• Carbon letters
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• 제15권1호
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• pp.57-66
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• 2014

Three activated carbons (ACs) were prepared using NaOH (N) as an activating agent. Hydrofluoric acid pre-leached rice husk was used as a precursor. After leaching, the precursor was washed with distilled water, dried, crushed, and then sieved; a size fraction of 0.3-0.5 mm was selected for carbonization in the absence of air at $600^{\circ}C$. The carbonization product (LC) was mixed with NaOH at ratios of 1:2, 1:3, and 1:4 (wt of LC: wt of NaOH) and the produced ACs after activation at $800^{\circ}C$ were designated NLC21, NLC31, and NLC41, respectively. Surface and textural properties were determined using nitrogen adsorption at $-196^{\circ}C$, scanning electron microscopy images, thermogravimetric analysis, and Fourier transform infrared spectra. These ACs were used as adsorbents for lead(II) from aqueous solutions. The effects of the textural properties and the chemistry of the carbon surfaces were investigated and the impact of the operation conditions on the capacity for lead(II) sorption was also considered. Modification of NLC41 with $H_2O_2$ and $HNO_3$ gave two other adsorbents, $H_{NLC41}$ and $N_{NLC41}$ respectively. These two new samples exhibited the highest removal capacities for lead(II), i.e.117.5 and 128.2 mg/g, respectively. The adsorption data fitted the Langmuir isotherm and the kinetic adsorption followed pseudo-second order kinetics. The thermodynamic parameters have been determined and they indicated a spontaneous endothermic process.

• 한국재료학회지
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• 제19권5호
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• pp.233-239
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• 2009

The electrocatalytic behavior of the PtCo catalyst supported on the multi-walled carbon nanotubes (MWNTs) has been evaluated and compared with commercial Pt/C catalyst in a polymer electrolyte membrane fuel cell(PEMFC). A PtCo/MWNTs electrocatalyst with a Pt:Co atomic ratio of 79:21 was synthesized and applied to a cathode of PEMFC. The structure and morphology of the synthesized PtCo/MWNTs electrocatalysts were characterized by X-ray diffraction and transmission electron microscopy. As a result of the X-ray studies, the crystal structure of a PtCo particle was determined to be a face-centered cubic(FCC) that was the same as the platinum structure. The particle size of PtCo in PtCo/MWNTs and Pt in Pt/C were 2.0 nm and 2.7 nm, respectively, which were calculated by Scherrer's formula from X-ray diffraction data. As a result we concluded that the specific surface activity of PtCo/MWNTs is superior to Pt/C's activity because of its smaller particle size. From the electrochemical impedance measurement, the membrane electrode assembly(MEA) fabricated with PtCo/MWNTs showed smaller anodic and cathodic activation losses than the MEA with Pt/C, although ohmic loss was the same as Pt/C. Finally, from the evaluation of cyclic voltammetry(CV), the unit cell using PtCo/MWNTs as the cathode electrocatalyst showed slightly higher fuel cell performance than the cell with a commercial Pt/C electrocatalyst.

• 폴리머
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• 제26권4호
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• pp.477-482
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• 2002

페놀수지 원료에 인산 경화제를 사용하여 유리상탄소를 제조할 때, 활성화제인 KOH를 첨가하여 미세구조를 제어하였다. KOH의 첨가량에 따라 수율 및 물성을 조사하였다. KOH를 첨가하지 않고 제조한 유리상탄소는 미세기공을 거의 포함하지 않지만, KOH의 첨가량이 증가될수록 미세구조가 발달하여 KOH/페놀수지 비가 0.9에서 비표면적율 870 $m^2/g$정도까지 증가시킨 다공질의 유리상탄소를 얻을 수 있었다. 탄화수율은 KOH의 첨가량이 증가될수록 감소하여 40% 수준에서 15%까지 떨어졌고, 전기비저항은 50${\times}$$10^{-4}$에서 60${\times}$$10^{-4}$$\Omega$.cm으로 약간 증가하였으며, 물 속에서 측정한 겉보기 밀도는 1.5에서 0.9g/$cm^3$까지 감소하였다.

