ABSTRACT
The influence of calcination temperature on copper spatial localization in Y-stabilized ZrO2 powders was studied by attenuated total reflection, diffuse reflectance, electron paramagnetic resonance, transmission electron microscopy, electron energy loss, and energy-dispersive X-ray spectroscopies. It was found that calcination temperature rise in the range of 500-700 °C caused the increase of copper concentration in the volume of ZrO2 nanocrystals. This increase was due to Cu in-diffusion from surface complexes that contained copper ions linked with either water molecules or OH groups. This copper in-diffusion led also to an enhancement of absorption band peaked at ~270 nm that was ascribed to the formation of additional oxygen vacancies in nanocrystal volume. Further increasing of calcination temperature from 800 up to 1000 °C resulted in outward Cu diffusion accompanied by a decrease of the intensity of the 270-nm absorption band (i.e., oxygen vacancies' number), the transformation of ZrO2 tetragonal (cubic) phase to monoclinic one as well as the enhancement of absorption band of dispersed and crystalline CuO in the 600-900 nm range.
ABSTRACT
Biological apatites (tooth enamel, bone) and their synthetic analogues were exposed to gamma rays, UV light, or thermal treatment and studied by electron paramagnetic resonance (EPR). The thermal generation of CO2- radicals in synthetic apatite was observed for the first time. It was shown that the experimental EPR spectra of all of the above-mentioned materials are caused by the contribution of two types of CO2- radicals: axial and orthorhombic. The ratio of their concentrations depends on the characteristic energy of the external influence (i.e., the energy of quantum for radiation or kT for thermal treatment) and also on the quality of the initial material (defectiveness). Based on the analysis of EPR spectra recorded immediately after gamma-irradiation, the authors conclude that the main short-lived radical in bioapatites is CO3(3)- . The unified mechanism of CO2- radical formation in hydroxyapatites at different external influences is proposed; the main stages of transformation are CO3(2)- + e --> CO3(3)- --> CO2-, where the electron (e) originates from the ionization of impurities by radiation/temperature.
Subject(s)
Bone and Bones/chemistry , Bone and Bones/radiation effects , Carbon Dioxide/chemistry , Dental Enamel/chemistry , Dental Enamel/radiation effects , Hydroxyapatites/chemistry , Hydroxyapatites/radiation effects , Animals , Biomimetic Materials/chemistry , Biomimetic Materials/radiation effects , Carbon Dioxide/radiation effects , Cattle , Dose-Response Relationship, Radiation , Free Radicals/chemistry , Humans , Radiation Dosage , SwineABSTRACT
Anisotropy of EPR spectra of tooth enamel plates irradiated with gamma-rays and UV light has been studied. UV-irradiated enamel plates exhibit a stronger anisotropy than gamma-irradiated plates. Investigation of samples cut out of different teeth and irradiated to different doses showed that the value of anisotropy is characteristic of each type of irradiation; it equals to approximately 0.35 for gamma- rays and 0.50 for UV light. It is suggested that the difference in the anisotropy values can be attributed to different relative amounts of oriented and disordered radicals produced by the two types of radiation. This can be used for separating gamma- and UV-contributions to the total EPR signal of a tooth exposed to both types of radiation.
Subject(s)
Dental Enamel/chemistry , Gamma Rays/adverse effects , Ultraviolet Rays/adverse effects , Animals , Anisotropy , Dental Enamel/radiation effects , Electron Spin Resonance Spectroscopy , Humans , Tooth/chemistry , Tooth/radiation effectsABSTRACT
The EPR spectrum of tooth enamel caused by 13C hyperfine interactions of the CO2- radical were studied on gamma-irradiated powdered samples annealed for 40 min at different temperatures up to 250 degrees C. The lineshape and hyperfine splitting of the spectra were found to depend on the annealing temperature. Experimental spectra were compared with calculated ones assuming that EPR spectra are formed by two CO2- species--axial (rotating) and orthorhombic (braked) radicals. We assumed that the axial CO2- radicals are centers located in perfect areas of the hydroxyapatite crystals of tooth enamel whereas the orthorhombic CO2- radicals are rotating centers which are braked by defects. The thermal treatment of enamel samples leads to defective annealing and transformation of the orthorhombic centers into axial ones. This results in an increasing axial CO2- radical contribution to the EPR spectrum with increase of annealing temperature.
Subject(s)
Carbon Dioxide , Dental Enamel/radiation effects , Carbon Isotopes , Dental Enamel/chemistry , Electron Spin Resonance Spectroscopy/methods , Humans , ThermodynamicsABSTRACT
The paper is concerned with the results of therapy of a severe form of postmenopausal osteoporosis in 5 patients using the combination of estrogens, 1-alpha-hydroxycholecalciferol and calcitonin. The treatment with the above drugs was accompanied by marked improvement of the general status. It was characterized by an increase in daily calcium excretion with urine, normalization of the concentration of calcium, inorganic phosphorus and serum alkaline phosphatase activity. A conclusion was made that the combined use of estrogens and 1-alpha-hydroxycholecalciferol produced a more marked clinical effect than each drug separately.