Fiber Clustering Research Articles

Fiber dispersion as a quality assessment metric for pultruded thermoplastic composites

Fiber-reinforced polymer composites are often assessed by measuring void content via thresholding of optical microscope cross-sectional images, relying on contrast to differentiate between voids and surrounding material. This is effective when dealing with primarily closed voids, a characteristic common to thermoset matrix composites. However, composites that exhibit fiber impregnation issues, often due to high matrix viscosity as in thermoplastic composites, will typically contain open pores which are infiltrated by the mounting resin used to embed the sample for grinding and polishing. Voids filled with this resin can be difficult to optically distinguish from the matrix, leading to inaccurate void content measurements. To circumvent this, a strategy for assessing impregnation quality based on fiber dispersion is proposed. During impregnation processes, the fiber network exhibits a tendency to become locally compacted by flow fronts, leading to low permeability regions with fiber clusters that are less likely to become fully impregnated. Fiber dispersion quantifies the percentage of non-clustered fibers from positional data and provides information on degree of impregnation and the locations of interfiber voids. The effects of processing speed and temperature on fiber dispersion are investigated in the production of continuous carbon fiber-reinforced polyetherimide (PEI) additive manufacturing feedstock material from commingled yarn using multi-die pultrusion. Fiber dispersion is observed to increase with slower pultrusion speeds, correlating with higher flexural strength and stiffness properties. This increase in fiber dispersion with longer die residency time indicates that the decompaction of fiber clusters is highly time-dependent and occurs by migration of fibers away from cluster boundaries.

Film Thickness Decay and Wear Behavior of Grease-Lubricated Point Contact under Cyclic Variable Loads

For wind turbine applications, there is a cyclic load-varying process between rolling elements and raceways in pitch bearings. This kind of motion can also lead to radial fretting. However, this is seldom addressed under grease-lubricated conditions in the literature. In this study, grease-lubricated point contact problems have been investigated experimentally under cyclic load-varying conditions. The findings revealed that as the load-varying range diminishes, the variation in grease film distribution becomes more subtle and the rate of discharge of thickener fiber clusters in the stick zone decelerates. This is due to the fact that the rate of change in the Hertz contact radius is reduced and the migration of grease is weakened during the unloading process. Due to the large apparent viscosity of grease with a high soap content, entrapped grease is not easily discharged during loading, and the thickness of the film in the stick zone progressively increases as the soap content of the grease is augmented. This also causes the variable load zone to wear out more easily. As the grease is subjected to repeated loading and unloading, there is a gradual reduction in film thickness, and larger thickener fiber clusters tear, resulting in a flattened form and shear thinning. Grease containing sulphur–phosphorus additives demonstrates a superior effect on reducing fretting wear within the large variable load range but generally proves effective for smaller load-varying ranges. This study may offer insights into the degradation of grease under variable load motion and methods to prevent radial fretting wear.

PhyberSIM: a tool for the generation of ground truth to evaluate brain fiber clustering algorithms.

Diffusion Magnetic Resonance Imaging tractography is a non-invasive technique that produces a collection of streamlines representing the main white matter bundle trajectories. Methods, such as fiber clustering algorithms, are important in computational neuroscience and have been the basis of several white matter analysis methods and studies. Nevertheless, these clustering methods face the challenge of the absence of ground truth of white matter fibers, making their evaluation difficult. As an alternative solution, we present an innovative brain fiber bundle simulator that uses spline curves for fiber representation. The methodology uses a tubular model for the bundle simulation based on a bundle centroid and five radii along the bundle. The algorithm was tested by simulating 28 Deep White Matter atlas bundles, leading to low inter-bundle distances and high intersection percentages between the original and simulated bundles. To prove the utility of the simulator, we created three whole-brain datasets containing different numbers of fiber bundles to assess the quality performance of QuickBundles and Fast Fiber Clustering algorithms using five clustering metrics. Our results indicate that QuickBundles tends to split less and Fast Fiber Clustering tends to merge less, which is consistent with their expected behavior. The performance of both algorithms decreases when the number of bundles is increased due to higher bundle crossings. Additionally, the two algorithms exhibit robust behavior with input data permutation. To our knowledge, this is the first whole-brain fiber bundle simulator capable of assessing fiber clustering algorithms with realistic data.

