Accelerated Aging Process Research Articles

Monitoring migration and transformation of nanomaterials in polymeric composites during accelerated aging

The incorporation of small amounts of nanoadditives in polymeric compounds can introduce new mechanical, physical, electrical, magnetic, thermal and/or optical properties. The properties of these advanced materials have enabled new applications in several industrial sectors (electronics, automotive, textile...). In particular, for the nanomaterials (NM) described in this work, multi-walled carbon nanotubes (MWCNT) and silicon dioxide nanoparticles (SiO2 NP), the following properties have been described: MWCNT act as nucleating agents in thermoplastics, and change viscosity, affecting dispersion, orientation, and therefore mechanical, thermal, and electrical properties; and SiO2 NP act as flame retardant and display improved electrical and mechanical properties.The work described here is focused on the evaluation of the migration and transformation of NM included in polymer nanocomposites (NC) during accelerated climatic ageing. To this aim, we generated polyamide 6 (PA6) NC with different degree of compatibility between the NM and the polymeric matrix. These NC were submitted to accelerated aging conditions to simulate outdoor conditions (simulation of the use phase of the polymeric NC). The NC contain as nanofillers MWCNT and SiO2 NP with different surface properties to influence the compatibility with the polymeric matrix. The generated NC were evaluated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) with Energy-dispersive X-ray spectroscopy (EDX), thermogravimetry (TGA) and differential scanning calorimetry (DSC) before and after the aging process, to monitor the compatibility of the NM with the matrix: dispersion within the matrix, migration during aging, and modification of the polymer properties.The dispersion of SiO2 NP in the NC depended on their compatibility with the matrix. However, independently of their compatibility with the matrix, SiO2 NP were aggregated at the end of the accelerated aging process. In addition, degradation of the matrix and migration of nanoparticles to the surface was observed as well in the different types of SiO2 NP aged NC. Oppositely, compatibilized MWCNT (MWCNTMB) decreased the degradation of the polymer. Nevertheless, the nanomaterial migrated likewise to the surface during the ageing process.In order to evaluate the possible changes in the structure of nanomaterials due to the aging process, NM were extracted from the polymer by calcination. The nanomaterials extracted were analyzed by TGA, Fourier transform infrared spectroscopy (FT-IR), BET and TEM and its properties compared with calcinated raw NM. SiO2 hydrophilic nanoparticles were not affected by the aging process. However, both types of MWCNT were affected by the aging of the NC.

Elaboration of an Accelerated Oven CNG Heavy Duty Vehicles Catalyst Ageing for Road Ageing Simulation

The study of automotive catalyst deactivation is associated with technical, economical and environmental problems. The deactivation phenomenon can be divided into three main groups: thermal, chemical and mechanical. Both fresh and road aged commercial metallic honeycombs were used to determine an ageing impact on catalytic activity. Accelerated catalyst ageing procedures were performed to simulate thermal ageing process observed during the real conditions (30,000 km of mileage). Different water quantities and times ageing were used to simulate accelerated ageing process. SEM, DRX, N2 adsorption and TPR analyses were carried out to explain catalyst deactivation.

A sensory approach for the monitoring of accelerated red wine aging processes using multi-block methods

Two young red wines from D.O. Navarra (Spain) were separately subjected to accelerated aging in tanks with oak chips added and micro-oxygenation. Wine samples were collected during each process and were analyzed by a sensory panel according to 17 descriptors. A two-fold monitoring approach, aimed at both checking panel performance and tracking the impact of chips/micro-oxygenation treatments on sensory properties, was proposed for process control and optimisation. In a first stage this approach focused on investigating panel performance by suitably combining uni- and multivariate methods. Significant product effects were found for 7 and 6 attributes in the first and second aging series, respectively. Although panel performance was acceptable in both cases, moderate differences between assessors were detected, stressing the need for adopting a consensus approach to properly handle them. Thus, the STATIS method was subsequently applied to find an optimal compromise solution for the significant attributes describing each process. The resulting compromise matrix provided the consensus sensory profiles of samples at different aging stages. The assignment of individual weights was consistent with previous findings on assessors’ agreement. The first principal component of the compromise matrix, which accounted for 86.5% and 90.9% of the variance in each trial data, revealed a sample trend directly related to the time-course evolution of each process, and contrasted the attributes fruit and herbaceous with the other significant descriptors (related to the wood–wine interaction). This is the first time that a multi-block methodology has been used for monitoring sensory changes during accelerated aging processes.

