The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform
Agustinus Setiadarma - One of the best experts on this subject based on the ideXlab platform.
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reliable heavy oil Solvent Viscosity mixing rules for viscosities up to 450 k oil Solvent Viscosity ratios up to 4 105 and any Solvent proportion
Fluid Phase Equilibria, 2003Co-Authors: Maria A Barrufet, Agustinus SetiadarmaAbstract:Abstract This paper presents an evaluation of various heavy oil Viscosity models using new experimental data for mixtures of a heavy oil sample from Canada’s heavy oil reserves and n-decane used as a Viscosity reducer. We measured viscosities at temperatures ranging from ambient to 450 K using a versatile mercury capillary tube. We evaluated several mixing rules to predict the mixture Viscosity as a function of temperature and the viscosities of the constituents. The most promising mixing rule follows a methodology proposed originally by Lederer. We used our own experimental data to calibrate this mixing rule, which only has two adjustable parameters, and used the same coefficients to predict the blending Viscosity of mixtures of bitumen and a synthetic oil Solvent reported in the literature. This mixing rule can reproduce blending viscosities within the uncertainty of the experiments for oil–Solvent Viscosity ratios up to 4×105, temperatures from ambient to 450 K, and mixtures of any Solvent proportion. This paper provides a valuable new experimental Viscosity of heavy oil and n-decane and a reliable mixing rule that has been independently validated with literature data and can be used to estimate diluent quantities required to reduce oil Viscosity for pipeline transportation of heavy oil, to design Solvent stimulation of wells, and to provide viscosities for thermal reservoir simulators for heavy oil recovery processes.
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Reliable heavy oil–Solvent Viscosity mixing rules for viscosities up to 450 K, oil–Solvent Viscosity ratios up to 4 × 105, and any Solvent proportion
Fluid Phase Equilibria, 2003Co-Authors: Maria A Barrufet, Agustinus SetiadarmaAbstract:Abstract This paper presents an evaluation of various heavy oil Viscosity models using new experimental data for mixtures of a heavy oil sample from Canada’s heavy oil reserves and n-decane used as a Viscosity reducer. We measured viscosities at temperatures ranging from ambient to 450 K using a versatile mercury capillary tube. We evaluated several mixing rules to predict the mixture Viscosity as a function of temperature and the viscosities of the constituents. The most promising mixing rule follows a methodology proposed originally by Lederer. We used our own experimental data to calibrate this mixing rule, which only has two adjustable parameters, and used the same coefficients to predict the blending Viscosity of mixtures of bitumen and a synthetic oil Solvent reported in the literature. This mixing rule can reproduce blending viscosities within the uncertainty of the experiments for oil–Solvent Viscosity ratios up to 4×105, temperatures from ambient to 450 K, and mixtures of any Solvent proportion. This paper provides a valuable new experimental Viscosity of heavy oil and n-decane and a reliable mixing rule that has been independently validated with literature data and can be used to estimate diluent quantities required to reduce oil Viscosity for pipeline transportation of heavy oil, to design Solvent stimulation of wells, and to provide viscosities for thermal reservoir simulators for heavy oil recovery processes.
Stephen J Hagen - One of the best experts on this subject based on the ideXlab platform.
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Solvent Viscosity and friction in protein folding dynamics
Current Protein & Peptide Science, 2010Co-Authors: Stephen J HagenAbstract:The famous Kramers rate theory for diffusion-controlled reactions has been extended in numerous ways and successfully applied to many types of reactions. Its application to protein folding reactions has been of particular interest in recent years, as many researchers have performed experiments and simulations to test whether folding reactions are diffusion-controlled, whether the Solvent is the source of the reaction friction, and whether the friction-dependence of folding rates generally can provide insight into folding dynamics. These experiments involve many practical difficulties, however. They have also produced some unexpected results. Here we briefly review the Kramers theory for reactions in the presence of strong friction and summarize some of the subtle problems that arise in the application of the theory to protein folding. We discuss how the results of these experiments ultimately point to a significant role for internal friction in protein folding dynamics. Studies of friction in protein folding, far from revealing any weakness in Kramers theory, may actually lead to new approaches for probing diffusional dynamics and energy landscapes in protein folding.
