• Journal of Periodontal and Implant Science
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• 제42권3호
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• pp.81-87
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• 2012

Purpose: The characteristics of oxidized titanium (Ti) surfaces varied according to treatment conditions such as duration time and temperature. Thermal oxidation can change Ti surface characteristics, which affect many cellular responses such as cell adhesion, proliferation, and differentiation. Thus, this study was conducted to evaluate the surface characteristics and cell response of thermally treated Ti surfaces. Methods: The samples were divided into 4 groups. Control: machined smooth titanium (Ti-S) was untreated. Group I: Ti-S was treated in a furnace at $300^{\circ}C$ for 30 minutes. Group II: Ti-S was treated at $500^{\circ}C$ for 30 minutes. Group III: Ti-S was treated at $750^{\circ}C$ for 30 minutes. A scanning electron microscope, atomic force microscope, and X-ray diffraction were used to assess surface characteristics and chemical composition. The water contact angle and surface energy were measured to assess physical properties. Results: The titanium dioxide ($TiO_2$) thickness increased as the treatment temperature increased. Additional peaks belonging to rutile $TiO_2$ were only found in group III. The contact angle in group III was significantly lower than any of the other groups. The surface energy significantly increased as the treatment temperature increased, especially in group III. In the 3-(4,5-Dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide assay, after 24 hours of incubation, the assessment of cell viability showed that the optical density of the control had a higher tendency than any other group, but there was no significant difference. However, the alkaline phosphatase activity increased as the temperature increased, especially in group III. Conclusions: Consequently, the surface characteristics and biocompatibility increased as the temperature increased. This indicates that surface modification by thermal treatment could be another useful method for medical and dental implants.

• 한국재료학회지
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• 제22권12호
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• pp.682-688
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• 2012

In this study we aimed to examine the co-doping effects of 1/6 mol% $Co_3O_4$ and 1/4 mol% $Cr_2O_3$ (Co:Cr = 1:1) on the reaction, microstructure, and electrical properties, such as the bulk defects and the grain boundary properties, of ZnO-$Bi_2O_3-Sb_2O_3$ (ZBS; Sb/Bi = 0.5, 1.0, and 2.0) varistors. The sintering and electrical properties of Co,Cr-doped ZBS, ZBS(CoCr) varistors were controlled using the Sb/Bi ratio. Pyrochlore ($Zn_2Bi_3Sb_3O_{14}$), ${\alpha}$-spinel ($Zn_7Sb_2O_{12}$), and ${\delta}-Bi_2O_3$ were formed in all systems. Pyrochlore was decomposed and promoted densification at lower temperature on heating in Sb/Bi = 1.0 by Cr rather than Co. A more homogeneous microstructure was obtained in all systems affected by ${\alpha}$-spinel. In ZBS(CoCr), the varistor characteristics were improved (non-linear coefficient, ${\alpha}$ = 20~63), and seemed to form ${Zn_i}^{{\cdot}{\cdot}}$(0.20 eV) and ${V_o}^{\cdot}$(0.33 eV) as dominant defects. From impedance and modulus spectroscopy, the grain boundaries were found to be composed of an electrically single barrier (0.94~1.1 eV) that is, however, somewhat sensitive to ambient oxygen with temperature. The phase development, densification, and microstructure were controlled by Cr rather than by Co but the electrical and grain boundary properties were controlled by Co rather than by Cr.

• 대한화학회지
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• 제38권11호
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• pp.785-791
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• 1994

$Sr_1-_xY_xMnO_3$ (x = 0.0∼1.0)을 citrate법으로 합성하고 조성에 따른 구조적 전기적 성질의 변화를 알아보았다. X-ray diffraction method에 의해 각 산화물의 구조를 결정한 결과, $Sr_1-_xY_xMnO_3$ (x = 0.0∼1.0) system은 조성에 따라 4L-hexagonal perovskite(x = 0.0∼0.3) 구조, rhombohedral perovskite(x = 0.3∼0.7)구조를 거쳐 hexagonal nonperovskite(x=0.7∼1.0) 구조까지 3가지의 다른 결정구조를 갖는 것으로 관찰되었다. 이러한 $Sr_1-_xY_xMnO_3$ system의 구조 변화는 yttrium 양이 증가함에 따라 cell parameter가 증가하는 경향을 보였으며, 이는 $Mn^{4+}$ 대신 $Mn^{3+}$가 증가함에 따른 것으로 믿어진다. $SrMnO_3$의 $Sr^{2+}$ 자리에 $Y^{3+}$를 치환할수록 conductivity가 크게 증가하는 것이 관찰되었다. 4L-hexagonal구조를 갖는 $Sr_{0.9}Y_{0.1}MnO_3$와 pseudocubic perovskite 구조를 갖는 $Sr_{0.5}Y_{0.5}MnO_3$의 온도에 따른 전기저항 측정결과, $Sr_{0.9}Y_{0.1}MnO_3$에서 더 큰 energy gap을 갖는 것으로 관찰되었으며, 이 결과는 4L-hexagonal구조가 metal-metal 결합에 의해 안정화되어 있기 때문인 것으로 설명된다.

