V. Reynoso | Universidade Estadual Paulista "Júlio de Mesquita Filho" (original) (raw)

Papers by V. Reynoso

Research paper thumbnail of ESTUDO DA FORMAÇÃO DE CdTe OBTIDO PELO MÉTODO DOS PRECURSORES POLIMÉRICOS

Research paper thumbnail of The Dependence of Electrical and Structural Properties with Aging of Superconductor Ceramics

This work presents the results of electrical resistance measurements as a function of temperature... more This work presents the results of electrical resistance measurements as a function of temperature and x-ray diffractometry for 2223 superconductor pellets (critical temperature at around 110 K), after keeping them for 14 years under normal ambient conditions (25ºC, 1atm and 50-70% humidity). The pellets were obtained after pressing a precursor powder previously prepared by a chemical process. The results indicate that the samples obtained from the chemical process are very stable, which represents extremely important results for technological applications.

Research paper thumbnail of Event-Related Brain Potentials during a Semantic Priming Task in Children with Learning Disabilities Not Otherwise Specified

PLoS ONE, 2014

Learning disabilities (LDs) are the most common psychiatric disorders in children. LDs are classi... more Learning disabilities (LDs) are the most common psychiatric disorders in children. LDs are classified either as "Specific" or "Learning Disorder Not Otherwise Specified". An important hypothesis suggests a failure in general domain process (i.e., attention) that explains global academic deficiencies. The aim of this study was to evaluate event-related potential (ERP) patterns of LD Not Otherwise Specified children with respect to a control group. Forty-one children (8-10.6 years old) participated and performed a semantic judgment priming task while ERPs were recorded. Twenty-one LD children had significantly lower scores in all academic skills (reading, writing and arithmetic) than twenty controls. Different ERP patterns were observed for each group. Control group showed smaller amplitudes of an anterior P200 for unrelated than related word pairs. This P200 effect was followed by a significant early N400a effect (greater amplitudes for unrelated than related word pairs; 350-550 ms) with a right topographical distribution. By contrast, LD Not Otherwise Specified group did not show a P200 effect or a significant N400a effect. This evidence suggests that LD Not Otherwise Specified children might be deficient in reading, writing and arithmetic domains because of their sluggish shifting of attention to process the incoming information.

Research paper thumbnail of Estudo das propriedades ópticas em vidros 0,3La2S3-0,7Ga2S 3

Química Nova, 1998

ABSTRACT

Research paper thumbnail of The structure and optical dispersion of the refractive index of tellurite glass

Optical Materials, 2011

The structure and optical properties of a 80TeO2–(20−x)Li2O–xTiO2 glass system where x=0, 5, 10, ... more The structure and optical properties of a 80TeO2–(20−x)Li2O–xTiO2 glass system where x=0, 5, 10, and 15mol% has been investigated using FTIR spectroscopy and Brewster angle measurements. The sample preparation, linear refractive index and density measurements, and infrared spectroscopic analysis are described. The refractive index and density of the studied tellurite glass samples increase when the amount of Ti in the

Research paper thumbnail of Effects of the particle size and nucleation temperature on tellurite 20Li2O–80TeO2 glass crystallization

Materials Science and Engineering: A, 2006

20Li 2 O-80TeO 2 glasses were heat annealed at different temperatures between T g and T x and stu... more 20Li 2 O-80TeO 2 glasses were heat annealed at different temperatures between T g and T x and studied by using XRD, FTIR spectroscopy and DSC techniques to understand the crystallization kinetics in this glass matrix. The infrared band structure of this glass is similar to what was observed in glassy TeO 2 . XRD results reveal the presence of three distinct crystalline ␥-TeO 2 , ␣-TeO 2 and Li 2 Te 2 O 5 phases during the crystallization process. This is a first report of ␥-TeO 2 phase crystallization in this glass matrix. DSC results confirm the crystallization of three distinct structures in the glass. In summary, our results suggest a crystallization hierarchy on this glass matrix since the ␥-TeO 2 and ␣-TeO 2 phases crystallization occurs before the Li 2 Te 2 O 5 phase crystallization.

