9 results on '"Ferreira W"'
Search Results
2. The Impact of the Right Coronary Artery Geometric Parameters on Hemodynamic Performance.
- Author
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Pinho, N., Sousa, L. C., Castro, C. F., António, C. C., Carvalho, M., Ferreira, W., Ladeiras-Lopes, R., Ferreira, N. D., Braga, P., Bettencourt, N., and Pinto, S. I. S.
- Abstract
Purpose: Coronary artery geometry can have a significant impact in the hemodynamic behavior of coronary blood flow, influencing atherosclerotic plaque formation. The present work focuses on, through a statistical study, the connection between several geometric parameters of the right coronary artery—ostium cross-sectional area, angles between the common trunk and the side-branches, tortuosity, curvature and cross-sectional area in each side-branch—and their influence on hemodynamic descriptors. Parameters such as low wall shear stress and local disturbed flow, which are associated with atherosclerosis formation, were analysed. Methods: Computed tomography images of ten healthy individuals were selected to reconstruct in vivo three-dimensional models of right coronary arteries. Blood flow was simulated through a compliant model with realistic boundary conditions. Calculated hemodynamic descriptors values were correlated with the geometric parameters using the Pearson correlation coefficient (r) and the p value. Results: The strongest correlations were found in the middle and distal segments of the right coronary artery. A decrease in the ostium area promotes a decrease in the WSS magnitude from the proximal to the distal segment (r = 0.82). Very strong correlations (r > 0.90) were achieved between geometric parameters (cross-sectional area, angle, tortuosity) of the right-ventricular branch and the wall shear stress magnitude in the middle and distal segments. Conclusions: Low values of tortuosity, smaller cross-sectional area and higher angle of the right-ventricular branch leads to a hemodynamic behavior more propitious to atherosclerosis formation, within the study cases. The right-ventricular branch seems to have the highest influence in the hemodynamic behavior of the right coronary artery. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
3. Mott Transition in GdMnO3: an Ab Initio Study.
- Author
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Ferreira, W. S., Moreira, E., and Frazão, N. F.
- Abstract
Orthorhombic GdMnO
3 is studied using density functional theory considering the pseudo-potential plane-wave method within local-spin-density approximation, LSDA. The electronic band structure and density of states, for several hydrostatic pressures, are studied. The Mott transition was observed at 60 GPa. Calculated lattice parameters are close to the experimental measurements, and some indirect band gaps (S→Γ) were obtained within the LSDA level of calculation, between the occupied O-2p and unoccupied Gd-4f states. The variation of the gap reduces with increasing pressure, being well fitted to a quadratic function. [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
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4. Frailty syndrome: Visceral adipose tissue and frailty in patients with symptomatic severe aortic stenosis.
- Author
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Pinheiro, Marília, Mancio, J., Conceição, G., Ferreira, W., Carvalho, M., Santos, A., Vouga, L., Gama Ribeiro, V., Leite-Moreira, A., Falcão-Pires, I., and Bettencourt, N.
- Subjects
AORTIC stenosis ,ADIPOSE tissues ,HUMAN body composition ,FRAIL elderly ,ABDOMINAL adipose tissue ,DIAGNOSIS - Abstract
Background/Objectives: In patients with severe aortic stenosis (AS), frailty is a clinically relevant measure of increased vulnerability that should be included in the preoperative risk assessment. Bioelectrical impedance analysis (BIA) derived phase angle (PA) reflects cell membrane integrity and function. Few studies are available on the relative contribution of adiposity distribution on frailty, and about the influences of frailty and visceral obesity in PA value. Therefore, we aimed to evaluate associations among frailty, visceral fat depots and PA in patients with symptomatic severe AS. Methods: In a cohort of patients with symptomatic severe AS and preserved ejection fraction, we examined the associations between frailty, visceral fat depots and bioelectrical impedance analysis (BIA) derived phase angle (PA); and between visceral fat and PA. Frailty was defined according the Fried et al. scale criteria and the body fat distribution was determined by multidetector computed tomography and by BIA. Results: Of the fifty-five included patients, 26 were frail (47%). Adjusting for age and gender, frailty was associated with indexed epicardial adipose tissue volume (EATVi) (the odds of frailty increased 4.1-fold per additional 100 cm3/m2 of EAT [95% confidence interval (CI) of 1.03 to 16.40, p=0.04] and with PA (OR of 0.50, 95% CI, 0.26 to 0.97, p=0.04), but not with body mass index (BMI), waist circumference (WC), indexed total, visceral and subcutaneous abdominal fat areas (TAFAi, VAFAi and SAFAi) nor with indexed mediastinal adipose tissue volume (MATVi). In an age and gender adjusted linear model, PA was inversely correlated with EATVi (β=-0.008, 95% CI, -0.016 to -0.001, p=0.03), but not with BMI, WC, nor with MATVi, VAFAi, SAFAi and TAFAi. Conclusions: In patients with symptomatic severe AS, EATVi is associated with frailty, independently of age and gender, but not with MAFVi or VAFAi. Moreover, frailty and EATVi are associated with impaired cell membrane integrity and function assessed by PA. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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- View/download PDF
5. Structure and physical properties of EuYMnO ceramics.
- Author
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Moreira, J., Almeida, A., Ferreira, W., Chaves, M., Oliveira, J., Silva, J., Sá, M., Vilela, S., and Tavares, P.
