Note on the germination of Vochysia tucanorum seeds treated with growth regulators

(Nota sobre a germina����o de sementes de Vochysia tucanorum tratadas com reguladores vegetais). O objetivo deste trabalho foi avaliar a resposta germinativa sob luz branca e escuro de sementes de Vochysia tucanorum Mart. tratadas com GA3 e CEPA. Sementes rec��m-coletadas de uma ��rea de Cerrado foram armazenadas durante 14 dias em duas temperaturas (25 �� 2 ��C e 7 �� 1 ��C). Ap��s o per��odo de armazenamento, as sementes foram pr��-tratadas com ��gua destilada (controle), ��cido giber��lico (GA3), ��cido 2-cloroetilfosf��nico (CEPA) e uma mistura de GA3 + CEPA; em seguida, as sementes foram semeadas em placas de Petri sobre papel filtro umedecido com ��gua destilada e colocadas para germinar em escuro e sob luz branca. Os resultados sugerem que as sementes n��o s��o fotobl��sticas nem dormentes, no entanto um comportamento fotobl��stico emerge quando as sementes foram previamente armazenadas em baixa temperatura e embebidas em solu����es de GA3 e CEPA. em geral, n��o houve diferen��a entre as temperaturas de armazenamento de 7 ��C e 25 ��C. A germina����o sob luz branca de sementes pr��-tratadas com CEPA + GA3 e CEPA foi antecipada, em compara����o com o controle de ��gua destilada, sendo que o efeito da mistura CEPA + GA3 foi mais pronunciado do que o de CEPA sozinho. Assim, a taxa de germina����o de sementes de V. tucanorum, sob luz branca, pode ser melhorada pela embebi����o das mesmas em solu����es de CEPA ou de CEPA + GA3.

Efeito da aplica����o de etileno no pH, acidez, ��ndice refratom��trico e a����cares totais de frutos de manga, colhidos em est��gio pr��-climat��rico

Este trabalho teve como objetivo o estudo da a����o do etileno no amadurecimento de frutos de manga, tentando contribuir para o conhecimento da fisiologia do amadurecimento destes frutos. Foram utilizadas mangas (Mangifera indica L.), variedade Keitt, colhidas em est��gio pr��-climat��rico. Estes frutos receberam tratamento com ethrel (500 e 1.000 ppm, com exce����o da testemunha) e foram submetidos ��s seguintes determina����es: pH, acidez, ��ndice refratom��trico e a����cares totais. A an��lise e interpreta����o dos resultados mostrou a inexist��ncia de diferen��a estat��stica entre esses 3 tratamentos, indicando que a aplica����o de ethrel n��o trouxe nenhuma vantagem na melhoria de qualidade dos frutos.

Reguladores vegetais e o desbaste qu��mico de frutos de tangor murcote

O tangor 'Murcote' apresenta necessidade de desbaste de frutos devido a altern��ncia de produ����o, caracterizado por anos de excessiva produ����o intercalado com anos de baixa produ����o, evitando assim, a diminui����o da qualidade dos frutos. O presente trabalho teve por objetivo avaliar a efici��ncia de reguladores vegetais, a auxina ANA (��cido naftalenac��tico) e ethephon (etileno) no desbaste qu��mico de frutos de tangor 'Murcote' aplicado 40 dias ap��s o pleno florescimento. O experimento foi conduzido em Prat��nia, SP, onde plantas de 5 anos de idade, enxertadas sobre o limoeiro 'Cravo', foram pulverizadas com ANA a 0, 100, 200, 300 e 400 mg L-1 e com ethephon a 200, 300 e 400 mg L-1, ambos em solu����o aquosa juntamente com adjuvante n��o i��nico a 0,05%. A contagem dos frutos foi realizada previamente aos tratamentos em 2 ramos marcados por planta. O ANA n��o interferiu significativamente no desbaste de frutos, com porcentagens de queda variando entre 7 a 14%, enquanto que as pulveriza����es com ethephon mostraram maior efici��ncia no desbaste de frutos, principalmente na dose de 400 mg L-1, promovendo 66,6% de queda de frutos, sem contudo induzir a abscis��o foliar. As doses inferiores de ethephon tamb��m promoveram desbaste de frutos da ordem de 40%. As porcentagens de queda de frutos foram pequenas, para plantas pulverizadas com ANA, enquanto que a aplica����o de ethephon promoveu maior efici��ncia no desbaste de frutos.

