Spontaneous rotational inversion in Phycomyces

The filamentary fungus Phycomyces blakesleeanus undergoes a series of remarkable transitions during aerial growth. During what is known as the Stage IV growth phase, the fungus extends while rotating in a counterclockwise manner when viewed from above (Stage IVa) and then, while continuing to grow, spontaneously reverses to a clockwise rotation (Stage IVb). This phase lasts for 24 - 48 hours and is sometimes followed by yet another reversal (Stage IVc) before the overall growth ends. Here, we propose a continuum mechanical model of this entire process using nonlinear, anisotropic, elasticity and show how helical anisotropy associated with the cell wall structure can induce spontaneous rotation and, under appropriate circumstances, the observed reversal of rotational handedness

Rotation, inversion, and perversion in anisotropic elastic cylindrical tubes and membranes

Cylindrical tubes and membranes are universal structural elements found in biology and engineering over a wide range of scales. Working in the framework of nonlinear elasticity we consider the possible deformations of elastic cylindrical shells reinforced by one or two families of anisotropic fibers. We consider both small and large deformations and the reduction from thick cylindrical shells (tubes) to thin shells (cylindrical membranes). In particular, a number of universal regimes can be identified including the possibility of inversion and perversion of rotation

Nonlinear Morphoelastic Plates I: Genesis of Residual Stress

Volumetric growth of an elastic body may give rise to residual stress. Here a rigorous analysis of the residual strains and stresses generated by growth in the axisymmetric Kirchhoff plate is given. Balance equations are derived via the global constraint principle, growth is incorporated via a multiplicative decomposition of the deformation gradient, and the system is closed by a response function. The particular case of a compressible neo-Hookean material is analyzed and the existence of residually stressed states is established

Nonlinear morphoelastic plates II: exodus to buckled states

Morphoelasticity is the theory of growing elastic materials. This theory is based on the multiple decomposition of the deformation gradient and provides a formulation of the deformation and stresses induced by growth. Following a companion paper, a general theory of growing nonlinear elastic Kirchhoff plate is described. First, a complete geometric description of incompatibility with simple examples is given. Second, the stability of growing Kirchhoff plates is analyzed

Transport in Almost Integrable Models: Perturbed Heisenberg Chains

The heat conductivity kappa(T) of integrable models, like the one-dimensional spin-1/2 nearest-neighbor Heisenberg model, is infinite even at finite temperatures as a consequence of the conservation laws associated with integrability. Small perturbations lead to finite but large transport coefficients which we calculate perturbatively using exact diagonalization and moment expansions. We show that there are two different classes of perturbations. While an interchain coupling of strength J_perp leads to kappa(T) propto 1/J_perp^2 as expected from simple golden-rule arguments, we obtain a much larger kappa(T) propto 1/J'^4 for a weak next-nearest neighbor interaction J'. This can be explained by a new approximate conservation law of the J-J' Heisenberg chain.Comment: 4 pages, several minor modifications, title change

Manifestations of Drag Reduction by Polymer Additives in Decaying, Homogeneous, Isotropic Turbulence

The existence of drag reduction by polymer additives, well established for wall-bounded turbulent flows, is controversial in homogeneous, isotropic turbulence. To settle this controversy we carry out a high-resolution direct numerical simulation (DNS) of decaying, homogeneous, isotropic turbulence with polymer additives. Our study reveals clear manifestations of drag-reduction-type phenomena: On the addition of polymers to the turbulent fluid we obtain a reduction in the energy dissipation rate, a significant modification of the fluid energy spectrum especially in the deep-dissipation range, a suppression of small-scale intermittency, and a decrease in small-scale vorticity filaments.Comment: 4 pages, 3 figure

Organised crime and public sector corruption

Foreword: In 2006, the Australian Government introduced the Anti-money Laundering and Counter-Terrorism Financing Act 2006 (Cth) which increased regulatory controls over businesses potentially able to facilitate organised criminal activities such as money laundering. The implementation of tougher legislation and associated law enforcement interventions may result in criminal organisations adjusting their tactics in order to continue their activities without detection. In this paper, the risk and potential impact of tactical displacement by organised criminals is discussed with regard to the potential for increased attempts by organised crime groups to corrupt public servants. There is a paucity of research exploring the nature and extent of public sector corruption committed by organised crime groups. This discussion is informed by literature on ‘crime scripts’ originally developed by Cornish (1994) and the 5I’s crime prevention framework developed by Ekblom (2011). Making use of public-source information about the commission of such crimes, as exemplified in two recent corruption cases, some intervention strategies are proposed that may be effective in reducing the risks of corruption of public sector officials by organised crime groups in Australia