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We have evaluated the linearity of commercial digital voltmeters (DVMs) using a programmable Josephson voltage standard (PJVS) system. The PJVS system is composed of a 524 288-niobium nitride-based Josephson junction array that has the ability to generate arbitrary output voltages up to 17 V with a resolution of 12 bits. In our system, the junction array is operated in a 10-K compact cooler without a liquid-helium coolant. Up to now, we have succeeded in generating accurate dc voltage levels of up to approximately 13 V using this system. In this paper, we demonstrate our PJVS system as a tool for investigating the linearity characteristics of commercial DVMs, with an accuracy level of 0.1 µV/V or better, and discuss the uncertainty sources in these measurements. Index Terms-DC voltage, digital voltmeter (DVM), Josephson junction array, linearity, mechanical cooler, precision measurements, programmable Josephson voltage standard (PJVS). the development of the resistance calibration system based on the quantumHall effect. He has also been involved in programmable and pulse-driven ac Josephson voltage standards, including the Johnson noise thermometry project. He has served as the Chief of the Quantum Electrical Standards Section since 2010, and the Head of the Electricity and Magnetism Division with NMIJ, AIST, since 2013. He is involved in quantum current standards and metrology triangle experiments, which combine three quantum electrical effects. His current research interests include condensed matter and material physics, and their application to metrology. Dr. Kaneko was a recipient of the 2012 NCSLI Measure Editor's Choice Award.

We describe a search for gravitational waves from compact binaries with at least one component with mass 0.2 M⊙–1.0 M⊙ and mass ratio q ≥ 0.1 in Advanced LIGO and Advanced Virgo data collected between 1 November 2019, 15:00 UTC and 27 March 2020, 17:00 UTC. No signals were detected. The most significant candidate has a false alarm rate of $0.2 \, \rm {yr}^{-1}$. We estimate the sensitivity of our search over the entirety of Advanced LIGO’s and Advanced Virgo’s third observing run, and present the most stringent limits to date on the merger rate of binary black holes with at least one subsolar-mass component. We use the upper limits to constrain two fiducial scenarios that could produce subsolar-mass black holes: primordial black holes (PBH) and a model of dissipative dark matter. The PBH model uses recent prescriptions for the merger rate of PBH binaries that include a rate suppression factor to effectively account for PBH early binary disruptions. If the PBHs are monochromatically distributed, we can exclude a dark matter fraction in PBHs fPBH ≳ 0.6 (at 90% confidence) in the probed subsolar-mass range. However, if we allow for broad PBH mass distributions we are unable to rule out fPBH = 1. For the dissipative model, where the dark matter has chemistry that allows a small fraction to cool and collapse into black holes, we find an upper bound fDBH < 10−5 on the fraction of atomic dark matter collapsed into black holes.

Complex fluids have a non-uniform local inner structure. The non-uniformity of polymer and worm-like micellar solutions were characterized by the local viscosity distribution obtained by optical tweezers with the inverse integral transformation method.

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