• Advances in nano research
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• 제5권4호
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• pp.359-372
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• 2017

Metallic copper nanoparticles were synthesised by reduction of copper ions in aqueous solution, and metal-metal bonding by using the nanoparticles was studied. A colloid solution of metallic copper nanoparticles was prepared by mixing an aqueous solution of $CuCl_2$ (0.01 M) and an aqueous solution of hydrazine (reductant) (0.2-1.0 M) in the presence of 0.0005 M of citric acid and 0.005 M of n-hexadecyltrimethylammonium bromide (stabilizers) at reduction temperature of $30-80^{\circ}C$. Copper-particle size varied (in the range of ca. 80-165 nm) with varying hydrazine concentration and reduction temperature. These dependences of particle size are explained by changes in number of metallic-copper-particle nuclei (determined by reduction rate) and changes in collision frequency of particles (based on movement of particles in accordance with temperature). The main component in the nanoparticles is metallic copper, and the metallic-copper particles are polycrystalline. Metallic-copper discs were successfully bonded by annealing at $400^{\circ}C$ and pressure of 1.2 MPa for 5 min in hydrogen gas with the help of the metalli-ccopper particles. Shear strength of the bonded copper discs was then measured. Dependences of shear strength on hydrazine concentration and reduction temperature were explained in terms of progress state of reduction, amount of impurity and particle size. Highest shear strength of 40.0 MPa was recorded for a colloid solution prepared at hydrazine concentration of 0.8 M and reduction temperature of $50^{\circ}C$.

• 한국육종학회지
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• 제42권5호
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• pp.448-454
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• 2010

The objective of this study was to rapidly evaluate fatty acids in a collection of foxtail millet (Setaria italica (L.) P. Beauv) of different origins so that this information could be disseminated to breeders to advance germplasm use and breeding. To develop the calibration equations for rapid and nondestructive evaluation of fatty acid content, near-infrared reflectance spectroscopy (NIRs) spectra (1104-2494 nm) of samples ground into flour (n=100) were obtained using a dispersive spectrometer. A modified partial least-squares model was developed to predict each component. For foxtail millet germplasm, our models returned coefficients of determination ($R^2$) of 0.91, 0.89, 0.98 and 0.98 for strearic acid, oleic acid, linoleic acid, and total fatty acids, respectively. The prediction of the external validation set (n=10) showed significant correlation between references values and NIRs values ($r^2=0.97$, 0.91, 0.99 for oleic, linoleic, and total fatty acids, respectively). Standard deviation/standard error of cross-validation (SD/SECV) values were greater than 3 (3.11, 5.45, and 7.50 for oleic, linoleic, and total fatty acids, respectively). These results indicate that these NIRs equations are functional for the mass screening and rapid quantification of the oleic, linolenic, and total fatty acids characterizing foxtail millet germplasm. Among the samples, IT153491 showed an especially high content of fatty acids ($84.06mg\;g^{-1}$), whereas IT188096 had a very low content ($29.92mg\;g^{-1}$).

• 대한약침학회지
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• 제22권1호
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• pp.41-48
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• 2019

Objective: The aim of the study was to evaluate the hepatoprotective activity of the bark extract (Ethanol: Water) in the ratio of (3:1) of Rhizophora mucronata (BERM) by intoxicating the $HepG_2$ cell lines with different toxicants viz, $CCL_4$, Ethanol and Paracetamol with different concentrations of the extract were used. The $HepG_2$ cell lines were subjected to MTT Assay for studying the cytotoxicity. Methods: $HepG_2$ cells were plated using 96 well plate in 10% bovine serum, exposed to different toxicants viz, 2% $CCl_4$, 60% Ethanol and 14 mM Paracetamol respectively. The various test concentrations (18.85, 37.5, 75, 150 and $300{\mu}g/ml$) of bark extract of Rhizophora mucronata was added and incubated for 24 hours. Medium was removed after incubation period and 0.5 mg/ml MTT(3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) was added and again incubated for 4 hours at 37oC. Then MTT was removed the crystals was dissolved in DMSO and absorbance was measured at 570 nm. Results: The result showed that dose dependent increase in percentage of viability at the doses of 18.85, 37.5, 75, 150, $300{\mu}g/ml$. Te results for the $CCl_4$ intoxicated, at $300{\mu}g/ml$ of the concentration of the extract, the % of viable cells was found out to be 99.6%, for Ethanol intoxicated, 97.67%, and Paracetamol induced, 75.37%, IC50 was $21.53{\mu}g/ml$, $12.61{\mu}g/ml$ and $21.42{\mu}g/ml$ respectively. Conclusion: Thus, we conclude that, the extract possesses defensive effect against different toxicants and can be used as an alternate drug for hepatotoxicity.

