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Thesis |
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1
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JULIANA CRISTINA PEREIRA LIMA PAULINO
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Evidence of Layered Double Hydroxides as adsorbent agents in aquatic matrices
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Advisor : LUCAS MEILI
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COMMITTEE MEMBERS :
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ANAMALIA FERREIRA DA SILVA
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CAMILA BRAGA DORNELAS
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JOSEALDO TONHOLO
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KELYANE DA SILVA
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LUCAS MEILI
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PATRICIA DE CARVALHO NAGLIATE
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Data: Feb 28, 2023
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Show Abstract
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Human actions have affected the quality of water resources causing great impact to the environment around the world, significantly reducing their availability for consumption. Faced with the priority need to remove contaminants and pollutants in the most diverse aquatic matrices, the development of new technologies for this purpose becomes essential. Some decontamination processes employ solid materials for adsorption, providing low cost associated with high efficiency. The lamellar double hydroxides (HDLs) in addition to being versatile, show promise in adsorption processes. A Scoping Review was carried out in order to obtain a global overview of what has been studied on the use of lamellar double hydroxides as adsorbing agents for contaminants and pollutants in aquatic matrices. Data collection was performed by searching publications by three independent reviewers on online platforms (a) Web of Science (WoS); (b) Scopus; (c) Science Direct; (d) National Library of Medicine (PubMed), (e) Google Scholar and (f) Open Grey; through the use of keywords: layered double hydroxides, environment, contaminant, pollutant, aqueous medium, aqueous solution, adsorption, adsorbent and adsorbent agent. The inclusion criteria were: publications indexed in selected databases that contribute in a relevant way to the research question and open access. The chronology used was from the date of origin of each electronic platform until the year 2021. Based on the eligibility criteria, 17 studies were selected, from 14 different nationalities, with their publication period between 2005 and 2021, denoting the scientific effort of 103 researchers. The predominance of the origin of the studies was recorded, as well as the composition of the HDLs used, the contaminants, the pollutants or reaction media in which they were used, the synthesis method used and the most relevant considerations of each research. This work evidenced the main information that describes the HDLs as promising materials and of significant relevance as an adsorbent of contaminating agents and pollutants in aquatic matrices, highlighting the challenges identified for the emergence of new studies on the subject.
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2
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JONATHAS MATIAS DE OLIVEIRA
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DIRECT LASER WRITIG MICROFABRICATION OF INTEGRATED OPTICAL DEVICES
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Advisor : EDUARDO JORGE DA SILVA FONSECA
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COMMITTEE MEMBERS :
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JOSÉ FERRAZ DE MOURA NUNES FILHO
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ANDRE DE LIMA MOURA
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CLEBER RENATO MENDONCA
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EDUARDO JORGE DA SILVA FONSECA
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MARCOS VINICIUS DIAS VERMELHO
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Data: Mar 3, 2023
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Show Abstract
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The three-dimensional microfabrication via direct laser writing techniques has opened a window of opportunities for research and technological applications in several areas such as optical communication, microfluidics, synthesis of new materials, 3D scaffolding for cell culture, construction of optical microdevices, and others. The possibility of building a 3D optical device directly on a substrate or inside a transparent bulk has driven research groups and engineers around the world to design and develop integrated micro-optical systems capable of manipulating light signals and making them interact with mechanical, electronic, fluid, chemical and biological elements. The works developed during this Phd represents a small but substantial contribution for this line of research. Initially, the twophoton polymerization technique was used to write a helical axicon, a light micromodulator able to convert Gaussian beams into structured beams possessing orbital angular momentum, whose profile is described by a superposition of high-order Bessel beams. By means of a modifying laser process, we have written channel waveguides inside silver-doped tellurite glassy blades. The waveguide’s optical properties and the writing parameters were analyzed as a function of the matrix composition and of the silver nanoparticles concentration. Finally, we have built annular waveguides, capable for guiding light beams carrying orbital angular momentum, inside boroaluminosilicate glassy blades. In addition, we have proposed a coupling method that permits tuning the guided modes for the same waveguide and no need to modify the input beam. Our findings expand the available degrees of freedom for optical beams in photonic circuits, simplify the design of integrated optical chips and broaden the spectrum of possible applications for these systems.
