Early Stage Of Aging Research Articles

Thermal degradation and thermo-oxidative aging behavior of vinylidene fluoride-containing fluoroether rubber

Vinylidene fluoride-containing fluoroether rubber has better low temperature performance, expansion resistance and heat resistance. After curing by peroxide, it can be applied to a variety of fuel mixtures and is expected to be widely used in aerospace as a sealing material or other fields. In this work, the thermal degradation and thermo-oxidative aging behavior of Vinylidene fluoride-containing fluoroether rubber cured by 2,5-dimethyl-2,5-di-(tert‑butylperoxy) hexane/Triallyl isocyanurate (DBPH/TAIC) were investigated. For comparison, raw rubber without any crosslinking has been taken. The results indicated that the thermal degradation of vinylidene fluoride-containing fluoride rubber started with the degradation of TAIC in addition to the removal of HF on the backbone and the breakage of the side chain of ether monomers. During thermo-oxidative aging, the main chain formed C = C structure under the mechanism of dehydrofluorination. Meanwhile, the molecular chain broke under the action of thermal oxygen and was accompanied by the formation of carbonyl groups. The destruction of the polymer cross-linked structure occured at the TAIC cross-linking point and mainly occurred in the early stage of aging. However, the crosslinking was not completely disrupted, as the crosslinking density increased with aging time. The destruction and recombination of the crosslinked structure occurred simultaneously during the whole aging process and were dominated by recombination. Over-crosslinking after aging reduced the tensile properties of composites. This work contributes to a better comprehending of the stability of fluoroether rubber seals in a thermal-oxygen environment.

Molecular dynamics study on the influence of thermal aging on the mechanical properties of epoxy resins for high voltage bushing.

Thermal aging significantly deteriorates the mechanical properties and service performance of epoxy resins used for the high-voltage bushing. Current studies on the thermal aging behavior of epoxy resins mainly focus on experimental observations. However, an in-depth understanding of the mechanism of thermal aging of epoxy resins requires the monitoring of structural evolution of epoxy resins during thermal aging at the molecular level. To thoroughly analyze the intrinsic factors affecting structural evolution and the effect of thermal aging on the mechanical properties of epoxy resin for high-voltage bushing, epoxy resin models with different crosslinking degrees were established and thermal aging treatments at various temperatures and time periods were carried out by molecular dynamics simulation. It was found that the tensile strength of the epoxy resin was enhanced with the increase of the crosslinking degree, which was related to the elevation of the proportion of C-N and O-H bonds in its structure. With the increase of thermal aging temperature, the tensile strength of the epoxy resin decreased, which was related to the formation of weak bonds. At the early stage of thermal aging and after a period of high-temperature thermal aging, the strength of epoxy resin significantly decreases. The thermal aging of the epoxy resin is accelerated under external loading. In addition, the crosslinking degree and curing agent also affect the thermal aging resistance of epoxy resins. The results of this study can provide guidance for predicting and improving the thermal aging resistance of epoxy resins. Materials Studio was used to construct molecular models and complete crosslinking reactions. DGEBA and 44DDS (or 33DDS) were mixed at a ratio of 2:1, followed by crosslinking reaction. During this process, the Nose method was used to control temperature, the Berendsen method was used to control pressure, and the polymer consistent force field (PCFF) was used to control the motion and force of atoms. Isobaric-isothermal ensemble (NPT ensemble) was used to heat up epoxy resin models to various thermal aging temperatures of 400K, 500K, 600K and 700K. The models were maintained at these temperatures for different thermal aging times of 100ps, 200ps, 300ps, 400ps, 500ps, 600ps, 700ps and 800ps. Afterwards, the models were cooled down to 300K and subjected to uniaxial tensile testing at this temperature with a strain rate of 1 × 109s-1. The structural configurations and stress-strain data during the tensile process were recorded. The flow stress of the material was derived by counting the average stress in the 20-50% strain interval.

Associations of Dietary Diversity Trajectories with Frailty among Chinese Older Adults: A Latent Class Trajectory Analysis Based on a CLHLS Cohort.