Low heart-type fatty acid binding protein level during aging may protect down syndrome people against atherosclerosis

BackgroundAging is considered an important independent risk factor for atherosclerosis. Down syndrome people (DS) display an accelerated aging process compared to healthy subjects, anyway they are relatively resistant to developing atherosclerosis. The mechanisms involved in such protective effect are not well known. Since heart-type fatty acid binding protein (H-FABP) is a protein involved in the transport of fatty acids and it has been recently correlated with the presence of atherosclerosis, we aimed to measure H-FABP level both in DS and in healthy subjects during aging to evaluate the association between this molecule, aging and atherosclerosis.FindingsWe quantified plasmatic H-FABP level in three groups of male DS and age-matched healthy subjects (children, age 2–14 years; adults, age 20–50 years; elderly, > 60 years) using a biochip array analyzer. We observed that aging is associated with increased H-FABP level in healthy subjects but not in DS which display both the same protein level in the different ages of life and have also lower level compared to their age-matched healthy subjects.ConclusionReduced H-FABP level during aging in DS may play a protective role against atherosclerosis. The potential involvement of H-FABP in the relationship between aging, atherosclerosis and development of coronary artery disease needs further investigations.

The developmental origins of ageing: study protocol for the Dutch famine birth cohort study on ageing

IntroductionEvidence from animal studies suggest that the rate of ageing may be influenced not only by genetic and lifestyle factors, but also by the prenatal environment. We have previously shown...

MTOR signalling: the molecular interface connecting metabolic stress, aging and cardiovascular diseases

The continuing increase in the prevalence of obesity and metabolic disorders such as type-II diabetes and an accelerating aging population globally will remain the major contributors to cardiovascular mortality and morbidity in the 21st century. It is well known that aging is highly associated with metabolic and cardiovascular diseases. Growing evidence also shows that obesity and metabolic diseases accelerate aging process. Studies in experimental animal models demonstrate similarity of metabolic and cardiovascular phenotypes in metabolic diseases and old age, e.g. insulin resistance, oxidative stress, chronic low grade inflammation, cardiac hypertrophy, cardiac fibrosis, and heart failure, as well as vascular dysfunctions. Despite intensive research, the molecular mechanisms linking metabolic stress, aging, and ultimately cardiovascular diseases are still elusive. Although the mammalian target of rapamycin (mTOR) signalling is a well known regulator of metabolism and lifespan in model organisms, its central role in linking metabolic stress, aging and cardiovascular diseases is recently emerging. In this article, we review the evidence supporting the role of mTOR signalling as a molecular interface connecting metabolic stress, aging and cardiovascular diseases. The therapeutic potentials of targeting mTOR signalling to protect against metabolic and age-associated cardiovascular diseases are discussed.

Development of new ecological long-lasting dispensers of semiochemicals for the control of Bactrocera oleae (Rossi)

A new controlled-release pheromone 1,7-dioxaspiro[5,5]undecane dispenser has been developed, which is useful for monitoring the population and controlling Bactrocera oleae (Rossi, 1790) (Diptera: Tephritidae). For this purpose, several kinds of dispensers based on attapulgite were designed and tested in this study. The designed dispensers, together with the commercial-brand olive fruit fly 'Long-Life Lure', which was used as a reference, were evaluated in the field, and in parallel were subjected to an accelerated ageing process in a chamber with a constant temperature and air speed. The residual pheromone content was periodically determined by liquid-gas chromatography in order to obtain the half-life of dispensers and the pheromone release rate. The mesoporous dispenser proved to have the best performance in the field, with a half-life of 5 months and an average emission speed of 0.6 mg day(-1) , parameters very close to those obtained with the commercial dispenser tested. In addition, to evaluate the effectiveness of the different dispensers in the field, a duplicate comparative study of captures was designed, and a colony monitoring study of the olive fruit fly was performed using various food and sex attractants. Although no significant differences in captures were found between the dispensers tested, the highest number of captures was obtained on average with the mesoporous dispensers demonstrating good pheromone emission characteristics.

Health Monitoring of a Power Supply Using Multivariate Regression

Due to the increasing use of electronics in critical aircraft control systems, it has become more and more important in the aerospace industry to understand how the degradation process of electronic devices occurs. Power supplies are devices of special interest since their internal components such as diodes, capacitors, MOSFETs (Metal Oxide Semiconductor Field Effect Transistor) and IGBTs (Insulated Gate Bipolar Transistors) operate under continuous stress conditions and often present elevated failure rates. The aim of this work is to present a methodology for detecting the gradual health degradation of a COTS (Commercial off-the-shelf) power supply. An accelerated aging process for power MOSFETs was conducted. During this experiment, power MOSFETs were subjected to thermal overstress in order to increase die- junction temperature above rated value through large current from drain to source. Multivariate regression analysis was applied to the raw data collected during the tests in order to assess the power supply health status.

