42 results on '"Oliveira, C. L."'
Search Results
2. Nanoindentation in finite thickness viscoelastic materials.
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Costa, D. F. S., de Araújo, J. L. B., Oliveira, C. L. N., and de Sousa, J. S.
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ATOMIC force microscopy ,NANOINDENTATION ,VISCOELASTIC materials ,FINITE geometries ,FINITE element method ,FINITE, The - Abstract
In this work, we present an analytical model to describe atomic force microscopy force curves of standard linear solid and power-law viscoelastic materials by taking indenter geometry and finite thickness effects into account. We show that conical/pyramidal cantilevers are less susceptible to finite thickness effects than other shapes, such as spherical and flat punch indenters. This is confirmed by finite element modeling of the stress field distribution within the sample. We also perform a systematic error analysis for the cases where finite thickness samples are analyzed with an infinite thickness force model. In particular, we show that for spherical indenters and indentation depth up to 20% of sample thickness, the mechanical response of viscoelastic materials will wrongly mimic a purely elastic behavior even within timescales where viscoelastic relaxation should appear. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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3. Sublinear drag regime at mesoscopic scales in viscoelastic materials.
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Ferreira, A. E. O., de Araújo, J. L. B., Ferreira, W. P., de Sousa, J. S., and Oliveira, C. L. N.
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DRAG force ,MACROMOLECULES - Abstract
Stressed soft materials commonly present viscoelastic signatures in the form of power-law or exponential decay. Although exponential responses are the most common, power-law time dependencies arise peculiarly in complex soft materials such as living cells. Understanding the microscale mechanisms that drive rheologic behaviors at the macroscale shall be transformative in fields such as material design and bioengineering. Using an elastic network model of macromolecules immersed in a viscous fluid, we numerically reproduce those characteristic viscoelastic relaxations and show how the microscopic interactions determine the rheologic response. The macromolecules, represented by particles in the network, interact with neighbors through a spring constant k and with fluid through a non-linear drag regime. The dissipative force is given by γv
α , where v is the particle's velocity, and γ and α are mesoscopic parameters. Physically, the sublinear regime of the drag forces is related to micro-deformations of the macromolecules, while α ≥ 1 represents rigid cases. We obtain exponential or power-law relaxations or a transitional behavior between them by changing k, γ, and α. We find that exponential decays are indeed the most common behavior. However, power laws may arise when forces between the macromolecules and the fluid are sublinear. Our findings show that in materials not too soft not too elastic, the rheological responses are entirely controlled by α in the sublinear regime. More specifically, power-law responses arise for 0.3 ⪅ α ⪅ 0.45, while exponential responses for small and large values of α, namely, 0.0 ⪅ α ⪅ 0.2 and 0.55 ⪅ α ⪅ 1.0. [ABSTRACT FROM AUTHOR]- Published
- 2024
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4. Development and Validation of an UV Spectrophotometric Method for Determination of Thiamphenicol in Dosage Form
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Martins, Y. A. and De Oliveira, C. L. C. G.
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- 2019
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5. Combining Small-Angle X-ray Scattering and X-ray Powder Diffraction to Investigate Size, Shape and Crystallinity of Silver, Gold and Alloyed Silver-Gold Nanoparticles
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Garcia, P. R. A. F., Loza, K., Daumann, S., Grasmik, V., Pappert, K., Rostek, A., Helmlinger, J., Prymak, O., Heggen, M., Epple, M., and Oliveira, C. L. P.
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- 2019
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6. Double power-law viscoelastic relaxation of living cells encodes motility trends
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de Sousa, J. S., Freire, R. S., Sousa, F. D., Radmacher, M., Silva, A. F. B., Ramos, M. V., Monteiro-Moreira, A. C. O., Mesquita, F. P., Moraes, M. E. A., Montenegro, R. C., and Oliveira, C. L. N.
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- 2020
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7. Magnetic, structural and cation distribution studies on FeO · Fe (2-x) Nd xO3 (x = 0.00, 0.02, 0.04, 0.06 and 0.1) nanoparticles
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Araujo, W. W. R., Araujo, J. F. D. F., Oliveira, C. L. P., Brito, G. E. S., and Figueiredo Neto, A. M.
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- 2019
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8. Alterations promoted by acid straightening and/or bleaching in hair microstructures.
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Lima, C. R. R. C., Lima, R. J. S., Bandeira, A. C. C., Couto, R. A. A., Velasco, M. V. R., Bordallo, H. N., and Oliveira, C. L. P.
- Subjects
INELASTIC neutron scattering ,SMALL-angle X-ray scattering ,HAIR dyeing & bleaching ,NEUTRON spectroscopy ,NEUTRON scattering ,CYTOPLASMIC filaments ,X-ray scattering ,DENATURATION of proteins - Abstract
Human hair is a biopolymer constituted mainly of keratin intermediate filaments, lipids, pigments and water. Cosmetic treatments usually interact with the hair at the molecular level, inducing changes in its components and modifying the physicochemical and mechanical properties of the fibers. Here, the effect of acid straightening on the morphology and ultrastructure of Caucasian hair was investigated by a group of complementary experimental methods: wide‐, small‐ and ultra‐small‐angle X‐ray scattering; high‐resolution 3D X‐ray microscopy; quasi‐elastic neutron scattering and inelastic neutron scattering; thermogravimetry–mass spectrometry; and differential scanning calorimetry (DSC). X‐ray diffraction patterns showed that acid straightening associated with a flat iron (∼180°C) changed the cortex of the fiber, shown by denaturation of the intermediate filaments (measured by DSC). The increase in the spacing of the lipid layers and the observation of the dehydration behavior of the fiber provided indications that water may be confined between these layers, while neutron spectroscopy showed alterations in the vibration mode of the CH2 groups of the lipids and an increase of the proton (H+) mobility in the hair structure. The latter may be associated with the extremely low pH of the formulation (pH ≃ 1). Additionally, this investigation showed that bleached hair (one‐time bleached) is more damaged by the action of acid straightening than virgin hair, which was shown by a threefold increase in the percentage of total porosity of the tresses. The obtained results demonstrate that the investigation approach proposed here can provide very important thermodynamic and structural information on induced changes of hair structure, and certainly can be applied for the evaluation of the action mode and efficiency of cosmetic treatments. [ABSTRACT FROM AUTHOR]
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- 2023
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9. C-reactive protein in Brazilian adolescents: distribution and association with metabolic syndrome in ERICA survey
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Giannini, D T, Kuschnir, M C C, de Oliveira, C L, Bloch, K V, Schaan, B D, Cureau, F V, de Carvalho, K M B, Dias, K.M.B., Dias, G.M., and Szklo, M.
