Characterization of superparamagnetic iron oxide coated with silicone used as contrast agent for magnetic resonance image for the gastrointestinal tract.

The present work is a report of the characterization of superparamagnetic iron oxide nanoparticles coated with silicone used as a contrast agent in magnetic resonance imaging of the gastrointestinal tract. The hydrodynamic size of the contrast agent is 281.2 nm, where it was determined by transmission electron microscopy and a Fe3O4 crystalline structure was identified by X-ray diffraction, also confirmed by Mössbauer Spectroscopy. The blocking temperature of 190 K was determined from magnetic measurements based on the Zero Field Cooled and Field Cooled methods. The hysteresis loops were measured at different temperatures below and above the blocking temperature. Ferromagnetic resonance analysis indicated the superparamagnetic nature of the nanoparticles and a strong temperature dependence of the peak-to-peak linewidth deltaH(pp), giromagnetic factor g, number of spins N(s) and relaxation time T2 were observed. This behavior can be attributed to an increase in the superexchange interaction.

Synthesis and characterization of silica-coated nanoparticles of magnetite

Magnetic nanoparticles coated with silica have been subjected of extensive,and, in many aspects, also intensive investigations because of their potentialapplication in different technological fields, particularly in biomedicine. This work was conceived and is being carried out in two main parts: (1) synthesis of the ferrimagnetic nanoparticles, specifically magnetite, and (2) coating these particles with tetraethyl orthosilicate (TEOS). The nanosized magnetite sample was preparedby the reduction–precipitation and the nanomagnetite particles were coated by the sol-gel method, based on the hydrolysis of tetraethyl orthosilicate (TEOS). The so obtained materials were characterized with powder X-ray diffraction (XRD), FTIR spectroscopy, saturation magnetization measurements, and 57Fe Mössbauer spectroscopy at room temperature.

Catalytic effect of magnetic nanoparticles over the H2O2 decomposition reaction.

This paper compares the rate of decomposition of hydrogen peroxide when controlled nano-sized magnetite powders are used as catalysts. Two different nano-sized powders and a Fe0/Fe3O4 composite have been used. The nanoparticle samples were synthesized by: (i) a chemical reduction-precipitation method and, (ii) by reduction under H2 atmosphere at 250 degrees C, of a hematite sample previously prepared. The composite, Fe0/Fe3O4, was prepared by thermal controlled reduction of nanoparticles of Fe2O3 obtained from hematite under H2 at 300 degrees C. The samples were characterized by Fourier-transform infrared, X-ray diffraction, and Mössbauer spectroscopy at room temperature, and surface area. The catalytic effect was studied in the decomposition reaction of H2O2 by measuring the formation of gaseous O2. The results showed the presence of pure Fe3O4 for nano magnetite samples and Fe0 and Fe3O4 for the composite sample. The average particle sizes of the magnetite, calculated from reflection 311 by using Scherrer equation were about 33 and 10 nm for the samples obtained by hematite reduction and reduction-precipitation, respectively. Kinetic studies of the decomposition of peroxide showed a higher decomposition rate for the hydrogen peroxide reaction when nanoparticles prepared by reduction-precipitation method were used as catalysts. The high catalytic activity associated to nanoparticles is discussed in terms of the high surface area of these samples.

Relato do aprendizado em estágio de observação da prática médica / A report on what was learned in the medical practice observation stage

Apresenta-se uma proposta pedagógica, não habitual nas escolas médicas tradicionais, que introduz precocemente o aluno de graduação em um estágio de observação da prática médica. Alunos do segundo semestre do curso médico preparados para fazer uma observação participativa do atendimento aos pacientes e entrevistas com profissionais de saúde, desenvolveram a aprendizagem e a reflexão sobre comunicação do profissional de saúde com sua clientela a partir dos fatos observados. Resultados indicam que a experiência com a disciplina propiciou aos alunos um estilo próprio de entrevistar e abordar o paciente, que enfatiza a integridade do ser e as representações do seu mundo, em contraposição à comunicação médico-paciente que acontece durante a anamnese estruturada e na consulta médica feita na rotina ambulatorial com grande demanda.

Surface modifications of alumina-silica glass fiber.

A commercial glass fiber with Al(2)O(3) (68.4%) and SiO(2) (27.6%) as major components and CaO, TiO(2), Fe(2)O(3), and CuO as minor components was used as substrate in a silica sol-gel coating process. After cleaning, fiber samples were immersed into tetraethoxysilane (TEOS) at room temperature for 1 h, and then individual fiber samples were soaked into a simulated body fluid (SBF) solution,1 and removed after 5, 10, 15, and 20 days. Zeta potential and Energy Dispersive Spectroscopy (EDS) analyses showed that the fiber surfaces were effectively coated with a silica layer, which improved the formation of an HA layer upon immersion into SBF solution for 5 days. The coating became even more continuous after 10-day immersion. Fourier Transform Infrared Spectroscopic (FTIR) analyses confirmed that the coating layer has P--O vibration bands characteristic of hydroxyapatite (HA) near 1060 and 600 cm(-1).

A sol-gel derived bioactive fibrous mesh.

Nonwoven sheets of bioactive fibers were produced using a sol-gel process. A high velocity spray process was used to prepare fibers of two compositions in the SiO(2)-CaO-P(2)O(5) ternary system. Both discontinuous fibers and dispersed fibers were evaluated. Viscosity and pH of the sol were the two primary processing variables studied. The formation of hydroxy carbonate apatite (HCA) on the surface of the fibers was used to evaluate the kinetics of the bioactivity in a simulated body fluid (SBF). Diffuse reflection infrared fourier transform spectroscopic (DRIFTS) analysis confirmed the presence of HCA (P-O). A homogenous layer of HCA, as observed with SEM (scanning electron microscopy), typically formed after 3-h immersion in the SBF. The concentration of HCA formed was greater for samples richer in silica. The new bioactive fiber sheets produced by this process are chemically more stable than powders or monoliths prepared from similar precursors. Potential applications are as scaffold for both mineralized and nonmineralized structural tissues.

Hydroxyapatite-zirconia composites prepared by precipitation method.

Chemical routes to prepare ceramic precursor powders are frequently envisaged, especially when the aspects related to the microstructure are important and need to be controlled. An understanding of which parameters of synthesis and thermal treatment can influence the mechanical properties of hydroxyapatite compounds is essential for the production of such materials. Hydroxyapatite-zirconia composites have been prepared, in this study, by a precipitation method. This led to the formation of homogeneous powders with a very defined particle-size distribution. Ceramic pellets prepared from these powders were easily compacted and sintered without cracking. As expected, the presence of the zirconia phase improved composite densities and appeared to have an important role in thermal stabilization of the hydroxyapatite phase.