# IF - Artigos publicados em periódicos

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Item Teleportation of a weak coherent cavity field state(2016) Cardoso, Wesley Bueno; Wen-Chao, Qiang; Avelar, Ardiley TorresMostrar mais In this paper we propose a scheme to teleport a weak coherent cavity field state. The scheme relies on the resonant atom-field interaction inside a high-Q cavity. The mean photon-number of the cavity field is assumed much smaller than one, hence the field decay inside the cavity can be effectively suppressed.Mostrar mais Item Modulation of localized solutions in an inhomogeneous saturable nonlinear Schrödinger equation(2017) Alves, Luciano Calaça; Cardoso, Wesley BuenoMostrar mais In this paper we study the modulation of localized solutions by an inhomogeneous saturable nonlinear medium. Throughout an appropriate ansatz we convert the inhomogeneous saturable nonlinear Schrödinger equation in a homogeneous one. Then, via a variational approach we construct localized solutions of the autonomous equation and we present some modulation patterns of this localized structures. We have checked the stability of such solutions through numerically simulations.Mostrar mais Item Zero-dimensional limit of the two-dimensional Lugiato-Lefever equation(2017) Cardoso, Wesley Bueno; Salasnich, Luca; Malomed, Boris A.Mostrar mais We study effects of tight harmonic-oscillator confinement on the electromagnetic field in a laser cavity by solving the two-dimensional Lugiato-Lefever (2D LL) equation, taking into account self-focusing or defocusing nonlinearity, losses, pump, and the trapping potential. Tightly confined (quasi-zero-dimensional) optical modes (pixels), produced by this model, are analyzed by means of the variational approximation, which provides a qualitative picture of the ensuing phenomena. This is followed by systematic simulations of the time-dependent 2D LL equation, which reveal the shape, stability, and dynamical behavior of the resulting localized patterns. In this way, we produce stability diagrams for the expected pixels. Then, we consider the LL model with the vortical pump, showing that it can produce stable pixels with embedded vorticity (vortex solitons) in remarkably broad stability areas. Alongside confined vortices with the simple single-ring structure, in the latter case the LL model gives rise to stable multi-ring states, with a spiral phase field. In addition to the numerical results, a qualitatively correct description of the vortex solitons is provided by the Thomas-Fermi approximation.Mostrar mais Item Quasi-one-dimensional approximation for Bose–Einstein condensates transversely trapped by a funnel potential(2019) Santos, Mateus Calixto Pereira dos; Malomed, Boris A.; Cardoso, Wesley BuenoMostrar mais Starting from the standard three-dimensional (3D) Gross–Pitaevskii equation (GPE) and using a variational approximation, we derive an effective one-dimensional nonpolynomial Schrödinger equation (1D-NPSE) governing the axial dynamics of atomic Bose–Einstein condensates (BECs) under the action of a singular but physically relevant funnel-shaped transverse trap, i.e. an attractive 2D potential ∼−1/r (where r is the radial coordinate in the transverse plane), in combination with the repulsive self-interaction. Wave functions of the trapped BEC are regular, in spite of the potential's singularity. The model applies to a condensate of particles (small molecules) carrying a permanent electric dipole moment in the field of a uniformly charged axial thread, as well as to a quantum gas of magnetic atoms pulled by an axial electric current. By means of numerical simulations, we verify that the effective 1D-NPSE provides accurate static and dynamical results, in comparison to the full 3D GPE, for both repulsive and attractive signs of the intrinsic nonlinearity.Mostrar mais Item Anderson localization induced by interaction in linearly coupled binary Bose-Einstein condensates(2021) Santos, Mateus Calixto Pereira dos; Cardoso, Wesley BuenoMostrar mais In this paper we investigate the existence of Anderson localization induced by one specific component of a binary Bose-Einstein condensate (BEC). We use a mean-field approach, in which each type of particle of the BEC is considered as a specific field, and we consider that only one kind of particle is subject to a quasiperiodic potential, which induces a localization in the partner field. We assume the system is under a Rabi coupling, i.e., a linear coupling mixing the two-field component, and we investigate the conditions associated with the parameter values of the system for observing the localization. Numerical simulations are performed, confirming the existence of Anderson localization in the partner field.Mostrar mais Item Parametrically driven localized magnetic excitations with spatial inhomogeneity(2019) Manickam, Saravanan; Cardoso, Wesley BuenoMostrar mais In this paper we study an