Flow injection analysis of ethyl xanthate by gas diffusion and UV detection as CS(2) for process monitoring of sulfide ore flotation

A sensitive and robust analytical method for spectrophotometric determination of ethyl xanthate, CH(3)CH(2)OCS(2)(-) at trace concentrations in pulp solutions from froth flotation process is proposed. The analytical method is based on the decomposition of ethyl xanthate. EtX(-), with 2.0 mol L(-1) HCl generating ethanol and carbon disulfide. CS(2). A gas diffusion cell assures that only the volatile compounds diffuse through a PTFE membrane towards an acceptor stream of deionized water, thus avoiding the interferences of non-volatile compounds and suspended particles. The CS(2) is selectively detected by UV absorbance at 206 nm (epsilon = 65,000 L mol(-1) cm(-1)). The measured absorbance is directly proportional to EtX(-) concentration present in the sample solutions. The Beer`s law is obeyed in a 1 x 10(-6) to 2 x 10(-4) mol L(-1) concentration range of ethyl xanthate in the pulp with an excellent correlation coefficient (r = 0.999) and a detection limit of 3.1 x 10(-7) mol L(-1), corresponding to 38 mu g L. At flow rates of 200 mu L min(-1) of the donor stream and 100 mu L min(-1) of the acceptor channel a sampling rate of 15 injections per hour could be achieved with RSD < 2.3% (n = 10, 300 mu L injections of 1 x 10(-5) mol L(-1) EtX(-)). Two practical applications demonstrate the versatility of the FIA method: (i) evaluation the free EtX(-) concentration during a laboratory study of the EtX(-) adsorption capacity on pulverized sulfide ore (pyrite) and (ii) monitoring of EtX(-) at different stages (from starting load to washing effluents) of a flotation pilot plant processing a Cu-Zn sulfide ore. (C) 2010 Elsevier By. All rights reserved.

Biolabeling with nanoparticles based on Y(2)O(3):Nd(3+) and luminescence detection in the near-infrared

Neodymium based fluorescence presents several advantages in comparison to conventional rare earth or enzyme-substrate based fluorescence emitting sources (e.g.Tb, HRP). Based on this fact we have herein explored a Nd-based fluoroimmunoassay. We efficiently detected the presence of an oxidized low-density lipoprotein (oxLDL) in human plasma a well-known marker for cardiovascular diseases, which causes around 30% of deaths worldwide. Conventional fluoroimmunoassay uses time-resolved luminescence techniques, with detection in the visible range, to eliminate the fluorescence background from the biological specimens. By using an immunoassay based on functionalized Y(2)O(3):Nd(3+) nanoparticles, where the excitation and emission processes in the Nd(3+) ion occur in the near-infrared (NIR) region, we have succeeded in eliminating the interferences from the biological fluorescence background, avoiding the use of time-resolved techniques. This yields higher emission intensity from the Nd(3+)-nanolabels and efficient detection of anti-oxidized low-density lipoproteins (anti-oxLDL) by Y(2)O(3):Nd(3+)-antibody-antigen conjugation, leading to a novel biolabeling method. (C) 2010 Elsevier B.V. All rights reserved.

A New Indirect Electroanalytical Method to Monitor the Contamination of Natural Waters with 4-Nitrophenol Using Multiwall Carbon Nanotubes

The electrochemical detection of the hazardous pollutant 4-nitrophenol (4-NP) at low potentials, in order to avoid matrix interferences, is an important research challenge. This study describes the development, electrochemical characterization and utilization of a multiwall carbon nanotube (MWCNT) film electrode for the quantitative determination of 4-NP in natural water. Electrochemical impedence spectroscopy measurements showed that the modified surface exhibits a decrease of ca. 13 times in the charge transfer resistance when compared with a bare glassy carbon (GC) surface. Voltammetric experiments showed the possibility to oxidize a hydroxylamine layer (produced by the electrochemical reduction of 4-NP on the GC/MWNCT surface) in a potential region which is approximately 700 mV less positive than that needed to oxidize 4-NP, thus minimizing the interference of matrix components. The limit of detection for 4-NP obtained using square-wave voltammetry (0.12 mu mol L(-1)) was lower than the value advised by EPA. A natural water sample from a dam located in Sao Carlos (Brazil) was spiked with 4-NP and analyzed by the standard addition method using thee GC/MWCNT electrode, without any further purification step. the recovery procedure yielded a value of 96.5% for such sample, thus confirming the suitability of the developed method to determine 4-NP in natural water samples. The electrochemical determination was compared with that obtained by HPLC with UV-vis detection.

