• Title/Summary/Keyword: Adhesion properties

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Evaluation of Physical Properties according to Mixing Ratio and the Survey of the Current Situation for Epoxy Resin used in Conservation (문화재 보존처리에 사용되는 에폭시수지의 사용현황과 배합비율에 따른 물성 변화 연구)

  • Lee, Eun Ji;Jang, Sung Yoon
    • Journal of Conservation Science
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    • v.32 no.2
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    • pp.223-234
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    • 2016
  • Two-component epoxy resin is widely used in the cultural heritage restoration field. However according to mixing ratio of resin and hardener, curing property, mechanical strength and chemical structure differ which have possibility to effect the stability of cultural heritage. Result of questionnaire survey shows hands-on workers in the conservation field tend to mix the epoxy resin with his or her eye measurement when the using amount is small or mix additional hardener to shorten the pot life of epoxy resin. This research aims to analyze the curing property, mechanical strength and chemical structure of rapid curing type epoxy resin and medium curing type one depending on relative ratio of 0.25~4 of hardener to resin. When the amount of hardener was 0.5~2 times more than the resin, exothermic heat and curing speed were both increased. In case of included hardener to resin was lower than official ratio, mechanical strength (tensile shear strength, tensile strength and compressive strength) became higher along with active cross-linking bonding of the epoxy resin. Medium curing type epoxy relatively had lower exothermic heat and slower reaction during curing process. It was observed to be put to definite point of mechanical strength under lower content of hardener than official ratio. While, hardener ratio more than twice the resin slowed down the curing greatly and lowered the adhesion strength also. In conclusion, under the lower mixing rate of hardener than official ratio would show relatively fast reaction with similar mechanical strength. Over the official ratio on the other hand, material property drops rapidly. Accordingly, mixing ratio of epoxy resin is expected to be influential to the stability of cultural heritage.

Cell Biological Function of Secretome of Adipose-Derived Stem Cells on Human Dermal Fibroblasts and Keratinocytes (인체 섬유아세포 및 케라티노사이트에 대한 지방줄기세포 분비물의 세포생물학적 기능)

  • Lee, Jae-Seol;Lee, Jong-Hwan
    • Microbiology and Biotechnology Letters
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    • v.40 no.2
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    • pp.117-127
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    • 2012
  • The beneficial effects of adipose-derived stem cell conditioned media (ADSC-CM) for skin regeneration have previously been reported, despite the precise mechanism of how ADSC-CM promotes skin regeneration remaining unclear. ADSC-CM contains various secretomes and this may be a factor in it being a good resource for the treatment of skin conditions. It is also known that ADSC-CM produced in hypoxia conditions, in other words Advanced Adipose-Derived Stem cell Protein Extract (AAPE), has excellent skin regenerative properties. In this study, a human primary skin cell was devised to examine how AAPE affects human dermal fibroblast (HDF) and human keratinocyte (HK), which both play fundamental roles in skin regeneration. The promotion of collagen formation by HDFs was observed at 0.32 mg/ml of AAPE. AAPE treatment significantly stimulated stress fiber formation. DNA gene chips demonstrated that AAPE in HKs (p<0.05) affected the expression of 133 identifiable transcripts, which were associated with cell proliferation, migration, cell adhesion, and response to wounding. Twenty five identified proteins, including MMP, growth factor and cytokines such as CD54, FGF-2, GM-CSF, IL-4, IL-6, VEGF, TGF-${\beta}2$, TGF-${\beta}3$, MMP-1, MMP-10, and MMP-19, were contained in AAPE via antibody arrays. Thus, AAPE might activate the HK biological function and induce the collagen synthesis of HDF. These results demonstrate that AAPE has the potential to be used for clinic applications aimed at skin regeneration.

Manufacturing Techniques and the Conservation Treatment of Chimi - (Ridge-end tile) Excavated from the Beopcheonsa Temple Site, Wonju - (원주 법천사지 토제 치미의 제작기법과 보존처리)

  • Lee, Seung Gang;Jo, Seong Yeon;Huh, Il Kwon
    • Journal of Conservation Science
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    • v.35 no.5
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    • pp.518-527
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    • 2019
  • This investion studies the manufacturing techniques of chimi(ridge-end roof tiles based on the) fragments excavated from the Wonju Beopcheonsa temple site(Historic site No. 466) and aids in the conservation of the fragments. The results of the investigation are categorized into the production of the body parts, the wing and the feather attachment, the production of the decorative parts, the scratches in the upper and lower part, the perforations connecting the upper and lower parts, and the formative features(bending phenomenon). The procedures in the conservation treatment of the chimi was performed in a sequential order beginning with a preliminary examination, followed by the removal of foreign substances, coating, joining and restoration, and color retouching. A three-dimensional scanning data was employed to restore the missing parts after adhesion to determine the location, size, and angle of the original shape. The restored chimi measures 118 cm in height and weighs 121 kg, which makes it the fifth largest in size among any chimi(including restored) in Korea. We expect that the pointed feathers will make the chimi from the Beopcheonsa temple site a rare reference as no specimens with these features have been found in Korea until now.

