Microstructural Alterations Research Articles

Perinatal influences on academic achievement and the developing brain: a scoping systematic review.

In this PRISMA-compliant systematic review, we identify and synthesize the findings of research in which neuroimaging and assessments of achievement have been used to examine the relationships among aspects of developmental programming, neurodevelopment, and achievement in reading and mathematics. Forty-seven studies met inclusion criteria. The majority examined the impact of prematurity (n = 32) and prenatal alcohol exposure (n = 13). Several prematurity studies reported a positive correlation between white-matter integrity of callosal fibers and executive functioning and/or achievement, and white matter properties were consistently associated with cognitive and academic performance in preterm and full-term children. Volumetric studies reported positive associations between academic and cognitive abilities and white and gray matter volume in regions such as the insula, putamen, and prefrontal lobes. Functional MRI studies demonstrated increased right-hemispheric language processing among preterm children. Altered activation of the frontoparietal network related to numerical abilities was also reported. Prenatal alcohol exposure studies reported alterations in white matter microstructure linked to deficits in cognitive functioning and academic achievement, including mathematics, reading, and vocabulary skills. Volumetric studies reported reductions in cerebral, cerebellar, and subcortical gray matter volumes associated with decreased scores on measures of executive functioning, attention, working memory, and academic performance. Functional MRI studies demonstrated broad, diffuse activation, reduced activation in canonical regions, and increased activation in non-canonical regions during numeric tasks. A preponderance of studies linked prematurity and prenatal alcohol exposure to altered neurodevelopmental processes and suboptimal academic achievement. Limitations and recommendations for future research are discussed. Identifier: DOI 10.17605/OSF.IO/ZAN67.

A multiscale finite element modeling for predicting the surface integrity induced by thermo-mechanical loads during high-speed milling of Ti-6Al-4V

High-speed milling (HSM) of Ti-6Al-4V is subjected to complex thermo-mechanical loads, leading to alteration in metallurgical conditions within the cutting deformation zones, adversely impacting the mechanical performances of manufactured products. Hence, inclusive insight into microstructural alterations within the Adiabatic Shear Band (ASB) and the milled surface becomes essential for better service performance. This study first developed a Finite Element (FE) milling model to simulate the machining process of Ti-6Al-4V. The proposed FE model is validated through experimental results regarding cutting forces (CFs), cutting temperature (CT), and chip geometry, where the absolute relative error between simulations and experiments was less than 15 %. Secondly, Zenner-Holloman (Z-H) and Hall-Petch (H-P) equations were incorporated into a user-defined subroutine to simulate dynamic recrystallization (DRX) for grain size and microhardness prediction. Simulation results revealed that the grains became finer in the ASB than on the milled surface. In particular, when the cutting speed and feed rate were increased to 350 m/min and 0.30 mm/tooth, the grain size in the ASB decreased from 14 to 0.68 and 0.44 µm, while in the topmost milled surface, it reduced to 7.06 and 6.75 µm, respectively. Conversely, microhardness exhibited an inverse correlation with grain size and increased with cutting speed and feed rate. Furthermore, the impact of increased plastic strain and temperature on the grains during chip segmentation was also examined. Finally, the proposed FE model validity was established by comparing simulated results with experimental data using advanced characterization techniques. This research significantly contributes to a comprehensive understanding of microstructural evolution and its implications for the mechanical performance of machined titanium components.

The influence of trace vanadium on the solidification process, microstructure, and mechanical properties of gray cast iron

This study employed optical microscopy (OM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) to investigate the impact of vanadium (V) on the microstructure and mechanical properties of gray cast iron (GCI) HT250. Additionally, Thermo-Calc software was employed to explore the influence of V on the solidification process. The results indicate that adding trace amounts of V in GCI forms a face-centered cubic VC phase, with the precipitation temperature of the VC phase gradually increasing. When the V content reaches 0.28 wt%, the VC phase begins to precipitate during the eutectic reaction. The incorporation of V consumes carbon, reducing the graphite content and promoting the formation of type D graphite. As the V content increases, there is an enlargement in the pearlite area ratio, a decrease in the pearlite layer spacing, and a reduction in the size of eutectic cells. These microstructural alterations lead to enhanced mechanical properties. The tensile strength peaks at 336 MPa with a V content of 0.77 wt%, representing a 29% increase compared to samples without added V. Similarly, the Vickers hardness increases with increasing V content, reaching a peak of 373 HV at 0.92 wt% V, a 27% increase compared to samples without V addition. However, at this point, the tensile strength decreases to 322 MPa.

