Prazosin의 항고혈압 효과에 대한 임상적 관찰

서세웅,이균태,김연호,조성락,신영우,신영기 최신의학사 1984 最新醫學 Vol.27 No.8

Effects of Silane Treatment on 3D Printed PLA/MFC Composites Fabricated by Fused Deposition Modeling

( Young-rok Seo ),( Sang-u Bae ),( Birm-june Kim ),( Min Lee ) 한국목재공학회 2020 한국목재공학회 학술발표논문집 Vol.2020 No.1

Recently, interest in 3D printing has increased in the technical field because complex objects can be manufactured without special tools. Among the various 3D printing methods, fused deposition modeling (FDM) is the most popular. In terms of polymer matrix, polylatic acid (PLA) is most widely used to make filaments in FDM 3D printing. However, PLA has fundamental drawbacks of high cost, poor toughness and high density, which limit its applicability. To overcome this, research is underway to apply the most abundant renewable natural resource, cellulose fiber, as a filler. Microfibrillated cellulose (MFC) is a filler with a high aspect ratio and is known to be useful in successfully transferring the stresses generated by external impacts. But, hydrophilic groups at the end of the MFC cause agglomeration, and to address this problem, the surface of the MFC was modified with a silane coupling agent. After that, PLA/MFC based FDM 3D printing filaments were fabricated. In our study, the silane-treated MFC was observed to be compatible with PLA by Fourier transform infrared spectra and scanning electron micrographs. Also, the addition of silane-treated MFC to 3D printed PLA/MFC composites improved mechanical properties (impact, tensile, and flexure) compared to untreated-MFC. Additionally, thermogravimetric analysis showed that in 3D printed PLA/MFC composites, silane-treated MFC delays thermal decomposition and imparts thermal stability compared to untreated MFC. In conclusion, the silane-treated MFC presented its applicability as a suitable filler for FDM 3D printing filaments based on PLA. - 84

< 전시-P-42 > A Study on the Mechanical and Morphological Properties of Nanoclay and Carbon Fiber Reinforced Recycled WPCs

( Young-rok Seo ),( Sang-u Bae ),( Jae-gyoung Gwon ),( Sun-young Lee ),( Birm-june Kim ) 한국목재공학회 2019 한국목재공학회 학술발표논문집 Vol.2019 No.1

Wood-plastic composites (WPCs) are a kind of composite material combining wood-based elements with plastics. Currently, WPCs are mainly used for exterior decking, fencing and railing, roofing, and patio furniture. Hence, WPC products are inevitably exposed to various outdoor conditions leading to degradation. Somewhat degraded WPCs are regarded as waste WPCs (W-WPCs) and there is a need to recycle the W-WPCs. Since the W-WPCs have deteriorated properties, to manufacture recycled WPCs (R-WPCs) having reliable performance, nanoclay (NC) and carbon fiber (CF) were selected as functional fillers. NC imparts balanced performance to filled composites by controlling dispersibility even if only a small amount is used. CF has been extensively used as a reinforcing filler in advanced engineered composites due to its low density and excellent performances. R-WPCs were prepared by adding different proportions of NC and CF (50/50 masterbatch pellets) into W-WPC granules. Composite specimens used in this study were fabricated by melt compounding and injection molding processing. Mechanical properties (impact, flexural, and tensile properties) of R-WPCs were investigated by universal testing machine (UTM) and impact tester. Morphological properties were observed by scanning electron microscope (SEM). The impact, flexural and tensile strength results showed that the strength improved by incorporation of NC and CF. This is because CF had a long fiber length with high aspect ratio and the surface sizing of CF enhanced the interfacial bonding between the polymer matrix and CF. But, the impact strength decreased with the incorporation of more than 5wt.% NC. This indicates that the incorporation of an appropriate amount of NC showed better toughening effects with CF, but a large amount of NC incorporation resulted in fracture failure due to aggregation of NC. The flexural and tensile modulus were improved with the incorporation of CF, but were not significantly changed by incorporation of NC. This is because CF has strong rigidity and increase the longitudinal fiber orientation in R-WPCs, while NC causes aggregations and weakens the interfacial bonding between the polymer matrix and NC. SEM images showed good adhesions between the polymer matrix and fillers. As a results of this study, the incorporation of appropriate functional fillers (NC and CF) can be expected to improve the performances of R-WPCs.

