Changes In Anisotropy Research Articles

Synthesis and Electrochemistry of Stacking Fault-Free β-NaMnO2.

Understanding the solid-state chemistry of corrugated layered sodium manganese oxide (β-NaMnO2) has been hindered by stacking faults (SFs), particularly in the presence of α-type planar domains among β-type corrugated MnO2 layers. Thus, their prospects as cathode materials for Na-ion batteries have never been assessed comprehensively. The partial substitution of Cu for the Mn in β-NaMnO2 yields SF-free β-phase, as confirmed via atomic scale scanning transmission electron microscopy. The SF-free material enables the identification of unique phase transitions during electrochemical Na extraction/insertion, showing drastic gliding of the corrugated layers. The proposed gliding mechanism is validated both experimentally, using ex situ synchrotron X-ray diffraction, and theoretically, through density functional theory calculations. Minor structural changes observed in SF-containing materials indicated that gliding is extremely sensitive to SFs. Given that the SF-free β-material exhibits excellent cycle stability in a Na cell, the corrugated layer is concluded to have high resilience and reversibility against repeated large anisotropic structural changes involving slab gliding, providing a new insight into the design of long-life rechargeable batteries.

Magnetic Behavior of Co2+-Doped NiFe2O4 Nanoparticles with Single-Phase Spinel Structure

This study reports the synthesis and characterization of CoxNi1−xFe2O4 (x = 0, 0.2, 0.4, 0.6, 0.8, 1) nanoparticles using a co-precipitation method. In this approach, metal ions are precipitated in the presence of a stabilizing agent, which is a common and effective method for nanoparticle preparation. The microstructure and magnetic properties were studied after calcination at 600 °C and heat treatment at 1000 °C. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy confirmed the formation of a single-phase spinel structure. The average crystallite size, calculated using the (311) diffraction peak and the Scherrer equation, ranged from 13 to 19 nm. Scanning electron microscopy (SEM) showed that the nanoparticles had a spherical morphology. Thermogravimetric and differential thermal analysis (TG-DTA) revealed a three-step weight loss process. Magnetic measurements, including remanent magnetization, saturation magnetization, and coercivity, were performed using a vibrating sample magnetometer (VSM) at room temperature. The replacement of Ni2+ with Co2+ enhanced the magnetic properties, resulting in increased magnetic moment and anisotropy. These effects are attributed to changes in cation distribution, exchange interactions, surface effects, and magnetocrystalline anisotropy. Overall, Co2+ doping improved the magnetic behavior of nickel ferrite, indicating its potential for application in memory devices and magnetic recording media.

Time-Varying Crustal Velocities and Changing Radial Anisotropy Coincident with Eruptive Phases at Turrialba Volcano

Abstract Seismic ambient noise interferometry is a prevalent tool for monitoring volcanic and seismic hazards. Most studies rely solely on vertical seismic components to assess time-varying velocity changes, yet velocity information extracted from the horizontal components is a powerful complementary investigation tool because it provides constraints on changes in radial anisotropy. Here, we measure relative fractional seismic velocity changes of both vertical and transverse components at the erupting Turrialba volcano. Velocity changes associated with some eruptive phases were present in all seismic components and had strong frequency dependence. Some eruptive phases also showed significant velocity perturbations at lower frequencies as well as divergent behavior between transverse and vertical components. This indicates a positive change in radial anisotropy surrounding the volcano during the eruptive episodes. From our results, we propose two instances of high volcanic fluid pulses at the bottom of the shallow magma reservoir feeding Turrialba that would have altered numerous microcracks and increased pore fluids. A sudden decrease in velocity, and a surge in seismic displacement, during the second pulse coincides with a large eruption in May 2016.

Cholesterol inhibits HCN channels through dual mechanisms in neuropathic pain.