Expression Analysis of Galectin-1 from Fat in Berkshire Pigs

  • Jung, Won Yong;Cho, Eun Seok;Kwon, Eun Jung;Park, Da Hye;Chung, Ki Hwa;Kim, Chul Wook
    • Asian-Australasian Journal of Animal Sciences
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    • v.21 no.2
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    • pp.167-176
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    • 2008
  • Galectins are a group of animal lectins consisting of galectin-type carbohydrate recognition domains (CRD) with relatively minor domains. The biological properties of galectins include the regulation of inflammation, intercellular adhesion, cell differentiation and cell death. The diverse kinds of galectin suggest variety in their biological roles. Galectin-1 is released during adipocyte differentiation and is associated with fat which is one of the important factors for meat quality. To verify expression level, a 0.5 kb clone of galectin-1 was obtained from cDNA prepared from back fat tissue of a Sancheong Berkshire pig with good quality meat, and the galectin-1 gene identified. The deduced amino acid sequence of the galectin-1 gene was compared with those obtained from other species. By using RT-PCR and Real time-PCR, an attempt was made to determine the expression level of galectin-1 and to compare with various tissues (tenderloin and back fat) taken from pigs in different groups. Grouping of pigs was based on growth-stage (weighing 60, 80, and 110 kg) and the sub-speciation (Yorkshire and Sancheong Berkshire pigs). We attempted to determine influences of pig species, growth stages and tissue variations on the expression level of the galectin-l gene and it was revealed that the expression pattern of the galectin-1 gene was significantly different (p<0.01 or p<0.05). Galectin-1 genes were expressed more highly in the back fat tissues of pigs weighing 110 kg than in those weighing 60 kg or 80 kg. However, the lowest expression was seen in the tenderloin tissues of pigs weighing 110 kg. Sancheong Berkshire pigs showed higher expression of the galectin-1 gene compared to Yorkshire pigs. Accordingly, it is considered that the expression pattern of the galectin-1 gene influences the growth of back fat tissues and the pig speciation relationship. Previous studies suggested that different expression of galectin-1 genes represents variety among the breeds and is closely related to fat tissue growth, conjugation and catabolism. Further, this study suggests that the expression of galectin-1 at a specific growth stage and tissue contributes significantly to the overall meat quality of Sancheong Berkshire pigs.

Cytotoxicity Assessments of Portulaca oleracea and Petroselinum sativum Seed Extracts on Human Hepatocellular Carcinoma Cells (HepG2)

  • Farshori, Nida Nayyar;Al-Sheddi, Ebtesam Saad;Al-Oqail, Mai Mohammad;Musarrat, Javed;Al-Khedhairy, Abdulaziz Ali;Siddiqui, Maqsood Ahmed
    • Asian Pacific Journal of Cancer Prevention
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    • v.15 no.16
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    • pp.6633-6638
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    • 2014
  • The Pharmacological potential, such as antioxidant, anti-inflammatory, and antibacterial activities of Portulaca oleracea (PO) and Petroselinum sativum (PS) extracts are well known. However, the preventive properties against hepatocellular carcinoma cells have not been explored so far. Therefore, the present investigation was designed to study the anticancer activity of seed extracts of PO and PS on the human hepatocellular carcinoma cells (HepG2). The HepG2 cells were exposed with $5-500{\mu}g/ml$ of PO and PS for 24 h. After the exposure, cell viability by 3-(4,5-dimethylthiazol-2yl)-2,5-biphenyl tetrazolium bromide (MTT) assay, neutral red uptake (NRU) assay, and cellular morphology by phase contrast inverted microscope were studied. The results showed that PO and PS extracts significantly reduced the cell viability of HepG2 in a concentration dependent manner. The cell viability was recorded to be 67%, 31%, 21%, and 17% at 50, 100, 250, and $500{\mu}g/ml$ of PO, respectively by MTT assay and 91%, 62%, 27%, and 18% at 50, 100, 250, and $500{\mu}g/ml$ of PO, respectively by NRU assay. PS exposed HepG2 cells with $100{\mu}g/ml$ and higher concentrations were also found to be cytotoxic. The decrease in the cell viability at 100, 250, and $500{\mu}g/ml$ of PS was recorded as 70%, 33%, and 15% by MTT assay and 63%, 29%, and 17%, respectively by NRU assay. Results also showed that PO and PS exposed cells reduced the normal morphology and adhesion capacity of HepG2 cells. HepG2 cells exposed with $50{\mu}g/ml$ and higher concentrations of PO and PS lost their typical morphology, become smaller in size, and appeared in rounded bodies. Our results demonstrated preliminary screening of anticancer activity of Portulaca oleracea and Petroselinum sativum extracts against HepG2 cells, which can be further used for the development of a potential therapeutic anticancer agent.

