Carlos Castro Perez | Universidad de La Laguna (original) (raw)
Papers by Carlos Castro Perez
Rev Invest Clin 1998; Volumen 50 (5): 419-422 ARTICULO DE INVESTIGACION Anticuerpos contra Toxopl... more Rev Invest Clin 1998; Volumen 50 (5): 419-422 ARTICULO DE INVESTIGACION Anticuerpos contra Toxoplasma gondii en pacientes con VIH RESUMEN Objetivo. Conocer la prevalencia de anticuerpos contra T. gondii tipo IgG (Ac-T gondii) en pacientes con VIH residentes de la península de Yucatán. Métodos. Fueron 95 pacientes con VIH y 100 donadores de sangre como grupo control. Se midieron los Ac-T gondii por un ELISA de fase sólida de 3ª generación. Se recolectaron datos clínicos demográficos. Resultados. Hubo mayor frecuencia (p = 0.003) de anticuerpos en donadores (69%, IC = 59-78%) que en pacientes (47%,. No se asoció la presencia de Ac-T gondii con alguna de las variables encuestadas (género, lugar de residencia, grupo etario). En los pacientes con VIH/SIDA no hubo relación de anticuerpos con cuenta de linfocitos CD4 ni con categoría clínica de la infección. Conclusiones. La alta prevalencia de Ac-T gondii en ambos grupos sugiere que esta zoonosis es endémica en la península de Yucatán, lo cual justifica la determinación rutinaria de Ac-T gondii y protocolos terapéuticos en los pacientes con VIH/SIDA ya que un porcentaje alto de ellos estaría en riesgo de desarrollar toxoplasmosis encefálica.
Materials Research-ibero-american Journal of Materials, 2005
Synthetic porous ceramics can be used as three-dimensional scaffolds for bone repair. The aim of ... more Synthetic porous ceramics can be used as three-dimensional scaffolds for bone repair. The aim of this work is to correlate process parameters with scaffolds structural characteristics. The factorial 2 level experimental design was chosen to study the effect of the Ca/P ratio (1.58 or 1.67), calcination temperature (1000 or 1150 °C) and porogen content (20 or 40%) on the calcium phosphate samples characteristics. The influence of such parameters was determined by X-ray diffraction, infrared spectroscopy and image analysis. It was observed that phase composition was basically a function of the Ca/P ratio of the raw material. The use of the porogen did not alter the hydroxyapatite (HA)/tricalcium phosphate (TCP) content, but induced changes in the relative content of TCP phase (a or b). It is possible to design a porous sample with defined characteristics, and the model herein used can be considered as having a good predictive power.
Physical Chemistry Chemical Physics, 2000
Phys. Chem. Chem. Phys., 2000, 2, 4225-4230 DOI:10.1039/B004339G (Paper). Structure of vanadate i... more Phys. Chem. Chem. Phys., 2000, 2, 4225-4230 DOI:10.1039/B004339G (Paper). Structure of vanadate in calcium phosphate and vanadate apatite solid solutions. Carlos Bauer Boechata, Jean-Guillaume Eonb, Alexandre Malta ...
Physical Chemistry Chemical Physics, 2000
Phys. Chem. Chem. Phys., 2000, 2, 4225-4230 DOI:10.1039/B004339G (Paper). Structure of vanadate i... more Phys. Chem. Chem. Phys., 2000, 2, 4225-4230 DOI:10.1039/B004339G (Paper). Structure of vanadate in calcium phosphate and vanadate apatite solid solutions. Carlos Bauer Boechata, Jean-Guillaume Eonb, Alexandre Malta ...
