Coupling effects of morphology and inner pore distribution on the mechanical response of calcareous sand particles

Calcareous sand is typically known as a problematic marine sediment because of its diverse morphology and complex inner pore structure.However,the coupling effects of morphology and inner pores on the mechanical properties of calcareous sand particles have rarely been investigated and understood.In this study,apparent contours and internal pore distributions of calcareous sand particles were obtained by three-dimensional(3D)scanning imaging and X-ray micro-computed tomography(X-mCT),respectively.It was revealed that calcareous sand particles with different outer morphologies have different porosities and inner pore distributions because of their original sources and particle transport processes.In addition,a total of 120 photo-related compression tests and 4923D discrete element simulations of four specific shaped particles,i.e.bulky,angular,dendritic and flaky,with variations in the inner pore distribution were conducted.The macroscopic particle strength and Weibull modulus obtained from the physical tests are not positively correlated with the porosity or regularity in shape,indicating the existence of coupling effect of particle shape and pore distribution.The shape effect on the particle strength first increases with the porosity and then decreases.The particle crushing of relatively regular particles is governed by the porosity,but that of extremely irregular particles is governed by the particle shape.The particle strength increases with the uniformity of the pore distribution.Particle fragmentation is mainly dependant on tensile bond strength,and the degree of tensile failure is considerably impacted by the particle shape but limited by the pore distribution.

Developments for collagen hydrolysates as a multifunctional antioxidant in biomedical domains

Antioxidant collagen hydrolysates refers to the peptides mixture with antioxidant properties identified from hydrolyzed collagen.Due to its specific structural,biological and physicochemical properties,collagen hydrolysates have been explored as a multifunctional antioxidant in the biomedical field.In this review,we summarize recent advances in antioxidant collagen hydrolysates development.Initially,the preparation process of antioxidant collagen hydrolysates is introduced,including the production and separation methods.Then the effects and the mechanisms of amino acid composition and collagen peptide structure on the antioxidant activity of collagen hydrolysates are reviewed.Finally,the applications of antioxidant collagen hydrolysates in biomedical domains are summarized,with critical discussions about the advantages,current limitations and challenges to be resolved in the future.