Search

The low-field nuclear magnetic resonance (NMR) inversion method based on traditional least-squares QR decomposition (LSQR) always produces some oscillating spectra. Moreover, the solution obtained by traditional LSQR algorithm often cannot reflect the true distribution of all the components. Hence, a good solution requires some manual intervention, for especially low signal-to-noise ratio (SNR) data. An approach based on the LSQR algorithm and L-curve is presented to solve this problem. The L-curve method is applied to obtain an improved initial optimal solution by balancing the residual and the complexity of the solutions instead of manually adjusting the smoothing parameters. First, the traditional LSQR algorithm is used on 2D NMR T 1 – T 2 data to obtain its resultant spectra and corresponding residuals, whose norms are utilized to plot the L-curve. Second, the corner of the L-curve as the initial optimal solution for the non-negative constraint is located. Finally, a 2D map is corrected and calculated iteratively based on the initial optimal solution. The proposed approach is tested on both simulated and measured data. The results show that this algorithm is robust, accurate and promising for the NMR analysis. [ABSTRACT FROM AUTHOR]

Petroleum products such as LPG (cooking gas), kerosene, gasoline, diesel oil, among others, are obtained from the refining of crude oil. Among these, the diesel has great importance in the Brazilian road system where fuel consumption leads the rankings in the road sector in Brazil. The high consumption (approximately 50% of total) makes this fuel target to adulteration by irregular products like kerosene, which has low cost and good miscibility with the fuel. Adulteration causes irreparable damage to the car, such as sudden drops in engine, difficulties in starting, increased fuel consumption, degradation of machine performance and environmental harm as emissions of particulate matter during the combustion. This study proposes a new methodology, the nuclear magnetic resonance in the time domain (TD-NMR) to detect the adulteration of four commercial diesel oils with kerosene. Results of the study show that the diesel oil has a transverse relaxation time ( T 2 ) around 0.67 s, while the adulterant kerosene is 1.33 s, and the adulterated samples in the range of 5–100% presented T 2 between 0.67 and 1.33 s. The TD-NMR methodology proposed showed excellent agreement with quantification of adulterant content detected by mid-infrared (MIR) which is the standard technique to detect non-compliance of fuel. [ABSTRACT FROM AUTHOR]

The effects of divalent ions on the elasticity and the pore collapse of chalk were studied through rock-mechanical testing and low-field Nuclear Magnetic Resonance (NMR) measurements. Chalk samples saturated with deionized water and brines containing sodium, magnesium, calcium and sulfate ions were subjected to petrophysical experiments, rock mechanical testing and low-field NMR spectroscopy. Petrophysical characterization involving ultrasonic elastic wave velocities in unconfined conditions, porosity and permeability measurements, specific surface and carbonate content determination and backscatter electron microscopy of the materials were conducted prior to the experiments. The iso-frame model was used to predict the bulk moduli in dry and saturated conditions from the compressional modulus of water-saturated rocks. The effective stress coefficient, as introduced by Biot, was also determined from density and ultrasonic velocities measured on core plugs. Low-field NMR spectroscopy was used in addition to the mechanical testing to prove any changes observed after the saturation related to the surface-to-volume ratio of the pore space in each of the samples or to surface relaxivity. Backscatter-electron (BSE) images were recorded in order to identify the texture of the core plugs under investigation. The experimental results revealed that both elasticity and pore collapse are influenced by the presence of divalent ions in distinct ways. Compressional wave velocities indicate that saturation with water rich in magnesium and calcium ions softens the contact among the mineral grains. Pore collapse strength is deteriorating after the saturation of chalk with water rich in divalent ions. The presence of calcium and sulfate ions in the saturating fluid results in pore collapse at lower stresses than in the case when samples are saturated with deionized water or sodium chloride solution. Low field NMR spectrometry revealed precipitation of crystals in the pore space of chalk saturated with Mg-rich brine. The precipitation of Mg-carbonates was not used to explain the deteriorating pore collapse strength and effects on the elasticity after the saturation since none of the other plugs saturated with divalent ions (Ca 2+ and SO 4 2 + ) experienced it. [ABSTRACT FROM AUTHOR]

Low-field NMR was used for analysis of water binding in fat-in-water emulsions. Bovine fat was used and native potato starch was used as an emulsifying agent. Starch can be applied as an emulsifying agent although the starch content should not be lower than 0.17 g/g of water at fat concentrations in water amounting to 25%. Interactions of bovine fat with chains of starch exceeded the actions of water molecules with the polymer, leading to advantageous conformation changes. Bovine fat restricts the unfavourable influence of starch retrogradation. This, in turn, leads to a slowing of the syneresis process. [ABSTRACT FROM AUTHOR]

