Accelerated Aging Process Research Articles

Investigating the effect of the aging process on LDPE composites with UV protective additives

The contact with ultraviolet rays coming from sunlight causes color changes and deterioration in the main chain structures of composites in outdoor applications and affects the physical and mechanical properties of composite materials negatively. Photodegradation can be slowed and the mechanical strength of composite structures can be improved with adding photostabilizers in polymer matrix production. In this study, we modified low-density polyethylene (LDPE) polymer with an amine light stabilizer (Chimassorb 944), a light absorbent (Tinuvin 326), and an antioxidant (Irganox 1010) and then reinforced with jute fabric (JF). We examined the effect of protective additives, which are used to reduce the harmful effects of sunlight, on JF-reinforced LDPE composites. The color change, physical, and mechanical properties of the composites were determined after 120- and 240-h accelerated aging processes. The results indicate that both the antioxidants and the amine light stabilizers were more effective photostabilizers for JF-reinforced LDPE composites than the absorbents.

Use of ultrasound at a pilot scale to accelerate the ageing of sherry vinegar

In the present work, the accelerated ageing process of sherry vinegar has been studied at pilot scale by means of the joint application of ultrasound, micro-oxygenation and wood chips (American oak, French oak and Spanish oak). The CIELab parameters have been studied as well as the polyphenolic and volatile content of the aged vinegar samples. Vinegars aged with American oak presented different chromatic characteristics to those aged with French and Spanish oak and a lower polyphenolic and volatile content than the latter ones. On the other hand, Spanish oak generated vinegars with a higher content of volatile compounds and an intermediate polyphenolic profile between those obtained using French and American oak. In addition, the use of ultrasound for a period between 4 and 21 days, generated vinegars with similar characteristics to others that were aged in the traditional way for between 2 and 6 months. It has been demonstrated that the use of ultrasound, combined with micro-oxygenation and chip addition, is a technique which can accelerate the ageing process of vinegars at a pilot scale, so it could be a viable alternative to obtain sherry vinegars aged in a shorter time.

Sedentary Time And Markers Of Physical Function In Those With Established Type 2 Diabetes

PURPOSE: An accelerated ageing process places those with type 2 diabetes mellitus (T2DM) at risk of physical functional impairments at a younger age. Although the importance of moderate-to-vigorous physical activity (MVPA) is acknowledged, emerging research suggests that sedentary time may be also be important. Therefore, the aim was to examine cross-sectional associations between device-assessed sedentary time and markers of physical function in a population with T2DM and to determine whether associations were modified by the recommended levels of MVPA. METHODS: Participants with T2DM (>6months), aged 18-75 years were recruited as part of an ongoing, cross-sectional study (CODEC) conducted in the Midlands, UK. Participants were asked to wear an accelerometer (GENEActiv, ActivInsights Ltd, Kimbolton, UK) on their non-dominant wrist for 7 days to quantify habitual levels of sedentary time and MVPA. Generalised linear models examined the associations between sedentary time, the short physical performance battery (SPPB), the sit-to-stand 60 second test (STS60) and 4 metre timed walk. Interaction terms determined whether results were consistent across MVPA categories (active [>150min/wk of MVPA] vs. inactive [<150min/wk of MVPA]) RESULTS: 621 participants had valid accelerometer and physical function data (age 63.6±8.4 years, 34.5% female, BMI=31.0±5.0kg/m2). Following adjustment for various covariates, including age, sex, ethnicity, medication and MVPA, sedentary time was detrimentally associated with SPPB score, STS60 reps and walk time. When results were stratified by MVPA (active (24.5%) vs. inactive (75.5%)), each 60 minutes of sedentary time was associated with a 0.3 lower SPPB score (p=0.020), 1.4 fewer STS60 reps (p=0.016) and 0.2s longer walk time (p=0.043) in the inactive group only. No significant associations were found in the active group. CONCLUSION: Sedentary time is adversely associated with markers of physical function, but associations were only present in those individuals who do not meet current physical activity recommendations for health. Along with promoting MVPA, future therapeutic interventions that focus on reducing sedentary time in those with T2DM and impaired physical function may be warranted in inactive individuals. Supported by NIHR Leicester BRC.

