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Search Results: 1 - 10 of 174297 matches for " Cesar F. Santos "
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Molecular Beam-Thermal Desorption Spectrometry (MB-TDS) Monitoring of Hydrogen Desorbed from Storage Fuel Cell Anodes
Rui F. M. Lobo,Diogo M. F. Santos,Cesar A. C. Sequeira,Jorge H. F. Ribeiro
Materials , 2012, DOI: 10.3390/ma5020248
Abstract: Different types of experimental studies are performed using the hydrogen storage alloy (HSA) MlNi 3.6Co 0.85Al 0.3Mn 0.3 (Ml: La-rich mischmetal), chemically surface treated, as the anode active material for application in a proton exchange membrane fuel cell (PEMFC). The recently developed molecular beam—thermal desorption spectrometry (MB-TDS) technique is here reported for detecting the electrochemical hydrogen uptake and release by the treated HSA. The MB-TDS allows an accurate determination of the hydrogen mass absorbed into the hydrogen storage alloy (HSA), and has significant advantages in comparison with the conventional TDS method. Experimental data has revealed that the membrane electrode assembly (MEA) using such chemically treated alloy presents an enhanced surface capability for hydrogen adsorption.
Application of Hartree-Fock Method for Modeling of Bioactive Molecules Using SAR and QSPR  [PDF]
Cleydson B. R. Santos, Cleison C. Lobato, Francinaldo S. Braga, Sílvia S. S. Morais, Cesar F. Santos, Caio P. Fernandes, Davi S. B. Brasil, Lorane I. S. Hage-Melim, Williams J. C. Macêdo, José C. T. Carvalho
Computational Molecular Bioscience (CMB) , 2014, DOI: 10.4236/cmb.2014.41001
Abstract:
The central importance of quantum chemistry is to obtain solutions of the Schr?dinger equation for the accurate determination of the properties of atomic and molecular systems that occurred from the calculation of wave functions accurate for many diatomic and polyatomic molecules, using Self Consistent Field method (SCF). The application of quantum chemical methods in the study and planning of bioactive compounds has become a common practice nowadays. From the point of view of planning it is important to note, when it comes to the use of molecular modeling, a collective term that refers to methods and theoretical modeling and computational techniques to mimic the behavior of molecules, not intend to reach a bioactive molecule simply through the use of computer programs. The choice of method for energy minimization depends on factors related to the size of the molecule, parameters of availability, stored data and computational resources. Molecular models generated by the computer are the result of mathematical equations that estimate the positions and properties of the electrons and nuclei, the calculations exploit experimentally, the characteristics of a structure, providing a new perspective on the molecule. In this work we show that studies of Highest Occupied Molecular Orbital Energy (HOMO), Low Unoccupied Molecular Orbital Energy (LUMO) and Map of molecular electrostatic potential (MEP) using Hatree-Fock method with different basis sets (HF/3-21G*, HF/3-21G**, HF/6-31G, HF/6-31G*, HF/6-31G** and HF/6-311G), that are of great importance in modern chemistry, biochemistry, molecular biology, and other fields of knowledge of health sciences. In order to obtain a significant correlation, it is essential that the descriptors are used appropriately. Thus, the quantum chemical calculations are an attractive source of new molecular descriptors that can, in principle, express all the geometrical and electronic properties of molecules and their interactions with biological receptor.
Efeito do uso do traje de neoprene sobre variáveis técnicas, fisiológicas e perceptivas de nadadores
Santos, Karini Borges dos;Bento, Paulo Cesar Barauce;Rodacki, André Luiz Félix;
Revista Brasileira de Educa??o Física e Esporte , 2011, DOI: 10.1590/S1807-55092011000200002
Abstract: in open water swimming competitions, athletes are prone to environmental conditions and are frequently exposed to low temperatures, in contrast to what occurs in indoor competitions. in some circumstances the use of special swimming suits is allowed to avoid hypothermia. the aim of this study was to verify the effects of the use of a neoprene swimming suit in comparison to a conventional swimming suit on a number of cinematic and psychophysiological variables. twenty athletes experienced in swimming competitions (12 triathletes and 8 swimmers; 22.0± 6.6 yearsold), whose the performance was 75 ± 7.7% of the national record. athletes performed two maximal and two submaximal 400m crawl simulated competition with a whole body neoprene swimming suit and with a conventional swimming suit. mean speed (vm) stroke length (cb), stroke frequency (fb), swimming index (in), rate of perceived effort (pse), heart rate, and blood lactate concentration (lac) were compared between conditions. the time to perform maximal trials with the use of the neoprene swimming suit was 6.4% shorter than when wearing the traditional swimming suit. fb and the psychophysiological variables remained unchanged, while cb increased in response to the use of the neoprene swimming suit. the use of the neoprene swimming suit in submaximal trials provided smaller fb, fc, lac and pse and larger cb and in in comparison to the use of the traditional swimming suit. the results indicated that the neoprene swimming suit increases performance in biomechanical, physiological and perceptive aspects. the vm increase in maximal efforts does not depend exclusively on changes in fb and cb. possibly, increments of the parameters related to the swimming may have improved the mechanical efficiency of the movement, which may have provided a movement economy that resulted in a better performance.
