Considering the viscoelastic memory effect, we study the correlated motion of two hydrodynamically coupled colloidal particles, each of which confined in a harmonic potential well, in a Kelvin-type and Maxwell-type vi...Considering the viscoelastic memory effect, we study the correlated motion of two hydrodynamically coupled colloidal particles, each of which confined in a harmonic potential well, in a Kelvin-type and Maxwell-type viscoelastic medium. We find that viscoelastic relaxation plays a significant role in modifying the correlation, particularly the cross correlation. We also find that both the real and imaginary parts of the response function are significantly different from the viscous medium case. In particular there is a phase shift between the vanishing imaginary part and the maximal real part of the response function in a viscoelastic medium. In addition imaginary part of the cross correlation response function exhibits a net energy loss （gain） behavior when the elasticity parameter of the medium is larger （smaller） than the critical value for Kelvin （Maxwell） viscoelastic fluid. Some implication of our results and their connection with previous works are discussed.展开更多
The purpose of this study was to explore the triphasic mechanical properties of osteoarthritic cartilage with different pathological grades.First,samples of cartilage from rabbits with different stages of osteoarthrit...The purpose of this study was to explore the triphasic mechanical properties of osteoarthritic cartilage with different pathological grades.First,samples of cartilage from rabbits with different stages of osteoarthritis (OA) were graded.Following this,the cartilage was strained by a swelling experiment,and changes were measured using a high-frequency ultrasound system.The result,together with fixed charge density and water volume fraction of cartilage samples,was used to estimate the uniaxial modulus of the cartilage tissue,based on a triphasic model.For the control cartilage samples,the uniaxial elastic modulus on the cartilage surface was lower than those in the middle and deep layers.With an increase in the OA grade,the uniaxial elastic modulus of the surface,middle and deep layers decreased.A significant difference was found in the surface elastic modulus of different OA grades (P<0.01),while no significant differences were identified for OA cartilages of Grades 1 and 2 in the middle and deep layers (P<0.01).Compared with Grades 1 and 2,there was a significant reduction in the elastic modulus in the middle and deep layers of Grade 3 OA cartilage (P<0.05).Overall,this study may provide a new quantitative method to evaluate the severity of OA using the mechanical properties of cartilage tissue.展开更多
基金The project supported by National Natural Science Foundation of China under Grant Nos. 10475009 and 10465004, the Abdus Salam International Centre for Theoretical Physics （ICTP）, Trieste, Italy under the Associate Programm, and the Foundation for New Century Excellent Talents in University of China. Authors thank Profs. K.F. He and Z.Q. Huang for useful discussions.
文摘Considering the viscoelastic memory effect, we study the correlated motion of two hydrodynamically coupled colloidal particles, each of which confined in a harmonic potential well, in a Kelvin-type and Maxwell-type viscoelastic medium. We find that viscoelastic relaxation plays a significant role in modifying the correlation, particularly the cross correlation. We also find that both the real and imaginary parts of the response function are significantly different from the viscous medium case. In particular there is a phase shift between the vanishing imaginary part and the maximal real part of the response function in a viscoelastic medium. In addition imaginary part of the cross correlation response function exhibits a net energy loss （gain） behavior when the elasticity parameter of the medium is larger （smaller） than the critical value for Kelvin （Maxwell） viscoelastic fluid. Some implication of our results and their connection with previous works are discussed.
基金supported by the National Natural Science Foundation of China (Grant No.31170896)Natural Science Foundation of Shandong Province (Grant No.ZR2009CMO32)
文摘The purpose of this study was to explore the triphasic mechanical properties of osteoarthritic cartilage with different pathological grades.First,samples of cartilage from rabbits with different stages of osteoarthritis (OA) were graded.Following this,the cartilage was strained by a swelling experiment,and changes were measured using a high-frequency ultrasound system.The result,together with fixed charge density and water volume fraction of cartilage samples,was used to estimate the uniaxial modulus of the cartilage tissue,based on a triphasic model.For the control cartilage samples,the uniaxial elastic modulus on the cartilage surface was lower than those in the middle and deep layers.With an increase in the OA grade,the uniaxial elastic modulus of the surface,middle and deep layers decreased.A significant difference was found in the surface elastic modulus of different OA grades (P<0.01),while no significant differences were identified for OA cartilages of Grades 1 and 2 in the middle and deep layers (P<0.01).Compared with Grades 1 and 2,there was a significant reduction in the elastic modulus in the middle and deep layers of Grade 3 OA cartilage (P<0.05).Overall,this study may provide a new quantitative method to evaluate the severity of OA using the mechanical properties of cartilage tissue.
