Main Damage Mechanisms Research Articles

COVID-19 and the nervous system: pathogenesis, mechanisms, and outcomes

In the acute period of COVID-19, more than 1/3 patients develop neurological symptoms, 25% of which can be attributed to direct damage to the central nervous system. Most often, all these complications arise due to the penetration of the virus into the systemic circulation, its dissemination and damage to the vascular endothelium. All clinical manifestations associated with the penetration of COVID-19 into the nervous tissue can be divided into several groups:1) signs of damage to the central nervous system, including headache, impaired consciousness, encephalitis, cerebrovascular diseases, seizures and ataxia; 2) signs of damage to the peripheral nervous system, such as anosmia/hyposmia, dysgeusia, visual disturbances, neuralgia and Guillain-Barre syndrome; and 3) signs of damage to the musculoskeletal system, such as myopathy, myalgia and fatigue.The aim of the review was to identify the main sources and mechanisms of nerve tissue damage in COVID-19 disease.Literature search was conducted in the Web of Science, PubMed and Scopus databases. The search was carried out by the following keywords: «COVID-19», «nerve tissue», «endothelial dysfunction», «oxidative stress», «neuroinflammation». The literature search yielded 329 results, of which 234 articles.As a result of the analysis of the articles, 2 main groups of studies were identified: descriptive and experimental. The pathogenesis of damage to the nervous system by the COVID-19 virus has two sources: by infecting nerve endings, such as olfactory sensory neurons, and retrograde penetration of the virus into the brain.

THE EFFECT OF POLYPHENOL COMPOUNDS ON Ca2+-INDUCED MITOCHONDRIAL POTORAGE (mPTP) IN TOXIC HEPATITIS

As a result of the development of industrial technologies and changes in the ecological environment, various xenobiotics released into the environment are increasing. Increasing exposure to xenobiotics may lead to the development of diseases associated with toxic hepatitis (TG) in the population. The following exogenous factors can cause TG: industrial and household toxic substances, chlorinated hydrocarbons, naphthalene and biphenyls, benzene, metals and other inorganic elements, monomers used for the production of polymer materials, plastics, hydrazine and its derivatives, as well as dioxins and radionuclides. All of these exogenous toxins have a cumulative damaging effect on the liver, so they must be converted into non-toxic compounds for the body and eliminated. The main mechanisms of toxic damage to the liver are lipid peroxidation, protein denaturation, reduction of ATF, mitochondrial dysfunction, inhibition of membrane receptors.

Research advances on CaMKs-mediated neurodevelopmental injury.

Calcium/calmodulin-dependent protein kinases (CaMKs) are important proteins in the calcium signaling cascade response pathway, which can broadly regulate biological functions in vivo. Multifunctional CaMKs play key roles in neural development, including neuronal circuit building, synaptic plasticity establishment, and neurotrophic factor secretion. Currently, four familial proteins, calcium/calmodulin-dependent protein kinase I (CaMKI), calcium/calmodulin-dependent protein kinase II (CaMKII), eukaryotic elongation factor 2 kinase (eEF2K, popularly known as CaMKIII) and calcium/calmodulin-dependent protein kinase IV (CaMKIV), are thought to have been the most extensively studied during neurodevelopment. Although their spatial structures are extremely similar, as well as the initial starting point of activation, both require the activation of calcium and calmodulin (CaM) complexes to be involved in the process, and the phosphorylation sites and modes of each member are different. Furthermore, due to the high structural similarity of CaMKs, their members may play synergistic roles in the regulation of neural development, but different CaMKs also have their own means of regulating neural development. In this review, we first describe the visualized protein structural forms of CaMKI, CaMKII, eEF2K and CaMKIV, and then describe the functions of each kinase in neurodevelopment. After that, we focus on four main mechanisms of neurodevelopmental damage caused by CaMKs: CaMKI/ERK/CREB pathway inhibition leading to dendritic spine structural damage; Ca2+/CaM/CaMKII through induction of mitochondrial kinetic disorders leading to neurodevelopmental damage; CaMKIII/eEF2 hyperphosphorylation affects the establishment of synaptic plasticity; and CaMKIV/JNK/NF-κB through induction of an inflammatory response leading to neurodevelopmental damage. In conclusion, we briefly discuss the pathophysiological significance of aberrant CaMK family expression in neurodevelopmental disorders, as well as the protective effects of conventional CaMKII and CaMKIII antagonists against neurodevelopmental injury.

