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Search Results: 1 - 10 of 71377 matches for " Roberto Fernando Souza Freitas "
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Synthesis and Characterization of Poly(D,L-Lactide-co-Glycolide) Copolymer  [PDF]
Cynthia D’Avila Carvalho Erbetta, Ricardo José Alves, Jarbas Magalh?es Resende, Roberto Fernando de Souza Freitas, Ricardo Geraldo de Sousa
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2012, DOI: 10.4236/jbnb.2012.32027
Abstract: The copolymer poly(D,L-lactide-co-glycolide) is one of the most interesting polymers for medical applications. This interest is justified by the fact that it is bioreabsorbable, biocompatible and non-toxic, while its degradation kinetics can be modified by the copolymerization ratio of the monomers. In this study, copolymers were synthesised at 175?C by opening the rings of the cyclic dimers of the D,L-lactide and glycolide monomers in the presence of stannous octoate initiator and lauryl alcohol co-initiator. The application of vacuum to the reaction medium, coupled with adequate stirring, is essential for obtaining good results. The following analytical techniques were used to characterise the synthesised copolymers: Differential Scanning Calorimetry (DSC), Thermogravimetry (TG), Nuclear Magnetic Resonance Spectroscopy (NMR) and Fourier Transform Infrared Spectroscopy (FTIR). Both the input monomers and the reaction products were analysed. Important characteristics, such as melting temperature, glass transition temperature, thermal stability, chemical composition and the ratio of the monomers in the synthesised copolymer, were obtained from these analyses. These results helped to infer the absence of residual monomers in the synthesised copolymers.
Rheological and Thermal Behavior of High-Density Polyethylene (HDPE) at Different Temperatures  [PDF]
Cynthia D’Avila Carvalho Erbetta, Getúlio F. Manoel, Ana Paula Lelis Rodrigues Oliveira, Maria Elisa Scarpelli Ribeiro e Silva, Roberto Fernando Souza Freitas, Ricardo Geraldo Sousa
Materials Sciences and Applications (MSA) , 2014, DOI: 10.4236/msa.2014.513094
Abstract: In the present work, rheological properties of HDPE samples were measured at temperatures of 150°C, 190°C and 230°C. It was shown, by oscillatory tests, at low frequencies, that, for temperatures of 150°C and 190°C, there was a predominance of the viscous behavior over the elastic one. At 230°C, there was a predominance of the elastic contribution, and there was an increase of the molar mass compared with the ones obtained from the tests at 150°C and 190°C. The results obtained from the temperature ramp oscillatory test showed that, up to around 248°C, the viscous behavior prevailed, the opposite being observed at higher temperatures. At 230°C the sample showed significantly lower values of strain when compared with the ones observed at 150°C and 190°C. Oxidative induction time (OIT), melting point and degree of crystallinity were determined by differential scanning calorimetry (DSC). The DSC results and the rheological measurements showed a completely different behavior for the HDPE samples at 230°C compared with the 150°C and the 190°C ones, suggesting that HDPE, at the temperature of 230°C, underwent thermo-oxidative degradation with the initial predominance of crosslinking.
Synthesis, Characterization, and Study of PLGA Copolymer in Vitro Degradation  [PDF]
Anamaria Teodora Coêlho Rios Silva, Barbara Camilla Oliveira Cardoso, Maria Elisa Scarpelli Ribeiro e Silva, Roberto Fernando Souza Freitas, Ricardo Geraldo Sousa
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2015, DOI: 10.4236/jbnb.2015.61002
Abstract: The poly(lactic-co-glycolic acid), known as PLGA, is one of the main bioreabsorbable polymers used in the field of medicine today. This copolymer is widely applied in sutures, devices geared toward the controlled release of medication, and the guided regeneration of bone tissue as it presents a short degradation time. This work aimed to synthesize the 82/18 PLGA (expressed by the mass ratio of D,L-lactide and glycolide, respectively), to characterize and study the in Vitro degradation in the form of rods in phosphate buffer solution (PBS). The copolymer was synthesized by opening the cyclic dimer rings of the monomers D,L-lactide and glycolide, in the presence of the tin octanoate initiator and of the lauryl alcohol co-initiator. The characterization of the copolymer and the follow-up of its in vitro degradation were studied using: Differential Scanning Calorimetry (DSC), Thermogravimetry (TG), Infrared Molecular Absorption Spectroscopy with Fourier Transform (FTIR), Rheometry, and Scanning Electron Microscopy (SEM). Through these characterization techniques, it was possible to obtain the glass transition temperature, thermal stability, chemical composition, morphology, and molar mass of both the synthesized and the degraded copolymer. The molar mass of the synthesized copolymer was, approximately, 106 g·mol-1. The degradation rate of PLGA significantly increased from the 19th to the 28th day in PBS. After 28 days in PBS, the glass transition temperature and the molar mass reduced from 45°C to 17°C and from 1.5 × 106 g·mol-1 to 7.5 × 10g·mol
Rheological Study of Polymers Used as Viscosity Index Improvers for Automotive Lubricant Oils  [PDF]
Ana Paula Pena Almeida, Ana Paula Lelis Rodrigues de Oliveira, Cynthia D’ávila Carvalho Erbetta, Ricardo Geraldo de Sousa, Roberto Fernando de Souza Freitas, Maria Elisa Scarpelli Ribeiro e Silva
Journal of Modern Physics (JMP) , 2014, DOI: 10.4236/jmp.2014.512110

In this work, a rheological study of automotive lubricant oils, neutral light paraffinic (NLP) and neutral medium paraffinic (NMP), additivated with two commercial viscosity index improvers-VIIs, based on hydrogenated poly (isoprene-co-styrene), at different concentrations, was carried out. The study included the determination of the kinematic viscosity of the mixtures, the calculation of the viscosity indexes and their behavior when subjected to various rheometric experiments, including stress sweep, steady state flow, creep and recovery, and temperature ramp oscillatory tests. The obtained results showed the efficacy of the additives as viscosity index improvers, enabling a significant increase in the viscosity index of the pure oils at relatively low concentrations. The determination of the storage (G’) and of the loss (G”) moduli for the mixtures oil/VII additives showed a large predominance of the viscous effect over the elastic one. Except when under low shear stress, the mixtures showed a pseudoplastic behavior, with the flow curves being adjusted to fit the Ostwald-de-Waele model (Power Law), with negative flow behavior indexes.

