Although the assembly of aluminosilicate foams and large-pore hexagonal mesostructures from zeolite BEA, MFI, and FAU seeds requires a reduction in pH from initially very basic values (pH > 12) to acidic values in the range <2.0−6.5, the protozeolitic nanoclusters persist under these conditions and substantially improve the hydrothermal stability of the resulting mesostructures when exposed to 20% steam at 800 °C.

No abstract

The material point method (MPM) enhanced with B-spline basis functions, referred to as B-spline MPM (BSMPM), is developed and demonstrated using representative quasi-static and dynamic example problems. Smooth B-spline basis functions could significantly reduce the cell-crossing error as known for the original MPM. A Gauss quadrature scheme is designed and shown to be able to diminish the quadrature error in the BSMPM analysis of largedeformation problems for the improved accuracy and convergence, especially with the quadratic B-splines. Moreover, the increase in the order of the B-spline basis function is also found to be an effective way to reduce the quadrature error and to improve accuracy and convergence. For plate impact examples, it is demonstrated that the BSMPM outperforms the generalized interpolation material point (GIMP) and convected particle domain interpolation (CPDI) methods in term of the accuracy of representing stress waves. Thus, the BSMPM could become a promising alternative to the MPM, GIMP, and CPDI in solving certain types of transient problems. KEYWORDS B-spline basis functions, Gauss quadrature, large deformation, material point method, mesh refinement, transient problems

No abstract

Establishing an appropriate degradation rate is critical for tissue engineering scaffolds. In this study, the degradation rate of silk fibroin three-dimensional scaffolds was regulated by changing the molecular weight (MW) of the silk fibroin. The solubility of silk fibroin depends primarily on the ionic ability of the slovent to dissolve silk fibroin, therefore, we regulated the MW of the silk fibroin using LiBr, Ca(NO₃)₂ and CaCl₂ to dissolve the silk fibers. SDS-PAGE analysis showed that the MW of the CaCl2-derived silk fibroin was lower than the MW produced using LiBr and Ca(NO₃)₂. In vitro and in vivo degradation results showed that the scaffolds prepared by low-MW silk fibroin were more rapidly degraded. Furthermore, FTIR and amino acid analysis suggested that the amorphous regions were preferentially degraded by Collagenase IA, while the SDS-PAGE and amino acid analysis indicated that the scaffolds were degraded into polypeptides (mainly at 10-30 kDa) and amino acids. Because the CaCl₂-derived scaffolds contained abundant low MW polypeptides, inter-intramolecular entanglement and traversing of molecular chains in the crystallites reduced, which resulted in rapid degradation. The in vivo degradation results suggested that the degradation rate of the CaCl₂-derived scaffolds was better matched to dermis regeneration, indicating that the degradation rate of silk fibroin can be effectively regulated by changing the MW to achieve a suitable dermal tissue regeneration rate.