High dietary diversity has been found to be associated with frailty. However, the trajectory of dietary diversity intake in relation to frailty is unclear. Using the latent class trajectory modeling approach, we identified distinctive dietary variety trajectory groups among 2017 participants based on the Chinese Longitudinal Healthy Longevity Survey acquired at four time points within a 10-year period. Frailty status was assessed using a frailty index comprising 37 health deficits. Dietary diversity was quantified using the dietary variety score (DVS), based on food category consumption frequency. Logistic regression analyses were employed to explore the association between DVS change trajectories and frailty. This study identified two distinct DVS trajectories: "Moderate-Slow decline-Slow growth", encompassing 810 (40.16%) individuals, and "Moderate-Slow growth-Accelerated decline", including 1207 (59.84%) individuals. After adjusting for covariates, the odds ratio for DVS in the "Moderate-Slow decline-Slow growth" group was 1.326 (95% confidence interval: 1.075-1.636) compared to the "Moderate-Slow growth-Accelerated decline" group. The "Moderate-Slow decline-Slow growth" trajectory continued to decrease and was maintained at a low level in the early stages of aging. Sustaining a high dietary diversity trajectory over time, particularly in the early stages of aging, could potentially decrease the risk of frailty among older Chinese adults.

Performance evolution and mechanism of asphalt crack sealant under UV aging: A continuity study

Asphalt crack repair materials, known as crack sealants, are directly exposed to ultraviolet (UV) radiation in asphalt pavements. This exposure causes the gradual aging and deterioration of both their surface and internal properties. To study this phenomenon, the sealant was subjected to UV irradiation for a range of 0–385 hours, with the basic properties of the aged sealant tested every 55 hours. Several techniques were employed to investigate the changes in the internal chemical composition of the sealant, including Fluorescence microscopy (FM), gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FT-IR). The results revealed that the UV aging of the sealant mainly occurs in the thinner surface layer, which becomes progressively lighter in color. Notably, obvious surface cracks form after aging process. The cone penetration and softening point of the sealant exhibit an exponential or logarithmic change corresponding to the aging time. The most pronounced changes occur during the early stages of UV aging, with the properties tending to stabilize after approximately 220 h of aging. In addition, the FM images showed that the dispersed polymer particles within the sealant gradually transform into a continuous network structure after aging over time. The GPC spectrum of the aged sealant shifts to the left, indicating an increase in molecular weight, particularly in the polymer modifier. This is consistent with the transformation observed in the FT-IR analysis, which demonstrates that UV irradiation leads to the breaking and recombination of polymer chemical bonds in the sealant. The FT-IR analysis reveals the conversion of monosubstituted benzene to polysubstituted benzene in the polymer modifier, which also correlates with the formation of the network structure observed in the FM images and the increase in molecular weight detected in the GPC spectrum of the polymer modifier.

Experimental measurement and molecular dynamics simulation analysis of thermal aging performance in composite solid propellants

As a complex mixed system, the aging mechanism of high-energy composite materials involves the aging of each component itself, interactions between components, and transformation of microstructural and thermodynamic properties. The study of a single component or performance parameter has great limitations for elaborating the cognitive complexity of aging processes, making it difficult to reveal the underlying principles of physicochemical property transformation. Thus, it can only be applied as an empirical summary. In view of this, this study comprehensively utilized numerical analysis and experimental detection to explore the evolution of micromolecular conformation and changes in macro aging performance from four aspects of composite systems, including binder aging, plasticizer migration, bond interface debonding, and mechanical property transformation. There was good consistency observed between molecular simulation and thermal aging experiments, indicating that there was basically no post curing process for HTPB propellants using TDI as the curing agent. In the early stage of aging, scission chain was the main process and, in the later stage of aging, oxidation crosslinking the main process. Oxidative crosslinking increased the mean square radius of gyration and glass transition temperature of the binder system, reduced the peak value of radial distribution function, and revealed the reason for the change of propellant hardness and CC and CO double bond content. However, chain degradation increased the number of polar groups, enhanced intermolecular polarity, reduced the solubility parameter, and increased the free volume fraction of the mixed system and the dioctyl sebacate diffusion coefficient. This resulted in an increase in the tangent value of the HTPB propellant loss angle from 0.43 to 0.44° and a decrease in the glass transition temperature from 203.3 to 202.0 K. The binding energy at the interfaces of AP/HTPB and Al/HTPB increased first and then decreased, which was consistent with SEM images of bonding interfaces. The joint effect of binding energy and mechanical properties of the binder system promoted the transformation of the stress-strain curve of aging propellant.

