Cristalização de biomateriais vitrocerâmicos e mineralização em meio fisiológico simulado

Doutoramento em Ciência e Tecnologia dos MateriaisSão propostos novos modelos teóricos, que generalizam o modelo clássico de Avrami-Nakamura, apropriados para a cinética de nucleação e de crescimento em regime transiente, e/ou com sobreposição entre o estágio de nucleação e o de crescimento. Foram efectuadas simulações com base em resultados da literatura, reportados para o dissilicato de lítio. Foram examinadas as limitações dos métodos correntemente usados para obter estimativas de parâmetros cinéticos, com base em resultados de ATD. Desenvolveram-se e investigaram-se vidros e materiais vitrocerâmicos susceptíveis de aplicação biomédica com a formulação molar 0.45SiO2– (0.45-x)MgO–xK2O–0.1(3CaO⋅P2O5) (0 ≤ x ≤ 0.090), preparados mediante a substituição de Mg2+ por K+. A cristalização das fritas de vidro foi estudada por ATD, DRX e SEM. Foram detectados picos exotérmicos correspondentes à cristalização de fosfato (cristalização em volume) do tipo whitlockite Ca9MgK(PO4)7 a aproximadamente 900ºC, e de forsterite (Mg2SiO4) acompanhada de alguma diopside (CaMgSi2O6; cristalização superficial) a temperaturas superiores. A microestrutura predominante da fase fosfato é do tipo placa, aparentando cristalizar por um mecanismo de crescimento bidimensional. Foi usada espectroscopia de impedâncias para monitorizar a cristalização em condições em que os ensaios de ATD ou de DSC revelam limitações, recorrendo a alterações significativas de propriedades eléctricas associadas à cristalização da fase de fosfato. Os vidros e vidros cerâmicos desenvolvidos revelaram bioactividade em meio acelular in vitro, desenvolvendo camadas apatíticas em SBF. A morfologia, composição e aderência da camada de apatite pôde ser modulada com base na substituição parcial de Mg2+ por K+. Foram depositadas camadas de apatite sobre vidros ceramizados (x=0 e 0.09), em SBF a 37ºC. A adesão da camada de apatite foi quantificada pela técnica de indentação deslizante tendo sido relacionada com o tempo de imersão em SBF, com a composição e estrutura da fase vítrea, e com a morfologia da fase cristalina dos vidros cerâmicos. Foi investigada a estrutura de três vidros (x=0, 0.045 e 0.090) por MAS-RMN (29Si e 31P), verificando-se que nos vidros mais ricos em Mg, a participação da unidade estrutural Q3 é mais significativa, e que a estrutura dos vidros inclui grupos ortofosfato (PO4 3-) mais próximos de iões Ca2+ do que dos iões Mg2+, sendo estes incorporados preferencialmente na rede de silicato. A substituição parcial de Mg2+ por K+ permitiu ajustar a cristalização dos materiais vitrocerâmicos e modular a bioactividade pretendida. Resultados de FTIR revelaram precipitação de fosfato octacálcico (Ca8H2(PO4)6⋅5H2O) no vidro sem K, enquanto que a morfologia da camada adquire a forma de hemisférios parcialmente sobrepostos, espalhados sobre a superfície. Os vidros com K apresentam uma camada de hidroxiapatite acicular, cuja cristalinidade e espessura de agulhas tende a aumentar com o teor de K.We propose new theoretical models, which generalize the classical Avrami-Nakamura models. These