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Showing 1 to 20 of 26 for “"spin-lattice relaxation time"”.
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NMR investigations of ionic host polymer systems
… A key experimental approach is the use of spin-lattice relaxation time measurements (I H, 7Li and 19F) to act as a probe of structure and dynamics. 19F spin-lattice relaxation time investigations in LiCF3S03 and PEO/LiCF3S03 systems are interpreted in terms of a mechanism in which the …
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Crosslinking and Entanglement Effects in Polybutadiene
Proton relaxation measurements have been used to investigate the effects of crosslinking and entanglements on segmental motion in polybutadiene. The temperature dependence of T(,1), the spin-lattice relaxation time, T(,2), the spin-spin relaxation time, and T(,1(,(rho))), the spin-lattice …
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Nmr and Polarization Microscopy Studies of Sodium Alkyl Carboxylate Solids and Melts
… self-diffusion measurements and the ('23)Na spin-lattice relaxation time, T(,1), and quadrupole coupling constant,
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NMR study of the unfolding of ribonuclease A, and dynamical studies of liquids in confined geometries
… studied by 1D and 2D $\sp1$H NMR spectroscopy, spin-lattice relaxation time measurements, and the pressure-jump hydrogen-exchange method. It was found that the pressure denatured states of RNase A display some characteristics of a molten globule, and all three $\alpha$-helices and the …
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Nuclear magnetic resonance study of the bonding of carbon monoxide to palladium and platinum surfaces
… the first reported NMR observation of a spin larger than 1/2 adsorbed on a metal surface. At low temperatures, the 13c resonance of CO on Pd is centered at 540 ppm down field from the 13 C resonance of tetramethylsilane (TMS). The line position is interpreted as the sum of a chemical …
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Modulation and cross-relaxation effects on the lineshape of strongly saturated nuclear magnetic resonance in solids
… explained the lineshape by assuming that the spin system in the rotating frame can be divided into two parts which have unequal temperatures, and which are able to cross relax. For two limiting cases, large HI' and HI small, but still large enough to saturate, we have calculated the lineshape …
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Synthesis and modification of pamam dendrimers as histone replacement molecules
… the dendritic branches has been studied using 1H spin-lattice relaxation time experiments, and the results have been compared for the differently cored materials. Chapter 3 examines the modification of the dendrimer surfaces with acetyl, poly(ethylene glycol) and fluorescent groups and reports the …
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Instrument and Application Development in Saturation Recovery and Rapid Scan Electron Paramagnetic Resonance
… to gain insight into molecular changes on this timescale. RS-EPR performed at low temperatures using a closed cycle helium system and a cryostat containing a region with low electrical conductivity provides very wide (>9000 G) spectra free of passage effects near 5 K, expanding the capabilities …
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N.M.R. Studies of the Formation of Molecular Complexes in the Liquid Phase
… are studied by the use of 1H chemical shifts and spin-lattice relaxation times. The purpose of the work is to confirm the validity of procedures which have been developed previously to obtain more meaningful parameters than hitherto describing the formation of such complexes, and to investigate …
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Nuclear magnetic resonance studies of molecular interactions and structures
… on the liquid structure has been studied using spin-lattice relaxation time, 1H chemical shift, and nuclear Overhauser effect measurements. The main purpose of the work has been to validate a model for molecular interaction involving local ordering of benzene around chloroform. A chemical method …
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Rapid Scan Electron Paramagnetic Resonance (EPR) and Digital EPR Development
… spectra, such as for immobilized nitroxides, spin-labeled proteins, irradiated tooth and fingernail samples were demonstrated in this dissertation. The scan width has been increased from 55 G to 160 G. The signal to noise (<em>S/N</em>) improvement for slowly tumbling spin-labeled protein …
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Anisotropic spin-lattice relaxation times of trivalent rare earth ions in anhydrous lanthanum trichloride
… of the temperature and angular dependence oft,he spin-lattice relaxation time Tl have been made for cerium, praseodymium, neodymium, samarium, terbium, and erbium , in single crystals of anhydrous lanthanum tric~loride. The experiments were performed on samples cqntaining ~ 2 at.% rpre earth …
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Dynamic Nuclear Polarization in Samarium Doped Lanthanum Magnesium Nitrate
… effect have been derived in detail using the spin temperature theory and the complete expression for the steady-state enhancement of the nuclear polarization has been calculated. For well-resolved solid effect transitions at microwave frequencies Ï ~ Ï <sub>e</sub> ± Ï <sub>n</sub>, the …
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Experimental and computational techniques in carbon-13 NMR
… approach significantly reduces the calculation time, greatly facilitating iterative nonlinear least squares fitting of experimental spectra. This algorithm has been modified to produce partially relaxed lineshapes and spectra of partially ordered samples.;Calculations for rapidly spinning …
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Molecular dynamics of polymers by means of NMR field cycling relaxometry
… based on a power law dependence of the NMR spin-lattice relaxation time (T1) as a function of the Larmor frequency, predicted by Kimmich and Fatkullin, which were developed from the renormalized Rouse formalism. Three different regions of power laws explaining the relaxation dispersion for …
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Synthesis and Characterization of Platinum-Based Fuel Cell Catalysts
… shifted 13C NMR resonances, weaker Korringa relaxation, and thermal diffusion at higher temperatures. The change in CO 2pi* Fermi level local density of states (Ef-LDOS) suggested Ru weakened Pt-CO bond. The Ru spontaneous deposition was further applied to carbon-supported Pt nanoparticles of …
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Making Nuclear Magnetic Hyperpolarization Practical through Storage in Disconnected Eigenstates
… hyperpolarized signal is still limited by the spin-lattice relaxation time, T1. Disconnected eigenstates provide a mechanism by which hyperpolarization can be stored for several times T1. This thesis contributes to the knowledge of these states in four important ways. First, the decay of …
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Nanodiamonds for biological applications: Synthesis by laser ablation and sensing of local magnetic environment by optical spectroscopy of NV centers
… of the NV centers and to the ground state spin dynamics of these color centers, I describe the set up used for the experimental characterization of the NDs. All NDs used in my experiments, characterized by different sizes and coatings, presented high fluorescence levels, the result of a …
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Investigation of the Wood/Phenol-Formaldehyde Adhesive Interphase Morphology
… analysis according to the Ngai coupling model of relaxation successfully applies to the in-situ lignin glass transition of yellow-poplar and spruce woods. No significant difference in intermolecular coupling is detected between the two woods. It is then demonstrated that combining simple DMA …
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