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Metabolic syndrome X -- Physiological aspects -- Demographic aspects ,Teenagers -- Health aspects ,Youth -- Health aspects ,C-reactive protein -- Physiological aspects ,Pediatric research ,Food/cooking/nutrition ,Health - Abstract
Background/Objectives: C-reactive protein (CRP) is a marker of inflammation that has been shown to be predictive of cardiovascular diseases in adults. To evaluate the distribution of CRP as well as its association with metabolic syndrome and its components. Subjects/Methods: This is a cross-sectional study on adolescents aged 12-17, participants in the Study of Cardiovascular Risk in Adolescents (ERICA). Anthropometric, biochemical and blood pressure data were collected from 6316 adolescents, selected from a random sample of students in the cities of Brasilia, Fortaleza, João Pessoa, Manaus, Porto Alegre and Rio de Janeiro. Metabolic syndrome was defined by the criteria proposed by International Diabetes Federation for adolescent. Poisson regression model with robust variance, taking into consideration the study's complex sampling design, was used to determine multivariate-adjusted prevalence rate ratios expressing the relationship of metabolic syndrome with CRP. Results: In adolescents with metabolic syndrome, CRP concentrations were five times higher (1.01 mg/l; interquartile range (IQR): 0.54-3.47) compared with those without metabolic syndrome (0.19 mg/l; IQR: 0.10-0.78). In multivariate Poisson regression analysis adjusted by sex, age and skin color, the prevalence of elevated CRP (>3.0 mg/l) was almost three times higher in adolescents with metabolic syndrome than in those without this condition (prevalence ratio (PR): 2.9; 95%CI: 2.0-4.3; P Conclusions: The association of CRP with metabolic syndrome and its components suggests that inflammation may be useful in assessing cardiovascular risk in adolescents., Author(s): D T Giannini [sup.1] , M C C Kuschnir [sup.2] , C L de Oliveira [sup.3] , K V Bloch [sup.4] , B D Schaan [sup.5] , F V [...]
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- 2017
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10. Water activity in lamellar stacks of lipid bilayers: “Hydration forces” revisited
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Leite Rubim, R., Gerbelli, B. B., Bougis, K., Pinto de Oliveira, C. L., Navailles, L., Nallet, F., and Andreoli de Oliveira, E.
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- 2016
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11. Stabilising lamellar stacks of lipid bilayers with soft confinement and steric effects
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Bougis, K., Leite Rubim, R., Ziane, N., Peyencet, J., Bentaleb, A., Février, A., Oliveira, C. L. P., Andreoli de Oliveira, E., Navailles, L., and Nallet, F.
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- 2015
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12. Detection of Trypanosoma cruzi DNA in blood by PCR is associated with Chagas cardiomyopathy and disease severity
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Sabino, E. C., Ribeiro, A. L., Lee, T. H, Oliveira, C. L., Carneiro-Proietti, A. B., Antunes, A. P., Menezes, M. M., Ianni, B. M., Salemi, V. M., Nastari, L., Fernandes, F., Sachdev, V., Carrick, D. M., Deng, X., Wright, D., Gonçalez, T. T., Murphy, E. L., Custer, B., and Busch, M. P.
- Published
- 2015
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13. Anisotropic Brownian motion in ordered phases of DNA fragments
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Dobrindt, J., Rodrigo Teixeira da Silva, E., Alves, C., Oliveira, C. L. P., Nallet, F., Andreoli de Oliveira, E., and Navailles, L.
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- 2012
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14. Liquid crystalline cellulosic elastomers: free standing anisotropic films under stretching
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Sena, C., Godinho, M. H., Oliveira, C. L. P., and Figueiredo Neto, A. M.
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- 2011
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15. The development of new oral vaccines using porous silica.
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Oliveira, C L P, Lopes, J L S, Sant’Anna, O A, Botosso, V F, Bordallo, H N, and Fantini, M C A
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- 2022
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16. Electrical properties of polyaniline films formed in acid with and without Cs+ ions in the electrolyte
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Maggio, S. R., Oliveira, C. L. F., Aguirre, M. J., and Zagal, J. H.
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- 1994
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17. Multiple power-law viscoelastic relaxation in time and frequency domains with atomic force microscopy.
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de Sousa, F B, Babu, P K V, Radmacher, M, Oliveira, C L N, and de Sousa, J S
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VISCOELASTIC materials ,ATOMIC force microscopy ,POLYACRYLAMIDE - Abstract
Complex viscoelastic materials exhibit power law (PL) relaxations, as opposed to simple materials described by exponential decays. Other interesting materials, like living cells, hold a universal double PL behavior whose exponents depend on the health and type of the cells. Usually, only dynamic assays are considered capable to study such viscoelastic relaxation mechanisms. In this work, we propose analytical responses with single or multiple power-law relaxation behavior by generalizing classical viscoelastic models in terms of fractional derivatives of arbitrary order α (0 1). In addition, we demonstrate that simple atomic force microscopy force curves are powerful methods to directly observe the viscoelastic relaxation of such complex materials. In order to validate our findings, we compare the viscoelastic relaxation exponents measured directly from simple force curves (SFCs) with those measured with dynamic techniques in both living cells and polyacrylamide gels. We believe the fractional models unveiled here describe a variety of complex materials and may be used (with SFCs) to explore sophisticated viscoelastic phenomena. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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18. Nanostructure and giant Hall effect in T[M.sub.x][(Si[O.sub.2]).sub.1-x] (TM=Co, Fe, Ni) granular system
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Socolovsky, L. M., Oliveira, C. L. P., Denardin, J. C., Knobel, M., and Torriani, I. L.