• 환경생물
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• 제35권2호
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• pp.207-214
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• 2017

본 연구에서 배초향 종자의 다양한 저장조건에서의 활력변화를 조사하여 종자 등온흡습곡선, 활력 공식을 예측하였다. 그 결과 배초향의 등온흡습곡선은 전형적인 S 형태로 나타났으나 Phase I이 관찰되지 않아 상대습도 11% 이전에서 단분자층 수분함량이 형성될 것으로 보인다. Log 수분함량에 대한 Log 수명(${\sigma}$)의 영향은 선형 반응을 보였다. 하지만 낮은 상대습도 조건(RH 11%)의 수명은 예측값보다 비교적 낮게 나타났다. 온도에 대한 수명의 반응은 2차 선형 반응을 보였으며, 모델의 예측값에 대하여 특별한 경향이 나타나지 않았다. Universal constant를 사용하는 Two step model을 활용한 배초향 종자 활력 공식의 예측 결과 높은 온도, 높은 수분함량에서는 비교적 모델과 비슷한 경향이 관찰되었으나, 낮은 온도, 낮은 수분함량에서는 데이터의 변이가 크게 나타나는 경향이 관찰되었다. 이는 야생 종자인 배초향 종자가 지닌 휴면, 활력의 불균일성과 같은 요인에 의한 것으로 판단된다. 배초향 종자의 활력 공식을 활용한 P85예측 결과 종자은행에서의 표준 조건에서 가장 긴 저장 기간을 보였다. 종자은행의 표준 건조조건에서 건조된 배초향 종자의 P85는 종자은행 장기저장조건 ($-20^{\circ}C$)이 196년으로 예측되었다. 하지만 one step 모형에서는 P85가 560년으로 예측되어 활력 공식의 예측 방식 선정의 중요성을 보여줬다. 배초향 종자와 같은 야생식물은 대량의 연구재료를 확보하기 쉽지 않기 때문에 일반적인 작물 종자 장기저장 프로세스와는 다르게 수명 예측을 활용하여 갱신 시기, 모니터링 시기의 최적화가 필요하다. 본 결과로 도출된 배초향 종자의 P85는 이러한 프로세스의 최적화의 기준으로 활용 가능할 것으로 사료된다.

• Advances in aircraft and spacecraft science
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• 제5권2호
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• pp.225-237
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• 2018

The difficulties of satellite vibration testing are due to the commonly expressed qualification requirements being incompatible with the limited performance of the entire controlled system (satellite + interface + shaker + controller). Two features cause the problem: firstly, the main satellite modes (i.e., the first structural mode and the high and low tank modes) are very weakly damped; secondly, the controller is just too basic to achieve the expected performance in such cases. The combination of these two issues results in oscillations around the notching levels and high amplitude beating immediately after the mode. The beating overshoots are a major risk source because they can result in the test being aborted if the qualification upper limit is exceeded. Although the abort is, in itself, a safety measure protecting the tested satellite, it increases the risk of structural fatigue, firstly because the abort threshold has been already reached, and secondly, because the test must restart at the same close-resonance frequency and remain there until the qualification level is reached and the sweep frequency can continue. The beat minimum relates only to small successive frequency ranges in which the qualification level is not reached. Although they are less problematic because they do not cause an inadvertent test shutdown, such situations inevitably result in waiver requests from the client. A controlled-system analysis indicates an operating principle that cannot provide sufficient stability: the drive calculation (which controls the process) simply multiplies the frequency reference (usually called cola) and a function of the following setpoint, the ratio between the amplitude already reached and the previous setpoint, and the compression factor. This function value changes at each cola interval, but it never takes into account the sensor signal phase. Because of these limitations, we firstly examined whether it was possible to empirically determine, using a series of tests with a very simple dummy, a controller setting process that significantly improves the results. As the attempt failed, we have performed simulations seeking an optimum adjustment by finding the Least Mean Square of the difference between the reference and response signal. The simulations showed a significant improvement during the notch beat and a small reduction in the beat amplitude. However, the small improvement in this process was not useful because it highlighted the need to change the reference at each cola interval, sometimes with instructions almost twice the qualification level. Another uncertainty regarding the consequences of such an approach involves the impact of differences between the estimated model (used in the simulation) and the actual system. As limitations in the current controller were identified in different approaches, we considered the feasibility of a new controller that takes into account an estimated single-input multi-output (SIMO) model. Its parameters were estimated from a very low-level throughput. Against this backdrop, we analyzed the feasibility of an LQG control in cancelling beating, and this article highlights the relevance of such an approach.

