Aging Regime Research Articles

Durability of Hybrid Composite Beam Bridges Subjected to Various Environmental Conditioning

AbstractThe hybrid composite beam (HCB) is a novel idea that combines conventional construction materials (i.e., steel and concrete) with fiber-reinforced polymer (FRP) composites in a new configuration. This hybridization aims to optimize the beam’s structural performance and produce a structural element that is more durable than conventional members. This study examined the durability of a commercial glass FRP (GFRP) laminate that was used to encase the HCB elements in a recently constructed HCB bridge. The E-glass/vinyl ester laminate was subjected to five aging regimes. These conditioning regimes simulated an alkaline attack, a salt attack, a salt attack that was preceded by ultraviolet (UV) irradiation exposure, and sustained stresses that were accompanied by controlled thermal cycles and natural weathering. The durability of the E-glass/vinyl ester laminate was examined in terms of changes that occurred in the ultimate tensile strength. A microstructural analysis was performed on both unconditioned ...

Influence of disorder on ageing and memory effects in non-equilibrium critical dynamics of 3D Ising model relaxing from an ordered state

We have performed a numerical investigation of the influence of disorder on the dynamical non-equilibrium evolution of a 3D site-diluted Ising model from a low-temperature initial state with magnetization m0 = 1. It is shown that two-time dependences of the autocorrelation and integrated response functions for systems with spin concentrations p = 1.0, 0.95, 0.8, 0.6 and 0.5 demonstrate ageing properties with anomalous slowing-down relaxation and violation of the fluctuation-dissipation ratio. It was revealed that during non-equilibrium critical dynamics in the long-time regime the autocorrelation functions for diluted systems are extremely slow due to the pinning of domain walls on impurity sites. We have found that the fluctuation-dissipation ratio for diluted systems with spin concentration p < 1 while the pure system is characterized by . The autocorrelation function power-law delay becomes the same as for the time dependence of the magnetization in the critical point and is characterized by exponent . Also, for diluted systems we reveal memory effects for critical evolution in the ageing regime with realization of cyclic temperature change and quenching at .

Effect of heat treatment on the microstructures and mechanical properties of Al-5.5Zn-2.5Mg alloy

The Al-5.5 Zn-2.5 Mg (wt%) ternary alloy was prepared using a vacuum melting furnace and a casting furnace. Microstructural and mechanical properties of the alloy were investigated as-cast and under heat-treated conditions. To investigate the effect of heat treatment, numerous designed Al-5.5 Zn-2.5 Mg samples were homogenized under different conditions and then aged under different regimes. The effects of heat treatment on the microstructures were examined by OM, SEM, and TEM, and mechanical properties of the Al-Zn-Mg alloy were studied. A good combination of high microhardness and reasonable tensile strength were obtained by successive and suitable heat treatments. After aging for 24h at 150°C, the peak microhardnes and tensile strength values were achieved as 157MPa and 188.8MPa, respectively. The microscopic fracture surfaces of the aged samples under different homogenization and aging conditions were observed using scanning electron microscopy. Fractographic analysis of the tensile fracture surfaces shows that the type of fracture changed significantly from ductile to more ductile depending on the aging regime.

Unveiling the structural arrangements responsible for the atomic dynamics in metallic glasses during physical aging.

Understanding and controlling physical aging, that is, the spontaneous temporal evolution of out-of-equilibrium systems, represents one of the greatest tasks in material science. Recent studies have revealed the existence of a complex atomic motion in metallic glasses, with different aging regimes in contrast with the typical continuous aging observed in macroscopic quantities. By combining dynamical and structural synchrotron techniques, here for the first time we directly connect previously identified microscopic structural mechanisms with the peculiar atomic motion, providing a broader unique view of their complexity. We show that the atomic scale is dominated by the interplay between two processes: rearrangements releasing residual stresses related to a cascade mechanism of relaxation, and medium range ordering processes, which do not affect the local density, likely due to localized relaxations of liquid-like regions. As temperature increases, a surprising additional secondary relaxation process sets in, together with a faster medium range ordering, likely precursors of crystallization.

