• Bulletin of the Korean Chemical Society
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• 제21권12호
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• pp.1202-1206
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• 2000

Transmission of substituent effects through 5-membered heteroaromatic rings is investigated theoretically at the RHF/6-31+G and B3LYP/6-31+G levels using the equilibria for the $OH^- addition to five-membered heteroaromatic aldehydes (5MHA). The transmission efficiency (S) in 5MHA(A) increases in the order NH>O>S>PH but the order exactly reverses in 5MHA($T^-$). This is originated by the delocalizability of the ${\pi}$ lonepair on Y, $$n_\pi$(Y)$. A better correlation is obtained with ${\sigma}_p^-$ in the Hammett plots with positive slope, $p_z$ > 0, indicating that the substituent (Z) effects are not transmitted by a direct conjugation. The magnitude of $p_z$ for Y=NH is the largest among the heteroaromatic systems, which is consistent with the largest transmission efficiency change $({\Delta}S)$. The equilibria for the addition processes are favorable in the gas phase $({\Delta}G^o<0)$, which reverses to unfavorable in aqueous solution $({\Delta}G^o>0)$ due to the relatively large salvation energy of $OH^-$ in the initial state in aqueous solution. The orders of ${\Delta}G^o$ and $p_z$ in the gas phase are almost maintained in solution.

• 한국강구조학회 논문집
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• 제13권4호
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• pp.363-372
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• 2001

본 연구의 목적은 보항복형 비가새 골조의 $P-{\Delta}$영향을 실험적 방법을 통하여 조사하는데 있다. 이를 위하여 4개의 1층 1스팬의 보항복형 비가새 골조에 대한 가력실험을 실시하였다. 실험의 변수로는 기둥의 강성과 축력비를 적용하였다. 실험결과 저축력 상태의 보항복형 비가새 골조에서는 축력의 정량적인 크기가 $P-{\Delta}$효과로서 골조의 안정성에 영향을 미치는 것으로 나타났다. 그리고 최대수평하중은 기둥의 강성과 지점 회전강성에 비례하여 증가하며 저축력상태의 보항복형 비가새 골조는 붕괴가구 형성이 비교적 안정적인 상태에서 이루어짐을 알 수 있었다. 그리고 한계상태설계기준의 $B_2$ 계수는 골조의 비탄성거동시 $P-\Delta$효과를 적절히 고려하지 못하는 것으로 판단된다.

• 대한약침학회지
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• 제22권2호
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• pp.95-101
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• 2019

Objectives: Angiotensin II (AngII), a major product of renin-angiotensin system (RAS) has important role in induction of hypertension and antihypertensive effect of several medicinal plant was mediated by effect on this agent. Therefore, this study examined the possible effect of hydroalcoholic extract of Crocus sativus (C. sativus) on hypertension induced by AngII. Methods: Six groups (n = 6) of rats were used as follow: 1) Control, 2) AngII (300 ng/kg), 3) Losartan (Los, 10 mg/kg) + AngII and 4-6) C. sativus extract (10, 20 & 40 mg/kg,) + AngII. The femoral artery and vein were cannulated for recording cardiovascular parameters and drugs administration, respectively. All drugs were injected intravenously (i.v). Los and all doses of C. sativus injected 10 min before AngII. Systolic blood pressure (SBP), mean arterial blood pressure (MAP) and heart rate (HR) were recorded throughout the experiment and those peak changes (${\Delta}$) were calculated and compared to control and AngII. Results: AngII significantly increased ${\Delta}MAP$, ${\Delta}SBP$ and ${\Delta}HR$ than control (P < 0. 01 to P < 0.001) and these increments were significantly attenuated by Los. All doses of C. sativus significantly reduced peak ${\Delta}MAP$, ${\Delta}SBP$, and ${\Delta}HR$ than AngII group (P < 0. 05 to P < 0.001). In addition, peak ${\Delta}MAP$, ${\Delta}SBP$ in doses 10 and 20 were significant than Los + AngII group (P<0.05 to P< 0.01) but in dose 40 only MAP was significant (P<0.05). Peak ${\Delta}HR$ in all doses of C sativus was not significant than Los+ AngII. Conclusion: Regarding the improving effect of the C. sativus extract on AngII induced hypertension, it seems that this ameliorating effect partly mediated through inhibition of RAS.

