Fiber Damage Research Articles

New insights into the damage assessment and energy dissipation weight mechanisms of ceramic/fiber laminated composites under ballistic impact

Ceramics/composite laminated armor structures have become the mainstream in the design of bulletproof materials. To obtain systematic improvements in composite targets, it is essential to design the structure of each ceramic/fiber to ensure synergistic energy matching between them. However, the challenges of heavy workload and high-costs limit the experimental testing of these composites. In this report, B4C ceramics/ultra-high molecular weight polyethylene (UHMWPE) composite targets are studied and the impact of ceramic splicing size, impact position and size on the anti-elastic performance is predicted. Finite element analysis is used to comprehensively analyze critical obstacles of the failure damage, energy dissipation weight and ballistic mechanism of each material. Prediction results indicate that ceramics damage, fiber damage, and fiber delamination account for about 65%, 21%, and 14% of the total energy consumption, respectively. Square splicing and large size ceramics/fiber composites are found to have the best anti-elastic properties when the center position is impacted. This is ascribed to the transversal rapid stress wave propagation on the ceramic surface and the beneficial energy dissipation of the composite-backing arising from the longitudinal stress wave transfer of homogeneous panels. The results provide insights for identifying viable design methods for each structure, optimizing the matching of panels and backplanes, which reduces the number of experimental tests need to validate a given structure.

A systematic study on material properties of water retted Sterculia and Bauhinia fiber

Lignocellulose biomass forms an important component of traditional and next generation composite materials. To obtain desired properties, the biomass needs to be chemo‒mechanically processed at different levels. The raw lignocellulose fiber obtained from Sterculia villosa (Roxb.) and Bauhinia vahlii is traditionally believed to have high water stability; and therefore used in rural areas of South Asian regions to secure objects submerged under water. In this research, we systematically studied several material properties of raw Sterculia and Bauhinia fiber samples retted for 0, 20, 30 and 55 days (n=8). Water retting resulted in significant decrease in lignin and extractives content (p<0.05) and increase in cellulose content. Fiber bundle strength of Sterculia fiber increased with retting time (R2= 0.7) but Bauhinia fiber did not show significant change (p>0.05). Interestingly, water retting resulted in increased thermal stability in both fiber types. These findings suggested that the fiber studied have excellent water stability. The observed trend in mechanical and thermal properties could have resulted from crystallinity change and/or nominal fiber damage as supported by XRD and SEM imaging data; respectively. These findings suggested that Sterculia and Bauhinia fiber biomass could be an important component of biodegradable composite materials which are intended for high wetting and/or humid conditions.

Corneal confocal microscopy identifies corneal nerve loss and increased Langerhans cells in presymptomatic carriers and patients with hereditary transthyretin amyloidosis

BackgroundHereditary transthyretin amyloidosis (ATTRv amyloidosis) is a rare, but life-threatening protein misfolding disorder due to TTR gene mutations. Cardiomyopathy (ATTRv-CM) and polyneuropathy (ATTRv-PN) with early small nerve fibre involvement are the most common manifestations. Timely diagnosis and treatment initiation are key to limiting progression of disease. Corneal confocal microscopy (CCM) is a non-invasive method to quantify corneal small nerve fibres and immune cell infiltrates in vivo.MethodsThis cross-sectional study investigated the utility of CCM in 20 patients with ATTRv amyloidosis (ATTRv-CM, n = 6; ATTRv-PN, n = 14) and presymptomatic carriers (n = 5) compared to 20 age- and sex-matched healthy controls. Corneal nerve fibre density, corneal nerve fibre length, corneal nerve branch density, and cell infiltrates were assessed.ResultsCorneal nerve fibre density and nerve fibre length were significantly lower in patients with ATTRv amyloidosis compared to healthy controls regardless of the clinical phenotype (ATTRv-CM, ATTRv-PN) and corneal nerve fibre density was significantly lower in presymptomatic carriers. Immune cell infiltrates were only evident in patients with ATTRv amyloidosis, which correlated with reduced corneal nerve fibre density.ConclusionsCCM identifies small nerve fibre damage in presymptomatic carriers and symptomatic patients with ATTRv amyloidosis and may serve as a predictive surrogate marker to identify individuals at risk of developing symptomatic amyloidosis. Furthermore, increased corneal cell infiltration suggests an immune-mediated mechanism in the pathogenesis of amyloid neuropathy.

