S Y Ryu

Pusan National University, Tsau-liang-hai, Busan, South Korea

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Publications (34)63.47 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.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 05/2015; 795. DOI:10.1016/j.nima.2015.05.046 · 1.22 Impact Factor
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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.
    Journal of Instrumentation 03/2014; 9(04). DOI:10.1088/1748-0221/9/04/C04009 · 1.40 Impact Factor
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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.
    The European Physical Journal Conferences 03/2014; 66:09015. DOI:10.1051/epjconf/20146609015
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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.
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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.
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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.
    Physical Review Letters 03/2012; 108(9):092001. · 7.51 Impact Factor

  • Physical Review Letters 02/2012; 108(9). DOI:10.1103/PhysRevLett.108.092001 · 7.51 Impact Factor
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    J K Ahn · J S Kim · H M Lee · H Kim · T H Kim · J N Park · Y S Kang · H S Lee · S J Kim · J Y Park · S Y Ryu · W G Kang · S K Kim ·
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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.
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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.
    Applied radiation and isotopes: including data, instrumentation and methods for use in agriculture, industry and medicine 09/2011; 69(9):1294-8. DOI:10.1016/j.apradiso.2011.05.006 · 1.23 Impact Factor
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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.
  • YP Yun · J H Do · S R Ko · SY Ryu · J H Kim · H C Song · YD Park · K S Ahn · S H Kim ·
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    ABSTRACT: This study was undertaken to evaluate the antithrombotic effects of Korean Red Ginseng (KRG) and its new prescription (KRGP) consisting of five herbs such as Korean red ginseng, Ganoderma, Cinnamomi Cortex, Glycyrrhizae Radix and Laminaria. In rats with blood stasis induced by high molecular weight dextran, KRG and KRGP significantly restored not only the number of platelets and fibrinogen, but also suppressed the fibrin degradation products (FDP) to normal range. In platelet aggregation assay with human platelet rich plasma (PRP), KRG and KRGP significantly inhibited thrombin and collagen-induced platelet aggregation. The IC(50) values of KRG and KRGP were >2 and 0.23+/-0.01 mg/ml for thrombin, 0.32+/-0.01 and 0.17+/-0.02 mg/ml for collagen and 0.72+/-0.25 and >2 mg/ml for ADP, respectively. In coagulation assay, KRG and KRGP significantly prolonged activated partial prothrombin time (APPT) and prothrombin time (PT) as compared with control data. KRGP was found to be more effective than KRG alone on antithrombotic activity. These results suggest that KRGP may exert its antithrombotic activity due to inhibition of platelet aggregation and coagulation activity more than KRG.
    Journal of Ethnopharmacology 10/2001; 77(2-3):259-64. DOI:10.1016/S0378-8741(01)00303-8 · 3.00 Impact Factor
  • B N Kang · K S Jeong · S J Park · S J Kim · T H Kim · H J Kim · SY Ryu ·
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    ABSTRACT: Recent studies have shown that somatostatin (SOM) inhibits interleukin 6 (IL-6) and interferon gamma (IFNgamma) production by lymphocytes and peritoneal macrophages, whereas substance P (SP) enhances these cytokines production. To define the mechanism of the cytokine production enhancements and inhibitions by SOM and SP, we examined the expression of apoptosis modulator, p53, Bcl-2, Bax, inducible nitric oxide synthase (iNOS), Fas, caspase-8 and nitric oxide (NO) in thioglycolate-elicited peritoneal macrophages. SOM caused up-regulation of p53, Bcl-2, Fas and caspase-8 activities, and down-regulation of iNOS expression and NO production. On the other hand, SP slightly induces p53 and highly induces Bcl-2, iNOS expression and NO production. These data suggest that apoptosis by SOM may occur by a Bax- and NO-independent p53 accumulation, and through Fas and caspase-8 activation pathways, and that the inducible expression of Bcl-2 and NO production by SP may contribute to prevent the signals of apoptosis by Bax, and via Fas and caspase-8 activation.
