• Restorative Dentistry and Endodontics
• /
• 제34권4호
• /
• pp.356-363
• /
• 2009

본 연구의 목적은 흰 쥐의 상악 대구치를 발거한 후 치주인대세포를 압력을 이용한 저속 냉동 보관법으로 냉동 보관시 치주인대세포의 활성도를 저속 냉동법, 냉장 보관법과 비교하여 평가하고자 하였다. 생후 4주된 암컷 Sprague-Dawley계 흰쥐의 상악 좌우 제 1,2 대구치를 발거하여 각 군 당 18개의 쥐 치아를 MTT, WST-1 검색에 이용하였다. 실험군은 4개군으로 대조군은 즉시 발치군이며, $4^{\circ}C$냉장고에 일주일간 보관한 냉장군, 발치 후 동해방지제 처리과정을 거쳐 $4^{\circ}C$에서 $-35^{\circ}C$까지 $-0.5^{\circ}C$/min 속도로 서서히 냉동시킨 뒤 $-196^{\circ}C$에 냉동한 저속 냉동군, 3MPa의 압력을 가하고 $-0.5^{\circ}C$/min 속도로 $4^{\circ}C$에서 $-35^{\circ}C$까지 서서히 냉동시킨 뒤 $-196^{\circ}C$에 냉동한 압력 저속 냉동군으로 나누었다. 보존액은 F medium을 사용했으며 동해방지제로 10% dimethylsulfoxide(DMSO)를 사용하였다. 일주일 후 해동하여 MTT, WST-1검색을 시행한 뒤 치근면을 단위면적으로 표준화하기 위해 MTT, WST-1 측정값을 Eosin 염색 후 530nm에서 측정한 흡광도 값으로 나누었다. 통계 분석을 위해 one way ANOVA를 시행하였으며 사후 검정으로는 Tukey 방법을 사용하였고 결과는 다음과 같다. 1. MTT 검색에 의한 흡광도를 Eosin 염색 후 측정한 흡광도로 나눈 값에서는 압력 저속 냉동군은 즉시 발치군보다 유의성 있게 세포 활성도가 낮았으나(p<0.05), 저속 냉동군이나 냉장군과 비교할 때는 높은 세포 활성도를 보이며 통계적 유의성이 있었다(p<0.05). 2. WST-1 검색에 의한 흡광도를 Eosin 염색 후 측정한 흡광도로 나눈 값에서도 MTT 검색과 마찬가지로 압력 저속 냉동군에서는 즉시 발치군보다 유의성 있게 세포 활성도가 낮았으나(p<0.05), 저속 냉동군이나 냉장군과 비교할때는 높은 세포 활성도를 보이며 통계적 유의성이 있었다(p<0.05). 위의 결과를 통해, 3MPa(30기압) 압력을 이용한 저속 냉동 보관법은 $4^{\circ}C$냉장법이나 압력을 사용하지 않은 다른 냉동 보관법에 비해 우수한 쥐 치아의 치주인대세포의 활성도를 보여 차후 치아의 재식/이식을 위한 중-장기 치아보관을 위한 방법으로의 가능성을 제시하였다.

