• Bulletin of the Korean Chemical Society
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• v.26 no.8
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• pp.1246-1250
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• 2005

We have evaluated the hydroxyl group-solvent specific interactions by using a Lichrosorb RP18 stationary phase and by measuring the retention data of carefully selected solutes in 50/50, 60/40, 70/30, 80/20, and 90/10(v/v%) methanol/water eluents at 25, 30, 35, 40, 45, and 50 ${^{\circ}C}$. The selected solutes are 3 positional isomers of phenylpropanol, that is, 1-phenyl-1-propanol, 1-phenyl-2-propanol, and 3-phenyl-1-propanol. There exist clear discrepancies in ${\Delta}H^o$ (solute transfer enthalpy from the mobile to the stationary phase) and $T{\Delta}S^o$ (solute transfer entropy) among positional isomers. The difference in ${\Delta}H^o$ and $T{\Delta}S^o$ between secondary alcohols (1-phenyl-1-propanol and 1-phenyl-2-propanol)is negligible compared to the difference between the primary alcohol (1-phenyl-3-propanol) and secondary alcohols. The $T{\Delta}S^o$ values of 3-phenyl-1-propanol are close to those of butylbenzene while the $T{\Delta}S^o$ values of secondary alcohols are close to those of propylbenzene. The difference in ${\Delta}{\Delta}H^o$ (specific solute-mobile phase interaction enthalpy) between the primary alcohol and the secondary alcohol decreases with increase of methanol content in the mobile phase. A unique observation is an extremum for 1-phenyl-3-propanol in the plot of $T{\Delta}{\Delta}S^o$ vs. methanol volume %. The positive sign of $T{\Delta}{\Delta}S^o$ of 3-phenyl-1-propanol implies that the entropy of 3-phenyl-1-propanol is greater than that of the hypothetical alkylbenzene (the same size and shape as phenylpropanol) in the mobile phase.

• New Physics: Sae Mulli
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• v.68 no.12
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• pp.1293-1301
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• 2018

The basic magnetic properties of commercially available High-$T_c$ Superconductor (HTS) GdBCO-coated conductor (GdBCO-CCs) were investigated by using physical property measurement system-vibrating sample magnetometer (PPMS-VSM). From the zero-field-cooled (ZFC) m(T) curve, the $T_c$ was found to be ~93 K. After removing the background m(H) data, we obtained both the net m(H) data and the ${\Delta}m_{irr}$. The $H_{irr}(T)$ coincided very well with the power-law relation $H_{irr}=H_{irr}(0)(1-T/T_c)^n$ with $$n{\sim_=}1.19$$. The magnetic flux behavior was investigated by using the ${\delta}$ values in the relationship $J_c{\propto}{\Delta}m_{irr}{\propto}H^{-{\delta}}$. A ${\delta}{\approx}0$ region denoting an independent magnetic flux pinning effect, a ${\delta}{\approx}0.6{\sim}1.2$ region representing a collective flux pinning effect due to the interaction, and a ${\delta}{\gg}2$ region representing freely moving magnetic fluxes caused by the Lorentz force were observed. The boundary line between ${\delta}{\approx}0$ and ${\delta}{\approx}0.6{\sim}1.2$ is denoted by a $H_1$, and the one between ${\delta}{\approx}0.6{\sim}1.2$ and ${\delta}{\gg}2$ is denoted by a $H_2$. The ${\delta}(T)$ was obtained in the region of $H_1$ < H < $H_2$. As the temperature was decreased, the ${\delta}$ value gradually decreased.

• Journal of the Korean Chemical Society
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• v.25 no.3
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• pp.152-159
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• 1981

The rates of solvolysis for p-nitrobenzyl chloride have been measured by the electric conductivity method in aqueous ethanol from 0.0 to 0. 5 mole fraction of ethanol under various pressures up to 1200bar at 50 and $60{\circ}C$. The activation parameters, ${\Delta}V_\0^{\neq},\ {\Delta}H^{\neq}$ and ${\Delta}S^{\neq}$ are evaluated from the rate constants. The results indicated that ${\Delta}V_\0^{\neq}$ exhibits an extremum behaviors near 0.3 mole fraction of ethanol and ${\Delta}H^{\neq}$ and ${\Delta}S^{\neq}$ near 0.1 mole fraction of ethanol. This behaviors are discussed in terms of solvent structure variation and the pressure dependences of ${\Delta}H^{\neq},\ {\Delta}H^{\neq}$ and ${\Delta}S^{\neq}$ are also discussed individually. The signs of the pressure dependence of ${\Delta}H^{\neq}$${\Delta}S^{\neq}$ are shown to be consistent with those required by the Maxwell relationships for classical thermodynamic systems.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.450-455
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• 2001

An analytical study is made of transient adjustment process of an initially stationary, stably-stratified fluid in a square. The boundary walls are highly-conducting. The overall Rayleigh number $R_a$ is large. Considerations are given to both opposing (${\delta}w/{\delta}T>0$) and cooperating (${\delta}w/{\delta}T<0$) configurations. The flow character in opposing configuration can be classified into (a) a forced-convection dominaut mode (${\delta}w/{\delta}T>1/\sqrt{2}$), (b) a buoyancy-convection dominant mode ($0<{\delta}w/{\delta}T<1/\sqrt{2}$), and (c) a static mode (${\delta}w/{\delta}T{\cong}1/\sqrt{2}$). Global evolutionary processes are depicted. and physical rationalizations are provided.