Fluoxetine and norfluoxetine analysis by direct injection of human plasma in a column switching liquid chromatographic system

A column switching LC method is presented for the analysis of fluoxetine (FLU) and norfluoxetine (NFLU) by direct injection of human plasma using a lab-made restricted access media (RAM) column. A RAM-BSA-octadecyl silica (C-18) column (40 min x 4.6 mm, 10 mu m) is evaluated in both backflush and foreflush elution modes and coupled with a C-18 lab-made (50 mm x 4.6 mm, 3 pm) analytical column in order to perform online sample preparation. Direct injection of 100 mu L, of plasma samples is possible with the developed approach. In addition, reduction of sample handling is obtained when compared with traditional liquid-liquid extraction (LLE) and SPE. The total analysis time is around 20 min. A LOQ of 15 ng/mL is achieved in a concentration range of 15-500 ng/mL, allowing the therapeutic drug monitoring of clinical samples. The precision values achieved are lower than 15% for all the evaluated points with adequate recovery and accuracy. Furthermore, no matrix interferences are found in the analysis and the proposed method shows to be an adequate alternative for analysis of FLU in plasma.

Building a Learning Architecture : e-Learning and e-Services

With the rapid advancement of the webtechnology, more and more educationalresources, including software applications forteaching/learning methods, are available acrossthe web, which enables learners to access thelearning materials and use various ways oflearning at any time and any place. Moreover,various web-based teaching/learning approacheshave been developed during the last decade toenhance the capability of both educators andlearners. Particularly, researchers from bothcomputer science and education are workingtogether, collaboratively focusing ondevelopment of pedagogically enablingtechnologies which are believed to improve theinfrastructure of education systems andprocesses, including curriculum developmentmodels, teaching/learning methods, managementof educational resources, systematic organizationof communication and dissemination ofknowledge and skills required by and adapted tousers. Despite of its fast development, however,there are still great gaps between learningintentions, organization of supporting resources,management of educational structures,knowledge points to be learned and interknowledgepoint relationships such as prerequisites,assessment of learning outcomes, andtechnical and pedagogic approaches. Moreconcretely, the issues have been widelyaddressed in literature include a) availability andusefulness of resources, b) smooth integration ofvarious resources and their presentation, c)learners’ requirements and supposed learningoutcomes, d) automation of learning process interms of its schedule and interaction, and e)customization of the resources and agilemanagement of the learning services for deliveryas well as necessary human interferences.Considering these problems and bearing in mindthe advanced web technology of which weshould make full use, in this report we willaddress the following two aspects of systematicarchitecture of learning/teaching systems: 1)learning objects – a semantic description andorganization of learning resources using the webservice models and methods, and 2) learningservices discovery and learning goals match foreducational coordination and learning serviceplanning.

Mercados internos de capital: uma questão de sobrevivência

Procuramos apresentar neste trabalho a importância e os efeitos dos mercados internos de capitais, e as conseqüências quando da sua aplicação. Para isso, aplicamos inicialmente um modelo básico de mercados internos de capitais, avaliando os pontos atingidos e algumas idéias não abrangidas por ele. Exemplificamos com uma situação de aplicação de recursos entre divisões de uma pequena empresa diversificada e seu fracasso devido à má alocação desses recursos. Na seqüência, identificamos modelos que, quando aplicados às situações em que os mercados internos de capitais não funcionaram, foram capazes de apontar o porquê, indicando possíveis interferências e impedimentos. Por fim, aplicamos um modelo que permite comprovar a ineficiência na transferência de recursos quando esses vão na direção das divisões com as piores oportunidades de investimento.

