182 research outputs found

    Synthesis of titanate nanofibers co-sensitized with ZnS and Bi2S3 nanocrystallites and their application on pollutants removal

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    The synthesis of nanocomposite materials combining titanate nanofibers (TNF) with nanocrystalline ZnS and Bi2S3 semiconductors is described in this work. The TNF were produced via hydrothermal synthesis and sensitized with the semiconductor nanoparticles, through a single-source precursor decomposition method. ZnS and Bi2S3 nanoparticles were successfully grown onto the TNF's surface and Bi2S3-ZnS/TNF nanocomposite materials with different layouts were obtained using either a layer-by-layer or a co-sensitization approach. The samples' photocatalytic performance was first evaluated through the production of the hydroxyl radical using terephthalic acid as probe molecule. All the tested samples show photocatalytic ability for the production of this oxidizing species. Afterwards, the samples were investigated for the removal of methylene blue. The nanocomposite materials with best adsorption ability for the organic dye were the ZnS/TNF and Bi2S3ZnS/TNF. The removal of the methylene blue was systematically studied, and the most promising results were obtained considering a sequential combination of an adsorption-photocatalytic degradation process using the Bi2S3ZnS/TNF powder as a highly adsorbent and photocatalyst material.Comment: 26 pages, 10 figure

    Efeito do NPK, via foliar, no conteúdo de nutrientes das folhas do algodoeiro (Gossypium hirsutum L.)

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    This research was carried out in greenhouse situated in the Escola Superior de Agricultura Luiz de Queiroz, São Paulo State, Brazil, in 1975/76, to study the influence of NPK spraying on leaves, on the NPK com position in leaves to cotton plant (Gossypium hirsutum L.) cv. IAC-13-1. The experimental design was a Randomized Complete Blocks with the treatments combined in a 2 x 3³ factorial with 3 replications. The treatments were: spraying-two (4 and 8), fertilizers three (N,P,K) in three levels (0,1,2). This three levels had the following averages according to the number of spraying, such as: four spraying - N0 = 0, N1 = 0,44, N2 = 0,84; P0 = 0, P1= 0,05, P2 = 0,09; K0 = 0, K1 = 0,33, K2 = 0,66; eight spraying - N0 = 0; N1 = 0,91, N2 = 1,87; P0 = 0, P1 = 0,10, P2 = 0,20; K0 = 0, K1 = 0,70, K2 = 1,40. The levels are expressed in Kg/ha and the source of fertilizers used were; NH4NO3; NaH2PO5H2O and KC1 for N, P(2)0(5) and K(2)0 respectively. The evaluation of the treatments were done based upon: percentage of N, P, K dry matter of young leaves and old leaves. The following conclusions could be drawn from this research: the N caused increase in P level in old leaves. The cotton plants no treated with N increased the percentage of K in old leaves. The P caused reduction in N levels in old and young leaves; increased the P levels in old leaves in N presence. The K increased the P leavel in old and young leaves, descreased the K levels in old leaves.O experimento foi conduzido em vasos, nas condições de casa de vegetação da Escola Superior de Agricultura "Luiz de Queiroz", Estado de São Paulo, Brasil, no período de 1975/76. O objetivo foi verificar a influência de pulverizações foliares com NPK na composição de N, P, K nas folhas velhas e folhas novas do algodoeiro (Gossypium hirsutum L.) cv. IAC-13-1. O delineamento experimental foi inteiramente casualizado em esquema fatorial 2 x 3³, em três repetições; sendo dois números de pulverizações (4 e 8), três macronutrientes (N, P, K) em três dosagens (0, 1,2). Cada parcela foi constituída por um vaso com duas plantas. Os tratamentos utilizados constam da Tabela 1 . Os níveis com seus valores médios de N, P2O5 e K2O utilizados em 4 pulverizações: N0=0,N1=0,44,N2=0,84; P0=0, P1= 0,05, P2=0,09; K0=0,K1=0,33,K2=0,66, em 8 pulverizações, N0=0,N1=0,91,N2=1,87; P0=0,P1=0,10, P2=0,20; K0=0,K1=0,70, K2=1,40 em kg/ha, sendo fontes de nutrientes o NH4N0(3), NaH2P0(4)H(2)0 e KCl para N, P(2)0(5) e K(2)0 respectivamente. Os parâmetros empregados na avaliação dos tratamentos foram: teores de N, P, K em folhas velhas e novas do algodoeiro. Nas condições dos experimentos pode-se tirar as seguintes conclusões: A aplicação do efeito quadrático nos seus teores encontrados nas folhas novas apenas em 8 pulverizações, provocando aumento dos teores de P nas folhas velhas. Os algodoeiros não tratados com N revelaram maior teor de K na matéria seca das folhas velhas. O P causou diminuição dos teores de N nas folhas velhas e novas; aumentou os teores de P nas folhas velhas, quando em presença de N. O K aumentou o P nas folhas velhas e novas, diminuiu, porém, o seu teor nas folhas velhas