    Regulatory Peptides 10/2001; 101(1-3):43-9. DOI:10.1016/S0167-0115(01)00264-6 · 1.83 Impact Factor
  • K S Ahn · J H Kim · S R Oh · SY Ryu · H K Lee ·
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    ABSTRACT: The inhibitory activity of stilbenes isolated from medicinal plants on cell adhesion molecules on the surface of THP-1 human monocytic cell lines was investigated. Among ten stilbenes tested, four stilbenes displayed a significant inhibitory activity on the expression of both intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). A cell-to-cell adhesion assay showed that 3,5-dihydroxy-4'-methoxystilbene and 2,3,4',5-tetrahydroxystilbene-2-O-beta-D-glucopyranoside as well as resveratrol blocked significantly TNF-alpha-inducing cell-cell adhesion between human umbilical vein endothelial cells (HUVEC) and THP-1 cells.
    Planta Medica 11/2000; 66(7):641-4. DOI:10.1055/s-2000-8634 · 2.15 Impact Factor
  • S Y Ryu · M H Oak · K M Kim ·
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    ABSTRACT: Yomogin (1), an eudesmane sesquiterpene isolated from Artemisia princeps, was tested for the effects on the degranulation process of cultured mast cells and on the nitric oxide production in LPS-activated murine macrophages. It demonstrated a significant inhibition on the release of beta-hexosaminidase from the cultured RBL-2H3 cells in a dose-dependent manner (IC50 value, 50 microM) and also exhibited a potent inhibition on the nitric oxide production from the activated RAW264.7 cells (IC50 value, 3 microM).
    Planta Medica 04/2000; 66(2):171-3. DOI:10.1055/s-0029-1243124 · 2.15 Impact Factor
  • H Oh · S E Lee · J A Yang · C Y Chung · S Y Ryu · M D Huh · S K Jo · C H Son · S H Kim ·
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    ABSTRACT: We have studied, by a nonisotopic in situ end-labeling (ISEL) technique, the frequency of apoptosis in the intestinal crypt cell of adult mice and in the external granular layer(EGL) of the cerebellum of fetuses by gamma-ray irradiation from 60Co or diagnostic ultrasound exposure. The extent of changes following 200 cGy(1090 cGy/min) was studied at 2, 4, 6, 8, 12, or 24 hours after exposure. The maximal frequency was found 4-8 hours after exposure. The mice that received 18, 36, 54, 108, 198, 396 cGy of gamma-rays or diagnostic ultrasound (7.5 MHz, 4.2 mW, ISPTA = 7.9 mW/cm2, IsppA = 114.3 W/cm2) for 10 or 30 minutes were examined 6 hours after irradiation. Measurements performed after gamma-ray irradiation showed a dose-related increase in apoptotic cells in each of the mice studied. The dose-response curves were analyzed with alpha linear-quadratic model: the frequency (number per crypt) of apoptotic cells in the intestinal crypt of adult mice was y = (0.0386 +/- 0.004204)D + (-0.0000535 +/- 0.00001120)D2 + 0.15475(r2 = 0.952, y = apoptotic cell per crypt cell, D = dose in cGy), and the frequency (percentage of apoptotic cell in the EGL) of apoptotic cell in the EGL of fetus was y = (0.1349 +/- 1.175)D + (-0.001522 +/- 0.334)D2 + 0.0477(r2 = 0.981, y = % of apoptotic cell in the EGL, D = dose in cGy). In the experiment of ultrasound exposure, the frequencies of apoptosis were 0.181 +/- 0.055(10 minutes exposure) and 0.325 +/- 0.294 (30 minutes exposure) in the crypt cells and 0.106 +/- 0.130% (10 minutes exposure) and 0.167 +/- 0.220%(30 minutes exposure) in the EGL. We estimated the relative dose of the yield from the experiment with ultrasound by substituting the yield from ultrasound exposure into the curue from the gamma-irradiation. The relative doses of ultrasound exposure compared with gamma-irradiation were 0.692 cGy(10 minutes exposure) and 1.334 cGy(30 minutes exposure) in the experiment for crypt cells and 0.432 cGy(10 minutes exposure) and 0.885 cGy(30 minutes exposure) in the experiment for EGL. Although there is presently no evidence to indicate that diagnostic ultrasound involves a significant risk, it is not wise to use diagnostic ultrasound indiscriminately.
