Fiber Rupture Research Articles

Effects of terbuthylazine on myocardial oxidative stress and ferroptosis via Nrf2/HO-1 signaling pathway in broilers

Terbuthylazine (TBA) is one of the most commonly used and effective herbicides. However, due to its affinity for soil organic matter and water solubility, TBA can lead to biological health concerns. This study exposed broilers to TBA (0 mg/kg bw, 0.4 mg/kg bw, 4 mg/kg bw) for 28 days. The results showed significant pathological damage in broiler myocardial tissue, such as widening of the interstitial space, rupture of muscle fibers, and deposition of myocardial collagen fibers. In addition, Under the 0.4 mg/kg bw TBA exposure, myocardial oxidative stress was observed in broilers, which was accompanied by the activation of Nrf2/HO-1 pathway and the increased protein and mRNA levels of NQO1, NOX2 and SOD2 antioxidant enzymes. However, Nrf2/HO-1 protein and mRNA levels were reversed at 4 mg/kg bw TBA exposure. Meanwhile, the Nrf2/HO-1 mediated antioxidant defense was impaired. In contrast with the low dose, the protein and gene expression levels of NQO1, NOX2, and SOD2 were reduced in 4 mg/kg bw TBA group. The expression of GPX4 and SLC7A11 was significantly downregulated at both protein and mRNA levels. Beyond that, ACSL4 expression was significantly up-regulated, and the protein result was consistent with the mRNA expression, demonstrating the occurrence of ferroptosis. In general, TBA exposure activated the Nrf2/HO-1 pathway, resulting in ferroptosis. This study links ferroptosis to the Nrf2/HO-1 pathway, providing new insights into the potential role of TBA in myocardial toxicity.

Investigation on the effect of multiwalled carbon nanotubes in carbon fiber‐reinforced epoxy composites manufactured using vacuum infusion process and hand layup process followed by vacuum bagging

AbstractEpoxy/carbon fiber (CF) composites are widely used for structural applications owing to their exceptional mechanical and physical characteristics. The main aim of this work is to individually analyze the impact of multiwalled carbon nanotubes (MWCNTs) as nanofillers in epoxy/MWCNTs/CF composites prepared by vacuum infusion process (VIP) and hand layup followed by vacuum bagging technique (HLVB). Optimal Manufacturing Strategies were followed at various stages of manufacturing which include the selection of effective dispersion technique for MWCNTs, identification of optimal weight percentage of MWCNTs in epoxy/MWCNTs nanocomposites and preparation of epoxy/MWCNTs/CF composites. For HLVB samples, tensile and flexural strengths increased from 337.5 to 475 MPa and 615.40 to 677.09 MPa. For VIP samples tensile and flexural strengths increased from 371 to 521 MPa and 714.19 to 769.02 MPa. Thermogravimetric analysis (TGA) indicated improvement in the thermal stability of epoxy with the incorporation of MWCNTs/CF and improved weight percentage retention of 84.7% at 375°C. Fracture analysis of the epoxy/MWCNTs/CF composites prepared using VIP were analyzed by FE‐SEM and revealed that constant fiber rupture caused by better interface and improved bridging mechanism eventually led to enhanced mechanical performance. The predominant immediate fracture mechanism of MWCNTs also indicated this improved interfacial interaction.Highlights Pull‐out fracture mechanism was predominantly seen in high viscous epoxy/MWCNTs composites Immediate fracture mechanism of MWCNTs were predominant in low viscous epoxy/MWCNTs sample Constant fiber rupture of VIP samples indicated improved fiber matrix interface Incorporation of MWCNTs showed improved weight percentage retention 0.5 wt% MWCNTs incorporated VIP epoxy/CF composites showed improved performance

Fast continuous in-situ XCT of additively manufactured carbon fiber reinforced tensile test specimens