An investigation on the wear properties of the photocurable components produced by additive manufacturing for dentistry applications: Combined influences of UV exposure time, building direction, and sliding loads

AbstractAdditive manufacturing (AM) of polymers is a highly versatile technology that can be applied to many independent sectors like automotive, aviation, medicine, and dentistry. Since it has great potential for rapid prototyping, clean‐process concepts, and the ability to produce complex shapes, the layer‐by‐layer printing method is one of the most promising alternatives for future industrial production efforts. In that sense, different from the previous studies, this work aims to elucidate the friction and wear properties of the special dental samples manufactured via photopolymerization‐based AM technology according to both for printing parameters, and dry sliding test variables. Also, this is the first initiation to examine the combined influences of the UV exposure time, building direction, and sliding force on the surface roughness, hardness, friction coefficient, wear rate, and main plastic damage mechanism of the printed samples. The results showed that the maximum average hardness value was detected as 89.8 Shore D for vertically built samples printed with 8 s exposure time. In addition, vertically printed samples exhibited better wear resistance than the horizontal samples and the rising exposure time generally affected affirmatively the hardness levels of the samples. The lowest volume loss of 78 mm3 belonged to the vertical sample at 5 N. Further, increasing test force levels caused a decrease in the friction coefficient results and triggered the volume loss increase in the samples. Among all samples, the calculated friction coefficient values changed between 0.3 and 0.87. On the other side, scanning electron microscopy (SEM), and energy‐dispersive spectroscopy (EDS) analyses pointed out that ascending exposure times led to the altering contact surface matchings determining the final volume loss outcomes.Highlights To obtain better surface quality, vertical printing was a useful option. Horizontally printed samples exhibited higher friction coefficients. Curing time positively impacted the wear resistance for both orientations. Grooves and debris parts were observed on surfaces with low exposure times.

Probing fretting wear behavior of gauge-changeable spline axle under rotational bending loads

The latest generation of gauge-changeable trains in China feature designs with their wheels and axles connected by spline couples and cylindrical fits. In comparison to the interference fitted wheelset, the spline axle with clearance fit is more prone to fretting damage. In this study, the stress distribution of spline axle was analyzed using finite element method. Then, a rotatory bending test on scaled wheel/axle samples was conducted to reveal the fretting wear behavior of the gauge-changeable axle. During traction, the contact stress of the spline peaks at 311 MPa on the tooth’s root side, with a corresponding relative slip of 14 μm. Fretting wear is observed in the spline axle, the damage zone of the wheel seat can be categorized into five bands (A–E), and severely damaged areas are covered with red-brown debris. Moreover, the main damage mechanism of untreated spline axle and surface-modified spline axle is delamination accompanied with oxidation. The improved properties of plasma nitriding and grease lubricant are attributed to the high surface hardness and residual compressive stress, as well as low frictional stress.

Cerebroprotective Potential of Andrographolide Nanoparticles: In silico and In vivo Investigations.

Ischemic stroke remains the leading cause of death and disability, while the main mechanisms of dominant neurological damage in stroke contain oxidative stress and inflammation. Docking studies revealed a binding energy of - 6.1 kcal/mol for AG, while the co-crystallized ligand (CCl) exhibited a binding energy of - 7.3 kcal/mol with NOS. AG demonstrated favourable hydrogen bond interactions with amino acids ASN A:354 and ARG A:388 and hydrophobic interactions with GLU A:377. Molecular dynamics simulations throughout 100 ns indicated a binding affinity of - 27.65±2.88 kcal/mol for AG, compared to - 18.01±4.02 kcal/mol for CCl. These findings suggest that AG possesses a superior binding affinity for NOS compared to CCl, thus complementing the stability of NOS at the docked site.AG has limited applications owing to its low bioavailability, poor water solubility, and high chemical and metabolic instability.The fabrication method was employed in the preparation of AGNP, SEM analysis confirmed spherical shape with size in 19.4±5 nm and investigated the neuroprotective effect in cerebral stroke rats induced by 30 min of carotid artery occlusion followed by 4 hr reperfusion, evaluated by infarction size, ROS/RNS via GSH, MPO, NO estimationand AchE activity, and monitoring EEG function. Cortex and hippocampal histology were compared between groups. AGNP treatment significantly decreased Infarction size and increased GSH levels (p<0.01**), decreased MPO (p<0.01**), NO (p<0.01**), AchE (p<0.01**), restored to normal EEG amplitude, minimizing unsynchronized polyspikes and histological data revealed that increased pyramidal cell layer thickness and decreased apoptotic neurons in hippocampus, cortex appeared normal neurons with central large vesicular nuclei, containing one or more nucleoli in compared to AG treatment. Based on brain biochemical, histopathology reports AGNP exhibited significant cerebroprotective activity compared to AG on ischemic rats.

