RESUMO
BACKGROUND: The erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser has been widely used in the dental clinic; however, few studies have demonstrated the advantages of the use of this laser for bone osteotomies. The purpose of this study is to evaluate and compare the bone repair process of defects generated by the Er,Cr:YSGG laser or conventional drills. METHODS: Ninety-six rats were divided into two groups of 48 animals (drill group and laser group). After surgical exposure of the right tibia, the animals were subjected to a 2-mm-diameter osteotomy created by conventional drills (drill group) or by the Er,Cr:YSGG laser (laser group). The animals were sacrificed 0, 3, 7, 14, 30, and 60 days after the creation of the defect, and histologic sections were obtained and used for histomorphometric and immunohistochemical analyses for the detection of osteocalcin, osteoprotegerin, receptor activator of nuclear factor κ-B ligand, vascular endothelial growth factor, and caspase-3. RESULTS: The osteotomy with the drill produced well-delimited and smooth walls, whereas the osteotomies in the laser group were irregular and presented an amorphous basophilic line and bone necrosis that was slowly resorbed during the repair process. Despite these characteristics, bone repair was similar between groups at various time points, and, at 60 days, the defects in both groups were completely repaired by newly formed bone. CONCLUSION: The repair process of osteotomies created by the Er,Cr:YSGG laser, despite producing thermal damage to bone tissue, is comparable to that with conventional drills.
Assuntos
Osteotomia , Animais , Cromo , Érbio , Gálio , Lasers de Estado Sólido/uso terapêutico , Ratos , Escândio , Fator A de Crescimento do Endotélio Vascular , ÍtrioRESUMO
An on-line scandium preconcentration and determination system implemented with inductively coupled plasma optical emission spectrometry associated with flow injection was studied. Trace amounts of scandium were preconcentrated by sorption on a minicolumn packed with oxidized multiwalled carbon nanotubes, at pH 1.5. The retained analyte was removed from the minicolumn with 30% (v/v) nitric acid. A total enrichment factor of 225-fold was obtained within a preconcentration time of 300 s (for a 25 mL sample volume). The overall time required for preconcentration and elution of 25 mL of sample was about 6 min; the throughput was about 10 samples per hour. The value of the detection limit was 4 ng L(-1) and the precision for 10 replicate determinations at 100 ng L(-1) Sc level was 5% relative standard deviation, calculated from the peak heights obtained. The calibration graph using the preconcentration system was linear with a correlation coefficient of 0.9996 at levels near the detection limits up to at least 10 mg L(-1). After optimization, the method was successfully applied to the determination of Sc in an acid drainage from an abandoned mine located in the province of San Luis, Argentina.
Assuntos
Análise de Injeção de Fluxo/métodos , Mineração , Nanotubos de Carbono/química , Escândio/análise , Espectrofotometria Atômica/métodos , Ácidos/química , Argentina , Concentração de Íons de Hidrogênio , Oxirredução , Reprodutibilidade dos Testes , Escândio/química , Águas Residuárias/química , Poluentes Químicos da Água/análiseRESUMO
The consistency of the published values for fission averaged cross-sections of threshold reactions induced in a nuclear reactor is analyzed. The influence of the literature data involved in the determination of these cross-sections is discussed. Renormalizations based on cross-sections value for the standard reactions, isotopic abundances of the precursors and radiation emission probabilities of the radionuclide under study and the monitor, are applied to the evaluation of the cross-sections for the reactions: (46)Ti(n,p)(46)Sc; (47)Ti(n,p)(47)Sc; (48)Ti(n,p)(48)Sc; and (64)Zn(n,p)(64)Cu.
Assuntos
Radioisótopos de Cobre/química , Nêutrons , Fissão Nuclear , Radiometria/métodos , Escândio/química , Titânio/química , Radioisótopos de Zinco/química , Radioisótopos de Cobre/efeitos da radiação , Isótopos/química , Isótopos/efeitos da radiação , Doses de Radiação , Escândio/efeitos da radiação , Titânio/efeitos da radiação , Radioisótopos de Zinco/efeitos da radiaçãoRESUMO
We describe the preparation, the crystal structure refined from neutron powder diffraction (NPD) data, and study of the permittivity of two related double perovskites, Pb2Sc(Ti0.5Te0.5)O6 and Pb2Sc(Sc0.33Te0.66)O6. These compounds were synthesized by standard ceramic procedures; Rietveld refinements from room temperature NPD data show that the crystal structures are well defined in a cubic unit cell (space group Fm3m) with double parameter, a = 2a0 ≈ 8 Å. They contain a completely ordered array of ScO6 and (B,Te)O6 (B = Sc, Ti) octahedra sharing corners; the PbO12 polyhedra present an off-center displacement of the lead atoms along the [1 1 1] directions, due to the electrostatic repulsion between the Pb(2+) 6 s electron lone-pair and the Pb-O bonds of the cuboctahedron. Both compounds present a low temperature, highly dispersive maximum in permittivity, the position of which follows the Vogel-Fulcher relation with freezing temperatures of 156 and 99 K for Pb2Sc(Ti0.5Te0.5)O6 and Pb2Sc(Sc0.33Te0.66)O6, respectively, exhibiting a typical phenomenology of relaxors.