The reinforcement of fused filament fabricated (FFF) components with continuous fibers allows for high versatility in the design of mechanical properties for a specific applications needs. However, the bonding quality between continuous fibers and the FFF matrix material has high impact on the overall performance of the composite. To investigate the bonding quality within additively manufactured (AM) continuous fiber reinforced specimens, tensile tests have been performed which revealed a sudden reduction in tensile stress, that most likely was not related to actual rupture of continuous fibers. Consequently, within this work we will expand upon these findings and present results of fast on-the-fly in-situ investigations performed on continuous carbon fiber reinforced specimens of the same AM build. During these investigations, specimens are loaded under the same conditions while fast XCT scans, with a total scan time of 12 seconds each, were performed consecutively. The resulting three-dimensional image data reveals internal meso- and macro-structural changes over time/strain to find the cause of the aforementioned reduction in tensile stress.

Pull-out behaviour of steel fibres embedded in ultra-high-performance concrete after exposure to high temperatures

The paper examined the bond-slip behaviour of steel fibres embedded in ultra-high-performance concrete (UHPC) after exposure to elevated temperatures. Different types of steel fibres were cast into the halved UHPC dog-bone-shaped samples, including straight fibres, three types of hooked-end fibres and corrugated fibres. The bond response was investigated through single fibre pull-out tests on the samples unheated and heated to 200, 400 and 600 °C. In addition, the effects of polypropylene (PP) fibre addition and heating rate on steel fibre’s bond behaviour were also investigated. The results revealed an increase in bond strength when the straight and hooked-end fibre samples were heated to 200 °C, while the bond strength of the corrugated fibre decreased at the same temperature. Bond strength reductions were observed at higher temperatures. In addition, the straight fibres led to the lowest pull-out resistance as both the hooked-end and the corrugated fibres significantly enhanced the bond strength. With the hooked-end or corrugated fibres, the failure mode gradually shifted from pull-out failure to fibre rupture. Besides, adding PP fibres increased the bond strength of straight fibres at 400 °C but reduced the bond strengths of hooked-end fibres at ambient and high temperatures. High heating rate also led to a greater bond strength for the straight fibres at 200 °C and 400 °C.

Effects of electroacupuncture on gait and proliferation and differentiation of muscle satellite cell in rats with acute blunt trauma of gastrocnemius muscle

To observe the effects of electroacupuncture on threshold of pain, gait, proliferation and differentiation of muscle satellite cell in rats with acute blunt trauma of gastrocnemius muscle, and to explore the possible mechanism of electroacupuncture in promoting the repair of acute injury of skeletal muscle. A total of 48 SD rats were randomly divided into a blank group (6 rats), a model group (24 rats) and an electroacupuncture group (18 rats). In the model group and the electroacupuncture group, the model of acute blunt trauma of gastrocnemius muscle was established by self-made impactor. In the electroacupuncture group, electroacupuncture was applied at "Chengshan" (BL 57) and "Yanglingquan" (GB 34) on the right side, with disperse-dense wave, in frequency of 2 Hz/100 Hz, once a day, 30 min each time. Electroacupuncture intervention was performed for 3, 7 and 14 days according to the sampling time. On the 1st, 3rd, 7th and 14th days after modeling, the mechanical withdrawal pain threshold of hindfoot was detected by Von Frey method; the standing time and the maximum contact area of the right hindfoot were recorded by Cat Walk XTTM animal gait analysis instrument; the morphology of the right gastrocnemius muscle and the number of inflammatory cells were observed by HE staining; the positive expression of paired box gene 7 (Pax7) and myogenic differentiation (MyoD) of the right gastrocnemius muscle was detected by immunofluorescence. After modeling, the muscle fiber rupture and massive infiltration of red blood cells and inflammatory cells were observed in the right gastrocnemius muscle; after electroacupuncture intervention, the morphology of muscle fiber was intact and the infiltration of inflammatory cells was improved. Compared with the blank group, in the model group, the differences of mechanical withdrawal pain threshold between the left and right foot were increased (P<0.05), the standing time was shortened and the maximum contact area of the right hindfoot was decreased (P<0.05), the number of inflammatory cells and the positive expression of Pax7 and MyoD of the right gastrocnemius muscle were increased (P<0.05) on the 1st, 3rd, 7th and 14th days after modeling. Compared with the model group, in the electroacupuncture group, the differences of mechanical withdrawal pain threshold were decreased (P<0.05), the standing time was prolonged (P<0.05), the number of inflammatory cells of right gastrocnemius muscle was decreased (P<0.05) on the 7th and 14th days after modeling; the maximum contact area of the right hindfoot was increased (P<0.05), the positive expression of MyoD of the right gastrocnemius muscle was increased (P<0.05) on the 3rd, 7th and 14th days after modeling; the positive expression of Pax7 of the right gastrocnemius muscle was increased (P<0.05) on the 3rd day after modeling. Electroacupuncture can effectively improve the pain threshold and gait in rats with acute blunt trauma of gastrocnemius muscle, and promote the repair of skeletal muscle injury, the mechanism may be related to the up-regulation of Pax7 and MyoD, so as to promoting the proliferation and differentiation of muscle satellite cell.