Revisiting the response of microstructure and performance to cold pre-strain and the early aging stage in Al–Zn–Mg–Cu alloy

In recent years, extensive research on dynamic precipitation has led to a growing interest in exploring how deformation affects microstructure and mechanical properties. In this study, the response of microstructure and performance to cold pre-strain and the early aging stage in the Al–Zn–Mg–Cu alloy was investigated using a combination of modelling and experimental approaches. A Kampmann-Wagner based numerical framework was developed and applied to the Al–Zn–Mg–Cu alloy. The deformation or quenching induced dislocations and vacancies, their dynamics and acceleration on the diffusivities of solute atoms, and the competition between homogeneous and heterogeneous nucleation were considered in the framework. The effect of the different pre-strain levels (0%–10%) on the evolution of vacancies, dislocations, precipitation kinetics and hardening are given in detail. The results suggest that the acceleration of precipitation kinetics and hardening during the aging process following pre-strain is primarily attributed to the overall increase in diffusivity resulting from deformation-induced dislocations, rather than vacancies. The simulation framework developed in the current work effectively captures the evolution of microstructure and mechanical properties, which has significant practical implications for materials manufacturing.

Evolution of asphalt performance under the coupled aging of ultraviolet, high temperature and water

During the service of asphalt pavement, it is affected by natural environmental factors for a long time, and the pavement performance declined. In order to simulate the cumulative effects of multiple aging components, the indoor "ultraviolet radiation, high temperature and water" multi-factor cyclic coupling aging test was designed. The properties of asphalt during cyclic coupled aging were measured by conventional physical properties tests, photoelectric colorimetric tests, and Fourier Transform Infrared Spectroscopy test. Then the surface morphology of asphalt was observed by camera and optical microscope. After asphalt aged, a large number of oxidation functional groups were formed, causing asphalt to become hard and brittle, adhesion to diminish, and surface roughness to increase. Ultraviolet light and high temperatures led to the exudation and dissolution of the liquid constituents within the asphalt, which were subsequently washed away by water. The thermal stress induced the shrinkage and wrinkle of the asphalt film, resulting in the formation of cracks. Under high temperatures, a limited number of cracks could potentially self-repair during the early stages of aging. Nevertheless, as the aging process progressed, the self-healing capacity of the asphalt diminished, leading to the widening and deepening of cracks. Concurrently, water infiltrated along the cracks into the inner layers of the asphalt, exacerbating the degradation of its properties.

Variation of Young's modulus suggested the main active sites for four different aging plastics at an early age time

Precisely determining which bonds are more sensitive when plastic aging occurs is critical to better understand the mechanisms of toxic release and microplastics formation. However, the relationship between chemical bonds with the active aging sites changes and the aging behavior of plastics at an early age is still unclear. Herein, the mechanical behavior of four polymers with different substituents was characterized by the high-resolution AFM. Young's modulus (YM) changes suggested that the cleavage of C-Cl bonds in PVC, C-H bonds in PE and PP, and C-F bonds in PTFE are the main active aging sites for plastic aging. The aging degree of the plastics followed the order of PVC > PP > PE > PTFE. Two aging periods exhibited different YM change behavior, the free radical and cross-linking resulted in a minor increase in YM during the initiation period. Numerous free radicals formed and cross-linking reaction happened, causing a significant increase in YM during the propagation period. Raman spectroscopy verified the formation of microplastics. This research develops promising strategies to quantitatively evaluate the aging degrees using AFM and establish the relationship between chemical bonds and mechanical behavior, which would provide new method to predict plastic pollution in actual environments.

