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417. Multi-frequency composite pulse sequences for sensitivity enhancement in hexagonal boron nitride quantum sensor

Author

Gu, Hao, Nakamura, Yuki, Sasaki, Kento, and Kobayashi, Kensuke

Abstract

A negatively charged boron vacancy (VB−) in hexagonal boron nitride (hBN) has recently started to be used as a magnetic sensor. However, VB−has magnetic resonance spectra broadened by hyperfine interactions, which decreases the signal contrast and thus degrades the magnetic field sensitivity. Here we propose multi-frequency composite pulse sequences to enhance the contrast of the measurement signal in the Rabi oscillation. We demonstrate that the sequence using five microwave frequencies enhances the signal contrast, improving the sensitivity by a factor of 2.3 compared to the conventional sequence.

Published
2023
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418. Superconductivity and physical properties of Ba24Si100 determined from electric transport, specific-heat capacity, and magnetic susceptibility measurements

Author

Rachi, Takeshi, Yoshino, Harukazu, Kumashiro, Ryotaro, Katajima, Masaki, Kobayashi, Kensuke, Yokogawa, Keiichi, Murata, Keizo, Kimura, Noriaki, Aoki, Haruyoshi, Fukuoka, Hiroshi, Yamanaka, Shoji, Shimotani, Hidekazu, Takenobu, Taishi, Iwasa, Yoshihiro, Sasaki, Takahiro, Kobayashi, Norio, Miyazaki, Yuji, Saito, Kazuya, Guo, Fang Zhun, Kobayashi, Keisuke, Osaka, Keiichi, Kato, Kenichi, Tanaka, Masaki, and Tanigaki, Katsumi

Subjects
Condensed Matter::Superconductivity
Abstract

Both Ba24Si100 and Ba24Ge100 with crystallographically identical structure are found to be superconducting at 1.4 and 0.27 K, respectively. Physical properties of this superconductor Ba24Si100 are studied by electric transport, specific heat capacity, and magnetic susceptibility measurements. The density of states at the Fermi level NEF=0.148 states eV-1(Siatom)-1 and a distinct jump of Cp at the superconducting transition temperature ΔCp=0.272JK-1mol-1 are obtained. An exponential fit of Cp below the superconducting states gives an energy gap 2Δ=0.423meV and shows that this is a superconductor having s-wave character or isotropic energy gap. On the basis of our experimental data other important physical parameters are also derived.

Published
2005

424. Universality of non-equilibrium fluctuations in strongly correlated quantum liquids

Author

Ferrier, Meydi, Arakawa, Tomonori, Hata, Tokuro, Fujiwara, Ryo, Delagrange, Raphaëlle, Weil, Raphaël, Deblock, Richard, Sakano, Rui, Oguri, Akira, and Kobayashi, Kensuke

Abstract

Interacting quantum many-body systems constitute a fascinating research field because they form quantum liquids with remarkable properties and universal behaviour. In fermionic systems, such quantum liquids are realized in helium-3 liquid, heavy fermion systems, neutron stars and cold gases. Their properties in the linear-response regime have been successfully described by the theory of Fermi liquids. The idea is that they behave as an ensemble of non-interacting ‘quasi-particles’. However, non-equilibrium properties have still to be established and remain a key issue of many-body physics. Here, we show a precise experimental demonstration of Landau Fermi liquid theory extended to the non-equilibrium regime in a zero-dimensional system. Combining transport and ultra-sensitive current noise measurements, we have unambiguously identified the SU(2) (ref. ) and SU(4) (refs ,,,,) symmetries of a quantum liquid in a carbon nanotube tuned in the universal Kondo regime. Whereas the free quasi-particle picture is found valid around equilibrium, an enhancement of the current fluctuations is detected out of equilibrium and perfectly explained by an effective charge induced by the residual interaction between quasi-particles. Moreover, an as-yet-unknown scaling law for the effective charge is discovered, suggesting a new non-equilibrium universality. Our method paves a new way to explore the exotic nature of quantum liquids out of equilibrium through their fluctuations in a wide variety of physical systems.

Published
2016
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427. Daily transient discontinuation of extracorporeal LVAD to prevent thromboembolism of mechanical aortic valve prosthesis.

