Desempenho da alface em cultivo orgânico com e sem cobertura morta e diferentes lâminas d'água

O experimento foi conduzido no período de 27/05/2006 a 02/08/2006 no SIPA (Sistema Integrado de Produção Agroecológica), localizado no município de Seropédica-RJ. Nesse trabalho, objetivou-se avaliar o desempenho da cultura da alface (Lactuca sativa L.) cultivada sob diferentes lâminas de irrigação em um solo sem e com cobertura de palhada da leguminosa gliricídia. Foram conduzidos dois experimentos simultâneos, utilizando o delineamento experimental de blocos ao acaso, em ambos os experimentos, nos quais foram aplicadas 5 lâminas de irrigação, correspondendo a 25, 50, 80, 100, 115 % da evapotranspiração da cultura (ETc), sendo a produção final avaliada por meio da determinação da massa fresca, área foliar e número de folhas. Até o nível de 100% ETc, todas as variáveis analisadas tiveram seus valores aumentados, e para o nível de 115%, houve um decrescimento das mesmas. Na produção de massa fresca total, o sistema de cultivo com utilização de cobertura morta foi superior ao sem cobertura não diferenciando estatisticamente ao nível de 5 % probabilidade pelo teste F somente nas lâminas de 25 e 115% ETc.

Respostas do híbrido de sorgo-sudão às adubações nitrogenada e potássica: características estruturais e produtivas

A pesquisa foi instalada no Setor de Forragicultura da FCAV/UNESP-Jaboticabal, para avaliar o híbrido de sorgo-sudão AG 2501C no outono e inverno. O manejo da pastagem foi conduzido, simulando o sistema de lotação intermitente. O experimento foi desenvolvido de março a setembro de 2002. A forrageira foi submetida a nove tratamentos: três doses de N (100, 200 e 300 kg/ha) e três doses de K (0, 80 e 160 kg/ha de K2O), em delineamento experimental de blocos casualizados com três repetições em esquema de parcelas subdivididas. As características estudadas foram massas, secas, inicial de planta inteira, folha e colmo e massa seca residual; relação lâmina/colmo; índice de área foliar (IAF); interceptação da radiação fotossinteticamente ativa (RFA) e coeficiente de extinção luminosa. Os tratamentos não influenciaram a massa seca inicial (MSI) e residual (MSR) da planta inteira, folha e colmo e massa seca residual. Os resultados médios para MSI, MSR, folha e colmo foram 2801,2; 964,7; 1462,8 e 1085,2 kg/ha de MS, por ciclo de pastejo, respectivamente. Houve redução da relação lâmina/colmo e da porcentagem de folhas, enquanto a porcentagem de colmos aumentou. Houve interação entre N e K para IAF, interceptação de luz e coeficiente de extinção.

Análise de crescimento e anatomia foliar da planta medicinal Ageratum conyzoides L. (Asteraceae) cultivada em diferentes substratos

Ageratum conyzoides L. (Asteraceae) é uma espécie herbácea que ocorre em áreas de cerrado e, por se tratar de planta medicinal, é cultivada em escala familiar. O objetivo deste trabalho foi estudar possíveis alterações no desenvolvimento das plantas quando cultivadas em solos com texturas diferentes (solo de cerrado, franco arenoso ou solo de terra roxa, muito argiloso). Foram analisados aos 40, 70 e 90 dias, o comprimento do caule e da raiz, massa seca da parte aérea (caule e folhas) e das raízes, número de folhas e área foliar; além de parâmetros anatômicos foliares, como a densidade de tricomas. Os resultados mostraram que os comprimentos do caule e da raiz aumentaram no decorrer do experimento, independentemente do substrato (com exceção do comprimento da raiz de plantas cultivadas em solo de terra roxa). Porém, o comprimento do caule foi sempre maior nas plantas cultivadas em solo de cerrado, enquanto o comprimento da raiz foi significativamente maior somente aos 90 dias de cultivo neste solo. As biomassas secas da raiz e do caule também foram maiores nas plantas cultivadas em solo de cerrado por 70 e 90 dias, respectivamente. A massa seca foliar foi maior nas plantas cultivadas em solo de cerrado a partir dos 70 dias de experimento. Esse aumento foi devido ao maior número de folhas produzidas e a maior área foliar dessas plantas. No geral, a anatomia foliar não diferiu, porém o número de tricomas glandulares foi maior nas plantas cultivadas em solo de cerrado. Os resultados indicaram que esta espécie tem melhor desenvolvimento quando cultivada em solo mais arenoso.

