Degeneration and Reorganization of Vestibular Epithelia after Local Aminoglycoside Application in the Mammalian Inner Ear

The development of degeneration of vestibular end organs and their possible reorganization have been observed over a 2 year period after local application of sisomicin in the inner ear using scanning electron microscopy (SEM). Degeneration of stereocilia took place as early as 5 days after the treatment in the utricule, the saccule and the cristae. At 10 days, almost the entire surface of these sensory epithelia presented a smooth aspect without specific structure. However, after 15 days, an epithelial reorganization developed with clear limits between cells. At 25 days, systematic kinociliary structures were observed at the apical surface of the cells. Five months after the treatment, the new kinocilium was still present and sometimes stereociliary-like structures appeared in the three types of vestibular organs. Two years after treatment, the kinocilium persisted and the embryonic-like ciliary tufts had disappeared. These SEM observations suggest that in mammals some vestibular epithelial regeneration is possible but stops at a stage which could correspond to an early developmental level

O potencial pedagógico da Hora do Conto para o desenvolvimento da Comunicação Oral

O presente relatório é produto de um projeto de investigação que pretendeu caracterizar a adequação e dinamização da hora do conto com a finalidade de promover o desenvolvimento da comunicação oral, implementada numa sala de 3/4 anos e a adequação didática de um processo de intervenção educativa de estratégias para a promoção do desenvolvimento da Oralidade (incidindo na dinamização da hora conto) implementado numa turma de 3.º ano do 1.º Ciclo do Ensino Básico. Tendo consciência da desvalorização que é atribuída à temática em análise, acreditamos que os profissionais de educação se tornam responsáveis pelo desenvolvimento e aperfeiçoamento das capacidades de comunicação das crianças/alunos. Neste sentido, consideramos que foi extremamente importante investir neste domínio e nas competências a ele associado, nas vertentes de compreensão e expressão orais. Para atingir os objetivos delineamos, planificamos, construímos, aplicamos e avaliamos em sala de aula, um conjunto de intervenções educativas adotando como estratégia principal a dinamização da hora do conto. Assim sendo, podemos verificar através dos resultados obtidos, que efetivamente, a hora do conto e a utilização de diferentes estratégias para a dinamização da mesma, contribuíram positivamente para o desenvolvimento das competências orais dos intervenientes, potenciando melhorias, a vários níveis, nomeadamente na vertente de compressão e de expressão oral dos dois grupos de aplicação.This report is the product of a research project that aimed to characterize the adequacy and dynamization of the story time with the purpose of promoting the development of oral communication, implemented in a 3/4 year classroom and the didactic adequacy of a process of educational intervention strategies to promote the development of Orality (focusing on the dynamization of the story time) implemented in a 3rd year class of the 1st Cycle of Basic Education. Being aware of the devaluation that is attributed to the theme under analysis, we believe that education professionals become responsible for the development and improvement of communication skills of children/students. In this sense, we believe that it was extremely important to invest in this field and in the skills associated with it, in the areas of understanding and oral expression. In order to achieve the objectives, we delineate, plan, build, apply and evaluate in the classroom, a set of educational interventions adopting as the main strategy the dynamization of the story time. Therefore, we can verify through the results obtained, that effectively, the story time and the use of different strategies for the dynamization of the tale, contributed positively to the development of the oral skills of the participants, enhancing improvements, at various levels, particularly in the compression and oral expression of the two groups of application. Keywords: Oral Communication; Compression and Oral Expression; Story Time; Pre-School; 1st Cycle of Basic Education

Synthesis of Barium Hexaferrite and Catalytic Behavior in the Combustion of Methane

Barium hexaferrite doped with iridium was synthesized by two methods : the citrate gel and the polyacrylamide gel methods. The nature of phases obtained and the specific surface area were determined after heat treatments in air at 700°C, 900°C and in air containing 10% humidity at 1200°C. The catalytic activity in the combustion of methane was measured after heat treatment at 900°C. These hexaferrites showed a good catalytic activity after treatment at 900°C. However this catalytic activity and the specific surface disappeared after heat treatment at 1200°C