• 한국수학교육학회지시리즈C:초등수학교육
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• 제19권3호
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• pp.211-222
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• 2016

본고는 미국수학교사협의회(NCTM)의 대표적 최신 출판물인 원리에서 실천으로(Principles to Actions)에 제시된 8개 항목의 수학교수관행(Mathematics Teaching Practices: MTPs)을 분석의 틀로 이용하여, 초중등 예비교사들이 수업지도안 수정활동에 참여한 과정을 보고하고 있다. 이 과제는 주어진 수업지도안을 분석하고 수정하는 활동을 포함한 4단계의 과정으로 구성되었다. 57명의 예비교사들이 한 학기 간에 걸쳐 이 과제에 참여하였으며, 각 단계에서 수집된 자료는 귀납적 내용분석을 하였다. 예비교사들의 수업지도안 작성에 대한 초기개념은 수업관행(가령 MTPs)을 미약하게 반영하고 있었으며, 지도안 구성요소들의 기능보다는 형식을 더 강조하는 경향을 보였다. 그러나 MTPs를 수업지도안 분석의 틀로 이용하는 기회가 주어졌을 때, 예비교사들이 MTPs 에 대한 다양한 해석을 보여주었고, MTPs를 수업지도안에 포함시키려는 노력을 하였으며, MTPs 간의 상호연계성에 더 주목하는 경향을 보였다. 본고는 이 수업지도안 수정과정에서 예비교사들이 겪은 도전 및 갈등도 제시하고 있다. 이런 점에서 본 연구 결과는 교사교육 프로그램에서 MTPs의 효과적 사용 가능성 여부를 조사하는 연구에 시사점을 제시하고 있다.

• KSBB Journal
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• 제7권2호
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• pp.118-125
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• 1992

1.에멀젼형 화장품시료의 오염정도는 P. aeruginosa의 증식을 촉진하는 fatty acids, waxs, oils, steroids 등의 유기물에 의존하였다. 2. 오염의 결과, 물성의 변화로서 화장품시료의 pH가 40일 경과시 7.6에서 6.0으로 변화되었다. P. aeruginosa의 영양원으로서는 상대적으로 낮은 굴절률을 갖는 물질들이 소모되어 화장품시료(물:오일=70:30)의 굴절률이 1.4430에서 1.4530으로 변화 되었다. 3. 오염이 진행되는 동안 화장품시료의 相의 안정서이 파괴되었으며, 약간의 변색, 변취와 함께 creaming 및 응집현상이 나타났다. 4. P. aeruginosa의 최적증식조건인 pH7.0, 온도$20^{\circ}C$에서, 물과 오일의 부피비에 의한 균증식은 70:30, 80:20, 30:70, 90:10, 50:50의 순서로 되었다. 5. 방부살균제를 첨가하여 challenge test를 한 결과, P. aeruginosa의 증식이 억제되었으며 40일 경과시 균수는 방부살균제를 첨가하지 않은 경우 $10^8$개/ml에서 p-hydroxy benzoic acid propyl ester + phosphoric acid buffer solution첨가로 $5{\times}10^3$ 개/ml로 감소되었다. 6. 시험균주인 P. aeruginosa에 대한 항균력은 p-hydroxy benzoic acid propyl ester + phosphoric acid buffer solution>p-hydroxy benzoic acid buthyl ester + acetic acid buffer solution>p-hydroxy benzoic acid methyl ester + phosphoric acid buffer solution>p-hydroxy benzoic acid methyl ester + p-hydroxy benzoic acid propyl ester>p-hydroxy benzoic acid buthyl ester + potassium chloride sodium hydroxide buffer solution>p-hydroxy benzoic acid buthyl ester + p-hydroxy benzoic acid propyl ester>p-hydroxy benzoic acid methyl ester + acetic acid vbuffer solution>acetic acid buffer solution _ potassium chloride sodium hydroxide buffer solution의 순으로 우수하였으며 pH, 농도, 균수등은 양호한 수준을 유지하였다.