Educação ambiental em escolas públicas: fundamentos para o raciocínio ecológico

A organizaçao logica do pensamento ocidental caracteriza-se pela predominancia de valores estáticos, fragmentados e abstratos. A abstração do pensamento favoreceu o desenvolvimento de uma ciencia e tecnologia alheias a relação de interdependncia entre o homem e seu ecossistema. A soberania da ciencia fragmentada, apoiada por conceitos ideológicos, políticos e economicos capitalistas, tem permitido interferencias humanas desestabilizadoras em seu ambiente. Gerou ainda uma concepç~o de desenvolvimento que combina progresso, viol~ncia e destruiç~o. Estas concepcses refletem-se nos valores e formas de organizac.o , , da sociedade ocidental, perpetuando-se através de seus sistemas educativos, entre estes, a educaç~o em escolas publicas. A urgente necesidade da ativaç~o do equilibrio ecológico, através da integraç~o do homem aos ecossistemas naturais, principalmente em paises do terceiro mundo, requer uma revis~o de valores sociais, politicos e econ8micos e uma reo~ganizaç~o do pensamento ocidental voltando-o para bases holisticas e dinamicas. A escola pública no Brasil, pode vir a ser uma peça fundamental neste processo, aproveitando-se deste movimento para reestrutur.r as bases de seu sistema educativo.

As dimensões da sustentabilidade nas relações de poder: O Comércio Justo no setor alimentício brasileiro

A presente pesquisa tem por objetivo descrever e explicar como as dimensões econômica, social e ambiental interferem nas relações de poder setor alimentício brasileiro certificado Comércio Justo. A tese defendida é de que as dimensões da sustentabilidade – econômica, social e ambiental – interferem nas relações de poder entre organizações, tendo abrangência de impacto distintas. A base teórica de análise das relações de poder envolveu a conjunção entre as teorias de dependência de recursos, racionalidade limitada, custos de transação e a relação entre justiça e poder. O estudo demonstra como ocorrem interferências das dimensões elencadas, sendo a análise realizada a partir de: 1. conflitos ao longo da inserção d o Comércio Justo no Brasil; 2. estruturação das redes e parcerias; 4. uso de discursos; 5. papel de tecnologias e recursos; 6. preço; 7. entendimentos sobre justiça. O estudo é de cunho qualitativo, assumindo o caráter descritivo e interpretativo. A coleta de dados foi realizada por intermédio de: 1. pesquisa bibliográfica; 2. investigação documental e na internet – notadamente com auxílio da ferramenta alertas do google; 3. entrevistas; 4. pesquisa de campo. A amostra foi composta por dezenove representantes de organizações, inseridas no contexto dos produtores de alimentos certificados. A coleta teve o corte longitudinal. Realizou- se a análise discursiva, do conteúdo das entrevistas. A análise de dados resultou de leituras e triangulações diversas entre objetivos da pesquisa, referencial teórico e resultados da pesquisa. Como resultado do estudo, concluiu-se que há parcialidade nas relações, sendo afetadas predominantemente por interferências da dimensão econômica. A dependência em recursos proporciona relações assimétricas. Tecnologias e conhecimentos, por intermédio da dimensão social, servem de instrumentos para: 1. minorar as diferenças entre os atores; 2. proporcionar um diferencial efetivo, que não apoiado exclusivamente na certificação. A configuração de organizações, parcerias e redes é passível de redução de assimetrias, quando compreendidas necessidades de pessoas, conhecimentos específicos e, portanto, da relevância da dimensão social. A variável ambiental é relevante, sobretudo em termos de recursos e processos produtivos. Porém, o impacto da dimensão ambiental gera interferências superiores, quando há: 1. a conscientização sobre sua relevância; 2. demandas sociais e de mercado por adaptações em processos. Logo, interferências do meio ambiente nas relações de poder são originárias, principalmente, daquelas de caráter social e econômico. Conclui-se, portanto, que há validade na tese da existência de distinção no impacto e interferências das dimensões da sustentabilidade, nas relações de poder entre organizações.

O DOI-CODI carioca: memória e cotidiano no "Castelo do Terror"

