Sphingosine-1-phosphate-induced Flk-1 transactivation stimulates mouse embryonic stem cell proliferation through S1P₁/S1P₃-dependent β-arrestin/c-Src pathways

Ryu, J.M.,Baek, Y.B.,Shin, M.S.,Park, J.H.,Park, S.H.,Lee, J.H.,Han, H.J. Elsevier 2014 Stem cell research Vol.12 No.1

Although recent findings showed that the bioactive lipid metabolites can regulate the ES cell functions, the physiological relevance of interaction between sphingosine-1-phosphate (S1P) and Flk-1 and its related signaling molecules are not yet clear in ES cell proliferation. In the present study, S1P<SUB>1-5</SUB> receptors were expressed in mouse ES cells and S1P increased S1P<SUB>1-3</SUB> receptor expression level. S1P treatment stimulated the cellular proliferation in S1P<SUB>1/3</SUB>-dependent manner, located in lipid rafts. In response to S1P, β-arrestin was recruited to S1P<SUB>1/3</SUB> receptor and c-Src was activated. S1P also increased the binding of S1P<SUB>1/3</SUB> receptor with Flk-1. Similar to responses for VEGF, S1P increased Flk-1 phosphorylation, which was blocked by β-arrestin siRNA, and PP2, but not by VEGF-A<SUB>164</SUB> antibody or VEGF siRNA. In addition, S1P induced VEGF expression and VEGFR2 kinase inhibitor (SU1498) blocked the S1P-induced cellular proliferation. However, VEGF-A<SUB>164</SUB> antibody or VEGF siRNA partially blocked S1P-induced cellular proliferation, suggesting that both VEGF-dependent Flk-1 activation and VEGF-independent Flk-1 activation are involved in S1P-induced ES cell proliferation. S1P and VEGF-induced phosphorylation of ERK and JNK were blocked by pretreatment with SU1498. Moreover, inhibition of ERK and JNK blocked S1P-induced cellular proliferation. In conclusion, S1P-elicited transactivation of Flk-1 mediated by S1P<SUB>1/3</SUB>-dependent β-arrestin/c-Src pathways stimulated mouse ES cell proliferation.

S-1 plus irinotecan and oxaliplatin for the first-line treatment of patients with metastatic colorectal cancer: a prospective phase II study and pharmacogenetic analysis

Kim, S Y,S Hong, Y,K Shim, E,Kong, S-Y,Shin, A,Baek, J Y,Jung, K H Nature Publishing Group 2013 The British journal of cancer Vol.109 No.6

<P><B>Background:</B></P><P>S-1 is an oral fluoropyrimidine that mimics infusional 5-fluorouracil. The aim of this phase II trial was to explore the clinical efficacy of the triplet regimen TIROX, which consists of S-1, irinotecan and oxaliplatin.</P><P><B>Methods:</B></P><P>Forty-two chemo-naive patients with metastatic colorectal cancer (mCRC) were planned to be enrolled and be treated with irinotecan 150 mg m<SUP>−2</SUP> followed by oxaliplatin 85 mg m<SUP>−2</SUP> on day 1 and S-1 80 mg m<SUP>−2</SUP> per day from day 1 to 14 every 3 weeks. Polymorphisms in the <I>UGT1A1</I>, <I>UGT1A6</I>, <I>UGT1A7</I> and <I>CYP2A6</I> genes were analysed.</P><P><B>Results:</B></P><P>Between July 2007 and February 2008, 43 patients were enrolled. An objective response was noted in 29 patients (67.4%, 95% confidence interval: 53.4–81.4), of which 2 achieved durable complete responses. The median progression-free survival was 10.0 months and the median overall survival was 19.2 months. Significant grade 3 or 4 adverse events were neutropenia (45.2%), febrile neutropenia (9.5%), diarrhoea (7.1%) and vomiting (9.5%). Increased gastrointestinal toxicities were associated with the presence of <I>UGT1A6*2</I> or <I>UGT1A7*3</I> and an improved tumour response was noted in those without variant alleles of <I>CYP2A6</I> or <I>UGT1A1*60</I>.</P><P><B>Conclusion:</B></P><P>The combination of S-1, irinotecan and oxaliplatin showed favourable efficacy and tolerability in untreated patients with mCRC.</P>

