Diffusion Measurements at Long Observation Times in the Presence of Spatially Variable Internal Magnetic Field Gradients

Seland, John Georg; Sørland, Geir Humborstad; Zick, Klaus; Hafskjold, Bjørn

doi:10.1006/jmre.2000.2101

Cited by 63 publications

(67 citation statements)

References 11 publications

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“…Although the internal gradients present in the emulsion are small, between 5 and 10 G/cm estimated from the half-height line width of the water resonance 36,37 and the good agreement of the results of the other experiments with the expected values, it would appear that they cannot be discounted for the surface to volume experiment. In such experiments, it is necessary that the data are acquired by applying pulse gradients that are small.…”

Section: Resultsmentioning

confidence: 84%

Structure, Diffusion, and Permeability of Protein-Stabilized Monodispersed Oil in Water Emulsions and Their Gels: A Self-Diffusion NMR Study

et al. 2010

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Self-diffusion NMR is used to investigate monodispersed oil in water emulsions and the subsequent gel formed by removing the water through evaporation. The radius of the oil droplets in the emulsions is measured using a number of diffusion methods based on the measurement of the mean squared displacement of the oil, water, and tracer molecules. The results are consistent with the known size of the emulsions. Bragg-like reflections due to the restricted diffusion of the water around the oil droplets are observed due to the low polydispersity of the emulsions and the dense packing. The resulting data are fitted to a pore glass model to give the diameter of both the pools of interstitial water and the oil droplets. In the gel, information on the residual three-dimensional structure is obtained using the short time behavior of the effective diffusion coefficient to give the surface to volume ratio of the residual protein network structure. The values for the surface to volume ratio are found to be consistent with the expected increase of the surface area of monodisperse droplets forming a gel network. At long diffusion observation times, the permeability of the network structure is investigated by diffusion NMR to give a complete picture of the colloidal system considered.

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Section: Resultsmentioning

confidence: 84%

Structure, Diffusion, and Permeability of Protein-Stabilized Monodispersed Oil in Water Emulsions and Their Gels: A Self-Diffusion NMR Study

et al. 2010

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“…So, it can be expected that the pore size in gel calculated at 293 K will vary with that obtained at 300 K. On the basis of the obtained results, we can conclude that in the investigated gels the average pore sizes range from several to tens of micrometres. With a good approximation to a circular cross-sectional shape, the diameter of the barrier (distance between the matrix backbone) for diffused molecules in the gel can be calculated as [31]: Figure 4 shows the graph of structural parameters (porosity /, tortuosity s and pore d and barrier b diameters of the gels) as a function of gelator concentration in the samples. In the range from 2.0 to 5.0 wt% of gelator concentration in the samples, the pore diameters d and porosity / are changing about 5%.…”

Section: Resultsmentioning

confidence: 99%

The structural parameters of rigid matrix of saccharide-based gel described by short and long diffusion regime analysis

Kowalczuk

2017

J Mater Sci

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The tortuosity-porosity relation and internal structure diameters in a selected organogel are studied. The diffusion coefficient measured by pulsed field gradient NMR at short and long observation times can be used to estimate the tortuosity and the pore surface-to-volume (S/V pore ) ratio of a porous material (Latour et al. in J Magn Res A 112:83-91, 1995; Mair et al. in Magn Res Imaging 19:345-351, 2001; Mitra et al. in Phys Rev B 47(14):8565-8574, 1993; Valiullin and Skirda in J Chem Phys 114:452-458, 2001). The value of S/V pore allows to calculate the average pore and barrier diameters. In the experiment, the timedependent diffusion coefficient of toluene in a low molecular weight gelator methyl-4,6-O-(p-nitrobenzylidene)-a-D-glucopyranoside (Gluco-NO 2 ) matrix was measured. The results revealed the relation between the diffusion coefficient of toluene and the concentration of gelator Gluco-NO 2 in the system. With increasing Gluco-NO 2 compound in the sample, the diffusion coefficient of toluene decreases. On the basis of the diffusion coefficient behaviour as a function of time and gelator concentration, the fibrous structure of the gel matrix was identified and the structural parameters of the system were investigated.

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“…This variation indicated that, compared to the control phantom, the glass bead systems were characterized by severe magnetic heterogeneities. The magnitudes of the background gradients were estimated to be 29.5 and 9.6 G/cm for the 90 and 150 μm glass bead phantoms, respectively [18].…”

Section: Resultsmentioning

confidence: 99%

Improved diffusion measurement in heterogeneous systems using the magic asymmetric gradient stimulated echo (MAGSTE) technique

Sun

2007

Journal of Magnetic Resonance

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A magic asymmetric gradient stimulated echo (MAGSTE) sequence was recently proposed to improve molecular diffusion measurements in the presence of spatially varying background gradients. Its effectiveness has been demonstrated previously with simulated background gradients and in phantoms that contain bulk susceptibility differences. In this study, we investigated the MAGSTE technique in microscopically heterogeneous systems, and compared it with the conventional bipolar pulsed gradient stimulated echo (bPGSTE) sequence. We demonstrated that the MASGTE measurements, compared to the bPGSTE method, varied significantly less when the diffusion encoding/decoding interval (δ) was changed. In addition, the MAGSTE technique provided good characterization of the surface area-to-volume ratio for heterogeneous systems investigated in this study. In sum, this study showed that the MAGSTE technique provided diffusion measurements superior to those of the bPGSTE sequence, especially in the presence of severe heterogeneous background gradients.

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Diffusion Measurements at Long Observation Times in the Presence of Spatially Variable Internal Magnetic Field Gradients

Cited by 63 publications

References 11 publications

Structure, Diffusion, and Permeability of Protein-Stabilized Monodispersed Oil in Water Emulsions and Their Gels: A Self-Diffusion NMR Study

Structure, Diffusion, and Permeability of Protein-Stabilized Monodispersed Oil in Water Emulsions and Their Gels: A Self-Diffusion NMR Study

The structural parameters of rigid matrix of saccharide-based gel described by short and long diffusion regime analysis

Improved diffusion measurement in heterogeneous systems using the magic asymmetric gradient stimulated echo (MAGSTE) technique

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