Academic literature on the topic 'Molecular diffusion coefficient'
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Journal articles on the topic "Molecular diffusion coefficient"
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Miyamoto, Shuichi, and Kazumi Shimono. "Molecular Modeling to Estimate the Diffusion Coefficients of Drugs and Other Small Molecules." Molecules 25, no. 22 (November 16, 2020): 5340. http://dx.doi.org/10.3390/molecules25225340.
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Diffusion is a spontaneous process and one of the physicochemical phenomena responsible for molecular transport, the rate of which is governed mainly by the diffusion coefficient; however, few coefficients are available because the measurement of diffusion rates is not straightforward. The translational diffusion coefficient is related by the Stokes–Einstein equation to the approximate radius of the diffusing molecule. Therefore, the stable conformations of small molecules were first calculated by molecular modeling. A simple radius rs and an effective radius re were then proposed and estimated using the stable conformers with the van der Waals radii of atoms. The diffusion coefficients were finally calculated with the Stokes–Einstein equation. The results showed that, for the molecules with strong hydration ability, the diffusion coefficients are best given by re and for other compounds, rs provided the best coefficients, with a reasonably small deviation of ~0.3 × 10−6 cm2/s from the experimental data. This demonstrates the effectiveness of the theoretical estimation approach, suggesting that diffusion coefficients have potential use as an additional molecular property in drug screening.
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Wei, Qing Hua, Ya Nen Wang, Ming Ming Yang, Wei Hong Chai, and Ying Feng Zhang. "Molecular Dynamics Study of H2O Molecular Diffusion Behavior in PAM/PVA Polymer Blends." Advanced Materials Research 1119 (July 2015): 268–72. http://dx.doi.org/10.4028/www.scientific.net/amr.1119.268.
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The theoretical method of molecular dynamics was applied to study H2O molecular diffusion behavior in PAM/PVA Polymer blends, investigated the effects of component ratios, temperatures and water contents on diffusion coefficient. Results show that with the increase of PVA content in blend systems, the H2O molecule diffusion coefficient first increased and then decreased. This indicates there is an optimum component ratio to make the H2O molecule diffusion coefficient maximum. There is a certain influence of temperature on H2O molecular diffusion in PAM/PVA blend system, the higher the temperature, the bigger the H2O molecular diffusion coefficient. When the less H2O molecules contained in system, there is a less impact on the diffusion coefficient. As the number of H2O molecules reaches a certain amount, the effect on the diffusion coefficient is more obvious.
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Islam, Md Shafiqul, Sayem Ahmeed, and Sumon Kumar Ghosh. "Diffusion study of chloride and binding of water in concrete pore by molecular dynamics simulation using LAMMPS." Challenge Journal of Concrete Research Letters 12, no. 3 (September 15, 2021): 88. http://dx.doi.org/10.20528/cjcrl.2021.03.002.
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As for the communication between concrete and the particles, the surface shows Cl− shock and Na adsorption. With expanded particle focus, the solid adsorption capacity for Cl− is upgraded as a result of a detailed overview of the dynamic molecular simulation studies examining the chloride diffusion coefficient. Different characteristics of the diffusion process, including molecular models, system-size effects, temperature, and pressure conditions, and the type of protection, are discussed. This paper focus on Molecular Dynamic Simulation to determine the diffusion coefficient of chloride ion and water molecules in concrete. The diffusion coefficient for NaCl salt obtained 6.60178x10-10m2/s and the diffusion coefficient for CaCl2 salt obtained 7.29305x10-10m2/s. So, the average chloride diffusion coefficient 6.9475x10-10m2/s. Diffusion coefficient obtained from graph 5.562x10-10m2/s. Diffusion coefficients for water molecules for NaCl solution are 6.125x10-10m2/s, 6.85x10-10m2/s, 1.044x10-10m2/s, 8.525x10-10m2/s, 6.25x10-10m2/s. diffusion coefficient of water molecules in CaCl2 solution are 4.5x10-10m2/s, 6.725x10-10m2/s, 1.254x10-10m2/s, 7.725x10-10m2/s, 1.3x10-10m2/s. Average value obtained for water molecule diffusion are 4.545x10-10m2/s, 7.4062x10-10m2/s and 1.149x10-10m2/s. This diffusion of chloride effects the binding of water in concrete pore.
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Bhandari, Dipendra, and N. P. Adhikari. "Molecular dynamics study of diffusion of krypton in water at different temperatures." International Journal of Modern Physics B 30, no. 11 (April 28, 2016): 1650064. http://dx.doi.org/10.1142/s0217979216500648.
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Molecular dynamics study of diffusion of two krypton atoms in 300 SPC/E water molecules at temperatures 293, 303, 313, 323 and 333 K has been carried out. Self-diffusion coefficient of krypton and water along with their mutual diffusion coefficients are estimated. Self-diffusion coefficient for krypton is calculated by using Mean Square Displacement (MSD) method and Velocity Autocorrelation (VACF) method, while that for water is calculated by using MSD method only. The mutual diffusion coefficient is estimated by using the Darken’s relation. The diffusion coefficients are found to follow the Arrhenius behavior. The structural properties of the system have been estimated by the study of solute–solute, solvent–solvent, and solute–solvent Radial Distribution Function (RDF).
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Xu, Bo, and Zhenqian Chen. "Formaldehyde diffusion within crystalline and amorphous cellulose at different temperatures and electric fields: A molecular dynamics study." Indoor and Built Environment 28, no. 2 (October 16, 2017): 175–85. http://dx.doi.org/10.1177/1420326x17736908.
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To provide a microcosmic theoretical support for the reduction of formaldehyde in building material, the diffusion process was investigated by molecular dynamics simulation. In addition, the diffusion model of formaldehyde molecules in crystalline and amorphous cellulose was built, and diffusion coefficients at different temperatures and electric fields were studied. The simulation temperature was from 293 to 393 K and electric field was from 0 to 400 kV/m. Diffusion coefficient increased with greater temperature and electric field both in crystalline and amorphous region. However, the diffusion coefficient in amorphous region could be ignored for it was two orders of magnitude lower than diffusion coefficient in crystalline region. The relationship between diffusion coefficient and temperature, and the relationship between diffusion coefficient and electric field were obtained by simulation, verified by the experiment. Temperature was shown to have a significant contribution to formaldehyde diffusion than electric field. Compared with experimental studies, the molecular dynamics simulation could only analyse the diffusion coefficient qualitatively because of the difference between micro-scale and macro-scale.
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Xiaoming, Du. "Molecular Dynamics Study of Hydrogen on Alkali-Earth Metal Cations Exchanged X Zeolites." International Journal of Chemical Engineering 2014 (2014): 1–9. http://dx.doi.org/10.1155/2014/701057.
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The self-diffusion of hydrogen in Ca2+-, Mg2+- and Ba2+-exchanged X zeolites (Mg46X, Ca46X, and Ba46X) has been studied by molecular dynamics (MD) simulations for various temperatures and loadings. The results indicate that in the temperature range of 77–298 K and the loading range of 1–80 molecules/cell, the self-diffusion coefficients are found to range from1.2×10-9 m2·s−1to2.3×10-7 m2·s−1which are in good agreement with the experimental values from the quasielastic neutron scattering (QENS) and pulse field gradients nuclear magnetic resonance (PFG NMR) measurements. The self-diffusion coefficients decrease with loading due to packing of sorbate-sorbate molecules which causes frequent collusion among hydrogen molecules in pores and increases with increasing temperature because increasing the kinetic energy of the gas molecules enlarges the mean free path of gas molecule. The mechanism of diffusion of hydrogen molecules in these zeolites is transition diffusion. Knudsen diffusion occurs at low loading and the molecular bulk diffusion occurs at higher loading. For given temperature and loading, the self-diffusion coefficients decrease in the orderBa46X<Mg46X<Ca46X, due to the different sizes and locations of the divalent cations. Moreover, the effect of concentration of molecular hydrogen on self-diffusion coefficient also is analyzed using radial distribution function (RDF).
