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Search Results: 1 - 10 of 613498 matches for " R. de C. F. de;Lyra "
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An edge-based unstructured finite volume procedure for the numerical analysis of heat conduction applications
Lyra, P. R. M.;Lima, R. de C. F. de;Guimar?es, C. S. C.;Carvalho, D. K. E. de;
Journal of the Brazilian Society of Mechanical Sciences and Engineering , 2004, DOI: 10.1590/S1678-58782004000200007
Abstract: in recent years, there has been a significant level of research on the application of unstructured mesh methods to the simulation of a variety of engineering and scientific problems. great progress has been achieved in such area and one of the most successful methodologies consists on the use of the finite volume method (fvm). the unstructured fv formulation is very flexible to deal with any kind of control volume and therefore any kind of unstructured meshes, which are particularly important when complex geometries or automatic mesh adaptation are required. in this article, an unstructured finite volume vertex centered formulation, which was implemented using an edge-based data structure, is deduced and detailed for the solution of heat conduction problems. the numerical formulation is initially described considering a tri-dimensional model and latter particularized for bi-dimensional applications using triangular meshes. the presented procedure is very flexible and efficient to solve potential problems. it can also be extended to deal with a broader class of applications, such as models involving convection-diffusion-reaction terms, after considering the appropriate discretization of the convection-type term. in order to demonstrate the potentiality of the method, some model problems are investigated and the results are validated using analytical or other well-established numerical solutions.
An axisymmetric finite volume formulation for the solution of heat conduction problems using unstructured meshes
Lyra, P. R. M.;Lima, R. de C. F. de;Carvalho, D. K. E. de;Silva, G. M. L. L. da;
Journal of the Brazilian Society of Mechanical Sciences and Engineering , 2005, DOI: 10.1590/S1678-58782005000400009
Abstract: in this work, a finite volume formulation developed for two-dimensional models is extended to deal with axisymmetric models of heat conduction applications. this formulation uses a vertex centered finite volume method and it was implemented using an edge-based data structure. the time and domain discretization using triangular meshes is described in details, including the treatment of boundary conditions, source terms, and domains with multiple materials. the proposed formulation is validated and proves to be effective and flexible through the solution of simple model problems.
The use of an axisymmetric formulation of the Finite Volume Method for the thermal analysis of the retina and ocular tissues following implantation of retinal prosthesis
Silva, G. M. L. L. da;Lima, R. de C. F. de;Lyra, P. R. M.;Carvalho, D. K. E. de;Fernandes, A.;
Journal of the Brazilian Society of Mechanical Sciences and Engineering , 2012, DOI: 10.1590/S1678-58782012000300011
Abstract: this study analyzes the heat transfer in human eyes following implantation of retinal prostheses using an axisymmetric formulation of the finite volume method. the model used consisted of a vertex centered unstructured grid finite volume method in an edge-based data structure and an explicit time integration. the results of the finite volume thermal analysis in ocular tissues were determined in the presence of two types of retinal implants: subretinal and epiretinal. for the subretinal device, the maximum temperature reached in the retina was 36.78°c (309.78 k) and the irreversible thermal damage occurred at 200 days. in the case of the epiretinal implant, the maximum temperature reached at the retinal/chip interface was 36.92°c (309.92 k) and the irreversible thermal damage occurred at 180 days. our results indicate that tin spite of its higher dissipation power, the epiretinal implant produces thermal damages similar to that caused by the subretinal implant. the computational tool which was developed was able to effectively calculate temperature profiles and thermal damage values to retinal implants and is also capable to calculate temperature profile in any other geometry of interest, for example with other types s of external thermal source like laser beans.
Association between dyslipidemia and anthropometric indicators in adolescents
Vieira Cunha Lima,S. C.; Oliveira Lyra,C.; Galv?o Bacurau Pinheiro,L.; Medeiros de Azevedo,P. R.; Arrais,R. F.; Campos Pedrosa,L. F.;
Nutrición Hospitalaria , 2011,
Abstract: the dyslipidemia associated with excess weight is a risk profile global call for cardiovascular disease (cvd). the aim of this study was to investigate the association between dyslipidemias and other risk factors for cardiovascular diseases (cvd) in adolescents, considering sexual maturation. a cross-sectional study was carried out with 432 adolescents from public schools, aged 10-19 years. the correlations between the variables from the lipid profile and the body mass index (bmi), waist circumference (wc), waist-to-height ratio (whtr), sexual maturation, familial history and maternal education were evaluated using pearson's correlation coefficient. low high-density lipoprotein cholesterol (hdl-c) was the most prevalent dyslipidemia (50.5%), regardless of gender. there were significant correlations between triglycerides and bmi (r = 0.30, p<0.01), wc (r = 0.32, p < 0.01) and whtr (r = 0.33, p < 0.01). the linear model, which took into consideration sexual maturation, age and bmi, explain about 1 to 10.4% of the lipid profile variation. the low hdl-c was the most prevalent dyslipidemia in all adolescents and hypertriglyceridemia was most prevalent in overweight adolescents. associations between dyslipidemias and anthropometric indicators (bmi and rca) detected in this study can generate the hypothesis of the risk factors for cvd in adolescents.
