• The Journal of Advanced Prosthodontics
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• 제7권2호
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• pp.146-150
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• 2015

PURPOSE. This in vitro study aimed to compare the failure load and failure characteristics of two different zirconia framework designs of premolar crowns when subjected to static loading. MATERIALS AND METHODS. Two types of zirconia frameworks, conventional 0.5 mm even thickness framework design (EV) and 0.8 mm cutback of full contour crown anatomy design (CB), were made for 10 samples each. The veneer porcelain was added on under polycarbonate shell crown made by vacuum of full contour crown to obtain the same total thickness of the experiment crowns. The crowns were cemented onto the Cobalt-Chromium die. The dies were tilted 45 degrees from the vertical plane to obtain the shear force to the cusp when loading. All crowns were loaded at the lingual incline of the buccal cusp until fracture using a universal testing machine with cross-head speed 0.5 mm/min. The load to fracture values (N) was recorded and statistically analyzed by independent sample t-test. RESULTS. The mean and standard deviations of the failure load were $1,170.1{\pm}90.9$ N for EV design and $1,450.4{\pm}175.7$ N for CB design. A significant difference in the compressive failure load was found (P<.05). For the failure characteristic, the EV design was found only cohesive failures within veneering porcelain, while the CB design found more failures through the zirconia framework (8 from 10 samples). CONCLUSION. There was a significant difference in the failure load between two designs, and the design of the framework influences failure characteristic of zirconia crown.

• The Journal of Advanced Prosthodontics
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• 제7권6호
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• pp.454-459
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• 2015

PURPOSE. To determine whether the fracture strengths and failure types differed between metal and zirconia frameworks veneered with pressable or layering ceramics. MATERIALS AND METHODS. A phantom molar tooth was prepared and duplicated in 40 cobalt-chromium abutments. Twenty metal (IPS d.SIGN 15, Ivoclar, Vivadent, Schaan, Liechtenstein) and 20 zirconia (IPS e.max ZirCAD, Ivoclar) frameworks were fabricated on the abutments. Each framework group was randomly divided into 2 subgroups according to the veneering material: pressable and layering ceramics (n=10). Forty molar crowns were fabricated, cemented onto the corresponding abutments and then thermocycled ($5-55^{\circ}C$, 10,000 cycles). A load was applied in a universal testing machine until a fracture occurred on the crowns. In addition, failure types were examined using a stereomicroscope. Fracture load data were analyzed using one-way ANOVA and Tukey HSD post-hoc tests at a significance level of 0.05. RESULTS. The highest strength value was seen in metal-pressable (MP) group, whereas zirconia-pressable (ZP) group exhibited the lowest one. Moreover, group MP showed significantly higher fracture loads than group ZP (P=.015) and zirconia-layering (ZL) (P=.038) group. No significant difference in fracture strength was detected between groups MP and ML, and groups ZP and ZL (P>.05). Predominant fracture types were cohesive for metal groups and adhesive for zirconia groups. CONCLUSION. Fracture strength of a restoration with a metal or a zirconia framework was independent of the veneering techniques. However, the pressing technique over metal frameworks resisted significantly higher fracture loads than zirconia frameworks.

• Clinical and Experimental Reproductive Medicine
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• 제21권3호
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• pp.297-303
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• 1994

The effect of radiation on the steroidogenesis of rat ovary was investigated. For this purpose, female rats aged 7-8 weeks were exposed to a single dose of ${\gamma}$ radiation(320 rad or 800 rad) by the cobalt-60. At fourth(day of the first estrus) and eighth(day of the second estrus) days after irradiation, the concentrations of serum steroid hormones were determined by radioimmunoassays (RIA). The correlation between survival rate(Y) and radiation dose(X) was Y=-0.06X+100(r=0.89, n=10). Lethal dose$(LD)_{50(30)}$ and $LD_{20(30)}$ were 833.33rad and 333.33rad respectively. The weights of body and ovary was decreased significantly by the $LD_{50(30)}$ irradiation during the 4 days, but both weights were recovered at day 8. The serum levels of 17a-hydroxyprogesterone(170HP) and estradiol($E_2$) in the irradiated rats were not generally different from those of control. However, the levels of testosterone(T) and 19-norterstosterone(19NT) in the irradiated rat at $LD_{50(30)}$ and $LD_{20(30)}$ radiation doses were decreased, while progesterone levels in serum of the irradiated rats were slightly increased. These results suggest that irradiation may inhibit the first step of steroidogenesis, especially the conversion of P to T, in the rat ovary.

