Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, 2006
The distribution of Fe in skin was assessed to monitor body Fe status in human hereditary hemochr... more The distribution of Fe in skin was assessed to monitor body Fe status in human hereditary hemochromatosis. The paper reports on data from nine patients with hemochromatosis that were studied along the therapeutic programme. Systemic evaluation of Fe metabolism was carried out by measuring with PIXE technique the Fe concentration in plasma and blood cells, and by determining with biochemical methods the indicators of Fe transport in serum (ferritin and transferrin). The Fe distribution and concentration in skin was assessed by nuclear microscopy and Fe deposits in liver estimated through nuclear magnetic resonance. Elevated Fe concentrations in skin were related to increased plasma Fe (p < 0.004), serum ferritin content (p < 0.01) and Fe deposits in liver (p < 0.004). The relationship of Fe deposits in organs and metabolism markers may help to better understand Fe pools mobilisation and to establish the quality of skin as a marker for the disease progression and therapy efficacy.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007
The permeability of skin to nanoparticles of titanium dioxide (TiO 2) used in sunscreens as a ref... more The permeability of skin to nanoparticles of titanium dioxide (TiO 2) used in sunscreens as a reflector of the UV wavelengths of sunlight, was examined using nuclear microscopy techniques. Special attention was given to the permeation characteristics of these nanoparticles across the outer layers of skin, the stratum corneum, in healthy and psoriatic skin condition. Aspects that may influence the interpretation of results such as sample preparation difficulties and skin condition were focused. Sample preparation can damage the integrity of the corneocyte layers inducing unwanted artefacts that may bias the evaluation of results. Irradiation conditions may also introduce distortions in the labile structures of human skin. Skin condition, such as loss of corneocyte cohesion occurring in psoriasis also influence the permeation profile of the nanoparticles. Weighing and accounting for these features in the examination of skin by nuclear microscopy is crucial to accurately assess the TiO 2 nanoparticles permeation depth.
... Phenylalanine Product Crystals during Fermentation. Maria C. Cuellar, Adrie JJ Straathof,Emil... more ... Phenylalanine Product Crystals during Fermentation. Maria C. Cuellar, Adrie JJ Straathof,Emile JAX van de Sandt, Joseph J. Heijnen and Luuk AM van der Wielen. Industrial &amp; Engineering Chemistry Research 2010 49 (2), 682-689. ...
Chemical Engineering and Processing: Process Intensification, 2008
Nývlt method was used to determine the kinetic parameters of commercial xylitol in ethanol:water ... more Nývlt method was used to determine the kinetic parameters of commercial xylitol in ethanol:water (50:50 %w/w) solution by batch cooling crystallization. The kinetic exponents (n, g and m) and the system kinetic constant (B N) were determined. Model experiments were carried out in order to verify the combined effects of saturation temperatures (40, 50 and 60 • C) and cooling rates (0.10, 0.25 and 0.50 • C/min) on these parameters. The fitting between experimental and calculated crystal sizes has 11.30% mean deviation.
A number of factors can influence the behavior of yeast during fermentation. Some of these factor... more A number of factors can influence the behavior of yeast during fermentation. Some of these factors (initial wort concentration, initial pH and percentage of corn syrup in the composition of the wort) were studied in order to determine their influence on the productivity of fermentation. Fermentations were carried out at 25oC utilizing a 23 factorial design of these factors. The results showed that the percentage of corn syrup had no influence on process productivity, whereas initial pH and especially initial wort concentration did. It can be concluded that using pH and initial wort concentration values higher than those utilized in this work (5.5 and 20oP, respectively) will result in a higher productivity.
A eucalyptus hemicellulose fraction was hydrolysed by treating eucalyptus wood chips with sulfuri... more A eucalyptus hemicellulose fraction was hydrolysed by treating eucalyptus wood chips with sulfuric acid. The hydrolysate was used as the substrate to grow Paecilomyces variotii IOC-3764 cultured for 72 or 96 hours. The influence of the inhibitors, nutrients and fermentation time was verified by a 28-4 and, subsequently, a 25-1 fractional factorial design. The effects of the inhibitors (acetic acid and furfural), nutrients (rice bran, urea, potassium nitrate, ammonium sulfate, magnesium sulfate and sodium phosphate) and fermentation time were investigated. The highest yield (10.59 g/L of biomass) was obtained when the microorganisms were cultivated for 72 hours in a medium composed of 30 g/L rice bran, 9.4 g/L ammonium sulfate (2 g/L nitrogen) and 2 g/L sodium phosphate.
