• Title/Summary/Keyword: molecular diffusion

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Nonlinear effects in solution NMR: A numerical study on dynamics of dipolar demagnetizing field and radiation damping

  • Sangdoo Ahn;Lee, Sanghyuk
    • Journal of the Korean Magnetic Resonance Society
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    • v.3 no.2
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    • pp.71-83
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    • 1999
  • The dynamics of the dipolar demagnetizing field is investigated by numerical simulation. The effects of radiation damping, molecular diffusion, and relaxation processes on the dipolar demagnetizing field are examined in terms of the modulation pattern of the z-magnetization and the signal intensity variation. Simulations for multi-components suggest applications for sensitivity enhancement in favorable conditions.

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Quantum Mechanical Effects on Dynamical Behavior of Simple Liquids

  • Kim, Tae-Jun;Kim, Hyo-Joon
    • Bulletin of the Korean Chemical Society
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    • v.32 no.7
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    • pp.2233-2236
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    • 2011
  • We evaluate quantum-mechanical velocity autocorrelation functions from classical molecular dynamics simulations using quantum correction approaches. We apply recently developed approaches to supercritical argon and liquid neon. The results show that the methods provide a solution more efficient than previous methods to investigate quantum-mechanical dynamic behavior in condensed phases. Our numerical results are found to be in excellent agreement with the previous quantum-mechanical results.

Controlled Drug Release Using Biodegradable Polymer (체분해성 고분자를 이용한 약물의 조절방출)

  • Na, Jae Woon;Cha, Wol Suk;Kim, Sun Il
    • KSBB Journal
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    • v.5 no.4
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    • pp.377-382
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    • 1990
  • The characteristics controlled drug release have been studied for biodegradable polymer matrix. Polymer matrix was prepared from glycerine, prednisolone and dextran. Mathematical analysis of the data showed that the release behavior actually conformed to the Higuchi's diffusion controlled model. The release time was increased as drug loading doses increased, whereas decreased as glycerine concentration increased. The release rate did not change by varying molecular weight of dextran.

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Dynamics of Interdiffusion at Interface between Partially Miscible Polymers

  • 김운천;박형석
    • Bulletin of the Korean Chemical Society
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    • v.20 no.12
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    • pp.1479-1482
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    • 1999
  • We have studied the behavior of interdiffusion between partially miscible polymer pair from a theoretical viewpoint by applying the reptation model for collective interdiffusion and spinodal decomposition in polymer mixtures with different molecular weights. We find that our predictions agree well with the experiments of Klein and co-workers, where the exponent α of the initial increase of interfacial width with time in $t^{\alpha}$ is significantly lower than 0.5 for free diffusion.

A Nonlinear Theory of Diffusion-Driven Instability in the Oregonator

  • Lee, Myung-Ho;Lee, Dong-Jae;Shin, Kook-Joe;Lee, Young-Hoon;Ko, Seuk-Beum
    • Bulletin of the Korean Chemical Society
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    • v.8 no.3
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    • pp.196-200
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    • 1987
  • A nonlinear theory presented previously is applied to the Oregonator, which is a model for the Belousov-Zhabotinskii reaction, to study instability near the critical point driven by diffusions. The result shows that the theory may be applied to an actual system.

The Radial Distribution Functions of the Scaled OSS2 Water

  • Lee, Song Hi
    • Journal of the Korean Chemical Society
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    • v.56 no.6
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    • pp.669-672
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    • 2012
  • Classical molecular dynamics (MD) simulations using a scaled OSS2 potential originally derived from ab initio calculations are used to study the radial distribution functions of water. The original OSS2 water potential is shown to represent a glassy or an ice at ambient temperature, but the diffusion coefficient increases on increasing the temperature of the system or decreasing the density. This suggests scaling the OSS2 potential. The O-O, O-H, and H-H radial distribution functions and the corresponding coordination numbers for the scaled OSS2 potential, obtained by MD simulation, are in good agreement with the experiment results and calculations for the SPC/E water potential over a range of temperatures.

