Diffusion in a generalized Rubinstein-Duke model of electrophoresis with kinematic disorder

Using a generalized Rubinstein-Duke model we prove rigorously that kinematic disorder leaves the prediction of standard reptation theory for the scaling of the diffusion constant in the limit for long polymer chains $D \propto L^{-2}$ unaffected. Based on an analytical calculation as well as Monte Carlo simulations we predict kinematic disorder to affect the center of mass diffusion constant of an entangled polymer in the limit for long chains by the same factor as single particle diffusion in a random barrier model.Comment: 29 pages, 3 figures, submitted to PR

A Proposed Expert System for the Management of Lucerne - LATIS

Research and Development/Tech Change/Emerging Technologies,

Climate change effects on pasture systems in south-eastern Australia.

Climate change projections for Australia predict increasing temperatures, changes to rainfall patterns, and elevated atmospheric carbon dioxide (CO2) concentrations. The aims of this study were to predict plant production responses to elevated CO2 concentrations using the SGS Pasture Model and DairyMod, and then to quantify the effects of climate change scenarios for 2030 and 2070 on predicted pasture growth, species composition, and soil moisture conditions of 5 existing pasture systems in climates ranging from cool temperate to subtropical, relative to a historical baseline. Three future climate scenarios were created for each site by adjusting historical climate data according to temperature and rainfall change projections for 2030, 2070 mid-and 2070 high-emission scenarios, using output from the CSIRO Mark 3 global climate model. In the absence of other climate changes, mean annual pasture production at an elevated CO2 concentration of 550 ppm was predicted to be 24-29% higher than at 380 ppm CO2 in temperate (C-3) species-dominant pastures in southern Australia, with lower mean responses in a mixed C-3/C-4 pasture at Barraba in northern New South Wales (17%) and in a C-4 pasture at Mutdapilly in south-eastern Queensland (9%). In the future climate scenarios at the Barraba and Mutdapilly sites in subtropical and subhumid climates, respectively, where climate projections indicated warming of up to 4.4 degrees C, with little change in annual rainfall, modelling predicted increased pasture production and a shift towards C-4 species dominance. In Mediterranean, temperate, and cool temperate climates, climate change projections indicated warming of up to 3.3 degrees C, with annual rainfall reduced by up to 28%. Under future climate scenarios at Wagga Wagga, NSW, and Ellinbank, Victoria, our study predicted increased winter and early spring pasture growth rates, but this was counteracted by a predicted shorter spring growing season, with annual pasture production higher than the baseline under the 2030 climate scenario, but reduced by up to 19% under the 2070 high scenario. In a cool temperate environment at Elliott, Tasmania, annual production was higher than the baseline in all 3 future climate scenarios, but highest in the 2070 mid scenario. At the Wagga Wagga, Ellinbank, and Elliott sites the effect of rainfall declines on pasture production was moderated by a predicted reduction in drainage below the root zone and, at Ellinbank, the use of deeper rooted plant systems was shown to be an effective adaptation to mitigate some of the effect of lower rainfall

SGS Animal Production Theme: effect of grazing system on animal productivity and sustainability across southern Australia

The effects of various grazing management systems on sown, naturalised, and native pastures were studied at 6 different locations in the temperate high rainfall zone (HRZ, >600 mm rainfall/year) of southern Australia, as part of the Sustainable Grazing Systems (SGS) Program. The treatments examined had different pasture species and fertiliser management, with grazing method ranging from set stocking (continuous grazing) to rotation with rests based on pre- and post-grazing herbage mass or season and plant phenology. Sites were located at: Albany, Western Australia; Manilla, Barraba, Nundle, New South Wales; (grazed by wethers); and Carcoar, New South Wales; Maindample, Ruffy, north-east Victoria; Vasey, western Victoria; (grazed by ewes and lambs). Grazing method significantly (P0.05), when a growing season index (P0.05) factors included solar radiation, annual average temperature, fertiliser applied in the current year, and average annual perennial and broadleaf percent composition. The implications of these data for productivity and sustainability (as assessed by perenniality and water use) were encouraging. Generally, there were positive relationships between increased stocking rate and the probability of achieving a zero mm soil water surplus in winter, and between increased productivity and the proportion of perennial grass species where extremes of treatments were compared at each site. The results indicate that stocking rate can be increased without jeopardising sustainability, that grazing management can bring about more sustainable pastures, that there is scope to increase productivity particularly through increasing soil fertility, and growing season length can be used to predict potential carrying capacity. These are positive outcomes that graziers in the HRZ of southern Australia can use to enhance productivity (thus profitability) and sustainability