Anisotropy Measurements Research Articles

Fluoroalkylated Non-fullerene Acceptor as Surface Segregated Monolayer for Controlling Molecular Orientation of Acceptor Layer in Organic Photovoltaics.

A fluoroalkyl-containing electron acceptor (Y-SSM) is designed and synthesized to control the orientation of the benchmark non-fullerene acceptor Y6 in thin films. Due to the low surface energy of the two fluoroalkyl chains at the terminal part of Y-SSM, it spontaneously segregates to the film surface during spin coating, forming a monolayer of edge-on oriented Y-SSM. The Y-SSM monolayer leads to crystallization of the underlying Y6 to induce a standing-up orientation in the bulk of the films, which is strikingly different from pure Y6 films that tend to be a face-on orientation. Solid evidence for standing-up Y6 in the film is provided by two-dimensional grazing incidence wide-angle X-ray scattering and optical anisotropy measurements based on variable angle spectroscopic ellipsometry. The surface Y-SSM can be partially removed by washing with hexane without disrupting the orientation of Y6, resulting in exposure of the standing-up Y6 on the surface. Organic photovoltaics based on a planar heterojunction structure with standing-up Y6 show a significant increase in short-circuit current density, reaching 2.5 times the value compared to face-on oriented Y6, due to the improved charge generation efficiency resulting from the different relative orientation with respect to PM6.

ΛCDM model against gravity-thermodynamics conjecture: observational constraints after DESI 2024

In the context of the gravity-thermodynamics conjecture based on the Tsallis entropy-area relation, we investigate the standard ΛCDM cosmology and examine some potential deviations from it. Utilizing recent updates from geometrical datasets, including the DESI BAO measurements (2024), Planck CMB anisotropy measurements (2018), and the Pantheon+ catalogue for SNIa (2022), we conduct a thorough analysis via the window of Tsallis cosmology. In the first step, our analysis reveals no significant deviation from the standard model when using DESI BAO data alone, Pantheon+ data alone, or a combination of both. In the next step, we incorporate all datasets by adding the CMB data to our analysis, indicating a potential deviation from the standard model within the framework of Tsallis cosmology. Imposing the Planck prior to the sound horizon at the baryon drag epoch, we observe support for the standard model and consistency between our constraints on the Hubble constant and the Planck value. Finally, we compare the Tsallis and ΛCDM cosmologies using the Akaike Information Criterion (AIC).

Impact of a Palladium(II)-tris(2-carboxyethyl)phosphine Complex on Normal Cells: Toxicity and Membrane Interaction

Palladium(II) complexes with tris(2-carboxyethyl)phosphine (PdTCEP) show promise for biomedical applications due to their distinct chemical characteristics. This study explored the toxicity of PdTCEP towards normal human cells and examined its interactions with model cell membranes. Two cell types were used to evaluate cytotoxicity: human microvascular endothelial cells (HMEC-1) and red blood cells (RBCs). In HMEC-1 cells, PdTCEP reduced survival to about 80% at 15 µM, with the most significant drop—down to 40%—occurring at 40 µM. The production of reactive oxygen species (ROS) increased in a manner dependent on both dose and time, especially after 72 h of incubation. Despite these effects, PdTCEP caused only minor hemolysis in RBCs, with hemolysis levels staying below 10% even at higher concentrations. Fluorescence anisotropy measurements showed that PdTCEP minimally affects the hydrophobic core of the lipid bilayer, with slight changes observed at concentrations above 40 µM. Generalized polarization (GP) analysis indicated a slight decrease in lipid polar head packing with increasing PdTCEP concentration. Complementary FTIR analysis supported these findings by providing detailed insights into PdTCEP-membrane interactions. This research underscores PdTCEP’s selective cytotoxicity and structural effects on membranes, suggesting its promise for more in-depth biological and pharmacological studies.

The Influence of Length and Sequence of Complementary Oligonucleotides on the Spectral and Time-Resolved Fluorescence Properties of an H-Type Excitonic Dimer-Bearing Antisense Oligonucleotide.

