Magnetic Resonance Microscopy Research Articles

High-Performance Materials Improve the Early Shrinkage, Early Cracking, Strength, Impermeability, and Microstructure of Manufactured Sand Concrete

The poor early shrinkage and cracking performances of manufactured sand concrete, waste powder concrete, and recycled aggregate concrete are the main difficulties in engineering applications. To solve these problems, early shrinkage and cracking, strength, and impermeability tests were performed on high-volume stone powder manufactured sand concrete mixed with fly ash and slag powder (FS), a shrinkage-reducing agent (SRA), polyvinyl alcohol (PVA) fibers, and a superabsorbent polymer (SAP). Furthermore, the microstructures and pore structures of these concretes were revealed using nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM). The results showed that the mixture of FS, SRA, PVA fibers, and SAP could effectively inhibit the shrinkage strain and cracking area of the concrete. The effect of the SAP on reducing the early shrinkage of the concrete is the greatest, and the shrinkage strain can be reduced by 76.49%. The PVA fibers had the most obvious effect on inhibiting the early cracking of the concrete, and the total cracking area was reduced by 66.91%. Significantly, the incorporation of the FS can improve the particle gradation and the pore structure and improve its compactness. The PVA fibers not only provide good carriers for cement-based materials but also enhance the bonding force between the particles inside the concrete, filling the pores inside the concrete, inhibiting the loss of water, and reducing the generation of internal microcracks. The FS and PVA can reduce the shrinkage and cracking risk and improve the strength and impermeability of the concrete. Although the SRA and SAP can reduce the shrinkage and cracking risks, it will lead to a significant decrease in the later strength and impermeability. The main reason is that the SRA leads to an increase in micropores in the matrix and microcracks near the aggregate, which are not conducive to the development of the strength and penetration resistance of the MS. Similarly, the SAP can promote the rapid formation of ettringite (Aft) at an early age and improve the early shrinkage, early cracking, and early strength of the concrete. However, with an increase in age, the residual pores, after SAP dehydration, will cause the deterioration of the concrete pore structure, resulting in the deterioration of the strength and impermeability.

The Effect of Battery Configuration on Dendritic Growth: A Magnetic Resonance Microscopy Study on Symmetric Lithium Cells

The potential of metallic lithium to become the anode material for next-generation batteries is hampered by significant challenges, chief among which is dendrite growth during battery charging. These dendritic structures not only impair battery performance but also pose safety risks. Among the non-destructive analytical techniques in battery research, Magnetic Resonance Imaging (MRI) stands out as a promising tool. However, the direct imaging of lithium by 7Li MRI is limited by its low sensitivity and spatial resolution, making it a less effective way of imaging dendrite growth. Instead, a recently introduced indirect imaging approach which is based on 1H MRI of the electrolyte was used in this study. This method was used to sequentially 3D image and thus monitor the charging process of lithium metal symmetric cells in three different electrical circuits, namely those composed of a single cell, four cells in parallel, and four cells in series. The measured sequential images allowed for the measurement of dendrite growth in each cell using volumetric analysis. The growth results confirmed the theoretical prediction that the growth across cells is uneven in a parallel circuit, and even in a series circuit. The methods presented in this study can also be applied to analyze many other dendrite-related issues in batteries.

Understanding the role of natural pozzolana in regulating the early hydration reaction process and microstructure of Portland cement

The present study examines the regulatory role of natural pozzolana (NP) on the early-age hydration process and microstructural development of Portland cement. Through a series of experiments, including low-field nuclear magnetic resonance (NMR), X-ray diffraction (XRD), thermogravimetric (TG) analysis and scanning electron microscopy (SEM), it was found that NP significantly influences the hydration kinetics and chemical shrinkage of cement paste. The addition of NP was shown to reduce the early-age chemical shrinkage and refine the microstructure by decreasing the quantity of harmful pores and increasing harmless pores, as evidenced by the bimodal distribution observed in pore size distribution (PSD) analysis. XRD and TG results indicate that NP reacts with calcium hydroxide to form additional calcium silicate hydrate (C-S-H) gel, thus improving the interfacial transition zone and resistance to carbonation. SEM micrographs further confirm the improved microstructure with fewer microcracks. The findings suggest that NP can be effectively utilized to optimize the early-age performance of concrete, offering a sustainable approach to improving its durability and long-term structural integrity.

