Early Stage Of Aging Research Articles

Effect of GPa-level pressure on the microstructure and properties of Cu-8Ni-1.8Si alloy

Reducing or completely eliminating the reticular grain boundary phases in alloys is crucial for enhancing the mechanical and electrical properties of Cu-Ni-Si alloys with high nickel and silicon content (Ni + Si > 5wt.%). In this study, we investigated the microstructure, mechanical properties, and electrical conductivity of Cu-8Ni-1.8Si (wt.%) alloy prepared by high-pressure solidification (HPS) and subsequent aging treatment. The interfacial growth stabilizes as the pressure reduces the crystal growth rate, inhibits the diffusion of solute atoms, and increases the solute partition coefficient. The reticulated Ni31Si12 and granular Ni2Si phases disappear under 6GPa pressure, forming a complete Cu (Ni, Si) solid solution. After direct aging treatment, the precipitated phase of the HPS alloy is β-Ni3Si at the early stage of aging. At the peak aging state, β-Ni3Si and δ-Ni2Si phases coexist in the matrix. Additionally, the Avrami equations for the phase transition kinetics of HPS alloys at different aging temperatures were derived from the electrical conductivity data, and the strength contributions from solid solution strengthening and precipitation strengthening were calculated. The alloy aged at 450 °C exhibited the largest volume fraction and the smallest average size of precipitates, resulting in a more pronounced obstruction effect of nano precipitates on dislocation bypassing and demonstrating the best precipitation strengthening effect. At the peak aging states, the alloy's hardness reaches 367.5 HV, and the compressive yield strength reaches 788.2MPa. These results indicate that high pressure is an effective method to improve the solid solution degree of alloying elements and enhance the mechanical properties of Cu-Ni-Si alloys.

Effect of Cu on precipitation hardening and clustering behavior of Al-Zn-Mg alloys in the early stage of aging

Effect of Cu on precipitation hardening and clustering behavior of Al-Zn-Mg alloys in the early stage of aging

Non-monotonically changes in double Schottky barrier of MnCO3–doped ZnO varistors during DC aging

Abstract ZnO varistors play a crucial role as core component in metal oxide arresters due to their excellent nonlinear current density-electrical field (J–E) characteristics. After long-term operation under DC stress (DC aging), the J–E curves of ZnO varistors invented in the last decade cross with the original curve. Unexpectedly, the ‘crossover’ phenomenon cannot be explained by the vastly-accepted ion migration mechanism by which the barrier height monotonically declines after DC aging. In the present study, aging and recovery experiments were carried out on MnCO3-doped ZnO varistors. The symmetry of J–E characteristics in the same direction as and the opposite direction to the DC stress was compared, parameters of double Schottky barrier were analyzed, and evolution of point defects was deduced using dielectric spectra. It was found that, in addition to ion migrations, there are electrons ionized by zinc interstitials filling the interface states in the early stage of aging. Because these processes are dominant in different stages, the barrier height changes non-monotonically. MnCO3 can suppress the formation of zinc interstitials, so it simultaneously inhibits ion migrations and filling of the interface states by electrons. When 0.38 mol% MnCO3 is doped, J–E characteristics and the Schottky barrier of ZnO varistors show the smallest deviations during aging and recovery. The findings are helpful in updating criteria for the long-term stability of ZnO varistors and suggest that modifications to their formulae targeting the suppression of the filling the interface states by electrons are also expected to bolster the stability.

Exploring aortic stiffness in aging mice: a comprehensive methodological overview.

Stiffening of the vascular network is associated with the early stages of vascular aging, leading to cardiovascular disorders (hypertension), renal failures, or neurodegenerative diseases (Alzheimer's). Unfortunately, many people remain undiagnosed because diagnostic methods are either unsuitable for a large population or unfamiliar to clinicians which favor the hypertension evaluation. In preclinical research, stiffness studies are often partially conducted. We think that the evaluation of aortic stiffness is essential as it would improve our understanding of aging diseases progression. We propose here a systematic method using decision trees in a multi-scale and multimodal approaches. Our method was evaluated by analyzing the aortic situation in old and young mice. We demonstrate that both the endothelial and smooth muscle cells exhibit pronounced functional alterations in favor of constriction. Additionally, there is significant remodeling of the extracellular matrix, leading to a drastic degradation of elastic fibers and the accumulation of collagen in the aortic wall. This series of changes contributes to the development of vascular rigidity, a preliminary stage of arterial hypertension. Our results suggest that our method should improve preclinical understanding and encourage clinicians to equip themselves with tools for assessing vascular function, as it is an essential issue for preventing numerous pathologies.