An inherited LMNA gene mutation in atypical Progeria syndrome

Hutchinson-Gilford Progeria syndrome (HGPS) is a rare genetic disorder, characterized by several clinical features that begin in early childhood, recalling an accelerated aging process. The diagnosis of HGPS is based on the recognition of common clinical features and detection of the recurrent heterozygous c.1824C>T (p.Gly608Gly) mutation within exon 11 in the Lamin A/C encoding gene (LMNA). Besides "typical HGPS," several "atypical progeria" syndromes (APS) have been described, in a clinical spectrum ranging from mandibuloacral dysplasia to atypical Werner syndrome. These patients's clinical features include progeroid manifestations, such as short stature, prominent nose, premature graying of hair, partial alopecia, skin atrophy, lipodystrophy, skeletal anomalies, such as mandibular hypoplasia and acroosteolyses, and in some cases severe atherosclerosis with metabolic complications. APS are due in several cases to de novo heterozygous LMNA mutations other than the p.Gly608Gly, or due to homozygous BAFN1 mutations in Nestor-Guillermo Progeria syndrome (NGPS). We report here and discuss the observation of a non-consanguineous Moroccan patient presenting with atypical progeria. The molecular studies showed the heterozygous mutation c.412G>A (p.Glu138Lys) of the LMNA gene. This mutation, previously reported as a de novo mutation, was inherited from the apparently healthy father who showed a somatic cell mosaicism.

Degradation induced decrease of the radiative quantum efficiency in organic light-emitting diodes

The efficiency decrease during electrical operation of organic light-emitting diodes is a crucial issue for both applied and fundamental research. In order to investigate degradation processes, we have performed an efficiency analysis for phosphorescent state-of-the-art devices in the pristine state and after an accelerated aging process at high current density resulting in a luminance drop to less than 60% of the initial value. This loss in efficiency can be explained by a decrease of the radiative quantum efficiency of the light-emitting guest/host system from 70% to 40%, while other factors determining the efficiency are not affected.

The long-term performance of cementitious composites reinforced with coir fibre

Effective prediction of the long-term performance of natural fibre-reinforced cementitious materials is vital for their application. In this study, coir fibres of two different average lengths were combined with cementitious materials and chemical agents to form coir fibre-reinforced cementitious composites (CFRCCs). The composites long-term performance was assessed and compared with two different accelerated ageing processes, i.e. a cement-saturated water ageing, and alternate freeze–thaw ageing. The flexural properties were compared with the properties of the reference mortar. Overall, the flexural strength of 400 days naturally aged CFRCC specimens was weaker than that of the reference mortar. The toughness and ductility of the fibre-reinforced specimens, however, improved. The cement-saturated water ageing method gave a precise prediction of the flexural strength development of 400-day-old specimens, and the freeze–thaw ageing method worked very well for the toughness performance estimation of CFRCCs.

Neuroimaging studies of the aging HIV-1-infected brain

Highly active antiretroviral therapy (HAART) has increased life expectancy among HIV-infected individuals, and by 2015, at least half of all HIV-infected individuals will be over 50 years of age. Neurodegenerative processes associated with aging may be facilitated by HIV-1 infection, resulting in premature brain aging. This review will highlight brain abnormalities in HIV patients in the setting of aging, focusing on recent neuroimaging studies of the structural, physiological, functional and neurochemical changes. Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy studies performed during the pre-HAART era or on antiretroviral-naive subjects suggest an accelerated aging process, while those on HAART-treated subjects suggest premature brain atrophy. Diffusion tensor imaging studies yielded conflicting findings on the relationship between HIV and age in neuroasymptomatic individuals. Functional MRI studies found evidence of premature or accelerated aging processes in the brains of HIV subjects. Lastly, many age-related illnesses such as diabetes, stroke, and depression, as well as comorbid substance abuse, may further exacerbate the aging process in the HIV-infected brain, leading to premature or accelerated age-related brain changes. Given the different pathologic or physiologic changes in the brain assessed by the different neuroimaging techniques, using a multimodal approach in longitudinal follow-up studies is recommended for future studies.