Highly loaded carbon fiber filaments for 3D‐printed composites

AbstractComposites play progressively significant roles across a spectrum of applications involving high‐performance materials and products within industries such as aerospace, naval, automotive, construction, missiles, and defense technology. Notably, oriented fiber composites have garnered substantial attention due to their advantageous attributes like a high strength‐to‐weight ratio and controlled anisotropy. Nonetheless, challenges persist in uneven fiber alignment, fiber clustering within the matrix material, and constraints on fiber volume, impeding the mass production of oriented fiber‐reinforced composites. In this study, we present a novel approach to 3D printing of uniformly aligned short fiber reinforcement in a composite of heavily loaded carbon and nylon. Capitalizing on the additive manufacturing potential of rapidity and precision, the extrusion process induces carbon fiber (CF) alignments in filaments via shear forces. The 3D‐printed structures that were created displayed impressive potential for customization. They consistently demonstrated improved mechanical and thermal properties when compared to the original nylon structures. Our methodology for producing uniformly dispersed and aligned short fiber reinforcement in polymer composites promises to propel the advancement of design and manufacturing for high‐performance composite materials and components.

Sex differences in white matter bundle properties across menopausal transition states

AbstractBackgroundWomen develop Alzheimer’s disease (AD) at a 2:1 rate compared to men. Changes associated with menopause exacerbate a midlife bioenergetic crisis that, when unsuccessfully resolved, leads to white matter degradation and ultimately brain atrophy. Understanding how white matter structural properties differ between sexes and evolve over midlife transitions may provide insight into the exacerbated AD risk for women. Here, we report differences in white matter bundle properties comparing pre‐ (n = 40, 44.1±3.34y), peri‐ (n = 60, 49.6±3.90y), and post‐menopausal women (n = 70, 56.0±4.12y) to age‐matched males.MethodDiffusion weighted MRI was acquired for each participant. Data were preprocessed with QSIPrep and analyzed using a fixel‐based approach implemented in MRtrix (v. 3.0.3). Fiber density (FD), cross‐section (FC), and a combined density/cross‐section metric (FDC) were compared between sexes after controlling for age, education, APOE ε4 carrier status, and total brain volume (FC and FDC only). Continuous covariates were standardized to 2 standard deviations. Analyses were conducted using connectivity‐enhanced fixel‐based permutation analyses and thresholded at family‐wise error corrected p<0.05.ResultPre‐, peri‐, and post‐ menopausal women exhibited greater FD and FDC in the corpus callosum, inferior occipto‐frontal fasciculus, cortico‐spinal, and cingulum bundles. By contrast, males had greater fiber cross section in the splenium of the corpus callosum (compared to pre‐), (compared to peri‐), and in fibers near the left uncinate fasciculus and inferior longitudinal fasciculus (compared to both peri‐ and post‐menopausal women). After controlling for age, education, total brain volume, and APOE ε4 carrier status, a smaller cluster of fibers in the left splenium survived multiple comparisons correction demonstrating greater fiber cross‐section in post‐menopausal women compared to peri‐menopausal women.ConclusionWomen across menopausal transition states exhibited greater fiber density than their age‐matched male counterparts in commissural and association tracts, which agrees with previous work demonstrating stronger inter‐hemispheric connections in women. However, peri‐ and post‐menopausal females exhibited 4‐8% decrease in fiber cross section in uncinate fasciculus fibers, which have been implicated in Alzheimer’s related cognitive decline. These findings suggest that reductions in white matter cross‐section, particularly in regions associated with Alzheimer’s disease, may begin for women in menopause and be an early indicator of neurodegenerative risk.

