• Title/Summary/Keyword: co-cure

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Discovery of Argyrin-Producing Archangium gephyra MEHO_001 and Identification of Its Argyrin Biosynthetic Genes

  • Choi, Juo;Park, Taejoon;Kang, Daun;Lee, Jeongju;Kim, Yungpil;Lee, Pilgoo;Chung, Gregory J.Y.;Cho, Kyungyun
    • Microbiology and Biotechnology Letters
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    • v.49 no.4
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    • pp.493-500
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    • 2021
  • Argyrins are a group of anticancer and antibacterial octapeptide bioactive substances isolated from myxobacteria. In this study, we showed that the myxobacterium Archangium gephyra MEHO_001, isolated in Korea, produces argyrins A and B. MEHO_001 cells tend to aggregate when cultured in liquid media. Hence, a dispersion mutant, MEHO_002, was isolated from MEHO_001. The MEHO_002 strain produced approximately 3.5 times more argyrins than that produced by the wild-type strain MEHO_001. We determined the whole-genome sequence of A. gephyra MEHO_002 and identified a putative argyrin biosynthetic gene cluster comprising five genes, arg1-arg5, encoding non-ribosomal peptide synthases and tailoring enzymes. Inactivation of arg2 by plasmid insertion disrupted argyrin production. The amino acid sequences of the proteins encoded by arg2-arg5 of A. gephyra MEHO_002 were 90-98% similar to those encoded by the argyrin biosynthetic genes of Cystobacter sp. SBCb004, an argyrin-producing myxobacterium with identical domain organization.

Screening of Myxobacteria Carrying Tubulysin Biosynthetic Genes

  • Hyun, Hyesook;Choi, Juo;Kang, Daun;Kim, Yungpil;Lee, Pilgoo;Chung, Gregory J.Y.;Cho, Kyungyun
    • Microbiology and Biotechnology Letters
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    • v.49 no.1
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    • pp.32-38
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    • 2021
  • Tubulysins are a group of secondary metabolites produced by myxobacteria that inhibit the function of the eukayotic cytoskeleton. We developed a pair of PCR primers that specifically amplified tubulysin biosynthetic genes. Using these primers, eight out of the eighty-one strains of myxobacteria belonging to the Cystobacteraceae family that harbored putative tubulysin biosynthetic genes were screened through PCR analysis. The selected strains included two Archangium gephyra, two Stigmatella sp., two Vitiosangium cumulatum, and two unidentified myxobacteria. LC-MS analysis of the culture extracts from the selected strains revealed that A. gephyra KYC4066 produced putative tubulysin A and B.

Effect of Various Cross-linking Types on the Physical Properties in Carbon Black-Filled Natural Rubber Compound (천연고무 배합물에서 가교형태 변화가 물성에 미치는 영향)

  • Park, Byung-Ho;Jung, Il-Gouen;Park, Sung-Soo
    • Polymer(Korea)
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    • v.25 no.1
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    • pp.63-70
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    • 2001
  • The objective of this study was to investigate the effect of cure type on the processing and physical properties under conditions of similar stress-strain properties. On the carbon black filled natural rubber(NR) based compound, the induction time decreased, but the cure rate became fast with increasing loading of sulfur donor agent. Tensile strength was little affected on the curing type. However, elongation generally decreased with increasing accelerator. Effect of cure type on the blow-out properties was followings: CV

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A STUDY ON THE FITNESS OF THE RESIN RECORD BASE (레진기초상의 적합도에 관한 연구)

  • Ji, Jae-Seon;Han, Sang-Hoon;Oh, Sang-Chun;Cho, Hye-Won
    • The Journal of Korean Academy of Prosthodontics
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    • v.34 no.3
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    • pp.611-619
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    • 1996
  • The purpose of this study was to evaluate the fitness of 4 kinds of resin record base materials. The record base materials used on the edentulous cast in this study were Triad VLC resin (Dentsply International Inc., U.S.A.), custom tray resin (Kerr Ltd., U.S.A.), heat-cure resin (Dentimex Co., Holland), and self-cure resin (Dentimex Co., Holland). The gap width between record base and cast were measured in the ridge crest and midpalatal area with microhardness tester. The results obtained were as follows : 1. Among the 4 kinds of record base, heat-cure Vertex fitted best on the cast. Triad and Fomatray fitted better than self-cure Vertex. Self-cure Vertex had the poorest fit. 2. The quality of the fit of the record base varied at different locations on the cast. The record base fit better in the ridge crest than midpalatal area. 3. In the midpalatal area, there's no significant difference in the fit of Fomatray, Triad and heat-cure Vertex. They all fit better than self-cure Vertex. 4. In the ridge crest, heat-cure Vertex fit better than any other record base.

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Investigation of cure cycle for co-cured metal/composite hybrid structures without fabricating thermal residual stress (동시경화 하이브리드 금속/복합재료 구조물의 제조 잔류 열응력 제거를 위한 경화사이클에 관한 연구)

  • Kim Hak Sung;Park Sang Wook;Lee Dai Gil
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2004.10a
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    • pp.83-87
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    • 2004
  • In this work, the cure cycle of co-cured metal/composite structure was investigated to decrease fabricating thermal residual stresses between the metal and the composite material. DSC (Differential scanning calorimetry) experiment and static lap shear test of co-cured aluminum/composite double lap joint as well as the curvature experiment of co-cured steel/composite strip were performed to investigate the effect of curing cycle on the thermal residual stress of co-cured hybrid structures. From the experiments, it was found that post curing method after abrupt cooling of co-cured aluminum/composite hybrid structure at certain point of degree of cure during curing process could eliminate fabricating the thermal residual stresses.