• Journal of Korean Academy of Oral Health
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• 제42권4호
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• pp.210-215
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• 2018

Objectives: The main objectives of this study were to verify the antibacterial activity of two essential oils, lavender and peppermint, against dental caries and to review their synergistic effect when used in combination. Our results provide basic data for the evaluation of the use of these two substances towards the prevention and cure of dental caries. Methods: The sample solutions of lavender and peppermint oils were prepared in three different concentrations (30%, 50%, and 70% (v/v)) by diluting them with third-distilled water and Tween 20. Streptococcus mutans was selected as the bacterial species for testing. The disk diffusion method was used to measure the antibacterial activity of the sample solutions. For generating growth curves and measuring the number of clusters of the bacterial, the liquid medium-dilution method was used; the absorbance of the medium was measured at 600 nm after 3, 6, 12 and 24 hours. Results: When the antibacterial activity of the oils was tested via the disk diffusion method, the activity improved with increasing concentrations of all the sample solutions of peppermint, lavender, and the blend, but there was no significant difference between them with respect to the type of oil. In the growth curves of S. mutans, growth inhibition was observed after 12 hours. The inhibitory effect of 30% lavender oil on growth was 64.9% and 80.1% after 12 and 24 hours of treatment, respectively whereas that of peppermint oil was 71.3% and 80.1% after 12 and 24 hours of treatment, respectively. The inhibitory effect of the blended oil was 71.9% and 81.0% after 12 and 24 hours of treatment, respectively. Conclusions: Further research is still required in order to determine the efficacy of lavender and peppermint oils, as well as other essential oils, for wider use in preventing dental caries.

• 분석과학
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• 제32권4호
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• pp.139-146
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• 2019

A simple and reliable analytical method based on high-performance liquid chromatography-ultraviolet detection was established for the analysis of the flowers of Chrysanthemum morifolium (CM). Luteolin-7-O-glucoside (LU7G) was chosen as a target analyte considering its content, availability, and ease of analysis. Chromatographic separation of LU7G was achieved using a Phenomenex Gemini $C_{18}$ column ($250{\times}4.6mm$, $5{\mu}m$) run with a mobile phase consisting of 0.5 % acetic acid in water and 0.5 % acetic acid in acetonitrile at a flow rate of $1.0mL\;min^{-1}$. The detection wavelength and column temperature were set at 350 nm and $40^{\circ}C$, respectively. Method validation was performed according to the AOAC guidelines and the method was specific, linear ($R^2=0.9991$ for $50-300{\mu}g\;mL^{-1}$), precise (${\leq}3.91%$RSD), and accurate (100.1-105.7 %). The limits of detection and quantification were 3.62 and $10.96{\mu}g\;mL^{-1}$, respectively. The established method was successfully applied to determine the contents of LU7G in various batches of bulk CM extracts and labscale CM extract. The developed method is a readily applicable method for the quality assessment of CM and its related products.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2019년도 전력전자학술대회
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• pp.230-232
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• 2019