Research paper thumbnail of Effect of PbS impurity on crystallization mechanism of phosphate glasses studied by differential scanning calorimetry

Materials Letters, 2002

In this work, differential scanning calorimetry (DSC) was used to study effect of PbS impurity on... more In this work, differential scanning calorimetry (DSC) was used to study effect of PbS impurity on crystallization mechanism of phosphate glasses. Bulk glasses presented one crystallization peak while powdered glasses presented two distinct crystallization peaks. For both undoped and doped glasses were determined the activation energies for the crystallization and the Avrami n parameters. The activation energies for undoped phosphate glass were 336 F 6 and 213 F 3 kJ mol À 1 , respectively, associated with first and second crystallization peaks. For doped glass, the obtained energies were 373 F 9 and 286 F 7 kJ mol À 1 . The calculated Avrami parameters, based on first crystallization peaks, for undoped and doped glasses were 2.25 F 0.01 and 1.75 F 0.02, respectively. These values suggest that the first DSC peak, in both glasses, may be associated with surface crystallization. D

Research paper thumbnail of Evidence of distinct phase transformations in lithium phosphate glass Li 2 O P 2 O 5

Journal of Physics D: Applied Physics, 2002

The purpose of this work is to study the Li2O–P2O5 glass using the differential scanning calorime... more The purpose of this work is to study the Li2O–P2O5 glass using the differential scanning calorimetry (DSC) and x-ray diffraction (XRD) techniques to understand the crystallization process in this glass matrix. To study the glass by DSC, screened samples with different particle sizes to resolve the crystallization peaks were used. Both crystallization peaks were attributed to Li6P6O18 and LiPO3 phases.

Research paper thumbnail of Crystallization kinetics in phosphate sodium-based glass studied by DSC technique

Journal of Physics and Chemistry of Solids, 2003

In this work, differential scanning calorimetry (DSC) was used to study the mechanism of crystall... more In this work, differential scanning calorimetry (DSC) was used to study the mechanism of crystallization of 50P2O5–27.8Na2O–16ZnO–6.2Al2O3 glass. DSC measurements were performed on bulk and powdered glasses with different particle size. The curve for bulk glass shows one crystallization peak while powdered glasses presented two distinct crystallization peaks. Based on DSC studies, the activation energies obtained were 336±6 and 213±3kJmol−1, associated with first and second crystallization peaks, respectively. Analyzing the DSC parameters as a function of particle size, the Avrami n parameter suggests that the peak at low temperature may be associated with surface crystallization while the peak at high temperature is associated with bulk crystallization.

Research paper thumbnail of Relation among optical, thermal and thermo-optical properties and niobium concentration in tellurite glasses

Journal of Non-Crystalline Solids, 2010

In this work, optical, thermal, thermo-optical and spectroscopic properties of the 80TeO 2 -(20− ... more In this work, optical, thermal, thermo-optical and spectroscopic properties of the 80TeO 2 -(20− x)Li 2 O-xNb 2 O 5 (x = 5, 10 and 15 mol%) glasses were investigated by using the thermal lens spectrometry, X-Ray diffraction, Raman spectroscopy, modulated differential scanning calorimetry and Brewster angle method. The influence of Nb 2 O 5 in the glass structure was interpreted by the thermal diffusivity, specific heat, thermal conductivity, temperature coefficient of the optical path length, refractive index and band gap energy. The calculated optical basicity and polarizability allowed bettering understanding the obtained results, reinforcing the assumption on the glass structural change.

Research paper thumbnail of Preparation and characterization of tellurium oxide based glass: Li2O-TiO2-TeO2 system

Journal of Non-Crystalline Solids, 1995

... The preparation and characterization of xLi 2 O:5TiO 2 :(100 − x)TeO 2 glass systems with x =... more ... The preparation and characterization of xLi 2 O:5TiO 2 :(100 − x)TeO 2 glass systems with x = 5, 10, 15, 20 and 25 mol% are described. ... Soc. Jpn. 58 (1989) 2167. [7] J, Heo, D. Lain, GH Sigel Jr., E,A. Mendoza and DA Hensley, J, Am, Ceram. So 75 (I992) 277. ...

