Resumo O objetivo deste trabalho foi avaliar a prevalência de Uso Problemático de Internet (UPI) entre adolescentes (N = 466) e sua possível associação com problemas emocionais e qualidade de vida. Estudantes (Midade = 12,8; DP = 1,9) de cinco escolas públicas de um município do Estado de São Paulo participaram deste estudo e preencheram quatro instrumentos: Questionário sociodemográfico; Internet Addiction Test (IAT); Depression Anxiety Stress Scale (DASS -21) e Pediatric Quality of Life Inventory (PedsQL). Não se encontrou relação significante entre a frequência e intensidade dos sintomas de depressão, ansiedade e estresse em comparação com aqueles que não possuem problemas com o uso da internet. Em relação à qualidade de vida, também não foram observadas diferenças entre os grupos. Entretanto, aqueles que possuíam uma percepção de uso de internet prejudicial a suas atividades cotidianas apresentaram maior pontuação média do instrumento IAT e maiores níveis de estresse. Esses achados indicam que a percepção do uso do uso de internet foi a principal variável associada com sintomas emocionais.

Abstract This study aimed to evaluate the prevalence of Problematic Internet Use (PIU) among adolescents (N = 466) and its possible association with emotional problems and quality of life. Students (Mage = 12.8 years; SD = 1.9) from five public schools in a city in the State of São Paulo participated in this study and completed four instruments: a sociodemographic questionnaire; Internet Addiction Test (IAT); Depression Anxiety Stress Scale (DASS-21) and Pediatric Quality of Life Inventory (PedsQL). No significant differences were detected about the frequency and intensity of symptoms of depression, anxiety, and stress compared to those who did not have problems with the use of the Internet. No differences were observed between the groups in respect of quality of life either. However, those individuals who felt that their internet use impaired their daily activities presented higher average IAT scores and higher levels of stress. These findings indicated that the perception of internet use was the main variable associated with emotional symptoms.

Resumen Este estudio tuvo como objetivo evaluar la prevalencia del Uso Problemático de Internet (UPI) entre adolescentes (N = 466) y su posible asociación con problemas emocionales y calidad de vida. Los estudiantes (Midade = 12,8; DS = 1,9) de cinco escuelas públicas en una ciudad de la provincia de São Paulo participaron en este estudio y completaron cuatro instrumentos: un cuestionario sociodemográfico; Internet Addiction Test (IAT); Depression Anxiety Stress Scale (DASS-21) y Pediatric Quality of Life Inventory (PedsQL). No se detectaron diferencias significativas sobre la frecuencia y la intensidad de los síntomas de depresión, ansiedad y estrés en comparación con aquellos que no tuvieron problemas con el uso de Internet. Tampoco se observaron diferencias entre los grupos con respecto a la calidad de vida. Sin embargo, aquellas personas que sintieron que su uso de Internet perjudicaba sus actividades diarias presentaron escores promedios más altos de IAT y niveles más altos de estrés. Estos hallazgos indicaron que la percepción del uso de Internet fue la principal variable asociada a los síntomas emocionales.

The crystallization kinetics of ceramics composed by Bi2O3-ZnO-Nb2O5 (BZN) was studied using non-isothermal method. The BZN samples were prepared by the polymeric precursors method. Phase evolution was evaluated by X ray diffraction and the thermal events were evaluated by differential scanning calorimetry (DSC). The crystallization of BZN occurs from 500 to 700 °C, which corresponds to a secondary event in DSC curves. The principal exothermic event in these curves is related to the decomposition of organic material and was isolated from the crystallization peak by deconvolution into two Gaussian curves. Those related to crystallization processes were evaluated in terms of crystallized fraction. Kinetic parameters were determined from Ligero (E = 242 ± 7) kJ.mol-1 and Kissinger (E = 241 ± 24) kJ.mol-1 methodologies and they are very close. The activation energy Ea = (241 ± 24) kJ.mol-1 and (242 ± 7) kJ.mol-1 (by the Kissinger and Ligero methodology, respectively), frequency factor k0 =10(13).s-1 and exponent of Avrami n = (1.3 ± 0.1) were determined. The n value indicates that the crystallization is diffusion controlled, with decreasing nucleation rate. Scanning electronic microscopy showed the presence of nanoparticulated powder.

Bismuth zinc niobate pyrochlores Bi1.5ZnNb1.5O7 (alpha-BZN), and Bi2(Zn1/3Nb2/3)2O 7 (beta-BZN) have been synthesized by chemical method based on the polymeric precursors. The pyrochlore phase was investigated by differential scanning calorimetry, infrared spectroscopy, and X ray diffraction. Powder and sintered pellets morphology was examined by scanning electron microscopy. The study of alpha-BZN phase formation reveals that, at 500 °C, the pyrochlore phase was already present while a single-phased nanopowder was obtained after calcination at 700 °C. The crystallization mechanism of the beta-BZN is quite different, occurring through the crystallization of alpha-BZN and BiNbO4 intermediary phases. Both compositions yielded soft agglomerated powders. alpha-BZN pellets, sintered at 800 °C for 2 hours, presented a relative density of 97.3% while those of beta-BZN, sintered at 900 °C for 2 hours, reached only 91.8%. Dielectric constant and dielectric loss, measured at 1 MHz, were 150 and 4 x/10-4 for a-BZN, and 97 and 8 x 10-4 for beta-BZN.