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Physics - Abstract
Granular T[M.sub.x][(Si[O.sub.2]).sub.1-x] (TM=Co, Fe, Ni) thin films are thermally treated at different temperatures and their magnetotransport and structural properties are analyzed. Results reveal that the changes in giant Hall effect upon annealing could depend on a particular combination of nanoparticle diameter, interparticle distance, and size distribution.
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- 2006
19. Nanostructure and giant Hall effect in TMx(SiO2)1-x (TM=Co,Fe,Ni) granular system.
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Socolovsky, L. M., Oliveira, C. L. P., Denardin, J. C., Knobel, M., and Torriani, I. L.
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NANOSTRUCTURED materials , *NANOSTRUCTURES , *ANNEALING of metals , *HALL effect , *X-ray scattering - Abstract
Granular TMx(SiO2)1-x (TM=Co,Fe,Ni) thin films were thermally treated at different temperatures and their magnetotransport and structural properties were studied. Hall resistivity decreases with thermal annealing. Structure was analyzed based on small angle x-ray scattering results. A model of polydisperse system of hard spheres was used for obtaining structural parameters. Analysis reveals that a volume fraction of transition-metal atoms (less than 29%) are forming nanospheres. Changes in giant Hall effect upon annealing can depend on a particular combination of nanoparticle diameter, interparticle distance, and size distribution. [ABSTRACT FROM AUTHOR]
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- 2006
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20. Study of the morphological evolution of vanadium pentoxide nanostructures under hydrothermal conditions.
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Avansi, W., Oliveira, C. L. P., Ribeiro, C., Leite, E. R., and Mastelaro, V. R.
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VANADIUM pentoxide , *NANOSTRUCTURES , *SMALL-angle X-ray scattering , *ELECTRON microscopy , *HYDROTHERMAL synthesis - Abstract
A detailed study on the morphological evolution of one-dimensional (1D) vanadium pentoxide (V2O5) nanostructures was performed. Small-angle X-ray scattering (SAXS) and electron microcopy techniques were used for the analyses of the influence of synthesis parameters on a hydrothermal synthesis method of V2O5 nanostructures based on the degradation of a peroxocomplex precursor. A mechanism that explains the morphological evolution under different experimental conditions is proposed and the role of the dehydration process as well as the importance of the oriented attachment (OA) mechanism is discussed. [ABSTRACT FROM AUTHOR]
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- 2016
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21. Genome-wide identification and in silico characterisation of micro RNAs, their targets and processing pathway genes in Phaseolus vulgaris L.
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Sousa Cardoso, T. C., Portilho, L. G., Oliveira, C. L., McKeown, P. C., Maluf, W. R., Gomes, L. A. A., Teixeira, T. A., Amaral, L. R., Spillane, C., Souza Gomes, M., and Whelan, J.
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GENOMICS ,KIDNEY bean ,RNA analysis ,PLANT development ,SPECIES - Abstract
Common bean ( Phaseolus vulgaris L., Fabaceae) is a globally important staple crop, which is an important source of calories, protein and essential micronutrients. At the genomic level little is known regarding the small non-coding RNAs within the common bean genome. One of the most important classes of such small non-coding RNAs is micro RNAs (mi RNAs), which control mRNA and protein expression levels in many eukaryotes. Computational methods have been applied to identify putative mi RNAs in the genomes of different organisms. In this study, our objective was to comprehensively identify and characterise mi RNAs from the genome and transcriptome of P. vulgaris, including both mature and precursor mi RNA forms. We also sought to identify the putative proteins involved in mi RNA processing and the likely target genes of common bean mi RNAs. We identified 221 mature mi RNAs and 136 precursor mi RNAs distributed across 52 different mi RNA families in the P. vulgaris genome. Amongst these, we distinguished 129 novel mature mi RNAs and 123 mi RNA precursors belonging to 24 different mi RNA families. We also identified 31 proteins predicted to participate in the mi RNA-processing pathway in P. vulgaris. Finally, we also identified 483 predicted mi RNA targets, including many which corroborate results from other species, suggesting that mi RNA regulatory systems are evolutionarily conserved and important for plant development. Our results expand the study of mi RNAs and their target genes in common bean, and provide new opportunities to understand their roles in the biology of this important staple crop. [ABSTRACT FROM AUTHOR]
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- 2016
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22. Fracturing Highly Disordered Materials.
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Moreira, A. A., Oliveira, C. L. N., Hansen, A., Araújo, N. A. M., Herrmann, H. J., and Andrade Jr., J. S.
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ORDER-disorder models , *BONE fractures , *SPINE , *BODY cavities , *PERCOLATION - Abstract
We investigate the role of disorder on the fracturing process of heterogeneous materials by means of a two-dimensional fuse network model. Our results in the extreme disorder limit reveal that the backbone of the fracture at collapse, namely, the subset of the largest fracture that effectively halts the global current, has a fractal dimension of 1.22 ± 0.01. This exponent value is compatible with the universality class of several other physical models, including optimal paths under strong disorder, disordered polymers, watersheds and optimal path cracks on uncorrelated substrates, hulls of explosive percolation clusters, and strands of invasion percolation fronts. Moreover, we find that the fractal dimension of the largest fracture under extreme disorder, df = 1.86 ± 0.01, is outside the statistical error bar of standard percolation. This discrepancy is due to the appearance of trapped regions or cavities of all sizes that remain intact till the entire collapse of the fuse network, but are always accessible in the case of standard percolation. Finally, we quantify the role of disorder on the structure of the largest cluster, as well as on the backbone of the fracture, in terms of a distinctive transition from weak to strong disorder characterized by a new crossover exponent. [ABSTRACT FROM AUTHOR]
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- 2012
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23. INVASION PERCOLATION WITH A HARDENING INTERFACE UNDER GRAVITY.
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OLIVEIRA, C. L. N., WITTEL, F. K., ANDRADE JR., J. S., and HERRMANN, H. J.