Research paper thumbnail of Magneto-optical rotation of heavy-metal oxide glasses

Journal of Non-Crystalline Solids, 1998

Magneto-optical rotation was measured at room temperature for glasses containing Bi 2 O 3 ±CdO±Ge... more Magneto-optical rotation was measured at room temperature for glasses containing Bi 2 O 3 ±CdO±GeO 2 (BCG), and Bi 2 O 3 ±PbO±GeO 2 ±B 2 O 3 (BPGP). A pulsed magnetic ®eld between 50 and 80 KG was used to measure Faraday rotation at 632.8 nm as a function of the concentration of Bi and Cd for BCG and Bi and Pb for BPGB. Verdet constant as high as 0.162 min G À1 cm À1 at 632.8 nm for the BPGB sample with the highest concentrations of Bi and Cd was found. Verdet constant increases linearly with the heavy-metal concentration for the BPGB whereas it reaches some saturation for the BCG system. Measurements of the magneto-optical rotation at other wavelengths in the visible and the refractive index at 632.8 nm are also reported. Ó

Research paper thumbnail of CdTe quantum dots by melt heat treatment in borosilicate glasses

Journal of Non-Crystalline Solids, 1997

... [26] HL Fragnito, JMM Rios, AS Duarte, E. Palange, JA Medeiros Neto, CL Cesar, LC Barbosa. OL... more ... [26] HL Fragnito, JMM Rios, AS Duarte, E. Palange, JA Medeiros Neto, CL Cesar, LC Barbosa. OL Alves, CH Brito Cruz, J. Phys= Condensed Mater. 5 (1993) A179. [27] A. Paul, Chemistry of Glasses (Chapman and Hall, London, 1982) p. 148. [28] JA Duffy, MD Ingrain, J ...

Research paper thumbnail of Superconductors of the BPSCCO system obtained from rapid cooling process

Journal of Materials Science: Materials in Electronics, 2005

Research paper thumbnail of Shell-core CdTeS quantum dots in glass

Journal of Materials Science Letters, 1996

The search for quantum sized particles (quantum dots) in colloids and in glasses has been of grea... more The search for quantum sized particles (quantum dots) in colloids and in glasses has been of great interest over the past ten years [1]. Quantum dots, different to quantum wells and quantum wires, have quantum confinement in three dimensions. Recently new progress in colloidal materials has shown the possibility of band gap engineering even inside these quantum sized particles, or more precisely--making structures inside a quantum dot. The structural quantum dot (SQD) can have a capped (or seed) structure, shell-core structure, ...

Research paper thumbnail of Improvement of size dispersion in CdTe quantum dots in glass by using double annealing process

Journal of Materials Science Letters, 1996

The semiconductor doped glasses (SDG) or quantum dots (QD) in glass have been of great interest a... more The semiconductor doped glasses (SDG) or quantum dots (QD) in glass have been of great interest as fast non-linear optical materials for over a decade [1]. There have been intensive studies on their quantum confinement and optical non-linearities. There are two major problems that prevent SDG from becoming practical optical devices. The first problem is the trap-related transitions that slow down the response of the material [2]. For CdTe quantum dots, traps were eliminated in a recent approach [3]. The inhomogeneity of quantum dots ...

Research paper thumbnail of The influence of semiconductor concentration on the size dispersion of quantum dots in glass

Journal of Materials Science Letters, 1996

Research paper thumbnail of CdTe quantum dots in Era3+-doped borosilicate glass

Journal of Materials Science Letters, 1996

Research paper thumbnail of Optical properties of CdTe quantum dots in praseodymium-doped borosilicate glass

Journal of Materials Science Letters, 1996

Research paper thumbnail of Laser induced darkening in CdTe quantum dots without traps

Journal of Materials Science Letters, 1996

The irreversible laser induced darkening effect found in semiconductor doped glasses (SDG) or gla... more The irreversible laser induced darkening effect found in semiconductor doped glasses (SDG) or glass based quantum dots (QD) is one of the barriers to the practical application of these materials in fast optical switching and non-linear optical devices.(We refer to this effect only in SDGs or glass based QD. This effect has also often been called photodarkening. We must make a distinction with the" photo-darkening" in glasses, which was defined over 20 years ago as" spectral red shift after laser exposure". Here, in our case and in the ...