Investigation into white matter microstructure differences in visual training by using an automated fiber tract subclassification segmentation quantification method

Visual training has emerged as a useful framework for investigating training-related brain plasticity, a highly complex task involving the interaction of visual orientation, attention, reasoning, and cognitive functions. However, the effects of long-term visual training on microstructural changes within white matter (WM) is poorly understood. Therefore, a set of visual training programs was designed, and automated fiber tract subclassification segmentation quantification based on diffusion magnetic resonance imaging was performed to obtain the anatomical changes in the brains of visual trainees. First, 40 healthy matched participants were randomly assigned to the training group or the control group. The training group underwent 10 consecutive weeks of visual training. Then, the fiber tracts of the subjects were automatically identified and further classified into fiber clusters to determine the differences between the two groups on a detailed scale. Next, each fiber cluster was divided into segments that can analyze specific areas of a fiber cluster. Lastly, the diffusion metrics of the two groups were comparatively analyzed to delineate the effects of visual training on WM microstructure. Our results showed that there were significant differences in the fiber clusters of the cingulate bundle, thalamus frontal, uncinate fasciculus, and corpus callosum between the training group compared and the control group. In addition, the training group exhibited lower mean fractional anisotropy, higher mean diffusivity and radial diffusivity than the control group. Therefore, the long-term cognitive activities, such as visual training, may systematically influence the WM properties of cognition, attention, memory, and processing speed.

Performance and mechanisms of ultraviolet laser ablation of plain-woven CFRP composites

Plain-woven carbon-fiber-reinforced-polymer (CFRP) composites prove advantageous in designing and manufacturing aeronautic and aerospace structures due to their excellent mechanical properties. Their harsh service environment usually leads to aircraft surface pits, scratches, and other types of defects, which result in internal damages that reduce their strength, influencing their safety and reliability. With laser-controlled ablation, surface damage removal was implemented. However, the multiscale characteristics of plain-woven CFRP (macroscopic plain-woven textiles, mesoscopic fiber clusters, together with microscopic fiber and epoxy resin) lead to complex thermal–mechanical ablation action, prone to secondary surface damages and resin residue. Aiming at the requirement of high-performance removal of the damaged zone, a comprehensive investigation of the influence of laser ablation strategies, including the wavelength, defocus distance, scanning speed, hatch distance, scanning passes, etc., on generating morphologies was conducted. Results identified that the severe anisotropy of plain-woven CFRP gained a wide heat-affected zone (HAZ), which was restrained by adopting an ultraviolet (UV) laser ablation means. A high-quality laser ablation zone without visible resin residue and broken carbon fiber has been presented by one-pass laser ablation when a particular scarfing conditions combination was used. Meanwhile, a depth-controlled surface-forming approach was gained, accompanied by multiple laser scanning. Subsequently, a hybrid laser treatment strategy was provided for characteristic structure generation, and a novel stepwise structure was constructed for verification.

Effects of Nandrolone Decanoate on Skeletal Muscle and Neuromuscular Junction of Sedentary and Exercised Rats.

Background and Objectives: Nandrolone decanoate (ND) is the most widely used among the anabolic androgenic steroids (AAS), synthetic substances derived from testosterone, to improve muscular and health gains associated with exercises. The AAS leads to physical performance enhancement and presents anti-aging properties, but its abuse is associated with several adverse effects. Supraphysiological doses of AAS with or without physical exercise can cause morphological and functional alterations in neuromuscular interactions. This study aims to investigate the effects of ND supraphysiological doses in neuromuscular interactions, focusing on the soleus muscle and its neuromuscular junctions (NMJs) in rats, associated or not with physical exercise. Materials and Methods: Forty male Sprague Dawley rats were divided into four groups: sedentary and exercised groups, with or without ND at the dose of 10 mg/kg/week. The animals were treated for eight weeks, with intramuscular injections, and the soleus muscle was collected for morphological analyses. Results: The supraphysiological doses of ND in the sedentary group caused muscle degeneration, evidenced by splitting fibers, clusters of small fibers, irregular myofibrils, altered sarcomeres, an increase in collagen deposition and in the number of type I muscle fibers (slow-twitch) and central nuclei, as well as a decrease in fibers with peripheral nuclei. On the other hand, in the ND exercise group, there was an increase in the NMJs diameter with scattering of its acetylcholine receptors, although no major morphological changes were found in the skeletal muscle. Thus, the alterations caused by ND in sedentary rats were partially reversed by physical exercise. Conclusions: The supraphysiological ND exposure in the sedentary rats promoted an increase in muscle oxidative pattern and adverse morphological alterations in skeletal muscle, resulting from damage or post-injury regeneration. In the ND-exercised rats, no major morphological changes were found. Thus, the physical exercise partially reversed the alterations caused by ND in sedentary rats.