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Green, Peter F., and Edward J. Kramer. "Diffusion in Polymer Alloy Melts." MRS Bulletin 12, no. 8 (December 1987): 42–47. http://dx.doi.org/10.1557/s0883769400066744.
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AbstractDiffusion in polymer alloys or blends can be used to extract information on the fundamentals of the dynamics of individual polymer chains in the melt and the thermodynamics of the interaction between unlike polymer species. The dynamics of individual chains are available from measurements of the tracer diffusion coefficients, D*, of the various species while the thermodynamics of interaction, represented by the Flory parameter, x, can be obtained from measurements of the mutual diffusion or interdiffusion coefficient, D. We will show that these quantities can be measured conveniently by forward recoil spectrometry (FRES), an ion beam analysis technique that can determine the concentration versus depth profile of polymers labeled with deuterium diffusing into unlabeled polymer matrices.For high enough molecular weight of the matrix, the tracer diffusion coefficient of both species in the blend scale as D0N−2, where N is the number of monomer segments per diffusing chain; the constant D0, however, can differ by more than 104 for chemically different molecules diffusing in the same blend, suggesting that conventional concepts of chain dynamics in melts, such as monomer friction coefficients, need to be reexamined. The mutual diffusion coefficient is controlled by the faster species in the blend (the one with the larger D*N product) in agreement with what was found in metallic alloys (but in sharp disagreement with the “slow” theory of mutual diffusion which predicts that the slower species controls). Since the combinatorial (ideal) entropy of mixing of polymers is low, the thermodynamic driving force for diffusion is dominated by enthalpy and excess entropy of mixing (x) to a degree unprecedented for atomic or small molecule systems. This means that one can observe not only a thermodynamic “slowing down” of diffusion when x becomes positive as one nears the spinodal but also a large thermodynamic “speeding up” of diffusion when x is negative. Measurements of mutual diffusion turn out to be one of the most sensitive methods available for measuring x.
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Nejad, Marjan A., and Herbert M. Urbassek. "Adsorption and Diffusion of Cisplatin Molecules in Nanoporous Materials: A Molecular Dynamics Study." Biomolecules 9, no. 5 (May 27, 2019): 204. http://dx.doi.org/10.3390/biom9050204.
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Using molecular dynamics simulations, the adsorption and diffusion of cisplatin drug molecules in nanopores is investigated for several inorganic materials. Three different materials are studied with widely-varying properties: metallic gold, covalent silicon, and silica. We found a strong influence of both the van der Waals and the electrostatic interaction on the adsorption behavior on the pore walls, which in turn influence the diffusion coefficients. While van der Waals forces generally lead to a reduction of the diffusion coefficient, the fluctuations in the electrostatic energy induced by orientation changes of the cisplatin molecule were found to help desorb the molecule from the wall.
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Szmyt, Wojciech, Carlos Guerra, and Ivo Utke. "Diffusion of dilute gas in arrays of randomly distributed, vertically aligned, high-aspect-ratio cylinders." Beilstein Journal of Nanotechnology 8 (January 9, 2017): 64–73. http://dx.doi.org/10.3762/bjnano.8.7.
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In this work we modelled the diffusive transport of a dilute gas along arrays of randomly distributed, vertically aligned nanocylinders (nanotubes or nanowires) as opposed to gas diffusion in long pores, which is described by the well-known Knudsen theory. Analytical expressions for (i) the gas diffusion coefficient inside such arrays, (ii) the time between collisions of molecules with the nanocylinder walls (mean time of flight), (iii) the surface impingement rate, and (iv) the Knudsen number of such a system were rigidly derived based on a random-walk model of a molecule that undergoes memoryless, diffusive reflections from nanocylinder walls assuming the molecular regime of gas transport. It can be specifically shown that the gas diffusion coefficient inside such arrays is inversely proportional to the areal density of cylinders and their mean diameter. An example calculation of a diffusion coefficient is delivered for a system of titanium isopropoxide molecules diffusing between vertically aligned carbon nanotubes. Our findings are important for the correct modelling and optimisation of gas-based deposition techniques, such as atomic layer deposition or chemical vapour deposition, frequently used for surface functionalisation of high-aspect-ratio nanocylinder arrays in solar cells and energy storage applications. Furthermore, gas sensing devices with high-aspect-ratio nanocylinder arrays and the growth of vertically aligned carbon nanotubes need the fundamental understanding and precise modelling of gas transport to optimise such processes.
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Andryuschenko, Vladimir, and Valery Rudyak. "Self-Diffusion Coefficient of Molecular Fluid in Porous Media." Defect and Diffusion Forum 312-315 (April 2011): 417–22. http://dx.doi.org/10.4028/www.scientific.net/ddf.312-315.417.
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The paper deals with the molecular-dynamics simulation of the self-diffusion of fluid molecules in porous media using the hard-sphere potential. A study is made of the velocity autocorrelation functions of the molecules and dependences of the self-diffusion coefficient on the pore sizes, po-rosity, fluid density, and adsorption time.
Dissertations / Theses on the topic "Molecular diffusion coefficient"
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Ayoub, Pierre. "Molecular dynamics study of pyrene excimer formation and oxidation in lipid bilayer models." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAE038/document.
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Nous proposons une nouvelle approche pour déterminer le coefficient de diffusion dans des membranes lipidiques se basant sur la formation d'excimères. Alors que les autres modèles statistiques considèrent le système comme un ensemble de points sur un réseau, nous utilisons un modèle à gros grain afin d'étudier des bicouches lipidiques simulées à l'aide du champs de force Martini. Nous déterminons le taux de réaction dépendant du temps à partir des probabilités de survie obtenues a posteriori à l'aide des trajectoires numeriques des bicouches symétriques de DOPC (1,2-Dioleoyl-sn-glycero-3-phosphocholine) et POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) simulées à 283 K et 293 K respectivement. Les dynamiques de collision sont obtenues en distinguant virtuellement les molécules simulées. Les sondes fluorescentes sont supposées semblables aux lipides, et par conséquent, ne modifient pas la dynamique. Nous obtenons une expression générale pour la probabilité de survie en combinant approximation des paires indépendantes et propriétés d'échelle, mais aucune hypothèse n'est faite pour le taux de formation d'excimère. En superposant les intensités d'émission de fluorescence normalisées, déterminées numériquement, aux courbes de titrations expérimentales, nous obtenons deux ensembles de résultats pour le coefficient de diffusion latéral, selon que l'association entre feuillets est autorisée ou pas. Nous utilisons un rayon de capture de 0.5 nm, la distance à partir de laquelle les deux sondes réagissent pour former un excimère. En comparant la dynamique Martini aux expériences de fluorescence, il est possible d'estimer le facteur d'accélérationWe propose a novel approach to extract the lateral diffusion coefficient in lipid bilayers using excimer formation. In contrast to previous statistical models that modeled the system as points undergoing jumps from site to site on a lattice, we use coarse-grained molecular dynamics to study lipid bilayers simulated using the Martini force field. We derive time dependent reaction rates from survival probabilities obtained a posteriori from numerically generated trajectories of symmetric DOPC (1,2-Dioleoyl-sn-glycero-3-phosphocholine) and POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) bilayers at 283K and 293K respectively. Collision dynamics are determined by virtually relabeling the simulated molecules. The fluorescent probes are assumed to behave like ordinary membrane lipids and therefore the dynamics remain unaffected. We derive a generalized expression for the survival probability combining independent pairs and size scaling assumptions, but no assumption is made regarding the kinetic rate of the excimer formation process. By fitting the numerically determined normalized fluorescence emission intensities to experimental titration curves, we obtain two sets of results for the lateral diffusion coefficients depending whether interleaflet excimer association is allowed or not. We use a capture radius of 0.5 nm, the distance at which the probes react to form excimers. By relating Martini dynamics to real fluorescence experiments, we estimate the numerical Martini acceleration factor. We also study mixtures of oxidized-non oxidized DOPC and POPC bilayers using a hydroperoxidized model of these lipids for different concentrations of the oxidized component (3.1%, 25% and 50%). Using pair correlation functions, we extract structural information on the systems and determine whether the two components are prone to mixing or not. Finally, we calculate the thermodynamic mixing parameters within the framework of the virial expansion
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Vaz, Graça Raquel Veiga. "Experimental measurement and molecular dynamics simulation of diffusivities in supercritical mixtures." Doctoral thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/14917.
