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PURPOSE: A long-standing issue in identifying developmental language disorder (DLD) in multilingual children is differentiating between effects of language experience and genuine impairment when clinicians often lack suitable norm-referenced assessments. In this tutorial we demonstrate, via a case study, that it is feasible to identify DLD in a multilingual child using the CATALISE diagnostic criteria, Language Impairment Testing in Multilingual Settings (LITMUS) assessment tools, and telepractice. METHOD: This tutorial features a case study of one 6-year-old Urdu-Cantonese multilingual ethnic minority child, and seven age- and grade-matched multilinguals. They were tested via Zoom using Urdu versions of the Multilingual Assessment Instrument for Narratives (LITMUS-MAIN), the Crosslinguistic Lexical Task (LITMUS-CLT), the Crosslinguistic Nonword Repetition Test (LITMUS-CL-NWR), and the Sentence Repetition Task (LITMUS-SRep). RESULT: The child scored significantly lower in the LITMUS tests compared to her peers in her best/first language of Urdu. Together with the presence of negative functional impact and poor prognostic features, and absence of associated biomedical conditions, the findings suggest this participant could be identified as having DLD using the CATALISE diagnostic criteria. CONCLUSION: The result demonstrates the promise of this approach to collect reference data and identify DLD in multilingual children. The online LITMUS battery has the potential to support identification of multilingual DLD in any target language.
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BACKGROUND: In 2016/17, the CATALISE Consortium published the results of a multinational and multidisciplinary Delphi consensus study, representing agreement among professionals about the definition and process of identification of children with Developmental Language Disorder (DLD) (Bishop et al., 2016, 2017). The extent to which the current clinical practice of UK speech and language therapists (SLTs) reflects the CATALISE consensus statements is unknown. AIMS: To investigate how UK SLTs' expressive language assessment practices reflect the CATALISE documents' emphasis on the functional impairment and impact caused by DLD, by examining: whether multiple sources of assessment information are gathered; how standardised and non-standardised sources are combined in clinical decision-making, and how clinical observation and language sample analysis are utilised. METHODS AND PROCEDURES: An anonymous, online survey was carried out between August 2019 and January 2020. It was open to UK-based paediatric SLTs who assess children up to age 12 with unexplained difficulties using language. Questions probed different aspects of expressive language assessment which are referred to in the CATALISE consensus statements and supplementary comments, and asked about participants' familiarity with the CATALISE statements. Responses were analysed using simple descriptive statistics and content analysis. OUTCOMES AND RESULTS: The questionnaire was completed by 104 participants, from all four regions of the United Kingdom, working in a range of clinical settings with different levels of professional experience of DLD. The findings indicate that clinical assessment practices broadly align with the CATALISE statements. Although clinicians carry out standardised assessments more frequently than other types of assessment, they also gather information from other sources and use this alongside standardised test scores to inform clinical decisions. Clinical observation and language sample analysis are commonly utilised to evaluate functional impairment and impact, along with parent/carer/teacher and child report. However, asking about the child's own perspective could be more widely utilised. The findings also highlight a lack of familiarity with the details of the CATALISE documents among two thirds of the participants. CONCLUSIONS AND IMPLICATIONS: Assessment practices broadly align with the CATALISE statements, but there is a need for greater clarity regarding terminology and the assessment of functional language impairment and impact. This research should prompt discussion in the profession about how to further develop and adopt expressive language assessment practices which reflect the CATALISE consensus and support effective assessment. WHAT THIS PAPER ADDS: What is already known on the subject The CATALISE consortium documents on Developmental Language Disorder (DLD) were published in 2016/17. The extent to which expressive language assessment practice in the United Kingdom reflects the new definition and statements on assessment has not previously been investigated. What this paper adds to existing knowledge This survey indicates that speech and language therapists in the United Kingdom assessing children for DLD mostly balance standardised language test scores with other sources of information in clinical decision-making, and utilise clinical observation and language sample analysis to consider functional impairment and the impact of the language disorder. However, important questions are raised regarding the robustness and objectivity with which these key parameters are currently defined and evaluated. What are the potential or actual clinical implications of this work? Clinicians, individually and at service level, are encouraged to reflect on their assessment of functional impairment and the impact of language disorder and to take steps to incorporate this where necessary. Professional guidance and clinical tools to facilitate robust, objective assessment would support clinical practice that aligns with expert consensus.