A Study on Adhesion Characteristics and Physical Properties of Animal Glue Added Genipin (제니핀을 첨가한 아교의 접착 특성과 물성 변화 연구)

  • Lee, Jun Ho;Yu, Ji A;Chung, Yong Jae
    • Journal of Conservation Science
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    • v.34 no.3
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    • pp.157-166
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    • 2018
  • In this study, gelatin binding ability was increased by adding cross linking agent to improve adhesive characteristic of animal glue. Animal glue added genipin measured gel strength and viscosity, the structural analysis, the color retention degree, elution degree, and rupture strength. And the water resistance and ultraviolet light resistance with the addition of genipin were compared. As a result of the study, the gel strength and viscosity increased with the amount of genipin. As a result of the structural analysis, in gelatin, the absorption peak of the triple structure of collagen structurally stabilized was observed. As a result of the color retention degree, the film was observed because of the lowered brightness. The amount of elution glue was increased with addition of genipin at $50^{\circ}C$ distilled water condition and rupture strength has increased with the amount of genipin. In the water resistance and light fastness, there was no appearance before and after deterioration due to the addition of genipin. Based on the results of this study, it confirmed the adhesive characteristics of animal glue added genipin and examined the experimental method applicable for animal glue. After the addition of genipin, flexibility, re-solving, adhesive force, and curing speed, which are unique characteristics of glue, can be improved without disappearing, so it is expected that it will be applicable to production of animal glue and conservation of cultural heritage when homogeneous glue is secured.

Preparation and Characterization of Hyaluronic Acid Loaded PLGA Scaffold by Emulsion Freeze-Drying Method (히알루론산을 함유한 PLGA 지지체의 제조 및 특성결정)

  • Ko, Youn-Kyung;Kim, Soon-Hee;Jeong, Jae-Soo;Park, Jung-Soo;Lim, Ji-Ye;Kim, Moon-Suk;Lee, Hae-Bang;Khang, Gil-Son
    • Polymer(Korea)
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    • v.31 no.6
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    • pp.505-511
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    • 2007
  • Poly(lactide-co-glycolide)(PLGA) and hyaluronic acid (HA) has been widely used as biocompatible scaffold materials to regenerate tissue. In this present study, we fabricated microporous PLGA and HA loaded PLGA scaffolds by a emusion freeze-drying method. In order to confirm that the release profile of cytokine or water-soluble drugs, we manufactured the granulocyte macrophage colony stimulating factor(GM-CSF) loaded PLGA and HA-PLGA scaffold. All scaffolds were characterized using scanning electron microscope(SEM), mercury porosimeter and wettability measurement. Cell proliferation and viability were assessed by a 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium-bromide (MTT) test. The porosity of HA-PLGA scaffold was greater than 95% with the total pore area of $261\;m^2/g$. The HA-FLGA scaffold exhibited well interconnected pores to allow greater cell adhesion and prolixferation. It was proven by higher cell viability in the HA-PLGA scaffold than PLGA alone. This may be due to the enhanced natural properties and higher water retention capacity of HA.

A Study on the Electron Beam Crosslinking of Acrylic Pressure Sensitive Adhesives for Polarizer Film (전자선 조사를 통한 편광필름용 아크릴계 고분자의 가교화 반응에 대한 연구)

