低温動作(87)Sr光格子時計の研究

学位の種別: 課程博士審査委員会委員 : (主査)東京大学教授 香取 秀俊, 東京大学教授 五神 真, 東京大学教授 古澤 明, 東京大学准教授 井上 慎, 東京理科大学教授 盛永 篤郎University of Tokyo(東京大学

Frequency ratios of Sr, Yb and Hg based optical lattice clocks and their applications

This article describes the recent progress of optical lattice clocks with neutral strontium ($^{87}$Sr), ytterbium ($^{171}$Yb) and mercury ($^{199}$Hg) atoms. In particular, we present frequency comparison between the clocks locally via an optical frequency comb and between two Sr clocks at remote sites using a phase-stabilized fibre link. We first review cryogenic Sr optical lattice clocks that reduce the room-temperature blackbody radiation shift by two orders of magnitude and serve as a reference in the following clock comparisons. Similar physical properties of Sr and Yb atoms, such as transition wavelengths and vapour pressure, have allowed our development of a compatible clock for both species. A cryogenic Yb clock is evaluated by referencing a Sr clock. We also report on a Hg clock, which shows one order of magnitude less sensitivity to blackbody radiation, while its large nuclear charge makes the clock sensitive to the variation of fine-structure constant. Connecting all three types of clocks by an optical frequency comb, the ratios of the clock frequencies are determined with uncertainties smaller than possible through absolute frequency measurements. Finally, we describe a synchronous frequency comparison between two Sr-based remote clocks over a distance of 15 km between RIKEN and the University of Tokyo, as a step towards relativistic geodesy.Comment: 11 pages, 5 figures, invited review article in Comptes Rendus de Physique 201

Multimodal treatment for resectable epithelial type malignant pleural mesothelioma

BACKGROUND: Malignant pleural mesothelioma is a rare malignancy. The outcome remains poor despite complete surgical resection. PATIENTS AND METHODS: Eleven patients with histologicaly proven epithelial type malignant pleural mesothelioma undergoing extrapleural pneumonectomy with systemic chemotherapy and/or radiotherapy before and after surgical resection were retrospectively reviewed. RESULTS: Ten out of 11 patients underwent complete surgical resection, of these 7 patients had stage I disease. Of these 7 patients, 5 are alive without any recurrence, a 2-year survival rate of 80% was observed in this group. There was no operative mortality or morbidity. CONCLUSION: Extrapleural pneumonectomy with perioperative adjuvant treatment is safe and effective procedure for epithelial type malignant pleural mesothelioma

Frequency Ratio of 199Hg and 87Sr Optical Lattice Clocks beyond the SI Limit

We report on a frequency ratio measurement of a Hg199-based optical lattice clock referencing a Sr87-based clock. Evaluations of lattice light shift, including atomic-motion-dependent shift, enable us to achieve a total systematic uncertainty of 7.2×10−17 for the Hg clock. The frequency ratio is measured to be νHg/νSr=2.629 314 209 898 909 60(22) with a fractional uncertainty of 8.4×10−17, which is smaller than the uncertainty of the realization of the International System of Units (SI) second, i.e., the SI limit.UTokyo Research掲載「水銀・ストロンチウム光格子時計の高精度直接比較に成功」 URI: http://www.u-tokyo.ac.jp/ja/utokyo-research/research-news/highly-precise-comparison-of-mercury-and-strontium-optical-lattice-clocks.htmlUTokyo Research "Highly-precise comparison of mercury and strontium optical lattice clocks" URI: http://www.u-tokyo.ac.jp/en/utokyo-research/research-news/highly-precise-comparison-of-mercury-and-strontium-optical-lattice-clocks.htm

Cryogenic optical lattice clocks

The accuracy of atomic clocks relies on the superb reproducibility of atomic spectroscopy, which is accomplished by careful control and the elimination of environmental perturbations on atoms. To date, individual atomic clocks have achieved a 10−18 level of total uncertainties, but a two-clock comparison at the 10−18 level has yet to be demonstrated. Here, we demonstrate optical lattice clocks with 87Sr atoms interrogated in a cryogenic environment to address the blackbody radiation-induced frequency shift3, which remains the primary source of systematic uncertainty and has initiated vigorous theoretical and experimental investigations. The systematic uncertainty for the cryogenic clock is evaluated to be 7.2 × 10−18, which is expedited by operating two such cryo-clocks synchronously. After 11 measurements performed over a month, statistical agreement between the two cryo-clocks reached 2.0 × 10−18. Such clocks\u27reproducibility is a major step towards developing accurate clocks at the low 10−18 level, and is directly applicable as a means for relativistic geodesy.UTokyo Research掲載「次世代時間標準「光格子時計」の高精度化に成功」 URI: http://www.u-tokyo.ac.jp/ja/utokyo-research/research-news/precise-futuristic-timekeeping-with-optical-lattice-clocks.htmlUTokyo Research "Precise futuristic timekeeping with optical lattice clocks" URI: http://www.u-tokyo.ac.jp/en/utokyo-research/research-news/precise-futuristic-timekeeping-with-optical-lattice-clocks.htm

Chemical and Biological Properties of S-1-Propenyl-ʟ-Cysteine in Aged Garlic Extract

S-1-Propenyl-ʟ-cysteine (S1PC) is a stereoisomer of S-1-Propenyl-ʟ-cysteine (SAC), an important sulfur-containing amino acid that plays a role for the beneficial pharmacological effects of aged garlic extract (AGE). The existence of S1PC in garlic preparations has been known since the 1960’s. However, there was no report regarding the biological and/or pharmacological activity of S1PC until 2016. Recently, we performed a series of studies to examine the chemical, biological, pharmacological and pharmacokinetic properties of S1PC, and obtained some interesting results. S1PC existed only in trace amounts in raw garlic, but its concentration increased almost up to the level similar of SAC through aging process of AGE. S1PC showed immunomodulatory effects in vitro and in vivo, and reduced blood pressure in a hypertensive animal model. A pharmacokinetic study revealed that S1PC was readily absorbed after oral administration in rats and dogs with bioavailability of 88–100%. Additionally, S1PC had little inhibitory influence on human cytochrome P450 activities, even at a concentration of 1 mM. Based on these findings, S1PC was suggested to be another important, pharmacologically active and safe component of AGE similar to SAC. In this review, we highlight some results from recent studies on S1PC and discuss the potential medicinal value of S1PC