    In vivo (Athens, Greece) 03/2000; 14(2):345-9. · 0.97 Impact Factor
  • S Y Ryu · K S Jeong · W K Yoon · S J Park · B N Kang · S H Kim · B K Park · S W Cho ·
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    ABSTRACT: We have investigated whether lipopolysaccharide (LPS) induces substance P (SP) and somatostatin (SOM) in popliteal lymph nodes in vivo and whether macrophages are a source of SP and SOM in vitro. We have also investigated the effect of SP and SOM treatment on the production of cytokines. SP reached a maximum 3 days after injection of LPS (100 microg/footpad) and then declined. SOM expression after LPS injection reached a maximum at 5-7 days. Stimulation of thioglycolate-elicited peritoneal macrophages with LPS (20 microg/ml), recombinant interferon-gamma (rIFN-gamma, 100 U/ml), and LPS plus rIFN-gamma induced SOM and SP. Thioglycolate-elicited, unstimulated peritoneal macrophages also synthesized these peptides. SOM (10(-12)-10(-8) M) significantly inhibited IL-6 and IFN-gamma production, whereas SP at those concentrations enhanced cytokine production by activated lymphocytes and macrophages. These findings suggest that neuropeptides which originate from macrophages and nerve fibers act as immunomodulators to mediate changes in the pattern of cytokine production.
    NeuroImmunoModulation 02/2000; 8(1):25-30. · 1.88 Impact Factor
  • K S Jeong · S J Park · C S Lee · T W Kim · S H Kim · S Y Ryu · B H Williams · R L Veech · Y S Lee ·
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    ABSTRACT: Cyclocreatine (CCr), a substrate analogue of creatine kinase (CK: EC, exhibits anti-tumor activity in vitro and in vivo. We examined the effects of CCr on the hepatocarcinogenesis of F344 rats caused by treatment with diethylnitrosamine (DEN), partial hepatectomy (PH) or 2-acetylaminofluorene (2-AAF). The rats were given a single intraperitoneal injection of 200 mg of DEN per kg in 0.85% NaCl solution at four weeks of age. Two weeks later they were divided into two groups. One group was continuously fed a commercial powder diet containing 0.02% 2-AAF for 12 weeks and the other was continuously fed a commercial powder diet containing 1% CCr plus 0.02% 2-AAF for 12 weeks. A third group of rats as a control was given only a normal powder diet for 12 weeks. All the groups were subjected to a two-thirds partial hepatectomy (PH) at 3 weeks under avertin anesthesia. To elucidate the inhibitory effect of CCr on chemical induced hepatocarcinogenesis, we examined not only the distribution of glutathione-S-transferase placental form (GST-P) a marker used for tumorigenesis, but also the inhibition of the degree of apoptosis. The number (No./cm2) and area (mm2/cm2) of GST-P positive liver foci were significantly lower in the 2-AAF + CCr treated when compared to the group treated with 2-AAF only. Our data suggest that CCr inhibits the degrees of GST-P-positive cells and apoptosis and is active against hepatocarcinogenesis in rat models. This result points out the unique nature of an anticancer agent that inhibits progression of chemically induced hepatocarcinogenesis of rats.
