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Estudo do efeito inibidor do solicato de sódio na corrosão de uma liga de ali-mg-si, em meio de diferentes concentrações de cloreto

Souza, Jupiter Palagi de
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
POR
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26.72%
No presente trabalho, estudou-se o efeito inibidor do silicato de sódio na corrosão de uma liga de AI-Mg-Si em meio arejado e desarejado, contendo quantidades variadas de Ion cloreto no pW = 10,O . Nos diferentes tipos de ensaios realizados, tais como, traçado de curvas de polarização, ensaios galvanostáticos e com par galvânico, utilizou-se corpos de prova anodizados ou polidos. Os resultados experimentais mostraram que 1 g/l de silicato de sódio neutro de composição Na2O : 3.3 SiO2, demonstrou total efeito inibidor da corrosão da liga de A1-Mg-Si, em solução contendo até 60 p.p.m. de NaC1. Em concentrações de 1060 p.p,m. e maiores de NaC1, o silicato mostrou apenas efeito retardador da corrosão, com diminuição da incidência de pites. A análise dos produtos de corrosão, formadas sobre a superficie dos pites, feita usando-se raio-X e espectroscopia de infravermelho, mostrou que esses produtos têm estrutura amorfa e contêm silicato e grupos hidroxila. Finalmente, medidas de capacitância da dupla camada, confirmaram a existência de uma película que se forma sobre a superfície da liga de alumínio, quando em solução de silicato.; The present work analyses the inhibitor effect of sodium silicate on the corrosion of an A1-Mg-Si alloy in aereated and deaereated solutions containing varying amounts of chlorfde ions...

Root instrumentation with an erbium:yttrium-aluminum-garnet laser: Effect on the morphology of fibroblasts

Rossa Júnior, Carlos; Silvério, Karina G.; Zanin, Iriana C. J.; Brugnera Júnior, Aldo; Sampaio, José Eduardo C.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 496-502
ENG
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Objective: The purpose of this study was to evaluate the effect of erbium:yttrium-aluminum-garnet laser instrumentation of root surfaces on the morphology of fibroblasts from continuous lineage. Method and materials: Dentinal slices with 4 mm2 of surface area were obtained from teeth extracted for severe periodontal involvement. Specimens were assigned to one of three treatment groups: group 1, application of the laser with an energy level of 250 mJ at 103 pulses per second; group 2, application of the laser with an energy level of 80 mJ at 166 pulses per second; and group 3, similar to group 2, but with concomitant water irrigation of the device. The specimens were incubated in multiwell plates containing cell culture media. After 24 hours, the specimens were submitted to routine preparation for scanning electron microscopy. Three independent and blind examiners used photomicrographs to evaluate the morphology of the fibroblasts: 0 = without cells; 1 = flat cells; 2 = round cells; and 3 = combination of round and flat cells. Results: Statistical analysis indicated that there were significant differences among treatment groups and that group 3 was significantly different from groups 1 and 2. Conclusion: There was no difference between groups 1 and 2 in the morphology of fibroblasts. Laser instrumentation with concomitant irrigation impaired the adhesion of fibroblasts to dentinal surfaces.

Comparison of the shear bond strengths of conventional mesh bases and sandblasted orthodontic bracket bases

Torres Lugato, Isabel Cristina Prado; Pignatta, Lilian Maria Brisque; Arantes, Flávia de Moraes; Santos, Eduardo César Almada
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 407-414
ENG
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36.45%
This study aimed to compare in vitro the shear bond strength between metallic brackets (Abzil) with conventional mesh bases and metallic brackets with bases industrially sandblasted with aluminum oxide using three adhesive systems, in order to assess the influence of sandblasting on adhesiveness and to compare 3 different bonding systems. Two hundred and forty bovine incisors were used and randomly divided into 6 groups (40 teeth in each group), according to the bracket base and to the bonding system. The brackets were direct-bonded in bovine teeth with 3 adhesive systems: System A - conventional Transbond™ XT (3M -Unitek); System B - Transbond™ Plus Self Etching Primer + Transbond™ XT (3M - Unitek) and System C - Fuji ORTHO LC resin-reinforced glass ionomer cement in capsules (GC Corp.). Shear bond strength tests were performed 24 hours after bonding, in a DL-3000 universal testing machine (EMIC), using a load cell of 200 kgf and a speed of 1 mm/min. The results were submitted to statistical analysis and showed no significant difference between conventional and sandblasted bracket bases. However, comparison between the bonding systems presented significantly different results. System A (14.92 MPa) and system C (13.24 MPa) presented statistically greater shear bond strength when compared to system B (10.66 MPa). There was no statistically significant difference between system A and system C.

