带电圆盘导体电场的电势和场强

导出了带电薄圆盘导体空间电场的电势和场强表达式，并作出了相应的分布曲线．     

Behavior of highly deformable relaxor-ferroelectric-based ceramics in an electric field

The deformation characteristics of multicomponent barium-doped piezoelectric ceramics mPbMg_1/3Nb_2/3O_3-n PbNi_1/3Nb_2/3O_3-y PbZn_1/3Nb_2/3O_3-x PbTiO₃ are studied in electric fields E = 0–12 kV/cm. Anomalies are detected in the dependences of elastic strain ξ₃ and piezoelectric modulus d ₃₃ ^eff on the external dc electric field. The history of the materials is shown to affect the change of piezoelectric modulus d ₃₃ ^eff in an electric field. The revealed dependences are used to propose a method to increase the efficiency of operation of piezoelectric actuators.     

Cochlear outer hair cell bending in an external electric field

We have used a high-resolution motion analysis system to reinvestigate shape changes in isolated guinea pig cochlear outer hair cells (OHCs) evoked by low-frequency (2-3 Hz) external electric stimulation. This phenomenon of electromotility is presumed to result from voltage-dependent structural changes in the lateral plasma membrane of the OHC. In addition to well-known longitudinal movements, OHCs were found to display bending movements when the alternating external electric field gradients were oriented perpendicular to the cylindrical cell body. The peak-to-peak amplitude of the bending movement was found to be as large as 0.7 microm. The specific sulfhydryl reagents, p-chloromercuriphenylsulfonic acid and p-hydroxymercuriphenylsulfonic acid, that suppress electrically evoked longitudinal OHCs movements, also inhibit the bending movements, indicating that these two movements share the same underlying mechanism. The OHC bending is likely to result from an electrical charge separation that produces depolarization of the lateral plasma membrane on one side of the cell and hyperpolarization on the other side. In the cochlea, OHC bending could produce radial distortions in the sensory epithelium and influence the micromechanics of the organ of Corti.     

An isoelectrically trapped enzyme reactor operating in an electric field

Membrane enzyme reactors constitute an attempt at integrating catalytic conversion, product separation and/or concentration and catalyst recovery into a single operation. Whereas conventional membrane reactors confine an enzyme, in a free form, to one side of a membrane by size exclusion, electrostatic repulsion, or physical or chemical immobilization onto an intermediate support (gel, liposome), the membrane reactor here described is shown to operate under an entirely new principle: enzyme confinement into an isoelectric trap located in a multicompartment electrolyzer operating in an electric field. Two isoelectric membranes, having pI values encompassing both the enzyme pI and the pH of its optimum of activity, act by continuously titrating the enzyme trapped inside, thus preventing it from escaping the reaction chamber. Charged products generated by the enzyme catalysis are continuously electrophoretically transported away from the reaction chamber and collected into other chambers stacked either towards the cathodic or anodic sides. In a urease reactor, ammonia is continuously harvested towards the cathode, thus allowing >95% substrate consumption with maintenance of enzyme integrity over much longer time periods than in a batch reactor. In a trypsin reactor, casein is digested and biologically active peptides are continuously harvested in a pure form into appropriate isoelectric traps. In a third example, pure D-phenylglycine is produced from a racemate mixture, via an acylation reaction onto a cosubstrate (the ester methyl-4-hydroxyphenyl acetate), brought about by the enzyme penicillin G acylase.