Structural characterization and Curie temperature determination of a sodium strontium niobate ferroelectric nanostructured powder

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Physical Vapor Deposited Thin Films of Lignins Extracted from Sugar Cane Bagasse: Morphology, Electrical Properties, and Sensing Applications

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Spray layer-by-layer films based on phospholipid vesicles aiming sensing application via e-tongue system

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Ultrathin films of lignins as a potential transducer in sensing applications involving heavy metal ions

Lignins extracted from sugar cane bagasse using different alcohols in the organosolv-CO(2) supercritical pulping process have been applied in the fabrication of ultrathin films through the Langmuir-Blodgett technique. Langmuir films were characterized by surface pressure versus mean molecular area (Pi-A) isotherms to exploit the sensitivity of nanostructured lignin films to metallic ions (Cu(2+), Cd(2+) and Pb(2+)). The Pi-A isotherms were shifted to larger molecular areas when heavy metal ions are present into the subphase, which might be related to electrostatic repulsions between metallic ions entrapped within the lignin molecular structure. Taking the advantage of metal incorporation, Langmuir monolayers were transferred onto solid substrates forming Langmuir-Blodgett (LB) films to be used as a transducer in an "electronic tongue" system to detect Cu(2+) in aqueous solution below threshold standard established by the Brazilian regulation. Both techniques impedance spectroscopy and electrochemistry have been used in these experiments. Complementary, Fourier transform infrared (FTIR) spectroscopy recorded for LB films before and after soaking into Cu(2+) aqueous solution revealed an interaction between the lignin phenyl groups and the metallic ion. (C) 2007 Elsevier B.V.. All rights reserved.

Toward the Optimization of an e-Tongue System Using Information Visualization: A Case Study with Perylene Tetracarboxylic Derivative Films in the Sensing Units

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Indicadores cardiovasculares em repouso e durante um teste incremental em jovens do sexo masculino

O presente estudo comparou valores de glicemia, frequência cardíaca em repouso e durante exercício, além da composição corporal entre hipertensos e normotensos. A amostra foi composta por 32 jovens do sexo masculino, com média de idade de 22,6 anos. Inicialmente, aferiu-se a pressão arterial, para divisão em dois grupos: hipertensos e normotensos. Posteriormente foram mensurados, glicemia em jejum, impedância bioelétrica, antropometria, e a frequência cardíaca no repouso, durante o teste de esforço máximo e na fase de recuperação. A análise estatística foi composta pelo teste t- Student e análise de variância para medidas repetidas two-way, entre os grupos. O valor de significância adotado foi p = 0,05. Os dados analisados mostraram que indivíduos hipertensos apresentam maiores índices metabólicos e valores hemodinâmicos do que indivíduos normotensos, sendo estes indicadores de risco cardiovascular.

Exploiting Distinct Molecular Architectures of Ultrathin Films Made with Iron Phthalocyanine for Sensing

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Sensor array made with nanostructured films to detect a phenothiazine compound

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Prevalência de doença arterial obstrutiva periférica (DAOP) e alterações sensoriais em pacientes diabéticos tipo 2: impacto da DAOP sobre a qualidade de vida, nível de atividade física e composição corporal

Diabetes Mellitus (DM) affected approximately 171 million people in the world in the year 2000 as described by the World Health Organization (WHO). Because DM is a multisystem disease it can cause several complications especially those related to the cardiovascular system. The Peripheral Arterial Disease (PAD) of the lower limbs and the Diabetic Distal Symmetric Polyneuropathy (DDSP) can affect the DM patient causing consequences as the diabetic foot and eventually amputations. The main objective of this study was to determine the prevalence of PAD and sensorial impairment in 73 type 2 DM (DM2) patients and also assess the impact of PAD on quality of life, level of physical activity and body composition. For clinical assessment it was used: the ankle-brachial index (ABI); quantitative sensorial test for tactile sensibility (ST), pain (SD), vibration (SV); Achilles tendon reflex (RA); quality of life questionnaire (SF-36); modified Baecke physical activity questionnaire and bioelectric impedance. Prevalence of PAD in the studied population was 13.7%. ABI was inversely correlated to age (p=0,03; rhô= -0,26), diabetes duration (p=0,02; rhô= -0,28) and blood pressure (p= 0,0007; rhô= -0,33). There were lower scores for physical health summary on the SF-36 in DM2 patients; however, the presence of PAD predominantly mild did not significantly impact quality of life, body composition or physical activity level assessed by questionnaire. Fourteen patients (19.2%) present bilateral and symmetrical alterations in two or more sensorial tests compatible to DPN diagnosis. Abnormalities in ST, SD and SV were present in 27.3%, 24.6% and 8.2%; respectively. There was association of results from ST abnormalities with RA and mainly with SD, suggesting the importance of 10g monofilament use in DM2 routine assessment. In conclusion, the prevalence of PAD in subclinical DM2 was slightly higher compared to the general population and in agreement to previously published data in DM patients. The PAD severity was predominantly mild and still without repercussion on quality of life and body composition. Our study demonstrated a significant prevalence of both PAD and DPN in DM2 without previous diagnosis of these complications and indicates the necessity of early preventive and therapeutic interventions for this population