• Steel and Composite Structures
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• 제14권1호
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• pp.1-20
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• 2013

This paper presents the formulation for a novel force-based 1-D compound-element that captures both material and second order P-${\Delta}$ nonlinearities in steel frames. At the nodal points, the element is attached to nonlinear rotational and a translational springs which represent the flexural and axial stiffness of the connections respectively. By decomposing the total strain in the material as well as the generalised displacements of the flexible connections to their elastic and inelastic components, a secant solution strategy based on a direct iterative scheme is introduced and the corresponding solution strategy is outlined. The strain and slope of the deformed element are assumed to be small; however the equilibrium equations are satisfied for the deformed element taking account of P-${\Delta}$ effects. The formulation accuracy and efficiency is verified by some numerical examples on the nonlinear static, cyclic and dynamic analysis of steel frames.

• Korea-Australia Rheology Journal
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• 제21권1호
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• pp.59-69
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• 2009

The prediction of pressure drop for a droplet flow in a confined micro channel is presented using FE-FTM (Finite Element - Front Tracking Method). A single droplet is passing through 5:1:5 contraction - straight narrow channel - expansion flow domain. The pressure drop is investigated especially when the droplet flows in the straight narrow channel. We explore the effects of droplet size, capillary number (Ca), viscosity ratio ($\chi$) between droplet and medium, and fluid elasticity represented by the Oldroyd-B constitutive model on the excess pressure drop (${\Delta}p^+$) against single phase flow. The tightly fitted droplets in the narrow channel are mainly considered in the range of $0.001{\leq}Ca{\leq}1$ and $0.01{\leq}{\chi}{\leq}100$. In Newtonian droplet/Newtonian medium, two characteristic features are observed. First, an approximate relation ${\Delta}p^+{\sim}{\chi}$ observed for ${\chi}{\geq}1$. The excess pressure drop necessary for droplet flow is roughly proportional to $\chi$. Second, ${\Delta}p^+$ seems inversely proportional to Ca, which is represented as ${\Delta}p^+{\sim}Ca^m$ with negative m irrespective of $\chi$. In addition, we observe that the film thickness (${\delta}_f$) between droplet interface and channel wall decreases with decreasing Ca, showing ${\delta}_f{\sim}Ca^n$ Can with positive n independent of $\chi$. Consequently, the excess pressure drop (${\Delta}p^+$) is strongly dependent on the film thickness (${\delta}_f$). The droplets larger than the channel width show enhancement of ${\Delta}p^+$, whereas the smaller droplets show no significant change in ${\Delta}p^+$. Also, the droplet deformation in the narrow channel is affected by the flow history of the contraction flow at the entrance region, but rather surprisingly ${\Delta}p^+$ is not affected by this flow history. Instead, ${\Delta}p^+$ is more dependent on ${\delta}_f$ irrespective of the droplet shape. As for the effect of fluid elasticity, an increase in ${\delta}_f$ induced by the normal stress difference in viscoelastic medium results in a drastic reduction of ${\Delta}p^+$.

• 대한치과기공학회지
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• 제23권1호
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• pp.85-93
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• 2001

The purpose of this study was to evaluate the effects of commercial home-tooth bleaching agents on the color of tooth. Twenty five sound extracted teeth were randomly divided into five groups. The color differences between before and after treatment with five types of tooth bleaching agents (7.5% hydrogen peroxide Nite White $Excel^{(R)}$, 10% carbamide peroxide Nite White $Excel^{(R)}$, 16% carbamide peroxide Nite White $Excel^{(R)}$, 10% carbamide peroxide Insta-BriteTM, 20% carbamide peroxide Insta-$Brite^{TM}$) were evaluated. The results were as follows: 1. By 2 week home tooth bleaching agent applications, the values ($L^*$) of bovine teeth increased as high as 4.38 $\sim$ 8.80 when comparing to those of the samples before treatment, and the color difference (${\Delta}E^*$) showed as high as 10.16 $\sim$ 15.04. 2. 16% carbamide peroxide Nite White Excel induced significantly greater ${\Delta}L^*$ than other test edgroups except for 7.5% hydrogen peroxide Day White Excel, and significantly greater ${\Delta}E^*$ than other tested groups by 2 week bleaching agent treatments (p<0.01). 3. 16% carbamide peroxide Nite White Excel(${\Delta}L^*$=8.80, ${\Delta}E^*$=15.04) induced significantly greater ${\Delta}L^*$ and ${\Delta}E^*$ than 10% carbamide peroxide Nite White Excel(${\Delta}L^*$=5.01, ${\Delta}E^*$=10.16)(p<0.01), but significant difference between 10% carbamide peroxide Insta-Brite(${\Delta}L^*$=4.38, ${\Delta}E^*$=10.51) and 20% carbamide peroxide Insta-Brite(${\Delta}L^*$=5.63, ${\Delta}E^*$=11.23) was not shown in ${\Delta}L^*$ and ${\Delta}E^*$(p>0.01). 4. 16% carbamide peroxide Nite White Excel(${\Delta}L^*$=8.80, ${\Delta}E^*$=15.04) which were applied in night time induced significantly greater ${\Delta}L^*$ and ${\Delta}E^*$ than 7.5% hydrogen peroxide Day White Excel(${\Delta}L^*$=8.47, ${\Delta}E^*$=12.75) which were applied in day time. Conclusions: These results demonstrate that all the commercial home-tooth bleaching agents have appreciable bleaching effect on teeth, and the effects of home-tooth bleaching agents which are used during night time are affected by content of carbamide peroxide. Especially the whitening effect of home tooth bleaching agents that are used through night time is greater than that of short time-applying tooth bleaching agent.

