Yasuyuki Miyakita

Magnetic field effect on electrochemical oscillations during iron dissolution

A fairly low magnetic field of ca. 30 mT was found to affect the period and the amplitude of the self-sustained current oscillation of an iron electrode. This was observed much distinctively when the direction of the applied field was normal to the electrode surface, i.e., non-magnetohydrodynamic (MHD) configuration. The Flade potential of the iron electrode was not affected by the magnetic field intensity of up to 4 T. The observed magnetic field effect was attributed to the depression of the natural convection in the vicinity of the electrode surface which was caused by the two local paramagnetic body forces, the magnetic field gradient force and/or the concentration gradient force.

Response of relaxation oscillatory electrochemical networks to external input

We have studied the response of simple networks of relaxation oscillatory electrode pairs to inputs through external cells. Such networks are shown to respond to constant inputs by decreasing or increasing the period depending whether the connection with the external cell is excitatory or inhibitory. The response to pulse inputs is determined by the phase of the relaxation oscillations; within the refractory region the network remains unaffected whereas within the excitable region an increase in the period is observed accompanied by the induction of new peaks.

Nonlinear optical properties of oligothiophene self-assembled monolayers on gold substrate

At the present state molecular electronic is based on monolayer arrays of molecules with a final goal to use the individual molecules as functional electronic devices. For functioning of a molecular device the properties of individual molecules are utilized. The variety of functional molecules is almost infinite; nevertheless the use of only conducting and insulating molecules gives a possibility to construct a nanometer device. 1 There are two main techniques for the fabrication of such functioning films: selfassembling of molecules and scanning tunneling microscope ~STM!-manipulating. The latter technique allows precise building of the surface structures, but not their extensive production. Self-assembling of the molecules ~including embedding of molecular wires into an insulating matrix 2 ! offers an easy way to achieve this goal. The properties of the molecules arranged in a SAM differ from the properties of the isolated molecules due to a dipole‐dipole interaction. This is why it is important to be able to calculate ~and predict! the properties of the densely packed layers if the properties of a single molecule are known and vice versa. Among the variety of molecules possessing selfassembling oligothiophenes were subjected to extensive studies. This is because of the unique optical and electronic properties of these molecules and also due to the possibility of varying the length of the molecule in a controlled way by a successive duplication of an aromatic ring. These molecules are conjugated: They possess an extended delocalized p-electron cloud along the chain axes. The molecules are considered to be very promising for optical signal processing because of their large, ultrafast nonlinear optical response, and high laser damage threshold. In this paper we present the results of measurements and self-consistent calculations of linear and nonlinear optical polarizability of an individual molecule in self-assembled monolayer of oligothiophenes on Au~111! substrate based on nonlinear optical interferometry. II. THEORETICAL BACKGROUND SHG interfereometry is based on the measurements of interference patterns appearing due to the superposition of ~at least! two SH fields: From the sample, Es , and from the reference, Eref . The total SHG intenisty is described by an equation, which is similar for the one for a linear interference, 3

SYNCHRONIZATION PHENOMENA IN NETWORKS OF COUPLED RELAXATION ELECTROCHEMICAL OSCILLATIONS

Networks of weakly coupled discrete electrochemical oscillators have the ability of synchronizing rapidly in-phase or out-of-phase, depending on the network geometry. It is shown that a network consisting of N relaxation electrochemical oscillators, coupled through inhibitory connections, can have (N - 1)! coexisting out-of-phase states, each state being a permutation of a periodic spiking sequence. The out-of-phase states can be modified by shots of laser pulse perturbations and the phase relation is stored as a coded spatiotemporal pattern. The ability of the network to function as a re-writable memory of (N - 1)! different spatiotemporal patterns is demonstrated experimentally for N = 4.