• 농업과학연구
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• 제36권1호
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• pp.41-50
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• 2009

Fucoidan is a uniquely-structured sulfated fucose-rich polysaccharide derived from brown algae. Recently, the abalone glycosidase-digested fucoidan extract (fucoidan extract) derived from seaweed Cladosiphon novae-caledoniae Kylin (Mozuku) draws much attention because of its clinical anti-cancer effect in Japan. Here, we report the cancer cells-specific apoptosis inducing effects of the fucoidan extract. The fucoidan extract suppressed the growth of various anchorage-dependent and -independent cancer cells. The fucoidan extract contained low molecular weight components, which induced apoptosis of human leukemic HL 60 cells but not of human lymphocytes. It was shown that the fucoidan extract lead caspase 3/7 activation and loss of mitochondrial membrane potential in HL 60 cells. Another function of the fucoidan extract was also observed. It has been known that sugar chain expression on the surface of cancer cell membrane changes dependent on their malignancy. The analysis on sugar chain expression profiling using FITC-labeled lectins revealed that the expression of concanavalin A (Con A) binding sugar chain was enhanced by the treatment of human lung adenocarcinoma A549, human uterine carcinoma HeLa and human fibrosarcoma HT1080 cells with the fucoidan extract. Con A-induced apoptosis of cancer cells was stimulated in a dose-and time-dependent manner by the treatment with the fucoidan extract but not of human normal fibroblast TIG-1 cells.

• Restorative Dentistry and Endodontics
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• 제26권2호
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• pp.180-187
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• 2001

The structure of current guides is largely illogical and without any rational use of color ordering. The shade guides are generally made of plastic (rather than the actual composite material) and do not accurately depict the true shade. translucency. or opacity of the composite resin after polymerization. To solve this problem, information based on evaluations of natural teeth and material that use the same method and experimental conditions is necessary. The present investigation measured the color of natural maxillary anterior teeth in vivo and compared the results with those of composite resins. 269 Korean subjects were selected for this study. Intact central incisor. lateral incisor. and canine were selected. The clinical crowns were free of caries or restorations. The middle site of the coronal portion on the labial surface of the tooth was measured by Chroma Meter. The five light activated. resin-based materials (Amelogen, Denfil, Elitefil, Spectrum, Z100) were used in this study. Resin composite was condensed into plastic mold with a diameter of 8mm and a thickness of 4mm. pressed between glass plates to flatten the surfaces. and polymerized using a Visilux II visible light activation unit. The surfaces were polished sequentially on wet sandpaper. Color measurements of each specimen were accomplished by Chroma Meter. A computer program that compares each tooth color with each composite resin color was written and the minimum CIELAB color difference ($\Delta$E$^*$) between tooth and each material was calculated. Under the conditions of this study: 1. Teeth tend to become darker with advancing age. 2. Canines were darker. more yellow. and less green than incisors. 3. The teeth from the women were lighter. more green. and less yellow than the male teeth. 4. In general. composite resins were lighter. more green. and less yellow than teeth. Deficiencies were noted in Hues in YR range. 5. Mean color differences between the five composite resin products and teeth were detectable to the naked eye($\Delta$E$^*$>1.0). 6. In comparing the mean $\Delta$E$^*$ values of materials. Spectrum showed the least followed by Z100, Elitefil, Amelogen, Denfil in increasing order.

• 한국자기학회지
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• 제3권4호
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• pp.298-304
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• 1993

Pd/Co 다층박막을 동시열증착장치로 제작하여, 토오크 자력계, 홀 효과 측정장치 및 X-선 회절기를 이용하여 기판 온도, Pd하지층에 따른 구조적 자기적 및 열적 특성변화를 연구하였다. 기판 온도가 증가함에 따라 $150^{\circ}C$까지는 계면구조 및 각 층의 결정성이 향상되고, (111) 집합조직이 발달되었으며 따라서 계면자기이방성 및 수직자기 이방성에너지는 증가하였다. 그러나 보자력은 감소 하였는데 이는 입자의 성장으로 인한 자구벽 고착효과 감소에 기인된 것으로 보이며 Pd하지층이 두꺼 울 수록 다층박막의 입자크기는 컸다. $200^{\circ}C$ 이상에서는 계면에서 상호확산에 의하여 다층막의 구조의 열화는 촉진되었다. 열처리 초기에 주 피이크 강도의 변화는 컸으며 그 후부터는 작은 폭으로 감소하였다. 초기의 큰 강도 변화는 구조이완등의 현상에 기인된 것으로 추측되며 그 후는 확산에 의 해서이다. 다층박막의 상호확산에 필요한 활성화 에너지는 14.9 KCal/mole.K 였다.

• Applied Biological Chemistry
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• 제26권1호
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• pp.1-7
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• 1983

일반 품종(아끼바레와 밀양 15) 및 다수확품종(밀양 30, 수원 287, 수원 294와 이리 342)의 벼를 무게비로 8% 도정하고, 쌀을 온도 $4{\sim}32^{\circ}C$에서 $5{\sim}50$분간 침지시키면서 수화속도를 비교하였다. 침지시간 50분후의 쌀의 평형 수분함량은 아끼바레와 밀양 15가 30%내외, 수원 287과 밀양 30이 29%내외이었고, 수원 294와 이리 342는 다소 낮은 값을 보였다. 물의 확산계수는 아끼바레는 밀양 14와, 밀양 30은 수원 287과, 수원 294는 이리 342와 비슷한 값을 보였다. 확산계수는 밀양 30과 수원 287이 가장 컸으며, 수원 294와 이리 342가 가장 작았다.

