Enamel remineralization by fluoride-releasing materials: Proposal of a pH-cycling model

This study proposes a pH-cycling model for verifying the dose-response relationship in fluoride-releasing materials on remineralization in vitro. Sixty bovine enamel blocks were selected for the surface microhardness test (SMH 1). Artificial caries lesions were induced and surface microhardness test (SMH 2) was performed. Forty-eight specimens were prepared with Z 100, Fluroshield, Vitremer and Vitremer 1/4 diluted - powder/liquid, and subjected to a pH-cycling model to promote remineralization. After pH-cycling, final surface microhardness (SMH 3) was assessed to calculate percent recovery of surface microhardness (%SMH R). Fluoride present in enamel (μg F/mm 3) and in the pH-cycling solutions (μg F) was measured. Cross-sectional microhardness was used to calculate mineral content (ΔZ). There was no significant difference between Z 100 and control groups on analysis performed on - %SMH R, ΔZ, μ F and μ F/mm 3 (p>0.05). Results showed a positive correlation between %SMH R and μg F/mm 3 (r=0.9770; p=0.004), %SMH R and μg F (r=0.9939; p=0.0000001), DZ and μg F/mm 3 (r=0.9853; p=0.0002), ΔZ and μg F (r=0.9975; p=0.0000001) and between μg F/mm 3 and μg F (r=0.9819; p=0.001). The pH-cycling model proposed was able to verify in vitro dose-response relationship of fluoride-releasing materials on remineralization.

Numerical assessment of mass conservation on a MAC-type method for viscoelastic free surface flows

A numerical study of mass conservation of MAC-type methods is presented, for viscoelastic free-surface flows. We use an implicit formulation which allows for greater time steps, and therefore time marching schemes for advecting the free surface marker particles have to be accurate in order to preserve the good mass conservation properties of this methodology. We then present an improvement by using a Runge-Kutta scheme coupled with a local linear extrapolation on the free surface. A thorough study of the viscoelastic impacting drop problem, for both Oldroyd-B and XPP fluid models, is presented, investigating the influence of timestep, grid spacing and other model parameters to the overall mass conservation of the method. Furthermore, an unsteady fountain flow is also simulated to illustrate the low mass conservation error obtained.

Preconcentration and determination of metal ions from fuel ethanol with a new 2,2'-dipyridylamine bonded silica

A silica surface chemically modified with [3-(2,2'-dipyridylamine) propyl] groups was prepared, characterized, and evaluated for its metal ion preconcentration in fuel ethanol. To our knowledge, we are the first authors who have reported the present modification on silica gel surface. The material was characterized using infrared spectra, scanning electronic microscopy, and 13C and 29Si solid-state NMR spectra. Batch and column experiments were conducted to investigate for metal ion removal from fuel ethanol. The results showed that the Langmuir model describes the sorption equilibrium data of the metal ions in a satisfactory way. From the Langmuir isotherms, the following maximum adsorption capacities (in mmolg -1) were determined: 1.81 for Fe(III), 1.75 for Cr(III), 1.30 for Cu(II), 1.25 for Co(II), 1.15 for Pb(II), 0.95 for Ni(II), and 0.87 for Zn(II). Thermodynamic functions, the change of free energy (ΔG), enthalpy (ΔH), and entropy (ΔS) showed that the adsorption of metal ions onto Si-Pr-DPA was feasible, spontaneous, and endothermic. The sorption-desorption of the metal ions made possible the development of a preconcentration and quantification method of metal ions in fuel ethanol. © 2012 Elsevier Inc.