The objective of this research was to improve Glucose-6-phosphate dehydrogenase (G6PD) production... more The objective of this research was to improve Glucose-6-phosphate dehydrogenase (G6PD) production by Saccharomyces cerevisiae W303-181, which carry the plasmid YEpPGK-G6PD, by varying the following cultivation conditions: pH value (4.8, 5.7 and 6.6); inoculum concentration (0.1, 0.6 and 1.1 g/L) and initial glucose concentration (20.0, 30.0 and 40.0 g/L). The effect of those variables on G6PD production capability was studied by the application of response surface statistical analysis. The results showed that the highest G6PD production (1594.2 U/L), specific activity (1189.7 U/g cell) and productivity (45.6 U/L.h) occurred at pH 4.8, inoculum concentration of 0.1 g/L and initial glucose concentration of 20.0 g/L, under agitation of 150 rpm at 30 o C after 36 h. In this work, the strain expressed about 21 fold more activity than the wild S. cerevisiae strain, being an attractive and promising new source of this enzyme.
A large number of advantages are obtained from the use of highly concentrated worts during the pr... more A large number of advantages are obtained from the use of highly concentrated worts during the production of beer in a process referred to as "high-gravity". However, problems related to slow or stuck fermentations, which cause the lower productivity and possibility of contamination, are encountered. This study examines the influence of factors pH, percentage of corn syrup, initial wort concentration and fermentation temperature on the fermentation parameters, namely productivity, wort attenuation and the yield coefficient for sugar-to-ethanol conversion. The results show that productivity increased when the higher temperature, the higher wort concentration and the lower syrup percentage were used, while wort attenuation increased when lower wort concentration and no syrup were used. The yield coefficient for sugar-to-ethanol conversion was not influenced by any of the factors studied.
In the present work, the ethanol oxidation reaction (EOR) was investigated using PtSn/C electroca... more In the present work, the ethanol oxidation reaction (EOR) was investigated using PtSn/C electrocatalysts in the following two phases: 92% alloyed prepared by the polymeric precursor method (PPM) and 6% alloyed prepared by a sol-gel method (SGM). The TEM experiments show particle sizes of 3-5 nm for both catalysts. The electrocatalytic activity for both materials was investigated using chronoamperometry, and at 0.5 V vs. RHE, the current density for the EOR on the PPM material was approximately 5 times higher than on the SGM material. From in situ ATR-FTIR experiments, it can be seen that the non-alloyed materials led to CO 2 formation with slow kinetics, whereas alloyed materials led to acetic acid formation with fast kinetics. The enhancement in the electrocatalytic behavior for ethanol oxidation was explained by acetic acid formation.
This paper presents a study on the ethanol oxidation reaction using SnO 2 @Pt/C core-shell struct... more This paper presents a study on the ethanol oxidation reaction using SnO 2 @Pt/C core-shell structures as electrocatalysts. All the materials used, including Pt/C and PtSn/C E-tek, were 20% (w/w) metal on carbon. The formation of core-shell nanoparticles (SnO 2 @Pt/C) was measured by UV-vis spectrophotometry. Xray diffraction measurements showed Pt (shell) diffraction patterns without influence from the SnO 2 core and without any shift in 2Â values for Pt. The diameters of the core-shell particle structures, measured using high-resolution transmission electron microscopy images, were in the range of 3-16 nm. The electrochemical profile for SnO 2 @Pt/C in an acidic medium (H 2 SO 4 at a concentration of 0.5 mol L −1) was almost the same as the typical electrochemical behavior for Pt in an acidic medium. Furthermore, the onset potential for the ethanol oxidation reaction using SnO 2 @Pt/C was almost the same as that for PtSn/C E-tek (0.23 V versus the reversible hydrogen electrode). However, the mass current peak densities for ethanol oxidation were 50% higher on SnO 2 @Pt/C than on PtSn/C E-tek. In the polarization curve, the mass current density for ethanol oxidation was higher at all potentials for SnO 2 @Pt/C when compared to Pt/C and PtSn/C E-tek. At 0.5 V, the current mass density for ethanol oxidation on SnO 2 @Pt was 2.3 times of that for the same process on the commercial material. The electrocatalytic activity of SnO 2 @Pt/C for ethanol oxidation was associated with an increase in the electrochemically active surface area. However, an electronic effect should also be considered because the Pt shell changes its electronic structure in the presence of the foreign core.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, 2006
