Bistability and hysteresis of dipolar dynamos generated by turbulent convection in rotating spherical shells

Bistability and hysteresis of magnetohydrodynamic dipolar dynamos generated by turbulent convection in rotating spherical fluid shells is demonstrated. Hysteresis appears as a transition between two distinct regimes of dipolar dynamos with rather different properties including a pronounced difference in the amplitude of the axisymmetric poloidal field component and in the form of the differential rotation. The bistability occurs from the onset of dynamo action up to about 9 times the critical value of the Rayleigh number for onset of convection and over a wide range of values of the ordinary and the magnetic Prandtl numbers including the value unity

A local defect resonance for linear and nonlinear ultrasonic thermography

An efficient wave-defect interaction is the key to a high thermal response of flaws in ultrasonic thermography. To selectively enhance defect vibrations a concept of local defect resonance is developed and applied to ultrasonic activation of defects. The frequency match between the defect resonance frequency and the probing ultrasonic wave results in a substantial rise of a local defect temperature. The defect resonance is accompanied by depletion of the excitation frequency vibration due to nonlinear frequency conversion to higher harmonics. The local generation of higher frequency components provides a high thermal defect response in such an acoustically nonlinear thermography mode

Financing health care in high-income countries

The main lesson from the experience of high-income countries with health care financing is a simple one: financing reforms should support the ultimate goal of universal coverage. Most high-income countries started with voluntary health insurance systems, which were then gradually extended to compulsory social insurance for certain groups and finally reached universal coverage, either as nationwide social health insurance schemes or as tax-financed national health services. The risk pooling and prepayment functions are essential. Moreover, the revenue collection mechanisms, whether as general tax revenues or payroll taxes, are secondary to the basic object of providing financial protection through effective risk pooling mechanisms. The experience of high-income countries indicates that private health insurance, medical savings accounts, and other forms of private resource collection are supplementary methods for increasing universal coverage.

Aerobee 150 structural and aerodynamic pitch coupling

Aerobee 150 structural and aerodynamic pitch coupling failure analysis based on flight performance data reductio

Dynamo Effects Near The Transition from Solar to Anti-Solar Differential Rotation

Numerical MHD simulations play increasingly important role for understanding mechanisms of stellar magnetism. We present simulations of convection and dynamos in density-stratified rotating spherical fluid shells. We employ a new 3D simulation code for the solution of a physically consistent anelastic model of the process with a minimum number of parameters. The reported dynamo simulations extend into a "buoyancy-dominated" regime where the buoyancy forcing is dominant while the Coriolis force is no longer balanced by pressure gradients and strong anti-solar differential rotation develops as a result. We find that the self-generated magnetic fields, despite being relatively weak, are able to reverse the direction of differential rotation from anti-solar to solar-like. We also find that convection flows in this regime are significantly stronger in the polar regions than in the equatorial region, leading to non-oscillatory dipole-dominated dynamo solutions, and to concentration of magnetic field in the polar regions. We observe that convection has different morphology in the inner and at the outer part of the convection zone simultaneously such that organized geostrophic convection columns are hidden below a near-surface layer of well-mixed highly-chaotic convection. While we focus the attention on the buoyancy-dominated regime, we also demonstrate that conical differential rotation profiles and persistent regular dynamo oscillations can be obtained in the parameter space of the rotation-dominated regime even within this minimal model.Comment: Published in the Astrophysical Journa

A compendium of NASA Aerobee sounding rocket launchings for 1966

Compendium of Aerobee sounding rocket launchings for 196