P. V. dos Santos

Universidade Federal de Alagoas

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M. T. de Araújo

Universidade Federal de Alagoas

A.S. Gouveia-Neto

Universidade Federal de Alagoas

J.F. Carvalho

Universidade Federal de Goiás

Sidney J. L. Ribeiro

Universidade Estadual Paulista (Unesp)

Younès Messaddeq

Universidade Estadual Paulista (Unesp)

M. V. D. Vermelho

Universidade Federal de Alagoas

Fábia Castro Cassanjes

Universidade Federal de Alfenas

E. A. Gouveia

Universidade Federal de Alagoas

André L. Moura

Universidade Federal de Alagoas

Askery Canabarro

Universidade Federal de Alagoas

Cooperative Institutions

Universidade Federal de Alagoas

Universidade de São Paulo

Universidade Estadual Paulista (Unesp)

Universidade Estadual de Campinas (UNICAMP)

Instituto Federal Goiano

Centre National de la Recherche Scientifique

Universidade Federal Rural de Pernambuco

Centro Universitário de Araraquara

Brazilian Agricultural Research Corporation

Coordenação de Aperfeicoamento de Pessoal de Nível Superior

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Quality assessment of added of cassava maltodextrin and bagasse ice cream during storage.

ENERGIA NA AGRICULTURA (2019)

Daiana de Souza Fernandes P. V. dos Santos Magali Leonel

Maltodextrin

Ice cream

Bagasse

Quality Assessment

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Sensitized thulium blue and red upconversion emission and energy-transfer processes in Nd/sup 3+//Yb/sup 3+//Tm/sup 3+/-codoped PbGeO/sub 3/-based glass excited around 800 nm

A.S. Gouveia-Neto P. V. dos Santos Luciano A. Bueno Sidney J. L. Ribeiro Younes Messadeq

This paper reports on the generation of bright blue and red upconversion luminescence through the sensitization of thulium ions in Nd/sup 3+//Yb/sup 3+//Tm/sup 3+/ triply-doped 70%XoPbGeO/sub 3/:15%PbF/sub 2/:15%CdF/sub 2/-glass excited by a diode laser source around 800 nm. The upconversion fluorescence spectra of Tm/sup 3+/ ions under 800 nm excitation is presented, for a sample codoped with Yb and a Nd/sup 3+//Yb/sup 3+//Tm/sup 3+/ triply-doped sample. It is observed that the presence of Nd/sup 3+/ in the system, produces a tenfold enhancement in the blue emission associated to the /sup 1/G/sub 4/ - /sup 3/H/sub 6/ transition of Tm/sup 3+/ ions, as compared to samples doped with Tm/sup 3+//Yb/sup 3+/. The dependence of the upconversion emission intensity as a function of the excitation power was examined and a quadratic power law behavior was obtained indicating the participation of two pump photons in the upconversion excitation mechanism. The upconversion excitation process of the Tm/sup 3+/ ion /sup 1/G/sub 4/ emitting level was achieved by an initial energy-transfer process from the 800 nm excited Nd/sup 3+/ to Yb/sup 3+/. The excited Yb/sup 3+/ then, transfer its energy to a Tm/sup 3+/ ion at the /sup 3/H/sub 4/ level excited by a pump photon at 800 nm.

Photon Upconversion

Thulium

Ytterbium

10.1109/eqec.2003.1314073

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Sensitized thulium blue upconversion emission in Nd3+/Tm3+/Yb3+ triply doped lead and cadmium germanate glass excited around 800 nm

Journal of Applied Physics (2003)

A.S. Gouveia-Neto Ernande B. Costa P. V. dos Santos Luciano A. Bueno Sidney J. L. Ribeiro