The successful pilot trial of methane hydrate production in the South China Sea has proven the technical feasibility of natural gas hydrates (NGHs) exploitation in clayey-silty reservoirs. As a key issue of NGHs exploitation in clayey-silty sediments, the variation of permeability with hydrate saturation (S h) has not been thoroughly studied. In this study, a triaxial core holder was designed to simulate the synthesis and dissociation of gas hydrates in a clayey-silty core plug sample. In the process of hydrate synthesis and multi-step dissociation, the water content and distribution in different pores were quantitatively determined by a nuclear magnetic resonance (NMR) spectrometer, and the variation of water content under different S h was successively monitored. Meanwhile, in each depressurization phase, the gas permeabilities k (S h) with respect to different S h were measured under constant effective stress. Results highlight that the change of k (S h) is more prevalent in clayey-silty sediments than that in sandstones. As S h increases from 0 to 10.43%, the permeability ratio (k (S h) to sedimentary permeability k s) in clayey-silty sediments decreases to 0.01–0.02; whereas in sandstones, the permeability ratio falls between 0.4 and 0.8. To predicate the permeability change in clayey-silty sediments, the previous Cubic model is improved and a Power-exponential model is presented. In the updated model, the variable of power parameter n can characterize different reservoir types. Specifically, in artificial sandstones, sandpacks or sandy reservoirs, the n values range from 3.1 to 8.3, while in clay packs or clayey-silty sediments, the n values are from 19.1 to 30.7. The Power-exponential model provides reference values for the prediction of different types of gas hydrate reservoirs such as permafrost and marine sediments. • Hydrates are synthesized in the clayey-silty sediments from the South China Sea. • The synthesis and dissociation of hydrates are monitored by an NMR spectrometer. • The permeability reduction is more obvious in the clayey-silty sediments. • A Power-exponential model can predict the permeability change in different reservoirs. • The power parameter indicates the influence of pore complexity on permeability change. [ABSTRACT FROM AUTHOR]

In the present study, to mimic the natural confinement of crude oils, model experiments are conducted with crude oils having different physical properties and maltenes of parent crude oils without asphaltenes confined into engineered nanoporous silica rods with pore diameters of 2.5 and 10.0 nm and white powdered nanoporous silica with pore diameters of 2.5 and 4.0 nm. This will help with suggesting potential treatments for enhancing crude oil recovery. Low-field nuclear magnetic resonance (LF-NMR) relaxometry has been applied to achieve this goal. The nanoporous proxies resemble real-life nanoporous rocks of reservoirs. The dynamics of confined crude oils with different o API gravity deviate from bulk dynamics, and deviation changes depending on the o API gravity. This suggests that treatments must be decided appropriately before crude oil production. Similar treatments could be applied for light and medium-heavy crude oils. Mathematical analysis of NMR relaxation curves of confined crude oils with different fractions of SARA (saturates, aromatics, resins, asphaltenes) indicates that the conventional SARA approach needs a better definition for the confined state of matter. The NMR relaxation behavior of confined maltenes shows that resin molecules might act like saturates in natural confinement with various scale pores from nano to micro and even macro, or aromatics might show resin-like behaviors. Confinement of brine and a light crude oil into white powdered nanoporous silica proxies demonstrates that brine could be utilized along with some additives such as nanoparticles for oil recovery. Therefore, these issues must be evaluated in deciding the proper treatments for crude oil production., Competing Interests: The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Ok.)

We review basic principles of low-resolution proton NMR spin diffusion experiments, relying on mobility differences in nm-sized phases of inhomogeneous organic materials such as block-co- or semicrystalline polymers. They are of use for estimates of domain sizes and insights into nanometric dynamic inhomogeneities. Experimental procedures and limitations of mobility-based signal decomposition/filtering prior to spin diffusion are addressed on the example of as yet unpublished data on semicrystalline poly( ϵ -caprolactone), PCL. Specifically, we discuss technical aspects of the quantitative, dead-time free detection of rigid-domain signals by aid of the magic-sandwich echo (MSE), and magic-and-polarization-echo (MAPE) and double-quantum (DQ) magnetization filters to select rigid and mobile components, respectively. Such filters are of general use in reliable fitting approaches for phase composition determinations. Spin diffusion studies at low field using benchtop instruments are challenged by rather short 1 H T 1 relaxation times, which calls for simulation-based analyses. Applying these, in combination with domain sizes as determined by small-angle X-ray scattering, we have determined spin diffusion coefficients D for PCL (0.34, 0.19 and 0.032 nm 2 /ms for crystalline, interphase and amorphous parts, respectively). We further address thermal-history effects related to secondary crystallization. Finally, the state of knowledge concerning the connection between D values determined locally at the atomic level, using 13 C detection and CP- or REDOR-based “ 1 H hole burning” procedures, and those obtained by calibration experiments, is summarized. Specifically, the non-trivial dependence of D on the magic-angle spinning (MAS) frequency, with a minimum under static and a local maximum under moderate-MAS conditions, is highlighted. [ABSTRACT FROM AUTHOR]

