Sample records for distribution constants
from WorldWideScience.org

Sample records 1 - 5 shown.



1

Distribuição de metais e caracterização das constantes de troca entre espécies metálicas e frações húmicas aquáticas de diferentes tamanhos moleculares/ Metal distribution and characterization of exchange constants between metal species and aquatic humic fractions with different molecular sizes

Araújo, Adriana Barbosa; Rosa, André Henrique; Rocha, Julio Cesar; Romão, Luciane Pimenta Cruz
2002-12-01

Resumo em inglês In this work the metal distribution and exchange constants between metal species and aquatic humic fractions with different molecular sizes were studied. The aquatic humic substances (AHS) were extracted by XAD-8 resin from water sample collected from Itapitanguí river, São Paulo State, Brazil. The AHS were fractionated in six fractions with different molecular sizes (>100 - (mais) or fractions F1 and F6 whereas molar ratios C/N didn´t show any differences regarding the humification degree between the fractions. The UV-Vis absorbance a254/a436 ratio showed higher results for F4 and F5, probably by less condensed features. FTIR studies showed high similarity in the functional groups in the fractions. The highest percentage of traces of Co, Al, Fe, Mn, Cu, Zn and Ni (determined by ICP-AES) was preferably complexed by fractions F3 and F4 with a greater amount of dissolved organic carbon (DOC). In addition, the exchange constants, determined by ultrafiltration method, showed complexes AHS-Fe and AHS-Al with higher stability than complexes AHS-Co in all fractions.

Scientific Electronic Library Online (Portuguese)

2

Processamento e avaliação das propriedades de tubos cerâmicos porosos para microfiltração de emulsões/ Processing and evaluation of porous ceramics for micro filtration of emulsions

Rosa, D. S.; Salvini, V. R.; Pandolfelli, V. C.
2006-06-01

Resumo em português Cerâmicas porosas têm sido utilizadas em diversas aplicações tecnológicas como coletores de partículas sólidas, isolantes térmicos e acústicos. As áreas de biotecnologia e biomedicina utilizam cerâmicas porosas como reatores em processos de fermentação e em implantes, respectivamente. Adicionalmente, estes materiais apresentam grande aplicação na área de microfiltração de líquidos e emulsões, como a purificação de combustíveis através da separaçã (mais) o da água e óleo, e na separação das proteínas do leite. O objetivo deste trabalho é o de produzir tubos de cerâmicas porosas para microfiltração de combustíveis. A primeira etapa compreendeu a produção de tubos cerâmicos porosos por colagem de suspensões e avaliação de suas propriedades físicas, fluidodinâmicas e mecânicas finais. Já a segunda etapa consistiu na análise do desempenho destes tubos durante a microfiltração de combustíveis. As propriedades finais das cerâmicas porosas foram avaliadas em função das variações na composição da suspensão e nas condições de queima. Após queima, os tubos cerâmicos apresentaram porosidade na faixa de 48 a 65%, distribuição estreita de diâmetro de poros menores que 1 µm, e constantes de permeabilidade Darciana (k1) e não Darciana (k2) da ordem de 10-15 m² e 10-11 m, respectivamente. Essas propriedades são similares aos tubos comerciais importados e, portanto, essas cerâmicas porosas desenvolvidas têm um grande potencial de aplicação em processos de microfiltração. Resumo em inglês Porous ceramics have been applied in a broad range of technological purposes, such as dust collectors, thermo-acoustic insulators and burners. In the biotechnology and biomedicine areas, porous ceramics have been applied as reactors in fermentation processes and as implants, respectively. Besides that, they can also be used in the micro filtration process of liquids and emulsions, such as fuel purification through separation of water from oil, and in the separation of pro (mais) teins of the milk. The objective of this work is the production of porous ceramics tubes for fuel micro filtration. The first stage of the research was the production of porous ceramics by colloidal processing and evaluation of its final physical, fluid dynamic and mechanical properties. In a second stage the performance of these ceramic tubes during the micro filtration of fuel was analysed. The final properties of porous ceramics were evaluated according to the changes in the composition and sintering conditions. After firing, the ceramic tubes had their porosity in the range of 48 to 65%-vol, narrow distribution with pore diameters bellow than 1 µm and constants of Darcian (k1) and nonDarcian (k2) permeability of 10-15 m² and 10-11 m, respectively. These properties are similar to the commercial imported products and therefore these ceramics have a great potential of application in micro filtration processes.