O objetivo dessa dissertação é analisar a memória de seis ex-prisioneiros políticos do Destacamento de Operações de Informações-Centro de Operações de Defesa Interna do Rio de Janeiro (DOI-CODI/RJ), entrevistados recentemente, entre os anos de 2002 e 2004, sobre o cotidiano vivido nessa instituição em 1970. Naquele ano, dentro do Sistema de Segurança Interna (SISSEGIN), os DOI-CODI haviam sido criados e distribuídos por todas as Regiões Militares do país, tornando-se a principal instituição de repressão aos opositores políticos que optaram pela luta armada como forma de derrotar a ditadura militar brasileira. Assim, as narrativas desses seis ex-prisioneiros são, além de fontes essenciais, o principal objeto de estudo deste trabalho. Através delas, torna-se possível acessar aspectos cruciais para a caracterização do cotidiano vivido pelos presos em um desses órgãos, ― o DOI-CODI do Rio de Janeiro ―, uma vez que esse passado se liga ao presente por meio de suas memórias. Diante disso, a fim de melhor entender tais memórias, a formação e a atuação dos DOI-CODI também são aqui analisadas, colocando as narrativas dos ex-prisioneiros políticos entrevistados em diálogo com uma bibliografia especialmente selecionada, além de uma fonte a respeito do DOI feita por um de seus agentes quando este órgão ainda estava em atividade, em 1978. Para que a essas memórias seja aplicada uma crítica efetiva, necessária a todo trabalho histórico, o estudo se debruça ainda sobre as interferências que o presente exerce na construção que fazem com relação ao passado vivido no DOI-CODI/RJ, com o objetivo de esclarecer as bases sobre as quais são construídas cerca de trinta anos depois.

Ensaios sobre mercados artificiais com dois ativos utilizando algoritmos genéticos

A abordagem de Modelos Baseados em Agentes é utilizada para trabalhar problemas complexos, em que se busca obter resultados partindo da análise e construção de componentes e das interações entre si. Os resultados observados a partir das simulações são agregados da combinação entre ações e interferências que ocorrem no nível microscópico do modelo. Conduzindo, desta forma, a uma simulação do micro para o macro. Os mercados financeiros são sistemas perfeitos para o uso destes modelos por preencherem a todos os seus requisitos. Este trabalho implementa um Modelo de Mercado Financeiro Baseado em Agentes constituído por diversos agentes que interagem entre si através de um Núcleo de Negociação que atua com dois ativos e conta com o auxílio de formadores de mercado para promover a liquidez dos mercados, conforme se verifica em mercados reais. Para operação deste modelo, foram desenvolvidos dois tipos de agentes que administram, simultaneamente, carteiras com os dois ativos. O primeiro tipo usa o modelo de Markowitz, enquanto o segundo usa técnicas de análise de spread entre ativos. Outra contribuição deste modelo é a análise sobre o uso de função objetivo sobre os retornos dos ativos, no lugar das análises sobre os preços.

Análise de volatilidade, integração de preços e previsibilidade para o mercado brasileiro de camarão

The present paper has the purpose of investigate the dynamics of the volatility structure in the shrimp prices in the Brazilian fish market. Therefore, a description of the initial aspects of the shrimp price series was made. From this information, statistics tests were made and selected univariate models to be price predictors. Then, it was verified the existence of relationship of long-term equilibrium between the Brazilian and American imported shrimp and if, confirmed the relationship, whether or not there is a causal link between these assets, considering that the two countries had presented trade relations over the years. It is presented as an exploratory research of applied nature with quantitative approach. The database was collected through direct contact with the Companhia de Entrepostos e Armazéns Gerais de São Paulo (CEAGESP) and on the official website of American import, National Marine Fisheries Service - National Oceanic and Atmospheric Administration (NMFS- NOAA). The results showed that the great variability in the active price is directly related with the gain and loss of the market agents. The price series presents a strong seasonal and biannual effect. The average structure of price of shrimp in the last 12 years was R$ 11.58 and external factors besides the production and marketing (U.S. antidumping, floods and pathologies) strongly affected the prices. Among the tested models for predicting prices of shrimp, four were selected, which through the prediction methodologies of one step forward of horizon 12, proved to be statistically more robust. It was found that there is weak evidence of long-term equilibrium between the Brazilian and American shrimp, where equivalently, was not found a causal link between them. We concluded that the dynamic pricing of commodity shrimp is strongly influenced by external productive factors and that these phenomena cause seasonal effects in the prices. There is no relationship of long-term stability between the Brazilian and American shrimp prices, but it is known that Brazil imports USA production inputs, which somehow shows some dependence productive. To the market agents, the risk of interferences of the external prices cointegrated to Brazilian is practically inexistent. Through statistical modeling is possible to minimize the risk and uncertainty embedded in the fish market, thus, the sales and marketing strategies for the Brazilian shrimp can be consolidated and widespread