  • Park, Jung-Jin;Choi, Hong-June;Ko, Hwan-Soon;Jeong, Eun-Hwan;Youk, Ji-Ho
    • Polymer(Korea)
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    • v.36 no.3
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    • pp.344-350
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    • 2012
  • New pressure sensitive adhesives (PSAs) for polarizer film were prepared by electron beam (e-beam) radiation to acrylic copolymers, and their adhesive properties were investigated. The acrylic copolymers were synthesized by free radical polymerization of $n$-butylacrylate (BA), 2-hydroxyethyl methacrylate (HEMA), and acrylic acid (AA). The acrylic copolymers were coated on PET release films to a thickness of 25 ${\mu}m$, laminated to polarizer films, and then radiated with e-beam at room temperature. Gel fractions of all the acrylic copolymers after e-beam radiation at 50 kGy were higher than 93%, and their crosslinking densities were increased with increasing the content of HEMA units. PSA prepared by e-beam radiation of acrylic copolymer synthesized with a feed ratio of BA/HEMA/AA = 89.5/10/0.5 (w/w/w) at a dose of 50 kGy exhibited the best adhesion performances in terms of peel strength, creep resistance, durability and reliability, and light leakage. It is expected that the preparation method of PSAs via e-beam irradiation will improve the producibility and workability of polarizer film for liquid crystal display.

A Study on Application of Enzyme Additives to Improve Drying Speed of Urushi Lacquer (옻칠의 건조속도 향상을 위한 효소첨가제 적용 연구)

  • PARK, Ji Hyeon;PARK, Jung Hae;KIM, Soo Chul
    • Journal of the Korean Wood Science and Technology
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    • v.48 no.3
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    • pp.326-344
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    • 2020
  • Laccase was applied to improve the drying speed of urushi lacquer to confirm a potential use of laccase as an enzyme additive. As a result of applying laccase of lacquer and white-rot fungi, drying times for both Korean and Chinese specimens were reduced. All of the specimens to which laccase was applied were dried(set to touch) within 60 minutes from the start of the drying, and the drying rate was improved as the content ratio of laccase increased. In addition, although there were differences in hardening drying time between Korean and Chinese lacquers, it was confirmed that hardening drying took place even at room with temperature of 20 ± 2 ℃ and humidity of 55-60%. As a result of lacquer layer analysis of the dried specimens, the drying speed was improved when the content ratio of laccase to urushiol was 5:1, and there were no differences in chromaticity and adhesion, confirmed that the layers were stable. It was observed that the gloss of both Korean and Chinese lacquers were reduced when laccase was applied. However, according to the analysis of FT-IR and Py-GC/MS, the changes in components were not as sufficient to affect the physical properties. Thus, its applicability as an additive was confirmed.

Wettability of titanium implants depending upon surface properties (타이타늄 표면 처리 특성에 따른 젖음성에 관한 연구)

  • Han, Young-Soo;Shin, Sang-Wan
    • The Journal of Korean Academy of Prosthodontics
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    • v.47 no.1
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    • pp.12-20
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    • 2009
  • Statement of problem: When an implant is fixed, a fixture comes into contact with a tissue fluid. Adhesion of a tissue fluid to a surface of implant is various case by case. Purpose: The ultimate goal of this work is to analyze a correlation between a surface roughness and wettability of implant specimens. A measurement for wettability is performed considering 4 types of specimen implant with surface treatments different from each other to investigate the change of wettability with the elapse of time. Material and methods: Firstly, 20 specimens of titanium were prepared. The specimen were made of a commercial Titanium Grade IV with the diameter of 10 mm and the thickness of 1 mm. According to the method of surface treatment, the specimens were classified into 4 groups of 5 specimens per group. Group A: Machined Surface Group B: Anodized surface Group C: RBM (HA blasting) surface Group D: CMP (calcium methaphosphate) coating surface. Surface roughness of specimen was measured using SV-3000S4 (Mituyoto, Japan). The measurement was based on the standard of JIS1994. Sessile drop method was used to measure the wettability, which measures contact angle between implant disc and saline with the time interval of 5, 10, and 15 seconds. SPSS 11.0 was used to analyze the collected data. In order to analyze the difference of wettability and surface roughness according to implant surface treatment method. The statistical significance was tested with the confidence level of 95%. Pearson's correlation coefficient was used to evaluate the correlation of surface roughness and wettability. Results: The difference of surface roughness was statistically significant in the order of Group C ($1.69{\pm}0.26$), Group D ($1.58{\pm}0.16$), Group B ($0.78{\pm}0.14$) Group A ($0.18{\pm}0.05$). The wettability has also a statistically significant difference, which was in the order of group B ($17.70{\pm}2.66$), Group C ($27.86{\pm}4.52$), Group D ($66.28{\pm}3.70$) Group A ($70.52{\pm}8.00$). There was no difference in wettability with the passage of time. Conclusions: 1. The surface roughness was high in the order of RBM, CMP, Anodized, Machined group (P<.05). 2. The wettability was high in the order of Anodized, RBM, CMP, Machined group (P<.05). 3. There was no statistical significance in the correlation of surface roughness and wettability.