Magnetic Resonance Methods Research Articles

Experimental Study on the Mechanism of Enhanced Imbibition with Different Types of Surfactants in Low-Permeability Glutenite Reservoirs

Due to the complex physical properties of low-permeability glutenite reservoirs, the oil recovery rate with conventional development is low. Surfactants are effective additives for enhanced oil recovery (EOR) due to their good ability of wettability alteration and interfacial tension (IFT) reduction, but the reason why imbibition efficiencies vary with different types of surfactants and the mechanism of enhanced imbibition in the glutenite reservoirs is not clear. In this study, the imbibition efficiency and recovery of surfactants including the nonionic, anionic, and cationic surfactants as well as nanofluids were evaluated and compared with produced water (PW) using low-permeability glutenite core samples from the Lower Urho Formation in the Mahu oil field. Experiments of IFT, wettability, emulsification, and imbibition at high-temperature and high-pressure were conducted to reveal the underlying EOR mechanisms of different types of surfactants. The distribution and utilization of oil in different pores during the imbibition process were characterized by a combined method of mercury intrusion and nuclear magnetic resonance (NMR). The main controlling factors of surfactant-enhanced imbibition in glutenite reservoirs were clarified. The results demonstrate that the micropores and mesopores contribute most to imbibition recovery in low-permeability glutenite reservoirs. The anionic surfactant KPS exhibits a good capacity of reducing IFT, wettability alteration, and oil emulsification with the highest oil recovery of 49.02%, 8.49% higher than PW. The nonionic surfactant OP-10 performs well on oil emulsification and wetting modification with imbibition recovery of 48.11%. This study sheds light on the selection of suitable surfactants for enhanced imbibition in low-permeability glutenite reservoirs and improves the understanding of oil production through enhanced imbibition.

Investigating Interaction Dynamics of an Enantioselective Peptide‐Catalyzed Acylation Reaction

Modern nuclear magnetic resonance (NMR) methods like carbon relaxation dispersion in the rotating frame (13C‐R1ρ) and proton chemical exchange saturation transfer (1H‐CEST) are key methods to investigate molecular recognition in biomacromolecules and to detect molecular motions on the µs to s timescale, revealing transient conformational states. Changes in kinetics can be linked to binding, folding, or catalytic events. Here, we investigated whether these methods allow detection of changes in the dynamics of a small, highly selective peptide catalyst during recognition of its enantiomeric substrates. The flexible tetrapeptide Boc‐l‐(π‐Me)‐His‐AGly‐l‐Cha‐l‐Phe‐OMe, used for the monoacetylation of cycloalkane‐diols, is probed at natural abundance using 13C‐R1ρ and 1H‐CEST. Indeed, we detected differences in dynamics of the peptide upon interaction with the diol. Importantly, these differ depending on the enantiomer of the substrate used. These enantiospecific influences of the substrates on the dynamics of the peptide are rationalized using computational techniques. We find that even though one enantiomer reacts faster, as confirmed by reaction monitoring, the other is more tightly bound in DCM (as confirmed by 1H‐saturation transfer difference (STD) measurements). These findings provide insights into the recognition of the substrates and explain the selectivity differences observed between the solvents toluene and DCM.

New Bis 4-Bromobenzene Sulphonate Compound: Synthesis, Characterizaton, DFT study, Antibacterial and Leishmanicidal activity

The new bis 4-bromobenzene sulphonate compound called as ((1E,1'E)-(1,4-phenylenebis(azanylylidene))bis(methanylylidene))bis(4,1-phenylene) bis(4-bromobenzenesulfonate) (I) was synthesized. Fourier transform infrared (FTIR), proton and carbon-13 nuclear magnetic resonance (1H- and 13C-NMR) methods were used to confirm the molecular structure. All calculations were performed at DFT/B3LYP/6-311G(d,p) level. IR and NMR spectral data were compared with experimental ones and the details of molecular structure were investigated. The antimicrobial activity of the synthesized compound (I) was determined by Alamar blue microdilution method against seven different established standard bacteria and one parasite isolate. The compound I exhibited antibacterial activity at different concentrations. Compound I was found to have antimicrobial activity on all bacterial species and L. infantum parasite, albeit at different concentrations. Compound I has the most effective antibacterial activity on S. flexneri and the least effect on S. aureus and E. cloacea bacteria. In order for the synthesized compound to be used as a drug candidate, in vivo control studies in a series of experimental animal models and whether it has toxic effects on human cells should be tested. In silico analysis was conducted on four different proteins using the synthesized compound I to investigate the essential interactions responsible for its antibacterial activity. The docking results of compound I supported its antibacterial activity, revealing high inhibition constants.