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Doutoramento em Engenharia QuímicaThis work focuses diffusivities due to their importance in the design and simulation of rate-controlled processes. Three approaches are followed: phenomenological modeling through the development of predictive macroscopic models, molecular dynamics simulations, and experimental measurement by the chromatographic peak broadening technique. Self-diffusion coefficients of model and real fluids were firstly studied using entropy based scaling laws. Rosenfeld, Dzugutov and Bretonnet expressions were tested using a large database previously compiled, involving 1727 data points. It was shown that they fail in the entire range of density and temperature, and that diffusivity depends not only on residual entropy but also on the size/geometry of the molecule (through a chain size parameter). For these reasons, a new universal correlation using artificial neural networks was proposed, which relates self-diffusivities with residual entropy and chain size parameter. It is valid for both model and real fluids, whether spherical or asymmetrical, polar or non-polar (global AARD = 9.13%). Moreover, a simple analytical expression was devised for spherical systems, and provides only 4.61% of error based uniquely on residual entropy. Three modified hydrodynamic expressions were proposed to accurately estimate tracer diffusivities (D12) in supercritical carbon dioxide (SC-CO2), based on the Wilke-Chang, Scheibel and Lusis-Ratcliff equations. They relate D12 with the ratio between temperature and solvent viscosity (T/η1), and solute molar volume at normal boiling point (Vbp), as in the original models. The introduction of two universal constants reduce the average errors from [11.70– 23.16]% to [8.26–8.51]% for a large database of 150 systems and 4484 data points over wide ranges of temperature and pressure. In an attempt to adopt more reliable solute properties, four improved Stokes- Einstein based models were devised by modifying Wilke-Chang, Scheibel, Lusis-Ratcliff, and Tyn-Calus equations, where Vbp values were substituted by critical volumes. They achieve similar results to the previous approach (AARD = 7.86-8.56%) for an equivalent database. Further statistics confirmed the good and sturdy nature of these models to accurately predict tracer diffusivities in SC-CO2 for any kind of solute. Another predictive model was developed for supercritical systems, combining two terms – background plus singular – to accurately estimate diffusivities not only far but also near the critical point, where asymptotic behavior is observed. The model achieves an average error of 6.20% for a large database, performing equally well for polar and non-polar solutes, and in the whole pressure-temperature plane, while expressions from literature deliver 11.62- 75.17% errors. Molecular dynamics simulations were performed to study the diffusivities of propanone, butanone, 2-pentanone and 3-pentanone in SC-CO2. They were computed using Einstein formula, and their dependence on temperature, pressure (or density), and molecular size was analyzed. A local structural analysis was further accomplished by calculating some radial distribution functions and coordination numbers to disclose and interpret the local environment of CO2 around each group composing ketone molecules. An experimental setup to measure diffusion coefficients by chromatographic peak broadening technique was designed, assembled and tested. Tracer diffusivities of α-pinene in SC-CO2 were determined at 313.15, 323.15 and 333.15 K, and pressures from 175 to 275 bar. The dependency of D12 upon temperature, pressure, solvent density, and hydrodynamic behavior has been examined in detail. Finally, the experimental data were modeled using equations developed in this work and good results were obtained (AARD = 2.48 – 3.56%); well-known expressions from the literature were also considered.
Neste trabalho estudaram-se coeficientes de difusão devido à sua importância no projeto e simulação de processos conduzidos por cinética. Foram seguidas três abordagens: modelação fenomenológica através do desenvolvimento de modelos macroscópicos preditivos, simulações de dinâmica molecular e medição experimental pela técnica cromatográfica de abertura de pico. Os coeficientes de autodifusão foram primeiramente focados, analisando-se leis de redução baseadas na entropia residual. As expressões de Rosenfeld, Dzugutov e Bretonnet foram testadas usando uma extensa base de dados compilada previamente, envolvendo 1727 pontos. Mostrou-se que estas equações falham em toda a gama de densidade e temperatura, e que a difusividade depende não só da entropia residual mas também do tamanho/geometria da molécula (através de um parâmetro que caracteriza o tamanho da cadeia). Por estas razões propôs-se uma correlação universal baseada em redes neuronais, que relaciona os coeficientes de autodifusão com a entropia residual e o parâmetro de tamanho da molécula. Esta é válida para fluidos modelo e reais, quer sejam moléculas esféricas ou não esféricas, polares ou apolares (AARD global = 9.13%). Para além disso, uma expressão analítica simples foi desenvolvida para sistemas esféricos, baseada apenas na entropia residual, dando origem um erro médio de 4.61%, Três expressões hidrodinâmicas modificadas foram propostas para estimar com exatidão difusividades binárias a diluição infinita (D12) em dióxido de carbono supercrítico (SC-CO2), baseadas nas equações de Wilke-Chang, Scheibel e Lusis-Ratcliff. Estas relacionam D12 com a razão entre a temperatura e a viscosidade do solvente (T/η1), e com o volume molar do soluto à temperatura normal de ebulição (Vbp), tal como o fazem os modelos originais. A introdução de duas constantes universais reduziu os erros médios de [11.70–23.16]% para [8.26–8.51]%, calculados para uma extensa base de dados de 150 sistemas e 4484 pontos experimentais, varrendo gamas largas de pressão e temperatura. Com o objetivo de se utilizar propriedades de soluto mais plausíveis, foram propostos quatro modelos baseados na relação de Stokes-Einstein, modificando as equações de Wilke-Chang, Scheibel, Lusis-Ratcliff e Tyn- Calus, onde os valores de Vbp foram substituídos por volumes críticos. Estas fornecem resultados similares aos da abordagem anterior (AARD = 7.86- 8.56%) para uma base de dados equivalente. O cálculo de outras grandezas estatísticas permitiu confirmar a solidez destes modelos para prever difusividades binárias de quaisquer solutos em SC-CO2. Foi proposto outro modelo preditivo para sistemas supercríticos, combinando dois termos – regular e singular – para estimar corretamente difusividades não apenas longe mas também junto ao ponto crítico, onde se sabe existir um comportamento assimptótico de D12. O modelo fornece um erro médio de 6.20% para toda a base de dados, com bom desempenho para solutos polares e não polares em toda a gama pressão-temperatura, enquanto as expressões da literatura atingem erros de 11.62-75.17%. Foram efetuadas simulações de dinâmica molecular para estudar as difusividades de propanona, butanona, 2-pentanona e 3-pentanona em SCCO2. Estas foram calculadas usando a relação de Einstein, e as suas dependências com a temperatura, pressão (ou densidade) e tamanho molecular foram analisadas. Foi ainda conduzida uma análise estrutural local dos sistemas através do cálculo de funções distribuição radial e números de coordenação, para discriminar e interpretar o ambiente local do CO2 em torno de cada grupo que compõe as moléculas de cetona. Foi concebida, instalada e testada uma instalação experimental para medir coeficientes de difusão pelo método cromatográfico de abertura de pico. Foram determinadas difusividades de α-pineno a diluição infinita em SC-CO2 a 313.15, 323.15 e 333.15 K, e pressões entre 175 e 275 bar. Examinou-se em pormenor a dependência de D12 com a temperatura, pressão e densidade do solvente, e o seu comportamento hidrodinâmico. Por fim, os valores experimentais foram modelados usando equações desenvolvidas neste trabalho e obtiveram bons resultados (AARD = 2.48 – 3.56%); foram também consideradas expressões bem conhecidas da literatura.
