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Phosphodiesterase inhibitor improves renal tubulointerstitial Hypoxia of the Diabetic rat Kidney
( Hui Kyoung Sun ),( Yun Mi Lee ),( Kum Hyun Han ),( Han Seong Kim ),( Seon Ho Ahn ),( Sang Youb Han ) 대한내과학회 2012 The Korean Journal of Internal Medicine Vol.27 No.2
Background/Aims: Renal hypoxia is involved in the pathogenesis of diabetic nephropathy. Pentoxifyllin (PTX), a nonselective phosphodiesterase inhibitor, is used to attenuate peripheral vascular diseases. To determine whether PTX can improve renal hypoxia, we investigated its effect in the streptozocin (STZ)-induced diabetic kidney. Methods: PTX (40 mg/kg, PO) was administered to STZ-induced diabetic rats for 8 weeks. To determine tissue hypoxia, we examined hypoxic inducible factor-1α (HIF-1α), heme oxygenase-1 (HO-1), vascular endothelial growth factor (VEGF), and glucose transporter-1 (GLUT-1) levels. We also tested the effect of PTX on HIF-1α in renal tubule cells. Results: PTX reduced the increased protein creatinine ratio in diabetic rats at 8 weeks. HIF-1α, VEGF, and GLUT-1 mRNA expression increased significantly, and the expression of HO-1 also tended to increase in diabetic rats. PTX significantly decreased mRNA expression of HIF-1α and VEGF at 4 and 8 weeks, and decreased HO-1 and GLUT-1 at 4 weeks. The expression of HIF-1α protein was significantly increased at 4 and 8 weeks in tubules in the diabetic rat kidney. PTX tended to decrease HIF-1α protein expression at 8 weeks. To examine whether PTX had a direct effect on renal tubules, normal rat kidney cells were stimulated with CoCl2 (100 μM), which enhanced HIF-1α mRNA and protein levels under low glucose conditions (5.5 mM). Their expressions were similar even after high glucose (30 mM) treatment. PTX had no effect on HIF-1α expression. Conclusions: PTX attenuates tubular hypoxia in the diabetic kidney.
AN EXTENSION OF GENERALIZED VECTOR QUASI-VARIATIONAL INEQUALITY
Kum Sang-Ho,Kim Won-Kyu Korean Mathematical Society 2006 대한수학회논문집 Vol.21 No.2
In this paper, we shall give an affirmative answer to the question raised by Kim and Tan [1] dealing with generalized vector quasi-variational inequalities which generalize many existence results on (VVI) and (GVQVI) in the literature. Using the maximal element theorem, we derive two theorems on the existence of weak solutions of (GVQVI), one theorem on the existence of strong solution of (GVQVI), and one theorem on strong solution in the 1-dimensional case.
Kum, Chong-K.,Sung, Yu-Taek,Kim, Yong-Su,Lee, Hyung-Gon,Kim, Woo-Nyon,Lee, Heon-Sang,Yoon, Ho-Gyu The Polymer Society of Korea 2007 Macromolecular Research Vol.15 No.4
The effects of a compatibilizer on polypropylene (PP)/poly(acrylonitrile-butadiene-styrene) (ABS) blends were studied. Blends of the PP/ABS, with PP-g-SAN copolymer as a compatibilizer, were prepared using a twin screw extruder. The flexural and impact strength of the PP/ABS blends with the PP-g-SAN copolymer increased significantly with PP-rich compositions on the addition of the PP-g-SAN copolymer at 3 phr. The increase in the mechanical properties of the PP/ABS/PP-g-SAN blend may have been due to the toughening effects of the ABS in the PP-rich compositions. In the morphology study of the PP/ABS/PP-g-SAN (80/20) blend with the PP-g-SAN copolymer, the minimum droplet size, $5.1{\mu}m$, was observed with the addition on phr of the PP-g-SAN copolymer. The complex viscosity of the PP/ABS/PP-g-SAN (80/20) blends increased with the addition of3 phr of the PP-g-SAN copolymer. From the above mechanical properties, morphology and complex viscosity results for the PP/ABS blends, it is suggested that the compatibility is more increased with the PP-rich composition (PP:ABS=80/20 wt%) of the PP/ABS blend on the addition of 3 phr of the PP-g-SAN copolymer.