• Korean Journal of Optics and Photonics
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• v.28 no.1
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• pp.33-38
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• 2017

The universality of the quasi-linear relation between the order parameter S and the normalized birefringence ${\Delta}n_{rel}$, $S=(1+a){\Delta}n_{rel}-a{\Delta}n^2_{rel}$ is confirmed. It is verified that the refractive index of liquid crystals distributed with regular polyhedral symmetry is isotropic and it is given as $\frac{1}{n^2_{av}}=\frac{1}{3}\(\frac{1}{n^2_e}+\frac{2}{n^2_o}\){\cdot}S$ and ${\Delta}n_{rel}$ of angular weighted liquid crystals that are initially distributed with regular polyhedral symmetry, are numerically calculated. Also ${\Delta}n_{rel}$ and S of liquid crystals that are conically distributed, keeping the rotational symmetry about z-axis are calculated as the apex angle of the cone is varied. Based on these calculated results, it is confirmed that the quasi-linear relation between S and ${\Delta}n_{rel}$ is universal, independent of the details of the distribution function.

• Membrane Journal
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• v.8 no.3
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• pp.157-169
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• 1998

The effects of solvents (DMAc, NMP, 1,4-dioxane) and nonsolvents ($H_2O$, Methanol, n-hexane) on the morphology of 6FDA-p-TeMPD polyimide membrane, prepared by the wet phase inversion method, were studied. In the polymer/solvent/nonsolvent ternary system, the binodal curve, the coagulation value and the relative light transmission were measured, and the solubility parameter difference was calculated. The onset state and rate of liquid-liquid alemixing were predicted and the morphology of membrane was analyzed. It is found that the finger-like pores are formed within discontinuous polymer nodules when the binoclal curve is close to the polymer-solvent (P-S) axis, the coagulation value is small, the reduction of light transmission is easy to occur and the order of solubility parameter difference ($\Delta \delta_{i-j}$) is $\Delta \delta_{S-NS} > \Delta \delta_{P-NS} > \Delta \delta_{P-S}$. The dense skin with small nodules and the sponge type sublayer with macrovoid are formed in the case that the binodal curve is distant from the P-S axis, the onset time of liquid-liquid demixing is long and the order of $\Delta \delta_{i-j}$ is $\Delta \delta_{P-NS} >(\Delta \delta_{S-NS} < > \Delta \delta_{P-S})$. The thick layer of fine nodule coagulation and loosely grown sublayer of nodules appear when the binodal curve is distant from the P-S axis, the onset time of liquid-liquid demixing is very long and the order of $\Delta \delta_{i-j}$가 $\Delta \delta_{S-NS} > (\Delta \delta_{P-NS}$\lessgtr$ > (\Delta \delta_{P-NS} < >)\Delta \delta_{P-S}$ ).

• Molecules and Cells
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• v.38 no.12
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• pp.1054-1063
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• 2015

Mitochondria play a crucial role in eukaryotic cells; the mitochondrial electron transport chain (ETC) generates adenosine triphosphate (ATP), which serves as an energy source for numerous critical cellular activities. However, the ETC also generates deleterious reactive oxygen species (ROS) as a natural byproduct of oxidative phosphorylation. ROS are considered the major cause of aging because they damage proteins, lipids, and DNA by oxidation. We analyzed the chronological life span, growth phenotype, mitochondrial membrane potential (MMP), and intracellular ATP and mitochondrial superoxide levels of 33 single ETC component-deleted strains during the chronological aging process. Among the ETC mutant strains, 14 ($sdh1{\Delta}$, $sdh2{\Delta}$, $sdh4{\Delta}$, $cor1{\Delta}$, $cyt1{\Delta}$, $qcr7{\Delta}$, $qcr8{\Delta}$, $rip1{\Delta}$, $cox6{\Delta}$, $cox7{\Delta}$, $cox9{\Delta}$, $atp4{\Delta}$, $atp7{\Delta}$, and $atp17{\Delta}$) showed a significantly shorter life span. The deleted genes encode important elements of the ETC components succinate dehydrogenase (complex II) and cytochrome c oxidase (complex IV), and some of the deletions lead to structural instability of the membrane-$F_1F_0$-ATP synthase due to mutations in the stator stalk (complex V). These short-lived strains generated higher superoxide levels and produced lower ATP levels without alteration of MMP. In summary, ETC mutations decreased the life span of yeast due to impaired mitochondrial efficiency.