Performance and carrier transport analysis of In_0.7Ga_0.3As quantum-well MOSFETs with Al₂O₃/HfO₂ gate stack

Son, S.W.,Park, J.H.,Baek, J.M.,Kim, J.S.,Kim, D.K.,Shin, S.H.,Banerjee, S.K.,Lee, J.H.,Kim, T.W.,Kim, D.H. Pergamon Press ; Elsevier Science Ltd 2016 Solid-State Electronics Vol.123 No.-

In this paper, we have fabricated and characterized In<SUB>0.7</SUB>Ga<SUB>0.3</SUB>As quantum-well (QW) metal-oxide-semiconductor field-effect-transistors (MOSFETs). We have employed the gate dielectric of the Al<SUB>2</SUB>O<SUB>3</SUB>/HfO<SUB>2</SUB> (0.6/2nm) bi-layer stack by ALD. The fabricated device with L<SUB>g</SUB>=4μm exhibits a record maximum transconductance (g<SUB>m_max</SUB>) in excess of 520μS/μm at >1μm region, and reasonably good electrostatic integrity, such as SS=110mV/decade and DIBL=43mV/V. Also, we have investigated the gate length scaling behavior in terms of output, transconductance, and transfer characteristics. In particular, our devices feature very uniform values of the electrostatic integrity, such as SS=100-110mV/decade, V<SUB>T</SUB>=-0.25V to -0.2V and DIBL=40-50mV/V, as L<SUB>g</SUB> decreases from 10μm to 4μm. Furthermore, we have explored the impact of source resistance (R<SUB>S</SUB>) onto the device characteristics of the InGaAs QW MOSFETs. In doing so, we have modeled both measured extrinsic transconductance (g<SUB>m_ext</SUB>) and intrinsic transconductance (g<SUB>m_int</SUB>) as a function of L<SUB>g</SUB>.

Effects of sevoflurane on collagen production and growth factor expression in rats with an excision wound

LEE, H.-J.,KWON, J.-Y.,SHIN, S.-W.,BAEK, S.-H.,CHOI, K.-U.,JEON, Y.-H.,KIM, W.-S.,BAE, J.-H.,CHOI, H.-J.,KIM, H.-K.,BAIK, S.-W. Blackwell Publishing Ltd 2010 Acta anaesthesiologica Scandinavica Vol.54 No.7

<P>Background</P><P>Sevoflurane is a widely used inhalation anesthetic, but there are no studies on its effect on the wound-healing process. This study was undertaken to evaluate the effect of exposure time to sevoflurane on wound healing.</P><P>Method</P><P>Male Sprague–Dawley rats were used. Two circular full-thickness skin defects 8 mm in diameter were made on the dorsum of the rats. The animals were divided into six groups according to exposed gas type and time: S1 (sevoflurane, 1 h), S4 (sevoflurane, 4 h), S8 (sevoflurane, 8 h), O1 (oxygen, 1 h), O4 (oxygen, 4 h), and O8 (oxygen, 8 h). The surface area of the wounds was measured 0, 1, 3, and 7 days after surgery. Separately, the mean blood pressures (MBP) and arterial oxygen pressures (PaO<SUB>2</SUB>) were monitored during the sevoflurane exposure. Collagen type I production and transforming growth factor-β1 (TGF-β1) and basic fibroblast growth factor (bFGF) expression on the wound surface were analyzed. Routine histological analysis was also performed.</P><P>Result</P><P>Exposure duration to sevoflurane had no influence on MBP and PaO<SUB>2</SUB>. The reduction in wound size and collagen type I production was delayed in S8. The expression of TGF-β1 and bFGF on the wound surface in S8 was significantly attenuated in S8. The histology of the S8 demonstrated a delayed healing status.</P><P>Conclusions</P><P>Prolonged exposure to sevoflurane might alter the inflammatory phase of the wound-healing process by attenuation of growth factor expression such as TGF-β1 and bFGF and subsequently by reduced collagen production.</P>

Intensity dependency of photovoltaic cell parameters under high illumination conditions: An analysis