Influence of Transplanting Age on Paddy Yield under the System of Rice Intensification

Agronomic practices such as transplanting age, plant spacing, and water application regimes in irrigated paddy production can have a significant impact towards the performance in rice growth and yield. A study was conducted to investigate the optimum transplanting age for maximum rice productivity under the systems of rice intensification (SRI) technology. The study treatments adopted were three representing 8, 12 and 15 days old seedlings replicated 3 times each. The experiment was set in randomized complete block design (RCBD) and transplanted at spacing 25 cm × 25 cm between rice hills. The rice variety tested was TXD 306 Super SARO, which was recommended by the ministry of Agriculture in Tanzania. Data was collected throughout the growing season in two mixed short rains and dry season of September 2013/2014 and September 2014/2015. Data collected included biomass at vegetative, flowering and harvesting stages, total number of tillers per hill, number of productive tillers per hill, number of grains per panicle and rice grain yield at the end of the season. Data was analyzed using SAS software version 9.1. The results suggested that transplanting at younger age of 8 to 12 days was recommended for Mkindo area in Mvomero Distirct, and other areas with similar soil conditions and agro ecological characteristics.

Comparison of four monolithic zirconia materials with conventional ones: Contrast ratio, grain size, four-point flexural strength and two-body wear

ObjectivesTo test the mechanical and optical properties of monolithic zirconia in comparison to conventional zirconia. Materials and methodsSpecimens were prepared from: monolithic zirconia: Zenostar (ZS), DD Bio ZX2 hochtransluzent (DD), Ceramill Zolid (CZ), InCoris TZI (IC) and a conventional zirconia Ceramill ZI (CZI). Contrast ratio (N=75/n=15) was measured according to ISO 2471:2008. Grain sizes (N=75/n=15) were investigated with scanning electron microscope. Four-point flexural strength (N=225/n=15/zirconia and aging regime) was measured initially, after aging in autoclave or chewing simulator (ISO 13356:2008). Two-body wear of polished and glazed/veneered specimens (N=108/n=12) was analyzed in a chewing simulator using human teeth as antagonists. Data were analyzed using 2-/1-way ANOVA with post-hoc Scheffé, Kruskal–Wallis-H, Mann–Whitney-U, Spearman–Rho, Weibull statistics and linear mixed models (p<0.05). ResultsThe lowest contrast ratio values were found for ZS and IC and CZ. IC showed the largest grain size followed by DD and CZI. The smallest grain size was observed for ZS followed by CZ. There was no correlation between grain size and contrast ratio. The aging regime showed no impact on flexural strength. All non-aged and autoclave-aged specimens showed lower flexural strengths than the control group CZI. Within groups aged in chewing simulator, ZS showed significantly lower flexural strength than CZI. CZI showed higher material and antagonist wear than monolithic polished and glazed groups. Glazed specimens showed higher material and antagonist loss compared to polished ones. There was no correlation between roughness and wear. ConclusionsMonolithic zirconia showed higher optical, but lower mechanical properties than conventional zirconia.

Aging worlds in contradiction: gerontological observations in the Mediterranean region

This article discusses the existing and developing aging regimes in the Northern and Southern rim countries of the whole Mediterranean region which are all undergoing considerable social and political transformation processes. It is argued that several eye-opening theoretical interventions for such a gerontological project may lead to some methodological problems and pitfalls, which have to be dealt with productively. Central collective concepts of such an analysis (as the change-oriented “modernization effects” of societal aging and the continuity-oriented gaze at the “unity of the region”) have to be reconsidered and ought to be more differentiated in order to allow smaller social entities (such as kinship and community systems and their connectivity) to be central orientations for analyzing poverty and care management in old age in the Mediterranean region. How to reconnect such a rather micro-political agenda with large processes and big structures of aging policies in the region however still remains an open question.

