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Terence Cosgrove - One of the best experts on this subject based on the ideXlab platform.
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Use of water Spin-Spin Relaxation rate to probe the solvation of cyclodextrins in aqueous solutions.
The journal of physical chemistry. B, 2008Co-Authors: Edvaldo Sabadini, Fernanda Do Carmo Egídio, Fred Yukio Fujiwara, Terence CosgroveAbstract:1H spin−spin Relaxation rate constant, R2, of water was measured by using the Carr−Purcell−Meiboom−Gill sequence in aqueous solutions of native cyclodextrins (α, β, and γ-CD) and chemically modified CDs in order to probe the structuring of the water surrounding these cyclic carbohydrate molecules. R2 values for water in solutions containing glucose and dextran were also measured for comparison. A two-site model for bonded and free water molecules was used to fit the results for the dependence of R2 on the solute concentrations. The order of Relaxation rates for water in aqueous solution at a fixed specific hydroxyl group concentration is glucose > dextran ≅ CDs. No significant difference was observed for R2 of water in solutions containing native CDs, which indicates that the size and nature of the cavity has a small effect on the spin−spin Relaxation times of water. The lower Relaxation rate for water in CD solutions was attributed to the intramolecular hydrogen bonding formed between the secondary hydro...
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NMR Spin−Spin Relaxation Studies of Silicate-Filled Low Molecular Weight Poly(dimethylsiloxane)s
Langmuir, 2002Co-Authors: Terence Cosgrove, Claire Roberts, Tania Garasanin, Randall Gene Schmidt, Glenn GordonAbstract:Nuclear magnetic resonance (NMR) spin−spin Relaxation measurements were used to investigate the mobility of poly(dimethylsiloxane) (PDMS) polymers, below the molecular entanglement point, when mixed with trimethylsilyl-treated polysilicate nanoparticles. The results showed that a high molecular weight polysilicate caused a dramatic reduction in the overall PDMS chain mobility at all concentrations. The Relaxation decays were deconvoluted into multiple exponential decays using nonlinear least squares and the DISCRETE algorithm. The components of these decays were associated qualitatively with adsorbed and nonadsorbed polymer segments. When compared with differential scanning calorimetry measurements, the reduction in the mobility of the PDMS chains as seen in the NMR experiments corresponded to a shift in the glass transition to higher temperatures, a decrease in the specific heat increment at the glass transition, and a loss in the ability of the polymer to crystallize at high concentrations of polysilicate.
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Self-diffusion and Spin-Spin Relaxation in blends of linear and cyclic polydimethylsiloxane melts
Polymer, 1996Co-Authors: Terence Cosgrove, Peter C. Griffiths, J. Hollingshurst, Michael J. Turner, M.j. Shenton, J.a. SemlyenAbstract:Self-diffusion and Spin-Spin Relaxation measurements have been performed on a series of blends of narrow-fraction linear and cyclic polydimethylsiloxane polymers in the melt by pulsed nuclear magnetic resonance techniques. The results obtained are compared to the viscosity behaviour on the same samples and discussed in terms of the reptation and Rouse theories commonly invoked for the dynamics of single-component systems. The dynamics of the blend samples are shown to deviate from the expected behaviour above a critical ring size which can be understood through a mechanism based on ring threading.
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Self-diffusion, viscosity and Spin-Spin Relaxation in liquid poly(propylene oxide) melts
Polymer, 1994Co-Authors: Terence Cosgrove, Peter C. Griffiths, J. R. P. WebsterAbstract:Abstract Self-diffusion, viscosity and Spin-Spin Relaxation have been measured for a series of low molecular weight liquid poly(propylene oxide) melts. The data are discussed within the framework of theories commonly invoked for polymer dynamics including the Rouse chain and free volume effects. The average diffusion coefficients of a range of bimodal blends have also been measured and the results interpreted using the Rouse model.