Genesis of artesian waters

Mankind has entered the era of fresh water scarcity. And the questions of the origin of these waters, as well as the methods of effective search for underground fresh water, become fundamental for the assessment of the prospects of water supply of the Earth's population not only in theoretical, but also in applied values. The article considers the volcanic-marine paradigm of artesian water genesis, which allows a logical explanation of a number of deep freshwater phenomena that cannot be resolved by other theories. The main consequences of the volcanic-marine paradigm are: (a) artesian water is recoverable, (b) deep freshwater resources are included in the water cycle in nature like groundwater, (c) the problem of extracting potable artesian water is not a resource problem for mankind, but a technological problem. At present, artesian water is searched for by drilling wells (direct method) and by geophysical methods of groundwater exploration—electrical survey, seismic survey and magnetic resonance method. At the same time, the great depth of artesian water, up to 1000 m, makes it difficult to locate it using geophysical methods. The article considers the geophysical method of direct detection of artesian water in various geological structures at great depths. This method and the service based on it have been named “Geodirect RSS/NMR”. Their physical basis is the resonance between the pre-recorded spectrum of the sought substance (in our case, artesian water) and the spectrum of radiations recorded by the satellite instrumentation in the infrared range. The presence of resonance allows direct identification of artesian water flows and reservoirs without interpretation of indirect data.

Power spectral density imaging for polymeric films using ex-situ solid-state magnetic resonance with needlelike ferromagnet.

An ex-situ solid-state nuclear magnetic resonance (NMR) method employing localized magnetic field gradients generated by a needlelike ferromagnet is described. The depth profiling of a multilayer polymeric film using the proposed method and spin density imaging is successfully acquired. The imaging of the variable-frequency spinlattice relaxation rate in the depth direction reveals differences in the spectral density function for molecular dynamics between the surface and interior of the film. This may be due to the differences in the correlation time distribution of the molecular dynamics between the surfaces and interior of the film.

Characterization and quantitative analysis of unfrozen water at ultra-low temperatures: Insights from NMR and MD study

Unfrozen water, integral to numerous processes such as heat transfer, frost heave, and hydro-thermo-mechanical simulations, has been traditionally studied at 0 ∼ −30 °C, but remains under-investigated at ultra-low temperatures. Understanding this component at ultra-low temperatures and its categorization requires more explorative, quantitative research, particularly considering the ubiquity of frozen soils. The nuclear magnetic resonance (NMR) and molecular dynamics (MD) methods were employed to characterize and quantify unfrozen water during 0 ∼ −80 °C. Our results indicated that bulk and capillary water could completely freeze at −3°C and −5°C, respectively, but only bound water exists below −10 °C. The evolution of unfrozen water with temperature in MD agreed with our NMR results, where the existence of unfrozen water molecules was due to the breakage of hydrogen bonds in ice molecules and the surface effect of clay. This mechanism elucidated the water–ice-clay atomic system’s role in quantifying experimentally measured unfrozen water content. These findings have important implications for frozen soil engineering, polar region development, artificial freezing technology, and lunar soil exploration.

Influence of hydrogen bond donor compound type on the properties of betaine based deep eutectic solvents: A computational and experimental approach