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PERCOLATION , *PERCOLATION theory , *SEEPAGE , *GLUE , *FLUIDS - Abstract
We propose a modified Invasion Percolation (IP) model to simulate the infiltration of glue into a porous medium under gravity in 2D. Initially, the medium is saturated with air and then invaded by a fluid that has a hardening effect taking place from the interface towards the interior by contact with the air. To take into account that interfacial hardening, we use an IP model where capillary pressures of the growth sites are increased with time. In our model, if a site stays for a certain time at interface, it becomes a hard site and cannot be invaded anymore. That represents the glue interface becoming hard due to exposition with the air. Buoyancy forces are included in this system through the Bond number which represents the competition between the hydrostatic and capillary forces. We then compare our results with results from literature of non-hardening fluids in each regime of Bond number. We see that the invasion patterns change strongly with hardening while the non-hardening behavior remains basically not affected. [ABSTRACT FROM AUTHOR]
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- 2010
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24. Lifetime of quasi-bound states in open semiconductor quantum structures.
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de Oliveira, C. L. N., de Sousa, J. S., Freire, J. A. K., Farias, G. A., Freire, V. N., and Degani, M. H.
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- 2005
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25. Two new sealed sample cells for small angle x-ray scattering from macromolecules in solution and complex fluids using synchrotron radiation.
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Cavalcanti, L. P., Torriani, I. L., Plivelic, T. S., Oliveira, C. L. P., Kellermann, G., and Neuenschwander, R.
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X-ray scattering ,X-rays ,ELECTROMAGNETIC waves ,MACROMOLECULES ,MOLECULES ,COMPLEX fluids ,AMORPHOUS substances ,RADIATION - Abstract
Two different vacuum tight sample cells for in situ temperature dependent small angle scattering from liquids are presented in this article. In the first one, the sample fills a 1 mm thickness gap sealed on both sides by two thin parallel mica windows (volume 300 μl). In the second one, the liquid is injected into a 1 mm cylindrical capillary tube (volume 130 μl). The cells are lodged into temperature controlled chambers directly connected to the beamline vacuum path. Several important improvements with respect to similar instrumentation previously reported are: (1) versatile application of the mica cell, that can be used for all types of samples (gels, liquid crystals, and dispersions in organic solvents) and (2) the design of the chamber for the capillary cell allows registration of wider angle data and a convenient replacement of the capillary tube after each experiment. Signal to background ratio and data reproducibility were tested using protein solutions. We give a brief report of scattering experiments performed with different protein samples and two-dimensional data collection. [ABSTRACT FROM AUTHOR]
- Published
- 2004
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26. Steps toward determination of the size and structure of the broad-line region in active galactic nuclei. II - an intensive study of NGC 5548 at optical wavelengths
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Peterson, B. M., Balonek, T. J., Barker, E. S., Bechtold, J., Bertram, R., Bochkarev, N. G., Bolte, M. J., Bond, D., Boroson, T. A., Carini, M. T., Carone, T. E., Christensen, J. A., Clements, S. D., Cochran, A. L., Cohen, R. D., Crampton, D., Dietrich, M., Elvis, Martin S., Ferguson, A., Filippenko, A. V., Fricke, K. J., Gaskell, C. M., Halpern, J. P., Huchra, J, Hutchings, J. B., Kollatschny, W., Koratkar, A. P., Korista, K. T., Krolik, J. H., Lame, N. J., Laor, A., Leacock, R. J., MacAlpine, G. M., Malkan, M. A., Maoz, D., Miller, H. R., Morris, S. L., Netzer, H., Oliveira, C. L. M., Penfold, J., Penston, M. V., Perez, E., Pogge, R. W., Richmond, M. W., Romanishin, W., Rosenblatt, E. I., Saddlemyer, L., Sadun, A., Sawyer, S. R., Shields, J. C., Shapovalova, A. I., Smith, A. G., Smith, H. A., Smith, P. S., Sun, W.-H., Thiele, U., Turner, T. J., Veilleux, S., Wagner, R. M., Weymann, R. J., Wilkes, Belinda Jane, Wills, B. J., Wills, D., and Younger, P. F.
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Active Galactic Nuclei ,Galactic Structure ,Seyfert Galaxies ,Astronomical Photometry ,Astronomical Spectroscopy ,Emission Spectra ,Iue ,Light Curve ,Visible Spectrum - Abstract
A large, international program of ground-based optical spectroscopy and photometry of the variable Seyfert 1 galaxy NGC 5548 undertaken in support of an IUE monitoring campaign is described. This contribution presents the data base and describes the methods used to correct for systematic differences between spectra from different sources. Optical continuum and H-beta emission-line light curves are derived from the spectra. The behavior of the optical continuum is qualitatively the same as the behavior of the ultraviolet continuum. Cross-correlation of the ultraviolet and optical continuum measurements does not reveal any significant lag between them. The h-beta emission-line variations show the same basic pattern as seen in the continuum and ultraviolet emission lines, with H-beta lagging behind the continuum by about 20 days. This is significantly larger than the about 10 day lag deduced for Ly-alpha., Astronomy
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- 1991
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27. Subcritical fatigue in fuse networks.
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Oliveira, C. L. N., Vieira, A. P., Herrmann, H. J., and Andrade jr., J. S.
- Abstract
We obtain the Paris law of fatigue crack propagation in a fuse network model where the accumulated damage in each resistor increases with time as a power law of the local current amplitude. When a resistor reaches its fatigue threshold, it burns irreversibly. Over time, this drives cracks to grow until the system is fractured into two parts. We study the relation between the macroscopic exponent of the crack-growth rate —entering the phenomenological Paris law— and the microscopic damage accumulation exponent, γ, under the influence of disorder. The way the jumps of the growing crack, Δa, and the waiting time between successive breaks, Δt, depend on the type of material, via γ, are also investigated. We find that the averages of these quantities, and , scale as power laws of the crack length a, and , where is the average rupture time. Strikingly, our results show, for small values of γ, a decrease in the exponent of the Paris law in comparison with the homogeneous case, leading to an increase in the lifetime of breaking materials. For the particular case of γ = 0, when fatigue is exclusively ruled by disorder, an analytical treatment confirms the results obtained by simulation. [ABSTRACT FROM AUTHOR]
- Published
- 2012
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28. Magnetic and structural study of electric double-layered ferrofluid with MnFe2O4@γ-Fe2O3 nanoparticles of different mean diameters: Determination of the magnetic correlation distance.
