Nuclear Magnetic Resonance Relaxation Times Research Articles

Hydraulic Conductivity Calibration of Logging NMR in a Granite Aquifer, Laramie Range, Wyoming.

In granite aquifers, fractures can provide both storage volume and conduits for groundwater. Characterization of fracture hydraulic conductivity (K) in such aquifers is important for predicting flow rate and calibrating models. Nuclear magnetic resonance (NMR) well logging is a method to quickly obtain near-borehole hydraulic conductivity (i.e., KNMR ) at high-vertical resolution. On the other hand, FLUTe flexible liner technology can produce a K profile at comparable resolution but requires a fluid driving force between borehole and formation. For three boreholes completed in a fractured granite, we jointly interpreted logging NMR data and FLUTe K estimates to calibrate an empirical equation for translating borehole NMR data to K estimates. For over 90% of the depth intervals investigated from these boreholes, the estimated KNMR are within one order of magnitude of KFLUTe . The empirical parameters obtained from calibrating the NMR data suggest that "intermediate diffusion" and/or "slow diffusion" during the NMR relaxation time may occur in the flowing fractures when hydraulic aperture are sufficiently large. For each borehole, "intermediate diffusion" dominates the relaxation time, therefore assuming "fast diffusion" in the interpretation of NMR data from fractured rock may lead to inaccurate KNMR estimates. We also compare calibrations using inexpensive slug tests that suggest reliable KNMR estimates for fractured rock may be achieved using limited calibration against borehole hydraulic measurements.

Solid-State Nuclear Magnetic Resonance (NMR) and Nuclear Magnetic Relaxation Time Analyses of Molecular Mobility and Compatibility of Plasticized Polyhydroxyalkanoates (PHA) Copolymers.

The molecular mobility and compatibility of plasticized polyhydroxyalkanoates (PHA) were investigated, focusing on changes due to copolymerization using either flexible poly (butylene succinate) (PBS) or rigid poly(lactic acid) (PLA) units. For the case of a poly(3-hydroxybutyrate) (PHB) unit in plasticized PHA, copolymerization of either PBS or PLA decreased 1H and 13C spin-lattice relaxation times in the laboratory frame (T1H and T1C) in the same manner, while PBS produced a lower 1H spin-lattice relaxation time in the rotating frame (T1ρH) than PLA. Both the signals of 1H MAS (magic-angle spinning) and 13C PST (pulse saturation transfer) MAS nuclear magnetic resonance (NMR) spectra were sharpened and increased by copolymerization with PBS. A variable temperature relaxation time analysis showed that the decrease of T1H values was dominated by the 1H spin diffusion via the interface between PHB and the added polyester because of the good compatibility. Meanwhile, the decrease of T1C values was dominated by increasingly rapid molecular motions of PHB because of the lowered crystallinity due to the plasticization. Slow molecular motions (kHz order) were enhanced more by the addition of PBS than PLA, although rapid molecular motions (MHz order) were enhanced by either polyester. Several NMR parameters were beneficial for analyzing the manufacturing process as the indexes of polymer compatibility and molecular motions.

NMR relaxometry for adsorption studies: Proof of concept with copper adsorption on activated alumina

Abstract Water pollution by heavy metal is a major environmental problem. Adsorption is one of the most used and promising heavy metal removal techniques. The development and evaluation of new adsorbents is thus an important topic. Some heavy metal ions – like Cu2+, Mn2+, Cr3+ … – are paramagnetic and known to affect the Nuclear Magnetic Resonance (NMR) relaxation times T1 and T2 of water protons in aqueous solutions. These relaxation times can be used to evaluate the paramagnetic ion concentration in solution. For the adsorption of Cu2+on activated alumina, we show, after a comparison with conventional methods, that NMR T2 relaxometry can be used to perform kinetics study and obtain a Langmuir isotherm. The T2 relaxometric experiment is performed at 0.47 T directly in an NMR tube with 350 µl of solution and 45 mg of adsorbent. For the kinetics study, a single tube is used since the measurement is nondestructive. The NMR experiments allow to determine a maximum Cu2+ adsorption capacity qmax = 4.32 mgCu/gAl2O3 and an equilibrium adsorption constant K = 0.61 mM−1. T1 based relaxometry can also be used to evaluate the amount of Cu2+ adsorbed on alumina, directly on the wet sorbent. Even if it is limited to paramagnetic heavy metal ion and necessitates rather high metal concentration, NMR relaxometry could become an interesting additional tool for the study of heavy metal adsorption.

