Analytical Model to Describe Damage in CFRP Specimen When Subjected to Low Velocity Impacts

Abstract In the light of an increment of the safety of CFRP components subjected to low-velocity impacts, the identification of a damage onset threshold is desired. Hence the suitability of an analytical model for the estimation of the critical load of delamination onset and the resulting delaminated area, as well as for the approximation of the load-displacement curve, has been investigated. The Olsson's analytical model, available in the literature, is considered and applied in this study for the prediction of the mechanical behaviour of composite specimens subject to low-velocity impacts. Comparisons with experimental results have been carried out to demonstrate the accuracy of the presented model. Impact tests were performed in accordance with ASTM D7136 standard and damage was assessed by means of ultrasonic testing and computed tomography

Prolonged exposure of cortical neurons to oligomeric amyloid-β impairs NMDA receptor function via NADPH oxidase-mediated ROS production: protective effect of green tea (–)-epigallocatechin-3-gallate

Excessive production of Aβ (amyloid β-peptide) has been shown to play an important role in the pathogenesis of AD (Alzheimer's disease). Although not yet well understood, aggregation of Aβ is known to cause toxicity to neurons. Our recent study demonstrated the ability for oligomeric Aβ to stimulate the production of ROS (reactive oxygen species) in neurons through an NMDA (N-methyl-d-aspartate)-dependent pathway. However, whether prolonged exposure of neurons to aggregated Aβ is associated with impairment of NMDA receptor function has not been extensively investigated. In the present study, we show that prolonged exposure of primary cortical neurons to Aβ oligomers caused mitochondrial dysfunction, an attenuation of NMDA receptor-mediated Ca2+ influx and inhibition of NMDA-induced AA (arachidonic acid) release. Mitochondrial dysfunction and the decrease in NMDA receptor activity due to oligomeric Aβ are associated with an increase in ROS production. Gp91ds-tat, a specific peptide inhibitor of NADPH oxidase, and Mn(III)-tetrakis(4-benzoic acid)-porphyrin chloride, an ROS scavenger, effectively abrogated Aβ-induced ROS production. Furthermore, Aβ-induced mitochondrial dysfunction, impairment of NMDA Ca2+ influx and ROS production were prevented by pre-treatment of neurons with EGCG [(−)-epigallocatechin-3-gallate], a major polyphenolic component of green tea. Taken together, these results support a role for NADPH oxidase-mediated ROS production in the cytotoxic effects of Aβ, and demonstrate the therapeutic potential of EGCG and other dietary polyphenols in delaying onset or retarding the progression of AD

High-Dose Testosterone Propionate Treatment Reverses the Effects of Endurance Training on Myocardial Antioxidant Defenses in Adolescent Male Rats

This study was aimed at evaluation of changes in activities of selected antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase) and contents of key nonenzymatic antioxidants (glutathione, protein thiol groups, and α- and γ-tocopherols) in the left heart ventricle of young male Wistar rats subjected to endurance training (treadmill running, 1 h daily, 5 days a week, for 6 weeks) or/and testosterone propionate treatment (8 or 80 mg/kg body weight, intramuscularly, once a week, for 6 weeks) during adolescence. The training alone increased the activities of key antioxidant enzymes, but lowered the pool of nonenzymatic antioxidants and enhanced myocardial oxidative stress as evidenced by elevation of the lipid peroxidation biomarker malondialdehyde. The lower-dose testosterone treatment showed mixed effects on the individual components of the antioxidant defense system, but markedly enhanced lipid peroxidation. The higher-dose testosterone treatment decreased the activities of the antioxidant enzymes, lowered the contents of the nonenzymatic antioxidants, except for that of γ-tocopherol, reversed the effect of endurance training on the antioxidant enzymes activities, and enhanced lipid peroxidation more than the lower-dose treatment. These data demonstrate the potential risk to cardiac health from exogenous androgen use, either alone or in combination with endurance training, in adolescents

