Low-temperature fate of the 0.7 structure in a point contact: a Kondo-like correlated state in an open system

Besides the usual conductance plateaus at multiples of 2e(2)/h, quantum point contacts typically show an extra plateau at approximately 0.7(2e(2)/h), believed to arise from electron-electron interactions that prohibit the two spin channels from being simultaneously occupied. We present evidence that the disappearance of the 0.7 structure at very low temperature signals the formation of a Kondo-like correlated spin state. Evidence includes a zero-bias conductance peak that splits in a parallel field, scaling of conductance to a modified Kondo form, and consistency between peak width and the Kondo temperature.     

Coherent optical neural networks and the generalization characteristic

Coherent optical neural-network systems are presented by which we are to realize (1) control of optical neural-network behavior by carrier frequency modulation and (2) frequency-domain multiplexing as a new degree of neural parallelism. In the coherent optical neural network, lightwave carries amplitude, phase, and frequency signals which are processed through optical neural connections consisting of transparency, delay, and optical nonlinear neurons. The neural learning process is realized by adjusting the delay time and the transpar-ency of the optical connections by regarding the carrier frequency as a learning parameter. A simulation experiment demonstrates that the proposed system learns desired output signals depending on the optical carrier frequencies, which leads to the above advantages. It is also found that the generalization characteristics depends on built-in input delays. The generalization quality is discussed from the viewpoint of function approximation or synthesis using sinusoidal basis functions.     

Electrical and optical properties of chalcogenide amorphous semiconductors modified with Ni

The electrical and optical properties of the chalcogenide semiconductor (Se₃₂Te₃₂As₄Ge₃₂)_100?xNixitx have been studied. As the Ni concentration is increased the electrical dc conductivity is drastically increased and variable range hopping conduction becomes dominant even above room temperature. The optical energy gap decreases with the Ni concentration from 1.18–0.95 eV. Ni-atoms in the chalcogenide semiconductor donate free electrons which occupy the gap state. This occupation causes the shift of the Fermi level toward the conduction band. It is an effect of this shift that the thermal activation energy is decreased. The decrease in optical energy gap is independent of the shift of the Fermi level and is ascribable to the appearance of the additional level located at 0.95 eV above the top of the valence band. This level originates from the 3d-level of the Ni-atom.     

Graphical representation of the solutions of the schrödinger equations for a particle in various model potentials

Several one-dimensional Schrödinger equations for a particle trapped in various model potentials are solved analytically or approximately, and the results are plotted by an X—Y plotter. Typical results are illustrated. Several interesting features of the relations between the shape of the potential and the solution of the Schrödinger equation are pointed out. Combination of these results allows reasonable guesses about the forms of the energy levels and wavefunctions for complicated but realistic problems.     

Studies on neutron activation analysis using ion exchange preconcentration

Three convenient procedures are described for applying anion exchange resins to the preconcentration and irradiation support in neutron activation analysis. For each procedure the amounts of interferences were determined. The effect of the form, cross-linkage, pore size, and particle size of the resins on the elimination of interferences was investigated. Some other associated problems are also presented, viz. effect of concentration and temperature of washing solution, effect of irradiation time, and comparison with filter