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels regulate the excitability of dorsal root ganglion (DRG) neurons, particularly in the context of neuropathic pain. Cholesterol, a major component of lipid-ordered membrane domains (OMDs), has recently been identified as a critical modulator of HCN channel function. Using FLIM-FRET-based OMD probes and a fluorescent cholesterol sensor GRAM-W, we investigated the effects of cholesterol supplementation on nociceptor DRG neurons from a rat model of spared nerve injury (SNI). We developed a method to distinguish at least two phases of membrane remodeling during cholesterol enrichment: an initial phase marked by OMD expansion and increased accessible cholesterol, followed by a second phase with continued cholesterol accumulation without further OMD expansion. These cholesterol dynamics were further validated through changes in fluorescence anisotropy and homo-FRET measurements of GRAM-W. Temporal analysis of cholesterol enrichment revealed two mechanisms of HCN channel modulation: through expansion of OMDs and elevation of free cholesterol. In SNI DRG neurons with low cholesterol and small OMDs, both mechanisms are active, while in naïve DRG neurons-characterized by high cholesterol and large OMDs-modulation occurs only via increased free cholesterol. These findings deepen our understanding of cholesterol's role in modulating ion channels and contributing to neuropathic pain.

Laboratory observation of stress and saturation effects on shear-wave anisotropy

Shear-wave splitting, also known as shear-wave birefringence, has been used widely to evaluate subsurface anisotropy. Yet, the effect of stress and fluid saturation on S-wave anisotropy is still not well understood. We present a laboratory study carried out on a Bentheim sandstone sample subjected to different stress and saturation conditions. The S-wave stress-induced anisotropy of the sample is measured using a laser Doppler interferometer (LDI), which allows us to estimate the particle displacement vector at the central point onto the surface of the sample. Based on the derived hodograms, we infer the polarization of the fast S wave and the degree of the S-wave anisotropy. For the dry sample, we observe a shift of the polarization direction toward the direction of the applied stress and an increase of the anisotropy degree in some cases, most likely due to the preferential opening of cracks in the direction along the applied stress. For the water-saturated case, no significant change in the S-wave anisotropy is observed.

Fast diffusion and stable topotactic reaction in single crystal conversion anode

Fast diffusion and stable topotactic reaction in single crystal conversion anode

Stress‐Dependent Wave Propagation in Fractured Rocks With Nonlinear Elastic and Hyperelastic Deformations

Abstract Stress‐induced progressive deformations in fractured rocks with increasing differential stress generally undergo nonlinear elastic (due to crack closure), hyperelastic (due to stress accumulation), and inelastic (due to crack growth) deformations prior to mechanical failure. Wave propagation in such rocks involves the complex interaction of fracture‐ and stress‐induced changes in both velocity and anisotropy. By focusing on nonlinear elastic and hyperelastic deformations, we incorporate acoustoelasticity into the traditional Hudson and Padé–Hudson models of penny‐shaped ellipsoidal cracks to describe the coupling of fracture‐ and stress‐induced anisotropies. The resulting acoustoelastic Hudson model (AHM) and Padé AHM can be used to describe the stress‐dependent anisotropy of fractured rocks with varying crack densities. We integrate the dual‐porosity model into the Padé AHM to account for the stress‐induced closure of cracks with nonlinear elastic deformations. The plane‐wave analyses and effective‐moduli calculations of fractured rocks with varying crack densities and loading stresses determine the accuracy of these models under the isotropic (hydrostatic) and anisotropic (uniaxial and pure‐shear) prestresses. The resulting Thomsen parameters are applied to experimental data to validate their applicability. Finite‐difference simulations are implemented to differentiate the contribution of fracture‐ and stress‐induced anisotropies through wavefront changes, depending on fracture orientation, crack density, prestress mode, and loading direction. Particular attention is paid to the anisotropic prestress perpendicular to the fracture strike, where the stress‐induced crack closure reduces the fracture anisotropy so that the stress‐induced anisotropy dominates the shape of wavefronts.