Tracking the Dimensionality Transition from a Three Dimensional Single Crystal to a Two Dimensional Perovskite

AbstractThis work carefully studied the transition from 3D perovskite to 2D perovskite. Our system includes single crystals (SCs) of MAPbBr3, which were dipped in a solution of barrier molecules. Three monoammonium cations and one di‐ammonium cation were studied. Absorbance and cathodoluminescence were used to follow the formation of low‐dimensional perovskite on the SC surface. Quantitative nuclear magnetic resonance and scanning electron microscopy assist in quantitatively tracking the exchange process. We followed the barrier molecules′ concentration during the exchange process and their penetration depth into the 3D single crystal. The short aliphatic chain penetrates much farther into the crystal (ca. 450 μm) than the long aliphatic chain barrier molecule. In contrast, the process time is the opposite: the long aliphatic chain requires 5 days to achieve an equilibrium state compared with 15 days for the short aliphatic chain. Ab initio calculations indicate that the exchange process initiates due to the methylammonium vacancies on the surface, and the process is inhibited by the interactions between the −NH3 group and the PbBr2 planes. This work sheds light on the kinetics and thermodynamics of the transition from 3D to 2D perovskites, which is important for stabilizing the hybrid perovskites.

Mechanical Properties and Sulfate Freeze–Thaw Resistance of Calcium Carbonate Whisker-Reinforced Iron Ore Tailings Concrete

Iron ore tailings from iron ore mines pose environmental challenges. However, their reuse could provide significant environmental benefits. This study focused on producing clean concrete using iron ore tailings as crushed stone aggregate (IOTA) and calcium carbonate whiskers (CWs) as reinforcement. Five mixture groups were prepared: normal concrete (NAC) with natural crushed stone aggregate (NA), iron ore tailings concrete (TAC) with IOTA, and CW (10%, 20%, and 30%)-reinforced TAC (TAC-CW). Mechanical properties like the compressive strength (fcu) and splitting tensile strength (fst), as well as sulfate freeze–thaw (F-T) cycle resistance, were thoroughly investigated. Additionally, pore structure and microstructure were characterized using nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM) techniques. The results showed that IOTA’s complete replacement of NA decreased concrete mechanical properties and frost resistance, but incorporating CWs effectively compensated for these losses. Specifically, the fcu and fst of TAC-CW20 with 20% CWs increased by 23.26% and 49.6% compared to TAC and were higher than those of NAC. With increasing F-T cycles, concrete internal pore structure significantly deteriorated, and corrosive products increased significantly, which was further confirmed by SEM. TAC-CW20 significantly optimized pore structure. Overall, the successful application of iron ore tailings as eco-friendly materials enhanced concrete performance and reduced the environmental impact of construction activities.

Lung computed tomography image enhancement using U‐Net segmentation

AbstractThe goal of image enhancement methods is to improve image's quality. The efficacy of U‐net is evident through its extensive utilization across various significant image modalities, involving computed tomography (CT) scans, magnetic resonance imaging, X‐rays, and microscopy. In this study, we provided a novel and efficient strategy to improve lung CT images based on segmentation using U‐Net architecture. Subsequently, contrast enhancement was performed using adaptive histogram equalization and dark channel prior methods. Finally, the lightness of the lung CT image was enhanced using nonlinear mapping. The contrast enhancement performance of the suggested method is quantified by various measures like the average gradient, mean of the local standard deviation, contrast enhancement measure, and structural similarity index. The performance of the suggested method is compared against other methods, and the results indicate that the suggested method achieves better quality measures of 23.4907, 55.20341, 0.961674, and 0.4143 for the four performance metrics.

Oligodendrocyte progenitor cells' fate after neonatal asphyxia-Puzzling implications for the development of hypoxic-ischemic encephalopathy.

