Producing an explanatory proof in a 9th grade classroom

Este artigo apresenta parte de um estudo fundamentado na problemática da demonstração na matemática escolar. Descreve o modo como quatro alunos do 9.º ano exploraram uma tarefa relacionada com a descoberta de eixos de simetria em várias figuras geométricas. A demonstração, que os mesmos construíram, teve essencialmente uma função explicativa. O papel da professora na negociação do significado de demonstração e da sua necessidade é igualmente analisado. Os alunos desenvolvem primeiro uma compreensão prática sem consciência das razões que fundamentam as afirmações matemáticas e só depois uma compreensão teórica que os conduz à construção de uma demonstração.

In situ NIR spectroscopy monitoring of plasmid production processes effect of producing strain, medium composition and the cultivation strategy

BACKGROUNDWhile the pharmaceutical industry keeps an eye on plasmid DNA production for new generation gene therapies, real-time monitoring techniques for plasmid bioproduction are as yet unavailable. This work shows the possibility of in situ monitoring of plasmid production in Escherichia coli cultures using a near infrared (NIR) fiber optic probe. RESULTSPartial least squares (PLS) regression models based on the NIR spectra were developed for predicting bioprocess critical variables such as the concentrations of biomass, plasmid, carbon sources (glucose and glycerol) and acetate. In order to achieve robust models able to predict the performance of plasmid production processes, independently of the composition of the cultivation medium, cultivation strategy (batch versus fed-batch) and E. coli strain used, three strategies were adopted, using: (i) E. coliDH5 cultures conducted under different media compositions and culture strategies (batch and fed-batch); (ii) engineered E. coli strains, MG1655endArecApgi and MG1655endArecA, grown on the same medium and culture strategy; (iii) diverse E. coli strains, over batch and fed-batch cultivations and using different media compositions. PLS models showed high accuracy for predicting all variables in the three groups of cultures. CONCLUSIONNIR spectroscopy combined with PLS modeling provides a fast, inexpensive and contamination-free technique to accurately monitoring plasmid bioprocesses in real time, independently of the medium composition, cultivation strategy and the E. coli strain used.

New heterogeneous catalysts for trans-esterification of triglycerides

This paper describes preliminary work done towards the development of new metallic heterogeneous catalysts to be used in the transesterification reaction of triglycerides, which is of considerable interest in the production of biodiesel. Biodiesel, is a mixture of mono-alkyl esters of fatty acids, and is currently manufactured by transesterification of triglycerides with methanol using NaOH or KOH as liquid base catalyst. Catalysts as such are corrosive to the equipment, and as these catalysts are in liquid phase must be neutralized after the completion of the reaction, typically using HCl, thus producing salt streams. Moreover, due to the presence of free fatty acids it reacts to form soaps as unwanted by-products, hence requiring more expensive separation processes. Therefore, there is a great need on the development of industrial processes for biodiesel production using solid acid catalysts. The key benefit of using solid acid catalysts is that no polluting by-products are formed and the catalysts do not have to be removed since they do not mix with the biodiesel product.

Conceptual, methodological and ethical issues in children's research in Portugal

Methodological issues in research with children have sparked a growing interest by the Sociology of Childhood since the last decades. In Portugal, this interest is more recent, but it has had a significant increase. Considering several researches, namely master thesis, supervised by the authors on the framework of Sociology of Childhood, this proposal intends to characterize some methodological complexities in research with children in Portugal, when we consider their voice and agency in the knowledge producing about them. The goal of this paper is to contribute to the methodological discussion on research with children through the identification of a set of challenges related to: (i) the diversity of methodologies uses in children’s research, (ii) ethical concerns and (iii) the role of the researcher.

Magma flow, exsolution processes and rock metasomatism in the Great Messejana-Plasencia dyke (Iberian Peninsula)

