Dynamical aspects of fragmentation

In this short communication we address the problem of reducibility in a highly excited Lennard-Jones system. We show that the probability of emitting $n$ fragments can be described in terms of a single probability through the binomial expression. However, the Arrhenius law does not hold and the process can be viewed as a mixture of sequential and simultaneous fragmentation events.Comment: Proceedings for VI Latin American Symposium on Nuclear Physics and Applications, Iguazu, Argentina (2005). To be published in Acta Phys. Hung.

Dynamical properties of constrained drops

In this communication we analyze the behavior of excited drops contained in spherical volumes. We study different properties of the dynamical systems i.e. the maximum Lyapunov exponent MLE, the asymptotic distance in momentum space $d_{\infty}$ andthe normalized variance of the maximum fragment NVM. It is shown that the constrained systems behaves as undergoing a first order phase transition at low densities while as a second order one at high densities. The transition from liquid-like to vapor-like behavior is signaled both by the caloric curves, thermal response functions and the MLE. The relationship between $MLE,d_{\infty}$, and the CC is explored.Comment: 7 pages, 9 figures in a two column forma

Mediating boundaries between knowledge and knowing: ICT and R4D praxis

Research for development (R4D) praxis (theory-informed practical action) can be underpinned by the use of Information and Communication Technologies (ICTs) which, it is claimed, provide opportunities for knowledge working and sharing. Such a framing implicitly or explicitly constructs a boundary around knowledge as reified, or commodified – or at least able to be stabilized for a period of time (first order knowledge). In contrast ‘third-generation knowledge’ emphasizes the social nature of learning and knowledge-making; this reframes knowledge as a negotiated social practice, thus constructing a different system boundary. This paper offers critical reflections on the use of a wiki as a data repository and mediating technical platform as part of innovating in R4D praxis. A sustainable social learning process was sought that fostered an emergent community of practice among biophysical and social researchers acting for the first time as R4D co-researchers. Over time the technologically mediated element of the learning system was judged to have failed. This inquiry asks: How can learning system design cultivate learning opportunities and respond to learning challenges in an online environment to support R4D practice? Confining critical reflection to the online learning experience alone ignores the wider context in which knowledge work took place; therefore the institutional setting is also considered

Practical lessons for winning support for radical transport projects

This paper proposes that while many plans and solutions to the transport problems of the 21st Century have been mooted, very few have succeeded in significantly improving the situation within Europe. It is suggested that many schemes face problems at the project implementation stage due to adverse public and/or political reaction. This paper incorporates a series of vignettes, several of which are based on indepth interviews with practitioners directly involved in the implementation of 'radical'transport schemes from around the world in an attempt to draw lessons as to how they overcame this, not least in terms of how the implementation of alternative strategies by European policy-makers could be shaped and adopted world-wide

Use of Water Balance Models to Examine the role of Climate in Annual Legume Decline in Southern Australia

fhe content of annual medic and subclover (Trifo/ium subterraneum) in rasture Leys has been declining in southern Australia over the last decade. The models GROWEST and ASW were used to simulate available soil water, dry matter yield and seed production of a temperate annual pasture legume using actual climatic data for Forbes in 1987-89. GROWEST was also used to predict DM and seed production and the site and composition of the seed bank for the period 1957-89 for the subclover cultivars Dalkeith and Woogenellup. The period 1979-82 consisted of below average seasons with DM yields restricted to below 3000 kg/ha/year. It was largely after this period of drought that clover decline was first observed to be. a problem in eastern Australia in areas reliant on soft-seeded cultivars such as Woogene!lup. GROWEST and the ASW model are a start in developing useful predictive tools so that optimum hard seed levels, maturity and a range of other parameters can be predicted for different environments

Expansion dynamics of Lennard-Jones systems

The dynamics of the expansion of a Lennard-Jones system, initially confined at high density and subsequently expanding freely in the vacuum, is confronted to an expanding statistical ensemble, derived in the diluted quasi-ideal Boltzmann approximation. The description proves to be fairly accurate at predicting average one-body global observables, but important deviations are observed in the configuration-space structure of the events. Possible implications for finite expanding physical systems are outlined