• 한국전기전자재료학회논문지
• /
• 제19권2호
• /
• pp.116-125
• /
• 2006

We have presented a nanoelectromechanical (NEM) model based on atomistic simulations. Our models were applied to a NEM device as called a nanotube random access memory (NRAM) operated by an atomistic capacitive model including a tunneling current model. We have performed both static and dynamic analyses of a NRAM device. The turn-on voltage obtained from molecular dynamics simulations was less than the half of the turn-on voltage obtained from the static simulation. Since the suspended carbon nanotube (CNT) oscillated with the amplitude for the oscillation center under an externally applied force, the quantity of the CNT-gold interaction in the static analysis was different from that in the dynamic analysis. When the gate bias was applied, the oscillation centers obtained from the static analysis were different from those obtained from the dynamics analysis. Therefore, for the range of the potential difference that the CNT-gold interaction effects in the static analysis were negligible, the vibrations of the CNT in the dynamics analysis significantly affected the CNT-gold interaction energy and the turn-on voltage. The turn-on voltage and the tunneling resistance obtained from our tunneling current model were in good agreement with previous experimental and theoretical works.

• 약학회지
• /
• 제52권6호
• /
• pp.500-506
• /
• 2008

Apigenin, a natural flavonoid found in a variety of vegetables and fruits, has been shown to possess many biological functions. In this study we found that apigenin stimulated melanin synthesis in a dose-dependent manner in B16 murine melanoma cells. Since in our previous study $K^+$-$Cl^-$-cotransport (KCC) has been shown to mediate the mechanism of action of apigenin in neuronal cells, we further investigated the role of KCC in the melanogenesis-stimulating effect of apigenin in B16 cells. At nontoxic concentrations apigenin induced $Cl^-$-dependent $K^+$ efflux, a hallmark of KCC activity, which was markedly prevented by a specific KCC inhibitor R-(+)-[(2-n-butyl-6,7-dichloro-2-cyclopentyl-2,3-dihydro-1-oxo-1H-inden-5-yl)oxy]acetic acid (DIOA). These results indicate that KCC is functionally present, and activated by apigenin in the B16 cells. In addition, the apigenin-induced stimulation of melanogenesis was also significantly inhibited by DIOA. NEthylmaleimide (NEM), a known KCC activator, induced $Cl^-$ efflux and stimulated melanogenesis in a concentration-dependent fashion. Both effects of NEM were significantly inhibited by DIOA. Taken together, these results suggest that apigenin can modulate melanogenesis through the activation of a membrane ion transporter, KCC in B16 cells. These results further suggest that apigenin may be a good candidate in the therapeutic strategy for hypopigmentation disorders, such as vitiligo.

• 한국식품위생안전성학회:학술대회논문집
• /
• 한국식품위생안전성학회 2002년도 춘계학술발표대회 및 심포지움
• /
• pp.138-138
• /
• 2002

Oxidative stress has been associated with a number of diseases in human. Among the sources that can generate oxidative stress, it has been reported that iron can generate reactive oxygen species (ROS)with thiol. In iron overload state, increased thiol levels in plasma appeared to be associated with human mortality. In this study we examined whether iron could interact with thiols in plasma, generating ROS. In human plasma, unlike with Fe(III), Fe(II) increased lucigenin-enhanced chemiluminescence in concentration-dependent manner, and this was inhibited by SOD. Boiling of plasma did not affect chemiluminescence induced by Fe(II). Hovever, thiol depletion in plasma by pretreatment with N-ethylmaleimide (NEM)decreased Fe(II)-induced chemiluminescence significantly, suggesting that Fe(II) generated superoxide anion by the nonenzymatic reaction with plasma thiol. Consistent with this findings, albumin, the major thiol contributor in plasma, also generated ROS with Fe(II) and this generation was inhibited by pretreatment with NEM. Treatment with Fe(II) to plasma resulted un significant reduction of oxygen radical absorbance capacity (ORAC) value, suggest that total antioxidant capacity could diminished in iron overload state. In conclusion, In iron overload state, plasma may be affected by oxidative stress mediated by nonenzymatic reaction of Fe (II)with plasma thiol.

