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Lee, Kyuhong,Son, Chang-Young,Lee, Sang-Bok,Lee, Sang-Kwan,Lee, Sunghak Elsevier 2010 Materials science & engineering. properties, micro Vol.527 No.4
<P><B>Abstract</B></P><P>Zr-based amorphous matrix composites reinforced with metallic continuous fibers were fabricated by liquid pressing process, and their fracture property improvement was explained by directly observing microfracture processes. About 60vol.% of metallic fibers were homogeneously distributed inside the amorphous matrix. Apparent fracture toughness of the tungsten-fiber-reinforced composites was lower than that of monolithic amorphous alloy, while that of the tantalum-fiber-reinforced composite was higher. According to the microfracture observation, shear bands or cracks were initiated at the amorphous matrix, and the propagation of the initiated shear bands or cracks was effectively blocked by fibers, thereby resulting in stable crack growth which could be confirmed by the fracture resistance curve (R-curve) behavior. This increase in fracture resistance with increasing crack length improved fracture properties of the fiber-reinforced composites, and could be explained by the formation of multiple shear bands or multiple cracks at the amorphous matrix, blocking of crack or shear band propagation, and multiple necking at metallic fibers.</P>
Lee, Hye Jeong,Choi, Na Young,Park, Yo Seph,Lee, Seung-Won,Bang, Jin Seok,Lee, Yukyeong,Ryu, Jae-Sung,Choi, Seong-Jin,Lee, Sang-Hyub,Kim, Gwang Soo,Chung, Hyun Woo,Ko, Kisung,Lee, Kyuhong,Ko, Kinarm Elsevier 2018 Reproductive toxicology Vol.78 No.-
<P><B>Abstract</B></P> <P>Animal models and human studies showed that <I>in utero</I> cigarette smoke exposure decreases sperm counts of offspring. This study used a mouse model to investigate the effects of maternal exposure to cigarette smoke on reproductive systems in F1 and F2 male offspring. Female ICR mice were exposed either to clean air or to cigarette smoke during pregnancy at the post-implantation stage. Epididymal sperm counts were decreased in a cigarette smoke dose–dependent manner in F1 (by 40–60%) and F2 males (by 23–40%) at postnatal day 56. In F1, the seminiferous epithelium heights were lower in the cigarette smoke–exposed groups than in the control group, and these effects were sustained in F2 males. Results suggest that maternal cigarette smoke exposure during pregnancy can have a multigenerational adverse effect on sperm counts in male offspring, which is mediated through <I>in utero</I> exposure of fetal germ cells to cigarette smoke.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Maternal cigarette smoke exposure caused low sperm counts of male offspring. </LI> <LI> Seminiferous epithelium heights of male offspring were decreased in the exposed groups. </LI> <LI> Maternal cigarette smoke exposure has a multigenerational adverse effect. </LI> </UL> </P>
Air Pollution Exposure and Cardiovascular Disease
Lee, Byeong-Jae,Kim, Bumseok,Lee, Kyuhong Korean Society of ToxicologyKorea Environmental Mu 2014 Toxicological Research Vol.30 No.2
Ambient air pollution (AAP) and particulate matters (PM) have been closely associated with adverse health effects such as respiratory disease and cardiovascular diseases. Previous studies have examined the adverse health effects associated with short- and long-term exposure to AAP and outdoor PM on respiratory disease. However, the effect of PM size ($PM_{2.5}$ and $PM_{10}$) on cardiovascular disease has not been well studied. Thus, it remains unclear how the size of the inhalable particles (coarse, fine, or ultrafine) affects mortality and morbidity. Airborne PM concentrations are commonly used for ambient air quality management worldwide, owing to the known effects on cardiorespiratory health. In this article, we assess the relationship between cardiovascular diseases and PM, with a particular focus on PM size. We discuss the association of $PM_{2.5}$ and $PM_{10}$, nitrogen dioxide ($NO_2$), and elemental carbon with mortality and morbidity due to cardiovascular diseases, stroke, and altered blood pressure, based on epidemiological studies. In addition, we provide evidence that the adverse health effects of AAP and PM are more pronounced among the elderly, children, and people with preexisting cardiovascular and respiratory conditions. Finally, we critically summarize the literature pertaining to cardiovascular diseases, including atherosclerosis and stroke, and introduce potential studies to better understand the health significance of AAP and PM on cardiovascular disease.