• 대한의용생체공학회:의공학회지
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• 제27권3호
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• pp.131-141
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• 2006

A visual decision by clinical experts like physical therapists is a best way to detect onset and offset time of muscle activation. The current computer-based algorithms are being researched toward similar results of clinical experts. The new algorithm in this paper has an ability to extract a trend from noisy input data. Kalman smoother is used to recognize the trend to be revealed from disorderly signals. Histogram of smoothed signals by Kalman smoother has a clear boundary to separate muscle contractions from relaxations. To verify that the Kalman smoother algorithm is reliable way to detect onset and offset time of muscle contractions, the algorithm of Robert P. Di Fabio (published in 1987) is compared with Kalman smoother. For 31 templates of subjects, an average and a standard deviation are compared. The average of errors between Di Fabio's algorithm and experts is 109 milliseconds in onset detection and 142 milliseconds in offset detection. But the average between Kalman smoother and experts is 90 and 137 milliseconds in each case. Moreover, the standard deviations of errors are 133 (onset) and 210 (offset) milliseconds in Di Fabio's one, but 48 (onset) and 55 (offset) milliseconds in Kalman smoother. As a result, the Kalman smoother is much closer to determinations of clinical experts and more reliable than Di Fabio's one.

• 한국생물물리학회:학술대회논문집
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• 한국생물물리학회 2003년도 정기총회 및 학술발표회
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• pp.29-29
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• 2003

Compartmentation of intracellular signaling pathways serves as an important mechanism conferring the specificity of G protein-coupled receptor (GPCR) signaling. In the heart, stimulation of $\beta$$_2$-adrenoceptor ($\beta$$_2$-AR), a prototypical GPCR, activates a tightly localized protein kinase A (PKA) signaling, which regulates substrates at cell surface membranes, bypassing cytosolic target proteins (eg, phospholamban). Although a concurrent activation of $\beta$$_2$-AR-coupled $G_{i}$ proteins has been implicated in the functional compartmentation of PKA signaling, the exact mechanism underlying the restriction of the $\beta$$_2$-AR-PKA pathway remains unclear. In the present study, we demonstrate that phosphatidylinositol 3-kinase (PI3K) plays an essential role in confining the $\beta$$_2$-AR-PKA signaling. Inhibition of PI3K with LY294002 or wortmannin enables $\beta$$_2$-AR-PKA signaling to reach intracellular substrates, as manifested by a robust increase in phosphorylation of phospholamban, and markedly enhances the receptor-mediated positive contractile and relaxant responses in cardiac myocytes. These potentiating effects of PI3K inhibitors are not accompanied by an increase in $\beta$$_2$-AR-induced cAMP formation. Blocking $G_{i}$ or $G_{$\square$$\square$}$ signaling with pertussis toxin or $\beta$ARK-ct, a peptide inhibitor of $G_{$\square$$\square$}$, completely prevents the potentiating effects induced by PI3K inhibition, indicating that the pathway responsible for the functional compartmentation of $\beta$$_2$-AR-PKA siglaling sequentially involves $G_{i}$, $G_{$\square$$\square$}$, and PI3K. Thus, PI3K constitutes a key downstream event of $\beta$$_2$-AR- $G_{i}$ signaling, which confines and negates the concurrent $\beta$$_2$-AR/Gs-mediated PKA signaling.gnaling.

• Preventive Nutrition and Food Science
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• 제12권4호
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• pp.242-250
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• 2007

This study evaluated the storage stability of a variety of sauce products in the Korean market, determined primary quality indices for three typical products, and proposed functional relationships that are useful for determining shelf life at different temperatures. Most of the products examined were found to combine hurdles of low pH, low water activity, and the use of heat processing as methods for producing the required storage stability while maintaining the sensory quality of the products. For a meat extract solution produced for cold noodles (pH=4.3; $a_w=0.98$), the primary quality change determining shelf life was lipid oxidation, determined here by the TBA value. The primary quality index of a soybean paste seasoning mix (pH=4.0; $a_w=0.78$), which had a microbial load of 2.8 log (CFU/g), was a decrease in its pH. The primary quality index for a sandwich spread (pH=4.0; $a_w=0.88$) was changes in its surface color. The temperature dependence of changes in the primary quality indices can be described by the Arrhenius equation, which can estimate the shelf life at any arbitrary limit as a function of temperature. The activation energies for changes in the primary quality indices of the meat extract solution, the soybean paste seasoning, and the sandwich spread were 20.3, 27.2, and 43.5 kJ/mol, respectively.