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Trastornos del Desarrollo del Lenguaje , Logopedia , Humanos , Niño , Logopedia/métodos , Terapia del Lenguaje/métodos , Habla , Reino Unido , Trastornos del Desarrollo del Lenguaje/diagnósticoRESUMEN
Resumen Se sintetizaron catalizadores (SNX#WPA) basados en ácido tungstofosfórico, en soportes de nanoestructuras de sílice (SNX), con distribución de diámetros y tamaños de mesoporos variables. Las SNX se prepararon en medio de octano/agua, usando poliestireno y bromuro de cetiltrimetilamonio como plantillas. Los materiales se caracterizaron por DRX, TEM y adsorción/desorción de nitrógeno. La relación octano/agua influyó tanto en la morfología y el tamaño de las SNX como en la distribución del tamaño de poro. Las SNX obtenidas utilizando relaciones OCT/H2O en el rango de 0,07-0,35, presentan mesoporos pequeños (5-6 nm) y grandes (28-34 nm), generados principalmente por poliestireno. Los mesoporos grandes y su contribución de volumen fueron claramente más altos que en las muestras SN1, SN2 y SN3. La estructura y la morfología de SNX#WPA fueron similares a las de las SNX usadas como soporte. Además, la caracterización de todos los materiales SNX#WPA por FT-IR y 31P NMR indicó la presencia de especies [PW12O40]3- y [H3-XPW12O40](3-X)- sin degradar. Según los resultados de la valoración potenciométrica, los sólidos presentaron sitios ácidos muy fuertes. Se evaluó la actividad de SNX#WPA como catalizadores en la síntesis de quinoxalinas, a partir de lo cual se obtuvieron altos rendimientos, sin formación de subproductos. De ello resultó que los materiales preparados son catalizadores altamente selectivos y reutilizables.
Abstract Tungstophosphoric acid supported on silica nanostructures (SNX#WPA) with variable diameter and mesopore size distribution were synthetized. Silica nanostructures (SNX) were prepared in octane/aqueous media using polystyrene and CTAB as organic templates. The materials were characterized by XRD, SEM, TEM and dinitrogen adsorption/ desorption isotherm analysis. The octane/ water ratio influenced the morphology and size of SNX prepared, as well as its pore size distribution. The SNX samples obtained using OCT/H2O ratios in the range 0.07-0.35 (SN4, SN5, and SN6 samples). present small (5-6 nm) and large (28-34 nm) mesopores (mainly generated by polystyrene). Large mesopores and their volume contribution were clearly higher than in the SN1, SN2, and SN3 samples. The structure and morphology of SNX#WPA samples were similar to those of the SNX. Furthermore, the characterization of all the SNX#WPA materials by FT-IR and 31P NMR indicated the presence of undegraded [PW12O40]3- and [H3-XPW12O40](3-X)-species. According to the potentiometric titration results, the solids presented very strong acid sites. The performance of SNX#WPA materials as catalysts in the synthesis of quinoxalines was evaluated. The yields achieved were high, without formation of by-products resulting from competitive reactions or decomposition products, so the prepared materials are highly selective and reusable catalysts.
Resumo Catalisadores (SNX#WPA) baseados em ácido tungsofosfórico suportado em nanoestruturas de sílica (SNX) foram sintetizados com distribuição de tamanhos e diâmetros variados de mesoporos. Os SNX foram preparados em meio octano/aquoso usando poliestireno e brometo de cetiltrimetilamônio como modelos orgânicos. Os materiais foram caracterizados por DRX, TEM e adsorção/ dessorção de nitrogénio. A razão octano/ agua influenciou a morfologia e o tamanho do SNX, bem como a distribuição do tamanho dos poros. O SNX obtido usando razões OCT/ H2O na faixa de 0,07-0,35, possui mesoporos pequenos (5-6 nm) e grandes (28-34 nm) (gerados principalmente por poliestireno). Mesoporos grandes e sua contribuição em volume foram claramente maiores do que nas amostras SN1, SN2 e SN3. A estrutura e a morfologia do SNX#WPA foram semelhantes às do SNX usado como suporte. Além disso, a caracterização de todos os materiais SNX#WPA por FT-IR e 31P NMR indicou a presença das espécies [PW12O40]3- e [H3-XPW12O40](3-X)- sem degradar. De acordo com os resultados da titulação potenciométrica, os sólidos apresentaram locais ácidos muito fortes. A atividade do SNX#WPA como catalisadores na síntese de quinoxalinas foi avaliada, produzindo altos rendimentos, sem formação de subprodutos, resultando em materiais catalisadores altamente seletivos e reutilizáveis.
