• 한국지반환경공학회 논문집
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• 제15권10호
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• pp.5-13
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• 2014

본 연구에서는 철도노반에서의 동결융해로 인한 피해를 줄이고자 뛰어난 단열효과와 강도를 가진 XPS(eXtruded PolyStyrene)와 PE골재(polyethylene aggregates)를 사용하여 동상을 억제하는 방법을 연구하고자 대형동토실에서 모형시험을 수행하였다. 이를 위해 노반과 PE골재의 혼입비율을 변화시켜 건조밀도와 함수비, 온도에 따른 열전도율을 측정하였다. 시험결과 노반에 혼입된 PE골재 비율에 비례하여 단열효과가 증가하였지만, 간극의 함수비와 온도변화에 민감하였다. 또한 철도노반을 모사한 모형시험에서 각 단열재의 두께와 설치순서를 다르게 한 후 단열효과를 비교 결과, XPS의 단열효과가 우수한 것으로 나타났으며 XPS판자가 상부, PE골재가 하부에 설치될 때 그 반대의 경우보다 단열효과가 뛰어난 것으로 나타났다.

• 한국구조물진단유지관리공학회 논문집
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• 제24권5호
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• pp.95-102
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• 2020

이 연구에서는 입경이 큰 골재를 사용하면서 2% 이상의 인장변형률 성능을 나타내는 고연성 PE 섬유보강 시멘트 복합체 개발을 목적으로 골재의 크기와 입도분포에 따른 고연성 섬유보강 시멘트 복합체의 인장거동 특성을 살펴보고자 하였다. 0.6 mm 이하의 입경들로 구성된 규사를 사용한 배합을 기준으로 최대입경 2.36 mm, 4.75 mm, 5.6 mm, 6.7 mm의 강모래 및 강자갈을 사용한 배합을 비교하여 성능평가를 실시하였다. 골재의 입도분포는 수정 A&A 모델에 기반한 최적입도분포곡선에 가깝도록 세분화된 입경별 혼합비율을 조절하였다. 직접인장실험을 통해 구한 인장거동은 모든 배합에서 뚜렷한 인장변형률 경화 거동을 보였다. 골재 입경별 혼합비율을 조절하여 입도분포가 최적곡선에 가깝도록 한 경우에는 모든 배합에서 규사를 사용한 경우보다 높은 인장변형률 성능을 나타내었다. 또한 골재의 최대입경이 커서 입도분포가 넓을수록 높은 인장변형률 성능을 보였으며, 최대입경 5.6 mm, 6.7 mm의 굵은 골재를 포함하는 경우 각각 4.83%와 5.89%의 매우 높은 인장변형률 성능을 나타내었다. 이 연구를 통해 적절한 입도분포 조절을 통해 굵은 골재를 사용하면서도 고연성 섬유보강 시멘트 복합체의 제조가 가능함을 보였다.

• Journal of Pharmaceutical Investigation
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• 제22권2호
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• pp.115-124
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• 1992

The characteristics and stabilities of phosphatidylcholine liposomes covalently coupled with immunoglobulin fragments prepared by the REV method were investigated by the dynamic light scattering, absorbance and calcein release. Using a sulfhydryl-reactive phospholipid derivative of N-[4$({\rho}-maleimido-phenyl)$ butyl] phosphatidylethanolamine (MPB-PE), Fab' antibody fragments were covalently combined with preformed large unilamellar vesicles (LUV), Coupling ratio was $250\;{\mu}g$ of $Fab'/{\mu}mol$ of phospholipid in vesicles, From dynamic light scattering, it was found that the size of the vesicles increases as the ratio of cholesterol to lipid increases, but that apparently, the size of liposomes was not sensitive to the existence of Fab' fragments. Regardless of inserting Fab' fragments, the absorbance of liposomes decreased as the amounts of bile salt (BS) added. At very low BS concentrations, BS/lipid aggregates would be formed in the outer vesicles monolayer, while, at the high BS concentrations, mixed micelles would be preferred. The vesicles incorporated with Fab' fragments, however, are more resistant to the bile salts than the MPB-PE vesicle are. The absorbance of vacant liposomes and calcein release resulted in that the Fab' vesicles and MPB-PE vesicles by the REV method are very stable, but that those by the sonication method sufferred the significant change of turbidities.