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.

Influence of milling time on mechanically assisted synthesis of Pb0.91Ca0.1TiO3 powders

Pb0.91Ca0.1TiO3 powders (PCT) were prepared by mechanochemical synthesis from high-energy ball milling process. The influence of milling time on the phase formation, crystal structure, specific surface area, density and powder morphology was observed. We adopted the Rietveld refinement technique to investigate the crystal structure of the PCT powders. Scanning electron microscopy (SEM) analysis revealed that PCT powders milled for 5 h showed a wide distribution of particle agglomerates while milled for 35 h showed a decrease in agglomerates size. Further prolongation of milling time resulted in the agglomerates growth. (C) 2006 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Structural characteristics of gels prepared from sonohydrolysis and conventional hydrolysis of TEOS: an emphasis on the mass fractal as determined from the pore size distribution

Silica gels were preparated from fixed proportion mixtures of tetraethoxysilane, water and hydrocloric acid, using either ultrasound stimulation (US) or conventional method (CO) in the hydrolysis step of the process. Wet gets were obtained with the same silica volume concentration and density. According to small-angle X-ray scattering, the structure of the wet gels can be described as mass fractal structures with mass fractal dimension D = 2.20 in a length scale xi = 7.9 nm, in the case of wet gels US, and D = 2.26 in a length scale 6.9 nm, in the case of wet gels CO. The mass fractal characteristics of the wet gels US and CO account for the different structures evolved in the drying of the gels US and CO in the obtaining of xerogels and aerogels. The pore structure of the dried gels was studied by nitrogen adsorption as a function of the temperature. Aerogels (US and CO) present high porosity with pore size distribution (PSD) curves in the mesopore region while xerogels (US and CO) present minor porosity with PSD curves mainly in the micropore region. The dried gels US (aerogels and xerogels) generally present pore volume and specific surface area greater than the dried gels CO. The mass fractal structure of the aerogels has been studied from an approach based on the PSD curves exclusively. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and characterization of Li2ZnTi3O8 spinel using the modified polymeric precursor method

In this work we report the synthesis procedure, crystallographic, structural and magnetic properties of the Li2ZnTi3O8 spinel obtained using a modified polymeric precursor method. This synthesis method generates very reactive and property-controlled nanoparticles. The samples were characterized using X-ray powder diffraction (XRD) associated to the Rietveld refinement method, thermogravimetric analysis (TG), specific surface area, scanning electron microscopy (SEM) and magnetic susceptibility measurements.The phase formation temperature of the lithium zinc titanate spinel was observed to decrease due to the homogeneity and highly controlled nanometric particle size. (C) 2003 Elsevier B.V. All rights reserved.

Efficacy of pre- and postinoculation application of Fungicides to expanding young citrus leaves for control of melanose, scab, and alternarial brown spot

