Resumo O presente texto tem como objetivo discutir interpretações para o conceito de diálogo, como forma de interação entre professor e alunos. Algumas dessas interpretações emergiram da prática de estágio de futuras professoras de Matemática e de uma disciplina de estágio supervisionado de um curso de Licenciatura em Matemática. O estudo faz parte de uma pesquisa de doutorado a respeito da aprendizagem do diálogo por futuros professores. O referencial teórico é baseado especialmente no conceito de diálogo de Alrø e Skovsmose, no contexto da Educação Matemática Crítica. Os dados da pesquisa são episódios da prática docente de estagiárias, tentando colocar em ação o diálogo com seus alunos, e, também, de momentos de orientação com as docentes supervisoras quando refletia-se sobre essas práticas, o que favorecia dizer sobre a aprendizagem do diálogo. Neste artigo, discute-se sobre a impossibilidade de exaurir o conceito, tendo em vista a multiplicidade e transitoriedade do diálogo. Participação, discussão, incerteza, movimento e investigação são as interpretações de diálogo apresentadas neste texto.

Abstract This paper aims to discuss interpretations for the dialogue concept, as a form of interaction between teacher and students. Some of these interpretations emerged from the teaching practice of prospective mathematics teachers and from a supervised teaching practice course on mathematics. The paper is part of a doctoral research on the learning of dialogue by prospective teachers. The theoretical framework is based especially on the dialogue concept proposed by Alrø and Skovsmose in the context of critical mathematical education. The research data are episodes from teaching practices, when the prospective teachers tried to put into action the dialogue with the students, and also from moments of reflection on these practices, which favored to address dialogue learning. This paper argues that it is impossible to exhaust the concept, considering the multiplicity and transience of the dialogue. Participation, discussion, uncertainty, movement, and investigation are the interpretations for dialogue presented in this paper.

In this work, carbon dots (CDs) prepared by a one-step hydrothermal method were employed for the determination of quercetin in teas and beers. The fluorescence quenching of CDs was proportional to the concentration of quercetin. Under optimum experimental conditions, linear quenching was observed for quercetin in the range of 1.0 to 10 mg L-1 (F/F0 = (0.1511 ± 0.0075)[Q] + (0.8922 ± 0.0384), R2 = 0.9926), at room temperature, using 80 μL CDs and 0.1 mol L-1 Na2HPO4/NaOH buffer solution (pH 11.0). A limit of detection (3σ criterion) of 0.85 mg L-1, and a relative standard deviation of 0.21% (n = 3) for 4.0 mg L-1 quercetin solution was obtained. Addition and recovery tests with tea and beer samples were performed resulting in recoveries at the range between 80 and 118%. This procedure served successfully to determine quercetin in beer and tea samples presenting high sample throughput.

Resumo O texto trata de uma pesquisa realizada sobre a aprendizagem do diálogo por futuros professores de matemática. Os objetivos da investigação foram compreender tal processo de aprendizagem e teorizar sobre o diálogo. Baseada nas ideias teóricas de Alrø e Skovsmose a respeito do diálogo em educação matemática, uma disciplina de estágio supervisionado foi desenvolvida para ser o contexto da produção dos dados. A prática de diálogo dos futuros professores foi acompanhada, e episódios de tal prática constituíram um primeiro nível de dados. Em momentos de orientação e imaginação pedagógica, os licenciandos refletiram sobre tais episódios e suas falas constituíram dados sobre dados. Um episódio mostrando a tentativa de uma estagiária de colocar em ação o diálogo com seus alunos é apresentado. Elementos essenciais do diálogo, como escuta ativa, estranhamento e descentramento, são enfatizados. Uma interpretação de diálogo baseada no movimento de ir até onde o outro está é discutida.

Abstract This text concerns a research on the process of dialogue learning by prospective mathematics teachers. The aim was to understand such learning process and theorize about the dialogue. Based on theoretical ideas about the dialogue from Alrø and Skovsmose, we designed a teaching practice course on mathematics as the context of data production. The dialogue practice of the prospective teachers was followed and the episodes from those practices constituted a first level of data. In moments of supervision and pedagogical imagination, the prospective teachers reflected on such episodes and their conversation constituted data about data. An episode about a prospective teacher's attempt to put the dialogue in action with her students is presented. Essential elements of dialogue such as active listening, estrangement, and decentring are emphasized. We discuss an interpretation for dialogue based on the movement of going where the other is.

In general, inductively coupled plasma mass spectrometry (ICP-MS) food analysis requires numerous sample treatment steps that imply an increase of analysis time and the use of chemicals. In this study, the main objective was to evaluate the applicability of the direct analysis by ICP-MS to determine twelve elements (Al, As, Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Se and Zn) in tea and herbal beverages. Direct analysis method was compared with two other sample treatments: minimum treatment (acid dilution) and using a destructive method (microwave assisted digestion). Besides the lowest time of analysis, direct analysis provides a reliable response and agrees with the “green chemistry” principles. High sensitivity was also observed by low values of limits of detection and quantification, in general, below 2.5 µg L-1. The method accuracy was evaluated by spiked experiments and values ranged between 82 and 120%. Low values of coefficient of variation were also observed, 2 to 17%, for all analytes. The method exhibited applicability for commercial tea samples as well as for drinks made by herb infusion.

