Electrostatic Interactions Between Glycosaminoglycan Molecules

The electrostatic interactions between nearest-neighbouring chondroitin sulfate glycosaminoglycan (CS-GAG) molecular chains are obtained on the bottle brush conformation of proteoglycan aggrecan based on an asymptotic solution of the Poisson-Boltzmann equation the CS-GAGs satisfy under the physiological conditions of articular cartilage. The present results show that the interactions are associated intimately with the minimum separation distance and mutual angle between the molecular chains themselves. Further analysis indicates that the electrostatic interactions are not only expressed to be purely exponential in separation distance and decrease with the increasing mutual angle but also dependent sensitively on the saline concentration in the electrolyte solution within the tissue, which is in agreement with the existed relevant conclusions

Experimental study on the microstructure and nanomechanical properties of the wing membrane of dragonfly

Detailed investigations on the microstructure and the mechanical properties of the wing membrane of the dragonfly are carried out. It is found that in the direction of the thickness the membrane was divided into three layers rather than a single entity as traditionally considered, and on the surfaces the membrane displays a random distribution rough microstructure that is composed of numerous nanometer scale columns coated by the cuticle wax secreted. The characteristics of the surface structure are measured and described. The mechanical properties of the membranes taken separately from the wings of live and dead dragonflies are investigated by the nanoindentation technique. The Young's moduli obtained here are approximately two times greater than the previous result, and the reasons that yield the difference are discussed

Effect Of A Negative Poisson Ratio In The Tension Of Ceramics

The effect of a negative Poisson ratio is experimentally revealed in the tension deformation of a natural layered ceramic. This effect can increase the volume strain energy per unit volume by 1100% and, simultaneously, decrease the deformation strain energy per unit volume by about 44%, so that it effectively enhances the deformation capacity by about 1 order of magnitude in the tension of the material. The present study also shows that the physical mechanisms producing the effect are attributed to the climbing on one another of the nanostructures in the natural material, which provides a guide to the design of synthetic toughening composites

Effect of temperature-dependent surface heat transfer coefficient on the maximum surface stress in ceramics during quenching

We study the difference in the maximum stress on a cylinder surface sigma(max) using the measured surface heat transfer coefficient h(m) instead of its average value h(a) during quenching. In the quenching temperatures of 200, 300, 400, 500, 600 and 800 degrees C, the maximum surface stress sigma(mmax) calculated by h(m) is always smaller than sigma(amax) calculated by h(a), except in the case of 800 degrees C; while the time to reach sigma(max) calculated by h(m) (f(mmax)) is always earlier than that by h(a) (f(amax)). It is inconsistent with the traditional view that sigma(max) increases with increasing Biot number and the time to reach sigma(max) decreases with increasing Biot number. Other temperature-dependent properties also have a small effect on the trendof their mutualratios with quenching temperatures. Such a difference between the two maximum surface stresses is caused by the dramatic variation of h(m) with temperature, which needs to be considered in engineering analysis