S.Y. Ryu

Osaka University, Suika, Ōsaka, Japan

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Publications (79)83.15 Total impact

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    ABSTRACT: We have developed a time-of-flight (ToF) array consisting of 24 plastic scintillators for triggering and timing measurements in a series of planned experiments to study double-strangeness hadronic and nuclear systems at the K1.8 beamline of J-PARC. Each ToF scintillator is 180 cm long with a cross-section of , and is read out by H1949-51 photomultiplier tubes at both ends. The timing and attenuation properties of the scintillators are measured using cosmic-ray muons and β rays from 90Sr. The cosmic-ray muon events are triggered by three pairs of 120-cm-long plastic scintillators, sandwiching the ToF array. The intrinsic time resolutions of the scintillators are estimated to be in the range 60-100 ps, which is adequate for reliable separation between π and K at . The attenuation length is measured to be approximately 210 cm, which is half that for a bulk scintillator.
    No preview · Article · May 2015 · Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment
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    ABSTRACT: We have developed a GEM-TPC for H-dibaryon search at J-PARC E42, which reconstructs charged particles from the H-dibaryon decay in (K; K+) reaction. Since 10(6) cps/cm(2) K- beams are injected to the TPC, GEMs and a gating grid are adopted to suppress positive ion feedback. The TPC is also designed to have good position resolutions corresponding to the Lambda Lambda invariant mass resolution of a few MeV/c(2). The design of the E42 TPC, and performance evaluations of a prototype TPC are described.
    No preview · Article · Mar 2014 · Journal of Instrumentation
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    ABSTRACT: H-dibaryon has been predicted as a stable 6-quark color-singlet state. It has been searched for by many experiments but has never been discovered. Recent lattice QCD calculations predict H-dibaryon as a weakly bound or a resonant state close to the Lambda Lambda threshold. E224 and E522 experiments at KEK observed peaks in Lambda Lambda invariant mass spectra near the threshold in (K-, K+) reactions, which were statistically not significant. Therefore, we proposed a new experiment E42 at J-PARC. It will measure decay products o Lambda Lambda and Lambda pi p in a (K-, K+) reaction. We design a large acceptance spectrometer based on a Time Projection Chamber (TPC) immersed in a dipole magnetic field. The TPC surrounds a target to cover nearly 4 pi acceptance, and accepts K- beams up to 10(6) counts per second. To suppress drift field distortion at high beam rates, we adopt Gas Electron Multipliers (GEMs) for electron amplification and a gating grid. We show an overview of the experiment, the design of the spectrometer, and the R&D status of the TPC prototype.
    Full-text · Article · Mar 2014 · The European Physical Journal Conferences
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    ABSTRACT: The purpose of this paper is to establish the cytogenetic analyses of human peripheral blood samples caused by simulation of partial-body exposures. Either accidental or occupational partial-body exposure to ionizing radiation poses significant health hazards that are indicated by induction of chromosome aberrations (CA). The percentages of mixtures of blood samples irradiated in vitro with 2 Gy of gamma rays were 10, 25, 50, 75 and 100.0%. Lymphocytes were cultured for 48 hr, harvested with standard procedures and then first-division metaphase cells were analyzed. It showed that the frequencies of unstable CA depend on the proportion of the irradiated blood. All frequencies of the observed CA was lower than that of predicted or calculated from 100% exposed blood, except in one case, indicating a phenomenon of "dilution" of the un-irradiated into irradiated lymphocytes that may take place a bystander effects. Our data showed that the quantification of CA in human peripheral blood lymphocytes may be an important tool of dose assessment for partial-body exposure to ionizing radiation.
    No preview · Article · Jan 2014 · Pakistan Veterinary Journal
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    ABSTRACT: A search for $K^-pp$ bound state (the lightest kaonic nucleus) has been performed using the $\gamma d \rightarrow K^+ \pi^- \rm{X}$ reaction at E$_\gamma$=1.5-2.4 GeV at LEPS/SPring-8. The differential cross section of $K^+ \pi^-$ photo-production off deuterium has been measured for the first time in this energy region, and a bump structure was searched for in the inclusive missing mass spectrum. A statistically significant bump structure was not observed in the region from 2.22 to 2.36 GeV/$c^2$, and the upper limits of the differential cross section for the $K^-pp$ bound state production were determined to be 0.1$-$0.7 $\mu$ b (95$%$ confidence level) for a set of assumed binding energy and width values.
    Full-text · Article · Jun 2013
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    ABSTRACT: We report the measurement of differential cross sections for $\omega$ and $\eta'$ photoproduction from protons at backward angles ($-1.0<\cos\Theta_{C.M}^{X}<-0.8$) using linearly polarized photons at $E_{\gamma}=$$1.5-3.0$ GeV. Differential cross sections for $\omega$ mesons are larger than the predicted $u$-channel contribution in the energy range $2.0\leq\sqrt{s}\leq2.4$ GeV. The differential cross sections for $\omega$ and $\eta'$ mesons become closer to the predicted $u$-channel contribution at $\sqrt{s}>2.4$ GeV. A bump structure in the $\sqrt{s}$ dependence of the differential cross sections for $\eta'$ mesons was observed at $\sqrt{s}\sim$2.35 GeV.
