Compósitos magn��ticos baseados em hidrotalcitas para a remo����o de contaminantes ani��nicos em ��gua

In this work the adsorption features of hydrotalcites (Al, Mg- CO3) and the magnetic properties of iron oxides have been combined in a composite to produce a magnetic adsorbent. These magnetic composites can be used as adsorbents for anionic contaminants in water and subsequently removed from the medium by a simple magnetic process. The magnetic hydrotalcites were characterized by XRD, magnetization measurements, N2 adsorption isotherms and M��ssbauer spectroscopy. These magnetic adsorbents show remarkable adsorption capacity for anionic contaminants in water.

Aplica����es de fibras lignocelul��sicas na qu��mica de pol��meros e em compósitos

The use of lignocellulosic fibers and their constituents, as raw materials in the production of polymeric and composite materials, represent an exceptional opportunity of sustainable technological development. In the present report works that discuss promising alternatives of obtaining and use of materials such as cellulose, hemicellulose, lignin, cellulose nanocrystals and biocomposites were revised. The advance in the use of biomass can be, in a near future, capable of going beyond the application difficulties of these vast materials, especially in relation to the economical unviability, by the production of high performance polymeric and composite materials. This advance would represent a higher profitability to some areas of agrobusiness, especially the sector of biofuels, which produces elevated amounts of biomass waste.

Materiais híbridos �� base de s��lica obtidos pelo m��todo sol-gel

This review deals with silica based hybrid materials obtained by the sol-gel method. It involves concepts, classifications and important definitions regarding the sol-gel method that allows obtaining materials with organic and inorganic components dispersed in a molecular or nanometric level. We discuss the properties and characteristics of hybrid materials related to experimental synthesis conditions. We devote a special attention to the nanostructured materials, where the self-organization is imposed by the organic component. Finally, we present some important applications of these materials based on their specific properties.

Propriedades din��micas de fluidos por simula����o computacional: m��todos híbridos atom��stico-cont��nuo

Computational methods for the calculation of dynamical properties of fluids might consider the system as a continuum or as an assembly of molecules. Molecular dynamics (MD) simulation includes molecular resolution, whereas computational fluid dynamics (CFD) considers the fluid as a continuum. This work provides a review of hybrid methods MD/CFD recently proposed in the literature. Theoretical foundations, basic approaches of computational methods, and dynamical properties typically calculated by MD and CFD are first presented in order to appreciate the similarities and differences between these two methods. Then, methods for coupling MD and CFD, and applications of hybrid simulations MD/CFD, are presented.

Materiais híbridos org��nico-inorg��nicos (ormosil) obtidos por sol-gel com potencial uso como filtro solar

This work aimed at the synthesis and characterization of particles of modified silica containing the organic filter dibenzoylmethane (DBM) by the hydrolytic sol-gel method, with modifications to the St��ber route. The structures of the resulting Xerogels were characterized by diffuse reflectance UV-VIS spectroscopy in the solid state, infrared absorption spectroscopy, Scanning Electron Microscopy (SEM) and 29Si Nuclear Magnetic Resonance (29Si NRM). The results showed favorable formation of hybrid organic-inorganic nanoparticles with efficient absorption/reflectance of radiation in the UV / VIS range, which enables their potential use as sunscreen.

Esterifica����o de ��cidos graxos utilizando zirc��nia sulfatada e compósitos carv��o ativado/zirc��nia sulfatada como catalisadores

In this work sulfated zirconia (SZr) and activated carbon/SZr composites produced by impregnation method with or without heating treatment step (CABC/SZr-I and CABC/SZr-I SC) and by the method of synthesis of SZr on the carbon (CABC/SZr-S) was used as catalysts in the esterification reactions of fatty acids. The SZr presented very active, conversions higher than 90% were obtained after 2 h of reaction. The activity of the composite CABC/SZr-I20%SC was up to 92%, however, this was directly related to time and temperature reactions. CABC/SZr-I and CABC/SZr-S were less active in esterification reactions, what could be attributed to its low acidity

Avalia����o das propriedades de compósitos de polipropileno refor��ados com casca de aveia

The preparation of oat-reinforced polypropylene nanocomposites with different fiber contents by means of melt-processing was investigated. Composite properties were evaluated by Scanning Electron Microscopy (SEM), Flexural Modulus, Dynamic Mechanical Analysis (DMA), Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). Findings confirmed that the oat composite properties were affected by fiber type and content. Improvements in mechanical properties were obtained using fiber contents < 20% w.t.

