Propriedades eletrônicas, estruturais e constantes elásticas do ZnO

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Morphology and anatomy in Heliconia angusta Vell. and H. velloziana L. Emygd. (Zingiberales: Heliconiaceae) from the Atlantic forest of southeastern Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Morphology of the testicles of some brazilian species of Diplopoda and their phyllogenetic relations

The morphology of the testicles of some Brazilian species of Diplopoda is described. One type is scalariform, with two deferent ducts and the other consists of some single deferent duct. Phyllogenetic considerations on the structure are made.

Zoeal morphology of Pachygrapsus transversus (Gibbes) (Decapoda, Grapsidae) reared in the laboratory

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Germination of Styrax camporum Pohl. seeds in response to substrate types, moisture contents and the seed morphology

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Surface morphology and optical characterization of OC1 OC6-PPV films

We report optical and morphological properties of poly(2-methoxy-5-hexyloxy-p-phenylenevinylene) (OC1OC6-PPV) films processed by casting, spin-coating (SC) and Langmuir-Blodgett (LB) techniques. The absorption spectra are practically the same, with an absorption maximum at approximately at 500 nm. For the photoluminescence (PL) spectra at low temperature (T=10K), a small but significant difference was noted in the cast film, in comparison with the LB and SC films. The zero-phonon transition shifted from 609 nm for the LB film to 615 and 621 nm for the SC and cast films, respectively. At room temperature, the PL spectra are similar for all films, and blue shifted by ca. 25 nm in comparison with the spectra at low temperature due to thermal disorder. Using atomic force microscopy (AFM) we inferred that the distinctive behavior of the cast film, probably associated with structural defects, is related to the large thickness of this film. The surface roughness, which was surprisingly higher for the LB film, apparently played no role in the emission properties of OC1OC6-PPV films.

Sinterização e caracterização de segunda fase em sistemas SnO2-ZnO

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Comparison of leaf morphology and anatomy among Malva sylvestris (gerânio-aromático), Pelargonium graveolens (falsa-malva) and Pelargonium odoratissimum (gerânio-de-cheiro)

Malva sylvestris é comumente confundida com Pelargonium graveolens e Pelargonium odoratissimum devido às semelhanças na morfologia foliar. As folhas de M. sylvestris possuem antocianinas com propriedades citotóxicas, antiinflamatória, antitumoral e antioxidante já comprovadas cientificamente. As folhas de P. odoratissimum apresentam óleo essencial com propriedades antibacteriana e espasmolítica, e o óleo essencial da folha de P. graveolens possui atividade antimicrobiana e antifúngica. O objetivo deste estudo foi analisar morfo-anatomicamente as folhas destas espécies, apontando diferenças que possam ser utilizadas para esclarecer controvérsias na sua utilização como planta medicinal. Com a finalidade de se comparar anatomicamente a estrutura de cada planta, as amostras foram observadas por Microscopia de Luz e Microscopia Eletrônica de Varredura (MEV). A anatomia foliar entre as espécies foi bem distinta. Malva sylvestris apresentou tricomas do tipo capitado, estrelado e tector, além de drusas e células mucilaginosas. A distinção entre P. graveolens e P. odoratissimum foi observada em relação aos tricomas. Ambas as espécies apresentaram tricomas glandulares e tectores, sendo que P. graveolens se diferencia pela maior altura dos tricomas tectores e menor quantidade destes em relação ao P. odoratissimum. Este trabalho permitiu constatar diferenças anatômicas, auxiliando na taxonomia e classificação entre estas espécies.

Morphology of the digestive tube of Macuxitermes triceratops and its phylogenetic implications (Isoptera: Termitidae: Nasutitermitinae)

The gross morphology of digestive tube of Macuxitermes triceratops is described and illustrated. The gut of this species is very similar to those of Embiratermes and Ibitermes, and does not show any obvious autopomorphic character. The phylogenetic relations of this genus are discussed based on the available evidence, and it is concluded that it is probably the sister group of Armitermes + Curvitermes + Cryilliotermes.

EFFECT OF CR2O3 ON THE ELECTRICAL-PROPERTIES OF MULTICOMPONENT ZNO VARISTORS AT THE PREBREAKDOWN REGION

The effect of Cr2O3 on the electrical properties of the multicomponent ZnO varistors was investigated using voltage-current curves and impedance spectroscopy. The structure and morphological modifications were analysed by X-ray diffraction and scanning electron microscopy, respectively. It was observed in samples with addition 0.1 mol% Cr2O3 that there was an improvement in the electrical properties of the varistors, but the increase in concentration had a deleterious effect on the potential barrier at the grain boundary. The excess Cr2O3 segregates at the grain-boundary region and increases the donor concentration, leading to a higher leakage current.

Nonlinear electrical behaviour of the Cr2O3, ZnO, CoO and Ta2O5-doped SnO2 varistors

The effects of Cr2O3 on the properties of (Zn, Co, Ta)-doped SnO2 varistors were investigated in this study. The samples with different Cr2O3 concentrations were sintered at 1400 degrees C for 2 h. The properties of (Zn, Co, Ta, Cr)-doped SnO2 varistors were evaluated by XRD. dilatornetry, SEM, I-V and impedance spectroscopy. DC electrical characterization showed a dramatic increase ill the breakdown electrical field and in the nonlinear coefficient with the increase in Cr2O3 concentration. The grain size was found to decrease from 13 to 5 mu m with increasing the Cr2O3 content. The impedance data, represented by means of Nyquist diagrams, show two time constants, one at low frequencies and the other at high frequencies. (c) 2005 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

WO3 and ZnO-doped SnO2 ceramics as insulating material

SnO2 ceramics doped with ZnO and WO3 were prepared by mixed oxide method. The effect of ZnO and WO3 additives could be explained by the substitution of Sn4+ by Zn2+ and W6+. The addition of WO3 inhibits the grain growth due to the segregation of SnZnWO8 and ZnWO6 at the grain boundaries without strong influence on the densification process. The electrical characterization (log E x log J) shows that the ternary system SnO2-ZnO-WO3 exhibits a very high resistivity of around 10(14) Omega M. Independently of the WO3 concentration, the electrical conductivity of the Sn02-ZnO-WO3 system is always lower than that of the undoped tin dioxide. (C) 2005 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

ZnO varistors from intensively milled powders

Two ways of application of intensive milling in ZnO varistors processing were compared. First was intensive milling of mixture of previously prepared constituent phases. In this case, intensive milling was applied only to obtain highly activated nanocrystalline varistor powder mixtures. Second application is intensive milling of simple mixture of oxides that could result not only in activation and formation of nanocrystal line powders, but also in mechanochernical reaction and synthesis of constituent phases. Powders and ceramics samples were characterized by XRD and SEM analysis. as well as by de electrical measurements (nonlinearity coefficients, leakage current and breakdown field). Differences in microstructural and electrical properties of obtained varistors were discussed and optimal milling and processing conditions were recommended. The best electrical characteristics were found in sample ZI -DMCP-m, which exhibited leakage current of 2.5 mu A/cm(2), nonlinear coefficient reaching 58 and breakdown field of 8950 V/cm. (c) 2007 Elsevier Ltd. All rights reserved.