Beltrami States for Compressible Barotropic Flows

Beltrami states for compressible barotropic flows are deduced by minimizing the total kinetic energy while keeping the total helicity constant. A Hamiltonian basis for these Beltrami states is also sketched

Motion of a Vortex Filament in the Local Induction Approximation: Reformulation of the Da Rios-Betchov Equations in the Extrinsic Filament Coordinate Space

In recognition of the highly non-trivial task of computation of the inverse Hasimoto transformation mapping the intrinsic geometric parameter space onto the extrinsic vortex filament coordinate space a reformulation of the Da Rios-Betchov equations in the latter space is given. The nonlinear localized vortex filament structure solution given by the present formulation is in detailed agreement with the Betchov-Hasimoto solution in the small-amplitude limit and is also in qualitative agreement with laboratory experiment observations of helical-twist solitary waves propagating on concentrated vortices in rotating fluids. The present formulation also provides for a discernible effect of the slipping motion of a vortex filament on the vortex evolution

Divorticity and Dihelicity In Two-Dimensional Hydrodynamics

A framework is developed based on the concepts of {\it divorticity} ${\textbf B}$(\equiv\nabla\times\bfo, \bfo being the vorticity) and \textit{dihelicity} g \lp \equiv\bfv\cdot\textbf{B}\rp for discussing the theoretical structure underlying two-dimensional (2D) hydrodynamics. This formulation leads to the global and Lagrange invariants that could impose significant constraints on the evolution of divorticity lines in 2D hydrodynamics

Screened alpha decay in dense astrophysical plasmas and magnetars

This paper shows that ultrastrong magnetic fields (such as those of magnetars) and dense astrophysical plasmas can reduce the half life of alpha decaying nuclei by many orders of magnitude. In such environments the conventional Geiger-Nuttall law is modifed so that all half lives are shifted to dramatically lower values. Those effects, which have never been investigated before, may have significant implications on the universal abundances of heavy radioactive elements and the cosmochronological methods that rely on them.Comment: 15 RevTex pages, 3 ps figures (minor revision). This work was presented during the conference ''Supernova, 10 years of SN1993J'', April 2003, Valencia, Spain. Accepted for publication in Phys.Rev.

Characteristics of plasma Beltrami states

Beltrami states in several models of plasma dynamics – incompressible magnetohydrodynamic (MHD) model, barotropic compressible MHD model, incompressible Hall MHD model, barotropic compressible Hall MHD model, electron MHD model, barotropic compressible Hall MHD with electron inertia model, are considered. Notwithstanding the diversity of the physics underlying the various models, the Beltrami states are shown to exhibit some common features like – certain robustness with respect to the plasma compressibility effects (albeit in the barotropy assumption), the Bernoulli condition. The Beltrami states for these models are deduced by minimizing the appropriate total energy while keeping the appropriate total helicity constant

Thomas-Fermi model for an atom in a very strong magnetic field: thermal effects

Thermal effects on the Thomas-Fermi model for atoms in a very strong magnetic field are considered. The binding energy of the atom is calculated with the thermal effects taken into account

Zonal shear flows with a free surface: Hamiltonian formulation and linear and nonlinear stability

General theoretical results via a Hamiltonian formulation are developed for zonal shear flows with the inclusion of the vortex stretching effect of the deformed free surface (equivalent barotropic model). These results include a generalization of the Flierl-Stern-Whitehead zero angular momentum theorem for localized nonlinear structures (whether or not on a ß-plane), and sufficient conditions for linear and nonlinear stability in the Liapunov sense-the latter are given as estimates in terms of an L2-type perturbation norm which are global in time and are derived via bounds on the equilibrium potential vorticity gradient

Erratum to "Motion of a vortex filament in the local induction approximation : reformulation of the Da Rios-Betchov equations in the extrinsic filament coordinate space"

The large-scale application of one of the most promising clean and renewable sources of energy, hydrogen fuel cells, still awaits efficient and cost-effective electrocatalysts for the oxygen reduction reaction (ORR) occurring on the cathode. We demonstrate that truly rational design renders electrocatalysts possessing both qualities. By unifying the knowledge on surface morphology, composition, electronic structure, and reactivity, we solve that trimetallic sandwich-like structures are an excellent choice for optimization. Their constituting species are expected to couple synergistically yielding reaction-environment stability, cost-effectiveness, and tunable reactivity. This cooperative-action concept enabled us to predict two advantageous ORR electrocatalysts: Pd/Fe/W(110) and Au/Ru/W(110). Density functional theory calculations of the reaction free-energy diagrams suggest that these materials are more active toward ORR than the so-far best Pt-based catalysts. Our designing concept advances also a general approach for engineering advanced materials. © 2012 American Chemical Society

Generalized point-vortex model for the motion of a dipole-vortex on the β-plane

In this paper, several refinements of the point-vortex model to describe the motion of a dipole vortex on the ß-plane are undertaken. These include the effects of finite ß, squeezing and stretching of the dipole vortices due to bottom topography, and effects of the secondary vorticity field associated with the advection of the ambient fluid