• Archives of Pharmacal Research
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• 제16권3호
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• pp.180-185
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• 1993

The acid dissociation constants of certain Schiff bases derived from isatin with p-substituted benzoyl hydrazines and somee amino acids of glycine, $\beta$-and $\alpha$-alanine, valine, $\beta$-phenyl-$\alpha$-alanine and anthranilic acid have been detemined potentiometrically at different temperatures in different aquo-organic solvent mixtures (ethnol, dioxane, dimethyl formamide, methanol, acetone and tetrahydrofurance). The pKa values were demonstrated on the light of the different electornic and steric effects of the substituents and the sovlent characteristics. In all the mixed media used, ionization of the compounds decreased by increasing the mole fraction of the organic cosolvent. Theemodynamic parameters $(\Delta{H}^\circ,\;\Delta{G}^\circ,\;\Delta{S}^\circ)$ were evaluated. The structural effects of the investigated compounds on these parameters were reported and discussed.

• Earthquakes and Structures
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• 제22권5호
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• pp.517-526
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• 2022

In this paper, nonlinear P-delta effects are studied on the seismic performance, and the modal responses of a flexural frame, considering large deformations. Using multiple scales method, the nonlinear differential equations of motion are estimated, and the nonlinear interactions between the frame's degrees of freedom are outcropped. The results of time and frequency domain analyzes of a dynamic model are examined under internal resonance cases, and the linear and nonlinear responses are investigated in each modal cases. Also, changing the modal responses with respect to the amplitude and frequency of the harmonic forces is evaluated. It is shown that the dominant absorption of energy is in the first natural frequency of the frame, in the case of earthquake excitation, and when a harmonic force is applied to the frame, the peaks of the frequency domain responses depending on the frequency of harmonic force are in the first, and second or third natural frequency of the structure.

• 대한화학회지
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• 제32권5호
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• pp.464-475
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• 1988

Fe(Ⅲ) 및 Mn(Ⅱ)과 p-aminoazobenzene 및 그 유도체가 반응하여 형성된 착물들에 대하여 가시-자외선 및 적외선 분광광도법과 전기전도도방법을 이용하여 용매의 효과, donor의 염기도와 착물형성에 미치는 영향을 조사하였다. 그 결과 착물의 조성비, 안정도 상수 및 몰흡광계수를 구하여 van't Hoff식으로부터 ${\Delta}H^{\circ}$, ${\Delta}G^{\circ}$ 및 ${\Delta}S^{\circ}$를 계산하였으며 반응성과 등속도관계를 고려하여 반응속도와 평형조절인자를 알게 되었다.

• Journal of Ginseng Research
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• 제34권3호
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• pp.219-226
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• 2010

In the present study, we investigated whether a gross deletion in the nef gene ($g{\Delta}nef$) is induced by Korean red ginseng (KRG) intake. Ten patients were treated with KRG powder for 3 years in the absence of antiretroviral drug therapy. On average, $3,555{\pm}1,042\;g$ KRG was administered per person over $36.1{\pm}2.4$ months. There was a mild decrease in CD4 T cell count ($75{\pm}110/{\mu}L$) over the $36.1{\pm}2.4$ months (p = 0.059). We obtained 355 nef amplicons using 71 peripheral blood mononuclear cell samples over a 3-year period. All ten patients exhibited g${\Delta}$nef (range, 3.2 to 45.9%). At baseline, 3 of 78 amplicons (3.8%) exhibited $g{\Delta}nef$, whereas 18.8% (52/277) revealed $g{\Delta}nef$ during KRG-intake (p<0.001). The proportion of $g{\Delta}nef$ was significantly correlated with monthly dose of KRG (r=0.89, p<0.001). The median time for first detection of $g{\Delta}nef$ was 13 months. In conclusion, our data show that $g{\Delta}nef$ is inducible by KRG intake and its proportion is dependent on the duration of KRG intake and dose of KRG.