Characterization and nutrient release from silicate rocks and influence on chemical changes in soil

Silva,Douglas Ramos Guelfi; Marchi,Giuliano; Spehar,Carlos Roberto; Guilherme,Luiz Roberto Guimarães; Rein,Thomaz Adolpho; Soares,Danilo Araújo; Ávila,Fabrício William
Fonte: Sociedade Brasileira de Ciência do Solo Publicador: Sociedade Brasileira de Ciência do Solo
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2012 EN
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26.53%
The expansion of Brazilian agriculture has led to a heavy dependence on imported fertilizers to ensure the supply of the growing food demand. This fact has contributed to a growing interest in alternative nutrient sources, such as ground silicate rocks. It is necessary, however, to know the potential of nutrient release and changes these materials can cause in soils. The purpose of this study was to characterize six silicate rocks and evaluate their effects on the chemical properties of treated soil, assessed by chemical extractants after greenhouse incubation. The experimental design consisted of completely randomized plots, in a 3 x 6 factorial scheme, with four replications. The factors were potassium levels (0-control: without silicate rock application; 200; 400; 600 kg ha-1 of K2O), supplied as six silicate rock types (breccia, biotite schist, ultramafic rock, phlogopite schist and two types of mining waste). The chemical, physical and mineralogical properties of the alternative rock fertilizers were characterized. Treatments were applied to a dystrophic Red-Yellow Oxisol (Ferralsol), which was incubated for 100 days, at 70 % (w/w) moisture in 3.7 kg/pots. The soil was evaluated for pH; calcium and magnesium were extracted with KCl 1 mol L-1; potassium...

Performance of lowland rice seeds coated with dolomitic limestone and aluminum silicate

Tavares,Lizandro Ciciliano; Rufino,Cassyo de Araújo; Dörr,Caio Sippel; Barros,Antônio Carlos Souza Albuquerque; Peske,Silmar Teichert
Fonte: Associação Brasileira de Tecnologia de Sementes Publicador: Associação Brasileira de Tecnologia de Sementes
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2012 EN
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46.99%
The objective of this study was to evaluate the performance of seeds of two cultivars of lowland rice (Oryza sativa L.), coated with dolomitic limestone and aluminum silicate. It was used a completely randomized experimental design, with the treatments arranged in a 4 X 2 factorial scheme [4 treatments: dolomitic limestone; dolomitic limestone + aluminum silicate; aluminum silicate, at the dosages of 50 g/100 kg of seeds; and control (without the products) X 2 cultivars: IRGA424 and IRGA 422 CL], totaling eight treatments with four replications each. The variables analyzed were: fresh and dry weights of aerial biomass; plant height; leaf area at 10, 20, and 30 days after emergence (DAE). The physiological quality of seeds was also assessed using tests of: seed emergence; first count of germination; emergence speed index; and field emergence. It was concluded that the coating of rice seeds with dolomitic limestone and aluminum silicate does not affect seed germination and field seedling emergence. Aluminum silicate used via seed coating on cultivar IRGA 424 promoted greater leaf area, after 20 DAE. The dolomitic limestone and the aluminum silicate used via seed coating generated plants with larger dry biomass, after 20 DAE, for the cultivar IRGA 422 CL.