Case Report : Chromoblastomycosis Caused by Phialophora richardsiae

( Young Min Son ),( Hong Kyu Kang ),( So Young Na ),( Hye Young Lee ),( Jin Ok Baek ),( Jong Rok Lee ),( Joo Young Roh ),( Yiel Hea Seo ) 대한피부과학회 2010 Annals of Dermatology Vol.22 No.3

Chromoblastomycosis is a chronic fungal disease of the skin and subcutaneous tissues caused by a group of dematiaceous (black) fungi. The most common etiologic agents are Fonsecaea pedrosoi and Cladophialophora carrionii, both of which can be isolated from plant debris. The infection usually follows traumatic inoculation by a penetrating thorn or splinter wound. Several months after the injury, painless papules or nodules appear on the affected area; these papules then progress to scaly and verrucose plaques. We report a case of chromoblastomycosis caused by Phialophora richardsiae, which has been rarely associated with chromoblastomycosis. The case involved a 43-year-old male, who for the past 2 months had noted an erythematous, pustulous plaque that was somewhat dark brown in color on his right shin; the plaque also had intermittent purulent discharge and crust formation. On histopathological examination, chronic granulomatous inflammation and sclerotic cells were seen. The tissue fungus culture grew out the typical black fungi of P. richardsiae, which was confirmed by polymerase chain reaction. The patient has been treated with a combination of terbinafine and itraconazole for 3 months with a good clinical response. (Ann Dermatol 22(3) 362∼366, 2010)

Study on the Cytotoxic Mechanisms of Bacillus thuringiensis Delta-Endotoxin, a Bioinsecticide : Effect on $K^+$ Channel of Insect Cell Lines

Seo, Young-Rok,Ryu, Jae-Chun,Lee, Jun-Jae,Yu, Yong-Man,Han, Sung-Sik 한국곤충학회 1998 Entomological Research Vol.28 No.2

생물농약으로서 잘 알려져 있는 Bacillus thuringiensie(Bt) $\delta$-endotoxin의 곤충세포주 이온 채널에 대한 세포독성학적 효과를 연구하였다. 본 실험에서는 하나의 양이온의 등장액에서 세포팽창을 측정하여 나비목의 세포주에 대한 Bt독소의 영향을 평가하였다. 세포팽창은 $\delta$-endotoxin의 결정이 용해된 TC-100배지와 KCl-sucrose 등장액에 모두에 의해서 자극되었다. 결과를 통해 Bt 독소에 대한 세포팽창이 $K^{+}$ 이온과 관련되어있다고 볼 수 있었다. 세포팽창 은 Bt 독소에 의해 유도된 $K^{+}$ 이온의 유입과 동시에 $H_2O$의 침입에 의한 것임을 보여주었는데, 이는 세포팽창의 자극은 독소가 용해된 KCl-sucrose 등장액에서는 관찰되었으나 sucrose 등장액에서는 관찰되지 않았기 때문이다. 더 나아가 4-AP와 ouabain과 같은 $K^{+}$채널을 차단하는 시약을 사용한 실험들은 Bt 독소에 의해 유도된 세포팽창에 뚜렷한 영향을 주었다. 결과로부터, 4-AP에 의해 유도되어 증가된 세포팽창이 $K^{+}$ leaky channels을 통한 $K^{+}$ 유출의 차단에 의해 야기되었다고 볼 수 있었고, $Na^{+}$, $K^{+}$-ATPase의 저해제인 ouabain에 의한 세포팽창의 억제는 $Na^{+}$, $K^{+}$-ATPase활성이 감소에 의해 $K^{+}$ 유입의 감소에 의한 것이라 볼 수 있었다. The cytotoxic effects of Bacillus thuringiensis (Bt) $\delta$-endotoxin, a well-known bioinsecticide, were investigated on the ion channels of insect cell lines. This study attempted to evaluate the effect of Bt toxin on lepidopteran cell lines by measuring the cell swelling in isotonic solution containing only one cation. Cell swelling was stimulated in KCl-sucrose isotonic solution as well as TC-100 media containing solubilized crystal $\delta$-endotoxin. It suggested that cell swelling by Bt toxin is related to a $K^{+}$ channel. Cell swelling may be due to the stimulation $K^{+}$ influx and simultaneously the penetration of $H_2O$ induced by Bt toxin, because the stimulation of swelling was observed with solubilized toxin in KCl-sucrose isotonic solution, but not in sucrose isotonic solution. Moreover specific $K^{+}$ channel blockers, such as 4-aminopyrimidine (4-AP) and ouabain, showed the significant effect on cell swelling induced by Bt toxin. We suggest that the increased cell swelling induced by 4-AP is caused by blocking of $K^{+}$ efflux through $K^{+}$ leaky channels. The inhibition of cell swelling by ouabain, which is a well- known inhibitor of $Na^{+}$, $K^{+}$-ATPase, is suggested to be due to decreased $K^{+}$ influx following diminishment of $Na^{+}$, $K^{+}$-ATPase activities.

