K Miyagi

University of the Ryukyus, Okinawa, Okinawa, Japan

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Publications (104)114.19 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: A 72-year-old man was hospitalized in Okinawa due to a high fever and rash, after returning from Bali, Indonesia, in February 2014; dengue was clinically suspected, and IgM for dengue is positive in commercial kit. Serologically, the patient showed secondary sero-reactivity. Significant rises in neutralization titers (N-titers) against all four serotypes of dengue virus (DENV) and Japanese encephalitis virus (JEV) strains were recognized between acute- and convalescent-phase sera. N-titer against dengue virus serotype 1 (DENV-1) was the highest among those for all serotypes of DENV. Interestingly, N-titers against JEV strains, were significantly higher than those against all types of DENV. Virus was isolated from the acute-phase serum, and identified as DENV-1 designated as RD14/Okinawa. The symptoms of the case were due to DENV-1 infection. Phylogenetic analysis by sequencing indicated that isolate RD14/Okinawa furthermore belongs to genotype I of DENV-1, which is closely related to Southeast Asian strains and isolates during the dengue outbreak in Japan in 2014. We should undertake control measures against dengue in Okinawa, which is a subtropical area with Aedes albopictus activity throughout year.
    06/2015; DOI:10.7883/yoken.JJID.2015.061
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    ABSTRACT: IL-17A is involved in the immune system of the lung. Legionella can potentially cause severe pneumonia. The present study was aimed to evaluate the role of IL-17A in Legionella pneumonia cases. IL-17A was quantified in sera from patients with Legionella pneumonia and control subjects. IL-17A was detected in sera from 4 out of 31 Legionella pneumonia cases; the cytokine was not detected in any control cases. There was no difference in peripheral white blood cell counts or other serum biomarkers (C-reactive protein, and lactate dehydrogenase) between IL-17A positive cases and IL-17A negative cases. The IL-17A positive cases all survived, while 8 out of 27 IL-17A negative cases did not survive in this cohort. IL-17A could be detected in broncho-alveolar (BA) fluids from available 7 samples of Legionella pneumonia cases within our cohort. Concentrations of IL-17A and IFN-γ in BA fluids were not associated with each other. IL-17A might have significant role in some cases of Legionella pneumonia.
    Japanese journal of infectious diseases 12/2014; 68(2). DOI:10.7883/yoken.JJID.2014.171 · 1.20 Impact Factor
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    ABSTRACT: In recent clinical practice, high-flow nasal cannula (HFNC) therapy has been used to improve oxygenation in adults with acute respiratory failure (ARF). However, bronchoscopy using HFNC in ARF has not yet been reported. Herein, we describe 5 cases of ARF where bronchoalveolar lavage (BAL) was employed successfully using an HFNC. We were able to discontinue or reduce the HFNC fraction of inspired oxygen (FiO2) 30 min after completion of the bronchoscopy. Only 1 patient needed non-invasive positive pressure ventilation for 16 h after bronchoscopy. The HFNC may be a useful tool for ARF patients who require bronchoscopy.
    09/2014; 52(5). DOI:10.1016/j.resinv.2014.06.006
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    ABSTRACT: High mobility group box 1 (HMGB-1) protein is involved in acute lung injury due to various etiologies. We evaluated HMGB-1 levels in sera and bronchoalveolar fluids in patients with pneumonia caused by Legionella pneumophila. Levels of HMGB-1 in the sera of patients with L. pneumophila pneumonia (32 cases) and control subjects (24 cases) were determined. Serum HMGB-1 levels in Legionella pneumonia were similar to those of the control subjects. No significant correlation between HMGB-1 levels and other biomarkers and the outcome of cases was observed. In contrast, HMGB-1 levels, as well as interferon-γ, in bronchoalveolar (BA) fluids from severe L. pneumophila pneumonia (7 cases) were significantly higher than those in the sera of identical patients. HMGB-1 levels in BA fluids were relatively higher in pneumonia cases with ALI than those without ALI. Our findings suggest that intra-pulmonary HMGB-1 may be involved in the pathophysiology of pneumonia caused by L. pneumophila.
