Frequency ratio of an In ion clock and a Sr optical lattice clock.

We report on the first, to the best of our knowledge, frequency ratio measurement of an singleion clock and a optical lattice clock. A hydrogen maser serves as a flywheel oscillator to measure the ratio by independent optical combs. From 89,000 s of measurement time, the frequency ratio / is determined to be 2.

New bounds on dark matter coupling from a global network of optical atomic clocks.

We report on the first Earth-scale quantum sensor network based on optical atomic clocks aimed at dark matter (DM) detection. Exploiting differences in the susceptibilities to the fine-structure constant of essential parts of an optical atomic clock, i.e.

Advanced Satellite-Based Frequency Transfer at the 10 Level.

Advanced satellite-based frequency transfers by two-way carrier-phase (TWCP) and integer precise point positioning have been performed between the National Institute of Information and Communications Technology and Korea Research Institute of Standards and Science. We confirm that the disagreement between them is less than at an averaging time of several days. In addition, an overseas frequency ratio measurement of Sr and Yb optical lattice clocks was directly performed by TWCP.

Months-long real-time generation of a time scale based on an optical clock.

Time scales consistently provide precise time stamps and time intervals by combining atomic frequency standards with a reliable local oscillator. Optical frequency standards, however, have not been applied to the generation of time scales, although they provide superb accuracy and stability these days. Here, by steering an oscillator frequency based on the intermittent operation of a Sr optical lattice clock, we realized an "optically steered" time scale TA(Sr) that was continuously generated for half a year.

SI-traceable measurement of an optical frequency at the low 10 level without a local primary standard.

SI-traceable measurements of optical frequencies using International Atomic Time (TAI) do not require a local primary frequency reference, but suffer from an uncertainty in tracing to the SI second. For the measurement of the Sr lattice clock transition, we have reduced this uncertainty to the low 10 level by averaging three sets of ten-day intermittent measurements, in which we operated the lattice clock for 10 s on each day. Moreover, a combined oscillator of two hydrogen masers was employed as a local flywheel oscillator (LFO) in order to mitigate the impact of sporadic excursion of LFO frequency.

Frequency Measurement System of Optical Clocks Without a Flywheel Oscillator.

We developed a system for the remote frequency comparison of optical clocks. The system does not require a flywheel oscillator at the remote end, making it possible to evaluate optical frequencies even in laboratories, where no stable microwave reference, such as an Rb clock, a Cs clock, or a hydrogen maser exists. The system is established by the integration of several systems: a portable carrier-phase two-way satellite frequency transfer station and a microwave signal generation system by an optical frequency comb from an optical clock.

Direct comparison of optical lattice clocks with an intercontinental baseline of 9000 km.

We have demonstrated a direct frequency comparison between two ⁸⁷Sr lattice clocks operated in intercontinentally separated laboratories in real time. Two-way satellite time and frequency transfer technique, based on the carrier-phase, was employed for a direct comparison, with a baseline of 9000 km between Japan and Germany. A frequency comparison was achieved for 83,640 s, resulting in a fractional difference of (1.

Direct comparison of a Ca+ single-ion clock against a Sr lattice clock to verify the absolute frequency measurement.

Optical frequency comparison of the (40)Ca(+) clock transition ν(Ca)((2)S(1/2-)(2D(5/2), 729 nm) against the (87)Sr optical lattice clock transition ν(Sr) ((1)S(0)-(3)P(0), 698 nm) has resulted in a frequency ratio ν(Ca) / ν(Sr) = 0.957 631 202 358 049 9(2 3). The rapid nature of optical comparison allowed the statistical uncertainty of frequency ratio ν(Ca) / ν(Sr) to reach 1 × 10(-15) in 1000s and yielded a value consistent with that calculated from separate absolute frequency measurements of ν(Ca) using the International Atomic Time (TAI) link.

Detection of mutant uromodulin in transgenic mouse harboring a mutant human UMOD gene.

Uromodulin is the most abundant protein secreted in urine, and the mutated form of the uromodulin gene is associated with uromodulin-associated kidney disease (UAKD). Although uromodulin accumulates in the kidney of UAKD patients, it is unclear whether this is the wildtype or mutant form. In this study, we established a liquid chromatography (LC)-mass spectrometry/mass spectrometry (MS/MS)-based method for the detection of uromodulin mutants, using the C148W mutant as a target molecule.

All-optical link for direct comparison of distant optical clocks.

We developed an all-optical link system for making remote comparisons of two distant ultra-stable optical clocks. An optical carrier transfer system based on a fiber interferometer was employed to compensate the phase noise accumulated during the propagation through a fiber link. Transfer stabilities of 2 × 10(-15) at 1 second and 4 × 10(-18) at 1000 seconds were achieved in a 90-km link.

Development of LC-MS method for detection of mutant uromodulin protein.

Mutations in the uromodulin gene cause the autosomal disorders familial juvenile hyperuricemic nephropathy (FJHN) and medullary cystic kidney disease type 2 (MCKD2). However, methods to detect the mutant form of the uromodulin protein have not been developed. In this study, we developed a liquid chromatography-mass spectrometry (LC-MS) method for detection of the mutated uromodulin peptide (C148W).

Trapping of neutral mercury atoms and prospects for optical lattice clocks.

We report vapor-cell magneto-optical trapping of Hg isotopes on the (1)S(0)-(3)P(1) intercombination transition. Six abundant isotopes, including four bosons and two fermions, were trapped. Hg is the heaviest nonradioactive atom trapped so far, which enables sensitive atomic searches for "new physics" beyond the standard model.

Electrodynamic trapping of spinless neutral atoms with an atom chip.

Three-dimensional electrodynamic trapping of neutral atoms has been demonstrated. By applying time-varying inhomogeneous electric fields with micron-sized electrodes, nearly 10(2) strontium atoms in the 1S0 state have been trapped with a lifetime of 80 ms. In order to design the electrodes, we numerically analyzed the electric field and simulated atomic trajectories in the trap, which showed reasonable agreement with the experiment.

Required thermal environments for the quadriplegic persons: Analyses of questionnaires and experiments on their daily life.

A physically disabled person often has additional disabilities on adaptation to the thermal environment. Since 1976, our group has carried out a series of studies to find required thermal conditions for disabled persons on several typical disabilities. This paper reports on the results of our latest questionnaire and experiments on daily thermal environment for quadriplegic persons.

Secondary aneurysm due to arterial injury during surgical procedures.

Most secondary aneurysms following trauma to the cerebral artery were reported as a complication of head injury. Three cases of aneurysm due to arterial injury during operations are reported. A search of the world literature revealed ten other cases.