• 한국진공학회지
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• 제16권1호
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• pp.27-32
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• 2007

양자우물의 두께가 다른 4종류의 $In_xGa_{1-x}N(x=0.15)/GaN$ 다중 양자우물 구조의 PL 스펙트럼을 분석하여 InGaN에서의 결정상 분리 현상을 조사하였다. 우물폭이 1.5 nm에서 6.0 nm로 증가함에 따라, PL스펙트럼은 비대칭성이 점점 강해지는 이중 피크의 특성을 나타내었다. 곡선맞춤을 수행하여 분리한 2개의 피크를 분석하여, InGaN 우물에서의 부준위 천이에 해당하는 고에너지 피크의 세기는 줄어드는 반면, 상분리에 의하여 생성된 저에너지 피크의 강도는 점점 강해짐을 볼 수 있었다. 이것은 InGaN 우물에는 In 조성이 다소 다른 2개의 결정상이 존재하여, 우물폭 증가와 함께 InN 상분리가 강해지면서 In 조성이 큰(In-rich) InGaN 결정상이 상대적으로 증대됨을 보여 주는 결과로 해석된다. 우물 두께가 6.0 nm인 시료에서는 저에너지 영역(${\sim}2.0eV$)에서 또 하나의 피크이 관측되었는데, 이것은 GaN에서 잘 알려져 있는 결함에 기인한 황색준위(YB)와 그 근원이 같은 것으로, InN의 상분리가 임계값 이상으로 발달하여 생성된 결함과 관련된 준위인 것으로 해석된다.

• Journal of Nutrition and Health
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• 제33권1호
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• pp.23-32
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• 2000

The purpose of this study was to investigate the effcts of n-3, n-6 fatty arid and d-limonene on histopathological and biochemical changes in experimental rat hepatocarcinogenesis. To attain the above objectives, weanling Sprague-Dawley female rats were intraperitoneally injected twice with a dose of diethylnitrosamine(DEN, 50mg/kg body weight) and after 1 week 0.05% phenobarbital was provided with water. Sardine oil rich in n-3 fatty acids and corn oil rich in n-6 fatty acids were fed at 15% by weight and 5% d-limonene was added to the diet in each group. Ten weeks or 20 weeks after DEN treatment, rats were sacrifirced. The formation of glutathione S-transferase placental form positive(GST-P$\^$+/) foci was significantly decreased by the treatment of either sardine oil or d-limonene HMG-CoA reductase activity was not affected by dietary oils and d-limonene. Protein kinase C (PKC) activity was decreased by either sardine oil or d-limonene. Particularly d-limonene decreased the membrane PKC activity. Membrane Cholesterol/Phospholipid(Chol/PL) ratio was significantly decreased by d-limonene in sardine oil group. The data showed that GST-P$\^$+/ foci number was positively correlated with membrane PKC activity and serum cholesterol and negatively correlated with liver cholesterol level. These results suggest informations about the correlation between histopathological and biochemical changes such as cholesterol metabolism and PKC activity in experimental hepatocarcinogenesis and thereby can elucidate the possible mechanism related to the cancer inhibition.(Korean J Nutrition 33(1) : 23-32, 2000)

• Bulletin of the Korean Chemical Society
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• 제34권4호
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• pp.1096-1100
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• 2013

The kinetic studies on the reactions of O-methyl (1), O-propyl (3) and O-isopropyl (4) phenyl phosphonochloridothioates with substituted anilines and deuterated anilines have been carried out in acetonitrile at $55.0^{\circ}C$. A concerted $S_N2$ mechanism is proposed for the anilinolyses of 1, 3 and 4. The anilinolysis rates of the phosphonochloridothioates are predominantly dependent upon the steric effects over the inductive effects of the two ligands. The deuterium kinetic isotope effects (DKIEs; $k_H/k_D$) are primary normal with 1 and 3, while secondary inverse with 4. Primary normal and secondary inverse DKIEs are rationalized by frontside and backside nucleophilic attack transition state, respectively. The DKIEs of the phosphonochloridothioates do not have any consistent correlations with the two ligands.