Influence of acid-base properties of doped TiO2 supports on the activity of Pd-Cu/(Mg, Nb)-TiO2 catalysts for nitrate hydrogenation

International @ INGENIERIE+SDA:NOGInternational audienceWe investigated the influence of the acid-base properties of TiO2-based supports on the performances of Pd-Cu catalysts for nitrates hydrogenation in water. TiO2 supports doped with Mg or Nb (1-7 wt.%) were prepared by co-hydrolysis of metal alkoxides. The surface area increased and the crystallinity decreased for Mg- and Nb-doped TiO2, all solids exhibiting mesoporosity with average pore sizes smaller than 20 nm. Mg-doping introduces a strong basic character whereas Nb-doped TiO2 becomes acidic. Pd-Cu bimetallic catalysts supported on TiO2 and Mg- or Nb-TiO2 were found very active for the catalytic hydrogenation of nitrates, but the selectivity to ammonium was high. Nb-doping slightly decreased the reactivity of nitrates, Mg-doping improved the reactivity of nitrites, but the selectivity to ammoniums was only marginally modified. The activity and products selectivity were only moderately affected by the properties of the support, which suggests that this property is not relevant to the reaction mechanism

Comparison of nitrates reduction in water using different reactor configuration

internationa

determination of the most active sites for co hydrogenation over supported cobalt by selective poisoning with tin

SSCI-VIDE+ING+APN:NOG:YSC:FRMInternational audience1.IntroductionSynthetic fuels and base chemicals can be obtained from both fossil and renewable sources through the conversion of synthesis gas (“syngas”, a mixture of carbon oxides and H2) [1]. The nature of the reaction mechanism of the Fischer-Tropsch synthesis over cobalt-based catalysts is still a debate, as well as the nature of the active sites [2,3]. IR-based techniques are useful in investigating syngas conversion because CO is both a reactant and a molecular probe often used to characterize metal surfaces. We recently reported that the most active cobalt sites were likely those associated with the formation of bridged CO(ads), which are thought to be located at the particle edges or steps [4]. This conclusion was reached by noting that the poisoning of cobalt by chloride affected more bridged CO(ads) than linear CO(ads) [4].We report herein an operando diffuse reflectance FT-IR spectroscopy (DRIFTS) study in which the hydrogenation of CO is monitored on Co and Sn-Co catalysts. Sn-modified cobalt catalysts were synthesized to obtain similar poisoning effects, using an element less volatile than chlorine. Sn does not adsorb CO at the temperatures investigated, so the carbonyl band observed in the region 2100-1700cm-1 by FT-IR could be attributed to CO adsorbed only on cobalt atoms.2.ExperimentalA 15 wt.% Co/Al2O3 catalyst used for the CO hydrogenation was prepared with the method reported by Shi et al.[5]. Commercial reagents of Co(NO3)2.6H2O, γ-alumina and citric acid were used. Two Sn-modified catalysts were prepared by adding tin (according to a yet undisclosed method) on the as-prepared 15 wt.