S��ntese e caracteriza����o de hidrog��is compósitos a partir de copol��meros acrilamida-acrilato e caulim: efeito da constitui����o de diferentes caulins do nordeste brasileiro

Superabsorbent hydrogels based on poly (acrylamide-co-acrylate) and different kaolins, were prepared by free-radical aqueous copolymerization. FTIR and WAXS techniques were employed for characterization of a series of hydrogels, obtained by varying the percentage of clay, crosslinking and constitution of kaolin. The water absorbency at equilibrium (Weq) decreased with increasing clay content and the amount of crosslinking agent. Superabsorbent hydrogel (Weq > 1084 g H2O/g gel) was obtained as 10 wt% of white kaolin and 0.05 mol% of crosslinking agent were used. The hydrogel proved sensitive to pH variation and the presence of salts.

Compósitos biodegrad��veis de amido de mandioca e res��duos da agroind��stria

The objectives of this work were to produce biodegradable composites using starch and different agro-industrial wastes (coconut fiber, soy bran and sugarcane bagasse) using a baking process, and to study the effects of these components on the resultant composite properties. The addition of different residues yielded trays with different properties. Samples manufactured with soy bran showed the highest density and water uptake at relative humidities &#8805; 60%. The addition of sugarcane bagasse resulted in less dense and resistant samples whereas coconut fiber composites showed the highest breaking stress. The samples fabricated in this study represent an alternative packaging option for foods with low water content.

Estudo da libera����o controlada do herbicida ametrina em compósitos �� base de PVA: carv��o ativado

Herbicides have great importance in agricultural productivity for weed control, given their competition with crops. However, inadequate application of herbicides may lead to environmental problems, which can be minimized through controlled release of the active compounds. This may be achieved by protecting the herbicide in a structure with adequate porosity, where the diffusional behavior can determine release. Thus, in this study we evaluated a novel structure, a composite based on activated carbon bonded by polyvinyl alcohol (PVA) as pellets, to deliver a triazine herbicide. The product obtained was shown to be adequate for its purpose, since it was possible to process regular pellets, where the PVA percentage determined the properties.

DESENVOLVIMENTO DE MATERIAIS H��BRIDOS MICRO-MESOPOROSOS DO TIPO ZSM-12/MCM-41

Micro-mesoporous hybrid materials of ZSM-12/MCM-41 type with different micro- and mesoporosity contributions were prepared by a procedure that uses the desilication of the zeolite in an alkaline medium, followed by recrystallization onto the mesostructure, where the zeolite is used as the silica source in the formation of mesoporous phase. The materials were characterized by X-ray diffraction, nitrogen adsorption-desorption at 77 K, scanning electron microscopy and thermal analysis. The results showed that the methodology utilized is efficient for obtaining hybrid materials of ZSM-12/MCM-41 type with optimized micro-and mesoporosity.

Efeito da inocula����o do fitoplasma do enfezamento sobre o desenvolvimento e produ����o de híbridos de milho

O efeito isolado do fitoplasma sobre o desenvolvimento e a produ����o de dez híbridos de milho (Zea mays) foi avaliado em condi����es controladas. Plantas com dez dias de idade foram experimentalmente inoculadas atrav��s de dez insetos infetivos de Dalbulus maidis por planta. Plantas infetadas foram comparadas com plantas livres de fitoplasma quanto �� sintomatologia e �� altera����o de alguns componentes de produ����o. As plantas infetadas exibiram avermelhamento foliar, prolifera����o de espigas anormais e enfezamento em maior ou menor grau, em fun����o de cada h��brido. Para os híbridos mais suscet��veis, al��m da grande propor����o de gr��os mi��dos, foram constatadas redu����o de at�� 35% na altura de plantas, 98% na produ����o de gr��os, 72% no tamanho de espigas, 50% no n��mero de fileiras/espiga, 98% no n��mero de gr��os/espiga e 18% na germina����o de sementes.

