• 센서학회지
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• 제27권4호
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• pp.237-241
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• 2018

The real-time enrichment and detection of pathogens are serious issues and rapidly evolving field of research because of the ability of these pathogens to cause infectious diseases. In general, bacterial detection is accomplished by conventional colony counting or by polymerase chain reaction (PCR) after DNA extraction. As colony counting requires considerable time to cultivate, PCR is an attractive method for rapid detection. A small number of pathogens can cause diseases. Hence, a pretreatment process, such as enrichment is essential for detecting bacteria in an actual environment. Thus, in this study, we developed a microfluidic chip capable of performing rapid enrichment of bacteria and the extraction of their genes. A lectin, i.e., Concanavalin A (ConA), which shows binding affinity to the surface of most bacteria, was coated on the surface of magnetic particles to nonspecifically capture bacteria. It was subsequently concentrated through magnetic forces in a microfluidic channel. To lyse the captured bacteria, magnetic particles were irradiated by a wavelength of 532nm. The photo-thermal effect on the particles was sufficient for extracting DNA, which was consequently utilized for the identification of bacteria. Our device will help monitor the existence of bacteria in various environmental situations such as water, air, and soil.

• 한국물환경학회지
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• 제22권6호
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• pp.991-995
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• 2006

The layered double hydroxide with the insertion of chloride ions (LDH-Cl), which was synthesized by the co-precipitation method, was applied to investigate the fundamental aspects of the absorptive agent for phosphate removal from wastewater. The adsorption capacity was best described by the Langmuir-FreundIich isotherm, and the estimated isotherm parameters indicate that the LDH-CI capacity for the phosphate removal is much higher than that observed using a natural adsorbent material such iron oxide tailing. The kinetic experiment also showed that the LDH-Cl adsorption reaction rapidly at the adsorptive rate of 0.55 mg-P/g-LDH/min, implying that this adsorbent can be of use in the full-scale applications. The pH had a minimal effect on the LDH adsorption capacity in the range of 5 to 11, although the capacity dropped at the low pHs because of the change in LDH surface properties. Furthermore, other anions such as $Cl^-$ and $NO_3{^-}$ commonly found in the wastewater streams insignificantly affected the phosphate removal efficiencies, while $HCO_3{^-}$ ions had a negative effect on the LDH adsorption capacity due to its high selectivity. The phosphate removal experiment using the actual secondary effluent from a wastewater treatment plant showed the similar decrease in adsorption capacity, indicating that the bicarbonate ions in the wastewater were competing with phosphate for the adsorptive site in the surface of the LDH-Cl. Overall, the synthetic adsorbent material, LDH-Cl, can be a feasible alternative over other conventional chemical agents, since the LDH-Cl exhibits the high phosphate removal capacity with the low sensitivity to other environmental conditions.

• 한국전기전자재료학회논문지
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• 제25권1호
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• pp.29-32
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• 2012

Lead-free $0.98(Na_{0.5},K_{0.5})NbO_3-0.02Li(Sb_{0.17}Ti_{0.83})O_3$ (hereafter 0.98NKN-0.02LST) ceramics doped with $Ag_2O$ were prepared using a conventional mixed oxide method. The specimen showed superior structural and electrical properties when 1 mol% $Ag_2O$ was doped. For the 0.98NKN-0.02LST+1.0mol%$Ag_2O$ ceramics sintered at $1,100^{\circ}C$, piezoelectric constant ($d_{33}$) of sample showed the optimum values of 207 pC/N. The 0.98NKN-0.02LST+1.0 mol%$Ag_2O$ ceramics are a promising candidate for lead-free piezoelectric materials.

• 한국전기전자재료학회논문지
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• 제26권5호
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• pp.355-359
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• 2013

In this paper, the $0.995(Li_{0.04}(Na_{0.56}K_{0.44})_{0.96}(Nb_{0.90}Ta_{0.10})_{0.998}Zn_{0.005}O_3+0.005KNbO_3+xwt%\;TeO_2$ lead-free piezoelectric ceramics for energy harvesting devices were fabricated by the conventional mixed oxide method. The microstructure, dielectric, and piezoelectric properties were investigated as a function of the $TeO_2$ addition. All the specimens showed an orthorhombic phase structure. At the composition ceramics doped with 0.1 wt%$TeO_2$, the optimum values of $d_{33}$= 212 pC/N, $d_{33}{\cdot}g_{33}=9.54pm^2/N$, and kp=0.448 were obtained, respectively. The results indicate that the composition ceramics is a promising candidate for energy harvesting devices applications.