Sustainable hybrid composites of recycled polypropylene and construction debris

We prepared composites of recycled polypropylene and construction debris aiming to obtain a sustainable hybrid material, with prospective application in the construction industry. We varied the amount of debris in 0, 1, 2, 3 and 7 m/m/% and the compounded materials were analysed by scanning electron microscopy, thermogravimetry/derivative thermogravimetry, differential scanning calorimetry, Fourier-transform infrared spectroscopy, melt flow rate, wide angle X-ray diffractometry, nuclear magnetic resonance relaxation time and dynamic mechanical analysis. The melt flow rate varied non-linearly according to the debris content. The thermal stability of recycled polypropylene was slightly improved due to the presence of debris particles. The degree of crystallinity of the recycled polypropylene also showed a non-linear change, and we noticed some transcrystallization phenomenon in the polymeric matrix. The glass transition temperature decreased for all composites, denoting an increase in the segmental mobility of the polymeric chains. Considering the domains curves of the nuclear magnetic resonance, there was some interaction between polymer and debris particles, mainly ascribed to the nanometric portion of the hybrid debris particles. We concluded that this hybrid composite may become of great interest to the construction industry, used as replacement for closing boards.

Implications of white striping and spaghetti meat abnormalities on meat quality and histological features in broilers

During the past few years, there has been an increasing prevalence of broiler breast muscle abnormalities, such as white striping (WS) and wooden breast conditions. More recently, a new muscular abnormality termed as spaghetti meat (SM) because of the altered structural integrity of the Pectoralis major muscle often associated with WS has emerged. Thus, this study aimed at evaluating the effects of WS and SM conditions, occurring alone or combined within the same P. major muscle, on meat quality traits and muscle histology. In two replications, 96 P. major muscles were classified into four classes: normal (N), WS, SM and WS/SM. The whole fillet was used for weight assessment and morphometric measurements, then each sample was cut in order to separate the superficial layer from the deep one and used to evaluate proximate composition, histological features, nuclear magnetic resonance relaxation times, functional properties and both myofibrillar and sarcoplasmic proteins profile. Fillets affected by WS and SM abnormalities exhibited higher weights and increased thickness and length. SM condition was associated with a relevant decrease in protein content coupled with a significant increase in moisture level, whereas fat content was affected only by the simultaneous presence of WS. Histological evaluations revealed that abnormal samples were characterized by several degenerative aspects that almost completely concerned the superficial layer of the fillets. White striped fillets exhibited necrosis and lysis of fibers, fibrosis, lipidosis, loss of cross striation and vacuolar degeneration. Moreover, SM samples were characterized by poor fiber uniformity and a progressive rarefaction of the endo- and peri-mysial connective tissue, whereas WS/SM fillets showed intermediate histological features. Nuclear magnetic resonance relaxation analysis revealed a higher proportion of extra-myofibrillar water in the superficial section of all the abnormal fillets, especially in SM samples, which consequently led to a reduction of the water holding capacity of meat. As for functional properties, abnormal fillets exhibited a lower protein solubility and higher ultimate pH values on both the superficial and deep sections. Although abnormal fillets exhibited higher yellowness values, no relevant effect on meat color was observed. The occurrence of WS and SM abnormalities led to increased carbonylation levels and more intense proteolytic processes. Overall, muscle abnormalities mainly affect the superficial layer of P. major muscle and particularly the occurrence of SM myopathy seems to implicate a more pronounced modification of meat quality traits than the mere presence of WS.