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Benayada, Bencheriet. "Détermination des coefficients de diffusion rotationnelle : Application à l'autoassociation entre molécules polyaromatiques." Nancy 1, 1988. http://www.theses.fr/1988NAN10019.
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Il s'agit d'une étude fondamentale de l'influence de l'autoassociation de molécules polyaromatiques pr mesure des coefficients de diffusion rotationnelle à partir des temps de relaxation T1 des carbones protonés. Des molécules comme le fluoranthène, le chrysène ou le benzanthracène sont des rotateurs plans asymétriques ou toupies non symétriques (molécules planes possédant deux axes principaux, par rapport auxquels les moments d'inertie sont différents). La mesure du temps de relaxation dipolaire est directement liée au paramètre caractérisant la réorientation moléculaire, appelée temps de corrélation efficace
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Herrán, Fernando. "Validation, improvement and implementation of sorption mathematical models using a quartz crystal microbalance (QCM)." Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10063.
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Ce travail de thèse a été réalisé, dans le cadre de la convention CIFRE 1538/2010, au sein d'adixen Vacuum Products (aVP) à Annecy (France). Il a été en partie financé par le projet S.P.A.M. (Surface Physics for Advanced Manufacturing). Il s'agit d'un projet ITN financé par le programme Pierre et Marie Curie de la Communauté Européenne rassemblant des partenaires universitaires et industriels dont aVP. L'objectif de ce programme était de contribuer à l'étude et au développement de la lithographie et en particulier la lithographie à ultraviolet extrême (EUVL). Ce travail porte sur la problématique de la contamination moléculaire dans l'industrie des semi-conducteurs ainsi que les besoins de maitrise de contamination pour la photolithographie EUVL. Pour ce faire, des modèles mathématiques de sorption ont été recherchés, testés et validés à l'aide d'une microbalance à quartz (QCM). Cette technique, possédant une très haute sensibilité (au niveau du ng), permet d'étudier les phénomènes de sorption relatifs à tout matériau déposable sur un cristal de quartz mis au contact de différents gaz dont la pression partielle est maitrisée. Par conséquent, le protocole détaillé dans cette thèse peut être utilisé pour d'autres types d'expériences dans toute discipline nécessitant une telle précision. Le déroulement de notre plan d'expérience comprend deux types de matériaux naturellement différents : un polymère (PCBA) d'une part et deux substrats métalliques (SS AISI 304 et CuC1) d'autre part pour lesquels le transfert de masse n'intervient pas de la même manière. Les gaz d'étude ont été sélectionnés pour leur intérêt dans l'industrie des semi-conducteurs (vapeur d'eau, HF). Le résultat de l'interaction des gaz d'étude avec les substrats ciblés est suivi en direct par la QCM, ce qui permet non seulement de valider et/ou améliorer les modèles mathématiques déjà disponibles dans la bibliographie mais aussi de les ajuster aux données obtenues expérimentalement. Nous pouvons ainsi non seulement prévoir le comportement des contaminants à l'équilibre (isothermes) et à l'état transitoire mais aussi réaliser des estimations de sorption à des températures autres que celles retenues pour notre plan d'expérienceThis thesis was carried out within the framework of the CIFRE 1538/2010 convention at adixen Vacuum Products (aVP) in Annecy (France). It is has been partly funded by the ITN project SPAM (Surface Physics for Advanced Manufacturing). SPAM is an ITN project funded by the Pierre and Marie Curie program of the European Community bringing together academic institutions and industrial partners including aVP. The objective of this program was to contribute to the study and development of lithography and extreme ultraviolet lithography (EUVL). This work deals with the issues caused by the airborne molecular contamination (AMC) in the semiconductor industry and their control needs in EUVL and the current photolithography. In order to tackle the problem, sorption mathematical models have been investigated and validated using a quartz crystal microbalance (QCM). This technique, which confers a high sensitivity (ng level), allows the study of the sorption phenomena related to any deposable material onto a quartz crystal in contact with different gases whose concentrations are accurately controlled. Consequently, the protocol detailed in this thesis may be used for other types of experiments in any discipline requiring such precision. The conduct of our experimental plan includes two types of naturally different materials: a polymer (PCBA) on the one hand and two metallic substrates (stainless steel AISI 304 and CuC1) on the other hand, for which the matter transfer does not occur in the same manner. Studied gases were selected for their interest in the semiconductor industry (water vapor, HF). The resulting interaction between the studied gases and the targeted substrates is continuously followed by the QCM, which allows not only to validate the mathematical models already proposed by the literature but also to fit the experimentally obtained data. This enables us not only to predict the behavior of the AMC at equilibrium (isotherms) and the transient state but also to provide sorption estimations at temperatures other than those specified in our experimental plan
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Borsali, Redouane. "Etude theorique du comportement dynamique des melanges ternaires de polymere en solution : etude experimentale par spectroscopie rayleigh quasi-elastique." Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13138.
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L'etude d'un melange ternaire de polymeres en solution semidiluee presente deux modes de relaxation. Mise en evidence par diffusion de lumiere quasi-elastique de deux processus de diffusion: le premier, lent, correspond au mouvement relatif des deux polymeres; le second, rapide, correspond au mouvement cooperatif du reseau physique forme par les deux polymeres
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Trochmann, Jose Luiz Lino. "Simulação atomistica como ferramenta para investigação dos mecanismos de difusão : coeficientes de autodifusão de gases simples em matriz polimerica." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266175.
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Orientador: Sergio Persio RavagnaniTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: Neste trabalho de tese foi realizado um estudo do potencial de predição de propriedades de transporte em matrizes poliméricas de poli - imidas, utilizando a simulação dinâmica molecular de gases simples como Oxigênio, Nitrogênio e Dióxido de Carbono. A propriedade de transporte de interesse prático, a permeabilidade de uma membrana polimérica a um dado penetrante, envolve a determinação de propriedades de ordem cinética e termodinâmica, respectivamente a determinação do coeficiente de difusão e da solubilidade deste penetrante na matriz polimérica. Atenção especial foi conferida à propriedade cinética, pela predição do coeficiente de autodifusão dos penetrantes. Num procedimento experimental clássico é de vital importância para significância das conclusões derivadas dos experimentos, o uso de amostras de membranas poliméricas adequadamente preparadas quanto à composição química, estrutura física e morfologia. Analogamente, quando se utiliza a simulação molecular para a predição de propriedades, tais como o coeficiente de autodifusão, também é de fundamental relevância para os resultados obtidos, a qualidade dos modelos moleculares das matrizes poliméricas, que serão usados como base. Assim para a preparação de modelos moleculares com o adequado empacotamento, um procedimento para a obtenção de modelos bem equilibrados foi desenvolvido neste trabalho. Os modelos moleculares desenvolvidos foram usados para a obtenção dos valores de massa específica em função da temperatura, e comparados aos valores experimentais disponíveis e quando necessário a, valores preditos por meio da expressão de massa específica em função da temperatura, acima e abaixo da temperatura de transição. A capacidade do modelo molecular desenvolvido em predizer a massa especifica e temperatura de transição vítrea foi usada como critério para a validação da adequação do empacotamento proposto para o referido modelo molecular da matriz polimérica. Os modelos validados de empacotamento, células amorfas, foram utilizados para o cálculo do coeficiente de autodifusão dos gases acima mencionados, através do da simulação dinâmica molecular. A comparação dos coeficientes de autodifusão obtidos das poli-imidas aromáticas e éster imidas, BAAF, 6FDA-ODA, PMDA-ODA e BA-20DA, para os gases O2, N2 e CO2, com os dados experimentais, permitiu concluir a adequação das células amorfas e do esquema de simulação dinâmica molecular para a predição do coeficiente de autodifusão.. A versão preditiva de Vrentas e Duda, baseada na teoria do volume livre, foi utilizada para a predição dos coeficientes de autodifusão da água e do etanol para as poli-imidas acima. , Estes valores, quando comparados com os valores obtidos através da simulação dinâmica molecular mostram a validade de ambas as teorias para a predição da cinética de difusão de penetrantes em matrizes poliméricas complexas
Abstract: In this thesis a study of the predictive potential of the molecular dynamic simulation was performed for transport properties of light gases in polyimide matrix. From de practical point of view permeability is the property of most interest, and involves kinetics as well as thermodynamics properties, diffusion coefficient and solubility of the penetrants molecule in the bulk polymeric matrix, this work will be focus in the former. As important as is in as experimental work, a well prepared polymeric membrane is essential for the significance of the draw conclusions. Therefore a special attention was take in the preparation of the bulk molecular polymeric model, the so called amorphous cell, in order to obtain well-equilibrated molecular packing models for the polyimide matrixes. The amorphous cells were prepared throughout thermodynamic transforms, using one or more of the statistical ensembles and cell specific volume obtained as a function of temperature, this data was compared against the experimental data available, and when necessary to data obtained via predictive methods. The molecular packing model ability to predict the glass transition temperature was used as criteria to validate de amorphous cell, to be used in the molecular dynamic' simulations allow the matrix to be locally flexible and coupled to the classic molecular dynamics simulation. The resulting self diffusion coefficients for the polyimide, BAAF, 6FDA-ODA, PMDAODA and BA-20DA for the gases O2, N2 e CO2 were compared to the experimental data. The lack of quality experimental diffusion data available for polyimide membranes for larger penetrants as water and ethanol, showed up as a good opportunity to assess the predictive capability of the molecular dynamic simulation for self diffusion coefficients, considering the relevant technological relevance of polyimide membranes for pervaporation process. The data of self diffusion coefficient produced by the predictive version of free-volume theory after Vrentas and Duda, was compared with the data produced via coupled molecular dynamic simulation for the water and ethanol penetrants, showing the relevance of both theories for the prediction of penetrants kinetic in complex polymeric matrixes
Doutorado
Ciencia e Tecnologia de Materiais
Doutor em Engenharia Química
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Tesson, Stéphane. "Un champ de force polarisable pour l'étude des argiles à l'échelle moléculaire." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066536/document.