Novel deep eutectic solvents (DESs) based on Betaine as a hydrogen bond acceptor and Urea, Lactic acid, Glycerol, 1.2 - Propanediol, Xylitol as a hydrogen bond donor were prepared. Using computational approach, a theoretical analysis of compounds reactivity for hydrogen bond formation was carried out to justify the intermolecular interactions reactivity for hydrogen bond formation among the components. Through frontier molecular orbital theory and HOMO−LUMO values and various quantum chemical parameters, viz., ionization potential, electron affinities, electro negativity, chemical potential, global softness and hardness, electrophilicity and nucleophilicity indexes were calculated for all DESs. The calculated parameter namely charge transfer (ΔN) was used to evaluate the effectiveness of the formation of the DES. The value of charge transfer varies in the range 0.053–0.2836 eV and is higher for systems Betaine – Glycerol and Betaine – 1,2 - Propanediol. Electronegativity of the HBD varies in 4.2465< χ >7.2179 eV. They are promising options for applications that need to contact with water because of their hydrophilic nature. The formation of hydrogen bonds during the formation of DES was confirmed using the nuclear magnetic resonance (NMR) method. Donors of hydrogen bonds are able to ensure the formation of DES with Betaine, but the choice of the donor depends on the specific conditions of use and requirements for the solvent. Thermal behavior, surface tension, viscosity, electrical conductivity, рН of the prepared DES was investigated. Systems of the Betaine based DES with Xylitol and Urea have higher thermal stability (> 150 ºC). The highest values of surface tension are observed for DESs with Glycerol (65.02⋅103 J/m2) and 1.2-Propanediol (54.29⋅103 J/m2). The Betaine-Urea deep eutectic solvents (DES-1) and Betaine-Lactic acid (DES-2) systems have fairly high electrical conductivity (0.0091 and 0.4160 Sm/m). The effect of water on the properties (electrical conductivity, рН and surface tension) of DESs was investigated. The surface tension measurements revealed a broad range of surface tension, with water content being a major factor. This work has the effect of supplying new theoretical approach for a more deliberate comprehension on design of betaine-based DES as novel solvents for use in applications.

ALKALI ALCOHOLYSIS OF 2-PHENYL-gem-DICHLOROCYCLOPROPANE UNDER MICROWAVE RADIATION CONDITIONS

By alkaline alcoholysis of 2-phenyl-gem-dichlorocyclopropane, α-phenylacrolein acetals were synthesized under microwave irradiation (MWI) conditions: [1-(diethoxymethyl)vinyl]benzene, [1-(di-propyloxymethyl)vinyl]benzene, [1-(di- iso-propyloxymethyl)vinyl]benzene, [1-(dibutoxymethyl)vinyl]benzene, [1-(di-iso-butoxymethyl)-vinyl]benzene, {1-[bis(1-methylbutoxy)methyl]vinyl}benzene, [1-(dially-loxymethyl)vinyl]benzene, 1,1-[(2-phenylprop-1-en-3,3-diyl)bis(oxymethylene)]dibenzene. It was found that microwave radiation reduces the synthesis time by 70%, while the yield is more than 80%, and the selectivity of acetal formation is more than 90%. Using the method of competitive kinetics, it was established that primary alcohols such as ethanol, propanol and butanol are similar in activity. The structures of the obtained compounds were studied using nuclear magnetic resonance (NMR) and chromatography-mass spectrometry methods. The formation of acetals is proven by the presence of signals from the quaternary carbon atom in the region δс 142.35-146.49 ppm, and a doublet signal from protons at δн 5.01–5.71 ppm. and a singlet signal of the proton of the methine group in the region at 4.89-5.50 ppm. Analysis of the mass spectra of acetals showed the presence of maximum intensity of oxonium ions, due to α-, β-break relative to the oxygen atom. For the obtained acetals, the presence in the mass spectra of [M-H]+ cations, formed as a result of the release of a hydrogen radical from a molecular radical ion, was recorded. The peaks of [M-R]+ and [M-H]+ ions were inferior in intensity to [M-RO]+ cations. Most likely, this is explained by the stability of the [M-RO]+ cations relative to [M-C6H5C2H2]+ and [M-H]+, as well as the ease of eliminating RO• from the alkoxy group. In addition, for acetals of this type, the formation of a radical cation with m/z = 132 was observed, resulting from the release of the R radical from the second alkoxy group. Also, the mass spectra of acetals were characterized by the presence of a cation m/z = 77 and an intensity of 29-80%. Borisova Yu.G., Musin A.I., Voinov A.V., Spirikhin L.V., Raskil’dina G.Z., Sultanova R.M., Zlotskii S.S. Alkali alcoholysis of 2-phenyl-gem-dichlorocyclopropane under microwave radiation conditions. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 11. P. 15-21. DOI: 10.6060/ivkkt.20246711.7046.

