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[en] Strontium sorption on HA was investigated by batch method. HA was prepared from CA(OH)2 and H3PO4 water solution. It has defined Ca/P ratio and specific surface. Strontium desorption was examined in the presence of Ca2+ ions. The amount of sorption and desorption was determined, and it was shown that HA is more effective sorbent for low concentration solutions. (author)
[en] Highlights: • GO-SiO2 rGO-SiO2 composites were prepared via chemical-thermal method. • HA-SiO2 and tHA-SiO2 composites were obtained by wet chemical techniques. • The morpho-structural characteristics of composites were evaluated and compared. • The rGO-SiO2 and tHA-SiO2 showed the highest antibacterial effect on E. Coli and S. Aureus.
[en] Highlights: • Hydroxyapatite nanostructures were synthesized by phosphate surfactant. • Spindle-type nanoparticles formed by the oriented attachment mechanism. • Rod-shaped and sheet-like nanostructures formed in the lamellar structure. • Phosphate surfactants act as a capping agent or lamellar template.
[en] Structures of some bisphosphonates (clodronate, etidronate, pamidronate, alendronate, risedronate, zoledronate) were relaxed and analyzed by DFT method. By comparing their adsorption energies onto hydroxyapatite (001) surface with and without solvation effect and analyzing HOMOs (highest occupied molecular orbitals), LUMOs (lowest unoccupied molecular orbitals), and DOS (density of states) of bisphosphonates and hydroxyapatite (001) surface, it can be shown that the binding affinity of alkyl N-BPs (bisphosphonates containing nitrogen atom in an alkyl chain) is the highest among bisphosphonates, and the adsorption energy of bisphosphonates onto hydroxyapatite (001) surface is the main factor to determine the binding affinity of bisphosphoates with bone material.
[en] Etchable length reduction of thermal-neutron induced fission tracks is observed in four apatites that experienced temperatures no greater than approximately 230C subsequent to track formation. In each apatite, the mean etchable fission track lengths parallel (lc) and perpendicular (la) to the crystallographic c-axis as well as the arithmetic (conventional) mean (1m) decrease by approximately 0.5 μm during the time interval ∼10 min-∼3 weeks after irradiation. Two crystallographic orientation dependencies of mean etchable fission track length at room temperature are identified: (a) 1c>1a in all cases (tracks etched for 25 s at 230C in 5 M HNO3) and (b) la decreases approximately twice as fast as lc. These measurements strongly support previous suggestions that natural charged-particle tracks in crystalline materials, including fission tracks, undergo slow annealing at low ambient temperatures. The observed sensitivity of induced fission tracks in apatite to low-temperature annealing requires that care be taken to avoid heating apatites before and during track etching for so-called ''initial'' mean track length measurements. (author)
[en] Allogenous bone chips and hydroxyapatite (HA) chips have been known as good options for filling an inevitable void after open wedge high tibial osteotomy (OWHTO). However, there are concerns regarding bone healing after the use of these grafts. The purpose of this study was to compare the bone healing represented by the osteoconductivity and absorbability between allogenous bone chips and HA chips in OWHTO. The outcomes of bone healing of 53 patients who received an allogenous bone chip graft and 41 patients who received an HA chip graft were retrospectively evaluated, and the results were compared between the two groups. Osteoconductivity and absorbability were serially evaluated for the assessment of bone healing at 6 weeks, 3 months, 6 months, and 1 year postoperatively. The osteoconductivity of the allogenous bone chips was greater than that of the HA chips at 6 weeks postoperatively (p < 0.05). However, there were no statistically significant differences from 3 months to 1 year postoperatively. The absorbability showed no statistically significant differences 6 weeks and 3 months after OWHTO; however, the allogenous bone chip group showed a greater absorbability at 6 months and 1 year postoperatively (42.8 ± 14.2 vs. 34.6 ± 13.8, p = 0.006 at 6 months postoperatively; 54.6 ± 14.4 vs. 43.0 ± 14.0, p < 0.001 at 1 year postoperatively). However, the two graft materials showed similar results of HKA angle, WBL ratio, posterior tibial slope. Graphical abstract:
[en] Recently Miller et al. (1990) published the results of the third interlaboratory comparison of fission-track ages for the 1988 Fission-Track Dating Workshop held at Besancon. The samples distributed to the Fission Track community were a zircon (88-1), two apatites (88-2 and 88-3) and a glass (88-4). The above authors discussed the results and concluded that, whereas zircon 88-1, apatite 88-3 and glass 88-4 seemed to be adequate for interlaboratory comparison, apatite 88-2 needed further investigation because of the wide range in measured age, especially in comparison with apatite 88-3, analysed by the same workers. One of the sample characteristics which could produce a large scatter of age is the large inter-grain track-content variation shown by apatite 88-2. The results of an extensive analysis of apatites 88-2 and 88-3 is presented to support this view. (author)
[en] Hydroxyapatite prepared by heating flux-grown chlorapatite in steam at 1200 deg C for two weeks has a monoclinic space group P21/b. The structure of such a specimen determined by X-ray diffraction methods is described. The distortions of the monoclinic hydroxyapatite structure from the very closely related hexagonal one usually found in apatites are very similar to those distortions that have been found in monoclinic chlorapatite