• 한국세라믹학회지
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• 제33권7호
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• pp.823-831
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• 1996

Due to the intrinsic low surface activation of ${\gamma}$-alumina it has been used limitely in practice. Accordingly forward enhancing its utility ${\gamma}$-alumina surface was treated with slfuricf aicd nitric acid and chloric acid respec-tively. Subsequently the effects of surface activity on the surface electrical characteristics were investigated. The ${\gamma}$-alumina was prepared by the precipitation of aluminium nitrate [Al(NO3)3.9H2O] using ammonia water as a precipitator and it was chemically treated with such acids mentioned above. The surface and morphology of the acid-treated ${\gamma}$-alumina were analysed by XRD, BET and the surface activities were measured by the amine titration methods. The interfacial properties of the ${\gamma}$-alumina dispersed in electrolyte solution were esti-mated by the surface charge density measured using potentiometric tiration. Based on the relation between surface charge density and the acid amount the following results were drawn for the surface and interfacial electrical properties ; Acidic properties of surface-treated alumina increase with anion load on alumina surface. P. Z. C decreases with acid amount on alumina surface. The surface charge densities were apart from electrolyte ionic strength. The acidity of ${\gamma}$-alumina is linearly dependent on the P. Z,.C when the ${\gamma}$-alumina was dispersed in aqueous electrolyte solution.

• 한국표면공학회지
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• 제41권3호
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• pp.94-101
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• 2008

A new convenient magnet array module is designed to investigate effects of magnetic field array on magnetron discharge characteristics. Magnetic field analysis showed good agreement of measured discharge region by a CCD device which has a high quantum efficiency over visible wavelength range. OES (optical emission spectroscopy) showed major emission peaks are from electronic transitions in 400 nm range and 800 nm range. Effects of driving voltage characteristics were analyzed in a point of electron drift trajectories and ionizing collision frequencies. Pulsed dc with a fast rising and falling time was analyzed to have potential to increase ionization collisions by putting a burst of hot electrons and to raise sheath potential. From measured voltage and current waveform, maximum of -1000 V peak was generated with $-400\;V_{rms}$ conditions. Possibility of a properly designed magnetron cathode was shown to be used as a melting device. Cu was successfully melted with power density of a several tens of $W/cm^2$.

• Journal of Microbiology and Biotechnology
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• 제33권9호
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• pp.1250-1256
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• 2023

Herein, different extracts of Scenedesmus deserticola JD052, a green microalga, were evaluated in vitro as a potential anti-aging bioagent. Although post-treatment of microalgal culture with either UV irradiation or high light illumination did not lead to a substantial difference in the effectiveness of microalgal extracts as a potential anti-UV agent, the results indicated the presence of a highly potent compound in ethyl acetate extract with more than 20% increase in the cellular viability of normal human dermal fibroblasts (nHDFs) compared with the negative control amended with DMSO. The subsequent fractionation of the ethyl acetate extract led to two bioactive fractions with high anti-UV property; one of the fractions was further separated down to a single compound. While electrospray ionization mass spectrometry (ESI-MS) and nuclear magnetic resonance (NMR) spectroscopy analysis identified this single compound as loliolide, its identification has been rarely reported in microalgae previously, prompting thorough systematic investigations into this novel compound for the nascent microalgal industry.

• Journal of Microbiology and Biotechnology
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• 제20권6호
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• pp.959-967
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• 2010

Down syndrome (DS) is an abnormality of the 21st chromosome that commonly occurs in children born to older women. Thus, amniotic fluid (AF) is usually collected from such women for prenatal diagnosis. This study analyzed human AF supernatants (AFS) using a mass spectrometric (MS) approach to search for candidate biomarkers of a DS pregnancy. The AFS were collected from older pregnant women at weeks 16-18 of their gestation by amniocentesis for cytogenetic analysis. The AFS from the pregnancies carrying DS (n=4) or chromosomally normal (n=6) fetuses, as revealed by the cytogenetic analysis, were then subjected to global protein profiling based on liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS). Affinity chromatography was also applied prior to the LC-ESI-MS/MS to minimize the masking effect of highly abundant albumin and immunoglobulin and thereby increase the diversity of the identified proteins. As a result, at least 30 new AFS proteins were identified and 44 AFS proteins were found to be differentially expressed between the DS and normal cases, where 6 of the proteins were unique to the DS cases and 11 were unique to the chromosomally normal cases. In addition, in the DS cases, 19 AFS proteins were downregulated and 8 were upregulated to varying degrees. A Western blot analysis confirmed the LC-ESI-MS/MS data, indicating that the combined detection of apolipoprotein A-II (apoA-II) and alpha-fetoprotein (AFP) could be a potential tool for diagnosing DS cases.

