Een involutie in de kegelsneden-ruimte.

Het is op de volgende wijze mogelijk de kegelsneden van de ruimte één aan één involutorisch aan elkaar toe te voegen. Twee punten T1 en T2 als toppen en een kegelsnede alfa als richtlijn bepalen twee kwadratische kegels: respectievelijk t1 en t2. Deze beide kegels hebben behalve de kegelsnede a nog een kegelsnede algemeen. Zie: Inleiding

Quantized hall effect in disordered GaAs layers wit h3D spectrum un tilted magnetic fields

info:eu-repo/semantics/publishe

Point-contact spectroscopy at very low temperature

Metallic point contacts were investigated at very low temperatures down to 50 mK using a piezoelectric stepping motor for the adjustment of these point contacts in a dilution refrigerator. Conductance fluctuations are observed in the magnetoresistance of pressure-type AgAg point contacts. The voltage dependence of the fluctuation pattern is analyzed in view of the energy-dependent ballistic transport of the conduction electrons through the contact. Andreev reflection is observed in the current-voltage characteristics of point contacts between the normal metal Ag and the heavy-fermion superconductor UPt3. The comparison of structures in the differential resistance of a AgUPt3 point contact as a function of voltage with those for a conventional isotropic superconductor points to an anisotropic superconducting order parameter for UPt3. © 1995.info:eu-repo/semantics/publishe

Transport phenomena in polymer-graphite composite materials

SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Determination of the gap anisotropy of heavy-fermion superconductors by point contacts

The study of Andreev-reflection process in Normal/Superconductor point-contacts provides direct information abourt the nodal structure of the superconducting eneregy gap Δ in momentum (k)-space. A comparative study of experimental point-contact results id performed on three heavy-fermion duperconductord: UPt3, CeCu2Si2 and URu2Si2. Th experimental data point clearly to a gap with zeroes for UPt3 while for CeCu2Si2 and URu2Si2 the gap would have a finite non-zero value everywhere in k-space. © 1994.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Bimorph stepping motor for point-contact experiments

A rotating piezoelectric device, which uses the so‐called slip‐stick mechanism for micropositioning is presented. The device is especially designed for use in point‐contact experiments at very low temperatures in high magnetic fields. Two typical applications are presented.info:eu-repo/semantics/publishe

Slow domains in semi-insulating GaAs in high magnetic fields

We report on the drastic effect of a transverse high magnetic field on the low-frequency current oscillations in semi-insulating GaAs at room temperature, related to the propagation of slow high-electric-field domains. At a critical magnetic field Bc, we find a sharp transition between two ranges of the domain drift velocity, indicating a substantial change in the behavior of the involved deep level. Bc depends linearly on the applied voltage. The amplitude of the current oscillations decreases with increasing magnetic field, which reflects the interaction between the latter and the contact region. © 1995 American Institute of Physics.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Break junction measurements on Bi2Sr2Ca1Cu2O8+x single crystals: Analysis of the superconducting pairing symmetry

SCOPUS: ar.jinfo:eu-repo/semantics/publishe