Optical-resolution photoacoustic microelastography system for elasticity mapping: Phantom study and practical application.

Elastography is a noninvasive technique for characterizing the mechanical properties of biological tissues. Conventional methods have limitations in resolution and sensitivity, hindering disease detection in clinical diagnostics. To address these issues, this study developed an optical-resolution photoacoustic microelastography (OR-PAME) system. Using an agar tissue phantom with varying agar concentrations and contrast agents, PAME evaluated elasticity distribution under compression in both lateral and axial dimensions. It indirectly measured elastic properties by correlating photoacoustic responses, temporal lags, and induced displacement. We also applied the system to the study of the distribution of elastic characteristics of the liver tissue after ablation, which confirmed the potential of OR-PAME in the study of elastic characteristics. Quantitative analysis showed greater lateral displacement in regions with reduced agar concentrations, indicating decreased stiffness. PAME also detected vertical displacement along the axial plane, validating its efficacy in elastographic imaging. By improving resolution and penetration, PAME provides superior visualization of elasticity distribution. Its methodology correlates microstructural alterations with tissue biomechanics, holding potential implications in medical diagnostics.

Mechanical characterization of porcine ureter for the evaluation of tissue-engineering applications.

Introduction: Clinics increasingly require readily deployable tubular substitutes to restore the functionality of structures like ureters and blood vessels. Despite extensive exploration of various materials, both synthetic and biological, the optimal solution remains elusive. Drawing on abundant literature experiences, there is a pressing demand for a substitute that not only emulates native tissue by providing requisite signals and growth factors but also exhibits appropriate mechanical resilience and behaviour. Methods: This study aims to assess the potential of porcine ureters by characterizing their biomechanical properties in their native configuration through ring and membrane flexion tests. In order to assess the tissue morphology before and after mechanical tests and the eventual alteration of tissue microstructure that would be inserted in material constitutive description, histological staining was performed on samples. Corresponding computational analyses were performed to mimic the experimental campaign to identify the constitutive material parameters. Results: The absence of any damages to muscle and collagen fibres, which only compacted after mechanical tests, was demonstrated. The experimental tests (ring and membrane flexion tests) showed non-linearity for material and geometry and the viscoelastic behaviour of the native porcine ureter. Computational models were descriptive of the mechanical behaviour ureteral tissue, and the material model feasible. Discussion: This analysis will be useful for future comparison with decellularized tissue for the evaluation of the aggression of cell removal and its effect on microstructure. The computational model could lay the basis for a reliable tool for the prediction of solicitation in the case of tubular substitutions in subsequent simulations.

Posttraumatic survivor guilt is associated with white matter microstructure alterations

BackgroundMilitary veterans with posttraumatic stress disorder (PTSD) commonly experience posttraumatic guilt. Guilt over commission or omission evolves when responsibility is assumed for an unfortunate outcome (e.g., the death of a fellow combatant). Survivor guilt is a state of intense emotional distress experienced by the weight of knowing that one survived while others did not. MethodsThis study of the Translational Research Center for TBI and Stress Disorders (TRACTS) analyzed structural and diffusion-weighted magnetic resonance imaging data from 132 male Iraq/Afghanistan veterans with PTSD. The Clinician-Administered PTSD Scale for DSM-IV (CAPS-IV) was employed to classify guilt. Thirty (22.7 %) veterans experienced guilt over acts of commission or omission, 34 (25.8 %) experienced survivor guilt, and 68 (51.5 %) had no posttraumatic guilt. White matter microstructure (fractional anisotropy, FA), cortical thickness, and cortical volume were compared between veterans with guilt over acts of commission or omission, veterans with survivor guilt, and veterans without guilt. ResultsVeterans with survivor guilt had significantly lower white matter FA compared to veterans who did not experience guilt (p < .001), affecting several regions of major white matter fiber bundles. There were no significant differences in white matter FA, cortical thickness, or volumes between veterans with guilt over acts of commission or omission and veterans without guilt (p > .050). LimitationsThis cross-sectional study with exclusively male veterans precludes inferences of causality between the studied variables and generalizability to the larger veteran population that includes women. ConclusionSurvivor guilt may be a particularly impactful form of posttraumatic guilt that requires specific treatment efforts targeting brain health.