Low field nuclear magnetic resonance (LF-NMR) has several applications in the oilfield industry such as in predicting the viscosity and evaluating porosity, permeability, fluid saturation of reservoir rocks, and the water content in fluids. However, the studies to determine the physical and chemical properties of petroleum distillates are uncommon. So, the aim of this study was to determine the physical and chemical properties of distillates using the transverse relaxation time (T 2 ) in the range from 73.43 to 1810.74 ms. LF-NMR was employed in this research, due to its rapid and non-destructive analytical method. From LF-NMR data, it was possible to estimate the molar mass, correlation index, characterization factor, API gravity, relative hydrogen index, and number of hydrogen in distillates obtained up to 350 °C. T 2 and the properties determined by standard methodologies (ASTM D-1218, D-445-06, D-664-06, D-2892, and D-4052) were strongly correlated. So, low field NMR constitutes an interesting alternative to ASTM methods. The results also show that changes in the chemical and physical properties depend on boiling point and molecular mobility. Besides, LF-NMR enabled the classification of the fractions into gasoline, kerosene, and light and heavy gas oil. [ABSTRACT FROM AUTHOR]

The effects of using electrospun chitosan fibres as a wrapping material for dry-ageing beef was studied and compared to traditional dry-ageing and wet-ageing of beef for up to 21 days. The chitosan treatment showed improved results in terms of yield, reduction of microbial counts, yeasts and moulds, and lighter appearance compared to traditional dry-ageing. Weight and trimming losses were minimal in the wet-ageing beef. However, significant growth of lactic acid bacteria was observed in this group. Transverse relaxation times indicated a lower degree of muscle denaturation during ageing in the chitosan dry-ageing beef compared to the traditional dry-ageing meat. A principal component analysis furthermore indicated that 60.6% of the variation between samples and ageing treatments could be described by differences in the water content and distribution in the muscle. The study showed that electrospun chitosan fibre mats have potential as a wrapping material for improved quality during dry-ageing of beef. [ABSTRACT FROM AUTHOR]

Blends formed by starch and poly(lactic acid) (PLA) are very promising from environmental and economic standpoints, because starch is an abundant and cheap natural polymer and PLA is a biodegradable polymer that has good mechanical properties. In this study, starch-PLA blends were prepared by solution casting, employing chloroform and distilled water as a solvent pair. Then, dispersions containing 1, 3 and 5% montmorillonite clay and a dispersion containing 0.1% silica were added to the starch-PLA blends. The new materials obtained were characterized by X-ray diffraction, thermal analysis and, especially, nuclear low-field nuclear magnetic resonance (LF-NMR) relaxometry to measure the proton spin-lattice relaxation. All blends composed of starch and PLA showed significant increase in relaxation time due to the homogenous mixing of both polymers as a consequence of strong intermolecular interaction between them. Addition of clays caused substantial modification of the material and a large unique domain was observed. As a consequence, the domains corresponding to pure polymers were not observed. With the addition of the clay NT25, intermediate degradation temperatures were observed at concentrations of 3 and 5%, compared to the degradation temperatures of pure polymers. The X-ray diffraction results indicated the formation of an intercalated nanocomposite. There was an increase in the organization of the material compared to previous results observed for polymeric material, indicating the formation of an intercalated structure. [ABSTRACT FROM AUTHOR]

Water binding in fat-in-water emulsions with native potato starch was investigated at the molecular level using the low-field nuclear magnetic resonance method. Analysis of relaxation time changes with temperature allowed determination of activation energy values for water molecules. Application of potato starch as an emulsifier required selection of an appropriate polymer content. Optimal water binding was recorded when emulsions contained 6 parts of potato starch per 10 parts of fat. Activation energy values of water molecule rotations were more than twice values in comparable gels. Emulsions were more stable than starch gels with the same polymer concentration in water. Comparison of fat-water emulsions demonstrated that use of porcine fat allowed development of emulsions in which water was more strongly bound. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effects of rapid chilling ( RC) of carcasses on the quality of pork longissimus dorsi ( LD) compared to conventional chilling ( CC). Carcasses subjected to RC were chilled at −20 °C for 1.5 h and then moved to 4 °C until 24 h post-mortem, while carcasses that were CC were placed directly in a chill at 4 °C for 24 h post-mortem. RC accelerated the rates of temperature decline post-mortem ( P < 0.01) and increased pH values at 1.5 and 8 h post-mortem ( P < 0.05). RC could significantly decrease the denaturation of myosin and sarcoplasmic proteins during post-mortem ageing. Samples of RC had a significant lower purge loss compared to CC group during post-mortem ageing ( P < 0.05). Our study implies that RC could influence the biochemical changes of pork LD which may further regulate water-holding capacity during post-mortem ageing. [ABSTRACT FROM AUTHOR]

Composite films made with Arabinoxylans (AXs) (with high, middle and low level of substitution by arabinose) and (1 → 3)(1 → 4)-β- d -glucans (BGs) extracted from cereal cell walls have been prepared and analyzed using microscopy (SEM and LSCFM), DSC, mechanical tests and TD-NMR spectroscopy. The objectives were to correlate molecular and physico-chemical properties of films with mechanical and hydration properties of wheat cell walls. A phase separation phenomenon was observed for films made with highly substituted AXs and BGs at a ratio AX/BG of 60/40. This phase separation was correlated with lower dipolar interactions between polysaccharide chains and a decrease of ultimate strain and stress of films. Highly substituted AX and BG composite films exhibited very weak mechanical properties in agreement with weaker interactions between the polymer chains. This effect was supported by NMR results showing that interactions between AXs and BGs decreased with increased substitution of AXs in composite films. Lower dipolar interactions between polysaccharides favored the water mobility in relation with a higher specific surface area of polysaccharides in films but also higher distances between polysaccharide chains so larger nanopores in composite films made within highly substituted AXs. These multiscale characterizations agreed with the structural changes observed in wheat grain during its development. [ABSTRACT FROM AUTHOR]