Tuning Self-Aggregation and Nuclearity in Multinuclear CoII Complexes: Synthesis, Structural Diversity, and Changes in Magnetic Anisotropy and Relaxation Behavior

Tuning Self-Aggregation and Nuclearity in Multinuclear Co^II Complexes: Synthesis, Structural Diversity, and Changes in Magnetic Anisotropy and Relaxation Behavior

Multi-temperature cooling performance of GdFeCo thin films with high magnetic entropy change and evolution of perpendicular magnetic anisotropy with thickness

Abstract To investigate the effect of thin film thickness on magnetic, magnetocaloric, and perpendicular magnetic anisotropy, we prepared Ta (5nm)/GdFeCo/Ta(5nm) heterostructure with GdFeCo thickness varying from 50 nm to 180 nm. The compensation temperature (Tcomp) and Curie temperature (Tc) shift significantly as the thickness increases. The temperature-dependent magnetization reveals that the Tcomp (224.74 K) is lower than room temperature for the 50 nm thin film, suggesting a CoFe-rich phase. The isothermal magnetic entropy change (|Sm|) is measured at both Tcomp and Tc corresponds to second order magnetic phase transition. |Sm| is found to be 0.24 J/kgK for 90 nm rises to 0.6 J/kgK for 180 nm. Doubling of the thickness from 90 nm to 180 nm results to increase in |Sm| of about 150%. In addition, a significant magnetic entropy change (0.31 J/kgK for 50 nm thin film @ 15 kOe field) is noticed near the Curie temperature for all thin films. For all higher thicknesses, a discernible change in magnetic entropy is observed at Tc. The magnetic anisotropy estimated using Hall effect and MOKE measurements demonstrates perpendicular magnetic anisotropy begins to dominate around room temperature for films with thickness greater than 90 nm as their compensation temperature falls around room temperature. We demonstrate GdFeCo thin films could potentially be suitable for multi-temperature magnetic cooling applications. 


White matter fractional anisotropy decreases precede hyperintensities in Alzheimer’s disease

White matter fractional anisotropy decreases precede hyperintensities in Alzheimer’s disease

Thermal responses of 3D-printed liquid crystal elastomer microcubes

ABSTRACT Liquid crystal elastomers (LCEs) are stimuli-responsive materials allowing for pre-programed shape changing via precisely tailoring spatially variant orientation, or the director of the liquid crystal mesogens. A considerable challenge remains on fabricating micron-sized LCE structures with well-defined director patterns. In this work, we focus on 3D-printed LCE microcubes that are a few microns in size and have a uniform director at a pre-designable angle relative the cube side. We characterise their glass transition and nematic-to-isotropic transition temperatures and demonstrate that upon heating from the nematic phase at room temperature to the isotropic phase, the microcubes exhibit anisotropic shape changes depending on the director orientations with respect to the cube sides. These findings represent a step towards designing and fabricating LCE microstructures with programmable shape morphing.

High-Frequency repetitive transcranial magnetic stimulation enhances white matter integrity in a rat model of ischemic stroke: A diffusion tensor imaging study using tract-based spatial statistics.

High-Frequency repetitive transcranial magnetic stimulation enhances white matter integrity in a rat model of ischemic stroke: A diffusion tensor imaging study using tract-based spatial statistics.