Kinetics of interface state-limited hole injection in alpha-naphthylphenylbiphenyl diamine (alpha-NPD) thin layers

Injection-limited operation is identified in thin-film, alpha-NPD-based diodes. A detailed model for the impedance of the injection process is provided which considers the kinetics of filling/releasing of interface states as the key factor behind the injection mechanism. The injection model is able to simultaneously account for the steady-state, current-voltage (J-V) characteristics and impedance response. and is based on the sequential injection of holes mediated by energetically distributed surface states at the metal-organic interface. The model takes into account the vacuum level offset caused by the interface dipole, along with the partial shift of the interface level distribution with bias voltage. This approach connects the low-frequency (similar to 1 Hz) capacitance spectra, which exhibits a transition between positive to negative values, to the change in the occupancy of interface states with voltage. Simulations based on the model allow to derive the density of interface states effectively intervening in the carrier injection (similar to 5 x 10(12) cm(-2)), which exhibit a Gaussian-like distribution. A kinetically determined hole barrier is calculated at levels located similar to 0.4 eV below the contact work function. (C) 2008 Elsevier B.V. All rights reserved.

Transducer Loading Effect on the Performance of PZT-Based SHM Systems

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Influence of degradation on the electrical conduction process in ZnO and SnO2-based varistors

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structural integrity identification based on smart materials and neural networks

This paper presents a non-model based technique to detect, locate, and characterize structural damage by combining the impedance-based structural health monitoring technique with an artificial neural network. The impedance-based structural health monitoring technique, which utilizes the electromechanical coupling property of piezoelectric materials, has shown engineering feasibility in a variety of practical field applications. Relying on high frequency structural excitations (typically>30 kHz), this technique is very sensitive to minor structural changes in the near field of the piezoelectric sensors. In order to quantitatively assess the state of structures, two sets of artificial neural networks, which utilize measured electrical impedance signals for input patterns, were developed. By employing high frequency ranges and by incorporating neural network features, this technique is able to detect the damage in its early stage and to estimate the nature of damage without prior knowledge of the model of structures. The paper concludes with an experimental example, an investigation on a massive quarter scale model of a steel bridge section, in order to verify the performance of this proposed methodology.

Structural Health Monitoring in Smart Structures Through Time Series Analysis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Investigação da estabilidade térmica e das propriedades elétricas do TiO2 em função da dopagem com Ce(SO4)2

The metalic oxides have been studies due to differents applications as materials semiconductor in solar cells, catalysts, full cells and, resistors. Titanium dioxide (TiO2) has a high electric conductivity due to oxygen vacancies. The Ce(SO4)2.2H2O doped samples TiO2 and TiO2 pure was obtained sol-gel process, and characterized by X-ray diffractometry,thermal analysis, and impedance spectroscopy. The X-ray diffraction patterns for TiO2 pure samples shows at 700°C anatase phase is absent, and only the diffraction peaks of rutile phase are observed. However, the cerium doped samples only at 900°C rutile in the phase present with peaks of cerium dioxide (CeO2). The thermal analysis of the TiO2 pure and small concentration cerium doped samples show two steps weight loss corresponding to water of hydration and chemisorbed. To larger concentration cerium doped samples were observed two steps weight loss in the transformation of the doped cerium possible intermediate species and SO3. Finally, two steps weight loss the end products CeO2 and SO3 are formed. Analyse electric properties at different temperatures and concentration cerium doped samples have been investigated by impedance spectroscopy. It was observed that titanium, can be substituted by cerium, changing its electric properties, and increased thermal stability of TiO2 anatase structure