Magma flow in dykes is still not well understood; some reported magnetic fabrics are contradictory and the potential effects of exsolution and metasomatism processes on the magnetic properties are issues open to debate. Therefore, a long dyke made of segments with different thickness, which record distinct degrees of metasomatism, the Messejana-Plasencia dyke (MPD), was studied. Oriented dolerite samples were collected along several cross-sections and characterized by means of microscopy and magnetic analyses. The results obtained show that the effects of metasomatism on rock mineralogy are important, and that the metasomatic processes can greatly influence anisotropy degree and mean susceptibility only when rocks are strongly affected by metasomatism. Petrography, scanning electron microscopy (SEM) and bulk magnetic analyses show a high-temperature oxidation-exsolution event, experienced by the very early Ti-spinels, during the early stages of magma cooling, which was mostly observed in central domains of the thick dyke segments. Exsolution reduced the grain size of the magnetic carrier (multidomain to single domain transformation), thus producing composite fabrics involving inverse fabrics. These are likely responsible for a significant number of the 'abnormal' fabrics, which make the interpretation of magma flow much more complex. By choosing to use only the 'normal' fabric for magma flow determination, we have reduced by 50 per cent the number of relevant sites. In these sites, the imbrication angle of the magnetic foliation relative to dyke wall strongly suggests flow with end-members indicating vertical-dominated flow (seven sites) and horizontal-dominated flow (three sites).

Trying To understand all-equity firms

This paper studies all equity firms and shows which are in US firms, the main drivers of zero-debt policy. I analyze 6763 U.S. listed companies in years 1987-2009, a total of 77442 firms year. I find that financial constrained firms show a higher probability to become unlevered. In the opposite side, firms producing high cash flow are also likely to become unlevered, paying their debt. Some firms create economies of scale in the use of funds, increasing the probability of become unlevered. The industry characteristics are also important to explain the zero-debt policy. However is the high perception of risk, the most important factor influencing this extreme behavior, which is consistent with trade-off theory.

Light pollution and energy efficiency: a case study of the village of Vialonga

Since industrialization and the formation of larger urban centers in the nineteenth century, pollution of the environment was always present in daily life in various ways, namely in the form of light. Light pollution can cause various consequences, both for humans and for their ecosystem, producing effects on environmental, social, economic and scientific level. In Portugal, the lighting is responsible for 3% of total electricity consumption, energy costs are in some cases more than 50% towards the costs incurred by municipalities with energy, checking-in recent years a trend similar to that improvement of illumination levels in the region (about 4 to 5% per year). Proper use of lighting brings many benefits both to the citizen and environment, since greater energy efficiency can contribute to reducing CO2 emissions, energy costs, as well as to decrease the use of resources not-renewable and/or contamination of renewable resources, which can occurs in the process of obtaining electricity. The present study has a main goal to analyze the illuminance levels associated to the public lighting of the village of Vialonga, Vila Franca de Xira (Portugal), to verify if it is efficient. The aim is also to relate the efficiency of street lighting with the existence of light pollution.

Occupational exposure to aflatoxin (AFB1) in poultry production

Aflatoxin B1 (AFB1) has been recognized to produce cancer in human liver. In addition, epidemiological and laboratory studies demonstrated that the respiratory system was a target for AFB1. Exposure occurs predominantly through the food chain, but inhalation represents an additional route of exposure. The present study aimed to examine AFB1 exposure among poultry workers in Portugal. Blood samples were collected from a total of 31 poultry workers from six poultry farms. In addition, a control group (n = 30) was included comprised of workers who undertook administrative tasks. Measurement of AFB1 in serum was performed by enzyme-linked immunosorbent assay (ELISA). For examining fungi contamination, air samples were collected through an impaction method. Air sampling was obtained in pavilion interior and outside the premises, since this was the place regarded as the reference location. Using molecular methods, toxicogenic strains (aflatoxin-producing) were investigated within the group of species belonging to Aspergillus flavus complex. Eighteen poultry workers (59%) had detectable levels of AFB1 with values ranging from <1 ng/ml to4.23 ng/ml and with a mean value of 2 ± 0.98ng/ml. AFB1 was not detected in the serum sampled from any of the controls. Aspergillus flavus was the fungal species third most frequently found in the indoor air samples analyzed (7.2%) and was the most frequently isolated species in air samples containing only Aspergillus genus (74.5%). The presence of aflatoxigenic strains was only confirmed in outdoor air samples from one of the units, indicating the presence of a source inside the building in at least one case. Data indicate that AFB1 inhalation represents an additional risk in this occupational setting that needs to be recognized, assessed, and prevented.

