• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
• /
• pp.207.1-207.1
• /
• 2013

Tantalum oxide has been extensively investigated as one of the promising Resistive switching materials applicable to Resistive Dynamic Access Memories. Impedance spectroscopy offers simultaneous measurements of electrical and dielectric information, separation of electrical origins among bulk, grain boundaries, and interfaces, and the monitoring of electrical components. Such benefits have been combined with the resistive states of resistive switching devices which can be described in terms of equivalent circuits involving resistors, capacitors, and inductors, The current work employed pulsed laser deposition in order to prepare the oxygen-deficient tantalum oxide. The fabricated devices were controlled between highresistance and low-resistance states in controlled current compliance modes. The corresponding electrical phenomena were monitored both in the dc-based current-voltage characteristics and in the ac-based impedance spectroscopy. The origins of the electrical switching are discussed towards optimized ReRAM devices in terms of interfacial effects.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2016년도 추계학술대회 논문집
• /
• pp.59-75
• /
• 2016

Reduced or black $TiO_{2-x}$ materials with oxygen-deficiency have been achieved by creating oxygen vacancies and/or defects at the surface using different methods. Fascinatingly, they exhibited an extended absorption in VIS and IR instead of only UV light with bandgap decrease from 3.2 (anatase) to ~1 eV. However, despite the dramatic enhancement of optical absorption in black $TiO_{2-x}$ materials, they have failed to show expected visible light-assisted water splitting efficiency. This was ascribed to the high concentration of the surface defects and/or oxygen vacancies, considered as an electron donor to enhance donor density and improve the charge transportation in black $TiO_2$ can also act as charge recombination centers, which eventually decrease photocatalytic activity. Therefore, a black ot reducd $TiO_2$ material with optimized properties would be highly desired for visible light photocatalysis. In this report, a new controlled magnesiothermic reduction has been developed to synthesize reduced black $TiO_{2-x}$ in the presence $H_2/Ar$ for photocatalytic $H_2$ production from methanol-water system. The material possesses an optimum band gap and band position, oxygen vacancies, and surface defects and shows significantly improved optical absorption in the visible and infrared region. The synergistic effects enable the reduced $TiO_{2-x}$ material to show an excellent hydrogen production ability along with long-term stability under the full solar wavelength range of light and visible light, respectively, in the methanol-water system in the presence of Pt as a co-catalyst. These values are superior to those of previously reported black $TiO_2$ materials. On the basis of all the results, it can be realized that the outstanding activity and stability of the reduced of $TiO_{2-x}$ NPs suggest that a balanced combination of different factors like $Ti^{3+}$, surface defects, oxygen vacancy, and recombination center is achieved along with optimized bandgap and band position during the preparation employing magnesiothermic reduction in the presence of $H_2$. The controlled magnesiothermic reduction in the presence of $H_2$ is one of the best alternative ways to produce active and stable $TiO_2-based$ photocatalyst for $H_2$ production.

• 공업화학
• /
• 제22권2호
• /
• pp.185-189
• /
• 2011

본 연구에서는 화학적 공침법을 적용하여 가스상 이산화탄소 분해를 위한 나노크기의 M-페라이트(M=Co, Ni, Cu, Zn)를 제조하였다. 열중량 분석 결과, 시험제조한 모든 시료의 최고 무게 감소율은 $350^{\circ}C$ 미만에서 발생하였다. 소성온도가 증가할수록 결정형은 우수하여 표면촉매활성화를 기대할 수 있지만, 입자결정의 크기가 크고, 비표면적이 낮은 페라이트가 합성됨을 알 수 있었다. FT-IR 분석으로부터 $375{\sim}406cm^{-1}$의 범위에서 octahedral site에 착화물이 존재함을 확인 할 수 있었으며, 이는 페라이트 내 스피넬 구조가 형성되어 있음을 보여주는 것이라고 믿는다. 본 연구로부터 얻은 이산화탄소 분해반응을 위한 금속페라이트의 최적 열처리 온도는 $500^{\circ}C$인 것으로 나타났다.

• 한국해양생명과학회지
• /
• 제2권2호
• /
• pp.62-69
• /
• 2017

양식업이 발달한 통영 오비도 주변해역에서 하계 해양환경요인의 변화 특성과 그에 따른 식물플랑크톤의 변화양상을 파악하여, 가두리 양식 생물에 미칠 수 있는 잠재적인 환경요인을 분석하였다. 조사는 2개의 정점에서 2016년 6월부터 9월까지 격주로 4개월간 수행되었다. 6월과 7월은 강한 수온 성층이 형성되었으며, 8월에는 특이적으로 강한 양쯔강 희석수의 영향으로 8월 10일 29℃ 전후로 고수온이 관찰되었다. 조사기간 동안 질산염+아질산염, 암모늄, 인산염, 규산염은 각각 0.08~5.11 μM, 0.08~34.62 μM, 0.01~ 1.15 μM, 1.46~31.79 μM의 범위를 보였다. Chlorophyll a 농도는 0.49~7.39 ㎍ l^-1의 범위를 보였다. 9월의 빈번한 잦은 강우 및 양식어장에서 용출된 영양염류는 장시간 지속되지 못하고 빠르게 소비되거나 확산되었다. 이후 강우로 인한 영양염 유입과 함께 표층을 중심으로 Chaetoceros debilis, C. pseudocurvisetus, Pseudonitzschia delicatissima와 같은 규조류가 최대 4.74 × 10⁹ cells l^-1로 크게 증식하였다. 또한 용존산소 변동은 4.52~7.62 ㎍ l^-1로 식물플랑크톤 대증식 이후 조사에서 유기물질이 분해됨에도 불구하고 빈산소 수괴(< 4.00 mg l^-1)의 형성은 관찰되지 않았다. 따라서 본 해역은 하계의 식물플랑크톤 증식 및 가두리양식장이 밀집됨에도 불구하고, 다른 반폐쇄적 만과 달리 해류 순환이 원활한 특징으로 인해 빈산소 수괴는 나타나지 않았다.