Topological abnormalities of the morphometric similarity network of the cerebral cortex in schizophrenia

A morphometric similarity (MS) network can be constructed using multiple magnetic resonance imaging parameters of each cortical region. An MS network can be used to assess the similarity between cortical regions. Although MS networks can detect microstructural alterations and capture connections between histologically similar cortical areas, the influence of schizophrenia on the topological characteristics of MS networks remains unclear. We obtained T1- and diffusion-weighted images of 239 healthy controls and 190 individuals with schizophrenia to construct the MS network. Group comparisons of the mean MS of the cortical regions and subnetworks were performed. The strengths of the connections between the cortical regions and the global and nodal network indices were compared between the groups. Clinical associations with the network indices were tested using Spearman’s rho. Compared with healthy controls, individuals with schizophrenia had significant group differences in the mean MS of several cortical regions and subnetworks. Individuals with schizophrenia had both superior and inferior strengths of connections between cortical regions compared with those of healthy controls. We observed regional abnormalities of the MS network in individuals with schizophrenia regarding lower centrality values of the pars opercularis, superior frontal, and superior temporal areas. Specific nodal network measures of the right pars opercularis and left superior temporal areas were associated with illness duration in individuals with schizophrenia. We identified regional abnormalities of the MS network in schizophrenia with the left superior temporal area possibly being a key region in topological organization and cortical connections.

Microstructural alterations of coal induced by interaction with sequestered supercritical carbon dioxide

A total of four samples with different coal ranks were exposed to supercritical CO2 (SC–CO2) fluids for one week at 313.15 K and 12 MPa. FTIR and X-ray diffraction were combined to explore the changes in functional groups, mineral compositions and aromatic microcrystallite structures of coal samples before and after SC-CO2 interaction. The results indicate that a great number of aliphatic hydrocarbons in coal are extracted and the content is reduced by 47.83–83.08 %, whereas the oxygen-containing groups are slightly changed within 8 %. The content of carbonate minerals is decreased by 29.05–46.11 % after SC-CO2 saturation, while quartz content is enhanced. The changes in coal crystalline structures are attributed to the mineral dissolution and hydrocarbon extraction during SC-CO2 saturation. Numerous voids are generated among aromatic layers after mineral dissolution, which directly enlarges the layer spacing of aromatic sheets. The extraction of aliphatic hydrocarbons can not only further increase layer spacing, but also loosen the coal macromolecular structure. Consequently, the directional alignment of aromatic microcrystallites is reduced within coal, leading to the decline of stacking height and aromatic layers. These findings are of significance for assessing both the recovery of CO2-enhanced coalbed methane and the trapping of CO2 in coal reservoirs.

Assessment of Gray Matter Microstructural Alterations in Alzheimer's Disease by Free Water Imaging.

Cortical neurodegenerative processes may precede the emergence of disease symptoms in patients with Alzheimer's disease (AD) by many years. No study has evaluated the free water of patients with AD using gray matter-based spatial statistics. The aim of this study was to explore cortical microstructural changes within the gray matter in AD by using free water imaging with gray matter-based spatial statistics. Seventy-one participants underwent multi-shell diffusion magnetic resonance imaging, 11C-Pittsburgh compound B positron emission tomography, and neuropsychological evaluations. The patients were divided into two groups: healthy controls (n = 40) and the AD spectrum group (n = 31). Differences between the groups were analyzed using voxel-based morphometry, diffusion tensor imaging, and free water imaging with gray matter-based spatial statistics. Voxel-based morphometry analysis revealed gray matter volume loss in the hippocampus of patients with AD spectrum compared to that in controls. Furthermore, patients with AD spectrum exhibited significantly greater free water, mean diffusivity, and radial diffusivity in the limbic areas, precuneus, frontal lobe, temporal lobe, right putamen, and cerebellum than did the healthy controls. Overall, the effect sizes of free water were greater than those of mean diffusivity and radial diffusivity, and the larger effect sizes of free water were thought to be strongly correlated with AD pathology. This study demonstrates the utility of applying voxel-based morphometry, gray matter-based spatial statistics, free water imaging and diffusion tensor imaging to assess AD pathology and detect changes in gray matter.