Diferenciais socioecon?micos na realiza??o de exame de urina no pré-natal
Silveira,Mariangela F; Barros,Aluísio J D; Santos,Iná S; Matijasevich,Alicia; Victora,Cesar G;
Revista de Saúde Pública , 2008, DOI: 10.1590/S0034-89102008000300001
Abstract: objective: urinalysis is an essential component of the prenatal routine, as urinary tract infections during pregnancy may lead to preterm delivery and neonatal morbidity. the objective of the study was to analyze factors associated to the solicitation of urinalysis during pregnancy. methods: during 2004, 4,163 women living in the urban area of pelotas (southern brazil) and who had received prenatal care were interviewed after delivery in the maternity hospitals of the city. prevalence of the non-performance of urinalysis was analyzed in relation to socioeconomic and demographic variables, as well as to characteristics of prenatal care. after a bivariate analysis, logistic regression was conducted to identify factors associated with the outcome, controlling for possible confusion factors at a 5% level of significance. results: the prevalence of not having had the test was 3%. the multivariate analysis showed that black skin color, poverty, low schooling, being unmarried and having fewer than six prenatal visits were associated with a higher probability of not carrying out the test. women who were black, poor and with low schooling presented a 10% probability of not being examined, compared to 0.4% for mothers who were white, wealthy and highly educated. conclusions: despite the fact that urinalysis is essential for preventing complications for the mother and newborn, 3% of the women were not screened. screening coverage may serve as an indicator to assess the quality of prenatal care. pregnant women who are black, poor, with low schooling and unmarried should be targeted in programs for improving the quality of care.
Physics of Electrolytic Gas Evolution
Cesar A. C. Sequeira,Diogo M. F. Santos,Biljana Sljukic,Luis Amaral
Physics , 2013, DOI: 10.1007/s13538-013-0131-4
Abstract: A brief analysis of the physics and effects of electrolytic gas evolution is presented. Aspects considered include bubble nucleation, growth, and detachment, enhancement of mass and heat transfer, and decrease of apparent electrical conductivity of bubble containing electrolytes. This analysis is mainly oriented to hydrogen/oxygen evolving electrodes.
Determinants of preterm birth: Pelotas, Rio Grande do Sul State, Brazil, 2004 birth cohort
Silveira, Mariangela F.;Victora, Cesar G.;Barros, Aluísio J. D.;Santos, Iná S.;Matijasevich, Alicia;Barros, Fernando C.;
Cadernos de Saúde Pública , 2010, DOI: 10.1590/S0102-311X2010000100019
Abstract: prematurity is a leading cause of neonatal mortality and a global health problem that affects high, middle and low-income countries. several factors may increase the risk of preterm birth. in this article, we test the hypothesis that different risk factors determine preterm birth in different income groups by investigating whether risk factors for preterm deliveries in the 2004 pelotas (rio grande do sul state, brazil) birth cohort vary among those groups. a total of 4,142 women were included in the analysis. preterm births were equally common among women who had spontaneous vaginal deliveries as for those with induced or operative births. in the multivariate analysis the factors that remained significantly associated with preterm birth were black skin color, low education, poverty, young maternal age, primiparity, previous preterm birth, inadequacy of prenatal care and reported hypertension. in the analyses repeated after stratification by family income terciles, there was no evidence of effect modification by income and no clear difference between the socioeconomic groups. no association between cesarean section and preterm delivery was found. further studies are required to understand the causes of the epidemic of preterm births in brazil.
Aumento da prematuridade no Brasil: revis?o de estudos de base populacional
Silveira,Mariangela F; Santos,Iná S; Barros,Aluísio J D; Matijasevich,Alicia; Barros,Fernando C; Victora,Cesar G;
Revista de Saúde Pública , 2008, DOI: 10.1590/S0034-89102008000500023
Abstract: objective: the greatest cause of infant mortality in brazil is perinatal conditions, mostly associated with preterm delivery. the objective of the study was to evaluate the evolution of preterm delivery rates in brazil. methods: a review was conducted using the medline and lilacs databases, including published studies in periodicals, thesis and dissertations since 1950. exclusion criteria were: studies related to clinical trials and those with complications at gestation and preterm delivery and care. inclusion criteria were: population-based studies on prevalence of preterm delivery in brazil, with representative sample of the studied population, and using primary data. out of 71 studies found, analysis was carried out on 12. results: the prevalence of preterm delivery found ranged from 3.4% to 15.0% in the southern and southeastern regions between 1978 and 2004, with a rising trend from the 1990s onwards. studies in the northeastern region between 1984 and 1998 found prevalences of preterm delivery ranging from 3.8% to 10.2%, also with a rising trend. conclusions: data from the national live birth information system do not corroborate these trends. rather, they show differences between the preterm rates given by this system and the rates measured in the studies included in this review. because of the important role of preterm birth in relation to infant mortality in brazil, it is important to identify the cause of these increases and to plan interventions that can diminish their occurrence.
