Marisa Pereira

Effect of Pt bottom electrode texture selection on the tetragonality and physical properties of Ba0.8Sr0.2TiO3 thin films produced by pulsed laser deposition

The effect of platinum (Pt) bottom electrode texture on the tetragonality, dielectric, ferroelectric, and polarization switching response of pulsed laser deposited Ba0.8Sr0.2TiO3 (BST) thin films has been studied. The x-ray diffraction and Raman analysis revealed the higher tetragonality of BST films when they were grown on higher (111) textured Pt layer. The properties like dielectric permittivity, polarization, switching time, and leakage currents were found to be correlated to tetragonality and orientation of the BST films. The polarization current was observed to be higher in BST films on Pt epitaxial layer and it exhibits exponential dependence on the electric field. The voltage-current measurements displayed Ohmic behavior of leakage current irrespective of Pt texture for low voltages (up to 1 V), whereas at higher voltages the conduction mechanism was found to be dependent on texture selection of bottom Pt electrode.

Pneumonia tuberculosa: um estudo de 59 casos confirmados microbiologicamente

OBJECTIVE To study the clinical, epidemiological, radiographic and endoscopic features of individuals with tuberculous pneumonia. METHODS We evaluated 2,828 consecutive tuberculosis patients treated at a public health center between December of 2005 and February of 2007. Of those, 59 (2.1%) had pulmonary involvement consistent with fistula between a lymph node and a bronchus. RESULTS Of the 59 patients studied, 43 (73%) were between 20 and 50 years of age, 31 (53%) were male, and 28 (47%) were Black. The most common symptoms were cough (in 100%), fever (in 88%), expectoration (in 81%), and weight loss (in 40%). Comorbidities were reported in 35 cases (59%), the most common being HIV infection (in 20%) and diabetes (in 15%). On chest X-rays, consolidation was observed, predominantly in the upper lobes (in 68%). The diagnostic confirmation (identification of AFB) was made through the sputum smear microscopy in the majority of the cases and by bronchoscopy (BAL examination or bronchial biopsy) in the remainder. Bronchial lesions were clearly indicative or suggestive of fistula in three cases and five cases, respectively. CONCLUSIONS Tuberculous pneumonia presents as acute respiratory infection, initiating with a dry cough that is followed by fever. Chest X-rays show alveolar consolidation. In most cases, tuberculous pneumonia was accompanied by at least one comorbid condition, the most common being HIV infection, and the etiological diagnosis was made through sputum smear microscopy for AFB. Bronchoscopy findings were indicative of bronchial fistula in eight cases (13%).OBJECTIVE: To study the clinical, epidemiological, radiographic and endoscopic features of individuals with tuberculous pneumonia. METHODS: We evaluated 2,828 consecutive tuberculosis patients treated at a public health center between December of 2005 and February of 2007. Of those, 59 (2.1%) had pulmonary involvement consistent with fistula between a lymph node and a bronchus. RESULTS: Of the 59 patients studied, 43 (73%) were between 20 and 50 years of age, 31 (53%) were male, and 28 (47%) were Black. The most common symptoms were cough (in 100%), fever (in 88%), expectoration (in 81%), and weight loss (in 40%). Comorbidities were reported in 35 cases (59%), the most common being HIV infection (in 20%) and diabetes (in 15%). On chest X-rays, consolidation was observed, predominantly in the upper lobes (in 68%). The diagnostic confirmation (identification of AFB) was made through the sputum smear microscopy in the majority of the cases and by bronchoscopy (BAL examination or bronchial biopsy) in the remainder. Bronchial lesions were clearly indicative or suggestive of fistula in three cases and five cases, respectively. CONCLUSIONS: Tuberculous pneumonia presents as acute respiratory infection, initiating with a dry cough that is followed by fever. Chest X-rays show alveolar consolidation. In most cases, tuberculous pneumonia was accompanied by at least one comorbid condition, the most common being HIV infection, and the etiological diagnosis was made through sputum smear microscopy for AFB. Bronchoscopy findings were indicative of bronchial fistula in eight cases (13%).

Structural and Electrical Properties of Nanostructured Ba0.8Sr0.2TiO3 Films Deposited by Pulsed Laser Deposition

Barium Strontium Titanate Ba0.8Sr0.2TiO3 (BST) thin films have been deposited on Pt/Ti/SiO2/Si substrates by pulsed laser deposition technique. The X-ray diffraction (XRD) shows that the films crystallize in a perovskite phase. XRD and Atomic Force Microscopy (AFM) characterization reveal that the grains are nano-sized. Rutherford Backscattering Spectrometry (RBS) analysis shows the stoichiometry of the films to be close to the stoichiometry of the target. The Raman spectroscopy shows that the films exhibit the tetragonal structure by the presence of the Raman active modes at 301 cm-1 and 729 cm-1, at room temperature. Leakage current measurements of Au/ Ba0.8Sr0.2TiO3/Pt capacitors have been done, at room temperature, to investigate the conduction mechanisms of the films. We found that there are two different conduction regions in the capacitors, namely, an ohmic behavior at low voltages and a Schottky emission mechanism at high voltages. The Schottky barrier height has been estimated to be 0.99 eV.