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Search Results: 1 - 10 of 616386 matches for " Tania María de Castro Carvalho Neto "
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Revolución científica, tecnológica y energética: la influencia sobre el pensamiento económico de los siglos XVI Y XVII
Sinclair Mallet Guy Guerra,Gustavo de Conti Macedo,Tania María de Castro Carvalho Neto
Revista Galega de Economía , 2006,
Abstract: Este trabajo sitúa algunos de los escritos económicos de los siglos XVI y XVII en el contexto de las revoluciones científicas y tecnológicas de ese período y precedentes, fase de transición del feudalismo al capitalismo. También discute el cambio del centro de atención de los autores, ya que de asuntos teológicos, lógicos y éticos se pasa a tratar las cosas prácticas de la vida , tal y como ocurrió en los dos siglos estudiados. Para ello se da relevancia al trabajo de William Petty. Continúa discutiendo el progreso en la apropiación de sistemas energéticos y como este hecho transformó la realidad feudal dirigiéndola hacia una economía mercantilista, alterando también las preocupaciones de los letrados en relación con las cuestiones sociales, induciéndolos a percibir el comercio internacional como uno de los factores que explicarían el enriquecimiento de un estado. Finalmente, el pensamiento económico del período fue analizado detalladamente procurando resaltar en los escritos la influencia de los sistemas energéticos y de la tecnología, así como la visión sobre estos temas de los autores o de las escuelas de pensamiento.
Dissipative quantum systems modeled by a two level reservoir coupling
A. O. Caldeira,A. H. Castro Neto,T. Oliveira de Carvalho
Physics , 1993, DOI: 10.1103/PhysRevB.48.13974
Abstract: The coupling between a quantum dynamical system and a two-level system reservoir is analysed within the framework of the Feynman-Vernon theory. We stress the differences between this new reservoir and the well-known bath of oscillators and show that, in order to obtain the Langevin equation for the system of interest in the high temperature regime, we have to choose a spectral distribution function $J(\omega)$ which is finite for $\omega=0$.
Consumo hídrico e coeficiente de cultura da mamoneira na microrregi?o de Lavras, Minas Gerais
Rios, Gervásio F. A.;Carvalho, Luiz G. de;Magina, Flávio de C.;Castro Neto, Pedro;Silva, Bruno M.;Fraga, Ant?nio C.;
Revista Brasileira de Engenharia Agrícola e Ambiental , 2011, DOI: 10.1590/S1415-43662011001200009
Abstract: the study was carried out in order to evaluate the evapotranspiration (etc) and crop coefficient (kc) of castor bean by drip irrigation system, under the climatic conditions of lavras, minas gerais state, brazil, from 01/24 to 08/30/2008. the etc was determined by the energy balance according to the bowen ratio method and kc by the methods and recommendations of the fao-56 paper, from 02/14 to 06/03/2008, corresponding to phases i (growth), ii (vegetative), iii (fruiting) and iv (maturity). for this purpose, in the center of the experimental area, the sensors were installed to measure the temperature and relative humidity, at two levels above the crop canopy; the net radiation (rn) and the soil heat flux (g) at 0.08 m under the soil surface. the average etc values in phases i, ii and iii were 2.48, 2.68 and 3.04 mm d-1, respectively. the respective kc in these phases were 0.27, 0.46, 0.87 and 0.57 in maturity phase, within the limits and recommendations of the fao-56 paper.
Donor and Acceptor Levels in Semiconducting Transition Metal Dichalcogenides
A. Carvalho,A. H. Castro Neto
Physics , 2013, DOI: 10.1103/PhysRevB.89.081406
Abstract: Density functional theory calculations are used to show that it is possible to dope semiconducting transition metal dichalcogenides (TMD) such as MoS$_2$ and WS$_2$ with electrons and/or holes either by chemical substitution or by adsorption on the sulfur layer. Notably, the activation energies of Lithium and Phosphorus, a shallow donor and a shallow acceptor, respectively, are smaller than 0.1 eV. Substitutional halogens are also proposed as alternative donors adequate for different temperature regimes. All dopants proposed result in very little lattice relaxation and, hence, are expected to lead to minor scattering of the charge carriers. Doped MoS$_2$ and WS$_2$ monolayers are extrinsic in a much wider temperature range than 3D semiconductors, making them superior for high temperature electronic and optoelectronic applications.
