Aging Regime Research Articles

Effects of Natural Antioxidant Agents on the Bitumen Aging Process: An EPR and Rheological Investigation

Bitumen aging is the major factor contributing to the deterioration of the road pavement. Oxidation and volatilization are generally considered as the most important phenomena affecting aging in asphalt paving mixtures. The present study was carried out to investigate whether various antioxidants provided by natural resources such as phospholipids, ascorbic acid as well as lignin from rice husk, could be used to reduce age hardening in asphalt binders. A selected bituminous material was modified by adding 2% w/w of the anti-aging natural additives and subjected to accelerated oxidative aging regimes according to the Rolling Thin Film Oven Test (RTFOT) method. The effects of aging were evaluated based on changes in sol-gel transition temperature of modified bitumens measured through Dynamic Shear Rheology (DSR). Moreover, changes of Electron Paramagnetic Resonance (EPR) spectra were monitored on the bituminous fractions asphaltene and maltene separated by solvent extraction upon oxidative aging. The phospholipids-treated binder exhibited the highest resistance to oxidation and the lowest age-hardening effect compared to the other tested anti-oxidants. The combination of EPR and DSR techniques represents a promising method for elucidating the changes in associated complex properties of bitumen fractions promoted by addition of free radical scavengers borrowed by green resources.

Body size and gastrointestinal morphology of nutria (Myocastor coypus) reared on an extensive or intensive feeding regime.

Although plasticity of growth rates is mainly associated with ectotherm species, it does occur in endotherms as well, but has not been documented systematically for many species. We compared the effect of 2 common types of feeding systems, differing in energetic value, on body size and gastrointestinal tract morphology in nutrias (Myocastor coypus). A total of 30 extensively (E) fed and 20 intensively (I) fed animals were used in the study. We noted significant effects of age, sex, and feeding regime on body weight and length, with 1-yr-old females attaining 3.7 ± 0.4 kg and 33.4 ± 1.5 cm on E and 4.9 ± 0.3 kg and 36.1 ± 2.3 cm on I. A significant treatment-sex interaction indicated that treatment had a greater effect on the length growth in males (1-yr-old males attaining 4.0 ± 0.2 kg and 34.7 ± 1.2 cm on E and 5.4 ± 0.4 kg and 41.0 ± 1.4 cm on I). The differences matched individual literature reports of free-ranging or intensively fed nutrias. The majority of gastrointestinal tract measurement results were only related to body weight, without additional effect of the diet regime, except for a higher small intestinal tissue weight on I (79 ± 14 g vs. 61 ± 7 g on E). In contrast, the wet content weight of the stomach, caecum, and the total gastrotinestinal tract was higher on E (196 ± 34 g vs. 164 ± 51 g on I). Overall, we observed strong influence of dietary regime on body development but not on digestive anatomy, indicating a distinct phenotypic flexibility in growth rates in nutrias.

Bond strength’s degradation of GFRP-concrete elements under aggressive exposure conditions

An experimental study was performed to determine the environmental durability of adhesive bond between Glass Fibre Reinforced Polymer pultruded profile and concrete. The specimens were subjected to two artificial ageing regimes before being tested to failure. Some specimens were exposed to 50 freeze-thaw cycles and other were immersed in water at 45 °C for varying time periods. Furthermore, some specimens were exposed to natural outdoor conditions to up to one year. The water effect on the adhesion of the joints was found to be significant, especially at longer immersion times; the shear strength of push out specimens reduced by 71% after ten months of immersion and the failure mode was shifted from cohesive within concrete to adhesive at the adhesive/concrete interface. The results also show that the ultimate shear strength deteriorated measurably during freeze-thaw cycling, about 56% of reduction was obtained after just 50 cycles, while after one year of outdoor exposure, the shear strength dropped by 27.7% compared to those without ageing. The study suggests that the ageing tests can provide information about the effects of environmental agents in the durability of bonded structures but cannot estimate the real amount of deterioration in real service life of such structures.

Enhanced ductility in dynamic strain aging regime in a Fe-25Ni-20Cr austenitic stainless steel

Contrary to the commonly observed embrittlement during dynamic strain aging, we report in this note distinct enhancement in ductility in a Nb-containing and nitrogen stabilized Fe-25(wt%)Ni-20Cr austenitic stainless steel (Alloy 709) at temperatures from 623 K to 873 K at 10−4 s−1 where serrated flow is noted. This observation is rationalized in terms of the influence of strain hardening parameters and strain rate sensitivity on uniform elongation and ductility respectively.