Catalysis Today, 1996
The promoting effects of a noble metal (Pd, Pt, Rh) added to Co/Nb 2 0 s catalysts were studied b... more The promoting effects of a noble metal (Pd, Pt, Rh) added to Co/Nb 2 0 s catalysts were studied by varying the Me/Co atomic ratios. Acid niobium was calcined to niobium pentoxide. The surface and bulk structures of the calcined materials were characterized by XPS and TPR techniques. The catalytic performance was obtained with CO hydrogenation. The addition of a noble metal promoted the reduction of C0 3 + and Co 2 + phases at the surface. XPS results revealed that Co 2 + species are well dispersed as a thin layer around the niobium support together with C0 3 04 crystallites islands. The C0304/C02~ratio depends on the surface area of the support. XPS measurements also revealed that Pd~, Rh 2 0 3 and Pt0 2 are the main phases in the mono and bimetallic catalysts. The activity of the bimetallic catalysts increased and the stability was already attained. The selectivities towards C t and oxygenates increased with the addition of Rh up to an atomic ratio of 0.5 and decreased beyond that. This behavior is similar for both temperatures of reduction at 573 and 773 K. Pt wt.-% Co wt.-% Pt/Co ratio a Rhwt.-% Cowt.-% Pd/Rh ratio •
Catalysis Today, 2003
Ammonium oxalate complex of niobium was investigated as an aqueous precursor for the preparation ... more Ammonium oxalate complex of niobium was investigated as an aqueous precursor for the preparation of x% Nb2O5/Al2O3 (x=5, 10, 20 and 30wt.%) samples. Catalysts with the same Nb2O5 contents were also prepared from the traditional niobium oxalate/oxalic acid aqueous solution. The catalysts were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), temperature-programmed reduction (TPR), infrared spectroscopy of chemisorbed pyridine
Applied Catalysis B-environmental, 2009
Catalysis Today, 2005
ABSTRACT Interpretation of kinetics is the focus of this contribution based on our experiences an... more ABSTRACT Interpretation of kinetics is the focus of this contribution based on our experiences and particularly with selected characterizations besides the commonly reaction kinetic data in a differential reactor. The usual reaction kinetic models, such as Langmuir–Hinshelwood (L-H) and power law equations were used for three different cases besides one or two spectroscopic surface characterizations, allowing explaining the kinetic parameters.The activity and selectivity are dependent on the catalyst and if they are structure sensitive, they depend strongly on the surface active sites, suffering transformations during the reaction, which have to be taken in account. FTIR and ISS measurements in situ explain the interface metal oxide site formation during CO oxidation and methane reforming and XPS data the structure transformation at the surface after different pre-treatment and propane oxidation. It was observed that in reducible oxide supports the oxygen is responsible for the surface interaction between different structures, affecting strongly the reaction rate.
Catalysis Today, 2006
... a, NUCAT/PEQ/COPPE, Federal University of Rio de Janeiro, Centro de Tecnologia, Bloco G, sala... more ... a, NUCAT/PEQ/COPPE, Federal University of Rio de Janeiro, Centro de Tecnologia, Bloco G, sala 128, Cidade Universitária, CEP: 21945-970, Rio de Janeiro, RJ, Brazil. b, Escola de Química, Federal University of Rio de Janeiro ...
Physical Chemistry Chemical Physics, 1999
ABSTRACT Niobia-supported cobalt catalysts were prepared by incipient wetness impregnation and we... more ABSTRACT Niobia-supported cobalt catalysts were prepared by incipient wetness impregnation and were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), temperature-programmed reductioon (TPR) and magnetic measurements. At least two different types of cobalt species were present on the calcined catalysts: Co3O4 particles and Co2+ surface species. At high cobalt content, Co3O4 particles are the main species whereas the percentage of Co2+ species linked to the support increases as the cobalt loading is decreased. XPS results revealed that the Co2+ species could be better represented by a mixture of Co2Nb5O14 and CoNb2O6. TPR analyses allowed one to quantify the percentage of Co3O4 particles on the niobia-supported Co catalyst. However, due to partial reduction of niobia, TPR alone did not permit the quantification of the reduction degree of cobalt in these catalysts. Magnetic measurements linked to a TPR technique is a possible way to measure the reduction degree of cobalt in Co/Nb2O5 catalysts. After reduction at high temperature, the mixture of cobalt niobates was reduced and NbO2 produced led to the strong metal-support interaction (SMSI) effect.