Solvent-cast films of blends of synthetic oligo([R,S]-3-hydroxybutyrate) (OHB) and bacterial PHB were prepared in distinct compositions. The oligomeric amorphous OHB was prepared via ROP of β− butyrolactone in solution employing a new initiator based on Mg(II)/Ti(IV) complex. The FTIR spectroscopy was used to observe the behavior of the vibration modes sensitive to crystallinity with increasing amorphous component content in the polymer blends. Considering the changes in the vibrational spectra, the degree of crystallinity of bacterial PHB was successfully decreased with the addition of OHB. The level of homogeneity of the polymer mixtures was also assessed by DSC and relaxometry. An exponential response was observed between the blend composition and the T 1 H values detected by LF-NMR, and similar behavior was observed for the correlation between the experimental T g values and the relaxation times. [ABSTRACT FROM AUTHOR]

Wheat starch-based model systems and wheat flour dough with the same water content (close to 45 %) were investigated upon heating (20-90 °C) using time-domain H NMR spectroscopy with the aim of assigning each spin-spin relaxation time ( T) measured to a specific proton fraction. On the basis of the signal evolution according to Curie's law for pure starch and pure water, temperature-associated changes for each T value and their mass intensity were interpreted and assigned to water and/or biopolymer proton fractions related to the reversible swelling of starch or its gelatinization. The addition of 2 % ( w/ w) salt to model samples and dough induced few changes during the reversible swelling process but impacted on the measurements performed above 60 °C. Finally, studies performed on starch-based model systems improved understanding of the complex thermal processing of starch in dough by taking into account phenomena other than the starch swelling and gelatinization, such as gluten denaturation and changes in water-biopolymer interactions. [ABSTRACT FROM AUTHOR]

This article describes theoretical and practical results of experiments with home-made receive coils for an NMR scanner. A receive coil must ensure good sensitivity of the whole receiving chain, therefore the qualities of the coil are analysed together with a preamplifier. The coil must be tuned to the operating frequency of the scanner and matched to the input resistance of the preamplifier for effective processing of the induced signal. A technique for calculating matching device parameters using an optimization procedure is presented. The accuracy of the tuning and matching is analysed in the article and documented in figures. A technique for tuning the coils utilizing the spectral qualities of the noise produced by the receive coil or flowing through it is presented. The results are documented in figures for two coils and compared with assumed theoretical curves. The qualitative as well as the quantitative agreement is good. It has been proved that by fulfilling some conditions, accurate matching is not necessary and the noise spectrum can be utilized for tuning a receive coil. [ABSTRACT FROM AUTHOR]

Polyethylene (PE) is available in various grades ranging from high-density to very-low density (co-)polymers. The morphology of PE strongly influences its properties and is extensively studied, including the content of phases. Most studies are usually concerned only with the crystallinity and non-critically adopt the classical three-component model of PE, which considers a crystalline (rigid) and an amorphous (mobile) phase separated by an interfacial (semi-rigid) component. We provide evidence that this assignment of the semi-rigid and mobile components can be incorrect at lower PE densities. The phase composition of industrial PE samples with crystallinities from 35 to 82 wt. % was studied using low-field 1 H NMR and the characteristic dimensions of the lamellar stacks were measured using small-angle X-ray scattering (SAXS). Based on our results, we propose a new interpretation of PE morphology at crystallinities below 60 wt. %, which considers the rigid crystalline phase, the constrained (semi-rigid) amorphous phase inside the lamellar stacks and the free (mobile) amorphous phase outside the stacks. Interfacial chain segments are also present, but not detected as a separate component. Moreover, experimental data are compared with model predictions based on reconstructed 3D replicas of PE spherulites and an excellent agreement in the phase content is obtained. Our findings are important for the estimation of application properties (e.g., effective diffusivity), which strongly depend on the spatial distribution of the amorphous and crystalline phases. [ABSTRACT FROM AUTHOR]