We have previously found that the presence of an H-type excitonic dimer formed by two fluorophores covalently bound to an oligonucleotide allows the delivery of such a polymer into live cells without inducing toxicity. We are now using time-resolved fluorescence measurements in solution to understand the molecular dynamics of an antisense probe and how pairing with complementary sense strands of various lengths and degrees of complementarity affects the antisense strand's properties. We report that a DNA strand composed of 30 residues and labeled with an H-type excitonic Cyanine-5/Cyanine-5 dimer shows a predominant 1.9 ns lifetime decay term accompanied by a shorter (0.5 ns) secondary lifetime. Similar values were measured for this excitonic dimer-bearing antisense strand following binding with a series of sense strands of varying lengths and compositions. However, significant differences in both time-resolved and steady-state anisotropy values were found, depending on the level of duplex formation through hydrogen bonding between sense and antisense sequences. More specifically, the anisotropy measurements of the double-labeled single-chain probe showed increases as the two intramolecular fluorophores were induced to separate with values dependent on the length and sequence of complementary sense strands. These differences suggest induced changes in the degrees of wobbling, tumbling, and spinning.

Chasing cosmic inflation: constraints for inflationary models and reheating insights

We investigate the impact of different choice of prior's range for the reheating epoch on cosmic inflation parameter inferencein light of cosmic microwave background (CMB) anisotropy measurements from the Planck 2018 legacy releasein combination with BICEP/Keck Array 2018 data and additional late-time cosmological observations such as uncalibratedType Ia supernovae from the Pantheon catalogue, baryon acoustic oscillations and redshift space distortionsfrom SDSS/BOSS/eBOSS.Here, we explore in particular the implications for the combination of reheating and inflationary-model parameter spaceconsidering R+R 2 inflation and a broad class of α-attractor and D-brane models.Propagating the uncertainties due to an unknown reheating phase, these inflationary models completely cover the n s-r parameter space allowed by Planck and BICEP/Keck dataand represent good targets for future CMB and large-scale structure experiments.We perform a Bayesian model comparison of inflationary models, taking into account the reheating uncertaintiesassuming a conservative but accurate modelling of inflationary predictions.R+R 2 inflation, T-model α-attractor inflation for n=1, E-model α-attractor inflation for n=1/2,and KKLT inflation for p=5 are the better performing models, with none being preferred at a statistically significant level.

Estimation of Stresses in a Plate with a Concentrator through Ultrasonic Measurements of Acoustic Anisotropy

Introduction. Acoustic anisotropy is measured during ultrasonic nondestructive testing. It estimates the magnitude of stresses by the acoustoelasticity method. The literature describes in detail the application of this approach in the case of a biaxial strength of extended structures: main pipelines, rail strings, steam generators, and others. They assume the presence of a uniform field with zero or weak gradients of stresses and deformations. However, the problem of timely detection and assessment of critical stresses caused by local concentrators through ultrasonic testing has not been solved. The presented material is intended to fill this gap. The work is aimed at determining the possibilities of the acoustoelasticity method to estimate the difference in the main biaxial stresses around the concentrator — a circular cutout in a rectangular plate.Materials and Methods. A 510×120×15 mm plate with a central hole of 40 mm in diameter was cut from a sheet of commercial-purity aluminum of the AMc brand (AW-3003 according to ISO) across the rolling direction, and subjected to uniaxial step loading in an Instron-8850 testing machine. For ultrasonic measurements, an acoustic sensor with a carrier frequency of 5 MHz was used. The stresses were calculated by solving the problem of stretching an isotropic linear-elastic plate in the ANSYS finite element modeling package and by the relations of the plane Kirsch problem obtained in the polar coordinate system.Results. The research allows us to state that the results of analytical and numerical calculations largely coincide only for points located near the zone of greatest stress concentration. In all other cases, the indicators differ several times in sign and modulus. The difference is explained by the fact that Kirsch's approach assumes the action of compressive stresses in the area of location of some points, but this factor is absent if we are talking about a real plate. It has been established that in the area of material with predominant tensile stresses, the acoustoelasticity method allows for a quantitative estimate of their difference with an error not exceeding the engineering one. Calculations based on the Kirsch relations correlate with the others only at points with the maximum concentration of tensile stresses.Discussion and Conclusion. The results of the study provide applying the acoustoelasticity method to estimate the magnitude of tensile biaxial stresses in the area around the fabrication holes. They are consistent with well-known scientific results and make it possible to rationally select the measurement points of acoustic anisotropy. The results of this scientific work can be applied in ultrasonic non-destructive testing using the acoustoelasticity method.