Catalysis Today, 2005
ABSTRACT This study involves the characterization of a series Co/x% Nb2O5/Al2O3 catalysts.The tem... more ABSTRACT This study involves the characterization of a series Co/x% Nb2O5/Al2O3 catalysts.The temperature-programmed surface reaction technique (TPSR) and in situ diffuse reflectance spectroscopy (DRS) results have shown a transient behavior of the catalysts, distinguishing very well the Co/Al2O3 from the Co/Nb2O5·Al2O3 catalysts.DRS and temperature-programmed reduction (TPR) results indicate the presence of Co2+, besides Co0 and Co0–NbOx, which affect greatly the performance of the catalysts.These results allowed us to propose that the interface Co2+–Co0 is responsible for the mathanation reaction, while the Co0–NbOx is responsible for the hydrocarbon chain grow. The relative amount of each specie on the surface plays a fundamental role on the selectivity behavior of CO hydrogenation.
Applied Clay Science, 2010
... 173 (1998), pp. 247256. Abstract | PDF (301 K) | View Record in Scopus | Cited By in Scopus ... more ... 173 (1998), pp. 247256. Abstract | PDF (301 K) | View Record in Scopus | Cited By in Scopus (83). Bellotto et al., 1996 M. Bellotto, B. Rebours, O. Clause, J. Lynch, D. Bazin and E. Elkaim, A reexamination of hydrotalcite crystal chemistry, J. Phys. Chem. 100 (1996), pp. ...
Catalysis Today, 2008
The present work aims to evaluate the performance of the CeZrO 2 mixed oxide for the NO x decompo... more The present work aims to evaluate the performance of the CeZrO 2 mixed oxide for the NO x decomposition in the absence of a noble metal. The Ce 75 Zr 25 O 2 mixed oxide was prepared by co-precipitation of hydroxides and was characterized by X-ray diffraction (XRD) before and after pretreatments, thermogravimetric analysis (TG) and temperature programmed desorption of NO (TPD). XRD results allowed confirming the formation of a solid solution. TG results showed slight loss of mass during the reduction of the mixed oxide. TPD results showed NO decomposition even at room temperature either for reduced or calcined samples, however a significant decrease of the temperature of the NO decomposition besides an increasing amount of N 2 for the reduced sample, which is attributed to superficial structure changes of the mixed oxide. #
Rev Invest Clin 1998; Volumen 50 (5): 419-422 ARTICULO DE INVESTIGACION Anticuerpos contra Toxopl... more Rev Invest Clin 1998; Volumen 50 (5): 419-422 ARTICULO DE INVESTIGACION Anticuerpos contra Toxoplasma gondii en pacientes con VIH RESUMEN Objetivo. Conocer la prevalencia de anticuerpos contra T. gondii tipo IgG (Ac-T gondii) en pacientes con VIH residentes de la península de Yucatán. Métodos. Fueron 95 pacientes con VIH y 100 donadores de sangre como grupo control. Se midieron los Ac-T gondii por un ELISA de fase sólida de 3ª generación. Se recolectaron datos clínicos demográficos. Resultados. Hubo mayor frecuencia (p = 0.003) de anticuerpos en donadores (69%, IC = 59-78%) que en pacientes (47%,. No se asoció la presencia de Ac-T gondii con alguna de las variables encuestadas (género, lugar de residencia, grupo etario). En los pacientes con VIH/SIDA no hubo relación de anticuerpos con cuenta de linfocitos CD4 ni con categoría clínica de la infección. Conclusiones. La alta prevalencia de Ac-T gondii en ambos grupos sugiere que esta zoonosis es endémica en la península de Yucatán, lo cual justifica la determinación rutinaria de Ac-T gondii y protocolos terapéuticos en los pacientes con VIH/SIDA ya que un porcentaje alto de ellos estaría en riesgo de desarrollar toxoplasmosis encefálica.