- Author
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Gonçalves, E. S., Cornejo, D. R., Oliveira, C. L. P., Neto, A. M. Figueiredo, Depeyrot, J., Tourinho, F. A., and Aquino, R.
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MAGNETIC fluids , *IRON oxides , *MANGANESE oxides , *ELECTRIC double layer , *NANOPARTICLES analysis , *MAGNETIC properties - Abstract
Magnetic fluids based on manganese ferrite nanoparticles were studied from the structural point of view through small angle x-rays scattering (SAXS) and from the magnetic point of view through zero-field cooling and field cooling (ZFC-FC) and ac susceptibility measurements (MS). Three different colloids with particles mean diameters of 2.78,3.42, and 6.15 nm were investigated. The size distribution obtained from SAXS measurements follows a log-normal behavior. The ZFC-FC and MS results revealed the presence of an important magnetic interaction between the nanoparticles, characterized by a magnetic correlation distance ?. The colloidal medium can be pictures as composed by magnetic cluster constituted by N interacting particles. These magnetic clusters are not characterized by a physical aggregation of particles. The energy barrier energy obtained is consistent with the existence of this magnetic clusters. Besides the magnetic interaction between particles, confinement effects must be included to account for the experimental values of the magnetic energy barrier encountered. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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29. Measuring the viscoelastic relaxation function of cells with a time-dependent interpretation of the Hertz-Sneddon indentation model.
- Author
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Lima IVM, Silva AVS, Sousa FD, Ferreira WP, Freire RS, de Oliveira CLN, and de Sousa JS
- Abstract
The Hertz-Sneddon elastic indentation model is widely adopted in the biomechanical investigation of living cells and other soft materials using atomic force microscopy despite the explicit viscoelastic nature of these materials. In this work, we demonstrate that an exact analytical viscoelastic force model for power-law materials, can be interpreted as a time-dependent Hertz-Sneddon-like model. Characterizing fibroblasts (L929) and osteoblasts (OFCOLII) demonstrates the model's accuracy. Our results show that the difference between Young's modulus E Y obtained by fitting force curves with the Hertz-Sneddon model and the effective Young's modulus derived from the viscoelastic force model is less than 3%, even when cells are probed at large forces where nonlinear deformation effects become significant. We also propose a measurement protocol that involves probing samples at different indentation speeds and forces, enabling the construction of the average viscoelastic relaxation function of samples by conveniently fitting the force curves with the Hertz-Sneddon model., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Author(s).)
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- 2024
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30. Antigenic and physicochemical characterization of Hepatitis B surface protein under extreme temperature and pH conditions.
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Lopes JLS, Oliveira DCA, Utescher CLA, Quintilio W, Tenório ECN, Oliveira CLP, Fantini MCA, Rasmussen MK, Bordallo HN, Sant'Anna OA, and Botosso VF
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- Animals, Circular Dichroism, Female, Fluorescence, Hepatitis B Vaccines chemistry, Hepatitis B Vaccines immunology, Hepatitis B virus chemistry, Hydrogen-Ion Concentration, Immunogenicity, Vaccine, Mice, Mice, Inbred BALB C, Protein Denaturation, Silicon Dioxide chemistry, Surface Plasmon Resonance, Vaccine Potency, Hepatitis B Surface Antigens chemistry, Hepatitis B Surface Antigens immunology, Protein Stability, Temperature
- Abstract
Hepatitis B virus causes acute and chronic infections in millions of people worldwide and, since 1982, a vaccine with 95% effectiveness has been available for immunization. The main component of the recombinant hepatitis B vaccine is the surface antigen protein (HBsAg). In this work, the effect of pH, ionic strength and temperature on the native state of the HBsAg antigen were studied by a combination of biophysical methods that included small angle X-ray scattering, synchrotron radiation circular dichroism, fluorescence and surface plasmon resonance spectroscopies, as well as in vivo and in vitro potency assays. The native conformation, morphology, radius of gyration, and antigenic properties of the HBsAg antigen demonstrate high stability to pH treatment, especially in the pH range employed in all stages of HBsAg vaccine production and storage. The HBsAg protein presents thermal melting point close to 56 °C, reaching a more unfolded state after crossing this point, but it only experiences loss of vaccine potency and antigenic properties at 100 °C. Interestingly, a 6-month storage period does not affect vaccine stability, and the results are similar when the protein is kept under refrigerated conditions or at room temperature (20 °C). At frozen temperatures, large aggregates (>200 nm) are formed and possibly cause loss of HBsAg content, but that does not affect the in vivo assay. Furthermore, HBsAg has a well-ordered secondary structure content that is not affected when the protein is formulated with silica SBA-15, targeting the oral delivery of the vaccine. The combined results from all the characterization techniques employed in this study showed the high stability of the antigen at different storage temperature and extreme values of pH. These findings are important for considering the delivery of HBsAg to the immune system via an oral vaccine., (Copyright © 2019 Elsevier Ltd. All rights reserved.)