Molecular Investigation of SNAC as an Oral Peptide Permeation Enhancer in Lipid Membranes via Solid-State NMR.

Oral peptide therapeutics are increasingly favored in the pharmaceutical industry for their ease of use and better patient adherence. However, they face challenges with poor oral bioavailability due to their high molecular weight and surface polarity. Permeation enhancers (PEs) like salcaprozate sodium (SNAC) have shown promise in clinical trials, achieving about 1% bioavailability. One proposed mechanism for enhancing permeation is membrane perturbation or fluidization, though direct experimental proof and quantitative analysis of these effects are still needed. This study employs solid-state NMR (ssNMR) to investigate how SNAC interacts with hydrated DMPC liposomes, measuring enhancements in membrane fluidity across interfacial and transmembrane regions. The methodology involves analyzing phosphate lipid headgroups and acyl chains using static 31P chemical shift anisotropy and 2H quadrupolar coupling measurements alongside 1H and 13C magic angle spinning NMR for motional averaging of 1H-1H and 1H-13C dipolar couplings. Our findings indicate an overall increase in the uniaxial motion of phospholipids with SNAC in a PE concentration-dependent manner. It boosts lipid headgroup dynamics and enhancement plateaus at 25% between 24 and 72 mM concentrations. SNAC effectively enhances the fluidity of the hydrophobic center by 43% at 72 mM PE concentration, more significantly than the interfacial region. It is worth noting that the extent of liposome dissolution and conversion to micelles increases as SNAC concentration rises. Including a model peptide drug, octreotide, introduces a competitive equilibrium in this complex PE-lipid-peptide system, further influencing membrane dynamics for peptide permeation. Interestingly, the membrane enhancement does not show the expected plateau, and a less significant lipid mobility increase is observed in the presence of octreotide, suggesting a less substantial impact compared to peptide-free systems, which is likely due to peptide-PE interactions that consume monomeric SNAC, reducing its interaction with the lipid membrane. This study provides the first quantitative and site-specific ssNMR measurements of membrane mobility influenced by one representative PE as a snapshot of PE lipid interaction in a liposome model, demonstrating how peptide drugs modulate competitive equilibria and PE-induced lipid dynamics.

Modelling Small Vessel Disease Using Regional MRI Markers, and Mediating Effects on Cognitive Decline

AbstractBackgroundThe location of proposed brain MRI markers of small vessel disease (SVD) might reflect their pathogenesis and may translate into differential associations with cognition. We derived regional MRI markers of SVD and studied: (i) associations with cognitive performance, (ii) patterns most likely to reflect underlying SVD, (iii) mediating effects on the relationships of age and cardiovascular disease (CVD) risk with cognition.MethodIn 891 participants from The Multi‐Ethnic Study of Atherosclerosis, we segmented enlarged perivascular spaces (ePVS), white matter hyperintensities (WMH) and microbleeds (MBs) using deep learning‐based algorithms, and calculated white matter (WM) microstructural integrity measures of fractional anisotropy (FA), trace (TR) and free water (FW) using automated DTI‐processing pipelines. Measures of global and domain‐specific cognitive performance were derived from a comprehensive cognitive evaluation based on the UDS v3 neuropsychological battery.ResultMean (SD) age was 73.6 (7.9) years; 474 (53%) participants were women. In generalized linear models adjusted for demographics, vascular risk factors, and APOE ε4 carriership, higher basal ganglia ePVS count was associated with worse global, language, and attention cognitive performance (Table 1). Higher periventricular WMH volume was associated with worse global, delayed memory, language, phonemic, and attention performance. Higher WM FA was associated with better global, delayed memory, language, and attention performance. Higher WM TR was associated with worse global, delayed memory, language, phonemic, and attention performance. Exploratory factor analysis revealed that basal ganglia ePVS (standardized loading=0.51), thalamus ePVS (0.43), periventricular WMH (0.85), subcortical WMH (0.65), and WM FA (‐0.73) and TR (0.84) loaded onto the same factor, likely reflecting underlying SVD. Structural equation models demonstrated that SVD mediated the effect of age on cognition (β[95%CI]= ‐0.071[‐0.088,‐0.053]) through the pathways: Age→SVD→Cognition (‐0.044[‐0.063,‐0.026]) and Age→SVD→Brain Atrophy→Cognition (‐0.006[‐0.012,‐0.002]) – Figure 1, and the effect of CVD risk on cognition (‐0.028[‐0.044,‐0.012]) through the pathways: CVD Risk→SVD→Cognition (‐0.021[‐0.031,‐0.013]) and CVD Risk→SVD→Brain Atrophy→Cognition (‐0.007[‐0.012,‐0.003]) – Figure 2.ConclusionThe location of the proposed MRI markers of SVD likely reflects distinct etiopathogenic substrates and should be considered when examining associations with cognitive or other health‐related outcomes. SVD mediates the relationships of age and CVD risk with cognition via both atrophy‐related and unrelated pathways.