• Preventive Nutrition and Food Science
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• 제22권2호
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• pp.107-117
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• 2017

The purpose of this study was to evaluate the antioxidant and anticholinesterase activities of yellow and white bitter yams from South Western Nigeria using methanolic extraction and simulated gastrointestinal digestion models. The phenolic compounds in the bitter yam varieties were evaluated by high performance liquid chromatography with a diode array detector (HPLC-DAD). The total phenolic content of the bitter yams was measured by the Folin-Ciocalteu method, reductive potential by assessing the ability of the bitter yam to reduce $FeCl_3$ solution, and the antioxidant activities were determined by the 2,2-diphenyl-1-picrylhydrazyl radical ($DPPH^{\cdot}$) scavenging activity, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation ($ABTS^{{\cdot}+}$) scavenging activity, nitric oxide radical ($NO^{\cdot}$) scavenging ability, hydroxyl radical scavenging ability, and ability to inhibit $Fe^{2+}$-induced lipid oxidation. The HPLC-DAD analysis revealed the presence of some phenolic compounds in the studied bitter yam varieties, with varying degree of quantitative changes after cooking. The antioxidant indices (total phenolic content, total flavonoid content, reducing power, $DPPH^{\cdot}$ scavenging activity, $ABTS^{{\cdot}+}$ scavenging activity, and $NO^{\cdot}$ scavenging activity) were higher in the simulated gastrointestinal digestion model compared to the methanolic extract, with the in vitro digested cooked white bitter yam ranking higher. Similarly, the in vitro digested yams had a higher inhibitory action against lipid oxidation compared to the methanolic extracts, with the cooked white bitter yam ranking high. The methanolic extracts and in vitro enzyme digests showed no acetylcholinesterase inhibitory abilities, while methanolic extracts and the in vitro enzyme digest displayed some level of butyrylcholinesterase inhibitory activities. Therefore the studied bitter yams could be considered as possible health supplements.

• 전기학회논문지
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• 제57권7호
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• pp.1208-1212
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• 2008

In this study, both structural and microwave dielectric properties of the $Ba_5B_4O_{15}$ (B=Ta, Nb) cation-deficient perovskite ceramics with sintering temperature were investigated. All samples of the $Ba_5B_4O_{15}$ (B=Ta, Nb) ceramics were prepared by the conventional mixed oxide method and sintered at $1325^{\circ}C{\sim}1575^{\circ}C$. The bulk density and dielectric constant of the $Ba_5Ta_4O_{15}$ ceramics were increased continuously with increasing of sintering temperature. The quality factor of the $Ba_5Ta_4O_{15}$ ceramics was increased in as the sintering temperature increases from $1375^{\circ}C{\sim}1475^{\circ}C$ but decreased at the temperatures above $1475^{\circ}C$. And the bulk density, dielectric constant and quality factor of the $Ba_5Nb_4O_{15}$ ceramics were increased in as the sintering temperature increases from $1325^{\circ}CP{\sim}1400^{\circ}C$ but decreased at the temperatures above $1400^{\circ}C$. In the case of the $Ba_5Ta_4O_{15}$ sintered at $1475^{\circ}C$ and $Ba_5Nb_4O_{15}$ ceramics sintered at $1400^{\circ}C$, the dielectric constant, quality factor, and temperature coefficient of the resonant frequency (TCRF) were 25.15, 53,105 GHz, -3.06 $ppm/^{\circ}C$ and 39.55, 28,052 GHz, +5.7 ppm/$^{\circ}C$, respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 일렉트렛트 및 응용기술
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• pp.112-116
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• 2002

The $0.95MgTiO_3-0.05SrTiO_3$ ceramics with $V_2O_5$(10wt%) were prepared by the conventional mixed oxide method. The structural properties were investigated with sintering temperatue by XRD. According to the X-ray diffraction pattern of the $0.95MgTiO_3-0.05SrTiO_3$ ceramics with $V_2O_5$(10wt%), the ilmenite $MgTiO_3$ and perovskite $SrTiO_3$ structures were coexisted and secondary phase $MgTi_2O_5$ were appeared. In the case of $0.95MgTiO_3-0.05SrTiO_3$ ceramics with $V_2O_5$(10wt%), dielectric constant, quality factor and temperature coefficient of resonant frequency were 15.84~18.28, 12627~23138GHz, -21.414~1.568$ppm/^{\circ}C$, respectively.