• BMB Reports
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• v.30 no.5
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• pp.370-377
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• 1997

A novel assay method is described for rapid quantitation of reaction rate of sterol ${\Delta}^7$-reductase (${\Delta}^7$-SR) which catalyzes reduction of the ${\Delta}^7$-double bond of sterols. Of six different organ tissues-liver, small intestine, brain, lung, kidney, and testis-. ${\Delta}^7$-SR activity was detected only in liver (2.30 nmol/min/mg protein) and testis (0.11 nmol/min/mg protein). Using a newly developed method which employs diet-induced enzyme proteins and ergosterol as substrate, we assessed both kinetics ($K_m=210\;{\mu}M$, $V_{max}=1.93\;nmol/min/mg$) and inhibition of the rat hepatic ${\Delta}^7$-SR against well-studied cholesterol lowering agents such as triparanol ($IC_{50}=16\;{\mu}M$). 3-$\beta$-[2-(diethylamino)ethoxy]androst-5-en-17-one (U18666A) ($IC_{50}=5.2\;{\mu}M$), and trans-1.4-bis(2-chlorobenzylaminomethyl)cyclohexane dihydrochloride (AY-9944) ($IC_{50}=0.25\;{\mu}M$). Of the three well-known AY-9944-sensitive cholesterogenic enzymes (i.e., ${\Delta}^7$-SR, sterol ${\Delta}^8$-isomerase, and sterol ${\Delta}^14$-reductase). ${\Delta}^7$-SR was found to be the most sensitive enzyme with a noncompetitive inhibition of this compound ($K_i=0.109\;{\mu}M$). Substrate specificity studies of the microsomal ${\Delta}^7$-SR indicate that the relative reaction rate for 7-dehydrocholesterol and ergosterol are 5.6-fold and 1.6-fold higher than that for lathosterol. ${\Delta}^7$-SR activity was also modulated by feeding rats a diet supplemented with 0.5% ergosterol (>2.6-fold) in addition to 5.0% cholestyramine plus 0.1% lovastatin ($\simeq$5.0-fold). Finally, microsomal ${\Delta}^7$-SR was solubilized by 1.5% 3-[3-(cholamidopropyl)-dimethylammonio]-1-propanesulfonate (CHAPS) and enriched on PEG (0~10%) precipitation, which should be suitable for further purification of the enzyme.

• Journal of Welding and Joining
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• v.5 no.1
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• pp.16-22
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• 1987

오스테나이트계 스테인레스강 용접부의 .delta.-페라이트 생성인자에 관한 위의 실험결과로부터 아래의 결론을 얻을 수 있다. (1) 오스테나이트계 스테인레스강 용접부의 .delta.-페라이트는 에너지적으로 불안정한 상으로서, 오스테나이트로의 변태가 비가역적(irreversible)이다. (2) .delta.-페라이트의 생성 및 변태에는 합금원소의 확산이 반드시 수반되며, 최종 .delta.-페라 이트 함량은 정성적으로 다음과 같이 표시된다. 페라이트함량=primary페라이트-변태한 페라이트 (3) .delta.-페라이트 생성에 일차적으로 영향을 미치는 이자는 화학조성(Cr-당량/Ni-당량)이며, primary 변태양상 및 냉각속도에도 크게 의존한다. (4) 용착부 .delta-페라이트는 대개 Vermicular와 Lathy의 혼합조직으로 존재하며, 열영향을 받 을수록 에너지적으로 안정한 Globuar 형상으로 변해간다.

• Bulletin of the Korean Chemical Society
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• v.16 no.1
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• pp.53-58
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• 1995

Heats of solution of aniline (AN), benzylamine (BA), ethyl-(EBS) and 2-phenylethyl benzenesulfonates (PEB) are calorimetrically measured in acetonitrile-methanol mixtures at 25.0 $^{\circ}C$. The activation parameters, ${\Delta}H^{\neq}$, ${\Delta}S^{\neq}$ and ${\Delta}G^{\neq}$, are determined for the reactions of EBS and PEB with AN and BA using the kinetic data at three temperatures. Calorimetric transfer enthalpies of initial state, ${\delta}H_t^{0{\rightarrow}x})$(IS), and kinetically derived activation enthalpies, ${\delta}\;{\Delta}H^{\neq}$, in the MeCN-MeOH mixtures are combined to determine the transfer enthalpies of transition state, ${\delta}H_t^{0{\rightarrow}x})$(TS); ${\delta}H_t^{0{\rightarrow}x})$(IS) = ${\delta}{\Delta}H^{\neq}\;+\;{\delta}H_t^{0{\rightarrow}x}$(IS) The preferential solvation of anionic charge in the TS predicts a loose TS with a greater degree of bond cleavage for the reactions of PEB than for EBS, and also for the reactions with BA compared to the reactions with AN.