• 미생물학회지
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• 제5권2호
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• pp.79-85
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• 1967

Kim, Jong Hyup., (Div. of Biology, Atomic Energy Research Institute,Korea.;) Studies on the Cellulor Metabolism in Microorganisms as influenced by Gamma-irradiation(III): On the Changes of Free Amino acid Pool and content of Protein in Yeast clls irradiated by .gamma.-ray. 1. The strain of Saccharomyces cerevisiae had been cultured synchronously in aerobic condition and irradiatel by gamma-ray from the source of cobalt-60. Drying in vacuum oven at $90^{\circ}C$ C over 12 hours, then changes of protein content (Kjeldahl) and free amino acid pool have been assayed with use of spectrophotometer. Results obtained were compared with those of unirradiated normal cells. 2. It is proved that amount of protein content in the irradiated cells increases to seven percent more than those of normal cells in the same weight of dried samples. It seems like carbohydrate breakown had been stimulated by irradiation and that relative contents of protein shows higher values than those of normal in the same weight of samples. 3. The amount of free amino acid pool in the irradiated cells shows less value about ten percent than those of normal cells, and rate of decreasing is also weak than those of standard reagent solution of amino acid. We may assume that free amino acid pool would be protected against radiation damage in living cells and more stable than in vitro. 4. The component of free amino acid pool have been assayed on second dimensional paper chromatogram, and the identified amino acids are as follows; aspartic acid, serine, glutamic acid, cystine, lysine, glycine, threonine, histidine, arginine, tyrosine, phenylalanine, valine and leucine. 5. Distributional presence of free amino acids are identical to that of normal cells except arginine, it is cosumable that radiation effect is univerlsal to all amino acid. However it is obvious that there are differences in radiolabilities of amino acids in irradiated cells.

• 생명과학회지
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• 제15권4호
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• pp.641-646
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• 2005

Salmonella typhimurium TML이 Int-407 숙주세포에 부착하는 정도는 S. typhimurium이 낮은 농도의 철이 함유된 배지에서 배양되었을 때보다 LB 액체배지 또는 높은 농도의 철이 함유된 배지에서 생육한 것에서 약 10배 정도의 높은 수준으로 관찰되었다. 고농도의 철이 포함된 배양조건이 살모넬라가 숙주세포에 부착시키는 정도를 향상시키는데 반해, 칼슘, 코발트, 구리, 인산, 마그네슘 그리고 망간과 같은 다른 양이온은 그렇지 않다. 이것은 아마도 철이 Salmonella가 부착에 필요한 요소들의 발현을 활성화하는 역할을 하는 것으로 추정된다. 철 농도에 따른 부착정도의 차이들은 type 1 fimbriae, mannose resistant hemagglutinin과 flagellum등을 생성하지 않는 다양한 S. typhimurium 돌연변이주들에서도 관찰되는 것으로 미루어보아 이들 구조체들과 상관이 없는 밝혀지지 않은 어떤 인자가 부착성 증가에 관여하는 것으로 사료된다. fur유전자가 불활성화된 S. typhimurium 돌연변이주의 부착성이 야생형 Salmonella와 유사한 방식으로 철에 의해 조절되었는데, 이는 철 농도에 따른 부착성의 변화에 관여하는 잠재적인자의 발현이 Fur 단백질과 독립적으로 이루어진다는 것을 나타낸다.

• 자원리싸이클링
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• 제22권3호
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• pp.43-49
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• 2013

NCM계 폐리튬전지 공정 스크랩 재활용의 연구에 일환으로서 리튬화합물의 회수와 NCM 전구체를 제조하기 위한 침출거동에 대하여 살펴보았다. 이와 같은 목적을 달성하고자 수소를 이용하여 NCM계 스크랩 분말을 환원한 후, 먼저 $CO_2$ 가스로 탄산리튬을 회수하고, 산에 의한 침출거동을 연구하였다. 수소에 의한 환원율은 $800^{\circ}C$에서 약 93%를 나타내었으며, 수세에 의해 약 99%순도의 탄산리튬을 제조하였다. 그리고 수소환원 처리 전후 분말에 대한 산 침출거동을 비교한 결과, 수소환원 처리에 의하여 2M 황산농도에서 코발트 32%, 니켈 45%의 침출효과가 향상되었으며, 망간의 경우에는 약 90% 정도 침출되었다.