Equivalent heat transfer modeling for poplar fiber clusters based on thermography

Equivalent heat transfer modeling for poplar fiber clusters based on thermography

In vivo mapping of the deep and superficial white matter connectivity in the chimpanzee brain

Mapping the chimpanzee brain connectome and comparing it to that of humans is key to our understanding of similarities and differences in primate evolution that occurred after the split from their common ancestor around 6 million years ago. In contrast to studies on macaque species’ brains, fewer studies have specifically addressed the structural connectivity of the chimpanzee brain and its comparison with the human brain. Most comparative studies in the literature focus on the anatomy of the cortex and deep nuclei to evaluate how their morphology and asymmetry differ from that of the human brain, and some studies have emerged concerning the study of brain connectivity among humans, monkeys, and apes. In this work, we established a new white matter atlas of the deep and superficial white matter structural connectivity in chimpanzees. In vivo anatomical and diffusion-weighted magnetic resonance imaging (MRI) data were collected on a 3-Tesla MRI system from 39 chimpanzees. These datasets were subsequently processed using a novel fiber clustering pipeline adapted to the chimpanzee brain, enabling us to create two novel deep and superficial white matter connectivity atlases representative of the chimpanzee brain. These atlases provide the scientific community with an important and novel set of reference data for understanding the commonalities and differences in structural connectivity between the human and chimpanzee brains. We believe this study to be innovative both in its novel approach and in mapping the superficial white matter bundles in the chimpanzee brain, which will contribute to a better understanding of hominin brain evolution.

Decoupling the effects of varying amplitude and frequency in the electrical stimulation of optic nerve fibers

Abstract Introduction. Computational models of optic nerve stimulation can allow to estimate the neural response of optic nerve fibers electrical stimulation and thus can be exploited to tune stimulation parameters to obtain a specific target perception. In principle, such tuning should be performed in an automatic way, so that the chosen stimulation parameters minimize some given cost function related to the quality of resulting the visual perception, but the use of such automatic methods is still under study and no satisfactory solution is available yet. In the absence of automatic methods, stimulation parameters are customarily set via manual tuning, which can be extremely time-consuming if performed in a non-principled way. Methods. We build biophysically-accurate hybrid models of monopolar and bipolar electrical stimulation of optic nerve fibers to study how the fibers firing rates depend upon the stimulation parameters. Results. In the case of monopolar sinusoidal stimulation of optic nerve fibers, we show that the amplitude of stimulation controls the size of the recruited cluster of fibers, and that the frequency controls their firing rate, independently. Instead, for bipolar stimulation, we show that when cross-talk is non negligible it is very difficult to obtain rules of thumb linking the firing rate of target fibers to stimulation parameters. Conclusion. We show that, if the stimulation amplitude is kept such that neighboring stimulating sites do not produce cross-talk, it is possible to reconstruct visual scenes “pixel-by-pixel” without needing any optimization process. If on the contrary current steering is required and cross-talk is non negligible, then it is very difficult to obtain rules of thumb and the development and use of automatic optimization techniques should be preferable.

Structural impairment in superficial and deep white matter in schizophrenia.

Although disconnectivity among brain regions has been one of the main hypotheses for schizophrenia, the superficial white matter (SWM) has received less attention in schizophrenia research than the deep white matter (DWM) owing to the challenge of consistent reconstruction across subjects. We obtained the diffusion magnetic resonance imaging (dMRI) data of 223 healthy controls and 143 patients with schizophrenia. After harmonizing the raw dMRIs from three different studies, we performed whole-brain two-tensor tractography and fiber clustering on the tractography data. We compared the fractional anisotropy (FA) of white matter tracts between healthy controls and patients with schizophrenia. Spearman's rho was adopted for the associations with clinical symptoms measured by the Positive and Negative Syndrome Scale (PANSS). The Bonferroni correction was used to adjust multiple testing. Among the 33 DWM and 8 SWM tracts, patients with schizophrenia had a lower FA in 14 DWM and 4 SWM tracts than healthy controls, with small effect sizes. In the patient group, the FA deviations of the corticospinal and superficial-occipital tracts were negatively correlated with the PANSS negative score; however, this correlation was not evident after adjusting for multiple testing. We observed the structural impairments of both the DWM and SWM tracts in patients with schizophrenia. The SWM could be a potential target of interest in future research on neural biomarkers for schizophrenia.