Premature birth or complications during labor can cause temporary disruption of cerebral blood flow, often followed by long-term disturbances in brain development called hypoxic-ischemic (HI) encephalopathy. Diffuse damage to the white matter is the most frequently detected pathology in this condition. We hypothesized that oligodendrocyte progenitor cell (OPC) differentiation disturbed by mild neonatal asphyxia may affect the viability, maturation, and physiological functioning of oligodendrocytes. To address this issue, we studied the effect of temporal HI in the in vivo model in P7 rats with magnetic resonance imaging (MRI), microscopy techniques and biochemical analyses. Moreover, we recreated the injury in vitro performing the procedure of oxygen-glucose deprivation on rat neonatal OPCs to determine its effect on cell viability, proliferation, and differentiation. In the in vivo model, MRI evaluation revealed changes in the volume of different brain regions, as well as changes in the directional diffusivity of water in brain tissue that may suggest pathological changes to myelinated neuronal fibers. Hypomyelination was observed in the cortex, striatum, and CA3 region of the hippocampus. Severe changes to myelin ultrastructure were observed, including delamination of myelin sheets. Interestingly, shortly after the injury, an increase in oligodendrocyte proliferation was observed, followed by an overproduction of myelin proteins 4 weeks after HI. Results verified with the in vitro model indicate, that in the first days after damage, OPCs do not show reduced viability, intensively proliferate, and overexpress myelin proteins and oligodendrocyte-specific transcription factors. In conclusion, despite the increase in oligodendrocyte proliferation and myelin protein expression after HI, the production of functional myelin sheaths in brain tissue is impaired. Presented study provides a detailed description of oligodendrocyte pathophysiology developed in an effect of HI injury, resulting in an altered CNS myelination. The described models may serve as useful tools for searching and testing effective of effective myelination-supporting therapies for HI injuries.

Microstructure and chloride transport of aeolian sand concrete under long-term natural immersion

Abstract River sand was consumed in large quantities, and alternatives to river sand were urgently needed. There are a large number of natural resources of aeolian sand in western China. Aeolian sand was prepared into aeolian sand concrete (ASC). It can greatly reduce the consumption of river sand and inhibit the process of desertification to protect the environment. ASC is a new type of concrete material prepared by using aeolian sand as fine aggregate. To clarify the chloride ion transport behaviour in the ASC under long-term natural immersion, the aeolian sand was 100% substituted for the river sand to prepare the full ASC with three water–binder ratios. The ASC was naturally immersed in 3 and 6% NaCl solutions for a long time, and nuclear magnetic resonance and microscopic scanning electron microscopy techniques were used. The change rule of chloride ion content at different depths of the ASC was studied, and its microstructure characteristics under different erosion times were analysed. The results showed that the free chloride ion concentration at different depths of the ASC increased with increasing water–binder ratio, immersion time, and chloride concentration. After soaking in the salt solution, the hydration products in the ASC reacted with chloride ions to form Friedel salt, which filled the internal pores and microcracks of the ASC, improved its interface transition zone structure, and increased the compactness of the test piece. The porosity of the three groups of ASC with different water–binder ratios decreased by 0.95, 1.03, and 1.15% after soaking in 6% salt solution for 12 m. To study the diffusion law of chloride ions in ASC, combined with influencing factors such as temperature, humidity, D value, deterioration effect and chloride ion combination, Fick’s second law was modified, and a chloride ion diffusion model of ASC with high accuracy was established, with a fitting correlation number above 0.93, which provided a reference for the research and application of ASC in saline areas.

SOmicsFusion: Multimodal coregistration and fusion between spatial metabolomics and biomedical imaging

We present SOmicsFusion, a software toolbox for ’fusing’ spatial omics with classical biomedical imaging modalities, capitalizing on their inherent correspondences and complementarity when characterizing the same subject. By augmenting radiological and histological images with spatially resolved molecular profiling, this fusion offers a panoramic characterization of the biochemical perturbations underlying pathological conditions, thereby advancing our understanding of diseases like brain disorders and cancers. The cornerstone of SOmicsFusion is a coregistration tool that leverages an innovative two-stage machine learning pipeline to tackle the longstanding challenge of spatially aligning data from fundamentally different modalities, priming them for subsequent fusion analysis that often requires precise pixel-wise correspondence between the datasets. Specifically, the pipeline utilizes an original dimension reduction algorithm for representational domain alignment, followed by a Deep Learning-based method for spatial domain alignment. SOmicsFusion is demonstrated using mass spectrometry imaging (MSI)-mediated spatial metabolomics and four other modalities: magnetic resonance imaging (MRI), microscopy, brain atlas, and spatial transcriptomics. By reducing coregistration errors by 38–69% compared to existing pipelines, SOmicsFusion enhances the precision of associating molecule distribution with anatomy and pathology features, ultimately leading to more statistically robust findings. Furthermore, SOmicsFusion incorporates various downstream analysis tools, including overlay visualization, spatial correlation/co-expression analysis, pansharpening, and automated anatomy annotation. These tools facilitate the extraction of biological insights that would be unattainable through individual modalities alone. For instance, the coregistration and correlation between MSI and in vivo MRI datasets unveil that the spatial heterogeneity in metabolites stems from the temporal heterogeneity in the development of cerebral ischemia-reperfusion injury.