MP68-01 PATTERN ANALYSIS OF LASER FIBER DEGRADATION ACCORDING TO THE LASER SETTING: IN VITRO STUDY OF THE DOUBLE-FIRING PHENOMENON

You have accessJournal of UrologyCME1 Apr 2023MP68-01 PATTERN ANALYSIS OF LASER FIBER DEGRADATION ACCORDING TO THE LASER SETTING: IN VITRO STUDY OF THE DOUBLE-FIRING PHENOMENON Sang Won So, Gyoohwan Jung, Hyeji Park, and Sung Yong Cho Sang Won SoSang Won So More articles by this author , Gyoohwan JungGyoohwan Jung More articles by this author , Hyeji ParkHyeji Park More articles by this author , and Sung Yong ChoSung Yong Cho More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003331.01AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: It is essential to understand the mechanism of the various causes of laser fiber damage and an ideal method of reducing endoscope damage induced by laser emission in multiple sites. This study classified the different patterns of laser fiber degradation according to laser settings and analyzed the role of cavitation bubbles to find a desirable way of minimizing endoscope damage. METHODS: A total of 118 laser fibers were analyzed after 1-,3-, and 5-min laser emission to artificial stones under the settings of 1J-10Hz, 1J-20Hz, 1J-30Hz, and 2J-10Hz. Every 3cm from the fiber tip was marked and examined with a digital microscope and a high-speed camera. The images of the fibers and the movement of cavitation bubbles were taken with a distance of 1 to 5 mm from the gel. RESULTS: Seven types of fiber damage (charring, limited and extensive peeled-off, bumpy, whitish plaque, crack, and break-off) coincided during laser emission. Damages rapidly increased with emission time>3 min regardless of the laser settings. The damaged lengths covered 5 mm on average, and the fibers at 5-min emission were significantly shorter than others. The fiber durability of 1J-10Hz setting was better than other settings after 3-min laser emission. Backward movement of the cavitation bubbles was found at the 1-mm distance from the gel, and the damaged lengths were longer than the diameters of the cavitation bubbles because of their proximal movement. CONCLUSIONS: The damage patterns of the laser fiber tips were classified into seven types. The heat damage around the surface of the laser fiber can be increased according to the high-energy or high-frequency laser setting, a short distance to the stone, a short distance from the tips of flexible ureteroscopes, no cutting laser fiber procedures, and the inappropriate use of irrigation fluid or laser fiber jacket. Source of Funding: This work was supported by a grant No. 2019R1C1C1008339 mainly and another one No. 2017R1A2B3007907 in part of the National Research Foundation (NRF) grant funded by the Korean government (MSIT) © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e952 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Sang Won So More articles by this author Gyoohwan Jung More articles by this author Hyeji Park More articles by this author Sung Yong Cho More articles by this author Expand All Advertisement PDF downloadLoading ...