Neighborhood disadvantage is associated with compromised white matter microstructure among older adults over a 9‐year follow‐up period

AbstractBackgroundSocioeconomic neighborhood disadvantage has been linked to accelerated biological aging, cognitive decline, and core Alzheimer’s disease neuropathology independent of individual‐level factors. Our recent work indicates neighborhood disadvantage is also implicated in cerebrovascular changes known to exacerbate the development of AD, including neurovascular and hemodynamic dysfunction. Here, we investigated how neighborhood disadvantage relates to microstructural changes in white matter, a sensitive biomarker for emerging cerebrovascular disease and related neurodegeneration.MethodsVanderbilt Memory and Aging Project participants (n = 316, 73±7 years, 41% female) underwent 3T multimodal MRI serially over a 9‐year follow‐up period (mean follow‐up = 5.8 years). Area Deprivation Index (ADI), representing neighborhood disadvantage, was quantified at baseline based on 17 components (e.g., income, education, employment, housing conditions). Diffusion tensor imaging (DTI) data were acquired and post‐processed through an established tract‐based spatial statistics pipeline to generate fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD) measures. Linear regressions related baseline ADI to each DTI measure adjusting for age, sex, race/ethnicity, education, cognitive status, Framingham Stroke Risk Profile (minus age), and apolipoprotein ε4 status. Linear mixed effects regression models related baseline ADI to longitudinal changes in each DTI measure adjusting additionally for follow‐up time.ResultsIn cross‐sectional analyses, higher baseline ADI was related to lower AD in the cingulum tract (β = ‐3.16^‐07, p‐value = 0.04) but unrelated to other tracts examined (p‐values>0.08). In longitudinal analyses, higher baseline ADI was related to increased AD (β = 1.241^‐7, p‐value = 0.04), MD (β = 1.193^‐7, p‐value = 0.04), and RD (β = 1.150^‐7, p‐value = 0.05) in the fornix tract over time. Baseline ADI was unrelated to longitudinal changes in other tracts examined (p‐values>0.20).ConclusionsNeighborhood disadvantage relates to worse white matter integrity among older adults at study entry and over time, particularly in the fornix and other limbic white matter tracts. This observation is particularly noteworthy given the modest level of disadvantage seen in this cohort. Findings support the hypothesis that adverse environmental conditions, including low‐quality housing and community‐wide resource constraints, may promote white matter tract degradation reflective of early vascular dysfunction or neurodegeneration. Future studies should investigate biological and behavioral correlates mediating observed associations, including the role of social stressors, built environment, and access to high quality health resources.

A halo model approach to describe clustering and emission of the two main star-forming galaxy populations for cosmic infrared background studies