Rheology and early age evaluation of 3D printable cement-limestone filler pastes with nanoclays and methylcellulose

Nanoclays (NC) are known to increase the structural build-up of cement-based materials (CBM) while methylcellulose (MC) is used to increase open time and workability, helping to prevent cold joints in 3D Printing applications. The combination and compatibility of both NC and MC could lead to the design of new 3D printable CBM able to tackle all the manufacturing process requirements. The aim of the study is to evaluate the effect of sepiolite nanoclay and MC on rheology and early age (EA) parameters of cement-limestone filler pastes for 3D printing applications, identifying fresh structural build up and setting mechanisms. The effect of two cement types with coarser and finer particle size distribution (CEM I 42.5-R and CEM I 52.5-R, respectively) was considered. Pastes rheology was characterized by Cone Penetration Test (CPT) and Dynamic Shear Rheometer (DSR). EA was monitored by P- and S-waves Ultrasonic Pulse Velocity (UPV), internal temperature, capillary pressure and drying shrinkage. Fresh Shear Yield Stress (τ0) and shear elastic modulus (G), effective thixotropy (Athix), critical strain (γcrit) and their evolution over time were calculated form CPT and DSR experimental results. A limit of usability was defined for τ0 up to 20 kPa for CPT with a 30º tip cone. Although pastes with both NC and MC showed thixotropy, NC reduced γcrit while MC strongly increased it. NC significantly increased Athix and ΔG with coarser particle size cement when compared to the finer cement. MC delayed hydration reaction and setting, while NC did not affect early age stages. On the other hand, combining NC and MC increased superplasticiser demand and reduced effective thixotropy (Athix). Finally, an integrated overview of the physical and chemical mechanisms involved in rheology and early age properties of cement-based systems and the key experimental parameters for their identification was proposed.

Precipitation strengthening behavior of Custom 455 stainless steel during tempering at 420 °C

After solid solution at 850 °C, the Custom 455 was aged at 420 °C for different times. The hardness changes were measured using a Vickers hardness tester, and the microstructure and composition of the second phase were studied using atom probe tomography (APT) and high-resolution transmission electron microscopy (HRTEM). The APT results indicate that in the early stage of aging, Cu atoms first segregate and attract Ti to form CuTi clusters; As the aging time increases, Ti atoms in CuTi clusters attract Ni and form CuTiNi clusters, resulting in a rapid increase in sample hardness; Subsequently, CuNiTi clusters grew and gradually separated into Cu-rich and NiTi-rich particles; As the aging time further increases, some NiTi-rich particles grow into rod-shaped Ni3Ti precipitates, while others have Si atoms and grow into spherical G phase particles. The orientation relationship between Cu-rich phase, Ni3Ti phase, and G phase is: [100]M//[0–11]Cu//[-12–10]Ni3Ti//[100]G, (011)M//(111)Cu//(0004)Ni3Ti//(022)G. The formation of the Cu-rich, Ni3Ti, and G phase resulted in a hardness peak of 538 HV after 16 h of aging. Subsequently, the decrease in hardness caused by the coarsening of the Cu-rich and Ni3Ti particles was offset by the newly formed G phase, resulting in a slow decrease in hardness.

Using acoustic emission to understand the early-age reaction and cracking evolution of alkali-activated slag-brick powder paste

Real-time monitoring and accurately understanding the continuous occurring psychical-chemical characterization during the hardening process of alkali-activated materials present a formidable challenge. In this study, the early-age reaction process of alkali-activated slag-waste brick powder paste (ASWP) was in-situ and continuous monitored by using acoustic emission (AE) system and temperature. A novel machine learning method was employed to categorize the evolution of AE signals into three distinct stages: reaction acceleration, reaction stabilization and volume shrinkage stage. During reaction acceleration stage (0–2h), the waste brick powder (WBP) increased AE counts rate (4000–7300 counts/h), with RT values exceeding 200μs, indicating the settlement of WBP. Additionally, WBP reduced the high r-value AE activity in volume shrinkage stage, effectively mitigated the drastic volume shrinkage, and delayed its occurrence time by approximately 4 h. Semi-quantitative analyses of FTIR and TG-DTG indicate that WBP reduced gel phase formation in the early-age stage, decreasing the relative areas in Q2 site by 16% before 36 h. However, WBP positively impacted ASWP hydration at long ages, increasing Q2 site d areas by 60%–100%. AE technique offers a new perspective for in-depth understanding of the reaction mechanism and microstructural development of alkali-activated materials in situ and continuously.

