Magnetic compressibility and ion-temperature-gradient-driven microinstabilities in magnetically confined plasmas

The electromagnetic theory of the strongly driven ion-temperature-gradient (ITG) instability in magnetically confined toroidal plasmas is developed. Stabilizing and destabilizing effects are identified, and a critical $\beta_{e}$ (the ratio of the electron to magnetic pressure) for stabilization of the toroidal branch of the mode is calculated for magnetic equilibria independent of the coordinate along the magnetic field. Its scaling is $\beta_{e}\sim L_{Te}/R,$ where $L_{Te}$ is the characteristic electron temperature gradient length, and $R$ the major radius of the torus. We conjecture that a fast particle population can cause a similar stabilization due to its contribution to the equilibrium pressure gradient. For sheared equilibria, the boundary of marginal stability of the electromagnetic correction to the electrostatic mode is also given. For a general magnetic equilibrium, we find a critical length (for electromagnetic stabilization) of the extent of the unfavourable curvature along the magnetic field. This is a decreasing function of the local magnetic shear

Ibis and the city: bogan kitsch and the avian revisualization of Sydney

The Australian White Ibis (Ibis) ( Threskiornis molucca) is one of three endemic Ibis species in Australia. In a short time frame beginning in the 1970s, this species has moved from inland waterways to urban centres along the eastern and southeastern seaboards, Darwin and the Western Australian southwest. Today Ibis are at home in cities across the country, where they thrive on the food waste, water resources and nesting sites supplied by humans. In this article, the authors focus on Sydney to argue that the physical and cultural inroads of Ibis, and the birds’ urban homeliness, are resignifying urban surfaces and the multispecies ecologies in which contemporary Australians operate. They explore how the very physical and sensory presence of Ibis disrupts the assumptions of many urban Australians, and visitors from overseas, that cities are human-centric or human-dominant, non-hybrid assemblages. They also introduce to this discussion of disrupted human expectations a cultural parallel, namely, the recent rise of Ibis in popular culture as an icon-in-the-making of the nation and as a totem of the modern Australian city itself. This trend exemplifies an avian-led revisualization of urban spaces, and is notable for its visual appeals to Ibis kitsch, and to working class or ‘bogan’ sensibilities that assert their place alongside cosmopolitan visions of being Australian. Sometimes kitsch Ibis imagery erupts across the urban landscape, as occurs with many Ibis murals. At other times it infiltrates daily life on clothing, on football club, university and business logos, as tattoos on people’s skin, and as words in daily idiom, confirmed by terms such as ‘picnic pirates’, ‘tip turkeys’ and ‘bin chickens’. The article uses a visual vignette methodology to chart Ibis moves into Sydney and the realms of representation alike, and thus to reveal how new zoöpolitical entanglements are being made in the 21st century. </jats:p

Efficient optimisation of structures using tabu search

This paper presents a novel approach to the optimisation of structures using a Tabu search (TS) method. TS is a metaheuristic which is used to guide local search methods towards a globally optimal solution by using flexible memory cycles of differing time spans. Results are presented for the well established ten bar truss problem and compared to results published in the literature. In the first example a truss is optimised to minimise mass and the results compared to results obtained using an alternative TS implementation. In the second example, the problem has multiple objectives that are compounded into a single objective function value using game theory. In general the results demonstrate that the TS method is capable of solving structural optimisation problems at least as efficiently as other numerical optimisation approaches

Object-Oriented Paradigms for Modelling Vascular\ud Tumour Growth: a Case Study

Motivated by a family of related hybrid multiscale models, we have built an object-oriented framework for developing and implementing multiscale models of vascular tumour growth. The models are implemented in our framework as a case study to highlight how object-oriented programming techniques and good object-oriented design may be used effectively to develop hybrid multiscale models of vascular tumour growth. The intention is that this paper will serve as a useful reference for researchers modelling complex biological systems and that these researchers will employ some of the techniques presented herein in their own projects

Transient abnormal myelopoesis in an infant with Down syndrome

No Abstract

Dynamical Phase Transitions In Driven Integrate-And-Fire Neurons

We explore the dynamics of an integrate-and-fire neuron with an oscillatory stimulus. The frustration due to the competition between the neuron's natural firing period and that of the oscillatory rhythm, leads to a rich structure of asymptotic phase locking patterns and ordering dynamics. The phase transitions between these states can be classified as either tangent or discontinuous bifurcations, each with its own characteristic scaling laws. The discontinuous bifurcations exhibit a new kind of phase transition that may be viewed as intermediate between continuous and first order, while tangent bifurcations behave like continuous transitions with a diverging coherence scale.Comment: 4 pages, 5 figure