Adverse reactions following routine anticholinergic eye drops in a paediatric population: an observational cohort study

ObjectivesTo investigate the presence, nature and relationship to age, sex, ethnicity and body mass index (BMI) of adverse reactions following routine cycloplegic eye drops in children.DesignProspective observational cohort study.SettingOphthalmology outpatient...

Relaxation dynamics of vortex lines in disordered type-II superconductors following magnetic field and temperature quenches.

We study the effects of rapid temperature and magnetic field changes on the nonequilibrium relaxation dynamics of magnetic vortex lines in disordered type-II superconductors by employing an elastic line model and performing Langevin molecular dynamics simulations. In a previously equilibrated system, either the temperature is suddenly changed or the magnetic field is instantaneously altered which is reflected in adding or removing flux lines to or from the system. The subsequent aging properties are investigated in samples with either randomly distributed pointlike or extended columnar defects, which allows us to distinguish the complex relaxation features that result from either type of pinning centers. One-time observables such as the radius of gyration and the fraction of pinned line elements are employed to characterize steady-state properties, and two-time correlation functions such as the vortex line height autocorrelations and their mean-square displacement are analyzed to study the nonlinear stochastic relaxation dynamics in the aging regime.

Influence of Supports on Pd Catalysts for the Selective Catalytic Reduction of NOx with H2 and CO

A major concern of current commercial catalysts for the selective catalytic reduction (SCR) of nitrogen oxides (NOx) (DeNOx) is the lack of sufficient catalytic activity at low temperatures (below 200°C) that typically occur during cold start and urban driving conditions. To address this issue, a study was undertaken to develop an (H2 + CO)-SCR Pd-based catalyst to obtain high DeNOx activity in this low-temperature range. A series of catalysts with Pd loaded on supports containing various amounts of γ-alumina (γ-Al2O3) (0–65 wt%), CBV-2314 (15–100 wt%), and TiO2 (0–20 wt%) were tested for DeNOx activity and aging in a catalyst testing unit (CTU). The results showed that each component in the support played a role in the NOx conversion, depending on the temperature. Catalysts with Pd supported on {[γ-Al2O3 (60 wt%) + CBV-2314 (20 wt%)]–TiO2 (20 wt%)} achieved the best overall DeNOx activity. Catalysts with various Pd loadings (0.05 wt% to 0.5 wt%) were prepared with a {[γ-Al2O3 (60 wt%) + CBV-2314 (20 wt%)] − TiO2 (20 wt%)} support. The catalysts loaded with 0.05 wt% and 0.2 wt% Pd demonstrated the best overall DeNOx activity (up to 90 % NOx conversion starting at 150 °C). These catalysts were subjected to an accelerated aging regime. Based on the aging studies, the 0.2 wt% Pd / {[γ-Al2O3 (60 wt%) + CBV-2314 (20 wt%)] − TiO2 (20 wt%)} composition was the most active and stable catalyst.

The effect of aging on machinability of 15Cr–5Ni precipitation hardened stainless steel

This study is an attempt to correlate the microstructure and mechanical properties of commercial 15Cr–5Ni precipitation-hardening stainless steel in different aging regimes such as solution treated (Condition A), over-aged (Condition H1150-M) and peak-aged (Condition H900) with their machinability behavior. Aging was done on 15Cr–5Ni precipitation-hardenable stainless steel samples in a temperature range of 480–760°C. Over aging of the above material resulted in an improvement of ductility and a substantial reduction in tensile strength. Heat treated samples were machined in order to study the effects of machining parameters on machinability aspects such as cutting forces, surface roughness, chip morphology and tool wear. Experimental investigation revealed a strong correlation between the rate of cooling after aging and cutting forces. Air cooled samples exhibited higher cutting forces compared to furnace cooled samples. The surface finish is found to be improved for H900 air cooled sample, which has higher hardness than that of as received sample and H1150-M condition.