• Journal of Pharmaceutical Investigation
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• 제20권3호
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• pp.135-144
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• 1990

The effects of bile salts (BS) on the stability of dioleoylphosphatidylethanolamine (DOPE) liposomes were investigated, observing apparent absorbance of vacant liposomes and calcein release from entrapped liposomes. Unilamellar liposomes were prepared by using a small quantity of palmitoly-immunoglobulin G(IgG) ($2.5{\times}10^{-4}$ mo1/lipid mol) to stabilize the bilayer phase of the unsaturated DOPE which by itself does not form stable liposomes. The destabilization of PE immunoliposomes by papain, clearly demonstrates that the IgG is essential for stabilization of PE bilayer. Approximately 4% of the entrapped calcein was released from the PE liposomes after 1 hr from liposome formation. Calcein release and absorbance of liposomes depended on the BS/lipid ratio because of the solubilization of lipid molecule in bilayer and the formation of mixed micelles. At very low BS concentrations, the incorporation of BS induced BS/lipid aggregates in the outer vesicles monolayer, while high BS concentrations, mixed micelles were formed. Chelate and its conjugates as $3{\alpha},\;7{\alpha},\;12{\alpha}-trihydroxy$ BS induce the concentration of the $3{\alpha}$, $12{\alpha}-dihydroxy$ BS at half-maximal solubilization of immunoliposomes to approximately 2.5-, or 5-fold. Conjugation of BS with glycine or taurine slightly enhanced their capacities to perturb membranes.

• Biotechnology and Bioprocess Engineering:BBE
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• 제6권4호
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• pp.264-268
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• 2001

Aggregates of specific cells are often regarded as better from in artificial organs and mammalian cell bioreactors in terms of cell-specific functionality. In this study, the morphology and liver specific functions of freshly harvested primary rat hepatocytes, which were cultivated as spheroids and entrapped in a synthetic thermo-reversible extracellular matrix, were examined and compared to a control (hepatocytes in single cell form). A copolymer of N-isopropylacrylamide(98 mole % in feed) and acrylic acid (poly (NiPAAm-co-AAC)), a thermo- reversible copolymer gel ma- trix, was used to entrap hepatocytes either in spheroids or single cells. During a 7-day culture pe-riod, the spheroids maintained higher viability and produced albumin and urea at a relatively con-stant rate, while, the single cell culture showed a slight increase in cell numbers and a reduction in albumin secretion Hepatocytes cultrured as spheroids present a potentially useful three-dimensional cell culture system for application in bioartificial liver device.

• 대한수의학회지
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• 제40권3호
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• pp.587-599
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• 2000

This study was conducted to observe the severity of the disease and pathogenecity of Babesia gibsoni parasite on the splenectomized dogs(SPD) and nonsplenectomized(intact) dogs (NSPD) experimentally infected with B gibsoni. The average prepatent period was 4 days in the SPD and 8 days in the NSPD, respectively. Peak parasitaemia(PE) ranged from 26% to 34% of erythrocytes infected in the SPD and from 4% to 5% in the NSPD. Latent parasitaemia was still detectable 40 days as low as under 1.0% of erythrocytes infected after the initial parasitaemia in the SPD. Blood packed cell volume(PCV) decreased to as little as 6.4% to 6.9% in the SPD. The clinical signs were mild fever and anemia in the NSPD, remissions and exacervations of temperature, intermittent or spike-like increases of temperature, progressive polychromatophilic macrocytic anemia with anisocytosis, icterus, marked loss of appetite, rarely haemoglobinuria, and deep brown-yellowish urine in the SPD. Gross pathologic changes mainly involved slightly enlargement of liver and spleen in the NSPD and marked enlargement of liver in the SPD. Anatomic changes associated with the disease included diffuse periportal and centrilobular hephatitis, and membranoproliferative glomerulonephritis. Hyaline droplets, resulting protein metabolic alterations, were found in the convoluted ephithelium of the kidney. The density of lymphocytes within the liver sinusoids was markedly increased. Aggregates of large monocytes and macrophages were demonstrated in the centrilobular veins of the liver. The density of these cells in the centrilobular veins were greatest in the SPD. The forms of B gibsoni parasite found in the acute stage of SPD were large signet ring form, small signet ring form, pyriform, elongated form, comma form, head-phone form, oval form, peared form, racket-like form, amoeboid form, triangle form, quartered form, dot form, band form and multiple, and rosette form, et al. The severity of the disease and pathogenecity of B gibsoni parasite were mild in the NSPD but fatal in the SPD.