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Yun, Jungheum,Bae, Tae‐,Sung,Lee, Sunghun,Lee, Seunghun,Rha, Jongjoo,Lee, Gun‐,Hwan WILEY‐VCH Verlag 2012 Plasma Processes and Polymers Vol.9 No.2
<P><B>Abstract</B></P><P>The chemical and morphological features of the interface between plasma‐treated polymer substrates and oxide coatings are investigated to clarify the influence of the interfacial features on the adhesive and cohesive properties in the polymer–oxide system. It is found that one‐dimensional polymer protrusions and polymer–oxide composite structures develop sequentially in the early growth stages of silicon oxide films on both acrylate hard coat and bare polyethylene terephthalate surfaces exposed to strong plasma‐ion irradiation. These interfacial nanostructures cause a dramatic decrease in the wettability of the polymers with silicon oxide films, thus leading to a weak boundary layer, which results in adhesion failures at the polymer–oxide interface. </P>
Synthesis, Structures, and Catalytic Properties of Ionic Metallacyclodimeric Palladium(II) Complexes
Sung Min Kim,Kyung Hwan Park,Haeri Lee,So Yun Moon,정옥상 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.12
Metallacyclodimeric complexes of [(Me4en)Pd(L)]2(ClO4)4 (Me4en = N,N,N',N'-tetramethylethylenediamine; L = dimethylbis(4-pyridyl)silane (dmps), methylvinylbis(4-pyridyl)silane (mvps)) have been synthesized, and their structures have been characterized by X-ray single crystallography. The skeletal structures consist of one 20-membered metallamacrocycle, two 5-membered metallacycles, and four pyridyl groups. The local geometry around the palladium(II) ion approximates to a typical square planar arrangement with four nitrogen donors. Delicate difference in catalytic effects on hydrogenation was investigated based on the structure of catalyst and substrates.
Adhesive and Structural Failures of Oxide Coatings on Plasma‐Treated Polymers
Yun, Jungheum,Lee, Sunghun,Bae, Tae‐,Sung,Yun, Youngmok,Lee, Seunghoon,Kwon, Jung‐,Dae,Lee, Gun‐,Hwan WILEY‐VCH Verlag 2011 Plasma Processes and Polymers Vol.8 No.9
<P><B>Abstract</B></P><P>This study discloses (i) the chemical and morphological modifications in acrylate hard‐coat and bare polyethylene terephthalate polymers occurring in the course of Ar plasma treatments and (ii) the effects of these modifications on the adhesion, barrier performance, and cohesion of silicon oxide coatings deposited on the polymers. It is concluded that the deterioration in these coating properties is dominated by the formation of nanoscopic globular polymer protrusions on the polymer surface as a result of plasma treatment. The protrusions evolve even under very mild plasma conditions in which an ion fluence of less than 1 × 10<SUP>16</SUP> ions · cm<SUP>−2</SUP> is applied with low‐energy ion irradiation of 6 eV. The polymer protrusions dictate the nucleation and subsequent growth of a coating by promoting the development of a three‐dimensional granular morphology in the coating. At the initial oxide nucleation stage, the wetting behavior of silicon oxide on the polymer surface in the presence of nanoscopic protrusions is directly limited by the area number density and size of the protrusions. Incomplete wetting of the protrusions with a silicon oxide coating hinders adhesion between the oxide and the polymer surface. The reduction in the contact area between the oxide and the protrusions is identified as the reason that a weak boundary layer forms at the oxide–polymer interface. Furthermore, the formation of nanoscopic defects, predominantly pinholes, is inevitable in the granular coating morphology on the polymer protrusions and weakens the oxide coating's barrier performance and cohesion strength. Variations in the polar surface free energy and chemical composition of the plasma‐treated polymer surface are irrelevant to the wetting dynamics whenever the protrusions develop on the polymer surface. The effects of the polar surface free energy and chemical composition are valid only to the extent that the plasma treatment improves the wettability of a polymer surface without protrusion formation. </P>
( Sung-joon Yun ),( Moon-hwan Kim ) 대한물리치료학회 2015 대한물리치료학회지 Vol.27 No.4
Purpose: The purpose of this study was to examine the electromyographic (EMG) activity of the abdominal muscles and to compare the activity ratios of the bilateral rectus abdominis (RA) to oblique abdominal muscles during shoulder abduction in opposite directions with single leg raising (SLR) performed in the supine position on a foam roller. Methods: Fifteen healthy subjects were recruited to the study. Each subject lay on the foam roller and performed left single leg raising with right or left shoulder 90° abduction (Abd); performed in a random order. Surface EMG recordings of selected abdominal muscles (i.e., the RA, external oblique abdominis [EO], internal oblique abdominis [IO], and transverse abdominis [TrA]) were normalized to maximum voluntary isometric contraction. EO/RA and IO and TrA/RA ratios were determined with surface EMG. Data were analyzed by Independent t-test. The statistical significance level was p<0.05. Results: The results were as follows: (1) the right RA, left EO, and right IO and TrA muscle activities increased significantly at the left SLR with left Abd compared to the left SLR with right Abd (p<0.05); and (2) the ratio of right EO/RA activity increased significantly at the left SLR with right Abd compared to left Abd (p<0.05). Conclusion: These findings suggest that left SLR with left Abd on a foam roller is an appropriate exercise for activation of specific oblique abdominal muscles.
