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161.
María Sánchez-Campillo Elvira Larqué Daniel González-Silvera Rebeca Martínez-Tomás Manuel García-Fernández Francisco Avilés Anna Wellner Lucy Bialek Soledad Parra Marie Alminger Salvador Zamora Francisca Pérez-Llamas 《Food chemistry》2012
Ten subjects consumed one serving of an optimised or a reference soup produced using modified or traditional processing methods, respectively. Both soups contained the same proportions of carrot, tomato and broccoli, but with 5% olive oil in the optimised soup and 2.5% in the reference soup. The β-carotene content in 600 mL of the optimised/reference soups was 4.10/2.90 mg, and the lycopene content was 3.90/2.71 mg. The β-carotene and lycopene concentrations in chylomicrons isolated from blood serum samples were similar for both groups. Only 50% of subjects could be considered as carotenoid responders and, in agreement with in vitro accessibility data, the β-carotene concentration in the chylomicrons of these subjects was significantly higher in the group consuming the optimised soup, while no changes were found for lycopene. Postprandial chylomicrons from the optimised soup group exhibited significantly higher antioxidant activity in HepG2 cells than the other group. The stimulation of HepG2 cells by human postprandial chylomicrons seems useful for evaluating the antioxidant effect of different food matrices. 相似文献
162.
María Paz San Andrs Marina Baos-Cabrera Lucía Gutirrez-Fernndez Ana María Díez-Pascual Soledad Vera-Lpez 《International journal of molecular sciences》2021,22(10)
The potential of tannic acid (TA) as a dispersing agent for graphene (G) in aqueous solutions and its interaction with riboflavin have been studied under different experimental conditions. TA induces quenching of riboflavin fluorescence, and the effect is stronger with increasing TA concentration, due to π-π interactions through the aromatic rings, and hydrogen bonding interactions between the hydroxyl moieties of both compounds. The influence of TA concentration, the pH, and the G/TA weight ratio on the quenching magnitude, have been studied. At a pH of 4.1, G dispersed in TA hardly influences the riboflavin fluorescence, while at a pH of 7.1, the nanomaterial interacts with riboflavin, causing an additional quenching to that produced by TA. When TA concentration is kept constant, quenching of G on riboflavin fluorescence depends on both the G/TA weight ratio and the TA concentration. The fluorescence attenuation is stronger for dispersions with the lowest G/TA ratios, since TA is the main contributor to the quenching effect. Data obey the Stern–Volmer relationship up to TA 2.0 g L−1 and G 20 mg L−1. Results demonstrate that TA is an effective dispersant for graphene-based nanomaterials in liquid medium and a green alternative to conventional surfactants and synthetic polymers for the determination of biomolecules. 相似文献
163.
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165.
Karla Calfumán Maria Jesús Aguirre Paulina Cañete-Rosales Soledad Bollo Rosa Llusar Mauricio Isaacs 《Electrochimica acta》2011,56(24):8484
This paper describes the electrochemical reduction of nitrite ion in neutral aqueous solution mediated by tetraruthenated metalloporphyrins (Co(II), Ni(II) and Zn(II)) electrostatically assembled onto a Nafion film previously adsorbed on glassy carbon or ITO electrodes. Scanning electron microscope (SEM-EDX) and transmission electron microscopy (TEM) results have shown that on ITO electrodes the macrocycles forms multiple layers with a disordered stacking orientation over the Nafion film occupying hydrophobic and hydrophilic sites in the polyelectrolyte. Atomic force microscopy (AFM) results demonstrated that the Nafion film is 35 nm thick and tetraruthenated metalloporphyrins layers 190 nm thick presenting a thin but compacted morphology. Scanning electrochemical microscopy (SECM) images shows that the Co(II) tetraruthenated porphyrins/Nf/GC modified electrode is more electrochemically active than their Ni and Zn analogues.These modified electrodes are able to reduce nitrite at −660 mV showing enhanced reduction current and a decrease in the required overpotential compared to bare glassy carbon electrode. Controlled potential electrolysis experiments verify the production of ammonia, hydrazine and hydroxylamine at potentials where reduction of solvent is plausible demonstrating some selectivity toward the nitrite ion. Rotating disc electrode voltammetry shows that the factor that governs the kinetics of nitrite reduction is the charge propagation in the film. 相似文献
166.
Soledad G. AspromonteÁlvaro Sastre Alicia V. Boix María J. CoceroEsther Alonso 《Microporous and mesoporous materials》2012,148(1):53-61
CoO and Co3O4 nanoparticles were uniformly dispersed inside mesoporous MCM-41 and Al-MCM-41 supports using supercritical CO2 reactive deposition. This method represents a one-pot reproducible procedure that allows the dissolution of the organocobalt precursor and supports impregnation in supercritical CO2 at 70 °C and 110 bar, followed by the precursor thermal decomposition into cobalt species at 200 °C and 160 bar. By the relative concentration of the cobalt precursor [cobalt (II) bis (η5-ciclopentadienil)], the load of cobalt nanoparticles was controlled and then determined by Inductively Coupled Plasma (ICP-OES). The synthesis of CoO and Co3O4 species inside the MCM-41 and Al-MCM-41 substrates was confirmed by X-ray Photoelectron (XPS) and Laser Raman Spectroscopies (LRS). By N2 adsorption and Small Angle X-ray Scattering (SAXS), it was determined that the hexagonal arrangement as well as the surface area and pore size of the substrates changed after the addition of cobalt. By means of X-ray mapping from SEM images, a homogeneous distribution of cobalt nanoparticles was observed inside the mesopores when the cobalt loading was 1 wt.%. In addition, spherical cobalt nanoparticles of average diameter close to 20 nm were detected on the outer surface of MCM-41 and Al-MCM-41 supports when the cobalt content was higher. On the other hand, by Transmission Electron Microscopy (TEM), it was possible to measure the interplanar distance of the crystalline plane of the outer nanoparticles, which was later compared with the theoretical distance values which allowed identifying the CoO and Co3O4 phases. 相似文献
167.
