Co oxidation: effect of Ce and Au addition on MnOx catalysts

The effect of cerium and/or gold addition to a manganese oxide which was greatly active in CO oxidation was studied. The catalysts obtained by this way were characterized by N2 adsorption, XRF, XRD and TPR, and their catalytic activity was measured in the CO oxidation reaction. The pure MnOx catalyst was active in the CO oxidation but the addition of 5 wt % cerium decreased their catalytic activity. Adding 2 wt % gold improved the activity of MnOx and Ce/MnOx and caused a slight decrease of the catalyst specific area and of the average oxidation state of manganese in catalysts, which was found between 3.3 and 3.6. The order of activity found on the basis of T50 for the four catalysts was: Au/MnOx > Au/Ce/MnOx > MnOx > Ce/MnOx, with T50 of 89, 95, 99 and 139 °C, respectively. The solids Au/MnOx and Au/Ce/MnOx presented a T10 of 30 and 49 °C, indicating that gold favored the conversion at room temperature. The effect of water vapor on the reaction was also analyzed, finding a decrease in the catalytic activity of all catalysts, due to the blocking of active sites in the catalyst surface.Fil: Peluso, Miguel Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Centro de Investigación y Desarrollo En Ciencias Aplicadas; ArgentinaFil: Hernández Enciso, W. Y.. Universidad de Sevilla. Consejo Superior de Investigaciones Cientificas. Instituto de Ciencia de Materiales de Sevilla; EspañaFil: Dominguez, M. I.. Universidad de Sevilla. Consejo Superior de Investigaciones Cientificas. Instituto de Ienia de Materiales de Sevilla; EspañaFil: Thomas, Horacio Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Centro de Investigación y Desarrollo En Ciencias Aplicadas; ArgentinaFil: Centeno, M. A.. Universidad de Sevilla. Consejo Superior de Investigaciones Cientificas. Instituto de Ciencia de Materiales de Sevilla; EspañaFil: Sambeth, Jorge Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Centro de Investigación y Desarrollo En Ciencias Aplicadas; Argentin

Co oxidation: effect of Ce and Au addition on MnOx catalysts

The effect of cerium and/or gold addition to a manganese oxide which was greatly active in CO oxidation was studied. The catalysts obtained by this way were characterized by N2 adsorption, XRF, XRD and TPR, and their catalytic activity was measured in the CO oxidation reaction. The pure MnOx catalyst was active in the CO oxidation but the addition of 5 wt % cerium decreased their catalytic activity. Adding 2 wt % gold improved the activity of MnOx and Ce/MnOx and caused a slight decrease of the catalyst specific area and of the average oxidation state of manganese in catalysts, which was found between 3.3 and 3.6. The order of activity found on the basis of T50 for the four catalysts was: Au/MnOx > Au/Ce/MnOx > MnOx > Ce/MnOx, with T50 of 89, 95, 99 and 139 °C, respectively. The solids Au/MnOx and Au/Ce/MnOx presented a T10 of 30 and 49 °C, indicating that gold favored the conversion at room temperature. The effect of water vapor on the reaction was also analyzed, finding a decrease in the catalytic activity of all catalysts, due to the blocking of active sites in the catalyst surface.Centro de Investigación y Desarrollo en Ciencias Aplicada

Rivastigmine but not vardenafil reverses cannabis-induced impairment of verbal memory in healthy humans

RATIONALE: One of the most often reported cognitive deficits of acute cannabis administration is an impaired recall of previously learned information. OBJECTIVE: The aim of the present study was to determine whether cannabis-induced memory impairment in humans is mediated via glutamatergic or cholinergic pathways. METHODS: Fifteen occasional cannabis users participated in a double-blind, placebo-controlled, six-way cross-over study. On separate test days, subjects received combinations of pretreatment (placebo, vardenafil 20 mg or rivastigmine 3 mg) and treatment (placebo or 1,376 mg cannabis/kg body weight). Cognitive tests were administered immediately after inhalation of treatment was finished and included measures of memory (visual verbal learning task, prospective memory test, Sternberg memory test), perceptual-motor control (critical tracking task), attention (divided attention task) and motor impulsivity (stop signal task). RESULTS: The results of this study demonstrate that subjects under the influence of cannabis were impaired in all memory tasks, in critical tracking, divided attention and the stop signal task. Pretreatment with rivastigmine attenuated the effect of cannabis on delayed recall and showed a trend towards significance on immediate recall. When cannabis was given in combination with vardenafil, there were no significant interaction effects in any of the tasks. CONCLUSIONS: The present data therefore suggest that acetylcholine plays an important role in cannabis-induced memory impairment, whereas similar results for glutamate have not been demonstrated in this study