Occurrence characteristics and factors that influence shale oil in the Jurassic Lianggaoshan Formation, northeastern Sichuan Basin

Well Ping'an 1, located in the northeastern Sichuan Basin, tested 112.8 m3/d of oil from the Lianggaoshan Formation, marking an important breakthrough in shale oil production. However, due to the influence of complex lithofacies, high thermal maturity, and limited exploration, the occurrence and factors that influence shale oil across the different lithofacies of the Lianggaoshan Formation remain unclear, thereby severely impeding exploration and development. This study systematically examines the occurrence and factors that influence shale oil (adsorbed oil and free oil) in the Lianggaoshan Formation through an integrated approach involving petrology, geochemistry, scanning electron microscopy, nuclear magnetic resonance spectroscopy, multi-temperature pyrolysis, and gas chromatography. Results demonstrate the following: (1) Residual shale oil (adsorbed oil) in the study area predominantly exists as oil films, precipitated oil, and residues (asphalt). Oil films appear on the edges of organic matter (OM), clay minerals, pyrite, and felsic minerals. Crude oil adheres as thin layers to mineral edges, with part of the oil resulting from the lipophilic properties of OM. Precipitated oil tends to accumulate around organic pores, and at higher maturity stages, heavy oil components adhere to mineral surfaces as residues. The hydrocarbon loss of the sample is serious, and free oil is difficult to observe due to experimental processing. (2) Based on the experimental results of preserved cored samples, the shale oil in the study area is mainly free oil (0.86–4.46 mg/g, average 1.99 mg/g), followed by adsorbed oil (0.0007–1.36 mg/g, average 0.43 mg/g). The presence of higher concentrations of clay minerals and total organic carbon (TOC) correlates with increased quantities of free and adsorbed oil in the Lianggaoshan Formation. (3) The two-dimensional nuclear magnetic resonance method combined with the “e” index method was employed to quantify the free oil volumes in shale reservoirs of varying maturity within the study area. The recovery coefficient initially increases rapidly and then gradually with increasing Ro (vitrinite reflectance) values. Compared with other lithofacies types, OM-rich laminated argillaceous shale and OM-poor laminated siliceous shale have higher free oil content, which makes them easier to produce, in other words, these two lithofacies should be preferred as favorable exploration and development targets.

Targeted Magnetic Nanoparticles for Beta-Amyloid Detection.

Background/Objectivities: The presence of beta-amyloid plaques is a part of the pathogenesis of Alzheimer's disease, but there is currently no universally accepted method for magnetic resonance (MR) imaging of the disease. However, it is known that magnetic nanoparticles (MNPs) can improve the T2 contrast in MR images of various targets. Methods: We used cubic MNPs, which were produced by thermal decomposition and then it was covalently bonded to a modified fluorescently labeled tetrapeptide, HAEE-Cy5, for visualizing beta-amyloid plaques. The interaction of MNPs-HAEE-Cy5 and beta-amyloid was determinate by confocal microscopy using SH-SY5Y cell line. Results: MNPs exhibit relatively high relaxivity (approximately 200 mM-1s-1), which is crucial for enhancing target visibility in MR imaging. HAEE provides targeted delivery of MNPs by specifically interacting with beta-amyloid, while the fluorescent label Cy5 enables monitoring the efficacy of the interaction through confocal microscopy. Conclusions: The MNPs modified with HAEE-Cy5 demonstrated excellent binding to beta-amyloid plaques in vitro, as shown by experiments on the SH-SY5Y cell line. These results suggest that the proposed method has potential for use in future MR imaging studies of Alzheimer's disease.

Heteronuclear Fe-Mn Cyclopentadienyl Complexes Supported on Boehmite. Thermochemistry and Thermodynamics of their Decomposition