Probing bundle-wise abnormalities in patients infected with human immunodeficiency virus using fixel-based analysis: new insights into neurocognitive impairments.

Changes in white matter (WM) underlie the neurocognitive damages induced by a human immunodeficiency virus (HIV) infection. This study aimed to examine using a bundle-associated fixel-based analysis (FBA) pipeline for investigating the microstructural and macrostructural alterations in the WM of the brain of HIV patients. This study collected 93 HIV infected patients and 45 age/education/handedness matched healthy controls (HCs) at the Beijing Youan Hospital between January 1, 2016 and December 30, 2016.All HIV patients underwent neurocognitive evaluation and laboratory testing followed by magnetic resonance imaging (MRI) scanning. In order to detect the bundle-wise WM abnormalities accurately, a specific WM bundle template with 56 tracts of interest was firstly generated by an automated fiber clustering method using a subset of subjects. Fixel-based analysis was used to investigate bundle-wise differences between HIV patients and HCs in three perspectives: fiber density (FD), fiber cross-section (FC), and fiber density and cross-section (FDC). The between-group differences were detected by a two-sample t -test with the false discovery rate (FDR) correction ( P <0.05). Furthermore, the covarying relationship in FD, FC and FDC between any pair of bundles was also accessed by the constructed covariance networks, which was subsequently compared between HIV and HCs via permutation t -tests. The correlations between abnormal WM metrics and the cognitive functions of HIV patients were explored via partial correlation analysis after controlling age and gender. Among FD, FC and FDC, FD was the only metric that showed significant bundle-wise alterations in HIV patients compared to HCs. Increased FD values were observed in the bilateral fronto pontine tract, corona radiata frontal, left arcuate fasciculus, left corona radiata parietal, left superior longitudinal fasciculus III, and right superficial frontal parietal (SFP) (all FDR P <0.05). In bundle-wise covariance network, HIV patients displayed decreased FD and increased FC covarying patterns in comparison to HC ( P <0.05) , especially between associated pathways. Finally, the FCs of several tracts exhibited a significant correlation with language and attention-related functions. Our study demonstrated the utility of FBA on detecting the WM alterations related to HIV infection. The bundle-wise FBA method provides a new perspective for investigating HIV-induced microstructural and macrostructural WM-related changes, which may help to understand cognitive dysfunction in HIV patients thoroughly.

Improving dispersion of recycled GFRP fiber in cement mortar with sodium hexametaphosphate

The dispersion of recycled glass fiber reinforced plastic (rGFRP) fibers in cement mortars has a significant impact on both the workability and mechanical properties of the composites. In this study, the dispersity of three types of rGFRP fibers was improved in two methods: Method 1: the dispersant (Sodium Hexametaphosphate, SHMP) was directly added into the mortar, and Method 2: the rGFRP fibers were pre-dispersed by the SHMP solution and then added into the mortar. The effect of the two fiber-dispersion methods on workability, mechanical properties, and microstructure of the rGFRP fiber reinforced mortars were investigated by Zeta potential test, mechanical tests, Mercury intrusion porosimetry and X-ray micro-CT analysis. The results showed that Method 2 had more significant improvement in mechanical strength than Method 1 for all types of rGFRP fiber reinforced mortar. The flexural strength of the mortars increased by 58.3%, 43.2% and 105.4% with 7.5 wt% GF1, GF2 and GF3 treated by Method 2, respectively, compared to their untreated counterparts. The pre-dispersion of the fibers with SHMP facilitated better dispersion of the large rGFRP fiber clusters in the mortar by increasing the surface charge of the fibers and enhancing repulsion between them, thus improving the mechanical performance of the mortar. The results of this study will promote the utilization of rGFRP fiber in construction materials.

A Riemannian Framework for Structurally Curated Functional Clustering of Brain White Matter Fibers.