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BACKGROUND: Children with language disorder across languages have problems with verb morphology. The nature of these problems varies according to the typology of the language. The language analyzed in this paper is the Standard Bangla spoken in Dhaka, Bangladesh, by more than 200 million people. It is an underexplored language with agglutinative features in its verb inflections. Some information on the acquisition of the language by typically developing children is available, but to date we have no information on the nature of ALD. As in many places in the developing world, the circumstances for research into language disorder are challenging, as there is no well-ordered infrastructure for the identification of these children and approaches to intervention are not evidence based. This study represents the first attempt to characterize the nature of morphosyntactic limitations in standard Bangla-speaking children with language disorder. AIMS: To describe the performance of a group of children with language disorder on elicitation procedures for three Bangla verb inflections of increasing structural complexity-present simple, present progressive and past progressive-and to compare their abilities on these forms with those of a group of typically developing Bangla-speaking children. METHODS & PROCEDURES: Nine children with language disorder (mean age = 88.11 months) were recruited from a special school in Dhaka. Eight of the children also had a differentiating or co-occurring condition. They responded to three tasks: a semi-structured conversation to elicit present simple, and two picture-based tasks to elicit present progressive and past progressive. Their performance was compared with data available from a large group of younger typically developing children. OUTCOMES AND RESULTS: Group data indicated a comparable trajectory of performance by the children with language disorder with the typically developing children (present simple > present progressive > past progressive), but with significantly lower mean scores. Standard deviations suggested considerable individual variation and individual profiles were constructed for each child, revealing varying patterns of ability, some of which did not accord with the typical developmental trajectory and/or substitution patterns. CONCLUSIONS & IMPLICATIONS: This study identified verb morphology deficits in Bangla-speaking children with language disorder who had asociated conditions. Variation in performance among the children suggests that individual profiles will be most effective in guiding intervention.
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Lenguaje Infantil , Trastornos del Desarrollo del Lenguaje/psicología , Factores de Edad , Bangladesh , Niño , Conducta Infantil , Preescolar , Femenino , Humanos , Trastornos del Desarrollo del Lenguaje/diagnóstico , MasculinoRESUMEN
A recent project entitled CATALISE used the Delphi method to reach a consensus on terminology for unexplained language problems in children. 'Developmental language disorder' (DLD) was the term agreed by a panel of 57 experts. Here I reflect on points of difficulty that arose when attempting to reach a consensus, using qualitative information from comments made by panel members to illustrate the kinds of argument used. One issue of debate was the use of labels, in particular the term 'disorder', which was seen as having both pros and cons. The potential for labels to stigmatize or create low expectations was a particular concern. However, labels could also ensure language problems were not trivialized and could help avoid stigma by providing an explanation for behaviours that might otherwise meet with disapproval. Further debate surrounded issues of how best to identify cases of disorder. Although it was agreed there should be a focus on cases with a poor prognosis, it was recognized that our knowledge of factors related to prognosis was still incomplete. Furthermore, there was a tension between use of standardized tests, which allow for a relatively objective and reliable assessment of language, and more qualitative observations, which can capture functional aspects of communication that are not always picked up on formal assessment. Debate also surrounded the issue of the relationship between DLD and other conditions. Some favoured drawing a distinction between DLD and language disorders associated with other conditions, and others regarded such distinctions as unnecessary. We concluded that it was misleading to assume co-occurring conditions were causes of language disorder, but it was helpful to distinguish DLD from cases of language disorder associated with 'differentiating conditions' that had a known or likely biomedical origin, including brain injury, sensorineural hearing loss, genetic syndromes, intellectual disability and autism spectrum disorder. Furthermore, DLD could co-occur with milder neurodevelopmental disorders that did not have a clear biomedical aetiology. Normal-range non-verbal IQ has traditionally been incorporated in the diagnosis of DLD, but this was rejected as unsupported by evidence. DLD is a category that has utility in identifying children who would benefit from speech-language therapy services, but it should not be thought of as a well-defined condition. DLD has a multifactorial aetiology, is heterogeneous in terms of language features and overlaps with other neurodevelopmental disorders. Our notions of DLD are likely to be refined by further research into aetiology, associated characteristics and intervention effectiveness.