• 한국식품위생안전성학회지
• /
• 제20권4호
• /
• pp.258-266
• /
• 2005

현재 우리나라에서 허용된 식품첨가물인 감초추출물 및 에리스리톨의 경우 천연감미료로서 식품의 제조$\cdot$가공시 다양하게 사용되고 있으나 유통식품 중 식품 중 이들 첨가물의 함유여부 및 함유량을 파악할 수 있는 분석방법이 확립되어 있지 않은 실정이다. 따라서, 본 연구에서는 식품 중 감초추출물 및 에리스리톨의 분석방법을 확립하고, 이를 적용하여 국내유통식품 중 감초추출물 및 에리스리틀의 사용실태를 파악하고자 하였다. 식품 중 감초추출물 및 에리스리톨의 분석방법에 대한 최근 국내의 문헌 및 연구논문 등 기초 자료를 참고로 감초추출물 TLC및 HPLC분석방법과 에리스리톨 HPLC 분석방법을 비교$\cdot$검토하였다. 그 결과 감초추출물은 실리카겔 TLC판을 이용하였으며 TLC 최적용매조건은 부틸알콜 : 4N 암모니아용액 : 에틸알콜 50:20:10)이었다. HPLC 분석은 글리실리진산 (glycyrrhizic acid)을 표준물질로 하여 역상계 컬럼인 Capcell pak $C_{18}$ UG120을 사용하였으며 이동상, UV파장, 컬럼온도는 각각 아세토니트릴 : 물 (38:62), 254 nm 및 $40^{\circ}C$이었다. 에리스리톨의 HPLC 분석은 에리스리톨(meso- erythritol을 표준물질로 하여 역상계 컬럼인 Shodex Asahipak NH2P-50 4E 및 RI 검출기를 사용하였으며 이동상, 컬럼온도는 각각 아세토니트릴 : 물 (75:25), $30^{\circ}C$이었다. 글리실리진산은 서울,부산 등 11개 도시에서 구매한 국내 유통 가공식품 중 장류 18품목, 소스류 12품목, 건강기능식품류 15품목, 음료류 26품목, 주류 8품목, 과자류 23품목, 절임류 3품목 등 총 7종 105품목을 대상품목으로 하였으며 이 중 장류, 소스류, 건강기능식품, 음료류, 주류에서 각각 ND$\∼$48.7 ppm, ND$\∼$5.3 ppm, ND$\∼$988.9 ppm, ND$\∼$180.7 ppm, ND$\∼$2.6 ppm의 글리실리진산이 검출되었고, 나머지 품목은 모두 불검출이었다. 에리스리틀의 경우 껌류 13품목, 캔디류 15품목, 음료류 12품목, 건강기능식품류 12품목등 총 4종 52품목을 대상품목으로 하었으며, 껌류 및 건강기능식품에서 각각 ND$\∼$155.62 ppm, ND$\∼$398.14 ppm의 에리스리톨이 검출되었으며, 나머지 품목은 모두 불검출이었다. 본 연구결과는 식품 중 천연감미료인 감초추출물 및 에리스리톨의 분석방법 확립함으로써 국내유통식품의 감초추출물 및 에리스리톨 사용실태파악 및 사후 식품의 품질관리에 기여할 수 있을 것으로 사료된다.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
• /
• pp.107-108
• /
• 2008

The spectacular development of AMLCDs, been made possible by a-Si:H technology, still faces two major drawbacks due to the intrinsic structure of a-Si:H, namely a low mobility and most important a shift of the transfer characteristics of the TFTs when submitted to bias stress. This has lead to strong research in the crystallization of a-Si:H films by laser and furnace annealing to produce polycrystalline silicon TFTs. While these devices show improved mobility and stability, they suffer from uniformity over large areas and increased cost. In the last decade we have focused on microcrystalline silicon (${\mu}c$-Si:H) for bottom gate TFTs, which can hopefully meet all the requirements for mass production of large area AMOLED displays [1,2]. In this presentation we will focus on the transfer of a deposition process based on the use of $SiF_4$-Ar-$H_2$ mixtures from a small area research laboratory reactor into an industrial gen 1 AKT reactor. We will first discuss on the optimization of the process conditions leading to fully crystallized films without any amorphous incubation layer, suitable for bottom gate TFTS, as well as on the use of plasma diagnostics to increase the deposition rate up to 0.5 nm/s [3]. The use of silicon nanocrystals appears as an elegant way to circumvent the opposite requirements of a high deposition rate and a fully crystallized interface [4]. The optimized process conditions are transferred to large area substrates in an industrial environment, on which some process adjustment was required to reproduce the material properties achieved in the laboratory scale reactor. For optimized process conditions, the homogeneity of the optical and electronic properties of the ${\mu}c$-Si:H films deposited on $300{\times}400\;mm$ substrates was checked by a set of complementary techniques. Spectroscopic ellipsometry, Raman spectroscopy, dark conductivity, time resolved microwave conductivity and hydrogen evolution measurements allowed demonstrating an excellent homogeneity in the structure and transport properties of the films. On the basis of these results, optimized process conditions were applied to TFTs, for which both bottom gate and top gate structures were studied aiming to achieve characteristics suitable for driving AMOLED displays. Results on the homogeneity of the TFT characteristics over the large area substrates and stability will be presented, as well as their application as a backplane for an AMOLED display.