Ortet Age and Clonal Effects on Growth and Market Value of Fraser Fir (Abies fraseri) Grafts as Christmas Trees

Grafting provides a means to clonally produce Fraser fir (Abies fraseri (Pursh) Poir.) Christmas trees that have desirable traits such as faster growth, greater crown density, increased pest resistance, or more desirable foliage attributes than seedling stock. Grafting Fraser fir to disease resistant rootstocks also provides a means to ameliorate the impact of root rot, predominantly caused by Phytophthora cinnamomi Rands. The influence of ortet age on growth and market value of grafts has not been studied for Fraser fir Christmas tree production. A field trial was established in 2004 near Independence, Virginia (USA), with the objectives of assessing (1) the effect of ortet age (stock plants = 6 to 8, 10 to 12, and 18 to 20 years) and (2) shearing regimes (fixed leader length versus variable leader length) on growth, quality, and market value of Fraser fir Christmas trees. Commercial height, Christmas tree grade (based on U. S. Dept. of Agric. standards), and net present value (US dollars) were assessed at the time of harvest. Cone damage to quality was rated after 8 years in the field. Scions from Fraser fir Christmas trees 2 m or taller produced grafts that expressed maturation, resulting in lower tree quality, heavier cone damage, and decreased market value compared to seedling stock. In contrast, the quality and market value of grafts was similar to that of seedlings when scions were collected from young Fraser fir Christmas trees. For Christmas tree production, scions should be collected from the upper whorls of trees no older than 2 to 3 years in the field (6 to 8 years from seed). The effect of age on Fraser fir clones varies so that pre-screening might identify some older selections suitable for use as scion donors. Fixed versus variable shearing regimes had little effect on tree value, although some individual clones responded better to one regime or the other.

Effect of metal ratio in alumina-supported Pd-Rh nanoalloys on its performance in three way catalysis

The bimetallic Pd-Rh three-way catalysts were prepared by an incipient wetness impregnation of γ-Al2O3 with a joint solution of [Pd(NH3)4](NO3)2 and Na3 [Rh(NO2)6]. The ratio of the metals was varied by changing the ratio of the salt-precursors. The samples with Pd:Rh ratio of 3:2, 7:3 and 4:1 were compared in simultaneous oxidation of carbon monoxide, propane, propylene, and reduction of nitrogen monoxide at a lambda factor of 1.003 and 0.95. Stability tests were performed in a prompt thermal aging regime (consecutive heating-cooling cycles with a final temperature of 320, 600 and 800 °C). The samples were characterized by UV–vis and luminescence spectroscopies, and by testing reaction of ethane hydrogenolysis. It was found that the sample with Pd:Rh ratio of 3:2 is characterized with strong palladium-rhodium interaction, which makes this catalyst more stable at high temperature if compare with other alloyed Pd-Rh samples. Moreover, the mechanism of the three-way catalytic process over Pd:Rh (3:2) sample differs from other cases and involves a larger contribution of reactions with nitrogen oxide.

Synthesis and study of Pd-Rh alloy nanoparticles and alumina-supported low-content Pd-Rh catalysts for CO oxidation

Palladium and rhodium are known to be partly miscible metals. In present work, the peculiarities of coordination compound [Pd(NH3)4]3[Rh(NO2)6]2 decomposition with formation of nanosized solid solutions under different atmospheres were studied by means of thermal gravimetry. Formation of alloy nanoparticles were confirmed by powder X-ray diffraction analysis, scanning and transmission electron microscopies. A bimetallic Pd-Rh/alumina catalyst was prepared by incipient wetness impregnation using coordination compound [Pd(NH3)4]3[Rh(NO2)6]2 as a precursor. Monometallic reference samples were obtained using [Pd(NH3)4](NO3)2 and Na3[Rh(NO2)6], correspondingly. Catalytic performance and stability of the catalysts were examined in a model reaction of CO oxidation in a prompt thermal aging regime. The environment of precursor decomposition was shown to affect noticeably both the initial activity and stability of the samples in the studied reaction. Reductive atmosphere in comparison with inert and oxidative ones facilitates the formation of the smallest active component species, which demonstrate highest initial activity but worst stability.