    Journal of Infection and Chemotherapy 12/2013; 20(5-6). DOI:10.1016/j.jiac.2013.10.014 · 1.38 Impact Factor
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    ABSTRACT: A 61-year-old woman who had received treatment for tuberculous pleurisy for 2 months visited our outpatient clinic. Chest computed tomography (CT) showed the presence of a lens-shaped pleural mass with pulmonary infiltration, despite the decreased pleural effusion. Two weeks later, chest CT showed an increase in the size of the mass and expansion of the intrapulmonary shadow. Percutaneous CT-guided lung biopsy was performed, and histopathological examination revealed granulomatous inflammation without caseous necrosis or acid-fast bacilli. Sputum culture was negative for acid-fast bacilli. Anti-tuberculosis medication was continued, and the lesions eventually resolved. These lesions were diagnosed as pleural tuberculomas, and the intrapulmonary infiltration was considered to be due to the paradoxical worsening of the patient's condition.
    Kekkaku: [Tuberculosis] 11/2013; 88(11):735-8.
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    ABSTRACT: We demonstrate dynamic control of the effective area (A eff) of photonic crystal fibers (PCFs) in the range of 18.1–8.22 μm2 and the mode field diameter in the range of 4.78–3.42 μm. This control was realized by altering their structural properties and varying the germanium (Ge) doping rate, which changed the refractive index difference (Δn Ge) between 1.0 and 3.0% relative to the refractive index of the silica cladding. This was achieved by adjusting the Ge doping rate in the core and changing the radius (d core) of the doped region, i.e., by changing the equivalent refractive index, using numerical calculations. Numerical results were verified by comparison with experimental results for a fabricated Gedoped PCF obtained by far-field scanning based on the ITU-T Petermann II definition. The proposed approach will simultaneously decrease Aeff and achieves high light confinement and high nonlinearity in PCFs. It enables architectonics/controllability of highly nonlinear PCFs with passive optical devices in photonic networks and life science applications.
    Optical Review 07/2013; 20(4). DOI:10.1007/s10043-013-0059-5 · 0.55 Impact Factor
  • International Journal of Antimicrobial Agents 06/2013; 42:S133-S134. DOI:10.1016/S0924-8579(13)70530-2 · 4.26 Impact Factor
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    ABSTRACT: With the increase in global transportation, imported malaria has become a significant public health concern in Japan. In the present study, we retrospectively analyzed all imported malaria cases in Okinawa Prefecture from 1988 to 2012. In that period, 23 patients with imported malaria were admitted to the University of the Ryukyus Hospital. Malaria types observed included Plasmodium falciparum (14 cases), P. vivax (7 cases), combined P. falciparum and P. ovale (1 case), and combined P. vivax and P. malariae (1 case). All cases were resolved by anti-malarial treatment. The clinical data from these patients highlights the importance of collecting patient travel history and ensuring an adequate supply of both diagnostic test and drug treatments in Okinawa.
    01/2013; 66(1):32-5. DOI:10.7883/yoken.66.32
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    ABSTRACT: We can obtain important optical transmission values of Germanium (Ge) doped-photonic crystal fibers (PCFs) of the effective area (Aeff) (variable range 7 to 25 [μm2]), extreme higher nonlinear coefficient (γ) (variable range 8.22-18.1[W-1 km-1]), and lower confinement loss (Lc) than conventional pure-SiO2 based PCFs by changing Ge-doped rate, respectively with core regions, using numerical analysis and actual measurement results, bi-directionally.
    Advanced Technologies for Communications (ATC), 2013 International Conference on; 01/2013
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    ABSTRACT: This paper discusses about the tailoring supercontinuum (SC) generation based on a highly nonlinear germanium (Ge) doped photonic crystal fiber (HNL-GePCF) with all normal group velocity dispersion (GVD). Using finite element method (FEM) with a circular perfectly matched boundary layer (PML), it is shown through simulations that how simply the center wavelength can be shifted from one center point to another after optimizing at a particular wavelength using the proposed HNL-GePCF. Moreover, SC spectra at 1.06, 1.31 and 1.55μm have been generated using picosecond optical pulses produced from relatively less expensive laser sources.