    Full-text · Article · Jun 2013 · Progress of Theoretical and Experimental Physics
  • R. Yu · W.-H. Shin · S. Kim · K.-H. Son · D.-M. Kwak · S.R. Kim · S.-Y. Ryu · S.-J. Park
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    ABSTRACT: Acute gastric ulcer is caused by the unbalance between cell proliferation and apoptosis in gastric mucosa. Platycodin D (PD) has been reported to have a variety of pharmacological properties, including antioxidant and antiinflammatory effect. In the present study, we investigated the protective effect of PD on the basis of cell proliferation/ apoptosis and cyclooxygenase-2 (COX-2) expression in the acute gastric ulcer induced by ibuprofen in Rats. Acute gastric damage was induced by the repeated treatment of ibuprofen (200 mg/kg) with 8 hrs interval in a day. PD was orally administrated at concentrations of 2.5 and 5 mg/kg every day for 5 days before the induction of acute gastric ulcer. Macroscopically, ibuprofen caused a significant increase in the number of lesions in the gastric mucosa. But pretreatment of PD significantly reduced ibuprofen-induced gastric lesion score and prevented excessive mucus depletion in gastric mucosa. Also, pretreatment of PD counteracted significantly Ki-67 decrease in the proliferating zone of gastric glandular portion and highly reduced or delayed apoptotic cells on TUNEL assay. In addition, COX-2 expression was increased in gastric mucosa bearing erosions or ulcers but pretreatment of PD reduced COX-2 expression in gastric lesions. These results show that pretreatment of PD has a protective effect against ibuprofen-induced gastric damage, not only by counteracting a decrease of cell proliferation, but also by inhibiting or delaying apoptosis via regulation of COX-2 within the gastric mucosa.
    No preview · Article · Feb 2013 · Journal of Veterinary Clinics
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    ABSTRACT: A mass was detected in the oral cavity from a 18-year-old female miniature poodle dog. Grossly, the mass was soft to hard, red to purple, and 1.5 × 1.5 × 1 cm in size. Histopathologically, the mass was composed of hyperplastic gingival epithelium, well-vascularized stroma, closely packed pleomorphic cells, and numerous giant cells with multiple nuclei and abundant eosinophilic cytoplasm. Immunohistochemically, tumor cells were positive for alkaline phosphatase and cytokeratin 7, but not positive for CD68 unlike in human. The mass was diagnosed to peripheral giant cell granuloma in oral cavity through typical clinical and histopathological features.
    No preview · Article · Jan 2013 · Journal of Veterinary Clinics
  • C. Sim · H.C. Kim · H.Y. Son · J.Y. Jung · S.Y. Ryu · B.K. Park
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    ABSTRACT: We describe Dirofilaria immitis occurring in the peritoneal cavity of a dog from Korea. Two worms were found in the fat of the umbrical cord area during operation for an umbrical cord hernia in a dog (four year old, female, Maltese). In gross findings, the worms were slander white and measured 132 mm (female), 111 mm (male). The tail of the male was spirally coiled. In light microscopy, the uterus was filled with not fully developed eggs. Scanning electron microscopy revealed that the cuticule was smooth on the head but those of the tail exhibited complex cuticular striation in the male. Head papillae were located in a cephalic plate forming a rectangular pattern dorsoventrally, with 4 inner labial papillae and four outer cephalic papillae. The mouth opening was very small and the bursal cavity was absent. Laterally there was a pair of amphids.
    No preview · Article · Jan 2013 · Veterinární medicína
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    ABSTRACT: Mushrooms have a long history of use in traditional medicine, and hundreds of novel constituents in mushrooms with miraculous biological properties have been identified recently. Although diverse effects for medicinal use of mushrooms such as anticancer activity are proven, their reversal activities of drug resistance in cancer cells was rarely reported so far. In the search for novel medicinal use of mushrooms, we tested the multidrug resistance (MDR) reversal activities of diverse mushrooms collected from Korea. Among, the mushroom extracts tested, Cantharellus cibarius (M02) and Russula emetica (M12) revealed MDR reversal activities of paclitaxel in the P-glycoprotein (Pgp)-positive HCT 15 and MES-SA/dX5 cancer cells, but not in the Pgp-negative A549 and MES-SA cancer cells. In addition, these mushrooms also enhanced the cytotoxicity of doxorubicin, another well-kwown Pgp-associated anticancer drug against MES-SA/DX5 cells, but not against MES-SA cells. Meanwhile, the cytotoxicity of cisplatin, a well-known Pgp-non-associated anticancer drug, was not affected by the mushrooms all the cells tested. From these results, we suspected that some ingredients of M02 and M12 have Pgp-associated MDR reversal activities.
    No preview · Article · Dec 2012 · Natural Product Sciences
  • CW Choi · JS Choi · GH Yon · YK Ko · SY Ryu · CJ Kim · YI Kwon · YH Kim

