Hernán Javier Ferrari - Academia.edu (original) (raw)

Papers by Hernán Javier Ferrari

Research paper thumbnail of Dinámica de flujo magnético a tiempos cortos en superconductores de alta temperatura crítica

Http Digital Bl Fcen Uba Ar, 2000

Research paper thumbnail of AC susceptibility and local intergranular magnetic field in high-Tc superconductors

Physica C: Superconductivity, 1993

ABSTRACT

Research paper thumbnail of Irreversibility effects in polycrystalline high-Tc superconductors studied by AC susceptibility

Physica C: Superconductivity, 1994

Local magnetic-field effects in the high-Tc polycrystalline superconductor La1.8Sr0.2CuO4-delta w... more Local magnetic-field effects in the high-Tc polycrystalline superconductor La1.8Sr0.2CuO4-delta were studied by means of AC susceptibility measurements with a superimposed DC magnetic field, which has proven to be a sensitive technique for detecting intergranular screening currents. Measurements were performed in different magnetic configurations, obtained by cycling the DC field. The effect of intragrain pinned vortices on the intergranular local field

Research paper thumbnail of Hysteretical temperature dependence of AC susceptibility in granular high-Tc superconductors

Physica C: Superconductivity, 1994

The AC susceptibility, x~,-(T), with superimposed DC magnetic field, H F", has been measured as a... more The AC susceptibility, x~,-(T), with superimposed DC magnetic field, H F", has been measured as a function of temperature in bulk sintered LaSrCuO, for zero-field cooled (ZFC) and field-cooled (FC) samples. Results are analyzed within Rim's critical-state model extended to a granular superconductor, where the role of grains is to determine the temperature-dependent effective permeability, &u(T), and the effective intergranular local field, H,*(H, Dc, T), which depends on the applied field, H,"c and the thermal and magnetic history, accounting for the observed hysteresis. A method to determine field-independent intergranular critical-state parameters (critical current at zero field and temperature-dependent density of pinning forces as well as h(T)) and the proper scaling of H,@(H F, T) for ZFC and FC conditions is described. The calculated AC susceptibility for the whole temperature range for both magnetic conditions reproduces the main features of the experimental results.

Research paper thumbnail of Time resolved nanosecond vortex dynamics in high Tc superconducting films

Cryogenics, 2004

We report on the observation of the rearrangement of vortices in the ns time scale following a fa... more We report on the observation of the rearrangement of vortices in the ns time scale following a fast magnetic field variation due to selective local heating of a high Tc superconducting film. Detailed simulations describing the measured photoinduced voltage signals along the film lead to a better understanding of vortex dynamics in fast regimes, where mean vortex velocities reach 10 4 m/s.

Research paper thumbnail of Thermal patterning of superconducting films

Physica C: Superconductivity, 2004

The transient shape control of a superconducting high T c film by selective optical heating has b... more The transient shape control of a superconducting high T c film by selective optical heating has been addressed in this work, using a non-conventional technique that combines the application of a pulsed magnetic field and the optical heating of the superconducting film by a synchronized pulsed laser. A zero field cooled (ZFC) film was partially protected by a mask before exposing it to the laser radiation. The temperature at the illuminated area rises causing very fast local lowering of the vortex pinning force or may even rise above T c. As a result, flux penetrates completely the heated area and an effective smaller sample remains in a superconducting critical state. Flux penetration is measured with a pickup coil for different positions of the mask. Results are described within the critical state model for a strip, where the time integrated voltage signal is approximated to the flux difference between the initial ZFC sample and the final critical state of the ''new'' (cold) ZFC sample.

Research paper thumbnail of Optical pulling force on dielectric particles via metallic slab surface plasmon excitation: a comparison between transmission and reflection schemes

Optics Letters

In this Letter, a simple structure formed by a metallic thin layer covering a high-index substrat... more In this Letter, a simple structure formed by a metallic thin layer covering a high-index substrate is used to design an optical tweezer. Owing to the interaction between the field scattered by the particle with an incident plane wave and the proposed structure, a pulling or attractive component of the optical force emerges. This component results in enhancement thanks to the surface plasmons (SPs) excitation arising from the elliptical polarization of the induced dipole moment on the particle. To further exploit the versatility of the proposed approach, we analyze two basic configurations: the reflection scheme, for which the plane wave impinges from the side where the particle is placed; and the transmission scheme, for which the incidence is made from the substrate side. Our results show that the intensity of the pulling force in the reflection scheme and for finite thickness metal layer reaches values exceeding more than twice those provided by a single metallic interface. We als...

