Influence of irradiant energy on degree of conversion, polymerization rate and shrinkage stress in an experimental resin composite system

Objective. This study evaluated the degree of conversion (DC), maximum rate of cure (R(p)(max)), and polymerization stress (PS) developed by an experimental dental composite subjected to different irradiant energies (3,6,12, 24, or 48J/cm(2)) under constant irradiance (500 mw/cm(2)). Methods. DC and R(p)(max) were monitored for 10 min on the bottom surface of 2-mm thick disks and on 150-mu m thick films (representing the top of the specimen) using ATR-FTIR. PS was monitored for 10 min in 2-mm thick disks bonded to two glass rods (O = 5 mm) attached to a universal testing machine. One-way ANOVA/Tukey tests were used and differences in DC and R(p)(max) between top and bottom surfaces were examined using Student`s t-test. Statistical testing was performed at a pre-set alpha of 0.05. Results. For a given surface, DC showed differences among all groups, except at the top between 24 and 48 J/cm(2). R(p)(max) was similar among all groups at the same surface and statistically higher at the top surface. PS also showed significant differences among all groups. Data for 48 J/cm(2) were not obtained due to specimen failure at the glass/composite interface. Significance. Increases in irradiant exposure led to significant increases in DC and PS, but had no effect on R(p)(max) (c) 2008 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Management, conservation and farming of saltwater crocodiles: An Australian case study of sustainable commercial use

Opinions differ about what types of policies are likely to be most effective in conserving wildlife species. For example, the Convention on International Trade in Endangered Species of Wild Flora and Fauna (CITES) is based on the premise that curbing the commercial use of endangered species favours their conservation, whereas the Convention on Biological Diversity envisages the possibility that such use may contribute to the conservation of species. In Australia, as illustrated in the case of the saltwater crocodile (Crocodylus porosus), the governments of the Northern Territory and Western Australia have favoured the latter policy in recent years, whereas Queensland has favoured the former approach. The saltwater crocodile management plan of the Northern Territory provides an instructive case study of the consequences of adopting a commercial use strategy to promote wildlife conservation. The methodology used in this study, which involves a survey of crocodile farm managers and managers of cattle properties in the Northern Territory as well as secondary data, is outlined, after providing background on the conservation status of saltwater crocodiles in Australia and the saltwater crocodile management plan of the Northern Territory. In the results section, after outlining the nature and structure of the Northern Territory crocodile farming industry, evidence is presented on whether or not the crocodile management plan of the Northern Territory encourages pastoralists to conserve crocodiles on their properties. This study concludes with a discussion of the overall conservation effectiveness of the crocodile management scheme of the Northern Territory and considers its possible implications for saltwater crocodile management in areas of Asia where the species occurs.

Sustainable agriculture

This paper provides an overview of concepts of sustainable agriculture and possible methods of attaining sustainability of agricultural yields and production. Reasons are given as to why modern industrialised agriculture might be less sustainable in terms of yields than traditional agriculture. The question of whether organic agriculture is likely to be more sustainable than non-organic agriculture is considered as well as organic agriculture’s likely impact on wild biodiversity. The impact of the development of agriculture on wild biodiversity is assessed because some environmentalists see the conservation of wild biodiversity as an important ingredient of sustainable development. However, there is a policy conflict between conservationist groups. Some see intensive agriculture (including silviculture) as favourable to the conservation of wild biodiversity whereas others oppose such production methods as being unfavourable to wild biodiversity conservation. Reasons why modern industrialised agricultural systems are so widely adopted (and continue to be adopted) despite their apparent lack of sustainability are suggested. Market systems may tend to lock producers into unsustainable production methods.

Modelling basin level allocation of water in the Murray-Darling Basin in a world of uncertainty, Murray-Darling Program Working Papers WPM05-1, Risk and Sustainable Management Group, 8 February 2005

Abstract: The Murray-Darling Basin comprises over 1 million km2; it lies within four states and one territory; and over 12, 800 GL of irrigation water is used to produce over 40% of the nation's gross value of agricultural production. This production is used by a diverse collection of some-times mutually exclusive commodities (e.g. pasture; stone fruit; grapes; cotton and field crops). The supply of water for irrigation is subject to climatic and policy uncertainty. Variable inflows mean that water property rights do not provide a guaranteed supply. With increasing public scrutiny and environmental issues facing irrigators, greater pressure is being placed on this finite resource. The uncertainty of the water supply, water quality (salinity), combined with where water is utilised, while attempting to maximising return for investment makes for an interesting research field. The utilisation and comparison of a GAMS and Excel based modelling approach has been used to ask: where should we allocate water?; amongst what commodities?; and how does this affect both the quantity of water and the quality of water along the Murray-Darling river system?