Water-in-oil emulsions constitute a widespread issue for the oilfield industry. Indeed, the phases of water-in-oil emulsions must be separated as soon as possible in the production chain. These emulsions can be fairly stable due to certain intrinsic components in crude oil; therefore, adding chemicals – demulsifiers – to aid this separation is very common. Selecting the ideal demulsifier can save time and money, and in this context two-dimensional (2D) low-field nuclear magnetic resonance (NMR) is a promising technique because it allows for the separate study of the oil and water phases without the need for physical separation. In this study, four laboratory-made emulsions were used to investigate the demulsification process via low-field 1 H NMR, allowing for the investigation of the correlation between the diffusion coefficient ( D ) and transverse relaxation time ( T 2 ) in 2D D – T 2 plots. The three commercial demulsifiers used in this process (A, B and C) were characterised by positive-ion electrospray ionisation (ESI(+)) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The ESI(+)–FT-ICR mass spectra recorded for the commercial demulsifiers showed distinct chemical profiles, with two samples (A and B) being composed of surfactants containing isoprene and glycol propylene oligomer species, where the ions detected in the m / z 200–700 region were separated by m / z 42 and 58 units, respectively. A more abundant and complex chemical profile was observed for sample C, in which pyridine and sulphoxide analogue species were identified. The 2D D – T 2 plots clearly showed that the separation of water and oil phases can be monitored and allowed for the classification of the demulsifiers according to their performance in the physical separation of the phases: demulsifier A > demulsifier B > demulsifier C. [ABSTRACT FROM AUTHOR]

The use of biodiesel shows innumerous advantages compared to fossil fuels, since biodiesel is a biodegradable and non-toxic fuel. Nowadays, most of the biodiesel commercialized in the world is produced by the transesterification reaction of vegetable oils with methanol and basic catalysis. Understanding the reaction kinetics and controlling its optimum progress for improving the quality of the final product and to reduce production costs is of paramount importance. The present work explores compact 1 H NMR spectroscopy to follow the course of the transesterification reaction in real time. For this purpose the magnet is integrated into a flow setup which allows one to transport the neat solution from the reactor into the measurement zone and back again into the reactor. A multivariate calibration model applying Partial Least Squares regression was built to analyze the measured data and to obtain information about the biodiesel conversion ratio with errors on the order of 1%. This information is used in combination with a Lorentzian deconvolution of the spectra to estimate the relative concentrations of methanol present in the ester-rich phase in comparison with the one in the glycerol phase, the second medium involved in the reaction mixture. Finally, we demonstrate that the conversion ratio can also be monitored by measuring the chemical shift of the hydroxylic protons of methanol and glycerol present in the ester-rich phase. These results demonstrate that a compact NMR spectrometer can provide spectra with good quality and time resolution suitable for real time quality control of biodiesel production. [ABSTRACT FROM AUTHOR]

Nuclear magnetic resonance (NMR) techniques are widely used to identify pure substances and probe protein dynamics. Edible oil is a complex mixture composed of hydrocarbons, which have a wide range of molecular size distribution. In this research, low-field NMR (LF-NMR) relaxation characteristic data from various sample oils were analyzed. We also suggest a new method for predicting the size of edible oil molecules using LF-NMR relaxation time. According to the relative molecular mass, the carbon chain length and the transverse relaxation time of different sample oils, combined with oil viscosity and other factors, the relationship between carbon chain length and transverse relaxation time rate was analyzed. Various oils and fats in the mixed fluid were displayed, reflecting the composition information of different oils. We further studied the correlation between the rotation correlation time and the molecular information of oil molecules. The molecular composition of the resulting fluid determines its properties, such as viscosity and phase behavior. The results show that low-field NMR can obtain information on the composition, macromolecular aggregation and molecular dynamics of complex fluids. The measurements of grease in the free-fluid state show that the relaxation time can reflect the intrinsic properties of the fluid. It is shown that the composition characteristics and states of complex fluids can be measured using low-field nuclear magnetic resonance.

Introduction: Nuclear magnetic resonance (NMR) is a powerful method for the non-invasive study of a wide range of objects. Among its many characteristics, molecular diffusion can be examined without the need for any chemical or isotopic tracers by applying magnetic field gradients within the NMR sequence., Aim: In our study, model cell suspensions were characterized by means of low-field (LF) (0.05 T) 1H NMR relaxometry. The proposed multi-parametric characterization based on independent 2D T1-T2 and D-T2 measurements was implemented to obtain a set of MR parameters as a specific signature for model cells., Material and Methods: The D-T2 and T1-T2 correlation measurements were conducted on yeast samples with different amounts of added water. Signals from intracellular and extracellular water compartments and free water were identified on D-T2 maps and their diffusion coefficients were extracted., Results: Mean D&#95;IC was equal to 8.4 × 10 -11 m 2 /s and mean D&#95;EC ranged from 1.0 × 10 -9 m 2 /s to 1.65 × 10 -9 m 2 /s. T1/T2 ratio was calculated and for IC space values in the range of 4.2-5.3 were observed. Finally, we demonstrated the possibility of detecting signals from cells for the samples with a low concentration of cell suspensions or a small amount of the sample., Conclusions: These findings are promising for more complex cell investigations in vitro and in vivo , without any contrast agents, applying solely biomarkers., Competing Interests: The authors declare no conflict of interest., (Copyright: © 2022 Termedia Sp. z o. o.)

