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Journal Articles

Observation of spin-space quantum transport induced by an atomic quantum point contact

Ono, Koki*; Higomoto, Toshiya*; Saito, Yugo*; Uchino, Shun; Nishida, Yusuke*; Takahashi, Yoshiro*

Nature Communications (Internet), 12(1), p.6724_1 - 6724_8, 2021/11

Quantum transport is ubiquitous in physics. So far, quantum transport between terminals has been extensively studied in solid state systems from the fundamental point of views such as the quantized conductance to the applications to quantum devices. Recent works have demonstrated a cold-atom analog of a mesoscopic conductor by engineering a narrow conducting channel with optical potentials, which opens the door for a wealth of research of atomtronics emulating mesoscopic electronic devices and beyond. Here we realize an alternative scheme of the quantum transport experiment with ytterbium atoms in a two-orbital optical lattice system. Our system consists of a multi-component Fermi gas and a localized impurity, where the current can be created in the spin space by introducing the spin-dependent interaction with the impurity. We demonstrate a rich variety of localized-impurity-induced quantum transports, which paves the way for atomtronics exploiting spin degrees of freedom.

Journal Articles

Highly sensitive detection of sodium in aqueous solutions using laser-induced breakdown spectroscopy with liquid sheet jets

Nakanishi, Ryuzo; Oba, Hironori; Saeki, Morihisa; Wakaida, Ikuo; Tanabe, Rie*; Ito, Yoshiro*

Optics Express (Internet), 29(4), p.5205 - 5212, 2021/02

 Times Cited Count:0 Percentile:0(Optics)

Laser-induced breakdown spectroscopy (LIBS) combined with liquid jets was applied to the detection of trace sodium (Na) in aqueous solutions. The sensitivities of two types of liquid jets were compared: a liquid cylindrical jet with a diameter of 500 $$mu$$m and a liquid sheet jet with a thickness of 20 $$mu$$m. Compared with the cylindrical jet, the liquid sheet jet effectively reduced the splash from the laser-irradiated surface and produced long-lived luminous plasma. The limit of detection (LOD) of Na was determined to be 0.57 $$mu$$g/L for the sheet jet and 10.5 $$mu$$g/L for the cylindrical jet. The LOD obtained for the sheet jet was comparable to those obtained for commercially available inductively coupled plasma emission spectrometers.

Journal Articles

New injection bump power supply of the J-PARC RCS

Takayanagi, Tomohiro; Ueno, Tomoaki*; Horino, Koki; Tobita, Norimitsu; Hayashi, Naoki; Kinsho, Michikazu; Irie, Yoshiro*; Okabe, Kota; Tani, Norio; Naito, Shingo*; et al.

Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1169 - 1174, 2015/09

The new injection bump power supply for the shift bump magnet of the beam injection sub-systems at the J-PARC (Japan Proton Accelerator Research Complex) 3-GeV RCS (Rapid Cycling Synchrotron) has been developed and manufactured. The power capacity of the new power supply was more than doubled with the injection beam energy upgrading of the LINAC (Linear Accelerator) from 181 MeV to 400 MeV. Furthermore, the low ripple noise on the output current was required to prevent the resonance of the RF shield loop at the ceramic duct with the excitation magnetic field. The power supply newly adopted a capacitor commutation method to form the trapezoid waveform pattern (bump waveform). This paper reports characteristic about the new power supply.

Journal Articles

Effect of liquid-sheet thickness on detection sensitivity for laser-induced breakdown spectroscopy of aqueous solution

Oba, Hironori; Saeki, Morihisa; Wakaida, Ikuo; Tanabe, Rie*; Ito, Yoshiro*

Optics Express (Internet), 22(20), p.24478 - 24490, 2014/10

 Times Cited Count:14 Percentile:66.41(Optics)

For aqueous-solution-based elemental analysis, we used a thin liquid sheet ($$mu$$m-scale thickness) in laser-induced breakdown spectroscopy with nanosecond laser pulses. Laser-induced plasma is emitted by focusing a pulsed Nd:YAG laser (1064 nm) on a 5- to 80-$$mu$$m-thick liquid sheet in air. To optimize the conditions for detecting elements, we studied how the signal-to-background ratio (SBR) for H$$alpha$$ Balmer and Na-neutral emission lines depends on the liquid-sheet thickness. The SBR of the H$$alpha$$ Balmer and Na-neutral lines was maximized for a sheet thickness of $$sim$$20 $$mu$$m at the laser energy of 100 mJ. The hydrodynamics of liquid flow induced by the laser pulse was analyzed by laser flash shadowgraph imaging. Time-resolved observation of the hydrodynamics and plasma emission suggests that the dependence of the SBR on the liquid-sheet thickness is correlated with the volume of flowing liquid that interacts with the laser pulses.

Journal Articles

High performance tokamak experiments with a ferritic steel wall on JFT-2M

Tsuzuki, Kazuhiro; Kimura, Haruyuki; Kawashima, Hisato; Sato, Masayasu; Kamiya, Kensaku; Shinohara, Koji; Ogawa, Hiroaki; Hoshino, Katsumichi; Bakhtiari, M.; Kasai, Satoshi; et al.

