process. The most common method involves bone transplantation, in which bone tissue is taken from one site to fill the defect in another site. The procedure thus involves two surgeries, which leads to an increased risk of complications. New, synthetic graft materials that can be used to fill defects and minimise the complications associated with bone tissue harvesting are therefore necessary. The synthetic materials available today lack the inherent biological factors of bone that stimulate the bone regeneration process. Much of today’s research concerning synthetic bone graft materials aims to solve this issue and researchers have suggested several different strategies. The purpose of this thesis is to improve the performance of acidic calcium phosphate cements, which are materials used as synthetic bone grafts. By combining these cements with drugs or ion additives, local delivery could be achieved with the potential to stimulate bone formation. Two different combinations were attempted in this thesis: cement in combination with simvastatin, or cement in combination with strontium halide salts. Both simvastatin and strontium are known to positively affect bone formation. The efficacy of the cements with the additives was evaluated using different bone cell cultures. The results regarding simvastatin showed that the cement’s mechanical property was not affected upon drug loading, and that the drug was released by a diffusion-controlled mechanism. Moreover, results showed that simvastatin stimulated the bone-forming cells (osteoblasts) to produce more bone tissue, while it inhibited bone-degrading cells (osteoclasts) from degrading the cement. These findings suggest that simvastatin could aid in the bone regeneration process in the local area surrounding the cement. The main purpose of the study using strontium halide salts was to increase the cement’s X-ray contrast, which is a property used to monitor cement during injection. In addition, strontium is believed to positively affect bone cells. The X-ray contrast did increase after the addition of 10 wt% strontium bromide or strontium iodide, while the cell study results did not indicate any significant effects on the bone-forming cells. In the last section of this thesis, zebrafish were used as a model to evaluate bone formation upon treatment with degradation products from synthetic bone grafts. The zebrafish is a small organism with 70 % gene homology to humans; due to its transparency, fast development and ease of handling, it is an interesting model for high-throughput studies. Silicate, which is an ionic degradation product of many different bone substitute materials, was used as a proof-of-concept to visualise bone formation in these fish. The results showed an increased bone formation upon treatment with 0.625 μM silicate ions. The results suggest that this model could be used as a complement to bone cell culture studies in pre-clinical evaluations of the degradation products of bone substitute materials, thus helping researchers to design materials with degradation products that could stimulate bone formation

Long-term variability of the leading seasonal modes of rainfall in south-eastern Australia

AbstractKnowledge of temporal and spatial variability of climate and rainfall can improve agriculture production and can help to manage risks caused by climate variability. Available high-quality monthly rainfall data from the Australian Bureau of Meteorology for 1907–2011 was used to investigate the leading seasonal mode of the long-term rainfall variability over south-eastern and eastern Australia. Spatio-temporal variations of seasonal rainfall and their connection to oceanic-atmospheric predictors were analysed. The links between the first two Principal Components of rainfall of each season with lagged Southern Oscillation Index (SOI), Indian Ocean Dipole (IOD) and Southern Annular Mode (SAM) were season-dependent. The relationship between these climatic indices changed within both inter-seasonal and decadal time scales. Spring and winter rainfalls were continuously positively correlated with lagged (SOI). However, summer rainfall variations indicated negative correlations with lagged SOI which increase from 1970. The correlations between lagged SOI and autumn variations were weak and change to a stronger relationship from 1990. Correlations between lagged (IOD) which varied across all seasons have recently been increasing. Variations in rainfall across all seasons were highly correlated with Southern Annular Mode (SAM) with different signs. Overall, the relationship between predictors and seasonal rainfall has changed after 1970. The results of running correlations between leading modes of seasonal rainfall and lagged SOI, SAM, and IOD indices indicates non-stationary in these links. The relationships of climatic indices and leading modes of seasonal rainfall changed since 1970, with stronger evidence in case of IOD. Recent changes in the relationships between climatic indices and rainfall need to be considered in climate prediction systems. The results of this study suggests that improvement in statistical regional rainfall forecast system with fixed climatic indices for each season and region is achievable by using suitable seasonal and regional climatic indices

Simvastatin and zinc synergistically enhance osteoblasts activity and decrease the acute response of inflammatory cells.

Several ceramic biomaterials have been suggested as promising alternatives to autologous bone to replace or restore bone after trauma or disease. The osteoinductive potential of most scaffolds is often rather low by themselves and for this reason growth factors or drugs have been supplemented to these synthetic materials. Although some growth factors show good osteoinductive potential their drawback is their high cost and potential severe side effects. In this work the combination of the well-known drug simvastatin (SVA) and the inorganic element Zinc (Zn) is suggested as a potential additive to bone grafts in order to increase their bone regeneration/formation. MC3T3-E1 cells were cultured with Zn (10 and 25 µM) and SVA (0.25 and 0.4 µM) for 10 days to evaluate proliferation and differentiation, and for 22 days to evaluate secretion of calcium deposits. The combination of Zn (10 µM) and SVA (0.25 µM) significantly enhanced cell differentiation and mineralization in a synergetic manner. In addition, the release of reactive oxygen species (ROS) from primary human monocytes in contact with the same concentrations of Zn and SVA was evaluated by chemiluminescence. The combination of the additives decreased the release of ROS, although Zn and SVA separately caused opposite effects. This work shows that a new combination of additives can be used to increase the osteoinductive capacity of porous bioceramics