- Abstract
This work is addressed to study the crystal structure and morphology, as well as the thermodynamic, dielectric and magnetic properties of EuYMnO ceramics, synthesized by urea sol-gel combustion method. The experimental results were systematically compared with data available for the corresponding single crystals. Though the effect of the anisotropy on both dielectric and magnetic properties is missing, they enabled us to investigate the main physical mechanisms associated with their magnetoelectric properties, in particular the one which drives the ferroelectric phase. The phase sequence and critical temperatures are in good agreement with the corresponding values reported for single crystals. Similarly, structural results evidence strong distortions of the crystal lattice, enhancing the ferromagnetic interactions over the antiferomagnetic ones. A significant contribution of the magnetic fluctuations above T was also evidenced from the magnetization studies. [ABSTRACT FROM AUTHOR]
- Published
- 2010
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6. Use of the BEAST model for biomonitoring water quality in a neotropical basin.
- Author
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Moreno, P., Franç, J. S., Ferreira, W. R., Paz, A. D., Monteiro, I. M., and Callisto, M.
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ENVIRONMENTAL impact analysis ,BIOINDICATORS ,WATERSHEDS ,ENVIRONMENTAL degradation ,ENVIRONMENTAL monitoring - Abstract
The use of predictive models in Neotropical basins is relatively new, and applying these models in large basins is hindered by the lack of ecological, geographical, and social-environmental knowledge. Despite these difficulties, we used data from the das Velhas River basin to apply the BEAST (Benthic Assessment of SedimenT) methodology to evaluate and classify the level of environmental degradation. Our two main objectives were to modify and implement the BEAST methodology for use in biomonitoring programs of Brazilian basins, and to test the hypothesis that a gradient of environmental degradation determines a gradient in the structure and composition of benthic macroinvertebrate assemblages. We evaluated 37 sites: 8 in the main river, 15 in the main tributaries with different impact levels, and 14 in tributaries with minimally disturbed conditions (MDC). The BEAST model allowed us to classify 16 test sites: two as natural, four as altered, three as highly altered, and seven as degraded. Our results indicated degradation of the das Velhas River basin near its urban areas. The BEAST model indicated that the pollution gradient found among the sites generated a gradient of the macroinvertebrate assemblages, corroborating the hypothesis. [ABSTRACT FROM AUTHOR]
- Published
- 2009
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7. Minimal Surfaces Obtained by Ribaucour Transformations.
- Author
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Corro, A., Ferreira, W., and Tenenblat, K.
- Abstract
We consider Ribaucour transformations between minimal surfaces and we relate such transformations to generating planar embedded ends. Applying Ribaucour transformations to Enneper's surface and to the catenoid, we obtain new families of complete, minimal surfaces, of genus zero, immersed in R
3 , with infinitely many embedded planar ends or with any finite number of such ends. Moreover, each surface has one or two nonplanar ends. A particular family is obtained from the catenoid, for each pair ( n, m), n≠ m, such that n m0 is an irreducible rational number. For any such pair, we get a 1-parameter family of finite total curvature, complete minimal surfaces with n+2 ends, n embedded planar ends and two nonplanar ends of geometric index m, whose total curvature is −4π( n+ m). The analytic interpretation of a Ribaucour transformation as a Bäcklund type transformation and a superposition formula for the nonlinear differential equation ΔΦ= e-2Φ is included. [ABSTRACT FROM AUTHOR]- Published
- 2003
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8. Effects of the Bi3+ substitution on the structural, vibrational, and magnetic properties of bismuth layer-structured ferroelectrics.
- Author
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Silva, P. H. T., Silva, M. A. S., da Silva, R. B., Correa, M. A., Bohn, F., de Menezes, A. S., Ferreira, W. C., Ayala, A. P., Sombra, A. S. B., and Fechine, P. B. A.
- Subjects
MAGNETIC properties ,CURIE-Weiss law ,BISMUTH ,MAGNETIC susceptibility ,MOSSBAUER spectroscopy ,FERROELECTRIC ceramics ,HIGH temperatures - Abstract
Bismuth layer-structured ferroelectric Bi
3 R2 Ti3 FeO15 (R = Bi, Nd, and Gd) ceramics were synthesized by conventional solid-state reaction. All the samples showed an orthorhombic structure with A21 am space group. Bi3 Nd2 Ti3 FeO15 and Bi3 Gd2 Ti3 FeO15 presented a reduction in the orthorhombicity when compared to Bi5 Ti3 FeO15 . The magnetic susceptibility of all samples followed the Curie–Weiss law, with negative values of the Curie–Weiss temperature, demonstrating that the magnetic interactions are antiferromagnetic in nature. The magnetization curves suggested a weak canted antiferromagnetic behavior for temperatures below 25 K, followed by a linear behavior in the curves at high temperatures. Mössbauer spectroscopy measurements revealed an increase of the quadrupole splitting values as the temperature decreases, indicating that the samples present local distortions, favoring the existence of weak ferromagnetic phase via the antisymmetric Dzyaloshinskii–Moriya interaction. [ABSTRACT FROM AUTHOR]- Published
- 2020
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9. A new species of Aspidosperma Mart. (Apocynaceae) from Bahia, Brazil.
- Author
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Marcondes-Ferreira, W.
- Abstract
A new species, Aspidosperma thomasii, collected in the vicinity of Uruçuca is described. It belongs to subgenus Aspidosperma section Aspidosperma and is closely related to the A. parvifolium A. DC. group. [ABSTRACT FROM AUTHOR]
- Published
- 1999
- Full Text
- View/download PDF
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