• Steel and Composite Structures
• /
• 제42권1호
• /
• pp.23-32
• /
• 2022

In this paper, a nonlinear numerical method to solve the large deflection problem is introduced. And the non-dimensional load-deflection behavior of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plates is parametrically investigated. The large deflection problem is formulated according to the von Kármán nonlinear theory and the (1,1,0)^* hierarchical model, and it is approximated by 2-D natural element method (NEM). The shear locking phenomenon is suppressed by the selectively reduced integration method. The nonlinear matrix equations are solved by combining the incremental loading scheme and the Newton-Raphson iteration method. The proposed method is validated from the benchmark experiments, where the propose method shows an excellent agreement with the reference methods. The nonlinear behavior of FG-CNTRC plates is evaluated in terms of the non-dimensional load-deflection curve, and it is parametrically investigated with respect to the existence/non-existence and gradient pattern of CNTs, the width-to-thickness and aspect ratios of plates and the type of boundary conditions. The non-dimensional central deflection is significantly reduced when CNTs and added, and it decreases with the volume fraction of CNTs. But, it shows a uniform increase in proportion to the width-to-thickness and aspect ratios. Both the gradient pattern of CNTs and the type of boundary conditions do also show the remarkable effects.

• Steel and Composite Structures
• /
• 제49권4호
• /
• pp.431-440
• /
• 2023

The functionally graded (FG) porous plates are usually characterized by the non-symmetric elastic modulus distribution through the thickness so that the plate neutral surface does not coincide with the mid-surface. Nevertheless, the conventional analysis models were mostly based on the plate mid-surface so that the accuracy of resulting numerical results is questionable. In this context, this paper presents the neutral surface-based static and free vibration analysis of FG porous plates and investigates the differences between the mid- and neutral surface-based analysis models. The neutral surface-based numerical method is formulated using the (3,3,2) hierarchical model and approximated by the last introduced natural element method (NEM). The volume fractions of metal and ceramic are expressed by the power-law function and the cosine-type porosity distributions are considered. The proposed numerical method is demonstrated through the benchmark experiment, and the differences between two analysis models are parametrically investigated with respect to the thickness-wise material and porosity distributions. It is found from the numerical results that the difference cannot be negligible when the material and porosity distributions are remarkably biased in the thickness direction.

• 한국작물학회지
• /
• 제54권3호
• /
• pp.279-286
• /
• 2009

본 연구는 우리나라 중서부지역인 충청지역에서 사료작물의 새로운 작부체계로 보리와 완두를 혼파재배할 때 기초자료로 이용하고자 혼파비율과 예취시기에 따른 사료가치변화를 구명하기 위하여 수행하였고 결과를 요약하면 다음과 같다. 건물수량은 보리의 파종비율이 높을수록 증가하였으며, 보리와 완두 혼파비율이 85 : 15% 파종구에서 5월 16일에 예취할 때 가장 많았다. 조단백질, 가급태단백질 및 가소화 단백질은 4월 25일 예취시에는 혼파비율간 유의차가 없으나, 5월 2일 예취 이후부터는 완두의 혼파비율이 높을수록 증가하는 경향이었다. 보리의 혼파비율이 높을수록, 예취시기가 늦을수록 ADF와 NDF는 증가하는 경향이었으며, RFV는 오히려 감소하는 경향이었다. TDN함량은 완두의 혼파비율이 높을수록 증가하였으나, 예취시기별로는 5월 9일 예취시까지는 예취시기가 늦을수록 감소하였고 그 이후는 예취시기가 늦을수록 증가하는 경향이었다. P와 Mg함량은 혼파비율간 유의차가 없었으며, 완두의 혼파비율이 높을수록, Ca은 증가하였고, K은 감소하였다. 예취시기별로는 P, Ca 및 K은 예취시기가 늦을수록 감소하였으나. Mg은 5월 9일 예취시기까지는 별 변동이 없었고, 그 이후 예취시 부터는 예취시기가 늦을수록 증가하였다. 에너지함량에서 ENE, NEM 및 NEG는 혼파비율과 예취시기 간에 유의성이 있어 완두의 혼파비율이 높을수록, 예취시기가 빠를수록 증가하였다. 건물중에 각 성분의 함량을 적한 수량에서 보면 단백질, P, Ca, K 및 Mg 등의 무기물 수량은 보리와 완두의 혼파비율이 75 : 25% 파종구에서, ENE, NEL, NEM 및 NEG 등의 에너지 수량과 TDN수량은 보리와 완두의 혼파비율이 85 : 15% 파종구에서 가장 높았다. 예취시기별로는 TDN 수량, 모든 무기물 및 에너지수량은 5월 16일에 예취하는 것이 가장 높았다.