Assuntos
Chumbo/química , Oxigênio/química , Escândio/química , Telúrio/química , Titânio/química , Elétrons , Modelos Moleculares , TemperaturaRESUMO
The capacity of Al3+-related cations (Sc3+, Ga3+, In3+, Be2+, Y3+, and La3+) to promote membrane rigidification and lateral phase separation was evaluated in liposomes containing zwitterionic (phosphatidylcholine, PC) and negatively charged (phosphatidylserine, PS) phospholipids. These effects were correlated with the capacity of the ions to stimulate Fe2+-supported lipid peroxidation. A13+, Sc3+, Ga3+, In3+, Be2+, Y3+, and La3+ (50-200 microM) increased the order parameter of the fluorescent probe 1,3-diphenylhexatriene incorporated in PC:PS membranes. In addition, the electron paramagnetic resonance spectra of spin-labeled fatty acids indicated a reduction in lipid motion induced by Sc3+, Y3+, and La3+. The effect was found to extend down to carbon 16 on the acyl chain. The ions (10-200 microM) were also able to induce lateral phase separation, as evaluated from the increase in fluorescence quenching of the probe 2-(6-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)dodecanoyl-1-hexadec anoyl-sn-glycero-3-phosphocholine. The ability of the ions to alter membrane lipid packing and induce lateral phase separation correlated in a positive manner (r2 = 0.91 and 0.90, respectively) with their capacity to stimulate the production of Fe2+-initiated 2-thiobarbituric-reactive species, a measure of lipid peroxidation. These results show that Al3+-related metal ions cause membrane rigidification and phase separation, which could affect membrane-related processes. The results support the hypothesis that ions without redox capacity can stimulate Fe2+-initiated lipid peroxidation by increasing lipid packing and by promoting the formation of rigid clusters. Both processes will bring phospholipid acyl chains closer together, thus favoring the propagation step of lipid peroxidation.
Assuntos
Peroxidação de Lipídeos/efeitos dos fármacos , Lipídeos de Membrana/química , Metais/toxicidade , Alumínio/toxicidade , Animais , Berílio/toxicidade , Cátions/química , Cátions/toxicidade , Espectroscopia de Ressonância de Spin Eletrônica , Gálio/toxicidade , Técnicas In Vitro , Índio/toxicidade , Lipossomos , Fluidez de Membrana/efeitos dos fármacos , Metais/química , Estrutura Molecular , Escândio/toxicidade , Termodinâmica , Ítrio/toxicidadeRESUMO
Seven representative wood species constituting Caatinger forest in north-east Brazil were chosen to analyze La, Ce, Sm, Eu, Yb, Sc, and Al by instrumental neutron activation analysis (INAA). Soil profiles were prepared where the trees were downed. Then soil and root samples from each horizontal soil layer, as well as the upper part of the wood, ground-level bark, and the bark at 1 m above were collected. In woods, the rare earth element (REE) was found to be mainly accumulated in root, which concentration was in the same order as that of soil. In all samples, concentration of La and Ce were found to be about ten times higher than those of the other REEs. The REE accumulation became higher, in both root and soil, in the order of La, Ce, and Sm. The partition rate of La and Eu was higher from soil to root, whereas Ce tended to be concentrated from root to bark. In the case of bark, there was no tendency of specific REE accumulating from ground level to the upper part. The correlation of La concentration to the other REE was higher in root than that of corresponding soil. Roots also showed higher correlation of REE to Al and Sc than that of soil or bark.
Assuntos
Alumínio/análise , Metais Terras Raras/análise , Escândio/análise , Poluentes do Solo/análise , Árvores/química , Brasil , Análise de Ativação de Nêutrons , Raízes de Plantas/química , MadeiraRESUMO
Scandium and ash methods' performances were compared in terms of soil content assessment in sugar cane loads, emphasizing the common sampling drawbacks. Both methods are adequate for such determination in controlled conditions. The scandium has demonstrated better analytical characteristics, since it is free from interferences of cane matrix, which decreases the accuracy of the ash method in normal mill conditions.