Bioconversion of D-glucose into D-glucosone by Glucose 2-oxidase from Coriolus versicolor at Moderate Pressures

Glucose 2-oxidase (pyranose oxidase, pyranose: oxygen-2-oxidoreductase, EC 1.1.3.10) from Coriolus versicolor catalyses the oxidation of D-glucose at carbon 2 in the presence of molecular O(2) producing D-glucosone (2-keto-glucose and D-arabino-2-hexosulose) and H(2)O(2). It was used to convert D-glucose into D-glucosone at moderate pressures (i.e. up to 150 bar) with compressed air in a modified commercial batch reactor. Several parameters affecting biocatalysis at moderate pressures were investigated as follows: pressure, [enzyme], [glucose], pH, temperature, nature of fluid and the presence of catalase. Glucose 2-oxidase was purified by immobilized metal affinity chromatography on epoxy-activated Sepharose 6B-IDA-Cu(II) column at pH 6.0. The rate of bioconversion of D-glucose increased with the pressure since an increase in the pressure with compressed air resulted in higher rates of conversion. On the other hand, the presence of catalase increased the rate of reaction which strongly suggests that H(2)O(2) acted as inhibitor for this reaction. The rate of bioconversion of D-glucose by glucose 2-oxidase in the presence of either nitrogen or supercritical CO(2) at 110 bar was very low compared with the use of compressed air at the same pressure. The optimum temperature (55 degrees C) and pH (5.0) of D-glucose bioconversion as well as kinetic parameters for this enzyme were determined under moderate pressure. The activation energy (E(a)) was 32.08 kJmol(-1) and kinetic parameters (V(max), K(m), K(cat) and K(cat)/K(m)) for this bioconversion were 8.8 Umg(-1) protein, 2.95 mM, 30.81 s(-1) and 10,444.06 s(-1)M(-1), respectively. The biomass of C. versicolor as well as the cell-free extract containing glucose 2-oxidase activity were also useful for bioconversion of D-glucose at moderate pressures. The enzyme was apparently stable at moderate pressures since such pressures did not affect significantly the enzyme activity.

Estudo das propriedades dos adjuvantes na compatibilidade/robustez cimento/adjuvante

A qualidade do betão pode ser controlada pelo comportamento da fluidez da pasta de cimento, o qual está relacionado com a dispersão das partículas de cimento. Um dos maiores avanços na tecnologia do betão tem sido o desenvolvimento de aditivos. Um destes tipos de aditivos, os Superplastificantes (SP), fornecem a possibilidade de se obter uma melhor dispersão das partículas de cimento, produzindo pastas com elevada fluidez. Com o desenvolvimento de betões de alta resistência e elevado desempenho, os superplastificantes tornaram-se indispensáveis. Os superplastificantes são adsorvidos nas partículas de cimento e esta adsorção depende da composição do clínquer do cimento e do tipo de SP utilizado. Com a difusão do emprego dos aditivos redutores de água, têm surgido vários problemas de compatibilidade cimento/adjuvante. Esta investigação dedicada aos superplastificantes, fortes redutores de água, visou estudar quais as propriedades que poderiam influenciar a sua compatibilidade/robustez com o cimento. Também se procurou ganhar experiência com as técnicas analíticas de caracterização de adjuvantes. Assim, utilizou-se um tipo de cimento e dois tipos de superplastificantes (poli(étercarboxilatos) e poli(naftalenossulfonatos)) disponíveis no mercado português. Mantendo a mesma razão água/cimento (A/C), pretendeu-se determinar a natureza química, grau de funcionalização, teor e tipo de contra-ião, teor de sulfatos/sulfonatos do adjuvante e o comportamento dos superplastificantes nas pastas cimentícias, de forma a poder determinar indicadores de compatibilidade entre cimentos e superplastificantes. Constatou-se que a natureza química, o grau de funcionalização e a quantidade consumida dos superplastificantes têm influência nas pastas. Os indicadores de compatibilidade por parte dos superplastificantes parecem estar relacionados com o comprimento da cadeia lateral de éter e com o rácio CO2R/CO2 -. A alteração do momento da adição do adjuvante tem influência na compatibilidade cimento/adjuvante, sendo benéfico para os poli(étercarboxilatos) e prejudicial para o poli(naftalenossulfonato).

Nanofiltration of Cork Wastewaters and Their Possible Use in Leather Industry as Tanning Agents

Cork processing wastewater is a very complex mixture of vegetal extracts and has, among other natural compounds, a very high content of phenolic/tannic colloidal matter that is responsible for severe environmental problems. In the present work, the concentration of this wastewater by nanofiltration was investigated with the aim of producing a cork tannin concentrate to be utilized in tanning. Permeation results showed that the permeate fluxes are controlled by both osmotic pressure and fouling/gel layer phenomena, leading to a rapid decrease of permeate fluxes with the concentration factor. The rejection coefficients to organic matter were higher than 95%, indicating that nanofiltration has a very good ability to concentrate the tannins and produce a permeate stream depleted from organic matter. The cork tannin concentrate obtained by nanofiltration and evaporation had total solids concentration of 34.8 g/l. The skins tanned by this concentrate were effectively converted to leather with a shrinking temperature of 7 degrees C.