    Optics & Laser Technology 09/2012; 44(6):1889–1896. DOI:10.1016/j.optlastec.2012.01.029 · 1.65 Impact Factor
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    ABSTRACT: Climatic conditions may have affected the incidence of influenza during the pandemic of 2009 as well as at other times. This study evaluated the effects of climatic conditions on influenza incidence in Okinawa, a subtropical region in Japan, during the 2009 pandemic using surveillance data from rapid antigen test (RAT) results. Weekly RAT results performed in four acute care hospitals in the Naha region of the Okinawa Islands from January 2007 to July 2011 were anonymously collected for surveillance of regional influenza prevalence. Intense epidemic peaks were noted in August 2009 and December 2009-January 2010 during the influenza pandemic of 2009. RAT positivity rates were lower during the pandemic period than during the pre- and post-pandemic periods. Lower ambient temperature was associated with higher influenza incidence during pre- and post-pandemic periods but not during the pandemic of 2009. Lower relative humidity was associated with higher influenza incidence during the pandemic as well as during the other two periods. The association of climatic conditions and influenza incidence was less prominent during the pandemic of 2009 than during pre- and post-pandemic periods.
    07/2012; 65(4):295-300. DOI:10.7883/yoken.65.295
  • Kazuya Miyagi, Yoshinori Namihira
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    ABSTRACT: The effective area (Aeff) can be dynamically controlled from 7 μm2 to 25 μm2, bidirectionally, by adjusting the dosage of germanium doping in the core region, as demonstrated through numerical analysis and experimental measurements.
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    ABSTRACT: A dispersion flattened photonic crystal fiber (PCF) having nonlinear coefficient 13.8 W−1km−1 at 1.55µm is proposed in this paper to generate supercontinuum (SC) in a telecommunication window (wavelength 1.45µm to 1.65µm). As this PCF has an ultra-flattened dispersion and near zero dispersion slope at the center wavelength 1.55 µm, simulation results show that this simple PCF offers the possibility to generate the SC spectrum at telecommunication window using picosecond pulse easily produced by less expensive laser sources. Moreover, this PCF also provides very low confinement loss in entire operating window.
    Communication Technology and Application (ICCTA 2011), IET International Conference on; 01/2011
  • Kazuya Miyagi, Yoshinori Namihira
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    ABSTRACT: We have demonstrated that the correction factor kn = Aeff/(πw2), is above 1.20 for photonic crystal fibers (PCFs) with structural parameters in the range of d/Λ ≅ 0.40-0.90. By using the far field scanning (FFS) technique and the finite difference method (FDM), the results of experimental measurements and numerical simulations differed by only 0.8% to 3.0% for two types of PCFs. The finding that kn≠1.0 for PCFs indicates that their electrical field distribution is non-Gaussian and cannot be determined by assuming a conventional step-index structure distribution for PCFs.
    2010 IEEE Region 10 Conference (TENCON 2010); 11/2010
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    ABSTRACT: We have demonstrated that the correction factor k n = A eff/(πw 2), where ω = MFD/2 (MFD: mode field diameter), is above 1.20 for photonic crystal fibers (PCFs) with structural parameters in the range of d/Λ ≅ 0.40 to 0.90 (d/Λ ratio of hole diameter d and pitch Λ). By using the far-field scanning (FFS) technique and the finite difference method, the results of experimental measurements and numerical simulations differed by only 0.9 to 3.0% for two types of PCFs. The finding that k n ≠ 1.0 for PCFs indicates that their electrical field distribution is non-Gaussian and cannot be determined by assuming a conventional step-index distribution for PCFs. It was also found that the ITU-T Petermann II definition is the most suitable for MFD measurements of PCFs with non-Gaussian distribution. Keywordsphotonic crystal fiber (PCF)-pure silica core fiber (PSCF)-mode field diameter (MFD)-effective area (A eff)-correction factor (k n )
    Optical Review 07/2010; 17(4):388-392. DOI:10.1007/s10043-010-0072-x · 0.55 Impact Factor
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    ABSTRACT: We investigated nonlinear coefficients 110, 74, and 54 [Wkm]-1 at 1.06, 1.31 and 1.55um wavelengths, respectively based on finite difference method. Also, broadband supercontinuum spectrum is numerically obtained in optical coherence tomography and telecommunication windows.
