A. Ando

Tohoku University, Japan

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Publications (205)240.61 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Measurement of negative hydrogen ions (H-) is one of the important diagnostics for development of negative ion sources. Cavity-Ring-Down (CRD) measurement system was successfully implemented for the H- density measurements in the Field-Effect-Transistor based Radio Frequency ion source. Reliability of the CRD system was experimentally confirmed, and basic characteristics of the H- ions and the ion source were studied. The measured H- density varied from 1015 to 1016 m-3 depending on the source parameters, such as input RF power, axial magnetic field in the driver region, and source pressure. The H- density increased linearly with increase of the RF power and the axial magnetic field increased, due to improvement of power transmission and plasma production efficiency. Source gas pressure dependence of the Hdensity showed an increase of H- density with the decrease of pressure. Higher electron temperature and lower neutral gas resulted in increased production of vibrationally excited molecules and decreased destructions of H- ions, which was feasible for in high H- density at low source pressure.
    02/2013;
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    ABSTRACT: This paper briefly summarizes a workshop held in Jyvaskyla the day after NIBS'12. The half-day workshop aimed at globally capturing the issue of performance variations in H- sources. There was a focus on production facilities and facilities that work under production-like conditions, because there are often high expectations to be met.
    02/2013;
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    ABSTRACT: To evaluate retrospectively the long-term effects of initial trabeculotomy combined with sinusotomy performed inferiorly. Enrolled were 128 eyes of 100 patients who received initial glaucoma surgery. In 36 eyes, the removal of Schlemm's canal endothelium was also performed (removed group). The results were compared with the intact group In the primary open angle glaucoma (POAG), mean intraocular pressure (IOP) at 3 years after surgery was 14.6 (intact) and 15.4 mmHg (removed). Kaplan-Meier life-table analysis showed that qualified success rates for the intact group at 8 years were 62.2% and for the removed group at 5 years 45.2% defined by 20 mmHg or lower. The results in developmental glaucoma (DG) were similar to those in POAG. No statistical differences in postoperative IOP between the intact and removed groups were seen in either POAG or DG. In exfoliation glaucoma (XFG), mean IOPs for the intact group at 3 years were 17.3 mmHg and for the removed group at 2 years 15.4 mmHg. The success rates for the intact group at 3.5 years were 25.2% and for the removed group at 4.5 years 64.3%. The results in the intact group were worse than in the POAG patients. Although visual disturbance was seen in 13% of the patients, the major cause was the progression of the cataracts. The long-term results were the same as those of previous reports on surgery performed superiorly, including the frequency of visual disturbance. However the removal of Schlemm's canal endothelium is necessary in XFG for better IOP control.
    Nippon Ganka Gakkai zasshi 08/2012; 116(8):740-50.
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    ABSTRACT: H(-) beam was successfully extracted from a cesium seeded ion source operated using a field effect transistor inverter power supply as a radio frequency (RF) wave source. High density hydrogen plasma more than 10(19) m(-3) was obtained using an external type antenna with RF frequency of lower than 0.5 MHz. The source was isolated by an isolation transformer and H(-) ion beam was extracted from a single aperture. Acceleration current and extraction current increased with the increase of extraction voltage. Addition of a small amount of cesium vapor into the source enhanced the currents.
    The Review of scientific instruments 02/2012; 83(2):02B122. · 1.52 Impact Factor
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    ABSTRACT: Hydrogen negative ion density measurements are required to clarify the characteristics of negative ion production and ion source performance. Both of laser photodetachment and cavity ring down (CRD) measurements have been implemented to a field-effect-transistor based radio-frequency ion source. The density ratio of negative hydrogen ions to electrons was successfully measured by laser photodetachment and effect of magnetic filter field on negative ion density was confirmed. The calculated CRD signal showed that CRD mirrors with >99.990% reflectivity are required and loss of reflectivity due to cesium contamination should be minimized.