Boehmite samples with compounds of the composition (C5H5)2FeMnX2(μ-CO)n, where X=Cl, Br and n=1.2, precipitated at room temperature from tetrahydrofuran solutions and then heated in an air flow up to 873 K were obtained and characterized using X-ray diffractometry, infrared Fourier spectroscopy, electron magnetic resonance and temperature-programmed desorption methods. It was shown that the thermal decomposition of these compounds applied to the boehmite samples in the range from room temperature to 873 K occurs stepwise and consists of at least two stages. The first stage of thermal decomposition occurs in the range of 453–753 K, and the second – in the range of 813–843 K. The XRD data show that when calcining at 873 K the boehmite samples with the applied compounds of the above composition and containing these compounds less than 10 wt.%, the diffraction patterns show only reflections characteristic of poorly crystallized aluminum oxide. However, the electron paramagnetic resonance (EPR) spectra of these samples clearly show intense signals characteristic of superpara/ferromagnetic particles of iron and manganese oxides, as well as EPR signals from isolated Fe3+ substituting Al3+ ions in the aluminum oxide structure. EPR spectra most of the iron and manganese is stabilized on the surface of poorly crystallized aluminum oxide in the form of nanostructured iron and manganese oxides.

Magnetic resonance cavitation imaging for the monitoring of ultrasound therapies

Objective.Focused ultrasound (FUS) is a promising non-invasive therapeutic approach that can be used to generate thermal and non-thermal bioeffects. Several non-thermal FUS therapies rely on FUS-induced oscillations of microbubbles (MBs), a phenomenon referred to as cavitation. Cavitation monitoring in real time is essential to ensure both the efficacy and the safety of FUS therapies. This study aims to introduce a new magnetic resonance (MR) method for cavitation monitoring during FUS therapies.Approach.By finely synchronizing the FUS pulse with an accelerated turbo spin-echo MR sequence, the cavitation effect could be quantitatively estimated on the acquired images at 1-Hz refresh rate. The proposed method was assessed in vitro in a water bath. A series of FUS pulses were generated on a silicone tube filled with MBs at different acoustic pressures (0.07-2.07 MPa) and pulse durations (20-2000μs). MR images and passive cavitation detection (PCD) signals were simultaneously acquired for each FUS pulse.Main results.Inertial cavitation was found to induce a quantitatively interpretable signal loss on the MR image. The transition from stable to inertial cavitation was identified on MR cavitation maps with high repeatability. These results were found to be in good agreement with PCD measurements in terms of pressure thresholds between stable and inertial cavitation. MR cavitation imaging was shown to be sensitive to short and even ultrashort FUS pulses, from 2 ms down to 20μs. The presented theoretical model suggests that the signal loss in MR cavitation imaging relies on susceptibility changes related to the diameter of the oscillating MBs.Significance.The proposed MR cavitation imaging method can both locate and characterize cavitation activity. It has therefore the potential to improve the efficacy and safety of FUS therapies, particularly for localized drug delivery applications.

Proton dose calculation with LSTM networks in presence of a magnetic field

Objective.To present a long short-term memory (LSTM) network-based dose calculation method for magnetic resonance (MR)-guided proton therapy.Approach.35 planning computed tomography (CT) images of prostate cancer patients were collected for Monte Carlo (MC) dose calculation under a perpendicular 1.5 T magnetic field. Proton pencil beams (PB) at three energies (150, 175, and 200 MeV) were simulated (7560 PBs at each energy). A 3D relative stopping power cuboid covering the extent of the PB dose was extracted and given as input to the LSTM model, yielding a 3D predicted PB dose. Three single-energy (SE) LSTM models were trained separately on the corresponding 150/175/200 MeV datasets and a multi-energy (ME) LSTM model with an energy embedding layer was trained on either the combined dataset with three energies or a continuous energy (CE) dataset with 1 MeV steps ranging from 125 to 200 MeV. For each model, training and validation involved 25 patients and 10 patients were for testing. Two single field uniform dose prostate treatment plans were optimized and recalculated with MC and the CE model.Results.Test results of all PBs from the three SE models showed a mean gamma passing rate (2%/2 mm, 10% dose cutoff) above 99.9% with an average center-of-mass (COM) discrepancy below 0.4 mm between predicted and simulated trajectories. The ME model showed a mean gamma passing rate exceeding 99.8% and a COM discrepancy of less than 0.5 mm at the three energies. Treatment plan recalculation by the CE model yielded gamma passing rates of 99.6% and 97.9%. The inference time of the models was 9-10 ms per PB.Significance.LSTM models for proton dose calculation in a magnetic field were developed and showed promising accuracy and efficiency for prostate cancer patients.