Durability Evaluation of Agro-Industrial Waste-Based Particle Boards Using Accelerated Aging Cycling Tests

The degradation of agro-industrial waste-based particle boards reinforced with sugar cane bagasse was evaluated by comparing their physical and mechanical properties. The particle boards were prepared with sugar cane bagasse particles (85% by weight of composite) and mixed with bi-component polyurethane resin based on castor oil (15% by weight). After mixing for 2 to 3 min, the resulting mixtures were pre-pressured. Standard molding conditions were: temperature, 100°C; pressure during heating, 5 MPa; and heating time, 10 min. The dimensions of the particle boards produced in the laboratory were 0.40 m x 0.40 m x 0.01 m. The boards were cut into testing specimens with dimensions 0.25 m × 0.05 m × 0.01 m. The accelerated aging test was carried out based on the ASTM D 1037 standard in order to determine the main factors that cause degradation and to identify their influence. The test consists of cycles of six treatment steps, i.e., immersion in water at 49°C for 1 h, steaming at 93°C for 3 h, freezing at-12°C for 20 h, drying at 99°C for 3 h, steaming at 93°C for 3 h, and drying at 99°C for 18 h. This cycle was applied six times for all specimens. Modulus of rupture (MOR), modulus of elasticity (MOE), internal bonding strength (IB), water absorption (WA%) and thickness swelling (TS%) were measured before and after the cycles of accelerated aging. The performance of the particle boards before accelerated aging presented acceptable mechanical performance, MOR: 21.86 ± 2.16 MPa, MOE: 2.77 ± 0.26 GPa, and IB: 1.18 ±0.40. The performance of the particle boards decreased after accelerated aging showed, MOR: 6.25 ± 0.70 MPa, MOE: 0.52 ± 0.10 GPa, and IB: 0.15 ± 0.07. The results were influenced by the temperature, relative humidity and warm water. After the accelerated aging process, the materials showed mechanical behavior similar to Low-Density grade Particleboard (LD1).

Accelerated aging of ipê seeds under controlled conditions of storage

This research was aimed at studying effects of storage and accelerated aging on germination and profile of storage proteins in Handroanthus albus seeds. These were stored into a cold chamber (± 8 ºC; RH ± 40%) and after periods of 0, 3, 6, 9, and 12 months of storage, were subjected to accelerated aging for 0, 24, 48, 72, and 96 hours. Relationships between germination and proteins profile were assessed. Germination test was performed at 25 ºC, under constant light. For protein extraction, 125 mg of seeds were macerated in 2 mL of extraction buffer (1M Tris-HCl; pH 8.8) and applied to SDS-PAGE polyacrylamide gel at 80 V .15 h-1. Twelve month storage, combined with 72 hours accelerated aging have increased germination in approximately 65% when compared to non-aged seeds or to seeds with 24 h of accelerated aging. Besides beneficial effects, degradation and synthesis of different proteins were observed. It was concluded that germination of Handroanthus albus seeds, when not subjected to accelerated aging, is favored by storage in cold chamber during three to six months, or from nine to 12 months when subjected to accelerated aging process. Storage proteins may be associated to those increases, and hence further studies are needed.

Investigation of accelerated thermal aging of EPDM polymer by electric tests in air and by means of a SEM technique in high vacuum

In the current work we will concentrate on the study of thermal accelerated ageing process. A specific example focuses on the degradation of Ethylene Propylene Diene Monomer (EPDM). The reference material and the aged specimens were characterized by electrical methods performed in air and by a method developed in vacuum of a scanning electron microscope (SEM). A temperature of 90° C in air is considered for aging. Maximum exposition times were 6600 h in hot air. Physical properties such as transverse resistivity and permittivity are monitored, as well as charging ability under electron irradiation. A qualitative interpretation of the results is given. This interpretation is based on the enhancement of the disorder in the aged material which resulted in higher density of localized surface defects in the band gap.

Editor’s choice

Editor’s choice

Use of styrene butadiene rubber industrial waste devulcanized by microwave in rubber composites for automotive application

The aim of this work was to develop and characterize styrene butadiene rubber (SBR) composites filled with SBR industrial scraps (SBR-r) devulcanized by microwave. The SBR-r was ground under ambient conditions and subjected to microwave exposure for 1, 2 and 3min. The composites were developed by the incorporation of 80phr (parts per hundred of rubber) of the devulcanized SBR-r into the rubber matrix and subsequent revulcanization. The rheometric and physical–mechanical properties (shore A hardness, compression set, tensile and tear strength) were determined. The samples were submitted to two types of accelerated aging processes, in an air oven (thermo-oxidation) and an artificial weathering test in a UV chamber (photo-oxidation). The results were compared with a control sample submitted to the same conditions. For further application in automotive profiles, the set of results indicated that the best performance was achieved by the composite containing SBR-r devulcanized for 2min in a microwave. For this composite, the changes in the chemical characteristics after aging were evaluated with cross-link density and Attenuated Total Reflectance–Fourier Transform Infrared Spectroscopy (ATR–FTIR) analyses. The results revealed that the aging mechanism was dependent on the presence of SBR-r and on the time of aging. The cross-link density analysis confirmed the occurrence of cross-link scissioning at shorter aging times and the formation of additional cross-linking in the postcure process. The ATR–FTIR results indicated an oxidative process occurring on the surface of the composites for both aging processes. Moreover, artificial weathering presented a more pronounced change in the chemical structure of the samples.