Light Triggerd Thyristor (LTT)는 HVDC 및 산업용 스위치 등에 사용되는 대전력 반도체소자이다. 일반적인 Thyristor가 전기적 신호에 의해 trigger 되는 것과는 다르게 LTT는 광신호에 의해 동작하는 소자이다. 본 논문에서는 5,000V, 2,200A 급의 4인치 LTT 소자의 제작 및 전기적인 특성평가 결과를 기술하였다. 4인치 LTT의 구조적인 특징은 전면부 중앙에 광신호가 주입되는 수광부가 위치해 있으며 입력 전류 증폭을 위한 4-단계 증폭 게이트 (gate) 구조를 가지도록 설계하였다. $400{\Omega}{\cdot}cm$ 비저항을 갖는 1mm 두께의 n-형 실리콘 웨이퍼에 boron 이온주입과 열처리 공정으로 약 $30{\mu}m$ 깊이의 p-base를 형성하였으며, 고내압 저지를 위한 edge termination은 VLD (variable lateral doping) 기술을 적용하였다. 제작된 4인치 LTT는 6,500 V의 순방향 항복전압 ($V_{DRM}$) 특성을 나타내었으며, 100V의 어노드전압 ($V_A$)과 20 mA의 게이트전류 ($I_G$)에 의하여 thyristor가 trigger 됨을 확인하였다. 제작한 LTT 소자는 disk형 press-pack 패키지를 진행한 후, LTT의 수광부에 $10{\mu}s$, 50 mW의 900 nm 광 펄스를 조사하여 전류 특성을 평가하였다. LTT 패키지 샘플에 60 Hz 주파수의 광 펄스를 조사한 경우 2,460 A의 순방향 평균전류 ($I_T$)와 $336A/{\mu}s$의 반복전류상승기울기 (repetitive di/dt)에 안정적으로 동작함을 확인하였다. 또한, 펄스 전류 시험의 경우 61.6 kA의 최대 통전 전류 (ITSM, surge current)와 $1,050A/{\mu}s$의 펄스전류 상승 기울기 (di/dt of on-state pulse current)에도 LTT의 손상 없이 동작함을 확인하였다.

• 한국재료학회지
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• 제29권8호
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• pp.491-496
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• 2019

In this study, we prepare pure $WO_3$ inverse opal(IO) film with a thickness of approximately $3{\mu}m$ by electrodeposition, and an ultra-thin $TiO_2$ layer having a thickness of 2 nm is deposited on $WO_3$ IO film by atomic layer deposition. Both sets of photoelectrochemical properties are evaluated after developing dye-sensitized solar cells(DSSCs). In addition, morphological, crystalline and optical properties of the developed films are evaluated through field-emission scanning electron microscopy(FE-SEM), High-resolution transmission electron microscopy(HR-TEM), X-ray diffraction(XRD) and UV/visible/infrared spectrophotometry. In particular, pure $WO_3$ IO based DSSCs show low $V_{OC}$, $J_{SC}$ and fill factor of 0.25 V, $0.89mA/cm^2$ and 18.9 %, achieving an efficiency of 0.04 %, whereas the $TiO_2/WO_3$ IO based DSSCs exhibit $V_{OC}$, $J_{SC}$ and fill factor of 0.57 V, $1.18mA/cm^2$ and 50.1 %, revealing an overall conversion efficiency of 0.34 %, probably attributable to the high dye adsorption and suppressed charge recombination reaction.

• International journal of advanced smart convergence
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• 제8권3호
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• pp.27-38
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• 2019

I reviewed about dyeing fastness and functional properties of the non-mordant dyed cotton and iron mordant dyed cotton with astringent persimmon juice. In the UV-VIS spectrum of astringent persimmon juice, the maximum absorption wavelength of the juice was 272.0 nm, which was a characteristic peak of tannin. In dyeing fastness, light fastness of the non-mordant dyed cotton was a little low at grade 2~3. But by the iron mordant treatment, the light fastness was good at grade 4. Dry cleaning fastness to discoloration and contamination was excellent at grade 4~5 for both the non-mordant dyed cotton and iron-mordant dyed cotton. Their rub fastness were grade 3 and grade 2~3 respectively, in the dry condition, and grade 2~3 and grade 3 respectively, in the wet condition. In the perspiration fastness of the non-mordant dyed cotton, the discoloration from acidity and alkalinity was grade 3~4 and grade 3, respectively, and contamination from acidity and alkalinity was relatively good at grade 4. Meanwhile, in the perspiration fastness of the non-mordant dyed cotton, discoloration from acidity and alkalinity was fair, both recording grade 3~4, and contamination from acidity and alkalinity was very good, both recording grade 4~5. In the ultraviolet protection effect of the non-mordant dyed cotton and iron-mordant dyed cotton, the ultraviolet protection factor was both 50+, both of which showed an excellent ultraviolet blocking effect. And the protection rate of UV-A appeared 98.4% and 99.1%, respectively, and the protection rate of UV-B showed 98.7% and 99.2, respectively. In addition, both exhibited an excellent deodorization rate over 99.9% or more, irrespective of the passage of time. Also, both showed an excellent antimicrobial activity over 99.9% or more against Staphylococcus aureus and Klebsiella pneumoniae.