Lubrication mechanism of C@Ag core–shell materials as grease additive

The preparation of a low shearing shell on the surface of carbon spheres (CS) is an attractive strategy to improve the lubrication properties of CS. In this study, core–shell structural C@Ag particles were prepared using CS as the hard core and Ag nanoparticles as the soft shell. Then, the additives were mixed with Polyalphaolefin 20 to prepare the C@Ag core–shell-enhanced lithium complex grease (C@Ag-LCG). The physicochemical properties, corrosion resistance, and tribological behaviors of LCGs were investigated. C@Ag-LCG exhibited the best high-temperature resistance and colloidal stability compared with the CS-enhanced lithium complex grease (LCG) and pure LCG. The dropping point and oil separation rate of 0.05 wt% C@Ag-LCG were 255 °C and 2.36 %, respectively. The tribological behavior of greases was tested using a four-ball friction tester, and the main damage mechanism was abrasive wear. The C@Ag additive reduced the average friction coefficient and wear spot diameter by 27.17 % and 26.12 %, respectively. The improved properties were attributed to the synergistic lubrication of hard CS core and soft Ag shell with the rolling, filling, and self-repairing effects, C@Ag deposit films and the self-lubricating oil film, as well as the thickener film and the tribochemical film at the frictional interfaces.

RUTTING IN ASPHALT MIXTURES – A REVIEW

Vehicles that pass over a pavement structure induce load and unload cycles that generate recoverable (resilient) and permanent (plastic) deformations within layers. Pavement has been developing studies since the decade of the 60´s with the purpose of attempting to understand the visco-elasto-plastic behavior of asphalt mixtures. This has the purpose of evaluating and understanding how the main damage mechanisms that are sought to be controlled in flexible pavement design methods are generated. One of the main damage mechanisms for these types of pavements is rutting. Based on the reviewed literature in relation to the phenomenon of rutting in asphalt mixtures, this article depicts and describes in summary, the main variables that influence the generation of said phenomenon in pavement. The end of the article presents the evolution of equations developed through theoretical and experimental studies in order to attempt to predict the phenomenon of rutting.

Subpicosecond laser ablation behavior of a magnesium target and crater evolution: Molecular dynamics study and experimental validation

Abstract The micro-ablation processes and morphological evolution of ablative craters on single-crystal magnesium under subpicosecond laser irradiation are investigated using molecular dynamics (MD) simulations and experiments. The simulation results exhibit that the main failure mode of single-crystal Mg film irradiated by a low fluence and long pulse width laser is the ejection of surface atoms, which has laser-induced high stress. However, under high fluence and short pulse width laser irradiation, the main damage mechanism is nucleation fracture caused by stress wave reflection and superposition at the bottom of the film. In addition, Mg[0001] has higher pressure sensitivity and is more prone to ablation than Mg [ 10 1 ¯ 0 ] . The evolution equation of crater depth is established using multi-pulse laser ablation simulation and verified by experiments. The results show that, under multiple pulsed laser irradiation, not only does the crater depth increase linearly with the pulse number, but also the quadratic term and constant term of the fitted crater profile curve increase linearly.