The cosmic infrared background (CIB), which is traced by the emission from dusty star-forming galaxies, provides a crucial window into the phases of star formation throughout cosmic history. These galaxies, although challenging to detect individually at high redshifts due to their faintness, cumulatively contribute to the CIB, which then becomes a powerful probe of galaxy formation, evolution, and clustering. Here, we introduce a physically motivated model for the CIB emission spanning a wide range of frequency and angular resolution, employing a halo model approach, and distinguishing, within dark matter halos, between two main populations of star-forming galaxies, namely normal late-type spiral and irregular galaxies, and the progenitors of early-type galaxies. The requirement to have two different galaxy populations is motivated by the dichotomy between elliptical and spiral galaxies observed in number counts. The emission from the two galaxy populations maps onto different regimes in frequency and resolution spaces. This allowed us to test an extended two-population CIB model and to constrain its clustering parameters – Mmin, the mass of a halo with 50% probability of having a central galaxy, and α, the power-law index regulating the number of satellite galaxies – through a fit to Planck and Herschel-SPIRE CIB anisotropy measurements. We find that while we were able to place constraints on some of the clustering parameters, the Planck frequency and multipole coverage cannot effectively disentangle the contributions from the two galaxy populations. On the other hand, the Herschel-SPIRE measurements separate out and constrain the clustering of both populations. Nonetheless, our work highlights an inconsistency of the results between the two data sets and therefore we are unable to provide a joint fit. This outcome has already been reported in other literature when fitting a single-population model and is still present in our extended scenario.

Connectivity in the Dorsal Visual Stream Is Enhanced in Action Video Game Players.

Action video games foster competitive environments that demand rapid spatial navigation and decision-making. Action video gamers often exhibit faster response times and slightly improved accuracy in vision-based sensorimotor tasks. Background/Objectives: However, the underlying functional and structural changes in the two visual streams of the brain that may be contributing to these cognitive improvements have been unclear. Methods: Using functional and diffusion MRI data, this study investigated the differences in connectivity between gamers who play action video games and nongamers in the dorsal and ventral visual streams. Results: We found that action video gamers have enhanced functional and structural connectivity, especially in the dorsal visual stream. Specifically, there is heightened functional connectivity-both undirected and directed-between the left superior occipital gyrus and the left superior parietal lobule during a moving-dot discrimination decision-making task. This increased connectivity correlates with response time in gamers. The structural connectivity in the dorsal stream, as quantified by diffusion fractional anisotropy and quantitative anisotropy measures of the axonal fiber pathways, was also enhanced for gamers compared to nongamers. Conclusions: These findings provide valuable insights into how action video gaming can induce targeted improvements in structural and functional connectivity between specific brain regions in the visual processing pathways. These connectivity changes in the dorsal visual stream underpin the superior performance of action video gamers compared to nongamers in tasks requiring rapid and accurate vision-based decision-making.

Rock Physics Modeling Studies on the Elastic and Anisotropic Properties of Organic-Rich Shale

Shale gas reservoirs have a large amount of resources, a wide range of burial, and great development potential. In order to evaluate the elastic properties of the shale, elastic wave velocity and anisotropy measurements of Longmaxi shale samples were carried out in the laboratory. Combined with the results of back scattering scanning electron microscopy (SEM) and digital mineral composition tests, the relationship between the anisotropy and the mineral components of the shale samples is discussed. It is found that the clay and kerogen combination distributed with an inorganic mineral background is the main cause of anisotropy. Then, the elastic properties of the organic-rich shale are analyzed with the anisotropic differential equivalent medium model (DEM). The clay and kerogen combination is established with kerogen as the background medium and clay mineral as the additive phase. The bond transformation is used to rotate the combination so that its directional arrangement is consistent with the real sedimentary situation of the stratum. Then, the clay and kerogen combination is added to the inorganic mineral matrix, with the organic and inorganic pores added to characterize the anisotropy of the shale to the greatest extent. It is found that the error between the wave velocity results calculated from the model and measured in the laboratory is less than 10%, which means the model is reliable. Finally, the effects of the microcracks and aspect ratio, kerogen content, and maturity on the elastic and anisotropic properties of shale rocks are simulated and analyzed with this model. The degree of anisotropy increases with the decrease in the pore aspect ratio and the increase in the microcracks content. The greater the kerogen content and maturity, the greater the anisotropy of rock. This study is of great significance for predicting the “sweet spot” of shale gas and optimizing hydraulic fracturing layers.

Exploring cognitive functions and brain structure in Hereditary Transthyretin amyloidosis using brain MRI and neuropsychological assessment.