The distribution of Fe in skin was assessed to monitor body Fe status in human hereditary hemochr... more The distribution of Fe in skin was assessed to monitor body Fe status in human hereditary hemochromatosis. The paper reports on data from nine patients with hemochromatosis that were studied along the therapeutic programme. Systemic evaluation of Fe metabolism was carried out by measuring with PIXE technique the Fe concentration in plasma and blood cells, and by determining with biochemical methods the indicators of Fe transport in serum (ferritin and transferrin). The Fe distribution and concentration in skin was assessed by nuclear microscopy and Fe deposits in liver estimated through nuclear magnetic resonance. Elevated Fe concentrations in skin were related to increased plasma Fe (p < 0.004), serum ferritin content (p < 0.01) and Fe deposits in liver (p < 0.004). The relationship of Fe deposits in organs and metabolism markers may help to better understand Fe pools mobilisation and to establish the quality of skin as a marker for the disease progression and therapy efficacy.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007
The permeability of skin to nanoparticles of titanium dioxide (TiO 2) used in sunscreens as a ref... more The permeability of skin to nanoparticles of titanium dioxide (TiO 2) used in sunscreens as a reflector of the UV wavelengths of sunlight, was examined using nuclear microscopy techniques. Special attention was given to the permeation characteristics of these nanoparticles across the outer layers of skin, the stratum corneum, in healthy and psoriatic skin condition. Aspects that may influence the interpretation of results such as sample preparation difficulties and skin condition were focused. Sample preparation can damage the integrity of the corneocyte layers inducing unwanted artefacts that may bias the evaluation of results. Irradiation conditions may also introduce distortions in the labile structures of human skin. Skin condition, such as loss of corneocyte cohesion occurring in psoriasis also influence the permeation profile of the nanoparticles. Weighing and accounting for these features in the examination of skin by nuclear microscopy is crucial to accurately assess the TiO 2 nanoparticles permeation depth.
... Phenylalanine Product Crystals during Fermentation. Maria C. Cuellar, Adrie JJ Straathof,Emil... more ... Phenylalanine Product Crystals during Fermentation. Maria C. Cuellar, Adrie JJ Straathof,Emile JAX van de Sandt, Joseph J. Heijnen and Luuk AM van der Wielen. Industrial &amp; Engineering Chemistry Research 2010 49 (2), 682-689. ...
Chemical Engineering and Processing: Process Intensification, 2008
Nývlt method was used to determine the kinetic parameters of commercial xylitol in ethanol:water ... more Nývlt method was used to determine the kinetic parameters of commercial xylitol in ethanol:water (50:50 %w/w) solution by batch cooling crystallization. The kinetic exponents (n, g and m) and the system kinetic constant (B N) were determined. Model experiments were carried out in order to verify the combined effects of saturation temperatures (40, 50 and 60 • C) and cooling rates (0.10, 0.25 and 0.50 • C/min) on these parameters. The fitting between experimental and calculated crystal sizes has 11.30% mean deviation.
A number of factors can influence the behavior of yeast during fermentation. Some of these factor... more A number of factors can influence the behavior of yeast during fermentation. Some of these factors (initial wort concentration, initial pH and percentage of corn syrup in the composition of the wort) were studied in order to determine their influence on the productivity of fermentation. Fermentations were carried out at 25oC utilizing a 23 factorial design of these factors. The results showed that the percentage of corn syrup had no influence on process productivity, whereas initial pH and especially initial wort concentration did. It can be concluded that using pH and initial wort concentration values higher than those utilized in this work (5.5 and 20oP, respectively) will result in a higher productivity.
A eucalyptus hemicellulose fraction was hydrolysed by treating eucalyptus wood chips with sulfuri... more A eucalyptus hemicellulose fraction was hydrolysed by treating eucalyptus wood chips with sulfuric acid. The hydrolysate was used as the substrate to grow Paecilomyces variotii IOC-3764 cultured for 72 or 96 hours. The influence of the inhibitors, nutrients and fermentation time was verified by a 28-4 and, subsequently, a 25-1 fractional factorial design. The effects of the inhibitors (acetic acid and furfural), nutrients (rice bran, urea, potassium nitrate, ammonium sulfate, magnesium sulfate and sodium phosphate) and fermentation time were investigated. The highest yield (10.59 g/L of biomass) was obtained when the microorganisms were cultivated for 72 hours in a medium composed of 30 g/L rice bran, 9.4 g/L ammonium sulfate (2 g/L nitrogen) and 2 g/L sodium phosphate.