Changes in seismic anisotropy at Ontake volcano: a tale of two eruptions

The interaction of faults, fractures, and hydromagmatic systems of volcanoes can lead to complicated stress patterns that vary over short spatial and temporal scales. Here we study stress-induced anisotropy using observations of shear-wave splitting at 12 stations across Ontake volcano, Japan. The results reveal a complicated pattern of anisotropy indicating that the volcano perturbs the local stress field. In 2007, a minor phreatic eruption (VEI 0) occurred at Ontake, but there is little evidence of changes in splitting parameters during this eruption. In contrast, the much large eruption of 2014 (VEI 3) shows clear temporal changes in splitting parameters following the eruption. The average background magnitude of anisotropy, as described by the delay time between the fast and slow shear wave, doubles to nearly 0.2 second at the onset of the 2014 eruption, but the percent anisotropy increases dramatically from 3% to 20%. Contemporaneously, the polarisation of the fast shear wave rotates towards sHmax. We interpret these observations in terms of basal heating of the hydrothermal system. We suggest that a lack of temporal variation in anisotropy parameters during the 2007 eruption indicates that a critical stress or crack density threshold must be overcome to exhibit a change in anisotropy, which may be indicative of a more significant eruption.

Phase-change-based polarization-selective switching for multilevel emittance modulation.

Smart modulation of emittance of a radiator, particularly through multilevel strategies, has garnered substantial interest due to its unparalleled adaptability and versatility. In this Letter, we present a smart multilevel radiator, capable of achieving four distinct levels of emittance modulation in the spectral range of 2.5-30 μm. Such a smart radiator is a relatively straightforward design, integrating In3SbTe2 (IST)-based linear grating on a VO2-based multilayer structure. The enhanced emittance tunability of the smart multilevel radiator is achieved, with total normal emittances of 0.11, 0.27, 0.54, and 0.82 for the four levels, respectively. The underlying mechanisms involve manipulating the Fabry-Perot (FP) resonance through the phase change of VO2 and in-plane anisotropy via the phase change of IST. The multilevel modulation of emittance exhibits remarkable stability and excellence under wide-angle incidence conditions. The development of this multilevel smart radiator has considerable potential for applications in thermal anti-counterfeiting, thermal management, and energy conservation.

Impact of Thermal and Ultraviolet Treatments on the Structural, Mechanical, and Laser Ablation Properties of Fluorinated Ethylene Propylene Films

Fluorinated ethylene propylene (FEP) films were subjected to heat, UV, and heat–UV treatments. Structural changes that occurred after these treatments were recorded via X-ray diffraction (XRD), microtensile, and laser ablation testing. XRD macromolecular orientation texture analysis revealed changes in the fraction of crystalline components and the degree of anisotropy of the FEP films after being subjected to different processing conditions. Heat treatment at 200 °C affected structural properties by rearranging the crystallites and resulting in a higher degree of anisotropy. By contrast, the UV treatment of FEP resulted in a lower degree of anisotropy. The changes in anisotropy and crystallinity of FEP films significantly affected their Young’s modulus and yield stress. The UV laser ablation threshold values were found to be lower for the heat-treated FEP films.

Chemical Control of the Néel Temperature and Magnetic Anisotropy in the Brownmillerites Ca2Fe2-xMnxO5, x = 0.10-0.25.

Brownmillerite oxides with the composition Ca2Fe2-xMnxO5 had been investigated previously for the limited range x = 0.5 to 1.0. Mn3+ preferentially occupies the octahedral site. This substitution has a strong impact on the magnetic properties as the magnetic ordering temperature, TN, is suppressed from 730 K for x = 0.0 to 465 K for x = 0.5 and the magnetic structure changes from Gx (x = 0.0) to Gy (x = 0.5-1.00). In this study, the compositions x = 0.10 and 0.25 are investigated using single-crystal X-ray and neutron diffraction methods. It is found that TN decreases linearly from x = 0.0 to x = 0.5, with values of 584(2)K for x = 0.25 and 684(2)K for x = 0.1. This behavior is rationalized in terms of a competition between antiferromagnetic and ferromagnetic exchange pathways in the perovskite layers involving Fe3+-Fe3+ and Fe3+-Mn3+ interactions. Profound changes in the magnetic anisotropy also occur as for both x = 0.25 and x = 0.1, the magnetic structure is neither Gx or Gy, but the moments lie between the a and b axes over nearly the entire temperature range. It has been shown that enhanced dielectric parameters are associated with another brownmillerite oxide, Ca2FeCoO5, in which nonaxial magnetic anisotropy is found within a narrow temperature range, 120-250 K. In the materials prepared in this study, this behavior should be evident at ambient temperature and over a wide temperature range.