    No preview · Article · Jul 2012 · Planta Medica
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    ABSTRACT: The exclusive reaction γp→K(+)π(-)Σ(+) was measured for the first time using linearly polarized photons at beam energies from 1.85 to 2.96 GeV. Angular distributions in the rest frame of the K(+)π(-) system were fitted to extract spin-density matrix elements of the K(*0) decay. The measured parity spin asymmetry shows that natural-parity exchange is dominant in this reaction. This result clearly indicates the need for t-channel exchange of the κ(800) scalar meson.
    No preview · Article · Mar 2012 · Physical Review Letters

  • No preview · Article · Feb 2012 · Physical Review Letters
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    ABSTRACT: We investigate the caesium concentrations in soils in mountain areas near Gori nuclear power plant in Korea, focusing on the measurement limits to the 134 Cs. In order to lower the minimum detectable amount (MDA) of activity for the 134 Cs, we have used the ammonium molybdophosphase (AMP) precipitation method to get rid of the 40 K existing in natural radioactivity, which reduces the MDA activity about ten times smaller than those without the AMP precipitation method. The MDA results for the 134 Cs were found to be in the range between 0.015 and 0.044 Bq/kg-dry weight. In order to diminish the background, we also have measured a part of the soil samples in Yangyang, a small town in the east coast of Korea. However, it turns out that in order to detect the 134 Cs in the samples the MDA should be reduced to the level of mBq/kg-dry weight.
    Full-text · Article · Jan 2012
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    O. Gendaram · Y.H. Choi · Y.S. Kim · S.Y. Ryu
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    ABSTRACT: Phytochemical studies on the whole extract of Sedum hybridum L., a Mongolian medicinal plant, has been undertaken to isolate active principles responsible for its anti-oxidative and antibacterial activities. Eighteen known compounds, i.e. (1) quercetin, (2) kaempferol, (3) herbacetin-8-O-β-D-xylopyranoside, (4) myricetin, (5) gossypetin-8-O-β-D-xylopyranoside, (6) gallic acid, (7) 2,4,6-tri-O-galloyl-D-glucopyranose, (8) 6-O-galloylarbutin, (9) myricetin-3-O-α-L-arabinofuranoside, (10) quercetin-3-O-α-L-arabinofuranoside, (11) caffeic acid, (12) ethylgallate, (13) (-) epigallocatechin-3-O-gallate, (14) palmitic acid, (15) stearic acid, (16) stearic acid ethyl ether, (17) β-sitosterol and (18) β-sitosteryl-O-β-D-glucopyranose have been isolated and their molecular structures identified by spectroscopic analysis. Thirteen substances including seven flavonol components (1, 2, 3, 4, 5, 9 and 10), five gallic acid derivatives (6, 7, 8, 12 and 13) and caffeic acid (11) exhibited significant, dose-dependent, DPPH radical scavenging activity. Galloyl esters 12 and 13 were revealed to be main active principles for the antibacterial property of the extract of Sedum hybridum L.
    Full-text · Article · Dec 2011 · Natural Product Sciences
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    ABSTRACT: We investigate the caesium concentrations in soils in mountain areas near Gori nuclear power plant in Korea, focusing on the measurement limits to the (134)Cs. In order to lower the minimum detectable amount (MDA) of activity for the (134)Cs, we have used the ammonium molybdophosphate (AMP) precipitation method to get rid of the (40)K existing in natural radioactivity, which reduces the MDA activity about 10 times smaller than those without the AMP precipitation method. The MDA results for the (134)Cs were found to be in the range between 0.015 and 0.044 Bq/kg-dry weight. In order to diminish the background, we also have measured a part of the soil samples in Yangyang, a small town in the east coast of Korea. However, it turns out that in order to detect the (134)Cs in the samples the MDA should be reduced to the level of mBq/kg-dry weight.
    Full-text · Article · Sep 2011 · Applied radiation and isotopes: including data, instrumentation and methods for use in agriculture, industry and medicine
