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Gradual Deterioration (gradual + deterioration)
Selected AbstractsTensile and compressive damage coupling for fully-reversed bending fatigue of fibre-reinforced compositesFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 6 2002W. Van Paepegem ABSTRACT Due to their high specific stiffness and strength, fibre-reinforced composite materials are winning through in a wide range of applications in automotive, naval and aerospace industry. Their design for fatigue is a complicated problem and a large research effort is being spent on it today. However there is still a need for extensive experimental testing or large safety factors to be adopted, because numerical simulations of the fatigue damage behaviour of fibre-reinforced composites are often found to be unreliable. This is due to the limited applicability of the theoretical models developed so far, compared to the complex multi-axial fatigue loadings that composite components often have to sustain in in-service loading conditions. In this paper a new phenomenological fatigue model is presented. It is basically a residual stiffness model, but through an appropriate choice of the stress measure, the residual strength and thus final failure can be predicted as well. Two coupled growth rate equations for tensile and compressive damage describe the damage growth under tension,compression loading conditions and provide a much more general approach than the use of the stress ratio R. The model has been applied to fully-reversed bending of plain woven glass/epoxy specimens. Stress redistributions and the three stages of stiffness degradation (sharp initial decline , gradual deterioration , final failure) could be simulated satisfactorily. [source] Iron chelation prevents lung injury after major hepatectomyHEPATOLOGY RESEARCH, Issue 8 2010Konstantinos Kalimeris Aim:, Oxidative stress has been implicated in lung injury following ischemia/reperfusion and resection of the liver. We tested whether alleviating oxidative stress with iron chelation could improve lung injury after extended hepatectomy. Methods:, Twelve adult female pigs subjected to liver ischemia for 150 min, 65,70% hepatectomy and reperfusion of the remnant liver for 24 h were randomized to a desferrioxamine (DF) group (n = 6) which received i.v. desferrioxamine to a total dose of 100 mg/kg during both ischemia and reperfusion, and a control (C) group (n = 6). We recorded hemodynamic and respiratory parameters, plasma interleukin-6 and malondialdehyde levels, as well as liver malondialdehyde and protein carbonyls content. Total non-heme iron was measured in lung and liver. Pulmonary tissue was evaluated histologically for its nitrotyrosine and protein carbonyls content and for superoxide dismutase (SOD) and platelet-activating factor acetylhydrolase (PAF-AcH) activities. Results:, Reperfusion of the remnant liver resulted in gradual deterioration of gas-exchange and pulmonary vascular abnormalities. Iron chelation significantly decreased the oxidative markers in plasma, liver and the lung and lowered activities of pulmonary SOD and PAF-AcH. The improved liver function was followed by improved arterial oxygenation and pulmonary vascular resistance. DF also improved alveolar collapse and inflammatory cell infiltration, while serum interleukin-6 increased. Conclusion:, In an experimental pig model that combines liver resection with prolonged ischemia, iron chelation during reperfusion of the remnant liver is associated with improvement of several parameters of oxidative stress, lung injury and arterial oxygenation. [source] A case of multiple metastasis in Late Holocene hunter-gatherers from the Argentine Pampean regionINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 5 2008L. H. Luna Abstract Chenque I site is a prehistoric cemetery located in Lihué Calel National Park (La Pampa province) in the Western Pampean region of Argentina. Hunter-gatherer societies made use of this site during the Final Late Holocene for at least 700 years (1030,370,BP). Currently 41 burial structures have been excavated, and more than 150 individuals have been recovered. There is great variability in mortuary patterns at the site (simple, multiple, primary, secondary burials, and also a variant not previously observed in the region). The life-ways of this population have been investigated through the evaluation of several biological and cultural factors. Several pathological conditions have also been identified in this cemetery. Burial no. 12 contains a skeleton of an adult male that shows multiple pathological lesions, compatible with a