Khan, F.,Baek, S.H.,Kim, J.H. Applied Science Publishers 2014 APPLIED ENERGY Vol.133 No.-

Previously, an analytical method was developed to extract the photovoltaic (PV) cell parameters, such as the shunt resistance, R<SUB>sh</SUB>, series resistance, R<SUB>s</SUB>, diode ideality factor, n, and reverse saturation current density, J<SUB>0</SUB>, through the use of the single current density-voltage (J-V) characteristics under high illumination conditions. Accurate knowledge of the PV cell parameters under different illumination conditions is of vital importance to PV design and performance. Although several attempts have been made to examine the dependency of the PV cell parameters on the illumination intensity P<SUB>in</SUB>, there are no reports on the dependence of the PV cell parameters on P<SUB>in</SUB> under high illumination conditions. In this regards, dependency of the analytically-predicted PV cell parameters on P<SUB>in</SUB> of Si solar cells with various structures has been investigated. The analytically-predicted values of R<SUB>sh</SUB> and R<SUB>s</SUB> decreased with increasing P<SUB>in</SUB>. The rate of change in R<SUB>sh</SUB>, however, was higher than that of R<SUB>s</SUB>. The decrease in R<SUB>sh</SUB> may be due to light induced degradation of PV cells. The decrease in R<SUB>s</SUB> values might be due to an increase in the conductivity of the active region. On the other hand, n and J<SUB>0</SUB> increased with increasing P<SUB>in</SUB>. This increase in n and J<SUB>0</SUB> might have a savior effect, reducing the curve factor CF and hence the performance of the PV cell. The rate change in all PV cell parameters was higher at lower P<SUB>in</SUB> values than at the higher P<SUB>in</SUB> values. The theoretically computed values of the open circuit voltage V<SUB>oc</SUB>, curve factor CF and efficiency η using this method showed good agreement with the experimentally measured values at various P<SUB>in</SUB>. The performance of the PV systems is dependent on the product of the J<SUB>sc</SUB>, V<SUB>oc</SUB> and CF. Therefore, it is important to determine the optimal value of P<SUB>in</SUB> to achieve the maximum output power (minimum losses due to R<SUB>sh</SUB>, R<SUB>s</SUB>, n and J<SUB>0</SUB>) from a PV system. By doing so, the cost per peak watt of solar energy can be minimized by enhancing the performance of PV systems.

Status of the KSTAR superconducting magnet system development

Kim, K.,Park, H.K.,Park, K.R.,Lim, B.S.,Lee, S.I.,Chu, Y.,Chung, W.H.,Oh, Y.K.,Baek, S.H.,Lee, S.J.,Yonekawa, H.,Kim, J.S.,Kim, C.S.,Choi, J.Y.,Chang, Y.B.,Park, S.H.,Kim, D.J.,Song, N.H.,Kim, K.P.,So International Atomic Energy Agency 2005 Nuclear fusion Vol.45 No.8

<P>The aim of the Korea superconducting tokamak advanced research (KSTAR) project is to develop a steady-state-capable advanced superconducting tokamak for establishing a scientific and technological basis for an attractive fusion reactor. Since the KSTAR mission includes the achievement of a steady-state-capable operation, the use of superconducting coils is an obvious choice for the magnet system. The KSTAR superconducting magnet system consists of 16 toroidal field (TF) and 14 poloidal field (PF) coils which include 8 central solenoid coils. Both the TF and PF coil systems use internally-cooled cable-in-conduit conductors (CICC). The TF coil system provides a magnetic field of 3.5 T at the plasma centre and the PF coil system provide a flux swing of 17 V s. The major achievement in the KSTAR magnet system development includes the development of CICC, a full size TF model coil, a background magnetic field generation coil system and the construction of a large scale superconducting magnet and the CICC test facility. TF and PF coils are at the stage of fabrication for the KSTAR completion in the year 2007.</P>

Metabolic engineering and adaptive evolution for efficient production of D-lactic acid in Saccharomyces cerevisiae

Baek, S. H.,Kwon, E. Y.,Kim, Y. H.,Hahn, J. S. Springer Science + Business Media 2016 Applied microbiology and biotechnology Vol.100 No.6