Assessment of articular cartilage degradation in response to an impact injury using µMRI

ABSTRACT Purpose Degradation of articular cartilage (AC) due to injury to the knee joint may initiate post-traumatic osteoarthritis (PTOA). Failure to diagnose the onset of the disease at an early stage makes the cure ineffective for PTOA. This study investigated the consequences of a mechanical injury to the knee in a rabbit model using microscopic magnetic resonance imaging (µMRI) at high resolution. Materials and methods A mechanical injury was induced to the knee joints of 12 rabbits. Cartilage blocks were extracted from the non-impacted and impacted knee joints after 2 and 14 weeks post-impact. The specimens were studied using µMRI T2 relaxation and inductively coupled plasma analysis to determine the early degradation of the articular cartilage. Results The data established a connection between T2 relaxation time and the early progression of knee PTOA after an impact injury. T2 values were found to be higher in the impacted cartilage at both 2 and 14 weeks, in particular, T2–55° values in the impacted samples displayed a significant rise of 6.93% after 2 weeks and 20.02% after 14 weeks. Lower glycosaminoglycan measurement and higher water content in the impacted cartilage confirmed the µMRI results. Conclusions This µMRI T2 study was able to detect cartilage damage in the impacted knees. In addition, greater degradation in the affected knees at 14 weeks than at 2 weeks indicated the progressive nature of cartilage deterioration over time. The µMRI results were in accord with the biochemical analysis, indicating the detection of early structural damage in the cartilage.

The Effect of Polymer-Solvent Interaction on the Swelling of Polymer Matrix Tablets: A Magnetic Resonance Microscopy Study Complemented by Bond Fluctuation Model Simulations.

Polymer matrix tablets are an important drug-delivery system widely used for oral drug administration. Understanding the tablet hydration process, both experimentally and theoretically, is, thus, very important for the development of drug delivery systems that exhibit high drug loading capacity and controlled release potential. In this study, we used magnetic resonance microscopy (MRM) to nondestructively and dynamically analyze the water hydration process of xanthan-based tablets. The swelling process was characterized by well-resolved fronts of erosion, swelling, and penetration. The experimental results were complemented by numerical simulations of the polymer matrix hydration process. In the simulations, the polymer tablet matrix was modeled as an assembly of interacting chains with embedded drug particles, while its hydration process was mediated by interaction with solvent particles. The swelling dynamics were modeled within a Monte Carlo-based bond fluctuation model (BFM) that elegantly accounted for steric and nearest-neighbor interactions. This study provides an efficient experimental-theoretical approach for the study of polymer matrix swelling processes.

A cryogenic tune and match circuit for magnetic resonance microscopy at 15.2T

Background and SignificanceAchievable signal to noise ratios (SNR) in magnetic resonance microscopy images are limited by acquisition times and the decreasing number of spins in smaller voxels. A common method of enhancing SNR is to cool the RF receiver coil. Significant SNR gains are realized only when the Johnson noise generated within the RF hardware is large compared to the electromagnetic noise produced by the sample. Cryogenic cooling of imaging probes is in common use in high field systems, but it is difficult to insulate a sample from the extreme temperatures involved and in practice imaging cryoprobes have been limited to surface or partial volume designs only. In order to use a solenoid in which the windings were not directly cooled and in close proximity to the sample, we designed a chamber to cool only the tune and match circuitry and show experimentally it is possible to achieve much of the theoretically available SNR gain. MethodsA microcoil circuit consisting of two tuning capacitors, one fixed capacitor, and SMB coaxial cable was designed to resonate at 650 MHz for imaging on a Bruker 15.2 T scanner. Sample noise increases with the sample diameter, so surface loops and solenoids of varying diameters were tested on the bench to determine the largest diameter coil that demonstrated significant SNR gains from cooling. A liquid N2 cryochamber was designed to cool the tune and match circuit, coaxial cable, and connectors, while leaving the RF coil in ambient air. As the cryochamber was filled with liquid N2, quality factors were measured on the bench while monitoring the coil's surface temperature. Improvements of SNR on images of ionic solutions were demonstrated via cooling the tune and match circuit in the magnet bore. ResultsAt 650 MHz, loops and solenoids < 3 mm in diameter showed significant improvements in quality factor on the bench. The resistance of the variable capacitors and the coaxial cable were measured to be 45% and 32% of room temperature values near the Larmor frequency. Images obtained with a 2 turn, 3 mm diameter loop with the matching circuit at room temperature and then cooled with liquid nitrogen demonstrated SNR improvements of a factor of 2. ConclusionsBy cooling the tune and match circuit and leaving the surface loop in ambient air, SNR was improved by a factor of 2. The results are significant because it allows for more space to insulate the sample from the extreme temperatures used in imaging cryoprobes.

