• Title/Summary/Keyword: Transition-state

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Multiconfiguration Molecular Mechanics Studies for the Potential Energy Surfaces of the Excited State Double Proton Transfer in the 1:1 7-Azaindole:H2O Complex

  • Han, Jeong-A;Kim, Yong-Ho
    • Bulletin of the Korean Chemical Society
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    • v.31 no.2
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    • pp.365-371
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    • 2010
  • The multiconfiguration molecular mechanics (MCMM) algorithm was used to generate potential and vibrationally adiabatic energy surfaces for excited-state tautomerization in the 1:1 7-azaindole:H2O complex. Electronic structures and energies for reactant, product, transition state were computed at the CIS/6-31G(d,p) level of theory. The potential and vibrationally adiabatic energies along the reaction coordinate were generated step by step by using 16 high-level Shepard points, which were computed at the CIS/6-31G(d,p) level. This study shows that the MCMM method was applied successfully to make quite reasonable potential and adiabatic energy curves for the excited-state double proton transfer reaction. No stable intermediates are present in the potential energy curve along the reaction coordinate of the excited-state double proton transfer in the 1:1 7-azaindole:H2O complex, indicating that these two protons are transferred concertedly. The change in the bond distances along the reaction coordinate shows that two protons move very asynchronously to make an H3O+-like moiety at the transition state.

TDDFT Potential Energy Functions for Excited State Intramolecular Proton Transfer of Salicylic Acid, 3-Aminosalicylic Acid, 5-Aminosalicylic Acid, and 5-Methoxysalicylic Acid

  • Jang, Sung-Woo;Jin, Sung-Il;Park, Chan-Ryang
    • Bulletin of the Korean Chemical Society
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    • v.28 no.12
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    • pp.2343-2353
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    • 2007
  • We report the application of time-dependent density functional theory (TDDFT) to the calculation of potential energy profile relevant to the excited state intramolecular proton transfer (ESIPT) processes in title molecules. The TDDFT single point energy calculations along the reaction path have been performed using the CIS optimized structure in the excited state. In addition to the Stokes shifts, the transition energies including absorption, fluorescence, and 0-0 transition are estimated from the TDDFT potential energy profiles along the proton transfer coordinate. The excited state TDDFT potential energy profile of SA and 3ASA resulted in very flat function of the OH distance in the range ROH = 1.0-1.6 A, in contrast to the relatively deep single minimum function in the ground state. Furthermore, we obtained very shallow double minima in the excited state potential energy profile of SA and 3ASA in contrast to the single minimum observed in the previous work. The change of potential energy profile along the reaction path induced by the substitution of electron donating groups (-NH2 and -OCH3) at different sites has been investigated. Substitution at para position with respect to the phenolic OH group showed strong suppression of excited state proton dislocation compared with unsubstitued SA, while substitution at ortho position hardly affected the shape of the ESIPT curve. The TDDFT results are discussed in comparison with those of CASPT2 method.

Transition Probabilities at Crossing in the Landau-Zener Problem

  • Park, Tae-Jun
    • Bulletin of the Korean Chemical Society
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    • v.26 no.11
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    • pp.1735-1737
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    • 2005
  • We obtain probabilities at a crossing of two linearly time-dependent potentials that are constantly coupled to the other by solving a time-dependent Schrödinger equation. We find that the system which was initially localized at one state evolves to split into both states at the crossing. The probability splitting depends on the coupling strength V0 such that the system stays at the initial state in its entirety when V0 = 0 while it is divided equally in both states when V0 . For a finite coupling the probability branching at the crossing is not even and thus a complete probability transfer at t is not achieved in the linear potential crossing problem. The Landau-Zener formula for transition probability at t is expressed in terms of the probabilities at the crossing.

Sensor Node Design based on State Transition Model (상태천이모델 기반의 센서 노드 설계)

  • Shin, DongHyun;Kim, Changhwa
    • Journal of Korea Multimedia Society
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    • v.20 no.8
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    • pp.1357-1368
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    • 2017
  • Sensor networks are used in various fields such as marine, defense, and smart home etc. Among the components of the sensor network, the sensor node collects sensor data, as one of the representative sensor network roles, and the sensor node makes a greate influence on the overall performance of the sensor network. Therefore, how to design the sensor node is an important issue in the sensor network field. However, the research on the sensor network architecture suitable for the sensor network installation environment has been made more important than the research on how to configure the sensor node. In this paper, we propose to identify elements to be considered for designing a sensor node that makes a large influence on the performance of the sensor network, and to easily implement the sensor node through the state transition model based on these elements.