Debt servicing, aggregate consumption, and growth

We develop a neo-Kaleckian growth model that emphasizes the importance of consumption behavior. In our model, workers first make consumption decisions based on their gross income, and then treat debt servicing commitments as a substitute for saving. Workers’ borrowing is induced by their desire to keep up with the consumption standard set by rentiers’ consumption, reflecting an aspect of the relative income hypothesis. As a result of this consumption and debt servicing behavior, consumer debt accumulation and income distribution have effects on aggregate demand, profitability, and economic growth that differ from those found in existing models. We also investigate the financial sustainability of the Golden Age and Neoliberal growth regimes within our framework. It is shown that distributional changes between the Golden Age and the Neoliberal regimes, together with corresponding changes in consumption emulation behavior via expenditure cascades, suffice to make the Neoliberal growth regime unsustainable.

Effect of dietary regime on metabolic control in phenylketonuria: Is exact calculation of phenylalanine intake really necessary?

BackgroundA phenylalanine (Phe) restricted dietary management is required in phenylketonuria (PKU) to maintain good metabolic control. Nevertheless, five different models of dietary regimes, which differ in their accuracy of Phe documentation, are used. To investigate the effect of the dietary regime on metabolic control, a multicenter evaluation was performed. Patients/Methods149 patients (max. 800mg Phe-intake/day; 108 children aged 1–9years and 41 adolescents aged 10–15years) could be included. They were separated according to age and dietary regime, revealed by a questionnaire on dietary habits. Dietary regimes vary from daily strict calculation of all Phe-intake (group 1) to a rather loose regime only estimating Phe-intake and including high protein food (group 5). Data were analyzed with respect to metabolic control (Phe-concentrations, Phe-concentrations above upper recommended limit during 6months before the interview), Phe-intake (mg/day) and age (years). ResultsMedian Phe-concentrations in children did not differ significantly among diet groups (group 1: 161; 2: 229, 3: 236, 4: 249, 5: 288μmol/l, p=0.175). However, exact daily Phe calculation led to significantly lower percentage of Phe concentrations above the upper recommended limit (group 1: 17, 2: 50, 3: 42, 4: 50, 5: 75%, p=0.035). All included patients showed good to acceptable metabolic control. Patients on the dietary regime with the least accuracy, consuming also high protein foods, showed the poorest metabolic control. Median Phe concentrations of all other groups remained within recommended ranges, including from groups not calculating special low protein foods, fruit and vegetables and using a simplified system of recording Phe-intake.In adolescents no significant differences among diet groups were revealed. ConclusionExact calculation of Phe content of all food is not necessary to achieve good metabolic control in children and adolescents with PKU. Excluding special low protein food, as well as fruit and vegetables from calculation of Phe-intake has no impact on metabolic control. However including protein rich food into the diet and simply estimating all Phe-intake appears insufficient. The simplification of dietary regime may be helpful in enhancing acceptability and feasibility.

NaOCl degradation of one-step one-bottle self-etch adhesives bonded to bovine dentine

Objective: The aim of the present study was to assess the influence of an in vitro aging regime (NaOCl storage) on dentine microtensile bond strength (μTBS) of five one-step one-bottle self-etch adhesives in comparison with bond strength of two-step self-etch adhesive.Material and methods: Flattened dentine surfaces from 30 bovine incisors were bonded with five one-step one-bottle self-etch adhesives (iBond, Clearfil S3 Bond, AdheSE One F, G-Bond, Optibond all-in-one) and one two-step self-etching adhesive (Clearfil SE Bond). Composite buildups were done with microhybrid resin composite. Bonded samples were sectioned into resin–dentine sticks of 0.8 mm2 cross section. Randomly selected 20 sticks were tested directly by microtensile bond strength testing machine, whereas another randomly selected 20 sticks were tested after being stored in solution of 10% NaOCl for 5 h. Data were analyzed by two-way analysis of variance (ANOVA) and Tukey’s honest significant difference (HSD) tests (p < 0.05).Results: All adhesives exhibited similar dentine bond strength with exception of G-Bond. After NaOCl storage, μTBS reduced in all groups significantly. The lowest μTBS were found for G-Bond. Rest of one-step self-etch adhesives presented similar μTBS with two-step self-etch adhesive.Conclusion: Interfaces of resin–dentine bonding are susceptible to NaOCl degradation. The amount of the destruction depends on adhesive system. NaOCl degradation of the nonresin encapsulated collagen fibers might decrease long-term stability of resin bonding with dentine.

