The Experts below are selected from a list of 50874 Experts worldwide ranked by ideXlab platform
Mitchell B. Schaffler - One of the best experts on this subject based on the ideXlab platform.
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osteocyte calcium signals encode strain magnitude and Loading Frequency in vivo
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Karl J. Lewis, Joyce Louie, David C. Spray, Robert J. Majeska, Sheldon Weinbaum, Dorra Frikhabenayed, Samuel Stephen, Mia M Thi, Zeynep Serefferlengez, Mitchell B. SchafflerAbstract:Osteocytes are considered to be the major mechanosensory cells of bone, but how osteocytes in vivo process, perceive, and respond to mechanical Loading remains poorly understood. Intracellular calcium (Ca2+) signaling resulting from mechanical stimulation has been widely studied in osteocytes in vitro and in bone explants, but has yet to be examined in vivo. This is achieved herein by using a three-point bending device which is capable of delivering well-defined mechanical loads to metatarsal bones of living mice while simultaneously monitoring the intracellular Ca2+ responses of individual osteocytes by using a genetically encoded fluorescent Ca2+ indicator. Osteocyte responses are imaged by using multiphoton fluorescence microscopy. We investigated the in vivo responses of osteocytes to strains ranging from 250 to 3,000 [Formula: see text] and frequencies from 0.5 to 2 Hz, which are characteristic of physiological conditions reported for bone. At all Loading frequencies examined, the number of responding osteocytes increased strongly with applied strain magnitude. However, Ca2+ intensity within responding osteocytes did not change significantly with physiological Loading magnitudes. Our studies offer a glimpse into how these critical bone cells respond to mechanical load in vivo, as well as provide a technique to determine how the cells encode magnitude and Frequency of Loading.
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Osteocyte calcium signals encode strain magnitude and Loading Frequency in vivo
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Karl J. Lewis, Dorra Frikha-benayed, Joyce Louie, Samuel J. Stephen, David C. Spray, Zeynep Seref-ferlengez, Robert J. Majeska, Sheldon Weinbaum, Mitchell B. SchafflerAbstract:Abstract Osteocytes are considered to be the major mechanosensory cells of bone, but how osteocytes in vivo process, perceive, and respond to mechanical Loading remains poorly understood. Intracellular calcium (Ca2+) signaling resulting from mechanical stimulation has been widely studied in osteocytes in vitro and in bone explants, but has yet to be examined in vivo. This is achieved herein by using a three-point bending device which is capable of delivering well-defined mechanical loads to metatarsal bones of living mice while simultaneously monitoring the intracellular Ca2+ responses of individual osteocytes by using a genetically encoded fluorescent Ca2+ indicator. Osteocyte responses are imaged by using multiphoton fluorescence microscopy. We investigated the in vivo responses of osteocytes to strains ranging from 250 to 3,000
Karl J. Lewis - One of the best experts on this subject based on the ideXlab platform.
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osteocyte calcium signals encode strain magnitude and Loading Frequency in vivo
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Karl J. Lewis, Joyce Louie, David C. Spray, Robert J. Majeska, Sheldon Weinbaum, Dorra Frikhabenayed, Samuel Stephen, Mia M Thi, Zeynep Serefferlengez, Mitchell B. SchafflerAbstract:Osteocytes are considered to be the major mechanosensory cells of bone, but how osteocytes in vivo process, perceive, and respond to mechanical Loading remains poorly understood. Intracellular calcium (Ca2+) signaling resulting from mechanical stimulation has been widely studied in osteocytes in vitro and in bone explants, but has yet to be examined in vivo. This is achieved herein by using a three-point bending device which is capable of delivering well-defined mechanical loads to metatarsal bones of living mice while simultaneously monitoring the intracellular Ca2+ responses of individual osteocytes by using a genetically encoded fluorescent Ca2+ indicator. Osteocyte responses are imaged by using multiphoton fluorescence microscopy. We investigated the in vivo responses of osteocytes to strains ranging from 250 to 3,000 [Formula: see text] and frequencies from 0.5 to 2 Hz, which are characteristic of physiological conditions reported for bone. At all Loading frequencies examined, the number of responding osteocytes increased strongly with applied strain magnitude. However, Ca2+ intensity within responding osteocytes did not change significantly with physiological Loading magnitudes. Our studies offer a glimpse into how these critical bone cells respond to mechanical load in vivo, as well as provide a technique to determine how the cells encode magnitude and Frequency of Loading.