Serum response factor promoting axonal regeneration by activating the Ras-Raf-Cofilin signaling pathway after the spinal cord injury.

Serum response factor (SRF) is important in muscle development, tissue repair, and neuronal regulation. This research aims to thoroughly examine the effects of SRF on spinal cord injury (SCI) and its ability to significantly impact the recovery and regeneration of neuronal axons. The researchers created rat models of SCI and scratch injury to primary spinal cord neurons to observe the expression of relevant factors after neuronal injury. We found that the SRF, Ras, Raf, and cofilin levels increased after injury and gradually returned to normal levels. Afterward, researchers gave rats with SCI an SRF inhibitor (CCG1423) and studied the effects with nuclear magnetic resonance and transmission electron microscopy. The SRF inhibitor rodents had worse spinal cord recovery and axon regrowth than the control group. And the apoptosis of primary neurons after scratch injury was significantly higher in the SRF inhibitor group. Additionally, the researchers utilized lentiviral transfection to modify the SRF expression in neurons. SRF overexpression increased neuron migration while silencing SRF decreased it. Finally, Western blotting and RT-PCR were conducted to examine the expression changes of related factors upon altering SRF expression. The results revealed SRF overexpression increased Ras, Raf, and cofilin expression. Silencing SRF decreased Ras, Raf, and Cofilin expression. Based on our research, the SRF promotes axonal regeneration by activating the "Ras-Raf-Cofilin" signaling pathway.

Fractal and Multifractal Characteristics on Pore Structure of Coal-Based Sedimentary Rocks Using Nuclear Magnetic Resonance

Summary Unconventional reservoirs have nanoscale pores, complex pore structures, and heterogeneity that directly affect reservoir storage performance and fluid transport capacity. In this study, shale, mudstone, and sandstone, three typical coal sedimentary rocks from the Daqiang coal mine in the Tifa Basin, were selected for nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM) investigation, with the aim to investigate the pore structure and multifractal characteristics of the coal sedimentary reservoirs and to qualitatively analyze the effects of the physical property parameters and the mineralogical compositions on the multifractal parameters. The distribution data of the NMR T2 spectra were analyzed. The results showed that (1) SEM analysis concluded that the pore system of the three different lithological samples (mudstone, shale, and sandstone) was dominated by mineral matrix pores (i.e., intergranular and intragranular pores) and in the sandstone samples, there were only a few biological pores found. (2) The distribution of the NMR T2 spectrum peaks indicates that the sandstone and shale T2 spectra are bimodal, dominated by micropores, and contain a small number of transitional pores; most of the T2 spectra of mudstone are single peaks in distribution, mainly dominated by micropores. (3) Multifractal parameters are positively correlated with porosity and significantly negatively correlated with permeability; multifractal parameters are significantly positively correlated with the content of clay minerals and kaolinite, which suggests that the increase in clay minerals and kaolinite content enhances the heterogeneity of the pore space. The negative correlation with the content of quartz suggests that the enrichment of quartz reduces the irregularity of the pore space.

Experimental study on influencing mechanism of the multiple effect of steel slag powder for coarse tailings cemented backfill.

The gradation of aggregate and the hydration reaction of cementitious materials are important factors affecting the performance of backfill materials. Steel slag powder (SSP) can be used as both aggregate and cementitious material according to different particle size. SSP has multiple influencing effects on coarse tailings cemented backfill (CTCB). Experiment with different content SSP in the CTCB was designed. And uniaxial compression, nuclear magnetic resonance and scanning electron microscopy techniques were used to characterize its macro and micro characteristics. The relationship model of aggregate characteristics on strength and porosity was established by analyzing the characteristics of aggregate using gradation and fractal. The conclusions mainly include: (1) SSP plays three main roles in the CTCB: optimizing the gradation, generating hydration reaction and influencing the hydration reaction of cement. (2) There are good gradation and fractal characteristics between SSP and coarse tailings, with a grading index of 0.30-0.61 and a fractal dimension of 2.12-2.61. (3) The relationship between strength, porosity and gradation, fractal dimension was quadratic function relation, and then the grading index and fractal dimension for optimal strength and pore characteristics are 0.45-0.49 and 2.33-2.40 respectively.