The effect of locked screw angulation on the biomechanical properties of the S.P.S. Free-Block plate

Objectives: Among the locked internal fixators is one denominated S.P.S. (Synthesis Pengo System) Free-Block, which was designed with a locking ring that allows the screw to be locked and positioned obliquely. Due to the paucity of biomechanical studies on this system, the present work aimed to evaluate the influence of locked screw angulation on the resistance of the S.P.S. Free--Block plate. Methods: Forty synthetic bone cylinders with 10 mm fracture gap were used. Forty seven-hole 3.5 mm stainless steel plates (two AO-like dynamic compression holes and five locked holes) were assembled according to the orientation of the locked screws: mono cortical screws were positioned at 90° to the long axis of the cylinder (Group 1), and monocortical screws were positioned at 70° to its cylinder long axis (Group 2). In both groups, AO-like dynamic compression hole screws were positioned bicortically and neutrally. For each group, six specimens were tested until failure, three in bending and three in compression, to determine the loads for fatigue testing. Subsequently, for each group, 14 specimens were tested for failure --seven by bending and seven in compression. Results: No significant failure differences were observed between Groups 1 and 2 under static-loading or fatigue test. Clinical significance: In a fracture gap model the orientation of the locked monocortical screws did not show any influence on the mechanical performance of the S.P.S. Free-Block to tests of axial compression and four-point bending. © Schattauer 2013.

Three-dimensional transient complex free surface flows: Numerical simulation of XPP fluid

In this paper we present a finite difference MAC-type approach for solving three-dimensional viscoelastic incompressible free surface flows governed by the eXtended Pom-Pom (XPP) model, considering a wide range of parameters. The numerical formulation presented in this work is an extension to three-dimensions of our implicit technique [Journal of Non-Newtonian Fluid Mechanics 166 (2011) 165-179] for solving two-dimensional viscoelastic free surface flows. To enhance the stability of the numerical method, we employ a combination of the projection method with an implicit technique for treating the pressure on the free surfaces. The differential constitutive equation of the fluid is solved using a second-order Runge-Kutta scheme. The numerical technique is validated by performing a mesh refinement study on a pipe flow, and the numerical results presented include the simulation of two complex viscoelastic free surface flows: extrudate-swell problem and jet buckling phenomenon. © 2013 Elsevier B.V.

In Situ Formation of Dendrites in Eumelanin Thin Films between Gold Electrodes

Eumelanin is a ubiquitous pigment in the human body, animals, and plants, with potential for bioelectronic applications because of its unique set of physical and chemical properties, including strong UV-vis absorption, mixed ionic/electronic conduction, free radical scavenging and anti-oxidant properties. Herein, a detailed investigation is reported of eumelanin thin films grown on substrates patterned with gold electrodes as a model system for device integration, using electrical measurements, atomic force microscopy, scanning electron microscopy, fluorescence microscopy, and time-of-flight secondary ion mass spectroscopy. Under prolonged electrical biasing in humid air, one can observe gold dissolution and formation of gold-eumelanin nanoaggregates, the assembly of which leads to the formation of dendrites forming conductive pathways between the electrodes. Based on results collected with eumelanins from different sources, a mechanism is proposed for the formation of the nanoaggregates and dendrites, taking into account the metal binding properties of eumelanin. The surprising interaction between eumelanin and gold points to new opportunities for the fabrication of eumelanin-gold nanostructures and biocompatible memory devices and should be taken into account in the design of devices based on eumelanin thin films. © 2013 WILEY-VCH Verlag GmbH & Co.

Ion beam analysis of a-C:H films on alloy steel substrate

An a-C:H thin film deposited by plasma immersion ion implantation and deposition on alloy steel (16MnCr5) was analyzed using a self-consistent ion beam analysis technique.In the self-consistent analysis, the results of each individual technique are combined in a unique model, increasing confidence and reducing simulation errors.Self-consistent analysis, then, is able to improve the regular ion beam analysis since several analyses commonly used to process ion beam data still rely on handling each spectrum independently.The sample was analyzed by particle-induced x-ray emission (for trace elements), elastic backscattering spectrometry (for carbon), forward recoil spectrometry (for hydrogen) and Rutherford backscattering spectrometry (for film morphology).The self-consistent analysis provided reliable chemical information about the film, despite its heavy substrate.As a result, we could determine precisely the H/C ratio, contaminant concentration and some morphological characteristics of the film, such as roughness and discontinuities.© 2013 Elsevier B.V.All rights reserved.