Transverse Shear Capacity Predictions of GFRP Bars Subjected to Accelerated Aging Using Artificial Neural Networks

This paper presents the results of three different types of glass fiber-reinforced polymer (GFRP) bars subjected to different harsh environmental conditions. Three types of pultruded GFRP bars, namely, Bar A (13.04 mm dia.), Bar B1 (13.02 mm dia.), Bar B2 (10.19 mm dia.), and Bar C (13.22 mm dia.) were subjected to accelerated aging. GFRP specimens were exposed to four conditionings (alkaline, alkaline with salt, acidic, and water), two temperature regimes (20°C and 60°C), and three time regimes (3, 6, and 12 months). The mechanical strength retention of the bars investigated based on the transverse shear strength (TSS) test, conforming to ASTM D7617M-11 revealed a decline in the shear strength characteristics of specimens proportionally with the exposure time. In general, Bar A, Bar B1, and Bar B2 performed well, but Bar C performed the worst since Bar C exhibited the least mechanical strength retention at elevated temperatures. Scanning electron microscopy (SEM) of the cross section of the conditioned specimens revealed the nature of the evolution of deterioration and the state of glass fibers, polymeric resin matrix, and fiber-matrix interface, validating the decrease in transverse shear capacity of the bars. SEM micrographs showed fiber damage, with debonding occurring at the fiber-matrix interface and cracking of the polymeric resin. Leaching out of glass fibers into the matrix of varying degrees upon conditioning was observed through the X-ray mapping of silicon. Furthermore, strength prediction models developed using multiple linear regression and artificial neural network (ANN) techniques were compared. Coefficients of correlation (R2) of 0.94 and 0.76 and root mean square errors (RMSE) of 7.43 and 12.00 were obtained with models developed using ANN and multiple linear regression, respectively, showing that ANN can be used as a robust tool for GFRP shear strength prediction.

Analysis of millisecond collision of composite high pressure hydrogen storage cylinder

For vehicle-mounted high-pressure hydrogen storage cylinders, impact resistance is an important indicator. This work aims at building a model of 70 MPa composite fully wound Ⅳ cylinder around T800 carbon fiber material, investigating the law of transient changes in the body of the bottle under different velocity impacts and the source of risk of bursting. Through millisecond impact analysis, the energy transfer path and transformation trend inside the cylinder are obtained. Meanwhile, it was found that there was a clear pattern of positive correlation between the tensile and compressive stresses generated by the difference between the internal pressure of the bottle and the impact pressure. The final results show that after the impact, the failure occurred firstly at the inner wall of the fiber corresponding to the impact point, and the fiber damage spreads in all directions. The thickness of the failure pavement increases from the inside to the outside.

Production of quasi-unidirectional woven fabrics from water-retted hemp fibers and mechanical characterization of their composites

Natural fiber reinforced polymer composites have attracted great attention in the past few decades due to increasing environmental awareness and various advantages of these materials in terms of mechanical properties, sustainability, renewability and biodegradability. In this study, hemp rovings with various amounts of twist were prepared using water-retted continuous hemp fiber bundles. Then these rovings were used to produce quasi-unidirectional (quasi-UD) woven hemp fabrics. These fabrics were utilized to manufacture epoxy composites. Tensile and flexural tests were carried out to determine the mechanical properties of the developed composites and the effect of yarn twist. The fracture pattern of the composites was investigated using scanning electron microscopy (SEM) analysis. The tensile strength of the composite with 45 turns/m twisted rovings was approximately 20% lower than that of the composite sample with zero-twist hemp rovings. Composites with a twist level of 45 turns/m also showed approximately 37% and 48% lower flexural strength and modulus values respectively when compared to composites with zero-twist yarns. This was attributed to the fact that the yarn twist causes the fibers to align at an angle to the loading direction resulting in reduced properties in the axial direction of the composites as well as fiber damage induced by twisting. SEM observations showed that the composite failure took place predominantly as total fiber fracture, fiber pull-out from the yarns and matrix cracking. There were also limited cases of fiber pull-out from the matrix.

Functional connectivity reveals different brain networks underlying the idiopathic foreign accent syndrome.