Quantifying intergranular corrosion susceptibility in AA2098‐T351 weldments through friction stir welding

AbstractIn this study, the intergranular corrosion (IGC) susceptibility of AA2098‐T351 welds, fabricated through friction stir welding (FSW), was systematically evaluated. The evaluation employed American Society for Testing and Materials (ASTM) G110‐92 practice and electrochemical impedance measurements, with comparative analyses against unwelded alloys (BS). The key findings depicted that FSW‐induced microstructure changes significantly influenced IGC susceptibility across different zones. Zones affected by FSW presented distinct susceptibilities compared with the base metal (BM). The ASTM G110‐92 test effectively differentiated the heat‐affected zone (HAZ) into segments with changing corrosion resistances based on welding temperature gradients. Cross‐sectional analyses using scanning electron microscopy (SEM) techniques correlated corrosion characteristics with microstructural features identified by transmission electron microscopy (TEM). Overall, FSW‐induced microstructural alterations emerged as a predominant factor influencing the varying susceptibilities of different zones to IGC, and electrochemical impedance measurements (EIS) validated the findings from ASTM G110‐92 practice.

Enhancing rheology and reducing lipid digestion of oil-in-water emulsions using controlled aggregation and heteroaggregation of soybean protein isolate-peach gum microspheres

There is a growing interest in developing highly viscous lipid foods using plant protein and polysaccharide gum-based emulsion technology. However, gaps remain in understanding the rheological, microstructural, and digestive properties of plant proteins like soybean protein isolate (SPI) in combination with various gums. This study investigates how combining SPI and peach gum (PG) affects rheology and lipolysis of oil-in-water (O/W) emulsions containing 20 wt% soybean oil. Emulsions with varying SPI and PG compositions including SPI-PG single and SPI/PG mixed droplet systems were prepared. Heating induced alterations in viscosity (e.g., SPI-PG from 14.88 to 90.27 Pa·s and SPI/PG from 9.66 to 85.32 Pa·s) and microstructure revealing aggregate formation at oil-water interface. The viscosity decreased significantly from the oral to intestinal phase (SPI-PG: 28.10 to 0.19 Pa·s, SPI/PG: 21.27 to 0.10 Pa·s). These changes affected lipid digestion, notably in SPI-PG and SPI/PG emulsions where a compact interface hindered lipolysis during digestion. Interestingly, free fatty acid (FFA) release during small intestinal phase followed a different order: SPI (82.51 %) > SPI-PG (70.77 %) > SPI/PG (63.60 %) > PG (56.09 %). This study provides insights into creating highly viscous O/W spreads with improved rheology, stability, and delayed lipid digestion, offering potential benefits in food product formulation.

Backside metallization affects residual stress and bending strength of the recast layer in laser-diced Si

Thin Silicon dies separated by laser dicing form a thin layer via redeposition of ablated silicon known as recast layer. This work analyzed the influence of the recast layer microstructure and nanoscale residual stress gradients on the bending strength of bare and metalized silicon dies <100 μm. Scanning and transmission electron microscopy revealed an intricate microstructure of ablated silicon and elements of the wafer backside metallization within the recast layer. Refined silicon grains decorated by nanoscopic metallic precipitates at their grain boundaries were observed. Cross-sectional synchrotron X-ray nanodiffraction revealed that the altered microstructure increased the tensile residual stress from 200 to 295 MPa for bare and metalized dies, respectively. Additionally, the metalized die exhibited gradients in residual stress and grain size between the die front- and backside. Despite their similar frontside bending strengths of ∼340 MPa, observed in 3-point bending experiments, a considerable strengthening of the backside from 425 up to 957 MPa was measured for bare and metalized die, respectively. The origins of the tensile residual stress and the influence of the backside metallization on the die bending strength are discussed.

Quantitative cellular pathology of the amygdala in temporal lobe epilepsy and correlation with magnetic resonance imaging volumetry, tissue microstructure, and sudden unexpected death in epilepsy risk factors.