Influência da ionosfera no posicionamento GPS: estimativas dos resíduos no contexto de duplas diferenças e eliminação dos efeitos de 2ª e 3ª ordem

Pós-graduação em Ciências Cartográficas - FCT

O efeito da orientação do parafuso bloqueado nas propriedades biomecânicas da placa S.P.S. Free-Block em corpos de prova nao osteoporóticos

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Representações sociais sobre a Aids e a Terapia Anti-Retroviral: influências no tratamento de pessoas vivendo com HIV/Aids

Com o advento da Terapia Anti -Retroviral, a Aids assumiu características de doença crônica, em especial nos países onde o acesso aos medicamentos é efetivamente garantido. O Brasil é tomado como modelo por possuir um programa que tem dado boas respostas à epidemia. Em novembro de 1996, foi promulgada, pelo Sistema Único de Saúde (SUS), a lei que dispõe sobre a obrigatoriedade do acesso gratuito a todos os que necessitarem de medicamentos anti -retrovirais. Os resultados obtidos com o tratamento – a redução progressiva da carga viral e a manutenção e/ou restauração do funcionamento do sistema imunológico – têm sido associados a benefícios marcantes na saúde física das pessoas soropositivas e permitido que elas retomem e concretizem seus projetos de vida. Porém, o acesso universal aos medicamentos que possibilita o tratamento para portadores do HIV gratuitamente ainda enfrenta problemas de adesão. Em uma compreensão mais restrita, adesão pode ser definida como o comportamento de uma pessoa – tomar remédio, seguir uma dieta ou fazer mudanças no estilo de vida – que corresponde às recomendações da equipe de saúde. Nesse contexto, esse estudo se propõe a analisar as representações sociais de sujeitos soropositivos sobre o tratamento anti-retroviral e suas implicações no processo de adesão a este tratamento, caracterizando as imagens e os sentidos que estes sujeitos soropositivos que aderiram ou não aderiram à terapia anti -retroviral possuem sobre este tipo de tratamento e as implicações na sua vida, destacando as objetivações e as ancoragens que compõem suas representações sociais. A metodologia foi pautada nas formulações teóricas sobre pesquisa qualitativa, priorizando -se a entrevista no enfoque do Método de Explicitação do Discurso Subjacente (MEDS), realizadas na Unidade de Referência em Doenças Infecciosas e Parasitárias Especiais (UREDIPE), vinculada à Secretaria de Estado de Saúde do estado do Pará (SESPA) e no Hospital Universitário João de Barros Barreto (HUJBB), mais especificamente na Clinica de Doenças Infecciosas e Parasitárias (DIP).

Desorption of heavy metals from ion exchange resin with water and carbon dioxide

Adsorption and regeneration of ion exchange resins were studied using a subcritical solution of a CO₂-H₂O mixture and a fixed bed column. The commercial Amberlite IRC-50/IRC-86 cation exchange resins and Amberlite IRA-67 anion exchange resin were tested for heavy metals (Pb, Cu, Cd) adsorption from a solution with different initial metal concentrations at different temperatures. After adsorption, the loaded resins were regenerated with water and carbon dioxide at different temperatures and a pressure of 25 MPa. The efficiency of the IRC-50 resin was lower than that of the IRC-86 resin for the adsorption of metals like Cd, Cu and Pb. Results obtained for desorption of these metals indicated that the process could be used for Cd and in principle for Cu. Sorption of metal ions depended strongly on feed concentration. Mathematical modeling of the metal desorption process was carried out successfully as an extraction process. For this purpose, the VTII Model, which is applied to extraction from solids using supercritical solvents, was used in this work.