Annealing Effects on $Zn_{0.9}Cd_{0.1}$/Se/ZnSe Strained Single Quantum Well (Zn_{0.9}Cd_{0.1}/ZnSe 변형된 단일 양자우물구조의 열처리 효과)

  • 김동렬;배인호;손정식
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.13 no.6
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    • pp.467-471
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    • 2000
  • The thermal annealing effect of $Zn_{0.9}Cd_{0.1}$ single quantum-well structures grown by molecular beam epitaxy is investigated. As the results of before and after rapid thermal annealed samples a red shift of E1-HH1 peak by Cd interdiffusion during thermal annealing of ZnCeSe/ZnSe sample was observed. In the case of annealed sample over $450^{\circ}C$ donor and acceptor impurities related peaks were observed which seems to be due to a diffusion of Ga and As from GaAs substrate. And also interdiffusion phenomena is idenified by the results of DCX measurements and which are consisten with the PL measurements.

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Re-determination of inelastic collision cross sections for $C_{3}F_{8}$ molecular gas in $C_{3}F_{8}-Ar$ mixture gases ($C_{3}F_{8}-Ar$혼합가스 상에서 $C_{3}F_{8}$분자가스의 비탄성단면적의 재결정)

  • Jeon, Byoung-Hoon
    • Proceedings of the KIEE Conference
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    • 2005.11a
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    • pp.21-23
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    • 2005
  • The electron transport coefficients, the electron drift velocity W, the longitudinal diffusion coefficient $ND_L$ in $C_{3}F_{8}-Ar$ mixture gases were measured by Double shutter drift tube and calculated by multi-term approximation of the Boltzmann equation over the wide E/N range from 0.03 to 100 Td. And an inelastic collision cross sections for $C_{3}F_{8}$ molecular gas were redetermined for quantitative characteristic analysis.

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Antimicrobial and Cytotoxic Activity of Di-(2-ethylhexyl) Phthalate and Anhydrosophoradiol-3-acetate Isolated from Calotropis gigantea (Linn.) Flower

  • Habib, M. Rowshanul;Karim, M. Rezaul
    • Mycobiology
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    • v.37 no.1
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    • pp.31-36
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    • 2009
  • A phytochemical study on the flower of Calotropis gigantea (Linn.) using silica gel column chromatography and preparative thin layer chromatography, led to the first time isolation of Di-(2-ethylhexyl) phthalate (compound 1) and anhydrosophoradiol-3-acetate (compound 2). The structures of these compounds were confirmed by spectroscopic analyses (IR, HRTOFMS and NMR). The antibacterial and antifungal activities of ethyl acetate extract, compound 1 and compound 2 were measured using the disc diffusion method. Ethyl acetate extract and compound 1 presented better results than compound 2. The minimum inhibitory concentrations (MICs) of the extract and compounds were found to be in the range of $16{\sim}128{\mu}g/ml$. The cytotoxicity ($LC_{50}$) against brine shrimp nauplii (Artemia salina) were also evaluated and found to be 14.61 ${\mu}g/ml$ for ethyl acetate, 9.19 ${\mu}g/ml$ for compound 1 and 15.55 ${\mu}g/ml$ for compound 2.

Vapor-liquid Interface of Argon by Using a Test-area Simulation Method

  • Lee, Song-Hi
    • Bulletin of the Korean Chemical Society
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    • v.33 no.1
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    • pp.167-170
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    • 2012
  • A test-area molecular dynamics simulation method for the vapor-liquid interface of argon through a Lennard-Jones intermolecular potential is presented in this paper as a primary study of interfacial systems. We found that the calculated density profile along the z-direction normal to the interface is not changed with time after equilibration and that the values of surface tension computed from this test-area method are fully consistent with the experimental data. We compared the thermodynamic properties of vapor argon, liquid argon, and argon in the vapor-liquid interface. Comparisons are made with kinetic and potential energies, diffusion coefficient, and viscosity.