Aluminum-dependent regulation of intracellular silicon in the aquatic invertebrate Lymnaea stagnalis

Desouky, Mahmoud; Jugdaohsingh, Ravin; McCrohan, Catherine R.; White, Keith N.; Powell, Jonathan J.
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
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Silicon is essential for some plants, diatoms, and sponges but, in higher animals, its endogenous regulation has not been demonstrated. Silicate ions may be natural ligands for aluminum and here we show that, in the freshwater snail (Lymnaea stagnalis), intracellular silicon seems specifically up-regulated in response to sublethal aluminum exposure. X-ray microanalysis showed that exposure of snails to low levels of aluminum led to its accumulation in lysosomal granules, accompanied by marked up-regulation of silicon. Increased lysosomal levels of silicon were a specific response to aluminum because cadmium and zinc had no such effect. Furthermore, intra-lysosomal sulfur from metallothionein and other sulfur-containing ligands was increased after exposure to cadmium and zinc but not aluminum. To ensure that these findings indicated a specific in vivo response, and not ex vivo formation of hydroxy-aluminosilicates (HAS) from added aluminum (555 μg/liter) and water-borne silicon (43 μg/liter), two further studies were undertaken. In a ligand competition assay the lability of aluminum (527 μg/liter) was completely unaffected by the presence of silicon (46 μg/liter), suggesting the absence of HAS. In addition, exogenous silicon (6.5 mg/liter)...

Polymer–Magnesium Aluminum Silicate Composite Dispersions for Improved Physical Stability of Acetaminophen Suspensions

Pongjanyakul, Thaned; Puttipipatkhachorn, Satit
Fonte: Springer US Publicador: Springer US
Tipo: Artigo de Revista Científica
Publicado em 25/03/2009 EN
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The aims of this study were to characterize the morphology and size of flocculates and the zeta potential and rheological properties of polymer–magnesium aluminum silicate (MAS) composite dispersions and to investigate the physical properties of acetaminophen (ACT) suspensions prepared using the composite dispersions as a flocculating/suspending agent. The polymers used were sodium alginate (SA), sodium carboxymethylcellulose (SCMC), and methylcellulose (MC). The results showed that SA, SCMC, and MC could induce flocculation of MAS by a polymer-bridging mechanism, leading to the changes in the zeta potential of MAS and the flow properties of the polymer dispersions. The microscopic morphology and size of the flocculates was dependent on the molecular structure of the polymer, especially ether groups on the polymer side chain. The residual MAS from the flocculation could create a three-dimensional structure in the SA–MAS and SCMC–MAS dispersions, which brought about not only an enhancement of viscosity and thixotropic properties but also an improvement in the ACT flocculating efficiency of polymers. The use of polymer–MAS dispersions provided a higher degree of flocculation and a lower redispersibility value of ACT suspensions compared with the pure polymer dispersions. This led to a low tendency for caking of the suspensions. The SCMC–MAS dispersions provided the highest ACT flocculating efficiency...

Sodium alginate-magnesium aluminum silicate composite gels: Characterization of flow behavior, microviscosity, and drug diffusivity

Pongjanyakul, Thaned; Puttipipatkhachorn, Satit
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
Publicado em 07/09/2007 EN
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The aims of the present study were to characterize the flow behavior and thixotropic properties of sodium alginate-magnesium aluminum silicate (SA-MAS) composite gels with various ratios of SA and MAS, and to investigate the drug diffusivity and microviscosity of the composite gels. Moreover, interaction of SA and MAS in the form of dry composite was examined by using Fourier Transform Infrared (FTIR), and a possible structure model of SA-MAS composite gel was illustrated. Incorporating MAS into the SA gels provided higher viscosity and changed the flow behavior from Newtonian to pseudoplastic with thixotropy. This was due to the formation of electrostatic force and inter-molecular hydrogen bonding between SA and MAS, leading to a denser matrix structure of the composite gels. Increasing the content of MAS decreased the drug diffusivity but increased the microviscosity of the composite gels. The denser matrix structure of the composite gels had a higher tortuosity, resulting in slower drug diffusion through water-filled channels in the gels. This finding suggested that incorporating MAS into the SA gels could improve the flow behavior and sustain drug release from the gels because of the formation of a matrix structure between SA and MAS in the gels.