Materials Research-ibero-american Journal of Materials, 2005
Synthetic porous ceramics can be used as three-dimensional scaffolds for bone repair. The aim of ... more Synthetic porous ceramics can be used as three-dimensional scaffolds for bone repair. The aim of this work is to correlate process parameters with scaffolds structural characteristics. The factorial 2 level experimental design was chosen to study the effect of the Ca/P ratio (1.58 or 1.67), calcination temperature (1000 or 1150 °C) and porogen content (20 or 40%) on the calcium phosphate samples characteristics. The influence of such parameters was determined by X-ray diffraction, infrared spectroscopy and image analysis. It was observed that phase composition was basically a function of the Ca/P ratio of the raw material. The use of the porogen did not alter the hydroxyapatite (HA)/tricalcium phosphate (TCP) content, but induced changes in the relative content of TCP phase (a or b). It is possible to design a porous sample with defined characteristics, and the model herein used can be considered as having a good predictive power.
Physical Chemistry Chemical Physics, 2000
Phys. Chem. Chem. Phys., 2000, 2, 4225-4230 DOI:10.1039/B004339G (Paper). Structure of vanadate i... more Phys. Chem. Chem. Phys., 2000, 2, 4225-4230 DOI:10.1039/B004339G (Paper). Structure of vanadate in calcium phosphate and vanadate apatite solid solutions. Carlos Bauer Boechata, Jean-Guillaume Eonb, Alexandre Malta ...
Physical Chemistry Chemical Physics, 2000
Phys. Chem. Chem. Phys., 2000, 2, 4225-4230 DOI:10.1039/B004339G (Paper). Structure of vanadate i... more Phys. Chem. Chem. Phys., 2000, 2, 4225-4230 DOI:10.1039/B004339G (Paper). Structure of vanadate in calcium phosphate and vanadate apatite solid solutions. Carlos Bauer Boechata, Jean-Guillaume Eonb, Alexandre Malta ...
Catalysis Today, 1996
The promoting effects of a noble metal (Pd, Pt, Rh) added to Co/Nb 2 0 s catalysts were studied b... more The promoting effects of a noble metal (Pd, Pt, Rh) added to Co/Nb 2 0 s catalysts were studied by varying the Me/Co atomic ratios. Acid niobium was calcined to niobium pentoxide. The surface and bulk structures of the calcined materials were characterized by XPS and TPR techniques. The catalytic performance was obtained with CO hydrogenation. The addition of a noble metal promoted the reduction of C0 3 + and Co 2 + phases at the surface. XPS results revealed that Co 2 + species are well dispersed as a thin layer around the niobium support together with C0 3 04 crystallites islands. The C0304/C02~ratio depends on the surface area of the support. XPS measurements also revealed that Pd~, Rh 2 0 3 and Pt0 2 are the main phases in the mono and bimetallic catalysts. The activity of the bimetallic catalysts increased and the stability was already attained. The selectivities towards C t and oxygenates increased with the addition of Rh up to an atomic ratio of 0.5 and decreased beyond that. This behavior is similar for both temperatures of reduction at 573 and 773 K. Pt wt.-% Co wt.-% Pt/Co ratio a Rhwt.-% Cowt.-% Pd/Rh ratio •
Catalysis Today, 2003
Ammonium oxalate complex of niobium was investigated as an aqueous precursor for the preparation ... more Ammonium oxalate complex of niobium was investigated as an aqueous precursor for the preparation of x% Nb2O5/Al2O3 (x=5, 10, 20 and 30wt.%) samples. Catalysts with the same Nb2O5 contents were also prepared from the traditional niobium oxalate/oxalic acid aqueous solution. The catalysts were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), temperature-programmed reduction (TPR), infrared spectroscopy of chemisorbed pyridine
Applied Catalysis B-environmental, 2009
Catalysis Today, 2005
ABSTRACT Interpretation of kinetics is the focus of this contribution based on our experiences an... more ABSTRACT Interpretation of kinetics is the focus of this contribution based on our experiences and particularly with selected characterizations besides the commonly reaction kinetic data in a differential reactor. The usual reaction kinetic models, such as Langmuir–Hinshelwood (L-H) and power law equations were used for three different cases besides one or two spectroscopic surface characterizations, allowing explaining the kinetic parameters.The activity and selectivity are dependent on the catalyst and if they are structure sensitive, they depend strongly on the surface active sites, suffering transformations during the reaction, which have to be taken in account. FTIR and ISS measurements in situ explain the interface metal oxide site formation during CO oxidation and methane reforming and XPS data the structure transformation at the surface after different pre-treatment and propane oxidation. It was observed that in reducible oxide supports the oxygen is responsible for the surface interaction between different structures, affecting strongly the reaction rate.