Study on the preparation of magnetic Janus nanofluids and oil displacement mechanism

Magnetic nanomaterials, known for their eco-friendliness, low toxicity, strong magnetic response, and reusability, have seen significant advancements in enhancing oil recovery. In this study, the surfactant and magnetic Janus nanoparticles (MJNP) were evaluated and optimized through Fourier transform infrared spectroscopy, ζ potential test, scanning electron microscope, emulsion performance evaluation and other analysis, so as to develop magnetic Janus nanofluids (MJNF). Study the flow behavior and enhanced oil recovery mechanism of this nanofluid in porous media through nuclear magnetic resonance (NMR) and numerical simulation methods. The results showed that when the concentration of surfactant (LAD-30) was 0.08%, the maximum water content of emulsion was 80%, and the viscosity increased by more than 90000%. In addition, when the MJNP concentration is 400 ppm or higher, a stable emulsion is formed at 90 °C. NMR experiment shows that through MJNF oil displacement, the oil recovery of small and medium-sized pores is significantly improved by 25.9% and 18.3%, which indicates that high viscosity emulsion can be formed in situ after MJNF injection, thus achieving consistency control. In addition, the numerical simulation results also found that MJNF injection can improve the oil-water saturation in the pore volume and enhance oil phase flow. The research results provide a new understanding for EOR of emulsion flooding.

Semaglutide Treatment Effects on Liver Fat Content in Obese Subjects with Metabolic-Associated Steatotic Liver Disease (MASLD)

Background: Metabolic-dysfunction-associated steatotic liver disease (MASLD) represents a major clinical complication of obesity. Methods: In this study, we used magnetic resonance (MR) methods to determine the effect of obesity treatment with semaglutide, a GLP-1 receptor agonist, on the liver fat content and selected metabolic variables. We investigated whether treatment would affect the acute response of liver fat to glucose and fructose administration and whether it would affect the fatty acid profile of VLDL-triglycerides. Sixteen obese non-diabetic men underwent a 16-week dietary intervention and 16-week treatment with subcutaneous semaglutide in a crossover design without a washout period. The order of the interventions was randomized. Results: After treatment, body weight of the subjects decreased by 5% and liver fat by a third, whereas dietary intervention had no impact on these parameters. The decrease in liver fat with semaglutide did not correlate with changes in body weight and other measures of adiposity and was unrelated to improved insulin sensitivity. Conclusions: The proportion of palmitic and palmitoleic acids in VLDL-triglycerides decreased after treatment, suggesting that the beneficial effects of semaglutide on liver fat are mediated by the suppression of de novo lipogenesis.

The influence of pore throat heterogeneity and fractal characteristics on reservoir quality: A case study of chang 8 member tight sandstones, Ordos Basin

The Chang 8 member of the Yanchang Formation in the Ordos Basin exhibits extensive development of tight sandstone reservoirs. In comparison to conventional reservoirs, these tight sandstone reservoirs demonstrate smaller pore-throat systems and stronger heterogeneity due to interactions between inherent sedimentary components and various diagenetic processes. To further investigate the influence of microscopic pore throat structure on macroscopic physical properties and oil content within the reservoir, a comprehensive study was conducted utilizing high pressure mercury injection, nuclear magnetic resonance, X-CT scanning, and other pore throat testing methods. This study was complemented by observation techniques such as polarizing microscope, scanning electron microscopy, and laser confocal imaging, to study the pore throat system of reservoirs under the influence of different sedimentary components and diagenesis. By comparison, it is observed that the radius of the primary pore throat system in the tight sandstone reservoir ranges from 0.01 to 1 μm. The structural characteristics of the pore throat system significantly impact the macroscopic physical properties of the reservoir. Due to variations in testing methods, high pressure mercury injection, nuclear magnetic resonance (NMR), and X-ray computed tomography (X-CT) reveal different fractal dimensions of the reservoir's pore throat system. Therefore, it is better to respectively utilize fractal dimension Df2, Df2-NMR, Df2-CT, and pore throat parameters to characterize the microscopic pore throat system with a radius ranging from 0.01 to 1 μm. The decrease in the average pore throat radius and the increased irregularity of pore shape contribute to heightened heterogeneity in the micro-pore throat structure within the reservoir. This negatively impacts its physical properties and oil content. Furthermore, it is important to note that the minimum threshold of pore throat radius plays a crucial role as a primary factor determining the fluid seepage capacity within this reservoir. Moreover, when isolated pores exist, reduced fluid mobility ensues, which further worsens the seepage conditions of the reservoir. The chlorite rims development reservoir shows a low fractal dimension in its micro-pore throats, contributing to superior macroscopic petrophysical properties and oil content. However, compression, siliceous cementation, and calcite cementation negatively impact the average pore throat radius by increasing micropores, inaccessible pores, and narrow throat content. This results in a stronger heterogeneity of the pore throat structure, leading to poor seepage conditions and lower oil content.