• 암석학회지
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• 제10권3호
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• pp.133-147
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• 2001

최근 기존 연대측정법의 한계를 극복하여 절대연령 측정 대상을 획기적으로 넓힐 수 있는 방법으로 개발되고 있는 단계적 용해에 의한 연대측정법을 국내 시료에 적용하여 이 방법에 의한 연대측정의 성공가능성에 대해 평가하여 보았다. 대상 시료는 옥천변성대 대전 남부지역 창리층의 함우라늄 흑색 점판암, 영남육괴 북동부의 선캠브리아 내덕리 화강암에서 분리한 전기석 및 옥방광산의 회중석 등을 선정하였다. 이들에 대한 단계적 용해를 위해 산의 종류와 시간을 달리하여 점차 그 세기를 늘려가며 납을 용출시켰으며, 각 단계에서 얻은 용액들에 대해 납 등위원소 비율과 함께 납과 우라늄 함량을 열이온화 질량분석기로 측정하였 다. 그 결과 창리층 혹색 점판암과 내덕리 화강암으로부터는 상당한 Pb 동위원소 값의 분산을 얻을 수 있었으며 단계적 용해에 의한 Pb-Pb 연대측정이 성공적일 수 있음을 보여준다. 단계적 용해 과정에서 시료의 종류마다 우라늄과 납의 거동이 다르며 이는 구성 광물의 종류에 따라 우라늄과 납이 차지하는 결정 내에서의 위치에 지배되는 것으로 판단된다.

• 전기학회논문지
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• 제66권4호
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• pp.659-665
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• 2017

Power semiconductor devices required the low on-resistance and high breakdown voltage. Wide band-gap materials opened a new technology of the power devices which promised a thin drift layer at an identical breakdown voltage. The diamond had the wide band-gap of 5.5 eV which induced the low power loss, high breakdown capability, low intrinsic carrier generation, and high operation temperature. We investigated the p-type pseudo-vertical diamond Schottky barrier diodes using a numerical simulation. The impact ionization rate was material to calculating the breakdown voltage. We revised the impact ionization rate of the diamond for adjusting the parallel-plane breakdown field at 10 MV/cm. Effects of the field plate on the breakdown voltage was also analyzed. A conventional diamond Schottky barrier diode without field plate exhibited the high forward current of 0.52 A/mm and low on-resistance of $1.71{\Omega}-mm$ at the forward voltage of 2 V. The simulated breakdown field of the conventional device was 13.3 MV/cm. The breakdown voltage of the conventional device and proposed devices with the $SiO_2$ passivation layer, anode field plate (AFP), and cathode field plate (CFP) was 680, 810, 810, and 1020 V, respectively. The AFP cannot alleviate the concentration of the electric field at the cathode edge. The CFP increased the breakdown voltage with evidences of the electric field and potential. However, we should consider the dielectric breakdown because the ideal breakdown field of the diamond is higher than that of the $SiO_2$, which is widely used as the passivation layer. The real breakdown voltage of the device with CFP decreased from 1020 to 565 V due to the dielectric breakdown.

• Journal of Microbiology and Biotechnology
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• 제28권7호
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• pp.1094-1104
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• 2018

The peel of astringent persimmon (Diospyros kaki Thunb. cv. Cheongdo-Bansi) is a by-product of dried persimmon (gotgam). We investigated if deastringent peel extracts of persimmon cv. Cheongdo-Bansi had antioxidative and neuroprotective properties. Two different extracts were prepared: thermally and nonthermally treated persimmon peel extracts (TPE and NTPE, respectively). Both TPE and NTPE were fractionated sequentially in n-hexane, chloroform, ethyl acetate, n-butanol, and water. The TPE and NTPE ethyl acetate fractions had the highest total phenolic and flavonoid contents as well as antioxidant capacities among all the fractions. Pretreatment of neuronal PC-12 and SH-SY5Y cells with the TPE and NTPE ethyl acetate fractions increased cell viability after exposure to oxidative stress. The ethyl acetate fraction of TPE attenuated oxidative stress inside both PC-12 and SH-SY5Y cells more effectively than that of NTPE. Furthermore, the TPE and NTPE ethyl acetate fractions inhibited acetylcholinesterase and butyrylcholinesterase. Analysis of ultra-high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry results revealed gallic acid, kaempferol, kaempferol-3-O-galactoside, kaempferol-3-O-glucoside, quercetin, quercetin3-O-galactoside, quercetin-3-O-galactoside-2'-O-gallate, and quercetin-3-O-glucoside as the major phenolics of the TPE and NTPE ethyl acetate fractions. Taken together, these results suggest that the ethyl acetate fraction of deastringent persimmon peel is rich in antioxidants and has potential as a functional food to reduce oxidative stress.