METHOD OF MUELLER-MATRIX MICROSCOPY OF NECROTIC CHANGES OF STRUCTURAL ANISOTROPY OF HUMAN BRAIN SUBSTANCE FOR DIAGNOSTIC OF CAUSE OF DEATH FROM HEMORRHAGE OF TRAUMATIC AND NON-TRAUMATIC GENESIS

In recent years, modern non-destructive and non-invasive methods of optical diagnostics of biological tissue and fluid preparations have become widely and effectively used in various branches of medicine. Among the wide range of optical methods, one of the most effective has been distinguished - laser polarimetric diagnostics of the polycrystalline structure of biological layers.Purpose of the work: to determine the set of markers for differential diagnosis of the cause of death from hemorrhages of traumatic and non-traumatic genesis into the substance of the brain of deceased persons by using the Mueller matrix mapping method with algorithmic reproduction of linear birefringence of native histological brain sections.Material and methods of the research. For the study, samples were selected in the form of native slices of the human brain from the parietal region of the deceased, the cause of death of which was hemorrhage of traumatic genesis - group II (total number n = 100), cerebral infarction of ischemic genesis - group III (n = 100), hemorrhage of non-traumatic genesis - group IV (n = 100), acute coronary insufficiency - group I - control (n = 40). The study material was frozen at a temperature of -70 ° C and then histological sections were made using a freezing microtome. In the laboratory of the Institute of Physical, Technical and Computer Sciences named after Yuri Fedkovych, studies of the obtained samples were carried out using a Stokes polarimeter using the method of multifunctional Mueller-matrix polarimetry of human brain substance preparations.Results of the research. Within the framework of complex algorithmic analysis, a set of statistical (asymmetry and kurtosis of the distributions of the Muller matrix invariant of linear birefringence – MMI LD), correlation (kurtosis and correlation area of the autocorrelation functions of the MMI LD distributions) and fractal (kurtosis of the power spectral density of the autocorrelation functions of the MMI LD distributions) diagnostic markers sensitive to necrotic changes in the polycrystalline structure of neural networks of native histological sections of the brain of deceased persons due to hemorrhages into the brain substance of traumatic and non-traumatic genesis was identified.Conclusions. A high (92%-93%) level of differential diagnosis of necrotic changes in the structural anisotropy of neural networks of the brain of deceased persons due to hemorrhages into the brain substance of traumatic and non-traumatic genesis was established.

FORENSIC MEDICAL CRITERIA FOR DIFFERENTIATION OF THE VOLUME OF BLOOD LOSS THROUGH ANALYSIS OF LINEAR DICHROISM MAPS OF HUMAN BIOLOGICAL TISSUES AND FLUIDS