Structural Analyses of Designed α-Helix and β-Sheet Peptide Nanofibers Using Solid-State Nuclear Magnetic Resonance and Cryo-Electron Microscopy and Introduction of Structure-Based Metal-Responsive Properties.

The 21-residue peptide α3, which is artificially designed and consists of three repeats of 7 residues, is known to rapidly assemble into the α-helix nanofiber. However, its molecular structure within the fiber has not yet been fully elucidated. Thus, we conducted a thorough investigation of the fiber's molecular structure using solid-state NMR and other techniques. The molecules were found to be primarily composed of the α-helix structure, with some regions near the C- and N-terminal adopting a 310-helix structure. Furthermore, it was discovered that β-sheet hydrogen bonds were formed between the molecules at both ends. These intermolecular interactions caused the molecules to assemble parallelly in the same direction, forming helical fibers. In contrast, we designed two molecules, CaRP2 and βKE, that can form β-sheet intermolecular hydrogen bonds using the entire molecule instead of just the ends. Cryo-EM and other measurements confirmed that the nanofibers formed in a cross β structure, albeit at a slow rate, with the formation times ranging from 1 to 42 days. To create peptide nanofibers that instantaneously respond to changes in the external environment, we designed several molecules (HDM1-3) based on α3 by introducing metal-binding sites. One of these molecules was found to be highly responsive to the addition of metal ions, inducing α-helix formation and simultaneously assembling into nanofibers. The nanofibers lost their structure upon removal of the metal ion. The change occurred promptly and was reversible, demonstrating that the intended level of responsiveness was attained.

Comparison of driven equilibrium and standard spin-echo sequence in MR microscopy: Analysis of signal dependence on RF pulse imperfection and diffusion

Rapid MR imaging of slowly relaxing samples is often challenging. The most commonly used solutions are found in multi spin-echo (RARE) sequences or gradient-echo (GE) sequences, which allow faster imaging of such samples with multiple acquisitions of k-space lines per excitation or imaging with very short repetition times (TRs). Another solution is the use of a spin-echo (SE) sequence superimposed with a driven equilibrium Fourier transform (DEFT) method. Such a (DE-SE) imaging sequence has two refocusing RF pulses that produce two spin-echoes. In the first echo, the signal is acquired from the k-space line, and in the second echo, a 90° RF pulse is applied, typically 180° out of phase with respect to the excitation RF pulse. This last RF pulse allows almost complete magnetization reversal back to the longitudinal orientation with minimal magnetization loss. The DE-SE sequence and its RARE variant are widely used in clinical imaging, but its use in MR microscopy has some peculiarities related to the usually less perfect RF pulse flip angles and diffusion. In this study, their effects are first theoretically analyzed and later verified by experiments on test samples performed on a 9.4 T system for MR microscopy. Experiments on a water-filled tube for TE = 3.4 ms and TR = 25–200 ms showed that the DE-SE sequence produces about 10 times more signal than the SE sequence in this TR range. Finally, the performance of the DE-SE sequence compared to the SE sequence was demonstrated on a biological sample. The presented DE-SE sequence has been shown to be effective for rapid imaging of samples with long T1 relaxation times in MR microscopy and can also be considered as a suitable method for rapid proton density weighed imaging of materials.

Deformation and kerogen macromolecular structure transformations of the Wufeng–Longmaxi shale under the control of the detachment layer