Lipoxygenases and Poly(ADP-Ribose) Polymerase in Amyloid Beta Cytotoxicity

The 12/15-lipoxygenase(s) (LOX), poly(ADP-ribose) polymerase (PARP-1) activity and mitochondrial apoptosis inducing factor (AIF) protein in the amyloid β (Aβ) toxicity were investigated in PC12 cells that express either wild-type (APPwt) or double Swedish mutation (APPsw) forms of human Aβ precursor protein. Different levels of Aβ secretion and free radicals formation characterize these cells. The results demonstrated a relationship between the Aβ levels and LOX protein expression and activity. High Aβ concentration in APPsw cells correlated with a significant increase in free radicals and LOX activation, which leads to translocation of p65/NF-κB into the nucleus. An increase in AIF expression in mitochondria was observed concurrently with inhibition of PARP-1 activity in the nuclear fraction of APPsw cells. We suggested that AIF accumulation in mitochondria may be involved in adaptive/protective processes. However, inhibition of PARP-1 may be responsible for the disturbances in transcription and DNA repair as well as the degeneration of APP cells. Under conditions of increased nitrosative stress, evoked by the nitric oxide donor, sodium nitroprusside (SNP, 0.5 mM), 70–80% of all cells types died after 24 h, significantly more in APPsw cells. There was no further significant change in mitochondrial AIF level and PARP-1 activity compared to corresponding non-treated cells. Only one exception was observed in PC12 control, where SNP significantly inhibits PARP-1 activity. Moreover, SNP significantly activated gene expression for 12/15-LOX in all types of investigated cells. Inhibitors of all LOX isoforms and specific inhibitor of 12-LOX enhanced the survival of cells that were subjected to SNP. We conclude that the LOX pathways may play a role in Aβ toxicity and in nitrosative-stress-induced cell death and that inhibition of these pathways offers novel protective strategies

Possible application of X-ray computed tomography (CT) in aviation

W artykule omówione zostały możliwości zastosowania metody CT w lotnictwie. Nowoczesna nieniszcząca metoda diagnostyczna, jaką jest tomografia komputerowa, pozwala na badania praktycznie wszystkich materiałów stosowanych w szeroko rozumianej branży lotniczej - od stopów chromowo - niklowych stosowanych do produkcji łopatek turbinowych, poprzez materiały kompozytowe, aż do nawierzchni lotniskowych. Metoda ta pozwala także na badania całych agregatów, bez konieczności ich demontażu np. podczas badań komisyjnych zdarzeń lotniczych. W artykule pokazano możliwości i ograniczenia zastosowania badań metodą CT na konkretnych przykładach detali lotniczych.The article describes the possibilities of the application of the CT method in aviation. The modern non-destructive diagnostic method, which is the computer tomography, enables to examine all materials applied in the widely understood aviation industry. From chromium-nickel alloys used to manufacture turbine blades, through composite materials, to runway pavements. This method enables to test all aggregates, without the necessity to dismantle them e.g. during commission tests of aircraft incidents. The article showed the possibilities and limitations of conducting tests with the CT method in particular examples of aircraft details

The rate of decohesion of a gas turbine blade as assessed with the X-ray computed tomography (CT)

The overheating of the material is among major reasons for failures/damages to gas turbine blades throughout the entire process of operating aircraft turbine engines. The essential method of diagnosing condition of the blades is metallographic examination being however a destructive technique. The paper has been intended to discuss one of non-destructive testing (NDT) methods, i.e. the X-ray computed tomography (CT), and capabilities of applying it to diagnose changes in condition of gas turbine blades. ‘Tomography’ is a comprehensive term to define a set of diagnostic techniques to produce three-dimensional images that present cross-sections through detail items under scrutiny. The CT is a transmission diagnostic technique that allows layered models (images) of details to be acquired. Most commonly, it is used in research laboratories and throughout the process of the product quality inspection. The paper delivers findings of the preliminary investigation into the assessment of health/maintenance status of gas turbine blades by means of the X-ray computed tomography. The results gained have been successfully verified using the metallographic examination techniques. It has been found that the radiographic imaging method enables recognition of types, sizes, and locations of internal faults in the blades while generating three-dimensional images thereof. Presented are capabilities of the high-resolution X-ray inspection machine with computed tomography (CT), V/tome/x, furnished with a 300 kV tube, and the CT data processing capabilities of the VG Studio Max software solution, high-performance CT reconstruction included (using an optional module). At the same time work is under way with the X-ray tube for nanotomography with the 0.5 m resolution to examine, in particular, modern composite materials