Research paper thumbnail of Terahertz Pulling Force Enhanced by Graphene Surface Modes

Latin America Optics and Photonics (LAOP) Conference 2022, 2022

Research paper thumbnail of Graphene surface modes enabling terahertz pulling force

Applied Optics

Plasmonic substrates are widely reported for their use in the manipulation of sub-wavelength part... more Plasmonic substrates are widely reported for their use in the manipulation of sub-wavelength particles. Here we analyze the optical force in the terahertz (THz) spectrum acting on a dielectric nanoparticle when located close to a graphene monolayer. When lying on a dielectric planar substrate, the graphene sheet enables the nano-sized scatterer to excite a surface plasmon (SP) well confined on the dielectric surface. Under quite general conditions, large pulling forces can be exerted on the particle as a consequence of conservation of linear momentum and a self-action effect. Our results show that the pulling force intensity critically depends on the particle shape and orientation. The low heat dissipation of graphene SPs paves the way for the development of a novel plasmonic tweezer for applications involving biospecimen manipulation in the THz region.

Research paper thumbnail of Optical force on dielectric nanoparticles placed near an Attenuated Total Reflection structure in Otto configuration

2022 IEEE Biennial Congress of Argentina (ARGENCON)

Research paper thumbnail of Flux and current distributions in type-II superconducting strips

Physica B: Condensed Matter, 2000

ABSTRACT Current density and penetrated magnetic flux distribution are calculated for a strip of ... more ABSTRACT Current density and penetrated magnetic flux distribution are calculated for a strip of constant thickness d that carries a time-dependent transport current I. Calculations assume a logarithmic activation energy U(j)∼ln(jc/j) to account for thermal activated motion of vortices, and a critical sheet current Jc(B,r)=jc(B,r)d that may be magnetic-field and position dependent (j and jc are the current and critical current densities).

Research paper thumbnail of Graphene plasmons on attenuated total reflection structures: a route to achieve large optical pusshing or pulling force intensities in the terahertz region

Journal of the Optical Society of America B

Research paper thumbnail of Flow invariants in a channel obstructed by a line of inclined rods

Scientific Reports

An experiment is conducted in a rectangular channel obstructed by a transverse line of four incli... more An experiment is conducted in a rectangular channel obstructed by a transverse line of four inclined cylindrical rods. The pressure on the surface of a central rod and the pressure drop through the channel are measured varying the inclination angle of the rods. Three assemblies of rods with different diameters are tested. The measurements were analyzed applying momentum conservation principles and semi-empirical considerations. Several invariant dimensionless groups of parameters relating the pressure at key locations of the system with characteristic dimensions of the rods are produced. It was found that the independence principle holds for most of the Euler numbers characterizing the pressure at different locations, that is, the group is independent of the inclination angle provided that the inlet velocity projection normal to the rods is used to non-dimensionalize the pressure. The resulting semi-empirical correlations can be useful for designing similar hydraulic units.

Research paper thumbnail of Magneto-Optical Imaging in an Undergraduate Laboratory Course

Magneto-Optical Imaging, 2004

... Videos (25 frames per second for approx. 1 min.) were recorded with a Sony XC-75 Monochrome c... more ... Videos (25 frames per second for approx. 1 min.) were recorded with a Sony XC-75 Monochrome camera, digitizing the signal with an acquisition card (Video Aims Labs's Highway Xtreme), with 8 bit resolution and 284 x 388 pixels. ...