Transition mechanism during the critical heat flux condition in flow and pool boiling (유동 및 풀비등에 있어서 한계열플럭스 상태하의 천이기구)

  • 김경근;김명환;권형정;김종헌;최순호
    • Journal of Advanced Marine Engineering and Technology
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    • v.13 no.4
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    • pp.40-53
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    • 1989
  • Boiling heat transfer phenomena is widely applied to BWR and electrical heating system because of its high heat transfer coefficient. In these systems, steady state heat transfer is dependent on nucleate boiling. When the heat generating rate is sharply increased or the cooling capacity of coolant is sharply decreased, sharp wall temperature rise is occurred under the critical heat flux(CHF) condition. This paper presents the simple wall temperature fluctuation model of transition mechanism in the repeating process of overheating and quenching, when coalescent bubble passes relatively slowly on the wall and simultaneously the transition from nucleate boiling to film boiling is carried at especially onset of the CHF state. The values calculated by the present model are resulted comparatively good with the measured.

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The Effects of Godulbaegi Extracts on the Fluidity of Phospholipid Liposomes by DSC (DPPC Liposome에 미치는 고들빼기 추출물의 DSC 연구)

  • 배송자;김남홍;노승배;정복미
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.27 no.3
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    • pp.518-524
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    • 1998
  • Liposomes have been widely employed as biomembrane-mimetic system and drug-delivery system. In these applications, the low stability of liposomes has been the most serious problem. They have relatively short half-lives and easily lysed through interactions with biological components. This study was performed to investigate the effects of godulbaegi extracts on the fludity of phospholipid liposomes. We used dipalmitoyl phosphatidylcholine(DPPC) liposomes which make most stable liposomes among the other phosphatidylcholines. The thermograms of the DPPC liposomal bilayers incorporated with the hexane extract of godulbaegi(Ixeris sonchifolia H.) were obtained, and the enthalpy changes and the sizes of cooperative unit of the transition were calculated. The incorporation of the Ixeris sonchifolia H. into the liposomal bilayers effectively reduced the transition temperature at which the transition from gel state to liquid-crystalline state occurs, broadened the thermogram peaks, and reduced the ratio of van't Hoff to calorimetric enthalpies. These results indicate indicate that the godulbaegi extracts (Ixeris sonchifolia H.) have significant effects on the fluidity of biological membrance.

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M-ary Multitrack Run-length Limited Codes for Optical Storage Systems (광기록저장장치를 위한 M-ary 다중트랙 RLL 코드)

    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.24 no.6A
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    • pp.888-893
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    • 1999
  • This paper introduces M-ary multitrack run-length (d.k) constrained codes for optical storage systems. We calculate capacities and densities of the codes. We have driven a general form of the state transition matrix for M-ary multitrack (d,k) codes. Using the largest eigenvalue of the transition matrix, we calculate the capacity and density. The capacity approaches to the limit with a small k constraint compared to single-track codes.

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Magnetoresistance behavior of La_{1-\chi}Sr_\chiCoO_{3-\delta} films around the metal-insulator transition

  • Park, J. S.;Park, H. G.;Kim, C. O.;Lee, Y. P.;V. G. Prokhorov
    • Journal of the Korean Vacuum Society
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    • v.12 no.S1
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    • pp.100-103
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    • 2003
  • The magnetoresistance (MR) of La1χSχCoO3δ films prepared by pulsed-laser deposition were investigated in order to clarify the magnetotransport properties around the metal-insulator transition. For the films in the metallic state (χ > 0.25), the MR(T) manifests a small peak at the Curie temperature due to the spin-disorder scattering. The transition of the film into the insulating state (χ 0.25) is accompanied by an essential growth of the MR and results in a significant increase in the MR(T) with decreasing temperature, due to a phase separation into the ferromagnetic-metal clusters and the insulating matrix.

NMR for magnetite

  • Lee, Soonchil
    • Journal of the Korean Magnetic Resonance Society
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    • v.22 no.4
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    • pp.101-106
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    • 2018
  • Magnetite is the oldest magnet material known to mankind. It is getting attention again from solid state physics researchers now a days because it is one of the most strongly correlated electron systems. Spin, charge, and orbital orders are interplaying with lattice and involved in the Verwey transition where magnetization, conductivity, and structure changes suddenly. The peculiar ordering states above and below the transition temperature mainly originate from the coexistence of Fe2+ and Fe3+ ions in the B site of the inverse spinel structure. In particular, the state of the charge and orbital order was the oldest and most intriguing problem. NMR has made significant contribution to the investigation of this question. A. Abragam stated that there is no doubt that NMR is a very powerful tool for the study of ferromagnetic and antiferromagnetic materials. In this mini-review, a short history of NMR investigation of magnetite is presented, providing a support to Abragam's claim.