Structural insights into T1 precipitation and age hardening by Zn alloying for T6 treated Al–Cu–Li based alloys with a high Cu/Li ratio

T1 (Al2CuLi) nano-phase precipitation has been a major focus in developing new multi-microalloyed Al–Cu–Li alloys. Nevertheless, more understanding is required. This work investigated the effect of Zn alloying on the microstructure and mechanical properties of multi-element Al–Cu–Li alloys with a high Cu/Li ratio using a combination of advanced electron microscopy and first-principles calculations. Zn alloying (i) induced a higher density of geometrically-necessary dislocations after solid-solution treatment, which increased the T1 nucleation rate during the early aging stage; (ii) promoted T1 growth by substituting Al or Cu atoms in the T1 structure; and (iii) profoundly increased the aging kinetics, the age hardening response, and the strength. In addition, the co-segregation of Zn, Mg and Cu at the T1/Al interface helped to stabilize the fine T1 nano-platelets. These structural insights into T1 precipitation and age hardening by Zn alloying can help to guide the optimal design of high-performance Zn micro-alloyed multi-element Al–Cu–Li alloys.

Age-related changes in meningeal lymphatic function are closely associated with vascular endothelial growth factor-C expression

Meningeal lymphatic vessels (MLVs) have crucial roles in removing metabolic waste and toxic proteins from the brain and transporting them to the periphery. Aged mice show impaired meningeal lymphatic function. Nevertheless, as the disease progresses, and significant pathological changes manifest in the brain, treating the condition becomes increasingly challenging. Therefore, investigating the alterations in the structure and function of MLVs in the early stages of aging is critical for preventing age-related central nervous system degenerative diseases. We detected the structure and function of MLVs in young, middle-aged, and aged mice. Middle-aged mice, compared with young and aged mice, showed enhanced meningeal lymphatic function along with MLV expansion and performed better in the Y maze test. Moreover, age-related changes in meningeal lymphatic function were closely associated with vascular endothelial growth factor-C (VEGF-C) expression in the brain cortex. Our data suggested that the cerebral cortex may serve as a target for VEGF-C supplementation to ameliorate meningeal lymphatic dysfunction, thus providing a new strategy for preventing age-related central nervous system diseases.

Effects of pre-deformation on microstructure, mechanical properties and corrosion performance of an Al-Cu-Mg-Ag alloys

The influence of pre-deformation on the microstructure, mechanical properties, and corrosion behavior of AA2029-T8 was investigated. The pre-deformation may potentially impede the formation of Mg-Ag clusters during the early stage of aging, altered the normal precipitation sequence of the alloy, and significantly increased dislocation density that facilitated non-uniform nucleation of S phase at dislocations, resulting in finer dispersion of precipitation. Moreover, it led to a decrease in Ω phase volume fraction and comparable aspect ratio(diameter/thickness). With increasing deformation, aging response was accelerated, leading to shorter time to peak strength but reduced plasticity. Additionally, the width of precipitate-free zone (PFZ) remained relatively unchanged with increasing pre-deformation; however, average size of grain boundary precipitates (GBPs) decreased while becoming more discontinuous. This resulted in narrowing intergranular corrosion (IGC) channels and decreased maximum corrosion depth as well as a transition from IGC to pitting corrosion behavior. These findings suggest that the mechanical properties and corrosion resistance of the alloy can be improved by increasing pre-deformation levels.

Enhancing creep formability and mechanical properties of creep-aged AA2050 alloys via slow heating

In this work, a new creep aging route (pre-deformation+slow-heated creep aging, PSHCA) of AA2050 alloys was developed by the slow heating (20 °C/h) from 120 °C to 180 °C. The PSHCA alloy exhibits high creep strain with a simultaneous increase of strength and plasticity. The yield strength, ultimate tensile strength, and elongation reached 544 MPa, 581 MPa, and 11.1%, respectively. Both the rolling pre-deformation before aging and stress field during aging promoted the increased dislocation density and dense precipitation of T1 phases in the aged alloys, hence, the strength was improved at the expense of plasticity. Meanwhile, the bimodal diameter distribution of T1 phase of the PSHCA alloy and the enrichment of Ag atoms at T1/matrix interface was promoted by slow heating, slowing down the thickening of T1 phases. This further promoted the plasticity of PSHCA alloys while maintaining high strength. Additionally, the slow precipitation of T1 phase at the early stage of aging promoted dislocation slip and thus improving the creep strain of PSHCA alloys. These findings pave a way in designing large-curved and high-performance Al-Li components by creep aging technology.

