• Environmental Engineering Research
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• 제14권4호
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• pp.226-236
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• 2009

The performance of phytoremediation has proven effective in the removal of nutrients and metals from aqueous systems. However, little information is available regarding the behavior of pesticides and their removal pathways in aquatic environments involving plant-uptake. A detailed understanding of the kinetics of pesticide removal by plants and information on compound/plant partition coefficients can lead to an effective design of the phytoremediation process for anthropogenic pesticide reduction. It was determined that the reduction rates of four organophosphorus (OP) and two organochlorine (OC) pesticides (diazinon, fenitrothion, malathion, parathion, dieldrin, hexachlorobenzene [HCB]) could be simulated by first-order reaction kinetics. The magnitude of k was dependent on the pesticide species and found within the range of 0.409 - 0.580 $d^{-1}$. Analytical results obtained by mass balances suggested that differential chemical stability, including diversity of molecular structure, half-lives, and water solubility, would greatly influence the removal mechanisms and pathways of OPs and OCs in a phytoreactor (PR). In the case of OP pesticides, plant accumulation was an important pathway for the removal of fenitrothion and parathion from water, while pesticide sorption in suspended matter (SM) was an important pathway for removal of dieldrin and HCB. The magnitude of the pesticide migration factor (${\Large M}_p^{pesticide}$) is a good indication of determining the tendency of pesticide movement from below- to above-ground biomass. The uncertainties related to the different phenomena involved in the laboratory phyto-experiment are also discussed.

• 접착 및 계면
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• 제7권4호
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• pp.32-38
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• 2006

A series of organic-inorganic hybrids, PCL/EP/$SiO_2$, involving epoxy resin and triethoxysilane-terminated polycaprolactone elastomer (PCL-TESi) were prepared via polymerization of diglycidyl ether of bisphenol A (DGEBA) with amine curing agent KB-2 and sol-gel process of PCL-TESi. The curing reactions were started from the initially homogeneous mixture of DGEBA, KB-2 and the PCL-TESi. The organicinorganic hybrids containing up to 4.95% (wt) of $SiO_2$ were obtained and characterized by FT-IR, transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA). It was experimentally shown that the swelling property in toluene, morphologies and thermal properties of the resulting hybrids were quite dependent on the contents of $SiO_2$. The crosslink network density decreases with increasing of the PCL-TESi. And in TEM, the phase separated morphology of these hybrids was found, which resulted from the coagulation of Si-O-Si networks resulting from $-Si(OC_2H_5)_3$ of PCL-TESi self-curing by hydrolytic silanol condensation, with the advancement of the curing reaction in the modified epoxy resin systems. Meanwhile, the change of the $SiO_2$ content made the morphologies changed from aggregated particles of Si-O-Si in the hybrid to nanocluster of interconnected Si-O-Si particles, then to aggregated Si-O-Si dispersing in the continuous cured epoxy phase again, and last to co-continuous interpenetrating network. The glass transition behavior of the hybrid material was cooperative motion of large chain segments, which were hindered by the inorganic Si-O-Si network. And in TG analysis, the characteristic temperature at 5% of weight loss was evidently increased from $120.5^{\circ}C$ of pure cured epoxy to $277.6^{\circ}C$ of 3.84% (wt) of $SiO_2$ modified epoxy due to the existence of Si-O-Si when PCL-TESi was added in the hybrid.

• Macromolecular Research
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• 제10권2호
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• pp.97-102
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• 2002

The mixtures of non-conjugated dienes, 4-methyl-1,4-hexadiene and 5-methyl-1,4-hexadiene (MHD), were successfully synthesized by the reaction of isoprene with ethylene using Fe(III)-based catalyst in toluene. The conversion was over 96 mol% on the basis of the initial amount of isoprene used. The production yield for MHD was nearly 50 mol%, the other was polyisoprene. The mixtures were successfully copolymerized with ethylene by using zirconium-based metallocenes. The products were characterized by the combinations of gas chromatography, high temperature gel permeation chromatography, $^1$H NMR, $^{13}$ C NMR, high temperature $^1$H NMR, UV/visible spectroscopy, and differential scanning calorimetry. It was found that 5-methyl-1,4-hexadiene was active enough to be incorporated into the copolymer chain but the corresponding isomeric material,4-methyl-1,4-hexadiene, was inactive in metallocene-catalyzed copolymerizations. Specifically, in the zirconocene-catalyzed copolymerizations of ethylene with MHD, ansa-structure catalysts seem to be more efficient than non-bridged type zirconocene. The degree of incorporation of MHD in the resulting copolymers was able to be controlled by the amount of non-conjugated dienes used initially.

