Regularities of formation of emboli of liquid polymer solutions in aqueous medium

Work on creating the basis for embolic compositions for the treatment of a wide range of pathologies of various organs was conducted. This basis is a solution of a biocompatible water-insoluble polymer in a biocompatible water-soluble solvent. Formation of the embolus in such an aqueous medium takes place in the transition of the solvent into the aqueous phase and the formation of a solid polymer clot occluding a blood vessel. Criteria for selection of the polymer and the solvent for the basis were formulated, and a number of polymers and solvents that meet these criteria were selected for further research. Research on the solubility of the selected polymers in solvents was carried out, and the rheoviscometric characteristics of polymer solutions, as well as parameters of solid emboli formation of polymer solutions in aqueous media, were found. The solution of cellulose acetate plasticized with OPADRY CA 500F190000 polyethylene glycol in dimethylsulfoxide with concentration of no less than 60 g/L was recognized as optimal for further studies.     

P-Faithful Partially Ordered Sets

We prove a theorem that describes P-faithful partially ordered sets.     

Structure and effects of annealing in colloidal matrix‐free Ge quantum dots

The structure of small (2–5 nm) Ge quantum dots prepared by the colloidal synthesis route is examined. Samples were synthesized using either GeO₂ or GeCl₄ as precursor. As‐prepared samples were further annealed under Ar or H₂/Ar atmosphere at different temperatures in order to understand the effect of annealing on their structure. It was found that as‐prepared samples possess distinctly different structures depending on their synthesis route as indicated by their long‐range ordering. An appreciable amount of oxygen was found to be bound to Ge in samples prepared with GeO₂ as a precursor; however, not for GeCl₄. Based on combined transmission electron microscope, Raman, X‐ray diffraction and X‐ray absorption measurements, it is suggested that as‐prepared samples are best described by the core‐shell model with a small nano‐crystalline core and an amorphous outer layer terminated either with oxygen or hydrogen depending on the synthesis route. Annealing in an H₂Ar atmosphere leads to sample crystallization and further nanoparticle growth, while at the same time reducing the Ge—O bonding. X‐ray diffraction measurements for as‐prepared and annealed samples indicate that diamond‐type and metastable phases are present.