Monotonous deformation behavior of ferritic FeCrAl alloy in the dynamic strain aging regime

Monotonous deformation behavior of a ferritic FeCrAl alloy at a temperature range from room temperature to 600 °C was studied using the uniaxial tensile tests. The results showed that dynamic strain aging (DSA) occurred at a strain rate of 3.333 × 10−4s−1 over the temperature range from 200 °C to 400 °C. Tensile tests were carried out at four different strain rates in the DSA temperature domain to investigate the combined action of temperature and strain rate on DSA. Negative strain rate sensitivity of ultimate tensile strength (UTS) was observed as the characteristic manifestation of DSA performed in FeCrAl alloy. It was also found out that, type A, A+B, B, C+D and C serrations appeared in turn in the stress-strain curves tested at a constant strain rate with the increase of temperature, and the decrease in strain rate shifted the DSA temperature range toward the lower temperature region. Statistical method was used on stress drops with DSA to investigate the character of serration. From the activation energy calculations with Mccormick's model, the solute atoms responsible for DSA were identified to be substitutional aluminum atoms.

Differences in blood circulation functioning in truck drivers related to age, experience and work regime

Differences in blood circulation functioning in truck drivers related to age, experience and work regime

The influence of hardening and ageing regimes on microstructure and properties of Cu – Cr – Zr alloy, used for the construction elements of the ITER blanket

The influence of hardening and ageing regimes on microstructure and properties of Cu – Cr – Zr alloy, used for the construction elements of the ITER blanket

Evidence for increasing digestive and metabolic efficiency of energy utilization with age of dairy cattle as determined in two feeding regimes

The changes taking place with age in energy turnover of dairy cattle are largely unknown. It is unclear whether the efficiency of energy utilization in digestion (characterized by faecal and methane energy losses) and in metabolism (characterized by urine and heat energy losses) is altered with age. In the present study, energy balance data were obtained from 30 lactating Brown Swiss dairy cows aged between 2 and 10 years, and 12 heifers from 0.5 to 2 years of age. In order to evaluate a possible dependence of age effects on diet type, half of the cattle each originated from two herds kept at the same farm, which were fed either on a forage-only diet or on the same forage diet but complemented with 5 kg/day of concentrate since their first calving. During 2 days, the gaseous exchange of the animals was quantified in open-circuit respiration chambers, followed by an 8-day period of feed, faeces, urine and milk collection. Daily amounts and energy contents were used to calculate complete energy balances. Age and feeding regime effects were analysed by parametric regression analysis where BW, milk yield and hay proportion in forage as consumed were considered as covariates. Relative to intake of gross energy, the availability of metabolizable energy (ME) increased with age. This was not the result of an increasing energy digestibility, but of proportionately lower energy losses with methane (following a curvilinear relationship with the greatest losses in middle-aged cows) and urine (continuously declining). The efficiency of utilization of ME for milk production (kl) increased with age. Potential reasons include an increase in the propionate-to-acetate ratio in the rumen because of a shift away from fibre degradation and methane formation as well as lower urine energy losses. The greater kl allowed older cows to accrete more energy reserves in the body. As expected, offering concentrate enhanced digestibility, metabolizability and metabolic utilization of energy. Age and feeding regime did not interact significantly. In conclusion, older cows seem to have digestive and metabolic strategies to use dietary energy to a certain degree more efficiently than younger cows.

Al–5.5Mg–1.5Li–0.5Zn–0.07Sc–0.07Zr alloy produced by gravity casting and heat treatment processing

ABSTRACTAl–5.5Mg–1.5Li–0.5Zn–0.07Sc–0.07Zr alloy was produced by gravity casting and heat treatment processing. After gravity casting based on the melting processing scheme designed specifically for the studied alloy, there was no obvious porosity and slag. In as-cast alloy, there were many network-shaped second phase particles enriched along the grain boundaries, most of which integrated into the α-Al matrix after solution heat treated at 500°C for 10 h. The grain growth was inconspicuous, which means low grain boundary stress concentration resulted by planar slip. To meet the requirement for industrial actuality, avoid the excessively detrimental effect of PFZs and utilize the order hardening effect of δ′ (Al3Li) phases sufficiently, 175°C/8 h was preferred as the aging regime. Optimal comprehensive mechanical properties were obtained after solid solution heat treated process (500°C/10 h) and subsequent aging treatment (175°C/8 h) with elongation, yield strength, and ultimate tensile strength reaching 8.7%, 270.5 MPa, and 435.5 MPa, respectively.

Unilateral NMR and Micro DSC Study of Artificially Aged Parchments

New and artificially aged parchments were studied by unilateral NMR and micro DSC. Samples were obtained by exposing new parchments to 80 �C and alternate 40 and 80% relative humidity for increasing times up to 32 days. The impact of accelerated ageing was assessed by measuring both the proton transverse relaxation times (T2eff) and thermodynamic parameters associated with thermal denaturation of fibrillar collagen. Depending on the ageing time, significant structural changes correlated with thermal stability and collagen heterogeneity were observed, in good agreement with changes in phase composition and relaxation times. The results suggest two ageing regimes depending on the balance between the two main processes which drive the behavior of parchments during thermal ageing, i.e. thermally induced cross linking and thermal destabilization and denaturation.