In greenhouse trials, copper hydroxide, pyraclostrobin, and famoxadone were applied to actively crowing young citrus seedlings to determine the duration of protection of young leaves provided by these fungicides against melanose, caused by Diaporthe citri, citrus scab, caused by Elsinoe fawcettii, and Alternaria brown spot, caused by Alternaria alternata. Fungicides were applied to different sets of potted plants of grapefruit for control of melanose, of rough lemon for control of scab, and of Dancy tangerine for control of Afternaria brown spot 1 to 6 days prior to inoculation. as well as on the day of inoculation. Leaf area of treated shoots was estimated on the day of fungicide application and the day of inoculation and disease severity evaluated subsequently. In most cases. copper hydroxide and famoxadone provided at least 50% control of all three diseases for only about 2 days after application. Generally, there was little or no disease control when the products were applied 4 or more days before inoculation. In contrast, pyraclostrobin usually provided a high level of control of all three diseases when applied up to 5 days prior to inoculation. The level of disease control decreased as the interval between a fungicide application and inoculation increased and the relationship between disease control and leaf expansion best fit a quadratic equation. Effective disease control was observed with copper hydroxide and famoxadone until leaf area had increased by 100 to 200%, whereas control with pyraclostrobin was observed up to 400 to 500% increase in leaf area. In postinoculation tests with scab and melanose, pyraclostrobin provided high levels of disease control (>75%) when applied up to 2 days after inoculation. whereas copper hydroxide and famoxadone had minimal postinoculation activity. Applications of pyraclostrobin to the spring flush growth of citrus trees are much more likely to provide control of melanose, scab, and Alternaria brown spot than those of famoxadone or copper hydroxide.

Mass fractal characteristics of sonogels prepared from sonohydrolysis of tetraethoxysilane with additions of dimethylformamide

Wet silica gels with similar to 1.4 x 10(-3) mol SiO2/cm(3) and similar to 90 vol.% liquid phase were prepared from the sonohydrolysis of tetraethoxysilane (TEOS) with different additions of dimethylformamide (DMF). Aerogels were obtained by CO2 supercritical extraction. The samples were studied mainly by small-angle X-ray scattering (SAXS) and nitrogen adsorption. Wet gels exhibit a mass fractal structure with fractal dimension D increasing from 2.23 to 2.35 and characteristic length xi decreasing from similar to 9.4 nm to similar to 5.1 nm, as the DMF/TEOS molar ratio is increased from 0 to 4. The supercritical process apparently eliminates some porosity, shortening the fractality domain in the mesopore region and developing an apparent surface/mass fractal (with correlated mass fractal dimension D-m similar to 2.6 and surface fractal dimension D-s similar to 2.3) in the micropore region. The fundamental role of the DMF addition on the structure of the aerogels is to diminish the porosity and the pore mean size, without, however, modify substantially the specific surface area and the average size of the silica particle of the solid network. (c) 2006 Elsevier B.V. All rights reserved.

Characterization of bismuth titanate ceramics derived by mechanochemical synthesis

Bismuth titanate, Bi(4)Ti(3)O(12) (BIT) nanosized powders have been successfully synthesized via high energy mechanochemical activation. The phase formation of BIT, crystal structure, microstructure, crystallite size and specific surface area were followed by XRD, scanning electron microscopy (SEM) and the BET specific surface area measurements. The BIT milled 2 h shows the orthorhombic crystalline structure with small amount of amorphous phase. The microstructure of Bi(4)Ti(3)O(12) ceramics sintered at 1000 degrees C for 12h exhibit plate-like grain structure.

Nanostructure and properties of ZnO films produced by the pyrosol process

Indium doped ZnO films were deposited by the pyrosol process on glass substrates at different temperatures from solutions containing In/Zn molar ratios up to 10%. The nanostructure of the films was investigated using grazing-incidence small angle X-ray scattering (GISAXS). The mass density was determined by X-ray reflectivity and the composition by X-ray photoelectron spectroscopy. The GISAXS measurements revealed an anisotropic pattern for films deposited at 573 and 623 K and a isotropic one for those deposited at higher temperatures. The anisotropic patterns indicate the presence of elongated nanopores with their long axes perpendicular to the film surface. In contrast, the isotropic nature of GISAXS patterns of films grown at high temperatures (673 and 723 K) suggests the presence of spherical voids. The pore size distribution function determined from the isotropic patterns indicates a multimodal size distribution. on the other hand, the measured mass density of the doped films with isotropic nanotexture is higher than that of the anisotropic films while the electric resistivity is significantly lower. This is in agreement with the detected strong reduction of the void density and specific surface area at approximately constant pore size.