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Lenguaje Infantil , Trastornos del Desarrollo del Lenguaje/clasificación , Terminología como Asunto , Factores de Edad , Niño , Preescolar , Consenso , Técnica Delphi , Humanos , Trastornos del Desarrollo del Lenguaje/diagnóstico , Trastornos del Desarrollo del Lenguaje/psicología , Trastornos del Desarrollo del Lenguaje/rehabilitación , Prejuicio , Pronóstico , Opinión PúblicaRESUMEN
Resumen Se describió la intervención del mineral magnetita como catalizador o como soporte catalitico, un material inorgánico con una estructura de espinela inversa (FeFe204), en el desarrollo de un número importante de reacciones quimicas de interes cientifico, tecnológico y ambiental. Debido a la necesidad actual de generar procesos quimicos eficientes y favorables ambientalmente, la magnetita se ha convertido en un material promisorio en los contextos de la quimica verde, la quimica fina y la catálisis heterogénea. Este óxido de hierro se ha estudiado en diversas reacciones: catalizador másico, soporte catalitico de metales y de óxidos metálicos, núcleo de catalizadores tipo core-shell, o modificado mediante el anclaje de organocatalizadores y complejos metálicos. Se discute el desempeno catalitico de estos sistemas basados en magnetita, en reacciones de catálisis asimetrica, ambiental, ácido-base, de óxido-reducción, de sintesis multicomponente y de acoplamiento C-C. Particularmente, dichos catalizadores han mostrado enorme importancia en ciertas reacciones de tipo Sonogashira, Sonogashira-Hagihara, Mannich, Ullman, Knoevenagel, Suzuki-Miyaura y Fenton heterogénea, entre otras. Finalmente, se detallaron algunos usos tecnológicos de la magnetita en el contexto nacional (Colombia) y se intentó localizar geográficamente los depósitos importantes.
Abstract This manuscript contains a review on the mediation of magnetite, an inorganic material with an inverse spinel structure (FeFe204), being used as either catalyst or catalytic support in many chemical reactions of scientific, technological and environmental interest. Because of current awareness on the efficient and environmentally friendly chemical processes, magnetite has become as a promising material in contexts such as green chemistry, fine chemistry, and heterogeneous catalysis. This iron oxide has been used in several reactions as bulk catalyst, catalytic support of either metals or metal oxides, core in catalysts type core-shell, or as solid modified by grafting with organocatalysts and metal complexes. The catalytic performance of these systems has been described in some chemical processes such as: asymmetric catalysis, environmental catalysis, acid-base catalysis, redox reactions, multicomponent synthesis reactions, and those of C-C coupling. Particularly, these catalysts have shown large importance in a variety of reactions: Sonogashira, Sonogashira-Hagihara, Mannich, Ullman, Knoevenagel, Suzuki-Miyaura, and the Fenton heterogeneous reaction, among others. Finally, some technological uses of magnetite in the national context (Colombia) are detailed, and localizing geographically the most important deposits of this mineral in the Colombian region was intended.