Extension of the Mechanical Threshold Stress Model to Static and Dynamic Strain Aging: Application to AA5754-O

Based on the mechanical threshold stress model and the visco-plastic self-consistent algorithm, a modified constitutive model is developed to model static strain aging and dynamic strain aging for application to a non-heat treatable aluminum alloy, AA5754-O. The implementation is based on a combination of the evolution of dislocation density and the effect of solutes on both mobile dislocations and forest dislocations. Using this model, the stress–strain behavior of AA5754-O is simulated in multi-path, multi-temperature, and variable strain rate tensile tests. The low temperature and strain rate sensitivities of the modified mechanical threshold stress model in the dynamic strain aging regime are successfully accounted for. The results show quantitative agreement with experimental data from multiple sources.

The influence of hydrological variability on inherent water use efficiency in forests of contrasting composition, age, and precipitation regimes in the Pacific Northwest

The Pacific Northwest (PNW) region of the United States has some of the most productive forests in the world. As precipitation regimes may shift with changing climate in this area, droughts are predicted to increase in both frequency and degree of severity, which will have a significant impact on already drought-prone ecosystems. When modeling ecosystem responses to drought, it is important to consider the physiology of individual tree species since the variations in drought sensitivity among species is easily overlooked when plants are characterized using broad plant functional types. Here we explore the use of inherent water-use efficiency as an index of drought sensitivity in semi-arid young and mature ponderosa pine forests and a mesic mature Douglas-fir forest in the PNW. Summer maximum of an evapotranspiration-based WUE (WUEi) was 2.5 times higher in young and mature pines in semi-arid climate than Douglas-fir in mesic climate (12.2 and 11.3 versus 4.7gCkPa per kg H2O, respectively). In contrast, annually averaged WUEi was similar among the sites (2.8gCkPa per kg H2O for pines and 2.4gCkPa per kg H2O for Douglas-fir). The effect of drought stress on WUEi was most pronounced in young pine, followed by mature pine and Douglas-fir (32, 11, and 6% increase in WUEi per % decline in soil water content, respectively) which reflect differences in age-related ecosystem structure (root system, stem capacitance, and soil water holding capacity). Among sites, the responses of WUEi to climate variability were largely driven by changes in evapotranspiration (ET) compared to gross primary productivity (GPP). However, in areas where evaporation is the primary component of ET, such as the open canopy ponderosa forests of the PNW, the contribution of soil processes to ET can overshadow the reaction of vegetation transpiration (T) to changes in water availability. In these cases, utilizing a transpiration-based WUE (WUEi_T) in vegetation models will yield a more accurate representation of plant activity during drought. These results highlight the importance of incorporating differences in species- and age-related WUEi in models in diverse forest types at regional and global scales to improve predictions in ecosystem responses to climate change.

Micro-CT imaging of live insects using carbon dioxide gas-induced hypoxia as anesthetic with minimal impact on certain subsequent life history traits

BackgroundLive imaging of whole invertebrates can be accomplished with X-ray micro-computed tomography (micro-CT) at 10-100 μm spatial resolution. However, image quality could be compromised by the movement of live subjects, producing image artefacts. We tested the feasibility of using CO2 gas to induce temporary full-immobilization of sufficient duration to image live insects based on their ability to tolerate hypoxic conditions. Additionally, we investigated the effects of these prolonged hypoxic conditions on several life history traits of a lepidopteran species.MethodsLive Colorado potato beetle (CPB) and true armyworm (TAW) adults were immobilized under a constant CO2 gas flow (0.5 L/min), and scanned using micro-CT (80 kVp; 450 μA). An L8 (24) orthogonal array (OA) was used to evaluate the effects of prolonged CO2-induced anesthesia on the recovery, longevity, and incidence of mating of TAW adults. The variable factors were age (immature and mature), sex (female and male), exposure time (3 and 7 h), and exposure regime (single and repeated).ResultsWith this method, successful 3D reconstruction and visualizations of CPB and TAW adults were produced at 20 micron voxel spacing at an acceptable radiation dose and image noise level. From the inverse-square relationship found between the radiation doses and image noise levels, the optimal scanning protocol produced an entrance dose of 6.2 ± 0.04 Gy with images of 129.6 ± 5.1 HU noise level during a 2.7 h scan.Independent OA experiments indicated that CO2 gas did not result in death of exposed TAW adults, except when older males were exposed for longer durations. Exposure time and sex were more influential factors affecting recovery, longevity, and mating success than age and exposure regime following CO2 exposure.ConclusionWe have demonstrated that using CO2 gas during micro-CT imaging effectively induces safe, repeatable, whole-body, and temporary immobilization of live insects for 3D visualizations without motion artefacts. Moreover, we have shown that exposed TAW individuals made a full recovery with very little impact on subsequent longevity, and mating success post hypoxia. This method is applicable to other imaging modalities and could be used for routine exploratory and time-course studies, for repeated scanning of live and intact individuals.