Central nervous system symptoms, such as cognitive dysfunction, have been reported in Hereditary Transthyretin Amyloidosis (ATTRv). However, there is a lack of neuroimaging studies investigating structural alterations in the brain related to cognition in ATTRv amyloidosis. This study aimed to investigate cognition and cortical morphology in a cohort of ATTRv patients. 29 ATTRv patients and 26 healthy controls completed neuropsychological assessment. 21 of these patients underwent 3T brain MRI, and 23 healthy subjects constituted the control group for MRI. Cortical measures of volume, thickness, fractional anisotropy (FA), and mean diffusivity (MD) were obtained for both groups. Correlation analyses between brain and cognitive measurements were performed. Patients displayed worse performance than controls in executive functions, verbal and visual memory, visuospatial domains, and language tests. Our study indicated cortical thinning in ATTRv patients in the temporal, occipital, frontal, and parietal areas. The inferior temporal gyrus correlated with verbal memory. Insula and, pars opercularis correlated with both verbal memory and executive function. Cortical thickness in the inferior temporal gyrus, pars opercularis, and insula were linked to memory and executive function. We observed no correlations between cortical volume measures and cognition. Further investigations are imperative to confirm these findings across different populations.

Measuring and modelling directional effects in the frame of TIRAMISU (Thermal InfraRed Anisotropy Measurements in India and Southern eUrope)

Abstract. TRISHNA (Thermal infraRed Imaging Satellite for High-Resolution Natural resource Assessment) is a cross-purpose thermal infrared (TIR) Earth Observation (EO) mission designed to deliver images at high spatial (60 m) and temporal (3 days) resolutions. Its launch is foreseen in 2026 with a nominal mission duration of 5 years. This Indo-French polar-orbiting mission will overcome the limitations of thermal-optical observations from Landsat series and ASTER: low revisit, morning observations. TRISHNA scenes will be fully harnessed to pioneer the first cutting-edge high-resolution global maps of the land surface temperature (LST) and land surface emissivity (LSE) of natural and managed agroecosystems, man-made structures, water bodies, bare soils, rocks, snow, ice and sea. The quality of the preprocessing (radiometric calibration, atmospheric and directional corrections) is mandatory to satisfy the specifications with an expected precision of 1 K on LST in order to meet the targeted objectives. For such, it will be necessary to correct LST from directional effects with emphasis on the hot spot effect that can have an impact on LST up to several K. This is the goal of the TIRAMISU project to analyze TIR multiangular signatures over various biomes thanks to a pivoting system of cameras and a multi-model approach (1D, 3D, paramaterization). The modeling tools include 3 categories of models: SCOPE 1D, DART 3D and parametric BRDF models that are computationally efficient to perform inversion at global scale.

Large-scale Cosmic-ray Anisotropies with 19 yr of Data from the Pierre Auger Observatory

Results are presented for the measurement of large-scale anisotropies in the arrival directions of ultra–high-energy cosmic rays detected at the Pierre Auger Observatory during 19 yr of operation, prior to AugerPrime, the upgrade of the observatory. The 3D dipole amplitude and direction are reconstructed above 4 EeV in four energy bins. Besides the established dipolar anisotropy in R.A. above 8 EeV, the Fourier amplitude of the 8–16 EeV energy bin is now also above the 5σ discovery level. No time variation of the dipole moment above 8 EeV is found, setting an upper limit to the rate of change of such variations of 0.3% yr−1 at the 95% confidence level. Additionally, the results for the angular power spectrum are shown, demonstrating no other statistically significant multipoles. The results for the equatorial dipole component down to 0.03 EeV are presented, using for the first time a data set obtained with a trigger that has been optimized for lower energies. Finally, model predictions are discussed and compared with observations, based on two source emission scenarios obtained in the combined fit of spectrum and composition above 0.6 EeV.