Research paper thumbnail of Micrometric periodic assembly of magnetotactic bacteria and magnetic nanoparticles using audio tapes

Journal of Applied Physics, 2012

We report micrometric periodic assembly of live and dead magnetotactic bacteria, Magnetospirillum... more We report micrometric periodic assembly of live and dead magnetotactic bacteria, Magnetospirillum magneticum AMB-1, which synthesize chains of magnetic nanoparticles inside their bodies, and of superparamagnetic Fe 3 O 4 and ferromagnetic CoFe 2 O 4 nanoparticles in aqueous suspensions using periodically magnetized audio tapes. The distribution of the stray magnetic field at the surface of the tapes was determined analytically and experimentally by magneto-optic imaging. Calculations showed that the magnetic field close to the tape surface was of the order of 100 mT, and the magnetic field gradient was larger than 1 T mm À1. Drops of aqueous solutions were deposited on the tapes, and bacteria and particles were trapped at locations where magnetic energy is minimized, as observed using conventional optical microscopy. Suspensions of M. magneticum AMB-1 treated with formaldehyde and kanamycin were studied, and patterns of trapped dead bacteria indicated that magnetic forces dominate over self-propelling forces in these experiments, in accordance with calculated values. The behavior of the different types of samples is discussed. V

Research paper thumbnail of Micrometric periodic assembly of magnetotactic bacteria and magnetic nanoparticles using audio tapes

JOURNAL OF APPLIED PHYSICS, 2012

We report micrometric periodic assembly of live and dead magnetotactic bacteria, Magnetospirillum... more We report micrometric periodic assembly of live and dead magnetotactic bacteria, Magnetospirillum magneticum AMB-1, which synthesize chains of magnetic nanoparticles inside their bodies, and of superparamagnetic Fe3O4 and ferromagnetic CoFe2O4 nanoparticles in aqueous suspensions using
periodically magnetized audio tapes. The distribution of the stray magnetic field at the surface of the tapes was determined analytically and experimentally by magneto-optic imaging. Calculations showed that the magnetic field close to the tape surface was of the order of 100 mT, and the magnetic field gradient was larger than 1 T mm1. Drops of aqueous solutions were deposited on the tapes, and bacteria and particles were trapped at locations where magnetic energy is minimized, as observed using conventional optical microscopy. Suspensions of M. magneticum AMB-1 treated with formaldehyde and kanamycin were studied, and patterns of trapped dead bacteria indicated that magnetic forces dominate over self-propelling forces in these experiments, in accordance with C 2012 American
calculated values. The behavior of the different types of samples is discussed.

Research paper thumbnail of Giant terahertz pulling force within an evanescent field propelled by wave coupling into radiation and bound modes

Manipulation of subwavelength objects by engineering the electromagnetic waves in the environment... more Manipulation of subwavelength objects by engineering the electromagnetic waves in the environment medium is pivotal for several particle handling techniques. In this letter, we theoretically demonstrate the possibility of engineering a compact and tunable plasmon-based terahertz tweezer using a graphene monolayer that is deposited on a high-index substrate. Under total-internal-reflection illumination, such device is shown to be capable of inducing an enhanced rotating polarizability thus enabling directional near-field coupling into the graphene plasmon mode and radiation modes in the substrate. As a result of the total momentum conservation, the net force exerted on the particle points in a direction opposite to the pushing force of the exciting evanescent field. Our results can contribute to novel realizations of photonic devices based on polarization dependent interactions between nanoparticles and electromagnetic mode fields.

Research paper thumbnail of Wall Pressures In a Channel Flow Obstructed By a Line of Inclined Rods: Invariant Groups and Semi-Empirical Correlations

An experiment is conducted in a rectangular channel obstructed by a transverse line of four incli... more An experiment is conducted in a rectangular channel obstructed by a transverse line of four inclined cylindrical rods. The wall pressure around the perimeter of a central rod and the pressure drop through the channel are measured varying the inclination angle of the rods. Three assemblies of rods with different diameters are tested. The measurements were analyzed applying momentum conservation principles and semi-empirical considerations. Several invariant dimensionless groups of parameters relating the pressure at key locations of the system with characteristic dimensions of the rods are produced. It was found that the independence principle holds for most of the Euler numbers characterizing the pressure at different locations, that is, the group is independent of the inclination angle provided that the inlet velocity projection normal to the rods is used to non-dimensionalize the pressure. The resulting semi-empirical correlations can be useful for designing similar hydraulic units.