• 한국전기전자재료학회논문지
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• 제14권3호
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• pp.197-201
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• 2001

The microwave dielectric properties of (1-x)Ba(Mg$_{1}$3/Ta$_{2}$3/)O$_3$-xBa(Co$_{1}$3/Nb$_{2}$3)O$_3$(x=0.25~0.5) ceramics depending on the Ba(Co$_{1}$3/Nb$_{2}$3/)O$_3$[BCN] contents and the possibility of application as a microwave dielectric resonator were investigated. The specimens were prepared by he conventional mixed oxide method using there sintering temperature of 1575$^{\circ}C$. It was found that Ba(Mg$_{1}$3/Ta$_{2}$3/)O$_3$[BMT] and BCN formed a solid solution with complex perovskite structure. As the mole fraction of BCN increased, dielectric constant increased while temperature coefficient of resonant frequency decreased. The highest value of quality factor, Qxf$_{0}$=138,205GHz, obtained in the sample of 0.9BMT-0.1BCN ceramics. In the range of x$\geq$0.4, the dielectric constant was about 30. The 0.55BMT-0.45BCN ceramics showed excellent microwave dielectric properties with $\varepsilon$$_{r}$=30.84, Qxf$_{0}$=75,325GHz and $\tau$$_{f}$=2.9015ppm/$^{\circ}C$.EX>.EX>.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1485-1487
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• 2002

The 0.96Mg$TiO_3$-0.04Sr$TiO_3$ ceramics with $V_2O_5$(5wt%) were prepared by the conventional mixed oxide method. The structural properties were investigated with sintering temperature by XRD and SEM. According to the X-ray diffraction patterns of the 0.96Mg$TiO_3$-0.04Sr$TiO_3$ceramics with $V_2O_5$(5wt%), the ilmenite $MgTiO_3$ and perovskite $SrTiO_3$ structures were coexisted and secondary phase $MgTi_2O_5$ were appeared. Increasing the sintering temperature, the grain size was increased and three types of grains were exhibited: larger circular grain, small square grain and lapth-shaped grain. In the case of 0.96Mg$TiO_3$-0.04Sr$TiO_3$ ceramics with $V_2O_5$(10wt%), dielectric constant, quality factor and temperature coefficient of resonant frequency were $15.24{\sim}18.55$, $22,890{\sim}42,100$GHz, -24.5${\sim}$+2.414ppm/$^{\circ}C$, respectively.

• 한국표면공학회지
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• 제40권3호
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• pp.117-124
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• 2007

The ITO films were deposited on glass substrates by RF-superimposed dc reactive magnetron sputtering and were annealed in $N_2$ vacuum furnace with temperatures in the range of $403K{\sim}573K$ for 30 minutes. Electrical, optical and structural properties of ITO films were examined with varying annealing temperatures from 403 K to 573 K. The resistivity of as-deposited ITO films was $5.4{\times}10^{-4}{\Omega}cm$ at the sputter conditions of applied RF/DC power of 200/200 W, $O_{2}$ flow of 0.2 seem and Ar flow of 0.2 seem. As a result of annealing in the temperature range of $403K{\sim}573K$, the crystallization occurred at 423 K that is lower than the crystallization temperature caused by a conventional sputtering method. And the resistivity decreased from $5.4{\times}10^{-4}{\Omega}cm\;to\;2.3{\times}10^{-4}{\Omega}cm$, the carrier concentration and mobility of ITO films increased from $4.9{\times}10^{20}/cm^3\;to\;6.4{\times}10^{20}/cm^3$, from $20.4cm^2/Vsec\;to\;41.0cm^2/Vsec$, respectively. The transmittance of ITO films in visible became higher than 90% when annealed in the temperature range of $423K{\sim}573K$. High quality ITO thin films made by RF-superimposed dc reactive magnetron sputtering and annealing in $N_2$ vacuum furnace will be applied to transparent conductive oxides of the advanced flat panel display.