    The Review of scientific instruments 02/2012; 83(2):02A731. · 1.52 Impact Factor
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    ABSTRACT: PURPOSE:: Large diurnal intraocular pressure (IOP) fluctuation (▵IOP) is believed to be one of the causes of progression in glaucomatous changes. Some fully medicated glaucoma patients whose IOPs are controlled during the regular office hours (10:00 to 16:00 h) still have progression in glaucomatous changes and IOP elevation during off-office hours. The purpose of this study was to determine whether ▵IOP is dampened after combined trabeculotomy and sinusotomy (LOT+SIN) in glaucoma patients with low IOPs during the regular office hours. PATIENTS AND METHODS:: Fourteen eyes of 8 open-angle glaucoma patients who had large ▵IOP despite low IOPs during the office hours were studied. The IOP was measured every 3 hours for 24 hours before and >3 months after the operation. The IOPs were measured in the sitting position with a Goldmann applanation tonometer. All patients underwent LOT+SIN. RESULTS:: All patients had IOP elevations >20 mm Hg between 0:00 and 3:00 hours before the operation, and none had an IOP peak after the operation. The postoperative mean IOP (16.5±1.7 to 13.9±2.0 mm Hg, P=0.00064), the maximum IOP (21.9±2.4 to 16.1±2.5 mm Hg, P=0.0020), and ▵IOP (8.9±2.7 to 4.3±1.2 mm Hg, P=0.0032) were significantly lower than the preoperative values. However, the minimum IOP was not reduced significantly (13.0±1.9 to 11.7±1.7 mm Hg). CONCLUSIONS:: The diurnal ▵IOPs are dampened by LOT+SIN in glaucoma patients with controlled IOPs during regular office hours. These results indicate that these surgical procedures can be used for the treatment of open-angle glaucoma patients.
    Journal of glaucoma 01/2012; · 1.74 Impact Factor
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    ABSTRACT: Characteristics of radio frequency (RF) plasma production were investigated using a FET inverter power supply as a RF generator. High density hydrogen plasma was obtained using an external coil wound a cylindrical ceramic tube (driver region) with RF frequency of lower than 0.5 MHz. When an axial magnetic field around 10 mT was applied to the driver region, an electron density increased drastically and attained to over 1019 m-3 in the driver region. Effect of the axial magnetic field in driver and expansion region was examined. Lower gas pressure operation below 0.5 Pa was possible with higher RF frequency. H- density in the expansion region was measured by using laser photo-detachment system. It decreased as the axial magnetic field applied, which was caused by the increase of energetic electron from the driver.
    09/2011;
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    ABSTRACT: The authors previously reported ornithine cytotoxicity in ornithine-δ-aminotransferase (OAT)-deficient human retinal pigment epithelial (RPE) cells as an in vitro model of gyrate atrophy of the choroid and retina (GA). Given that RPE cells are severely damaged by arginine combined with ornithine, they investigated the role of arginine metabolism using that in vitro model. Human telomerase reverse transcriptase (hTERT)-RPE cells were incubated with ornithine or other agents in the presence of 5-fluoromethylornithine (5-FMO), an OAT-specific inhibitor. mRNA expression was determined by quantitative real-time polymerase chain reaction, and the concentration of nitric oxide (NO) was quantified using a Griess assay. Furthermore, cytotoxicity was examined by morphologic observations and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assays, with the effect of arginase II examined using short interfering (si) RNA for arginase II and S-(2-boronoethyl)-L-cysteine (BEC), an arginase inhibitor. NO production in 5-FMO-treated hTERT-RPE cells was increased by ornithine, and the NO donors S-nitroso-N-acetyl-DL-penicillamine (SNAP) and S-nitrosoglutathione induced cytotoxicity. Ornithine increased the expression of arginase II mRNA in 5-FMO-treated cells. Arginase II upregulation was partially inhibited by an NO synthase inhibitor, N(G)-nitro-L-arginine methyl ester, which was mimicked by SNAP. Arginase II siRNA and BEC enhanced ornithine cytotoxicity, and arginase II silencing resulted in a further increase in NO production. These results demonstrate that NO is produced in our in vitro GA model, which induced cytotoxicity of RPE cells and upregulation of arginase II. NO may be involved in RPE degeneration in GA through the regulation of arginase II mRNA expression.
    Investigative ophthalmology & visual science 03/2011; 52(3):1493-500. · 3.43 Impact Factor
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    ABSTRACT: A plasma current of up to 70 kA has been sustained in WT-3 discharges by second harmonic (2Ωe) electron cyclotron (EC) waves alone, with zero loop voltage, after shutting off the Ohmic heating power. Further, in the case of high power EC wave injection, ramp-up discharges have been obtained. Pulse height analysis of hard X-rays in the line of sight at various angles to the toroidal field shows that the velocity distribution function of the high energy tail electrons is asymmetric in the toroidal direction. The 2Ωe EC wave is mainly absorbed by the tail electrons, and a 2Ωe EC driven current is generated by enhancing the asymmetry of the distribution. The figure of merit of 2Ωe EC current drive (ECCD) is ηEC(2) = (3.2-6.4) × 10−2 (1019 A/Wm2), which is one order of magnitude smaller than that of lower hybrid current drive in WT-3. This low value of ηEC(2) can be attributed to low confinement of the current carrying, high energy tail electrons produced by 2Ωe ECCD.