- Published
- 2019
- Full Text
- View/download PDF
31. Prevalence and screening of active tuberculosis in a prison in the South of Brazil.
- Author
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Pelissari DM, Kuhleis DC, Bartholomay P, Barreira D, Oliveira CLP, de Jesus RS, Possa LA, Jarczewski CA, Nemeth LT, de Araujo ND, Alves PBL, de Souza R, Arakaki D, Dal Molin DB, Werlang P, and Brouwer M
- Subjects
- Adolescent, Adult, Brazil epidemiology, Cross-Sectional Studies, Female, Humans, Male, Middle Aged, Prevalence, Risk Factors, Tuberculosis diagnosis, Young Adult, Mass Screening methods, Prisoners statistics & numerical data, Tuberculosis epidemiology
- Abstract
Setting: Tuberculosis (TB) remains a challenge in Brazil, particularly among prison inmates., Objective: To assess TB prevalence by active case finding in a public prison in southern Brazil., Design: Prison inmates were screened for TB using the presence of cough and chest X-ray (CXR) from October 2014 to August 2016. Presence of cough, irrespective of duration, and abnormal CXRs were further investigated using laboratory tests., Results: Of 10 326 inmates screened, 196 had confirmed TB (1898/100 000 inmates screened). At the first screening, 1759 inmates presented with cough only, 16 of whom had TB; among those with only abnormal CXR (n = 1273), 92 had TB. Xpert was positive in 155 patients, and negative in 15; these results were confirmed using culture. The remaining 26 patients did not undergo Xpert testing and were confirmed using microscopy (27%), culture (42%) or both (31%)., Conclusion: The combined use of symptom screening (cough) and CXR was much more effective in maximising TB yield than using either method alone. If patients presenting with cough alone had not been investigated, 10% of TB patients would have been missed; if those with abnormal CXR but no cough had not been investigated, 51% of TB patients would have been missed. We detected high TB prevalence in this prison by using active case finding.
- Published
- 2018
- Full Text
- View/download PDF
32. Genome-wide identification and in silico characterisation of microRNAs, their targets and processing pathway genes in Phaseolus vulgaris L.
- Author
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de Sousa Cardoso TC, Portilho LG, de Oliveira CL, McKeown PC, Maluf WR, Gomes LA, Teixeira TA, do Amaral LR, Spillane C, and de Souza Gomes M
- Subjects
- Amino Acid Sequence, Base Sequence, Catalytic Domain, Conserved Sequence, Genes, Plant, MicroRNAs metabolism, Molecular Sequence Data, Nucleic Acid Conformation, Phylogeny, Plant Proteins chemistry, Plant Proteins genetics, Plant Proteins metabolism, Protein Structure, Tertiary, Sequence Alignment, Computer Simulation, Genome, Plant, MicroRNAs genetics, Phaseolus genetics, RNA Processing, Post-Transcriptional genetics
- Abstract
Common bean (Phaseolus vulgaris L., Fabaceae) is a globally important staple crop, which is an important source of calories, protein and essential micronutrients. At the genomic level little is known regarding the small non-coding RNAs within the common bean genome. One of the most important classes of such small non-coding RNAs is microRNAs (miRNAs), which control mRNA and protein expression levels in many eukaryotes. Computational methods have been applied to identify putative miRNAs in the genomes of different organisms. In this study, our objective was to comprehensively identify and characterise miRNAs from the genome and transcriptome of P. vulgaris, including both mature and precursor miRNA forms. We also sought to identify the putative proteins involved in miRNA processing and the likely target genes of common bean miRNAs. We identified 221 mature miRNAs and 136 precursor miRNAs distributed across 52 different miRNA families in the P. vulgaris genome. Amongst these, we distinguished 129 novel mature miRNAs and 123 miRNA precursors belonging to 24 different miRNA families. We also identified 31 proteins predicted to participate in the miRNA-processing pathway in P. vulgaris. Finally, we also identified 483 predicted miRNA targets, including many which corroborate results from other species, suggesting that miRNA regulatory systems are evolutionarily conserved and important for plant development. Our results expand the study of miRNAs and their target genes in common bean, and provide new opportunities to understand their roles in the biology of this important staple crop., (© 2015 German Botanical Society and The Royal Botanical Society of the Netherlands.)
- Published
- 2016
- Full Text
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33. Magnetic and structural study of electric double-layered ferrofluid with MnFe(2)O(4)@γ-Fe(2)O(3) nanoparticles of different mean diameters: Determination of the magnetic correlation distance.
- Author
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Gonçalves ES, Cornejo DR, Oliveira CL, Figueiredo Neto AM, Depeyrot J, Tourinho FA, and Aquino R
- Abstract
Magnetic fluids based on manganese ferrite nanoparticles were studied from the structural point of view through small angle x-rays scattering (SAXS) and from the magnetic point of view through zero-field cooling and field cooling (ZFC-FC) and ac susceptibility measurements (MS). Three different colloids with particles mean diameters of 2.78,3.42, and 6.15 nm were investigated. The size distribution obtained from SAXS measurements follows a log-normal behavior. The ZFC-FC and MS results revealed the presence of an important magnetic interaction between the nanoparticles, characterized by a magnetic correlation distance Λ. The colloidal medium can be pictures as composed by magnetic cluster constituted by N interacting particles. These magnetic clusters are not characterized by a physical aggregation of particles. The energy barrier energy obtained is consistent with the existence of this magnetic clusters. Besides the magnetic interaction between particles, confinement effects must be included to account for the experimental values of the magnetic energy barrier encountered.
- Published
- 2015
- Full Text
- View/download PDF
34. SAXS models of TGFBIp reveal a trimeric structure and show that the overall shape is not affected by the Arg124His mutation.