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Osteocyte calcium signals encode strain magnitude and Loading Frequency in vivo
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Karl J. Lewis, Dorra Frikha-benayed, Joyce Louie, Samuel J. Stephen, David C. Spray, Zeynep Seref-ferlengez, Robert J. Majeska, Sheldon Weinbaum, Mitchell B. SchafflerAbstract:Abstract Osteocytes are considered to be the major mechanosensory cells of bone, but how osteocytes in vivo process, perceive, and respond to mechanical Loading remains poorly understood. Intracellular calcium (Ca2+) signaling resulting from mechanical stimulation has been widely studied in osteocytes in vitro and in bone explants, but has yet to be examined in vivo. This is achieved herein by using a three-point bending device which is capable of delivering well-defined mechanical loads to metatarsal bones of living mice while simultaneously monitoring the intracellular Ca2+ responses of individual osteocytes by using a genetically encoded fluorescent Ca2+ indicator. Osteocyte responses are imaged by using multiphoton fluorescence microscopy. We investigated the in vivo responses of osteocytes to strains ranging from 250 to 3,000
Gilles Robert - One of the best experts on this subject based on the ideXlab platform.
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influence of relative humidity and Loading Frequency on the pa6 6 thermomechanical cyclic behavior part ii energy aspects
Polymer Testing, 2015Co-Authors: Adil Benaarbia, Andre Chrysochoos, Gilles RobertAbstract:Abstract In this study, we investigated the influence of relative humidity (RH) and Loading rate on the energy response of PA6.6 matrix specimens. The latter were subjected to oligocyclic tensile-tensile tests at 3 different RH and 2 Loading rates. Infrared thermography was used to obtain a direct estimate of heat sources using the heat diffusion equation. Using the mechanical and thermal responses discussed in the first part of this work, complete energy rate balances were drawn up. In particular, the time courses of deformation, and dissipated and stored energy rates are discussed. The strong influence of the Loading Frequency and RH on the energy storage mechanisms is also highlighted.
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Influence of relative humidity and Loading Frequency on the PA6.6 cyclic thermomechanical behavior: Part I. mechanical and thermal aspects
Polymer Testing, 2014Co-Authors: Adil Benaarbia, Andre Chrysochoos, Gilles RobertAbstract:Using quantitative infrared techniques, this study investigated the influence of relative humidity (RH) and Loading rate on the mechanical and thermal responses of PA6.6 matrix specimens. The specimens were subjected to tensile and oligocyclic tensile-tensile tests at 3 different RHs. For tensile experiments, the studied samples were loaded at 4 displacement rates. For oligocyclic tensile-tensile fatigue tests, they were subjected to 2 distinct Loading frequencies with a 0.1 stress ratio. The overall aim of this study was to analyze the mechanical and thermal responses for each cyclic Loading case. The influence of the Loading Frequency on the hysteresis loops and self-heating was particularly highlighted. The plasticizing role of water and its influence on the glass transition temperature were also discussed relative to the nature of temperature variations accompanying the deformation processes. These thermal responses were associated with dissipation, standard and/or entropic thermoelastic coupling sources. These different heat sources and the complete energy rate balances will be analyzed in the second part of this paper.
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Influence of Relative Humidity on the Thermomechanical Behavior of PA6.6
2014Co-Authors: Adil Benaarbia, Andre Chrysochoos, Gilles RobertAbstract:An experimental protocol was developed to achieve complete energy balances associated with low cycle fatigue (LCF) of a polyamide 6.6 matrix (PA6.6). The protocol involves quantitative infrared techniques (IRT), and digital speckle image correlation (DIC). IRT data were used with a local heat diffusion equation to estimate strain-induced heat sources, namely dissipation and coupling sources, while DIC enabled strain and stress assessments. Both techniques were then successfully combined to quantify deformation, dissipated and stored energies and then to estimate the Taylor-Quinney ratio that is widely used in plasticity. In this paper, the effects of Loading Frequency and relative humidity were investigated. It was shown that an increase of relative humidity resulted in a decrease in the mean stored energy rate per cycle, while the stored energy ratio was much smaller at low than at high Loading Frequency. In addition, it was found that this ratio could be negative at the last fatigue stage, just before macroscopic crack inception. These energy properties will act safeguards for the future development of a thermomechanical model of PA6.6 matrix behavior.
Adil Benaarbia - One of the best experts on this subject based on the ideXlab platform.
