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Search Results: 1 - 10 of 1393 matches for " Kei Nishiyama "
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Microfluidic Analytical System with On-Line Luminol Chemiluminescence Detection Based on Annular Flow of Phase Separation Multiphase Flow  [PDF]
Junki Manai, Kei Nishiyama, Kazuhiko Tsukagoshi
Journal of Analytical Sciences, Methods and Instrumentation (JASMI) , 2017, DOI: 10.4236/jasmi.2017.72003
Abstract: Microfluidic analytical system was developed based on annular flow of phase separation multiphase flow with a ternary water-hydrophilic/hydrophobic organic solvent solution. The analytical system was combined with on-line luminol chemiluminescence detection for catechin analysis. The water (10 mM phosphate buffer, pH 7.3)-acetonitrile-ethyl acetate mixed solution (3:8:4, volume ratio) containing 60 μM luminol and 2 mM hydrogen peroxide as a carrier was fed into the capillary tube (open-tubular fused-silica, 75 μm inner diameter, 110 cm effective length) at a flow rate of 1.0 μL·min-1. The carrier solution showed stable chemiluminescence as a baseline on the flow chart. Eight catechins were detected as negative peaks for their antioxidant potential with different detection times. The system was applied to analyze the amounts of catechin in commercially available green tea beverages.
Retroperitoneoscopic donor nephrectomy with a gel-sealed hand-assist access device: retroperitoneoscopic donor nephrectomy
Kei Arai, Tsutomu Nishiyama, Noboru Hara, Takashi Kasahara, Kazuhide Saito, Kota Takahashi
BMC Urology , 2013, DOI: 10.1186/1471-2490-13-7
Abstract: Seventy-five consecutive donors receiving this procedure were retrospectively studied. A 2-cm skin incision was made at the midpoint between the tip of the 12th rib and superior border of the iliac bone in the midaxillary line, through which retroperitoneal space was made. Preperitoneal wound with a 6 -- 7-cm pararectal incision in the upper abdominal region was connected to the retroperitoneal space. A GelPort was put inside the pararectal surgical wound. The principle was pure retroperitoneoscopic surgery; hand-assist was applied for retraction of the kidney in the renal vessel control and graft extraction.The mean operation time including waiting time for recipient preparation was 242.2+/-37.0 (range: 214.0--409.0) min, and the mean amount of blood loss was 164.3+/-146.6 (range: 10.0--1020.0) ml. The mean WIT was 2.8+/-1.0 (range: 1.0--6.0) min. The shortage of renal vessels or ureter was observed in none of the grafts. No donor experienced blood transfusion, open conversion, or injury of other organs. Blood loss was greater in patients with body mass index (BMI) of 25 kg/m2 or higher than in those with BMI of <25 kg/m2 (218.4+/-98.8 vs. 154.8+/-152.1 ml, P=0.031). No donor had postoperative ileus or reported wound pain leading to decreased activity of daily life or wound cosmetic problem.Retroperitoneoscopic hand-assisted donor nephrectomy with the mentioned approach was suggested to be a feasible option without compromising safety, although further improvement in surgical techniques is warranted.
Near-Infrared and X-Ray Observations of XSS J12270-4859
Kei Saitou,Masahiro Tsujimoto,Ken Ebisawa,Manabu Ishida,Koji Mukai,Takahiro Nagayama,Shogo Nishiyama,Poshak Gandhi
Physics , 2011, DOI: 10.1093/pasj/63.sp3.S759
Abstract: XSS J12270-4859 (J12270) is an enigmatic source of unknown nature. Previous studies revealed that the source has unusual X-ray temporal characteristics, including repetitive short-term flares followed by spectral hardening, non-periodic dips, and dichotomy in activity; i.e. intervals filled with flares and those without. Together with a power-law X-ray spectrum, it is suggested to be a low-mass X-ray binary (LMXB). In order to better understand the object, we present the results of our near-infrared (NIR) photometry and linear polarimetry observations as well as X-ray spectroscopy observations, which overlap with each other partially in time, taken respectively with the InfraRed Survey Facility (IRSF) and the Rossi X-ray Timing Explorer (RXTE). We detected several simultaneous NIR and X-ray flares for the first time. No significant NIR polarization was obtained. We assembled data taken with IRSF, RXTE, Suzaku, Swift, and other missions in the literature and compared the flare profile and the spectral energy distribution (SED) with some representative high-energy sources. Based on some similarities of the repetitive NIR and X-ray flaring characteristics and the broad SED, we argue that J12270 is reminiscent of microquasars with a synchrotron jet, which is at a very low luminosity state of ~1e-4 Eddington luminosity for a stellar mass black hole or neutron star at a reference distance of 1 kpc.
Numerical Study on Nonlinear Sound Propagation for Parametric Array  [PDF]
Kei Fujisawa
Journal of Flow Control, Measurement & Visualization (JFCMV) , 2014, DOI: 10.4236/jfcmv.2014.23014
Abstract: This paper presents the numerical study on the nonlinear sound propagation for the parametric array using the compressible form of Navier-Stokes equations combined with the mass and energy conservation equations and the state equation. These governing equations are solved by finite difference time domain (FDTD) based method. The numerical result is shown for the parametric sound propagation in the near field of the sound source in cylindrical coordinate. The result indicates the generation of low-frequency unsteady beat by the interaction of two frequency sound waves in the near field, which grows to a difference frequency sound in the far field.
