A31P NMR study of the GI tract: Effect of fructose loading and measurement of transverse relaxation times

P. m. r. relaxation times ( T 1 and T 2 ) have been measured as a function of regain and temperature for water sorbed by lyophilized methaemoglobin. The purpose of the work was to gain information regarding the nature and extent of water binding by the protein molecules. The T 1 results are interpreted in terms of an exchange between the sixth ligand position of the Fe (III) and other adsorption sites on the protein. At high temperatures the relaxation rate at a given regain reaches a limiting value which allows the fraction of ferric ions hydrated to be calculated. Above 16% regain all the Fe (III) is hydrated. At 21 and 35% regains a maximum appears in the relaxation rate at about -46 °C indicating a contribution from a more mobile phase which produces a T 1 minimum at that temperature. The T 2 data are consistent with a model in which the main contribution to the transverse relaxation rate comes from a tightly bound fraction of the water with ω 0 Ƭ c ≫1. The temperature dependence of T 2 exhibits three different regions: ( a ) a low temperature region where lg T 2 ∝ T -1 ; ( b ) an intermediate region with a steeper increase of T 2 with temperature; and ( c ) a high temperature where T 2 levels off.

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57Fe Nuclear Transverse Relaxation Times in Fe and some Fe‐Rich Alloys: Suhl‐Nakamura Interaction

Journal of Applied Physics ◽

10.1063/1.1657734 ◽

1969 ◽

Vol 40 (3) ◽

pp. 1485-1486 ◽

Cited By ~ 2

Author(s):

Mary Beth Stearns

Keyword(s):

Relaxation Times ◽

Transverse Relaxation

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NMR Investigation of the Copper(II)-Ciprofloxacin System

Metal-Based Drugs ◽

10.1155/mbd.1999.1 ◽

1999 ◽

Vol 6 (1) ◽

pp. 1-4 ◽

Cited By ~ 3

Author(s):

Iztok Turel ◽

Janez Košmrlj ◽

Bjørn Andersen ◽

Einar Sletten

Keyword(s):

Acidic Medium ◽

Acidic Solution ◽

Relaxation Times ◽

Ring System ◽

Proton Relaxation ◽

X Ray ◽

Ph Values ◽

Nmr Study ◽

Terminal Nitrogen Atom ◽

Titration Data

A proton NMR study was performed on the copper(ll)-ciprofloxacin system. The proton relaxation times (T1) were determined from the titration data in acidic and basic media. In acidic medium the H5 signal is dramatically affected and it is assumed that copper is bonded to the quinolone through carbonyl and one of the carboxyl oxygens. Such bonding is in agreement with the X-ray literature data for the complex [Cu(cf)2]Cl2.6H2O isolated from the slightly acidic solution. There are additional significant changes in T1 of H3′ and H5′ atoms which suggest that the terminal nitrogen atom of the piperazine ring system-N4′ also interacts with copper in the basic conditions. Thus it is plausible that more than one species are present in the solution at high pH values.

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1H and 19F NMR Study of Cation and Anion Motions in Guanidinium Fluoroantimonates

Zeitschrift für Naturforschung A ◽

10.1515/zna-1995-0806 ◽

1995 ◽

Vol 50 (8) ◽

pp. 742-748 ◽

Cited By ~ 3

Author(s):

M. Grottel ◽

A. Kozak ◽

Z. Pająk

Keyword(s):

Solid Phase ◽

Relaxation Times ◽

Activation Parameters ◽

Lattice Relaxation ◽

Spin Lattice Relaxation ◽

Temperature Phase ◽

Fluorine Nmr ◽

Spin Lattice ◽

Nmr Study ◽

Guanidinium Cation

Abstract Proton and fluorine NMR linewidths, second moments, and spin-lattice relaxation times of polycrystalline [C(NH2)3]2SbF5 and C(NH2)3SbF6 were studied in a wide temperature range. For the pentafluoroantimonate, C3-reorientation of the guanidinium cation and C4-reorientation of the SbF5 anion were revealed and their activation parameters determined. The dynamical inequivalence of the two guanidinium cations was evidenced. For the hexafluoroantimonate, two solid-solid phase transitions were found. In the low temperature phase the guanidinium cation undergoes C3 reorien tation while the SbF6 anion reorients isotropically. The respective activation parameters were derived. At high temperatures new ionic plastic phases were evidenced.