• A novel test method coupling NMR + RSM data is proposed. • Pore-throats are mainly in size of 0.1 μm, taking a maximum of 48.39% of the space. • The relations of grouting effect with the permeability and pressure are discussed. • The optimal grouting pressure and the critical value of injectable permeability are found. Mudstone, a common sedimentary rock in coal measure strata, sees the softening and disintegration of its clay minerals such as kaolinite owing to groundwater, water accumulation in goaf, and high in-situ stress, resulting in serious deformation and shrinkage of roadway space. However, it can hardly be reinforced by grouting because of other factors such as dense occurrence and poor permeability. In view of this, the silica sol, a nano-sized grouting material featured with controllable solidification and colloidal compactness, may be able to grout the low-permeability mudstone. In this paper, using the response surface methodology (RSM) and low-field nuclear magnetic resonance (NMR), we designed a two-factor orthogonal experiment and proposed a new data coupling test method integrating the processes of design, monitoring, and analysis, thus illustrating the pore throat distribution characteristics and grouting feasibility of low-permeability mudstone and revealing the diffusion law of nano silica sol in this kind of rock under the dual influences of pressure and permeability. On this basis, the optimal grouting parameters as well as the critical value of injectability were eventually determined. Experimental results proved that low-permeability rocks primarily contained pore throats in the size of 0.1 μm; and as these rocks became less permeable, a larger proportion of throats narrower than this size were developed, accounting for 48.39% in 1 mD samples. The low-permeability mudstone, which was highly matched with the silica sol solution in the particle size of 6.23 nm, could be modified and reinforced. Based on a calculation model for response values, the experimental data were successively classified by permeability and grouting pressure, from which the following pore-sealing rates were obtained: A (60 ∼ 100 mD): 33.74%, B (30 ∼ 60 mD): 24.61%, C (0 ∼ 30 mD): 0.41%, D (2 ∼ 3 MPa): 0.75%, E (1 ∼ 2 MPa): 38.92%, and F (0 ∼ 1 MPa): 28.02%. This indicated that the grouting effect was proportional to permeability; and it first increased and then decreased under rising pressure. According to the response to these rates, the low-permeability mudstone had better be grouted with nano silica sol under the pressure of 0.804 MPa, with the critical value of injectable permeability being about 40.42 mD. [ABSTRACT FROM AUTHOR]

An accurate classification of pore fluid typing in coals is critical for understanding and assessing fluid flow characteristics during coalbed methane production, but the widely used nuclear magnetic resonance (NMR) single T 2 cutoff (T 2C) model remains some apparent defects. In this study, we proposed a novel NMR dual T 2 cutoffs model for fluid typing classification based on the multifractal theory. Firstly, the NMR and high-speed centrifugal combined measurements were performed for twenty-one coals with strikingly different ranks. Secondly, the multifractal analysis theory was introduced to investigate multifractal characteristics of the fully water-saturated NMR spectra. Thirdly, the correlations between dual T 2 cutoffs and multifractal parameters were systematically analyzed. Fourthly, a multifractal-based model was established to evaluate the NMR dual T 2 cutoffs values in coals. Results show that the pore fluid typing was re-divided into: absolute irreducible- (T 2 < T 2C1), absolute movable-(T 2 > T 2C2), and partial movable-fluid (T 2C1 < T 2 < T 2C2) based on dual T 2 cutoffs. The values of T 2C1 and T 2C2 were in the range of 0.049–0.455 ms and 36.12–102.34 ms, respectively. Multifractal numerical simulations indicate the coals have typical multifractal characteristics. The minimum multifractal dimension (D min), singularity strength subtraction (α max - α min), and singularity strength proportion (α max / α min) were linearly correlated with dual T 2 cutoffs, that can be further used for model-building. The dual T 2 cutoffs calculated from the proposed multifractal-based model qualitatively agree with those obtained from complicated laboratory experiments, indicating the accuracy of the established multifractal-based model in this study – from the validations of six non-modeling coals. It can be concluded that the proposed multifractal-based model is accurate and convenient, also be scalable in the applications of other rocks such as shales. • NMR T 2 dual cutoffs model was proposed for pore fluid typing classification. • Pore structure heterogeneity was characterized by multifractal analysis theory. • A convenient dual T 2 cutoffs determination method was established. [ABSTRACT FROM AUTHOR]

[Display omitted] • Low frequency ultrasound (LFU) enhanced antibrowning effect of AsA in fresh-cut potato; • LFU combined with AsA inhibited PPO activity more effectively than AsA treatment; • AsA loss in fresh-cut potato was weakened under LFU mediation; • LFU combined with AsA treatment reduced cellular membrane permeability; • LFU combined with AsA treatment kept low solute migration during storage. Ascorbic acid (AsA) is generally used as an antibrowning agent for fresh-cut potato (FCP). However, its browning inhibitory effect is temporary because of its rapid consumption during redox processes. In this study, the effect of browning inhibition in FCP slices was evaluated using low frequency ultrasound (LFU; 40 kHz, 200 W, 3 min) and AsA (0.2%, w/v) treatments alone or in combination. The results showed that LFU combined with AsA (LFU-AsA) treatment could achieve a better antibrowning effect than either treatment alone (higher L* , lower a* and Δ E*), and there was no adverse effect on texture properties. LFU-AsA treatment not only inhibited the activity of PPO more effectively than AsA treatment, but also enhanced the antibrowning effect by retaining higher AsA content. Moreover, it also maintained membrane integrity by limiting lipid peroxidation and solute migration during storage. Overall, LFU-AsA treatment would be a promising method in food preservation industries. [ABSTRACT FROM AUTHOR]