Preparation and Characterization of Nicotine–Magnesium Aluminum Silicate Complex-Loaded Sodium Alginate Matrix Tablets for Buccal Delivery

Kanjanabat, Sopaphan; Pongjanyakul, Thaned
Fonte: Springer US Publicador: Springer US
Tipo: Artigo de Revista Científica
Publicado em 19/05/2011 EN
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Nicotine (NCT) buccal tablets consisting of sodium alginate (SA) and nicotine–magnesium aluminum silicate (NCT–MAS) complexes acting as drug carriers were prepared using the direct compression method. The effects of the preparation pH levels of the NCT–MAS complexes and the complex/SA ratios on NCT release, permeation across mucosa, and mucoadhesive properties of the tablets were investigated. The NCT–MAS complex-loaded SA tablets had good physical properties and zero-order release kinetics of NCT, which indicate a swelling/erosion-controlled release mechanism. Measurement of unidirectional NCT release and permeation across porcine esophageal mucosa using a modified USP dissolution apparatus 2 showed that NCT delivery was controlled by the swollen gel matrix of the tablets. This matrix, which controlled drug diffusion, resulted from the molecular interactions of SA and MAS. Tablets containing the NCT–MAS complexes prepared at pH 9 showed remarkably higher NCT permeation rates than those containing the complexes prepared at acidic and neutral pH levels. Larger amounts of SA in the tablets decreased NCT release and permeation rates. Additionally, the presence of SA could enhance the mucoadhesive properties of the tablets. These findings suggest that SA plays the important role not only in controlling release and permeation of NCT but also for enhancing the mucoadhesive properties of the NCT–MAS complex-loaded SA tablets...

Influence of pH Modifiers and HPMC Viscosity Grades on Nicotine–Magnesium Aluminum Silicate Complex-Loaded Buccal Matrix Tablets

Pongjanyakul, Thaned; Kanjanabat, Sopaphan
Fonte: Springer US Publicador: Springer US
Tipo: Artigo de Revista Científica
Publicado em 03/05/2012 EN
Relevância na Pesquisa
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Hydroxypropyl methylcellulose (HPMC) tablets containing nicotine–magnesium aluminum silicate (NCT-MAS) complex particles and pH modifiers, namely, sodium chloride, citric acid, and magnesium hydroxide, were prepared using the direct compression method. The effects of HPMC viscosity grades and pH modifiers on NCT release and permeation of the matrix tablets were examined. The results showed that the higher the viscosity grade of HPMC that was used in the tablets, the lower was the unidirectional NCT release rate found. The unidirectional NCT permeation was not affected by the viscosity grade of HPMC because the NCT diffusion through the mucosal membrane was the rate-limiting step of the permeation. Incorporation of magnesium hydroxide could retard NCT release, whereas the enhancement of unidirectional NCT release was found in the tablets containing citric acid. Citric acid could inhibit NCT permeation due to the formation of protonated NCT in the swollen tablets at an acidic pH. Conversely, the NCT permeation rate increased with the use of magnesium hydroxide as a result of the neutral NCT that formed at a basic microenvironmental pH. The swollen HPMC tablets, with or without pH modifiers, gave sufficient adhesion to the mucosal membrane. Furthermore...

Manejo pós-colheita de Alpinia purpurata (Vieill) K. Schum (Zingiberaceae)