Molecular and Genomic Approaches on Nickel Toxicity and Carcinogenicity

Seo, Young-Rok,Kim, Byung-Joo,Ryu, Jae-Chun The Korean Society of Toxicogenomics and Toxicopro 2005 Molecular & cellular toxicology Vol.1 No.2

Nickel is the one of potent environmental, the occupational pollutants and the classified human carcinogens. It is a serious hazard to human health, when the metal exposure. To prevent human diseases from the heavy metals, it is seemingly important that understanding of how nickel exerts their toxicity and carcinogenic effect at a molecular and a genomic level. The process of nickel absorption has been demonstrated as phagocytosis, iron channel and diffusion. Uptaked nickel has been suggested to induce carcinogenesis via two pathways, a direct DNA damaging pathway and an indirect DNA damaging pathway. The former was originated from the ability of metal to generate Reactive Oxygen Species (ROS) and the reactive intermediates to interact with DNA directly. Ni-generated ROS or Nickel itself, interacts with DNAs and histones to cause DNA damage and chromosomal abnormality. The latter was originated from an indirect DNA damage via inhibition of DNA repair, or condensation and methylation of DNA. Cells have ability to protect from the genotoxic stresses by changing gene expression. Microarray analysis of the cells treated with nickel or nickel compounds, show the specific altered gene expression profile. For example, HIF-I (Hypoxia-Inducible Factor I) and p53 were well known as transcription factors, which are upregulated in response to stress and activated by both soluble and insoluble nickel compounds. The induction of these important transcription factors exert potent selective pressure and leading to cell transformation. Genes of metallothionein and family of heat shock proteins which have been known to play role in protection and damage control, were also induced by nickel treatment. These gene expressions may give us a clue to understand of the carcinogenesis mechanism of nickel. Further discussions on molecular and genomic, are need in order to understand the specific mechanism of nickel toxicity and carcinogenicity.

< 전시-P-43 > A Study on the Thermal Properties of Nanoclay and Carbon Fiber Reinforced Recycled WPCs

( Young-rok Seo ),( Sang-u Bae ),( Jae-gyoung Gwon ),( Sun-young Lee ),( Birm-june Kim ) 한국목재공학회 2019 한국목재공학회 학술발표논문집 Vol.2019 No.1

Waste wood plastic composites (W-WPCs), one of the growing waste resources in our daily lives, must be identified as a sustainable resource through recycling. However, in general, waste resources that have been exposed to outdoor conditions for a long time have deteriorated thermal properties. Thus, this study intended to improve the thermal properties of W-WPCs by incorporating hybrid functional fillers. Nanoclay (NC) and carbon fiber (CF) were used as fillers for the preparation of recycled WPCs (R-WPCs) based on W-WPCs. NC is being applied in various fields because it can achieve a balanced performance even if only a small amount is used. CF is increasingly available in advanced engineering materials because its performance is maintained at high temperatures. R-WPCs were prepared with different proportions of W-WPCs, NC and CF, and then melt-compounded. Thermal properties of R-WPCs were analyzed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). TGA results showed that the thermal stabilities of the R-WPCs were improved as the amount of fillers (NC and CF) increased. This is because the diffusion delay effect of the thermal decomposition products of NC and the heat resistance of CF exerted synergistic effect. In DSC results, melting point and cold crystallization temperature showed no difference between R-WPCs. Melting enthalpy is an important parameter since its magnitude is directly proportional to the overall level of the crystallinity possessed by the polymer. NC and CF used in this study are masterbatches containing 50% of polypropylene and 50% of fillers. As the amounts of fillers (NC and CF) increased, the amount of PP increased accordingly. As a result, the crystallinity values were increased. Also, the crystallization behavior of the composites is affected by amount and dispersion of fillers. Thereby, as the NC and CF were well dispersed in the R-WPCs, the hybrid filled composites showed the improvements of nucleating effect and crystallinity values. Therefore, the results of this study suggest that the hybrid incorporation of nano and engineering fillers (NC and CF) played an important role in improving the thermal properties of R-WPCs.