The objective of this research was to improve Glucose-6-phosphate dehydrogenase (G6PD) production... more The objective of this research was to improve Glucose-6-phosphate dehydrogenase (G6PD) production by Saccharomyces cerevisiae W303-181, which carry the plasmid YEpPGK-G6PD, by varying the following cultivation conditions: pH value (4.8, 5.7 and 6.6); inoculum concentration (0.1, 0.6 and 1.1 g/L) and initial glucose concentration (20.0, 30.0 and 40.0 g/L). The effect of those variables on G6PD production capability was studied by the application of response surface statistical analysis. The results showed that the highest G6PD production (1594.2 U/L), specific activity (1189.7 U/g cell) and productivity (45.6 U/L.h) occurred at pH 4.8, inoculum concentration of 0.1 g/L and initial glucose concentration of 20.0 g/L, under agitation of 150 rpm at 30 o C after 36 h. In this work, the strain expressed about 21 fold more activity than the wild S. cerevisiae strain, being an attractive and promising new source of this enzyme.
A large number of advantages are obtained from the use of highly concentrated worts during the pr... more A large number of advantages are obtained from the use of highly concentrated worts during the production of beer in a process referred to as "high-gravity". However, problems related to slow or stuck fermentations, which cause the lower productivity and possibility of contamination, are encountered. This study examines the influence of factors pH, percentage of corn syrup, initial wort concentration and fermentation temperature on the fermentation parameters, namely productivity, wort attenuation and the yield coefficient for sugar-to-ethanol conversion. The results show that productivity increased when the higher temperature, the higher wort concentration and the lower syrup percentage were used, while wort attenuation increased when lower wort concentration and no syrup were used. The yield coefficient for sugar-to-ethanol conversion was not influenced by any of the factors studied.
In the present work, the ethanol oxidation reaction (EOR) was investigated using PtSn/C electroca... more In the present work, the ethanol oxidation reaction (EOR) was investigated using PtSn/C electrocatalysts in the following two phases: 92% alloyed prepared by the polymeric precursor method (PPM) and 6% alloyed prepared by a sol-gel method (SGM). The TEM experiments show particle sizes of 3-5 nm for both catalysts. The electrocatalytic activity for both materials was investigated using chronoamperometry, and at 0.5 V vs. RHE, the current density for the EOR on the PPM material was approximately 5 times higher than on the SGM material. From in situ ATR-FTIR experiments, it can be seen that the non-alloyed materials led to CO 2 formation with slow kinetics, whereas alloyed materials led to acetic acid formation with fast kinetics. The enhancement in the electrocatalytic behavior for ethanol oxidation was explained by acetic acid formation.
This paper presents a study on the ethanol oxidation reaction using SnO 2 @Pt/C core-shell struct... more This paper presents a study on the ethanol oxidation reaction using SnO 2 @Pt/C core-shell structures as electrocatalysts. All the materials used, including Pt/C and PtSn/C E-tek, were 20% (w/w) metal on carbon. The formation of core-shell nanoparticles (SnO 2 @Pt/C) was measured by UV-vis spectrophotometry. Xray diffraction measurements showed Pt (shell) diffraction patterns without influence from the SnO 2 core and without any shift in 2Â values for Pt. The diameters of the core-shell particle structures, measured using high-resolution transmission electron microscopy images, were in the range of 3-16 nm. The electrochemical profile for SnO 2 @Pt/C in an acidic medium (H 2 SO 4 at a concentration of 0.5 mol L −1) was almost the same as the typical electrochemical behavior for Pt in an acidic medium. Furthermore, the onset potential for the ethanol oxidation reaction using SnO 2 @Pt/C was almost the same as that for PtSn/C E-tek (0.23 V versus the reversible hydrogen electrode). However, the mass current peak densities for ethanol oxidation were 50% higher on SnO 2 @Pt/C than on PtSn/C E-tek. In the polarization curve, the mass current density for ethanol oxidation was higher at all potentials for SnO 2 @Pt/C when compared to Pt/C and PtSn/C E-tek. At 0.5 V, the current mass density for ethanol oxidation on SnO 2 @Pt was 2.3 times of that for the same process on the commercial material. The electrocatalytic activity of SnO 2 @Pt/C for ethanol oxidation was associated with an increase in the electrochemically active surface area. However, an electronic effect should also be considered because the Pt shell changes its electronic structure in the presence of the foreign core.
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