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A Study on Gas Adsorption on Microporous Carbons
( Hak Hee Kim ),( Joachim K. Floess ) 한국공업화학회 1993 한국공업화학회 연구논문 초록집 Vol.1993 No.0
A study of physical adsorption of gases by microporous carbons was carried out. A volumetric adsorption apparatus, which was designed to measure the pressure, temperature, and gas sample volume before and after contact with the adsorbent, was used in order to collect adsorption data. The analysis of adsorption data gave quantitative information on the specific surface area, pore volume, and micropore size using various adsorption models such as the Brunauer-Emmett-Teller, Dubinin- Radushkevich, Langmuir, and Volmer models, and also gave information on the thermodynamic data such as the isosteric heat of adsorption, differential energy of adsorption, and differential entropy of adsorption in order to characterize the degree of the surface heterogeneity for both microporous carbons. The isosteric heat of adsorption of nitrogen on Spherocarb was calculated to be 3.39 kcal/mol, and that of nitrogen on Sucrose Char was calculated to be 5.08 kcal/mol from the van't Hoff plots of the Henry's law constants at temperatures from 77 K to 184 K. These chars have a higher adsorption energy than graphite. Based on changes in the isosteric heat of adsorption with coverage, adsorption sites on the Spherocarb and Sucrose Char are energetically inhomogeneous, The Volmer model which is based upon the mobile adsorption was compared with the Langmuir model which is based upon the localized adsorption. At 77 K, the fractional coverage of adsorption sites of the Langmuir isotherm on both carbons with same adsorption energy is always larger than that of the Volmer isotherm, but at 113 K that of the Langmuir isotherm is smaller than that of the Volmer isotherm in the low pressure regime, while that of the Langmuir isotherm is larger than that of the Volmer isotherm in the high pressure regime. It was observed that for large d/rG there exist two minima in the potential energy curves and these curves become wide and shallow. Whereas, for small d/r<sub>o</sub> there exists only one minimum in thepotential energy curves and these curves become narrow and deep. The potential energy profile for Sucrose Char is deeper and wider than that for Spherocarb when the 10:4 potential function was applied to slit shaped pores between single layer planes and the 9:3 potential function to slit shaped pores between slabs.
Prenatal Sonographic and MR Imaging Findings of Extensive Fetal Lymphangioma: A Case Report
SungEunRha,JaeYoungByun,HakHeeKim,Jong-ChulShin,HyunYoungAhn,Dong-chulKim,Kyo-YoungLee 대한영상의학회 2003 Korean Journal of Radiology Vol.4 No.4
We report the imaging findings in a case of fetal lymphangioma involving the retroperitoneum and right lower extremity, and diagnosed by ultrasonography and magnetic resonance (MR) imaging at 26 weeks of gestation. Prenatal ultrasonograms and T2-weighted single-shot fast spin-echo MR images clearly revealed an extensive, multilocular cystic mass with internal hemorrhage in the retroperitoneum extending to the lower extremity.
Direct-Current Treatment as a Safe Sterilization Method for Electrospun Biodegradable Polymer
HyeLeeKim,JeongHyunLee,MiHeeLee,HakHeeKim,JungsungKim,InhoHan,BongJooPark,JeongKooKim,DongWookHan,SooHyunKim,SeungJinLee,JongChulPark 한국조직공학·재생의학회 2011 조직공학과 재생의학 Vol.8 No.3
Sterilization is an essential process for biodegradable polymers to be used as biomaterials or tissue engi-neered-scaffolds. The characteristics of biodegradable scaffolds can change due to decomposition of constituentpolymers due to high temperature, pressure, or moisture during sterilization. This study investigated direct-current (DC) treatment as a safe method that can prevent structural change and deformation. Treatment of electrospun poly (lactic-co-glycolic acid) (PLGA) with DC showed a bactericidal effect within 40 sec at 4 V. When DC was appliedat 6 V to the electrospun PLGA, the bactericidal effect emerged within 30 sec. The morphology of fibers and molec-ular weight of PLGA polymer was maintained after DC treatment. In contrast, electrospun PLGA exposed to ethyl-ene oxide showed fiber degradation, and gamma or e-beam irradiation resulted in decreased molecular weight. Thedemonstrated improvement in chemical and physical stability of biodegradable polymers after DC sterilization mayhelp extend their application.