The Experts below are selected from a list of 19380 Experts worldwide ranked by ideXlab platform
Vadim N Gladyshev - One of the best experts on this subject based on the ideXlab platform.
-
age and diet associated metabolome remodeling characterizes the aging process driven by Damage accumulation
eLife, 2014Co-Authors: Andrei Avanesov, Kerry A Pierce, Sun Hee Yim, Byung Cheon Lee, Clary B Clish, Vadim N GladyshevAbstract:Aging is thought to be associated with increased molecular Damage, but representative markers vary across conditions and organisms, making it difficult to assess properties of Cumulative Damage throughout lifespan. We used nontargeted metabolite profiling to follow age-associated trajectories of >15,000 metabolites in Drosophila subjected to control and lifespan-extending diets. We find that aging is associated with increased metabolite diversity and low-abundance molecules, suggesting they include Cumulative Damage. Remarkably, the number of detected compounds leveled-off in late-life, and this pattern associated with survivorship. Fourteen percent of metabolites showed age-associated changes, which decelerated in late-life and long-lived flies. In contrast, known metabolites changed in abundance similarly to nontargeted metabolites and transcripts, but did not increase in diversity. Targeted profiling also revealed slower metabolism and accumulation of lifespan-limiting molecules. Thus, aging is characterized by gradual metabolome remodeling, and condition- and advanced age-associated deceleration of this remodeling is linked to mortality and molecular Damage.
-
age and diet associated metabolome remodeling characterizes the aging process driven by Damage accumulation
eLife, 2014Co-Authors: Andrei Avanesov, Kerry A Pierce, Sun Hee Yim, Byung Cheon Lee, Clary B Clish, Vadim N GladyshevAbstract:Aging is thought to be associated with increased molecular Damage, but representative markers vary across conditions and organisms, making it difficult to assess properties of Cumulative Damage throughout lifespan. We used nontargeted metabolite profiling to follow age-associated trajectories of >15,000 metabolites in Drosophila subjected to control and lifespan-extending diets. We find that aging is associated with increased metabolite diversity and low-abundance molecules, suggesting they include Cumulative Damage. Remarkably, the number of detected compounds leveled-off in late-life, and this pattern associated with survivorship. Fourteen percent of metabolites showed age-associated changes, which decelerated in late-life and long-lived flies. In contrast, known metabolites changed in abundance similarly to nontargeted metabolites and transcripts, but did not increase in diversity. Targeted profiling also revealed slower metabolism and accumulation of lifespan-limiting molecules. Thus, aging is characterized by gradual metabolome remodeling, and condition- and advanced age-associated deceleration of this remodeling is linked to mortality and molecular Damage.DOI: http://dx.doi.org/10.7554/eLife.02077.001.
Rui Miranda Guedes - One of the best experts on this subject based on the ideXlab platform.
-
Relationship between lifetime under creep and constant stress rate for polymer-matrix composites
Composites Science and Technology, 2009Co-Authors: Rui Miranda GuedesAbstract:Abstract The present article reviews two existing theoretical approaches for creep failure criteria of viscoelastic materials. One criterion is based on the continuum Damage mechanics (CDM) and the other is based on the fracture mechanics extended to viscoelastic materials. Although both theoretical frameworks are based on different physical concepts, the deduced lifetime expressions turn out to be equivalent even though its parameters have different physical interpretation. It is proved that both theoretical frameworks, when extended to variable stress loading cases, imply the linear Cumulative Damage (LCD) law. Additionally the relationship obtained between the creep–rupture and constant stress rate until failure is very simple. Moreover this simple relationship is obtained independently by two different Cumulative Damage laws, which do not obey the LCD law, and by experimental evidence using published data for two different polymer-matrix composites (PMC). Finally a micromechanical model, used for creep–rupture of unidirectional composites, is extended for constant stress rate until failure to corroborate the simple relationship obtained between the creep–rupture and constant stress rate until failure.