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Solvent friction changes the folding pathway of the tryptophan zipper TZ2.
Journal of Molecular Biology, 2009Co-Authors: Ranjani Narayanan, Leslie Pelakh, Stephen J HagenAbstract:Because the rate of a diffusional process such as protein folding is controlled by friction encountered along the reaction pathway, the speed of folding is readily tunable through adjustment of Solvent Viscosity. The precise relationship between Solvent Viscosity and the rate of diffusion is complex and even conformation-dependent, however, because both Solvent friction and protein internal friction contribute to the total reaction friction. The heterogeneity of the reaction friction along the folding pathway may have subtle consequences. For proteins that fold on a multidimensional free-energy surface, an increase in Solvent friction may drive a qualitative change in folding trajectory. Our time-resolved experiments on the rapidly and heterogeneously folding β-hairpin TZ2 show a shift in the folding pathway as Viscosity increases, even though the energetics of folding is unaltered. We also observe a nonlinear or saturating behavior of the folding relaxation time with rising Solvent Viscosity, potentially an experimental signature of the shifting pathway for unfolding. Our results show that manipulations of Solvent Viscosity in folding experiments and simulations may have subtle and unexpected consequences on the folding dynamics being studied.
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a limiting speed for protein folding at low Solvent Viscosity
Journal of the American Chemical Society, 2004Co-Authors: Stephen J HagenAbstract:Because protein folding dynamics are heavily overdamped, Kramers theory predicts the rate of folding to scale inversely with the reaction friction, which is usually interpreted to mean the Solvent Viscosity. This does not mean, however, that the speed of folding can increase without limit as Solvent Viscosity decreases. We show that, in a sufficiently fast-folding protein, the folding speed approaches a finite limit at low Solvent Viscosity, indicating a reaction controlled by internal friction.
Maria A Barrufet - One of the best experts on this subject based on the ideXlab platform.
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reliable heavy oil Solvent Viscosity mixing rules for viscosities up to 450 k oil Solvent Viscosity ratios up to 4 105 and any Solvent proportion
Fluid Phase Equilibria, 2003Co-Authors: Maria A Barrufet, Agustinus SetiadarmaAbstract:Abstract This paper presents an evaluation of various heavy oil Viscosity models using new experimental data for mixtures of a heavy oil sample from Canada’s heavy oil reserves and n-decane used as a Viscosity reducer. We measured viscosities at temperatures ranging from ambient to 450 K using a versatile mercury capillary tube. We evaluated several mixing rules to predict the mixture Viscosity as a function of temperature and the viscosities of the constituents. The most promising mixing rule follows a methodology proposed originally by Lederer. We used our own experimental data to calibrate this mixing rule, which only has two adjustable parameters, and used the same coefficients to predict the blending Viscosity of mixtures of bitumen and a synthetic oil Solvent reported in the literature. This mixing rule can reproduce blending viscosities within the uncertainty of the experiments for oil–Solvent Viscosity ratios up to 4×105, temperatures from ambient to 450 K, and mixtures of any Solvent proportion. This paper provides a valuable new experimental Viscosity of heavy oil and n-decane and a reliable mixing rule that has been independently validated with literature data and can be used to estimate diluent quantities required to reduce oil Viscosity for pipeline transportation of heavy oil, to design Solvent stimulation of wells, and to provide viscosities for thermal reservoir simulators for heavy oil recovery processes.
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Reliable heavy oil–Solvent Viscosity mixing rules for viscosities up to 450 K, oil–Solvent Viscosity ratios up to 4 × 105, and any Solvent proportion
Fluid Phase Equilibria, 2003Co-Authors: Maria A Barrufet, Agustinus SetiadarmaAbstract:Abstract This paper presents an evaluation of various heavy oil Viscosity models using new experimental data for mixtures of a heavy oil sample from Canada’s heavy oil reserves and n-decane used as a Viscosity reducer. We measured viscosities at temperatures ranging from ambient to 450 K using a versatile mercury capillary tube. We evaluated several mixing rules to predict the mixture Viscosity as a function of temperature and the viscosities of the constituents. The most promising mixing rule follows a methodology proposed originally by Lederer. We used our own experimental data to calibrate this mixing rule, which only has two adjustable parameters, and used the same coefficients to predict the blending Viscosity of mixtures of bitumen and a synthetic oil Solvent reported in the literature. This mixing rule can reproduce blending viscosities within the uncertainty of the experiments for oil–Solvent Viscosity ratios up to 4×105, temperatures from ambient to 450 K, and mixtures of any Solvent proportion. This paper provides a valuable new experimental Viscosity of heavy oil and n-decane and a reliable mixing rule that has been independently validated with literature data and can be used to estimate diluent quantities required to reduce oil Viscosity for pipeline transportation of heavy oil, to design Solvent stimulation of wells, and to provide viscosities for thermal reservoir simulators for heavy oil recovery processes.