Foreign accent syndrome (FAS) is characterized by new onset speech that is perceived as foreign. Available data from acquired cases suggests focal brain damage in language and sensorimotor brain networks, but little remains known about abnormal functional connectivity in idiopathic cases of FAS without structural damage. Here, connectomic analyses were completed on three patients with idiopathic FAS to investigate unique functional connectivity abnormalities underlying accent change for the first time. Machine learning (ML)-based algorithms generated personalized brain connectomes based on a validated parcellation scheme from theHuman Connectome Project (HCP). Diffusion tractography was performed on each patient to rule out structural fiber damage to the language system. Resting-state-fMRI was assessed with ML-based software to examine functional connectivity between individual parcellations within language and sensorimotor networks and subcortical structures. Functional connectivity matrices were created and compared against a dataset of 200 healthy subjects to identify abnormally connected parcellations. Three female patients (28-42 years) who presented with accent changes from Australian English to Irish (n = 2) or American English to British English (n = 1) demonstrated fully intact language system structural connectivity. All patients demonstrated functional connectivity anomalies within language and sensorimotor networks in numerous left frontal regions and between subcortical structures in one patient. Few commonalities in functional connectivity anomalies were identified between all three patients, specifically 3 internal-network parcellation pairs. No common inter-network functional connectivity anomalies were identified between all patients. The current study demonstrates specific language, and sensorimotor functional connectivity abnormalities can exist and be quantitatively shown in the absence of structural damage for future study.

Understanding the helicoidal damage behavior of bio-inspired laminates by conducting multiscale concurrent simulation and experimental analysis

Bio-inspired helicoidal structures exhibit excellent fracture toughness. A multiscale concurrent simulation of the damage propagation process is critical for understanding the fracture behavior of such structures with pre-existing cracks. However, such an analysis is extremely challenging owing to computational complexity. In this study, the in-plane critical stress intensity factor and energy release rate of six different helicoidal carbon-fiber-reinforced plastic structures are measured experimentally by conducting a single-edge-notch bending test. The damage distribution of the different structures is examined by performing computed tomography scanning. Several multiscale concurrent analyses are conducted by using the self-consistent clustering analysis method to study the specific damage propagation process and evaluate the fracture toughness contribution of different layers. The results indicate that the pitch angle significantly impacts the fracture toughness, whereas the stacking mode changes the crack propagation orientation. When the pitch angle is appropriately adjusted, the fiber damage length is enhanced, resulting in a significant increase in the fracture toughness. The interaction between fiber damage, matrix damage, and hybrid damage during the failure process is interpreted using the dissipated energy ratios of the fiber damage layer, transition layer, and matrix damage layer.

Acute Treatment with the M-Channel (Kv7, KCNQ) Opener Retigabine Reduces the Long-Term Effects of Repetitive Blast Traumatic Brain Injuries.

We investigated whether pharmacological increase of "M-type" (KCNQ, Kv7) K + channel currents by the M-channel opener, retigabine (RTG), acutely after repetitive traumatic brain injuries (rTBIs), prevents or reduces their long-term detrimental effects. rTBIs were studied using a blast shock air wave mouse model. Animals were monitored by video and electroencephalogram (EEG) records for nine months after the last injury to assess the occurrence of post-traumatic seizures (PTS), post-traumatic epilepsy (PTE), sleep-wake cycle architecture alterations, and the power of the EEG signals. We evaluated the development of long-term changes in the brain associated with various neurodegenerative diseases in mice by examining transactive response DNA-binding protein 43 (TDP-43) expression and nerve fiber damage ~ 2years after the rTBIs. We observed acute RTG treatment to reduce the duration of PTS and impair the development of PTE. Acute RTG treatment also prevented post-injury hypersomnia, nerve fiber damage, and cortical TDP-43 accumulation and translocation from the nucleusto the cytoplasm. Mice that developed PTE displayed impaired rapid eye movement (REM) sleep, and there were significant correlations between seizure duration and time spent in the different stages of the sleep-wake cycle. We observed acute RTG treatment to impair injury-induced reduction of age-related increase in gamma frequency power of theEGG, which has been suggested to be necessary for a healthy aged brain. The data show that RTG, administered acutely post-TBI, is a promising, novel therapeutic option to blunt/prevent several long-term effects of rTBIs. Furthermore, our results show a direct relationship between sleep architecture and PTE.

