Alessandro Fabricio CHAPARRO TORRES - Academia.edu (original) (raw)

Papers by Alessandro Fabricio CHAPARRO TORRES

Ciência Rural, 2004

No Brasil, pouca atenção se tem dado às formas e caminhos com que os fluxos energéticos se distri... more No Brasil, pouca atenção se tem dado às formas e caminhos com que os fluxos energéticos se distribuem nos sistemas produtivos. Na agropecuária, a atenção tem sido voltada a novas fontes de energia (biomassa) ou em tecnologia alternativa, visando a racionalização do uso de energia fóssil ou elétrica. Entretanto, a agricultura tem se desenvolvido baseada fortemente na utilização intensiva de máquinas agrícolas, com conseqüente uso de combustíveis fósseis. Um fator de estrangulamento muito forte no consumo energético geral tem sido a utilização massiva de fertilizantes derivados do petróleo nos agroecossistemas. Estudos de Balanços Energéticos visam determinar os pontos de estrangulamento energético fundamentando a busca por tecnologias poupadoras de energia, especialmente aquelas de origem fóssil (combustível, fertilizante, agrotóxicos, energia despendida na fabricação das máquinas e implementos, etc.). No Brasil, a Região Sul, é onde se encontram vários trabalhos buscando uma agricul...

SPIE Proceedings, 2005

In recent years, fiber optics has found major applications in sensor technology. In this paper, w... more In recent years, fiber optics has found major applications in sensor technology. In this paper, we develop a theoretical analysis on different configurations of couples of fibers, in order to determine the optimal configuration for a position sensor, which allows us to measure displacements ...

Optics Communications, 2010

The Journal of Physical Chemistry C, 2009

Sulfated aluminas were prepared by a sol− gel method, using sulfuric acid as both hydrolysis cata... more Sulfated aluminas were prepared by a sol− gel method, using sulfuric acid as both hydrolysis catalyst and sulfate source. The nominal amount of sulfate was varied between∼ 2 and 17% wt. Solids thus obtained present unique nanocapsular morphology with ...

The Journal of Physical Chemistry C, 2010

The rehydration process of calcined MgAl-layered double hydroxides (LDHs), with different Mg/Al m... more The rehydration process of calcined MgAl-layered double hydroxides (LDHs), with different Mg/Al molar ratios (2.0, 2.5, 3.0, 3.5, and 4.0), was analyzed at different temperatures and relative humidities. Kinetic results clearly showed that LDHs with Mg/Al molar ratios of 2.5 and 3.0 have the fastest H 2 O absorption. This behavior was attributed to the cations' structural ordering and to thermodynamic factors. In addition, results allowed obtaining the activation enthalpies for the LDH regeneration of the different samples as a function of the relative humidity. The different activation enthalpies, for each LDH and independently of the Mg/Al molar ratio, showed that the H 2 O absorption process is more dependent on temperature if the relative humidity is low. Finally, when we analyzed the activation enthalpies as a function of the Mg/Al molar ratio at a defined temperature, their values did not behave linearly. The water absorption process proved to be more dependent on temperature for the LDHs with molar ratios equal to 2.5 and 3.0.

Schizophrenia Research, 2003

in the brain, selectively affect glia, and alter neurotransmitters. It also may interact with ret... more in the brain, selectively affect glia, and alter neurotransmitters. It also may interact with retroviruses, herpesviruses, or other neurotrophic infectious agents. Finally, many antipsychotics and mood stabilizers inhibit Toxoplasma in cell cultures. Studies are underway using anti-Toxoplasma medications as adjunctive agents to treat individuals with schizophrenia. 2.58%) than in those without (risk difference: 0.40%, P interac-tion=0.003). Between 60% and 70% of the individuals exposed to both urbanicity and familial liability had developed psychotic disorder because of the synergistic action of the two proxy causes. Conclusion. Given the fact that familial clustering of psychosis is thought to reflect the effect of shared genes (1), the findings support a mechanism of gene-environment interaction in the causation of psychosis.

Physical Review Letters, 2006

Optik - International Journal for Light and Electron Optics, 2012

Optics Express, 2011

We present a novel optical method for edge enhancement in color images based on the polarization ... more We present a novel optical method for edge enhancement in color images based on the polarization properties of liquid-crystal displays (LCD). In principle, a LCD generates simultaneously two colorcomplementary, orthogonally polarized replicas of the digital image used as input. The currently viewed image in standard LCD monitors and cell phone's screens-which we will refer as the "positive image or true-color image"-is the one obtained by placing an analyzer in front of the LCD, in cross configuration to the back polarizer of the display. The orthogonally polarized replica of this image-the "negative image or complementarycolor image"-is absorbed by the front polarizer. In order to generate the positive and negative replica with a slight displacement between them, we used a LCD monitor whose analyzer (originally a linear polarizer) was replaced by a calcite crystal acting as beam displacer. When both images are superimposed laterally displaced across the image plane, one obtains an image with enhanced first-order derivatives along a specific direction. The proposed technique works under incoherent illumination and does not require precise alignment, and thus, it could be potentially useful for processing large color images in real-time applications. Validation experiments are presented.