Pore length scales and pore surface relaxivities of rock cores with different lithologies were studied on a 2 MHz Rock Core Analyzer. To determine the pore length scales of the rock cores, the high eigenmodes of spin bearing molecules satisfying the diffusion equation were detected with optimized encoding periods in the presence of internal magnetic fields B in . The results were confirmed using a 64 MHz NMR system, which supports the feasibility of high eigenmode detection at fields as low as 2 MHz. Furthermore, this methodology was combined with relaxometry measurements to a two-dimensional experiment, which provides correlation between pore length and relaxation time. This techniques also yields information on the surface relaxivity of the rock cores. The estimated surface relaxivities were then compared to the results using an independent NMR method. [ABSTRACT FROM AUTHOR]

This article describes the noise measurement of a preamplifier with high input impedance designed for experiments with receive coils in nuclear magnetic resonance (NMR). The noise of the preamplifier was determined in two ways. A circuital analysis of the preamplifier provided an equation for the preamplifier noise calculation and the noise voltage was measured with an NMR console and in accordance with known theory the measured analogue noise signal was modified to a discrete noise signal. An objective function with noise parameters of the preamplifier as variables was created. The noise parameters of the preamplifier were calculated with an optimization procedure and the results of the calculation and of the measurement compared. Qualitative and quantitative agreement was good. It was proved that the noise parameters of a preamplifier for NMR experiments can be measured with an NMR console and derived theory. [ABSTRACT FROM AUTHOR]

This study was designed to compare the effects of different stunning systems on the meat quality of broilers. This was done by investigating meat water-holding capacity, meat color, muscle glycogen, and lactate concentrations, as well as blood parameters, low-field nuclear magnetic resonance (NMR) transverse relaxation, and myofibrillar ultrastructures. A total of 160 broilers were divided into 4 treatment groups: a low-voltage stunning (LS) with a constant voltage of 15 V at 750 Hz for 10 s; a midvoltage stunning (MS) with a constant voltage of 50 V at 50 Hz for 10 s; a high-voltage stunning (HS) with a constant voltage of 100 V at 50 Hz for 5 s; and a control group with no stunning (NS). Blood samples were collected immediately after cutting the neck. Pectoralis major muscles were removed from the carcass after chilling and placed in ice. Breast muscle pH, meat color, glycogen, and lactate contents were determined at both 2 and 24 h postmortem. Drip loss, cooking loss, pressing loss, cooked breast meat shear values, low-field NMR, and ultrastructures of myofibrils were determined 24 h postmortem. The NS and MS treatments significantly increased (P < 0.05) blood plasma corticosterone, initial rate of glycolysis, and drip loss, and significantly reduced (P < 0.05) initial muscle pH and shear force values when compared with LS and HS. The results of low-field NMR reflect that NS and MS significantly decreased (P < 0.05) NMR transverse relaxation population 1 (T21) and increased (P < 0.05) NMR transverse relaxation population 2 (T22). The myofibrils of NS and MS samples showed significantly (P < 0.05) longer sarcomere length when compared with the LS and HS samples. The meat color, cooking loss, pressing loss, and final pH were not affected by the stunning methods. This study indicates that NS and MS treatments reduce meat water-holding capacity and decrease meat shear force when compared with LS and HS. [ABSTRACT FROM AUTHOR]

The changes of water mobility and fractal dimension (Df) during pork myofibrillar proteins (PMP) heat-induced gelation were investigated using low-field nuclear magnetic resonance (NMR) and image analysis, respectively. The NMR data were related to the gel microstructure which was explained as fractal dimension and pore size using principal component analysis (PCA). Distributed exponential analysis of the T2 relaxation revealed that three water components corresponding to the three water molecule states exist during the heat-induced gelation. A significant change of T2 was occurred when the temperature increased, T21 relaxation times decreased significantly from 403.70ms to 231.01ms with the temperature increasing from 50 to 70°C. The fraction of T21 distributions declined from 99.27% to 77.01% as the temperature increased from 40 to 60°C. Pronounced different gel network structure was observed during the myofibrillar proteins heat-induced gelation and different Df which was determined by box count method was found between all treatments although evidencing a narrow scale range (from 2.835 to 2.860). Good correlations were detected between the NMR T2 parameters and microstructural data. Overall, combined low-field NMR, image analysis and PCA provide powerful tools for elucidating the pork myofibrillar protein heat-induced gelation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Set-up for low-field 1H NMR detection of gas adsorption processes developed. [•] Relaxation time studies from 5 to 200bar methane gas pressure. [•] T 2 relaxation in microporous metal–organic frameworks and activated carbon. [•] Fast exchange of adsorbed CH4 between different pore space fractions. [•] NMR studies of adsorption isotherms, Henrys constant and CO2/CH4 separation factors. [ABSTRACT FROM AUTHOR]