Research paper thumbnail of ESTUDO DA FORMAÇÃO DE CdTe OBTIDO PELO MÉTODO DOS PRECURSORES POLIMÉRICOS

Research paper thumbnail of The Dependence of Electrical and Structural Properties with Aging of Superconductor Ceramics

This work presents the results of electrical resistance measurements as a function of temperature... more This work presents the results of electrical resistance measurements as a function of temperature and x-ray diffractometry for 2223 superconductor pellets (critical temperature at around 110 K), after keeping them for 14 years under normal ambient conditions (25ºC, 1atm and 50-70% humidity). The pellets were obtained after pressing a precursor powder previously prepared by a chemical process. The results indicate that the samples obtained from the chemical process are very stable, which represents extremely important results for technological applications.

Research paper thumbnail of Event-Related Brain Potentials during a Semantic Priming Task in Children with Learning Disabilities Not Otherwise Specified

PLoS ONE, 2014

Learning disabilities (LDs) are the most common psychiatric disorders in children. LDs are classi... more Learning disabilities (LDs) are the most common psychiatric disorders in children. LDs are classified either as "Specific" or "Learning Disorder Not Otherwise Specified". An important hypothesis suggests a failure in general domain process (i.e., attention) that explains global academic deficiencies. The aim of this study was to evaluate event-related potential (ERP) patterns of LD Not Otherwise Specified children with respect to a control group. Forty-one children (8-10.6 years old) participated and performed a semantic judgment priming task while ERPs were recorded. Twenty-one LD children had significantly lower scores in all academic skills (reading, writing and arithmetic) than twenty controls. Different ERP patterns were observed for each group. Control group showed smaller amplitudes of an anterior P200 for unrelated than related word pairs. This P200 effect was followed by a significant early N400a effect (greater amplitudes for unrelated than related word pairs; 350-550 ms) with a right topographical distribution. By contrast, LD Not Otherwise Specified group did not show a P200 effect or a significant N400a effect. This evidence suggests that LD Not Otherwise Specified children might be deficient in reading, writing and arithmetic domains because of their sluggish shifting of attention to process the incoming information.

Research paper thumbnail of Estudo das propriedades ópticas em vidros 0,3La2S3-0,7Ga2S 3

Química Nova, 1998

ABSTRACT

Research paper thumbnail of The structure and optical dispersion of the refractive index of tellurite glass

Optical Materials, 2011

The structure and optical properties of a 80TeO2–(20−x)Li2O–xTiO2 glass system where x=0, 5, 10, ... more The structure and optical properties of a 80TeO2–(20−x)Li2O–xTiO2 glass system where x=0, 5, 10, and 15mol% has been investigated using FTIR spectroscopy and Brewster angle measurements. The sample preparation, linear refractive index and density measurements, and infrared spectroscopic analysis are described. The refractive index and density of the studied tellurite glass samples increase when the amount of Ti in the

Research paper thumbnail of Effects of the particle size and nucleation temperature on tellurite 20Li2O–80TeO2 glass crystallization

Materials Science and Engineering: A, 2006

20Li 2 O-80TeO 2 glasses were heat annealed at different temperatures between T g and T x and stu... more 20Li 2 O-80TeO 2 glasses were heat annealed at different temperatures between T g and T x and studied by using XRD, FTIR spectroscopy and DSC techniques to understand the crystallization kinetics in this glass matrix. The infrared band structure of this glass is similar to what was observed in glassy TeO 2 . XRD results reveal the presence of three distinct crystalline ␥-TeO 2 , ␣-TeO 2 and Li 2 Te 2 O 5 phases during the crystallization process. This is a first report of ␥-TeO 2 phase crystallization in this glass matrix. DSC results confirm the crystallization of three distinct structures in the glass. In summary, our results suggest a crystallization hierarchy on this glass matrix since the ␥-TeO 2 and ␣-TeO 2 phases crystallization occurs before the Li 2 Te 2 O 5 phase crystallization.