• Bulletin of the Korean Chemical Society
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• 제23권8호
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• pp.1139-1143
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• 2002

Analysis of lysophosphatidic acids (LPAs) is of clinical importance as they can serve a potential marker for ovarian and other gynecological cancers and obesity. It is critically important to develop a highly sensitive and specific method for the early detection of gynecological cancers to improve the overall outcome of this disease. We have established a novel quantification method of LPAs in human plasma by negative ionization tandem mass spectrometry (MS-MS) using multiple reaction monitoring (MRM) mode without the conventional TLC step. Protein-bound lipids, LPAs in plasma were extracted with methanol : chloroform (2:1) containing LPA C14:0 as an internal standard under acidic condition. Following back extraction with chloroform and water, the centrifuged lower phase was evaporated and reconstituted in methanol. The reconstituted solution was directly injected into electrospray source of MS/MS. For MRM mode, Q1 ions selected were m/z 409, 433, 435, 437 and 457 which corresponds to molecular mass [M-H]- of C16:0, C18:2, C18:1, C18:0 and C20:4 LPA, respectively. Q2 ions selected for MRM were m/z 79, phosphoryl product. Using MS/MS with MRM mode, all the species of LPAs were completely separated from plasma matrix without severe interferences. This method allowed simultaneous detection and quantification of different species of LPAs in a plasma over a linear dynamic range of 0.01-25 ㎛olL-1 . The detection limit of the method was 0.3 pmol/mL, with a correlation coefficient of 0.9983 in most LPAs analyzed. When applied to the plasmas of normal and gynecological cancer patients, this new method differentiated two different groups by way of total LPA level.

• International Journal of Oral Biology
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• 제34권1호
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• pp.29-36
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• 2009

Cyclosporin A (CsA) has been used clinically as an immunosuppressive drug to prevent organ transplant rejection and in basic research as a mitochondrial permeability blocker. It has been reported that CsA has a protective role in severed neurons and a neurotrophic effect in neuronal cells. However, the molecular mechanisms underlying the stimulation of neuronal cell proliferation by CsA have not yet been elucidated. In our current study, we investigated CsA responsive proteins in PC12 cells using a systematic proteomic approach. The viability of these cells following CsA treatment increased in a dose- and time-dependent manner. Proteins in the CsA-treated PC12 cells were profiled by two-dimensional gel electrophoresis (2-DE) and identified by matrix-assisted laser desorption ionization time-of flight (MALDI-TOF) and electrospray ionization quadupole time-of-flight mass spectrometries (EIQ-TOFMS). This differential expression analysis showed significant changes for 10 proteins (6 up-regulated and 4 down-regulated) upon CsA treatment that were related to cell proliferation, metabolism and the stress response. These proteomics data further our understanding of the proliferation mechanisms of PC12 cells exposed to CsA and demonstrate that our methodology has potential to further elucidate the mechanisms and pathways involved.

• Journal of Microbiology and Biotechnology
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• 제29권4호
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• pp.548-557
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• 2019

Staphylococcus species have a ubiquitous habitat in a wide range of foods, thus the ability to identify staphylococci at the species level is critical in the food industry. In this study, we performed rapid identification of Staphylococcus species using Matrix-Assisted Laser Desorption/Ionization Time-of-Flight mass spectrometry (MALDI-TOF MS). MALDI-TOF MS was evaluated for the identification of Staphylococcus reference strains (n = 19) and isolates (n = 96) from various foods with consideration for the impact of sample preparation methods and incubation period. Additionally, the spectra of isolated Staphylococcus strains were analyzed using principal component analysis (PCA) and a main spectra profile (MSP)-based dendrogram. MALDI-TOF MS accurately identified Staphylococcus reference strains and isolated strains: the highest performance was by the EX method (83.3~89.5% accuracy) at species level identification (EDT, 70.3~78.9% accuracy; DT, less than 46.3~63.2% accuracy) of 24-h cultured colonies. Identification results at the genus level were 100% accurate at EDT, EX sample preparation and 24-h incubation time. On the other hand, the DT method showed relatively low identification accuracy in all extraction methods and incubation times. The analyzed spectra and MSP-based dendrogram showed that the isolated Staphylococcus strains were characterized at the species level. The performance analysis of MALDI-TOF MS shows the method has the potential ability to discriminate between Staphylococcus species from foods in Korea. This study provides valuable information that MALDI-TOF MS can be applied to monitor microbial populations and pathogenic bacteria in the food industry thereby contributing to food safety.