Mechanically activating formation of layered structured bismuth titanate

Bismuth titanatc-Bi(4)Ti(3)O(12) (BIT) with wide application in the electronic industry as capacitors, memory devices and sensors is the simplest compound in the Aurivillius family, which consists of (Bi(2)O(2))(2+) sheets alternating with (Bi(2)T(i)3O(10))(2-) perovskite-like layers. The synthesis of more resistive BIT ceramics would be preferable advance in obtaining of well-densified ceramic with small grains randomly oriented to limit the conductivity along the (Bi(2)O(2))(2+) layers. Having in mind that the conventional ceramic route for the synthesis can lead to non-stoichiometry in composition, in consequence of the undesirable loss in bismuth content through volatilization of Bi(2)O(3) at elevated temperature, our efforts were addressed to preparation of BIT by mechanical activation the constituent oxides. The nucleation and phase formation of BIT, crystal structure, microstructure, powder particle size and specific surface area were followed by XRD, Rietveld refinement analysis, thermal analysis, scanning electron microscopy (SEM) and the BET specific surface area measurements. (c) 2005 Elsevier B.V. All rights reserved.

Procedure optimization of silicate rocks dissolution in open vessels for ICP-AES analysis.

The main variables found on procedure of the dissolution silicate rocks using acid dissolution in teflon open vessel for analysis of micro elements by ICP-AES has been determined. The results obtained for some samples showed strong dependence of the rock mineralogical composition, then it was recommended an alkaline fusion step after acid dissolution. The decomposition procedure use 20 mi of an acid mixture of HF:HNO3 in the proportion 3:1 for a fraction of 250 mg pulverized sample. The recommended temperatures were 60 degrees C for attack and 90 degrees C for acid volatilization. The fusion step with 50 mg LiBO2 at 1000 degrees C may be used if non-attacked residue is observed in the solution. The whole time was 6 h per sample. Nine types os silicate rocks that show mineralogical and chemical different compositions were chosen for obtaining the optimization of the variables. The elements used were Ce, Y, Yb and Zr. In addition, ultrassonic nebulization has been used. The percentual standard deviations obtained for five determinations were 0.7 and 1.4 for triplicate samples. The mineralogical and textural information from the petrographical analysis of the samples indicated the need of increasing the fusion step on the optimized procedure.

Environmental implications of soil remediation using the Fenton process

This work evaluates some collateral effects caused by the application of the Fenton process to 1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane (DDT) and diesel degradation in soil. While about 80% of the diesel and 75% of the DDT present in the soil were degraded in a slurry system, the dissolved organic carbon (DOC) in the slurry filtrate increased from 80 to 880 mg l(-1) after 64 h of reaction and the DDT concentration increased from 12 to 50 mu g l(-1). Experiments of diesel degradation conducted on silica evidenced that soluble compounds were also formed during diesel oxidation. Furthermore, significant increase in metal concentrations was also observed in the slurry filtrate after the Fenton treatment when compared to the control experiment leading to excessive concentrations of Cr, Ni, Cu and Mn according to the limits imposed for water. Moreover, 80% of the organic matter naturally present in the soil was degraded and a drastic volatilization of DDT and 2,2-bis(4-chlorophenyl)-1,1-dichloroethylene was observed. Despite the high percentages of diesel and DDT degradation in soil, the potential overall benefits of its application must be evaluated beforehand taking into account the metal and target compounds dissolution and the volatilization of contaminants when the process is applied. (c) 2007 Elsevier Ltd. All rights reserved.