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Les argiles sont utilisées dans de nombreuses applications industrielles pour lesquelles l’étude des interactions entre l’eau et les matériaux argileux sont primordiales. Les mécanismes de rétention et de transport de l'eau et des ions à la surface des argiles peuvent être modélisés à l'échelle atomique grâce à des méthodes classiques comme la Dynamique Moléculaire. Ces méthodes nécessitent de paramétrer au préalable les interactions entre les atomes du système. L'objectif principal de cette étude est d'améliorer la description de ces systèmes via la paramétrisation d'un nouveau champ de force polarisable entièrement basée sur des calculs issus de la méthode de la Théorie de la Fonctionnelle de la Densité. Les propriétés structurales, thermodynamiques et dynamiques de la pyrophyllite, du talc, et de la Na-, Ca-, Sr- et Cs-montmorillonite (sèches et hydratées) ont été bien reproduites. Notamment, la structure des couches tétraédriques et celle des espaces interfoliaires sont en très bon accord avec les données expérimentalesThe wide use of clay minerals in industrial applications is partly due to their remarkable properties of water retention at the mineral surface. Retention and transport mechanisms of water molecules and ions at the surface of clays can be modeled at the atomic scale via different classical methods such as molecular dynamics. These methods require to parametrize in advance the interaction between the atoms of the system. The goal of this study is to improve the description of these systems via the parametrization of a new polarizable force field entirely based on density functional theory calculations.The structure, the thermodynamics and the dynamics properties of pyrophyllite, talc and Na-, Ca-, Sr- and Cs-montmorillonite are well reproduced. The atomic structure of sheets and interfoliar space are in good agreement with experimental results
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Foucat, Loïc. "Etude par rmn de la dynamique rotationnelle du malononitrile." Paris 6, 1987. http://www.theses.fr/1987PA066377.
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Etude de cette molecule de type rotateur asymetrique en solution dans ch::(2)cl::(2), tetrahydrofurane et diglyne. A l'aide de la theorie de la "relaxation couplee" determination des valeurs des trois constantes de diffusion du solute et des densites spectrales relatives aux mecanismes de relaxation dipole-dipole, intra-et intermoleculaire. Etude de l'influence du taux de deuteriation du solvant sur la relaxation du solute dans le cas de ch::(2)cl::(2). Ecart des densites spectrales par rapport aux previsions theoriques. Test de la validite de plusieurs modeles hydrodynamiques: celui de knauss et evans s'avere le mieux adapte
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Leroy, Frederic H. R., Allan D. Mackie, Pere Miró, Carles Bo, and Avalos Josep Bonet. "A molecular dynamics study of the diffusion coefficients in watertertbutyl alcohol mixtures." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-194585.
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Gustafson, Kurt E. "Molecular Diffusion Coefficients for Polycyclic Aromatic Hydrocarbons in Air and Water." W&M ScholarWorks, 1993. https://scholarworks.wm.edu/etd/1539617664.
Full textBooks on the topic "Molecular diffusion coefficient"
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Darrigol, Olivier. The Probabilistic Turn (1876–1884). Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198816171.003.0005.
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This chapter deals with writings in which Boltzmann expressed the statistical nature of the entropy law and temporarily made the relation between entropy and combinatorial probability a basic constructive tool of his theory. In 1881, he discovered that this relation derived from what we now call the microcanonical distribution, and he approved Maxwell’s recent foundation of the equilibrium problem on the microcanonical ensemble. Boltzmann also kept working on problems he had tackled in earlier years. He proposed a new solution to the problem of specific heats, and he performed enormous calculations for the viscosity and diffusion coefficients in the hard-ball model. In a lighter genre, he conceived a new way of determining molecular sizes, and he speculated on a gas model in which the molecular forces would be entirely attractive.
Book chapters on the topic "Molecular diffusion coefficient"
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Jerome, Neil Peter, and João S. Periquito. "Analysis of Renal Diffusion-Weighted Imaging (DWI) Using Apparent Diffusion Coefficient (ADC) and Intravoxel Incoherent Motion (IVIM) Models." In Methods in Molecular Biology, 611–35. New York, NY: Springer US, 2021. http://dx.doi.org/10.1007/978-1-0716-0978-1_37.
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AbstractAnalysis of renal diffusion-weighted imaging (DWI) data to derive markers of tissue properties requires careful consideration of the type, extent, and limitations of the acquired data. Alongside data quality and general suitability for quantitative analysis, choice of diffusion model, fitting algorithm, and processing steps can have consequences for the precision, accuracy, and reliability of derived diffusion parameters. Here we introduce and discuss important steps for diffusion-weighted image processing, and in particular give example analysis protocols and pseudo-code for analysis using the apparent diffusion coefficient (ADC) and intravoxel incoherent motion (IVIM) models. Following an overview of general principles, we provide details of optional steps, and steps for validation of results. Illustrative examples are provided, together with extensive notes discussing wider context of individual steps, and notes on potential pitfalls.This publication is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This analysis protocol chapter is complemented by two separate chapters describing the basic concepts and experimental procedure.
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Jerome, Neil Peter, Anna Caroli, and Alexandra Ljimani. "Renal Diffusion-Weighted Imaging (DWI) for Apparent Diffusion Coefficient (ADC), Intravoxel Incoherent Motion (IVIM), and Diffusion Tensor Imaging (DTI): Basic Concepts." In Methods in Molecular Biology, 187–204. New York, NY: Springer US, 2021. http://dx.doi.org/10.1007/978-1-0716-0978-1_11.