Yttrium effect on 475 °C brittleness of Fe–13Cr–6Al–2Mo-0.5Nb-0.15Zr alloy

The effect of yttrium on the 475 °C brittleness and microstructure stability of Fe–13Cr–6Al–2Mo-0.5Nb-0.15Zr alloy after long-term aging at 475 °C has been investigated. At the early stage of aging, the nanoscale metastable transition phase precipitates in large quantities. After aging for 10,000 h, the nanophase in the Y-free alloy has completely disappeared, and only a great deal of granular Laves phases are left, while a large number of nanoscale phases still exist in the grain of Y-containing alloys. This is because the addition of yttrium combines with vacancies, hinders the diffusion of Laves phase-forming elements, and has the result that the transformation of nanoscale phases Fe2(Mo0.3Nb0.7)Al to Laves phase is inhibited during the aging process of the Y-containing alloys. During aging, precipitation-free zones (PFZ) are formed in the surrounding area where the Laves phase and grain boundaries exist. The elongation of Y-containing alloys decreases with yttrium content, but it is still higher than that of Y-free alloy. The addition of yttrium improves the aging plasticity and weakens the degree of 475 °C brittleness of the alloy, and the effectiveness is diminished with the yttrium. This plays a key role in the further study of Fe–Cr–Al alloys for fuel cladding materials.

Tailoring Young's modulus by controlling Al bond length and strength using positive Li and negative Mg

For decades, it has been widely accepted that adding Mg to Al alloys decays Young's modulus of Al alloys. However, the fundamental mechanism for Young's modulus reduction is still pending. In this study, we experimentally produce the Al–Li alloys and Al–Li–Mg alloys using centrifugal casting and trace Young's modulus as a function of the evolution of their precipitation structures. Atomic-resolution high-angle-annular-dark-field (HAADF) imaging in scanning transmission electron microscopy (STEM) indicates that the precipitate sizes of Al–Li and Al–Li–Mg alloys are essentially the same in the early and late stages of aging. While atomic resolution HAADF suggests that although the lattice constants of δ′-Al3Li in Al–Li and Al–Li–Mg alloys (0.404 nm) are consistent in the early aging stage, it changes to 0.422 nm in the Al–Li–Mg alloy at the end of peak aging, showing a significant expansion to the same level as α-Al (0.421 nm). The nanoindentation results confirm that Young's modulus decreases strongly from 89.04 to 76.39 GPa for Al–Li–Mg alloys due to the lattice relaxation. Combining atomic-resolution HAADF and first-principles calculations, it has been found that Mg atoms diffuse into Al3(Li, Mg) crystals by replacing Li in the L12 δ′-Al3Li and thus doping the crystal. Further, it has been found that Mg atoms expand the spacing between Al–Al and Al–Li pairs thereby lowering the energy between Al–Al and Al–Li bonds, which in turn stretches their potential energy curves reducing Young's modulus.

Effects of Ni Content and Heat Treatment on the Properties, Microstructures, and Precipitates of Cu-0.2 wt% Be-x wt% Ni Alloys.