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3
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LEONARDO SOBREIRA RODRIGUES
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Poly(ε-caprolactone) fiber containing wax and red propolis extract from Alagoas for applications in the health area
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Advisor : LIGIA MARIA MANZINE COSTA
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COMMITTEE MEMBERS :
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RAFAEL SALOMÂO
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MÁRCIA REGINA DE MOURA AOUADA
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ADRIANA CARLA DE OLIVEIRA LOPES
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ADRIANA SANTOS RIBEIRO
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CAMILA BRAGA DORNELAS
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JOHNNATAN DUARTE DE FREITAS
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LIGIA MARIA MANZINE COSTA
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Data: Mar 7, 2023
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Show Abstract
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Since ancient times, the use of biomaterials has evolved along with civilization through various technological improvements over the years. In recent times, there has been a growing interest in combining two or more substances to form a new material, due to their synergistic properties resulting in improved properties. The red propolis extract is a promising additive that can increase bioactivity when incorporated into a material. Red propolis wax, on the other hand, is discarded as waste and has no commercial value. Therefore, this study aims to produce mats from polycaprolactone (PCL) incorporated with red propolis wax or hydroalcoholic extract from Alagoas red propolis, using the electrospinning technique to ensure the formation of fibrous structures. The concentrations of wax and red propolis extract ranged from 1% to 15%. The mats were evaluated for their physical, chemical, structural, vibrational, thermal, mechanical, and biological properties. High-performance liquid chromatography was employed to determine the flavonoid content of the red propolis extract, which was found to be higher than that of the wax. The morphology of the mats was analyzed by scanning electron microscopy, revealing an average diameter below 1.2 μm and an average porosity of approximately 52%. The vibrational spectrum was used to investigate the nature of the interactions, which were found to be strictly physical without the formation of new chemical bonds. X-ray diffraction was employed to investigate the crystallinity of the mats, and a decrease in crystallinity was observed as the wax/red propolis extract was added to the polymeric matrix. The wetting behavior of the mats was analyzed using the contact angle method, and it was found that samples with propolis extract presented greater swelling, with a contact angle of less than 90º, being wettable when the concentration is equal to or greater than 5%. Mechanical testing showed that the mat with 10% propolis exhibited the best values for maximum stress, elongation at break, and elastic modulus. Furthermore, these mats did not exhibit any toxic effects on cells. These results suggest that it was possible to form a fibrous biomaterial with potential for use in tissue engineering, such as bioactive dressings.
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4
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WILLIAMS RAPHAEL DE SOUZA MORAIS
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DEVELOPMENT OF GREEN CORROSION INHIBITORS DERIVED FROM PLANT EXTRACTS
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Advisor : JOSEALDO TONHOLO
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COMMITTEE MEMBERS :
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LIU YAO CHO
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EDUARDO JORGE DA SILVA FONSECA
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JOSEALDO TONHOLO
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MARCOS VINICIUS DIAS VERMELHO
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NATHALIA MARCELINO PEREIRA QUEIROZ
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Data: Jun 30, 2023
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Show Abstract
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Metallic materials and metallic alloys, are widely used as materials in the most diverse areas, due to their advantages. Carbon steel, for example, is the most widely used metal alloy and one of the most widely produced materials in the world. On the other hand, most metals and their alloys in their pure form are highly reactive and suffer corrosion, a thermodynamically spontaneous process, resulting in their deterioration. One of the most practical methods of protecting materials is the use of corrosion inhibitors. Some inhibitors, however, are potentially polluting and harmful to human health, this motivates the search for new formulations. The literature reports the use of natural products, called "green inhibitors", the plant extracts stand out within this class of inhibitors. In this perspective, in the present work it was accomplished a prospection about the applicability of vegetal extracts as green inhibitors of corrosion and the development of these inhibitors from 3 vegetal extracts of different sources: leaves of Eucalyptus globulus Labill, Sargassum vulgare seaweed and grains of Paullinia cupana (guaraná), in the protection of the 1020 carbon steel. In the prospection bases of scientific articles and patents were consulted and the documents found were analysed. The extracts were characterized by spectroscopic and chromatographic techniques, and their inhibition activities were evaluated by gravimetric and electrochemical techniques. A total of 335 articles and 42 patents related to the theme were retrieved, being most of the extracts prepared from leaves for the protection of carbon steel in acid medium. In the characterization of the extracts were identified types of bonds and compounds, as terpenes and phenolic acids, that demonstrate the possibility of application of these extracts as corrosion inhibitors. The used techniques showed that in all studied concentrations the extracts increased the charge transfer resistance, provoked potential displacement and decreased the parameters related to corrosion, reaching 89.97 % of maximum anticorrosive efficiency. Moreover, the adsorption of molecules, in the presence of the extracts, on active sites of the carbon steel surface was physisorption and obeyed the Frumkin adsorption isotherm. The proposed inhibitors are presented as non-toxic, cheap, abundantly available in nature and of easy extraction, characterizing them as green corrosion inhibitors.