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AbstractThe specialized function of the kidney is reflected in its unique structure, characterized by juxtaposition of disorganized and ordered elements, including renal glomerula, capillaries, and tubules. The key role of the kidney in blood filtration, and changes in filtration rate and blood flow associated with pathological conditions, make it possible to investigate kidney function using the motion of water molecules in renal tissue. Diffusion-weighted imaging (DWI) is a versatile modality that sensitizes observable signal to water motion, and can inform on the complexity of the tissue microstructure. Several DWI acquisition strategies are available, as are different analysis strategies, and models that attempt to capture not only simple diffusion effects, but also perfusion, compartmentalization, and anisotropy. This chapter introduces the basic concepts of DWI alongside common acquisition schemes and models, and gives an overview of specific DWI applications for animal models of renal disease.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This introduction chapter is complemented by two separate chapters describing the experimental procedure and data analysis.
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Nath, Sangeeta, Manli Deng, and Yves Engelborghs. "Fluorescence Correlation Spectroscopy to Determine the Diffusion Coefficient of α-Synuclein and Follow Early Oligomer Formation." In Methods in Molecular Biology, 499–506. Totowa, NJ: Humana Press, 2012. http://dx.doi.org/10.1007/978-1-61779-927-3_29.
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Pedram, Maysam Z., Amir Shamloo, Aria Alasti, and Ebrahim Ghafar Zadeh. "Steered Molecular Dynamic Simulation Approaches for computing the Blood Brain Barrier (BBB) Diffusion Coefficient." In IFMBE Proceedings, 1699–703. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-19387-8_413.
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Periquito, João S., Martin Meier, Thoralf Niendorf, Andreas Pohlmann, and Neil Peter Jerome. "Renal MRI Diffusion: Experimental Protocol." In Methods in Molecular Biology, 419–28. New York, NY: Springer US, 2021. http://dx.doi.org/10.1007/978-1-0716-0978-1_24.
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AbstractRenal diffusion-weighted imaging (DWI) can be used to obtain information on the microstructure of kidney tissue, and has the potential to provide MR-biomarkers for functional renal imaging. Here we describe in a step-by-step experimental protocol the MRI method for measuring renal diffusion coefficients in rodents using ADC or IVIM models. Both methods provide quantification of renal diffusion coefficients; however, IVIM, a more complex model, allows for the calculation of the pseudodiffusion and fraction introduced by tissue vascular and tubular components. DWI provides information of renal microstructure contributing to the understanding of the physiology and the underlying processes that precede the beginning of pathologies.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This experimental protocol chapter is complemented by two separate chapters describing the basic concept and data analysis.
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Orädd, Greger, and Göran Lindblom. "Lateral Diffusion Coefficients of Raft Lipids From Pulsed Field Gradient NMR." In Methods in Molecular Biology, 127–42. Totowa, NJ: Humana Press, 2007. http://dx.doi.org/10.1007/978-1-59745-513-8_10.
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Ribeiro, Ana C. F., Luis M. P. Verissimo, Artur J. M. Valente, S. C. G. S. Andrade, A. M. T. D. P. V. Cabral, and M. A. Esteso. "Theoretical Values of Diffusion Coefficients of Electrolytes in Aqueous Solutions: Important Parameters with Application in Fundamental and Technological Areas." In Optical and Molecular Physics, 327–417. Boca Raton: Apple Academic Press, 2021. http://dx.doi.org/10.1201/9781003150053-19.
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Cavalleri, G., and G. Mingari Scarpello. "Convenient Expressions of Diffusion Coefficients for Free Electrons in Gases in Presence of Ramsauer Effects." In Swarm Studies and Inelastic Electron-Molecule Collisions, 119. New York, NY: Springer New York, 1987. http://dx.doi.org/10.1007/978-1-4612-4662-6_28.
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Glazov, Vasilii M., Lidya M. Pavlova, and Kirill V. Rezontov. "Estimation of the Self and Mutual Diffusion Coefficients in Molten CdTe by a Molecular Dynamics Technique." In Centrifugal Materials Processing, 155–61. Boston, MA: Springer US, 1997. http://dx.doi.org/10.1007/978-1-4615-5941-2_14.
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Saltzman, W. Mark. "Diffusion in Biological Systems." In Drug Delivery. Oxford University Press, 2001. http://dx.doi.org/10.1093/oso/9780195085891.003.0009.
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Drug diffusion is an essential mechanism for drug dispersion throughout biological systems. Diffusion is fundamental to the migration of agents in the body and, as we will see in Chapter 9, diffusion can be used as a reliable mechanism for drug delivery. The rate of diffusion (i.e., the diffusion coefficient) depends on the architecture of the diffusing molecule. In the previous chapter a hypothetical solute with a diffusion coefficient of 10-7 cm2/s was used to describe the kinetics of diffusional spread throughout a region. Therapeutic agents have a multitude of sizes and shapes and, hence, diffusion coefficients vary in ways that are not easily predictable. Variability in the properties of agents is not the only difficulty in predicting rates of diffusion. Biological tissues present diverse resistances to molecular diffusion. Resistance to diffusion also depends on architecture: tissue composition, structure, and homogeneity are important variables. This chapter explores the variation in diffusion coefficient for molecules of different size and structure in physiological environments. The first section reviews some of the most important methods used to measure diffusion coefficients, while subsequent sections describe experimental measurements in media of increasing complexity: water, membranes, cells, and tissues. Diffusion coefficients are usually measured by observing changes in solute concentration with time and/or position. In most situations, concentration changes are monitored in laboratory systems of simple geometry; equally simple models (such as the ones developed in Chapter 3) can then be used to determine the diffusion coefficient. However, in biological systems, diffusion almost always occurs in concert with other phenomena that also influence solute concentration, such as bulk motion of fluid or chemical reaction. Therefore, experimental conditions that isolate diffusion—by eliminating or reducing fluid flows, chemical reactions, or metabolism—are often employed. Certain agents are eliminated from a tissue so slowly that the rate of elimination is negligible compared to the rate of dispersion. These molecules can be used as “tracers” to probe mechanisms of dispersion in the tissue, provided that elimination is negligible during the period of measurement. Frequently used tracers include sucrose [1, 2], iodoantipyrene [3], inulin [1], and size-fractionated dextran [3, 4].
Conference papers on the topic "Molecular diffusion coefficient"
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Hao, Qing, and Baruch B. Lieber. "Computational Investigation on the Dispersive Transport of Angiographic Contrast Injected Antegradely Into Flow in a Tube." In ASME 2007 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2007. http://dx.doi.org/10.1115/sbc2007-176423.
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When a solute such as angiographic contrast is introduced into a solvent such as blood analog fluid flowing in a straight circular tube, it spreads under the combined action of molecule diffusion and the variation of velocity over the cross-section [8]. If two molecules are being carried in the flow, for example, one in the center and one near the wall, the rate of separation caused by the difference in bulk velocity will greatly exceed that caused by molecule motion. Given enough time, any single molecule would wander randomly throughout the cross section of the pipe because of molecular diffusion, and would sample at random all the advective velocities [4]. Therefore, Taylor [8] adopted the Lagrangian approach to the problem, casting the equations in a coordinate system that moves with the average velocity of the flow and replacing the molecular diffusion coefficient with a dispersion coefficient, and the local concentration with the cross sectional mean concentration. Recasting Taylor’s equation in an inertial coordinate system one obtained the so called advection-dispersion equation.
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Coskuner, Yakup Berk, Elio Dean, Xiaolong Yin, and Erdal Ozkan. "Water Alternating Alkane Injection: A Molecular Dynamics Simulation Study." In SPE Improved Oil Recovery Conference. SPE, 2022. http://dx.doi.org/10.2118/209363-ms.
