• 한국표면공학회지
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• 제52권5호
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• pp.265-274
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• 2019

Formation behavior of PEO (Plasma Electrolytic Oxidation) films on AZ31 Mg alloy was investigated under application of 310 Hz AC as a function of $Na_3PO_4$ concentration from 0.02 M to 0.2 M. Film formation voltage and in-situ observation of arcs generated on the specimen surface were recorded with time, and surface morphologies of the PEO films were investigated using optical microscopy, confocal scanning laser microscopy and scanning electron microscopy. PEO film formation voltage decreased linearly with increasing $Na_3PO_4$ concentration which is attributed to the increase of solution pH. PEO films were grown uniformly over the entire surface in $Na_3PO_4$ solutions between 0.05 M and 0.1 M. However, non-uniform PEO films with white spots were formed in $Na_3PO_4$ solutions containing more than 0.1 M. Thickness and roughness of PEO films on AZ31 Mg alloy increased linearly with increasing $Na_3PO_4$ concentration and their increasing rates appeared to be much higher under 1 M than above 1 M. The experimental results suggest that phosphate ions can contribute to the formation of PEO films but higher $Na_3PO_4$ concentration more than 1 M results in local damages of PEO films due to repeated generation of white arcs at the same surface site of AZ31 Mg alloy.

• JSTS:Journal of Semiconductor Technology and Science
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• 제1권4호
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• pp.239-247
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• 2001

The Fluorescence-Activated Cell Sorter (FACS) is a well-established instrument used for identifying, enumerating, classifying and sorting cells by their physical and optical characteristics. For a miniaturized FACS device, a disposable plastic microchip has been developed which has a hydrodynamic focusing chamber using soft lithography. As the characteristics of the spatially confined sample stream have an effect on sample throughput, detection efficiency, and the accuracy of cell sorting, systematic fluid dynamic studies are required. Flow visualization is conducted with a laser scanning confocal microscopy (LSCM), and three-dimensional flow structure of the focused sample stream is reconstructed from 2D slices acquired at $1\mutextrm{m}$ intervals in depth. It was observed that the flow structure in the focusing chamber is skewed by unsymmetrical velocity profile arising from trapezoidal cross section of the microchannel. For a quantitative analysis of a microscopic flow structure, Confocal Micro-PIV system has been developed to evaluate the accelerated flow field in the focusing chamber. This study proposes a method which defines the depth of the measurement volume using a detection pinhole. The trajectories of red blood cells (RBCs) and their interactions with surrounding flow field in the squeezed sample stream are evaluated to find optimal shape of the focusing chamber and fluid manipulation scheme for stable cell transporting, efficient detection, and sorting

• 한국광학회지
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• 제14권4호
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• pp.392-398
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• 2003

구면 거울을 정밀하고 정확하게 측정할 수 있는 위상천이 회절격자 간섭계를 제시한다. 간섭계는 하나의 회절격자를 이용하여 간섭계의 기준광과 측정광을 분할하고, 다시 결합시켜 간섭무늬를 생성시키고 위상천이 시키는 간단한 구조로 설계되었다. 광원으로부터의 광을 큰 수치구경인 고정도의 집속렌즈의 초점에 위치한 회절격자 위에 집속하여 반사회절된 파면을 기준파면과 측정파면으로 사용한다 부가적인 기준면이 없이 회절격자 위의 매우 작은 영역이 기준면을 대신하므로 시스템 오차가 작다. 광섬유 형태의 공초점현미경 구조를 광원과 집속렌즈 사이에 설치하여 집속렌즈와 회절격자사이의 정렬오차를 최소화 하였다. 회절격자를 광축에 수직한 방향으로 이송함으로써 기준파면과 측정파면사이에 상대적인 위상천이를 일으켜서 일련의 위상천이된 간섭무늬를 쉽게 획득할 수 있다. 간섭계를 제작하고, 결상렌즈와 CCD를 이용해서 얻은 위상천이된 대상구면 거울의 간섭무늬들을 해석하여 전체적인 간섭계 시스템의 성능을 평가해 보았다.

