Tatyana Shibaeva

Synthesis of composite biomaterials in the hydroxyapatite-calcite system

New medical engineering processes for repair of human bone tissue damaged upon diseases or injury are based on implanting porous scaffolds made of bio� compatible materials with cultivated osteoforming cells into the defect site [1–5]. With time, this struc� ture is replaced by bone tissue formed de novo. Apart from biocompatibility with the body, the requirements to the scaffold material include also time coherence between the resorption and the formation of a new bone tissue. Materials based on calcium phosphates, especially hydroxyapatite (HA), which is analogous in the chemical and phase composition to the mineral component of bone tissue, is best suited for this pur� pose. However, HA is the calcium phosphate most resistant to resorption. The resorption kinetics can be controlled by introducing a second, more soluble phase to the HA. To this end, composite materials in the HA–tricalcium phosphate system were developed [4, 5]; however, these materials still suffer from a num�

Effect of a pipe-steel killing technology on the composition and number of nonmetallic inclusions

Pipes made from steels 19G, 17GS, 17G1S, 10G2FBYu, 13G1S-U, and 20KT of various manufacturers and technologies are studied. Electron microprobe and fractional gas analyses are used to determine the main types and number of nonmetallic inclusions (NIs). The effect of a modification procedure on the oxidic cleanness of steel 20KT (produced at JSC “Volzhskii Pipe Works”) is studied. The use of a silicocalcium-filled wire is shown to increase the total contamination of the steel by nonmetallic, in particular, calcium aluminate and magnesium spinel inclusions, which are conditionally related to corrosion-active nonmetallic inclusions (CANIs). Fractional gas analysis is shown to allow the number of oxide inclusions of various types to be accurately determined in pipe steels. No correlation is found between the volume fraction of oxide inclusions determined by fractional gas analysis and the number of CANIs determined by a metallo-graphic method.

Plasma coatings of mechanically doped Co-C-Mo and Co-C powders

X-ray structure analysis and metallography are applied for investigations into the phase composition and structure of powdered model alloys Co-9.2% C and Co-1% Mo-9.2% C after various treatments (mechanical doping, thermal treatment, sintering) and plasma coatings produced from these powders. It is demonstrated that carbides CoxCy are formed within mechanical doping and plasma spraying, which are absent in the equilibrium state diagram. High microhardness of plasma coatings (up to 8.3 GPa) is associated with formation of carbides and amorphous phase. Carbon losses at stages of plasma spraying of coatings are determined.

Влияние ДРОП-воздействия на эффективность использования световой энергии в процессе фотосинтеза у растений огурца

We studied the apparent quantum yield of photosynthesis in the leaves of cucumber ( Cucumis sativus L.) plants exposed to daily short-term (2 h) temperature drops to 12 ° C in the darkness (in the end of the night) or light (at the beginning of the day). In order to assess the effect of leaf age on their response to DROP, plants were exposed to DROP treatments when the first leaf was non-mature (in the exponential growth phase) or mature, or during the entire period of leaf expansion. It was shown that DROP causes a decrease in the efficiency with which light energy is utilized in photosynthesis regardless of leaf age. It is suggested that changes in the apparent quantum yield under the influence of DROP treatments are associated with changes in the pigment composition. Unlike leaf age, the presence of light during DROP treatments significantly affected the degree of changes in apparent quantum yield of photosynthesis. In particular, DROP in the light caused significantly greater reduction in the apparent quantum yield than DROP in the darkness. Moreover, DROP in the light reduced not only the apparent quantum yield, but also the rate of photosynthesis. DROP in the darkness did not affect the rate of photosynthesis. It is assumed that the decrease in the light use efficiency in DROPtreated plants results from the initiation of plant defense response to low temperatures that allow avoiding photosynthetic apparatus damage.

Fractionated-combustion analysis of carbonate-containing phases in composite materials of the hydroxyapatite-calcium carbonate system

Materials in the hydroxyapatite (HA)-calcium carbonate (CC) system were synthesized by a precipitation method from aqueous solutions. According to the data of X-ray phase analysis and IR spectroscopy, the powders consisted of CC and AB-type carbonate-substituted HA (CHA). In order to determine the content of carbonate-containing phases in materials, the temperature-temporal mode of fractionated-combustion analysis of carbon was developed. The quantitative phase ratios and the degree of substitution of carbonate groups in CHA were determined. It was shown that the degree of substitution of carbonate groups in CHA increased from 2.47 to 5.31 wt % as the CC content increased from 13.50 to 88.33 wt %.