Tadaaki Ikoma - One of the best experts on this subject based on the ideXlab platform.
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Solvent Viscosity effect on triplet triplet pair in triplet fusion
Journal of Physical Chemistry B, 2015Co-Authors: Kana Yokoyama, Yusuke Wakikawa, Tomoaki Miura, Junichi Fujimori, Tadaaki IkomaAbstract:The effect of the Solvent Viscosity dependence of time-resolved magnetoluminescence (ML) on the delayed fluorescence of 9,10-diphenylanthracene (DPA) sensitized by platinum octaethylporphyrin has clarified the structure and dynamics of the triplet–triplet pair (TT), i.e., the transition state of triplet fusion. Phase inversion of the ML effect with time provides evidence for the recycle dynamics of the excited triplet state for DPA in triplet fusion. The electron spin-relaxation by random molecular rotation causes intersystem crossing among the different spin states of the triplet–triplet pair and allows the 3,5TT to engage in triplet fusion. Therefore, slow-down of the molecular diffusion by an increase in the Solvent Viscosity can enhance the triplet fusion yield. However, the reduction of the ML effect observed in quite high Viscosity Solvents suggests that the substantially slow rotational motion decreases the triplet fusion yield due to steric factors in electron exchange from the triplet–triplet pair.
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Solvent Viscosity Effect on Triplet–Triplet Pair in Triplet Fusion
Journal of Physical Chemistry B, 2015Co-Authors: Kana Yokoyama, Yusuke Wakikawa, Tomoaki Miura, Junichi Fujimori, Tadaaki IkomaAbstract:The effect of the Solvent Viscosity dependence of time-resolved magnetoluminescence (ML) on the delayed fluorescence of 9,10-diphenylanthracene (DPA) sensitized by platinum octaethylporphyrin has clarified the structure and dynamics of the triplet–triplet pair (TT), i.e., the transition state of triplet fusion. Phase inversion of the ML effect with time provides evidence for the recycle dynamics of the excited triplet state for DPA in triplet fusion. The electron spin-relaxation by random molecular rotation causes intersystem crossing among the different spin states of the triplet–triplet pair and allows the 3,5TT to engage in triplet fusion. Therefore, slow-down of the molecular diffusion by an increase in the Solvent Viscosity can enhance the triplet fusion yield. However, the reduction of the ML effect observed in quite high Viscosity Solvents suggests that the substantially slow rotational motion decreases the triplet fusion yield due to steric factors in electron exchange from the triplet–triplet pair.
Vijay S Pande - One of the best experts on this subject based on the ideXlab platform.
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Solvent Viscosity dependence of the protein folding dynamics
Journal of Physical Chemistry B, 2008Co-Authors: Young Min Rhee, Vijay S PandeAbstract:Solvent Viscosity has been frequently adopted as an adjustable parameter in various computational studies (e.g., protein folding simulations) with implicit Solvent models. A common approach is to use low viscosities to expedite simulations. While using viscosities lower than that of aqueous is unphysical, such treatment is based on observations that the Viscosity affects the kinetics (rates) in a well-defined manner as described by Kramers' theory. Here, we investigate the effect of Viscosity on the detailed dynamics (mechanism) of protein folding. On the basis of a simple mathematical model, we first show that Viscosity may indeed affect the dynamics in a complex way. By applying the model to the folding of a small protein, we demonstrate that the detailed dynamics is affected rather pronouncedly especially at unphysically low viscosities, cautioning against using such viscosities. In this regard, our model may also serve as a diagnostic tool for validating low-Viscosity simulations. It is also suggested...