Research paper thumbnail of Terahertz binding of nanoparticles based on graphene surface plasmons excitations

Journal of Quantitative Spectroscopy and Radiative Transfer, 2021

This work studies the optical binding of a dimer composed by dielectric particles close to a grap... more This work studies the optical binding of a dimer composed by dielectric particles close to a graphene sheet. Using a rigorous electromagnetic method, we calculated the optical force acting on each nanoparticle. In addition, we deduced analytical expressions enabling to evaluate the contribution of graphene surface plasmons (GSPs) to optical binding. Our results show that surface plasmon on graphene excitations generate multiple equilibrium positions for which the distance between particles are tens of times smaller than the photon wavelength. Moreover, these positions can be dynamically controlled by adjusting the chemical potential on graphene. Normal and oblique incidence have been considered.

Research paper thumbnail of Magneto-optic study of the behavior of magnetic domains walls in ferrimagnetic garnet films placed over samples with in-plane magnetization

Physica B: Condensed Matter, 2012

Research paper thumbnail of Dinámica de flujo magnético a tiempos cortos en superconductores de alta temperatura crítica

Http Digital Bl Fcen Uba Ar, 2000

Research paper thumbnail of AC susceptibility and local intergranular magnetic field in high-Tc superconductors

Physica C: Superconductivity, 1993

ABSTRACT

Research paper thumbnail of Irreversibility effects in polycrystalline high-Tc superconductors studied by AC susceptibility

Physica C: Superconductivity, 1994

Local magnetic-field effects in the high-Tc polycrystalline superconductor La1.8Sr0.2CuO4-delta w... more Local magnetic-field effects in the high-Tc polycrystalline superconductor La1.8Sr0.2CuO4-delta were studied by means of AC susceptibility measurements with a superimposed DC magnetic field, which has proven to be a sensitive technique for detecting intergranular screening currents. Measurements were performed in different magnetic configurations, obtained by cycling the DC field. The effect of intragrain pinned vortices on the intergranular local field

Research paper thumbnail of Hysteretical temperature dependence of AC susceptibility in granular high-Tc superconductors

Physica C: Superconductivity, 1994

The AC susceptibility, x~,-(T), with superimposed DC magnetic field, H F", has been measured as a... more The AC susceptibility, x~,-(T), with superimposed DC magnetic field, H F", has been measured as a function of temperature in bulk sintered LaSrCuO, for zero-field cooled (ZFC) and field-cooled (FC) samples. Results are analyzed within Rim's critical-state model extended to a granular superconductor, where the role of grains is to determine the temperature-dependent effective permeability, &u(T), and the effective intergranular local field, H,*(H, Dc, T), which depends on the applied field, H,"c and the thermal and magnetic history, accounting for the observed hysteresis. A method to determine field-independent intergranular critical-state parameters (critical current at zero field and temperature-dependent density of pinning forces as well as h(T)) and the proper scaling of H,@(H F, T) for ZFC and FC conditions is described. The calculated AC susceptibility for the whole temperature range for both magnetic conditions reproduces the main features of the experimental results.

Research paper thumbnail of Time resolved nanosecond vortex dynamics in high Tc superconducting films

Cryogenics, 2004

We report on the observation of the rearrangement of vortices in the ns time scale following a fa... more We report on the observation of the rearrangement of vortices in the ns time scale following a fast magnetic field variation due to selective local heating of a high Tc superconducting film. Detailed simulations describing the measured photoinduced voltage signals along the film lead to a better understanding of vortex dynamics in fast regimes, where mean vortex velocities reach 10 4 m/s.

