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Search Results: 1 - 10 of 209642 matches for " Cynthia D’Avila Carvalho Erbetta "
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Synthesis and Characterization of Poly(D,L-Lactide-co-Glycolide) Copolymer  [PDF]
Cynthia DAvila 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 DAvila 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.
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
Abstract:

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.

Characterization and Lifetime Estimation of High Density Polyethylene Containing a Prodegradant Agent  [PDF]
Cynthia D. C. Erbetta, Raquel C. S. Azevedo, Karen S. Andrade, Maria Elisa S. R. e Silva, Roberto F. S. Freitas, Ricardo G. Sousa
Materials Sciences and Applications (MSA) , 2017, DOI: 10.4236/msa.2017.813072
Abstract: High density polyethylene (HDPE) samples, containing different concentrations of prodegradant additive d2w, were prepared. The properties of the samples were evaluated through differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), rheometry, and scanning electron microscopy (SEM). The work contributes to decreasing the products made of non-biodegradable polymeric materials derived from fossil sources which are have become a problem due to their increasingly inappropriate disposal and long degradation time in the environment. The obtained results indicated that there was no degradation of the samples due to processing. No significant changes in melting temperature, crystallinity, viscoelastic behavior, molecular weight and chemical composition were observed. Images from SEM analysis showed particles on HDPE surface, attributed to prodegradant additive d2w. Oxidation Onset Temperature (OOT) results showed that the additive d2w accelerated the degradation of HDPE. The activation energy (Ea) was determined by Ozawa-Wall-Flynn method. The obtained values were used for lifetime estimation of the samples. At 25°C, HDPE with d2w showed a lifetime 50% higher than that of HDPE without this additive. This fact is attributed to the presence of stabilizers in masterbatch d2w and the absence of oxygen in thermogravimetric analysis.
Síntese e caracteriza??o térmica e química do copolímero poli(D,L-lactídeo-co-glicolídeo)
Erbetta, Cynthia D. C.;Viegas, Carla C. B.;Freitas, Roberto F. S.;Sousa, Ricardo G.;
Polímeros , 2011, DOI: 10.1590/S0104-14282011005000063
Abstract: poly (d, l-lactide-co-glycolide) copolymer (plga) has attracted a great deal of interest due to their special characteristics as biomaterials since it is bioreabsorbable, biocompatible, nontoxic and the kinetics of degradation can be modified by the ratio of monomers in copolymerization. in this work, the copolymers were synthesized at 175 oc, by opening the ring of cyclic dimers of d,l-lactide and glycolide monomers in the presence of tin(ii) octanoate initiator and lauryl alcohol co-initiator. the efficient control of the vacuum in the medium combined with adequate stirring were essential to the success of the synthesis. characterization of the copolymers samples was carried out by using differential scanning calorimetry (dsc), thermogravimetry (tg) and fourier transform infrared spectroscopy (ftir). we analyzed not only the products of reaction but also the initial monomers. the new synthesis route employed was appropriate and the poly(d, l-lactide-co-glycolide) was successfully obtained.
Norepinephrine remains increased in the six-minute walking test after heart transplantation
Guimar?es, Guilherme Veiga;D' Avila, Veridiana;Bocchi, Edimar Alcides;Carvalho, Vitor Oliveira;
Clinics , 2010, DOI: 10.1590/S1807-59322010000600005
Abstract: objective: we sought to evaluate the neurohormonal activity in heart transplant recipients and compare it with that in heart failure patients and healthy subjects during rest and just after a 6-minute walking test. introduction: despite the improvements in quality of life and survival provided by heart transplantation, the neurohormonal profile is poorly described. methods: twenty heart transplantation (18 men, 49±11 years and 8.5±3.3 years after transplantation), 11 heart failure (8 men, 43±10 years), and 7 healthy subjects (5 men 39±8 years) were included in this study. blood samples were collected immediately before and during the last minute of the exercise. results: during rest, patients' norepinephrine plasma level (659±225 pg/ml) was higher in heart transplant recipients (463±167 pg/ml) and heathy subjects (512±132), p<0.05. heart transplant recipient's norepinephrine plasma level was not different than that of healthy subjects. just after the 6-minute walking test, the heart transplant recipient's norepinephrine plasma level (1248±692 pg/ml) was not different from that of heart failure patients (1174±653 pg/ml). both these groups had a higher level than healthy subjects had (545±95 pg/ml), p<0.05. conclusion: neurohormonal activity remains increased after the 6-minute walking test after heart transplantation.