% Co/Al2O3 catalyst, with Co/Sn molar ratios equal to 60 and 120. The hydrogenation of CO was performed using a modified high temperature DRIFT cell described in [4]. The reactor effluent was quantified using a 2m-pathlength FT-IR gas cell. The low mass of catalyst (30 mg) used in the reactor enabled to maintain low conversion and to operate essentially under differential conditions, making the DRIFTS cell a gradient-less reactor.3.ResultsThe rate of formation of methane, propene, and methanol were monitored for the three catalysts. The presence of tin lead to a significant activity loss of about 30% for the Co/Sn = 120:1 and 60% for the Co/Sn = 60:1. Such large activity losses for such low concentrations of poison suggest that most of the Sn remained at the particle surface, despite the fact that Co and Sn can form bulk alloyed phases.The operando DRIFTS spectra measured over a fresh alumina-supported cobalt sample exhibited both linear CO(ads), characterized by bands above 2000 cm-1, and bridged CO(ads), characterized by bands below 2000 cm-1. In contrast, Sn-modified sample exhibited a lower fraction of bands below 2000 cm-1, indicating that less bridged sites were available when Sn was present. A decomposition of the carbonyl signal was carried out to better characterize the changes in the DRIFTS band signal. The lowest number of Gaussian curves needed to obtain close fits of the original spectra was five (Figure 1.B). The band most affected by tin was that located at around 1860 cm-1, noted “Bridged CO(ads)”, the intensity of which decreased with increasing Sn content. It should be noted that this band may corresponds to various bridged and multi-bonded carbonyls. The plot of the relative loss of activity in product formation against the quantity of bridged carbonyls present on the surface of the catalyst appeared to yield an essentially linear relationship. 4.DiscussionThis work shows that it is possible to selectively poison cobalt using small concentrations of Sn. In addition, Sn appears to be preferentially titrating sites on which bridged CO(ads) are formed. This suggests that the sites associated with the bridged sites (possibly edges or steps) are the most active sites for Fischer-Tropsch synthesis. Step sites have already been proposed as being the most active sites for CO dissociation [6-9]. Methanol formation fitted less the linear relationship, possibly because it does not require CO dissociation and was shown to also involve formate species, located at the interface with the metal particles and an oxidic phase (CoOx or the support) [10].5.ConclusionsThe most active sites for CO hydrogenation over cobalt-based catalysts were shown to be related to sites on which CO adsorption led to bridged or multi-bonded species. Such sites could be selectively titrated by small concentrations of Sn.6.References[1] A.Y. Khodakov, W. Chu, P. Fongarland, Chem. Rev. 107 (2007) 1692-1744.[2] N. Fischer, E. van Steen, M. Claeys, J. Catal. 299 (2013) 67-80.[3] J. Schweicher, A. Bundhoo, N. Kruse. J. Am. Chem. Soc. 134 (2012) 16135-16138.[4] A. Paredes-Nunez, D. Lorito, Y. Schuurman, N. Guilhaume, F.C. Meunier, J. Catal. 329 (2015) 229–236.[5] L. Shi, C. Zeng, Q. Lin, W. Niu, N. Tsubaki, Catal. Today 228 (2014) 206-211.[6] Q. Ge, M. Neurock, J. Phys. Chem. B. 110 (2006) 15368[7] C.J. Weststrate, I.M. Ciobîca, A.M. Saib, D.J. Moodley, J.W. Niemantsverdriet, Catal. Today 228 (2014) 106.[8] P. van Helden, J.-A. van den Berg, I.M. Ciobîca, Catal. Sci. Tech. 2 (2012) 491.[9] R.A. van Santen, Acc. Chem. Res. 42 (2009) 57.[10] D. Lorito A. Paredes-Nunez, C. Mirodatos, Y. Schuurman, F. Meunier, Catal. Today, in press, doi:10.1016/j.cattod.2015.06.027