Silva, Antonio Tarciso Ciríaco da
Fonte: Universidade Federal de Alagoas; BR; Agronomia; Produção vegetal; Proteção de plantas; Programa de Pós-Graduação em Agronomia; UFAL Publicador: Universidade Federal de Alagoas; BR; Agronomia; Produção vegetal; Proteção de plantas; Programa de Pós-Graduação em Agronomia; UFAL
Tipo: Dissertação Formato: application/pdf
POR
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The growth of ornamental plant market in Brazil is remarkable nowadays with strong participation of Northeast region, particularly in Alagoas State on the commercialization of tropical flowers. Taking into account this economic aspect, it is of great importance for the productive chain of ornamental species the study of aspects of post harvest activities. Alpinia purpurata (Viell) K. Schum (Zingiberaceae) which occupies the second place in economic importance amongst tropical flowers. It is the main flower for growing and harvesting. The main objective of this research programme is to study the different aspects of Alpinia post-harvesting: (1) time of harvesting and cut of the basis of the stems, and (2) the use of solutions of pulsing ; and/or maintenance of the floral stem by using: (2.1.) biocide compounds and pH of the solution; (2.2) carbohydrates and carbohydrates plus biocides; (2.3) anti-ethylene compounds and antiethylene compounds plus carbohydrates; (2.4) elements as calcium and silicon; and (2.5) senescence retarding growth regulators. It was evaluated the influence of these factors in the water relations, quality and longevity of the stems. Six experiments were carried out in the laboratory (CECA) of the Federal University of Alagoas. In the first experiment...

Efeito da aplica????o de silicato de alum??nio no rendimento e qualidade de sementes de soja; Efeito da aplica????o de silicato de alum??nio no rendimento e qualidade de sementes de soja

SALINAS, Jadiyi Concepci??n Torales
Fonte: Universidade Federal de Pelotas; Agronomia; Programa de P??s-gradua????o em Ci??ncia e Tecnologia de Sementes; UFPel; BR Publicador: Universidade Federal de Pelotas; Agronomia; Programa de P??s-gradua????o em Ci??ncia e Tecnologia de Sementes; UFPel; BR
Tipo: Tese de Doutorado Formato: application/pdf
POR
Relevância na Pesquisa
26.95%
It was conducted three research projects aimed at better understanding of the effect of aluminum silicate on yield and quality of soybean seeds as a source of silicon in the mineral nutrition and plant protection. In the first study was evaluated the effect of five doses of aluminum silicate applied via foliar as a source of silicon in the mineral nutrition acting on the yield and quality of soybean seeds produced in Arroio Grande, Rio Grande do Sul, Brazil. In the second study was evaluated the effect of different doses of aluminum silicate, silicon source, applied to the soil and leaves in yield components of soybean seeds produced in San Lorenzo, Paraguay. And the third experiment was evaluated the effect of different doses and aluminum silicate, applied via foliar and soil as a source of silicon in the mineral nutrition and plant protection, acting as seeds produced in San Lorenzo, Paraguay. The results obtained in the three studies showed that aluminum silicate applied foliar or soil had no effect on yield components. Seeds from plants that received foliar or soil application of aluminum silicate. There are changes in their physiological quality.; Foram conduzidos tr??s trabalhos de pesquisa que visam melhor entender o efeito da aplica????o de silicato de alum??nio no rendimento e qualidade de sementes de soja como fonte de sil??cio na nutri????o mineral e prote????o de plantas. No primeiro trabalho avaliou-se o efeito de cinco doses de silicato de alum??nio aplicadas via foliar...

Desempenho de sementes de trigo recobertas com silicato de alum??nio; Performcance of seed wheat coated aluminum silicate

FONSECA, Daniel ??ndrei Robe
Fonte: Universidade Federal de Pelotas; Agronomia; Programa de P??s-gradua????o em Ci??ncia e Tecnologia de Sementes; UFPel; BR Publicador: Universidade Federal de Pelotas; Agronomia; Programa de P??s-gradua????o em Ci??ncia e Tecnologia de Sementes; UFPel; BR
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
46.88%
The present study, we used seeds of wheat, cv Fundacep horizon coated with six doses of aluminum silicate (0, 20, 30, 40, 50 and 60g per 100 kg seed). We conducted two research studies in order to verify the influence of the silicon used by seed, and to evaluate the physiological performance and yield components. In the first paper we studied the behavior of the physiological quality of seeds coated with aluminum silicate. The second was carried out the experiment evaluating the absorption by the plants and silicon influence on the rate of chlorophyll and the components of yield and quality physiological seed. The results showed that aluminum silicate improves the physiological quality of seeds have been subjected to stress and yield of wheat plants grown from seeds coated with aluminum silicate.; No presente trabalho utilizaram-se sementes de trigo, cultivar Fundacep Horizonte recobertas com seis doses de silicato de alum??nio (0, 20, 30, 40, 50 e 60 g por 100 kg de sementes). Foram conduzidos dois trabalhos de pesquisa no intuito de verificar a influ??ncia do sil??cio empregado via semente, bem como avaliar o desempenho fisiol??gico e os componentes de rendimento. No primeiro trabalho estudou-se o comportamento da qualidade fisiol??gica das sementes recobertas com silicato de alum??nio. No segundo foi realizado a condu????o do experimento avaliando-se a absor????o do sil??cio pelas plantas e a influ??ncia no ??ndice de clorofila...

