• Steel and Composite Structures
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• v.38 no.1
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• pp.103-120
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• 2021

This research examines the eccentric compression performance of composite columns composed of recycled aggregate concrete (RAC)-filled square steel tube and profile steel. A total of 17 specimens on the composite columns with different recycled coarse aggregate (RCA) replacement percentage, RAC strength, width to thickness ratio of square steel tube, profile steel ratio, eccentricity and slenderness ratio were subjected to eccentric compression tests. The failure process and characteristic of specimens under eccentric compression loading were observed in detail. The load-lateral deflection curves, load-train curves and strain distribution on the cross section of the composite columns were also obtained and described on the basis of test data. Results corroborate that the failure characteristics and modes of the specimens with different design parameters were basically similar under eccentric compression loads. The compression side of square steel tube yields first, followed by the compression side of profile steel. Finally, the RAC in the columns was crushed and the apparent local bulging of square steel tube was also observed, which meant that the composite column was damaged and failed. The composite columns under eccentric compression loading suffered from typical bending failure. Moreover, the eccentric bearing capacity and deformation of the specimens decreased as the RCA replacement percentage and width to thickness ratio of square steel tube increased, respectively. Slenderness ratio and eccentricity had a significantly adverse effect on the eccentric compression performance of composite columns. But overall, the composite columns generally had high-bearing capacity and good deformation. Meanwhile, the mechanism of the composite columns under eccentric compression loads was also analysed in detail, and the calculation formulas on the eccentric compression capacity of composite columns were proposed via the limit equilibrium analysis method. The calculation results of the eccentric compression capacity of columns are consistent with the test results, which verify the validity of the formulas, and the conclusions can serve as references for the engineering application of this kind of composite columns.

• Bulletin of the Korean Chemical Society
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• v.33 no.2
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• pp.409-414
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• 2012

Xanthorrhizol is a bisabolane type of natural sesquiterpene, the major component of essential oils of Curcuma xanthorrhiza. 2-(3-Methoxy-4-methylphenyl)propan-1-ol and 2-(3-hydroxy-4-methyl phenyl)propan-1-ol could be essential building block for enantioselective synthesis of xanthorrhizol. Enantioselective (c = 53%, E = $80{\pm}3$) for R-(+)-2-(3-hydroxy-4-methylphenyl) propan-1-ol and (c = 58%, E = $27{\pm}1$) for R-(+)-2-(3-methoxy-4-methylphenyl) propan-1-ol resolution processes were developed via lipase-catalyzed reaction. We found lipase Aspergillus oryzae (AOL) and Porcine pancreas (PPL) are selective to transesterification and hydrolysis in organic and aqueous phase. Modified demethylated substrate is appropriate for enantioselective hydrolysis reaction without any additives. Enantiopure chiral alcohol was crystallized from ethyl acetate/n-hexane co-solvent system. Gram scale resolved chiral intermediate will facilitate the synthesis of the unnatural S-(+)-xanthorrhizol, the corresponding isomer of the natural one.

• The Zoological Society Korea : Newsletter
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• v.15 no.1
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• pp.12-19
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• 1998

• Proceedings of the Korean Society of Applied Pharmacology
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• 1994.04a
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• pp.167-167
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• 1994

Thioglycerol과 Glycerol을 출발물질로 1번 탄소(C) 위치의 산소(O),또는 황(S)에 octadecyl기로 alkylation한 후, 2번 탄소(C)위치 산소(O)를 palmitoyl기로acetylation시켜 만든 thioether lipid 및 ether lipid유도체를 인산화시킨 rac-1-S-octa-decyl-2-O-palmitoyl-1-S-thioglycerol-3-phosphate (DL-PTBA-P)와 rac-1-O-octadecyl-2-O-palmitoylglycerol-3-phosphate (DL-PBA-P)등을 합성하였다. 이들 thioether lipid 및 ether lipid유도체는 그 자체로도 in vitro와 in vivo에서anti-neoplastic property를 가지고 있는데, 이들 중간체를 핵산 화합물로써 역시 강한 항암 작용에도 불구하고 독성등 부작용이 문제가 되고있는 Ara-C (일명 Cytarabine)의 인산화물인 ara-CMP morpholidate와 conjugation시켜 최종물질로서 ara-CDP-DL-PCA, ara-CDP-DL-PBA, ara-CDP-DL-PTCA 및 ara-CDP-DL-PTBA등을 합성하였다. 이들 중 ara-CDP-DL-PTBA가 본 과제와 관련하여 항암제로서 최종 개발하고자하는 주요 물질인 Cytoros이다.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.1
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• pp.26-32
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• 2020

Concrete recycling is becoming mandatory rather selective due to depletion of constructional materials and increase of concrete waste. Studies on recycling concrete are conducted in various point of view for long time. However, standard or guideline of many countries for the application of recycled aggregate concrete(RAC) has restrictions such as low replacement rate of coarse aggregate and no fine aggregate allowed due to inferior material properties of recycled aggregate. This study intends to figure out the feasibility of casting natural aggregate concrete(NAC) and RAC separately in a structural member. In making RAC, replacement rate of coarse aggregate was 50, 100% in RAC and treatment of interface of two concretes is introduced. RAC treatment of recycled aggregate or inclusion of additives was not done as it can increase embodied energy of concrete work. Double-shear test with uniformly distributed loading was adopted to evaluate shear strength at the interface of two concretes. After curing it was hard to distinguish interface of two concretes. Experimental result revealed that specimen with higher replacement rate showed higher shear-to-compressive strength ratio, which is possibly attributed to coarse aggregate size and roughness of sheared section. Further study on the effect of various parameters is required and subsequent research activity is on-going.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.1
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• pp.85-93
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• 2017