Avalia o de programas sociais: abordagens quantitativas e suas limita es
Chiechelski, Paulo Cesar Santos
Textos & Contextos (Porto Alegre) , 2005,
Abstract: O presente texto procura efetuar uma revis o das principais abordagens quantitativas encontradas na literatura especializada para empreender avalia es de programas sociais e caracterizar a importancia dessas atividades para o aperfei oamento dos processos de planejamento e de implementa o de políticas sociais. Adicionalmente, tem como propósito complementar realizar uma breve discuss o sobre as limita es técnicas e conceituais de tais abordagens para representar adequadamente a complexidade dos fen menos sociais.
An Overview of the Amazonian Craton Evolution: Insights for Paleocontinental Reconstruction  [PDF]
Mauro Cesar Geraldes, Armando Dias Tavares, Anderson Costa Dos Santos
International Journal of Geosciences (IJG) , 2015, DOI: 10.4236/ijg.2015.69084
Abstract: The Amazonian craton major accretionary and collisional processes may be correlated to supercontinent assemblies developed at several times in the Earth history. Based on geologic, structural and paleomagnetic evidence paleocontinent reconstructions have been proposed for Archean to younger times. The oldest continent (Ur) was formed probably by five Achaean cratonic areas (Kaapvaal, Western Dhawar, Bhandara, Singhhum and Pilbara cratons). Geologic evidences suggest the participation of the Archaean rocks of the Carajás region in the Ur landmass. Supercontinental 2.45 Ga Kenorland amalgamation is indicated by paleomagnetic data including Laurentia, Baltica, Australia, and Kalahari and Kaapvaal cratons. There is no evidence indicating that Amazonian craton was part of the Kenorland supercontinent. From 1.83 Ga to 1.25 Ga Columbia and Hudsonland supercontinents including Amazonian craton were proposed based on NE portion of the Amazonian craton (Maroni/Itacaiunas province) connection with West Africa and Kalahari cratons. Rodinia supercontinent reconstructions show Amazonia joined to Laurentia-Baltica as result of 1.1 Ga to 1.0 Ga fusion based on the Sunsas-Aguapei belts and Greenville and Sveconorwegian belts, respectivelly. The large Late Mesoproterozoic landmass included also Siberia, East Antartica, West Nile, Kalahari, Congo/Sao Francisco and Greenland. The 750 - 520 Ma Gondwana assembly includes most of the continental fragments rifted apart during the break-up of Rodinia followed by diachronic collisions (Araguaia, Paraguay and Tucavaca belts). The supercontinent Pangea is comprised of Gondwana and Laurentia formed at about 300 - 180 Ma ago. The Amazonian craton margins probably were not envolved in the collisional processes during Pangea because it was embebed in Neoproterozoic materials. As consequence, Amazonian craton borders have no record of the orogenic processes responsible for the Pangea amalgamation.
CdTe and CdSe Quantum Dots Cytotoxicity: A Comparative Study on Microorganisms
Suzete A.O. Gomes,Cecilia Stahl Vieira,Diogo B. Almeida,Jacenir R. Santos-Mallet,Rubem F. S. Menna-Barreto,Carlos L. Cesar,Denise Feder
Sensors , 2011, DOI: 10.3390/s111211664
Abstract: Quantum dots (QDs) are colloidal semiconductor nanocrystals of a few nanometers in diameter, being their size and shape controlled during the synthesis. They are synthesized from atoms of group II–VI or III–V of the periodic table, such as cadmium telluride (CdTe) or cadmium selenium (CdSe) forming nanoparticles with fluorescent characteristics superior to current fluorophores. The excellent optical characteristics of quantum dots make them applied widely in the field of life sciences. Cellular uptake of QDs, location and translocation as well as any biological consequence, such as cytotoxicity, stimulated a lot of scientific research in this area. Several studies pointed to the cytotoxic effect against micoorganisms. In this mini-review, we overviewed the synthesis and optical properties of QDs, and its advantages and bioapplications in the studies about microorganisms such as protozoa, bacteria, fungi and virus.
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