• 한국작물학회지
• /
• 제36권6호
• /
• pp.513-520
• /
• 1991

충남 예산에서 호밀을 답리작으로 재배할때 파종량과 예취기간가 수량 및 사료가치에 미치는 영향을 요약하면 다음과 같다. 1. 파종량이 많아질수록 호밀의 초장과 단위면 적당 경수는 증가하였으며 건물률은 감소하였다. 2. 청예 및 건물수량은 파종량이 많을수록 높았으며 예산에서 청예수량이 가장 높았던 예취기는 5월 15일, 건물수량이 가장 높았던 예취기는 5월 25일 이었다. 3. 파종량이 많을 수록 그리고 예취시기가 늦을수록조단백질, 가급태단백질 및 가소화단백질 함량은 감소하였으며, 반면에 조섬유함량(ADF와 NDF)은 증가하였다. 4. 파종량이 많을 수록 그리고 예취시기가 늦을수록 총가소화영양분(TDN) 함량과 상대적 사료가치는 감소하였다. TDN 수량은 파종량 18-28kg/10a, 5월 15-25일 수확시 가장 높았다. 5. 호밀의 에너지 함량은 파종량이 많을수록 그리고 예취시기가 늦을수록 감소하나, 단위면적당 에너지 생산량은 ENE와 NEL은 23kg/10a 파종-5월 15일 수확할때, NEM은 18kg/10a 파종-5월 15일 수확할때 가장 높았다. NEG는 18-28kg/10a 파종-5월 5일 수확할 때 가장 높았다.

• The Korean Journal of Physiology and Pharmacology
• /
• 제1권3호
• /
• pp.303-313
• /
• 1997

The role of the lower esophageal sphincter(LES) is characterized by the ability to maintain tone and to relax allowing the passage of a bolus. It is known that LES relaxation during swallowing may be induced by the cessation of the tonic neural excitation and the activation of non-adrenergic, non-cholinergic(NANC) inhibitory neurons. Furthermore, it is generally accepted that the relaxation of the smooth muscle is mediated primarily by the elaboration of adenosine 3',5'-cyclic monophosphate(cyclic AMP) and guanosine 3',5'-cyclic mono-phosphate(cyclic GMP) via activation of adenylate cyclase and guanylate cyclase, respectively. It is thus possible that cyclic nucleotides might be a second messenger involved in neural stimulation-induced relaxation of LES, although a relationship between relaxation and changes in cyclic nucleotides after neural stimulation has not been established. The present study was performed to define the participation of cyclic nucleotides in the relaxation of LES of dog in response to neural stimulation. Electrical field stimulation(EFS) caused relaxation of the canine isolated LES strips in a frequency-dependent manner, which was eliminated by pretreatment with tetrodotoxin$(1{\mu}M)$, but not by atropine$(100{\mu}M)$, guanethidine$(100{\mu}M)$ and indomethacin$(10{\mu}M)$. The nitric oxide synthase inhibitors, $N^G-nitro-L-arginine$, $N^G-nitro-L-arginine$ methyl ester and $N^G-monomethyl-L-arginine$ inhibited EFS-induced relaxation. Additions of sodium nitroprusside, a nitrovasodilator and forskolin, a direct adenylate cyclase stimulant, caused a dose-dependent relaxation of LES smooth muscle. Effects of sodium nitroprusside and forskolin were selectively blocked by the corresponding inhibitors, methylene blue for guanylate cyclase and N-ethylmaleimide(NEM) for adenylate cyclase, respectively. Dibutyryl cyclic AMP and dibutyryl cyclic GMP caused a concentration-dependent relaxation of the LES smooth muscle tone, which was not blocked by NEM or methylene blue, respectively. However, both NEM and methylene blue caused significant antagonism of the relaxation in LES tone in response to EFS. EFS increased the tissue cyclic GMP content by 124%, whereas it did not affect the tissue level of cyclic AMP. Based on these results, it is suggested that one of the components of canine LES smooth muscle relaxation in response to neural stimulation is mediated by an increase of cyclic GMP via the activation of guanylate cyclase. Additionally, an activation of cyclic AMP generation system was, in part, involved in the EFS-induced relaxation.