Cu-Be alloys exhibit excellent comprehensive performance in electrics, thermotics, and mechanics, and hence, they attract much attention. Among them, low-Be copper alloys are more environmentally friendly and promising. This study explores the effects of different Ni contents and heat treatment parameters on the properties, microstructures, and precipitates of Cu-0.2 wt% Be-x wt% Ni (0 < x < 2.0) alloys. The experimental results demonstrate that the fast cooling rate of cast alloys during solidification contributes to retention of the solute atoms in the copper matrix, which is beneficial for subsequent solid solution treatment. Furthermore, solid solution treatment slightly reduces the electrical conductivities, microhardness values, and compressive yield strengths of Cu-0.2 wt% Be-1.0/1.6 wt% Ni alloys. The optimal solution temperature and time are about 925 ℃ and 60 min, respectively. Aging treatment significantly increases the electrical conductivities, microhardness values, and compressive yield strengths of Cu-0.2 wt% Be-1.0/1.6 wt% Ni alloys. The best aging temperature is around 450 ℃. However, the properties of Cu-0.2 wt%Be-0.4 wt%Ni alloys remain unaffected by solution and aging treatments. Around x = 1.0, Cu-0.2 wt% Be-x wt% Ni alloys possess the best comprehensive properties, which are about 72%IACS of electrical conductivity, 241 HV of microhardness, and 281MPa of compressive yield strength, respectively. TEM and EDS analyses reveal that the precipitate evolution of Cu-0.2 wt% Be-1.0 wt% Ni alloys with aging time is GP zones → γ″ → γ'. Notably, a distinct double-peak age strengthening phenomenon emerges with Cu-0.2 wt% Be-1.0/1.6 wt% Ni alloys. The precipitation of plenty of GP zones at the early stage of aging should account for the first strengthening peak, and the strengthening mechanism transformation of the γ″ or γ' phase from shear to Orowan should induce the second strengthening peak. This work may help to design new low-Be copper alloys and their preparation processes.

Variety of yield strength caused by precipitations of L12-Ni3Al and B2-NiAl phases in alumina-forming austenitic steel

Alumina-forming austenitic (AFA) steel exhibits excellent high-temperature properties and has attracted significant attention in thermal power generation industry. Microstructure evolutions and yield strengths of 20Ni-AFA steel during isothermal aging are investigated. The results show that five types of phases are found in 20Ni-AFA steel during isothermal ageing: NbC, L12-Ni3Al, M23C6, B2-NiAl and Laves phases. Addition of Cu causes precipitation of L12-Ni3Al phase in 20Ni-AFA steel at the early stage of isothermal aging. L12-Ni3Al phase grows and gradually transforms into B2-NiAl phase which possesses a more stable structure with the extension in isothermal aging time. The transformation leads to yield strengths of 20Ni-AFA steel to decrease anomalously during 24-120 h isothermal aging. Yield strengths of 20Ni-AFA steel increase again as isothermal aging time continues to increase.

Evolution of Structure and Properties of SBS-Modified Asphalt during Aging Process

To explore the performance evolution mechanism of SBS-modified bitumen (SMB) during construction and service, the chemical structure, molecular weight and properties of styrene–butadiene–styrene triblock copolymer (SBS) and SMB under multiple aging levels were assessed via Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC) and a dynamic shear rheometer (DSR). The results indicate that the polybutadiene segments in SBS are susceptible to oxidative degradation, and the molecular weight of SBS decreases rapidly during the aging process. The complex modulus and temperature sensitivity of SMB show relatively small changes during the early aging stage, which is mainly attributed to the impact of SBS oxidative degradation. While its temperature sensitivity decreases sharply after double PAV aging, it means the influence of asphalt aging on its performance is dominant. And there is a significant difference in the effect of aging on the creep recovery behavior of SMB under high and low shear stresses. The percentage recovery (R) of SMB decreases and then increases under low shear stress as aging progresses. While the value R of SMB increases gradually under high shear stress with the extension of aging. Meanwhile, the viscoelastic properties of SMB have gradually transformed to those of aged matrix asphalt after serious aging, which is also confirmed by the gradual destruction and degradation of the SBS cross-linked network in the binder from a fluorescence micrograph. This research will help to understand the performance failure mechanism of SMB during service, providing a theoretical reference for the selection of maintenance and renovation opportunities during the service process of SBS-modified asphalt pavement, as well as the avenue to achieve high-performance recycling.

Environmental enrichment in middle age rats improves spatial and object memory discrimination deficits.