Femoral stem-bone interface analysis of logical uncemented stem
Spinelli, Leandro de Freitas;Macedo, Carlos Alberto de Souza;Galia, Carlos Roberto;Rosito, Ricardo;Schnaid, Fernando;Corso, Leandro Luis;Iturrioz, Ignácio;
Revista Brasileira de Engenharia Biomédica , 2012, DOI: 10.4322/rbeb.2012.031
Abstract: this paper evaluates the mechanical behavior of an uncemented hip stem using finite element analysis. the analysis is focused on the stem-bone interaction which is assessed by simulation of distinct conditions encountered daily on orthopedic practice of hip implants. logical uncemented femoral stem was used in this work. three distinct conditions have been modeled: a) exposed neck with fully embedded fins, b) partially exposed anti-rotational fins and c) fully exposed fins, representing real femoral hip conditions. anthropometric variations and different angulations for the stem neck were investigated for typical body weight of populations submitted to implants. the ratio of mobilized stress to yield stress is shown to be lower than 55% indicating a safety factor against stem failure. although small displacements are observed in all conditions, the displacement increases with the increase of both the length of exposed fins and the magnitude of applied forces. even for the extreme condition of fully exposed fins, the prostheses will support the working loads, and the risk of bone fracture still has a safety factor. stresses and displacements change considerably with neck angulations suggesting that anthropometric variations should be considered in the future to optimize prostheses performance. numerical analysis of the used uncemented femoral stem demonstrated that small stresses and strains are generated under working load conditions indicating that a proper factor of safety is obtained for the static conditions tested in the present study.
Mensura??o da press?o intra-abdominal nas unidades de tratamento intensivo: a opini?o dos médicos intensivistas
Japiassú, André M.;Falc?o, Haroldo;Freitas, Fernando;Freitas, Sandra;Souza, Paulo César P.;Lannes, Roberto;Sato, Ricardo I.;Dias, Analucia M.;Almeida, Gustavo F.;Soares, Márcio;Salluh, Jorge I.;
Revista Brasileira de Terapia Intensiva , 2007, DOI: 10.1590/S0103-507X2007000200008
Abstract: background and objectives: the adverse effects of intra-abdominal hypertension are known for many years. only recently proper attention has been given to routine intra-abdominal pressure (iap) monitoring. there is evidence that a quarter of intensive care units (icu) do not measure iap, due to a lack of knowledge of its importance or difficulty in results interpretation. the aim of this study is investigate the knowledge of icu physicians about abdominal compartimental syndrome and its management. methods: a questionnaire with 12 questions about this issue was mailed to icu physicians. results: the current knowledge of the international definitions of acs does not seem to be linked to the number of years of medical practice, but was associated with the time spent working on intensive care. although most physicians are aware of the existence of acs, less than half know the present international definitions. the iap monitoring is performed in patients at risk for acs, by means of the intravesical filling with 25 to 100 ml of liquids, in intervals varying from of 4 to 8 hours. there was no consensus on the value of iap values (with or without organ dysfunctions) for the clinical or surgical treatments of acs in this survey. conclusions: the knowledge of acs is satisfactory when we consider only physicians that devote most of their time to icu work. however, it is necessary to improve education and knowledge of most intensive care physicians regarding the presence and severity of intra-abdominal hypertension in rio de janeiro.