• The Korean Journal of Physiology and Pharmacology
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• 제25권5호
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• pp.479-488
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• 2021

This study aimed to develop docetaxel (DTX) loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles (DTX-NPs) and to evaluate the different pharmacological sensitivity of NPs to MCF-7 and MDA-MB-231 breast cancer cells. NPs containing DTX or coumarin-6 were prepared by the nanoprecipitation method using PLGA as a polymer and d-α-tocopherol polyethylene glycol 1000 succinate (TPGS) as a surfactant. The physicochemical properties of NPs were characterized. In vitro anticancer effect and cellular uptake were evaluated in breast cancer cells. The particle size and zeta potential of the DTX-NPs were 160.5 ± 3.0 nm and -26.7 ± 0.46 mV, respectively. The encapsulation efficiency and drug loading were 81.3 ± 1.85% and 10.6 ± 0.24%, respectively. The in vitro release of DTX from the DTX-NPs was sustained at pH 7.4 containing 0.5% Tween 80. The viability of MDA-MB-231 and MCF-7 cells with DTX-NPs was 37.5 ± 0.5% and 30.3 ± 1.13%, respectively. The IC₅₀ values of DTX-NPs were 3.92- and 6.75-fold lower than that of DTX for MDA-MB-231 cells and MCF-7 cells, respectively. The cellular uptake of coumarin-6-loaded PLGA-NPs in MCF-7 cells was significantly higher than that in MDA-MB-231 cells. The pharmacological sensitivity in breast cancer cells was higher on MCF-7 cells than on MDA-MB-231 cells. In conclusion, we successfully developed DTX-NPs that showed a great potential for the controlled release of DTX. DTX-NPs are an effective formulation for improving anticancer effect in breast cancer cells.

• Bulletin of the Korean Chemical Society
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• 제6권5호
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• pp.287-291
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• 1985

The addition of poly(styrenesulfonate) (PSS) to $Ru(bpy)_3^{2+}$ solutions shifted the emission peak by 3 nm to red, and increased emission intensity by 1.8 times. By contrast, poly(vinylsulfonate) (PVS) had little effect on the fluorescence spectrum. The effects of PSS on the spectral properties of $Ru(bpy)_3^{2+}$, were attributed to the presence of a hydrophobic phenyl group in PSS, which interact with $Ru(bpy)_3^{2+}$ by, at least in part, hydrophobic effect. The binding constant of $Ru(bpy)_3^{2+}$ to PSS in 0.1 M NaCl was $6{\times}10^4\;M^{-1}$, and this value was about $10^3$ times higher than those of methyl viologen ($MV^{2+}$) and $Cu^{2+}$. The Stern-Volmer constants of emission quenching of $Ru(bpy)_3^{2+}$ by $MV^{2+}$ and $Cu^{2+}$ in 0.1 M NaCl solutions were 426 and 40 $M^{-1}$, which correspond to second order rate constants($k_q$) of $1.1{\times}10^9\;and\; 1.0{\times}10^8\;M^{-1}s^{-1}$, respectively. The presence of PSS enhanced $K_{SV's}\;by\;{\sim}50$ times, whereas PVS increased the values only 1-4 times. The large enhancing effect of PSS, despite of lower charge density than PVS, was explained in terms of longer life-time of photoexcited $Ru(bpy)_3^{2+}$ bound to PSS and strong association of $Ru(bpy)_3^{2+}$ to PSS due to a specific interaction involving hydrophobic effect. The variation of $K_{SV's}$ on the concentrations of PVS and PSS were also investigated for $Ru(bpy)_3^{2+}-MV^{2+}\;and \;Ru(bpy)_3^{2+}-Cu^{2+}$ photoredox systems.