Caracteriza����o mec��nica e t��rmica de comp��sitos de poli (cloreto de vinila) refor��ados com fibras de sisal

Funda����o de Amparo �� Pesquisa do Estado de S��o Paulo (FAPESP)

Controle do amadurecimento de banana 'Prata-An��' armazenada sob refrigera����o e atmosfera modificada passiva com o uso do 1-metilciclopropeno

O 1- Metilciclopropeno (1-MCP) �� um produto inovador que inibe a a����o do etileno em vegetais, retardando o in��cio do amadurecimento de pom��ceas, frutas de caro��o e frutas tropicais. Com este trabalho objetivou-se avaliar a efici��ncia de diferentes concentra����es do 1-MCP no controle do amadurecimento de bananas 'Prata-An��' produzidas no Norte de Minas Gerais, armazenadas a 12��C e 95% de UR sob atmosfera modificada passiva. Os cachos foram colhidos no grau 1 de colora����o da casca, que corresponde ao est��dio verde de matura����o. Foram utilizadas somente as segundas pencas dos cachos selecionados e estas foram separadas em buqu��s de 4 frutos. Cada parcela constou de 4 repeti����es e cada repeti����o 1 buqu��. As concentra����es do 1-MCP aplicadas foram: 0, 30, 60 e 90 ppb. Os frutos foram acondicionados em bandejas de isopor e embalados em filme de PVC de 15 micras, armazenados a 12��C e 95% de UR, sendo avaliados aos 10, 15, 20, e 25 dias. As avalia����es realizadas constaram de di��metro, grau de colora����o da casca, firmeza, s��lidos sol��veis, acidez titul��vel e pH. A aplica����o do 1-MCP foi eficaz em retardar o amadurecimento de bananas 'Prata-An��' cultivadas na regi��o Norte de Minas Gerais. As concentra����es de 30, 60 e 90 ppb n��o apresentaram efeito diferenciado quanto ��s caracter��sticas avaliadas, podendo ser utilizada a concentra����o de 30 ppb, com economia do produto, obtendo-se os mesmos benef��cios das concentra����es de 60 e 90 ppb.

Inibidor da a����o do etileno na conserva����o p��s-colheita de Chrysanthemum morifolium Ramat cv. Dragon

A durabilidade e a qualidade p��s-colheita de flores de corte s��o atributos fundamentais na sua valora����o ao longo da cadeia produtiva e na satisfa����o dos consumidores. Objetivou-se, nesta pesquisa, verificar o efeito do tiossulfato de prata, associado ou n��o �� sacarose, na manuten����o da qualidade p��s-colheita de hastes de cris��ntemos (Chrysanthemum morifolium Ramat cv. Dragon) . O experimento foi conduzido sob delineamento inteiramente casualizado, em esquema fatorial testando solu����es de manuten����o com tiossulfato de prata (STS), sob cinco n��veis (��gua destilada; STS a 0,2 mM; STS a 0,2 mM + sacarose a 50 g L-1; STS a 0,4 mM; STS a 0,4 mM + sacarose a 50 g L-1); e data de amostragem, por tr��s n��veis (0; 3; 6 dias). Utilizaram-se tr��s repeti����es com duas hastes florais em cada tratamento. Foram feitas avalia����es f��sicas: colora����o, massa fresca e conte��do relativo de ��gua (CRA); avalia����es qu��micas: a����cares redutores e pigmentos; e avalia����es qualitativas: turgesc��ncia, cor das flores, e n��mero de bot��es, flores entreabertas e abertas. O tratamento com 0,2 mM de STS possibilitou melhor manuten����o da massa fresca das hastes. A concentra����o de pigmentos e carboidratos redutores foi maior naqueles tratamentos em que a sacarose foi associada. A colora����o e o conte��do relativo de ��gua foram favorecidos nos tratamentos STS a 0,2 e 0,4mM. A concentra����o de 0,2 mM de STS foi a que obteve os melhores resultados, prolongando a vida de vaso das hastes. A qualidade das hastes foi superior, tendo as melhores avalia����es de conte��do de ��gua, cor e turgesc��ncia.