Key technologies for laser-assisted precision grinding of 3D C/C-SiC composites

Due to their exceptional and distinctive qualities, 3D C/C-SiC composites are widely utilized in producing high-end equipment and the aerospace national defense industries. However, the hard and pseudo plastic nature of the material and its anisotropies make it challenging to process. To improve the processing quality of 3D C/C-SiC composites, laser-assisted precision grinding technology is introduced in this paper, which innovatively controls the depth of the thermally induced damage layer by adjusting the laser process parameters to reduce the hard brittleness of the material, and then the surface is created by precision grinding with a grinding wheel on this basis. Experiments on laser-induced damage, laser-assisted grinding, and diamond scratching were carried out to investigate the effect of laser parameters on material damage and the effect of laser-assisted grinding processes, with an emphasis on revealing the mechanism of material removal. The results show that laser irradiation causes complex reactions such as sublimation, decomposition, and oxidation of 3D C/C-SiC composites, resulting in SiO2 and Si and recondensed SiC, causing surface/subsurface damage. A maximum reduction in normal grinding force, tangential grinding force, specific grinding energy, and surface roughness of 35.6%, 43.6%, 43.58%, and 24.22%, respectively, compared to conventional grinding processes with laser-assisted grinding. After laser irradiation, the degree of brittle fracture in the precision grinding of workpieces is significantly reduced due to the degradation of matrix and fiber damage caused by laser irradiation, which reduces the hard and pseudo plastic properties of the material. The removal mechanism shows a trend of ductile domain removal in the grinding of thermally damaged layers, which reduces the grinding force and improves the surface quality.

Features of polyneuropathy in diabetes mellitus and chronic alcoholism

This article discusses the features of the pathogenesis and symptoms of two of the most common causes of polyneuropathy. On the one hand, the alcoholic genesis of nerve fiber damage is discussed - we will consider how chronic alcoholism provokes the appearance of polyneuropathy. On the other hand, an equally important and frequent inducer of a decrease in all types of sensitivity in patients is diabetes mellitus. Moreover, in some cases, polyneuropathy can occur even before the establishment of diabetes mellitus as a causal diagnosis. Thus, we see the need to highlight important aspects of pathogenesis, and, despite the differences in the development of both processes, the commonality of symptoms.

A newly proposed damage constitutive model for composite laminates under low-velocity impact by considering through-thickness compression damage

The existing damage constitutive models for a composite lamina under impact loading have mainly considered four failure modes: longitudinal fiber failure in tension and compression, matrix failure in tension and compression along the transverse direction. However, when subjected to an impact load in the out-of-plane direction, through-thickness compression failure may also occur in laminates. Therefore, the present paper has established a damage constitutive model considering through-thickness compression failure and has compared it to those constitutive models without such consideration to see the improvement in the impact response analysis and to discuss the necessity of including through-thickness compression damage in the simulation. To this end, impact testing was conducted on manufactured composite panels, and the results were used to validate the finite element simulation of composite laminates under impact. The results showed that the constitutive model with the compression failure mode in the thickness direction had higher accuracy in predicting the impact force, displacement, damage, and energy absorption of laminates. The predicted results by the developed constitutive model showed that through-thickness compression damage indeed occurred in the laminates during the impact process, and it was mainly concentrated in the layers near the impact side. In the layers near the rear side, the tension damage of longitudinal fiber and matrix mainly initiated and developed in the annular region around the impact center on the laminates.

