NUMERICAL SOLUHON TO THE PROBLEM ON DlFFUSION OF CATALYTIC AGENTS RELEASED FROM AN AIRPLANE

A solution to the problem on diffusion of catalytic agents released from an airplane is sought.The variation of falling velocities of agent particles with the altitudes is taken into account in the study of the problem.A comparison is also made between the calculated results obtained by using the finite-difference method and those by using the analytic method,the similarities and the differences between the two methods are revealed.

Layer-by-layer self-assembly and clinical application in orthopedics

Orthopedic implants for the treatment of bone defects from various causes have been challenged by insufficient osseointegration,bacterial infection,oxidative stress,immune rejection,and insufficient individualized treatment.These challenges not only impact treatment outcomes but also severely impact patients’daily lives.Layer-by-Layer(LbL)serves as a simple surface coating technique,in simple terms,to functionalize implants by sequentially adsorbing oppositely charged materials onto a substrate.In orthopaedics,LbL self-assembly technology solves some of the challenges by loading various drugs or biological agents on the implant surface and controlling their release precisely to the site of bone defects in a personalized way.This review will introduce the basic principle and the development of LbL in orthopaedics,review and analyze the chemical strategy of LbL in the preparation of bone implants to ensure the stability of the implant,and introduce the use of LbL bone implants in orthopaedics in recent years.The application of LbL includes the realization of programmed drug delivery and sustained release,thereby promoting osseointegration and the formation of new blood vessels,antibacterial,antioxidant,etc.This review focuses on the LbL technology,involving the technology selection for the preparation of bone implants,the chemical strategies of the stability guarantee of LbL implants,the pharmacological properties,loading and release mechanisms of loaded drugs,and the molecular mechanisms of osteogenesis and angiogenesis.The aim of this review is to provide an overview of current research advances,and a prospect in this field was also described.

Roles of polyacrylate dispersant in the synthesis of well-dispersed BaSO_4 nanoparticles by simple precipitation

Well-dispersed BaSO4 nanoparticles were synthesized in the presence of sodium polyacrylate （PAAS） by a simple precipitation method, with BaCl2 and （NH4）2SO4 as reactants. The different roles performed by PAAS in the synthesis of BaSO4 nanoparticles were investigated using X-ray diffractometry, Fourier transform infrared spectroscopy, and transmission electron microscopy. The results indicate that the assynthesized BaSO4 nanoparticles were spheres with an average diameter of 30 nm and that their surfaces were affected by the PAAS. Under a typical procedure employed, PAAS reacted with BaCl2 to yield an intermediate, serving as a control releasing agent and separating the nucleation and crystal growth processes of the BaSO4 nuclei. During formation of the BaSO4 nanospheres, the intermediate slowly dissolved and released barium and polyacrylate ions, inhibiting the growth and aggregation of newly formed BaSO4 seeds and resulting in particles of narrow diameter distribution and improved dispersibility. Moreover, these polyacrylate ions further modified the surfaces of the BaSO4 nanoparticles.