White matter (WM) consists of fibers that transmit information from one brain region to another, and functional fiber clustering that combines diffusion and functional MRI provides a novel perspective for exploring the functional architecture of axonal fibers. However, existing methods only concern functional signals in gray matter (GM), whereas the connecting fibers may not transmit relevant functional signals. There has been growing evidence that neural activity is encoded in WM BOLD signals as well, which provides rich multimodal information for fiber clustering. In this paper, we develop a comprehensive Riemannian framework for functional fiber clustering using WM BOLD signals along fibers. Specifically, we derive a novel metric that is highly discriminative of different functional classes while reducing the variability within classes and, in the meantime, enables low-dimensional coding of high-dimensional data. Our in vivo experiments show that the proposed framework is able to achieve clustering results with inter-subject consistency and functional homogeneity. In addition, we develop an atlas of WM functional architecture for standardizable yet flexible use and exemplify a machine-learning-based application for the classification of autism spectrum disorders, which further demonstrates the great potential of our approach in practical applications.

Effects of Polyethylene Fiber Dosage and Length on the Properties of High-Tensile-Strength Engineered Geopolymer Composite

This paper presents a high-tensile-strength engineered geopolymer composite (EGC) reinforced by polyethylene (PE) fibers. The influences of fiber dosage (1.5%, 1.75%, and 2.0%) and length (6, 12, and 18 mm) on the mechanical properties and strain-hardening performance of EGCs were examined. The results indicated that increasing either fiber dosage or length decreases the flowability of EGC due to the skeleton formed by fibers. The increase of fiber dosage from 1.5% to 2.0% enhanced the fiber bridging effect in the EGCs with 12-mm PE fibers and subsequently enhanced their compressive and tensile strengths by 9.0% and 12.7%, respectively. Differently, the increase of 18-mm fiber dosage from 1.5% to 2.0% introduced more voids inside the EGCs, which decreased their compressive and tensile strengths by 3.8% and 3.6%, respectively. Fiber clusters were more likely to occur in EGC with a higher dosage of longer fibers, which reduced its tensile strength. A higher fiber dosage improved both tensile strain capacity and crack control capacity of EGC. On the other hand, increasing the fiber length from 6 to 18 mm increased the tensile strength by 42.0%, strain capacity by 148.0%, and crack control ability of EGC by enhancing the fiber-bridging effect, although it was detrimental to the compressive strength of the EGCs with 18-mm fibers due to the magnified air-entrapping effect. In addition, a prediction model modified based on the test results can accurately predict the tensile strength of PE fiber–reinforced EGCs. The environmental assessment indicated that the developed EGCs exhibit dramatically lower environmental impacts than the conventional engineered cementitious composite.

Exploring the impact of hippocampal sclerosis on white matter tracts and memory in individuals with mesial temporal lobe epilepsy.

To investigate how the presence/side of hippocampal sclerosis (HS) are related to the white matter structure of cingulum bundle (CB), arcuate fasciculus (AF), and inferior longitudinal fasciculus (ILF) in mesial temporal lobe epilepsy (MTLE). We acquired diffusion-weighted magnetic resonance imaging (MRI) from 86 healthy and 71 individuals with MTLE (22 righ-HS; right-HS, 34 left-HS; left-HS, and 15 nonlesional MTLE). We utilized two-tensor tractography and fiber clustering to compare fractional anisotropy (FA) of each side/tract between groups. Additionally, we examined the association between FA and nonverbal (WMS-R) and verbal (WMS-R, RAVLT codification) memory performance for MTLE individuals. White matter abnormalities depended on the side and presence of HS. The left-HS demonstrated widespread abnormalities for all tracts, the right-HS showed lower FA for ipsilateral tracts and the nonlesional MTLE group did not differ from healthy individuals. Results indicate no differences in verbal/nonverbal memory performance between the groups, but trend-level associations between higher FA of visual memory and the left CB (r = 0.286, P = 0.018), verbal memory (RAVLT) and -left CB (r = 0.335, P = 0.005), -right CB (r = 0.286, P = 0.016), and -left AF (r = 0.287, P = 0.017). Our results highlight that the presence and side of HS are crucial to understand the pathophysiology of MTLE. Specifically, left-sided HS seems to be related to widespread bilateral white matter abnormalities. Future longitudinal studies should focus on developing diagnostic and treatment strategies dependent on HS's presence/side.

