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Size Effect of Defects on the Mechanical Properties of Graphene
박영호,현상일 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.6
Graphene, a two-dimensional material, has been studied and utilized for its excellent material properties. In reality, achieving a pure single-crystalline structure in graphene is difficult, so usually graphene may have various types of defects in it. Vacancies, Stone-Wales defects, and grain boundaries can drastically change the material properties of graphene. Graphene with vacancy defects has been of interest because it is a two-dimensional analogy of three-dimensional porous materials. It has efficient material properties, and can function as a part of modern devices. The mechanical properties have been studied by using molecular dynamics for either a single vacancy defect with various sizes or multiple vacancy defects with same defect ratios. However, it is not clear which one has more influence on the mechanical properties between the size of the defects and the defect ratio. Therefore, we investigated the hole-size effect on the mechanical properties of single-crystalline graphene at various defect ratios. A void defect with large size can have a rather high tensile modulus with a low fracture strain compared to a void defect with small size. We numerically found that the tensile properties of scattered single vacancies is similar to that of amorphous graphene. We suspect that this is due to the local orbital change of the carbon atoms near the boundary of the void defects, so-called the interfacial phase.
朴榮浩 釜山水産大學校 1973 釜山水産大學 硏究報告 Vol.13 No.1
In the present study, the effect of storage condition, particularly, high humidity to the changes in chemical components of dried lavers was investigated and some characteristic patterns of the changes were discussed. Dried lavers, Porphyra yezoensis Ueda, were stored at 20� under two different levels of humidity, that were 78% and lower than 7% as relative humidity, respectively. And the content of pigments, organic acids, sugars, and fatty acids were analyzed at 10,25 and 45 day intervals during the storage. Total acidity was also determined. Degradation of chlorophyll a was faster than other pigments such as carotenoids and phycobilins under high humidity. For instance, after 45 day storage, more than two-fold of chlorophll a was retained in low humidified sample compared with that in the case of high humidity whereas a remarkable difference in retention rate of carotenoids or phycobilins was not detected. phycobilins showed high stability under the condition of high humidty, particularly, in phycoerythrin than in phycocyanin. Eight kinds of non-volatile organic acid namely pyruvic, lactic, malonic, fumaric, oxalic, malic, succinic, and citric acid were gas chromatographically identified. The stability of theses acids appeared quite differently by storage humidity. The acids like oxalic, malic, and succinic, did not show an outstanding change under low humidity even after 45 day storage while both oxalic and malic acids remarkably decrased under high humidity and succinic acid contrary increased under the same condition. Citric acid, however, decreased under both cases of humidity. The total amount of volatile acid tended to increase throughout the storage under both high and low humidity, but the rate of increase was relatively greater in case of high humidity than that of low humidity. On the other hand, the same tendedcy was observed in change of total acidity in which the value tended to increase under the high humidity while that remained steady under the low humidity. In the free amino acid composition of dried lavers, alanine,glutamic and aspartic acid were dominant in content whereas such amino acids as methionine, cystine, histididine, comparatively low. It is noteworthy that the content of taurine was tremendously high as an amino acid related compound. During the storage, a significant change in the total amino acid level and individual variation was not detected. In another aspect of storage stability of chemical components, glucose remained with negligible change under both storage conditions and galactose increased rapidly under the high humidity while maintained a steady level under the low humidity. On the contrary, the floridoside decreased rapidly under the high humidity whereas slowly under the low. In the tendecy of strorage stability of fatty acid, tended to decrease in the low humidified material. Under high humidity, ?? acid appeared stable while ?? acid considerably increased. The total fatty acid level which was consisted of 14 kinds of fatty acid seemed to increase in high humidified material and to decrease in the low humidified material.
박영호,김선봉,변한석,염동민,박영범,이태기,김외경 한국수산학회 1993 한국수산과학회지 Vol.26 No.4
수산자원의 기능특성 해명을 위한 연구의 일환으로 전통수산발효식품으로 널리 이용되고 있는 멸치젓갈에 함유되어 있는 angiotensin-I 전환효소 저해물질을 추출하여 gel 여과에 의하여 분리된 획분들의 작용 및 특성에 대해서 살펴보았다. 그 결과를 요약하면 다음과 같다. 1. ACE 저해물질의 추출 조건을 검토하기 위하여 가장 높은 ACE 저해효과를 나타내는 숙성 60일차의 멸치젓갈을 ethanol 및 acetone의 농도를 각각 10, 25, 50 및 80%로 하여 추출하였을 때 ethanol 농도가 50%인 획분이 가장 우수한 저해효과를 나타내었다. 2. 멸치젓갈 숙성중 시료액의 50% ethanol 가용성 peptide-nitrogen 함량 및 ACE 저해효과는 아미노 질소 함량이 최고치에 달하는 숙성 60일차에 최대값을 나타내다가 그 후 다소 감소하는 경향을 나타내었다. 3. Gel 여과에 의한 멸치젓갈의 획분별 ACE 저해효과를 검토한 결과, 획분 C 및 D가 가장 높은 ACE 저해작용을 나타내어 이들을 rechromatography하여 분리한 단일 획분인 C′와 D′획분의 IC_(50)은 각각 97, 65 ㎍로 나타났다. 4. 분리한 단일 획분인 C′와 D′획분의 아미노산 조성은 다소 차이가 있었으며, C′획분은 threonine, glutamic acid 및 lysine의 함량이 많은 것으로 나타났으며, D′획분은 serine과 proline의 함량이 많은 것으로 나타났다. The present study was conducted to elucidate the body modulating function of fermented seafood products. Angiotensin converting enzyme(ACE) acts in blood pressure regulation, converting angiotensin Ⅰ to the potent vasoconstrictor angiotensin Ⅱ and inactivating the vasodilator bradykinin to raise blood pressure. Salted and fermented anchovy which is one of the traditional fermented seafood in Korea was tested for inhibitory activity against ACE. ACE inhibitory activity of salted anchovy during the period of fermentation was increased with the elapse of fermentation days until fermentation of 60 days, but thereafter decreased inversely. When the fermented product was extracted with 50% ethanol, the ACE inhibitory activity was the highest. And the ACE inhibitory activity was proportion to the content of 50% ethanol soluble peptide-nitrogen of the fermented product. From the profiles of gel permeation chromatography on a Bio-Gel P-2 of 50% ethanol soluble fraction obtained from salted and fermented anchovy fermented for 60 days at an ambient temperature, the higher activity fractions were C′(IC_(50)=97㎍ protein/㎖) and D′(IC_(50)=65㎍ protein/㎖). Amino acid analysis showed that the large quantify of threonine, glutamic acid, lysine for C′ and serine, proline for D′, respectively.