Yun, Chang-Ho,Jung, Keun-Hwa,Chu, Kon,Kim, So-Hyun,Ji, Ki-Hwan,Park, Hee-Kwon,Kim, Hwan-Cheol,Lee, Soon-Tae,Lee, Sang-Kun,Roh, Jae-Kyu 대한신경과학회 2010 Journal of Clinical Neurology Vol.6 No.2
<P><B>Background and Purpose</B></P><P>Endothelial impairment is a linking mechanism between obstructive sleep apnea (OSA) and cardiovascular diseases. Profiles of endothelial microparticles (EMPs) and endothelial progenitor cells (EPCs) reflect the degree of endothelial impairment. The aims of this study were to measure the levels of EMPs and progenitor cells in OSA, determine the correlations between these factors and OSA severity and the degree of atherosclerosis, and document any changes in these factors after therapy.</P><P><B>Methods</B></P><P>Subjects with (<I>n</I>=82) and without (<I>n</I>=22) OSA were recruited prospectively. We measured the number of colony-forming units (CFU) in cell culture as the endothelial progenitor cell index, and the number of EMPs using flow cytometry with CD31 [platelet endothelial cell adhesion molecule (PECAM)], CD42 (platelet glycoprotein), annexin V, and CD62E (E-selectin) antibodies at baseline and after 4-6 weeks of continuous positive airway pressure (CPAP) therapy. Carotid intima-media thickness (IMT) was regarded as a marker of atherosclerosis.</P><P><B>Results</B></P><P>The levels of PECAM<SUP>+</SUP>CD42<SUP>-</SUP> (<I>p</I><0.001), PECAM<SUP>+</SUP>annexin V<SUP>+</SUP> (<I>p</I><0.001), and E-selectin<SUP>+</SUP> microparticles (<I>p</I>=0.001) were higher in OSA subjects than in non-OSA subjects. The number of CFU did not differ between the two groups. OSA severity independently predicted the levels of PECAM<SUP>+</SUP>CD42<SUP>-</SUP> (<I>p</I>=0.02) and PECAM<SUP>+</SUP>annexin V<SUP>+</SUP> (<I>p</I>=0.004). Carotid IMT was correlated with OSA severity (<I>p</I><0.001), PECAM<SUP>+</SUP>CD42<SUP>-</SUP> (<I>p</I>=0.03), and PECAM<SUP>+</SUP>annexin V<SUP>+</SUP> (<I>p</I>=0.01). Neither OSA severity nor carotid IMT was correlated with either the number of CFU or E-selectin<SUP>+</SUP>. CPAP therapy decreased the occurrence of E-selectin<SUP>+</SUP> (<I>p</I><0.001) in 21 of the OSA subjects, but had no effect on the other microparticles of the number of CFU.</P><P><B>Conclusions</B></P><P>OSA led to the overproduction of EMPs, which moderately correlated with OSA severity and the degree of atherosclerosis, and partly responded to therapy. The endothelial impairment might contribute to future cardiovascular events.</P>