Aduba????o silicatada na produ????o e qualidade de sementes e fibras de algod??o (Gossypium hirsutum L.); Aduba????o silicatada na produ????o e qualidade de sementes e fibras de algod??o (Gossypium hirsutum L.)

GAMA, Juliana Sim??es Nobre
Fonte: Universidade Federal de Pelotas; Agronomia; Programa de P??s-gradua????o em Ci??ncia e Tecnologia de Sementes; UFPel; BR Publicador: Universidade Federal de Pelotas; Agronomia; Programa de P??s-gradua????o em Ci??ncia e Tecnologia de Sementes; UFPel; BR
Tipo: Tese de Doutorado Formato: application/pdf
POR
Relevância na Pesquisa
46.67%
This research aimed to evaluate the effect of silicon on cotton, through variables agronomic, physiological, yield and fiber quality and seeds produced. The experiments were conducted in 2012 and 2013. In the first year of cultivation, were evaluated five levels of Si: 0, 1000, 2000, 3000 and 4000 kg Si ha-1, applied to soil, 0, 45, 60, 135 and 180 kg Si ha-1 foliar, and 0, 100, 200, 300 and 400 g kg seed-1, applied through seed coating. In the second year, were evaluated five levels: 0, 45, 60, 135 and 180 kg Si ha-1 and 0, 2000, 4000, 6000 and 8000 kg Si ha-1, applied via foliar and soil, respectively. The silicon source used is aluminum silicate. Evaluations were performed at 25, 50, 75 and 100 days from emergence (DAE). The results of the experiments allow to conclude that aluminum silicate applied by seed coating does not interfere in the physiological characteristics of cotton. However, when applied by foliar and soil, increases the chlorophyll index and reduces the diameter of the stem of cotton plants. In relation to yield, the number of seeds per fruit and number of fruit and seeds per plant were negatively affected with the increase of Si foliar applied. The silicon improves some physical characteristics of the fiber such as reflectance...

Efeito das aflatoxinas e dos adsorventes sobre o desempenho zoot??cnico de alevinos e juvenis de jundi?? (Rhamdia quelen).; Aflatoxin and adsorbent effects on jundi?? fingerlings and juveniles performance

LOPES, Paulo Rodinei Soares
Fonte: Universidade Federal de Pelotas; Zootecnia; Programa de P??s-Gradua????o em Zootecnia; UFPel; BR Publicador: Universidade Federal de Pelotas; Zootecnia; Programa de P??s-Gradua????o em Zootecnia; UFPel; BR
Tipo: Tese de Doutorado Formato: application/pdf
POR
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46.8%
Three experiments were carried out at the Ictyology Laboratory (Departamento de Zootecnia UFPel) to evaluate: a) - aflatoxin effects and b) - adsorptive action of 2 adsorbents (sodium and calcium aluminum-silicate and glucomanane) on growth and hematologic paramaters of jundi?? (Rhamdia quelen) fingerlings, fed diets artificially contaminated. The first experiment consisted of 360 fingerlings (initial weight 4 g), raised during 90 days in thermo-regulated recirculation water system. Twelve treatments were compared, with 3 replications. Four levels of aflatoxin inclusion in diets (0, 150, 250 e 350 μgAFkg-1), with and without (0, 0.3 and 0,6%) adsorbent addition (sodium and calcium aluminum-silicate). Negative effect of aflatoxins significantly reduced (P<0.05) growth and weight gain of fingerlings, proportionately to increasing levels of aflatoxis in diet, without mortality occurrence. Adsorbent levels in diet did not diminish the effect of aflatoxins on fish performance. The second experiment evaluated the effect of aflatoxins and 2 adsorbents (sodium and calcium aluminum-silicate) on performance of 189 jundi?? juveniles (initial weight 43.13 g),grown during 60 days. Nine treatments with 3 replications, 3 levels of aflatoxin inclusion in diet (0...