The effects of particle sizes of expanded perlite on the mechanical properties and chloride penetration resistance of ECCs

This study presents the development of engineered cementitious composites (ECCs) incorporating expanded perlite particles (EPPs) with varying sizes, namely 150 mesh, 50–70 mesh, and 5–15 mesh, as well as an equivalent combination of these three sizes. The primary focus of the investigation was to evaluate the microstructures at different ages, mechanical properties, and chloride penetration resistance of ECCs incorporating EPPs. The results showed the presence of a compact interfacial transition zone (ITZ) between the matrix and EPPs, attributable to the internal curing effect. The incorporation of EPPs effectively mitigated fiber damage during fiber-matrix separation, thereby preventing premature fiber rupture. Specifically, the inclusion of 150 mesh EPP demonstrated improved mechanical properties compared to the control group. Furthermore, the addition of 5–15 mesh or mixed EPP enhanced the chloride penetration resistance of ECC, while contrasting results were observed for 150 mesh and 50–70 mesh EPPs. Additionally, this study explored the use of 150 mesh recycled rubber (RR) as an additional defect. ECCs with simultaneous incorporation of RR and EPPs (at a 2% content) exhibited excellent ductility, with an overall tensile strain ranging from 4.3% to 4.7%. The results for the combined addition of RR and EPPs aligned with those observed for the singular addition of EPPs in terms of chloride penetration resistance.

Effects of Age, Sex, and Extracellular Matrix Integrity on Aortic Dilatation and Rupture in a Mouse Model of Marfan Syndrome.

Transmural failure of the aorta is responsible for substantial morbidity and mortality; it occurs when mechanical stress exceeds strength. The aortic root and ascending aorta are susceptible to dissection and rupture in Marfan syndrome, a connective tissue disorder characterized by a progressive reduction in elastic fiber integrity. Whereas competent elastic fibers endow the aorta with compliance and resilience, cross-linked collagen fibers confer stiffness and strength. We hypothesized that postnatal reductions in matrix cross-linking increase aortopathy when turnover rates are high. We combined ex vivo biaxial mechanical testing with multimodality histological examinations to quantify expected age- and sex-dependent structural vulnerability of the ascending aorta in Fbn1C1041G/+ Marfan versus wild-type mice without and with 4-week exposures to β-aminopropionitrile, an inhibitor of lysyl oxidase-mediated cross-linking of newly synthesized elastic and collagen fibers. We found a strong β-aminopropionitrile-associated sexual dimorphism in aortic dilatation in Marfan mice and aortic rupture in wild-type mice, with dilatation correlating with compromised elastic fiber integrity and rupture correlating with compromised collagen fibril organization. A lower incidence of rupture of β-aminopropionitrile-exposed Marfan aortas associated with increased lysyl oxidase, suggesting a compensatory remodeling of collagen that slows disease progression in the otherwise compromised Fbn1C1041G/+ aorta. Collagen fiber structure and function in the Marfan aorta are augmented, in part, by increased lysyl oxidase in female and especially male mice, which improves structural integrity, particularly via fibrils in the adventitia. Preserving or promoting collagen cross-linking may represent a therapeutic target for an otherwise vulnerable aorta.