Rea����o de porta-enxertos híbridos ao Citrus tristeza virus

A tristeza causada pelo v��rus da tristeza dos citros (Citrus tristeza virus, CTV) �� uma das principais viroses dos citros (Citrus spp.) no Brasil. Alguns autores t��m utilizado a intensidade de caneluras produzidas nos ramos para selecionar plantas com resist��ncia ao v��rus. Neste trabalho foi avaliada a rea����o de porta-enxertos híbridos, provenientes do programa de melhoramento gen��tico de citros da Embrapa Mandioca e Fruticultura ao CTV e elaboradas duas escalas, uma fotogr��fica e outra diagram��tica, para quantifica����o de resist��ncia ao CTV. Entre os porta-enxertos avaliados, a maioria apresentou poucas caneluras, sendo portanto considerados resistentes �� tristeza. Verificou-se a manuten����o da resist��ncia ao v��rus nos híbridos produzidos a partir de progenitores que possu��am algum n��vel de resist��ncia.

Rea����o de híbridos de milho �� podrid��o branca da espiga

Neste trabalho, avaliou-se a rea����o de seis híbridos de milho (Zea mays)(AG 9012, C 808, P 3041, C 901, XL 212 e X 9403) de germoplasmas diferentes, a Diplodia maydis inoculados artificalmente nas espigas e �� infec����o natural de D. maydis e de D. macrospora. O h��brido X 9403 apresentou a menor incid��ncia de gr��os infetados e o rendimento de gr��os superior dos demais híbridos; o h��brido XL 212 apresentou incid��ncia e rendimento de gr��os intermedi��rios. Esses dois híbridos possuem textura de gr��os dentados. Os híbridos P 3041, AG 9012 e C 808, com textura de gr��os duro, apresentaram rendimentos inferiores e rea����es vari��veis a D. maydis e a D. macrospora. Esses resultados mostraram que existe variabilidade entre híbridos quanto �� rea����o �� podrid��o da espiga causada por D. maydis e a D. macrospora. Na identifica����o de materiais resistentes, se sugere utilizar m��todos artificiais de inocula����o, visando aumentar a press��o de sele����o e confiabilidade nos resultados.

Efeitos da intera����o de potyvirus em híbridos de meloeiro, variedades de melancia e abobrinha

Em raz��o da freq��ente ocorr��ncia de infec����o mista, na natureza, o presente trabalho objetivou estudar o efeito da intera����o de diferentes esp��cies de potyv��rus em meloeiro (Cucumis melo), melancia (Citrullus lanatus) e abobrinha (Cucurbita pepo). Foram usados os seguintes v��rus da fam��lia Potyviridae, g��nero Potyvirus: Papaya ringspot virus (PRSV); Watermelon mosaic virus, (WMV) e Zucchini yellow mosaic virus, (ZYMV). Os efeitos na sintomatologia das infec����es duplas e simples de PRSV, WMV e ZYMV foram avaliados em tr��s híbridos de meloeiro, duas variedades de melancia e abobrinha 'Caserta', em experimentos de casa de vegeta����o. Os tr��s v��rus, isoladamente ou em todas as duplas combina����es poss��veis, foram inoculados, em plantas dos híbridos de meloeiro Hy Mark, Gold Mine e Orange Flesh, variedades de melancia Crimson Sweet e Charleston Gray e abobrinha 'Caserta', usando-se dez plantas de cada h��brido ou variedade, por combina����o de v��rus. As inocula����es foram efetuadas por meio de extratos de folhas com infec����o simples dos respectivos v��rus. As plantas inoculadas com cada v��rus isoladamente e suas respectivas combina����es foram observadas quanto ao aparecimento de sintomas durante 30 dias ap��s as inocula����es. Amostras foliares das plantas inoculadas foram, tamb��m, testadas por ELISA indireto contra os anti-soros correspondentes para cada v��rus. As infec����es duplas em meloeiro, melancia e abobrinha revelaram, atrav��s da avalia����o sintomatol��gica, que existem intera����es sin��rgicas entre PRSV, WMV e ZYMV. As infec����es duplas envolvendo o ZYMV apresentaram alta severidade, exibindo sintomas n��o encontrados em infec����es simples, apesar da severidade nas infec����es isoladas do ZYMV.