Scientific Electronic Library Online (Portuguese)

3

Índice climático de crescimento para gramíneas forrageiras no Estado de São Paulo/ Climatic growth index for forage grasses in the State of São Paulo (Brazil)

Pedro Júnior, Mário José
1995-01-01

Resumo em português Utilizou-se o índice climático de crescimento (ICC) para gramíneas forrageiras, com base em temperatura, radiação solar e relação entre evapotranspiração real e potencial, a fim de estimar a produção de matéria seca (TAMS) de capim-colonião, gordura, jaraguá e pangola através da seguinte equação exponencial: ICC = a EXP (b ICC), onde a e b são constantes que diferem para cada espécie. Determinou-se o índice climático médio mensal para 47 localidades (mais) paulistas e regiões limítrofes. A variação espacial do índice para o inverno e para o verão é apresentada em forma de mapas. Os valores de ICC no inverno, período crítico, variaram de 0,1 a 0,15 na região central do Estado; no Norte e no Oeste, foram superiores a 0,15 e, na Serra da Mantiqueira, inferiores a 0,1. Resumo em inglês The climatic growth index (ICC) for forage grasses, based on temperature, solar radiation and the ratio of actual to potential evapotranspiration, was used to estimate dry matter production (TAMS) for the following grasses: "colonião" (Panicum maximum Jacq), "gordura" (Melinis minutiflora Pal de Beauv), "jaraguá" (Hyparrhenia rufa (Ness) Stapf) and "pangola" (Digitaria pentzii Stent), using exponential equations: ICC = a EXP (b ICC), where a and b are constants which di (mais) ffer for each specie analised. The monthly mean climatic index was calculated for forty seven localities of the State of São Paulo and neighbours. Its spatial distribution considering summer and winter is shown as maps. ICC values during the critical season of the winter varied from 0.1 to 0.15 for the central part of the State; at the northern and western regions it is larger than 0.15 and at the "Mantiqueira" mountains it is less than 0.1.

Scientific Electronic Library Online (Portuguese)

4

Método de estudo da adsorção de triadimenol com micro-colunas de solo e centrifugação/ Method for adsorption study of triadimenol using soil micro-columns and centrifugation

Guerreiro, Mário César; Anastácio, Alexandre dos Santos; Lima, José Maria de
2004-06-01

Resumo em inglês Normally, the determination of equilibrium constants (k d) in batch experiments uses a high solution to soil ratio, which does not represent field conditions. In this study we present an alternative method to evaluate adsorption constants, using micro-columns of soil at higher soil to solution ratios. The centrifugation force and equilibration time were investigated. The triadimenol distribution along the column profile is controlled by diffusion and equilibration times g (mais) reater than 24 h are needed to achieve reproducibility. The centrifugation force must be superior to 670 g in order to guarantee enough extraction of the liquid solution from the soil columns.

Scientific Electronic Library Online (Portuguese)

5

Complexação da tetraciclina, da oxitetraciclina e da clortetraciclina com o catião cobre (II). Estudo potenciométrico/ Tetracycline, oxytetracycline and chlortetracycline complexation with copper (II). Potentiometric study

Couto, Cristina M. C. M.; Montenegro, M. Conceição B. S. M.; Reis, Salette
2000-08-01

Resumo em inglês Stability constants of complexes formed by copper (II) with three different tetracyclines (tetracycline, oxytetracycline and chlortetracycline) have been determined potentiometrically with an automatic system in aqueous medium at 25,0 ± 0,2 ºC and I = 0,1 mol L-1 NaNO3. The protonation constants of the three tetracyclines were also determined under the same conditions. The distribution of the complexes was then simulated at therapeutic levels of the drugs.

Scientific Electronic Library Online (Portuguese)