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Accelerated Ageing (accelerated + ageing)
Selected AbstractsAccelerated ageing of polypropylene stabilized by phenolic antioxidants under high oxygen pressureJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Emmanuel Richaud Abstract Polypropylene (PP) samples stabilized by a hindered phenol (Irganox 1010) were submitted to thermal ageing at 80°C in air at atmospheric pressure or in pure oxygen at 5.0 MPa pressure. Both the polymer oxidation and the stabilizer consumption were monitored by Infrared spectrometry and thermal analysis. The stabilizer efficiency, as assessed by the ratio induction time/stabilizer concentration is almost constant at atmospheric pressure even when the stabilizer concentration is higher than its solubility limit in PP (0.4% or 24 × 10,3 mol L,1). In contrast, at high pressure, the efficiency decreases almost hyperbolically with the stabilizer concentration when this latter is higher than 6.0 × 10,3 mol L,1. The results indicate the existence of a direct phenol-oxygen reaction negligible at low oxygen pressure but significant at 5.0 MPa pressure. The reality of this reaction has been proved on the basis of a study of the thermal oxidation of a phenol solution in a nonoxidizable solvent. A kinetic model of PP oxidation in which stabilization involves three reactions has been proposed. It simulates correctly the effect of oxygen pressure and stabilizer concentration on carbonyl build-up and stabilizer consumption. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] HEPATITIS C AND ADDICTION: Chronic viral hepatitis is a significant contributor to the immunosenescent phenotype of parenteral drug addictionADDICTION BIOLOGY, Issue 2 2009Albert S. Reece ABSTRACT Intravenous drug addiction is known to be associated with an inordinate morbidity and mortality. As our previous report had identified an immune phenotype consistent with accelerated ageing, we wished to investigate how much of this change may have been related to chronic viral hepatitis. A total of 12 409 clinical pathology results from the period 1995,2007 were reviewed. To control for the differences in age, only patients less than 48 years of age were considered. A total of 636 substance use disorder (SUD) and 6103 non-SUD (N-SUD) patients were studied. They had comparable ages (mean ± SD 31.32 ± 6.90 versus 31.57 ± 9.23, P -value not significant), but the SUD group had more males (74.37% versus 53.20%, P < 0.001). For most of the changes examined splitting the two SUD groups into hepatitis C positive (HCV+) and hepatitis C negative (HCV,) demonstrated that the majority of the described changes were most marked in the HCV+ group. The globulins were higher in the HCV+ group and the albumin was lower and fell more markedly with age than in N-SUD or HCV, (all P < 0.001). The globulin/albumin ratio was significantly higher in HCV+ than HCV, or N-SUD (both P < 0.0001) and rose more with age. These changes were paralleled by the ESR, elevations in the CRP and lymphocyte count. Transaminases were elevated in SUD and HCV+ groups compared with N-SUD (all P < 0.02). At multivariate analysis ESR, lymphocyte count, dual hepatitis B and C seropositivity, AST and HCVAb were significant predictors of the serum globulin level and accounted for 21% of the variance. These data extend our earlier report and show that much of the immunosenescent phenotype of SUD, encompassing the known immunosuppression and the observed immunostimulation, is statistically related to chronic viral hepatitis. Important theoretical and practical management (vaccination) implications ensue. [source] The effect of accelerated ageing of building wiresFIRE AND MATERIALS, Issue 5 2007Viktor Emanuelsson Abstract The fire performance of two electric cables (building wires) designed for indoor use has been tested, both as new products and after accelerated thermooxidative ageing. The cables were aged for a maximum time of 16.5 weeks at 80°C. The cables are commercially available, and were constructed using a PVC material in one case and a non-halogenated polyolefin-based material, called Casico, in the other. The effects of ageing on the fire performance of the cables, and the chemical changes that have caused the observed fire behaviour, have been investigated and are discussed. Special attention is paid to the behaviour of the plasticizers that are used in the PVC cable, and how the fire behaviour is affected by the loss of plasticizers from the cable and by the migration of plasticizers between the parts of the cable (insulation, bedding and sheathing). Copyright © 2007 John Wiley & Sons, Ltd. [source] Oxypropylation of Lignins and Preparation of Rigid Polyurethane Foams from the Ensuing PolyolsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2005Hamid