Adrenal SGLT1 or SGLT2 as predictors of atherosclerosis under chronic stress based on a computer algorithm.

Chronic stress promotes the development of atherosclerosis, causing disruptions in the body's hormone levels and changes in the structural function of organs. The purpose of this study was to investigate the pathological changes in the adrenal gland in a model of atherosclerosis under chronic stress and to verify the expression levels of Sodium-glucose cotransporter (SGLT) 1 and SGLT2 in the adrenal gland and their significance in the changes of adrenal gland. The model mice were constructed by chronic unpredictable stress, high-fat diet, and Apoe-/- knockout, and they were tested behaviorally at 0, 4, 8 and 12 weeks. The state of the abdominal artery was examined by ultrasound, and the pathological changes of the aorta and adrenal glands were observed by histological methods, and the expression levels and distribution of SGLT1 and SGLT2 in the adrenal gland were observed and analyzed by immunofluorescence and immunohistochemistry. The predictive value of SGLT1 and SGLT2 expression levels on intima-media thickness, internal diameter and adrenal abnormalities were verified by receiver operating characteristic (ROC) curves, support vector machine (SVM) and back-propagation (BP) neural network. The results showed that chronic stress mice had elevated expression levels of SGLT1 and SGLT2. The model mice developed thickening intima-media and smaller internal diameter in the aorta, and edema, reticular fiber rupture, increased adrenal glycogen content in the adrenal glands. More importantly, analysis of ROC, SVM and BP showed that SGLT1 and SGLT2 expression levels in the adrenal glands could predict the above changes in the aorta and were also sensitive and specific predictors of adrenal abnormalities. SGLT1 and SGLT2 could be potential biomarkers of adrenal injury in atherosclerosis under chronic stress.

Ballistic Behavior of Epoxy Composites Reinforced with Amazon Titica Vine Fibers (Heteropsis flexuosa) in Multilayered Armor System and as Stand-Alone Target.

Seeking to improve personal armor equipment by providing mobility and resistance to penetration, this research aimed to explore the potential of sustainable materials in order to assess their ability in ballistic applications. Titica vine fibers (TVFs) extracted from aerial roots of Heteropsis flexuosa from the Amazon region were incorporated at 10, 20, 30, and 40 vol% into an epoxy matrix for applications in ballistic multilayered armor systems (MASs) and stand-alone tests for personal protection against high-velocity 7.62 mm ammunition. The back-face signature (BFS) depth measured for composites with 20 and 40 vol% TVFs used as an intermediate layer in MASs was 25.6 and 32.5 mm, respectively, and below the maximum limit of 44 mm set by the international standard. Fracture mechanisms found by scanning electron microscopy (SEM) attested the relevance of increasing the fiber content for applications in MASs. The results of stand-alone tests showed that the control (0 vol%) and samples with 20 vol% TVFs absorbed the highest impact energy (Eabs) (212-176 J), and consequently displayed limit velocity (VL) values (213-194 m/s), when compared with 40 vol% fiber composites. However, the macroscopic evaluation found that, referring to the control samples, the plain epoxy shattered completely. In addition, for 10 and 20 vol% TVFs, the composites were fragmented or exhibited delamination fractures, which compromised their physical integrity. On the other hand, composites with 30 and 40 vol% TVFs, whose Eabs and VL varied between 166-130 J and 189-167 m/s, respectively, showed the best physical stability. The SEM images indicated that for composites with 10 and 20 vol% TVFs, the fracture mode was predominantly brittle due to the greater participation of the epoxy resin and the discrete action of the fibers, while for composites with 30 and 40 vol% TVFs, there was activation of more complex mechanisms such as pullout, shearing, and fiber rupture. These results indicate that the TVF composite has great potential for use in bulletproof vests.