    Nuclear Fusion 01/2011; 31(9):1673. · 2.73 Impact Factor
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    ABSTRACT: By injecting microwave power (120 kW, 35.6 GHz) into the WT-2 device, a toroidal plasma is produced by electron cyclotron heating near the upper-hybrid resonance. (1) The production mechanism is interpreted as the result of damping of electron Bernstein waves and described by a ray-tracing code. (2) The production mechanism of high-energy electrons in such a plasma is studied and interpreted as a competition between electron acceleration by the incident wave and deceleration by collisions. These electrons interact resonantly with the lower hybrid wave during the startup of an RF tokamak discharge. (3) The first experimental observation, in an ECR plasma, of the resulting macroinstability, consistent with a theory suggested by Peng et al., is reported. (4) This instability is suppressed by the lower-hybrid driven current, the required rotational transform being produced by this current.
    Nuclear Fusion 01/2011; 26(3):349. · 2.73 Impact Factor
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    ABSTRACT: A series of experiments has been conducted on the JIPP TII-U tokamak since 1989, using the newly constructed 130 MHz radiofrequency system. It has been predicted theoretically that the fast wave in this frequency range interacts weakly with particles. Two mechanisms of wave absorption have been identified in the experiment: electron Landau damping/transit time damping and 3rd harmonic ion cyclotron heating. The former mechanism is intimately connected with fast wave current drive and the latter can provide a new regime of plasma heating or a possible method of controlling the transport of alpha particles. It is found that the efficiency of the 3rd harmonic ion cyclotron heating is improved by using it in combination with neutral beam injection and ion cyclotron range of frequency heating. The heating efficiency obtained is as high as that of conventional heating. The experimental results are also analysed on the basis of a global wave theory which takes into account wave-particle interactions. These mechanisms of interaction are competing with each other; this will also be the case under more realistic reactor conditions.
    Nuclear Fusion 01/2011; 31(7):1369. · 2.73 Impact Factor
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    ABSTRACT: Toroidal plasma rotation driven not by the momentum input but by the electric field induced by loss of ions has been observed for plasmas heated by perpendicular neutral beam injection. The rotation is found to increase in the direction opposite to the plasma current when the plasma ions are heated by ion cyclotron resonance frequency waves. The rotation driven by the electric field is quantitatively consistent with that inferred from the ambipolarity of particle fluxes.
    Nuclear Fusion 01/2011; 31(5):943. · 2.73 Impact Factor
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    ABSTRACT: The H-mode, an improved confinement regime, was attained recently in JIPP T-IIU high power heating experiments, in a limiter configuration without any shaping of the plasma cross-section. This H-mode is unusual because it was obtained with heating in the ion cyclotron range of frequencies (ICRF). It was also attained with combined ICRF and neutral beam injection (NBI) heating. The threshold power level obtained with ICRF alone is similar to or less than that obtained in the combined heating case. The dependence of the power threshold of the H-mode on various plasma parameters has been studied. It increases with the plasma current and is insensitive to the plasma density, and there is an optimum value of the toroidal field intensity. The power deposition profile for ICRF heating has been analysed with a ray tracing code and used to explain the observed dependence on the toroidal magnetic field. The paper also discusses a class of discharges with improved confinement observed in the same series of experiments. These discharges had a power level close to the H-mode threshold power and exhibited a marked improvement of confinement. They were, however, different from H-mode discharges in the time evolution of the profiles.