Introduction: The levels of cadmium (Cd) and lead (Pb) in foods should be monitored as a function of health risks. Objective: To evaluate Cd and Pb levels in oral hospital diets and in an oral food complement (OFC) according to their respective consumption by patients, and to estimate the patient's exposition risk. Methods: The levels of Cd and Pb were determined by ICP-OES in samples of regular, blend, soft and renal diets and OFC, collected on 6 weekdays. About 14.3% of the diets and OFC served were analyzed. Results and discussion: 163 patients participated, with mean weights and ages of 62.7 kg and 56.5 years, respectively, the majority being men (59.5%). The mean Cd content consumed was greater for men fed the regular and blend diets and similar amongst the sexes for the soft diet. The consumption of Cd (max. 21.02 µg/day) was below the provisional tolerable monthly intake (PTMI). The mean Pb ingested (max. 199.49 µg/day) was similar amongst the sexes. The soft diet showed the highest Pb content in September/2010, whereas the other showed no variation according to season. In September/2010 and January/2011, the soft and regular diets associated with the OFC offered 207.50 and 210.50 µg/day of Pb, respectively. Conclusions: The combination of the diet with the OFC increased the risk of an excessive ingestion of Pb, and the vulnerability of the patients to an excessive exposition to Pb could be greater due to water and medications. It was concluded that whereas the calculated ingestion of Cd conformed to the PTMI, the Pb level and ingestion represented a risk to the health of the patients.

Introducción: Los niveles de cadmio (Cd) y plomo (Pb) en los alimentos deben ser controlados en función del riesgo para la salud. Objetivo: Evaluar los niveles de Cd y Pb en dietas hospitalarias orales y complemento alimentario oral (OFC) y sus ingestiones por pacientes, con estimativa del riesgo de exposición. Métodos: Los niveles de Cd y Pb se determinaron mediante ICP-OES en muestras de dietas regular, blanda, fluida, renal y OFC, recogidas 6 días non-consecutivos. Fueron analizados 14,3% de las dietas y OFC servidos. Resultados y discusión: 163 pacientes participaron, con pesos y edades medias de 62,7 kg y 56,5 años, respectivamente, en su mayoría varones (59,5%). La media de Cd consumida fue mayor entre hombres alimentados con dietas regular y fluida y similar entre los sexos para la blanda. El consumo de Cd (máx. 21,2 µg/día) estaba por debajo de la ingesta provisional mensual tolerable (IPMT). El contenido medio de Pb ingerido fue similar entre sexos (máx. 199,49 µg/día). La dieta blanda mostró mayor contenido de Pb en septiembre/2010, mientras que las otras no variaron según la temporada. En septiembre/2010 y enero/2011, las dietas regular y blanda asociadas al OFC aportaron 207,50 y 210,50 µg/día de Pb, respectivamente. Conclusiones: La combinación de la dieta con OFC aumentó el riesgo de ingestión excesiva de Pb. La vulnerabilidad de los pacientes a una exposición excesiva podría ser mayor en función del agua y medicamentos. La ingestión de Cd calculada cumple el IPMT, pero el nivel de Pb y su ingestión representan riesgo para los pacientes.

A composição de minerais foi investigada em 154 amostras de pólen apícola, provenientes de diferentes regiões do Brasil. A técnica de ICP OES foi utilizada para determinar Ca, Cu, Fe, K, Mg, Mn, Na, P, Se e Zn, após mineralização em sistema de microondas. Utilizando parâmetros instrumentais otimizados conseguiu-se boa exatidão e precisão na determinação simultânea dos minerais. Em geral, as amostras dos estados do Nordeste apresentaram teores de minerais mais elevados e produção constante durante o ano. Os minerais Mn, Se, Cu, Zn, Fe são os que poderiam ter maior contribuição na dieta, podendo atingir 70, 37, 27, 17 e 17%, respectivamente, da ingestão dietética diária recomendada no Brasil. A análise de componentes principais mostrou que Ca, Cu, Fe, K, Mg, Mn, Na, P e Zn podem ser usados na classificação do pólen nacional em função da origem geográfica. Os teores dos minerais variaram amplamente ao longo do ano.

The mineral composition of bee pollen was investigated in 154 samples from different Brazilian regions. Ca, Cu, Fe, K, Mg, Mn, Na, P, Se and Zn were determined by ICP OES after microwave mineralization. Employing optimized instrumental parameters, the method was shown to have a good precision and accuracy for the simultaneous determination of minerals. Overall, samples from the Northeastern states presented significantly higher amounts of minerals and showed constant production throughout the year. Manganese, Se, Cu, Zn and Fe were the elements that showed the greatest possible contributions to the diet, contributing with 70, 37, 27, 17 and 17%, respectively, of the Brazilian recommended daily intake. Principal component analysis (PCA) was applied to study geographic effects. The elements Ca, Cu, Fe, K, Mg, Mn, Na, P and Zn were important in explaining the classification of pollen according to their geographical origin. The mineral levels varied widely during the year.