• 한국임상수의학회지
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• 제35권5호
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• pp.178-183
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• 2018

The object of this study was to compare magnetic resonance imaging (MRI) findings and neurological signs in canine brain diseases. Brain diseases can cause severe neurological deficits and may be life-threatening. The antemortem diagnosis of the brain diseases is difficult for the clinician, since definitive diagnosis is based upon histopathological confirmation. Brain diseases are often associated with specific clinical signs, signalment, progression, and location. Accurate lesion localization through neurological examination and MRI findings is helpful for developing a differential diagnosis. A retrospective study was performed to compare the neurological examination of dogs with suspected brain disease to the MRI findings. Based on this study, neurological examination is a reliable way to localize most brain lesions. Postural reaction deficits do not provide sufficient information to localize lesions. Additionally, not all brain lesions present clinical signs and inflammatory lesions may cause no detectable abnormalities on MRI. Therefore, in clinical practice, a combination of neurological examination and MRI findings recommended for accurate brain lesion localization.

• 마이크로전자및패키징학회지
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• 제18권4호
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• pp.27-32
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• 2011

Tin(II) acetate와 tin(II) chloride의 주석 precursor를 사용하여 상온에서의 강제 환원 반응으로 주석 나노 입자를 합성시켰다. 0.015 g의 동일한 PVP 양을 첨가한 조건에서 PVP의 분자량이 클수록 비정상적으로 큰 입자들의 생성율이 증가되어 입도 범위가 매우 넓은 주석 나노 입자들이 생성됨을 확인할 수 있었다. 합성된 주석 나노 입자를 함유하는 DEG 용액의 DSC 분석 결과 1차 가열에서는 35 nm 미만 특정 크기 입자들의 수가 충분한 경우에서 DEG의 증발 흡열피크 외에도 특정 크기 입자들의 융점 강하 흡열 피크가 구분되게 검출되었다. 1차 DSC 측정 중 용융된 주석 나노 입자들은 서로 접촉하며 뭉쳐지는 현상이 발생하므로 2차 가열시에는 벌크 주석의 용융 피크에 해당하는 $232^{\circ}C$ 흡열 피크만이 관찰되었다.

• 치위생과학회지
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• 제14권2호
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• pp.101-106
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• 2014

본 연구는 저 출력 초음파 장치를 이용하여 osteoblastlike MG-63 세포에 1 MHz, 3 Mz 강도의 초음파 처리 후 조골세포의 변화를 관찰하였다. 3 MHz 강도의 주파수를 osteoblast-like MG-63 세포에 처리한 결과 7일 후 성장률이 대조군보다 증가하였다. 저 출력 초음파가 골의 치유에 영향을 미치는 인자를 확인하였을 때 ALP, osteocalcin, VEGF, colla 1A1의 증가를 확인하였으며, 1 MHz 주파수 처리시 integrin alpha 2의 발현이 대조군과 유사하게 발현되는 것을 확인하였다. 반면에, osteonectin, osteopontin, fibronectin, MMP 2 등은 변화가 없음을 확인하였다. 그러므로 본 연구는 저 출력 초음파 장치는 뼈 치유 촉진 단백질들의 발현을 증가시켜 구강 내 외과적 수술 시 골 치유 촉진 효과에 대한 가능성을 제시하였으며 임상에서 골 치유 촉진을 위한 장비로서의 사용 가능성을 제시하였다고 생각된다.

• 한국환경과학회지
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• 제5권5호
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• pp.593-603
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• 1996

용응탄산염 연료전지의 산소전극성능모사를 위한 이중기공구조의 filmed agglomerate model을 연구하였다. 이 모델에서는 전극과 전해질 계면의 물리, 화학적인 현상 및 전극반응기구를 고려하여 정상상태 에서 전극의 특성을 조업조건에 따라 표시할 수있다. 기존의 연구에서 기하학적인 구조를 가정하여 전극반응면적을 이론적으로 계산한 반면에 본 연구에서는 porosimeter를 이용한 기공도와 기공구조 분포 측정자료를 이용한 방법을 제시하였다. 계산결과는 전극재질, 기체조성, 전극두께, agglomerate 기공도 및 전해질 막의 두께에 따른 영향을 전류밀도와 과전압의 관계로 표시하였다. 또한 전극 재질로 perovskite (La0.8Sr0.2CoO3)와 NiO를 사용하여 실제전지를 이용한 성능을 측정하여 이론치와 비교하였다. 두전 극의 반쪽전지 실험에서 유사한 성능을 나타내었다. Perovskite 전극은 전극 기공도 65%, agglomerate 기공도 12% 그리고 전극두께 1.5~2mm에서 최적의 결과를 보여주었다. NiO전극의 경우 peroxide 반응기구에서 superoxide 반응기구의 계산결과보다 실험치와 일치하는 좋은 결과를 보였다.