Age-Related Homeostatic Plasticity at Rodent Neuromuscular Junctions.

Motor ability decline remains a major threat to the quality of life of the elderly. Although the later stages of aging co-exist with degenerative pathologies, the long process of aging is more complicated than a simple and gradual degeneration. To combat senescence and the associated late-stage degeneration of the neuromuscular system, it is imperative to examine changes that occur during the long process of aging. Prior to late-stage degeneration, age-induced changes in the neuromuscular system trigger homeostatic plasticity. This unique phenomenon may be important for the maintenance of the neuromuscular system during the early stages of aging. In this review, we will focus on age-induced changes in neurotransmission at the neuromuscular junction, providing the potential mechanisms responsible for these changes. The goal is to highlight these key elements and their role in regulating neurotransmission, facilitating future research efforts to combat late-stage degeneration in the neuromuscular system by preserving the functional and structural integrity of these elements prior to the late stage of aging.

Atomic mechanism of enhanced thermal stability in Al-Cu-Mg-Si alloys with a low Cu/Mg ratio

The Si-modified Guinier-Preston-Bagaryatsky (GPB) zones are claimed to be responsible for the high-thermal stability of Al-Cu-Mg-Si alloys with a low Cu/Mg ratio. However, the structure of this phase and its formation mechanism remain unclear. In the present study, the precipitation behaviors of two Al-Cu-Mg alloys with or without Si addition upon thermal aging at 200 °C are characterized using atomic-resolution imaging techniques and the ab initio calculation. It is found that the Si-modified GPB zone is needle-shaped β'/GPB composite with core/shell structure. The core part is β' phase (Mg9Si5), while the shell is composed of the conventional GPB zones. In the early stage of aging, β' phase precipitates rapidly and acts as the heterogeneous nucleus of GPB zones. With the aging time extending to 60 h, the diameter of the β'/GPB composites remains almost constant, since the GPB zones effectively hinder the coarsening of the internal β' phase, thus promoting the thermal stability of the alloy as compared with the Si-free alloy. Our results clarify the mechanism of Si, at atomic scale, to improve the thermal stability of Al-Cu-Mg alloys with a low Cu/Mg ratio.

Precipitation behavior and performance evolution of cold-rolled cu-Ti-Fe alloy during heat treatment

The CuTi alloy is extensively utilized for its high strength, excellent elasticity, and processability. Heat treatment processes are crucial for affecting the microstructure and properties. The effects of different aging processes on the microstructure and properties of cold-rolled Cu-Ti-Fe alloy were investigated, and the heat treatment parameters were optimized. The results show that the cold-rolled Cu-Ti-Fe alloy exhibits excellent comprehensive performance at 450 °C for 2 h, with the hardness of 342.2 HV, the electrical conductivity of 16.1 % IACS, and the tensile strength of 1051 MPa. The aggregation of solute atoms occurs in the early stages of aging. The uniformly distributed β'-Cu4Ti phase precipitates at peak aging, which has a coherent relationship with the matrix. The precipitation of Ti atoms enhances the electrical conductivity of the alloy, and the movement of dislocations is prevented by precipitates, increasing the strength. During the over-aging stage, the precipitates transform into β-Cu4Ti phases, losing complete coherency with the matrix. The coarsening of precipitates leads to the softening of the Cu-Ti-Fe alloy. Theoretical calculation results indicate that the thermal diffusion ability of solute atoms is the strongest and precipitates completely when the alloy aged at 450 °C. The precipitation strengthening mechanism plays a significant role in improving the strength.