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Combination of MRI and SEM to Assess Changes in the Chemical Properties and Permeability of Porous Media due to Barite Precipitation

Minerals ◽

10.3390/min10030226 ◽

2020 ◽

Vol 10 (3) ◽

pp. 226 ◽

Cited By ~ 3

Author(s):

Jenna Poonoosamy ◽

Sabina Haber-Pohlmeier ◽

Hang Deng ◽

Guido Deissmann ◽

Martina Klinkenberg ◽

...

Keyword(s):

Porous Media ◽

Magnetic Resonance ◽

Reactive Transport ◽

Relaxation Times ◽

Chemical Properties ◽

Column Experiment ◽

Transverse Relaxation Time ◽

Gas Production ◽

Transport Modelling ◽

Transverse Relaxation

The understanding of the dissolution and precipitation of minerals and its impact on the transport of fluids in porous media is essential for various subsurface applications, including shale gas production using hydraulic fracturing (“fracking”), CO2 sequestration, or geothermal energy extraction. In this work, we conducted a flow through column experiment to investigate the effect of barite precipitation following the dissolution of celestine and consequential permeability changes. These processes were assessed by a combination of 3D non-invasive magnetic resonance imaging, scanning electron microscopy, and conventional permeability measurements. The formation of barite overgrowths on the surface of celestine manifested in a reduced transverse relaxation time due to its higher magnetic susceptibility compared to the original celestine. Two empirical nuclear magnetic resonance (NMR) porosity–permeability relations could successfully predict the observed changes in permeability by the change in the transverse relaxation times and porosity. Based on the observation that the advancement of the reaction front follows the square root of time, and micro-continuum reactive transport modelling of the solid/fluid interface, it can be inferred that the mineral overgrowth is porous and allows the diffusion of solutes, thus affecting the mineral reactivity in the system. Our current investigation indicates that the porosity of the newly formed precipitate and consequently its diffusion properties depend on the supersaturation in solution that prevails during precipitation.

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Cross-linked polydimethylsiloxane colloid as novel contrast agent for gastrointestinal magnetic resonance imaging: Transient nuclear Overhauser effect within the interface

Journal of Biomaterials Applications ◽

10.1177/0885328220921528 ◽

2020 ◽

Vol 35 (2) ◽

pp. 264-273

Author(s):

Fu-Hu Su ◽

Wang-Chuan Xiao ◽

Sheann-Huei Lin ◽

Qiyong Li

Keyword(s):

Magnetic Resonance ◽

Nuclear Overhauser Effect ◽

Relaxation Times ◽

Resonance Imaging ◽

Transverse Relaxation ◽

Overhauser Effect ◽

Nuclear Magnetic Resonance Spectra ◽

Relaxation Experiments ◽

Longitudinal Relaxation ◽

Nuclear Overhauser

With good contrast in T1 and T2 weighted imaging as well as low toxicity in 3- (4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, this work proposes the cross-linked polydimethylsiloxane colloids as a novel non-ionic contrast agent for gastrointestinal magnetic resonance imaging. The experiments of nuclear magnetic resonance spectra and relaxation show that within the interface of the colloids, there are nuclear Overhauser effect and transient nuclear Overhauser effect (cross-relaxation). Regarding the longitudinal relaxation experiments of CH2CH2O segments of Tween 80, a two spins system is found and modeled well by the equation [Formula: see text] which is deduced based on the transient nuclear Overhauser effect proposed by Solomon. The arbitrary constant X is additionally added with the initial conditions ( Iz − I0) t=0 = −2 XS0 and ( Sz − S0) t=0 = −2 S0. For the two spins system, D1 and T1 are corresponding to longitudinal relaxation times of the bound water and the CH2CH2O respectively. Concerning the transverse relaxation experiments of the CH2CH2O, they agree with the equation with three exponential decays, defined by three relaxation times, likely corresponding to three mechanisms. These mechanisms possibly are intramolecular and intermolecular dipole–dipole (DD) interactions and scalar coupling. Within the interface, hydrogen bonding causes the positive nuclear Overhauser effect of the CH2CH2O’s nuclear magnetic resonance spectra, the transient nuclear Overhauser effect of the CH2CH2O’s longitudinal relaxation experiments and the intermolecular dipole–dipole interactions of the CH2CH2O’s transverse relaxation experiments.

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