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Hui‑Jun Yi,Jin‑Woo Kim,Young‑Lak Kim,Sangyong Shin 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.8
Wire-arc additive manufacturing has emerged as a technology that could replace the conventional manufacturing processof titanium alloys. However, it produces a coarse β grain, which can accumulate via several deposited materials, resulting isstrong texture and anisotropy. To investigate potential solutions, the effects of the cooling rate on the resulting microstructureand tensile properties were studied. The cooling rate of the deposited materials was adjusted by interpass temperaturecontrol. Under rapid cooling, fine α + α′ grain with a low aspect ratio were observed and tensile and hardness propertieswere also improved.
Shin, Young Min,Park, Jong-Seok,Jeong, Sung In,An, Sung-Jun,Gwon, Hui-Jeong,Lim, Youn-Mook,Nho, Young-Chang,Kim, Chong-Yeal 한국생물공학회 2014 Biotechnology and Bioprocess Engineering Vol.19 No.2
An artificial construct mimicking the intrinsic properties of the natural extracellular matrix in bones has been considered an ideal platform for bone tissue engineering, as it can present an appropriate microenvironment and regulate cell behaviours. In this report, we introduce biodegradable composite scaffolds consisting of polycaprolactone (PCL) and biphasic calcium phosphate (BCP). The scaffolds were fabricated by a salt-leaching process, and the ability of the scaffolds to facilitate osteogenic differentiation was investigated using human mesenchymal stem cells (hMSCs). The scaffolds had an inter-connected porous structure with quadrilateral pores of approximately $200{\sim}500{\mu}m$ in width. The mechanical properties of the scaffolds changed as the BCP content was increased in the starting mixture. In the hMSC experiment, although we found that hMSCs adhered to the surface, as well as the inside, of the scaffolds, the incorporated BCP did not increase the proliferation of the hMSCs over 7 days in culture. Interestingly, the alkaline phosphatase (ALP) activity was 4 times higher on the PCL/BCP composite scaffold ($0.12{\pm}0.03nmol/min/{\mu}g$ protein) thanon the PCL scaffold ($0.03{\pm}0.01nmol/min/{\mu}g$ protein), suggesting that BCP can aid in generating a local environment that promotes bone regeneration. Therefore, a strategy combining polymers and ceramics can be considered a useful platform for bone tissue engineering.
Inactivation of <i>Vibrio vulnificus</i> Hemolysin by Oligomerization but Not Proteolysis
Shin, Sung-Heui,Sun, Hui-Yu,Choi, Mi-Hwa,Park, Ra-Young,Bai, Young-Hoon,Kim, Choon-Mee,Kim, Soo-Young,Kim, Young-Ran,Lee, Shee-Eun,Rhee, Joon-Haeng Pharmaceutical Society of Japan 2005 BIOLOGICAL & PHARMACEUTICAL BULLETIN Vol.28 No.7
<P><I>Vibrio vulnificus</I> extracellular protease (VvpE) is believed to destroy its hemolysin (VvhA) in the late growth phase, without obvious experimental evidence. So, we attempted to elucidate the mechanism. The hemolytic activity steeply increased with the expression of the VvhA in the early growth phase, and then abruptly declined with the expression of VvpE in the late growth phase. However, the VvhA activity also abruptly declined in a VvpE-deficient mutant. In Western blot, the degradation of VvhA was not observed; instead, the oligomerization of VvhA increased with the concomitant loss of hemolytic activity. These results evidently indicate that the inactivation of VvhA is due to the novel oligomerization of VvhA by unknown mechanism, but not to the destruction of VvhA by VvpE, so that the routine functional assay measuring hemolytic activity cannot reflect the actual production of VvhA.</P>
Shin, Young Min,Kim, Taek Gyoung,Park, Jong-Seok,Gwon, Hui-Jeong,Jeong, Sung In,Shin, Heungsoo,Kim, Kyung-Soo,Kim, Dongyoon,Yoon, Myung-Han,Lim, Youn-Mook The Royal Society of Chemistry 2015 Journal of Materials Chemistry B Vol.3 No.13
<P>The alginate hydrogel has been used as an attractive scaffold for tissue regeneration. In particular, its simple cross-linking, high water absorption, and biocompatibility have facilitated its utility in regulating the interaction with cells or organs. However, three-dimensional (3D) networks of the alginate hydrogel do not provide fibrous anchorage sites such as the collagen fibres in the natural extracellular matrix (ECM). This has partially limited the survival of anchorage-dependent cells in the 3D hydrogel environment. In this report, we established a hybrid hydrogel containing fibrous particles (FP) that closely mimics the ECM. The RGD peptide-coupled FP (R-FP) has a wide range of distribution and was homogeneously dispersed in the hydrogel. The encapsulated human mesenchymal stem cells in the hydrogel could bind to the R-FP presenting remarkable spreading morphology, augmented viability and differentiation. These findings may elicit the significance of a physical interaction in which the R-FP provides structural and biological cues to the cells. This strategy can be widely applicable to a variety of hydrogel systems.</P>
낙동강 상류 수역에서 남조류 발생과 천이패턴 - Aphanizomenon 속을 중심으로 -
류희성 ( Hui Seong Ryu ),박혜경 ( Hae Kyung Park ),이혜진 ( Hae Jin Lee ),신라영 ( Ra Young Shin ),천세억 ( Se Uk Cheon ) 한국물환경학회 2016 한국물환경학회지 Vol.32 No.1
This study investigated the occurrences and succession patterns of harmful cyanobacteria, as well as environmental factors, during a 3-year period (September 2012 to August 2015) in the upper region of the Nakdong River around Sangju weir. A total of 27 cyanobacterial taxa were observed in this study, and classified into 26 species and 1 variety belonging to 11 genera, 5 families, and 3 orders. Cell density ranged from 24 to 42,001 cells/ml, with a geometric mean of 33 cells/ml, during the survey period. The dominant orders differed depending on the survey year; order Oscillatoriales in 2013, Chroococcales in 2014 and Nostocales in 2015. An Aphanizomenon bloom occurred in June 2015 at which time the highest cell density of 36,873 cells/ml was detected in the upper region of the Nakdong River, where as the Aphanizomenon spp. cell density (190-1,704 cells/ml) had been low prior to that time. An Aphanizomenon bloom also occurred at around the same time downstream in the Young River, a major inflow branch of the Nakdong River. The Aphanizomenon cell density along the Nakdong River increased markedly after joining of the YoungRiver, indicating that the Aphanizomenon bloom in the YoungRiver caused a bloom in the Nakdong River. Meteorological and environmental parameters, such as very low precipitation, higher water temperature, pH, and TP concentration, and lower TN/TP ratio, in May and June of 2015 than in 2013 and 2014 exerted marked effects on the Aphanizomenon bloom in June 2015 in the Young River.