Degradation and Microstructure of Palmdate Fibers-High Performance Cementitious Boards Exposed to Aging Conditions

It is essential to create more ecologically friendly and sustainable types of concrete due to severe emissions and the exhaustion of raw sources in cement manufacturing. The main objective was to determine if palmdate fibers were appropriate for use in wood-cement composite boards. A second objective is to improve the suitability of palmdate fibers for use in high-performance cementitious boards by pre-treatment procedures and carbon dioxide curing. The flexural strength and microstructural characteristics of the cement fiber boards were examined. In addition, durability tests including cycles of freezing and thawing, wetting and drying, and warm water immersion were also conducted. According to results, the use of treated palmdate fibers in high-performance cementitious boards was significant, because it increased flexural strength by 96%. Moreover, all CO2 cured boards showed higher flexural strength than control and pure carbonation curing 100% do not resulted in higher strength development. Also, X-ray diffraction patterns revealed, compared to control boards, CO2 cured boards showed more CaCO3 and lower Ca(OH)2 and according to SEM, aging exposures lead to make fibers rupture rather than pull out.

Improving the dynamic splitting properties of engineered cementitious composites using hybrid synthetic polymer and recycled steel fibres

To improve the dynamic mechanical behaviour and make full use of recycled waste tyres, this study investigates the feasibleness of partial replacement of polyvinyl alcohol (PVA) fibres with recycled tyre steel (RTS) fibres in engineered cementitious composites (ECC). A series of laboratory tests were carried out to evaluate the workability, elastic modulus and uniaxial tensile behaviour, as well as the quasi-static and dynamic splitting tensile behaviour of ECC containing PVA and RTS fibres. The experimental results indicate that the replacement of 0.25% PVA fibres with RTS fibres results in a 0.85 MPa drop in tensile strength, while a nearly one-tenth increase in first-crack strength appears as the stronger RTS fibre-to-matrix bonding is effective in controlling the initiation of the first crack. Under dynamic loading, the mono PVA fibre reinforced ECC gradually loses the specimen integrity due to the rupture of PVA fibres at higher strain rates, while the bridging effect of RTS fibres contributes to maintaining the specimen integrity even at the highest measured strain rates of 7.3–7.5 s−1. Moreover, the replacement of 0.5% RTS fibres can lead to up to 15.54% and 27.38% increase in dynamic splitting strength and dissipation energy, respectively, relative to that with 2.0% PVA fibres. In addition, the evolution of dynamic increase factor with strain rate is modelled by theoretical equations considering the content and length-to-diameter ratio of fibres, the predictions of which match well with the experimental results.

Bioinformatics analysis and key gene verification of sepsis myocardial macrophage microarray data based on GEO database

