Nanotextures of composites based on the interaction between hydroxyapatite and cellulose Gluconacetobacter xylinus

Organic-inorganic composite materials with different nanotextures have been prepared using three methods based on two nanosized and biocompatible compounds—cellulose Gluconacetobacter xylinus (CGX) and hydroxyapatite Ca₅(PO₄)₃OH (HA). The structure of the initial components and their composites has been studied using the methods of X-ray diffraction, electron microscopy, and computer simulation. During the combined aggregation of aqueous HA and CGX suspensions, the phenomenon of their adsorption, in the process of which the axis c of HA crystals is oriented parallel to the plane (?110) of CGX microfibrillas, was observed. By varying the quantitative ratio of the components and the methods of introducing HA into composites, it is possible to obtain a wide spectrum of materials for medical practice.     

Pulsed laser reshaping and fragmentation of upconversion nanoparticles — from hexagonal prisms to 1D nanorods through “Medusa”-like structures

One dimensional (1D) nanostructures attract considerable attention, enabling a broad application owing to their unique properties. However, the precise mechanism of 1D morphology attainment remains a matter of debate. In this study, ultrafast picosecond (ps) laser-induced treatment on upconversion nanoparticles (UCNPs) is offered as a tool for 1D-nanostructures formation. Fragmentation, reshaping through recrystallization process and bioadaptation of initially hydrophobic (β-Na_1.5Y_1.5F₆: Yb³⁺, Tm³⁺/β-Na_1.5Y_1.5F₆) core/shell nanoparticles by means of one-step laser treatment in water are demonstrated. “True” 1D nanostructures through “Medusa”-like structures can be obtained, maintaining anti-Stokes luminescence functionalities. A matter of the one-dimensional UCNPs based on direction of energy migration processes is debated. The proposed laser treatment approach is suitable for fast UCNP surface modification and nano-to-nano transformation, that open unique opportunities to expand UCNP applications in industry and biomedicine.

     

An investigation of uranium sorption on minerals of the surrounding rock

Present technological methods do not ensure complete extraction of uranium from ores, because a definite amount of it remains in the solid part of the residue, even under conditions of severe leaching. The bulk of the over-all uranium losses during hydrometallurgical processing of ores is due to this fact.This paper gives experimental data confirming that one of the causes of uranium losses with the solid part of the residue is its sorption on minerals of the surrounding rock. The sorption capacity of such minerals as montmorillonite, kaolinite, bauxite, and albite, and the possibility of uranium desorption by solutiom of various salts and acids, were investigated.Translated from Atomnaya Énergiya, Vol. 16, No. 1, pp. 51–55, January, 1964     

Small-size silicon accelerometer with a thermally compensated signal in the temperature range of 0–200°C

Translated from Izmeritel'naya Tekhnika, No. 3, pp. 24–25, March, 1991.     

On the Structure and Thermoelectric Properties of CoSi Obtained from a Supersaturated Solution–Melt in Sn

Semiconductors - The structure, composition, and thermoelectric properties of cobalt monosilicide obtained by crystallization from a supersaturated solution–melt in tin are studied. A...     

Platinum cross-linked chitosan hydrogels synthesized in water saturated with CO2 under high pressure

The creation of biocompatible composite hydrogels from renewable biopolymers with stabilized functional platinum nanoparticles seems to be an important scientific task. The formation of such hydrogels in a unique medium of carbonic acid under high pressure CO₂ is promising due to its sterilizing ability under pressure, biocompatibility after decompression and environmental friendliness. In the present work, stable chitosan hydrogels with platinum nanoparticles were obtained in such solutions. The hydrogel nature of the composites was confirmed by rotational rheology. The physicochemical characteristics were studied using Fourier transform infrared, X-ray photoelectron, ultraviolet–visible spectroscopies, transmission electron, scanning electron and atomic force microscopies. It was found that nanoparticles of oxidized Pt of approximately 4.5 nm in size are stabilized by chitosan in the composite. The resulting chitosan/Pt hydrogels were also tested for antimicrobial activity and shown strong activity against Gram-positive bacteria (B. subtilis and B. coagulans) and slight activity against E. coli.