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Search Results: 1 - 10 of 542089 matches for " D. S. Galv?o "
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Curved Graphene Nanoribbons: Structure and Dynamics of Carbon Nanobelts
B. V. C. Martins,D. S. Galvo
Physics , 2010, DOI: 10.1088/0957-4484/21/7/075710
Abstract: Carbon nanoribbons (CNRs) are graphene (planar) structures with large aspect ratio. Carbon nanobelts (CNBs) are small graphene nanoribbons rolled up into spiral-like structures, i. e., carbon nanoscrolls (CNSs) with large aspect ratio. In this work we investigated the energetics and dynamical aspects of CNBs formed from rolling up CNRs. We have carried out molecular dynamics simulations using reactive empirical bond-order potentials. Our results show that similarly to CNSs, CNBs formation is dominated by two major energy contribution, the increase in the elastic energy due to the bending of the initial planar configuration (decreasing structural stability) and the energetic gain due to van der Waals interactions of the overlapping surface of the rolled layers (increasing structural stability). Beyond a critical diameter value these scrolled structures can be even more stable (in terms of energy) than their equivalent planar configurations. In contrast to CNSs that require energy assisted processes (sonication, chemical reactions, etc.) to be formed, CNBs can be spontaneously formed from low temperature driven processes. Long CNBs (length of $\sim$ 30.0 nm) tend to exhibit self-folded racket-like conformations with formation dynamics very similar to the one observed for long carbon nanotubes. Shorter CNBs will be more likely to form perfect scrolled structures. Possible synthetic routes to fabricate CNBs from graphene membranes are also addressed.
Prediction of Giant Electro-actuation for Carbon Nanoscrolls
R. Rurali,V. R. Coluci,D. S. Galvo
Physics , 2006,
Abstract: We study by first-principles calculations the electro-mechanical response of carbon nanoscrolls. We show that although they present a very similar behavior to carbon nanotubes for what concerns the axial deformation sensitivity, they exhibit a radial response upon charge injection which is up to one order of magnitude larger. In association with their high stability, this behavior make them a natural choice for a new class of very efficient nano-actuators.
Prototyping: Major Advance in Surgical Planning and Customizing Prostheses in Patients with Bone Tumors of the Head and Neck  [PDF]
Terence P. Farias, Fernando Luiz Dias, Bruno Albuquerque Sousa, Mário Sérgio Galvo, Dênio Bispo, Ana Carolina Pastl
International Journal of Clinical Medicine (IJCM) , 2013, DOI: 10.4236/ijcm.2013.47A1001
Abstract: Major resections of bone tumors of the head and neck, owing to their small dimensions and their proximity to the organs in this region, cause important functional and aesthetic problems that significantly compromise patients’ quality of life. Therefore, therapeutic planning should always extend beyond the resection to include functional and aesthetic reconstruction, preferably immediately. Microsurgical reconstruction represents a significant advance, but has not yet been perfected. Rapid prototyping (RP) comes as a new technology for the purpose of assisting the surgeon in the visual and tactile aspects of surgery, providing diagnostic accuracy and increasing the success of surgical planning. The authors demonstrate the technological advances in the manufacture of customized mandibular prostheses with the assistance of RP and practical applications of these methods.
Thermophoretically Driven Carbon Nanotube Oscillators
V. R. Coluci,V. S. Timóteo,D. S. Galvo
Physics , 2010, DOI: 10.1063/1.3276546
Abstract: The behavior of a nanodevice based upon double-walled carbon nanotube oscillators driven by periodically applied thermal gradients (7 and 17 K/nm) is investigated by numerical calculations and classical molecular dynamics simulations. Our results indicate that thermophoresis can be effective to initiate the oscillator and that suitable heat pulses may provide an appropriate way to tune its behavior. Sustained regular oscillatory as well as chaotic motions were observed for the systems investigated in this work.
Doping of zigzag carbon nanotubes through the encapsulation of small fullerenes
K. S. Troche,V. R. Coluci,R. Rurali,D. S. Galvo
Physics , 2006,
Abstract: In this work we investigated the encapsulation of C$_20$ and C$_30$ fullerenes into semiconducting carbon nanotubes to study the possibility of bandgap engineering in such systems. Classical molecular dynamics simulations coupled to tight-binding calculations were used to determine the conformational and electronic properties of carbon nanotube supercells containing up to 12 fullerenes. We have observed that C$_20$ fullerenes behave similarly to a p-type dopant while C$_30$ ones work as n-type ones. For larger diameter nanotubes, where fullerene patterns start to differ from the linear arrangements (peapods), the doping features are preserved for both fullerenes, but local disorder plays an important role and significantly alters the electronic structure. The combined incorporation of both fullerene types (hybrid encapsulation) into the same nanotube leads to a behavior similar to that found in electronic junctions in Silicon-based electronic devices. These aspects can be exploited in the design of nanoelectronic devices using semiconducting carbon nanotubes.