Identification of Scientific Researches Conducted during UNIPLAC’S Medical Degree, Lages, Santa Catarina, Brazil  [PDF]
Vanessa Freitas Bratti, Patrícia Alves de Souza, Fernando Arruda Ramos, Márcia Adriane Andrade
Creative Education (CE) , 2014, DOI: 10.4236/ce.2014.51005
Abstract: Scientific Research held during graduation provides students with better training, by allowing the improvement of activities related to their future profession, a better relationship between teachers and students, as well as enabling the knowledge of research methodology. The purpose of this work is to identify the Scientific Research conducted during the medical degree at Universidade do Planalto Catarinense-UNIPLAC, since the implementation of this course at the University (2004) until July 2013. Through a descriptive and quantitative approach, the data related to the scientific research conducted during the medical degree were held. Fifty-eight Scientific Researches were performed by students, who were instructed by qualified teachers. From this information, the fields of knowledge covered by the Scientific Projects were recognized, as well as the profile of researchers. The epidemiology was the field related to the greatest approach and it covered twenty-eight Scientific Researches. Females predominate among the researchers, with a participation of thirty-one exhibitioners and fifteen advisors. The researches were carried out mainly by students who study the early years of medical degree. The tripod Research, Education and Extension are very important as they introduce the students to the scientific universe during graduation, encourage them to produce knowledge and technology through their own researches after the degree, contribute to a better academic background, and provide a continuous update during the professional life, and encourage self-taught professionals. This electronic document is a “live” template.
Analysis of the Hypervariable Regions (HVRs) of the wsp Gene of Wolbachia from Solenopsis invicta Ants in Southeastern Brazil  [PDF]
Rodrigo Fernando de Souza, Cíntia Martins, Roberto Manoel Pereira, Odair Correa Bueno
Advances in Entomology (AE) , 2014, DOI: 10.4236/ae.2014.23021
Abstract: Wolbachia is a bacterium that infects many arthropods with horizontal or vertical transmission. The introduction and spreading of Solenopsis invicta in new areas may have influenced the acquisition of Wolbachia as this ant species spread from its South America origin to other parts of the globe. The wsp gene of Wolbachia was analyzed using the WSP Typing and a similarity analysis was conducted to analyse the sharing of the symbiont among nests of S. invicta ants. The analyses revealed the presence of two groups of Wolbachia: strain A belonging to InvA S. invicta subgroup, and the strain B belonging to Acromyrmex insinuator. The wsp gene and its hypervariable regions are shared among the Wolbachia present in different types of ants inhabiting in the New World. Wolbachia strains found in the nests of S. invicta are ant-specialist symbionts which may have spread by several means among the ant population.
The CD133/1+ cell subset from human subcutaneous adult fat retains hemogenic potential  [PDF]
Camila Santos de Moraes, Paulo Roberto Albuquerque Leal, Daniel Fabiano Ferreira, Fernando Serra, Eliana Abdelhay, Claudia Sondermann Freitas
Stem Cell Discovery (SCD) , 2012, DOI: 10.4236/scd.2012.22006
Abstract: Research has shown that cells from adult fat tissue can effect long-term blood reconstitution. Fat-derived multipotentiality was ascribed to CD34+ perivascular populations from its prominent microvasculature, that represent mostly non-hemogenic, mesenchymal cells, although this tissue contains a CD34+45+ subset committed to a hemogenic fate. Here, in order to analyze cell subsets presenting hemogenic capabilities within fat, CD133/1+ and pericytes, the latter defined by CD140b (PDGFRb, Platelet-Derived Growth Factor Receptor Beta) expression, were immunomagnetically selected from stromal-vascular fractions (SVF). In Vitro Colony Forming Unit (CFU) assays were negative for CD140b+ pericytes and positive for CD133/1+ cells when a prolonged CFU assay was performed, revealing fat as another store of primitive progenitors that retain hemogenic potential.
Determination of Essential (Ca, Fe, I, K, Mo) and Toxic Elements (Hg, Pb) in Brazilian Rice Grains and Estimation of Reference Daily Intake  [PDF]
Bruno Lemos Batista, Letícia Ramos Nacano, Rodolfo de Freitas, Vanessa Cristina de Oliveira-Souza, Fernando Barbosa
Food and Nutrition Sciences (FNS) , 2012, DOI: 10.4236/fns.2012.31019
Abstract: The levels of Hg and Pb (toxic elements) and Ca, Fe, I, K, Mo (essential elements) were measured in 44 Brazilian rice samples divided among white polished (W), parboiled white (PW) and parboiled brown (PB). Rice grains were ana- lyzed by inductively coupled plasma mass spectrometry (ICP-MS). Concentrations of toxic elements varied from 0.3 to 13.4 and 0.4 to 14.5 ng?g–1 for Hg and Pb, respectively. The values for essential elements were in the same range of those for rice produced in other countries. In general parboiled samples presented higher levels of all elements in study compared to white samples. The Estimated Daily Intake through rice consumption was 0.44 μg for Pb, 0.22 μg for Hg, 0.65 μg for I, 39.5 μg for Mo, 0.43 mg for Fe, 4.1 mg for Ca and 88.9 mg for K. Our findings demonstrated that rice can contribute significantly to the RDIs of molybdenum and potassium, but it can not be considered an important source of I, Fe and Ca. Moreover, the estimated dail
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