Diffuse functional and structural abnormalities in fibrosis: Potential structural basis for sustaining atrial fibrillation

BackgroundStructural remodeling has been associated with increased incidence of atrial fibrillation, but how fibrotic regions allow atrial fibrillation to be sustained remains unclear. ObjectiveWith a novel transgenic goat model, we evaluated structural and functional differences between structurally remodeled and healthy regions of the atria. MethodsA novel transgenic goat model with cardiac-specific overexpression of transforming growth factor β1 was used. Ex vivo cardiac magnetic resonance imaging and histology were used to evaluate differences in fibrosis, fiber disarray, and structural anisotropy. Functional analysis examined conduction speeds and direction heterogeneity. By use of underlying fiber orientation obtained with diffusion tensor imaging, conduction anisotropy was calculated. ResultsThe transgenic goats had on average 21% of the left atria labeled fibrotic, determined from ex vivo cardiac magnetic resonance imaging. The histology samples within the labeled fibrotic regions showed an increase in fibrosis percentage. Fractional anisotropy, a measurement of structural anisotropy, was lower, whereas fiber direction heterogeneity, a measurement of the angle difference of the fiber from its neighbors, was greater, indicating increased fiber disarray in fibrotic regions. The fibrotic regions had slower conduction speeds and more aligned conduction directions, potentially allowing unidirectional conduction block to develop. Conduction anisotropy, measured on the underlying fiber directions, was found to be lower in the fibrotic regions. ConclusionFibrotic regions had slower conduction, and propagation tended to flow more unidirectionally. The direction of propagation differs from the underlying fiber direction, leading to lower conduction anisotropy. Functional and structural abnormalities of the fibrotic tissue may allow fibrotic regions to serve as a substrate for an arrhythmia to develop and to be sustained.

A Site-Wise Reliability Analysis of the ABCD Diffusion Fractional Anisotropy and Cortical Thickness: Impact of Scanner Platforms.

The Adolescent Brain and Cognitive Development (ABCD) project is the largest study of adolescent brain development. ABCD longitudinally tracks 11,868 participants aged 9-10 years from 21 sites using standardized protocols for multi-site MRI data collection and analysis. While the multi-site and multi-scanner study design enhances the robustness and generalizability of analysis results, it may also introduce nonbiological variances including scanner-related variations, subject motion, and deviations from protocols. ABCD imaging data were collected biennially within a period of ongoing maturation in cortical thickness and integrity of cerebral white matter. These changes can bias the classical test-retest methodologies, such as intraclass correlation coefficients (ICC). We developed a site-wise adaptive ICC (AICC) to evaluate the reliability of imaging-derived phenotypes while accounting for ongoing brain development. AICC iteratively estimates the population-level age-related brain development trajectory using a weighted mixed model and updates age-corrected site-wise reliability until convergence. We evaluated the test-retest reliability of regional fractional anisotropy (FA) measures from diffusion tensor imaging and cortical thickness (CT) from structural MRI data for each site. The mean AICC for 20 FA tracts across sites was 0.61 ± 0.19, lower than the mean AICC for CT in 34 regions across sites, 0.76 ± 0.12. Remarkably, sites using Siemens scanners consistently showed significantly higher AICC values compared with those using GE/Philips scanners for both FA (AICC = 0.71 ± 0.12 vs. 0.46 ± 0.17, p < 0.001) and CT (AICC = 0.80 ± 0.10 vs. 0.69 ± 0.11, p < 0.001). These findings demonstrate site-and-scanner related variations in data quality and underscore the necessity for meticulous data curation in subsequent association analyses.

Segmental abnormalities of white matter microstructure in multiple sclerosis and neuromyelitis optica spectrum disorder identified by automated fiber quantification

BackgroundMultiple sclerosis (MS) and neuromyelitis optica spectrum disorders (NMOSD) are different in pathogenesis, but both could lead to white matter (WM) microstructural damage. The aim of this study was to explore the differences in the patterns of WM fiber tract damage in relapsing-remitting MS (RRMS) and NMOSD by automated fiber quantification (AFQ). Materials and MethodsForty-one RRMS patients, 30 NMOSD patients and 30 healthy controls (HC) underwent MRI examination. AFQ was applied to identify and quantify 100 equally spaced nodes of specific WM fiber tracts for each participant. Measurements of fractional anisotropy (FA), mean diffusion (MD), axial diffusivity (AD) and radial diffusivity (RD) for each segment of a specific fiber tract were compared between RRMS, NMOSD and HC. ResultsThe decrease in FA was found in 7 fiber tracts in entire tract comparison and 9 fiber tracts in pointwise comparison in RRMS patients. However, the FA in left thalamic radiation (TR) and right uncinate fasciculus showed significant differences between RRMS and HC only in the pointwise comparison, but not in the entire tract comparison. The MD, AD and RD of WM fiber tracts in RRMS patients were extensively increased both in the entire level and in the pointwise level. NMOSD patients showed significant FA decrease in left TR and callosum forceps minor (CF_minor), and significant RD increase in CF_minor in the pointwise level. In the pointwise comparison between RRMS and NMOSD, significant FA decrease was found in right inferior fronto-occipital fasciculus and bilateral inferior longitudinal fasciculus in RRMS patients, focal or widespread MD, AD and RD increase was found in multiple fiber tracts. ConclusionThe AFQ approach is a more sensitive way to reflect WM microstructural abnormalities, revealing extensive WM microstructural damage in RRMS and limited WM fiber tract damage in NMOSD.