- Author
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Basaiawmoit RV, Oliveira CL, Runager K, Sørensen CS, Behrens MA, Jonsson BH, Kristensen T, Klintworth GK, Enghild JJ, Pedersen JS, and Otzen DE
- Subjects
- Extracellular Matrix Proteins genetics, Extracellular Matrix Proteins metabolism, Humans, Mutant Proteins chemistry, Mutant Proteins genetics, Mutant Proteins metabolism, Scattering, Small Angle, Transforming Growth Factor beta genetics, Transforming Growth Factor beta metabolism, Amino Acid Substitution genetics, Extracellular Matrix Proteins chemistry, Mutation, Missense, Protein Multimerization, Transforming Growth Factor beta chemistry
- Abstract
Human transforming growth factor β induced protein (TGFBIp) is composed of 683 residues, including an N-terminal cysteine-rich (EMI) domain, four homologous fasciclin domains, and an Arg-Gly-Asp (RGD) motif near the C-terminus. The protein is of interest because mutations in the TGFBI gene encoding TGFBIp lead to corneal dystrophy (CD), a condition where protein aggregates within the cornea compromise transparency. The complete three-dimensional structure of TGFBIp is not yet available, with the exception of a partial X-ray structure of the archetype FAS1 domain derived from Drosophila fasciclin-1. In this study, small-angle X-ray scattering (SAXS) models of intact wild-type (WT) human TGFBIp and a mutant (R124H) are presented. The mutation R124H leads to a variant of granular CD. The deduced structure of the TGFBIp monomer consists of four FAS1 domains in a simple "beads-on-a-string" arrangement, constructed by the superimposition of four consecutive Drosophila fasciclin domains. The SAXS-based model of the TGFBIp R124H mutant displayed no structural differences from WT. Both WT TGFBIp and the R124H mutant formed trimers at higher protein concentrations. The similar association properties and three-dimensional shape of the two proteins suggest that the mutation does not induce any major structural rearrangements, but points towards the role of other corneal-specific factors in the formation of corneal R124H deposits., (Copyright © 2011 Elsevier Ltd. All rights reserved.)
- Published
- 2011
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35. Development and validation of an UV spectrophotometric method for determination of gatifloxacin in tablets.
- Author
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Salgado HR and Oliveira CL
- Subjects
- Calibration, Gatifloxacin, Reference Standards, Reproducibility of Results, Spectrophotometry, Ultraviolet, Tablets, Anti-Infective Agents analysis, Fluoroquinolones analysis
- Abstract
A simple, sensitive and accurate spectrophotometric method was developed for the assay of gatifloxacin in raw material and tablets. Validation of the method yielded good results concerning range, linearity, precision and accuracy. The absorbance was measured at 287 nm for gatifloxacin tablet solutions. The linearity range was found to be 4.0-14.0 microg/mL for gatifloxacin. It was also found that the excipients in the commercial tablets did not interfere with the method.
- Published
- 2005
36. Small angle x-ray scattering from lipid-bound myelin basic protein in solution.
- Author
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Haas H, Oliveira CL, Torriani IL, Polverini E, Fasano A, Carlone G, Cavatorta P, and Riccio P
- Subjects
- Computer Simulation, Lipids analysis, Myelin Basic Protein analysis, Myelin Basic Protein classification, Protein Binding, Scattering, Radiation, Solutions, Lipids chemistry, Models, Molecular, Myelin Basic Protein chemistry, X-Ray Diffraction methods
- Abstract
The structure of myelin basic protein (MBP), purified from the myelin sheath in both lipid-free (LF-MBP) and lipid-bound (LB-MBP) forms, was investigated in solution by small angle x-ray scattering. The water-soluble LF-MBP, extracted at pH < 3.0 from defatted brain, is the classical preparation of MBP, commonly regarded as an intrinsically unfolded protein. LB-MBP is a lipoprotein-detergent complex extracted from myelin with its native lipidic environment at pH > 7.0. Under all conditions, the scattering from the two protein forms was different, indicating different molecular shapes. For the LB-MBP, well-defined scattering curves were obtained, suggesting that the protein had a unique, compact (but not globular) structure. Furthermore, these data were compatible with earlier results from molecular modeling calculations on the MBP structure which have been refined by us. In contrast, the LF-MBP data were in accordance with the expected open-coil conformation. The results represent the first direct structural information from x-ray scattering measurements on MBP in its native lipidic environment in solution.
- Published
- 2004
- Full Text
- View/download PDF
37. Extraction of DNA from human skeletal remains: practical applications in forensic sciences.
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Prado VF, Castro AK, Oliveira CL, Souza KT, and Pena SD
- Subjects
- Bone and Bones pathology, Child, Female, Homicide, Humans, Male, Paternity, Bone and Bones chemistry, DNA, Mitochondrial analysis, Forensic Medicine
- Abstract
We have developed an efficient protocol for the extraction of DNA from bone samples. The protocol precludes decalcification and associates an efficient extraction of the DNA with removal of inhibitors by binding of DNA to silica particles. Two forensic cases are described in detail to demonstrate the usefulness of the method.
- Published
- 1997
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- View/download PDF
38. Effects of L-NOARG on plus-maze performance in rats.
- Author
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De Oliveira CL, Del Bel EA, and Guimarães FS
- Subjects
- Animals, Arginine pharmacology, Dose-Response Relationship, Drug, Enzyme Inhibitors administration & dosage, Exploratory Behavior drug effects, Injections, Intraperitoneal, Injections, Intraventricular, Male, Nitroarginine administration & dosage, Rats, Rats, Wistar, Anxiety psychology, Enzyme Inhibitors pharmacology, Nitric Oxide Synthase antagonists & inhibitors, Nitroarginine pharmacology
- Abstract
Nitric oxide (NO) synthase, the enzyme responsible for NO formation, is located in brain regions such as amygdala and dorsolateral central grey, regions which are known to be involved in anxiety. To investigate the possible role of NO in anxiety, rats received acute i.p. injections of NG-nitro-l-arginine (L-NOARG, 7.5-120 mg kg-1), an inhibitor of NO synthase, and were tested in the elevated plus maze, an animal model of anxiety. The drug, at doses of 30-120 mg kg-1, decreased the percentage of entries and time spent on the open arms of the maze, but these doses, with exception of 30 mg, also decreased the number of entries into enclosed arms. These effects disappeared when the animals were tested after chronic L-NOARG treatment (3.75 to 60 mg kg-1 i.p., twice a day for four days). The effects of acute i.p. injection of 30 mg kg-1 of L-NOARG were blocked by i.c.v. pretreatment with 1000 nmol of l-arginine (but not 500 nmol). Thus, inhibition of NO formation in the central nervous system seems to decrease exploration of the elevated plus maze, an effect that disappears after four days of chronic (twice a day) L-NOARG administration.
- Published
- 1997
- Full Text
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39. [Anatomic variations of the coronary arteries].