Formas de silício e de alumínio num Latossolo sob semeadura direta tratado com calcário e silicato de cálcio e de magnésio; Forms of silicon and aluminum in an Oxisol under no tillage amended with lime and calcium-magnesium silicate

Antonangelo, João Arthur
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 23/06/2015 PT
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36.82%
O silício (Si) é benéfico ao desenvolvimento das plantas por proporcionar aumento na capacidade de defesa contra o ataque de pragas e de doenças, além de garantir porte ereto das plantas, o que aumenta a capacidade fotossintética dos vegetais. Fontes silicatadas, como silicatos de cálcio e de magnésio, fornecem Si ao solo e podem funcionar como corretivos de acidez. O acúmulo de resíduos vegetais e fertilizantes, mesmo no sistema semeadura direta (SSD), acelera o processo de acidificação do solo em curto prazo, principalmente em sua camada mais superficial. Esse processo é contínuo em solos tropicais úmidos e tem por consequência a baixa disponibilidade de nutrientes e elevados teores tóxicos de Al+3. Assim como no sistema convencional de manejo do solo, o SSD também demanda a aplicação de insumos, especialmente materiais corretivos de acidez. A aplicação de silicato pode interferir na disponibilidade de Si às plantas e nas formas desse elemento na solução do solo. O ácido silícico (H4SiO4) é a espécie de Si predominante em solos ácidos; e o aumento do pH pode causar sua desprotonação, gerando o ânion silicato (H3SiO4-). Estudos ligados ao Si em solos sob SSD são escassos, principalmente em experimentos de longa duração conduzidos sob condições de clima tropical úmido. Desde 2002 está sendo conduzido experimento de campo em um Latossolo Vermelho distroférrico sob SSD que recebeu aplicação superficial de calcário e de silicato de cálcio e de magnésio. Foram determinados os teores disponíveis de macronutrientes e silício...

On the Anomalous Silicate Absorption Feature of the Prototypical Seyfert 2 Galaxy NGC 1068

Koehler, Melanie; Li, Aigen
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 24/10/2012
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36.57%
The first detection of the silicate absorption feature in AGNs was made at 9.7 micrometer for the prototypical Seyfert 2 galaxy NGC 1068 over 30 years ago, indicating the presence of a large column of silicate dust in the line-of-sight to the nucleus. It is now well recognized that type 2 AGNs exhibit prominent silicate absorption bands, while the silicate bands of type 1 AGNs appear in emission. More recently, using the Mid-Infrared Interferometric Instrument on the Very Large Telescope Interferometer, Jaffe et al. (2004) by the first time spatially resolved the parsec-sized dust torus around NGC 1068 and found that the 10 micrometer silicate absorption feature of the innermost hot component exhibits an anomalous profile differing from that of the interstellar medium and that of common olivine-type silicate dust. While they ascribed the anomalous absorption profile to gehlenite (Ca_2Al_2SiO_7, a calcium aluminum silicate species), we propose a physical dust model and argue that, although the presence of gehlenite is not ruled out, the anomalous absorption feature mainly arises from silicon carbide.; Comment: 5 pages, 3 figures, published in MNRAS Letters

Experimental investigation of the elastoplastic response of aluminum silicate spray dried powder during cold compaction