Changes in memory performance are one of the main symptoms of normal aging. The storage of similar experiences as different memories (ie. behavioral pattern separation), becomes less efficient as aging progresses. Studies have focused on hippocampus dependent spatial memories and their role in the aging related deficits in behavioral pattern separation (BPS) by targeting high similarity interference conditions. However, parahippocampal cortices such as the perirhinal cortex are also particularly vulnerable to aging. Middle age is thought to be the stage where mild mnemonic deficits begin to emerge. Therefore, a better understanding of the timing of the spatial and object domain memory impairment could shed light over how plasticity changes in the parahipocampal-hippocampal system affects mnemonic function in early aging. In the present work, we compared the performance of young and middle-aged rats in both spatial (spontaneous location recognition) and non-spatial (spontaneous object recognition) behavioral pattern separation tasks to understand the comparative progression of these deficits from early stages of aging. Moreover, we explored the impact of environmental enrichment (EE) as an intervention with important translational value. Although a bulk of studies have examined the contribution of EE for preventing age related memory decline in diverse cognitive domains, there is limited knowledge of how this intervention could specifically impact on BPS function in middle-aged animals. Here we evaluate the effects of EE as modulator of BPS, and its ability to revert the deficits caused by normal aging at early stages. We reveal a domain-dependent impairment in behavioral pattern separation in middle-aged rats, with spatial memories affected independently of the similarity of the experiences and object memories only affected when the stimuli are similar, an effect that could be linked to the higher interference seen in this group. Moreover, we found that EE significantly enhanced behavioral performance in middle-aged rats in the spatial and object domain, and this improvement is specific of the high similarity load condition. In conclusion, these results suggest that memory is differentially affected by aging in the object and spatial domains, but that BPS function is responsive to an EE intervention in a multidomain manner.

Serum procalcitonin as a marker of neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD)

BackgroundNeonatal Intrahepatic Cholestasis (NICCD), as the early-age stage of Citrin deficiency involving liver dysfunction, lacks efficient diagnostic markers. Procalcitonin (PCT) has been identified as a biomarker for infection as well as various organ damage. This study aimed to explore the potential of PCT as a biomarker for NICCD. MethodsIn a single-center retrospective case-control study. Serum PCT concentrations before and after treatment of 120 NICCD patients, as the study group, were compared to the same number of cholestatic hepatitis patients, as the control group. The potential value of PCT to discriminate NICCD from control disease was further explored using Receiver Operating Characteristic (ROC) curve analysis and compared to those of other inflammatory markers. ResultsThere was a significantly higher level of PCT in NICCD patients than in the control group. PCT concentrations were only weakly correlated with neutrophil counts and CRP levels (p ˂ 0.05). At a cut-off value of 0.495 ng/mL, PCT exhibited a significantly higher diagnostic value compared to other inflammatory markers for discriminating NICCD from the control, with a sensitivity of 90.8 % and specificity of 98.3 %. ConclusionPCT might be used as an initial biomarker to discriminate children with NICCD from another hepatitis disease.

Effect of Al addition on Nb-rich phase precipitation behavior in ferritic stainless steel

The precipitation behavior of Nb-rich phase in Al-free and 1Al Nb-bearing ferritic stainless steels (FSSs) at 700 °C were investigated. The results show that Nb-bearing carbides and Laves phases with mutual transformation relationships are precipitated in both Al-free and 1Al Nb-bearing FSSs at the early stage of aging. At this stage, the coarsening rate of Laves phase is higher than that of Nb2C phase, and the addition of Al can promote the precipitation of Laves phase and weaken the precipitation of (Nb, Ti)2C phase. As the aging time extended to 60 min, the Nb-rich phase in the two experimental steels was mainly Laves phase, and the intragranular Laves phase showed feather like aggregation distribution. On the one hand, the added Al can be enriched in the Laves phase to produce a tailing morphology, on the other hand, it can reduce the diffusion rate of Nb atoms in the matrix, thereby weakening the aggregation state of the intragranular Laves phase. During the coarsening process of Laves phase, the addition of Al can reduce the coarsening rate of Laves phase by 7.45 times.