< 전시-P-39 > Effect of EPDM-g-MAH on the Performances of 3D-Printed PLA/Clay/Wood Nanocomposites by Fused Deposition Modeling

( Young-rok Seo ),( Sang-u Bae ),( Min Lee ),( Sang-min Lee ),( Birm-june Kim ) 한국목재공학회 2019 한국목재공학회 학술발표논문집 Vol.2019 No.1

3D printing technology is ideal for the development of prototypes or customized products because it can form complex shapes without special tools or molds. One type of 3D printing method, fused deposition modeling (FDM) is widely used because of its low cost, ease of handling, and popular open source programs. Polylactic acid (PLA), one of the most common 3D printing materials, is synthesized from sustainable resources and has biodegradability. Recently, wood flour (WF)-filled PLA 3D printing filaments have been studied. However, the 3D printing filaments using PLA and WF only, are still brittle and show poor interfacial adhesion between PLA and WF. Thus, in this study, PLA/WF filaments were prepared by incorporating maleic anhydride grafted ethylene propylene diene monomer (EPDM-g-MAH) and nanoclay (NC) to overcome the disadvantages of WF only-filled 3D printing filaments. The incorporation of NC was fixed at 2 wt%, and total 5 formulations of 3D-printed specimens were prepared with different ratios of EPDM-g-MAH. After that, the effect of EPDM-g-MAH on the mechanical, morphological, and x-ray diffraction (XRD) properties of PLA/WF 3D printing filaments were evaluated. Mechanical properties showed that the impact strength was improved with the incorporation of EPDM-g-MAH except for 15 wt% of EPDM-g-MAH. This is because EPDM-g-MAH with elastomeric characteristics caused toughening effect by improving compatibility between PLA and WF. However, the incorporation of large amounts of EPDM-g-MAH may rather restrict the toughening effect and led to decreased flexural and tensile properties by imparting ductility to PLA/WF filaments. Thereby, to minimize the performance reductions, the incorporation of NC was considered. As a result, good interfacial adhesions between fillers and polymer matrix were observed in SEM images. XRD patterns proved that the addition of EPDM-g-MAH promoted the exfoliation of NC silicate layers in PLA matrix. Therefore, EPDM-g-MAH coupling agent could be used as a promising functional additive for the fabrication of PLA/WF 3D printing filaments.

Batch Unscented Transformation for Satellite Orbit Determination Using A Satellite Laser Ranging (SLR)

Seo, Kyoung-Seok,Park, Sang-Young,Park, Eun-Seo,Kim, Young-Rok,Choi, Kyu-Hong 한국우주과학회 2008 한국우주과학회보 Vol.17 No.2

< 전시-P-44 > Effect of Nanoclay and Carbon Fiber on the Water Absorption and X-Ray Diffraction Properties of Recycled WPCs

( Young-rok Seo ),( Sang-u Bae ),( Jae-gyoung Gwon ),( Sun-young Lee ),( Birm-june Kim ) 한국목재공학회 2019 한국목재공학회 학술발표논문집 Vol.2019 No.1

Since the waste resources in our daily lives have an impact on environmental pollution, research on sustainable resources through recycling has attracted worldwide attention. So far, research on the recycling of wood or plastic has actively conducted, but there is little research on the recycling of waste wood plastic composites (W-WPCs). W-WPCs was deteriorated in performance, especially, water absorption. Therefore, in this study, various recycled WPCs (R-WPCs) based on W-WPCs was manufactured using functional fillers to improve performances. R-WPCs were prepared with different proportions of W-WPCs, nanoclay (NC) and carbon fiber (CF). The composite specimens used in this study were prepared by melt compounding and injection molding processing. The water absorption properties of R-WPCs were measured by water absorption and thickness swelling rate after immersion in distilled water for a certain period of time. X-ray diffraction (XRD) properties were analyzed to confirm the intercalation of NC in the composite matrix. In water absorption property results, CF filled R-WPCs showed very low water absorption rate and percentage. As the content of NC in R-WPCs increased, the water absorption decreased. This means the presence of high aspect ratio nano filler can create tortuous pathway for water molecules to diffuse into the composites. Similar trends were observed in thickness swelling properties as well. This suggests that the presence of NC in R-WPCs prevents the expansion of thickness caused by water and gives a dimensional stability to R-WPCs. In the XRD results, patterns of R-WPCs filled with both NC and CF showed broader peaks compared to R-WPCs without CF. This probably indicates that NC retains its original crystalline structure and shows a similar peak in the NC filled R-WPCs, but it is partially exfoliated in the NC/CF filled R-WPCs due to the presence of CF. Therefore, this study suggests that NC and CF are suitable functional fillers for the recycling of W-WPCs with deteriorated performances.