Nadji Abstract Summary: Different lignins were converted into polyols by a chain extension reaction with propylene oxide (PO). Thus, soda lignin from Alfa (Stipa tenacissima) (SL), organosolv lignin from hardwoods (OL), kraft lignin (KL) from softwood and oxidized organosolv lignin (OOL) were oxypropylated in a batch reactor at 180,°C in the presence of KOH as catalyst. The ensuing polyols were characterized by FTIR and 1H NMR spectroscopy, which showed that they had incorporated poly(propylene oxide) grafts into their structure. Their viscosity varied from 5 mPa,·,s to infinity, depending on the Lignin/PO ratio and their hydroxy index was in the range of 100,200, which made them suitable for rigid polyurethane foam (RPU) formulations. The RPUs thus obtained had a Tg of ca. 60,°C and a thermal conductivity of ,20 mW/m,·,K before ageing and ,25 mW/m,·,K after accelerated ageing for 10 d at 70,°C. The analyses of the gases inside the cells showed that these were mostly closed, since the partial pressure did not decrease significantly with ageing. Photograph of polyurethane foam made from OLOP. [source] Apical vulnerability to dendritic retraction in prefrontal neurones of ageing SAMP10 mouse: a model of cerebral degenerationNEUROPATHOLOGY & APPLIED NEUROBIOLOGY, Issue 1 2006A. Shimada The SAMP10 mouse is a model of accelerated ageing in which senescence is characterized by age-related atrophy of the cerebral cortex and limbic structures, poor learning and memory task performance with depressive behaviour and cholinergic and dopaminergic alterations. Here we studied age-related changes in the dendritic arbors and spine density of pyramidal cells in the medial prefrontal cortex of SAMP10 mice using a quantitative Golgi method. Dendrites of prefrontal neurones gradually retracted with ageing towards the soma with the relative preservation of overall complexity. Apical dendrites were much more severely affected than basal dendrites. The combined length of the apical dendrites and spine density were decreased by 45% and 55%, respectively, in mice at 12 months, compared with mice at 3 months of age. Immunohistochemical and immunoblot analyses indicated that expression of microtubule-associated protein (MAP) 2, a marker of dendrites, decreased in an age-related manner not only in the anterior cortex but also in the posterior cortex and olfactory structures in SAMP10 mice. Decreased expression of MAP2 mRNA caused the decrease in MAP2 protein expression. These results suggest that retraction of apical, but not of basal dendrites, with a loss of spines in prefrontal neurones, appears to be responsible for poor learning and memory performance in aged SAMP10 mice. It is also suggested that age-related dendritic retraction occurs in a wide area including the entire cerebral cortex and olfactory structures. [source] Pre-receptoral spectral absorption, healthy ageing and pre-clinical indications of retinal diseaseACTA OPHTHALMOLOGICA, Issue 2009E KONSTANTAKOPOULOU Purpose The aim of this study was to investigate how chromatic sensitivity changes as a function of age and to establish the extent to which such changes can be attributed to pre-receptoral spectral absorption of short wavelength light and/or changes in retinal mechanisms caused by ageing. Methods The absorption of blue light by the macular pigment (MP) and the crystalline lens and the subjects' sensitivity to rapid flicker were measured using the Macula Assessment Profile (MAP) test. Red-green (RG) and yellow blue (YB) chromatic detection thresholds were measured at the fovea for young and older subjects using the Colour Assessment and Diagnosis (CAD) test at 2.6, 26 and 65 cd/m2. The variables of interest included the spectral absorption of the lens, the optical density of the MP, subject's age and retinal illuminance. Results The absorption of blue light by the lens increased with age. Absorption of blue light by pre-receptoral filters did not affect RG chromatic sensitivity at any of the light levels investigated but had an effect on YB thresholds. The considerably higher colour vision thresholds of some subjects and the subsequent worsening of their chromatic sensitivity at the lower light level may reflect changes in the retina brought about by accelerated aging effects. Conclusion The effect of pre-receptoral absorption of blue light on chromatic sensitivity is small. Ageing affects the amount and spectral composition of the light reaching the photoreceptors and the processing of retinal signals. As a result, flicker sensitivity declines and colour vision deteriorates. Such effects arise mostly from changes in the retina. The MAP and CAD tests help us to detect the effects of accelerated ageing and retinal disease. [source] | |||||||||||||