New method for determining concentrations of the mixture components during rapid control

The paper discusses the features of the signal registration of nuclear magnetic resonance in a weak magnetic field from small volume of condensed medium. Method for determining the state of condensed medium in express mode, using measured by nuclear magnetic resonance relaxation time constants T1 and T2, is proposed. We have developed the new method of determining the composition of the investigated mixture and relative concentrations of its components. That method is applicable for mixtures that formed by condensed media similar in both physical structure and chemical composition.

Estimating spatial distribution of natural fractures by changing NMR [formula omitted] relaxation with magnetic nanoparticles

Natural fractures have been widely found and thought to be an important factor in creating a complex hydraulic fractures network and improving hydrocarbon production in shale reservoirs. Nuclear magnetic resonance (NMR) is extensively applied to measure in-situ petrophysical properties, and magnetic nanoparticles provide good contrast agents to distinguish hydrogen relaxation time for NMR. The objective of this paper was to estimate spatial distribution of natural fractures in shale gas reservoirs by applying magnetic nanoparticles to change the NMR relaxation times. Firstly, a three-dimensional (3D) reservoir model including multiple natural fractures was built to investigate the flow of nanoparticles and the distribution of volume magnetic susceptibility (VMS) when injecting magnetic nanoparticles. The sensitivity analyses about nanoparticle concentration and nanoparticles size were investigated. Secondly, a forward model was introduced about how to obtain Carr-Purcell-Meiboom-Gill (CPMG) echo decay trains from given relaxation times. Thirdly, an inversion method was presented to convert the typical CPMG echo decay curve into the distribution of T2 relaxation amplitudes and times. The inversion method was used to show the change of T2 amplitude and time for the two synthetic cases with and without magnetic nanoparticles.The dynamic distribution of nanoparticles concentration and VMS are graphically displayed along each time step in 3D mesh. The results show that magnetic nanoparticles bring much larger VMS while most nanoparticles only flow into these natural fractures (NF) directly connected with wellbore. The others’ NF have somewhat higher VMS than matrix. Additionally, based on various sensitivity cases, a higher concentration of nanoparticles yields a stronger magnetic field, and larger nanoparticle size could lead to higher VMS, although the nanoparticles face stronger flow resistance and less diffusion movement. The CPMG decay curve is a multi-dimensional exponential function related to relaxation amplitudes and times, and the least squares minimization technique can be applied to obtain the T2 amplitudes from CPMG curve. The comparison between two synthetic cases shows the amplitude for small T2 time increases and the amplitude for large T2 time reduces, which provides a clear indicator to detect the locations of natural fractures because their T2 largely reduce. The nanoparticle model provides valuable guidance about choosing parameters for optimizing magnetic nanoparticle injection design to enhance VMS and NMR signals. The inversion model introduces an efficient path for estimating T2 distribution and petrophysical properties from the acquired NMR CPMG signals. Additionally, magnetic Nanoparticles provide excellent relaxation contrasts to distinguish the magnetization signals of formation for estimating the spatial natural fractures distribution. Consequently, in-situ fracture characterization and the development of hydraulic fracture treatments could be beneficially improved.

Probing the interaction of the potassium channel modulating KCNE1 in lipid bilayers via solid-state NMR spectroscopy.

KCNE1 is known to modulate the voltage-gated potassium channel α subunit KCNQ1 to generate slowly activating potassium currents. This potassium channel is essential for the cardiac action potential that mediates a heartbeat as well as the potassium ion homeostasis in the inner ear. Therefore, it is important to know the structure and dynamics of KCNE1 to better understand its modulatory role. Previously, the Sanders group solved the three-dimensional structure of KCNE1 in LMPG micelles, which yielded a better understanding of this KCNQ1/KCNE1 channel activity. However, research in the Lorigan group showed different structural properties of KCNE1 when incorporated into POPC/POPG lipid bilayers as opposed to LMPG micelles. It is hence necessary to study the structure of KCNE1 in a more native-like environment such as multi-lamellar vesicles. In this study, the dynamics of lipid bilayers upon incorporation of the membrane protein KCNE1 were investigated using 31 P solid-state nuclear magnetic resonance (NMR) spectroscopy. Specifically, the protein/lipid interaction was studied at varying molar ratios of protein to lipid content. The static 31 P NMR and T1 relaxation time were investigated. The 31 P NMR powder spectra indicated significant perturbations of KCNE1 on the phospholipid headgroups of multi-lamellar vesicles as shown from the changes in the 31 P spectral line shape and the chemical shift anisotropy line width. 31 P T1 relaxation times were shown to be reversely proportional to the molar ratios of KCNE1 incorporated. The 31 P NMR data clearly indicate that KCNE1 interacts with the membrane. Copyright © 2017 John Wiley & Sons, Ltd.