Revasculariza??o cirúrgica do miocárdio com enxerto composto de artérias torácica interna esquerda e radial: compara??o do fluxo sangüíneo para artéria coronária esquerda com a técnica convencional
Castro Neto, Josué V.;Chaccur, Paulo;Carvalho, Alexandre R. de;Staico, Rodolfo;Albertal, Mariano;Farran, Jorge;Moreira, Luiz Felipe P.;Lisboa, Luiz Augusto;Oliveira, Sérgio A.;Paulista, Paulo P.;
Revista Brasileira de Cirurgia Cardiovascular , 2004, DOI: 10.1590/S0102-76382004000400007
Abstract: background: composite grafting techniques for coronary artery bypass grafts (cabg) have been widely used. however, it remains unclear whether this technique provides similar blood flow to the left coronary artery when compared to the conventional alternative. we sought to compare the total blood flow to the left coronary branches that are revascularized with left internal thoracic (lita) and radial artery (ra) grafts using composite and non-composite techniques. method: a total of 42 patients were randomly assigned to three groups according to the cabg technique to be used: group a or composite lita-ra in a y format (n=14); group b or modified composite lita-ra [intercoronary graft with ra and lita to ra at the level of the left anterior descending artery (lad), n=14)]; and group c or pedicled lita to the lad and aorto-coronary ra (n=14). the patients were submitted to postoperative blow flow velocity analysis using a 0.014 inch 12 mhz doppler flowire. coronary flow reserve (cfr) was calculated by determining the average hyperemic peak velocity (apv) after an injection of adenosine. results: proximal lita baseline apv was 28.4±4.8 cm/s in group a, 34.4±7.9 cm/s in group b (p=0.0384 x c) and 25.8± 8.6 cm/s in group c. the cfr was 2.1 ± 0.4, 2±0.3 and 2±0.4 in groups a,b and c respectively (p=0.7208 a, b x c). the total q to lca branches was 110±30 in group a, 145±59 in b and 133±58 ml/min in c (p=0.3232 a, b x c). conclusions: the lita-ra composite graft maintains an adequate cfr and conveys similar blood flow to the left coronary artery branches when compared with conventional cabg technique.
Jogos de gênero: o recreio numa escola de ensino fundamental
Cruz, Tania Mara;Carvalho, Marília Pinto de;
Cadernos Pagu , 2006, DOI: 10.1590/S0104-83332006000100006
Abstract: based upon an ethnographic study of children's break time in a primary school in s?o paulo, this article analyses the gender relations among children from 7 to 10 years old. we focus on the conflicting relationships between the sexes in an attempt to show the multiple forms of power play hidden behind apparently similar actions. by articulating the concept of conflict with simultaneous meanings of aggression and joking, we use the concept of "gender play" as one of the possible ways of sociability between boys and girls.
Strain-induced gap modification in black phosphorus
A. S. Rodin,A. Carvalho,A. H. Castro Neto
Physics , 2014, DOI: 10.1103/PhysRevLett.112.176801
Abstract: The band structure of single-layer black phosphorus and the effect of strain are predicted using density functional theory and tight-binding models. Having determined the localized orbital composition of the individual bands from first-principles, we use the system symmetry to write down the effective low-energy Hamiltonian at the $\Gamma$ point. From numerical calculations and arguments based on the crystal structure of the material, we show that the deformation in the direction normal to the plane can be use to change the gap size and induce a semiconductor-metal transition.
Excitons in anisotropic 2D semiconducting crystals
A. S. Rodin,A. Carvalho,A. H. Castro Neto
Physics , 2014, DOI: 10.1103/PhysRevB.90.075429
Abstract: The excitonic behavior of anisotropic two-dimensional crystals is investigated using numerical methods. We employ a screened potential arising due to the system polarizability to solve the central-potential problem using the Numerov approach. The dependence of the exciton energies on the interaction strength and mass anisotropy is demonstrated. We use our results to obtain the exciton binding energy in phosphorene as a function of the substrate dielectric constant.
Phosphorene nanoribbons
A. Carvalho,A. S. Rodin,A. H. Castro Neto
Physics , 2014, DOI: 10.1209/0295-5075/108/47005
Abstract: Edge-induced gap states in finite phosphorene layers are examined using analytical models and density functional theory. The nature of such gap states depends on the direction of the cut. Armchair nanoribbons are insulating, whereas nanoribbons cut in the perpendicular direction (with zigzag and cliff-type edges) are metallic, unless they undergo a reconstruction or distortion with cell doubling, which opens a gap. All stable nanoribbons with unsaturated edges have gap states that can be removed by hydrogen passivation. Armchair nanoribbon edge states decay exponentially with the distance to the edge and can be described by a nearly-free electron model.
Band nesting and the optical response of two-dimensional semiconducting transition metal dichalcogenides
A. Carvalho,R. M. Ribeiro,A. H. Castro Neto
Physics , 2013, DOI: 10.1103/PhysRevB.88.115205
Abstract: We have studied the optical conductivity of two-dimensional (2D) semiconducting transition metal dichalcogenides (STMDC) using ab-initio density functional theory (DFT). We find that this class of materials presents large optical response due to the phenomenon of band nesting. The tendency towards band nesting is enhanced by the presence of van Hove singularities in the band structure of these materials. Given that 2D crystals are atomically thin and naturally transparent, our results show that it is possible to have strong photon-electron interactions even in 2D
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