This paper presents mechanical properties and carbonation behavior of the recycled aggregate concretes(RAC) in which natural aggregate was replaced by recycled coarse aggregate and fine aggregate by specified concrete strength levels(21, 35, 50MPa). A total of 18 RAC were produced and classified into six series, each of which included three mixes designed with three specified concrete strength levels of 21MPa, 35MPa and 50MPa and three recycled aggregate replacement ratios of 0, 50 and 100%. Physical and mechanical properties of RAC were tested for slump test, compressive strength, and carbonation depth. The test results indicated that the slump of RAC could be improved or same by recycled coarse aggregate replacement ratios, when compared with natural aggregate. But slump of RAC was decreased as the recycled fine aggregate replacement ratios increase. Also, the test results showed that the compressive strength was decreased as the recycled aggregate replacement ratios increased and it had a conspicuous tendency to decrease when the content of the recycled aggregate exceeded 50%. Furthermore, the result indicated that the measured carbonation depth increases by 40% with the increase of the recycled aggregate replacement. In the case of the concrete having low level compressive strength, the increase of carbonation depth tends to be higher when using the RCA. However, the trend of carbonation resistivity in high level compressive strength concrete is similar to that obtained in natural aggregate concrete. Therefore, an advance on the admixture application and mix ratio control are required to improve the carbonation resistivity when using the recycled aggregate in large scale.

• Bulletin of the Korean Chemical Society
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• v.20 no.3
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• pp.362-364
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• 1999

• Elastomers and Composites
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• v.46 no.4
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• pp.304-310
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• 2011

In this study, we prepared poly(ethylene-ter-1-hexene-ter-divinylbenzene) using briged rac-$Et[Ind]_2ZrCl_2$ or unbriged $Cp_2ZrCl_2$ metallocene catalysts. Bridged rac-$Et[Ind]_2ZrCl_2$ catalyst showed relatively good results compared with unbridged one. When cocatalyst/catalyst molar ratio was 3000, catalytic activity indicated more than 8000(kg of polymer/$mol{\cdot}h$) which was very remarkable value. As a polymerization time increased, the weight-average molecular weight of the terpolymer gradually increased to some degree. In the case of a polymerization time of 50 minutes, the state of the terpolymer became amorphous. The range of the weight-average molecular weight and the densities of the terpolymer was 110,000~200,000 and $0.85{\sim}0.89g/cm^3$, respectively. The thermal properties and the structure of the terpolymer were also identified.

• BMB Reports
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• v.49 no.11
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• pp.623-628
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• 2016

GPR78 is an orphan G-protein coupled receptor (GPCR) that is predominantly expressed in human brain tissues. Currently, the function of GPR78 is unknown. This study revealed that GPR78 was expressed in lung cancer cells and functioned as a novel regulator of lung cancer cell migration and metastasis. We found that knockdown of GPR78 in lung cancer cells suppressed cell migration. Moreover, GPR78 modulated the formation of actin stress fibers in A549 cells, in a RhoA- and Rac1-dependent manner. At the molecular level, GPR78 regulated cell motility through the activation of $G{\alpha}q$-RhoA/Rac1 pathway. We further demonstrated that in vivo, the knockdown of GPR78 inhibited lung cancer cell metastasis. These findings suggest that GPR78 is a novel regulator for lung cancer metastasis and may serve as a potential drug target against metastatic human lung cancer.

• Nutrition Research and Practice
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• v.11 no.4
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• pp.275-280
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• 2017

BACKGROUND/OBJECTIVES: Re-epithelialization has an important role in skin wound healing. Astaxanthin (ASX), a carotenoid found in crustaceans including shrimp, crab, and salmon, has been widely used for skin protection. Therefore, we investigated the effects of ASX on proliferation and migration of human skin keratinocyte cells and explored the mechanism associated with that migration. MATERIAL/METHOD: HaCaT keratinocyte cells were exposed to $0.25-1{\mu}g/mL$ of ASX. Proliferation of keratinocytes was analyzed by using MTT assays and flow cytometry. Keratinocyte migration was determined by using a scratch wound-healing assay. A mechanism for regulation of migration was explored via immunocytochemistry and western blot analysis. RESULTS: Our results suggest that ASX produces no significant toxicity in human keratinocyte cells. Cell-cycle analysis on ASX-treated keratinocytes demonstrated a significant increase in keratinocyte cell proliferation at the S phase. In addition, ASX increased keratinocyte motility across the wound space in a time-dependent manner. The mechanism by which ASX increased keratinocyte migration was associated with induction of filopodia and formation of lamellipodia, as well as with increased Cdc42 and Rac1 activation and decreased RhoA activation. CONCLUSIONS: ASX stimulates the migration of keratinocytes through Cdc42, Rac1 activation and RhoA inhibition. ASX has a positive role in the re-epithelialization of wounds. Our results may encourage further in vivo and clinical study into the development of ASX as a potential agent for wound repair.