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5
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JOSÉ ANTONIO FRANÇA DE ARAÚJO
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STUDY ON MEAN FIELD MICROMECHANICAL MODELS FOR HOMOGENIZATION OF ELASTOPLASTIC COMPOSITES AND POROUS MATERIALS
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Advisor : SEVERINO PEREIRA CAVALCANTI MARQUES
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COMMITTEE MEMBERS :
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SAMIR MAGHOUS
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ADEILDO SOARES RAMOS JUNIOR
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EDUARDO NOBRE LAGES
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JOSE JULIO DE CERQUEIRA PITUBA
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MARCIO ANDRE ARAUJO CAVALCANTE
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SEVERINO PEREIRA CAVALCANTI MARQUES
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Data: Aug 29, 2023
Ata de defesa assinada:
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Show Abstract
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In this work, the effective elastic properties and elastoplastic behavior of biphasic materials were investigated through the micromechanics of mean fields. The materials have solid inclusions perfectly adhered to the matrix or randomly distributed pores in space, which can be aligned or misaligned. The elastoplastic behavior of the effective material is evaluated in the form of stress (or strain) rate using the incremental and homogenized method according to the Mori-Tanaka scheme. The flow of the biphasic material matrix is governed by the von Mises criterion, in which isotropic conditions and infinitesimal deformations are considered. After the flow, the isotropic constitutive tensor of the matrix takes the form of an anisotropic tangent constitutive tensor, in which, by mathematical approximation methods, the isotropic part can be used to determine the effective tangent constitutive tensor. During the elastoplastic behavior, it is assumed that the matrix has nonlinear isotropic hardening or linear kinematic hardening. To achieve the objectives of this work, algorithms were developed that enable the investigation of the limitations of using the tangent constitutive operator of the matrix, whether anisotropic or obtained by isotropic approximation, as well as the application of the tangent Eshelby tensor or Eshelby tensor for the Elastoplastic medium (EPM). The results obtained indicate that the accuracy of the elastoplastic behavior of a heterogeneous material can be affected by the choice of the method and the isotropic approximation procedure of the elastoplastic matrix constitutive operator. It was also observed that in composites that have rigid inclusions with ellipsoidal geometry, the Eshelby tensor for the EPM had limitations, providing satisfactory results only for rigid inclusions with spherical geometry. On the other hand, no limitations were observed regarding the pore geometry, showing satisfactory results for any aspect ratio. Finally, using the Eshelby tensor for the EPM, an approach was presented that deduces the strain concentration tensor for ductile matrices that have misaligned spherical or spheroidal pores, with good agreement observed with results published in the literature. the elastoplastic medium with an emphasis on porous materials.
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6
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THEO FORTES SILVEIRA CAVALCANTI
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DEVELOPMENT OF DENTAL MATERIALS WITH IMPROVED VALUE CONTAINING BRAZILIAN RED PROPOLIS
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Advisor : JOSEALDO TONHOLO
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COMMITTEE MEMBERS :
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GUILHERME BENJAMIN BRANDAO PITTA
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JOSE MARCOS DOS SANTOS OLIVEIRA
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JOSEALDO TONHOLO
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LUCAS MEILI
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MARCOS AURELIO BOMFIM DA SILVA
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MARCOS VINICIUS DIAS VERMELHO
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SONIA MARIA SOARES FERREIRA
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Data: Nov 6, 2023
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Show Abstract
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This thesis addresses alternative treatment for tooth caries, one of the endemic diseases that affects all humanity. It also presents the use of a natural product from regional biodiversity – Brazilian Red Propolis (PVA), an exclusive bioproduct from Alagoas, Brazil - as an additive for dental supplies that improves the quality of caries treatment, adding value and increasing treatment efficiency. The PVA obtained from a controlled source was prepared to obtain the hexane extract, which was duly qualified by liquid chromatography to determine flavonoid and phenol contents, the results of which reached between 7.35% and 117.6 mg of total phenols per gram of dry hexane extract. A DPPH scavenging study was carried out, where the IC50 of the DPPH radical scavenging capacity of the PVA hexane extract was 9.22 μg/mL while the IC50 of Trolox, used as standard, was 7.02 μg/mL. After qualifying the extract, 5 different ionomer compositions were formulated with the addition of PVA dry extract, which were subjected to antibacterial activity tests by diffusion, which confirmed the ability to release daidzein, liquiritigenin, pinobanksin, isoliquiritigenin and formononetin. Mechanical surface roughness tests were carried out, which revealed similar values between the surfaces of the glass ionomer in the control group and that of the ionomer with 0.5% hexane extract. The analysis of the microhardness of materials (Knoop hardness) proved that there was no statistically significant difference in the microhardness of the additives in relation to the commercial product of the non-additivated ionomer. The determination of the (qualitative) fluoride release profile was carried out by NMR using an unprecedented procedure, revealing the viability of fluoride release, regardless of the presence of PVA in the ionomer mixture. A fluoride release study was also carried out using fluorometry, demonstrating the quantitative release of fluoride, both in the presence and absence of PVA. The results of biological, chemical and mechanical tests, carried out in vitro and here presented, are very favorable to the indication of the use of PVA as an additive in glass ionomer, allowing us to recommend moving towards in vivo studies.
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