Deactivation studies of the SCR of NOx with hydrocarbons on Co-mordenite monolithic catalysts 总被引:1,自引:0,他引:1
Alicia V. Boix Soledad G. Aspromonte Eduardo E. Mir 《Applied Catalysis A: General》2008,341(1-2):26-34
The catalytic reduction of NOx with hydrocarbons (butane or methane) on CoMOR washcoated monolithic catalysts was studied in the presence of steam and excess oxygen. The significant changes observed in the catalytic behavior of CoMOR powder and monoliths depended essentially on the hydrocarbon nature (carbon number) and the concentration of water in the feed. When the reducing agent was methane, a low concentration of water (2%) decreased the NO to N2 conversion. However, when butane was used instead of methane, the maximum NOx conversions increased from 50 to 58% and from 52 to 64% for the CoMOR powder and monolith, respectively. The presence of water inhibited the NO adsorption when the reducing agent was methane but when butane was used, water helped to remove the surface-carbon deposits as indicated by TPO and XPS results. This fact explains the increase observed in the NOx conversion. The characterization with TPR and UV–vis spectroscopy showed that the main Co species present in the selective catalysts were the Co(II) ions exchanged at different sites of the mordenite and highly dispersed CoxOy moieties. More rigorous reaction conditions, i.e. 10% of water, led to the irreversible deactivation with both reductants. The Co3O4 phase was detected in all the deactivated powder and monolithic catalysts. The Co3O4 spinel was formed from the cobalt ion migration, which was promoted in wet atmosphere. In addition, for monolithic catalysts washcoated with CoMOR, the silica binder inhibited the water deactivation effect probably due to the silica–cobalt interaction, as a CoxOySi silicate. 相似文献
168.
In this work, we develop a lake eutrophication model to determine restoration policies for water quality improvement. This hybrid biogeochemical model has been formulated within a simultaneous dynamic optimization framework as an optimal control problem, whose solution provides limiting nutrient inflow profiles to the lake, as well as in-lake biomanipulation profiles. The water quality model comprises a set of partial differential algebraic equations in time and space, which result from dynamic mass balances on main phytoplankton groups, nutrients, dissolved oxygen and biochemical demand of oxygen. Spatial discretization has been performed in two layers. The simultaneous approach proceeds by discretizing control and state variables by collocation over finite elements and solving the large scale nonlinear program with an interior point method with successive quadratic programming techniques. 相似文献
169.
This work addresses a parameter estimation problem in an ecological water quality model through a simultaneous dynamic optimization approach. The model is based on first principles and has a large number of parameters, which must be estimated based on data collected in the water body under study. Gradients of state variables are considered along the water column, rendering a partial differential equation problem, which is transformed into a differential algebraic (DAE) one by spatial discretization in several water layers. Within a simultaneous approach, the DAE constrained optimization problem is transformed into a large-scale nonlinear programming problem, with a weighted least squares objective function. Main biogeochemical parameters have been obtained, which allow a close representation of the lake dynamics, as it is shown in the numerical results. 相似文献
170.
Lu��s S��nchez-del-Campo Magal�� S��ez-Ayala Soledad Chazarra Juan Cabezas-Herrera Jos�� Neptuno Rodr��guez-L��pez 《International journal of molecular sciences》2009,10(12):5398-5410
Dihydrofolate reductase (DHFR) is the subject of intensive investigation since it appears to be the primary target enzyme for antifolate drugs. Fluorescence quenching experiments show that the ester bond-containing tea polyphenols (-)-epigallocatechin gallate (EGCG) and (-)-epicatechin gallate (ECG) are potent inhibitors of DHFR with dissociation constants (KD)of 0.9 and 1.8 μM, respectively, while polyphenols lacking the ester bound gallate moiety [e.g., (-)-epigallocatechin (EGC) and (-)-epicatechin (EC)] did not bind to this enzyme. To avoid stability and bioavailability problems associated with tea catechins we synthesized a methylated derivative of ECG (3-O-(3,4,5-trimethoxybenzoyl)-(-)-epicatechin; TMECG), which effectively binds to DHFR (KD = 2.1 μM). In alkaline solution, TMECG generates a stable quinone methide product that strongly binds to the enzyme with a KD of 8.2 nM. Quercetin glucuronides also bind to DHFR but its effective binding was highly dependent of the sugar residue, with quercetin-3-xyloside being the stronger inhibitor of the enzyme with a KD of 0.6 μM. The finding that natural polyphenols are good inhibitors of human DHFR could explain the epidemiological data on their prophylactic effects for certain forms of cancer and open a possibility for the use of natural and synthetic polyphenols in cancer chemotherapy. 相似文献