Amygdala enlargement can occur in temporal lobe epilepsy, and increased amygdala volume is also reported in sudden unexpected death in epilepsy (SUDEP). Apnea can be induced by amygdala stimulation, and postconvulsive central apnea (PCCA) and generalized seizures are both known SUDEP risk factors. Neurite orientation dispersion and density imaging (NODDI) has recently provided additional information on altered amygdala microstructure in SUDEP. In a series of 24 surgical temporal lobe epilepsy cases, our aim was to quantify amygdala cellular pathology parameters that could predict enlargement, NODDI changes, and ictal respiratory dysfunction. Using whole slide scanning automated quantitative image analysis methods, parallel evaluation of myelin, axons, dendrites, oligodendroglia, microglia, astroglia, neurons, serotonergic networks, mTOR-pathway activation (pS6) and phosphorylated tau (pTau; AT8, AT100, PHF) in amygdala, periamygdala cortex, and white matter regions of interest were compared with preoperative magnetic resonance imaging data on amygdala size, and in 13 cases with NODDI and evidence of ictal-associated apnea. We observed significantly higher glial labeling (Iba1, glial fibrillary acidic protein, Olig2) in amygdala regions compared to cortex and a strong positive correlation between Olig2 and Iba1 in the amygdala. Larger amygdala volumes correlated with lower microtubule-associated protein (MAP2), whereas higher NODDI orientation dispersion index correlated with lower Olig2 cell densities. In the three cases with recorded PCCA, higher MAP2 and pS6-235 expression was noted than in those without. pTau did not correlate with SUDEP risk factors, including seizure frequency. Histological quantitation of amygdala microstructure can shed light on enlargement and diffusion imaging alterations in epilepsy to explore possible mechanisms of amygdala dysfunction, including mTOR pathway activation, that in turn may increase the risk for SUDEP.

Deep Rolling Techniques: A Comprehensive Review of Process Parameters and Impacts on the Material Properties of Commercial Steels

The proposed review demonstrates the effect of the surface modification process, specifically, deep rolling, on the material surface/near-surface properties of commercial steels. The present research examines the various process parameters involved in deep rolling and their effects on the material properties of AISI 1040 steel. Key parameters such as the rolling force, feed rate, number of passes, and roller geometry are analyzed in detail, considering their influence on residual stress distribution, surface hardness, and microstructural alterations. Additionally, the impact of deep rolling on the fatigue life, wear resistance, and corrosion behavior of AISI 1040 steel is discussed. Engineering components manufactured by AISI 1040 steel can perform better and last longer when deep rolling treatments are optimized with an understanding of how process variables and material responses interact. This review provides critical insights for researchers and practitioners interested in harnessing deep rolling techniques to enhance the mechanical strength and durability of steel components across diverse industrial settings. In summary, the valuable insights provided by this review pave the way for continued advancements in deep rolling techniques, ultimately contributing to the development of more durable, reliable, and high-performance steel components in diverse industrial applications. The establishment of generalized standardizations for the deep rolling process proves unfeasible because of the multitude of controlling parameters and their intricate interactions. Thus, specific optimization studies tailored to the material of interest are imperative for process standardization. The published literature on the characterization of surface and subsurface properties of deep-rolled AISI 1040 steel, as well as process parameter optimization, remains limited. Additionally, numerical, analytical, and statistical studies and the role of ANN are limited compared with experimental work on the deep rolling process.

Excessive interstitial free-water in cortical gray matter preceding accelerated volume changes in individuals at clinical high risk for psychosis.

Recent studies show that accelerated cortical gray matter (GM) volume reduction seen in anatomical MRI can help distinguish between individuals at clinical high risk (CHR) for psychosis who will develop psychosis and those who will not. This reduction is suggested to represent atypical developmental or degenerative changes accompanying an accumulation of microstructural changes, such as decreased spine density and dendritic arborization. Detecting the microstructural sources of these changes before they accumulate into volume loss is crucial. Our study aimed to detect these microstructural GM alterations using diffusion MRI (dMRI). We tested for baseline and longitudinal group differences in anatomical and dMRI data from 160 individuals at CHR and 96 healthy controls (HC) acquired in a single imaging site. Of the CHR individuals, 33 developed psychosis (CHR-P), while 127 did not (CHR-NP). Among all participants, longitudinal data was available for 45 HCs, 17 CHR-P, and 66 CHR-NP. Eight cortical lobes were examined for GM volume and GM microstructure. A novel dMRI measure, interstitial free water (iFW), was used to quantify GM microstructure by eliminating cerebrospinal fluid contribution. Additionally, we assessed whether these measures differentiated the CHR-P from the CHR-NP. In addition, for completeness, we also investigated changes in cortical thickness and in white matter (WM) microstructure. At baseline the CHR group had significantly higher iFW than HC in the prefrontal, temporal, parietal, and occipital lobes, while volume was reduced only in the temporal lobe. Neither iFW nor volume differentiated between the CHR-P and CHR-NP groups at baseline. However, in many brain areas, the CHR-P group demonstrated significantly accelerated changes (iFW increase and volume reduction) with time than the CHR-NP group. Cortical thickness provided similar results as volume, and there were no significant changes in WM microstructure. Our results demonstrate that microstructural GM changes in individuals at CHR have a wider extent than volumetric changes or microstructural WM changes, and they predate the acceleration of brain changes that occur around psychosis onset. Microstructural GM changes, as reflected by the increased iFW, are thus an early pathology at the prodromal stage of psychosis that may be useful for a better mechanistic understanding of psychosis development.