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Abstract In a recent study, we observed that the diffusion coefficient of common hydrocarbons in crude oils are more affected by the presence of different hydrocarbon components than the effect of confinement. Based on our previous observations, in this study, we investigated the efficiency of smaller-chain alkane injection into oil-soaked sandstone pores to dilute the oil with alkane. We used molecular dynamics simulations of C2, C3, C4 and C5 as well as a mixture of C3 and C4 to rank the effects of different alkanes on the diffusion and distribution of oil molecules in pore. As water-alternating-alkane injection would bring water into the pores, our simulations included water. Our results indicate that alkane injection into sandstone reservoirs has a significant potential due to the fact that it effectively dilutes the oil. Water always wets quartz surface relative to the oils. Injection of water therefore should be effective in detaching oil molecules on the surface. Presence of water layers did not affect the diffusion coefficients of oil molecules.
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Lawson, Richard A., Cheng-Tsung Lee, Wang Yueh, Laren Tolbert, and Clifford L. Henderson. "Mesoscale simulation of molecular glass photoresists: effect of PAG loading and acid diffusion coefficient." In SPIE Advanced Lithography, edited by Clifford L. Henderson. SPIE, 2008. http://dx.doi.org/10.1117/12.774619.
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O’Toole, Stephen, and Nicholas Stevens. "High Temperature Diffusion of Oxygen in Chromite." In ASME 2006 Pressure Vessels and Piping/ICPVT-11 Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/pvp2006-icpvt-11-93582.
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Molecular dynamics was used to calculate the diffusion coefficient of oxygen over a temperature range of 900–1700K. The chromite (FeCr2O4) system used consisted of 448 ions in a spinel structure. The spinel consisted of Fe2+ in tetrahedral sites and Cr3+ ions in octahedral sites surrounded by O2− ions. Schottky defects were made in the system by removing 10 oxygen ions, 4 iron ions and 4 chromium ions. The trajectory files from the simulations were examined for oxygen movement via a vacancy hopping mechanism and the mean-squared displacement of oxygen was plotted against time. A linear fit was performed to the plots and Einstein’s relationship was used to derive the diffusion coefficient from the gradient. The diffusion coefficients were then plotted against temperature and an Arrhenius expression was fitted to the trend and compared with the experimental trend calculated by Takada & Adachi.
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Zhang, Bingqing, Yue Guan, Sai Huang, Yun Ge, Xiaolin Huang, Yue Cao, Jianhua Jin, and Jian He. "Whole-lesion histogram analysis of apparent diffusion coefficient for distinguishing cervical cancers with different differentiation." In 2016 IEEE 10th International Conference on Nano/Molecular Medicine and Engineering (NANOMED). IEEE, 2016. http://dx.doi.org/10.1109/nanomed.2016.7883483.
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Kim, Min Jun, and Kenneth S. Breuer. "Enhanced Diffusion Due to Swimming Bacteria." In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-55014.
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The effect of bacterial motion of the diffusion of a high molecular weight molecule is studied by observing the mixing of two streams of fluid in a micro-fabricated flow cell. The presence of Escherichia coli (E.coli) in one of the streams results in an increase in the effective diffusion coefficient of Dextran, which rises linearly with the concentration of bacteria from a baseline value of 2 × 10−7 cm2/s to 8 × 10−7 cm2/s at a concentration of 2.1 × 109 /ml (approximately 0.5 % by volume). The diffusion process is also observed to undergo a change from standard “Fickian” diffusion to a superdiffusive behavior in which the diffusion exponent rises from 0.5 to 0.55 as the concentration of bacteria rises from 0 to 2.1 × 109/ml.
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Qi, Yingxia, and Minoru Takahashi. "Computer Simulation of Diffusion of Pb-Bi Eutectic in Liquid Sodium by Molecular Dynamics Method." In 10th International Conference on Nuclear Engineering. ASMEDC, 2002. http://dx.doi.org/10.1115/icone10-22236.
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Lead-bismuth eutectic is a potential candidate for coolant of secondary loops of sodium-cooled fast breeder reactors (FBR). The studies on the diffusion of liquid Pb-Bi in liquid Na are carried out corresponding to the case that liquid Pb-Bi leaks to liquid Na by accident. As the diffusion processes are the results of atomic motions, molecular dynamics method has been used to study the diffusion process. The self-diffusion coefficients of pure liquid Pb and Na, and liquid Pb-Bi are calculated and compared with ones by the empirical equations. The discrepancy between them could be eliminated by changing the densities of the liquids. The diffusion of lead-bismuth in sodium is simulated based on the changed densities under which the self-diffusion coefficients of individual liquid metals are close to those by the empirical equations. The simulation results show that the diffusion process of liquid Pb-Bi in liquid Na is a heat releasing process and the density of ternary liquid Na-Pb-Bi is higher than the average value of the densities of liquid Na and liquid Pb-Bi. It is also found that the diffusion coefficients of liquid Pb-Bi in liquid Na are much higher than their self-diffusion coefficients, indicating that liquid Pb-Bi are easy and quickly to diffuse in liquid Na. However, the diffusion coefficient of liquid Na is decreased due to the existence of liquid Pb-Bi, implying that liquid Na-Pb-Bi have a higher viscosity than that of pure liquid Na.
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Etminan, S. Reza, Parnian Haghighat, Brij B. Maini, and Zhangxin John Chen. "Molecular Diffusion and Dispersion Coefficient in a Propane-Bitumen System: Case of Vapour Extraction (VAPEX) Process." In SPE EUROPEC/EAGE Annual Conference and Exhibition. Society of Petroleum Engineers, 2011. http://dx.doi.org/10.2118/143633-ms.
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Shibahara, Masahiko, and Kiyoshi Takeuchi. "A Molecular Dynamics Study on the Effects of Nanostructural Clearances on Thermal Resistance at a Liquid-Solid Interface." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22152.
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The effects of the surface structures and the surface structural clearances at the nanometer scale on the thermal resistance at a liquid water-solid interface, as well as the self-diffusion behaviors of liquid molecules, were investigated directly by the non-equilibrium classical molecular dynamics simulations. When the potential parameter between liquid molecules and nanostructure atoms is equal to that between liquid molecules and solid wall atoms, the geometric surface area change depending on the nanostructures as well as their clearances and the self-diffusion coefficient change of the liquid molecules at the interface depending on the nanostructural clearances cause the thermal resistance change depending on the nanostructures at the liquid-solid interface. When the potential parameter between liquid molecules and nanostructure atoms is different from that between liquid molecules and solid wall atoms, the interfacial thermal resistance is dependent on the potential parameter between liquid molecules and nanostructure atoms itself rather than the geometric surface area in a molecular scale.
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Etminan, Shauheen S. R., Brij B. Maini, and Zhangxin John Chen. "Modeling the Diffusion Controlled Swelling and Determination of Molecular Diffusion Coefficient in Propane-Bitumen System Using a Front Tracking Moving Boundary Technique." In SPE Heavy Oil Conference-Canada. Society of Petroleum Engineers, 2014. http://dx.doi.org/10.2118/170182-ms.
Full textReports on the topic "Molecular diffusion coefficient"
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Glasscott, Matthew, Johanna Jernberg, Erik Alberts, and Lee Moores. Toward the electrochemical detection of 2,4-dinitroanisole (DNAN) and pentaerythritol tetranitrate (PETN). Engineer Research and Development Center (U.S.), March 2022. http://dx.doi.org/10.21079/11681/43826.
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Analytical methods to rapidly detect explosive compounds with high precision are paramount for applications ranging from national security to environmental remediation. This report demonstrates two proof-of-concept electroanalytical methods for the quantification of 2,4-dinitroanisol (DNAN) and pentaerythritol tetranitrate (PETN). For the first time, DNAN reduction was analyzed and compared at a bare graphitic carbon electrode, a polyaniline-modified (PANI) electrode, and a molecularly imprinted polymer (MIP) electrode utilizing PANI to explore the effect of surface-area and preconcentration affinity on the analytical response. Since some explosive compounds such as PETN are not appreciably soluble in water (<10 μg/L), necessitating a different solvent system to permit direct detection via electrochemical reduction. A 1,2-dichloroethane system was explored as a possibility by generating a liquid-liquid extraction-based sensor exploiting the immiscibility of 1,2-dichloroethane and water. The reduction process was explored using a scan rate analysis to extract a diffusion coefficient of 6.67 x 10⁻⁶ cm/s, in agreement with literature values for similarly structured nitrate esters. Once further refined, these techniques may be extended to other explosives and combined with portable electrochemical hardware to bring real-time chemical information to soldiers and citizens alike.