Predicting all-cause mortality from basic physiology in the Framingham Heart Study.

Using longitudinal data from a cohort of 1349 participants in the Framingham Heart Study, we show that as early as 28-38years of age, almost 10% of variation in future lifespan can be predicted from simple clinical parameters. Specifically, we found diastolic and systolic blood pressure, blood glucose, weight, and body mass index (BMI) to be relevant to lifespan. These and similar parameters have been well-characterized as risk factors in the relatively narrow context of cardiovascular disease and mortality in middle to old age. In contrast, we demonstrate here that such measures can be used to predict all-cause mortality from mid-adulthood onward. Further, we find that different clinical measurements are predictive of lifespan in different age regimes. Specifically, blood pressure and BMI are predictive of all-cause mortality from ages 35 to 60, while blood glucose is predictive from ages 57 to 73. Moreover, we find that several of these parameters are best considered as measures of a rate of 'damage accrual', such that total historical exposure, rather than current measurement values, is the most relevant risk factor (as with pack-years of cigarette smoking). In short, we show that simple physiological measurements have broader lifespan-predictive value than indicated by previous work and that incorporating information from multiple time points can significantly increase that predictive capacity. In general, our results apply equally to both men and women, although some differences exist.

Influence of grain size, aging conditions and tension rate on the mechanical behavior of titanium low-cost metastable beta-alloy in thermally hardened condition

Taking titanium low-cost metastable β alloy TIMETAL-LCB (Ti–1.5(wt.%)Al–4.5Fe–6.8Mo) as a program material, the influence of grain size, size of secondary α-phase precipitates after aging, and strain rate (in the range of 1.6×10−4–7.3×10−2s−1) on mechanical behavior was studied. Aging caused increase in strength and decrease in ductility parameters as compared to initial single-phase metastable (as-quenched) β condition with two different β grain sizes (Coarse Grained, CG, 200μm and Fine Grained, FG, 20μm), and these effects were more pronounced at higher strain rates. Aged FG conditions had essentially higher resource of ductility compared to CG ones after the same aging regimes. Obtained results are discussed in terms of mechanical properties changes induced by aging with respect to initial as-quenched condition. Analysis of area under the engineering stress–strain curves, characterizing the work expended on deformation until fracture and representing tensile toughness of the material, showed that it decreased after aging at all strain rates applied, with essential superiority of FG conditions over CG.

Nitrate leaching and residual effect in dairy crop rotations with grass–clover leys as influenced by sward age, grazing, cutting and fertilizer regimes

Intensive dairy farming, with grass-arable crop rotations is challenged by low N use efficiency that may have adverse environmental consequences. We investigated nitrate leaching and N fertility effects of grass–clover leys for five years in two organic crop rotations with different grassland proportions (33 and 67%) and five grassland managements in terms of cutting, grazing, fertilization and combinations thereof. In grass–clover, the combination of fertilization and grazing caused excessive leaching (average 60kg Nha−1) but leaving out either fertilization or full-time grazing substantially reduced leaching losses to on average 23kg Nha−1. There was no linear relationship between sward age and nitrate leaching. The annual N surplus of the grasslands was only weakly related to nitrate leaching (R2=0.05, P<0.01). The residual effect of grassland cultivation was highest following grazing and fertilization and lowest without fertilization or cutting-only management and was not influenced by grassland age. The arable part of the mixed crop rotation was nitrate leaky where crop coverage in autumn was insufficient. Nitrate leaching following the crops may roughly be divided into four groups: (1) low leaching (<10kg Nha−1) consisting of the barley wholecrop undersown with Italian ryegrass, (2) medium–low leaching (10–20kg Nha−1) consisting of barley with grass–clover undersown and the 1-yr-old grasslands, (3) medium leaching (25–50kg Nha−1) consisting of barley–pea and 2-4-yr-old grasslands with the 2-yr-old leaching the most (36–46kg Nha−1), and (4) high leaching (>50kg Nha−1) with lupin and maize, where especially maize was consistently high in all five years (average 81kg Nha−1). Great care should be taken during all phases of the dairy crop rotation where grasslands cause considerable build-up of fertility. With due care and the best management practice, nitrate leaching losses may be reduced to low levels.