Research paper thumbnail of Effect of PbS impurity on crystallization mechanism of phosphate glasses studied by differential scanning calorimetry

Materials Letters, 2002

In this work, differential scanning calorimetry (DSC) was used to study effect of PbS impurity on... more In this work, differential scanning calorimetry (DSC) was used to study effect of PbS impurity on crystallization mechanism of phosphate glasses. Bulk glasses presented one crystallization peak while powdered glasses presented two distinct crystallization peaks. For both undoped and doped glasses were determined the activation energies for the crystallization and the Avrami n parameters. The activation energies for undoped phosphate glass were 336 F 6 and 213 F 3 kJ mol À 1 , respectively, associated with first and second crystallization peaks. For doped glass, the obtained energies were 373 F 9 and 286 F 7 kJ mol À 1 . The calculated Avrami parameters, based on first crystallization peaks, for undoped and doped glasses were 2.25 F 0.01 and 1.75 F 0.02, respectively. These values suggest that the first DSC peak, in both glasses, may be associated with surface crystallization. D

Research paper thumbnail of Evidence of distinct phase transformations in lithium phosphate glass Li 2 O P 2 O 5

Journal of Physics D: Applied Physics, 2002

The purpose of this work is to study the Li2O–P2O5 glass using the differential scanning calorime... more The purpose of this work is to study the Li2O–P2O5 glass using the differential scanning calorimetry (DSC) and x-ray diffraction (XRD) techniques to understand the crystallization process in this glass matrix. To study the glass by DSC, screened samples with different particle sizes to resolve the crystallization peaks were used. Both crystallization peaks were attributed to Li6P6O18 and LiPO3 phases.

Research paper thumbnail of Crystallization kinetics in phosphate sodium-based glass studied by DSC technique

Journal of Physics and Chemistry of Solids, 2003

In this work, differential scanning calorimetry (DSC) was used to study the mechanism of crystall... more In this work, differential scanning calorimetry (DSC) was used to study the mechanism of crystallization of 50P2O5–27.8Na2O–16ZnO–6.2Al2O3 glass. DSC measurements were performed on bulk and powdered glasses with different particle size. The curve for bulk glass shows one crystallization peak while powdered glasses presented two distinct crystallization peaks. Based on DSC studies, the activation energies obtained were 336±6 and 213±3kJmol−1, associated with first and second crystallization peaks, respectively. Analyzing the DSC parameters as a function of particle size, the Avrami n parameter suggests that the peak at low temperature may be associated with surface crystallization while the peak at high temperature is associated with bulk crystallization.

Research paper thumbnail of Relation among optical, thermal and thermo-optical properties and niobium concentration in tellurite glasses

Journal of Non-Crystalline Solids, 2010

In this work, optical, thermal, thermo-optical and spectroscopic properties of the 80TeO 2 -(20− ... more In this work, optical, thermal, thermo-optical and spectroscopic properties of the 80TeO 2 -(20− x)Li 2 O-xNb 2 O 5 (x = 5, 10 and 15 mol%) glasses were investigated by using the thermal lens spectrometry, X-Ray diffraction, Raman spectroscopy, modulated differential scanning calorimetry and Brewster angle method. The influence of Nb 2 O 5 in the glass structure was interpreted by the thermal diffusivity, specific heat, thermal conductivity, temperature coefficient of the optical path length, refractive index and band gap energy. The calculated optical basicity and polarizability allowed bettering understanding the obtained results, reinforcing the assumption on the glass structural change.

Research paper thumbnail of Preparation and characterization of tellurium oxide based glass: Li2O-TiO2-TeO2 system

Journal of Non-Crystalline Solids, 1995

... The preparation and characterization of xLi 2 O:5TiO 2 :(100 − x)TeO 2 glass systems with x =... more ... The preparation and characterization of xLi 2 O:5TiO 2 :(100 − x)TeO 2 glass systems with x = 5, 10, 15, 20 and 25 mol% are described. ... Soc. Jpn. 58 (1989) 2167. [7] J, Heo, D. Lain, GH Sigel Jr., E,A. Mendoza and DA Hensley, J, Am, Ceram. So 75 (I992) 277. ...