A coupled model for precipitation strengthening in Mg-Zn alloys

A recently developed precipitation model is coupled to an original mechanical model to predict the strength evolution in Mg-Zn alloys during aging. The proposed models consider the strengthening effects of rod and plate-shaped precipitates on the most important deformation mechanisms in Mg alloys: basal slip, prismatic slip, and twinning. It is found that shearing of rod precipitates dominates the strengthening on basal slip at early aging stages, while the bypass mechanism dominates medium and over-aging stages. On prismatic planes, the bypass of rod precipitates dominates across all aging stages. The influence of different precipitate arrangements and aspect ratios on modelling results is also discussed. The strengthening from plate-shaped precipitates is found to be very poor for the studied slip modes. While for twinning, the strength evolution is nicely represented by bypassing of rod-shaped precipitates. The evolutions of tensile and compressive yield strength during aging are well predicted by considering the hardening on prismatic and twinning planes, respectively.

Abnormal aging behaviors induced by high-density dislocations for an ultra-high-strength titanium alloy prepared by laser-directed energy deposition

Additively manufactured high-strength titanium alloys generally possess equal strength and lower plasticity compared to wrought alloys owing to the different microstructures formed in the aging treatment. To examine the formation mechanism of these microstructures, an ultra-high-strength titanium alloy TB18(Ti-4.2Al-5V-5Cr-5Mo-1Nb) was prepared by laser direct energy deposition (LDED) and forging respectively, and the aging behaviors and microstructures were characterized and compared in depth. It is found that during aging, the precipitation of the LDEDed alloy is 1–2 h earlier than that of the wrought alloy, and precipitates primarily form at the reticular sub-grain boundaries. Fine short-rod α laths then form inside the sub-grains due to the inhibition of the reticulations. The sub-grain boundaries in LDEDed alloy are generated due to the local deformation and recovery of the inter-dendritic zone rich of Cr and O atoms and show high thermal stability in the solution treatment, which differs from that of the wrought alloys. These boundaries possess a dislocation density several times higher than that of the inner-grain zones and promote the prior precipitation of α laths with Type 2 orientations at the early stage of aging. In the tensile test of the aged alloys, the dislocations in the LDEDed alloy pile up at the α/β interface, which can cause stress concentration and damage the plasticity.

Research insight into the change of aggregation structure of BOPP films and its influence on electrical properties under accelerated thermal aging

AbstractBiaxially oriented polypropylene (BOPP) film used in pulse film capacitors withstands high temperatures for a long time. This leads to frequent faults in pulse film capacitors, affecting the reliability of the pulse system. In this paper, the thermal aging tests of BOPP films at 100°C for 10–80 days are carried out in this paper, and the physicochemical and electrical properties of the aging materials are characterized. The results show that more deep and shallow traps to BOPP films are introduced during the thermal aging process. With the increase in aging time, the breakdown field strength gradually decreases, and the conductivity decreases first and then increases. Under the action of thermal aging for a long time, the recrystallization of materials and the destruction of molecular chains by thermal aging are the main reasons for the increase of traps and the decrease of breakdown field strength. The former is dominant in the early stage of aging, and the latter is dominant in the late stage of aging. Therefore, the conductivity shows the law of slow decrease first and then rapid increase. The relevant research provides a theoretical foundation for the process improvement and life prediction of BOPP films.

The impact of glycol water exposure on PA6/GF30 properties

The current paper aims to study the behavior of Polyamide 6 (PA6) and Polyamide 6 reinforced with 30% of short glass fibers (PA6GF30) under glycol water (GW) mixture used for cars as coolant fluid. Samples were fully immersed in the mixture of GW (20:80) at 50°C, 70°C and 90°C for up to 80 days and periodically weighted. Results gathered revealed the occurrence of substantial changes especially for PA6 samples aged at 90°C. The long term ageing leads to the formation of ester species due to thermo-oxidation as pointed out by Infrared spectroscopy analysis. Moreover, dynamic mechanical analysis measurements showed that glycol water acted as an effective plasticizer in lowering the Tg of the polyamide 6. This plasticizer effect was confirmed by the gain of ductility at early stage of ageing for both materials (PA6 and PA6GF30). Nevertheless, after 80 days of ageing the effect of glycol water ageing is no longer physical in nature and an overall loss of mechanical properties was noticed. Indeed, an embrittlement of PA6 was measured that can be attributed to a decrease of the level of entanglements within the polymer. Nevertheless, for PA6GF30 material, the loss of strength and stiffness was the result of the interfacial debonding between the fibers and the matrix.