Shape Optimization Using the Navier-Stokes Equations in an e-Science Environment
Kum Won Cho,김병상,문종배,Chun-ho Sung 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.5
In this research, we implement an aerodynamic design shape optimization technique to a 3- dimensional wing in an e-Science environment. As an advanced computing toolkit, the Globus is used as a middleware connecting the geographically-distributed and heterogeneous computing resources. Before solving the grand problem in this environment, we experimented with geometrically simple 2- and 3-dimensional wing design problems in the e-Science environment. We introduce a brief overview of e-Science and an efficient design optimization algorithm. The experiments were performed on a simple Grid computing testbed consisting of Linux PC clusters. On the basis of this work, an aerodynamic design shape optimization technique will be implemented to a large-scale complicated design problem. In this research, we implement an aerodynamic design shape optimization technique to a 3- dimensional wing in an e-Science environment. As an advanced computing toolkit, the Globus is used as a middleware connecting the geographically-distributed and heterogeneous computing resources. Before solving the grand problem in this environment, we experimented with geometrically simple 2- and 3-dimensional wing design problems in the e-Science environment. We introduce a brief overview of e-Science and an efficient design optimization algorithm. The experiments were performed on a simple Grid computing testbed consisting of Linux PC clusters. On the basis of this work, an aerodynamic design shape optimization technique will be implemented to a large-scale complicated design problem.
Electromagnetic Properties of Dielectric and Magnetic Composite Material for Antenna
Sang Hoon Park,Won Ki Ahn,Jun Sig Kum,Jeong Keun Ji,Ki Ho Kim,Won Mo Seong 대한금속재료학회 ( 구 대한금속학회 ) 2009 ELECTRONIC MATERIALS LETTERS Vol.5 No.2
Electromagnetic properties of dielectric and magnetic composite materials were studied with various weight fractions and particle sizes of ferrite. The composite materials were prepared through Ni-Zn spinel ferrite and silicon elastomer, and were characterized with regard to permittivity, permeability, loss tangent(e), and loss tangent(u). Those properties of Ni-Zn spinel ferrite were approximately 7.0, 8.4, 0.01 and 0.1 MHz to 150 MHz, respectively; loss tangent(u), in particular, increased nearly exponentially with frequency above 80 MHz. Increase of loss tangent(u) was overcome by composite with polymer. The 40 wt. % loaded composite material changed these properties (approximately 3.8, 2.2, 0.003 and 0.1 at 161 MHz.); therefore, a higher frequency can be used. This material was optimized by particle size distribution. Composite material with smaller particle size is most useful because it shows similar magnetic loss of up to 211 MHz. Magneto-dielectric composite materials are more useful for antenna because they have lower values of complex permittivity and permeability, and higher application frequency. These results are certificated by simulation of antennas.
A CHARACTERIZATION OF SOLUTIONS OF AFFINE VARIATIONAL INEQUALITY DEFINED BY SECOND-ORDER CONE
Sang ho Kum 충청수학회 2007 충청수학회지 Vol.20 No.3
A variational inequality de¯ned by the second-order cone is considered, and it is shown that a necessary and su±cient condition for a solution of the variational inequality holds under some regularity condition.
( Sang Hoon Park ),( Jeong Keun Ji ),( Won Ki Ahn ),( Jun Sig Kum ),( Ki Ho Kim ),( Won Mo Seong ) 대한금속재료학회 ( 구 대한금속학회 ) 2008 ELECTRONIC MATERIALS LETTERS Vol.4 No.4
We studied the complex permittivity and permeability properties of magnesium-copper spinel ferrite under various heat-treatment conditions. We simulated two types of materials: dielectric and magneto-dielectric. Dielectric materials show the miniaturization of the antenna; however, decreases of bandwidth and efficiency are observed. Magneto-dielectric materials show the capability of improvement of bandwidth and efficiency with a miniaturization of the antenna. The target properties were established from simulated results of permittivity and permeability <10, and permittivity/permeability □ 1. Magnesium spinel ferrite was shown to increase the permittivity (from 7 to 11.7) and the permeability (from 5.5 to 8.2) with an increase of sintering temperature (from 1,150℃ to 1,350℃). However, the high sintering temperature (1,350℃) affected the increase of permittivity more than it did the permeability, and this condition deteriorated the ratio, loss, and resonance frequency. These problems were overcome with the substitution of copper (of formula Mg0.9Cu0.1Fe2O4), the addition of a sintering agent (alginate 1 wt%), and the condition of a lower sintering temperature (1,250℃). The new conditions showed equal value (□ 9.5) of the permittivity and permeability.