Experimental study on Mode Ⅰ fracture characteristics of laminated flattened-bamboo lumber combined with VIC-3D system

According to ASTM E399, Mode I fracture tests were conducted on compact tension (CT) specimens of laminated flattened-bamboo lumber (LFBL) loaded parallel to grain, in combination with the optical measurement system VIC-3D (video image correlate, 3D) to observe the evolution of strains and crack propagation. In the test results, the average fracture toughness of the specimen gradually decreased as the ratio of initial crack length to specimen width increased, and after the ratio reached 0.45, the fracture toughness value tended to be stable; the fracture toughness tests could only be considered valid if the thickness of the specimen was greater than or equal to 25 mm. Compared to large-thickness specimens, small-thickness specimens had a lower degree of brittleness; microscopic failure modes were classified as ground-tissue cracking and fiber damage. During the test, the tension-strain field was always concentrated at the tip of the extending crack. When the cracks extended to equal length, the specimens were in the same state, indicating that crack extension followed a self-consistent pattern. Furthermore, the compliance calibration method was used to develop the equation for the function of crack length-compliance.

Broadband supercontinuum generation in cascaded tapered liquid core fiber

Most recent broad supercontinuum sources have used nonlinear fibers with small core diameters, resulting in low coupling efficiency, limiting power level launching into the fiber, and low spectral power density. In this work, we numerically investigate tapered liquid-core fibers for supercontinuum generation that have a potential for both high coupling efficiency (with a standard SMF-28 fiber) and high nonlinear effects. Carbon disulfide is selected to fill into the fibers because of its high nonlinear refractive index and high transparency from the visible to the mid-infrared range. We consider cascaded fibers including SMF-28 and the tapered liquid-core fibers for all-normal and anomalous dispersion supercontinuum generation pumped by C-band femtosecond lasers (1560 nm, 90 fs). In such a case, we obtain all-normal dispersion supercontinuum generation with flat-top, broad bandwidth (1.0–2.5μm) via an input peak power of 27 kW. By changing the core diameter of the tapered fiber, we also yield anomalous dispersion supercontinuum generation with broad spectral bandwidth (1.0–3.3μm). In addition, the use of the cascaded tapered fibers is possible to mitigate fiber damage (via thermal effects of a high-power laser on the selected liquids) and increase stability of output supercontinuum spectra. In this context, supercontinuum generation in the cascaded fibers by using a picosecond laser with high average power (≈ 800 mW) is considered towards applications requiring high spectral power density (e.g., multiphoton imaging techniques).

Effects of Monoamino-Oxidase-A (MAO-A) Inhibition on Skeletal Muscle Inflammation and Wasting through Pancreatic Ductal Adenocarcinoma in Triple Transgenic Mice.

Cancer cachexia describes a syndrome of muscle wasting and lipolysis that is still largely untreatable and negatively impacts prognosis, mobility, and healthcare costs. Since upregulation of skeletal muscle monoamine-oxidase-A (MAO-A), a source of reactive oxygen species, may contribute to cachexia, we investigated the effects of the MAO-inhibitor harmine-hydrochloride (HH, intraperitoneal, 8 weeks) on muscle wasting in a triple-transgenic mouse model of pancreatic ductal adenocarcinoma (PDAC) and wild type (WT) mice. Gastrocnemius and soleus muscle cryo-cross-sections were analyzed for fiber type-specific cross-sectional area (CSA), fraction and capillarization using ATPase- and lectin-stainings. Transcripts of pro-apoptotic, -atrophic, and -inflammatory signals were determined by RT-qPCR. Furthermore, we evaluated the integrity of neuromuscular junction (NMJ, pre-/post-synaptic co-staining) and mitochondrial ultrastructure (transmission electron microscopy). MAO-A expression in gastrocnemius muscle was increased with PDAC vs. WT (immunohistochemistry: p < 0.05; Western blot: by trend). PDAC expectedly reduced fiber CSA and upregulated IL-1β in both calf muscles, while MuRF1 expression increased in soleus muscle only. Although IL-1β decreased, HH caused an additional 38.65% (p < 0.001) decrease in gastrocnemius muscle (IIBX) fiber CSA. Moreover, soleus muscle CSA remained unchanged despite the downregulation of E3-ligases FBXO32 (p < 0.05) and MuRF1 (p < 0.01) through HH. Notably, HH significantly decreased the post-synaptic NMJ area (quadriceps muscle) and glutathione levels (gastrocnemius muscle), thereby increasing mitochondrial damage and centronucleation in soleus and gastrocnemius type IIBX fibers. Moreover, although pro-atrophic/-inflammatory signals are reversed, HH unfortunately fails to stop and rather promotes PDAC-related muscle wasting, possibly via denervation or mitochondrial damage. These differential adverse vs. therapeutic effects warrant studies regarding dose-dependent benefits and risks with consideration of other targets of HH, such as the dual-specificity tyrosine phosphorylation regulated kinases 1A and B (DYRK1A/B).