Characterization of the exhaustion profile of activated carbon in industrial rum “filters” based on TGA, TD-GC/MS, colorimetry and NMR relaxometry

Spectrophotometric measurements applied on saturated granular activated carbons have been barely explored. Although Nuclear Magnetic Resonance (NMR) relaxation studies proved to be suitable to explore pore characteristics in different porous materials, characterization of granular activated carbons used in rum production have not been addressed yet. In this work, the feasibility of using NMR relaxometry and colorimetry in order to characterize the exhaustion degree of granular activated carbon (GAC) from a target rum “filter” is evaluated. Colorimetric measurements and the transverse NMR relaxation time distribution have been correlated with the amount of adsorbed organic compounds on these GAC. Samples from eight consecutive GAC layers of the rum filter have been assessed. The exhaustion profile for the rum “filter” is correlated with the colorimetric results, the 1H NMR T2-relaxometry measurements, the TD-GC/MS chromatograms and the CHNS-O elemental analysis. The proposed methods are not only of general use in GAC characterization but open possibilities for the rum producers to improve the management and economical use of the activated carbon at industrial scale.

Molecular dynamics simulations of NMR relaxation and diffusion of bulk hydrocarbons and water

Molecular dynamics (MD) simulations are used to investigate 1H nuclear magnetic resonance (NMR) relaxation and diffusion of bulk n-C5H12 to n-C17H36 hydrocarbons and bulk water. The MD simulations of the 1H NMR relaxation times T1,2 in the fast motion regime where T1=T2 agree with measured (de-oxygenated) T2 data at ambient conditions, without any adjustable parameters in the interpretation of the simulation data. Likewise, the translational diffusion DT coefficients calculated using simulation configurations agree with measured diffusion data at ambient conditions. The agreement between the predicted and experimentally measured NMR relaxation times and diffusion coefficient also validate the forcefields used in the simulation. The molecular simulations naturally separate intramolecular from intermolecular dipole-dipole interactions helping bring new insight into the two NMR relaxation mechanisms as a function of molecular chain-length (i.e. carbon number). Comparison of the MD simulation results of the two relaxation mechanisms with traditional hard-sphere models used in interpreting NMR data reveals important limitations in the latter. With increasing chain length, there is substantial deviation in the molecular size inferred on the basis of the radius of gyration from simulation and the fitted hard-sphere radii required to rationalize the relaxation times. This deviation is characteristic of the local nature of the NMR measurement, one that is well-captured by molecular simulations.

Xenon-Water Interaction in Bacterial Suspensions as Studied by NMR

Xenon is a perspective gas for creation of oxygen free environment for different applications of biomaterials. To use xenon in suspensions and products properly it is necessary to know the molecular mechanisms of its interactions with water and cells. This work reports the study of bacterial suspensions of Escherichia coli in the presence of xenon using nuclear magnetic resonance (NMR). The work studied how the spin-lattice relaxation times of water protons in suspension change under xenon conditions. Xenon is able to form clathrate hydrates with water molecules at a temperature above the melting point of ice. The work studied NMR relaxation times which reflect the rotation freedom of water molecules in suspension. Lower relaxation times indicate reduced rotational freedom of water. Single exponential behavior of spin-lattice relaxation of protons in the suspensions of microorganisms has been registered. A recovery of longitudinal magnetization in cell suspensions with xenon clathrates has been characterized by two peaks in T1-distribution. Fast relaxing T1-component was related to the intracellular water and depended on the amount of xenon clathrates. The obtained results elucidate how the NMR method can monitor the process of clathrate formation and how the xenon atoms and hydrates interact with cells.