-
creep and fatigue lifetime prediction of polymer matrix composites based on simple Cumulative Damage laws
Composites Part A-applied Science and Manufacturing, 2008Co-Authors: Rui Miranda GuedesAbstract:Abstract Presently, due to the energy saving concerns, there is an increase demand for lightweight structures for transportation industry, electric power wind generators among others. In this context design and maintenance of these civil engineering structures has put a stress on durability issues. The time scale for aeronautical applications is different for the rest of civil engineering structural applications therefore the durability experience accumulated on aeronautics is of little use. Usually civil engineering structures must remain in service for 50 years or more. Therefore the needs for real long-term mechanical performance prediction become quite important. Presently, for instance, the standards for buried GRP (Glass Fiber Reinforced Polymer Composites) pipes demand more than 10,000 h of creep tests in order to extrapolate data for two decades (in the time log scale) with a high level of confidence. The accelerated methodology proposed by Miyano et al. [Miyano Y, Nakada M, Sekine N. Accelerated testing for long-term durability of FRP laminates for marine use. J Composite Mater 2005;39:5–20] on Carbon and Glass Fiber Reinforced Polymers (CFRP and GFRP) laminates, rests on the fact that the time-superposition principle is the same for static, creep and fatigue strengths. Although not universally verified, it has been used successfully to predict fatigue lifetimes of many typical composites. In this context time-dependent failure criteria for viscoelastic materials is reviewed. Comparison between creep failure and static failure under constant stress/strain rate tests are analyzed. Cumulative Damage laws, including the classical Linear Cumulative Damage law (LCD), are introduced to enlighten these comparisons. Finally some applications to lifetime prediction under variable amplitude fatigue loading are presented. The empirical LCD law performance is compared against the other physical based Cumulative Damage laws using fatigue loading sequences invented to expose the incoherencies of LCD lifetime predictions.
Hiromichi Yoshino - One of the best experts on this subject based on the ideXlab platform.
-
fatigue characteristics of quasi isotropic cfrp laminates subjected to variable amplitude cyclic two stage loading
International Journal of Fatigue, 2006Co-Authors: Atsushi Hosoi, Hiroyuki Kawada, Hiromichi YoshinoAbstract:Abstract In this study the fatigue characteristics of quasi-isotropic carbon fiber reinforced plastics laminates subjected to variable amplitude cyclic two-stage loading were investigated. The Cumulative Damage was evaluated by considering residual strength as a parameter since the Linear Cumulative Damage rule, i.e., the Palmgren–Miner rule, did not show good agreement. Further, the internal microscopic Damage was observed with an optical microscope. As a result, it was found that Cumulative Damage subjected to variable amplitude cyclic loading could be expressed by considering residual strength. Additionally, we were able to predict the fatigue life of laminates subjected to variable amplitude cyclic two-stage loading.
Josef Lutz - One of the best experts on this subject based on the ideXlab platform.
-
experimental investigation of linear Cumulative Damage theory with power cycling test
IEEE Transactions on Power Electronics, 2019Co-Authors: Guang Zeng, Christian Herold, Torsten Methfessel, Marc Schafer, Oliver Schilling, Josef LutzAbstract:In this paper, several power cycling tests under single or combined test conditions were undertaken to investigate the applicability of linear Cumulative Damage theory in the lifetime prediction of power semiconductor devices. The validity of this theory was verified by an experimental method for one lifetime limit, which is an increase of forward voltage at load current by 5%. The corresponding failure mechanism is the degradation of bond wire contacts.
W W Stinchcomb - One of the best experts on this subject based on the ideXlab platform.
-
a Cumulative Damage model to predict the fatigue life of composite laminates including the effect of a fibre matrix interphase
International Journal of Fatigue, 1995Co-Authors: S Subramanian, K L Reifsnider, W W StinchcombAbstract:Abstract Recent experimental efforts have established the significance of the fibre-matrix interface /interphase in the long-term behaviour of polymeric composites. Results indicate that small alterations at the interface level could translate into orders-of-magnitude changes in fatigue life. However, there is no model currently available in the literature to predict these changes. In this paper, a micromechanics model that includes the effects of the fibre-matrix interface is used in a simple Cumulative Damage scheme to predict the tensile fatigue behaviour of composite laminates. A new parameter called the ‘efficiency of the interface’ is used to model the degradation of the in terface under fatigue loading. A rate equation that describes the changes in interfacial efficiency as a function of cycles is estimated using experimentally determined stiffness reduction data. The influence of this interfacial efficiency parameter on the tensile strength of unidirectional laminates is assessed using a micromechanics model. The effect of Damage on the stiffness of the laminate is estimated by solving a boundary value problem associated with the particular Damage mode (e.g. transverse matrix cracking). The fatigue life of the laminate is estimated by considering changes in stiffness due to creep and Damage in the subcritical elements, and changes in strength associated with the critical element (0° ply). The influence of a fibre-matrix interface is included in the model by considering the degradation in the interface (interfacial efficiency) under fatigue loading. Changes in the interface property are used in the micromechanics model to estimate changes in the in-situ tensile strength of the 0° ply. The stress state and the strength of the 0° ply, calculated including the effects of Damage, are then used in a maximum strain failure criterion to determine the fatigue life of the laminate. Predictions from this model are compared with experimental data. The predicted fatigue life and failure modes agree very well with the experimental data.