Eficácia de dados Hyperion/EO-1 para identifica??o de alvos agrícolas: compara??o com dados ETM+/Landsat-7
Tisot, Daniela A.;Formaggio, Antonio R.;Rennó, Camilo D.;Galvo, Lênio S.;
Engenharia Agrícola , 2007, DOI: 10.1590/S0100-69162007000300021
Abstract: the aim of this work was to assess hyperion/eo-1 hyperspectral data to discriminate agricultural fields, comparing that data classification accuracy with etm+/landsat-7 multi-spectral data classification accuracy. for this purpose, agricultural targets with well-defined and subtle spectral differences in franca municipality, s?o paulo state, brazil, imaged by both sensors in july, 2002, were discriminated by using a supervised classification (maximum likelihood) algorithm. agricultural targets with well-defined spectral differences were characterized by six land use/land cover classes, while five sugarcane varieties were used as targets with subtle spectral differences. when the broadband etm+ data were classified, the overall accuracy was 91.5% for six land use/land cover classes and 67.6% for five sugarcane variety classes, while for narrowband hyperion data the accuracies were 94.9% and 87.1%, respectively. this result shows the importance of hyperspectral data use for agricultural targets discrimination with similar spectral characteristics.
Discrimination of complex visual stimuli in Cebus apella: identity matching with pictures
Galvo, Olavo F.;Soares Filho, Paulo S. D.;Neves Filho, Hernando B.;Nagahama, Milena M.;
Psychology & Neuroscience , 2009, DOI: 10.3922/j.psns.2009.1.06
Abstract: do capuchin monkeys respond to photos as icons? do they discriminate photos of capuchin monkeys' faces? looking for answers to these questions we trained three capuchin monkeys in simple and conditional discrimination tasks and tested the discriminations when comparison stimuli were partially covered. three capuchin monkeys experienced in simultaneous simple discrimination and idmts were trained with repeated shifts of simple discriminations (rssd), with four simultaneous choices, and idmts (1 s delay, 4 choices) with pictures of known capuchins monkeys' faces. all monkeys did discriminate the pictures in both procedures. performances in probes with partial masks with one fourth of the stimulus hidden were consistent with baseline level. errors occurred when a picture similar to the correct one was available among the comparison stimuli, when the covered part was the most distinct, or when pictures displayed the same monkey. capuchin monkeys do match pictures of capuchin monkeys' faces to the sample. the monkeys treated different pictures of the same monkey as equivalent, suggesting that they respond to the pictures as icons, although this was not true to pictures of other monkeys. subsequent studies may bring more evidence that capuchin monkeys treat pictures as depictions of real scenes.
Hallazgos de Triatoma infestans en México
D.S. Rocha,C. Galvo,J. Jurberg,R. Carcavallo
Revista de Biología Tropical , 2001,
Elastic Properties of Nanowires
Alexandre F. da Fonseca,C. P. Malta,D. S. Galvo
Physics , 2005, DOI: 10.1063/1.2194309
Abstract: We present a model to study Young's modulus and Poisson's ratio of the composite material of amorphous nanowires. It is an extension of the model derived by two of us [Da Fonseca and Galvao, Phys. Rev. Lett. 92, 175502 (2004)] to study the elastic properties of amorphous nanosprings. The model is based on twisting and tensioning a straight nanowire and we propose an experimental setup to obtain the elastic parameters of the nanowire. We used the Kirchhoff rod model to obtain the expressions for the elastic constants of the nanowire.
Identifying carcinogenic activity of methylated and non-methylated polycyclic aromatic hydrocarbons (PAHs) through electronic and topological indices
Braga, R.S.;Barone, P.M.V.B.;Galvo, D.S.;
Brazilian Journal of Physics , 2000, DOI: 10.1590/S0103-97332000000300013
Abstract: polycyclic aromatic hydrocarbons (pahs) are a class of planar molecules, abundant in urban environment, which can induce chemical carcinogenesis. their carcinogenic power varies in a large range, from very strong carcinogens to inactive ones. in a previous study, we proposed a methodology to identify the pahs carcinogenic activity exploring electronic and topological indices. in the present work, we show that it is possible to simplify that methodology and expand its applicability to include methylated pahs compounds. using very simple rules, we can predict their carcinogenic activity with high accuracy (? 89%).
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