Stability of the toroidal magnetic field in stellar radiation zones

Understanding the stability of the magnetic field in radiation zones is of crucial importance for various processes in stellar interior like mixing, circulation and angular momentum transport. The stability properties of a star containing a prominent toroidal field in a radiation zone is investigated by means of a linear stability analysis in the Boussinesq approximation taking into account the effect of thermal conductivity. The growth rate of the instability is explicitly calculated and the effects of stable stratification and heat transport are discussed in detail. It is argued that the stabilizing influence of gravity can never entirely suppress the instability caused by electric currents in radiation zones although the stable stratification can significantly decrease the growth rate of instabilityComment: 12 pages, 3 figure

Anderson v. State, 135 Nev. Adv. Op. 56 (Nov. 27, 2019)

The Court determined that (1) when the government relies on the forfeiture exception of the Confrontation Clause to introduce a witness’s out-of-court statements, the burden of proof the litigant must meet is that of preponderance of the evidence; and (2) that a trial court does not abuse its discretion in denying a motion to substitute counsel and thereby violate the Sixth Amendment right to counsel when the trial court holds a Young hearing for each motion and enough evidence indicates there is not a complete breakdown in the attorney-client relationship

The Tayler instability of toroidal magnetic fields in a columnar gallium experiment

The nonaxisymmetric Tayler instability of toroidal magnetic fields due to axial electric currents is studied for conducting incompressible fluids between two coaxial cylinders without endplates. The inner cylinder is considered as so thin that even the limit of R_in \to 0 can be computed. The magnetic Prandtl number is varied over many orders of magnitudes but the azimuthal mode number of the perturbations is fixed to m=1. In the linear approximation the critical magnetic field amplitudes and the growth rates of the instability are determined for both resting and rotating cylinders. Without rotation the critical Hartmann numbers do {\em not} depend on the magnetic Prandtl number but this is not true for the growth rates. For given product of viscosity and magnetic diffusivity the growth rates for small and large magnetic Prandtl number are much smaller than those for Pm=1. For gallium under the influence of a magnetic field at the outer cylinder of 1 kG the resulting growth time is 5 s. The minimum electric current through a container of 10 cm diameter to excite the kink-type instability is 3.20 kA. For a rotating container both the critical magnetic field and the related growth times are larger than for the resting column.Comment: 7 pages, 9 figures, submitted to Astron. Nach

Optimizing the Allocation of Vaccines in the Presence of Multiple Strains of the Influenza Virus

During the annual flu season, multiple strains of the influenza virus are often present within a population. It is a significant challenge for health care administrators to determine the most effective allocation of two different vaccines to combat the various strains when treating the public. We employ a mathematical model, a system of differential equations, to find a strategy for vaccinating a population in order to minimize the number of infected individuals. We consider various strengths of transmission of the disease, availability of vaccine doses, vaccination rates, and other model parameters. This research may lead to more effective health care policies for vaccine administration

Tayler instability of toroidal magnetic fields in MHD Taylor-Couette flows

The nonaxisymmetric 'kink-type' Tayler instability (TI) of toroidal magnetic fields is studied for conducting incompressible fluids of uniform density between two infinitely long cylinders rotating around the same axis. It is shown that for resting cylinders the critical Hartmann number for the unstable modes does not depend on Pm. By rigid rotation the instability is suppressed where the critical ratio of the rotation velocity and the Alfven velocity of the field (only) slightly depends on the magnetic Prandtl number Pm. For Pm=1 the rotational quenching of TI takes its maximum. Rotation laws with negative shear (i.e. d\Omega/dR<0) strongly destabilize the toroidal field if the rotation is not too fast. For sufficiently high Reynolds numbers of rotation the suppression of the nonaxisymmetric magnetic instability always dominates. The angular momentum transport of the instability is anticorrelated with the shear so that an eddy viscosity can be defined which proves to be positive. For negative shear the Maxwell stress of the perturbations remarkably contributes to the angular momentum transport. We have also shown the possibility of laboratory TI experiments with a wide-gap container filled with fluid metals like sodium or gallium. Even the effect of the rotational stabilization can be reproduced in the laboratory with electric currents of only a few kAmp.Comment: 9 pages, 11 figures, sub

Cenozoic sedimentary and volcanic rocks of New Zealand: A reference volume of lithology, age and paleoenvironments with maps (PMAPs) and database.

This volume presents descriptive geological data and text about each Cenozoic sedimentary and volcanic geological unit to formation and member level (in some cases) exposed on land in New Zealand, including their lithology, stratigraphic age and inferred environment of deposition or emplacement. These data are illustrated as two types of PMAPS: a present-day paleoenvironment map of New Zealand; and as restored paleoenvironment maps, one for each million years from 65 Ma to the present. These information and data underpin the development of a new Cenozoic paleogeographical model of New Zealand