• BMB Reports
• /
• 제53권4호
• /
• pp.218-222
• /
• 2020

Excessive and hyperactive osteoclast activity causes bone diseases such as osteoporosis and periodontitis. Thus, the regulation of osteoclast differentiation has clinical implications. We recently reported that dehydrocostus lactone (DL) inhibits osteoclast differentiation by regulating a nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1), but the underlying mechanism remains to be elucidated. Here we demonstrated that DL inhibits NFATc1 by regulating nuclear factor-κB (NF-κB), activator protein-1 (AP-1), and nuclear factor-erythroid 2-related factor 2 (Nrf2). DL attenuated IκBα phosphorylation and p65 nuclear translocation as well as decreased the expression of NF-κB target genes and c-Fos. It also inhibited c-Jun N-terminal kinase (JNK) but not p38 or extracellular signal-regulated kinase. The reporter assay revealed that DL inhibits NF-κB and AP-1 activation. In addition, DL reduced reactive oxygen species either by scavenging them or by activating Nrf2. The DL inhibition of NFATc1 expression and osteoclast differentiation was less effective in Nrf2-deficient cells. Collectively, these results suggest that DL regulates NFATc1 by inhibiting NF-κB and AP-1 via down-regulation of IκB kinase and JNK as well as by activating Nrf2, and thereby attenuates osteoclast differentiation.

• 생명과학회지
• /
• 제27권1호
• /
• pp.72-77
• /
• 2017

S. Typhimurium SL1344는 성장을 위한 보조인자로 무기철이 요구된다. 철 킬레이트제인 ethylenediamine di-o-hydroxyphenylactic acid (EDDA)가 첨가 된 M9 최소배지에서 S. Typhimurium은 성장에 있어 철 이용이 완전하게 억제된다. 하지만, 세균이나 곰팡이와 같은 미생물들은 철이 부족한 환경에서 제한된 철을 이용하기 위해 사이드로포어를 생산한다. 사람에서 유래한 트랜스페린(hTf)-철 복합체를 M9 배지에 첨가한 조건에서 S. Typhimurium의 사이드로포어 생산은 완전하게 중단되었다. 반면, S. Typhimurium의 성장은 염화철($FeCl_3$)을 첨가한 조건과 동일한 수준으로 유지되었다. 이 결과는 사이드로포어의 생산 없이도 S. Typhimurium이 hTf에 부착된 철을 직접적으로 이용할 수 있다는 것을 알 수 있다. 돌연변이주의 구축과 이를 이용한 분석을 통하여 우리는 세균이 hTf-철 복합체를 직접적으로 이용할 수 있다는 것을 확인할 수 있었다.

• Clinical and Experimental Reproductive Medicine
• /
• 제43권4호
• /
• pp.193-198
• /
• 2016

Objective: Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common human enzyme defect. G6PD plays a key role in the pentose phosphate pathway, which is a major source of nicotinamide adenine dinucleotide phosphate (NADPH). NADPH provides the reducing equivalents for oxidation-reduction reductions involved in protecting against the toxicity of reactive oxygen species such as $H_2O_2$. We hypothesized that G6PD deficiency may reduce the amount of NADPH in sperms, thereby inhibiting the detoxification of $H_2O_2$, which could potentially affect their motility and viability, resulting in an increased susceptibility to infertility. Methods: Semen samples were obtained from four males with G6PD deficiency and eight healthy males as a control. In both groups, motile sperms were isolated from the seminal fluid and incubated with 0, 10, 20, 40, 60, 80, and $120{\mu}M$ concentrations of $H_2O_2$. After 1 hour incubation at $37^{\circ}C$, sperms were evaluated for motility and viability. Results: Incubation of sperms with 10 and $20{\mu}M\;H_2O_2$ led to very little decrease in motility and viability, but motility decreased notably in both groups in 40, 60, and $80{\mu}M\;H_2O_2$, and viability decreased in both groups in 40, 60, 80, and $120{\mu}M\;H_2O_2$. However, no statistically significant differences were found between the G6PD-deficient group and controls. Conclusion: G6PD deficiency does not increase the susceptibility of sperm to oxidative stress induced by $H_2O_2$, and the reducing equivalents necessary for protection against $H_2O_2$ are most likely produced by other pathways. Therefore, G6PD deficiency cannot be considered as major risk factor for male infertility.