models are suitable to describe the kinetics of nucleation and growth in transient regime, and/or with overlapping of nucleation and growth. Simulations and predictions were performed for lithium disilicate based on data reported in the literature. One re-examined the limitations of the models currently used to interpret DTA or DSC results, and to extract the relevant kinetic parameters. Glasses and glass-ceramics with molar formulation 0.45SiO2– (0.45-x)MgO–xK2O–0.1(3CaO⋅P2O5) (0 ≤ x ≤ 0.090) were prepared, crystallized and studied as potential materials for biomedical applications. Substitution of K+ for Mg2+ were used to prevent devritification on cooling, to adjust the kinetics of crystallization and to modify the in vitro behaviour of resulting biomaterials. The crystallization of the glass frits was studied by DTA, XRD and SEM. Exothermic peaks were detected corresponding to bulk crystallization of whitlockite-type phosphate, Ca9MgK(PO4)7, at approximately 900ºC, and surface crystallization of a predominant forsterite phase (Mg2SiO4) at higher temperatures. XRD also revealed the presence of diopside (CaMgSi2O6 in some samples. The predominant microstructure of the phosphate phase is of the plate-type, seemingly crystallizing by a 2-dimensional growth mechanism. Impedance spectroscopy revealed significant changes in electrical behaviour, associated to crystallization of the phosphate phase. This showed that electrical measurements can be used to study the kinetics of crystallization for cases when DTA or DSC experiments reveal limitations, and to extract estimates of relevant parameters from the dependence of crystallization peak temperature, and its width at half height. In vitro studies of glasses and glass-ceramics in acelular SBF media showed bioactivity and the development of apatite layers The morphology, composition and adhesion of the apatite layer could be changed by substitution of Mg2+ by K+. Apatite layers were deposited on the surface of glass-ceramics of the nominal compositions with x=0 and 0.09, in contact with SBF at 37ºC. The adhesion of the apatite layer was quantified by the scratch test technique, having been related with SBF’s immersion time, with composition and structure of the glass phase, and with the morphology of the crystalline phase of the glass-ceramics. The structure of three glasses (x=0, 0.045 and 0.090) were investigated by MAS-NMR ( 29Si and 31P), showing that the fraction of Q3 structural units increases with the contents of Mg, and that the structure of these glasses includes orthophosphate groups (PO4 3-) preferentially connected to Ca2+ ions. Mg2+ ions show preference towards the silicate network. Substitution of Mg2+ by K+ allowed one to change the bioactivity. FTIR data revealed octacalcium phosphate precipitation (Ca8H2(PO4)6⋅5H2O) in the glass without K, while the morphology of the layer acquires the shape of partially superimposed hemispheres, spread over the surface. The glasses with K present a layer of acicular hidroxyapatite, whose crystallinity and needles thickness tend to increase along with K content.FCT - SFRH/BD/1243/2000FSEIII Quadro Comunitário de Apoi