Stimulated echo acquisition mode (STEAM) diffusion tensor imaging with different diffusion encoding times in the supraspinatus muscle: Test-retest reliability and comparison to spin echo diffusion tensor imaging.

Diffusion tensor imaging (DTI) provides insight into the skeletal muscle microstructure and can be acquired using a stimulated echo acquisition mode (STEAM)-based approach to quantify time-dependent tissue diffusion. This study examined diffusion metrics and signal-to-noise ratio (SNR) in the supraspinatus muscle obtained with a STEAM-DTI sequence with different diffusion encoding times (Δ) and compared them to measures from a spin echo (SE) sequence. Ten healthy subjects (mean age 31.5 ± 4.7years; five females) underwent 3-Tesla STEAM and SE-DTI of the shoulder in three sessions. STEAM was acquired with Δ of 100/200/400/600 ms. The diffusion encoding time in SE scans was 19ms (b = 500s/mm2). Region of interest-based measurement of fractional anisotropy (FA), mean diffusivity (MD), and SNR was performed. Intraclass correlation coefficients (ICCs) were computed to assess test-retest reliability. ANOVA with post-hoc pairwise tests was used to compare measures between different Δ of STEAM as well as STEAM and SE, respectively. FA was significantly higher (FASTEAM: 0.38-0.46 vs. FASE: 0.26) and MD significantly lower (MDSTEAM: 1.20-1.33 vs. MDSE: 1.62×10-3mm2/s) in STEAM compared to SE (p < 0.001, respectively). SNR was significantly higher for SE (72.3 ± 8.7) than for STEAM (p < 0.001). ICCs were excellent for FA in STEAM (≥0.911) and SE (0.960). For MD, ICCs were good for STEAM100ms-600ms (≥0.759) and SE (0.752). STEAM and SE exhibited excellent reliability for FA and good reliability for MD in the supraspinatus muscle. SNR was significantly higher in SE compared to STEAM.

Decoupled deformation between crust and mantle beneath Indo-Burmese Wedge: A new seismotectonic model

Ongoing oblique convergence at the eastern margin of the Indo-Eurasian collision zone provides a natural laboratory for studying the deformation and dynamics of subduction beneath the Indo-Burmese Wedge (IBW). Here, we conduct the first comprehensive seismological investigations to understand the mechanical coupling between the crust and mantle beneath IBW using shear-wave splitting analysis and stress modeling. The deformation patterns in the crust signify a strong E-W compressional stress regime throughout IBW, with negligible influence from the major geological structures. These observations derived from local seismicity strongly support that the eastward active subduction of the Indian plate beneath the Burmese sliver is responsible for the crustal-scale deformation. Contrary to the crust, our splitting measurements from the mantle are in line with the major N-S trending arcs created by slip-partitioning due to transpressional oblique subduction. The splitting measurements with an N-S orientated fast axes and the estimated depth of the anisotropy source obtained from the spatial coherency of splitting parameters strongly suggest the presence of trench-parallel sub-slab flow system driven by slab retreat with westward trench migration, which can be the major controlling mechanism of the mantle deformation beneath IBW. Throughout the IBW, a significant change in the orientations of stress and splitting parameters between the crust and mantle supports a decoupled deformation scenario, implying the necessity of a new seismotectonic model. Our integrative study on the present stress patterns and decoupled deformation mechanism between crust and mantle combined with anisotropy measurements beneath the IBW suggests active subduction in the present scenario.