Microscale modelling of lightning damage in fibre-reinforced composites

In this work, three-dimensional (3D) finite element simulations were undertaken to study the effects of lightning strikes on the microscale behaviour of continuous fibre-reinforced composite materials and to predict and understand complex lightning damage mechanisms. This approach is different from the conventional mesoscale or macroscale level of analysis, that predicts the overall lightning damage in composite laminates, thus providing better understanding of lightning-induced thermo-mechanical damage at a fundamental level. Micromechanical representative volume element (RVE) models of a UD composite laminate were created with circular carbon fibres randomly distributed in an epoxy matrix. The effects of various grounding conditions (one-, two-, and four-side grounding), fibre volume fractions ( V f = 55, 60%, and 65%), and peak current amplitudes (10, 20, and 40 kA) on microscopic damage in RVE models were characterised to understand fibre, epoxy matrix, and fibre-matrix interfacial damage associated with a lightning strike. Thermal damage, estimated based on epoxy matrix decomposition temperature, was largely constant up to 20 kA before increasing significantly at 40 kA. Severe thermal damage steadily decreased with increasing V f. Thermo-mechanical damage was predicted using a ductile plasticity model with Drucker–Prager yield criterion for epoxy matrix failure, and cohesive surfaces for fibre-matrix interface debonding. Thermal strain had the largest contribution to thermo-mechanical damage, while dynamic pressure loading was negligible in all RVE models. The RVE model proposed in this work, to the best of the authors’ knowledge, is the first model predicting lightning-induced fibre-matrix interfacial damage.

MicroRNA-501 controls myogenin+/CD74+ myogenic progenitor cells during muscle regeneration

ObjectiveSkeletal muscle regeneration is markedly impaired during aging. How adult muscle stem cells contribute to this decrease in regenerative capacity is incompletely understood. We investigated mechanisms of age-related changes in myogenic progenitor cells using the tissue-specific microRNA 501. MethodsYoung and old C57Bl/6 mice were used (3 months or 24 months of age, respectively) with or without global or tissue-specific genetic deletion of miR-501. Muscle regeneration was induced using intramuscular cardiotoxin injection or treadmill exercise and analysed using single cell and bulk RNA sequencing, qRT-PCR and immunofluorescence. Muscle fiber damage was assessed with Evan`s blue dye (EBD). In vitro analysis was performed in primary muscle cells obtained from mice and humans. ResultsSingle cell sequencing revealed myogenic progenitor cells in miR-501 knockout mice at day 6 after muscle injury that are characterized by high levels of myogenin and CD74. In control mice these cells were less in number and already downregulated after day 3 of muscle injury. Muscle from knockout mice had reduced myofiber size and reduced myofiber resilience to injury and exercise. miR-501 elicits this effect by regulating sarcomeric gene expression through its target gene estrogen-related receptor gamma (Esrrg). Importantly, in aged skeletal muscle where miR-501 was significantly downregulated and its target Esrrg significantly upregulated, the number of myog+/CD74+ cells during regeneration was upregulated to similar levels as observed in 501 knockout mice. Moreover, myog+/CD74+-aged skeletal muscle exhibited a similar decrease in the size of newly formed myofibers and increased number of necrotic myofibers after injury as observed in mice lacking miR-501. ConclusionsmiR-501 and Esrrg are regulated in muscle with decreased regenerative capacity and loss of miR-501 is permissive to the appearance of CD74+ myogenic progenitors. Our data uncover a novel link between the metabolic transcription factor Esrrg and sarcomere formation and demonstrate that stem cell heterogeneity in skeletal muscle during aging is under miRNA control. Targeting Esrrg or myog+/CD74+ progenitor cells might improve fiber size and myofiber resilience to exercise in aged skeletal muscle.

