Three kinds of Aharonov-Bohm (AB)-type oscillation have been investigated in triangular antidot lattice fabricated from a GaAs/AlGaAs two-dimensional electron gas sample. The oscillation periods of Altshuler-Aronov-Spivak (AAS) effect and AB-type effect near zero magnetic field are determined by the unit cell area, whereas those of AB-type oscillations in the quantum Hall plateau transition regime are governed by the effective area of antidot. The evolution of the high-field AB-type oscillation as a function of gate voltage gives infomation on the profile of the self-consistent potential associated with compressible edge channels formed around antidot. The temperature dependences and decoherence mechanisms of the AAS and AB-type oscillations near zero magnetic field as well as the high-field ABtype oscillation are discussed.

Air buoyancy causes a significant systematic effect in precision mass determination of 1 kg silicon spheres. In order to correct this effect accurately, mass measurement of the silicon sphere was conducted using buoyancy artefacts; additionally, in order to stabilize atmospheric conditions, we used a vacuum chamber in which a mass comparator had been installed. The silicon sphere was also weighed in vacuum to verify the air buoyancy correction. Mass differences measured in air and in vacuum showed good agreement with each other in spite of the desorption effect from weight surfaces. Furthermore, the result of weighing under vacuum conditions demonstrated better repeatability than that obtained in air.

For the precise measurement of the mass of a weight, buoyancy correction of air for the volume of a weight is necessary. Although hydrostatic weighing is the most accurate method currently used in determining volume, it is a relatively complicated process requiring the weight to be wetted in a reference fluid. Since more weights with high accuracy of mass are being used, a more sophisticated method of determining volume that satisfies uncertainty requirements has been demanded to improve the efficiency of calibration. In this paper, an acoustic volumeter is proposed for the measurement of the volume of weights. An acoustic volumeter can measure volume in atmosphere in a simple manner. Consequently, it is not necessary to consider the contamination and mass change due to the liquid used in the hydrostatic weighing method. In practical applications, a procedure for measuring the volume of weights ranging from 100 g to 10 kg using an acoustic volumeter is proposed. The volumes obtained using an acoustic volumeter were compared with those obtained by the hydrostatic weighing method, and the reliability of the measurement was evaluated with a relative uncertainty below the order of 1 × 10−3. From the measurement results, it was shown that the use of an acoustic volumeter is effective for the measurement of the volume of weights.

The mercury U-tube manometer is a traditional pressure-measuring instrument and has played an important role as the primary standard in the atmospheric pressure range. It has also been used as the basis of standards for other pressure ranges. About thirty-five years ago, the National Research Laboratory of Metrology developed the precise mercury manometer using a white-light Michelson interferometer to detect the mercury menisci. We now introduce a new mercury U-tube manometer, developed as a national primary standard, to which some improvements and refinements have been added. Though the central principle is the same, the optical path of the reference arm of the interferometer has been redesigned to reduce the index-of-refraction corrections and some improvements have been incorporated to achieve more precise measurements on the U-tube conditions. The pressure range of the new manometer is 116 kPa and the uncertainty at 100 kPa is estimated to be about 0,4 Pa, in both absolute and gauge modes.

This paper describes the principle and performance of a novel manometer developed for the measurement of pressures in the range of up 1 kPa. A heterodyne interferometer using a Zeeman stabilized He-Ne laser was used to detect the displacement of oil surfaces which reflect the laser beam directly. A system of double U-tube and double interferometer was used to compensate errors caused by thermal and vibrational disturbances. The total uncertainty of the measured pressure P is estimated to be f (2,l + 0,032 P/Pa)mPa for gauge-mode pressures. The operation of the manometer has been confiied by the calibration of three capacitance diaphragm gauges at gauge-mode pressures of up to 876 Pa.