• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.232-232
• /
• 2010

Simulation Program (AFORS-HET 2.4.1) was used, include the basic structure of crystalline silicon thin film as above, under the intrinsic a-Si:H films bonded symmetrical structure (Symmetrical structure) were used. The structure of ITO, a-Si p-type, intrinsic a-Si, c-Si, intrinsic a-Si, a-Si n-type, metal (Al) layer has one of the seven. When thickness for each layer was given the change, the changes of a-Si p-type layer and the intrinsic a-Si layer on top had an impact on efficiency. Efficiency ratio of p-type a-Si:H layer thickness was sensitive to, especially a-Si: H layer thickness is increased in a rapid decrease in Jsc and FF, and efficiency was also decreased.

• Fibers and Polymers
• /
• v.7 no.3
• /
• pp.223-228
• /
• 2006

Hydrogels of semi-interpenetrating polymer networks (semi-IPNs) were prepared by two step reactions. Dimethylaminoethyl methacrylate (DMAM) and poly(ethylene glycol)-dimethacrylate (PEGDM) were copolymerized to yield hydrogels, and then acrylic acid (AA) monomer were adsorbed in the hydrogels followed by polymerization of AA to produce semi-IPNs. The swelling behavior of semi-IPNs depends largely on pH of medium, showing that the degree of swelling of the semi-IPNs exhibits a minimum at pH 6.0. It is observed that the elastic modulus of semi-IPNs is closely related to its swelling behavior.

• Korean Membrane Journal
• /
• v.6 no.1
• /
• pp.24-29
• /
• 2004

Poly(vinyl alcohol)(PVA) and hyaluronic acid(HA) hydrogel membranes were prepared with varying HA contents from 10 to 50 wt% of PVA. The water contents of the resulting PVA-HA hydrogel membranes in various pH conditions were measured. And the permeation coefficient of indomethacin was determined using several PVA-HA hydrogel membranes at various pH conditions and also 37$^{\circ}C$.

• Bulletin of the Korean Chemical Society
• /
• v.30 no.12
• /
• pp.3057-3060
• /
• 2009

Ionic palladium(II) complex, [($Me_4en)Pd(L)]_2(ClO_4)_4\;(Me_4$en = N,N,N',N'-tetramethylethylenediamine; L = bis-(4-(4-pyridylcarboxyl)phenyl)methane), allows to form a monodisperse submicrosphere without any template or additive. Surface-perchlorates on the submicrosphere have been exchanged by anionic pH indicators such as thymol blue, bromothymol blue, and bromocresol green. The ionic and amphiphilic properties of the palladium(II) complex appear to be primarily associated with the formation and easy surface-anion exchange of submicrosphere. The surface-anion exchange through the electrostatic interaction is a very good tool for the surface-modification. The color of the pH indicator-exchanged submicrospheres is very sensitive to pH and Hg$^{2+}$ cation, and thus they are promising to submicrospherical indicators.

• Archives of Pharmacal Research
• /
• v.19 no.1
• /
• pp.18-22
• /
• 1996

Acrylate-terminated poly (ethylene glycol) (PEG) macromer was prepared by the reaction of PEG with acryloyl chloride. Photopolymerization of PEG macromer resulted in the formation of cross-linked PEG network. Interpenetrating polymer networks (IPNs) based on PEG and poly(acrylic acid) (PAA) was obtained via template polymerization of AA to the PEG network by UV curing. The swelling degree of the IPNs hydrogel increased with an increase of pH value due to the association-dissociation between carboxylic acid of PAA and either of PEG through hydrogen bounding. The swelling-deswelling behavior proceeded reversibly for the IPNs upon changing pH. Release of indomethacin from the IPNs demonstrated "on-off" regulation with pH fluctuation.

• Proceedings of the Korean Society of Dyers and Finishers Conference
• /
• 2011.11a
• /
• pp.26-26
• /
• 2011

Colorimetric chemosensors are now considered as one of the most effective analytical method used in the environment monitoring. Colorimetric chemosensor for pH sensing can easily detect the primary danger or change of the surrounding environment pollution and source of infection and can prevent danger in the various fields. Quinaldine and Indole based colorants having the function of colorimetric chemosensors were synthesized and applied to textiles by the LBL method and electrospinning. The characteristics of colorant containing nanofibers and colored textiles were investigated if they can be used as environmental monitoring chemosensors.

• Journal of the Korean Chemical Society
• /
• v.63 no.4
• /
• pp.253-259
• /
• 2019

5-Aminoimidazole-4-carboxamide ribonucleotide (AICAR), a structural analog of adenosine monophosphate (AMP), promotes oxidative remodeling in muscle cells. AICAR activates AMP-dependent protein kinase (AMPK), thus increasing lipid metabolism, respiration, and mitochondrial counts. This process is called oxidative remodeling, which enhances the physical endurance of mice. To test this drug on an invertebrate that is genetically similar to humans, we used the small water crustacean Daphnia magna, which is sensitive to changes in water conditions. We tested the effects of pH on the efficacy of AICAR using two methods. One method measured oxygen consumption of Daphnia in oxygen chambers. The other method determined lipid levels of Daphnia through fluorescent tagging of lipids. The results showed that when exposed to AICAR at pH 6.58, D. magna consumed more oxygen and had lower overall levels of lipids, which is consistent with the expected effects of AICAR, such as increased respiration and lipid metabolism.