Contextos institucionais e escolariza??o: uma hipótese de classifica??o das escolas da rede privada de educa??o básica
Carvalho, Cynthia Paes de;
Revista Brasileira de Educa??o , 2006, DOI: 10.1590/S1413-24782006000100011
Abstract: on the basis of a dialogue with the literature of the sociology of education on the inter-generational transmission of cultural patrimony among the middle classes, particularly with respect to educational investment, a typology of schools and primary school trajectories was constructed. based on a hypothesis for the classification of private schools in rio de janeiro, the different school trajectories found are described and some results of the analysis of the data referring to the group studied are discussed. the conclusion highlights the heuristic potential of the characterisation designed in the sense of deepening the understanding of the set of primary school establishments and enriching the possibilities of analysis by going beyond the distinction between the public and private character of the schools.
Contextos institucionais e escolariza o: uma hipótese de classifica o das escolas da rede privada de educa o básica
Cynthia Paes de Carvalho
Revista Brasileira de Educa??o , 2006,
Abstract: En la interlocución con la literatura de la sociología de la educación sobre la transmisión intergeneracional del patrimonio cultural en las capas medias de la sociedad, particularmente lo que concierne a las inversiones en la educación, fue construída una tipología de las escuelas y de las trayectorias escolares de la educación básica. A partir de una hipótesis de clasificación de las escuelas privadas de ense anza en Río de Janeiro, son descriptos los diferentes trayectos escolares, encontrados y discutidos algunos resultados del análisis de los datos referentes al grupo estudiado. Se concluye resaltando el potencial heurístico de la caracterización delineada, en el sentido de ampliar la comprensión del conjunto de los establecimientos de ense anza básica y enriquecer las posibilidades de análisis, para lejos de la distinción del carácter público o privado de las escuelas.
Consumo de álcool entre vítimas de acidentes e violências atendidas em servi?os de emergência no Brasil, 2006 e 2007
Mascarenhas,Márcio Dênis Medeiros; Malta,Deborah Carvalho; Silva,Marta Maria Alves da; Carvalho,Cynthia Gazal; Monteiro,Rosane Aparecida; Morais Neto,Otaliba Libanio de;
Ciência & Saúde Coletiva , 2009, DOI: 10.1590/S1413-81232009000500020
Abstract: alcohol-related injuries are an important public health issue worldwide. the objective of this study was to describe the epidemiology of alcohol intake perceived by interviewers among injury victims seen at emergency departments in selected brazilian cities. cross-sectional data were collected from the injury surveillance system based on sentinel health services recently implemented in the country through intentional sampling in 2006 and 2007 and analyzed in epi info 3.5.1. alcohol intake perception was higher in violence-related injuries than in unintentional injuries (37.9% versus 8%). for violence-related injuries, highest proportions of alcohol intake perception were observed among males (43.7%), 20 to 39 years old (45.3%), blacks (40.5%), and low schooling level victims (40.3%). settings where these injuries occurred with the highest concerned proportions were taverns (78.2%) and public places (39.5%). higher alcohol intake perception was observed in assaults (39.1%), suicide attempts (25.4%), transport-related injuries (16.8%), and falls victims (5.9%).
Systolic blood pressure of dogs at hospital and domestic environment
Soares, Frederico Aécio Carvalho;Neuwald, Elisa Barp;Mombach, Ver?nica Santos;D'Avila, Ana Elize Ribeiro;Conrado, Francisco de Oliveira;González, Félix Hilario Diaz;
Ciência Rural , 2012, DOI: 10.1590/S0103-84782012005000036
Abstract: the measurement of blood pressure (bp) is an important assessment of the cardiovascular system, being influenced by physical and pathological conditions. certain situations of stress and anxiety during bp measurement can lead to elevated values in small animals, known in medicine as "white coat effect". the aim of this research was to compare systolic blood pressure (sbp) measurement using doppler ultrasonography in 45 adult healthy dogs in two environments, at a veterinary hospital and at home. comparison of heart rate, serum concentrations of cortisol and glucose intended to help the evaluation of the stress level of the animals. the mean of sbp at the veterinary hospital was 154.7mmhg and it was significantly (p<0.01) higher than at home (136.3mmhg). it was also observed that hr (mean=122.7bpm), and serum cortisol (median=4.5μg dl-1) and glucose (mean=95.9mg dl-1) concentrations were significantly higher (p<0.01) at the hospital, when compared with values obtained at home (109.6bpm; 1.5μg dl-1 and 85.5mg dl-1, respectively). in conclusion, the environment can influence sbp in dogs, due to factors related to stress.
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