An integrated characterization of the porosity in Qusaiba Shale, Saudi Arabia

A comprehensive sequential analysis including thin section petrography, Rock-Eval pyrolysis, X-ray diffraction, scanning electron microscope (SEM) imaging, and nuclear magnetic resonance (NMR) analysis has been used to characterize the porosity of the organic-rich Qusaiba Shale, Saudi Arabia. The studied samples consist mainly of dark to light grey, silty, flaky-to-subflaky, micaceous, non-calcareous, highly cemented shales. Three lithofacies identified from the petrographic analysis of the Qusaiba Shale include silty-clayey laminated mudstone, clay-rich mudstone, and mica-rich mudstone lithofacies. XRD analysis documented that the main minerals of the QS are: quartz, K-feldspar, muscovite, illite, chlorite, as well as minor amounts of pyrite and albite. The studied samples have a total organic content (TOC) ranging from 1.4% to 1.82% and Tmax ranges between 472°C and 529°C. SEM analysis showed that the QS hosts a wide range of pore sizes and types. The analysis allowed to identify three groups of porosity: inorganic-related, organic-related and microfracture-related porosity. Quartz, clay, mica and pyrite mineral grains are the main particles hosting the inorganic related porosity. The pore size of organic-related porosity type is typically less than 1µm, with a scattered, isolated, pinpoint shape. NMR relaxation time T2 of the studied samples indicates the presence of a porosity range between 1.1 and 2.8 p.u. with the maximum value attributed to clay-rich mudstone lithofacies and the minimum to silty-clayey laminated mudstone facies. Additionally, the longitudinal relaxation time T1 gives a porosity range between 6.6 and 0.9 p.u. with the highest value corresponding to the clay-rich mudstone lithofacies and the lowest values to silty-clayey laminated mudstone lithofacies. The T1 spectrum exhibits a bimodal configuration with a dominant primary peak at less than 1ms and a secondary peak located around 10ms. Both T1 and T2 reveal the contribution of organic-related microporosity to the total porosity of QS as previously indicated by SEM analysis. However, inorganic-related porosity, particularly in the mica and clay particles, also contribute to QS porosity.

Online NMR Flowing Fluid Measurements

Online nuclear magnetic resonance (NMR) is an efficient fluid detection method for fluid flowing measurement. In our previous work, the velocity effects on the motion NMR measurement were studied and the velocity correction method was proposed. However, the flow state effects on NMR measurement is more complicated than motion velocity effects. Thus, the influence of flow state on NMR measurement is investigated. A multi-functional low-field and online NMR fluid analysis system is developed to realize the rapid measurement of one-dimensional and two-dimensional NMR relaxation times of fluids under slow laminar flow state.

Collective water dynamics in the first solvation shell drive the NMR relaxation of aqueous quadrupolar cations.

Using molecular simulations, we analyze the microscopic processes driving the Nuclear Magnetic Resonance (NMR) relaxation of quadrupolar cations in water. The fluctuations of the Electric Field Gradient (EFG) experienced by alkaline and magnesium cations, which determine the NMR relaxation time, are mainly due to the dynamics of water molecules in their solvation shell. The dynamics of the ion plays a less important role, with the exception of the short-time dynamics in the lighter Li+ case, for which rattling in the solvent cage results in oscillations of the EFG autocorrelation function (ACF). Several microscopic mechanisms that may a priori contribute to the decay of the EFG-ACF occur in fact over too long time scales: entrance/exit of individual water molecules into/from the solvation shell, rotation of a molecule around the ion, or reorientation of the molecule. In contrast, the fluctuations of the ion-water distance are clearly correlated to that of the EFG. Nevertheless, it is not sufficient to consider a single molecule due to the cancellations arising from the symmetry of the solvation shell. The decay of the EFG-ACF, hence NMR relaxation, is in fact governed by the collective symmetry-breaking fluctuations of water in the first solvation shell.