<P>There is an increasing demand for microbial production of lactic acid (LA) as a monomer of biodegradable poly lactic acid (PLA). Both optical isomers, D-LA and L-LA, are required to produce stereocomplex PLA with improved properties. In this study, we developed Saccharomyces cerevisiae strains for efficient production of D-LA. D-LA production was achieved by expressing highly stereospecific D-lactate dehydrogenase gene (ldhA, LEUM_1756) from Leuconostoc mesenteroides subsp. mesenteroides ATCC 8293 in S. cerevisiae lacking natural LA production activity. D-LA consumption after glucose depletion was inhibited by deleting DLD1 encoding D-lactate dehydrogenase and JEN1 encoding monocarboxylate transporter. In addition, ethanol production was reduced by deleting PDC1 and ADH1 genes encoding major pyruvate decarboxylase and alcohol dehydrogenase, respectively, and glycerol production was eliminated by deleting GPD1 and GPD2 genes encoding glycerol-3-phosphate dehydrogenase. LA tolerance of the engineered D-LA-producing strain was enhanced by adaptive evolution and overexpression of HAA1 encoding a transcriptional activator involved in weak acid stress response, resulting in effective D-LA production up to 48.9 g/L without neutralization. In a flask fed-batch fermentation under neutralizing condition, our evolved strain produced 112.0 g/L D-LA with a yield of 0.80 g/g glucose and a productivity of 2.2 g/(L center dot h).</P>

M20J 시뮬레이터 개발을 위한 시스템 통합

홍승범,김용환,정식항,백중환,황수찬,황명신,김칠영 한국항공운항학회 1999 한국항공운항학회지 Vol.7 No.1

This paper proposes a system intergration method for M20J flight simulator development. The simulator consists of three modules. The first module is for flight dynamics simulation, and the second module is for avionic systems and flight instrument and the last module is for interface card which connects PC and input devices using rotary encoders and switches. Two computers are equipped in the simulator for instructor and trainee. An instructor can give a mission to a trainee, and control the flight simulation options through RS-232C serial port. Also, the instructor can monitor the training results of the trainee

A numerical study of the effectiveness factors of nickel catalyst pellets used in steam methane reforming for residential fuel cell applications

Baek, S.M.,Kang, J.H.,Lee, K.J.,Nam, J.H. Pergamon Press ; Elsevier Science Ltd 2014 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.39 No.17

A numerical study is performed to evaluate the effectiveness factors of commercial nickel catalyst pellets commonly used in small-scale steam methane reformers for residential fuel cell applications. Based on the intrinsic reaction kinetics of the steam reforming process, the standard composition of the partially reformed gas mixture is determined as a function of the methane conversion. The heterogeneous reforming reactions inside the spherical catalyst pellets are then modeled by considering the distributed reaction, multi-component diffusion and permeation, and conductive and convective heat transfer in the porous media. Various operating conditions, including the reforming temperature, steam-to-carbon (S/C) ratio, operating pressure, and geometrical parameters, such as the pellet diameter and mean pore size, are simulated. The effectiveness factors calculated for each condition are presented as a function of the methane conversion. Finally, simple correlations for the effectiveness factors are presented, and their accuracies are assessed.

Ultraviolet photodissociation spectroscopy of cold, isolated adenine complexes with a potassium cation

Baek, J.Y.,Choi, C.M.,Eun, H.J.,Park, K.S.,Choi, M.C.,Heo, J.,Kim, N.J. North Holland 2015 Chemical physics letters Vol.635 No.-

We obtain the ultraviolet photodissociation spectrum of adenine complexes with K<SUP>+</SUP> ion stored in a cold ion trap. The spectrum near the origin band of the S<SUB>0</SUB>-S<SUB>1</SUB> transition exhibits well-resolved vibronic bands, all of which are assigned from a single isomer by UV-UV hole-burning (HB) spectroscopy. Comparing the spectrum with theoretical spectra, we determine the structure of the isomer, where K<SUP>+</SUP> is bound not to 9H-adenine (A9) but to 7H-adenine (A7). We suggest that K<SUP>+</SUP>A7 ions are formed in solution through tautomerization, for which the energy barrier varies greatly depending on the binding site of the K<SUP>+</SUP> ion on A9.