Weibull distribution-based prediction model for compression after impact (CAI) strength of CFRP laminates

The aim of this research was to assess the appropriateness of the two-parameter Weibull distribution-based model to predict the compression after impact (CAI) strength and to develop both efficient and secure prediction scheme for laminated composite. Four levels of impact energy were considered (10 J, 25 J, 40 J and 55 J) and CAI tests were conducted. The scanning electron microscope were used to evaluate the representative damage pattern. Two-parameter Weibull function was utilized for statistically evaluating the CAI strength results. Experiment results showed that the wildest variance was observed at the impact energy range of 25–40 J for both layups. It was found fiber damage accompanied with high variance while the matrix and delamination damage corresponded to lower variance. To predict the CAI strength more efficiently, the time to first failure (TTFF) concept was used to draw CAI strength versus impact energy graphics under different reliabilities for reference. It was verified that the safe design strength curve under 0.99 reliability level was capable and secure enough to predict the residual strength in actual application considering the variance of composite.

Peripheral Nerve Denervation in Streptozotocin-Induced Diabetic Rats Is Reduced by Cilostazol

Background and Objective: Our previous study demonstrated that consistent treatment of oral cilostazol was effective in reducing levels of painful peripheral neuropathy in streptozotocin-induced type I diabetic rats. As diabetic neuropathy is characterized by hyperglycemia-induced nerve damage in the periphery, this study aims to examine the neuropathology as well as the effects of cilostazol treatments on the integrity of peripheral small nerve fibers in type I diabetic rats. Materials and Methods: A total of ninety adult male Sprague-Dawley rats were divided into the following groups: (1) naïve (control) group; (2) diabetic rats (DM) group for 8 weeks; DM rats receiving either (3) 10 mg/kg oral cilostazol (Cilo10), (4) 30 mg/kg oral cilostazol (Cilo30), or (5) 100 mg/kg oral cilostazol (Cilo100) for 6 weeks. Pain tolerance thresholds of hind paws toward thermal and mechanical stimuli were assessed. Expressions of PGP9.5, P2X3, CGRP, and TRPV-1 targeting afferent nerve fibers in hind paw skin and glial cells in the spinal dorsal horn were examined via immunohistochemistry and immunofluorescence. Results: Oral cilostazol ameliorated the symptoms of mechanical allodynia but not thermal analgesia in DM rats. Significant reductions in PGP9.5-, P2X3-, CGRP, and TRPV-1-labeled penetrating nerve fibers in the epidermal layer indicated denervation of sensory nerves in the hind paw epidermis of DM rats. Denervation significantly improved in groups that received Cilo30 and Cilo100 in a dose-dependent manner. Cilostazol administration also suppressed microglial hyperactivation and increased astrocyte expressions in spinal dorsal horns. Conclusions: Oral cilostazol ameliorated hyperglycemia-induced peripheral small nerve fiber damage in the periphery of diabetic rats and effectively mitigated diabetic neuropathic pain via a central sensitization mechanism. Our findings present cilostazol not only as an effective option for managing symptoms of neuropathy but also for deterring the development of diabetic neuropathy in the early phase of type I diabetes.