Biosynthesis of anti-HCV compounds using thermophilic microorganisms

This work describes the application of thermophilic microorganisms for obtaining 6-halogenated purine nucleosides. Biosynthesis of 6-chloropurine-2′-deoxyriboside and 6-chloropurine riboside was achieved by Geobacillus stearothermophilus CECT 43 with a conversion of 90% and 68%, respectively. Furthermore, the selected microorganism was satisfactorily stabilized by immobilization in an agarose matrix. This biocatalyst can be reused at least 70 times without significant loss of activity, obtaining 379 mg/L of 6-chloropurine-2′-deoxyriboside. The obtained compounds can be used as antiviral agents.Centro de Investigación y Desarrollo en Ciencias Aplicada

Estudio por espectroscopia DRIFTS de la oxidación de Co sobre el sistema Au/Mn-Ce : Análisis del rol del soporte

Una serie de sólidos Mn-Ce en relaciones atómicas 0:100, 50:50 y 100:0 fueronpreparados a partir de la precipitación alcalina con Na(OH) a pH=11. El estudio por DRXmuestra la formación de distintas fases cristalinas Mn2O3, α-MnO2 y CeO2 dependiendode la composición del sistema. Los sólidos secos y calcinados fueron impregnados conAu por el método de precipitación-depósito utilizando como precursor HAuCl4.4H2O. PorFRX se determino que el contenido en peso promedio de Au% alcanzaba un valor de1.14. El estudio de la oxidación de CO señala que los sólidos de composición 50:50 sonlos más activos, lo cual es atribuido a una mayor labilidad de los oxígenos de red y por lapresencia de pares redox Mn+4/Mn3+, Ce+4/Ce+3. Los resultados permiten sugerir que ladispersión del Au y su tamaño de partícula es función de la técnica de preparación y delcatión Ce. Finalmente, por el estudio DRIFTS se propone un mecanismo de reacciónpara cada uno de los Au/Mn-Ce y cuyos resultados sugieren que la formación de laespecie bicarbonato es la más favorable para la oxidación del CO a CO2.A series of Mn-Ce solids with 0:100, 50:50 and 100:0 atomic ratios were prepared from alkaline precipitation with Na(OH) at pH=11. The XRD test showed the formation of different crystalline phases Mn2O3, α-MnO2 and CeO2 depending on the system composition. By means of XPS spectroscopy it was determined the presence of Mn4+/Mn3+ and that the Ce3+ surface concentration increased with Ce content. The dried and calcined solids were impregnated with Au by the precipitation-deposit method using as precursor HAuCl4.4H2O. By XRF it was determined that the content in average weight of Au% reached a value of 1.14. The CO oxidation test showed that the solids of composition 50:50 were the most active, fact assigned to the formation of structural defects that allowed a higher lability of the lattice oxygens due to Mn+4/Mn3+, Ce+4/Ce+3 redox pairs. The results allowed inferring that the dispersion of Au and its particle size are function of the preparation technique. Finally, by DRIFTS test it was proposed a reaction mechanism for each Au/Mn-Ce. These results suggested that the bicarbonate species was the most favorable for oxidation from CO to CO2.Centro de Investigación y Desarrollo en Ciencias AplicadasComisión de Investigaciones Científicas de la provincia de Buenos AiresCentro de Tecnología de Recursos Minerales y Cerámic

Pharmacokinetics of acute tryptophan depletion using a gelatin-based protein in male and female Wistar rats

The essential amino acid tryptophan is the precursor of the neurotransmitter serotonin. By depleting the body of tryptophan, brain tryptophan and serotonin levels are temporarily reduced. In this paper, several experiments are described in which dose and treatment effects of acute tryptophan depletion (ATD) using a gelatin-based protein–carbohydrate mixture were studied in male and female Wistar rats. Two or three doses of tryptophan depleting mixture resulted in 65–70% depletion after 2–4 h in males. ATD effects were similar in females, although females may return to baseline levels faster. Treatment effects after four consecutive days of ATD were similar to the effects of 1 day of treatment. Object recognition memory was impaired 2, 4, and 6 h after the first of two doses of ATD, suggesting that the central effects occurred rapidly and continued at least 6 h, in spite of decreasing treatment effects on plasma tryptophan levels at that time point. The method of acute tryptophan depletion described here can be used to study the relationship between serotonin and behaviour in both male and female rats

The Effect of a Brief Mindfulness Intervention on Memory for Positively and Negatively Valenced Stimuli

A core component of mindfulness is non-judgmental observation of internal and external stimuli. The present study investigated the effect of mindfulness on memory for emotional stimuli. Participants were exposed to a brief mindfulness intervention and subsequently performed a verbal learning test consisting of positive, neutral, and negative words. Control participants received no intervention and directly performed the verbal learning test. After 20 min, participants recalled as many words as possible. Participants in the mindfulness condition remembered a significantly lower proportion of negative words compared to control participants. No differences between both groups were observed for the proportion of remembered positive words. These findings suggest that memory processes may be a potential mechanism underlying the link between mindfulness and subjective well-being