Sustained magnetization oscillations in polyaniline-Fe3O4 nanocomposites.

We report experiments with polyaniline-Fe3O4 (PANI-Fe3O4) nanocomposites synthesized under several different conditions. With a reaction carried out at room temperature and assisted by intense ultra-violet (UV) irradiation, we observe sustained oscillations in the magnetization with a period of about 25 min. The oscillations are interpreted as the result of an oscillatory chemical reaction in which part of the Fe(+2) ions of magnetite, Fe3O4, are oxidized by the UV irradiation to form Fe(+3) so that a fraction of the magnetite content transforms into maghemite, γ-Fe2O3. Then, Fe(+3) ions at the nanoparticle surfaces are reduced and transformed back into Fe(+2), when acting as an oxidizing agent for polyaniline in the polymerization process. Since maghemite has smaller magnetization than magnetite, the oscillating chemical reaction results in the oscillatory magnetization. The observations are interpreted with the Lotka-Volterra nonlinear coupled equations with parameters that can be adjusted to fit very well the experimental data.

The effect of ultrasonic waves in conducting polymer solution.

The effects of ultrasonic wave on the conducting polymer polyaniline dissolved in DMSO were observed. The UV-visible, infrared and NMR analysis show that the polymer undergo a redox and doping transition when the ultrasound wave interacts with the polymer dissolved into the solvent. The proposed mechanism to explain these effects is based on the solvent's hygroscopicity properties. The interaction with the ultrasonic wave, homolitically dissociates the water molecule producing radical species, and these species interact with the dissolved conducting polymer changing its oxidation and doped state. The resulting effects of that interaction are the modification of oxidation state of the conducting polymer and the decrease of the amount of water molecule in the solvent. From those results, we have proposed one straightforward method to eliminate water contamination in the solvent DMSO using ultrasonic waves.

Highly sensitive thermoluminescent carbon doped nanoporous aluminium oxide detectors.

In this work we present the synthesis, characterisation and the thermoluminescence (TL) response of nanoporous carbon doped aluminium oxide Al2O3:C produced by anodic oxidation of aluminium in organic and inorganic solvents. The X-ray and scanning electron microscopy (SEM) measurements reveal that the synthesised samples are amorphous and present highly ordered structures with uniform pore distribution with diameter of the order 50 nm. The photoluminescence and spectroscopic analysis in the visible and infrared regions show that the luminescence properties presented by the samples prepared in organic acid are due to carboxylate species, incorporated in anodic alumina films during the synthesis process. After an annealing treatment, part of the incorporated species decomposes and is incorporated into the structure of the aluminium oxide yielding a highly thermoluminescent detector (TL) . The results for X-ray irradiation in the range from 21 to 80 keV indicate a linear TL response with the dose in the range from 5 mGy to 1 Gy, suggesting that nanoporous aluminium oxide produced in the present route of synthesis is a suitable detector for radiation measurements.

Oral recurrent human herpes virus infection and bone marrow transplantation survival.

OBJECTIVE: This study was conducted to compare the survival rates of bone marrow transplantation (BMT) patients who were affected with the survival rates of those who were not affected by oral recrudescent human herpes virus-1 infection (HHV-1) after transplantation. STUDY DESIGN: Fifty-two consecutive patients who underwent BMT were included in the study. The time of death after BMT was displayed, by means of the Kaplan-Meier method, for the following parameters: age and gender of the patient, donor gender, primary disease, stem cells, conditioning regimen, platelet number after day 100, acute and chronic graft-versus-host disease, oral recurrent HHV-1 infection post-BMT, oral lichenoid lesions of graft-versus-host disease, graft-versus-host disease at the salivary glands, parenteral nutrition, and oral mucositis. The data were initially analyzed by means of the log-rank test and then included in the Cox proportional hazards model. RESULTS: The multivariate analysis demonstrated a significance of 5% for only the platelet numbers and oral recurrent HHV-1 infection. CONCLUSION: The present study provides evidence that platelet numbers below 100,000 cells/mm(3) after day 100 and oral recurrent HHV-1 infection are independent negative prognostic variables in BMT patients' 24-month survival rates.

Gamma ray detection using sol-gel glass doped with lanthanide ions.

In this work we discuss the synthesis, characterization and the use of rare earth doped silica glass prepared by the sol-gel technique as a gamma radiation detector. We obtain a glass material doped with rare earth ions in a high local symmetry, in contrast to the low symmetry found in glasses produced by conventional melting methods and technologies. The behavior of the luminescence spectra of the excited states of rare earth indicates a strong dependence with gamma radiation doses, where the magnetic dipole transition 5D0-->7F1 of the Eu3+ ions presents an huge enhancement of 900% for irradiation doses up to 400 Gy.

Conducting polymer/silicon heterojunction diode for gamma radiation detection.

In this work, alternative heterojunction devices to be used for gamma-radiation detection are presented. The high quality silicon/polyaniline heterostructures use polyaniline thin films as an active part of the device structure. Polyaniline thin films 40 nm thick were deposited onto silicon substrates (n-type, <100>, 1 ohm x cm) using the spin-coating technique from soluble polyaniline. The devices present excellent electrical characteristics, with a rectification ratio of 60,000 at +/- 1.0 V, reverse currents in the order of a few nA and ideality factor approximately 2. These electrical characteristics indicate great potential for their use in sensor applications. The heterojunction diode is very sensitive to gamma radiation in the dose range of 0-7000 Gy, presenting a linear response in the forward and reverse bias. The excellent electrical characteristics, together with the linear response with the dose strongly suggest the application of this device for spectrometry or dosimetry of low and high doses of gamma ray radiation.

Nonlinear-optical properties of a poly(vinyl alcohol)-polyaniline interpenetrating polymer network.

The nonlinear-optical properties of a semi-interpenetrating polymer network of poly(vinyl alcohol) glutaralde-hyde-polyaniline were studied. Large (>/=10(-12) cm(2)/W) and fast (<50 ps) refractive optical nonlinearites were observed. The potential of this novel material for photonic applications is evaluated.