Comparison between qualitative and semiquantitative catheter-tip cultures: laboratory diagnosis of catheter-related infection in newborns
Marconi, Camila;Cunha, Maria de Lourdes RS;Lyra, Jo?o C;Bentlin, Maria R;Batalha, Jackson EN;Sugizaki, Maria Fátima;Rugolo, Lígia MSS;
Brazilian Journal of Microbiology , 2008, DOI: 10.1590/S1517-83822008000200012
Abstract: this prospective study evaluated semiquantitative and qualitative catheter-culture methods for diagnosis of catheter-related infection (cri) in newborns. catheter tips from newborns admitted to the neonatal unit of the university hospital of the botucatu medical school, unesp were included in the study. catheter cultures were performed with both semiquantitative and qualitative techniques. for cri diagnosis, microorganisms isolated from catheter cultures and from peripheral blood cultures were identified and submitted to agent susceptibility test. the gold standard was the certain cri diagnosis when same microorganism (specie and profile of susceptibility to agents) was isolated from both catheter tips and peripheral blood culture. a total of 85 catheters from 63 newborns were included in the study. the semiquantitative culture method, despite presenting lower sensitivity (90%), showed higher specificity (71%) when compared to 100% of sensitivity and 60% of specificity in the qualitative method. the identification of the microorganisms obtained from the catheter cultures showed a prevalence of coagulase-negative staphylococci(cns) species. the specie staphylococcus epidermidis (77.5%) was the prevalent in the catheters with positive semiquantitative cultures. among 11 episodes with cri diagnosis, 8 (72.7%) were associated with cns species, of which 6 were s. epidermidis. two episodes of cri by s. aureus and one by candida parapsilosis were also detected. the semiquantitative catheter-culture method showed advantages for cri diagnosis in newborns when compared to the conservative qualitative method.
Utilidade da cultura da ponta de cateter no diagnóstico de infec??o neonatal
Marconi, Camila;Cunha, Maria de Lourdes Ribeiro de Souza da;Lyra, Jo?o C.;Bentlin, Maria R.;Batalha, Jackson E. N.;Sugizaki, Maria Fátima;Corrente, José E.;Rugolo, Lígia M. S. S.;
Jornal de Pediatria , 2009, DOI: 10.1590/S0021-75572009000100014
Abstract: objective: to determine the number of colony-forming units (cfu) that best correlates with catheter-related infections (cri) in newborns. methods: this was a prospective study of semiquantitative cultures of catheter tips obtained from newborns in the neonatal unit at faculdade de medicina de botucatu, state of s?o paulo, brazil. the microorganisms isolated from catheter and peripheral blood cultures were identified and submitted to a drug susceptibility test. the optimal cutoff point was determined by the receiver operating characteristic (roc) curve. results: a total of 85 catheters obtained from 63 newborns were studied. staphylococcus epidermidis was the predominant species in the catheters (75%). eight of 11 (72.7%) cri episodes were associated with coagulase-negative staphylococci, six of which were of the s. epidermidis type. roc curve analysis indicated that the optimal cutoff point for the diagnosis of cri was 122 cfu. conclusion: the cutoff point of 122 cfu correlated best with the diagnosis of cri in newborns.
Comparison of surfactant protein B polymorphisms of healthy term newborns with preterm newborns having respiratory distress syndrome
Lyra, P.P.R.;Vaz, F.A.C.;Moreira, P.E.;Hoffmann, J.W.;de Mello, D.E.;Diniz, E.M.A.;
Brazilian Journal of Medical and Biological Research , 2007, DOI: 10.1590/S0100-879X2006005000105
Abstract: polymorphisms and mutations in the surfactant protein b (sp-b) gene have been associated with the pathogenesis of respiratory distress syndrome (rds). the objective of the present study was to compare the frequencies of sp-b gene polymorphisms between preterm babies with rds and healthy term newborns. we studied 50 preterm babies with rds (inclusion criteria - newborns with rds and gestational age between 28 and 33 weeks and 6 days), and 100 healthy term newborns. four sp-b gene polymorphisms were analyzed: a/c at nucleotide -18, c/t at nucleotide 1580, a/g at nucleotide 9306, and g/c at nucleotide 8714, by pcr amplification of genomic dna and genotyping by crflp. the healthy newborns comprised 42 female and 58 male neonates; 39 were white and 61 non-white. the rds group comprised 21 female and 29 male preterm neonates; 28 were white and 22 non-white. weight ranged from 640 to 2080 g (mean: 1273 g); mean gestational age was 31 weeks and 2 days (range: 28-33 weeks and 6 days). when white children were analyzed separately, a statistically significant difference in the g/c polymorphism at 8714 was observed between groups (p = 0.028). all other genotype frequencies were similar for both groups when sex and race were analyzed together. analysis of the sp-b polymorphism g/c at nucleotide 8714 showed that among white neonates the gg genotype was found only in the rds group at a frequency of 17% and the gc genotype was more frequently found in healthy term newborns. these data demonstrate an association of gg genotype with rds.