inhomogeneous ferromagnet with uniaxial anisotropy and applied magnetic field via the magnetic field component of the propagating electromagnetic wave in the medium. It is observed that the magnetic excitations are governed by localized solutions and the corresponding electromagnetic wave is modulated in the form of soliton modes driven by the inhomogeneity. The localized solutions are obtained in an analytical way by employing a variational approach. The effect of different types of magnetic inhomogeneity is studied for three different types of ansätze. Interestingly, the regions of validity of each ansatz are slightly different, demonstrating that both may be interesting for understanding the whole system.Mostrar mais Item Localization of optical pulses in guided wave structures with only fourth order dispersion(2019) Cardoso, Wesley BuenoMostrar mais Inspired by the recent realization of pure-quartic solitons (Blanco-Redondo et al. (2016) [1]), in the present work we study the localization of optical pulses in a similar system, i.e., a silicon photonic crystal air-suspended structure with a hexagonal lattice. The propagation of ultrashort pulses in such a system is well described by a generalized nonlinear Schrödinger (NLS) equation, which in certain conditions works with near-zero group-velocity dispersion and third order dispersion. In this case, the NLS equation has only the fourth order dispersion term. In the present model, we introduce a quasiperiodic linear coefficient that is responsible to induce the localization. The existence of Anderson localization has been confirmed by numerical simulations even when the system presents a small defocusing nonlinearity.Mostrar mais Item An effective equation for quasi-one-dimensional funnel-shaped Bose–Einstein condensates with embedded vorticity(2022) Santos, Mateus Calixto Pereira dos; Cardoso, Wesley Bueno; Malomed, Boris A.Mostrar mais On the basis of a recently introduced model for the Bose–Einstein condensate (BEC) trapped in the 2D “funnel” potential, ∼ −r−1, we develop analysis for vortex modes, which are confined in the transverse direction by the self-attraction, or by the trapping potential, in the case of self-repulsion. Linear 3D wave functions are found exactly for eigenstates with an orbital momentum. In the case of self-repulsion, 3D wave functions are obtained by means of the Thomas–Fermi approximation. Then, with the help of the variational method, the underlying Gross–Pitaevskii equation is reduced to a 1D nonpolynomial Schr¨odinger equation (NPSE) for modes with zero or nonzero embedded vorticity, which are tightly confined by the funnel potential in the transverse plane. Numerical results demonstrate high accuracy of the NPSE reduction for both signs of the nonlinearity. The analysis is performed for stationary modes and for traveling ones colliding with a potential barrier. By means of simulations of NPSE with the self-attraction, collisions between solitons are studied too, demonstrating elastic and inelastic outcomes, depending on the impact velocity and underlying vorticity. A boundary of the stability of 3D vortices with winding number S = 1 against spontaneous splitting in two fragments is identified in the case of the self-attraction, all vortices with S ≥ 2 being unstable.Mostrar mais Item Effective equation for quasi-one dimensional tube-shaped Bose–Einstein condensates(2019) Santos, Mateus Calixto Pereira dos; Cardoso, Wesley BuenoMostrar mais In this letter we derive an effective 1D equation that describes the axial dynamics of a tube-shaped Bose–Einstein condensate. The dimensional reduction is achieved by using a variational approach starting from the 3D Gross–Pitaevskii equation (GPE) in presence of a nonharmonic external potential in the transverse direction and generic in the axial one. The resulting equation is a time-dependent 1D nonpolynomial Schrödinger equation (NPSE). In view to check the accuracy of our 1D-NPSE, we numerically investigated the ground state properties of such a system that are in perfect agreement with the results produced by the 3D-GPE. We also compare the results with those from an 1D cubic nonlinear Schrödinger equation and the Thomas–Fermi approximation. Finally, the dynamics of ground states obtained from our 1D-NPSE is verified numerically by considering a small change in the strength of the axial confining potential.Mostrar mais Item Double-layer Bose-Einstein condensates: a quantum phase transition in the transverse direction, and reduction to two dimensions(2020) Santos, Mateus Calixto Pereira dos; Malomed, Boris A.; Cardoso, Wesley BuenoMostrar mais We revisit the problem of the reduction of the three-dimensional (3D) dynamics of Bose-Einstein condensates, under the action of strong confinement in one direction (𝑧), to a 2D mean-field equation. We address this problem for the confining potential with a singular term, viz., 𝑉𝑧(𝑧)=2𝑧2+𝜁2/𝑧2, with constant 𝜁. A