Novel Pseudo-Two-Dimensional 19F NMR Spectroscopy for Rapid Simultaneous Detection of Amines in Complex Mixture.

Rapid detection of amines in complex mixtures presents a significant challenge. Here, we introduce a novel nuclear magnetic resonance (NMR) method for amine detection utilizing a probe with two fluorine atoms in distinct chemical environments. Upon interaction with an amine, the probe generates two atomic resonance peaks, which are used to create coordinates, revealing fluorine chemical shifts on the 19F NMR spectroscopy. This innovative approach allows for the clear distinction of amine signals in a two-dimensional plane. This method has been effectively employed in analyzing amines in pharmaceuticals and amino acids in Ophiopogon japonicus and dry white wine, providing a robust and general approach for amine analysis.

A modular, low-field magnetic resonance design with pre-polarization for characterizing flows

We have recently demonstrated a magnetic resonance method using variable τ spin echoes to simultaneously determine both the average velocity and flow behavior index in a variety of pipe flows. In this work, we present a new, modular, low-field design built specifically for use with our methodology. The design is based on low-cost ceramic magnets. It consists of a sensor built using a pitched magnet arrangement in combination with several modular pre-polarizing units to facilitate a controlled pre-polarization length for measurements on flows that require a significant amount of time in a magnetic field to become polarized (e.g., aqueous solutions). Here, measurements made with this design are shown for a range of flow rates that span the laminar regime and into the turbulent regime.

Light-Induced Metallic and Paramagnetic Defects in Halide Perovskites from Magnetic Resonance.

Halide perovskites are promising next-generation solar cell materials, but their commercialization is hampered by their propensity to degrade under operating conditions, particularly under heat, humidity, and light. Identifying degradation products and linking them to the degradation mechanism at the atomic scale is necessary to design more stable perovskite materials. Here we use magnetic resonance methods to identify and characterize the formation of both metallic lead clusters and Pb3+ defects upon light-induced degradation of methylammonium lead halide perovskite using nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) measurements. Paramagnetic relaxation enhancement (PRE) of the 1H NMR resonances demonstrates the presence of localized paramagnetic Pb3+ defects, a large Knight shift of the 207Pb NMR proves the presence of lead metal, and their relative proportions are determined by the differing temperature dependence in variable-temperature EPR. This work reconciles previous conflicting literature results, enabling the use of EPR spectroscopy to monitor photodegradation of perovskite devices.

Experimental investigations of the shear strength and deformation behavior of a frozen unsaturated silt

There are limited studies in literature with respect to the deformation and shear strength behavior of frozen unsaturated soils that consider sensitive changes in temperatures below 0 °C. For this reason, the focus of the present study is directed towards investigating the shear strength and deformation behavior of a frozen unsaturated silt. As a part of the study, one-dimensional freezing tests were performed on compacted silt samples with various initial water contents and dry densities. The pulsed nuclear magnetic resonance (P-NMR) method was used to obtain distribution of unfrozen water content of silt samples; this information was used to explain the deformation behavior during freezing. The volume change behavior in unsaturated soils due to freezing can be associated to three primary factors: expansion caused by the ice-water phase transition and shrinkage induced by ice-cementation and dehydration. A critical water saturation was also observed at which the frost heave is minimum, or no volume change occurs. In addition, conventional direct shear tests were performed on compacted unsaturated silt samples both in frozen and unfrozen conditions to determine and quantify the shear strength contribution arising from the different cohesion components. The investigations in this study provide valuable information that can be used in rational explanation of the strength and deformation behavior of unsaturated frozen soils.