• Tribology and Lubricants
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• 제36권4호
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• pp.199-206
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• 2020

CoCr-based alloys have been developed as wear-resistant materials owing to their excellent mechanical properties and strong wear resistance. The purpose of this study is to experimentally assess the frictional and wear characteristics of CoCr-based alloys slid against two different counter materials subjected to various normal forces to determine the expansion applicability of CoCr-based alloys. CoCrMo and CoCr alloys were selected as the target materials and NiCr and NiCrB alloys as counter materials. Experimental tests were performed using a pin-on-reciprocating plate tribo-tester under dry lubrication. Before performing the tests, the surface of the specimens was observed through confocal microscopy and the hardness was measured using a micro-Vickers hardness tester. The wear volume of the plate was calculated at the end of the tests using confocal microscope data, and the wear rate was quantitatively obtained based on Archard's wear law. From the results, the wear rates of the CoCrMo specimens that slid against NiCr and NiCrB are 7.69 × 10^-6 ㎣/Nm and 5.26 × 10^-6 ㎣/Nm, respectively. The wear rates of the CoCr specimens that slid against NiCr and NiCrB were higher than those of the CoCrMo specimens by factors of approximately 4 and 8, respectively. The CoCrMo specimens further exhibited lower friction characteristics than the CoCr specimens. The findings of this study will be useful for expanded applications of CoCr-based alloys as wear-resistant materials for various mechanical parts.

• International Journal of Oral Biology
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• 제38권1호
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• pp.5-12
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• 2013

Recent studies indicate that reactive oxygen species (ROS) can act as modulators of neuronal activity, and are critically involved in persistent pain primarily through spinal mechanisms. In this study, we investigated the effects of NaOCl, a ROS donor, on neuronal excitability and the intracellular calcium concentration ($[Ca^{2+}]_i$) in spinal substantia gelatinosa (SG) neurons. In current clamp conditions, the application of NaOCl caused a membrane depolarization, which was inhibited by pretreatment with phenyl-N-tert-buthylnitrone (PBN), a ROS scavenger. The NaOCl-induced depolarization was not blocked however by pretreatment with dithiothreitol, a sulfhydryl-reducing agent. Confocal scanning laser microscopy was used to confirm whether NaOCl increases the intracellular ROS level. ROS-induced fluorescence intensity was found to be increased during perfusion of NaOCl after the loading of 2',7'-dichlorofluorescin diacetate ($H_2DCF$-DA). NaOCl-induced depolarization was not blocked by pretreatment with external $Ca^{2+}$ free solution or by the addition of nifedifine. However, when slices were pretreated with the $Ca^{2+}$ ATPase inhibitor thapsigargin, NaOCl failed to induce membrane depolarization. In a calcium imaging technique using the $Ca^{2+}$-sensitive fluorescence dye fura-2, the $[Ca^{2+}]_i$ was found to be increased by NaOCl. These results indicate that NaOCl activates the excitability of SG neurons via the modulation of the intracellular calcium concentration, and suggest that ROS induces nociception through a central sensitization.

• Restorative Dentistry and Endodontics
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• 제43권1호
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• pp.2.1-2.10
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• 2018

Objectives: To determine the effect of size and insertion depth of irrigation needle on the amount of apical extruded debris and the amount of penetration depth of sealer using a confocal laser scanning microscope (CLSM). Materials and Methods: Twenty maxillary premolars were assigned to 2 groups (n = 10), according to the size of needle tip, 28 G or 30 G. Buccal roots of samples were irrigated with respective needle type inserted 1 mm short of the working length (WL), while palatal roots were irrigated with respective needle type inserted 3 mm short of the WL. Prepared teeth were removed from the pre-weighed Eppendorf tubes. Canals were filled with F3 gutta-percha cone and rhodamine B dye-labeled AH 26 sealer. Teeth were transversally sectioned at 1 and 3 mm levels from the apex and observed under a CLSM. Eppendorf tubes were incubated to evaporate the irrigant and were weighed again. The difference between pre- and post-weights was calculated, and statistical evaluation was performed. Results: Inserting needles closer to the apex and using needles with wider diameters were associated with significantly more debris extrusion (p < 0.05). The position of needles and level of sections had statistically significant effects on sealer penetration depth (p < 0.05 for both). Conclusions: Following preparation, inserting narrower needles compatible with the final apical diameter of the prepared root canal at 3 mm short of WL during final irrigation might prevent debris extrusion and improve sealer penetration in the apical third.

• KSBB Journal
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• 제22권4호
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• pp.239-243
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• 2007

본 연구에서는 미네랄오일에 유화제를 사용하여 한천 현탁액을 제조하고 여기에 피브로인을 첨가하여 마이크로캡슐을 제조하는 방법을 개발하였다. 먼저 한천 유화액에 첨가될 유화제의 농도를 10%로 결정하였고 피브로인을 투입하는 속도를 조절하여 피브로인으로 피막이 형성된 마이크로캡슐을 감압건조를 통하여 수분을 제거하고 에탄올 침전물로 회수하였다. 공초점 현미경으로 피브로인 피막이 형성되어 있음과 마이크로캡슐의 90%가 $1.32{\mu}m$에서 $6.0{\mu}m$사이에 존재함을 확인하였다. 에탄올 침전물 형태의 마이크로캡슐과 이들이 분산되는 것을 전자현미경으로 확인하였으며 열중량 분석을 통하여 마이크로캡슐은 중량비로 한천이 51.2%, 피브로인이 13.8%, Span 80이 1.4%로 구성되어있음을 확인하였다.