quantum phase transition is induced by the latter term, between the ground state (GS) of the harmonic oscillator and the 3D condensate split in two parallel noninteracting layers, which is a manifestation of the “superselection” effect. A realization of the respective physical setting is proposed, making use of resonant coupling to an optical field, with the resonance detuning modulated along 𝑧. The reduction of the full 3D Gross-Pitaevskii equation (GPE) to the 2D nonpolynomial Schrödinger equation (NPSE) is based on the factorized ansatz, with the 𝑧 -dependent multiplier represented by an exact GS solution of the 1D Schrödinger equation with potential 𝑉𝑧(𝑧). For both repulsive and attractive signs of the nonlinearity, the 2D NPSE produces GS and vortex states, that are virtually indistinguishable from the respective numerical solutions provided by full 3D GPE. In the case of the self-attraction, the threshold for the onset of the collapse, predicted by the 2D NPSE, is also virtually identical to its counterpart obtained from the 3D equation. In the same case, stability and instability of vortices with topological charge 𝑆=1, 2, and 3 are considered in detail. Thus, the procedure of the spatial-dimension reduction, 3D → 2D, produces very accurate results, and it may be used in other settings.Mostrar mais Item Spontaneous symmetry breaking induced by interaction in linearly coupled binary Bose–Einstein condensates(2022) Santos, Mateus Calixto Pereira dos; Cardoso, Wesley BuenoMostrar mais The spontaneous symmetry breaking (SSB) induced by a specific component of a linearly coupled binary Bose–Einstein condensate was analyzed. The model is based on linearly coupled Schrödinger equations with cubic nonlinearity and double-well potential acting on only one of the atomic components. By numerical simulations, symmetric and asymmetric ground states were obtained, and an induced asymmetry in the partner field was observed. In this sense, it is adequately demonstrated that the linear coupling mixing the two-field component (Rabi coupling) promotes the (in)balance between the atomic species, as well as the appearance of the Josephson and SSB phases.Mostrar mais Item Nonclassical properties and Anderson localization of quantum states in coupled waveguides(2022) Silva, Thais de Lima; Cardoso, Wesley Bueno; Avelar, Ardiley Torres; Malbouisson, Jorge Mário CarvalhoMostrar mais We consider the propagation of light beams through disordered lattices of coupled waveguides searching for Anderson localization and investigating the evolution of nonclassical properties of injected quantum states. We assume that the beam is initially in a variety of states, such as the complementary coherent state, the reciprocal binomial state, and the polynomial state. The statistical properties of the evolved states were analyzed numerically as functions of the localization and delocalization parameters averaged over many realizations of disorder. We also numerically reconstruct the Wigner function of the output state. Interestingly, we find that high values of disorder tend to preserve the quantum properties of some input states when we look at the input waveguide despite of the coupling between it and the neighboring waveguides.Mostrar mais Item Influence of fourth-order dispersion on the Anderson localization(2020) Santos, Mateus Calixto Pereira do; Cardoso, Wesley BuenoMostrar mais Anderson localization, which consists in the absence of wave dispersion due to disorder, brought to the field of optics and matter waves has greatly improved our understanding of fundamental processes, such as transport and multiple dispersion of light. In this paper, we investigate the existence of Anderson localization in the interplay of a standard group velocity dispersion and a fourth-order dispersion term in the nonlinear Schrödinger (NLS) equation in the presence of a quasiperiodic linear coefficient. We employ a variational approach with a Gaussian ansatz to describe the center of the localized state, while the tails are studied by direct numerical simulations of the NLS equation. These two approaches are important to distinguish the region of the solution presenting exponential decay, which is the main signature of the Anderson localization. The existence of Anderson localization has been confirmed by numerical simulations even when the system presents a small defocusing nonlinearity. In this sense, we reported how the fourth-order dispersion effect changes the existence region of the localized state by changing the critical values for the transition between the localized and delocalized states.Mostrar mais Item Scattering of solitons in binary Bose-Einstein condensates with spin-orbit and Rabi couplings(2019) Cardoso, Wesley Bueno; Teixeira, Rafael Marques PaesMostrar mais In this paper, we study the scattering of solitons in a binary Bose–Einstein condensate (BEC) including SO and Rabi couplings. To this end, we