Practical considerations for birefringence microscopy of myelin structure: Microscope design and tissue processing for effective imaging

Abstract Despite the interest in studying and quantifying the structural integrity of myelin in postmortem brain tissue, current methods for high-resolution imaging of myelin with optical microscopy are not sufficient. While imaging methods must have adequate resolution and sensitivity to detect microstructural alterations to myelin that are relevant in aging and neurodegenerative disease, an equally critical aspect is to minimize myelin damage that is induced during tissue processing steps. Birefringence microscopy (BRM) is a powerful technique that leverages the structural anisotropy of myelin to provide detailed, label-free images of myelin at any diffraction-limited optical resolution, while maintaining a simple and low-cost setup. Building on our previous work, we have developed a new BRM system and image processing pipeline that enable efficient, high-throughput imaging of myelin structure at multiple scales. Here, we utilize this system to systematically assess the damage to myelin that is induced by several common tissue processing steps in brain sections from the rhesus monkey. Images taken of the same myelinated axons, before and after each tissue processing step, provide direct evidence that mishandling of tissue during sample preparation can cause significant structural alterations to myelin. First, we report on key advancements to our BRM system, imaging procedure, and image processing pipeline, which provide significant increases to the speed and efficiency of BRM. These include integrating fast piezoelectric rotational stages, minimizing the number of images required (to three images) for determining birefringence parameter maps, and implementing an analytical solution for directly determining birefringence parameter maps. Second, using this BRM system, we demonstrate that effective myelin imaging requires (1) the avoidance of prolonged drying or dehydration of tissue, (2) the selection of the optimal mounting medium (85% glycerol), (3) the avoidance of tissue permeabilization with detergents (i.e., Triton X-100 and Saponin), and (4) the selection of a suitable tissue-section thickness (15, 30 and 60 µm) based on the region of interest. In addition to serving as a guide for new users interested in imaging myelin, these basic experiments in sample preparation highlight that BRM is very sensitive to changes in the underlying lipid structure of myelin and suggest that optimized BRM can enable new studies of myelin breakdown in disease. In this work, we show that BRM is a leading method for detailed imaging and characterization of myelin, and we provide direct evidence that the structure of myelin is highly sensitive to damage during inadequate preparation of brain tissue for imaging, which has previously not been properly characterized for birefringence imaging of myelin. For the most effective, high-resolution imaging of myelin structure, tissue processing should be kept to a minimum, with sections prevented from dehydration and mounted in 85% glycerol. With proper preservation of myelin structure, BRM provides exquisitely detailed images that facilitate the assessment of myelin pathology associated with injury or disease.

Decoding Early Psychoses: Unraveling Stable Microstructural Features Associated With Psychopathology Across Independent Cohorts