Effect of Si addition on the microstructure and liquid lead-bismuth eutectic cavitation erosion behaviors of AlCrFeMoTi laser clade coatings

High entropy alloys exhibit high resistance to the lead-bismuth eutectic (LBE), making them promising candidate materials for protective coatings. However, improving their mechanical properties and resistance to cavitation erosion in flowing LBE environment remains a challenge. In this study, AlCrFeMoTi coatings were synthesized using laser cladding, and Si was added to enhance their resistance to cavitation erosion. The results showed that the AlCrFeMoTi coatings mainly contained FeMoTi and Fe-Cr phases. After the addition of Si, a single phase FeMoTi was formed. Moreover, Si increased the hardness of the coatings by 9.6%. After cavitation erosion in LBE at 500 ℃, cracks formed on the surface of the coatings and the main damage mechanism of the coating was lamellar spalling. The addition of Si inhibited crack propagation and reduced the erosion depth of the coatings by 43.5%. It can be attributed to the addition of Si makes the oxidation homogeneous and the strengthening of the single-phase.

Extended Gurson-Tvergaard-Needleman model considering damage behaviors under reverse loading

Void nucleation, growth, deformation and coalescence are the main microscopic damage mechanisms for plastic deformation of sheet metals. To describe the effect of reverse loading on the microscopic damage accumulation and ductile fracture, the damage evolution equations in regard of void nucleation, void growth, shear void nucleation and shear deformation damage were modified. Through the further introduction of the combined hardening model, an extended Gurson-Tvergaard-Needleman (GTN) model was constructed in this study, to improve the predictive ability of ductile fracture under reverse loading conditions. Two typical reverse loading experiments including compression-tension and shear-reverse shear were performed. The number, size and shape of microscopic voids were qualitatively analyzed and compared through the microscopic observations, it is indicated that the preloading and loading sequence strongly affect the damage accumulation and the final ductile fracture, which is the microscopic damage mechanisms under reverse loading. The proposed GTN model was verified by the load responses and displacements at fracture (DAFs) of the conducted reverse loading experiments. The good agreement between numerical simulations and experimental results proves the rationality of the proposed GTN model and its accuracy to the prediction of ductile fracture under reverse loading conditions.

Time-dependent damage development during creep in carbon woven-ply polyphenylene sulfide laminates above the glass transition temperature

In order to understand the coupling between time-dependent behaviours (viscoelasticity, viscoplasticity) and damage mechanisms within carbon woven-ply polyphenylene sulfide (C/PPS) thermoplastic composites subjected to creep loadings at T &gt; Tg (Glass transition temperature), it is necessary to develop experimental protocols adapted to high temperature conditions. To this aim, the present study combines different complementary techniques (acoustic emission, edge replication, fractographic analysis, tomography) allowing in-situ analyses of the damage mechanisms that coexist and interact during the different phases of creep-type loadings. These techniques provide information to quantify and dissociate the different material behaviours (viscoelasticity, viscoplasticity, damage). Two main damage mechanisms are identified: intra-bundle cracking and inter-bundle cracking leading to extensive meta-delamination. Image analyses based on morphological operations allow the evaluation of the surface cracking density (intra- and inter-strand) from edge replicas. At macroscopic scale, the thermo-mechanical response is little influenced by the viscous behaviour of angle-ply C/PSS laminates though their thermo-mechanical behaviour is mainly driven by the PPS matrix. At micro and mesoscopic scales, the results clearly show the onset and propagation of time-dependent damage in C/PPS specimens. By implementing this protocol, the acoustic emission monitoring associated with the quantification of the cracking density proved to be relevant and complementary to study the coupling between viscous effects and damage within C/PPS laminates subjected to high temperature loading.

Therapeutic Opportunities of Apixaban in Patients With Atrial Fibrillation and Reducing the Risk of Cerebrovascular Complications in Chronic Kidney Disease

The review article is devoted to the possibilities of using the oral anticoagulant apixaban in patients with atrial fibrillation (AF) and to reduce the risk of cerebral complications in chronic kidney disease (CKD). The generality of risk factors and mechanisms of the occurrence of AF in patients with CKD are considered. The therapeutic possibilities have been demonstrated for the use of oral anticoagulants, in particular apixaban, in AF in the CKD association. The main mechanisms of kidney damage during therapy with vitamin K antagonists are shown. Apixaban is shown to be more effective than warfarin to prevent stroke regardless of the severity of renal dysfunction, and in patients with creatinine clearance less than 50 ml/min, the benefits of apixaban in reducing the frequency of major bleeding are most pronounced degrees. In AF patients with CKD C1-C4 gradations, dose adjustment of apixaban is not required. The safety of the use of apixaban in a full dose (5 mg 2 times a day) in patients with terminal CKD has been approved, subject to regular hemodialysis.