Congenital nuttaliasis of throughbred race horses in the State of Sâo Paulo

O artigo não apresenta resumo.The article has no abstract

Aesthetic Literacy in Young People’s and Adults’ Awareness From a Developmental Learning Perspective

In Brazilian schools, many teachers do not organize their teaching and students’ tasks and actions in a way that facilitates theoretical thinking based on the abstraction and generalization of the work content. Because many students struggle to accomplish the tasks and actions themselves, teachers guide them. Over time, the students begin to have more autonomy in executing the proposed activities, as they completed mental operations while learning. This article aims to investigate how young people’s and adults’ awareness of the countryside is formed based on visual elements and writing, facilitating an understanding of their reality. A didactic–formative experiment was performed based on the cultural–historical theory. The comic books produced by the participants allowed them to develop their overall thinking, moving from the abstract to the concrete. They also formed an awareness of reality, which allowed them to have greater autonomy in the production of these stories as a means of representation and transformation of reality

Microdureza de restaurações de resina composta expostas a agentes clareadores e coca cola

The purpose of this study was to evaluate the effect of 3 bleaching agents and a carbonated soft drink on composite resin restorations microhardness.. Forty fresh bovine incisive teeth were used. Next, they were embedded in acrylic resin, exception made to test facial surfaces, where standardized cavity preparations were carried out and restored composite resin ( Palfique Estelite –Toduyama). After samples were divided into 4 groups, baseline microhardness measurements were taken with a microdurometer (Future Tech – FM 700) ,that were used as experimental controls. Group 1: 10% carbamide peroxide (Whiteness Perfect – FGM) Group 2: soft drink Coca-Cola Group 3: 37% carbamide peroxide gel (Whiteness Super – FGM Group 4 35% hydrogen peroxide (Whiteness HP – FGM), Data were submitted to ANOVA and Tukey’s. Conclusions were that bleaching agents and Coca-Cola did not alter composite resin microhardness.O objetivo deste estudo foi avaliar os efeitos de três agentes clareadores e uma bebida carbonatada, à base de cola, sobre a microdureza de restaurações de resina composta. Foram utilizados quarenta dentes incisivos bovinos embutidos em resina acrílica, nas superfícies vestibulares foram realizados preparos cavitários padronizados e restaurados com resina composta (Palfique Estelite – Tokuyama). As amostras foram avaliadas em microdurômetro (Future Tech FM 700) após a divisão em quatro grupos, uma leitura inicial da microdureza serviu como controle do experimento. Grupo 1: peróxido de carbamida a 10% (Whiteness Perfect – FGM) Grupo 2: refrigerante Coca-Cola Grupo 3: peróxido de carbamida a 37% (Whiteness Super – FGM), Grupo 4: peróxido de hidrogênio a 35% (Whiteness HP – FGM). Os dados foram submetidos aos testes estatísticos ANOVA e Tukey. Conclui-se que os agentes clareadores e a Coca Cola não alteraram a microdureza da resina composta durante os 14 dias de desafio químico

A novel methodology to assess the relaxation rate of the intervertebral disc by increments on intradiscal pressure

Publicado em "Applied mechanics and materials, vol. 664 (2014) pp 379-383"The Intervertebral Disc (IVD) is subjected to several types of loading during daily routine events. However, the overloading on this structure induces higher Intradiscal Pressure (IDP), which could cause severe damage on its structure. This study describes a new approach to that allows monitorize and pressurize nuclear region of the IVD, with a cartilaginous endplate access, by the insertion of an external fluid, while a Motion Segment (MS-assembly composed by vertebra-disc-vertebra) is compressed at a physiological load. This methodology includes the use of a pneumatic structure that applies a certain pressure on the hydrostatic system, forcing a fluid to enter into the MS through a screw, with a drilled hollow along its entire length. Preliminary results indicated that this methodology presents high potential to efficiently pressurize the IVD, providing a useful tool to better understand the response of this structure under pressure.EC -European Commission(NMP-2009-SMALL-3-CP-FP 246351

A novel methodology for measurement of the intradiscal pressure and height disc variation of intervertebral disc under compression

The intervertebral disc (IVD) is subjected to several types of loading during daily routine events. However, the overloading on this structure induces higher intradiscal pressure (IDP), which could cause severe damage on its structure. This study describes a new approach to monitor IDP and determine the height disc variation by applying external pressure, while a motion segment (assembly composed by vertebra-disc-vertebra) compressed at a physiological load. This methodology includes the use of a pneumatic structure that applies a certain pressure on the hydrostatic system, forcing a fluid to enter into the motion segment, through a screw with a drilled hollow along its entire length with an internal bore. Preliminary results indicates these methodology presents high potential to efficiently pressurize the IVD, providing a useful tool to better understand the response of this structure under pressure

