Multidimensional dynamic NMR correlations in sedimentary rock cores at different liquid saturations.

In Nuclear Magnetic Resonance (NMR) spin echo measurements of confined liquids, the dynamic behaviour of liquid molecules are influenced by diffusion (D), translational displacement of molecules in internal gradients (G), and transverse surface relaxation (T). In this study, an experimental approach that enables characterisation of water and oil in rock core materials is presented. The approach is based on three-dimensional D-DG-T correlations, but the main focus is on the two-dimensional parts that involve DG-T and D-∣G∣.

MnDPDP: Contrast Agent for Imaging and Protection of Viable Tissue.

The semistable chelate manganese (Mn) dipyridoxyl diphosphate (MnDPDP, mangafodipir), previously used as an intravenous (i.v.) contrast agent (Teslascan™, GE Healthcare) for Mn-ion-enhanced MRI (MEMRI), should be reappraised for clinical use but now as a diagnostic drug with cytoprotective properties.

A fluid specific dimension of confinement as a measure of wettability in porous media.

The wettability of a reservoir rock is among the most important factors influencing oil recovery. This study presents how the application of a modified CPMG pulse sequence can determine the wettability of porous samples containing oil and water in the same pore network. This method can be applied as an average of the signal over the entire sample as well as with spatial resolution using slice selection.

Characterising oil and water in porous media using correlations between internal magnetic gradient and transverse relaxation time.

A method for characterising water and oil in a rock core plug using correlations between diffusion decay in internal magnetic gradient and transverse relaxation time (DG-T) is presented. The method is evaluated at different saturation levels and is compared with the measurement of correlations between diffusion and transverse relaxation time (D-T). It is shown how signals from water and oil can be separated based on their difference in diffusion decay in internal gradients.

Investigating pore geometry in heterogeneous porous samples using spatially resolved G-Δχ and G-Δν correlations.

This study presents a two-dimensional NMR pulse sequence for obtaining spatially resolved correlations between magnetic susceptibility induced internal gradients (G), and both the apparent difference in magnetic susceptibility (Δχ) and spectral frequency (Δν). G-Δχ correlations were utilized to generate spatially resolved pore size distributions, while the G-Δν correlations were used to additionally evaluate sample heterogeneity. The spatially resolved measurements were performed on a water saturated heterogeneous porous sample which contains one layer of 5-50 μm glass spheres (top layer) and one layer of 140-165 μm glass spheres (bottom layer).

Investigating mobility of crude oil adsorbates on mineral surfaces by NMR.

We have applied diffusion and relaxation Nuclear Magnetic Resonance experiments to investigate the translational and rotational mobility of adsorbents on quartz and calcite mineral surfaces. On both surfaces it was found that water is the dominant molecule. On the quartz surface the majority of water molecules have a relatively high degree of both rotational and translational mobility, while a minor fraction of water molecules, and all hydrocarbon molecules, have a significantly lower mobility.

Investigating structure-dependent diffusion in hydrogels using spatially resolved NMR spectroscopy.

Hypothesis: Incorporation of the drug-loaded surfactant micelles into polymer hydrogels is a common method used to achieve controlled drug delivery. The characterization of the diffusion processes in drug delivery systems is critical in order to tune the drug loading and release.

Experiments: We present a simple and efficient NMR protocol to investigate the transport of the surfactant molecules in hydrogels on micro- and macroscale under non-equilibrium conditions.

A multi-dimensional experiment for characterization of pore structure heterogeneity using NMR.

In a liquid saturated porous sample the spatial inhomogeneous internal magnetic field in general depends on the strength of the static magnetic field, the differences in magnetic susceptibilities, but also on the geometry of the porous network. To thoroughly investigate how the internal field can be used to determine various properties of the porous structure, we present a novel multi-dimensional NMR experiment that enables us to measure several dynamic correlations in one experiment, and where all of the correlations involve the internal magnetic field and its dependence on the geometry of the porous network. (Correlations: internal gradient - pore size, internal gradient - magnetic susceptibility difference, internal gradient - longitudinal relaxation, longitudinal relaxation - magnetic susceptibility difference.

Characterising oil and water in porous media using decay due to diffusion in the internal field.