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    ABSTRACT: Background: The purpose of this paper is to establish an easy and reliable biodosimeter protocol to evaluate the biological effects of proton beams. Materials and Methods: Human peripheral blood lymphocytes were irradiated using proton beams (LET: 34.6 keV μm−1), and the chromosome aberrations induced were analyzed using cytokinesis-blocked (CB) micronucleus (MN) assay. To determine the efficiency of MN assay in estimating the doses received by 50MeV proton beams and to monitor predicted dose of victims in accidental exposure, here we have evaluated the performance of MN analysis in a simulated situation after exposure with proton beams. Peripheral lymphocytes were irradiated by 50MeV proton beams up to 6Gy and analyzed by Giemsa staining of CB MN assay. Results: The detected MN was found to be a significant dose-effect curve in the manner of dose-dependent increase after exposure with proton beams in vitro. When plotting on a linear scale against radiation dose, the line of best fit was Y=0.004+(1.882x10−2±9.701x10−5) D+(1.43x10−3±1.571x10−5)D2. Our results show a trend towards increase of the number of MN with increasing dose. It was linear-quadratic and has a significant relationship between the frequencies of MN and dose (R2= 0.9996). The number of MN in lymphocyte that was observed in control group is 5.202±0.04/cell. Conclusion: Hence, this simple protocol will be particularly useful for helping physicians to decide medical therapy for the initial treatment of victims with rapid and precise dose estimation after accidental radiation exposure. Also it has potential for use as a valuable biomarker to evaluate the biological effectiveness for cancer therapy with proton beams. © 2011, Novim Medical Radiation Institute. All rights reserved.
    Full-text · Article · Mar 2011 · Iranian journal of radiation research (IJRR)
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    ABSTRACT: The ameliorating effect of the saponin rich fraction (SRF) prepared from the roots extract of Platycodon grandiflorum (Campanulaceae) on the scopolamine-induced cognitive dysfunction in mice were investigated by way of Moris water maze task. The mice with repeated oral administration of the SRF for four weeks showed markedly reduced the swimming time and swimming distance to reach the platform as well as the increase of number of crossing the platform on the Moris water maze task performed after scopolamine intoxication. The results suggest that SRF obtained from the roots extract of P. grandiflorum exert a cognitive enhancing effect on scopolamine-induced memory impairment in mice.
    No preview · Article · Mar 2011 · Korean Journal of Pharmacognosy
  • J.-H. Son · B.-K. Park · S.-H. Seo · H.-Y. Son · S.-W. Cho · S.-Y. Ryu
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    ABSTRACT: To examine the seroprevalence of Neospora caninum (N. caninum) infections in cattle raised at farms where an abortion had previously occurred in Gongju city and Yeongi-gun of Chungnam Province, 280 head of cattle from six farms were examined by ELISA. Thirty-two pregnant cattle from four farms were examined to determine the abortion rate in N. caninum-infected pregnant cattle and the infection pattern in newborn calves. The six farms where the abortions had previously occurred demonstrated positive reactions to N. caninum. Although the mean seropositive rate of the six farms was 17.5%, the range of seropisitivity was 3.4-57.1% due to the difference in seroprevalence between farms. The general pattern of seropositivity in cows was higher than in heifers. In addition, the abortion rate of N. caninumpositive in 18 out of 32 pregnant dams raised in four farms was 16.7%. The seroprevalence of newborn calves from N. caninum-positive pregnant animals differed according to the farm but was 86.7% overall. In contrast, 14 newborn calves from the N. caninum-negative pregnant cattle showed negative responses. This suggests that N. caninum is endemic and occurs through vertical transmission from chronically-infected dams. Therefore, aborted dams should be discarded.
    No preview · Article · Feb 2011 · Journal of Veterinary Clinics
  • S.-G. LEE · S. Y. RYU · J. W. AHN
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    No preview · Article · Sep 2010 · ChemInform

Publication Stats

760 Citations
83.15 Total Impact Points

Institutions

  • 2015
    • Osaka University
      Suika, Ōsaka, Japan
  • 2011-2014
    • Pusan National University
      • Department of Physics
      Tsau-liang-hai, Busan, South Korea
  • 2012
    • Inha University
      • Department of Physics
      Chemulpo, Incheon, South Korea
  • 2000-2011
    • Chungnam National University
      • College of Veterinary Medicine
      Daiden, Daejeon, South Korea
  • 1994-2010
    • Korea Research Institute of Chemical Technology
      • Division of Drug Discovery Research
      Daiden, Daejeon, South Korea
  • 2008
    • Keimyung University
      Sŏul, Seoul, South Korea