    Nuclear Fusion 01/2011; 30(7):1197. · 2.73 Impact Factor
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    ABSTRACT: The anti-aquaporin-4 (AQP4) antibody was recently reported to be associated with neuromyelitis optica (NMO). Optic nerve involvements in many NMO cases are bilateral and the prognosis is poor. However, it has been suggested that plasma exchange is effective for those patients when steroid pulse therapy is ineffective. Herein, we report successful treatment of a patient with NMO using double-filtration plasmapheresis (DFPP). A 22-year-old woman consulted a neurologist for neck pain in March 2008. High-intensity lesions were shown in the cervical spinal cord by T2-weighted magnetic resonance imaging. On July 15, the patient was referred to our department for a headache and pain and blurred vision in the left eye. The best-corrected visual acuity was 20/50 and 20/500 in the right and left eyes, respectively, with visual field defects observed in both. After 3 courses of steroid pulse therapy, anti-AQP4 antibodies were positive. In November, the patient again noticed visual acuity loss in the left eye and was treated by additional steroid pulse therapy, which was not effective. Next, she underwent plasma exchange therapy, though it was stopped due to hypotension and dyspnea. The next day, the patient underwent DFPP treatment and visual function gradually recovered. It is important to consider NMO when steroid pulse therapy is not effective. We successfully and safely treated NMO in a young adult patient using DFPP.
    Journal of ocular pharmacology and therapeutics: the official journal of the Association for Ocular Pharmacology and Therapeutics 08/2010; 26(4):381-5. · 1.46 Impact Factor
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    ABSTRACT: Characteristics of radio frequency (RF) plasma production are investigated using a field effect transistor inverter power supply as an RF wave source. With the frequency of around 0.3 MHz, an electron density over 10<sup>18</sup> m <sup>-3</sup> is produced in argon plasma. Although lower densities are obtained in hydrogen plasma, it drastically increased up to 5×10<sup>18</sup> m <sup>-3</sup> with an axial magnetic field of around 100 G applied in the driver region. Effects of the magnetic field and gas pressure are investigated in the RF produced plasma with the frequency of several hundred kilohertz.
    Review of Scientific Instruments 03/2010; · 1.60 Impact Factor
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    ABSTRACT: Fusion Energy Division, ORNL QUEST focuses on the steady state operation of the spherical tokamak by controlled PWI and electron Bernstain wave current drive. One of the main purposes of QUEST is an achievement of long duration discharge with MW-class injected power. As the result, QUEST should be operated in the challenging region on heat and particle handling. To do the particle handling, high temperature all metal wall up to 600K and closed divertors are planned, which is to realize the steady-state operation under recycling ratio, R=1. This is a dispensable check to DEMO, because wall pumping should be avoided as possible in the view of tritium retention. The program to execute QUEST experiments will be developed in increment step such as, I. low β steady state operation in limiter configuration, II. low β steady state operation in divertor configuration, III relatively high β steady state operation in closed divertor configuration. Phase I in the project corresponds to these two years, and final goal of phase I is to make full current drive plasma up to 20kA. Closed divertor will be designed and tested in the Phase II. QUEST is running from Oct., 2008 and the first results is introduced.
    Plasma and Fusion Research. 01/2010; 5.
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    ABSTRACT: We examined the effectiveness of latanoprost for reducing intraocular pressure (IOP) in Japanese patients with normal tension glaucoma (NTG) over a 5-year period. Design: Prospective interventional case series. The patients were classified into 2 groups based on mean IOP. A total of 38 patients with NTG were studied after being classified into the high-tension (mean IOP 16 mmHg or greater, n = 27) and low-tension (mean IOP lower than 15 mmHg, n = 11) groups. IOP was measured and Humphrey Field Analyzer (HFA) examinations were conducted at 6, 12, 24, 36, 48, and 60 months after beginning a daily administration of latanoprost. Mean IOP before administration was 17.6 mmHg in the high-tension group, which was reduced to 13.9, 14.6, 14.4, 14.1, 13.6, and 14.6 mmHg at 6, 12, 24, 36, 48, and 60 months, respectively, after beginning administration. That in the low-tension group was 13.6 mmHg before administration, and then was reduced to 12.2, 11.4, 11.5, 12.5, 10.5, and 11.5 mmHg, respectively, after beginning administration was noted. Mean deviation (MD) values in the HFA examinations were reduced by -4.27 and -1.49 dB after 5 years in the high- and low-tension groups, respectively. Latanoprost administration was effective in reducing IOP over a 5-year period in a range of 3.1-4.1 and 1.3-3.6 mmHg in NTG patients with high- and low-tension levels, respectively. In addition, our results indicate that latanoprost helped to prevent a decrease in MD values in both groups, as shown by the results of HFA examinations.