Catalysis Today, 2006
... a, NUCAT/PEQ/COPPE, Federal University of Rio de Janeiro, Centro de Tecnologia, Bloco G, sala... more ... a, NUCAT/PEQ/COPPE, Federal University of Rio de Janeiro, Centro de Tecnologia, Bloco G, sala 128, Cidade Universitária, CEP: 21945-970, Rio de Janeiro, RJ, Brazil. b, Escola de Química, Federal University of Rio de Janeiro ...
Physical Chemistry Chemical Physics, 1999
ABSTRACT Niobia-supported cobalt catalysts were prepared by incipient wetness impregnation and we... more ABSTRACT Niobia-supported cobalt catalysts were prepared by incipient wetness impregnation and were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), temperature-programmed reductioon (TPR) and magnetic measurements. At least two different types of cobalt species were present on the calcined catalysts: Co3O4 particles and Co2+ surface species. At high cobalt content, Co3O4 particles are the main species whereas the percentage of Co2+ species linked to the support increases as the cobalt loading is decreased. XPS results revealed that the Co2+ species could be better represented by a mixture of Co2Nb5O14 and CoNb2O6. TPR analyses allowed one to quantify the percentage of Co3O4 particles on the niobia-supported Co catalyst. However, due to partial reduction of niobia, TPR alone did not permit the quantification of the reduction degree of cobalt in these catalysts. Magnetic measurements linked to a TPR technique is a possible way to measure the reduction degree of cobalt in Co/Nb2O5 catalysts. After reduction at high temperature, the mixture of cobalt niobates was reduced and NbO2 produced led to the strong metal-support interaction (SMSI) effect.
Catalysis Today, 2005
ABSTRACT This study involves the characterization of a series Co/x% Nb2O5/Al2O3 catalysts.The tem... more ABSTRACT This study involves the characterization of a series Co/x% Nb2O5/Al2O3 catalysts.The temperature-programmed surface reaction technique (TPSR) and in situ diffuse reflectance spectroscopy (DRS) results have shown a transient behavior of the catalysts, distinguishing very well the Co/Al2O3 from the Co/Nb2O5·Al2O3 catalysts.DRS and temperature-programmed reduction (TPR) results indicate the presence of Co2+, besides Co0 and Co0–NbOx, which affect greatly the performance of the catalysts.These results allowed us to propose that the interface Co2+–Co0 is responsible for the mathanation reaction, while the Co0–NbOx is responsible for the hydrocarbon chain grow. The relative amount of each specie on the surface plays a fundamental role on the selectivity behavior of CO hydrogenation.
Applied Clay Science, 2010
... 173 (1998), pp. 247256. Abstract | PDF (301 K) | View Record in Scopus | Cited By in Scopus ... more ... 173 (1998), pp. 247256. Abstract | PDF (301 K) | View Record in Scopus | Cited By in Scopus (83). Bellotto et al., 1996 M. Bellotto, B. Rebours, O. Clause, J. Lynch, D. Bazin and E. Elkaim, A reexamination of hydrotalcite crystal chemistry, J. Phys. Chem. 100 (1996), pp. ...
Catalysis Today, 2008
The present work aims to evaluate the performance of the CeZrO 2 mixed oxide for the NO x decompo... more The present work aims to evaluate the performance of the CeZrO 2 mixed oxide for the NO x decomposition in the absence of a noble metal. The Ce 75 Zr 25 O 2 mixed oxide was prepared by co-precipitation of hydroxides and was characterized by X-ray diffraction (XRD) before and after pretreatments, thermogravimetric analysis (TG) and temperature programmed desorption of NO (TPD). XRD results allowed confirming the formation of a solid solution. TG results showed slight loss of mass during the reduction of the mixed oxide. TPD results showed NO decomposition even at room temperature either for reduced or calcined samples, however a significant decrease of the temperature of the NO decomposition besides an increasing amount of N 2 for the reduced sample, which is attributed to superficial structure changes of the mixed oxide. #