Prediction of Capacitor’s Accelerated Aging Based on Advanced Measurements and Deep Neural Network Techniques

Capacitors are widely used in electronic systems and have a key function in electromagnetic compatibility (EMC) compliance. However, the aging of capacitors results in an alteration of their parameters, which could pose a threat on the normal operation of systems as well as their EMC compliance. Normally, accelerated aging is employed to shorten the experiment time. After the aging, the capacitance and equivalent series resistance (ESR) are measured to evaluate the aging process. In this article, a new continuous characterization measurement setup is implemented in which the accelerated aging of the capacitors under test (CUTs) is continuously monitored during the overall accelerated aging process. It significantly improves the continuity of the measurement and eliminates the errors attributed to the interrupting of the aging process. This method is validated by comparing measurement results from the new measurement method with the results of the conventional method. This was done by subjecting two types of film capacitors to thermal and electrical stress in order to evaluate the accelerated aging effects. Furthermore, a conditional deep neural network with a dropout technique is proposed to predict the accelerated aging conditions of the capacitors. Instead of only forecasting the failure threshold, the proposed network is able to dynamically predict the accelerated aging conditions at different elevated temperatures and voltages. This leads to a serious reduction in the total measurement time from 1000 to 200 h.

Horsetail (Equisetum Arvense) as a Functional Filler for Natural Rubber Biocomposites.

Over the past decades, increased scientific and research activity has been observed in the development of new, innovative materials for various end uses. This is mainly due to the growing ecological, environmental, and material awareness of many industries and societies. Equisteum arvense-horsetail is a plant that has demonstrated its properties in pharmacological and clinical aspects as well as in vitro and in vivo biological activity. This article presents a new method of using horsetail as a natural, lignocellulosic filler for a natural rubber matrix. In-depth characteristics of the applied bio-additive were prepared based on several research techniques and methods such as ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy with energy dispersive X-RAY spectroscopy, thermogravimetric analysis, and flame atomic absorption spectroscopy. Elastomer composites were prepared as a function of horsetail content. Then, an analysis of their main functional properties was performed, including mechanical properties and susceptibility to accelerated aging processes such as thermo-oxidative, ultraviolet radiation, and weathering. The research emphasizes the significant value of horsetail in its new role—as an active filler of elastomer biocomposites. The obtained results confirmed that horsetail is lignocellulosic material thermally stable up to 180 °C. Horsetail is an active filler to natural rubber, positively affecting mechanical strength. Due to the presence of flavonoids and phenolic acids in horsetail, it can be used as a polymer anti-aging agent.

P0070ARE BIOMARKERS OF AGEING IN THE FORM OF TELOMERE LENGTH AND/OR THE DNA METHYLATION STATUS ASSOCIATED WITH FRAILTY PHENOTYPE IN PATIENTS WITH END STAGE KIDNEY DISEASE ON DIALYSIS?