Objective: Bioinformatics analysis was used to screen differentially expressed genes (DEGs) in macrophages of sepsis myocardial injury and to verify key genes. Methods: Experiment 1 (gene chip and bioinformatics analysis): The gene chip data GSE104342 of cardiac macrophages in septic mice was downloaded from Gene Expression Omnibus database. DEGs were obtained by R language analysis. DAVID online database was used to obtain gene ontology and kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis of DEGs. STRING online database was used for protein-protein interaction network analysis of DEGs, and then key genes were screened by using Cytoscape software and molecular complex detection (MCODE) plug-ins. Experiment 2 (sepsis model construction and related protein verification): Ten male C57BL/6 mice, aged 8-14 weeks. Five mice were randomly selected as control group, and 5 mice were selected as the sepsis group by building a mice sepsis model in vivo. Echocardiography was used to detect the cardiac function. Hematoxylin-eosin staining was used to assess the cardiac morphology. TUNEL staining was used to evaluate cardiomyocyte apoptosis. Immunofluorescence staining was used to detect the expression of differentiation antigen cluster 206 (CD206),inducible nitric oxide synthases (iNOS),F4/80,suppressor of cytokine signaling 3 (Socs3) ,interleukin 1 receptor antagonist (Il1rn) and chemokine C-C motif ligand 7 (Ccl7) protein. RAW264.7 macrophages were cultured in vitro and divided into 2 groups: LPS groupstimulated by lipopolysaccharide (LPS, 1 mg/L) and blank control group treated with equal-volume phosphate buffer solution. Reverse transcription-polymerase chain reaction (RT-PCR) was used to evaluate the expression of Socs3, Il1rn and Ccl7 in vitro. Results: Experiment 1: 24 647 genes were screened in GSE104342 dataset and 177 genes (0.72%) were differential expression, including 120 up-regulated genes and 57 down-regulated genes. Gene ontology enrichment analysis showed that DEGs were mainly involved in inflammatory response, immune response, apoptosis regulation and antigen processing and presentation. KEGG signaling pathway analysis showed that DEGs in cardiac macrophages of septic mice were mainly enriched in cytokine-cytokine receptor interaction, tumor necrosis factor signaling pathway, NOD like receptor signaling pathway. Three hub genes were obtained by STRING and Cytoscape analysis, including Socs3, Il1rn and Ccl7. Experiment 2: In vivo, it was found that compared with the control group, the cardiac function of the sepsis mice decreased significantly, the myocardial cells were significantly edema, inflammatory cell infiltration, myocardial fiber rupture, some myocardial nuclei dissolved and disappeared, and the cardiomyocyte apoptosis increased, suggesting that the sepsis myocardial injury model of mice was successfully constructed. Compared with the control group, the expression of CD206 in the myocardium of septic mice was down-regulated, the expression of iNOS, F4/80, Socs3, Il1rn and Ccl7 were up-regulated. In addition, there was co-localization between Socs3, Il1rn, Ccl7 and F4/80 protein. Compared with the blank control group, the expression of Socs3, Il1rn and Ccl7 significantly upregulated after LPS intervention in vitro by RT-PCR. Conclusions: The selected key genes Socs3, Il1rn and Ccl7 were up-regulated in myocardial macrophages of septic mice. Socs3, Il1rn and Ccl7 are expected to become new targets for the diagnosis and treatment of sepsis cardiac injury.

Effects of fiber content, inclination angle, and casting point on the fiber-matrix interaction of High-Strength Fiber-Reinforced Self Compacting Concrete

This experimental study examines the pullout behavior of aligned and inclined steel fibers embedded in High-Strength Fiber-Reinforced Self Compacting Concrete (HSFRSCC). The effects of four fiber contents (0, 0.25, 0.50, and 0.75%), three inclination angles (0°, 30°, and 45°), and three concrete casting points on the formwork were investigated. The analyses were performed based on load-slip relationships, maximum pullout load, dissipated energy, failure mode, and spalling area. The fiber pullout behavior evidenced the importance of the presence of fibers in the concrete matrix. The pullout loads and pullout energy presented a better performance than the unreinforced matrix when the fiber content was increased to 0.75%; the confinement effect of the fibers in the matrix explains this mechanism. Regarding the failure mode, some inclined fibers at 30° and 45° presented rupture during pullout, more recurrent for 45° and for the matrices that offered greater confinement (0 and 0.75%). Furthermore, the spalling area increased with the inclination angle; it was found that the presence of fibers in the matrix influences the propagation of cracks during the matrix spalling. In some cases, these can increase the susceptibility of fiber rupture during the pullout. Finally, it was inconclusive that the pulled fibers' position relative to the casting point and, consequently, the fiber orientation influences the pullout load.

Flexural properties of ultra-high performance fiber reinforced concrete based on three-dimensional random distribution of steel fibers

The distribution of fibers and the fiber bridging affect the flexural strength and energy dissipation of ultra-high-performance fiber reinforced concrete (UHFRC) members. In this study, an analytical model to predict the flexural behavior of UHPFRC was developed based on the three-dimensional random distribution of fibers. The probability distribution model of the fiber orientation was developed as a sine function, which agreed to the measured probability data from the randomly distributed fiber specimens. The number of fibers at the fracture surface was determined addressing the effect of fiber orientation. Based on the proposed model, the method to predict the load–deflection curve of UHPFRC beam was suggested addressing the fiber bridging stress at fracture surface and tension softening effect. For verification, the four points flexural tests were conducted for six UHPFRC beam specimens. The test results showed that the peak flexural strength and energy dissipation can be predicted by the proposed model. Further, the proposed model was applicable to predict the strength and deformation capacity of existing test specimens. Based on the proposed model, the aspect ratio of fibers to prevent the brittle failure due to fiber rupture was suggested addressing the fiber tensile strength and bond strength.