determination of the most active sites for co hydrogenation over supported cobalt by selective poisoning with tin

SSCI-VIDE+ING+APN:NOG:YSC:FRMInternational audience1.IntroductionSynthetic fuels and base chemicals can be obtained from both fossil and renewable sources through the conversion of synthesis gas (“syngas”, a mixture of carbon oxides and H2) [1]. The nature of the reaction mechanism of the Fischer-Tropsch synthesis over cobalt-based catalysts is still a debate, as well as the nature of the active sites [2,3]. IR-based techniques are useful in investigating syngas conversion because CO is both a reactant and a molecular probe often used to characterize metal surfaces. We recently reported that the most active cobalt sites were likely those associated with the formation of bridged CO(ads), which are thought to be located at the particle edges or steps [4]. This conclusion was reached by noting that the poisoning of cobalt by chloride affected more bridged CO(ads) than linear CO(ads) [4].We report herein an operando diffuse reflectance FT-IR spectroscopy (DRIFTS) study in which the hydrogenation of CO is monitored on Co and Sn-Co catalysts. Sn-modified cobalt catalysts were synthesized to obtain similar poisoning effects, using an element less volatile than chlorine. Sn does not adsorb CO at the temperatures investigated, so the carbonyl band observed in the region 2100-1700cm-1 by FT-IR could be attributed to CO adsorbed only on cobalt atoms.2.ExperimentalA 15 wt.% Co/Al2O3 catalyst used for the CO hydrogenation was prepared with the method reported by Shi et al.[5]. Commercial reagents of Co(NO3)2.6H2O, γ-alumina and citric acid were used. Two Sn-modified catalysts were prepared by adding tin (according to a yet undisclosed method) on the as-prepared 15 wt.% Co/Al2O3 catalyst, with Co/Sn molar ratios equal to 60 and 120. The hydrogenation of CO was performed using a modified high temperature DRIFT cell described in [4]. The reactor effluent was quantified using a 2m-pathlength FT-IR gas cell. The low mass of catalyst (30 mg) used in the reactor enabled to maintain low conversion and to operate essentially under differential conditions, making the DRIFTS cell a gradient-less reactor.3.ResultsThe rate of formation of methane, propene, and methanol were monitored for the three catalysts. The presence of tin lead to a significant activity loss of about 30% for the Co/Sn = 120:1 and 60% for the Co/Sn = 60:1. Such large activity losses for such low concentrations of poison suggest that most of the Sn remained at the particle surface, despite the fact that Co and Sn can form bulk alloyed phases.The operando DRIFTS spectra measured over a fresh alumina-supported cobalt sample exhibited both linear CO(ads), characterized by bands above 2000 cm-1, and bridged CO(ads), characterized by bands below 2000 cm-1. In contrast, Sn-modified sample exhibited a lower fraction of bands below 2000 cm-1, indicating that less bridged sites were available when Sn was present. A decomposition of the carbonyl signal was carried out to better characterize the changes in the DRIFTS band signal. The lowest number of Gaussian curves needed to obtain close fits of the original spectra was five (Figure 1.B). The band most affected by tin was that located at around 1860 cm-1, noted “Bridged CO(ads)”, the intensity of which decreased with increasing Sn content. It should be noted that this band may corresponds to various bridged and multi-bonded carbonyls. The plot of the relative loss of activity in product formation against the quantity of bridged carbonyls present on the surface of the catalyst appeared to yield an essentially linear relationship. 4.DiscussionThis work shows that it is possible to selectively poison cobalt using small concentrations of Sn. In addition, Sn appears to be preferentially titrating sites on which bridged CO(ads) are formed. This suggests that the sites associated with the bridged sites (possibly edges or steps) are the most active sites for Fischer-Tropsch synthesis. Step sites have already been proposed as being the most active sites for CO dissociation [6-9]. Methanol formation fitted less the linear relationship, possibly because it does not require CO dissociation and was shown to also involve formate species, located at the interface with the metal particles and an oxidic phase (CoOx or the support) [10].5.ConclusionsThe most active sites for CO hydrogenation over cobalt-based catalysts were shown to be related to sites on which CO adsorption led to bridged or multi-bonded species. Such sites could be selectively titrated by small concentrations of Sn.6.References[1] A.Y. Khodakov, W. Chu, P. Fongarland, Chem. Rev. 107 (2007) 1692-1744.[2] N. Fischer, E. van Steen, M. Claeys, J. Catal. 299 (2013) 67-80.[3] J. Schweicher, A. Bundhoo, N. Kruse. J. Am. Chem. Soc. 134 (2012) 16135-16138.[4] A. Paredes-Nunez, D. Lorito, Y. Schuurman, N. Guilhaume, F.C. Meunier, J. Catal. 329 (2015) 229–236.[5] L. Shi, C. Zeng, Q. Lin, W. Niu, N. Tsubaki, Catal. Today 228 (2014) 206-211.[6] Q. Ge, M. Neurock, J. Phys. Chem. B. 110 (2006) 15368[7] C.J. Weststrate, I.M. Ciobîca, A.M. Saib, D.J. Moodley, J.W. Niemantsverdriet, Catal. Today 228 (2014) 106.[8] P. van Helden, J.-A. van den Berg, I.M. Ciobîca, Catal. Sci. Tech. 2 (2012) 491.[9] R.A. van Santen, Acc. Chem. Res. 42 (2009) 57.[10] D. Lorito A. Paredes-Nunez, C. Mirodatos, Y. Schuurman, F. Meunier, Catal. Today, in press, doi:10.1016/j.cattod.2015.06.027