Our article is aimed at investigating the diagnostic effectiveness of using method of Mueller matrix reproduction of linear dichroism maps of the polycrystalline component of biological tissues and human blood in the task of objectively determining the volume of blood loss.The aim of the study. To assess the effectiveness of the method of Mueller matrix reproduction of linear dichroism maps of the polycrystalline component of biological tissues and human blood in the differential diagnosis of the degree of blood loss.Material and Methods. The study analyzed biological tissues of deceased individuals with varying degrees of blood loss: skin, brain, and blood samples (n=156) aged from 18 to 60. All samples were divided into a control (n=10; 0 mm³) and five experimental groups according to the amount of blood loss (from 500±100mm³ to 2500±100mm³). Statistical data processing was performed using MS® Excel® 2010™ and Statistica® software. Blood loss volume was estimated by analyzing changes in phase and amplitude anisotropy of tissues using an algorithm for calculating the specific value of blood loss.Results. Based on the analysis of the distributions of random values of the polycrystalline component of biological tissues and blood of deceased persons with different degrees of blood loss, the dynamics of changes in the value of statistical indicators for each experimental group, depending on the volume of blood loss, was established. The assessment of the accuracy of the proposed method showed a high level of reliability in determining the volume of blood loss for skin, brain and blood samples. The highest accuracy rates (92-94%) were recorded when using the asymmetry and excess of the linear dichroism distributions of blood films, which confirms the effectiveness of the method for forensic practice.Conclusions. 1. The sensitivity range of the differential Mueller matrix mapping method of linear dichroism to changes in the level of blood loss of for all studied samples was established – ΔV=0mm3÷2000mm3. 2. The magnitudes and ranges of changes in the accuracy of the differential Mueller matrix mapping method with algorithmic reproduction of linear dichroism maps of biological samples have been determined – ΔV=0mm3÷2000mm3 ↔ 86-92%; ΔV=2000mm3÷2500mm3 ↔ 56-68%. 3. The highest accuracy was recorded in blood analysis (excess SM4 ↔ 90-94%), which indicates the potential of this method for objective assessment of blood loss. At the same time, for brain and skin tissue, the accuracy of the method was lower, but still at a high level (80-90%). 4. The results obtained confirm the high efficiency of the Mueller matrix tomography method in determining the degree of blood loss. The method provides an accurate assessment of changes in the optical characteristics of biological tissues in response to blood loss, which can be used in forensic practice to establish the causes of death and reconstruct the mechanism of injury.

Association Between Changes in White Matter Volume Detected With Diffusion Tensor-Based Morphometry and Motor Recovery After Stroke.

Diffusion tensor-based morphometry (DTBM) provides a more accurate assessment of volumetric changes in white matter structures than conventional T1-based TBM techniques. We sought to determine whether DTBM could detect volume loss in the corticospinal tract (CST) and whether this marker was associated with impaired stroke recovery. Retrospective clinical MRI scans were obtained from a cohort of participants enrolled in a natural history study with acute anterior circulation ischemic stroke and unilateral arm impairment (NIH Stroke Scale [NIHSS] arm motor item score ≥2). Maps of the change in fractional anisotropy (delta FA) and the DTBM log of the Jacobian (LnJ, representing volumetric change) between scans, acquired <36 hours and 30 days after stroke, were computed. Voxel-wise Spearman rank-based analysis identified clustered regions of interest (ROIs) where the delta FA and LnJ from baseline to 30 days correlated with individual arm motor recovery scores on the NIHSS from baseline to 30 days. Qualitative comparisons were made between delta FA and LnJ maps for good and poor recovery groups (delta NIHSS arm item score ≥2 or <2, respectively) in reference to controls. Twenty-one participants with anterior circulation stroke were evaluated (mean age 63.6 years, median NIHSS arm motor item score 4, 48% female). Voxel-wise statistical maps identified 2 ROIs for delta FA and 4 ROIs for LnJ showing strong correlations with arm motor recovery (range of Spearman ρ = 0.77-0.81, all p < 0.01). The delta FA ROIs included the corona radiata and adjacent white matter, whereas LnJ ROIs included the centrum semiovale, corona radiata, internal capsule, and pons. Visual inspection of the average delta FA map from participants with poor arm motor recovery showed diffuse changes in the CST and adjacent subcortical regions while LnJ maps demonstrated more focal CST changes, particularly in the brainstem and internal capsule. DTBM detects focal volume loss in the CST over the first 30 days after stroke likely related to Wallerian degeneration. These volumetric changes may provide complementary information to FA in characterizing white matter loss after stroke. Like FA, DTBM shows strong correlations with arm motor recovery that could be useful for predicting recovery after stroke.

The optic radiations and reading development: A longitudinal study of children born term and preterm.

The optic radiations and reading development: A longitudinal study of children born term and preterm.