• Parasites, Hosts and Diseases
• /
• 제33권3호
• /
• pp.211-218
• /
• 1995

간흡충의 병원성과 단백분해효소 활성도의 상관성을 밝히기 위하여 간흡충 추출물과 분비배설물 의 단백분해효소 활성도와 세포독성을 평가하였고 분비배설물에서 단백분해효소를 부분정제하고 생화학적 성질을 규명하였다. 여러 가지 단백분해효소 억제제를 사용하여 단백분해효소의 활성을 측정한 결과 간흡충에는 Rf값을 서로 달리하는 효소분획으로 되어있음이 관찰되었으며. 이러한 효소 분획은 azocasein을 기질로 한 활성부위 잔기 억제 실험에서 서로 상이한 활성부위잔기를 갖고 있음을 알 수 있었다. 간흡충 분비배설물의 세포독성은 단백질 농도를 $120\mu\textrm{g}/ml$까지 증가시키자 세포독성이 3배 증가했고. 이 효과는 NEM과 ntipain에 의해 억제되었다. 이 사실은 cysteine 단백 분해효소가 세포독성에 관여하는 것을 보여주고 있었다 이 단백분해효소는 최적활성치가 pH 7.5 이었다. 이 효소를 분비배설물로부터 23배 정제하였고 이때 회수율은 14.5%이었다. 부분정제한 단백분해효소의 분자량은 24 kDa이었다. 이 효소는 NEM, antipain에 의해 효소활성이 억제되었고, 동시에 세포독성도 억제되었다. 이 사실로부터 부분정제한 효소의 활성부위잔기는 cysteine이고 이 효소가 또한 분비배설되어 세포독성을 나타낸다는 것을 알 수 있었다.

• 한국해양환경ㆍ에너지학회지
• /
• 제14권4호
• /
• pp.257-263
• /
• 2011

SBM을 이용하여 2006년 가막만의 담수, 염분, 영양염 등 물질 수지를 산정하였다. 담수유출량은 $-174.2{\sim}72.5{\times}10^3m^3/day$로 나타났으며 개방경계에서의 해수 교환에 의한 mixing volume은 $-2.4{\times}10^7\sim4.9{\times}10^7m^3/day$로 만 내외의 염분차이에 의해 크게 좌우 받았다. 육상기인 DIP와 DIN의 유입 flux의 범위는 397.0~1158 mole/day 및 1750~8328 mole/day의 범위로 다른 지역에 비해 낮았다. DIP의 소실 또는 생성은 물수지의 변동에 의해 크게 좌우 되는 특징을 보였으며, 또한, 물질체류시간에 의해 물질수지가 크게 좌우되어 NEM도 크게 달라지는 결과를 보였다.