Author

Inoue, Takamichi, Kitamura, Tadashi, Torii, Shinzo, Hirata, Mitsuhiro, Mishima, Toshiaki, Sughimoto, Koichi, Ohkubo, Hirotoki, Kobayashi, Kensuke, Motokawa, Mamika, Shibata, Miyuki, Matsushiro, Takuya, Tsuchida, Yuta, Miyata, Yurie, Ono, Minoru, and Miyaji, Kagami

Abstract

Patients with mechanical aortic valves are generally contraindicated for left ventricular assist device (LVAD) insertion because the prosthetic valve often becomes fixed in closed position. A 41-year-old woman with mechanical aortic valve prosthesis experienced sudden chest pain and developed cardiogenic shock. A paracorporeal pulsatile LVAD and a monopivot centrifugal pump as a right VAD (RVAD) were implanted. The mechanical aortic valve was intentionally left in place. Soon after the operation, LVAD support was discontinued daily for few seconds to allow the mechanical aortic valve to open and to avoid thrombus formation. The patient was successfully weaned off RVAD and received anticoagulation therapy with warfarin. On postoperative day 141, she was transferred to a university hospital where a HeartMate II LVAD was implanted, and the aortic valve was successfully replaced with a bioprosthetic valve. The patient is currently awaiting heart transplantation. [ABSTRACT FROM AUTHOR]

Published
2017
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428. A Potent, Long-Acting, Orally Active (2R)-2-[(1R)-3,3-Difluorocyclopentyl]-2-hydroxy-2-phenylacetamide: A Novel Muscarinic M3 Receptor Antagonist with High Selectivity for M3 over M2 Receptors

Author

Mitsuya, Morihiro, primary, Kobayashi, Kensuke, additional, Kawakami, Kumiko, additional, Satoh, Atsushi, additional, Ogino, Yoshio, additional, Kakikawa, Taro, additional, Ohtake, Norikazu, additional, Kimura, Toshifumi, additional, Hirose, Hiroyasu, additional, Sato, Akio, additional, Numazawa, Tomosige, additional, Hasegawa, Takuro, additional, Noguchi, Kazuhito, additional, and Mase, Toshiaki, additional

Published
2000
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444. Magnetism and Pressure-Induced Superconductivity of Checkerboard-Type Charge-Ordered Molecular Conductor Β-(meso-DMBEDT-TTF)2X (X = PF6 and AsF6).

Author

Shikama, Takahisa, Shimokawa, Tatsuya, Lee, Sanguchul, Isono, Takayuki, Ueda, Akira, Takahashi, Kazuyuki, Nakao, Akiko, Kumai, Reiji, Nakao, Hironori, Kobayashi, Kensuke, Murakami, Youichi, Kimata, Motoi, Tajima, Hiroyuki, Matsubayashi, Kazuyuki, Uwatoko, Yoshiya, Nishio, Yutaka, Kajita, Koji, and Mori, Hatsumi

Subjects
SUPERCONDUCTIVITY, MAGNETIC susceptibility, METAL insulator semiconductors, CRYSTALS, VALENCE (Chemistry)
Abstract

The metallic state of the molecular conductor Β-(meso-DMBEDT-TTF)2X (DMBEDT-TTF = 2-(5,6-dihydro-1,3-dithiolo[4,5-b][1,4]dithiin-2-ylidene)-5,6-dihydro- 5,6-dimethyl-1,3-dithiolo[4,5-b][1,4]dithiin, X = PF6, AsF6) is transformed into the checkerboard-type charge-ordered state at around 75-80 K with accompanying metalinsulator (MI) transition on the anisotropic triangular lattice. With lowering temperatures, the magnetic susceptibility decreases gradually and reveals a sudden drop at the MI transition. By applying pressure, the charge-ordered state is suppressed and superconductivity appears in Β-(meso-DMBEDT-TTF)2AsF6 as well as in the reported Β-(meso-DMBEDT-TTF)2PF6. The charge-ordered spin-gapped state and the pressure-induced superconducting state are discussed through the paired-electron crystal (PEC) model, where the spin-bonded electron pairs stay and become mobile in the crystal, namely the valence-bond solid (VBS) and the resonant valence bonded (RVB) state in the quarter-filled band structure. [ABSTRACT FROM AUTHOR]

Published
2012
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446. Simultaneous determination of glucose, 1,5-anhydro d-glucitol and related sugar alcohols in serum by high-performance liquid chromatography with benzoic acid derivatization.