Highlights: [•] Low-field MAS solid-state NMR at 0.45T. [•] Reduced anisotropic shielding effects at low field. [•] Increased second-order quadrupolar couplings at low-field. [•] 23Na second-order quadrupolar lineshape of NaNO3. [•] 31P–19F dipole–dipole coupling of K2PO3F. [ABSTRACT FROM AUTHOR]

The quality changes of duck meat during thermal sterilization using microwave, stepwise retort and general retort heating were evaluated. Results showed that compared with stepwise retort and general retort, duck meat subjected to microwave showed significantly higher gumminess, chewiness, cohesiveness and resilience as well as glutamic acid, lysine and total amino acids. Low-field NMR revealed that the relative content of immobilized water after microwave and stepwise retort treatment was significantly higher than that after general retort treatment. The relative content of 1-octen-3-ol with characteristic mushroom aroma was significantly higher with microwave and stepwise retort heating than with general retort heating, while 2-pentyl-furan with poor taste was only detected with general retort heating. The muscle bundles subjected to microwave were neatly arranged, similar to those with no thermal sterilization. Overall, the meat quality after three thermal sterilization treatment was microwave > stepwise retort > general retort., Competing Interests: Author MH was employed by Nanjing Huangjiaoshou Food Science and Technology Co., Ltd. Author YZ was employed by Henan Province Qi County Yongda Food Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Yang, Li, Wang, Luan, Sun, Huang, Wang and Zheng.)

The reaction of unsaturated substrates with hydrogen gas enriched in the para spin isomer leads to products with a high degree of nuclear singlet spin order. This leads to greatly enhanced NMR signals, with important potential applications such as magnetic resonance imaging (MRI) of metabolic processes. Although parahydrogen-induced polarization has the advantage of being cheap, compact, and mobile, especially when performed in ultralow magnetic fields, efficiency is lost when more than a few protons are involved. This strongly restricts the range of compatible substances. We show that these difficulties may be overcome by a combination of deuteration with the application of a sinusoidally modulated longitudinal field as a well as a transverse rotating magnetic field. We demonstrate a six-fold enhancement in the 13 C hyperpolarization of [1- 13 C, 2,3-d 2 ]-succinic acid, as compared with standard hyperpolarization methods, applied in the same ultralow field regime., (© 2022 The Authors. ChemPhysChem published by Wiley-VCH GmbH.)

During the oil production and processing stages, the asphaltene precipitation is one of the great operation problems of oil industry. It can precipitate in the formation, tubing, or surface, causing operating problems, such as reduction in oil recovery by changing the reservoir permeability and wettability, clogging of the pipelines, and difficulty in separations process. The quantification of asphaltenes in petroleum by ASTM D6560 standard method is very laborious and use of a larger solvent volume than necessary. The present work proposes the use of time domain nuclear magnetic resonance (TD-NMR) as new methodology to quantify the asphaltene precipitated in crude oil. Three (light, medium, and heavy) crude oils with asphaltenes content of 0.97, 1.88, and 7.00 wt% were mixed with n-heptane in different R (ml of solvent/g of oil) values and analyzed by means of transverse relaxation time (T 2 ). According NMR results, the R values enough for complete asphaltene precipitation for the oils A, B, and C were, respectively, equal to 16.50, 23.00, and 39.50 ml g -1 . These outcomes represent a reduction of 58.75%, 42.50%, and 1.25% in the solvent volume per mass of oil for the oil A, B, and C, respectively, compared to the ASTM D6560 method, which imposes 40 ml g -1 . Therefore, it has been shown that TD-NMR can be applied to estimate the amount of asphaltene precipitated in petroleum and have potential to be applied in routine analysis with advantages of saving time and costs., (© 2022 John Wiley & Sons Ltd.)

The objective of this study was to determine meat quality distributions and assess hardness distributions in raw and cooked breast fillets with the woody breast (WB) condition, in addition to evaluating the relationship between water properties and WB severity. A total of 90 breast fillets were collected and categorized as normal (NORM), mild (MILD) and severe (SEV). Breast weight, drip loss, compression measurements, cook loss, shear and texture profile analysis (TPA) values were measured for each sample by fillet location (cranial to caudal) and sampling depth (cranial-superficial, cranial-internal, middle-superficial, and middle-internal) in the raw and cooked meat state. Low-field NMR relaxation measurements were also collected for both the raw and cooked fillets. Results indicate that severe WB expressed increased hardness, a higher water content (bound water and free water) and reduced meat quality attributes in raw and cooked meat. Breast fillet hardness and meat quality distributions were unevenly distributed between fillets, compression measurements were higher mainly in the cranial region, and progressively decreased toward the caudal region for both raw and cooked fillets. Shear force and energy values were higher in the cranial region than in the middle region, and TPA values were higher in superficial regions rather than internal portions. Additionally, low-field NMR could be used to predict WB through variation in water properties as thermal processing reduces water distributing abilities in affected fillets., Competing Interests: Conflict of interestThe authors declare no conflict of interest., (© Association of Food Scientists & Technologists (India) 2022.)