Telomere length shortening in patients with dementia with Lewy bodies

Shortened telomere length has been considered to be associated with various age-related diseases, especially in dementia such as Alzheimer's disease and vascular dementia. However, changes in telomere length in dementia with Lewy bodies (DLB) remain unclear. To elucidate these changes, we set out to determine telomere length in peripheral leukocytes as well as the level of urinary 8-hydroxy-deoxyguanosine (8-OHdG) as a marker of oxidative stress in DLB. Blood samples were obtained from 33 patients with a clinical diagnosis of probable DLB and 35 age-matched, non-demented elderly controls (NEC). Telomere length was assessed by quantitative real-time polymerase chain reaction of genomic DNA extracted from leukocytes, whereas oxidative stress was assessed on the basis of urine 8-OHdG level, which was measured using high-performance liquid chromatography. Telomere length was significantly shorter in the DLB group than in the NEC group. Urinary 8-OHdG levels were significantly higher in the DLB group than in the NEC group. There was a negative correlation between telomere length and age in the DLB group; however, there were no significant relationships between telomere length and clinical findings including disease duration, severity of cognitive decline, presence or absence of fluctuation in cognitive function, visual hallucinations, and Parkinsonism. In both groups, the correlation between telomere length and urinary 8-OHdG levels was not significant. These findings indicate that the etiopathology of DLB is considered to be an accelerated aging process.

Hyperadiponectinemia protects against premature death in metabolic syndrome model mice by inhibiting AKT signaling and chronic inflammation

We previously reported that transgenic (Tg) expression of adiponectin significantly prolonged the lifespan of normal mice. The aim of this study was to elucidate the mechanism involved in the longevity effects of adiponectin using KK/Ta mice, a murine model of metabolic syndrome. We established a Tg line of KK/Ta (Tg-KK/Ta) mice expressing human adiponectin in the liver, and assessed their lifespan. The cause of death was determined by macroscopic and microscopic examinations immediately after death. The expressions of SIRT1, C-reactive protein (CRP), inflammatory cytokines, AMPK, and AKT were measured by quantitative real-time PCR, ELISAs, and/or western blotting. KK/Ta mice had lower serum adiponectin levels and shorter lifespan (57.6±13.9 vs 106.5±18.3 weeks, P<0.0001) than C57BL/6N mice. Tg adiponectin expression significantly extended the lifespan of KK/Ta mice (73.6±16.6 weeks, P<0.001) without affecting body weight, daily food consumption, or plasma glucose levels. Neoplasms were observed in only three of 22 KK/Ta mice that died spontaneously because of tumors. Atherosclerotic lesions were not detected in any mice. SIRT1 levels were not significantly different between KK/Ta and Tg-KK/Ta mice. Gene expressions of Crp, Tnfα, Il6, and Nfκb were increased in KK/Ta mice, but they were significantly attenuated in Tg-KK/Ta mice. Phosphorylated AMPK levels were increased and phosphorylated AKT levels were decreased in Tg-KK/Ta mice. The anti-inflammatory effects of adiponectin, achieved by inhibiting the AKT signaling pathway, may explain how adiponectin slows the accelerated aging process associated with the metabolic syndrome.

Aging Effect on the Tribological Behavior of a Novel 3Y‐TZP/Nb Biocomposite Against Ultra High Molecular Weight Polyethylene

The aim of this study was to evaluate the friction and wear behavior of ultra high molecular weight polyethylene (UHMWPE) against 3Y‐TZP and a novel 3Y‐TZP/niobium (Nb) biocomposite. The ceramic and the biocomposite materials were subjected to an accelerated aging process to evaluate the changes in the tribological behavior after this treatment. To carry out the tribological tests, a reciprocating pin‐on‐flat contact configuration was used. The results show a lower friction coefficient and wear rate for biocomposite/UHMWPE couples than those for 3Y‐TZP/UHMWPE couples. The present study demonstrates that the excellent wear properties of this new biocomposite should never be influenced by aging. Based on these data, the potential of zirconia‐Nb as an alternative bearing biomaterial is discussed.