Bosi, F.; Piccolroaz, A.; Gei, M.; Corso, F. Dal; Cocquio, A.; Bigoni, D.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 05/05/2014
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46.46%
Mechanical experiments have been designed and performed to investigate the elasto-plastic behaviour of green bodies formed from an aluminum silicate spray dried powder used for tiles production. Experiments have been executed on samples obtained from cold compaction into a cylindrical mould and include: uniaxial strain, equi-biaxial flexure and high-pressure triaxial compression/extension tests. Two types of powders have been used to realize the green body samples, differing in the values of water content, which have been taken equal to those usually employed in the industrial forming of traditional ceramics. Yielding of the green body during compaction has been characterized in terms of yield surface shape, failure envelope, and evolution of cohesion and void ratio with the forming pressure, confirming the validity of previously proposed constitutive models for dense materials obtained through cold compaction of granulates.; Comment: 17 pages; Journal of the European Ceramic Society, 2014

Toxidez de alumínio e manganês em sorgo sacarino (Sorghum bicolor (L.) moench): I. Efeitos do silicato e do carbonato de cálcio em solo podzólico vermelho amarelo var. laras; Induced toxicities of aluminum and manganese in sweet sorghum (Sorghum bicolor (L.) moench): I. Effects of the calcium silicate and carbonate in a laras red yellow podzolic soil

Primavesi, Ana Candida P. Aguirre; Malavolta, E.; Primavesi, Odo
Fonte: Universidade de São Paulo. Escola Superior de Agricultura Luiz de Queiroz Publicador: Universidade de São Paulo. Escola Superior de Agricultura Luiz de Queiroz
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; Formato: application/pdf
Publicado em 01/01/1986 POR
Relevância na Pesquisa
26.78%
Foram determinados produção de matéria seca de raízes, colmos e folhas e teores de P, Ca, Mg, K, Al, Mn e Fe de três cultivares de sorgo sacarino (Br500, Br602 e Ample-H-OK) crescendo em solo Podzólico Vermelho Amarelo Var. Laras, em presença e ausência de corretivos da acidez do solo (calcário e silicato). Ocorreram diferenças genotípicas na resposta aos corretivos. O melhor tratamento para a produção de matéria seca das folhas não foi necessariamente o melhor para a produção de matéria seca dos colmos. O calcário propiciou efeitos relativos melhores que o silicato na promoção do crescimento dos cultivares. O cultivar Br500 apresentou a melhor resposta ao calcário e Br602 ao silicato. A melhor produção de matéria seca de colmos do sorgo sacarino, proporcionado pela aplicação de corretivos, deveu-se principalmente à redução da saturação em alumínio e ao aumento da CTC efetiva, do Ca trocável e do pH do solo. O calcário promoveu a redução nos teores foliares de todos os elementos analisados, inclusive Al e Mn. O silicato acarretou aumentos nos teores de Ca, Mg, K, P e Al. Não foram constatados sintomas visuais de toxicidade de Mn nos níveis presentes, embora a produção de matéria seca total tenha sido afetada. Os cultivares foram afetados pelo Al trocável do solo na seguinte ordem decrescente: Ample-H-OK >;Br602 >; Br500.; Three sweet sorghum cultivars (Br500...

Nucleation and growth of zeolite A under reagent controlled conditions. Part II

Singh, Puyam S; White, John
Fonte: Royal Society of Chemistry Publicador: Royal Society of Chemistry
Tipo: Artigo de Revista Científica
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26.64%
Broad differences in the synthesis kinetics and the morphology of zeolite A from two silicate sources (soluble silicate and Ludox colloidal silica) and two different aluminium sources (aluminium isopropoxide and freshly prepared aluminium hydroxide) are reported. The differences are attributed to different rate limiting steps in the syntheses. The reactions have been followed by small angle X-ray scattering from the time of first mixing of the constituents until the final separation of zeolite A crystals. The soluble silicate and Ludox/aluminium hydroxide syntheses produce excellent cubic crystals in the 300 nm-1 μm size range. The products of the first synthesis have an interesting texture on the scale of nanometres but with aluminium isopropoxide as the aluminium source, the resulting zeolite A has a spherical morphology of size ca. 100 nm. Possible reasons for the development of these morphologies are discussed.