Optics Communications, 2006

The interferometric intensity patterns from a 2D shearing interferometer are shown and discussed.... more The interferometric intensity patterns from a 2D shearing interferometer are shown and discussed. The intensity patterns can be obtained in two different approaches incorporating differential and extended wavefront controlled displacements. The reliable directional sensitivity of this interferometer allows the optimization of the measurement parameters to estimate the wavefront of the intensity patterns by regularization techniques.

Optical Engineering, 2008

A Faraday current sensor using spatially inhomogeneous analyzers is presented. In the proposed op... more A Faraday current sensor using spatially inhomogeneous analyzers is presented. In the proposed optical architecture, the light waves coming from the sensor head travel in free space reaching a space-variant analyzer, and then they are acquired by a one—or two- dimensional photodetector array. This allows a full determination of the Faraday rotation induced by the electrical current, even in the case of a nonideal optical system e.g., analyzer with poor polarization ratio. The proposed method resembles well-known techniques of phase-shifting interferometry. Validation experiments using linearly variant and azimuthal radial analyzers are presented and different detection schemes are compared. © 2008 Society of Photo-Optical Instrumentation

Optical Engineering, 2009

Optical Engineering, 2012

The Journal of the Acoustical Society of America, 2005

The flexural vibrations of a locally periodic rod, which consists of N unit cells, are discussed ... more The flexural vibrations of a locally periodic rod, which consists of N unit cells, are discussed both from the experimental and theoretical points of view. Timoshenko’s beam theory and the transfer matrix method are used to calculate the normal-mode frequencies and amplitudes. The theoretical values are then compared with the experimental ones, which are obtained using an electromagnetic acoustic transducer (EMAT). Good agreement between the numerical results and the experimental measurements is obtained. It is shown that as N grows, a band spectrum emerges.

The Journal of the Acoustical Society of America, 2011

Whenever a state of a" distinct" and simple nature is immersed in a sea of states of a ... more Whenever a state of a" distinct" and simple nature is immersed in a sea of states of a different, more complicated, structure a strength function phenomenon appears: the amplitude of the distinct state is spread over the complicated eigenstates with a Lorentzian ...

Journal of Sound and Vibration, 2010

Theoretical and experimental results for flexural waves of a rectangular plate with free ends are... more Theoretical and experimental results for flexural waves of a rectangular plate with free ends are obtained. Both the natural frequencies and mode shapes are analyzed for the lower normal modes. To take into account the boundary conditions, a plane wave expansion method is used to solve the thin plate theory also known as the 2D Kirchhoff–Love equation. The excitation and

Journal of Modern Optics, 2010

Journal of Mechanics of Materials and Structures, 2007

We study the normal modes of torsional waves in an elastic beam consisting of a set of N cuboids ... more We study the normal modes of torsional waves in an elastic beam consisting of a set of N cuboids of varying heights. We present experimental, theoretical, and numerical results. We show that some analogies to the Wannier-Stark ladders resonances, originally introduced by Wannier in 1962, are exhibited by this classical system. The original ladders studied by Wannier consist of a series of equidistant energy levels for the electrons in a crystal in the presence of a static external electric field with the nearestneighbor level spacing proportional to the intensity of the external field. For the case of torsional waves in the beam we have observed a similar behavior, namely, the vibrations of the beam show resonances of equidistant frequencies with the nearest-neighbor spacing proportional to parameter γ associated with the geometry of the beam analogously to the electric field. However, this analogy is not perfect; we address the origin of the differences.

Journal of Marine Systems, 2010

We analysed changes in the coccolithophore assemblage over the last 11 000 years in laminated sed... more We analysed changes in the coccolithophore assemblage over the last 11 000 years in laminated sediments recovered near the mouth of the Gulf of California (NW Mexico). Coccolith preservation in the samples was good: the assemblage was represented by seven taxa. Statistical studies revealed that the group of "small" Gephyrocapsa was the dominant taxa and Florisphaera profunda and Emiliania huxleyi the following species in abundance. We calculated the ratio between inhabitants of the surface and deep photic zones, which allowed us to analyse variations in water column stratification. Oceanographic conditions during the Holocene were relatively constant, and the coccolithophore record was dominated by small placoliths, revealing upwelling conditions and high productivity, which progressively weakened towards the present. Two different events were found around 11 000 B.P. (Younger Dryas) and 6000 B.P. (mid-Holocene). Both intervals were characterised by the dominant presence of F. profunda in the assemblage, revealing stratification conditions in the water column and low productivity, the same oceanographic conditions defined during an ENSO (El Niño-Southern Oscillation) event.