Aging Processes in Ultrafine‐Grained Low‐Alloyed Bronzes Subjected to Equal Channel Angular Pressing

AbstractThe aging processes in Cu‐0.7% Cr, Cu‐0.9% Hf, and Cu‐0.7% Cr‐0.9% Hf alloys after equal channel angular pressing have been studied. ECAP leads to strong grain refinement (200 nm for Cu‐0.7% Cr‐0.9% Hf alloy). It was shown that the Cu5Hf particles are more efficient as strengthening phase than the particles of Cr‐based solid solution. Alloying with hafnium also improves the thermal stability of hardening and minimizes recrystallization processes at aging temperatures. Temperature‐time aging regimes of bronzes for achieving optimal combination of strength, ductility, and electrical conductivity were also determined. Ternary alloy after aging at 500 °C for 2.5 h has a tensile strength of 582 MPa, an elongation of 18%, and an electrical conductivity of 75% IACS.

The Changes of Germination Characteristics and Enzyme Activity of Barley Seeds under Accelerated Aging

AbstractSeed aging is the main problem of seed storage. Changes of enzyme activity and reduction of seedling growth are consequence of seed deterioration. An experiment was conducted to evaluate the effects of accelerated aging on germination indexes and enzyme activity of barley seeds. Seeds were incubated in closed plastic boxes for the accelerated aging treatments at 41°C. Three accelerate aging regimes were performed by placing seeds at 41°C and relative humidity (RH) of 90-100 % for 0, 4 and 8 day periods. Our results showed that increasing aging duration resulted higher reduction in germination percentage, germination index, mean time to germination, normal seedling percentage, catalase and ascorbate peroxidase. The highest germination percentage, germination index, normal seedling percentage and enzyme activity were achieved in control conditions (0 day of aging). Under aging conditions, germination percentage, means time to germination, germination index, normal seedling percentage and enzyme activity decrease significantly. Also, our results indicated that seed aging is related to decrease of enzymes and may contribute to low germination efficiency. The general decreases in enzyme activity in the seed lowers the respiratory capacity, which in turn lowers both the energy (ATP) and assimilates supply of the germinating seed, also decrease in antioxidant enzymes is linked to an increased accelerated ageing and decreased germination characteristics. Subsequently, proposed a positive relationship between antioxidant enzyme capacity and the vigour of the seed

Aging scaled Brownian motion.

Scaled Brownian motion (SBM) is widely used to model anomalous diffusion of passive tracers in complex and biological systems. It is a highly nonstationary process governed by the Langevin equation for Brownian motion, however, with a power-law time dependence of the noise strength. Here we study the aging properties of SBM for both unconfined and confined motion. Specifically, we derive the ensemble and time averaged mean squared displacements and analyze their behavior in the regimes of weak, intermediate, and strong aging. A very rich behavior is revealed for confined aging SBM depending on different aging times and whether the process is sub- or superdiffusive. We demonstrate that the information on the aging factorizes with respect to the lag time and exhibits a functional form that is identical to the aging behavior of scale-free continuous time random walk processes. While SBM exhibits a disparity between ensemble and time averaged observables and is thus weakly nonergodic, strong aging is shown to effect a convergence of the ensemble and time averaged mean squared displacement. Finally, we derive the density of first passage times in the semi-infinite domain that features a crossover defined by the aging time.