    Anticancer research 01/2000; 20(3A):1627-33. · 1.83 Impact Factor
  • S Y Ryu · K S Jeong · B N Kang · S J Park · W K Yoon · S H Kim · T H Kim ·
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    ABSTRACT: Iron, an essential element for all living organisms, is central importance in a number of crucial metabolic pathways, including the regulation of immune function. Iron delivery to cells is accomplished by the complexing of iron to transferrin (Tf), a monomeric iron-binding protein in the plasma, followed by specific binding of Tf to cell-surface receptors, endocytosis of the receptor-ligand complexes and ultimately, release of iron from endosomal vesicles to the cytoplasm. The purpose of this study was to evaluate the effect of cytokines, alone and in combination, on the factors that can affect the iron delivery in thioglycollate-elicited macrophages. In this study, IFN gamma induced a marked increase in Tf synthesis by macrophages, while IL-1, IL-6 and TNF alpha produced a more modest increase. Combinations of these cytokines were shown to be less effective in promoting macrophage Tf synthesis than the cytokines by themselves. IFN gamma alone and in combination with other cytokines was effective in inducing nitrite (NO) production and inducible nitric oxide synthetase (iNOS) expression in macrophages, while IL-1, TNF alpha and IL-6 individually, as well as in various combinations, were not. While all tested cytokines individually and in combination inhibited the expression of the transferrin receptor (TfR) on macrophages, IFN gamma alone and in combination with other cytokines most strongly repressed the TfR expression. TfR localization in macrophages after IFN gamma stimulation showed that TfR fluorescence was most intense in the perinuclear region after 6 hours and scattered diffusely throughout the cytoplasm after 24 hours. This data suggests that IFN gamma may enhance iron uptake during the early phase of macrophage activation, and in later phases, down-regulate TfR expression by inducing NO, thus contributing to intracellular oxidative stress reduction.
    Anticancer research 01/2000; 20(5A):3331-8. · 1.83 Impact Factor
  • S U Choi · S Y Ryu · S K Yoon · N P Jung · S H Park · K H Kim · E J Choi · C O Lee ·
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    ABSTRACT: In this study, we investigated the cytotoxicities of flavone (F01), 3-hydroxyflavone (F02), 6- hydroxyflavone (F03), 7-hydroxyflavone (F04), 3,6-dihydroxyflavone (F05), 5,7-dihydroxyflavone (F06) and 5,6,7-trihydroxyflavone (F07) to human cancer cells including P- glycoprotein (Pgp)-expressing HCT15 cells and its multidrug resistant subline, HCT15/CL02 cells. We also examined the effects of those flavonoids on the cell cycle of these cancer cells. HCT15/CL02 cells did not reveal resistance to all the flavonoids tested in comparison with HCT15 cells. In cell cycle analysis, all the flavonoids tested, except F01 and F04, reduced the G0/G1 population of SF295 cells at growth inhibitory concentrations, and increased G2/M (F02, F03 and F06) or S (F05 and F07) populations. In addition, F02 and F03 decreased the G2/M and G0/G1 population, and increased the S and G2/M population in HCT15 cells, respectively. Meanwhile, in HCT15/CL02 cells, F02 and F03 decreased the G0/G1 populations and increased the S population. In conclusion, we deemed that the flavonoids tested had diverse cytotoxic mechanisms, and exerted their cell growth inhibitory or killing activity by distinctive ways in different cells.
    Anticancer research 11/1999; 19(6B):5229-33. · 1.83 Impact Factor
  • SY Ryu · M H Oak · K M Kim ·
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    ABSTRACT: The activity-guided fractionation of the extract of the root of Salvia miltiorrhiza B. (Labiatae, Tanshen), led to the isolation of four active components responsible for the anti-allergic activity in vitro. Among them, 15,16-dihydrotanshinone-I and cryptotanshinone demonstrated significant inhibition of the release of beta-hexosaminidase from cultured RBL-2H3 cells in a dose-dependent manner; the IC50 values were calculated as 16 and 36 microM, respectively.
    Planta Medica 11/1999; 65(7):654-5. DOI:10.1055/s-2006-960839 · 2.15 Impact Factor

Publication Stats

579 Citations
63.47 Total Impact Points


  • 2011-2014
    • Pusan National University
      • Department of Physics
      Tsau-liang-hai, Busan, South Korea
  • 2000-2001
    • Chungnam National University
      • College of Veterinary Medicine
      Sŏngnam, Gyeonggi Province, South Korea
  • 1994-2001
    • Korea Research Institute of Chemical Technology
      Daiden, Daejeon, South Korea