• 한국가스학회지
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• 제13권5호
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• pp.33-38
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• 2009

일산화탄소, 수소와 같은 친환경 연료용 가스를 이용하여 메탄화 반응을 거쳐 합성 가스를 생성하였다. 이를 위한 촉매로 상용 알루미나에 담지된 Ni-Co 이원 금속을 증착침전법을 사용하여 제조하였으며 제조된 촉매의 촉매 활성 비교를 위하여 Ni, Co 단일 금속 촉매를 동일한 방법으로 제조하였다. 제조한 촉매를 TEM, XRD, TPR 분석을 실시하여 각각의 촉매 특성을 확인하였고 메탄화 반응을 진행하여 합성 가스 전환율을 측정하였다. 증착침전법으로 제조한 촉매의 경우, 금속 입자가 작은 크기로 분산된 것을 확인하였다. Ni, Co 두 금속이 담지된 이원 촉매는 Ni, Co가 각각 담지된 단일 금속 촉매에 비해 더욱 높은 활성을 나타내었으며 TPR 분석 결과, 이는 두 금속의 공존으로 인한 상호 작용을 통해 활성 수소를 보다 증가시켰기 때문으로 나타났다.

• 한국키틴키토산학회지
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• 제23권4호
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• pp.256-261
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• 2018

Recently, the number of cardiovascular disease-related deaths worldwide has increased. Therefore, the importance of percutaneous cardiovascular intervention and drug-eluting stents (DES) has been highlighted. Despite the great clinical success of DES, the re-endothelialization at the site of stent implantation is retarded owing to the anti-proliferative effect from the coated drug, resulting in late thrombosis or very late restenosis. In order to solve this problem, studies have been actively carried out to excavate new drugs that promote rapid re-endothelialization. In this study, we introduced hydrophilic drug, tauroursodeoxycholate (TUDCA), that improves the proliferation of endothelial progenitor cells and promotes apoptosis of vascular smooth muscle cells. In addition, we utilized shellac, which is a natural resin from lac bug to coat TUDCA on the surface of the metal. When using conventional coating method including biodegradable polymers and organic solvents, phase separation between polymer and drug occurred in the coating layer that caused incomplete incorporation of drug into the polymer layer. However, when using shellac as a coating polymer, no phase separation was observed and drug was fully covered with the polymer matrix. In addition, by adjusting the composition of coating solution and modifying the hydrophilicity of the metal surface using oxygen plasma, the surface roughness decreased due to the increased affinity between coating solution and metal surface. This result provides a method of depositing a hydrophilic drug layer on the stent.

• 방사선산업학회지
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• 제5권1호
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• pp.35-39
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• 2011

This study was investigated the effect of tumor cell cytotoxicity of gamma irradiated Chaga mushroom extract (CME). CME was prepared by hot water extraction at $70^{\circ}C$ for 4 hours and lyophilized. $Ten\;mg\;ml^{-1}$ of lyophilized CME powder was dissolved with deionized water and then irradiated at the doses of 10, 50, 100, and 150kGy by cobalt 60 gamma irradiator. The gamma-irradiated and non-irradiated CME were treated into the cancer cell, including human stomach cancer and human colon cancer. Cytotoxicity against the cancer cell was increased in gamma-irradiated CME and antioxidant activity was also increased in gamma-irradiated CME, as irradiation dose increased. Therefore, it was considered that gamma irradiation was effective method for improvement of the cancer cell cytotoxicity and antioxidant activity of Chaga mushroom extract.

• 한국자기학회지
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• 제4권1호
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• pp.25-31
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• 1994

코발트와 철의 이온을 혼합한 산성수용액 중에서, 알루미늄 양극산화피막에 전해석출 하여 제작된 자성막은, 코발트조성이 증가함에 따라 발크합금의 경우와 마찬가지로 상전이(phase shifting) 하였다. 입자직경이 $150\;{\AA}$의 시료의 경우 조성이 25-35 at% Co에서 큰 포화자화, 고항자력, 큰 자기이방성 에너지 및 우수한 각형비 등에 기인하는 큰 자기에너지 적($BH_{max}$)이 얻어진다. 그러나 입자직경이 $450\;{\AA}$의 경우에는, 코발트가 50-70 at% 일때 초기석출부 에 강자성체인 FeC가 아주 강하게 배향하므로, 입자의 큰 형상이방성(수직자기이방성)이 없어지고 면내 방향의 자기이방성을 나타낸다. 그리고 같은 조성에서 초기석출부를 제거하여 FeC의 영향을 없앨때, 주직자기이방성이 회복되었다.