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influence of relative humidity and Loading Frequency on the pa6 6 thermomechanical cyclic behavior part ii energy aspects
Polymer Testing, 2015Co-Authors: Adil Benaarbia, Andre Chrysochoos, Gilles RobertAbstract:Abstract In this study, we investigated the influence of relative humidity (RH) and Loading rate on the energy response of PA6.6 matrix specimens. The latter were subjected to oligocyclic tensile-tensile tests at 3 different RH and 2 Loading rates. Infrared thermography was used to obtain a direct estimate of heat sources using the heat diffusion equation. Using the mechanical and thermal responses discussed in the first part of this work, complete energy rate balances were drawn up. In particular, the time courses of deformation, and dissipated and stored energy rates are discussed. The strong influence of the Loading Frequency and RH on the energy storage mechanisms is also highlighted.
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Influence of relative humidity and Loading Frequency on the PA6.6 cyclic thermomechanical behavior: Part I. mechanical and thermal aspects
Polymer Testing, 2014Co-Authors: Adil Benaarbia, Andre Chrysochoos, Gilles RobertAbstract:Using quantitative infrared techniques, this study investigated the influence of relative humidity (RH) and Loading rate on the mechanical and thermal responses of PA6.6 matrix specimens. The specimens were subjected to tensile and oligocyclic tensile-tensile tests at 3 different RHs. For tensile experiments, the studied samples were loaded at 4 displacement rates. For oligocyclic tensile-tensile fatigue tests, they were subjected to 2 distinct Loading frequencies with a 0.1 stress ratio. The overall aim of this study was to analyze the mechanical and thermal responses for each cyclic Loading case. The influence of the Loading Frequency on the hysteresis loops and self-heating was particularly highlighted. The plasticizing role of water and its influence on the glass transition temperature were also discussed relative to the nature of temperature variations accompanying the deformation processes. These thermal responses were associated with dissipation, standard and/or entropic thermoelastic coupling sources. These different heat sources and the complete energy rate balances will be analyzed in the second part of this paper.
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Influence of Relative Humidity on the Thermomechanical Behavior of PA6.6
2014Co-Authors: Adil Benaarbia, Andre Chrysochoos, Gilles RobertAbstract:An experimental protocol was developed to achieve complete energy balances associated with low cycle fatigue (LCF) of a polyamide 6.6 matrix (PA6.6). The protocol involves quantitative infrared techniques (IRT), and digital speckle image correlation (DIC). IRT data were used with a local heat diffusion equation to estimate strain-induced heat sources, namely dissipation and coupling sources, while DIC enabled strain and stress assessments. Both techniques were then successfully combined to quantify deformation, dissipated and stored energies and then to estimate the Taylor-Quinney ratio that is widely used in plasticity. In this paper, the effects of Loading Frequency and relative humidity were investigated. It was shown that an increase of relative humidity resulted in a decrease in the mean stored energy rate per cycle, while the stored energy ratio was much smaller at low than at high Loading Frequency. In addition, it was found that this ratio could be negative at the last fatigue stage, just before macroscopic crack inception. These energy properties will act safeguards for the future development of a thermomechanical model of PA6.6 matrix behavior.
Shabnam Arbab-chirani - One of the best experts on this subject based on the ideXlab platform.
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A comprehensive energy approach to predict fatigue life in CuAlBe shape memory alloy
Smart Materials and Structures, 2015Co-Authors: Shima Sameallah, Vincent Legrand, Luc Saint-sulpice, Mahmoud Kadkhodaei, Shabnam Arbab-chiraniAbstract:Stabilized dissipated energy is an effective parameter on the fatigue life of shape memory alloys (SMAs). In this study, a formula is proposed to directly evaluate the stabilized dissipated energy for different values of the maximum and minimum applied stresses, as well as the Loading Frequency, under cyclic tensile Loadings. To this aim, a one-dimensional fully coupled thermomechanical constitutive model and a cycle-dependent phase diagram are employed to predict the uniaxial stress-strain response of an SMA in a specified cycle, including the stabilized one, with no need of obtaining the responses of the previous cycles. An enhanced phase diagram in which different slopes are defined for the start and finish of a backward transformation strip is also proposed to enable the capture of gradual transformations in a CuAlBe shape memory alloy. It is shown that the present approach is capable of reproducing the experimental responses of CuAlBe specimens under cyclic tensile Loadings. An explicit formula is further presented to predict the fatigue life of CuAlBe as a function of the maximum and minimum applied stresses as well as the Loading Frequency. Fatigue tests are also carried out, and this formula is verified against the empirically predicted number of cycles for failure.