derive a reduced ODE model in view to provide a variational description of the collisional dynamics. Also, we assume negative intra- and intercomponent interaction strengths, such that one obtains localized solutions even in the absence of external potentials. By performing extensive numerical simulations of this model we observe that, for specific conditions, the final propagation velocity of the scattered solitons can become highly sensitive to small changes in the initial conditions. Additionally, there are infinitely many intervals of regularity emerging from the obtained chaotic-like regions and forming a fractal-like structure of reflection/transmission windows. Finally, we investigate how the value of the spin-orbit coupling strength changes the critical velocities, which are minimum/maximum values for the occurrence of solitons bound-states, as well as the fractal-like structure.Mostrar mais Item Symmetry breaking in Bose-Einstein condensates confined by a funnel potential(2022) Miranda, Bruno Martins; Santos, Mateus Calixto Pereira dos; Cardoso, Wesley BuenoMostrar mais In this paper we consider a Bose-Einstein condensate in self-attraction regime, confined transversely by a funnel-like potential and axially by a double-well potential formed by the combination of two inverted Pöschl-Teller potentials. The system is well described by a one-dimensional nonpolynomial Schrödinger equation, for which we analyze the symmetry break of the wave function that describes the particle distribution of the condensate. The symmetry break was observed for several interaction strength values as a function of the minimum potential well. In addition, we analyzed the symmetric and asymmetric solutions using a real-time evolution method, in which it was possible to confirm the stability of the results. Finally, a comparison with the cubic nonlinear Schrödinger equation and the full Gross-Pitaevskii equation were performed to check the accuracy of the effective equation used here.Mostrar mais Item Molecular dynamics simulation of docking structures of SARS-CoV-2 main protease and HIV protease inhibitors(2021) Cardoso, Wesley Bueno; Mendanha Neto, Sebastião AntônioMostrar mais In this paper we investigate 10 different HIV protease inhibitors (HPIs) as possible repurposed-drugs candidates against SARS-CoV-2. To this end, we execute molecular docking and molecular dynamics simulations. The in silico data demonstrated that, despite their molecular differences, all HPIs presented a similar behavior for the parameters analyzed, with the exception of Nelfinavir that showed better results for most of the molecular dynamics parameters in comparison with the N3 inhibitor.Mostrar mais Item Effects of terpenes on fluidity and lipid extraction in phospholipid membranes(2015) Mendanha Neto, Sebastião Antônio; Alonso, AntonioMostrar mais Electron paramagnetic resonance (EPR) spectroscopy was used in a detailed study of the interactions of several terpenes with DPPC membranes. EPR spectra of a spin-label lipid allowed the identification of two well-resolved spectral components at temperatures below and above the main phase transition of the lipid bilayer. Terpenes caused only slight mobility increases in each of these spectral components; however, they substantially increased the population of the more mobile component. In addition, the terpenes reduced the temperature of the main phase transition by more than 8 °C and caused the extraction of the spin-labeled lipid. Nerolidol, which had the highest octanol–water partition coefficient, generated the highest amount of spin label extraction. Acting as spacers, terpenes should cause major reorganization in cell membranes, leading to an increase in the overall molecular dynamics of the membrane. At higher concentrations, terpenes may cause lipid extraction and thus leakage of the cytoplasmic content.Mostrar mais Item Portable proportional-integral-derivative controlled chambers for giant unilamellar vesicles electroformation(2019) Santos Junior, Juracy Leandro dos; Mendanha Neto, Sebastião Antônio; Vieira, Sílvio Leão; Gonçalves, CristhianeMostrar mais Liposomes are widely used as a cellular membrane model and may be obtained spontaneously when lipids with cylindrical structure are exposed to an aqueous environment. Giant unilamellar vesicles (GUVs) have diameters greater than 1 μm and allow obtaining mechanical information spatially resolved at the level of single vesicle. Such structures, have been explored as the main types of models for the study of membrane heterogeneity. The production of GUVs is obtained through the exposure of lipid films to an aqueous solution in the presence of electric fields and stable temperature. This process is called electroformation. This study proposes a novel system to provide a complete automated electroformation process using special chambers. A prototype based on a embedded electronic system was developed to generate