• 한국막학회:학술대회논문집
• /
• 한국막학회 1999년도 The 7th Summer Workshop of the Membrane Society of Korea
• /
• pp.39-42
• /
• 1999

Perfluoropolymers represent the ultimate resistance to hostile chemical environments and high service temperature, attributed to the presence of fluorine in the polymer backbone, i.e. to the high bond energy of C-F and C-C bonds of fluorocarbons. Copolymers of Tetrafluoroethylene (TEE) and 2, 2, 4Trifluoro-5Trifluorometoxy- 1, 3Dioxole (TTD), commercially known as HYFLON AD, are amorphous perfluoropolymers with glass transition temperature (Tg)higher than room temperature, showing a thermal decomposition temperature exceeding 40$0^{\circ}C$. These polymer systems are highly soluble in fluorinated solvents, with low solution viscosities. This property allows the preparation of self-supported and composite membranes with desired membrane thickness. Symmetric and asymmetric perfluoropolymer membranes, made with HYFLON AD, have been prepared and evaluated. Porous and not porous symmetric membranes have been obtained by solvent evaporation with various processing conditions. Asymmetric membranes have been prepared by th wet phase inversion method. Measure of contact angle to distilled water have been carried out. Figure 1 compares experimental results with those of other commercial membranes. Contact angles of about 120$^{\circ}$for our amorphous perfluoropolymer membranes demonstrate that they posses a high hydrophobic character. Measure of contact angles to hexandecane have been also carried out to evaluate the organophobic character. Rsults are reported in Figure 2. The observed strong organophobicity leads to excellent fouling resistance and inertness. Porous membranes with pore size between 30 and 80 nanometers have shown no permeation to water at pressures as high as 10 bars. However high permeation to gases, such as O2, N2 and CO2, and no selectivities were observed. Considering the porous structure of the membrane, this behavior was expected. In consideration of the above properties, possible useful uses in th field of gas- liquid separations are envisaged for these membranes. A particularly promising application is in the field of membrane contactors, equipments in which membranes are used to improve mass transfer coefficients in respect to traditional extraction and absorption processes. Gas permeation properties have been evaluated for asymmetric membranes and composite symmetric ones. Experimental permselectivity values, obtained at different pressure differences, to various single gases are reported in Tab. 1, 2 and 3. Experimental data have been compared with literature data obtained with membranes made with different amorphous perfluoropolymer systems, such as copolymers of Perfluoro2, 2dimethyl dioxole (PDD) and Tetrafluorethylene, commercialized by the Du Pont Company with the trade name of Teflon AF. An interesting linear relationship between permeability and the glass transition temperature of the polymer constituting the membrane has been observed. Results are descussed in terms of polymer chain structure, which affects the presence of voids at molecular scale and their size distribution. Molecular Dyanmics studies are in progress in order to support the understanding of these results. A modified Theodoru- Suter method provided by the Amorphous Cell module of InsightII/Discover was used to determine the chain packing. A completely amorphous polymer box of about 3.5 nm was considered. Last but not least the use of amorphous perfluoropolymer membranes appears to be ideal when separation processes have to be performed in hostile environments, i.e. high temperatures and aggressive non-aqueous media, such as chemicals and solvents. In these cases Hyflon AD membranes can exploit the outstanding resistance of perfluoropolymers.