Abstract Background and Aims There appears to be an accelerated ageing process seen among patients with end stage kidney disease. They often exhibit prematurely aged phenotypes which include frailty, sarcopenia and protein energy wasting. These phenotypes are associated with increased morbidity and mortality. The exact reason for premature ageing in this cohort is poorly understood. We hypothesised that biomarkers of cellular senescence and biological age may be associated with phenotypes of ageing observed in dialysis patients; in particular the frailty phenotype. Both telomere length (TL) and DNA methylation (DNAm) status have been recognised as predictors of biological age. The aim of the study was to investigate the relationship between TL and DNAm status with frailty phenotype among patients on dialysis. Method This was a single centre prospective observational study among eligible haemodialysis (HD) and peritoneal dialysis (PD) patients as per the inclusion and exclusion criteria. All recruited patients had their DNA extracted from peripheral leucocytes and frailty was measured by using the Fried Frailty Phenotype criteria. Extracted DNA was used to measure TL by quantitate polymerase chain reaction according to the modified Cawthon protocol. DNAm status was measured by sodium bisulphite conversion with targeted sequencing of 48 CpG sites. All baseline demographic data were obtained from electronic patient record. Results Between the period of December 2015 to July 2018, 239 dialysis (125 HD, 114 PD) patients were recruited. The age range of the study recruits were 23 to 83 years of age with a mean age of 54.3 years. There were 44 and 43 females in the HD and PD group respectively. All patients had TL measured and 228 patients (118 in HD, 110 in PD) had DNAm status measured successfully. Frailty assessments at baseline were completed in 213 patients (110 in HD, 103 in PD). A decrease in mean TL (p&amp;lt;0.001) and increased mean DNAm age (p&amp;lt;0.001) was observed in the frail group. TL and DNAm status were significantly associated with frailty in a univariate analysis, p=0.010 and p=0.014 respectively but only TL remained significant in a multivariate analysis to predict frailty, p=0.018. Increased frailty was observed in dialysis patients with shorter TL which remained significant following multivariate logistic regression analysis. A receiver operating characteristic curve analysis demonstrated that TL was a significant predictor of frailty, p&amp;lt;0.001 with an area under the curve of 0.64. A decrease of TL by one standard deviation was associated with a 52.2% increase risk of frailty when adjusted for age and gender in this dialysis cohort. Conclusion The study supports the hypothesis that TL; a biomarker of ageing is better associated with frailty, an ageing phenotype in comparison to DNAm status in dialysis patients. This is the first study to show a significant association between TL and frailty status in the dialysis patients. DNAm status is derived from an individual’s chronological age and may not be the best surrogate for chronological age. Therefore, to use this measure seems rather counter intuitive as the incorporation of chronological age might mask clinically significant associations that exist when the DNAm status is considered in isolation. These findings provide a preliminary proof of concept validation that TL is associated with frailty and may provide the basis of future research. The use of targeted methylation CpG sites may be a better predictor of frailty in this cohort which is an area that has sparked an interest.

Dietary Acid Load, Smoking Intensity and Total Mortality

Abstract Objectives Former smokers comprise 30–40% among breast cancer survivors. Smoking can cause many biological damages which can still exist in past smokers and make them more susceptible to certain dietary and environmental challenges. Past smokers may have accelerated aging process than never smokers. Limited studies have examined the impacts of dietary acid load total mortality among breast cancer survivors who are never or former smokers. Methods We leveraged an existing cohort, the Women's Healthy Eating and Living (WHEL) Study, which enrolled 3088 women with early stage breast cancer at baseline. This cohort collected dietary information through 24-hour recalls at years 0, 1, and 4, which enabled us to measure dietary acid load accurately and longitudinally. We assessed dietary acid load using two common dietary acid load scores, potential renal acid load (PRAL) score, and net endogenous acid production (NEAP) score. This cohort also assessed past smoking history by pack-years which allowed us to carefully and accurately past smoking intensity. Results In this study, we found that dietary acid load itself was not significantly associated with total mortality among never smokers but significantly associated with total mortality among past smokers who had pack-years &amp;gt;0. When we evaluated the joint impact of dietary acid load and pack-years, women with dietary acid load above median and pack-years ≥15 had 2.38 (95% CI 1.58–3.59) times of risk of total mortality as compared to the reference group (women with dietary acid load below median and pack-years = 0). Conclusions Results from our study will be important for patient care and aid in creating tailored precision nutrition recommendation for breast cancer survivors who are former smoker. Funding Sources University internal funds, NIH/NCI.