neoplastic disease. These lesions have been analysed using several methodological strategies: macroscopic, radiological and microscopic. This is the first time that this kind of disease has been identified from a prehistoric burial in Argentina. In this paper the location and characteristics of the lesions are evaluated, and the different neoplastic diseases that could have produced them are discussed. Since the people buried in this cemetery belonged to highly mobile societies, a key issue is to infer the consequences that this disease would have had on the dynamics of the group in which this person lived, because of the gradual deterioration of his health and physical strength. Copyright © 2007 John Wiley & Sons, Ltd. [source] Statistical simulation of flood variables: incorporating short-term sequencingJOURNAL OF FLOOD RISK MANAGEMENT, Issue 1 2008Y. Cai Abstract The pluvial and fluvial flooding in the United Kingdom over the summer of 2007 arose as a result of anomalous climatic conditions that persisted for over a month. Gaining an understanding of the sequencing of storm events and representing their characteristics within flood risk analysis is therefore of importance. This paper provides a general method for simulating univariate time series data, with a given marginal extreme value distribution and required autocorrelation structure, together with a demonstration of the method with synthetic data. The method is then extended to the multivariate case, where cross-variable correlations are also represented. The multivariate method is shown to work well for a two-variable simulation of wave heights and sea surges at Lerwick. This work was prompted by an engineering need for long time series data for use in continuous simulation studies where gradual deterioration is a contributory factor to flood risk and potential structural failure. [source] Multinucleated astrocytes in old demyelinated plaques in a patient with multiple sclerosisNEUROPATHOLOGY, Issue 3 2004Makoto Nishie A 51-year-old woman with MS of 26 years duration is reported. The patient's MS history began at the age of 25 years with an initial relapsing-remitting course, followed by slow progression without distinct relapses. She became bed-ridden at the age of 40 years. A post-mortem examination revealed numerous demyelinated plaques that exhibited fibrillary gliosis with Rosenthal fibers, but without lymphocytic cuffing or foamy macrophages. Activated microglia were found mainly in the marginal portion of the plaques. These plaques were consistent with so-called ,slowly expanding plaques'. Interestingly, multinucleated astrocytes were observed within the plaques, being more numerous in the area where microglial infiltration had occurred. These findings suggest that mild persistent inflammatory processes are present even in old plaques and that certain inflammatory stimuli cause multinucleation of astrocytes. This might explain the gradual deterioration without definite relapses observed in the late stage of MS. [source] Transmission-reducing immunity is inversely related to age in Plasmodium falciparum gametocyte carriersPARASITE IMMUNOLOGY, Issue 5 2006C. J. DRAKELEY SUMMARY Immunity to the sexual stages of Plasmodium falciparum is induced during natural infections and can significantly reduce the transmission of parasites to mosquitoes (transmission reducing activity; TRA) but little is known about how these responses develop with increasing age/exposure to malaria. Routinely TRA is measured in the standard membrane feeding assay (SMFA). Sera were collected from a total of 199 gametocyte carriers (median age 4 years, quartiles 2 and 9 years) near Ifakara, Tanzania; 128 samples were tested in the SMFA and generated TRA data classified as a reduction of > 50% and > 90% of transmission. TRA of > 50% was highest in young children (aged 1,2) with a significant decline with age (,2 trend = 5·79, P = 0·016) and in logistic regression was associated with prevalence of antibodies to both Pfs230 and Pfs48/45 (OR 4·03, P = 0·011 and OR 2·43 P = 0·059, respectively). A TRA of > 90% reduction in transmission was not age related but was associated with antibodies to Pfs48/45 (OR 2·36, P = 0·055). Our data confirm that antibodies are an important component of naturally induced TRA. However, whilst a similar but small proportion of individuals at all ages have TRA > 90%, the gradual deterioration of TRA > 50% with age suggests decreased antibody concentration or affinity. This may be due to decreased exposure to gametocytes, probably as a result of increased asexual and/or gametocyte specific immunity. [source] | ||||||||||