Towards a further understanding of cement hydration at the early-age stage in the presence of hydrophobic silane IBTEO

Hydrophobic silane hinders internal water penetration by tuning the surface wettability of concrete. The presence of hydrophobic groups in the silane was observed to adversely influence early cement hydration. This study employs a combination of calorimetry, X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), inductively coupled plasma optical emission spectroscopy (ICP-OES), and total organic carbon (TOC) analysis to investigate the effects of hydrophobic isobutyl-triethoxysilane (IBTEO) on cement hydration. The results demonstrate that the silicate reaction integral to cement hydration slows as the concentration of hydrophobic silane increases. The nucleation of hydration products, such as calcium silicate hydrate (C–S–H), exhibits heightened sensitivity to the presence of hydrophobic silane. Although hydrophobic silane marginally impacts the initial dissolution of cement particles, it significantly decreases ion dissolution after 60 min. This reduction in hydration rate and the consequent delay in the emergence of the second exothermic peaks in hydration are attributable to the negative impact of the hydrophobic functional groups on the silicate reactions and the formation of hydrogen bonds. These findings offer new perspectives on the impact of hydrophobic silanes on cement hydration, potentially guiding the development of silane-cement systems towards enhanced superhydrophobicity and improved permeability.

A Concept of Local Coordination Number for the Characterization of Solute Clusters within Atom Probe Tomography Data.

Identifying clusters of solute atoms in a matrix of solvent atoms helps to understand precipitation phenomena in alloys, for example, during the age hardening of certain aluminum alloys. Atom probe tomography datasets can deliver such information, provided that appropriate cluster identification routines are available. We investigate algorithms based on the local composition of the neighborhood of solute atoms and compare them with traditional approaches based on the local solute number density, such as the maximum separation distance method. For an ideal solid solution, the pair correlation functions of the kth nearest solute atom in the coordination number representation are derived, and the percolation threshold and the size distribution of clusters are studied. A criterion for selecting optimal control parameters based on maximizing the phase separation by the degree of clustering is proposed for a two-phase system. A map of phase compositions accessible for cluster analysis is constructed. The coordination number approach reduces the influence of density variations commonly observed in atom probe tomography data. Finally, a practical cluster analysis technique applied to the early stages of aluminum alloy aging is described.

Clinicopathological characteristics and prognosis of non-small cell lung cancer in Algeria: a single-center retrospective study

BackgroundLung cancer is the most commonly diagnosed cancer and the leading cause of cancer-related death in men in Algeria. Little is known about the characteristics of lung cancer in Algeria. This study aimed to determine the clinicopathological characteristics and prognosis of non–small cell lung cancer (NSCLC) patients in Algeria.MethodsThis retrospective study was performed on 269 pathologically confirmed cases of NSCLC at the Benbadis University Hospital of Constantine (2015–2023). Of these, 95 patients were included in the survival analysis. The clinicopathological and outcome data were investigated based on the patients’ medical records.ResultsThis study showed male predominance with sex ratio of 5.7, with a mean age of 61.8 years. Histologically, 67.3% of cases had adenocarcinoma (ADC) and 22.7% squamous cell carcinoma (SCC). ADC and SCC occurred more frequently in female (p = 0.02) and male (p = 0.003) patients, respectively. Smoking was estimated at 82.2% in men. Over 28% were non-smokers, of which 50.7% were women, and presented at younger age (p = 0.04). Most of our patients (75.5%) have an advanced stage at diagnosis. Around 70% of patients underwent chemotherapy (CT) as first-line treatment, with medians diagnostic and treatment delays of 4 and 1 months, respectively. The median overall survival (mOS) was estimated at 10.3 and 6.7 months in I-III and IV stages, respectively. Other factors that negatively impact OS were age > 65 years (p = 0.01), and the presence of symptoms (p = 0.005) and comorbidity (p = 0.004) in stage IV, and delayed treatment (p = 0.03) and receiving CT alone (p = 0.03) in stages I-III cases. Medians progression free survival (mPFS) in stage IV, III, and II patients were 4.1, 5.2, and 8.3 months, respectively, and negatively affected by the comorbidity (stage IV, p = 0.03) and receiving CT alone (stages II-III, p = 0.03).ConclusionsNSCLC presents at an early age and advanced stage in Algerian patients. ADC is the most frequent histological subtype and smoking remains the most important risk factor in men. Furthermore, the prognostic factors affecting survival are stage, age, comorbidity, symptoms, and treatment. Thus, tobacco control, early detection program, and access to novel therapies may be the best strategies to reduce NSCLC morbidity and mortality.