  • Kengo Taira, Seiji Fujino, Kazuya Miyagi
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    ABSTRACT: Electromagnetic wave analysis of two-dimensional metal waveguides is carried out by the finite element Galerkin time domain method (FEGTD). A TE10 wave excites a waveguide in which a rectangular or circular dielectric post is loaded, and the time course of the spatial distribution of the electromagnetic wave is calculated. We use Galerkin's method to discretize Maxwell's scalar equations directly in the spatial domain and solve the linear system of equations, which is a first-order differential equation with respect to time. To solve open-region problems, we postulate attenuated one-directional traveling waves in non-reflection absorbing regions arranged at the two terminal ends. Isoparametric finite elements and attenuated infinite elements are used.
    TENCON 2010 - 2010 IEEE Region 10 Conference; 01/2010
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    ABSTRACT: This paper reveals a novel dispersion compensating photonic crystal fiber (DC-PCF) for wide-band high-speed transmission systems. The finite-difference method with an anisotropic perfectly matched absorbing layers boundary condition is used to investigate the guiding properties. The designed novel DC-PCF shows that it is possible to obtain a larger negative dispersion coefficient, better dispersion slope compensation, and confinement losses less than 10−4 dB/m in the entire S+C+L telecommunication band by using a modest number of design parameters. The proposed module can be used in 40 Gb/s dense wavelength division multiplexing (DWDM) systems in optical fiber communication networks.
    Optics & Laser Technology 09/2009; 41(6-41):679-686. DOI:10.1016/j.optlastec.2009.02.001 · 1.65 Impact Factor
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    ABSTRACT: We numerically report the design of a modified octagonal photonic crystal fiber (M-OPCF) for broadband dispersion compensation covering the C and L communication bands, i.e., wavelengths ranging from 1530 to 1625 nm. It was shown that the proposed broadband compensating PCF can be designed to simultaneously exhibit a high negative dispersion coefficient and a relative dispersion slope (RDS) close to that of a conventional single-mode optical fiber (SMF). From our results, it was found that the M-OPCF has a large negative dispersion [-226 to -290 ps/(nm\cdotkm)] over the C- and L-bands, and an RDS close to that of an SMF of about 0.0034 nm-1. In addition to this, the effective dispersion, residual dispersion, confinement loss, and polarization properties of the proposed PCF are also reported and discussed.
    Japanese Journal of Applied Physics 05/2009; 48(5). DOI:10.1143/JJAP.48.052401 · 1.06 Impact Factor
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    ABSTRACT: The present article describes novel highly nonlinear photonic crystal fibers (HN-PCFs) with flattened chromatic dispersion and low confinement losses. The proposed design has been simulated based on the finite-difference method with anisotropic perfectly matched layers absorbing boundary condition. It is proved that the design novel HN-PCFs is obtained a nonlinear coefficient greater than 45W−1km−1 and low dispersion slope −0.009ps/(nm2.km) at 1.55μm wavelength. In addition, results from numerical simulation show that the ultra-flattened dispersion of 0±0.65ps/(nm.km) can be obtained in a 1.36–1.62μm wavelength range with confinement losses lower than 10−7dB/m in the same wavelength range. Another advantage of the proposed HN-PCFs is that it possessed modest number of design parameters.
    Optics Communications 04/2009; 282(7):1416-1421. DOI:10.1016/j.optcom.2008.12.005 · 1.54 Impact Factor

Publication Stats

951 Citations
114.19 Total Impact Points

Institutions

  • 1993–2014
    • University of the Ryukyus
      • • Faculty of Medicine
      • • Graduate School of Engineering and Science
      • • Department of Electrical and Electronics Engineering
      • • First Department of Internal Medicine
      • • Department of Neurosurgery
      Okinawa, Okinawa, Japan
  • 1994–2007
    • The University of Okinawa
      Okinawa, Okinawa, Japan