• Nutrition Research and Practice
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• 제17권1호
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• pp.1-12
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• 2023

BACKGROUND/OBJECTIVES: Male hypogonadism is a condition where the body does not produce enough testosterone and significantly impacts health. Age, obesity, genetics, and oxidative stress are some physiological factors that may contribute to testosterone deficiency. Previous studies have shown many pharmacological benefits of Schisandra chinensis (S. chinensis) Baillon as an anti-inflammatory and antioxidant. However, the molecular mechanism of attenuating hypogonadism is yet to be well established. This research was undertaken to study the effects of S. chinensis extract (SCE) on testosterone deficiency. MATERIALS/METHODS: S. chinensis fruit was pulverized and extracted using 60% aqueous ethanol. HPLC analysis was performed to analyze and quantify the lignans of the SCE. RESULTS: The 2,2-diphenyl-2-picrylhydrazyl and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) scavenging assays confirmed that the SCE and its major lignans (schisandrol A and gomisin N) inhibit oxidative stress. Effects of SCE analysis on the testosterone level under oxidative stress conditions revealed that both schisandrol A and gomisin N were able to recover the lowered testosterone levels. Through mRNA expression of TM3 Leydig cell, we observed that the SCE lignans were able to induce the enzymes involved in testosterone biosynthesis-related genes such as 3β-HSD4 (P < 0.01 for SCE, and P < 0.001 for schisandrol A and gomisin N), 17β-HSD3 (P < 0.001 for SCE, schisandrol A and gomisin N), and 17, 20-desmolase (P < 0.01 for schisandrol A, and P < 0.001 for SCE and gomisin N). CONCLUSIONS: These results support that SCE and its active components could be potential therapeutic agents for regulating and increasing testosterone production.

• 한국연소학회지
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• 제9권1호
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• pp.32-38
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• 2004

Characteristics of turbulent lifted flames in coflow jet have been investigated by varying initial temperature through the heating coflow air. In the turbulent regime, liftoff height increases linearly with fuel jet velocity and decreases nonlinearly as the coflow temperature increases. This can be attributed to the increase of turbulent propagation speed, which is strongly related to laminar burning velocity. Dimensionless liftoff heights are correlated well with dimensionless jet velocity, which are scaled with parameters determining local flow velocity and turbulent propagation speed. This implies that the turbulent lifted flames are stabilized by balance mechanism between local turbulent burning velocity and flow velocity. Blowout velocity can be obtained from the ratio of mixing time to chemical time. Comparing to previous researches, thermal diffusivity should be evaluated from the initial temperature instead of adiabatic flame temperature.

• International Journal of Automotive Technology
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• 제8권5호
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• pp.593-598
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• 2007

A new continuously variable transmission for bicycles(B-CVT) is developed by using a traction drive mechanism having inner and outer spherical rotors. The B-CVT has high power efficiency, large torque capacity, improved drivability and good packageability. The ratio change mechanism for the B-CVT is very simple, in contrast with other traction drive CVTs. After completing a conceptual design, a performance analysis and a detail design, a prototype of the B-CVT has been manufactured. The prototype has rated power of 100 watts, pedal speed of 6 rad/s and an overall speed ratio of 1.0-4.0. A bench test and an actual bicycle test have been performed to verify the practicability of the B-CVT.

• Journal of Photoscience
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• 제12권1호
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• pp.25-32
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• 2005

Binding of N-Alkyl phenothiazines (NAP) to bovine serum albumin (BSA) was studied by spectroscopic methods.It was found that the phenothiazine ring common to all drugs makes major contribution to interaction. However, the nature of alkylamino group at position 10 influences the protein binding significantly. Stern-Volmer plots indicated the presence of static component in the quenching mechanism. The high magnitude of rate constant of quenching indicated that the process of energy transfer occurs by intermolecular interaction and thus the drug-binding site is in close proximity to tryptophan residues of BSA. Binding studies in presence of hydrophobic probe, 8-anilino-1-naphthalein-sulphonic acid showed that there is hydrophobic interaction between drug and the probe and they do not share common sites in BSA. Thermodynamic parameters obtained from data at different temperatures showed that the binding of NAP to BSA predominantly involve hydrophobic forces. The effects of some cations and anions common ions were investigated on NAP-BSA interactions. The CD spectrum of BSA in presence of drug showedthat binding of drug leads to change in the helicity of the protein.