• Korean Journal of Animal Reproduction
• /
• v.23 no.3
• /
• pp.257-262
• /
• 1999

This study was carried out to evaluate the effect of pH and storage temperature on the viability of boar sperm diluted with extender KpA for swine artificial insemination. The results obtained in this experiment were summarized as follows : 1. The viability of boar sperm diluted with KpA was higher than that with BTS during storage and especially more than 60% of sperm viability in KpA was maintained through 6 days. The pH values of all extenders were kept during storage of semens following dilution. 2. The sperm diluted with acidic (pH 6.3~6.8) or alkalic (pH 7.8~8.0) KpA and stored at 4$^{\circ}C$ or 37$^{\circ}C$ were more sensitive in viability than that with neutral pH (6.8~7.3) and at 17$^{\circ}C$ storage. But pH values of all conditions were not increased rapidly. Especially acidic and alkalic diluents were more stable in pH after dilution. Conclusively, extender pH and storage temperature was the important factors for sperm viability. The KpA setting up around neutral pH was the optimal boar semen extender for maintaining liquid semen at 17$^{\circ}C$.

• Asian-Australasian Journal of Animal Sciences
• /
• v.5 no.3
• /
• pp.511-517
• /
• 1992

Ethanol was utilized by mixed rumen microbes, but addition of pentachlorophenol (25 mg/l), a methanogen inhibitor, suppressed the utilization of ethanol. Carbon monoxide (50% of the gas phase), a hydrogenase inhibitor, more strongly suppressed the utilization of ethanol, propanol, and butanol. These results suggest that the major ethanol utilizers are $H_2$ producers. Ethanol utilization was depressed at low pH (below 6.0). Since methanogens were shown to be relatively resistant to low pH, it appears that ethanol utilizers are particularly sensitive to low pH. Ruminococcus albus and R. flavefaciens in mono-culture produced ethanol from carbohydrate (glucose and cellobiose), even when a high level (170 mM) of ethanol was present. Ethanol was not utilized even in the absence of carbohydrate, but the co-culture of these bacteria with methanogens resulted in the utilization of ethanol, i.e., when $H_2$ was rapidly converted to $CH_4$, R. albus and R. flavefaciens utilized ethanol. These results suggest that ethanol is utilized when the electrons liberated by the oxidation of ethanol are rapidly removed, and ready electron disposal in ethanol-utilizing, $H_2$-producing bacteria is accomplished by the interspecies transfer of $H_2$.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.129-129
• /
• 2011

ISFET (ion sensitive field effect transistor)는 용액 중의 각종 이온 농도를 측정하는 반도체 이온 센서이다. ISFET는 작은 소자 크기, 견고한 구조, 즉각적인 반응속도, 기존의 CMOS공정과 호환이 가능하다는 장점이 있다. ISFET의 기본 구조는 기존의 MOSFET (metal oxide semiconductor field effect transistor)에서 고안되었으며, ISFET는 기존의 MOSFET의 게이트 전극 부분이 기준전극과 전해질로 대체되어진 구조를 가지고 있다. ISFET소자의 pH 감지 메커니즘은 감지막의 표면에서 pH용액 속의 이온들이 감지막의 표면에서 속박되어 막의 표면전위의 변화를 유발하는 것을 이용한다. 그 결과, ISFET의 문턱전압의 변화를 일으키게 되고 드레인 전류의 양 또한 달라지게 된다. ISFET의 높은 pH감지능력을 얻기 위하여 높은 high-k물질 들이 감지막으로서 연구되었다. Al2O3와 HfO2는 높은 유전상수, non-ideal 효과에 대한 immunity 그리고 높은 pH 감지능력 등 많은 장점을 가지고 있는 물질로 알려졌다. 본 연구에서는, SiO2/HfO2/Al2O3 (OHA) 적층막을 이용한 EIS (electrolyte- insulator-silicon) pH센서를 제작하였다. EIS구조는 ISFET로의 적용이 용이하며 ISFET보다 제작 방법과 소자 구조가 간단하다는 장점이 있다. HfO2은 22~25의 높은 유전상수를 가지며 높은 pH 감지능력으로 인하여 감지막으로서 많은 연구가 이루어지고 있는 물질이다. 하지만 HfO2의 물질이 가진 고유의 특성상 화학적 용액에 대한 non-ideal 효과는 다른 금속계열 산화막에 비하여 취약한 모습을 보인다. 반면에 Al2O3의 유전상수는 HfO2보다 작지만 화학용액으로 인한 손상에 대하여 강한 immunity가 있는 재료이다. 이러한 물질들의 성질을 고려하여 OHA의 새로운 감지막의 적층구조를 생각하였다. 먼저 Si과 high-k물질의 양호한 계면상태를 이루기 위하여 5 nm의 얇은 SiO2막을 완충막으로서 성장시켰다. 다음으로 높은 유전상수를 가지고 있는 8 nm의 HfO2을 증착시킴으로서 소자의 물리적 손상에 대한 안정성을 향상시켰다. 최종적으로 화학용액과 직접적인 접촉이 되는 부분은 non-ideal 효과에 강한 Al2O3을 적층하여 소자의 화학적 손상에 문제점을 개선시켰다. 결론적으로 감지막의 적층 모델링을 통하여 각각의 high-k 물질이 가진 고유의 특성에 대한 한계점을 극복함으로써 높은 pH 감지능력뿐만 아니라 신뢰성 있는 pH 센서가 제작 되었다.