BackgroundPatients with early psychosis (EP) (within 3 years after psychosis onset) show significant variability, which makes predicting outcomes challenging. Currently, little evidence exists for stable relationships between neural microstructural properties and symptom profiles across EP diagnoses, which limits the development of early interventions. MethodsA data-driven approach, partial least squares correlation, was used across 2 independent datasets to examine multivariate relationships between white matter properties and symptomatology and to identify stable and generalizable signatures in EP. The primary cohort included patients with EP from the Human Connectome Project for Early Psychosis (n = 124). The replication cohort included patients with EP from the Feinstein Institute for Medical Research (n = 78) as part of the MEND (Multimodal Evaluation of Neural Disorders) Project. Both samples included individuals with schizophrenia, schizoaffective disorder, and psychotic mood disorders. ResultsIn both cohorts, a significant latent component corresponded to a symptom profile that combined negative symptoms, primarily diminished expression, with specific somatic symptoms. Both latent components captured comprehensive features of white matter disruption, primarily a combination of subcortical and frontal association fibers. Strikingly, the partial least squares model trained on the primary cohort accurately predicted microstructural features and symptoms in the replication cohort. Findings were not driven by diagnosis, medication, or substance use. ConclusionsThis data-driven transdiagnostic approach revealed a stable and replicable neurobiological signature of microstructural white matter alterations in EP across diagnoses and datasets, showing strong covariance of these alterations with a unique profile of negative and somatic symptoms. These findings suggest the clinical utility of applying data-driven approaches to reveal symptom domains that share neurobiological underpinnings.

Quantification of microscale factors for fatigue failure in NiTi shape memory alloys

Fatigue behavior is intrinsically linked to microstructural alterations induced by cyclic loading. However, the quantification of microstructural defects associated with fatigue damage of NiTi shape memory alloys (SMAs) is lacking, which hinders the development of a physically based fatigue criterion. To this end, a multi-scale experimental analysis was conducted on cyclically deformed NiTi SMAs, which evidenced a strong correlation between microstructural inhomogeneity and localized deformation behavior. The microstructural change associated with fatigue was quantified in terms of stored strain–energy, with the highest values observed in the regions where fatigue cracks initiate. Consequently, stored energy is deemed as an effective fatigue indicator, offering valuable insights for future work in the design and optimization of SMAs’ structures against fatigue.

Differences in cortical microstructure according to body mass index in neurologically healthy populations using structural magnetic resonance imaging

Associations between brain structure and body mass index (BMI) are increasingly gaining attention. Although BMI-related regional alterations in brain morphology have been previously reported, the effect of BMI on the microstructural profiles, which provide information on the proxy of neuronal density within the cortex, is unexplored. In this study, we investigated the links between cortical layer-specific microstructural profiles and BMI in 302 neurologically healthy young adults. Using the microstructure-sensitive proxy based on the T1-and T2-weighted ratio, we estimated microstructural profile covariance (MPC) by calculating linear correlations of cortical depth-wise intensity profiles between different brain regions. Then, low-dimensional gradients of the MPC matrix were estimated using dimensionality reduction techniques, and the gradients were associated with BMI. Significant effects in the heteromodal association areas were observed. The BMI-gradient association map was related to the geodesic distance along the cortical surface, curvature, and sulcal depth, suggesting that the microstructural alterations occurred along the cortical topology. The BMI-gradient association map was further linked to cognitive states related to negative emotions. Our findings may provide insights into understanding the atypical cortical microstructure associated with BMI.

Antidepressant-related microstructural changes in the external capsule.

Several magnetic resonance imaging (MRI) studies have reported that antidepressant medications are strongly linked to brain microstructural alterations. Notably, external capsule alterations have been reported to be a biological marker for therapeutic response. However, prior studies did not investigate whether a change in the neurite density or directional coherence of white matter (WM) fibers underlies the observed microstructural alterations. This MRI-based case-control study examined the relationship between patients' current use of antidepressant medications and advanced measurements of external capsule WM microstructure derived from multishell diffusion imaging using neurite orientation dispersion and density imaging (NODDI). The study compared a group of thirty-five participants who were taking antidepressant medications comprising selective serotonin reuptake inhibitors (SSRIs) (n = 25) and serotonin and norepinephrine reuptake inhibitors (SNRIs) with a control group of thirty-five individuals matched in terms of age, sex, race, and atherosclerotic cardiovascular risk factors. All participants were selected from the Dallas Heart Study phase 2, a multi-ethnic, population-based cohort study. A series of multiple linear regression analyses were conducted to predict microstructural characteristics of the bilateral external capsule using age, sex, and antidepressant medications as predictor variables. There was significantly reduced neurite density in the bilateral external capsules of patients taking SSRIs. Increased orientation dispersion in the external capsule was predominantly seen in patients taking SNRIs. Our findings suggest an association between specific external capsule microstructural changes and antidepressant medications, including reduced neurite density for SSRIs and increased orientation dispersion for SNRIs.