19 research outputs found
Approach combining the Rietveld method and pairs distribution function analysis to study crystalline materials under high-pressure and/or temperature: Application to rhombohedral Bi2Te3 phase
An approach combining the Rietveld method and pairs distribution function
analysis to study crystalline materials under high pressure or temperature was
early proposed by us, and in this study, it was applied to investigate de
effect of high pressure on the rhombohedral Bi2Te3 phase. The refined
structural parameters obtained from the Rietveld refinement of the XRD patterns
measured for pressures up to 9.1 GPa were used as input data to simulate the
partial and total structure factors SBiBi, SBiTe, STeTe, and SBi2Te3. Fourier
transformation of the Sij factors permitted to obtain the partial and total
pairs distribution functions GBiBi, GBiTe, GTeTe, and GBi2Te3. The first
coordination shells of these Gij functions are formed by subshells and, with
increasing pressure in the 1.1 to 6.3 GPa range, occur a partial separation of
subshells. Also, the increase of pressure in this range promotes a drastic
reduction in the values of the intralayer angles TeBiTe, and consequently, in
the intralayer distance TeTe. A drastic reduction in the interlayers distance
Te-Te was also observed. Several studies are reported in the literature,
including one carried out by us, show the presence of an ETT in this pressure
range. The obtained results suggest that the ETT is related with the decrease
of the intralayer angles TeBiTe, and intra- and interlayer distance TeTe.
Experimental results describing the pressure dependence the thermoelectric
power, electrical resistivity, and power fator for rhombohedral Bi2Te3 are
reported, and an enhancement of the power factor in the 1.1 to 6.3 GPa range is
observed. The results obtained in this study give evidence that this
enhancement in the power factor is related with the decrease of the intralayer
angles TeBiTe, and with the decrease of intralayer- and interlayers homopolar
TeTe bonds
Recuperação de manguezais: um estudo de caso na baixada santista de São Paulo, Brasil
We wanted to know about the possibility of mangrove recovery in Cubatão, Baixada Santista, São Paulo. We planted propagules and transplanted seedlings of Rhizophora mangle in three experiment stands in Cubatão. The results showed higher survival and development in two stands. After, we made preliminaries plantations with another specie of mangrove Laguncularia racemosa. Then, we and local fisherman community planted R. mangle in bigger stands. The results and conclusions of this job are important for contribute politics of development and preservation in Baixada Santista, São Paulo.We wanted to know about the possibility of mangrove recovery in Cubatão, Baixada Santista, São Paulo. We planted propagules and transplanted seedlings of Rhizophora mangle in three experiment stands in Cubatão. The results showed higher survival and development in two stands. After, we made preliminaries plantations with another specie of mangrove Laguncularia racemosa. Then, we and local fisherman community planted R. mangle in bigger stands. The results and conclusions of this job are important for contribute politics of development and preservation in Baixada Santista, São Paulo
Applications of the Acousto-Optic Effect on Glass Integrated Optic Devices
International audienc
Applications of the Acousto-Optic Effect on Glass Integrated Optic Devices
International audienceWe present in this paper a study of acousto-optic interactions with guided waves on glass substrate. A beam of elastic of waves in the Megahertz range, generated with a PZT ceramic, crosses a waveguide realised by ion-exchange in a glass substrate. Elastic waves modify locally the refractive index of glass. We make use of this effect to propose novel integrated sensors like a polarization analyzer sensor and to improve devices like optical modulators and displacement sensor