• Journal of Periodontal and Implant Science
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• 제50권5호
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• pp.281-290
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• 2020

Purpose: The aim of this study was to compare microRNA (miRNA) gene expression in saliva using miRNA polymerase chain reaction (PCR) arrays in healthy and aggressive periodontitis (AP) patients. Methods: PCR arrays of 84 miRNAs related to the human inflammatory response and autoimmunity from the saliva samples of 4 patients with AP and 4 healthy controls were performed. The functions and diseases related to the miRNAs were obtained using TAM 2.0. Experimentally validated targets of differentially expressed miRNAs were obtained from mirTarBase. Gene ontology terms and pathways were analyzed using ConsensusPathDB. Results: Four downregulated miRNAs (hsa-let-7a-5p, hsa-let-7f-5p, hsa-miR-181b-5p, and hsa-miR-23b-3p) were identified in patients with AP. These miRNAs are associated with cell death and innate immunity, and they target genes associated with osteoclast development and function. Conclusions: This study is the first analysis of miRNAs in the saliva of patients with AP. Identifying discriminatory human salivary miRNA biomarkers reflective of periodontal disease in a non-invasive screening assay is crucial for the development of salivary diagnostics. These data provide a first step towards the discovery of key salivary miRNA biomarkers for AP.

• 한국실천공학교육학회논문지
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• 제2권1호
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• pp.35-41
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• 2010

효소촉매반응은 통상적으로 반응속도가 매우 빠르고 동시에 높은 선택성을 보여 주는 특정이 있다. 단순 효소촉매 반응속도식을 보통 Michaelis-Menten식이라고 부른다. 효소의 활성을 간섭하는 화학물질을 저해제라고 하는데, 효소활성의 저해에는 가역적저해와 비가역적저해의 두 가지 형태로 나타난다. 만일 저해제가 수소결합과 같은 약한 결합으로 효소에 붙게 되면 이런 경우 효소저해는 가역적인 저해로 나타난다. 많은 효소 반응들은 그 반응으로부터 생성되는 생성물 자체에 의해서도 가역적 저해를 받게 된다. 생성물의 생성속도와 더불어 기질의 감소속도식은 비선형 미분방정식으로 나타 낼 수가 있다. 본 연구는 공학 분야의 학부교육을 목적으로 단순 효소반응속도식과 보다 더 복잡한 저해 효소반응속도식에 대한 수치해석의 결과를 보고 하고자 한다.

• 한국세라믹학회지
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• 제11권2호
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• pp.22-30
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• 1974

This study was carried out to investigate the species of iron compounds in kaolin mineral and the bonding relation between the major kaolin and its subordinate iron compound existing as incidental mineral in common clay by means of chemical composition, X-ray diffraction, thermal differential and thermogravimetrie analysis for the application of clays in the field of ceramic raw material. The domestic clay are produced abounduntly in many places, but San-Cheong kaolin, Chu-An clay, and Yeong-Am clay were selected as samples in this experiment because of their frequent utilization in porcelain industry. Two kinds of samples with low and high iron content are picked up respectively from the place of production and elutriated under two micron size to determine the properties and concentration of iron compound very fine particles or colloidal substance of low crystalline grade. Therefore, hydrothermal treatment in autoclave was conducted considering the existence of low crystalline grade of iron compounds known as an amorphoue state in X-ray diffraction pattern furthermore, de-iron treatment of hydrothermal compound was done in order to identify the related iron compound before and after hydrothermal reaction and iron compound which is one of the samples was synthesized for the determination of their compounds state in more detail. The obtained results in this study are as follows: In San-Cheong kaolin, Chu-An clay and Yeong-Am clay 1) It is proved that species accompanying iron compound is $\alpha$-FeOOH form. 2) Iron compound is composed of very fine particles or colloidal substance. 3) The iron substance encircles the fine parts of clay minerals under 2 micron and acts as cementizing agent.