Synthesis, characterization and catalytic properties of nanocrystaline Y2O3-coated TiO2 in the ethanol dehydration reaction

Funda����o de Amparo �� Pesquisa do Estado de S��o Paulo (FAPESP)

Synthesis and sintering of ZrO2-CeO2 powder by use of polymeric precursor based on Pechini process

Nanocrystalline ZrO2-12 mol % CeO2 powders were synthesized using a polymeric precursor method based on the Pechini process. X-ray diffraction (XRD) patterns showed that the method was effective to synthesize tetragonal zirconia single-phase. The mean crystallite size attained ranges from 6 to 15 nm. The BET surface areas were relatively high reaching 97 m(2)/g. Studies by nitrogen adsorption/desorption on powders, dilatometry of the compacts, and transmission electron microscopy (TEM) of the powders, were also developed to verify the particles agglomeration state. Both citric acid : ethylene glycol ratio and calcination temperature affected the powder morphology, which influenced the sinterability and microstructure of the sintered material, as showed by scanning electron microscopy (SEM). (C) 2001 Kluwer Academic Publishers.

Electric measurements with constant current: A practical method for characterizing dielectric films

This article assesses the use of the constant current (CC) method for characterizing dielectric films. The method is based on charging the sample with a constant current (current stress) and measuring the corresponding voltage rise under the closed circuit condition. Our article shows that the CC method is an alternative to the constant voltage stressing method to study the electric properties of nonpolar, ferroelectric, and polar polymers. The method was tested by determining the dielectric constant of polytetrafluoroethylene, and investigating the electric conduction in poly(ethylene terephthalate). For the ferroelectric polymer poly(vinylidene fluoride), it is shown that hysteresis loops and the dependence of the ferroelectric polarization on the electric field can be obtained. (C) 2001 American Institute of Physics.

Doping of polyaniline by corona discharge

In the present article it is shown that a corona discharge can be employed to dope thin films of polyaniline (PANI) coated on poly(ethylene terephthalate) films, allowing the electrical conductivity to be tuned within the range 10(-10) to 0.3 S cm(-1). A study of the effect of different corona conditions, namely corona treatment for positive and negative polarities, air humidity, treatment time, corona current, and the geometry of the corona triode, on the electrical conductivity of the polyaniline is presented. The results indicate that the corona discharge leads to protonic doping of polyaniline similar to that which occurs in conventional protonic acid solution doping. Atomic force microscopic analysis shows that, as the PANI is exposed to the corona discharge, its globular morphology is disrupted leading to the appearance of droplet-like features and a significant decrease in the average height and surface roughness. Doping by corona discharge presents several advantages over the conventional solution method namely that it is a dry process which does not require use of chemicals reagents, and which is both rapid and avoids dopant migration. The latter can be important for applications of PANI in microelectronic devices. (C) 2000 American Institute of Physics. [S0021-8979(00)01608-X].

Mechanical properties, hydrophilicity and water activity of starch-gum film: effect of additives and deacetylated xanthan gum

The effect of deacetylated xanthan gum, additives (sucrose, soybean oil, sodium phosphate and propylene glycol) and pH modifications on mechanical properties, hydrophilicity and water activity of cassava starch-xanthan gum films has been studied. Sucrose addition resulted in the highest effect observed on cassava starch films elongation at break. The deacetylated xanthan gum had higher effect on elongation at break when comparing to the acetylated gum, although both gums presented an inferior effect in relation to the obtained with sucrose. However, when comparing to the control and PVC films, lower tensile strength resistance values were observed when adding sucrose. Increased water activity was observed for films added with sucrose, thus, increasing the material biodegradation. Sucrose and deacetylated xanthan gum addition resulted in a slight hydrophilicity increase. (C) 2004 Elsevier Ltd. All rights reserved.