Research paper thumbnail of Thermal patterning of superconducting films

Physica C: Superconductivity, 2004

The transient shape control of a superconducting high T c film by selective optical heating has b... more The transient shape control of a superconducting high T c film by selective optical heating has been addressed in this work, using a non-conventional technique that combines the application of a pulsed magnetic field and the optical heating of the superconducting film by a synchronized pulsed laser. A zero field cooled (ZFC) film was partially protected by a mask before exposing it to the laser radiation. The temperature at the illuminated area rises causing very fast local lowering of the vortex pinning force or may even rise above T c. As a result, flux penetrates completely the heated area and an effective smaller sample remains in a superconducting critical state. Flux penetration is measured with a pickup coil for different positions of the mask. Results are described within the critical state model for a strip, where the time integrated voltage signal is approximated to the flux difference between the initial ZFC sample and the final critical state of the ''new'' (cold) ZFC sample.

Research paper thumbnail of Optical pulling force on dielectric particles via metallic slab surface plasmon excitation: a comparison between transmission and reflection schemes

Optics Letters

In this Letter, a simple structure formed by a metallic thin layer covering a high-index substrat... more In this Letter, a simple structure formed by a metallic thin layer covering a high-index substrate is used to design an optical tweezer. Owing to the interaction between the field scattered by the particle with an incident plane wave and the proposed structure, a pulling or attractive component of the optical force emerges. This component results in enhancement thanks to the surface plasmons (SPs) excitation arising from the elliptical polarization of the induced dipole moment on the particle. To further exploit the versatility of the proposed approach, we analyze two basic configurations: the reflection scheme, for which the plane wave impinges from the side where the particle is placed; and the transmission scheme, for which the incidence is made from the substrate side. Our results show that the intensity of the pulling force in the reflection scheme and for finite thickness metal layer reaches values exceeding more than twice those provided by a single metallic interface. We als...

Research paper thumbnail of Terahertz Pulling Force Enhanced by Graphene Surface Modes

Latin America Optics and Photonics (LAOP) Conference 2022, 2022

Research paper thumbnail of Graphene surface modes enabling terahertz pulling force

Applied Optics

Plasmonic substrates are widely reported for their use in the manipulation of sub-wavelength part... more Plasmonic substrates are widely reported for their use in the manipulation of sub-wavelength particles. Here we analyze the optical force in the terahertz (THz) spectrum acting on a dielectric nanoparticle when located close to a graphene monolayer. When lying on a dielectric planar substrate, the graphene sheet enables the nano-sized scatterer to excite a surface plasmon (SP) well confined on the dielectric surface. Under quite general conditions, large pulling forces can be exerted on the particle as a consequence of conservation of linear momentum and a self-action effect. Our results show that the pulling force intensity critically depends on the particle shape and orientation. The low heat dissipation of graphene SPs paves the way for the development of a novel plasmonic tweezer for applications involving biospecimen manipulation in the THz region.

Research paper thumbnail of Optical force on dielectric nanoparticles placed near an Attenuated Total Reflection structure in Otto configuration

2022 IEEE Biennial Congress of Argentina (ARGENCON)

Research paper thumbnail of Flux and current distributions in type-II superconducting strips

Physica B: Condensed Matter, 2000

ABSTRACT Current density and penetrated magnetic flux distribution are calculated for a strip of ... more ABSTRACT Current density and penetrated magnetic flux distribution are calculated for a strip of constant thickness d that carries a time-dependent transport current I. Calculations assume a logarithmic activation energy U(j)∼ln(jc/j) to account for thermal activated motion of vortices, and a critical sheet current Jc(B,r)=jc(B,r)d that may be magnetic-field and position dependent (j and jc are the current and critical current densities).

Research paper thumbnail of Graphene plasmons on attenuated total reflection structures: a route to achieve large optical pusshing or pulling force intensities in the terahertz region

Journal of the Optical Society of America B

Research paper thumbnail of Flow invariants in a channel obstructed by a line of inclined rods

Scientific Reports

An experiment is conducted in a rectangular channel obstructed by a transverse line of four incli... more An experiment is conducted in a rectangular channel obstructed by a transverse line of four inclined cylindrical rods. The pressure on the surface of a central rod and the pressure drop through the channel are measured varying the inclination angle of the rods. Three assemblies of rods with different diameters are tested. The measurements were analyzed applying momentum conservation principles and semi-empirical considerations. Several invariant dimensionless groups of parameters relating the pressure at key locations of the system with characteristic dimensions of the rods are produced. It was found that the independence principle holds for most of the Euler numbers characterizing the pressure at different locations, that is, the group is independent of the inclination angle provided that the inlet velocity projection normal to the rods is used to non-dimensionalize the pressure. The resulting semi-empirical correlations can be useful for designing similar hydraulic units.