• Molecules and Cells
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• 제46권4호
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• pp.219-230
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• 2023

Down syndrome (DS) is the most common autosomal aneuploidy caused by trisomy of chromosome 21. Previous studies demonstrated that DS affected mitochondrial functions, which may be associated with the abnormal development of the nervous system in patients with DS. Runt-related transcription factor 1 (RUNX1) is an encoding gene located on chromosome 21. It has been reported that RUNX1 may affect cell apoptosis via the mitochondrial pathway. The present study investigated whether RUNX1 plays a critical role in mitochondrial dysfunction in DS and explored the mechanism by which RUNX1 affects mitochondrial functions. Expression of RUNX1 was detected in induced pluripotent stem cells of patients with DS (DS-iPSCs) and normal iPSCs (N-iPSCs), and the mitochondrial functions were investigated in the current study. Subsequently, RUNX1 was overexpressed in N-iPSCs and inhibited in DS-iPSCs. The mitochondrial functions were investigated thoroughly, including reactive oxygen species levels, mitochondrial membrane potential, ATP content, and lysosomal activity. Finally, RNA-sequencing was used to explore the global expression pattern. It was observed that the expression levels of RUNX1 in DS-iPSCs were significantly higher than those in normal controls. Impaired mitochondrial functions were observed in DS-iPSCs. Of note, overexpression of RUNX1 in N-iPSCs resulted in mitochondrial dysfunction, while inhibition of RUNX1 expression could improve the mitochondrial function in DS-iPSCs. Global gene expression analysis indicated that overexpression of RUNX1 may promote the induction of apoptosis in DS-iPSCs by activating the PI3K/Akt signaling pathway. The present findings indicate that abnormal expression of RUNX1 may play a critical role in mitochondrial dysfunction in DS-iPSCs.

• 대한화학회지
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• 제25권1호
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• pp.7-12
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• 1981

$p-CH_3, p-H, p-Cl 및 p-NO_2 기로 치환된 염화벤젠술포닐의 가용매분해반응을 MeOH-MeCN혼합용매계에서 연구하였다. 반응속도는 p-NO_2 > p-CH_3 > p-H > p-Cl의 순위로서 비직선 Hammett관계를 나타내어 S_N1-S_N2경계반응메카니즘으로 반응함을 알았다. 반응성은 모든 경우 약 90∼95% 메탄올용액에서 최대였으나, fi = \frac{k1}{ki}로 정의되는 각 기질의 메탄올 단위체 선택성(monomer selectivity)은 80% 메탄올 용액에서 최대이며, 그 크기 순위는 p-NO_2 > p-Cl > p-H > p-CH_3$로서 전이상태 구조가 tight할 수록 fi값이 크며 메탄올 단위체를 예민하게 선별 감지함을 알 수 있었다

• Bulletin of the Korean Chemical Society
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• 제32권4호
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• pp.1165-1169
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• 2011

Second-order rate constants ($k_N$) have been measured spectrophotometrically for nucleophilic substitution reactions of 2,4-dinitrophenyl phenyl thionocarbonate 4 with a series of Z-substituted pyridines in 80 mol % $H_2O$/20 mol % DMSO at $25.0{\pm}0.1^{\circ}C$. The Br${\o}$nsted-type plot for the reactions of 4 exhibits downward curvature (i.e., ${\beta}_1$ = 0.21 and ${\beta}_2$ = 1.04), indicating that the reactions proceed through a stepwise mechanism with a change in rate-determining step. It has been found that 4 is less reactive than its oxygen analogue, 2,4-dinitrophenyl phenyl carbonate 3, although the thionocarbonate is expected to be more electrophilic than its oxygen analogue. The $pK_a$ at the center of the Br${\o}$nsted curvature, defined as $pK_a^o$, has been analyzed to be 6.6 for the reactions of 4 and 8.5 for those of 3. Dissection of $k_N$ into the microscopic rate constants $k_1$ and $k_2/k_{-1}$ ratio has revealed that the reactions of 4 result in smaller $k_1$ values but larger $k_2/k_{-1}$ ratios than the corresponding reactions of 3. The larger $k_2/k_{-1}$ ratios have been concluded to be responsible for the smaller $pK_a^o$ found for the reactions of 4.