Processus interactionnel d’appropriation de la syntaxe et de variantes énonciatives diversifiées, indispensable pour l’accès à l’écrit

A investigação tem posto em evidência a correlação entre desenvolvimento linguístico e aprendizagem da leitura e da escrita. Procuramos, em primeiro lugar, explicar, do ponto de vista da linguística, as relações entre oral e escrita focalizando a linguagem da criança desde as primeiras produções à produção autónoma de variantes sintacticamente diversificadas. De seguida, abordamos a questão da passagem do oral à escrita dando especial atenção ao impacto sobre o funcionamento cognitivo do trabalho de ditado ao adulto. Finalmente, propomos pistas de reflexão sobre modalidades de interacção necessárias à entrada no modo escrito e ao seu percurso de aprendizagem dando conta de resultados de investigação acção e formação com a abordagem «Coup de pouce Langage».

Capacitive effects in pinpin photodiodes

The application of a-SiC:H/a-Si:H pinpin photodiodes for optoelectronic applications as a WDM demultiplexer device has been demonstrated useful in optical communications that use the WDM technique to encode multiple signals in the visible light range. This is required in short range optical communication applications, where for costs reasons the link is provided by Plastic Optical Fibers. Characterization of these devices has shown the presence of large photocapacitive effects. By superimposing background illumination to the pulsed channel the device behaves as a filter, producing signal attenuation, or as an amplifier, producing signal gain, depending on the channel/background wavelength combination. We present here results, obtained by numerical simulations, about the internal electric configuration of a-SiC:H/a-Si:H pinpin photodiode. These results address the explanation of the device functioning in the frequency domain to a wavelength tunable photo-capacitance due to the accumulation of space charge localized at the bottom diode that, according to the Shockley-Read-Hall model, it is mainly due to defect trapping. Experimental result about measurement of the photodiode capacitance under different conditions of illumination and applied bias will be also presented. The combination of these analyses permits the description of a wavelength controlled photo-capacitance that combined with the series and parallel resistance of the diodes may result in the explicit definition of cut off frequencies for frequency capacitive filters activated by the light background or an oscillatory resonance of photogenerated carriers between the two diodes. (C) 2013 Elsevier B.V. All rights reserved.

A Model to Evaluate Vertical Handovers on JRRM

In a heterogeneous cellular networks environment, users behaviour and network deployment configuration parameters have an impact on the overall Quality of Service. This paper proposes a new and simple model that, on the one hand, explores the users behaviour impact on the network by having mobility, multi-service usage and traffic generation profiles as inputs, and on the other, enables the network setup configuration evaluation impact on the Joint Radio Resource Management (JRRM), assessing some basic JRRM performance indicators, like Vertical Handover (VHO) probabilities, average bit rates, and number of active users, among others. VHO plays an important role in fulfilling seamless users sessions transfer when mobile terminals cross different Radio Access Technologies (RATs) boundaries. Results show that high bit rate RATs suffer and generate more influence from/on other RATs, by producing additional signalling traffic to a JRRM entity. Results also show that the VHOs probability can range from 5 up to 65%, depending on RATs cluster radius and users mobility profile.

O programa de formação contínua em matemática para professores do 1º ciclo e a melhoria do ensino da matemática

Neste artigo apresento uma análise do Programa de Formação Contínua em Matemática, que se desenvolveu em Portugal de 2005 a 2011. Começo por abordar a formação de professores que ensinam Matemática, tendo por base resultados da investigação que serviram de suporte para a definição do Programa de Formação Contínua em Matemática (PFCM). Serão depois analisados os dados do PFCM em termos do envolvimento dos professores do 1.º ciclo a quem ele se destinava. Faz-se uma avaliação da formação a partir de testemunhos dos formandos inseridos nos relatórios institucionais e/ou nos seus portefólios, para concluir que as características da formação foram determinantes para o aumento da confiança dos professores envolvidos e, em consequência, para a melhoria da aprendizagem da Matemática dos nossos alunos. Por fim, referem-se os resultados do TIMSS 2011, que vêm corroborar a afirmação feita anteriormente. Uma ideia forte que se transmite é a de que a formação contínua de professores tem de ter uma estreita ligação com a prática letiva