REALISING ACTIVE AGEING IN EUROPE

The potential of older people to contribute to societal progress is now widely accepted. The active ageing paradigm has encouraged policymakers to generate additional opportunities for older people, to be successful in their active and healthy experiences of ageing. The MOPACT project operationalised the concept of active ageing to generate evidence highlighting the optimistic view on ageing, taking the Active Ageing Index “AAI” as its starting point. This paper will report the results of this work, with a particular focus on identifying contexts and strategies across European countries that stimulate and sustain the activity, health, independence, and security of people of all ages. It combines the AAI evidence with the findings of rigorous scientific reviews undertaken across MOPACT WPs to develop an understanding about the active ageing regimes. It highlights key strategies required in promoting active and healthy ageing in different institutional and cultural contexts of the European countries.

Development of an iron-based alloy with a high degree of shape recovery

We examined a technological process for receiving an iron-based alloy with a shape memory effect, substantiated the choice of chemical composition of the alloy, and selected thermal treatment modes. Research results into scale resistance revealed at heating the samples in the temperature range of 600–1000 °C, surface oxidation was not observed. In the course of experiment on corrosion resistance of the alloy, we found that the alloy is corrosion resistant and is not inclined to change the weight when exposed to 10 % solution of sulfuric acid. Study into the microstructure confirmed the existence of dispersion hardening in the alloy after the aging regimes. Diffractogram of the alloy after hardening at a temperature of 1150 °C and cooling in the open air showed a surge that corresponds to γ-Fe, therefore, the content of residual austenite in the alloy is 100 %. Research results demonstrated that the degree of shape recovery of the proposed alloy is 78–97 %. The proposed alloy is plastic enough; it may undergo hot, warm and cold deformation in the open air. We constructed mathematical models of the impact of chemical composition of the alloy on tensile strength of the alloy and the values of a shape memory effect. The iron-based alloy with a shape memory effect can be obtained both under laboratory conditions and on industrial equipment.

Winter habitat associations of eastern spotted skunks in Virginia

ABSTRACTEastern spotted skunk (Spilogale putorius) populations have declined throughout much of their range in the eastern United States over recent decades. Declines have been attributed to habitat loss or change, increased competition with sympatric mesocarnivore species, or disease. To better understand the extant distribution of spotted skunks in the Appalachian Mountains of western Virginia, USA, we used a detection‐non‐detection sampling approach using baited camera traps to evaluate the influence of landscape‐level environmental covariates on spotted skunk detection probability and site occupancy. We conducted camera trap surveys at 91 sites from January to May in 2014 and 2015. Spotted skunk occupancy was associated with young‐aged forest stands at lower elevations and more mature forest stands at higher elevations. Both land cover types in this region can be characterized as having complex forest structure, providing cover that varies with stand age, species composition, elevation, and management regime. Our results provide insight into factors that influence spotted skunk spatial distribution and habitat selection, information that can be used to generate conservation assessments and inform management decisions. © 2017 The Wildlife Society.

Two-stage double peaks ageing and its effect on stress corrosion cracking susceptibility of Al-Zn-Mg alloy

Different artificial two-stage ageing behaviors and their effect on stress corrosion cracking (SCC) susceptibility of Al-Zn-Mg alloy have been investigated. The experimental results show that two hardness peaks present on the second-stage ageing-hardening curve when the first-stage ageing is dealt with comparatively lower temperature than the conventional one. The first peak is caused by dispersive and evenly distributed G.P. zones, while η′ phases and coarsened G.P. zones contribute to the second peak. Tensile strength of experimental alloy raises 9.6% (33.2MPa) and SCC susceptibility decreases 38.9% by applying the second peak ageing regime instead of conventional T73. Al-Zn-Mg alloy obtains high strength and SCC resistance due to its finely dispersive matrix precipitates (MPts), coarsened and discontinuous grain boundary precipitates (GBPs), as well as the narrow precipitate free zone (PFZ) in the second peak ageing condition.