Accelerated Aging Process of Bio-Oil Model Compounds: A Mechanism Study

Bio-oil, obtained from the pyrolysis of biomass, is identified as a potential material to produce transportation fuels and value-added chemicals. However, physical and chemical properties of bio-oil change versus time, known as “aging”, and the instability of bio-oil brings a critical hurdle to the commercial application of bio-oil. Therefore, expanding and deepening the understanding of aging mechanism of bio-oil is the key for later efficient application of bio-oil. In addition, the extreme complexity of pyrolysis bio-oil composition brings great difficulties in studying the aging mechanism. Thus, this study tries to better understand the aging mechanism by evaluating the aging performance for 39 model compound aging tests performed at 80℃ for 72 hours. Four kinds of reactions (self-condensation, esterification, aldol condensation, and phenol and aldehyde reaction) were investigated to understand the contribution of various compounds and reactions during aging process. It has been found that acid played an important role in aging process, as it acted as the reactant in esterification reaction and acted as the catalysis for aldol condensation and phenol and aldehyde reaction. Acids and alcohols reacted via esterification reaction, resulting in the decline of aliphatic C-O bonds. Due to the absence of acid, aromatic compounds were relatively stable in these tests. In comparison, aldehydes and HMF were active since self-condensation reactions for these chemicals were observed in absence of acid. Moreover, with the aid of acid, HMF showed high tendency towards polymerization, result in the increasing water content and molecule weight during accelerated aging process.

Durability of hemp concretes exposed to accelerated environmental aging

This study examines the evolution of the functional properties of two hemp concretes formulated with two different binders over 2 years in different environmental conditions. Stable environmental conditions (50% RH - 20°C) have been applied to hemp concretes to obtain the reference aging AREF. An accelerated aging process AWD is chosen, consisting of cycles of wetting and drying. In relation to the reference aging, no significant variation of the chemical, microstructural and functional properties is observed, whether in terms of the thermal, acoustic, hydric or mechanical behavior. During accelerated aging, variations of properties are observed: an increase of thermal conductivity, and water vapor sorption capacity for both binders and a decrease of acoustic performance for the lime-based binder. No variation of mechanical properties is observed. These results are linked to alterations of the chemical and microstructural properties: hydration and carbonation of the binder, mineralization, swelling and shrinkage and consumption of vegetal walls by micro-organisms. By comparing these results with measurements carried out under real conditions, this work shows that the performance of hemp concretes should remain stable for several years.

Temperature effect on rubber gasket under high-frequency load

The performance degradation of rubber gaskets under vibration compression is faster than that under static load, and the degree of performance degradation will continue to increase under humidity and thermal environment. For rubber gaskets under a long-term service, the mechanical properties of rubber gaskets were measured after accelerated aging process with different temperature in the temperature box. The precipitates of rubber structures were detected by energy-dispersive spectroscopy and scanning electron microscopy. Molecular chain of silicon rubber gasket quickly breaks to form free radicals under high-frequency stress, which initiate oxidation chain reaction and mechanochemical process. Surface leakage of silicon (Si) and magnesium (Mg) indicates that a larger percent of macromolecular chains are broken and decomposed. High temperature activates the molecular chain cracking or cross-linking, while high-frequency stress leads to transport leakage on chain decomposition. The oxygen diffusion rate and activation oxidation reaction were accelerated by the residual stress to rubber oxidation reaction rate.

Myotonic Dystrophy type 1 cells display impaired metabolism and mitochondrial dysfunction that are reversed by metformin.

Myotonic dystrophy type 1 (DM1; MIM #160900) is an autosomal dominant disorder, clinically characterized by progressive muscular weakness and multisystem degeneration. The broad phenotypes observed in patients with DM1 resemble the appearance of a multisystem accelerated aging process. However, the molecular mechanisms underlying these phenotypes remain largely unknown. In this study, we characterized the impact of metabolism and mitochondria on fibroblasts and peripheral blood mononuclear cells (PBMCs) derived from patients with DM1 and healthy individuals. Our results revealed a decrease in oxidative phosphorylation system (OXPHOS) activity, oxygen consumption rate (OCR), ATP production, energy metabolism, and mitochondrial dynamics in DM1 fibroblasts, as well as increased accumulation of reactive oxygen species (ROS). PBMCs of DM1 patients also displayed reduced mitochondrial dynamics and energy metabolism. Moreover, treatment with metformin reversed the metabolic and mitochondrial defects as well as additional accelerated aging phenotypes, such as impaired proliferation, in DM1-derived fibroblasts. Our results identify impaired cell metabolism and mitochondrial dysfunction as important drivers of DM1 pathophysiology and, therefore, reveal the efficacy of metformin treatment in a pre-clinical setting.