Associação entre diabetes e tuberculose: estudo caso controle

OBJETIVO Testar a associação entre diabetes e tuberculose. MÉTODOS Trata-se de estudo caso-controle, pareado por idade e sexo. Foram incluídos 323 casos novos de tuberculose com resultados positivos à baciloscopia. Os controles foram 323 sintomáticos respiratórios com baciloscopia negativa, oriundos dos mesmos serviços de saúde dos casos: ambulatórios de três hospitais de referência e seis unidades básicas de saúde responsáveis pelas notificações dos casos novos de tuberculose em Salvador, Bahia. A coleta de dados ocorreu entre 2008 e 2010. Os instrumentos utilizados foram entrevista estruturada, incluindo dados clínicos, glicemia capilar (em jejum ou pós-prandial) e o questionário CAGE para triagem de consumo abusivo de álcool. Foi realizada análise descritiva, exploratória e multivariada utilizando-se de regressão logística condicional. RESULTADOS A média de idade dos casos foi 38,5 (DP = 14,2) anos e dos controles, 38,5 (DP = 14,3) anos. Tanto entre os casos quanto entre os controles, a maioria (61%) dos indivíduos era do sexo masculino. Na análise univariada, houve associação entre ocorrência de diabetes e de tuberculose (OR = 2,37; IC95% 1,04–5,42), que permaneceu estatisticamente significante após ajuste pelos potenciais confundidores (OR = 3,12; IC95% 1,12–7,94). CONCLUSÕES A associação entre diabetes e tuberculose pode dificultar o controle da tuberculose, contribuindo para manutenção da elevada carga da doença. A situação demanda intensificação da detecção precoce de diabetes entre pessoas com tuberculose, na tentativa de maior efetividade das estratégias de controle da doença.OBJECTIVE To test the association between diabetes and tuberculosis. METHODS It is a case-control study, matched by age and sex. We included 323 new cases of tuberculosis with positive results for bacilloscopy. The controls were 323 respiratory symptomatic patients with negative bacilloscopy, from the same health services, such as: ambulatory cases from three referral hospitals and six basic health units responsible for the notifications of new cases of tuberculosis in Salvador, Bahia. Data collection occurred between 2008 and 2010. The instruments used were structured interview, including clinical data, capillary blood glucose (during fasting or postprandial), and the CAGE questionnaire for screening of abusive consumption of alcohol. Descriptive, exploratory, and multivariate analysis was performed using conditional logistic regression. RESULTS The average age of the cases was 38.5 (SD = 14.2) years and of the controls, 38.5 (SD = 14.3) years. Among cases and controls, most subjects (61%) were male. In univariate analysis we found association between the occurrence of diabetes and tuberculosis (OR = 2.37; 95%CI 1.04–5.42), which remained statistically significant after adjustment for potential confounders (OR = 3.12; 95%CI 1.12–7.94). CONCLUSIONS The association between diabetes and tuberculosis can hinder the control of tuberculosis, contributing to the maintainance of the disease burden. The situation demands increasing early detection of diabetes among people with tuberculosis, in an attempt to improve disease control strategies

An insight from the sea: provenance studies on Roman lead artefacts from the Arade River, Portimão (Portugal)

In the present study, 37 lead artefacts were characterised to identify possible lead sources allowing to establish trade fluxes concerning food and textile products during Roman times. These artefacts were uncovered by dredging works at the Arade River estuary (Portimão). The city of Portimão (Lusitania province) was an important harbour, where several fish-processing factories were installed, and Arade River provides major access to the hinterland, both displaying an important commercial activity during the Late Antiquity. The methodology includes the typological and chemical (elemental and Pb isotopes) characterisation of artefacts. Samples were divided into the following: (i) rectangular plaques with decorations in relief such as tridents, fishes, or palms leaf, an iconography known to be displayed in some African amphora handles; (ii) small plaques with one perforation and incised Roman numerals, probably related with textile products; and (iii) fishing net weights, smooth plaques of unknown functionality, and a small rectangular prismatic plaque, perhaps an ingot. Elemental analysis was performed by ICP-MS, and results were interpreted by multivariate statistical analysis, which suggested different processes to obtain raw materials, namely lead obtained by the reduction of litharge or smelting of silver-poor galena. Cluster analysis grouped most of samples with motif depictions, which were further analysed by MC-ICP-MS to determine Pb isotope ratios. The possible sources of lead were identified by combining archaeological data with the nearest Euclidean neighbours using a large database comprising the Iberian Peninsula and Mediterranean region. The Pb isotope signatures suggested lead sources located not only in the Iberian Peninsula but also in North Africa, evidencing a long-distance trade between those Roman provinces.info:eu-repo/semantics/publishedVersio