Lee, Kyuhong,Nam, Duk-Hyun,Lee, Sunghak,Kim, Choongnyun Paul Elsevier 2006 Materials science & engineering. properties, micro Vol.428 No.1
<P><B>Abstract</B></P><P>In this study, steel-based surface composites were fabricated with Fe-based metamorphic alloy powders by high-energy electron beam irradiation, and their microstructure, hardness, and wear resistance were investigated. Two kinds of Fe-based metamorphic powders were deposited on a plain carbon steel substrate, and then electron beam was irradiated on these powders to fabricate one-layered surface composites. Two-layered surface composites were also fabricated by irradiating electron beam again onto the powders deposited on the one-layered surface composites. The composite layers of 2.6–3.1mm in thickness were homogeneously formed without defects, and contained a large amount (up to 64vol.%) of Cr<SUB>2</SUB>B or Cr<SUB>1.65</SUB>Fe<SUB>0.35</SUB>B<SUB>0.96</SUB> borides in the Cr<SUB>0.19</SUB>Fe<SUB>0.7</SUB>Ni<SUB>0.11</SUB> or martensite matrix. Since the hardness and wear resistance of the surface composite layers were directly influenced by hard borides, they were two to four times greater than those of the steel substrate. These borides also played a role in improving the high-temperature hardness because they are insoluble and thermally stable even at high temperatures. These findings suggested that various applications of the fabricated surface composites to materials requiring high resistance to heat and abrasion were expected.</P>
Lee, Kyuhong,Son, Chang-Young,Kim, Jin Suk,Lee, Sunghak,Kim, Kyoo Young,Kim, Choongnyun Paul Elsevier 2006 Materials science & engineering. properties, micro Vol.441 No.1
<P><B>Abstract</B></P><P>Corrosion resistance of steel-based surface alloyed materials fabricated with Fe-based metamorphic powders by high-energy electron beam irradiation was investigated in this study. Two kinds of metamorphic powders were deposited on a plain carbon steel substrate, and then electron beam was irradiated on these powders to fabricate surface alloyed materials. In the surface alloyed layers, 48–64vol.% of Cr<SUB>2</SUB>B or Cr<SUB>1.65</SUB>Fe<SUB>0.35</SUB>B<SUB>0.96</SUB> borides were precipitated in the Cr<SUB>0.19</SUB>Fe<SUB>0.7</SUB>Ni<SUB>0.11</SUB> or martensite matrix, and thus their hardness was two to three times higher than that of the steel substrate. The overall corrosion resistance of the surface alloyed materials was better than that of an STS304 stainless steel or coatings fabricated by high-velocity oxygen fuel spraying of same powders. The observation results of pits formed on the corroded surface revealed that Cr<SUB>0.19</SUB>Fe<SUB>0.7</SUB>Ni<SUB>0.11</SUB> and martensite phases of the surface alloyed materials and coatings was selectively corroded, while borides were retained inside pits, by forming a galvanic coupling. These findings suggested that the fabricated surface alloyed materials presented good application possibilities as excellent wear- and corrosion-resistant materials.</P>
Lee, Kang-Yo,Oh, Sehee,Choi, You-Jin,Oh, Seon-Hee,Yang, Young-Su,Yang, Mi-Jin,Lee, Kyuhong,Lee, Byung-Hoon Oxford University Press 2013 Toxicological sciences Vol.136 No.1
<P>Amiodarone, bi-iodinated benzofuran derivative, is one of the most frequently prescribed and efficacious antiarrhythmic drugs. Despite its low incidence, amiodarone-induced pulmonary toxicity is of great concern and the leading cause of discontinuation. Autophagy is an essential homeostatic process that mediates continuous recycling of intracellular materials when nutrients are scarce. It either leads to a survival advantage or initiates death processes in cells under stress. In the present study, we investigated the role of autophagy in amiodarone-induced pulmonary toxicity. Amiodarone treatment–induced autophagy in H460 human lung epithelial cells and BEAS-2B normal human bronchial epithelial cells was demonstrated by increased LC3-II conversion, <I>Atg7</I> upregulation, and autophagosome formation. Autophagic flux, as determined by the lysosomal inhibitor bafilomycin A1, was also increased following amiodarone treatment. To determine the role of autophagy in amiodarone toxicity, amiodarone-induced cell death was evaluated in the presence of 3-methyladenine or by knocking down the autophagy-related genes <I>Atg7</I>. Inhibition of autophagy decreased cellular viability and significantly increased apoptosis. Intratracheal instillation of amiodarone in rats increased the number of inflammatory cells recovered from bronchoalveolar lavage fluid, and periodic acid-Schiff-positive staining in bronchiolar epithelial cells. However, induction of autophagy by rapamycin treatment inhibited amiodarone-induced pulmonary toxicity. In conclusion, amiodarone treatment induced autophagy, which is involved in protection against cell death and pulmonary toxicity.</P>