• 대한화장품학회지
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• 제40권3호
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• pp.247-257
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• 2014

새로운 베지클인 glyceryl citrate/ lactate/ linoleate/ oleate를 이용한 수중유형 형태의 아스타잔틴 나노에멀젼에 대해 항산화 효과, 세포 생존력, 단백질과 관련한 효소의 영향, 피부 침투도 그리고 피부에 대한 보습 및 탄력 등의 약용화장품적인 측면에서의 전반적 연구를 실시하였다. 항산화력 및 세포 생존력에 대해선 각각 DPPH법과 MMT assay를 이용하여 측정하였다. 아스타잔틴 나노에멀젼에 대한 또 다른 성질은 2D-Page를 이용한 단백질 분석 및 컨포칼, in-vivo 테스트를 통해 측정하였다. 본 연구를 통해, 아스타잔틴을 포함하는 나노에멀젼은 MMP발현에 관련한 단백질 억제 및 세포외 기질의 분해를 막고 라디칼의 소거에 매우 우수한 결과를 보였다. 종전의 레시친을 이용한 나노에멀젼 보다는 새로운 베지클을 이용한 아스타잔틴 나노에멀젼의 피부 침투가 매우 효과적임을 CLSM을 통해 측정하였다. 또한 28일 동안의 한국 성인 여성 11명을 통한 보습 및 탄력 인비보 테스트에서 우수한 효과를 확인할 수 있었다.

• 생명과학회지
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• 제22권10호
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• pp.1415-1419
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• 2012

Thymosin ${\beta}4$ 는 대장암에서 암 줄기세포 마커인 CD133을 지닌 세포에서 지니지 않은 세포에 비해 강하게 발현된다고 보고되어 있다. 본 연구에서는 thymosin ${\beta}4$와 줄기세포 마커인 CD133의 상관관계를 정상 위 조직에서 관찰하였다. Thymosin ${\beta}4$와 CD133의 발현 양상은 tissue microarray 조직상에서 면역화학적 방법으로 관찰하였으며 thymosin ${\beta}4$와 CD133의 존재 위치는 면역형광 염색법 및 confocal microscope를 사용하여 조사하였다. Thymosin ${\beta}4$와 CD133은 동일한 양상으로 발현되었으며 모두 위의 선조직에서 강하게 발현되었다. 면역 형광 염색법으로 두가지 단백질을 동시에 염색한 결과 두 단백질이 동일한 위치에서 함께 존재하는 것으로 규명되었다. 이러한 결과는 thymosin ${\beta}4$와 CD133은 정상위의 선조직에서 발현되며 두 단백질의 발현 양상 및 위치가 동일하여 서로 긴밀한 상호작용을 할 가능성을 제시하고 있다.

• Restorative Dentistry and Endodontics
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• 제39권4호
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• pp.276-281
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• 2014

Objectives: The purpose of this study was to compare the cutting efficiency of a newly developed microprojection tip and a diamond-coated tip under two different engine powers. Materials and Methods: The apical 3 mm of each root was resected, and root-end preparation was performed with upward and downward pressure using one of the ultrasonic tips, KIS-1D (Obtura Spartan) or JT-5B (B&L Biotech Ltd.). The ultrasonic engine was set to power-1 or -4. Forty teeth were randomly divided into four groups: K1 (KIS-1D / Power-1), J1 (JT-5B / Power-1), K4 (KIS-1D / Power-4), and J4 (JT-5B / Power-4). The total time required for root-end preparation was recorded. All teeth were resected and the apical parts were evaluated for the number and length of cracks using a confocal scanning micrscope. The size of the root-end cavity and the width of the remaining dentin were recorded. The data were statistically analyzed using two-way analysis of variance and a Mann-Whitney test. Results: There was no significant difference in the time required between the instrument groups, but the power-4 groups showed reduced preparation time for both instrument groups (p < 0.05). The K4 and J4 groups with a power-4 showed a significantly higher crack formation and a longer crack irrespective of the instruments. There was no significant difference in the remaining dentin thickness or any of the parameters after preparation. Conclusions: Ultrasonic tips with microprojections would be an option to substitute for the conventional ultrasonic tips with a diamond coating with the same clinical efficiency.