The impact of pore-scale magnetic field inhomogeneity on the shape of the nuclear magnetic resonance relaxation time distribution

Measurements of the nuclear magnetic resonance (NMR) signal’s behavior with time provide powerful noninvasive insight into the pore-scale environment. The time dependence of the NMR signal, which is a function of parameters called relaxation times, is intimately linked to the geometry of the pore space and has been used successfully to estimate pore size and permeability. The basis for the pore size and permeability estimates is that interactions occurring at the grain surface often function as the primary mechanism controlling the time dependence of the NMR signal. In this limit, called the fast diffusion limit, and when each pore can be considered to be isolated, the measured relaxation times are often interpreted as representative of pore sizes. In heterogeneous media, where the NMR signal is described by a distribution of relaxation times, the measured relaxation time distribution is often interpreted as representative of the underlying pore-size distribution. We have explored a scenario in which an additional relaxation mechanism, which arises due to magnetic field inhomogeneity across the pore space, violates the assumption that interactions occurring at the grain surface are the dominant relaxation mechanism. Using both synthetic and laboratory studies, we demonstrate that magnetic field inhomogeneity can lead to a complex relationship between the measured relaxation time distribution and the underlying pore-size distribution. Magnetic field inhomogeneity is observed to lead to a spatially heterogeneous magnetization density across the pore space requiring multiple eigenmodes to describe the evolution of the magnetization within a single pore during the NMR experiment. This results in a breakdown of the validity of the interpretation of the relaxation time distribution as representative of the underlying pore-size distribution for sediments with high magnetic susceptibility.

Models and methods for predicting hydraulic conductivity in near-surface unconsolidated sediments using nuclear magnetic resonance

Nuclear magnetic resonance (NMR) logging provides a relatively new approach for estimating the hydraulic conductivity [Formula: see text] of unconsolidated aquifers. We have evaluated results from model validation and uncertainty quantification using direct-push measurements of NMR mean relaxation times and [Formula: see text] in sands and gravels at three field sites. We have tested four models that have been proposed for predicting [Formula: see text] from NMR data, including the Schlumberger-Doll research, Seevers, and sum-of-echoes equations, all of which use empirically determined constants, as well as the Kozeny-Godefroy model, which predicts [Formula: see text] from several physical parameters. We have applied four methods of analysis to reanalyze NMR and [Formula: see text] data from the three field sites to quantify how well each model predicted [Formula: see text] from the mean log NMR relaxation time [Formula: see text] given the uncertainties in the data. Our results show that NMR-estimated porosity does not improve prediction of [Formula: see text] in our data set for any model and that all of the models can predict [Formula: see text] to within an order of magnitude using the calibrated constants we have found. We have shown the value of rigorous uncertainty quantification using the methods we used for analyzing [Formula: see text]-NMR data sets, and we have found that incorporating uncertainty estimates in our analysis gives a more complete understanding of the relationship between NMR-derived parameters and hydraulic conductivity than can be obtained through simple least-squares fitting. There is little variability in our data set in the calibrated constants we find, given the uncertainty present in the data, and therefore we suggest that the constants we find could be used to obtain first-order estimates of hydraulic conductivity in unconsolidated sands and gravels at new sites with NMR data available.

Solution Nuclear Magnetic Resonance Studies of Sterol Carrier Protein 2 Like 2 (SCP2L2) Reveal the Insecticide Specific Structural Characteristics of SCP2 Proteins in Aedes aegypti Mosquitoes.

Sterol carrier protein 2 like 2 from Aedes aegypti (AeSCP2L2) plays an important role in lipid transport in mosquitoes for its routine metabolic processes. Repeated unsuccessful attempts to crystallize ligand free SCP2L2 prompted us to undertake nuclear magnetic resonance (NMR) spectroscopy to determine its three-dimensional structure. We report here the three-dimensional structures and dynamics of apo-AeSCP2L2 and its complex with palmitate. The (15)N heteronuclear single-quantum coherence spectrum of apo-AeSCP2L2 displayed multiple peaks for some of the amide resonances, implying the presence of multiple conformations in solution, which are transformed to a single conformation upon formation of the complex with plamitate. The three-dimensional structures of apo-AeSCP2L2 and palmitated AeSCP2L2 reveal an α/β mixed fold, with five β-strands and four α-helices, very similar to the other SCP2 protein structures. Unlike the crystal structure of palmitated AeSCP2L2, both solution structures are monomeric. It is further confirmed by the rotational correlation times determined by NMR relaxation times (T1 and T2) of the amide protons. In addition, the palmitated AeSCP2L2 structure contains two palmitate ligands, bound in the binding pocket, unlike the three palmitates bound in the dimeric form of AeSCP2L2 in the crystals. The relaxation experiments revealed that complex formation significantly reduces the dynamics of the protein in solution.

