Low temperature transport measurements have been performed on nanofabricated Au wires a few p, m long contacting two Nb electrodes whose superconducting phase difference 50 was externally controlled. 58 was generated by passing a known supercurrent through a series array of 28 Nb-A10, -Nb Josephson junctions. The conductance of the Au wire displays a component in 58 with period 2m.These conductance oscillations arise from the change in scattering boundary conditions of quasiparticles in the Au wire at the Au-Nb interfaces due to Andreev reflection. PACS numbers: 74.50.+r, 73.50.Jt, 74.80.Fp When the size of a normal conducting system ap-

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Second-harmonic generation has been observed in submicrometer wires fabricated in GaAs-Al Gai-As heterostructures. The length and width of the wires are less than the elastic and inelastic mean free paths, while the width is comparable to the Fermi wavelength. In contrast with measurements on diffusive metal wires, the voltage response at the nth harmonic V(nf) to a small

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