Identifying the epigenetic drivers of an accelerated aging process

Aging impacts many important attributes of human beings such as the onset of diseases and the length of lifespans. Previous research demonstrated that DNA methylation based epigenetic clocks can be used to estimate biological age in both humans and mice. Interestingly, an accelerated aging process was observed in a short‐lived laboratory mouse strain (AKR/J, median lifespan = 288 days). By comparison, the more common laboratory mouse strain C57BL/6J lives substantially longer (median lifespan = 901 days). To elucidate the underlying mechanisms linking the accelerated aging process to a shortened lifespan, we used reduced representation bisulfite sequencing (RRBS) to profile DNA methylation in the cortex and the hippocampus extracted from these two strains, respectively (4 biological replicates per brain region for the C57BL/6J strain, 6 biological replicates per brain region for the AKR/J strain). At a 5X read depth cutoff, we detected 2,376,777 ± 195,194 unique CpG sites in the C57BL/6J strain samples and 2,288,300 ± 137,243 unique CpG sites in the AKR/J strain samples. Samples from the same brain region of the same strain clustered tightly based on their distinctive DNA methylation patterns. Using a publication‐supported R package, “DSS”, to compare between the two strains, we identified 14,625 differentially methylated cytosines (DMCs, Benjamini‐Hochberg FDR &lt;0.05; methylation difference ≥0.15) and 257 differentially methylation regions (DMRs, p&lt;0.05; methylation difference ≥0.15) from the cortex samples. Similarly, we found 14,215 DMCs (Benjamini‐Hochberg FDR &lt;0.05; methylation difference ≥0.15) and 304 DMRs (p&lt;0.05; methylation difference ≥0.15) from the hippocampus samples. Subsequent annotation of the DMRs from both sample groups revealed that 106 genes had significantly different methylation levels in their promoter regions. Pathway analysis demonstrated differential promoter methylation of genes (for example, Psat1, Smarca5, Rnf152 and Hspg2) enriched in the regulation of chromatin remodeling, cellular development, and metabolism. Importantly, Rnf152 and Hspg2 are associated with mouse aging. In summary, our study discovered potential epigenetic features involved in the accelerated aging process of a short‐lived mouse model. Future work should focus on the detailed functions of the identified genes and further understand their link to altered mice lifespans, eventually leading to strategies for improved healthcare in human lives.

Assess the heart disease risk of the Chinese elderly using a predictive model

The accelerating aging process worldwide makes chronic diseases the predominant risk for public health, and heart disease is in the top causes of the mortality of the elderly. Studies have verified the interventions can prevent, reduce or delay the onset of chronic diseases. This paper aims to find the domain predictors of heart disease by applying a machine learning technique Extreme Gradient Boosting to 89 predictors extracting from genetic, lifestyle, economic condition, isolation, stressful life events, nutrition and availability of medical service indexes. The individual-level data used is Chinese Longitudinal Healthy Longevity Survey with the time range of 2000 to 2002, and 2011 to 2014. We apply the imputation and oversampling technique to improve the prediction performance and use a step by step parameter tuning process to get the best hyper-parameters needed in the modeling. The fitted predictive model reaches a prediction accuracy of above 90% in the independent test data set. Comparing the first investigated period of 2000 to 2002 with the second period of 2011 to 2014, the predictors associated with economic condition play an important role in the prediction. The nutrition factor, surprisingly, does not contribute significantly to the prediction capability.

Analytical Characterization and Sensory Analysis of Distillates of Different Varieties of Grapes Aged by an Accelerated Method.

