In this paper, we investigate the effects of small boundary perturbation on the laminar motion of a conducting fluid in a rectangular duct under applied transverse magnetic field. A small boundary perturbation of magnitude ǫ is applied on cross-section of the duct. Using the asymptotic analysis with respect to ǫ, we derive the effective model given by the explicit formulae for the velocity and ...

We prove an analogue of the magnetic nodal theorem on quantum graphs: the number of zeros of the nth eigenfunction of the Schrödinger operator on a quantum graph is related to the stability of the nth eigenvalue of the perturbation of the operator by magnetic potential. More precisely, we consider the nth eigenvalue as a function of the magnetic perturbation and show that its Morse index at zer...

The magnetic Prandtl number PrM is the ratio of viscosity to resistivity. In astrophysical disks the diffusion of angular momentum (viscosity) and magnetic fields (resistivity) are controlled by turbulence. Phenomenological models of the evolution of large scale poloidal magnetic fields in disks suggest that the turbulent magnetic Prandtl number PrM,T controls the rate of escape of vertical fie...

We study Schrödinger operators with periodic magnetic field in R2, in the case of irrational magnetic flux. Positive measure Cantor spectrum is generically expected in the presence of an electric potential. We show that, even without electric potential, the spectrum has positive measure if the magnetic field is a perturbation of a constant one. Introduction Magnetic Schrödinger operators have b...

A method is presented to measure the radio-frequency (RF) vector magnetic field inside an object using resonance imaging (MRI). Conventional “B 1 mapping” in MRI can proton co-rotating component (B + ) of RF produced by a transmit coil. Here ...

conclusion both techniques provided quantitatively consistent results of in vivo velocity vector fields in right internal carotid artery (rca). pc mri represented a good estimation of main flow patterns inside the vasculature, which seems to be acceptable for clinical use. however, limitations of each technique should be considered while interpreting results. subjects and methods mr imaging was...

Context. Evershed clouds (ECs) represent the most conspicuous variation of the Evershed flow in sunspot penumbrae. Aims. We determine the physical properties of ECs from high spatial and temporal resolution spectropolarimetric measurements. Methods. The Stokes profiles of four visible and three infrared spectral lines are subject to inversions based on simple one-component models as well as mor...