    Journal of ocular pharmacology and therapeutics: the official journal of the Association for Ocular Pharmacology and Therapeutics 10/2009; 25(5):441-5. · 1.46 Impact Factor
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    ABSTRACT: Characteristics of radio frequency(rf) plasma production are investigated using a FET inverter power supply as an rf generator. The matching circuit in the inverter system is simple compared to a conventional 50 Ohm matching system and only an imaginary part of the impedance of rf transmission should be matched by adjusting operating frequency or capacitance of the circuit. An electron density over 10{sup 18} m{sup -3} is produced in argon plasma with 1 kW rf power. Lower densities are obtained in helium and hydrogen plasmas compared to the argon plasma. Effect of axial magnetic field in driver region is examined. Electron density more than 10{sup 18} m{sup -3} is obtained at the hydrogen gas pressure around 1 Pa with the help of the axial magnetic field.
    AIP Conference Proceedings 03/2009; 1097(1).
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    ABSTRACT: High power ion cyclotron resonance heating is performed in a fast-flowing plasma operated with hydrogen and helium gases. Ion heating is clearly observed in hydrogen plasma as well as in helium plasma. The resonance region of magnetic field is broader and wave absorption efficiency is higher in hydrogen plasma than those in helium plasma. The thermal energy of the heated ions is converted to the kinetic energy of the exhaust plume by passing through a diverging magnetic nozzle set in a downstream region. In the magnetic nozzle energy conversion occurred as keeping the magnetic moment constant, but some discrepancy was observed in larger gradient of magnetic field. The kinetic energy of the exhaust plume is successfully controlled by an input power of radio-frequency wave, which is one of the key technologies for the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) type plasma thruster.
    TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES SPACE TECHNOLOGY JAPAN 01/2009; 7.
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    ABSTRACT: In this paper, we report a case of severe optic neuropathy caused by dichloromethane inhalation. A 65-year-old man fell unconsciousness while cleaning a dichloromethane tank containing a small amount of dichloromethane (purity greater than 99%) and was transported to the emergency department of our hospital, after which he was treated with hyperbaric oxygen therapy. After 1 month, narrowing of the visual field in both eyes was noted and the patient was referred to our department for additional examinations. Visual acuity was 0.3 in both eyes, which demonstrated normal reactions to light, while the critical flicker frequency (CFF) values were 30 and 25 Hz in the right and left eye, respectively. There were no abnormal findings shown in slit-lamp and fundus examinations, except for a mild cataract. Concentric contractions of the visual field by 10 degrees in both eyes were shown by a Goldmann perimetry examination, while an electroretinogram (ERG) and visual evoked cortical potential (VECP) examination exhibited nearly normal results. We diagnosed the condition as optic neuropathy caused by organic solvent poisoning, based on the decreased visual acuity, decreased CFF values, and visual-field narrowing. Although the patient was treated with vitamin B(12), visual disturbance, optic nerve atrophy, and results of VECP examinations worsened in both eyes, whereas ERG examination results were normal. Based on our findings, we considered that the central nervous system, including the optic nerve, was more severely damaged than the retina due to the normal findings in the ocular fundus and ERG examinations. Since dichloromethane produces carbon monoxide when catabolized in the liver, carbon monoxide toxicity together with the direct toxic effect of dichloromethane were considered to contribute to optic neuropathy in this case. The outcome for the present patient was poor.
    Journal of ocular pharmacology and therapeutics: the official journal of the Association for Ocular Pharmacology and Therapeutics 01/2009; 24(6):607-12. · 1.46 Impact Factor

Publication Stats

1k Citations
240.61 Total Impact Points

Institutions

  • 1995–2012
    • Tohoku University
      • • Department of Electrical Engineering
      • • Graduate School of Engineering
      • • School of Engineering
      Japan
  • 2011
    • Niigata University
      Niahi-niigata, Niigata, Japan
    • University of Houston
      Houston, Texas, United States
  • 1983–2011
    • Kyoto University
      • Department of Physics II
      Kyoto, Kyoto-fu, Japan
  • 1997–2009
    • Kansai Medical University
      • Department of Ophthalmology
      Moriguchi, Osaka-fu, Japan
  • 2000–2003
    • Johns Hopkins University
      • Wilmer Eye Institute
      Baltimore, Maryland, United States
    • National Institutes of Health
      Maryland, United States
  • 1990–2002
    • National Institute for Fusion Science
      Tokitsu-chō, Gifu, Japan
    • Nagoya University
      • Department of Energy Engineering and Science
      Nagoya-shi, Aichi-ken, Japan
  • 1998
    • Himeji Institute of Technology
      Himezi, Hyōgo, Japan