Research paper thumbnail of Magneto-Optical Imaging in an Undergraduate Laboratory Course

Magneto-Optical Imaging, 2004

... Videos (25 frames per second for approx. 1 min.) were recorded with a Sony XC-75 Monochrome c... more ... Videos (25 frames per second for approx. 1 min.) were recorded with a Sony XC-75 Monochrome camera, digitizing the signal with an acquisition card (Video Aims Labs's Highway Xtreme), with 8 bit resolution and 284 x 388 pixels. ...

Research paper thumbnail of Micrometric periodic assembly of magnetotactic bacteria and magnetic nanoparticles using audio tapes

Journal of Applied Physics, 2012

We report micrometric periodic assembly of live and dead magnetotactic bacteria, Magnetospirillum... more We report micrometric periodic assembly of live and dead magnetotactic bacteria, Magnetospirillum magneticum AMB-1, which synthesize chains of magnetic nanoparticles inside their bodies, and of superparamagnetic Fe 3 O 4 and ferromagnetic CoFe 2 O 4 nanoparticles in aqueous suspensions using periodically magnetized audio tapes. The distribution of the stray magnetic field at the surface of the tapes was determined analytically and experimentally by magneto-optic imaging. Calculations showed that the magnetic field close to the tape surface was of the order of 100 mT, and the magnetic field gradient was larger than 1 T mm À1. Drops of aqueous solutions were deposited on the tapes, and bacteria and particles were trapped at locations where magnetic energy is minimized, as observed using conventional optical microscopy. Suspensions of M. magneticum AMB-1 treated with formaldehyde and kanamycin were studied, and patterns of trapped dead bacteria indicated that magnetic forces dominate over self-propelling forces in these experiments, in accordance with calculated values. The behavior of the different types of samples is discussed. V

Research paper thumbnail of Micrometric periodic assembly of magnetotactic bacteria and magnetic nanoparticles using audio tapes

JOURNAL OF APPLIED PHYSICS, 2012

We report micrometric periodic assembly of live and dead magnetotactic bacteria, Magnetospirillum... more We report micrometric periodic assembly of live and dead magnetotactic bacteria, Magnetospirillum magneticum AMB-1, which synthesize chains of magnetic nanoparticles inside their bodies, and of superparamagnetic Fe3O4 and ferromagnetic CoFe2O4 nanoparticles in aqueous suspensions using
periodically magnetized audio tapes. The distribution of the stray magnetic field at the surface of the tapes was determined analytically and experimentally by magneto-optic imaging. Calculations showed that the magnetic field close to the tape surface was of the order of 100 mT, and the magnetic field gradient was larger than 1 T mm1. Drops of aqueous solutions were deposited on the tapes, and bacteria and particles were trapped at locations where magnetic energy is minimized, as observed using conventional optical microscopy. Suspensions of M. magneticum AMB-1 treated with formaldehyde and kanamycin were studied, and patterns of trapped dead bacteria indicated that magnetic forces dominate over self-propelling forces in these experiments, in accordance with C 2012 American
calculated values. The behavior of the different types of samples is discussed.

Research paper thumbnail of Giant terahertz pulling force within an evanescent field propelled by wave coupling into radiation and bound modes

Manipulation of subwavelength objects by engineering the electromagnetic waves in the environment... more Manipulation of subwavelength objects by engineering the electromagnetic waves in the environment medium is pivotal for several particle handling techniques. In this letter, we theoretically demonstrate the possibility of engineering a compact and tunable plasmon-based terahertz tweezer using a graphene monolayer that is deposited on a high-index substrate. Under total-internal-reflection illumination, such device is shown to be capable of inducing an enhanced rotating polarizability thus enabling directional near-field coupling into the graphene plasmon mode and radiation modes in the substrate. As a result of the total momentum conservation, the net force exerted on the particle points in a direction opposite to the pushing force of the exciting evanescent field. Our results can contribute to novel realizations of photonic devices based on polarization dependent interactions between nanoparticles and electromagnetic mode fields.