Mechanochemical synthesis of PZT powders

PZT ceramic powders were successfully prepared from the mixture of PbO, ZrO2 and TiO2 by mechanochemical synthesis in a planetary ball mill, under different milling conditions. Phase evolution during synthesis was monitored by X-ray diffraction analysis. Intensive milling resulted in formation of the nanocrystalline, perovskite PZT powders after 1 h of milling. This is a significant improvement in comparison to milling conditions reported by other authors. Depending on milling parameters the presence of some other phases, such as unreacted ZrO2, was also detected in some samples. The changes in powder size and morphology due to intensive milling, were determined by SEM and TEM, while BET analysis was used to determine specific surface area of the powders. Conclusions about processes taking place during mechanochemical synthesis of PZT powders were made based on the results of characterization. (C) 2002 Elsevier B.V. B.V. All rights reserved.

2-Mercaptoimidazole covalently bonded to a silica gel surface for the selective separation of mercury(II) from an aqueous solution

Silica gel with a specific surface area of 365 m(2).g(-1) and an average pore diameter of 60 Angstrom was chemically modified with 2-mercaptoimidazole. The degree of functionalization of the covalently attached molecule, (drop SiO)(3)(CH2)(3) - MI, where MI is the 2-mercaptoimidazole bound to the silica surface by a propyl group, was 0.58 mmolg.(-1). In individual metal adsorption experiments from aqueous solutions by the batch procedure, the affinity order was Hg(II)much greater than Cd-II > Cu-II approximate to Zn-II approximate to Pb-II > Mn-II at solution pHs between 4 and 7. Due to the high affinity by the sulfur atom, Hg-II is strongly bound to the functional groups. When solution containing a mixture of Hg-II, Cd-II, Cu-II, Zn-II, Pb-II, and Mn-II ions was passed through a column packed with the adsorbent, Hg-II was the only one whose adsorption and elution was not affected by the presence of other ions.

Sol-gel entrapped cobalt complex

This work describes optimized conditions for preparation of a cobalt complex entrapped in alumina amorphous materials in the form of powder. The hybrid materials, CoNHG, were obtained by a nonhydrolytic sol-gel route through condensation of aluminum chloride with diisopropylether in the presence of cobalt chloride. The materials were calcined at various temperatures. The presence of cobalt entrapped in the alumina matrix is confirmed by ultraviolet visible spectroscopy. The materials have been characterized by X-ray diffraction (XRD), surface area analysis, thermogravimetric analysis (TGA), differential thermal analyses (DTA) and transmission electron microscopy (TEM). The prepared alumina matrix materials are amorphous, even after heat treatment up to 750 degreesC. The XRD, TGA/DTA and TEM data support the increase of sample crystallization with increasing temperature. The specific surface area, pore size and pore diameter changed as a function of the heat treatment temperature employed. Different heat treatment temperatures result in materials with different compositions and structures, and influence their catalytic activity. The entrapped cobalt materials calcined at 750 degreesC efficiently catalyzed the epoxidation of (Z)-cyclooctene using iodozylbenzene as the oxygen donor. (C) 2003 Elsevier B.V. All rights reserved.

PREPARATION AND CHARACTERIZATION OF TI(IV) OXIDE GRAFTED ONTO SILICA ON A SILICA-GEL SURFACE

Silica gel with a surface area of 500 m2g-1 and an average pore diameter of 60 angstrom was chemically modified with Ti(IV) oxide using the grafting method. The amount of metal oxide attached to the surface was 1.8.10(-3) mol g-1. The X-ray photoelectron spectra showed that the metal ion species on the surface are Ti(IV) in TiO2 and MTiO3 (M = Ca2+, Sr2+, Ba2+ and Pb2+), i.e. they have the binding energy of Ti2p3/2 = 458.7 eV. The dehydration of the solid at higher temperature increased the O(II)/Ti (O(II) = oxygen bound to titanium atom) ratio, presumably due to a reticulation of the hydrous Ti(IV) oxide on the silica surface at higher temperatures. Migration of Ti(IV) into the silica gel matrix was observed but the specific surface area was not significantly changed.