Microstructural evolution of Au/TiO2 nanocomposite films: The influence of Au concentration and thermal annealing

Nanocomposite thin films consisting of a dielectric matrix, such as titanium oxide (TiO2), with embedded gold (Au) nanoparticles were prepared and will be analysed and discussed in detail in the present work. The evolution of morphological and structural features was studied for a wide range of Au concentrations and for annealing treatments in air, for temperatures ranging from 200 to 800 °C. Major findings revealed that for low Au atomic concentrations (at.%), there are only traces of clustering, and just for relatively high annealing temperatures, T ≥ 500 °C. Furthermore, the number of Au nanoparticles is extremely low, even for the highest annealing temperature, T = 800 °C. It is noteworthy that the TiO2 matrix also crystallizes in the anatase phase for annealing temperatures above 300 °C. For intermediate Au contents (5 at.% ≤ CAu ≤ 15 at.%), the formation of gold nanoclusters was much more evident, beginning at lower annealing temperatures (T ≥ 200 °C) with sizes ranging from 2 to 25 nm as the temperature increased. A change in the matrix crystallization from anatase to rutile was also observed in this intermediate range of compositions. For the highest Au concentrations (> 20 at.%), the films tended to form relatively larger clusters, with sizes above 20 nm (for T ≥ 400 °C). It is demonstrated that the structural and morphological characteristics of the films are strongly affected by the annealing temperature, as well as by the particular amounts, size and distribution of the Au nanoparticles dispersed in the TiO2 matrix.

Evolution of the functional properties of titanium–silver thin films for biomedical applications: Influence of in-vacuum annealing

In this work, the thermal stability of TiAgx thin films, deposited by magnetron sputtering, was evaluated, envisaging their application in biomedical devices, namely as electrodes for biosignal acquisition. Based on the composition and microstructural characterization, a set of four representative TiAgx thin films was selected in order to infer whether they are thermally stable in terms of functional properties. In order to achieve this purpose, the structural and morphological evolution of the films with annealing temperature was correlated with their electrical, mechanical and thermal properties. Two distinct zones were identified and two samples from each zone were extensively analysed. In the first zone (zone I), Ti was the main component (Ti-rich zone) while in the second, zone II, the Ag content was more significant. The selected samples were annealed in vacuum at four different temperatures up to 500 oC. For the samples produced within zone I, small microstructural changes were observed due to the recrystallization of the Ti structure and grain size increment. Also, no significant changes were observed with annealing temperature regarding the f l ’ functional properties, being thermally stable up to 500 oC. For higher Ag contents (zone II) the energy supplied by thermal treatments was sufficient to activate the crystallization of Ti-Ag intermetallic phases. A strong increase of the grain size of these phases was also reported. The structural and morphological organization proved to be determinant for the physical responses of the TiAgx system. The hardness and Y g’s modulus were significantly improved with the formation of the intermetallic phases. The silver addition and annealing treatments also played an important role in the electrical conductivity of the films, which was once again improved by the formation of Ti-Ag phases. The thermal diffusivity of the films was practically unchanged with the heat-treatment. This set of results shows that this intermetallic-like thin film system has good thermal stability up to high temperatures (as high as 500 oC), which in case of the highest Ag content zone is particularly evident for electrical and mechanical properties, showing an important improvement. Hardness increases about three times, while resistivity values become half of those from the lowest Ag contents zone. These set of characteristics are consistent with the targeted applications, namely in terms of biomedical sensing devices.

Multifunctional Ti–Me (Me=Al, Cu) thin film systems for biomedical sensing devices

Ti-Me binary intermetallic thin films based on a titanium matrix doped with increasing amounts of Me (Me = Al, Cu) were prepared by magnetron sputtering (under similar conditions), aiming their application in biomedical sensing devices. The differences observed on the composition and on the micro(structural) features of the films, attributed to changes in the discharge characteristics, were correlated with the electrical properties of the intermetallic systems (Ti-Al and Ti-Cu). For the same Me exposed areas placed on the Ti target (ranging from 0.25 cm2 to 20 cm2) the Cu content increased from 3.5 at.% to 71.7 at.% in the Ti-Cu system and the Al content, in Ti-Al films, ranged from 11 to 45 at.%. The structural characterization evidenced the formation of metastable Ti-Me intermetallic phases for Al/Ti atomic ratios above 0.20 and for Cu/Ti ratios above 0.25. For lower Me concentrations, the effect of the α-Ti(Me) structure domains the overall structure. With the increase amount of the Me into Ti structure a clear trend for amorphization was observed. For both systems it was observed a significant decrease of the electrical resistivity with increasing Me/Ti atomic ratios (higher than 0.5 for Al/Ti atomic ratio and higher than 1.3 for Cu/Ti atomic ratio). Although similar trends were observed in the resistivity evolution for both systems, the Ti-Cu films presented lower resistivity values in comparison to Ti-Al system.