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Self-diffusion and Spin-Spin Relaxation in cyclic and linear polydimethylsiloxane melts
Macromolecules, 1992Co-Authors: Terence Cosgrove, Peter C. Griffiths, J. Hollingshurst, R. D. C. Richards, J.a. SemlyenAbstract:Self-diffusion and Spin-Spin Relaxation measurements have been performed on narrow fraction linear and cyclic polydimethylsilorane (PDMS) polymers in the melt, by pulsed NMR techniques. The effects of ring and chain molecular weight have been studied. The diffusion and Relaxation data exhibit interesting molecular weight dependencies, some of which were also found in the bulk visocisty. The Relaxation data show a noticeable change in molecular weight dependence at the critical molecular weight for entanglement for both the linear and cyclic polymers. The diffusion data are not, however, sensitive to this critical molecular weight effect
M. Sperlich - One of the best experts on this subject based on the ideXlab platform.
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Original contributionProton Spin-Spin Relaxation times as liver transplantation graft viability parameter
Magnetic resonance imaging, 1993Co-Authors: P. Holzmüller, Ewald Moser, H. Reckendorfer, Heinz Burgmann, E. Winklmayr, M. SperlichAbstract:In this study, Spin-Spin Relaxation time T2 of stored rat liver grafts was investigated and correlated with other viability parameters. Five different storage solutions were applied and T2 as well as overall tissue water content, bile flow, and energy charge were determined for increasing durations of cold storage (1–48 hr). Good correlation between T2 and tissue water content was detected. In a subset of experiments, dealing with additional warm ischemia after cold storage, the relative increase of T2 and energy charge showed a very good correlation. The results suggest the possible use of Relaxation time parameters as liver graft viability parameter in a combined protocol of rapid viability assays for human liver transplantation surgery.
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Spin-Spin Relaxation Times as Viability Parameter of Liver Transplantation Grafts Investigation on a Pig Model
Drugs and the Liver: High Risk Patients and Transplantation, 1993Co-Authors: R. Holzmüller, Ewald Moser, H. Reckendorfer, M. Sperlich, R. Steininger, W. Feigl, Heinz BurgmannAbstract:Primary graft non function is an unsolved problem in liver transplantation surgery since there is no possibility to determine organ viability and post transplant graft function before implantation. Previous investigations on a rat model showed highly significant correlations of proton nuclear magnetic resonance (NMR) Spin-Spin Relaxation times (T2) of livers, stored in different protecting solutions, and viability parameters (1–3), encouraging us to investigate our simple, rapid and cheap method on an other species and also in men.
Edvaldo Sabadini - One of the best experts on this subject based on the ideXlab platform.
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Correlation between viscosity, diffusion coefficient and Spin-Spin Relaxation rate in 1H NMR of water-alcohols solutions
Journal of Molecular Liquids, 2017Co-Authors: Manazael Zuliani Jora, Marcus V.c. Cardoso, Edvaldo SabadiniAbstract:Abstract In this paper we investigate correlations between viscosity (ηs), 1H Spin-Spin Relaxation times (T2) and diffusion coefficients (Ds) of protons obtained in a low field 1H NMR (20 MHz) of solutions of methanol, ethanol, 1-propanol, 2-propanol and tert-butanol with water in all range of concentrations. As each of these three properties are associated with different dynamics of the molecules (ηs: transportation across planes of flow; Ds: translational diffusion; T2: rotational diffusion), we investigate their correlations with the micro-heterogeneity of the different alcohol-water mixtures.
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Use of water Spin-Spin Relaxation rate to probe the solvation of cyclodextrins in aqueous solutions.
The journal of physical chemistry. B, 2008Co-Authors: Edvaldo Sabadini, Fernanda Do Carmo Egídio, Fred Yukio Fujiwara, Terence CosgroveAbstract:1H spin−spin Relaxation rate constant, R2, of water was measured by using the Carr−Purcell−Meiboom−Gill sequence in aqueous solutions of native cyclodextrins (α, β, and γ-CD) and chemically modified CDs in order to probe the structuring of the water surrounding these cyclic carbohydrate molecules. R2 values for water in solutions containing glucose and dextran were also measured for comparison. A two-site model for bonded and free water molecules was used to fit the results for the dependence of R2 on the solute concentrations. The order of Relaxation rates for water in aqueous solution at a fixed specific hydroxyl group concentration is glucose > dextran ≅ CDs. No significant difference was observed for R2 of water in solutions containing native CDs, which indicates that the size and nature of the cavity has a small effect on the spin−spin Relaxation times of water. The lower Relaxation rate for water in CD solutions was attributed to the intramolecular hydrogen bonding formed between the secondary hydro...