Nuclear Fusion, 43(10), p.1288 - 1293, 2003/10

 Times Cited Count:39 Percentile:76.12(Physics, Fluids & Plasmas)

no abstracts in English

Oral presentation

Evaluation of the electron distribution function for detached plasma in JT-60U

Uehara, Kazuya; Asakura, Nobuyuki; Sadamoto, Yoshiro*; Kawashima, Hisato; Kubo, Hirotaka; Nakano, Tomohide; Takenaga, Hidenobu; Fujimoto, Kayoko; Amemiya, Hiroshi*; Saito, Yoshifumi*

no journal, , 

The temperature and energy of electrons are important issues when energy and particle fluxes to the divertor are evaluated. To do this, we have analyzed the electron energy distribution function by differentiating the probe current with respect to the probe voltage numerically, where probe current has been measured in the divertor plasma of JT-60U. We have evaluated the electron temperature and the shape of the distribution function when the X point MARFE and the plasma detachment are formed.

Oral presentation

Analysis of elements in aqueous solution using laser-induced breakdown spectroscopy

Oba, Hironori; Toshimitsu, Masaaki; Saeki, Morihisa; Tanabe, Rie*; Ito, Yoshiro*; Wakaida, Ikuo

no journal, , 

no abstracts in English

Oral presentation

High sensitive analysis of elements in aqueous solution by using laser-induced breakdown spectroscopy

Oba, Hironori; Toshimitsu, Masaaki; Saeki, Morihisa; Tanabe, Rie*; Ito, Yoshiro*; Wakaida, Ikuo

no journal, , 

no abstracts in English

Oral presentation

High sensitive detection of elements in liquid samples by laser-induced breakdown spectroscopy with a liquid jet; Laser remote analysis for next generation nuclear fuel

Oba, Hironori; Saeki, Morihisa; Toshimitsu, Masaaki; Wakaida, Ikuo; Tanabe, Rie*; Ito, Yoshiro*

no journal, , 

We investigated the feasibility of laser-induced breakdown spectroscopy (LIBS) for the determination of elements in a liquid solution in the form of a jet flow and using nanosecond laser pulses. A comparison of LIBS sensitivity between two types of flows for liquid analysis was performed. A pipette nozzle tip was used to create a columnar flow of 520$$mu$$m diameter, whereas a trapezoidal-shaped groove nozzle tip produced an ultrathin sheet flow of 5$$sim$$40$$mu$$m thickness. The limit of detection of Na atoms was estimated to be about 14 ng/mL by use of the columnar flow, whereas 1.1 ng/mL in the case of the sheet flow.

Oral presentation

Quantitative analysis of metals in liquid-flow samples by laser induced breakdown spectroscopy

Oba, Hironori; Saeki, Morihisa; Wakaida, Ikuo; Tanabe, Rie*; Ito, Yoshiro*

no journal, , 

We applied single-pulse laser induced breakdown spectroscopy (LIBS) to liquid samples and evaluated detection sensitivity in both the liquid columnar flow and ultrathin sheet flow. The columnar flow of 0.52-mm diameter was prepared by a pipette-tip nozzle, whereas the ultrathin sheet flow with the thickness of 5$$sim$$20$$mu$$m was produced by a trapezoidal-shaped groove nozzle. The detection limits were estimated for alkali metal elements (Na, Rb, and Cs) under the optimum experimental condition. The detection limit of Na in an aqueous NaCl solution for the sheet flow is found to be 1.1 ppb, which is ten times lower compared to that for the columnar flow. The detection limits for Rb and Cs with the sheet flow were 7.1 ppb and 33 ppb, respectively. In this presentation, the feasibility of the LIBS measurement with the sheet flow for the simultaneous determination of elements in the mixed aqueous solution is also discussed.

Oral presentation

Laser-induced breakdown spectroscopy (LIBS) technique for analyzing elemental composition of samples under severe environments

Oba, Hironori; Saeki, Morihisa; Miyabe, Masabumi; Akaoka, Katsuaki; Wakaida, Ikuo; Iwanade, Akio; Ito, Chikara; Tanabe, Rie*; Ito, Yoshiro*; Sakka, Tetsuo*; et al.

no journal, , 

no abstracts in English

Oral presentation

Crystal structure of human drug metabolizing enzyme CYP2C9 in complex with losartan determined by X-ray crystallography

Adachi, Motoyasu; Maekawa, Keiko*; Matsuzawa, Yumiko*; Saito, Yoshiro*; Kuroki, Ryota

no journal, , 

CYP2C9 belongs to cytochrome P450 and play an important role as human drug metabolizing enzyme. In this study, to elucidate molecular mechanism in drug metabolizing reaction by wild-type CYP2C9 and its SNP mutant *30, X-ray structures of their CYP2C9 molecules complexed with the drug were determined. CYP2C9 was truncated at N-terminal, expressed in E. coli, and homogeneously purified for crystallization. CYP2C9 Losartan complex was crystallized by co-crystallization. As a result of experiments using synchrotron radiation, diffraction data were obtained at 2.1${AA}$ resolution. The electron density maps of bound Losartan were observed in the both complexes.

Oral presentation

Purification of cytochrome P450 2C9.1, 2C9.3 and 2C9.30 expressed in ${it E. coli}$ and their activities toward arachidonic acid ${it in vitro}$

Maekawa, Keiko*; Matsuzawa, Yumiko*; Adachi, Motoyasu; Kuroki, Ryota; Saito, Yoshiro*

no journal, , 

13 (Records 1-13 displayed on this page)
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