Research paper thumbnail of Wall Pressures In a Channel Flow Obstructed By a Line of Inclined Rods: Invariant Groups and Semi-Empirical Correlations

An experiment is conducted in a rectangular channel obstructed by a transverse line of four incli... more An experiment is conducted in a rectangular channel obstructed by a transverse line of four inclined cylindrical rods. The wall pressure around the perimeter of a central rod and the pressure drop through the channel are measured varying the inclination angle of the rods. Three assemblies of rods with different diameters are tested. The measurements were analyzed applying momentum conservation principles and semi-empirical considerations. Several invariant dimensionless groups of parameters relating the pressure at key locations of the system with characteristic dimensions of the rods are produced. It was found that the independence principle holds for most of the Euler numbers characterizing the pressure at different locations, that is, the group is independent of the inclination angle provided that the inlet velocity projection normal to the rods is used to non-dimensionalize the pressure. The resulting semi-empirical correlations can be useful for designing similar hydraulic units.

Research paper thumbnail of Terahertz binding of nanoparticles based on graphene surface plasmons excitations

Journal of Quantitative Spectroscopy and Radiative Transfer, 2021

This work studies the optical binding of a dimer composed by dielectric particles close to a grap... more This work studies the optical binding of a dimer composed by dielectric particles close to a graphene sheet. Using a rigorous electromagnetic method, we calculated the optical force acting on each nanoparticle. In addition, we deduced analytical expressions enabling to evaluate the contribution of graphene surface plasmons (GSPs) to optical binding. Our results show that surface plasmon on graphene excitations generate multiple equilibrium positions for which the distance between particles are tens of times smaller than the photon wavelength. Moreover, these positions can be dynamically controlled by adjusting the chemical potential on graphene. Normal and oblique incidence have been considered.

Research paper thumbnail of Magneto-optic study of the behavior of magnetic domains walls in ferrimagnetic garnet films placed over samples with in-plane magnetization

Physica B: Condensed Matter, 2012

Research paper thumbnail of Impacto del diámetro en la distribución de la presión alrededor de una elipse en un arreglo de barras cilíndricas paralelas para diferentes ángulos de inclinación respecto a un flujo de aire en un canal rectangular

Impact of diameter on the distribution of pressure around an ellipse in an arrangement of parallel cylindrical bars for different angles of inclination with respect to an air flow in a rectangular channel, 2021

Se realizó el estudio experimental de la distribución de presión alrededor de un obstáculo formad... more Se realizó el estudio experimental de la distribución de presión alrededor de un obstáculo formado por cuatro tubos cilíndricos de tres diámetros diferentes inmerso en un flujo transversal y a distintos ángulos de inclinación respecto al flujo. Se utilizó aire a presión atmosférica con flujo máximo de 0.038 kg/seg. Para cada diámetro y separación entre cilindros, la distribución de presión alrededor del obstáculo está fuertemente influenciado por el ángulo de inclinación, pero solo marginalmente afectado por el caudal (dentro del rango de trabajo). Debido a la condición de turbulencia del flujo de aire, con un número de Reynolds en la separación entre barras de 1695 a 5100, se obtuvo una muy buena concordancia entre los resultados experimentales y un modelo basado en la velocidad media del aire en ese espacio, mejor que un modelo basado en la curvatura de las líneas de corriente.

The experimental study of the pressure distribution around an obstacle formed by four cylindrical tubes of three different diameters immersed in a transversal flow and at different inclination angles with respect to the flow was carried out. Air at atmospheric pressure was used with a maximum flow of 0.038 Kg / sec. For each cylinder bore and spacing, the pressure distribution is strongly influenced by the angle of inclination, but only marginally affected by flow (within the working range). Due to the turbulent condition of the air flow, with a Reynolds number in the separation between bars from 1695 to 5100, a very good agreement was obtained between the experimental results and a model based on the average air speed in that space, better than a model based on the curvature of streamlines in the gap.