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Epel, Bernard, and Roger Beachy. Mechanisms of intra- and intercellular targeting and movement of tobacco mosaic virus. United States Department of Agriculture, November 2005. http://dx.doi.org/10.32747/2005.7695874.bard.
Full textAbstract:
To cause disease, plant viruses must replicate and spread locally and systemically within the host. Cell-to-cell virus spread is mediated by virus-encoded movement proteins (MPs), which modify the structure and function of plasmodesmata (Pd), trans-wall co-axial membranous tunnels that interconnect the cytoplasm of neighboring cells. Tobacco mosaic virus (TMV) employ a single MP for cell- cell spread and for which CP is not required. The PIs, Beachy (USA) and Epel (Israel) and co-workers, developed new tools and approaches for study of the mechanism of spread of TMV that lead to a partial identification and molecular characterization of the cellular machinery involved in the trafficking process. Original research objectives: Based on our data and those of others, we proposed a working model of plant viral spread. Our model stated that MPᵀᴹⱽ, an integral ER membrane protein with its C-terminus exposed to the cytoplasm (Reichel and Beachy, 1998), alters the Pd SEL, causes the Pd cytoplasmic annulus to dilate (Wolf et al., 1989), allowing ER to glide through Pd and that this gliding is cytoskeleton mediated. The model claimed that in absence of MP, the ER in Pd (the desmotubule) is stationary, i.e. does not move through the Pd. Based on this model we designed a series of experiments to test the following questions: -Does MP potentiate ER movement through the Pd? - In the presence of MP, is there communication between adjacent cells via ER lumen? -Does MP potentiate the movement of cytoskeletal elements cell to cell? -Is MP required for cell-to-cell movement of ER membranes between cells in sink tissue? -Is the binding in situ of MP to RNA specific to vRNA sequences or is it nonspecific as measured in vitro? And if specific: -What sequences of RNA are involved in binding to MP? And finally, what host proteins are associated with MP during intracellular targeting to various subcellular targets and what if any post-translational modifications occur to MP, other than phosphorylation (Kawakami et al., 1999)? Major conclusions, solutions and achievements. A new quantitative tool was developed to measure the "coefficient of conductivity" of Pd to cytoplasmic soluble proteins. Employing this tool, we measured changes in Pd conductivity in epidermal cells of sink and source leaves of wild-type and transgenic Nicotiana benthamiana (N. benthamiana) plants expressing MPᵀᴹⱽ incubated both in dark and light and at 16 and 25 ᵒC (Liarzi and Epel, 2005 (appendix 1). To test our model we measured the effect of the presence of MP on cell-to-cell spread of a cytoplasmic fluorescent probe, of two ER intrinsic membrane protein-probes and two ER lumen protein-probes fused to GFP. The effect of a mutant virus that is incapable of cell-to-cell spread on the spread of these probes was also determined. Our data shows that MP reduces SEL for cytoplasmic molecules, dilates the desmotubule allowing cell-cell diffusion of proteins via the desmotubule lumen and reduces the rate of spread of the ER membrane probes. Replicase was shown to enhance cell-cell spread. The data are not in support of the proposed model and have led us to propose a new model for virus cell-cell spread: this model proposes that MP, an integral ER membrane protein, forms a MP:vRNAER complex and that this ER-membrane complex diffuses in the lipid milieu of the ER into the desmotubule (the ER within the Pd), and spreads cell to cell by simple diffusion in the ER/desmotubule membrane; the driving force for spread is the chemical potential gradient between an infected cell and contingent non-infected neighbors. Our data also suggests that the virus replicase has a function in altering the Pd conductivity. Transgenic plant lines that express the MP gene of the Cg tobamovirus fused to YFP under the control the ecdysone receptor and methoxyfenocide ligand were generated by the Beachy group and the expression pattern and the timing and targeting patterns were determined. A vector expressing this MPs was also developed for use by the Epel lab . The transgenic lines are being used to identify and isolate host genes that are required for cell-to-cell movement of TMV/tobamoviruses. This line is now being grown and to be employed in proteomic studies which will commence November 2005. T-DNA insertion mutagenesis is being developed to identify and isolate host genes required for cell-to-cell movement of TMV.
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Friedman, Shmuel, Jon Wraith, and Dani Or. Geometrical Considerations and Interfacial Processes Affecting Electromagnetic Measurement of Soil Water Content by TDR and Remote Sensing Methods. United States Department of Agriculture, 2002. http://dx.doi.org/10.32747/2002.7580679.bard.
Full textAbstract:
Time Domain Reflectometry (TDR) and other in-situ and remote sensing dielectric methods for determining the soil water content had become standard in both research and practice in the last two decades. Limitations of existing dielectric methods in some soils, and introduction of new agricultural measurement devices or approaches based on soil dielectric properties mandate improved understanding of the relationship between the measured effective permittivity (dielectric constant) and the soil water content. Mounting evidence indicates that consideration must be given not only to the volume fractions of soil constituents, as most mixing models assume, but also to soil attributes and ambient temperature in order to reduce errors in interpreting measured effective permittivities. The major objective of the present research project was to investigate the effects of the soil geometrical attributes and interfacial processes (bound water) on the effective permittivity of the soil, and to develop a theoretical frame for improved, soil-specific effective permittivity- water content calibration curves, which are based on easily attainable soil properties. After initializing the experimental investigation of the effective permittivity - water content relationship, we realized that the first step for water content determination by the Time Domain Reflectometry (TDR) method, namely, the TDR measurement of the soil effective permittivity still requires standardization and improvement, and we also made more efforts than originally planned towards this objective. The findings of the BARD project, related to these two consequential steps involved in TDR measurement of the soil water content, are expected to improve the accuracy of soil water content determination by existing in-situ and remote sensing dielectric methods and to help evaluate new water content sensors based on soil electrical properties. A more precise water content determination is expected to result in reduced irrigation levels, a matter which is beneficial first to American and Israeli farmers, and also to hydrologists and environmentalists dealing with production and assessment of contamination hazards of this progressively more precious natural resource. The improved understanding of the way the soil geometrical attributes affect its effective permittivity is expected to contribute to our understanding and predicting capability of other, related soil transport properties such as electrical and thermal conductivity, and diffusion coefficients of solutes and gas molecules. In addition, to the originally planned research activities we also investigated other related problems and made many contributions of short and longer terms benefits. These efforts include: Developing a method and a special TDR probe for using TDR systems to determine also the soil's matric potential; Developing a methodology for utilizing the thermodielectric effect, namely, the variation of the soil's effective permittivity with temperature, to evaluate its specific surface area; Developing a simple method for characterizing particle shape by measuring the repose angle of a granular material avalanching in water; Measurements and characterization of the pore scale, saturation degree - dependent anisotropy factor for electrical and hydraulic conductivities; Studying the dielectric properties of cereal grains towards improved determination of their water content. A reliable evaluation of the soil textural attributes (e.g. the specific surface area mentioned above) and its water content is essential for intensive irrigation and fertilization processes and within extensive precision agriculture management. The findings of the present research project are expected to improve the determination of cereal grain water content by on-line dielectric methods. A precise evaluation of grain water content is essential for pricing and evaluation of drying-before-storage requirements, issues involving energy savings and commercial aspects of major economic importance to the American agriculture. The results and methodologies developed within the above mentioned side studies are expected to be beneficial to also other industrial and environmental practices requiring the water content determination and characterization of granular materials.