• BMB Reports
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• 제38권1호
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• pp.58-64
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• 2005

Myo-inositol monophosphate phosphatase (IMPP) is a key enzyme in the phosphoinositide cell-signaling system. This study found that incubating the IMPP from a porcine brain with pyridoxal-5'-phosphate (PLP) resulted in a time-dependent enzymatic inactivation. Spectral evidence showed that the inactivation proceeds via the formation of a Schiff's base with the amino groups of the enzyme. After the sodium borohydride reduction of the inactivated enzyme, it was observed that 1.8 mol phosphopyridoxyl residues per mole of the enzyme dimer were incorporated. The substrate, myo-inositol-1-phosphate, protected the enzyme against inactivation by PLP. After tryptic digestion of the enzyme modified with PLP, a radioactive peptide absorbing at 210 nm was isolated by reverse-phase HPLC. Amino acid sequencing of the peptide identified a portion of the PLP-binding site as being the region containing the sequence L-Q-V-S-Q-Q-E-D-I-T-X, where X indicates that phenylthiohydantoin amino acid could not be assigned. However, the result of amino acid composition of the peptide indicated that the missing residue could be designated as a phosphopyridoxyl lysine. This suggests that the catalytic function of IMPP is modulated by the binding of PLP to a specific lysyl residue at or near its substrate-binding site of the protein.

• Journal of Pharmaceutical Investigation
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• 제39권1호
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• pp.73-78
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• 2009

A simple LC-MS/MS method of rabeprazole in human plasma was developed and validated. Rabeprazole and Internal standard (I.S), omeprazole, were extracted from human plasma by liquid liquid extraction, chromatographic separation of rabaprazole in plasma was achieved at $45^{\circ}C$ with a Shiseido UG120 $C_{18}$ column and methanol-10 mM ammonium acetate buffer (pH 9.42 with ammonium water), as mobile phase. Rabeprazole produced a protonated precursor ion [$(M+H)^+$] at m/z 360.10 and corresponding product ion at m/z 242.21. Internal standard produced a protonated precursor ion [$(M+H)^+$] at 346.09 and corresponding product ion at m/z 198.09. This method showed linear response over the concentration range of $1{\sim}500\;ng/mL$ with correalation coefficient greater than 0.99. The lower limit of quantitation (LLOQ) using 0.2 mL plasma was 1 ng/mL, which was sensitive enough for pharmacokinetics studies. The method was specific and validated with a limit of quantitation of 1 ng/mL. The intra-day and inter-day precision and accuracy were acceptable for all samples including the LLOQ. The applicability of the method was demonstrated by analysis of plasma after administration of a single 10 mg dose to 36 healthy subject. From the plasma rabeprazole concentration versus time curves, the mean $AUC_t$ (The area under the plasma concentration-time curve from time 0 to 12 hr ) was $691.36{\pm}321.88\;ng{\cdot}hr/mL$, $C_{max}$ (maximum plasma drug concentration) of $353.21{\pm}131.52\;ng/mL$ reached $3.4{\pm}1.1\;hr$ after adiministration. The mean biological half-life of rabeprazole was $1.37{\pm}0.75\;hr$. Based on the results, this simple method could readily be used in pharmacokinetics studies.

• Clinical and Experimental Reproductive Medicine
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• 제16권2호
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• pp.205-210
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• 1989

To investigate the effects of ovarian cysts on the controlled ovarian hyper-stimulation cycles, 16 patients with 16 paired cycles for IVF-ET were analyzed. These patients had taken both type of cycles, i.e., with cyst(cyst group) and without cyst(control group). Mean diameter of ovarian cysts in cyst group was 18.2mm. There were no significant differences in hormone levels in early follicular phase between two groups. No significant differences were found in total dosage of hMG(IU) administered during the ovarian stimulation $843.8{\pm}123.0$ vs $891.0{\pm}129.8$, serum estradiol level (pg/ml) on the day of hCG administration($1542.8{\pm}1100.6$ vs $1567.5{\pm}1193.0$), the number of aspirated follicles $10.0{\pm}3.4$ vs $11.2{\pm}4.3$ and oocytes $5.3{\pm}3.3$ vs $6.2{\pm}3.1$, the fertilization rate(51.2 % vs 57.2 %) and the cleavage rate(40.5 % vs 52.0 %). Serum estradiol terminal patterns during COH in one group tended to be repeated in the other group. In conclusion, this study suggests that small ovarian cysts do not adversely impact on the controlled ovarian hyperstimulation parameters in IVF - ET program and the presence of small ovarian cyst without concomitant high basal serum estradiol level is not an indication of the cancellation of the controlled ovarian hyperstimulation for IVF-ET.