In the method Decay due to Diffusion in the Internal Field (DDIF), the diffusion behaviour of water molecules in the internal magnetic field makes it possible to determine a distribution of pore sizes in a sample. The DDIF experiment can also be extended to a DDIF-Carr-Purcell-Meiboom-Gill (DDIF-CPMG) experiment to measure correlations between the pore size and the transverse relaxation time, T2. In this study we have for the first time applied the DDIF experiment and the DDIF-CPMG experiment to porous materials saturated with both water and oil.

A comparison of retrospectively self-gated magnetic resonance imaging and high-frequency echocardiography for characterization of left ventricular function in mice.

Non-invasive imaging methods like echocardiography and magnetic resonance imaging (MRI) are very valuable in longitudinal follow-up studies of cardiac function in small animals. To be able to compare results from studies using different methods, and explain possible differences, it is important to know the agreement between these methods. As both self-gated high-field MRI and high-frequency echocardiography (hf-echo) M-mode are potential methods for evaluation of left ventricular (LV) function in healthy mice, our aim was to assess the agreement between these two methods.

Analyzing equilibrium water exchange between myocardial tissue compartments using dynamical two-dimensional correlation experiments combined with manganese-enhanced relaxography.

Water compartments were identified and equilibrium water exchange was studied in excised rat myocardium enriched with intracellular manganese (Mn(2+)). Standard relaxographic measurements were supplemented with diffusion-T(2) and T(1)-T(2) correlation measurements. In nonenriched myocardium, one T(1) component (800 ms) and three T(2) components (32, 120, and 350 ms) were identified.

Dynamic water changes in excised rat myocardium assessed by continuous distribution of T1 and T2.

Ischemic changes in excised rat myocardium were followed by series of T1 or T2 measurements from 1 to 60 min after isolated perfusion cessation, and the influence of manganese enhancement was investigated. An inverse Laplace transformation (ILT) of T1 or T2 data was used to resolve the number, time constants, and fractions of tissue water components in a continuous distribution. For T1 distributions, one single tissue component approximately 900 ms was significantly shortened and dispersed by manganese enhancement (25 and 200 microM MnCl2).

NMR-propagator measurements in porous media in the presence of surface relaxation and internal fields.

We measure the probability distribution P(zeta)--the propagator--of molecular displacements on Stokes flow through a pack of microporous glass beads and a carbonate rock. An optimized sampling of q-space is introduced for the measurement of a P(zeta) and its first moment zeta. Our results delineate and provide an understanding of the experimental regimes where background fields and surface relaxation distort the measured propagators.

Determination of water compartments in rat myocardium using combined D-T1 and T1-T2 experiments.

We have used combined D-T1 and T1-T2 correlation experiments to explore water compartments in rat heart tissue (myocardium). The results show that two main compartments can be identified, which we assign to extracellular (ec) and intracellular (ic) water. The exchange rate of water across the cell membrane was found to be on the order of 0.

Correlations between diffusion, internal magnetic field gradients, and transverse relaxation in porous systems containing oil and water.

The main focus in this study is to investigate the correlations between internal magnetic field gradients (G0) and transverse relaxation times in liquid-saturated packings of glass beads of different wettabilities. We show how these correlations can be expressed as two-dimensional (2D) diagrams of distribution functions between internal magnetic field gradients and T2 values. In the case where it is difficult to distinguish the signals from oil and water, we separate them based on their difference in diffusivity.

Background gradient suppression in pulsed gradient stimulated echo measurements.

Pulsed gradient spin echo (PGSE) experiments can be used to measure the probability distribution of molecular displacements. In homogeneous samples this reports on the molecular diffusion coefficient, and in heterogeneous samples, such as porous media and biological tissue, such measurements provide information about the sample's morphology. In heterogeneous samples however background gradients are also present and prevent an accurate measurement of molecular displacements.

A PFG-NMR Study of Restricted Diffusion in Heterogeneous Polymer Particles.

The diffusion resistance to monomers during heterogeneous polymerization of polyolefin particles may have a significant effect on the observed activity. This diffusivity is, in general, unknown. To gain more information on this diffusion resistance in such systems, PFG-NMR has been used to measure the diffusion of organic solvents in various systems of porous polymer particles.