Research paper thumbnail of Magneto-optical rotation of heavy-metal oxide glasses

Journal of Non-Crystalline Solids, 1998

Magneto-optical rotation was measured at room temperature for glasses containing Bi 2 O 3 ±CdO±Ge... more Magneto-optical rotation was measured at room temperature for glasses containing Bi 2 O 3 ±CdO±GeO 2 (BCG), and Bi 2 O 3 ±PbO±GeO 2 ±B 2 O 3 (BPGP). A pulsed magnetic ®eld between 50 and 80 KG was used to measure Faraday rotation at 632.8 nm as a function of the concentration of Bi and Cd for BCG and Bi and Pb for BPGB. Verdet constant as high as 0.162 min G À1 cm À1 at 632.8 nm for the BPGB sample with the highest concentrations of Bi and Cd was found. Verdet constant increases linearly with the heavy-metal concentration for the BPGB whereas it reaches some saturation for the BCG system. Measurements of the magneto-optical rotation at other wavelengths in the visible and the refractive index at 632.8 nm are also reported. Ó

Research paper thumbnail of CdTe quantum dots by melt heat treatment in borosilicate glasses

Journal of Non-Crystalline Solids, 1997

... [26] HL Fragnito, JMM Rios, AS Duarte, E. Palange, JA Medeiros Neto, CL Cesar, LC Barbosa. OL... more ... [26] HL Fragnito, JMM Rios, AS Duarte, E. Palange, JA Medeiros Neto, CL Cesar, LC Barbosa. OL Alves, CH Brito Cruz, J. Phys= Condensed Mater. 5 (1993) A179. [27] A. Paul, Chemistry of Glasses (Chapman and Hall, London, 1982) p. 148. [28] JA Duffy, MD Ingrain, J ...

Research paper thumbnail of Superconductors of the BPSCCO system obtained from rapid cooling process

Journal of Materials Science: Materials in Electronics, 2005

Research paper thumbnail of Shell-core CdTeS quantum dots in glass

Journal of Materials Science Letters, 1996

The search for quantum sized particles (quantum dots) in colloids and in glasses has been of grea... more The search for quantum sized particles (quantum dots) in colloids and in glasses has been of great interest over the past ten years [1]. Quantum dots, different to quantum wells and quantum wires, have quantum confinement in three dimensions. Recently new progress in colloidal materials has shown the possibility of band gap engineering even inside these quantum sized particles, or more precisely--making structures inside a quantum dot. The structural quantum dot (SQD) can have a capped (or seed) structure, shell-core structure, ...

Research paper thumbnail of Improvement of size dispersion in CdTe quantum dots in glass by using double annealing process

Journal of Materials Science Letters, 1996

The semiconductor doped glasses (SDG) or quantum dots (QD) in glass have been of great interest a... more The semiconductor doped glasses (SDG) or quantum dots (QD) in glass have been of great interest as fast non-linear optical materials for over a decade [1]. There have been intensive studies on their quantum confinement and optical non-linearities. There are two major problems that prevent SDG from becoming practical optical devices. The first problem is the trap-related transitions that slow down the response of the material [2]. For CdTe quantum dots, traps were eliminated in a recent approach [3]. The inhomogeneity of quantum dots ...

Research paper thumbnail of The influence of semiconductor concentration on the size dispersion of quantum dots in glass

Journal of Materials Science Letters, 1996

Research paper thumbnail of CdTe quantum dots in Era3+-doped borosilicate glass

Journal of Materials Science Letters, 1996

Research paper thumbnail of Optical properties of CdTe quantum dots in praseodymium-doped borosilicate glass

Journal of Materials Science Letters, 1996

Research paper thumbnail of Laser induced darkening in CdTe quantum dots without traps

Journal of Materials Science Letters, 1996

The irreversible laser induced darkening effect found in semiconductor doped glasses (SDG) or gla... more The irreversible laser induced darkening effect found in semiconductor doped glasses (SDG) or glass based quantum dots (QD) is one of the barriers to the practical application of these materials in fast optical switching and non-linear optical devices.(We refer to this effect only in SDGs or glass based QD. This effect has also often been called photodarkening. We must make a distinction with the" photo-darkening" in glasses, which was defined over 20 years ago as" spectral red shift after laser exposure". Here, in our case and in the ...