AI-enhanced "Two-thirds Guidelines" for Lipolifting: Addressing Multiple Hallmarks of Facial Aging.

Facial aging involves complex changes such as volume loss, ligament weakening, and skin quality alterations. The "two-thirds guidelines" emerge as a novel strategy to combat these aging signs, drawing from an extensive analysis of 2800 facial fat grafting procedures conducted over two decades. Guided by facial lipolifting data, including patient age, fat type (microfat and nanofat), and injection depth, this study devises a systematic framework for multilayer fat rejuvenation and ligament restoration. The two-thirds guidelines advocate injecting two-thirds of the patient's age for microfat and one-third for nanofat, with specific injection codes for lower, middle, and upper facial regions. A prospective study involving 400 patients confirms the efficacy of the two-thirds guidelines. However, applicability may vary for patients outside SD ranges, particularly concerning facial proportions and body mass index. Patients within the golden ratio range (1.4-1.9) report high satisfaction rates and a 50% fat graft uptake, with minimal complications. For patients outside this range, an artificial intelligence (AI) program was implemented. The two-thirds guidelines offer a comprehensive approach to facial rejuvenation, addressing volume loss, ligament weakening, and skin quality. They are applicable in early aging stages, promising enduring and natural outcomes while mitigating effects of weight fluctuations. These guidelines provide a safe, replicable, and adaptable approach to facial fat grafting, either standalone or in combination with facelift techniques, with minimized overfilling risks. A dataset obtained from 2800 patients serves as the foundation for developing an AI program tailored to aid doctors in diagnosing and treating similar cases.

Single-cell transcriptome sequencing partially revealed the changes of T cells in the early stage of aging kidney

Aging is a gradual, inevitable physiologic process. The organ aging is related to the persistence of chronic inflammation, but the understanding of inflammatory state during renal aging is lacking currently. Single-cell transcriptome sequencing was performed on aging mouse kidney to reveal the molecular phenotype and composition changes of different cell types. In the early stage of aging, immune cells such as T, B cells and mononuclear macrophages increased in kidney. The molecular state of T cells in aging kidney changed and polarized. Among them, we identified a group of GZMK+ CD8 + T cells with high expression of Eomes, Pdcd1 and Ifng and a group of Il17a+ T cells with high expression of Il17a and Il23r. Moreover, the cytokines and inflammations can aggravate tissue damage eventually. Furthermore, we found the interaction between different types of epithelial cells and T cells increased during the renal aging. These results identify the changes of T cells in the early stage of aging kidney and suggest that GZMK+CD8+ T cells might be a potential target to ameliorate age-associated dysfunctions of kidney(Graphical Abstract).

The precipitation mechanism of the secondary phase in Inconel 617B alloy during ageing

ABSTRACT Precipitation of the secondary phase is a key factor that influences the strengthening effect of nickel-based superalloy. The precipitation behaviours of the M23C6 carbide and γ′-Ni3(Ti, Al) phase in Inconel 617B alloy aged at 700°C for different times were studied by scanning electron microscopy, transmission electron microscopy and atom probe tomography. Plate-like carbide nucleated in the interior of grain and irregular shape carbide precipitated at grain boundary respectively during the early stage of ageing. γ′ particle co-precipitated around carbide is a common microstructure feature during ageing for 5–160 h. After ageing for 160 h, γ′ phase is the main secondary phase. The carbide only distributes on the grain boundary, high density γ′ particle homogeneously distributes in the matrix after a longer ageing time. Elemental partitioning to the secondary phases and composition profiles across different phases was quantitatively analysed. Enrichments of Ti and Al at the carbide/γ interface are directly observed, which act as the nucleation site of γ′ particles during ageing. Enrichments of B, Si and Co at different interfaces are also detected. Based on the experimental results, the precipitation mechanisms of γ′ particles and carbide were discussed.