    Spectrophotometric Determination Of Boron In Plants Using Monosegmented Continuous Flow Analysis

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    A monosegmented continuous flow analysis (MCFA) procedure for the spectrophotometric determination of boron using azomethine-H as colour reagent is presented. Under the experimental conditions described the calibration graph is linear up to 4.00 μg ml-1. The detection limit found is 0.02 μg ml-1, calculated from three times the standard deviation of the blank signal. The common interfering elements present in plants were investigated under dynamic MCFA conditions. As expected, iron and copper present the most severe interferences. This MCFA method for the determination of boron was used with test samples from the Plant Sample Exchange Programme (PSEP) of the Wageningen Agricultural University. The results compared favourably with those obtained by the conventional static procedure and those published by the PSEP.113289293CNRS/IN2P3; NSF; Arthritis National Research Foundation; NRF-2012004024; ANRF; Arthritis National Research Foundatio

    Electrochemical behavior of Ti/Al2O3 interfaces produced by diffusion bonding

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    In the field of biomedical applications a special interest exists regarding the study of the physicochemical and mechanical behaviour of materials, with special focus on the electrochemical degradation of metal/ceramic interfaces. In fact, etal/ceramic interfaces may be present in several biomedical devices, ranging from external or implantable sensors, to dental implants. Diffusion bonding represents an important technique since, in opposition to other production technologies, such as active metal brazing, avoid the possible liberation of certain chemical components harmful to health. The aim of this work is to study the electrochemical degradation of the interface formed between commercially pure Ti and Al2O3 produced by diffusion bonding, in contact with a physiological solution. The present approach included the evaluation of the contribution of individual and pairs of interfacial layers on the global degradation processes. For this propose d.c. electrochemical techniques were used to monitor the open-circuit potential, and to perform potentiodynamic polarization and galvanic corrosion evaluation. Also, electrochemical impedance spectroscopy was used as a complementary technique of the corrosion behaviour of the interface. Chemical composition and morphology of samples and corrosion products were evaluated by SEM and EDS analysis. According to experimental results, two principal reaction layers were formed in the interface: TiAl and Ti3Al. The TiAl layer appears to be the responsible for the strong increase in corrosion rate of the interface.Fundação para a Ciência e Tecnologia -POCTI/CTM/33384/2000; SFRH/BPD/ 5518/2001

    Balanços energéticos agropecuários: uma importante ferramenta como indicativo de sustentabilidade de agroecossistemas.

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    No Brasil, pouca atenção se tem dado às formas e caminhos com que os fluxos energéticos se distribuem nos sistemas produtivos. Na agropecuária, a atenção tem sido voltada a novas fontes de energia (biomassa) ou em tecnologia alternativa, visando a racionalização do uso de energia fóssil ou elétrica. Entretanto, a agricultura tem se desenvolvido baseada fortemente na utilização intensiva de máquinas agrícolas, com conseqüente uso de combustíveis fósseis. Um fator de estrangulamento muito forte no consumo energético geral tem sido a utilização massiva de fertilizantes derivados do petróleo nos agroecossistemas. Estudos de Balanços Energéticos visam determinar os pontos de estrangulamento energético fundamentando a busca por tecnologias poupadoras de energia, especialmente aquelas de origem fóssil (combustível, fertilizante, agrotóxicos, energia despendida na fabricação das máquinas e implementos, etc.). No Brasil, a Região Sul, é onde se encontram vários trabalhos buscando uma agricultura mais auto-sustentável, do ponto de vista da utilização da energia. Em vista da possibilidade de eventuais futuras crises energéticas, o presente trabalho procura analisar o estado-da-arte dos estudos em Balanço Energético, no Brasil e no Mundo, como uma ferramenta de indicação da sustentabilidade dos sistemas agropecuários

    Alfvén wave heating and runaway discharges in the TCABR tokamak

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    Recent results of experiments on Alfvén wave heating and runaway discharges carried out in the TCABR tokamak are presented. A new antenna type has been installed to allow wave excitation with higher RF currents and lower dynamic polarization of the antenna straps than for the one previously used. In spite of edge plasma heating, which causes influx of impurities, we have obtained a clear confirmation of wave deposition inside the plasma from a localized increase of the electron temperature measured with the ECE radiometer. Detailed profiles of the plasma density and Ha emission were obtained in runaway disharges with currents around 100 kA. These profiles confirm our model of a low-temperature plasma maintained in equilibrium by the relativistic electron beam. Analysis of the Ha and density spikes indicate that recombination plays a substantial role in the particle and energy balance
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