and control the desired field frequency and amplitude. Thermoelectric pellets with adequate heat dissipation associated with a thermistor clamped into the electroformation chambers were used to control the temperature. As results, images of confocal fluorescence microscope show that the automated process obtained through the proposed prototype using a standard electroformation protocol produced GUVs with a mean diameter of (5.1 ± 0.6) μm. Furthermore, the Peltier circuit was adequate to maintain the chamber at a controlled temperature during prolonged experiments and the use of micro-controllers made the system compact, in addition to ensuring a more stable temperature and AC field regime with immediate feedback from the sensors.Mostrar mais Item Hydration effects on the electronic properties of eumelanin building blocks(2016) Oliveira, Leonardo Bruno Assis; Fonseca, Tertius Lima da; Cabral, Benedito Jose Costa; Coutinho, Kaline Rabelo; Canuto, Sylvio Roberto AcciolyMostrar mais Theoretical results for the electronic properties of eumelanin building blocks in the gas phase and water are presented. The building blocks presently investigated include the monomeric species DHI (5,6-dihydroxyindole) or hydroquinone (HQ), DHICA (5,6-dihydroxyindole-2-carboxylic acid), indolequinone (IQ), quinone methide (MQ), two covalently bonded dimers [HM ≡ HQ + MQ and IM ≡ IQ + MQ], and two tetramers [HMIM ≡ HQ + IM, IMIM ≡ IM + IM]. The electronic properties in water were determined by carrying out sequential Monte Carlo/time dependent density functional theory calculations. The results illustrate the role played by hydrogen bonding and electrostatic interactions in the electronic properties of eumelanin building blocks in a polar environment. In water, the dipole moments of monomeric species are significantly increased ([54–79]%) relative to their gas phase values. Recently, it has been proposed that the observed enhancement of the higher-energy absorption intensity in eumelanin can be explained by excitonic coupling among eumelanin protomolecules [C.-T. Chen et al., Nat. Commun. 5, 3859 (2014)]. Here, we are providing evidence that for DHICA, IQ, and HMIM, the electronic absorption toward the higher-energy end of the spectrum ([180–220] nm) is enhanced by long-range Coulombic interactions with the water environment. It was verified that by superposing the absorption spectra of different eumelanin building blocks corresponding to the monomers, dimers, and tetramers in liquid water, the behaviour of the experimental spectrum, which is characterised by a nearly monotonic decay from the ultraviolet to the infrared, is qualitatively reproduced. This result is in keeping with a “chemical disorder model,” where the broadband absorption of eumelanin pigments is determined by the superposition of the spectra associated with the monomeric and oligomeric building blocks. TopicsMostrar mais Item The interaction of lipid-liganded gold clusters (Aurora ™) with lipid bilayers(2019) Sot Sanz, Jesus; Mendanha Neto, Sebastião Antônio; Busto, Jon V.; García Arribas, Aritz B.; Shengrong, Li; Burgess, Stephen W.; Shaw, Walt A.; Gil-Carton, David; Goñi, Félix M.; Alonso, AliciaMostrar mais Lipid bilayers of different phospholipid compositions have been prepared, in the form of vesicles, or of supported lipid bilayers, and doped with Aurora™ at 0.1 mol%. Aurora™ consists of an Au55 gold nanoparticle (about 1.4 nm in diameter) capped with triphenylphosphine ligands and a single diglyceride (distearoyl glycerol) ligand. Gold nanoparticles have been incorporated in the past inside liposomes, or grafted onto their surfaces, with diagnostic or therapeutic aims. Including the gold nanoparticles in a stable form within the lipid bilayers has serious technical difficulties. We have tested the hypothesis that, because of the diglyceride ligand, Aurora™ would allow the easy incorporation of gold nanoclusters into cell membranes or lipid bilayers. Our results show that Aurora™ readily incorporates into lipid bilayers, particularly when they are in the fluid phase, i.e. the state in which cell membranes exist. Calorimetric, fluorescence polarization or fluorescence confocal microscopy concur in showing that bilayer-embedded Aurora™hardly changes the physical properties of the bilayers, nor does it perturb the phase equilibrium in lipid mixtures giving rise to lateral phase separation in the plane of the membrane. Atomic force microscopy shows, in fluid bilayers, well-resolved particles, 1.2–2.9 nm in height, that are interpreted as single Aurora™conjugates. Cryo-transmission electron microscopy allows the clear observation of lipid bilayers with an enhanced contrast due to the Aurora™ gold nanoparticles; the single particles can be resolved at high magnification. Our studies support the applicability of Aurora™ as a membrane-friendly form of nano-gold particles for biological research or clinical applications.Mostrar mais