Resumo Foi descrita uma intervenção da mineral magnetita, um material inorgânico com estrutura de espinela inversa (FeFe204), como catalisador ou como suporte catalitico no desenvolvimento de um número importante de reações quimicas de interesse cientifico, tecnológico e ambiental. Devido à necessidade atual de gerar processos quimicos eficientes e favoráveis ambientalmente, a magnetita surge como um material promissório nos contextos da quimica verde, da quimica fina e da catálise heterogénea. Este óxido de ferro e objeto de estudo em diversas reações: catalizador mássico, suporte catalitico de metais e de óxidos metálicos, núcleo de catalizadores tipo core-shell, ou modificado mediante a ancoragem de organocatalizadores e complexos metálicos. E descrito o desempenho catalitico deste tipo de sistemas em algumas reacóes de catálise assimetrica, ambiental, ácido-base, de óxido-redução, de sintese multicomponente y de acoplamento C-C. Particularmente, ditos catalisadores tem mostrado enorme importáncia em certas reações do tipo Sonogashira, Sonogashira-Hagihara, Mannich, Ullman, Knoevenagel, Suzuki-Miyaura e a reação Fenton heterogénea, entre outras. Finalmente, são detalhados alguns usos tecnológicos da magnetita no contexto nacional (Colômbia) e realiza-se um esforço por localizar geograficamente os depósitos mais importantes do mineral no território colombiano.
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Objetivo. Evaluar tres tratamientos (lagunaje, fotocatálisis con TiO2 y desinfección química) para la inactivación de coliformes totales y Escherichia coli presentes en agua residual doméstica empleada para riego agrícola. Materiales y métodos. El agua residual fue caracterizada por medio de análisis físicos, químicos y microbiológicos. Posteriormente fue sometida a un tratamiento de lagunaje facultativo (TLF), pos tratamiento fotocatalítico (PTFTiO2/UV) y pos tratamiento químico (PTQ NaClO). Valorando la capacidad desinfectante de cada uno de ellos para inactivar coliformes totales y E. coli. A continuación se procesaron tres nuevos lotes de agua residual y se utilizaron para realizar pruebas de riego a escala de laboratorio por 30 días, empleando como modelo plantas de Lactuca sativa variedad Batavia y evaluando la concentración inicial y final de los dos grupos. Resultados. El PTFTiO2/UV fue significativamente superior que TLFLF y el PTQ NaClO (p<0,0001) obteniendo 100% de inactivación para coliformes y E. coli a los 30 minutos de irradiación a escala de reactor. Respecto a las pruebas de riego de L. sativa se demostró que al utilizar el agua tratada por PTFTiO2/UV no se presentó contaminación con E. coli y coliformes a los 30 días de proceso. Por el contrario en las plantas regadas con agua tratada por TLF y PTQ NaClO se observó un incremento en las dos poblaciones generando un problema de contaminación de las hortalizas al finalizar la prueba de laboratorio. Conclusión. La fotocatálisis heterogénea TiO2 fue un método eficaz para la reducción de coliformes y E.coli en aguas residuales domésticas.
Objective. To evaluate three treatments (facultative stabilization ponds, heterogeneous photocatalysis with TiO2 and chemical disinfection with sodium hypochlorite) for the inactivation of coliforms and Escherichia coli presen in domestic wastewaters used in agricultural irrigation. Materials and methods. Wastewater was characterized by physical, chemical and microbiological analyses and was then exposed to a facultative pond treatment (FPT), post-photocatalytic treatment (PTFTiO2/UV) and post-chemical treatment (PTQNaClO) to assess the disinfecting capacity of each method in the inactivation of total coliforms and E. coli. Three new samples of wastewater were processed and used in irrigation tests on a laboratory-scale basis for 30 days, using Lactuca sativa cultivar. Batavia as a model plant and evaluating the initial and final concentrations of the two groups. Results. PTFTiO2/UV was significantly higher than FPT and PTQNaClO (p<0.0001), obtaining 100% of inactivation of coliforms and E. coli after 30 minutes of irradiation at a reactor scale. Regarding the irrigation tests with L. sativa, we showed that using water treated by PTFTiO2/UV there is no contamination with E. coli and coliforms after 30 days. On the contrary, plants irrigated with water treated by FPT and PTQNaClO showed an increase in the two populations originating a contamination problem in the vegetable by the end of the laboratory experiments. Conclusion. The heterogeneous photocatalysis with TiO2 was an effective method in the reduction of coliforms and E. coli present in domestic wastewater.