Effect of ageing conditions on the low velocity impact behavior and damage characteristics of aramid-basalt/epoxy hybrid interply composites

Polymer composites reinforced with aramid and basalt fibres are widely used in aviation, automobile, marine and civil structural components. In these applications, composites are often exposed to different environments involving temperature and humidity, which leads to the deterioration of mechanical properties and service life of the structure. This study aimed at investigating the influence of different ageing conditions on the low velocity impact (LVI) performance of 2-D aramid-basalt/epoxy interply composites. Compression molding method of fabrication was employed to prepare the hybrid laminates. LVI coupons were made as per the ASTM D3763 standard and aged in distilled water medium at three different temperatures namely, ambient condition (25 ℃), sub-zero condition (−10 ℃), and humid condition (40 ℃ and 60% relative humidity) until the specimens attain moisture saturation. After ageing, specimens were put through low velocity impact testing at two different impact energies of 10 J and 15 J and results were compared with the pristine specimens. Ultrasonic C-Scan and Scanning Electron Microscopy (SEM) were utilized to analyse the delamination due to impact and micro structural assessment of the pristine and aged specimens. Studies revealed that, specimens aged under sub-zero conditions showed better impact response compared to all other ageing conditions. Furthermore, fibre rupture, matrix decomposition, weakened fibre–matrix interface bonding and delamination were the major damages observed in aged specimens.

Multiscale theoretical model shows that aging-related mechanical degradation of cortical bone is driven by microstructural changes in addition to porosity

This study aims to gain mechanistic understanding of how aging-related changes in the microstructure of cortical bone drive mechanical consequences at the macroscale. To that end, cortical bone was modeled as a bundle of elastic–plastic, parallel fibers, which represented osteons and interstitial tissue, loaded in uniaxial tension. Distinct material properties were assigned to each fiber in either the osteon or interstitial fiber “families.” Models representative of mature (20–60 yrs.) bone, and elderly (60+) bone were created by modeling aging via the following changes to the input parameters: (i) increasing porosity from 5% to 15%, (ii) increasing the ratio of the number of osteon fibers relative to interstitial fibers from 40% to 50%, and (iii) changing the fiber material properties from representing mature bone samples to representing elderly bone samples (i.e., increased strength and decreased toughness of interstitial fibers together with decreased toughness of osteon fibers). To understand the respective contributions of these changes, additional models isolating one or two of each of these were also created. From the computed stress–strain curve for the fiber bundle, the yield point (ϵy, σy), ultimate point (ϵu, σu), and toughness (UT) for the bundle as a whole were measured. We found that changes to all three input parameters were required for the model to capture the aging-related decline in cortical bone mechanical properties consistent with those previously reported in the literature. In both mature and elderly bundles, rupture of the interstitial fibers drove the initial loss of strength following the ultimate point. Plasticity and more gradual rupture of the osteons drove the remainder of the response. Both the onset and completion of interstitial fiber rupture occurred at lower strains in the elderly vs. mature case. These findings point to the importance of studying microstructural changes beyond porosity, such as the area fraction of osteons and the material properties of osteon and interstitial tissue, in order to further understanding of aging-related changes in bone.

Histological and clinical analysis of knee cyclops lesions.