Cracks developed during SrTiO3 thin-film preparation from polymeric precursors

Strontium titanate (SrTiO3) thin films were prepared by dip-coating Si(111) single-crystal substrates in citrate solutions of ethylene glycol, considering several citric acid/ethylene glycol (CA/EG) ratios. Measurements of intrinsic viscosity indicate that increasing the amount of EG increases the precursors' polymeric chains and increases the weight loss. After deposition the substrates were dried on a hotplate (approximate to 150 degrees C); this was followed by heat treatment at temperatures ranging from 500 to 700 degrees C using heating and cooling rates of 1 degrees C min(-1). SEM and optical microscopy investigations of the sintered films obtained from different CA/EG ratios indicate that there is a critical thickness above which the films present cracks. This critical thickness for SrTiO3 films deposited on the Si(111) substrate is about 150 nm, Measurements of crack spacing as a function of film thickness indicate that the origin of cracks cannot be explained by the elastic behavior of the film but rather by the viscoelastic relaxation of the film during pyrolysis and sintering. Copyright (C) 1999 John Wiley & Sons, Ltd.

Indium tin oxide films prepared via wet chemical route

In this work, indium tin oxide (ITO) films were prepared using a wet chemical route, the Pechini method. This consists of a polyesterification reaction between an alpha-hydroxicarboxylate complex (indium citrate and tin citrate) with a polyalcohol (ethylene glycol) followed by a post annealing at 500 degrees C. A 10 at.% of doping of Sn4+ ions into an In2O3 matrix was successfully achieved through this method. In order to characterize the structure, the morphology as well as the optical and electrical properties of the produced ITO films, they were analyzed using different experimental techniques. The obtained films are highly transparent, exhibiting transmittance of about 85% at 550 nm. They are crystalline with a preferred orientation of [222]. Microscopy discloses that the films are composed of grains of 30 nm average size and 0.63 nm RMS roughness. The films' measured resistivity, mobility and charge carrier concentration were 5.8 x 10(-3) Omega cm, 2.9 cm(2)/V s and -3.5 x 10(20)/cm(3), respectively. While the low mobility value can be related to the small grain size, the charge carrier concentration value can be explained in terms of the high oxygen concentration level resulting from the thermal treatment process performed in air. The experimental conditions are being refined to improve the electrical characteristics of the films while good optical, chemical, structural and morphological qualities already achieved are maintained. (C) 2007 Elsevier B.V. All rights reserved.

Chemical vapor deposition of multi-walled carbon nanotubes from nickel/yttria-stabilized zirconia catalysts

Multi-walled carbon nanotubes (MWNT) were produced by chemical vapor deposition using yttria-stabilized zirconia/nickel (YSZ/Ni) catalysts. The catalysts were obtained by a liquid mixture technique that resulted in fine dispersed nanoparticles of NiO supported in the YSZ matrix. High quality MWNT having smooth walls, few defects, and low amounts of by-products such as amorphous carbon were obtained, even from catalysts with large Ni concentrations (> 50 wt.%). By adjusting the experimental parameters, such as flux of the carbon precursor (ethylene) and Ni concentration, both the MWNT morphology and the process yield could be controlled. The resulting YSZ/Ni/MWNT composites can be interesting due to their mixed ionic-electronic transport properties, which could be useful in electrochemical applications.

Thermal degradation of geomembranes after exposure to heat

HDPE and PVC geomembranes are sensitive to changes in their properties when in contact with high temperatures. The effects of hot temperature on polymeric geomembranes are assessed by the ASTM D794 and ASTM D5721.This paper brings an analysis of degradation of the Poly Vinyl Chloride (PVC) and High Density Poly Ethylene (HDPE) geomembranes when exposed to conventional and air oven after specific periods.. Mechanical and physical properties were evaluated. OIT tests were also performanced to evaluate the level of oxidation degradation occurred on the HDPE geomembranes. Geomembranes of two thicknesses were tested: 1.0, 2.0 nun (PVC) and 0.8, 2.5 mm, (HDPE). The results obtained show, for example, that after the last period of exposure, the PVC geomembranes (1.0, 2.0 mm) were more rigid and stiffer than fresh samples. The HDPE geomembranes, on the other hand, when exposed to heat presented increases in deformation. OIT tests showed efficient to detect some level of degradation on the HDPE geomembranes.