A contribuição de técnicas modernas de reabilitação estrutural para autenticidade e integridade de edificações patrimoniais

This work discusses the study of the application of structural reinforcement and rehabilitation using modern techniques for interventions in repair works of historical buildings as well as the verification of the behavior of works that have already undergone different structural intervention techniques, with the objective of obtaining data to allow a comparative analysis of the advantages/disadvantages of techniques adapted in each case, regarding the interferences related the authenticity and integrity of the buildings belong to the constructed patrimony so as to obtain a basis for the theoretical foundation for choosing the best solution to be adopted in the case study which consists in an intervention of structural rehabilitation of the old historic building in the primary school "Augusto Severo"

An electroanalytical application of 2-aminothiazole-modified silica gel after adsorption and separation of Hg(II) from heavy metals in aqueous solution

2-Aminothiazole covalently attached to a silica gel surface was prepared in order to obtain an adsorbent for Hg(II) ions having the following characteristics: good sorption capacity, chemical stability under conditions of use, and, especially, high selectivity. The accumulation voltammetry of mercury(II) was investigated at a carbon paste electrode chemically modified with silica gel functionalized with 2-aminothiazole (SIAMT-CPE). The repetitive cyclic voltammogram of mercury(II) solution in the potential range -0.2 to + 0.6 V versus Ag/AgCl (0.02 mol L-1 KNO3; V = 20 mV s(-1)) show two peaks one at about 0.1 V and other at 0.205 V. The anodic wave peak at 0.205 V is well defined and does not change during the cycles and it was therefore further investigated for analytical purposes using differential pulse anodic stripping voltammetry in differents supporting electrolytes. The mercury response was evaluated with respect to pH, electrode composition, preconcentration time, mercury concentration, cleaning solution, possible interferences and other variables. The precision for six determinations (n = 6) of 0.02 and 0.20 mg L-1 Hg(II) was 4.1 and 3.5% (relative standard deviation), respectively. The detection limit was estimated as 0.10 mu g L-1 mercury(II) by means of 3:1 current-to-noise ratio in connection with the optimization of the various parameters involved and using the highest-possible analyser sensitivity. (c) 2006 Elsevier Ltd. All rights reserved.

Voltammetric determination of isoprenaline in pharmaceutical preparations using a copper(II) hexacyanoferrate(III) modified carbon paste electrode

The electroanalytical determination of isoprenaline in pharmaceutical preparations of a homemade carbon paste electrode modified with copper(II) hexacyanoferrate(III) (CuHCF) was studied by cyclic voltammetry. Several parameters were studied for the optimization of the sensor such as electrode composition, electrolytic solution, pH effect, potential scan rate and interferences in potential. The optimum conditions were found in an electrode composition (in mass) of 15% CuHCF, 60% graphite and 25% mineral oil in 0.5 mol l(-1) acetate buffer solution at pH 6.0. The analytical curve for isoprenaline was linear in the concentration range from 1.96 x 10(-4) to 1.07 x 10(-3) mol l(-1) with a detection limit of 8.0 x 10(-5) mol l(-1). The relative standard deviation was 1.2% for 1.96 x 10(-4) mol l(-1) isoprenaline solution (n=5). The procedure was successfully applied to the determination of isoprenaline in pharmaceutical preparations; the CuHCF modified carbon paste electrode gave comparable results to those results obtained using a UV spectrophotometric method. (C) 2004 Elsevier B.V. All rights reserved.

O uso pedagógico das TIC como expansão das capacidades : o ProInfo Natal/RN

The broad objective of the research The pedagogic use of ICT as development of teaching capacity: the case of ProInfo Natal/RN was to realize an evaluation of this program effectiveness in public schools. Specifically, we ve tried to observe if the program: a) succeeded by promoting the pedagogical use of new ICTs, b) stimulated the improvement of teaching and learning using ICT, and c) performed functionings and expanding its capabilities. The methodology consisted of literature revision; realization of half-structured interviews with administrators and teachers, and leading four focal groups with students in 9th grade of elementary school, were also made observations and analysis about the official documents which regulates the program. Our results showed that ProInfo presents various interferences in its effectiveness, causing a gap between its marks and the actual results of its use in everyday life of schools. We ve concluded that the program needs to challenge these weaknesses in order to contribute to the promotion of functionings and expanding its capabilities