Cell adhesion and growth on surfaces modified by plasma and ion implantation

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

Evaluation of Renal Protection From High Doses of Melatonin in an Experimental Model of Renal Ischemia and Reperfusion in Hyperglycemic Rats

Background. Melatonin is a free radical scavenger with important actions in the study of renal ischemia and reperfusion (I/R). This study evaluated possible renal protection of high doses of melatonin in an experimental model of I/R in which rats were submitted to acute hyperglycemia under anesthesia with isoflurane.Method. Forty-four male Wistar rats, weighing more than 300 g, were randomly divided into 5 groups: G1, sham (n = 10); G2, melatonin (n = 10; 50 mg.kg(-1)); G3, hyperglycemia (n = 9; glucose 2.5 g.kg(-1)); G4, hyperglycemia/melatonin (n = 10; 2.5 g.kg(-1) glucose + melatonin 50 mg.kg(-1)); and G5, I/R (n = 5). In all groups, anesthesia was induced with 4% isoflurane and maintained with 1.5% to 2.0% isoflurane. Intraperitoneal injection of melatonin (G1, G4), glucose (G3, G4), or saline (G1, G5) was performed 40 minutes before left renal ischemia. Serum plasma values for creatinine and glucose were determined at baseline (M1), immediately following reperfusion (M2), and 24 hours after completion of the experiment (M3). Histological analysis was performed to evaluate tubular necrosis (0-5).Results. Serum glucose was higher at M2 in the groups supplemented with glucose, hyperglycemia (356.00 +/- 107.83), and hyperglycemia/melatonin (445.3 +/- 148.32). Creatinine values were higher at T3 (P = .0001) for I/R (3.6 +/- 0.37), hyperglycemia/melatonin (3.9 +/- 0.46), and hyperglycemia (3.71 +/- 0.69) and lower in the sham (0.79 +/- 0.16) and melatonin (2.01 +/- 1.01) groups, P < .05. Histology showed no necrosis injury in the G1, lesion grade 2 in the G2, and severe acute tubular necrosis in the G3: (grade 4), G4: (grade 5) and G5: (grade 4) groups (P < .0001).Discussion. Melatonin protected the kidneys submitted to I/R in rats without hyperglycemia; however, this did not occur when the I/R lesion was associated with hyperglycemia.Conclusions. Due to its antioxidant and antiapoptotic action, melatonin was able to mitigate, but not prevent acute tubular necrosis in rats with hyperglycemia under anesthesia by isoflurane.

Comparing label free electrochemical impedimetric and capacitive biosensing architectures

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

Free radical entrapment and crystallinity of resin composites after accelerated aging as a function of the expiration date

This study evaluated the spin concentration and the crystallinity in different classifications of dental composites as a function of the material condition (new, aged and expired). Specimens were obtained according to the factors: composites: Filtek P60, Filtek Z250, Filtek Z350XT, and Filtek Silorane; and material conditions: new, aged, and expired. The syringe composites underwent an accelerated aging protocol (Arrhenius model). The magnetic properties of the composites were characterized using Electron Paramagnetic Resonance (EPR) and the concentration of spins (number of spins/mass) was calculated. The crystallinity of the composites tested was characterized with X-ray diffraction (XRD). Filtek P60 and Filtek Z250 presented similarities in terms of spin concentration and crystallinity, irrespective of the material condition. The aging protocol influenced the composite Filmic Z350XT that exhibited a significant increase in the spin concentration. Besides, lower intensity peaks of the organic matrix and amorphous silica were also observed for both aged and expired Filtek Z350XT. Although a significant lower spin concentration was observed for the silorane composite in comparison to that of the methacrylates, a decrease in the relative intensity of peaks of the amorphous region related to the organic components in the diffractograms was observed. The material conditions tested influence the crystallinity and the magnetic properties of the composites evaluated. (C) 2014 Elsevier Ltd. All rights reserved.