Measurement of local effective diffusivity in heterogeneous biofilms

Effective Diffusivity in Baroclinic Flow

Large-scale chaotic stirring stretches tracer contours into filaments containing fine spatial scales until smallscale diffusive processes dissipate tracer variance. Quantification of tracer transport in such circumstances is possible through the use of Nakamura’s ‘‘effective diffusivity’’ diagnostics, which make clear the controlling role of stirring, rather than small-scale dissipation, in lar...

Direct measurement of effective magnetic diffusivity in turbulent flow of liquid sodium.

The first direct measurements of effective magnetic diffusivity in turbulent flow of electroconductive fluids (the so-called β effect) under the magnetic Reynolds number Rm≫1 are reported. The measurements are performed in a nonstationary turbulent flow of liquid sodium, generated in a closed toroidal channel. The peak level of the Reynolds number reached Re≈3×10(6), which corresponds to the ma...

Local measurements of thermal diffusivity in homogeneous and heterogeneous samples by photoreflectance microscopy

We present a variant of the traditional photoreflectance microscopy. It allows thermal diffusivity measurements on samples as small as a few tens of microns, possibly of mediocre surface quality. In "photoreflectance microscopy", the sample is heated by a modulated laser beam focused by a microscope. A dc probe beam of lower intensity, also focused on the sample by the microscope, is reflected ...

Electromagnetic phenomena in heterogeneous media: Effective properties and local behavior

Effective Isentropic Diffusivity of Tropospheric Transport

Tropospheric transport can be described qualitatively by the slow mean diabatic circulation and rapid isentropic mixing, yet a quantitative understanding of the transport circulation is complicated, as nearly half of the isentropic surfaces in the troposphere frequently intersect the ground. A theoretical framework for the effective isentropic diffusivity of tropospheric transport is presented....