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Cavalcanti JS, de Lucena Oliveira M, Pais e Melo AV Jr, Balaban G, de Andrade Oliveira CL, and de Lucena Oliveira E
- Subjects
- Adult, Arteriovenous Anastomosis anatomy & histology, Female, Humans, Male, Coronary Vessels anatomy & histology
- Abstract
Purpose: To study the coronary arteries and their main branches showing the aspects of source, trajectory and anastomoses of these vessels at the subepicardial level., Methods: The study was carried out on 110 adult human hearts, of both sexes, fixed in 10% formaldehyde solution. The pericardium was removed to expose the coronary arteries and their branches at the subepicardial level., Results: In 38.18% of the cases the left coronary artery presented a trifurcation into anterior interventricular, circunflex and left marginal branches (35.70%) and into anterior interventricular, circunflex and lateral branches (64.30%). In 60% of the hearts examined, the left coronary artery presented a bifurcation into anterior interventricular and circunflex branches. In 1.82% of the cases these two branches arise directly from the aorta. An anastomosis, at the subepicardial level, between the anterior and posterior interventricular branches was observed in 56.36% of the hearts. In 88.18% the posterior interventricular branch arised from the right coronary artery, whereas in 11.82% this vessel arises from the circunflex branch. Anastomoses between the right coronary artery and the circunflex branch were found in 10% of the hearts (crux cordis). The dominance of the right coronary artery was present in 69.09% of the cases, of the left coronary artery in 11.82% and in 19.09% of the hearts had balanced distribution., Conclusion: The coronary arteries and their main branches present a great quantity of variations with regard to source, trajectory and anastomoses. This knowledge is important for the interpretation of coronary angiography and surgical myocardial revascularization.
- Published
- 1995
40. Midazolam and the N-methyl-D-aspartate (NMDA) receptor antagonist 2-amino-7-phosphonoheptanoic acid (AP-7) attenuate stress-induced expression of c-fos mRNA in the dentate gyrus.
- Author
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Titze-de-Almeida R, de Oliveira CL, Shida HW, Guimarães FS, and Del Bel EA
- Subjects
- Animals, Hippocampus metabolism, Hippocampus physiopathology, Immobilization, In Situ Hybridization, Male, RNA, Messenger genetics, Rats, Rats, Wistar, Receptors, N-Methyl-D-Aspartate physiology, Stress, Physiological metabolism, Stress, Physiological physiopathology, 2-Amino-5-phosphonovalerate analogs & derivatives, Amino Acids pharmacology, Gene Expression Regulation drug effects, Genes, fos, Hippocampus drug effects, Midazolam pharmacology, RNA, Messenger biosynthesis, Receptors, N-Methyl-D-Aspartate antagonists & inhibitors, Stress, Physiological genetics
- Abstract
1. The effects of restraint stress on c-fos mRNA expression in the dentate gyrus were investigated by in situ hybridization. 2. Confirming previous findings, c-fos mRNA expression increased after 30 min of forced restraint. 3. This effect was attenuated by a previous i.c.v. injection of the anxiolytic benzodiazepine midazolam (20 nmol/2 microliters) or the N-methyl-D-aspartate (NMDA) receptor antagonist 2-amino-7-phosphonoheptanoic acid (AP-7; 5 nmol/2 microliters). 4. These results suggest that the dentate gyrus is activated during restraint stress and that this activation may be modulated by benzodiazepine gamma-aminobutyric acidA (GABAA) or NMDA receptors.
- Published
- 1994
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41. Parasitism by Primasubulura jacchi (Marcel, 1857) Inglis, 1958 and Trichospirura leptostoma Smith and Chitwood, 1967 in Callithrix penicillata marmosets, trapped in the wild environment and maintained in captivity.
- Author
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de Resende DM, Pereira LH, de Melo AL, Tafuri WL, Moreira NI, and de Oliveira CL
- Subjects
- Animals, Brazil, Feces parasitology, Callithrix parasitology, Intestinal Mucosa parasitology, Nematoda isolation & purification
- Published
- 1994
- Full Text
- View/download PDF
42. Pharmacological and toxicological evaluation of Alpinia speciosa.
- Author
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Mendonça VL, Oliveira CL, Craveiro AA, Rao VS, and Fonteles MC
- Subjects
- Administration, Oral, Animals, Beverages toxicity, Brazil, Diuretics toxicity, Dogs, Hemodynamics drug effects, Injections, Intraperitoneal, Lethal Dose 50, Mice, Plant Extracts administration & dosage, Plant Extracts isolation & purification, Plant Extracts toxicity, Rats, Rats, Wistar, Sleep drug effects, Plants, Medicinal
- Abstract
Alpinia speciosa Schum or A. nutans is a plant of the Zingiberaceae family, known popularly as "colony" (colônia) and used as a diuretic and to control hypertension. We have determined the concentration of Na+ and K+ found in the alcoholic extract and in the tea concoction. They contained 51.0 mEq Na+, and 132 mEq K+ in the extract, and 0.0 mEq of Na+ and 26 mEq K+ in the tea. Phytochemical analysis of the leaves demonstrated the presence of catecquic tanins, phenols and alkaloids, and also some essential oils. When injected intra-peritoneally the hydroalcoholic extract, in a dose range of 100 to 1400 mg/kg, (or 2500-18000 mg/kg orally) produced in mice: writhing, psychomotor excitation, hypokinesis and pruritus. The LD50 by ip was 0.760 +/- 0.126 g/kg and 10.0 +/- 2.5 g/kg by oral administration for the hydroalcoholic extract. Subacute toxicity made by injecting daily for 30 days the LD10 in rats caused an increase in transaminases and lactate dehydrogenase, whereas other parameters such as blood glucose, urea and creatinine were normal. A histopathological analysis of liver, spleen, gut, lung and heart showed no alterations. The drug also produced a prolongation of the sleeping time. The hydroalcoholic extract induced in the rat and in the dog a dose-dependent fall in blood pressure in doses of 10 to 30 mg/kg. In isolated atria the extract induced a reduction of the frequency and in the inotropic responses. Neither the extract nor the tea had an effect on the diuresis of the rat.
- Published
- 1991
- Full Text
- View/download PDF
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