Bright blue upconversion emission by thulium ions in PbGeO3–PbF2–CdF2 glass triply doped with Nd3+–Tm3+–Yb3+ under diode laser excitation around 800 nm is reported. The results revealed that the Nd3+/Tm3+/Yb3+-codoped sample generated ten times more 475 nm blue upconversion fluorescence than the Yb3+-sensitized Tm3+-doped one, under the same excitation power. The upconversion process also showed a strong dependence upon the Yb3+ concentration. The results also indicated that the neodymium ions played a major role in the upconversion process by transfering the 800 nm excitation to thulium ions. The population of the Tm3+ ions G41 emitting level was accomplished through a multiion interaction involving ground-state absorption of pump photons around 800 nm by the Nd3+(4I9/2→2H9/2, 4F5/2) and Tm3+(3H6→3F4) ions followed by energy-transfer processes involving the Nd3+–Yb3+(4F3/2, 2F7/2→4I11/2, 2F5/2) and Yb3+–Tm3+(2F5/2, 3F4→2F7/2, 1G4) pairs.

Photon Upconversion

Thulium

Laser diode

Holmium

10.1063/1.1618352

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Citations (70)

Landscape changes at Chernobyl

P. V. dos Santos Neftalí Sillero Zbyszek Boratyński Ana Cláudia Teodoro

Thirty-three years ago, an accident at the Chernobyl Nuclear Power Plant released huge amounts of radioactive materials like cesium, strontium and plutonium into the atmosphere, which spread over a vast area. It is known that its effects can cause damage do the DNA of living beings, leading to death or altered fitness of the biota, but the effects of land abandonment under such conditions are not, as the vicinities of the power plant were permanently evacuated. Thus, the objective of this study was to analyze the state of primary production of the vegetation in the Chernobyl Exclusion Zone after the accident, comparing with its previous state. Through Normalized Difference Vegetation Index (NDVI) and radiation measurements, the relationship between these variables was assessed using Analysis of Variance (ANOVA) and Generalized Additive Models (GAM), to understand how the vegetation responded to the radiation exposure. The data considered was Landsat satellite imagery and sampled areas registered on the field. The results show that the NDVI increased over the years after the accident and that it is independent of the current radiation measured. This suggests that to some level of radiation exposure, the positive effects of land abandonment and/or the negative effects of radiation on abundance of herbivore species surpass the long term negative effects of radiation exposure on the vegetation. Nonetheless, above some radiation threshold level, primary production is expected to be negatively affected.

Fukushima Nuclear Accident

Biota

10.1117/12.2532564

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Citations (7)

Recording and erasure of photorefractive holograms in undoped BTO crystal at moderate to high intensities of 6397 nm laser under action of 532 nm laser pre-illumination

Journal of the Optical Society of America A (2018)

Wibsson Ribeiro Lopes Hissa Medeiros Graciella S. A. Santos T. C. Araujo J.F. Carvalho

We investigate recording and erasure of photorefractive holographic gratings in an undoped Bi12TiO20 crystal in a moderate to high intensity regime of the recording beams at 639.7 nm without and with the action of laser pre-illumination at 532 nm. The detected hologram without pre-illumination indicates the participation of two photorefractive electronic gratings in its recording process, and the diffracted signal by itself exhibits a fivefold enhancement when the total intensity increases from 38.4 to 214.5 mW/cm2. The dependence of the measured total diffraction efficiency on intensity was investigated and showed linear behavior. At least three gratings are present in the regime of pre-illumination and participate in the writing and erasure of holographic mechanisms. Two of them are electronic, and one is hole-based, with a phase difference of Δϕ between them. The theoretical approach used to analyze the total diffraction efficiency based upon the photorefractivity standard model, and considering the presence of the three gratings, showed good agreement with the holographic erasure experimental data and permitted us to compute Δϕ, which exhibited strong and unusual dependence on the total intensity.

Erasure

Crystal (programming language)

10.1364/josaa.35.001919

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Citations (5)

Phenomenological characterization of photoactive centers in Bi12TiO20 crystals using optical and electrical techniques

HAL (Le Centre pour la Communication Scientifique Directe) (2005)

J. Frejlich R. Montenegro N.R. Inocente-Junior P. V. dos Santos J.C. Launay

Characterization

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