NMR and MRI observation of water absorption/uptake in hemp shives used for hemp concrete

Hemp concrete used as a construction material is known to provide excellent thermal insulation and hydric regulation, and prevents condensation. Initial water content in the hemp and water exchanges between hemp and binder play a major role in these processes. Here we study how hemp absorbs liquid water. In that aim we rely on 1H NMR (Nuclear Magnetic Resonance) measurements which make it possible to distinguish water situated inside from water situated outside the hemp. Then, following the evolution of the distribution of NMR relaxation times we are able to quantify the effective amount of water entering the hemp as a function of time. We show that such a measure is better controlled than usual techniques such as weighing an immersed sample or the TC (Technical Committee) RILEM (Réunion Internationale des Laboratoires et Experts des Matériaux, systèmes de construction et ouvrages) method which cannot easily distinguish water inside hemp from water situated outside or wetting the external hemp surface. The water absorption in hemp occurs in two steps: about half the water enters the material in a time of the order of a minute, while the second half of water slowly penetrates over a time of the order of three days. Finally, from 1H micro NMR imaging we show that the first step corresponds to water entering the pith while the second one corresponds to water diffusing in the wood part of the shiv.

Unilateral NMR and thermal microscopy studies of vegetable tanned leather exposed to dehydrothermal treatment and light irradiation

Unilateral nuclear magnetic resonance (NMR) and imaging thermal microscopy (imageMHT) were performed on newly obtained and artificially aged vegetable tanned leathers. Calf and sheep leathers tanned with vegetal extracts of mimosa bark, quebracho and chestnut wood were compared. Ageing was simulated by exposing the leather samples to heating at 70°C in controlled atmosphere at 30% relative humidity and irradiating them with 4000lx in the visible light region for 8, 16, 32 and 64days. Proton spin-lattice relaxation times T1 and effective spin-spin relaxation times T2eff were measured at room temperature and their trend variation compared with the corresponding variations of shrinkage temperature Ts and total length of shrinkage interval measured by imageMHT. Newly obtained leather displayed different proton relaxation times and shrinkage temperatures depending on both the collagen origin and tannin type. Effective spin-spin relaxation values shown to be discriminative for collagen origin and sensitive to the cross-linking degree, whereas spin-lattice relaxation values were more sensitive to the tannin type. Both NMR relaxation times were sensitive to the changes in the water dynamics upon ageing due to the formation of collagen damaged intermediate states and shown a sudden change when the tannin matrix was depleted (e.g. de-tanning).

Characterization of yogurts made with milk solids nonfat by rheological behavior and nuclear magnetic resonance spectroscopy

The effect of adding milk solids nonfat (MSNF) on the physical properties and microstructure of yogurts was investigated. The physical properties of fat free yogurt, fat free with MSNF yogurt, whole fat yogurt, and whole fat with MSNF yogurt were analyzed using shear viscosity, viscoelasticity, and texture analysis. The two yogurts with MSNF had higher consistency coefficient (K), storage modulus (G′), yield stress, and hardness. To gain insight into the multiphase system, nuclear magnetic resonance (NMR) and brightfield microscope images were acquired. The addition of MSNF significantly modified NMR relaxation time; T1 values were reduced significantly. Brightfield microscope images showed that the size of the protein network of the two yogurts with MSNF added was greater than that of the two yogurts without MSNF added. The microstructural information supported the physical information. The results showed that the increase in MSNF contributed positively to strengthening the physical/mechanical properties of yogurt.