The wine spirits used for the elaboration of Brandy de Jerez are mainly obtained from wines produced from the Airén type of grape, which comes from the vineyards located in the region of La Mancha (Central Spain). This entails a limitation when achieving a product classified as “protected geographic designation”. For that purpose, it is necessary that the grape used for the wine spirit comes from the area and not from Castile la Mancha, as has happened until now. Due to this fact, it is necessary to search for a possible alternative grape variety which allows the produced brandy to be eligible for a “protected geographic designation”. For that purpose, an accelerated ageing process has been implemented with a method previously optimized to distillates obtained from wines from different varieties of grapes (Airén, Colombard, Corredera, Doradilla, Garrido Fino, Jaén blanco, Moscatel de Alejandría, Palomino Fino, Ugni Blanc, and Zalema) grown in the Jerez Area. They were evaluated, both from the analytical and sensory points of view. The distillates made from Jaén Blanco and Zalema have properties that make them interesting for future development and incorporation into oenological practice.

Comparison of glistenings formation and their effect on forward light scatter between the Acrysof SN60WF and Eternity Natural Uni NW-60 intraocular lenses

AimsTo compare the characteristics of glistenings and forward light scatter between the Alcon Acrysof SN60WF and Santen Eternity Natural Uni NW-60 intraocular lenses (IOLs).MethodsFive Acrysof SN60WF and five Eternity Natural...

Major depressive disorder and accelerated aging from a peripheral IGF-1 overexpression perspective

Over the past decades, data on the relationship between major depressive disorder (MDD) and accelerated aging processes were accumulated. Specific cognitive impairments, alterations in associated brain areas, a significant decrease in telomere length and expression of telomerase reverse transcriptase, oxidative and nitrosative stress, neuroinflammatory machinery, deficiency of growth factors (BDNF, IGF-1) in the brain of MDD patients resemble those that occur in aging. A decrease in the brain IGF-1 expression has been proven to disrupt mechanisms of neuroplasticity and promote cerebral inflammatory pathways, leading to morphological deterioration in the brain areas responsible for emotional and cognitive processing. From this point of view, the increase in systemic IGF-1 levels observed in most patients with MDD can be considered as a compensatory mechanism of enhancing the hypothalamic-pituitary-somatotropic axis activity in response to insufficient cerebral IGF-1 concentrations. Nevertheless, this compensatory mechanism may have a pathogenic value, improving the aging process in this patients population. This point of view has been confirmed by the evidence on the IGF-1-induced stimulation of the intracellular kinase-dependent pathways (Rho/ROCK kinase) involved in proliferation and telomere attrition in various organs, which can be considered as the underlying mechanism of aging. In line with these data, there is evidence that decreased IGF-1 signaling extends longevity in a wide range of biological species, including humans. Therefore, we hypothesized that systemic IGF-1 overexpression could be one of the pathological factors of accelerating aging in MDD patients. In this article, we analyzed data supporting this hypothesis.

Salicylic acid priming before and after accelerated aging process increases seedling vigor in aged soybean seed

ABSTRACTSeed vigor in soybean (Glycine max (L.) Merr.) declines under environmental stresses, and seed shows signs of aging. The aging effects may be alleviated, however, by seed priming with certain chemicals, such as salicylic acid (SA). The objective of this study was to investigate the effects of SA priming on activities of certain enzymes and lipid peroxidation in soybean seedlings under accelerated aging (AA) process. A factorial, completely randomized design with three replicates was used. Different aging durations (48 h and 72 h), SA priming solutions (0, 300 and 600 μM) and priming times (before aging, after aging and both before and after aging, i.e., double priming) were the experimental factors. Increasing aging duration significantly increased mean emergence time (MET) but decreased carotenoid content. Nonetheless, SA solution mitigated the adverse effect of seed deterioration on germination-related traits by increasing enzyme activity and reducing malondialdehyde (MDA) content, especially under double priming. A strong negative correlation (r = – 0.99**) was found between MDA content and chlorophyll a and chlorophyll b content. By contrast, the correlation between MDA content and MET (r = 0.95**) was found to be positive. The results suggested that double SA priming was an appropriate practical technique to improve seedling establishment from aged soybean seed.