Desenvolvimento de um Posto de Carregamento Lento com BMS e Interface com o Cockpit para o CEPIUM

Dissertação de mestrado integrado em Engenharia Eletrónica Industrial e de Computadores

Desenvolvimento de um protótipo didático de uma máquina de corte de pedra por fio diamantado

Dissertação de mestrado integrado em Engenharia Mecânica

Conversão sistemática do comportamento definido nos blocos funcionais da norma IEC 61 131-3 para autómatos finitos temporizados

Dissertação de mestrado integrado em Engenharia Mecânica

Frameworks no desenvolvimento de software: o caso da Elevation da PRIMAVERA BSS

Dissertação de mestrado integrado em Engenharia e Gestão de Sistemas de Informação

Comparação de diferentes métodos de avaliação da capacidade de carga de pavimentos rodoviários

Dissertação de mestrado integrado em Engenharia Civil

Desenvolvimento de um laboratório pedagógico de vias de comunicação na Universidade do Minho

Dissertação de mestrado integrado em Engenharia Civil

Estudo de betumes modificados recuperados de misturas produzidas pelo método húmido e pelo método seco

Dissertação de mestrado integrado em Engenharia Civil

Prevalência de dislipidemias em adultos da demanda laboratorial de Salvador, Brasil

OBJETIVO: Determinar a prevalência das dislipidemias em adultos da demanda laboratorial não-hospitalar da cidade de Salvador (BA). MÉTODOS: Casuística procedente de amostra probabilística de 25% dos laboratórios não-hospitalares da cidade que usavam o método enzimático para dosagem dos lípides séricos e controle de qualidade da Sociedade Brasileira de Patologia Clínica (93% do total); LDL estimado pela fórmula de Friedewald. Sorteados os meses ímpares de 1995 para o estudo. Critérios para dislipidemias, em mg/dl: colesterol ³240; LDL ³160; HDL <35 e triglicérides ³200. Análise: prevalências, seus intervalos de confiança (IC) a 95% e qui-quadrado (chi²). RESULTADOS: Excluídos uma recusa e um laboratório que arquivava laudos só por 3 meses, foram analisados dados de 24 dos 26 laboratórios amostrados. Dos 7392 adultos, 65,5% eram mulheres. Prevalências estimadas e valores dos IC a 95% para homens, foram: hipercolesterolemia =24,0% (20,5; 27,5); LDL elevado =26,1 (22,4; 29,3); HDL baixo =15,9 (14,2; 17,8) e hipertrigliceridemia =27,6 (25,7; 29,5). Para mulheres: hipercolesterolemia =30,0 (27,8; 32,2), LDL elevado =33,1 (30,8; 35,4); HDL baixo =8,0 (7,1; 8,9) e hipertrigliceridemia =30,4 (29,0; 31,4). Todas as prevalências diferiram significantemente inter-gênero (p, 0,05 a p<0,001). Também foram mais freqüentes nas mulheres os níveis indesejáveis do colesterol e LDL. CONCLUSÃO: As dislipidemias são importante fator de risco para aterosclerose na demanda laboratorial de Salvador em ambos os gêneros. Os resultados subsidiam os médicos para incentivar mudanças no estilo de vida que conduzam seus pacientes a níveis lipídicos desejáveis.

Prevalência de dislipidemias na demanda laboratorial de três diferentes prestadores de assistência