Objetivo. Avaliar três tratamentos (lagoas, fotocatálise com TiO2 e desinfecção química) para inativação de coliformes totais e Escherichia coli presentes em águas residuais domésticas utilizadas na irrigação dos cultivos. Materiais e métodos. O efluente foi caracterizado por analises físicos, químicos e microbiológicos. Posteriormente foi submetido a tratamento de lagoas facultativas (TLF), pós-tratamento fotocatalítico (PTF TiO2/UV) e pós-tratamento químico (PTQ NaClO). Avaliando a capacidade desinfetante de cada um para inativar coliformes totais e E. coli. Posteriormente, foram processados três novos lotes de águas residuais para testar a irrigação em escala de laboratório por 30 dias, utilizando-se como modelo plantas de Lactuca sativa variedade Batavia e avaliando a concentração inicial e final dos dois grupos. Resultados. O PTFTiO2/UV foi significativamente maior a TLFLF e PTQ NaClO (p<0,0001) apresentando 100% de inativação para coliformes e E. coli em 30 minutos de irradiação a escala do reator. Quanto aos testes de irrigação de L. sativa foi demonstrado que, ao utilizar a água tratada com PTFTiO2/UV não se apresentou contaminação com E. coli e coliformes a 30 dias do tratamento. Em contrapartida, em plantas irrigadas com água tratada por TLF e PTQ NaClO observou-se um aumento nas duas populações gerando um problema de contaminação de hortaliças no final do teste de laboratório. Conclusão. A fotocatálise heterogênea TiO2 foi um método eficaz para reduzirem coliformes e E. coli em águas residuais domésticas.
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En este trabajo se describe la preparación de la perovskita La0,75Sr0,25Co0,5Fe0,5O3, (LaSrCoFeO), empleando una ruta de química húmeda, mediante la polimerización con ácido cítrico, con el propósito de obtener materiales para potenciales aplicaciones electródicas en pilas de combustible de óxido sólido (SOFC); para ello, el sólido se caracterizó mediante difracción de rayos X (DRX), microscopia electrónica de barrido (SEM) y área superficial específica mediante el método BET, permitiendo determinar la formación de una fase tipo perovskita concordante con el registro JCPDS: 089-1267; la textura y el relieve encontrados son característicos del método de síntesis, confiriéndole al sólido cierto grado rugosidad. El tamaño de cristalito, calculado con el programa Scherrer Calculator, confirmó la presencia de cristalitos nanométricos, mientras que la composición global determinada mediante microanálisis de rayos X de energía dispersiva (EDX), indicó una buena concordancia entre la composición propuesta y la obtenida. La evaluación catalítica se realizó utilizando la descomposición de peróxido de hidrógeno en medio alcalino; este procedimiento permitió determinar que la reacción es de pseudo primer orden con respecto al peróxido, suponiendo que la masa de catalizador y la concentración de la base no inciden sobre la velocidad de reacción. Las isotermas de actividad, la energía aparente de activación, y en general la actividad observada, guardan buena correspondencia con resultados obtenidos para la descomposición de H2O2 sobre otros sólidos.
This paper describes the preparation of the La0,75Sr0,25Co0,5Fe0,5O3 perovskite (LaSrCoFeO), using a wet chemical route, through polymerization with citric acid, to obtain materials for potential applications like electrodes in solid oxide fuel cells (SOFC). The solid was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and specific surface area by the BET method. This allows the determination of the formation of a perovskite type phase consistent with JCPDS registration: 089-1267. The texture and relief found are characteristic of the method of synthesis, giving the strong degree of roughness. The size of crystallites, calculated with the Scherrer Calculator software confirmed the presence of nanometric crystallites. The overall composition determined by X-ray microanalysis of energy dispersive (EDX) indicated a good correlation between the proposed and obtained. The assessment was carried out using the catalytic decomposition of hydrogen peroxide in alkaline medium, revealed that the reaction is pseudo first order with respect to peroxide, assuming that the mass of catalyst and concentration of the alkali do not affect the reaction rate, isotherms activity, apparent activation energy. In general activity observed corresponds to physical adsorption process.