Author

Katayama, Masatoki, Matsuda, Yoshifumi, Kobayashi, Kensuke, Kaneko, Satoru, and Ishikawa, Hiromichi

Abstract

A new, simple and sensitive pre-column high-performance chromatographic method for the determination of diabetes marker d-glucose, 1,5-anhydro- d-glucitol and related compounds is reported. Sugars ( d-glucose, d-galactose, d-mannose, sucrose and arabinose) were derivatized with benzoic acid (BA) at 80°C for 60 min. l-Fucose, fructose, d-lactose, l-rhamnose, arabinose and ascorbic acid were not reacted. Sugar alcohols (xylitol, erythritol, mannitol, sorbitol myo-inositol) were also derivatized with BA at 80°C for 60 min. The fluorescence derivatives were separated on a TSK amide 80 column (4.6 mm i.d. × 250 mm, 5 µm) with acetonitrile-50 m m acetate buffer (pH 5.6; 4:96, v/v) as the mobile phase. The detection wavelength of beizoic acid derivatives was λex 275 nm and λem 315 nm. The detection limits of sugars were 10-80 µg/mL. The calibration graphs were linear up to 10 mg/mL. The relative standard deviations of 500 µg/mL sugars were 7.0-7.3%. The proposed method was compared with the enzymatic photometric glucose analysis method (Glucose B-Test II Wako). The correlation coefficient was 0.83 ( n = 20) and y = 0.82 x + 5.91, where y and x are concentrations in µg/mL obtained by the proposed pre-column HPLC and enzyme-photometric method, respectively. The detection limits of sugar alcohols were 100-1000 ng/mL. The calibration graphs were linear to 50 µg/mL and relative standard deviations of 10 µg/mL were 7.2-8.2%. The 1,5-AG data by the proposed method was also compared with the enzymatic photometric 1,5-AG analysis method (Rana AG 1,5-AG determination kit, Nihon Kayaku) and good correlation ( r = 0.91, n = 20) was also obtained. The proposed method was applied to the simultaneous determination of d-glucose, 1,5-AG and related sugar alcohols in serum from healthy males. Copyright © 2005 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Published
2006
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448. Frequency-tunable magnetic field sensing using continuous-wave optically detected magnetic resonance with nitrogen-vacancy centers in diamond.

Author

Okaniwa, Ryusei, Mikawa, Takumi, Matsuzaki, Yuichiro, Yamaguchi, Tatsuma, Suzuki, Rui, Tokuda, Norio, Watanabe, Hideyuki, Mizuochi, Norikazu, Sasaki, Kento, Kobayashi, Kensuke, and Ishi-Hayase, Junko

Subjects
*MAGNETIC resonance, *MAGNETIC fields, *COHERENCE (Physics), *ELECTRON spin, *NANODIAMONDS, *RADIO frequency, *IRRADIATION, *ELECTRON spin states
Abstract

The nitrogen-vacancy (NV) center is a promising candidate to realize practical quantum sensors with high sensitivity and high spatial resolution at room temperature and atmospheric pressure. In conventional high-frequency AC magnetometry with NV centers, the setup requires a pulse sequence with an appropriate time synchronization and strong microwave power. To avoid these practical difficulties, AC magnetometry using continuous-wave optically detected magnetic resonance (CW-ODMR) was recently demonstrated. That previous study utilized radio frequency (RF)-dressed states generated by the coherent interaction between the electron spin of the NV center and the RF wave. However, the drawback of this method is that the detectable frequency of the AC magnetic fields is fixed. Here, we propose and demonstrate frequency-tunable magnetic field sensing based on CW-ODMR. In the new sensing scheme, we obtain RF double-dressed states by irradiation with RF fields at two different frequencies. One creates the RF-dressed states and changes the frequency of the target AC field. The other is a target AC field that induces a change in the CW-ODMR spectrum by generating the RF double-dressed states through coherent interaction with the RF-dressed states. The sensitivity of our method is estimated to be comparable to or even higher than that of the conventional method based on the RF field with a single frequency. The estimated bandwidth is 7.5 MHz, higher than that of the conventional method using the RF-dressed states. Our frequency-tunable magnetic field sensor based on CW-ODMR paves the way for new applications in diamond devices. [ABSTRACT FROM AUTHOR]

Published
2024
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