Dissipation of DDT in a heavily contaminated soil in Mato Grosso, Brazil

After the prohibition of organochlorine-pesticide use in Brazil for controlling insect vector diseases, Mato Grosso State gathered the exceeding DDT and stored it irregularly in an open air area that belongs to the National Health Foundation, causing soil contamination. This study aimed to evaluate the contamination level and dissipation of p,p′-DDT and p,p′-DDE in this area. For that, surface soil samples were collected on 19 September 2000, 15 December 2000, 4 April 2001 and soil samples 30-40 cm; 60-70 cm and 90-100 cm deep were taken from five points in the studied area on 17 July 2001. The contaminants were determined by a small scale method which consists on extraction and clean-up steps combined into one step by transferring soil samples mixed with neutral alumina to a chromatographic column prepacked with neutral alumina and elution with hexane:dichloromethane (7:3 v:v). The eluate was concentrated and the analytes were quantified by gas chromatography with an electron-capture detector. p,p′-DDT at surface soil ranged from 3800 to 7300 mg kg -1. 30-40 cm deep soil sample concentrations varied from 0.036 to 440 mg kg -1 while 90-100 cm deep samples varied from 0.069 to 180 mg kg -1. Volatilization is probably the main dissipation process. The p,p′-DDT is moving slowly downward in the soil profile, however, the levels of this contaminant are high enough to present risk to underground waters. © 2005 Elsevier Ltd. All rights reserved.

Relação entre a adubação nitrogenada e as condições hídricas do solo para um cafezal de Piracicaba, SP

Although the management of the coffee crop is well established in Brazil, there is still room for its improvement in relation natural resources available in each region, aiming the increase in productivity. Here are presented results regarding the fate of the fertilizer nitrogen (N) applied to a coffee plantation related to the prevailing soil water conditions. Soil water balances are discussed, which allowed evaluation of the root distribution, determinations of the crop coefficient and of the soil water conditions during the development of the crop. Approximately, 60% of the root system was distributed in the 0-0.3 m soil layer and the average crop coefficient was 1.1 for 3 to 5 year old plants. Using an N label, the 15N, it was possible to study the distribution of N in the plant and in the soil and establishes general N balances, which also include losses like leaching and volatilization. After two years of ammonium sulfate application, at rates of 280 (1st year) and 350 (2nd year) kg.ha-1 of N, in four equal application performed during the period of positive growth rate, the recuperation of fertilizer N were 19.1% by the aerial plant part and 9.4% by the roots, 12.6% remained in the soil and 11.2% in the litter; 0.9% was lost by volatilization and 2.3% by leaching; 26.3% was exported through harvesting and 18.2% remained in non evaluated compartments. From the applied 630 kg.ha -1 of N during the two years, 180 kg.ha -1 of N were found in the plant (shoot and root), which corresponds to 28.6%; 150 kg.ha -1 of N remained available for the next years(soil and litter), and only 20 kg.ha -1 of N were effectively lost (volatilization and leaching).

Essential oils from medicinal and aromatic plants: A review of the gastroprotective and ulcer-healing activities

Gastric ulcer is an excoriated area of the gastric mucosa. It is among the predominant gastrointestinal chronic diseases. The essential oils represent an important part of the traditional pharmacopoeia in many countries and have been successfully used for gastroprotection and ulcer healing. Thus, this review presents the experimental activity of essential oils traditionally used in the gastric ulcer prevention and treatment, considering their families, part of the plant studied, bioassays, and their mechanisms of gastroprotection and ulcer healing, with the aim of stimulating novel studies in the search for a new phytomedicine to treat gastric diseases. © 2012 The Authors Fundamental and Clinical Pharmacology © 2012 Société Française de Pharmacologie et de Thérapeutique.

Fontes e doses de nitrogênio na nutrição, produção e qualidade do feijoeiro

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Estudo dos processos de nucleação e cristalização em vidros boratos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Síntese de perovskitas nanométricas com estrutura 'PB IND.1-x''M IND.X''TI''O IND.3'(M='BA', 'CA' e 'SR')

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Avaliação da presença de vapores no solo em antiga área industrial contaminada por hidrocarbonetos: concentrações medidas e simuladas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Coletores de amônia, fontes e formas de aplicação de nitrogênio em Panicum maximum CV. Tanzânia submetido a manejo intensivo

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Caracterização térmica de sacarose de cana-de-açúcar: amostras de padrão de referência, comercial e purificada

Pós-graduação em Química - IBILCE

Estudo da mobilidade do crômio em área de descarte inadequado de resíduos de couro: possível contaminação de solos, águas e sedimentos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Fontes e doses de nitrogênio revestidas ou não por polímeros na cultura do milho

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Avaliação do controle de azevém (Lolium multiflorum) nas condições de cana crua em Louisiana/EUA e dinâmica dos herbicidas na palha

Pós-graduação em Agronomia (Agricultura) - FCA