Analysis of Workability and Mechanical Properties of Alkali-Activated Recycled Aggregate Fiber Concrete

Alkali-activated recycled aggregate fiber concrete is an innovative material that combines alkali activation technology, recycled aggregates, and fiber reinforcement. This paper systematically analyzes the workability and mechanical properties of this concrete. Experimental studies assessed the workability of alkali-activated recycled aggregate fiber concrete, including its flowability and workability, and explored how these characteristics impact construction and use. Additionally, a detailed analysis of the concrete's mechanical properties, such as compressive strength, tensile strength, and flexural strength, was conducted. The results indicate that alkali-activated recycled aggregate fiber concrete maintains good workability while significantly enhancing mechanical properties, with excellent crack resistance and toughness. The paper also discusses the key factors affecting these properties and provides an outlook on future research directions and practical applications

Lipoprotein lipase regulates hematopoietic stem progenitor cell maintenance through DHA supply.

Lipoprotein lipase (LPL) mediates hydrolysis of triglycerides (TGs) to supply free fatty acids (FFAs) to tissues. Here, we show that LPL activity is also required for hematopoietic stem progenitor cell (HSPC) maintenance. Knockout of Lpl or its obligatory cofactor Apoc2 results in significantly reduced HSPC expansion during definitive hematopoiesis in zebrafish. A human APOC2 mimetic peptide or the human very low-density lipoprotein, which carries APOC2, rescues the phenotype in apoc2 but not in lpl mutant zebrafish. Creating parabiotic apoc2 and lpl mutant zebrafish rescues the hematopoietic defect in both. Docosahexaenoic acid (DHA) is identified as an important factor in HSPC expansion. FFA-DHA, but not TG-DHA, rescues the HSPC defects in apoc2 and lpl mutant zebrafish. Reduced blood cell counts are also observed in Apoc2 mutant mice at the time of weaning. These results indicate that LPL-mediated release of the essential fatty acid DHA regulates HSPC expansion and definitive hematopoiesis

Partially doubly strictly diagonally dominant matrices with applications

A new class of matrices called partially doubly strictly diagonally dominant (for shortly, PDSDD) matrices is introduced and proved to be a subclass of nonsingular $H$-matrices, which generalizes doubly strictly diagonally dominant matrices. As applications, a new eigenvalue localization set for matrices is given, and an upper bound for the infinity norm bound of the inverse of PDSDD matrices is presented. Based on this bound, a new pseudospectra localization for matrices is derived and a lower bound for distance to instability is obtained

Shear Bearing Capacity of Framework Joints of Steel-Reinforced Concrete-Filled Circular Steel Tube

In this paper, in order to investigate the shear mechanism and shear capacity of framework joints of steel-reinforced concrete-filled circular steel tube (SRCFCST), a numerical finite element model reflecting the mechanical behavior of framework joints of SRCFCST column-reinforced concrete beam is established through simulating concrete by the damage plastic constitutive model and simulating steel by the ideal elastic-plastic material, and its effectiveness is verified by experimental data. On account of uniform distribution of circular steel reinforced around the section and without definite flange and web, the shear mechanism of the framework joints of SRCFCST is analyzed on the basis of equivalent circular steel tube (CST) to the rectangular steel tube. The method for calculating the superposed shear bearing capacities of the joint core area is proposed, which is composed of four parts, i.e., concrete inside tube, concrete outside tube, hooping and steel-reinforced web; and the corresponding formulas for calculating shear bearing capacity are established. The comparative analysis of joints’ shear bearing capacity indicates that the results of numerical simulation and shear bearing capacity formulas coincide well with the experimental values, which can provide reference for the nonlinear analysis and engineering design of similar joints