A continuum damage coupled unified viscoplastic model for simulating the mechanical behaviour of a ductile cast iron under isothermal low-cycle fatigue, fatigue-creep and creep loading

A novel continuum damage coupled unified viscoplastic model is used for simulating the stress–strain responses of SiMo 4.06 cast iron under Low-Cycle Fatigue (LCF), fatigue-creep and creep loading for temperatures up to 650 °C. The advanced constitutive model that is developed within the framework of the Chaboche model allows the simulation of various effects including strain rate sensitivity, cyclic hardening and softening, static recovery and strain range dependency. The hyperbolic sine flow rule and the static recovery of kinematic hardening rule are proposed in order to effectively simulate both stress relaxation and creep strains. The isotropic damage variable is introduced into the constitutive equations to represent the effects of material degradation. Three main damage mechanisms are considered: fatigue, creep and ductile damage. In addition, the model is further modified to take into account the progressive microdefects closure effect. Finally, the prediction capability of the proposed model is illustrated for the experimental data obtained from the various uniaxial material tests. A good correlation was achieved between the simulated and the experimental results.

Damage Generated and Propagated by the AAR Reactive Aggregate from Kingston, Ontario, Canada.

It remains unclear in the literature what the cause of the so-called alkali-carbonate reaction (ACR) damage to concrete is. However, expansion and cracks as distress features are often attributed to the alkali-silica reaction (ASR). Therefore, this work aims to assess the damage to concrete generated and propagated by the so-called ACR-susceptible reactive aggregate through mechanical testing (i.e., the direct shear test), microscopy (the damage rating index-DRI), and other techniques. Distinct induced expansion levels (i.e., 0%, 0.05%, 0.12%, and 0.20%) were selected to compare the distress caused by ACR to concrete affected by ASR. The results show that the behavior of ACR, namely, as captured through the DRI, is inconsistent with that of ASR, thus attesting to ACR being a distinct distress mechanism. The damage captured through mechanical testing does not distinguish ACR from ASR; however, microscopy reveals that cracks in the cement paste are the main damage mechanism. The proportions of cracks in the cement paste are 40-50% of the total number of cracks, whereas open cracks in the aggregates normally characterizing ASR represent only up to 20% of the total cracks.

Electrochemical study on the fretting corrosion synergistic damage mechanism of 316L SS in different dissolved oxygen solution

Nowadays, material aging issues in the nuclear industry have received wide attention as they need costly maintenance strategies to deal with. Therefore, it is important to study the degradation mechanism of materials to improve their service life. In this study, in-situ electrochemical measurement techniques were used to investigate the fretting corrosion synergistic damage mechanism of 316L SS tube against zirconia ceramics plate in the solution with different dissolved oxygen (DO) concentrations. The results show that a more uniform passive film with the main composition of corundum oxides γ-Fe2O3 and oxyhydroxide γ-FeOOH formed on the wear scar under higher DO concentration, which hindered the charge transfer and improved corrosion resistance. The passive film modifies contact pressure and changes wear behavior, resulting in a 55.5 % reduction in the fretting corrosion damage. The main damage mechanism changes from abrasive wear to a mixing mechanism of surface fatigue and abrasive wear. The contribution of the synergistic damage effect was quantified, which is the key part of fretting corrosion damage and weakens with the increase of DO concentration. According to the experimental results, a prediction model of corrosion-induced wear damage was proposed based on the Archard equation, Hertz contact theory, and passive film coverage model.

RETRACTED: Coenzyme Q10 attenuates neurodegeneration in the cerebellum induced by chronic exposure to tramadol