Evaluation of recurrent laryngeal neuropathy in domestic and feral horse populations in Australia using histologic and immunohistochemical analysis: A pilot study.

Little is known about potential differences in the left recurrent laryngeal nerve (Lrln) and left cricoarytenoideus dorsalis (LCAD) muscle between domestic and feral horse populations. If a difference exists, feral horses may provide a useful control population for research related to recurrent laryngeal neuropathy (RLN) and increase our understanding of potential population pressures influencing the incidence RLN. The objective of this study was to compare the Lrln and LCAD of domestic and feral horses using histological and immunohistochemical techniques (IHC). Sixteen horses, domestic (n = 8) and feral (n = 8), without clinical or ancillary examinations that were processed at an abattoir had the Lrln and LCAD muscle harvested immediately following death. Carcass weights were recorded. Subjective and morphometric histologic assessment were performed on Lrln sections. The LCAD was assessed for myosin heavy chain (fibre type proportion, diameter and grouping using IHC. Fibre-type grouping consistent with RLN was seen in both groups. Regenerating fibre clusters were more common in domestic compared to feral horses (p = 0.04). No other histologic differences occurred between groups. Muscle fibre typing demonstrated a lower mean percentage of type IIX fibres in the feral group compared to the domestic group (p = 0.03). There was no difference in type I or IIA proportions or mean diameter of any fibre type between the groups. The domestic population showed evidence of nerve regeneration suggesting RLN in this group, yet this was not supported by the higher proportion of type IIX muscle fibres compared to the feral population. Further evaluation to clarify the significance and wider occurrence of the differences is indicated.

Statistical Analysis of the Ultimate Strength of Filaments, Tows and Minicomposites

The present paper investigates the failure of SiC and alumina-fiber-reinforced minicomposites in relation to the strength distributions of filaments, and the failure behavior of the reinforcing dry tows. The strength data are measured on single-filament, dry-tow and minicomposite specimens using tensile tests under commonly used test condition of strain-controlled loading. Pertinence of the normal distribution of strengths at different length scales is assessed using the construction of p-quantile diagrams, and the pertinence of the Weibull distribution was assessed by comparing to the normal distribution function. SiC and alumina minicomposites exhibited significantly different failure behaviors. Comparison with filament strength distributions and the behavior of the underlying tow in relation to the loading condition (stress- or strain-controlled conditions) allows for the interpretation of the results. The sensitivity of the results to loading conditions is highlighted. Various scenarios of minicomposite failure are discussed as alternatives to the stress concentration induced by clusters of broken fibers. It appears that the failure of alumina-fiber-reinforced minicomposites is stable and dictated by the highest-strength filaments, whereas the SiC-fiber-reinforced minicomposites exhibited premature failure that is attributed to the microstructural imperfections that induced overstressing by the fiber or fiber/matrix interactions.

Cross-subject variability of the optic radiation anatomy in a cohort of 1065 healthy subjects.

Optic radiations are tracts of particular interest for neurosurgery, especially for temporal lobe resection, because their lesion is responsible for visual field defects. However, histological and MRI studies found a high inter-subject variability of the optic radiation anatomy, especially for their most rostral extent inside the Meyer's temporal loop. We aimed to better assess inter-subject anatomical variability of the optic radiations, in order to help to reduce the risk of postoperative visual field deficiencies. Using an advanced analysis pipeline relying on a whole-brain probabilistic tractography and fiber clustering, we processed the diffusion MRI data of the 1065 subjects of the HCP cohort. After registration in a common space, a cross-subject clustering on the whole cohort was performed to reconstruct the reference optic radiation bundle, from which all optic radiations were segmented on an individual scale. We found a median distance between the rostral tip of the temporal pole and the rostral tip of the optic radiation of 29.2mm (standard deviation: 2.1mm) for the right side and 28.8mm (standard deviation: 2.3mm) for the left side. The difference between both hemispheres was statistically significant (p = 1.10-8). We demonstrated inter-individual variability of the anatomy of the optic radiations on a large-scale study, especially their rostral extension. In order to better guide neurosurgical procedures, we built a MNI-based reference atlas of the optic radiations that can be used for fast optic radiation reconstruction from any individual diffusion MRI tractography.