Critical wave-packet dynamics in the power-law bond disordered Anderson Model
R. P. A. Lima,F. A. B. F. de Moura,M. L. Lyra,H. N. Nazareno
Physics , 2005, DOI: 10.1103/PhysRevB.71.235112
Abstract: We investigate the wave-packet dynamics of the power-law bond disordered one-dimensional Anderson model with hopping amplitudes decreasing as $H_{nm}\propto |n-m|^{-\alpha}$. We consider the critical case ($\alpha=1$). Using an exact diagonalization scheme on finite chains, we compute the participation moments of all stationary energy eigenstates as well as the spreading of an initially localized wave-packet. The eigenstates multifractality is characterized by the set of fractal dimensions of the participation moments. The wave-packet shows a diffusive-like spread developing a power-law tail and achieves a stationary non-uniform profile after reflecting at the chain boundaries. As a consequence, the time-dependent participation moments exhibit two distinct scaling regimes. We formulate a finite-size scaling hypothesis for the participation moments relating their scaling exponents to the ones governing the return probability and wave-function power-law decays.
Liver histological alterations in patients with chronic hepatitis C and normal ALT levels in the city of Salvador, Northeast-Brazil
Santana, Nelma Pereira de;Freitas, Luiz A.R. de;Lyra, André Castro;Paraná, Raymundo;Santana, Genoile;Trepo, Christian;Lyra, Luiz G.C.;
Brazilian Journal of Infectious Diseases , 2005, DOI: 10.1590/S1413-86702005000200003
Abstract: patients with chronic hepatitis c can have variable clinical progression. hepatic histological alterations appear to be milder in asymptomatic subjects who have persistently normal alt levels. aims: to evaluate the severity of histological liver alterations in blood donors with normal and elevated alt levels. methods: we evaluated volunteer blood donors from the main blood bank of the city of salvador-brazil. those who were anti-hcv positive were invited to participate in the study. serum alt and ast levels were measured at two time points, two months apart. donors were divided into two groups: group i, individuals with alt > 1.5 times the upper limit of normal in at least one time point and group ii, individuals with normal or near normal alt, at both time points results: we evaluated 30,232 blood donors and 528 (1.7%) of them were anti-hcv positive. eighty-two attended our service and hcv infection was confirmed in 66 individuals. male gender predominated in both groups; the mean age was 36 for group i, and 33 for group ii. tattoos and intravenous illicit drug use were frequently-encountered risk factors. liver biopsy was done in 43 subjects. among donors with elevated alt, two (10%) had minimum alterations, while in group ii normal liver or minimum alterations were observed in six (26%) subjects. chronic hepatitis or cirrhosis was encountered in 35 (81%) individuals: three (15%) and five (21%) subjects had chronic hepatitis without inflammatory activity, 10 (50%) and 11 (48%) had minimum to moderate activity and five (25%) and one (4.3%) had cirrhosis, in groups i and ii, respectively (p was not significant). conclusions: the prevalence of anti-hcv among this population of volunteer blood donors was 1.7%, and these subjects had few liver histological alterations or chronic hepatitis and cirrhosis. liver injury severity was significant in patients with elevated alt, however subjects with normal levels may also present chronic hepatitis and cirrhosis.
Numerical simulation of two dimensional compressible and incompressible flows
Costa, G. K.;Lyra, P. R. M.;Lira, C. A. B. de Oliveira;
Journal of the Brazilian Society of Mechanical Sciences and Engineering , 2005, DOI: 10.1590/S1678-58782005000400005
Abstract: in this article, we make use of a stabilized finite element method to solve the complete set of navier-stokes equations. the methodology adopted is such that it allows for the use of different sets of variables, particularly the so called conservative and pressure variables. a space-time formulation using a simple augmented supg stabilizing term is proposed for the particular case of pressure variables. comparison with data published in the available literature is done and a reasonably good agreement is obtained.
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