Determinants of Health Expenditures: Stylized Facts and a New Signal  [PDF]
Kei Hosoya
Modern Economy (ME) , 2014, DOI: 10.4236/me.2014.513109
Abstract: This article further investigates the determinants of health expenditures by using aggregate data. Specifically, a panel data analysis of 25 OECD countries reveals that under several model specifications, the proxy for population ageing has no effect on health costs in accordance with recent findings. In contrast to this well-known result, an additional estimation conducted to check robustness revealed that the ageing variable becomes positive and significant. The significant effect may provide a new signal for a determinant of health expenditures. This result suggests that ageing is an important factor that cannot be ignored when considering variations in health expenditures.
Seeking a Better Recovery Process from Major Natural Disasters: A Lesson from Several Growth Models with Multiple Equilibria  [PDF]
Kei Hosoya
Theoretical Economics Letters (TEL) , 2017, DOI: 10.4236/tel.2017.75103
Abstract: Based on several existing growth models with multiple steady states, this paper examines economic conditions that enable recovery from major natural disasters. We focus on recovery from the 2011 Great East Japan Earthquake and Tsunami. More concretely, we survey three recently released studies, which indicate that the sense of direction for expectation formation has the potential to play an important role in recovering from large natural disasters. We also find an inference that the big-push development scenarios that traditionally appear in developing economies have a low affinity with disaster reconstruction in developed countries. After a discussion of these equilibrium selections, this paper makes further reference to economic environments needed for a sustainable recovery path toward a superior long-run, steady-state equilibrium. This equilibrium allows interpreting the terminal of a series of recovery programs in our context.
Construction of axisymmetric steady states of an inviscid incompressible fluid by spatially discretized equations for pseudo-advected vorticity
Takahiro Nishiyama
International Journal of Mathematics and Mathematical Sciences , 2005, DOI: 10.1155/ijmms.2005.3319
Abstract: An infinite number of generalized solutions to the stationary Euler equations with axisymmetry and prescribed circulation are constructed by applying the finite difference method for spatial variables to an equation of pseudo-advected vorticity. They are proved to be different from exact solutions which are written with trigonometric functions and a Coulomb wave function.
Bound-state energy of the d=3 Ising model in the broken-symmetry phase: Suppressed finite-size corrections
Yoshihiro Nishiyama
Physics , 2008, DOI: 10.1103/PhysRevE.77.051112
Abstract: The low-lying spectrum of the three-dimensional Ising model is investigated numerically; we made use of an equivalence between the excitation gap and the reciprocal correlation length. In the broken-symmetry phase, the magnetic excitations are attractive, forming a bound state with an excitation gap m_2(<2m_1) (m_1: elementary excitation gap). It is expected that the ratio m_2/m_1 is a universal constant in the vicinity of the critical point. In order to estimate m_2/m_1, we perform the numerical diagonalization for finite clusters with N \le 15 spins. In order to reduce the finite-size errors, we incorporated the extended (next-nearest-neighbor and four-spin) interactions. As a result, we estimate the mass-gap ratio as m_2/m_1=1.84(3).
Deconfinement criticality for the spatially anisotropic triangular antiferromagnet with the ring exchange
Yoshihiro Nishiyama
Physics , 2009, DOI: 10.1103/PhysRevB.79.054425
Abstract: The spatially anisotropic triangular antiferromagnet is investigated with the numerical diagonalization method. As the anisotropy varies, the model changes into a variety of systems such as the one-dimensional, triangular, and square-lattice antiferromagnets. Taking into account such a geometrical character, we impose the screw-boundary condition, which interpolates smoothly the one- and two-dimensional lattice structures. Diagonalizing the finite clusters with N=16,20,...,32 spins, we observe an intermediate phase between the VBS and Neel phases. Suppressing the intermediate phase by applying the ring exchange, we realize a direct VBS-Neel transition. The simulation data indicate that the transition is a continuous one with the correlation-length critical exponent \nu=0.80(15). These features are in agreement with the deconfinement-criticality scenario advocated by Senthil and coworkers in the context of the high-temperature superconductivity.
Numerical analysis of the dissipative two-state system with the density-matrix Hilbert-space-reduction algorithm
Yoshihiro Nishiyama
Physics , 1999, DOI: 10.1007/s100510051037
Abstract: Ground state of the dissipative two-state system is investigated by means of the Lanczos diagonalization method. We adopted the Hilbert-space-reduction scheme proposed by Zhang, Jeckelmann and White so as to reduce the overwhelming reservoir Hilbert space to being tractable in computers. Both the implementation of the algorithm and the precision applied for the present system are reported in detail. We evaluate the dynamical susceptibility (resolvent) with the continued-fraction-expansion formula. Through analysing the resolvent over a frequency range, whose range is often called `interesting' frequency, we obtain the damping rate and the oscillation frequency. Our results agree with those of a recent quantum Monte-Carlo study, which concludes that the critical dissipation from oscillatory to over-damped behavior decreases as the tunneling amplitude is strengthened.
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