We have measured the resistivity of epitaxial YBa2Cu3O7?δ thin film as a function of temperature, current density and the magnetic field up to 8 T. The current density dependence of the effective activation energy exhibits a slight increase in the low current density range below 103 A/cm2 and a logarithmic decline in higher current density with increasing current density. The magnetic field dependence of the effective activation energy showed a crossover of vortex state from a quasi-2D for H//ab-plane to a 3D line liquid state for H//c-axis. The possible dissipation mechanisms responsible for the ln H dependence of the effective activation energy were discussed. 相似文献
Rotary biofilm contactor (RBC) is a reactor consisting of plastic discs that act as supports for micro-organisms. The discs are mounted on a horizontal shaft and placed in a medium-containing vessel. During nitrogen-rich growth phase, mycelia ofRhizopus oryzae ATCC 20344 grew on and around the discs and formed the “biofilm” of self-immobilized cells on the surface of the plastic discs. During the fermentation phase, the discs are slowly rotated, and the biofilms are exposed to the medium and the air space, alternately. With RBC, in the presence of CaCO3,Rhizopus biofilm consumes glucose and produces fumaric acid with a volumetric productivity of 3.78 g/L/h within 24 h. The volumetric productivity is about threefolds higher with RBC than with a stirred-tank fermenter with CaCO3. Furthermore, the duration of fermentation is one-third of the stirred-tank system. The immobilized biofilm is active for over a 2-wk period with repetitive use without loss of activity.