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The Toughness of Castor Oil Modified Epoxy Resins by Various Cure Temperatures (경화온도에 따른 Castor Oil/epoxy의 강인성)

  • Kim, Jong Seok;Hong, Suk Pyo
    • Applied Chemistry for Engineering
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    • v.8 no.6
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    • pp.973-978
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    • 1997
  • The toughness and morphology of epoxy resin based on diglycidyl ether of bisphenol A(DGEBA) cured with of tris (dimethylaminomethy]) phenol(DMP-30) and castor oil (CO) as a toughening modifier have been studied. Mixtures of CO and an epoxy resin showed a higher miscibility than the classical CTBN modified epoxy resin. The glass transition temperature($T_g$) was decreased with the CO content and the cure temperature. It is interpreted that the networks of epoxy matrix obtained at high temperature are apparently looser and more flexible due to the lower crosslinking density. The toughness was slightly increased with the CO content at $40^{\circ}C$ of curing temperature. The toughness increased with increasing the cure temperature and CO content.

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Improvement of Toughness of Tetrafunctional Epoxy (TGDDM) Resin Using Polyamideimide (PAI) Resin (폴리아미드이미드 수지를 이용한 4관능성 에폭시 수지의 강인화 향상)

  • 박수진;허건영;이재락;홍영택;최길영
    • Polymer(Korea)
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    • v.26 no.5
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    • pp.599-606
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    • 2002
  • In this study, 4,4'-tetraglycidyl diaminodiphenyl methane (TGDDM)/polyamideimide (PAI) blends were cured using diaminodiphenyl sulfone (DDS). And the effect of addition of different PAI contents to neat TGDDM was investigated in the thermal, mechanical, and morphological properties of the blends. The cure behavior and thermal stability of the cured specimens were monitored by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. Also, the critical stress intensity factor (K$\_$IC/) was measured in UTM, and the phase separation behavior and final morphology of TGDDM/PAI blends were examined in scanning electron microscopy(SEM). As a result, the cure temperature and cure activation energy (E$\_$a/) were decreased with increasing the PAI content. The decreasing of cure temperature and cure activation energy were probably due to the presence of secondary amine group of PAI backbone used as co-initiator. But, the decomposition activation energy (E$\_$t/) and K$\_$IC/ value were increased up to 5. 10 phr of PAI content, respectively and they were decreased above the PAI contents. These results were explained on the basis of chain scission reaction by etherification. And morphology of blends observed from SEM was confirmed in co-continuous structures.

Photostabilization and Cure Kinetics of UV-Curable Optical Resins Containing Photostabilizers

  • Cho, Jung-Dae;Kim, Sung-Hwa;Chang, In-Cheol;Kim, Kwon-Seok;Hong, Jin-Who
    • Macromolecular Research
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    • v.15 no.6
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    • pp.560-564
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    • 2007
  • The photostabilization and cure kinetics of UV-curable, optical resins containing various formulations of photostabilizers were investigated to determine the system with the highest cure conversion and durability. Photo-DSC analysis revealed that increasing the concentration of a UV absorber (UVA) decreased both the crosslink density and the cure rate due to competition for the incident photons between the photoinitiator and the UVA, whereas including a hindered amine light stabilizer (HALS) hardly affected either the cure conversion or the cure rate due to its very low absorption of 365 nm. This result was confirmed by FTIR-ATR spectroscopy and UV-visible spectroscopy analyses. QUV ageing experiments showed that the cure conversion and durability were the highest for the UVA/HALS formulation at a ratio of 1 : 2, which is due to their synergistic action.

Cure Characteristics of Foaming EVA Compounds: Influence of EVA Types and Cure Systems

  • Choi, Sung-Seen;Bae, Jong Woo;Kim, Jung-Soo;Han, Dong-Hun
    • Elastomers and Composites
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    • v.51 no.3
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    • pp.212-217
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    • 2016
  • Influence of poly(ethylene-co-vinyl acetate) (EVA) types and cure systems on cure characteristics of foaming EVA compounds were investigated. Three kind EVAs with different VA contents were employed. Influence of triallyl cyanurate (TAC) and dicumylperoxide (DCP) content on the cure characteristics were examined. The minimum torque ($T_{min}$) and delta torque (${\Delta}T$) decreased as the VA content increased. The ${\Delta}T$ was increased by adding TAC and by increasing the DCP content. For the foaming EVA compounds without TAC, the cure times such as the minimum cure time ($t_{min}$), scorch time ($t_2$), and optimal cure time ($t_{90}$) did not show a specific trend according to the DCP contents. For the foaming EVA compounds containing TAC, the cure times decreased as the DCP content increased. From the experimental results, it was found that efficienct DCP/TAC ratio for improvement of the crosslink density was 1.1~2.0.

Cure Kinetics of Cycloaliphatic Epoxy/Silica System for Electrical Insulation Materials in Outdoor Applications

  • Lee, Jae-Young;Park, Jae-Jun;Kim, Jae-Seol;Shin, Seong-Sik;Yoon, Chan-Young;Cheong, Jong-Hoon;Kim, Young-Woo;Kang, Geun-Bae
    • Transactions on Electrical and Electronic Materials
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    • v.16 no.2
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    • pp.74-77
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    • 2015
  • The cure kinetics of a neat epoxy system and epoxy/silica composite were investigated by DSC analysis. A cycloaliphatic type epoxy resin was diglycidyl 1,2-cyclohexanedicarboxylate and curing agent was anhydride type. To estimate kinetic parameters, the Kissinger equation was used. The activation energy of the neat epoxy system was 88.9 kJ/mol and pre-exponential factor was 2.64×1012 min−1, while the activation energy and pre-exponential factor for epoxy/silica composite were 97.4 kJ/mol and 9.21×1012 min−1, respectively. These values showed that the silica particles have effects on the cure kinetics of the neat epoxy matrix.