Tectonism caused strong deformation of the organic-rich shale in the detachment layer of the Wufeng–Longmaxi Formation. In this study, the deformation of the samples collected from the detachment layers were observed using an optical microscope and field emission scanning electron microscopy. Fourier transform infrared spectroscopy (FTIR), 13C nuclear magnetic resonance, X-ray diffraction, and high-resolution transmission electron microscopy were employed to characterize the macromolecular structure of extracted kerogen samples. The research shows that tectonically deformed shale (TDS) is commonly developed in the detachment layer of the Wufeng–Longmaxi Formation, dominated by brittle–ductile and ductile deformation. In the brittle–ductile deformation stage, the aliphatic carbon (fal) decreases, manifested as the decrease of –CH or –CH2 (falH), from 6.77% to 3.12%. The Al/–OX (defined by FTIR A3000–2800/A1800–1520) gradually decreases, indicating that the brittle–ductile deformation has a stronger effect on the aliphatic structure. The aromaticity I and aromatic carbon (fa) show an increasing trend due to aromatization. In the ductile deformation stage, the fal and aliphatic carbon bonded to oxygen increase first and then decrease, falH decreases gradually, and the aliphatic side chain becomes shorter. The Al/–OX shows an increasing trend, and carbonyl decreases from 7.82% to 5.12%, indicating that the effect of ductile deformation on oxygen-containing functional groups is stronger. The fa shows an overall increasing trend, and the aromatic ring carbon and protonated aromatic carbon increase more significantly due to aromatic condensation. The change trend of the interlayer spacing is opposite in these two stages. However, both brittle–ductile and ductile deformation can improve the size and orientation of aromatic fringes to varying degrees, and the latter is more significant. The rigid mineral intrusion and organic matter (OM) chemical structure evolution are the two main reasons for the low development of OM pores in TDS.

Brain Structures in a Human Embryo Imaged with MR Microscopy.

To delineate brain microstructures in human embryos during the formation of the various major primordia by MR microscopy, with different contrasts appropriate for each target. We focused mainly on the internal structures in the cerebral cortex and the accessory nerves of the brain. To find appropriate sequence parameters, we measured nuclear magnetic resonance (NMR) parameters and created kernel density plots of T1 and T2 values. We performed T1-weighted gradient echo imaging with parameters similar to those used in the previous studies. We performed T2*-weighted gradient echo imaging to delineate the target structures with the appropriate sequence parameters according to the NMR parameter and flip angle measurements. We also performed high-resolution imaging with both T1- and T2*-weighted sequences. T1, T2, and T2* values of the target tissues were positively correlated and shorter than those of the surrounding tissues. In T1-weighted images with a voxel size of (30 µm)3 and (20 µm)3, various organs and tissues and the agarose gel were differentiated as in previous studies, and the structure of approximately 40 µm in size was depicted, but the detailed structures within the cerebral cortex and the accessory nerves were not delineated. In T2*-weighted images with a voxel size of (30 µm)3, the layered structure within the cerebral cortex and the accessory nerves were clearly visualized. Overall, T1-weighted images provided more information than T2*-weighted images, but important internal brain structures of interest were visible only in T2*-weighted images. Therefore, it is essential to perform MR microscopy with different contrasts. We have visualized brain structures in a human embryo that had not previously been delineated by MR microscopy. We discussed pulse sequences appropriate for the structures of interest. This methodology would provide a way to visualize crucial embryological information about the anatomical structure of human embryos.

The Combined Effect of Nanoclay Powder and Curing Time on the Properties of Class G Cement

When the cement paste is subjected to stresses, the cement matrix and its characteristics are dramatically influenced, especially in the early ages of cement hydration when the cement properties have not yet settled. Nanoclay, which is made up of very small particles, was used to improve the properties of cement. In this study, the early-age performance of cement made with nanoclay powder for use in oil wells is assessed. Ten cement samples were made and cured at varying times (6, 12, 24, 48, and 72 hours), wherein 1% by weight of cement of nanoclay was used in five samples, and in the other five samples, there was no nanoclay present in the cement. Failure properties, petrophysical parameters, and elastic properties were studied for all the cement samples. Nuclear magnetic resonance (NMR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were all used to describe the cement samples and determine how different curing times affected the cement’s mineralogical and microstructural features. The results displayed that compressive and tensile strengths were shown to increase with curing time for both the base (control) and nanoclay cement samples; however, the compressive and tensile strengths of the nanoclay cement samples were found to be greater than the base sample by 20.2% and 17.9%, respectively. This is due to the presence of more calcium silicate hydrate in these samples. Nanoclay cement had 76.9% lower permeability than control cement, which can be related to the capacity of the nanoclay particles to fill the microstructure dominating the base samples as curing time increased. Young’s modulus of the cement was lowered by 1.8%, while Poisson’s ratio was increased by 2.7% when nanoclay was incorporated. Nanoclay cement has a 29.2% smaller porosity than regular cement, and this porosity increases as the cement cures. The novelty of this work is that several properties of the class G cement were evaluated at the early stage of hydration, where the nanoclay particles were used to improve these properties.