A study of expected lifetime of XLPE insulation cables working at elevated temperatures by applying accelerated thermal ageing

Deterioration of cable insulation during its normal operation is a major concern. Usually, electric cables receive less periodic maintenance compared to the other electric components, although they are subjected to several environmental conditions during operation such as high temperature and oxidative atmospheres.In this study, a standardized accelerated thermal ageing technique was used, with the application of the Arrhenius model. This technique is commonly used in accelerated life testing to establish a lifetime-stress relationship and estimate cable lifetime. Two types of Cross-Linked Polyethylene (XLPE) material working at elevated temperatures between 95 and 105 °C were selected for testing. In such accelerated ageing processes, it is required for the insulation to reach a degradation level, which is considered the end of life for the material under evaluation. The end of life criteria (also called endpoint) is defined as a percentage reduction of elongation at break, which is considered in this study to be 50% retention of elongation at break. Thermal ageing was carried out according to the BS 7870-2 standard, while elongation at break was evaluated at several ageing stages. The uncertainty in the measurement was estimated. The short-term data points determined by ageing treatment is represented graphically in the Arrhenius plot. The extrapolation of such data was used to predict the long-term performance and estimate the cable lifetime. The lifetime for XLPE is expected to be between 40 and 60 years at 90 °C rated operating temperature. Experimental findings of this study show an estimated cable lifetime between 7 and 30 years for rated operating temperatures between 95 and 105 °C.

Evaluation of Stabilizing Additives Content in the Mechanical Properties of Elastomeric Compositions Subject to Environmental and Accelerated Aging

This research aimed to evaluate the ideal proportion of two stabilizers in elastomeric compositions indicated for tire sidewall. The stabilizers applied in different proportions were N-1,3-dimethyl-butyl-N'-phenyl-p-phenylenediamine (6PPD) and oligomerized 2,2,4-trimethyl-quinoline (TMQ). Nine compositions were prepared with 0.5, 1.5 and 2.5 phr of 6PPD combined with 0.5, 1.0 and 1.5 phr of TMQ. The compounds were exposed to accelerated aging processes, including thermo-oxidative, photochemical and ozone chamber. Also, the samples were aged in the environment for 440 days. At regular intervals, the samples were evaluated. Gas chromatography was used to quantify the content of 6PPD. Overall, the samples exposed to thermo-oxidative aging showed the greatest loss of mechanical properties (tear and tensile strength) as well as the 6PPD content. From the mechanical strength results, it was possible to conclude that the best combination of stabilizers was 2.5 phr of 6PPD and 1.0 of TMQ.

Physical deficits among people living with HIV: a review of the literature and implications for rehabilitation

Background: Life expectancy has improved significantly among people living with HIV (PLWH). However, there is evidence of an accelerated aging process among PLWH, which includes physical impairments. Relative to the other consequences of aging among PLWH, physical impairments have not received much attention in the literature. There is an emerging need to study physical deficits in this population.Objectives: The main purposes of this review are to explore factors contributing to physical dysfunction in this population, describe common physical impairments, discuss physical performance measures, and make recommendations for rehabilitation professionals regarding exercise prescription for PLWH.Major Findings: Factors contributing to physical impairments include HIV severity, comorbidities, inflammation, and oxidative stress. Problems with muscle strength and mass, gait, static and dynamic balance, aerobic capacity, and frailty are common among PLWH and can have a negative impact on fall risk and functional performance. Several physical performance measures can be used for screening and assessment purposes, including the Short Physical Performance Battery, Six-Minute Walk Test, 5-times sit-to-stand, Community Mobility and Balance Scale, and gait speed tests.Conclusions: Physical impairments are prevalent among PLWH. Rehabilitation providers should identify PLWH who are at risk of developing physical impairments. Exercise interventions including aerobic, resistance, and balance training appear to benefit PLWH. More research is warranted to investigate outcome measures that should be routinely used in clinical practice and the efficacy of exercise in this population.