Este estudo descreve a preparação da Perovskitas La0,75Sr0,25Co0,5Fe0,5O3 (LaSrCoFeO), utilizando uma rota química molhado, através da polimerização do ácido cítrico, a obtenção de materiais para aplicações potenciais em bateria eletrodos combustível de óxido sólido (SOFC), por esta razão, o som foi caracterizado por difração de raios X (XRD), microscopia eletrônica de varredura (MEV) e determinação de área superficial específica por BET, permitindo determinar a formação de uma fase tipo Perovskitas coerente com JCPDS inscrições: 089-1267, textura e relevo encontrado são características do método de síntese, que o forte grau de rugosidade. O tamanho dos cristalitos, calculada com a Scherrer Calculadora confirmou a presença de agregados nanométricos, que a composição global determinada por microanálise de raios X de energia dispersiva (EDX) indicou uma boa correlação entre o proposto e obtido. A avaliação foi realizada utilizando a decomposição catalítica de peróxido de hidrogénio em meio alcalino, revelou que a reacção é pseudo-primeira ordem com relação ao peróxido, supondo que a massa de catalisador e concentração da base não afeta a velocidade da reação, isotermas actividade, ativação aparente da energia, e na atividade geral observada corresponde a processos de adsorção física.
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The science of catalysis and surface science have developed, independently, key information for understanding catalytic processes. One might argue: is there anything fundamental to be discovered through the interplay between catalysis and surface science? Real catalysts of monometallic and bimetallic Co/Nb2O5 and Pd-Co/Nb2O5 catalysts showed interesting selectivity results on the Fischer-Tropsch synthesis (Noronha et al. 1996, Rosenir et al. 1993). The presence of a noble metal increased the C+5 selectivity and decreased the methane formation depending of the reduction temperature. Model catalyst of Co-Pd supported on niobia and alumina were prepared and characterized at the atomic level, thus forming the basis for a comparison with "real" support materials. Growth, morphology and structure of both pure metal and alloy particles were studied. It is possible to support the strong metal support interaction suggested by studies on real catalysts via the investigation of model systems for niobia in comparison to alumina support in which this effect does not occur. Formation of Co2+ penetration into the niobia lattice was suggested on the basis of powder studies and can be fully supported on the basis of model studies. It is shown for both real catalysts and model systems that oxidation state of Co plays a key role in controlling the reactivity in Fischer-Tropsch reactions systems and that the addition of Pd is a determining factor for the stability of the catalyst. It is demonstrated that the interaction with unsaturated hydrocarbons depends strongly on the state of oxidation.
As ciências da catálise e da superfície têm desenvolvido independentemente temas básicos para o entendimento de processos catalíticos. Pode-se até questionar se há ainda algo fundamental para ser descoberto através da interface entre catálise eciência da superfície? Catalisadores mono e bimetálicos de Co/Nb2O5 e Pd-Co/ Nb2O5 apresentaram resultados interessantes de seletividade na síntese de Fischer-Tropsch (Noronha et al. 1996, Roseniret al. 1993). A presença de metal nobre aumentou a seletividade de C+5 e diminuiu a formação de metano dependendo da temperatura de redução. Catalisadores modelo de Co-Pdsuportados em nióbia e alumina foram preparados e caracterizados a nível atômico, servindo de base para comparação do catalisador "real". Foram estudados o crescimento de partículas, bem como a morfologia e a estrutura de partículas de ambos, metal puro e ligas. É possível suportar as propostas que sugerem uma forte interação metal suporte em catalisadores reais através das pesquisas em sistemas modelos para nióbia quando comparadas com suportes de alumina onde estes efeitos não aparecem. A formação de Co2+ penetrando na rededa nióbia, sugerida para catalisadores em forma de pó, foi totalmente confirmada pelos estudos em catalisadores modelo. Mostrou-se ainda que para ambos os sistemas reais e modelos, que o estado oxidado do Co tem papel fundamental na reatividade das reações de Fischer-Tropsch e que a adição de Pd é um fator determinante para a estabilidade do catalisador. Demonstrou-se que a interação com hidrocarbonetos insaturados depende fortemente do estado oxidado do metal.