OBJETIVO: Detectar diferenças nas prevalências das dislipidemias em adultos da demanda laboratorial de três diferentes prestadores de assistência médica, em Salvador, 1995. MÉTODOS: Estudo seccional, clínico epidemiológico, baseado em resultados das dosagens de lípides séricos de uma amostra probabilística de 25% dos 104 laboratórios que usavam o mesmo método de dosagem e o mesmo padrão para controle de qualidade. O critério de dislipidemia foi o do II Consenso Brasileiro de Dislipidemias para adultos. Os resultados foram agrupados conforme procedência: Sistema Único de Saúde (SUS), convênios (C) e seguros privados + particulares (SP). Análise: prevalência com intervalos de confiança (IC) a 95%, e teste do chi². RESULTADOS: Dos 5.464 adultos com menção da procedência, 14,8% foram do SUS, 31,6% dos C e 53,6% dos S+P. As mais elevadas prevalências de hipercolesterolemia - 28,0% (IC 24,0; 32,0) e de LDL-c elevado - 30,4% (IC 27,6; 33,2) foram detectadas no grupo C. No grupo S+P concentraram-se as maiores prevalências de HDL-c anormal - 12,3% (IC 10,0; 13,8) e hipertrigliceridemia - 17,8% (IC 16,3; 19,3). Quase todas as diferenças entre as prevalências foram estatisticamente significantes, favoráveis às taxas mais baixas do SUS. CONCLUSÃO: O melhor perfil lipídico do grupo SUS sugere diferenças sociais nas prevalências das dislipidemias. Para os três prestadores de assistência, a prevalência do HDL-c <35mg/dL foi baixa quando comparada às das demais dislipidemias. Os resultados podem ser inferidos para a prática médica dos respectivos prestadores de assistência e indicam a necessidade de informação e de orientação dos usuários para redução das dislipidemias e melhoria do estilo de vida.

Contributos dos ambientes digitais online para a aprendizagem em contexto de atividades de apoio extraescolar

Dissertação de mestrado em Ciências da Educação (área de especialização em Tecnologia Educativa)

Effects of lisinopril on experimental ischemia in rats. Influence of infarct size

OBJECTIVE - Angiotensin-converting enzyme inhibitors (ACEIs) have gained importance in preventing or attenuating the process of ventricular remodeling after myocardial infarction. The significance of infarct size in regard to the response to ACEIs, however, is controversial. This study aimed to analyze the effects of lisinopril on mortality rate, cardiac function, degree of cardiac hypertrophy and fibrosis in rats with different infarct sizes. METHODS - Lisinopril (20 mg/kg/day) dissolved in drinking water was administered to rats immediately after coronary artery occlusion. After being sacrificed, the infarcted animals were divided into two groups: one group of animals with small infarcts (< 40% of the left ventricle) and another group of animals with large infarcts (> 40% of the left ventricle). RESULTS - The mortality rate was 31.7% in treated rats and 47% in the untreated rats. There was no statistical difference between the groups with small and large infarcts in regard to myocardial concentration of hydroxyproline. In small infarcts, the treatment attenuated the heart dysfunction characterized by lower levels of blood pressure and lower values of the first derivative of pressure and of the negative derivative of pressure. The degree of hypertrophy was also attenuated in small infarcts. In regard to large infarcts, no differences between the groups were observed. CONCLUSION - Treatment with the ACEIs had no effect on mortality rate and on the amount of fibrosis. The protective effect of lisinopril on heart function and on the degree of hypertrophy could only be detected in small infarcts

Effects of losartan on ventricular remodeling in experimental infarction in rats

OBJECTIVE: To evaluate the effects of losartan on ventricular remodeling and on survival after myocardial infarction in rats. METHODS: After surgical occlusion of left coronary artery, 84 surviving male Wistar rats were divided into two groups: LO treated with losartan (20mg/kg/day, n=33) and NT (n=51), without medication. After 3 months, we analyzed mortality; ventricular to body mass ratio (VM /BM); myocardial hydroxyproline concentration (HOP); isovolumetric pressure, +dp/dt, -dp/dt, and diastolic volume/left ventricle mass ratio (VO/LV). RESULTS: Mortality was: LO = 22%, and NT = 47% (p<0.05). Ventricular mass,(VM/BM, mg/g) was 4.14 ± 0.76 and 3.54±0.48, in the NT and LO groups, respectively (p<0.05). HOP (median) was 4.92 upsilong/mg in the LO and 5.54 upsilong/g in the NT group (p>0.05). The V0/LV values (median) were 0.24 mL/g in group LO and 0.31 mL/g in group NT (p<0.05) compared to NT group. There were no differences between the groups for +dp/dt and -dp/dt parameters. CONCLUSION: 1- The use of losartan myocardial infarction causes an attenuation of ventricular remodeling, bringing about an increased survival, an attenuation of ventricular hypertrophy and dilation, and an improvement of the isovolumetric pressure; 2- the treatment does not modify the myocardial collagen concentration.