Cyclops Syndrome, first described by Jackson and Schaefer in 1990, is known as a complication of anterior cruciate ligament reconstruction (ACLR). However further researches have demonstrated that cyclops can be present even without symptoms and/or in absence of ACLR, simply configuring itself as a lesion in patients with rupture of the native ligament. This is a retrospective cohort study in which we report our experience of 13 cyclops lesions found between 126 patients during a primary arthroscopic ACLR. Preoperative examination with tests of joint stability and range of movement measurement was performed and recorded. Accurate joint examination was performed during arthroscopy and the cyclops lesions found were removed and analyzed with haematoxylin-eosin coloration. Post-operative clinical examination was performed until 6 months of follow-up. Histological analysis showed proliferation of dense fibroelastic polypoid nodules with a macroscopically histological aspects of a "blue eye", hence the name Cyclops. At 6 months of follow-up after surgery, none of the patients reported pain at terminal extension or instability and they were all able to resume their previous activities. Our study confirmed that surgical reconstruction of the ACL is not the only condition in which the Cyclops Syndrome develops; in fact our histological analysis indicate that the Cyclops lesions develop like a reactive fibroproliferative process following the rupture of the native ACL fibers, as scar reaction to the trauma: for this reason an accurate arthroscopic detection of these Cyclops lesions is crucial during primary ACL reconstruction in order to obtain the best surgical outcomes.

A novel local to global (L2G) method for progressive fracture analysis of composite laminates

In this paper, we extend a recently developed local to global (L2G) method to capture complex progressive damage processes in composite laminates, which include intra-ply matrix/fiber failure and inter-ply delamination. The L2G builds and solves local problems for individual and interactive cracks, whose local solutions are returned as part of the trial solution for global iteration. It has been demonstrated that the proposed method has advantages of good-accuracy, high-efficiency, and robustness. It can deal with complex problem of cracks branching/merging and multiple interactive cracks. This paper uses the L2G to handle different intra-ply failure modes by adopting Hashin’s criterion, and cohesive zone model (CZM) element is used to capture delamination in inter-plies. Numerical examples of several different stacking open-hole composite laminates show that the proposed L2G is capable of modeling failure processes from minor matrix cracks initiation to final fiber rupture.

A spike-shaped anchorage for steel reinforced polymer (SRP)-strengthened concrete structures

Steel reinforced polymer (SRP) composite has recently emerged as an effective and economical solution for strengthening of reinforced concrete (RC) structures. Premature debonding failure of unanchored SRP at low load levels generally governs the performance of RC structures strengthened with externally bonded SRP. Therefore, a novel yet simple spike-shaped anchorage system was proposed in this study to prevent the debonding failure of SRP and to improve the interfacial shear capacity. Experimental investigation through single-lap shear tests of SRP-concrete joints showed that the anchorage system changed the failure mode from composite debonding to fiber rupture. In addition, the anchorage system substantially increased the peak load and reduced the interfacial slippage of the SRP-concrete joint compared to the unanchored condition. A numerical procedure based on the finite difference method was developed to predict the full-range load response, and results matched well with the full-range experimental responses of anchored and unanchored specimens. Parametric study of the test results and numerical simulation based on finite difference method both showed that the fiber rupture failure mode could be achieved for anchors in various positions along the bonded length. The closer the anchor is to the loaded end, the less global slip was obtained when the load reached the peak value.

The Effects of Postmortem Time on Muscle Trout Biochemical Composition and Structure.

Fish industry operators have to process fish that arrive at various postmortem times. Postmortem time constrains processing and impacts product quality, safety, and economic value. The objective identification of biomarkers is desirable to predict the postmortem day of aging and this requires a comprehensive longitudinal characterisation of postmortem aging. We analysed the postmortem aging process in trout over a 15-day window. Quantitative physicochemical measurements (pH, colour, texture, aw, proteolysis, and myofibrillar protein solubility) performed on the same fish over time revealed the levels of protein denaturation, solubility, and pH, among other parameters, change very little when assessed by conventional chemical methods. Histological analyses were performed on thin sections and revealed fibre ruptures after 7 days of storage on ice. Ultrastructures were observed by transmission electronic microscopy (TEM) and revealed that sarcomere disorganisation occurred more often after 7 days of storage. Label-free FTIR micro-spectroscopy combined with a SVM model accurately predicted the postmortem time. Spectra-based PC-DA models also enable the identification of biomarkers corresponding to Day 7 and Day 15 postmortem. This study provides insights on postmortem aging and raises prospects for the rapid assessment of trout's freshness status from label-free imaging.