BackgroundChronic use of tramadol can cause neurotoxic effects and subsequently cause neurodegeneration in the cerebellum. The main damage mechanisms identified are oxidative stress and inflammation. Currently, we investigated the effects of coenzyme Q10 (CoQ10) in attenuates of neurodegeneration in the cerebellum induced by chronic exposure to tramadol. Material and methodsSeventy-two male mature albino rats were allocated into four equal groups, including; non-treated group, CoQ10 group (which received CoQ10 at 200 mg/kg/day orally for three weeks), tramadol group (which received tramadol hydrochloride at 50 mg/kg/day orally for three weeks), and tramadol+CoQ10 group (which received tramadol and CoQ10 at the same doses as the previous groups). Tissue samples were obtained for stereological, immunohistochemical, biochemical, and molecular evaluations. Also, functional tests were performed to evaluate behavioral properties. ResultsWe found a significant increase in stereological parameters, antioxidant factors (catalase, glutathione, and superoxide dismutase), and behavioral function scores in the tramadol+CoQ10 group compared to the tramadol group (p < 0.05). In addition, malondialdehyde levels, the density of apoptotic cells, as well as the expression of pro-inflammatory (tumor necrosis factor-alpha, interleukin 1 beta, and interleukin 6) and autophagy (lysosome-associated membrane protein 2, autophagy-related 5, beclin 1, and autophagy-related 12) genes were considerably reduced in the tramadol+CoQ10 group compared to the tramadol group (p < 0.05). ConclusionWe conclude that the administration of CoQ10 has neuroprotective effects in the cerebellum of rats that have chronic exposure to tramadol.

Formation damage induced by working fluids sequentially interacting with tight sandstone oil reservoirs

Drilling fluid loss is a frequent downhole incident in the process of deep well drilling and completion. Drilling fluid will damage the formation permeability and affect well production, but some wells with high volume drilling fluids loss can have high production. To investigate the mechanism of drilling fluid loss damage in tight sandstone oil reservoirs, this study selects some core plugs and the working fluids from X field in Ordos Basin, China, conducts the evaluation experiments of drilling fluid damage and working fluid sequential contact damage, and analyzes the well history and well production performance data. Results show that the permeability recovery rate decreases continuously, after different fluid displacement. The permeability recovery rate of rock sample after drilling fluid displacement is 46.21–67.14%, and the permeability recovery rate after different working fluid displacement is 22.92–61.45%. Then well history and production fluctuations are analyzed. It shows the incompatibility of working fluid will cause superimposed damage to hydraulic fractures. The main damage mechanism caused by drilling fluid loss is incompatibility damage and particle invasion. Loss of drilling fluid will improve damage risk of the subsequent stimulation operations, though it doesn't show damage features in initial stage. Formation damage degree is related to the storage space type of reservoir. The results serve as a guide for the drilling fluid design of oil in tight sandstone formation.

Role of DNA damage and repair in chronic eye diseases

Vision is essential for everyday activities, yet the most common eye diseases — cataracts, diabetic retinopathy (DR), age-related macular degeneration (AMD), and glaucoma — lead to vision loss with age. Cataract surgery is one of the most frequently performed operations and results are usually excellent in the absence of accompanying eye pathology. However, patients with DR, AMD, and glaucoma often develop significant visual impairments. The pathogenesis of these multifactorial diseases often involves genetic and hereditary components, with recent data confirming the role of DNA damage and repair as important pathogenic factors. In this review, we describe in detail the main mechanisms of DNA damage and repair, including base excision repair, nucleotide excision repair, double-strand break repair, and discuss their role in the development of DR, AMD, and glaucoma.

A study of adhesive bonding in metal–metal, metal–CFRP, and CFRP–CFRP material combinations under shear deformation: Fracture morphologies and damage mechanisms

Safe design of adhesive joining in multi-materials in engineered structures requires the accumulation of numerous experimental data on the failure behavior of various adhesively-bonded material combinations under different loading conditions. The deep understanding of mechanical performance, fracturing morphologies, and main damage mechanisms is also quintessential for accelerating the development of proper physics-based and multi-scale models for assisting the design.Towards this goal, this work presents a comprehensive characterization of the failure behavior of adhesively-bonded metal–metal, metal–CFRP, and CFRP–CFRP material combinations under global shear deformation via single lap shear testing. Thanks to a synergistic combination of measurement methods by using Digital Imaging Correlation (DIC) and 3D optical profilometry, adhesive features on the adherend after failure were quantified and the main progressive damage mechanisms were identified.The characterization performed in this work provides quantitative data that contributes to a better understanding of shear failure in adhesive bonding across different bi-material combinations. The obtained results have practical implications, including the potential to enhance adhesive bonding design, identify failure causes in adhesive joints, and develop or validate computational models capable of capturing the observed behavior in various adhesively-bonded materials under global shear deformation.