H. Peemoeller - One of the best experts on this subject based on the ideXlab platform.
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Proton Spin–Spin Relaxation Study of the Effect of Temperature on White Cement Hydration
Journal of the American Ceramic Society, 2007Co-Authors: R. Holly, Eric J. Reardon, Carolyn M. Hansson, H. PeemoellerAbstract:The chemical and microstructural changes within a white cement paste were characterized in situ using proton nuclear magnetic resonance spin–spin Relaxation at 30 MHz, and X-ray diffraction. Paste samples with a water-to-cement ratio of 0.42 were cured at constant temperatures of 2°, 20°, 60°, and 100°C. Proton nuclear magnetic resonance spin–spin Relaxation allows tracking the evolution of the mixing water into the solid fractions of calcium silicate hydrate, calcium hydroxide, and monosulfate, and the liquid phases: the calcium silicate hydrate interlayer water, gel pore water, and capillary pore water. It is shown that the hydration process is markedly accelerated with increasing hydration temperature, and that proton nuclear magnetic resonance Relaxation measurements can quantitatively determine the proportions of water phases, their magnetic resonance characteristics, as well as the setting times of the cement during the hydration process.
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Proton Spin-Spin Relaxation study of hydration of a model nanopore.
Solid State Nuclear Magnetic Resonance, 2005Co-Authors: W.e. Troyer, R. Holly, H. Peemoeller, M.m PintarAbstract:Abstract The hydration pattern of controlled pore glass, with pore diameter of 237 A, was investigated using nuclear magnetic resonance. Water proton spin–spin Relaxation decay curves were monitored and modeled as two-component exponential decays as a function of hydration. The results are consistent with a geometric model involving a surface water layer and a bulk-like liquid fraction in the form of a plug. The amount of surface water increases as the sample hydrates, until hydration reached approximately a monolayer, at which point a water plug starts to form in the pore, and grow in length at the expense of the surface layer. The results are also analyzed in terms of, and compared to, a recently developed puddle pore-filling model [S.G. Allen, et al. J. Chem. Phys. 106 (1997) 7802–7809].
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Proton Spin-Spin Relaxation study of molecular dynamics and proteoglycan hydration in articular cartilage.
Biomaterials, 2000Co-Authors: M Ghiassi-nejad, H. Peemoeller, Peter A. Torzilli, M.m PintarAbstract:Spin-Spin Relaxation of proton magnetization in natural and deuterated articular cartilage is reported over a range of hydration. Information about macromolecular dynamics is deduced and a hydration stabilized macromolecular regime identified. There is good correspondence between NMR results and cartilage stoichiometry. A new measure for hydration of proteoglycans is found.
Ronald Y. Dong - One of the best experts on this subject based on the ideXlab platform.
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Detection of Second-Order Director Fluctuations by Deuteron Spin-Spin Relaxation at a Standard High Field
Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals, 1997Co-Authors: Ronald Y. DongAbstract:Abstract We report on the measurements of deuteron Spin-Spin Relaxation time T 2 in the nematic phase of MBBA and 5CB using the quadrupolar echo pulse train in a magnetic field of 7 T. The spectral densities J 0 (i) (0) at different carbon sites were derived from the T 2 and T 1 measurements. Using a model that combined rotational diffusion motion of individual molecules and their internal bond rotations, the spectral densities J 1 (i)(ω0) and J 2 (i)(2ω0) could be interpreted, while the measured J 0 (i)(0) were too large. It is argued that second-order director fluctuations contribute in part to the J 0 (i)(0) spectral densities. Thus T 2 measurements at a standard high magnetic field can be used to gain insights on director fluctuations.
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On the detection of second-order director fluctuations at a standard high field by Spin-Spin Relaxation
Chemical Physics Letters, 1996Co-Authors: Ronald Y. DongAbstract:Abstract We report measurements of the deuteron Spin-Spin Relaxation time T 2 in the nematic phase of p-methoxybenzylidene-p-n-butylaniline using the quadrupolar echo pulse train in a magnetic field of 7 T. The derived zero-frequency spectral densities J 0 (0) at different carbon sites, unlike the J 1 (Ω 0 ) and J 2 (2Ω 0 ) , could not be interpreted using molecular reorientation and internal bond rotations in the butyl chain. It is shown that experimental T 2 data at a high magnetic field could be used to gain information on second-order director fluctuations.
