Influence of doping on the preferential growth of alpha-MoO3

MoO3 is a lamellar material with applications in different areas, as solid lubricants, catalysis, solar cells, etc. In the present work, MoO3 powders, synthesized by the polymeric precursor method, were doped with nickel or cobalt. The powder precursors were characterized by TG/DTA. After calcination between 500 and 700 degrees C, the samples were characterized by X-ray diffraction, infrared and Raman spectroscopy and scanning electron microscopy. beta-MoO3 was obtained after calcination at low temperatures. With the temperature increase, alpha-MoO3 is observed, with a preferential growth of the (0 2k 0) planes, when the material is doped and calcined at 700 degrees C. Doping with nickel increases five times the preferential growth. As a consequence, plate-like particles are observed. (c) 2007 Elsevier B.V. All rights reserved.

Biologia populacional de Pareiorhina rudolphi (Loricariidae, Hypostominae) na microbacia do Ribeirão Grande, serra da Mantiqueira oriental, Estado de São Paulo

Pareiorhina rudolphi was sampled in streams of the Ribeirao Grande system, eastern Serra da Mantiqueira (22[degree]47[minute]08[second]S, 45[degree]28[minute]17[second] W). Samplings were carried out using an electrofishing device, during the months of July/2001, October/2001, February/2002 and April/2002. Sex-ratio diverged significantly from the expected 1: 1 ratio([chi]2 = 6.53; p < 0.05), standing at 1.6:1 (female: male). The spawning period for Pareiorhina rudolphi lasts from spring to summer, with, the highest observed, in October and February by the gonadosomantic index and the relative condition factor coincided with the spawning period. The length at sexual maturity of P. rudolphi is about 4.45 cm for both sexes. The absolute fecundity was low, and ranged from 4 to 11 oocytes. The periphyton was used as a direct food source by the species, which remain attached to the substrate with their large circular lips, and use their conspicuous Slightly Yellowish teeth to graze the periphyton. The growth parameters, natural mortality rate and survival rate for P, rudolphi were respectively: K = 0.35 year-1, L[infinity] = 7.2 cm, tmax = 8.6 years, M = 1.1 year-1, S = 33%. The characteristics presented by P. rudolphi occur in the environment function of a population adjustment, and not of species abundance.

Oriented enstatite inclusions in natural diamond.

Six crystal inclusions in a twinned diamond from the Tibagi River deposits near Telemaco Borba, Parana State, Brazil, were identified as forsterite (prismatic crystals) and enstatite (tabular crystals, with a 18.17, b 8.81, c 5.17 A). The prismatic forsterite inclusions are oriented along the <110> directions of the host diamond; the main direction of the tabular enstatite crystals is in the same orientation. The identity and orientation of the inclusions were obtained by X-ray precession camera. Enstatite (210) is nearly parallel with the (111) octahedral layer of diamond; a possible epitaxial relationship is discussed.-R.A.H.

Prevalence of taurodontism in premolars

Taurodontism does not involve molar teeth exclusively. To call attention to the occurrence of this phenomenon in premolars, 4,459 extracted mandibular and maxillary premolars were examined. Eleven showed evidence of taurodontism. Roentgenograms taken from a buccolingual direction confirmed the diagnosis of taurodont teeth.

On the equivalence of the mechanisms governing switching and hysteresis phenomena

The nucleation and growth model, which is usually applied to switching phenomena, is adapted for explaining surface potential measurements on the P(VDF-TrFE) (polyvinylidene fluoride-trifluoroethylene) copolymer obtained in a constant current corona triode. It is shown that the growth is one-dimensional and that the nucleation rate is unimportant, probably because surface potential measurements take much longer than the switching ones. The surface potential data can therefore be accounted for by a growth model in which the velocity of growth varies exponentially with the electric field. Since hysteresis loops can be obtained from surface potential measurements, it is suggested that similar mechanisms can be used when treating switching and hysteresis phenomena, provided that account is taken of the difference in the time scale of the measurements.

Problems related to the employment of thin uranium films as neutron dosimeters

Thin uranium films built on muscovite mica basis and obsidian samples having known ages were irradiated with thermal neutrons at the IPEN/CNEN reactor, São Paulo. Comparing thin film performance with the obsidian one, it was observed that the latter feel a greater neutron fluence. Nominal fluences at the used facility are in agreement with the results obtained analysing the obsidian samples. A probable hypothesis to explain this disagreement, namely, the uranium loss from the thin films, was ruled out. © 1995.

Managing large scale virtual environments using portals

This article describes a technique for Large Scale Virtual Environments (LSVEs) partitioning in hexagon cells and using portal in the cell interfaces to reduce the number of messages on the network and the complexity of the virtual world. These environments usually demand a high volume of data that must be sent only to those users who needs the information [Greenhalgh, Benford 1997].

Efeitos de parâmetros de extrusão nas propriedades físicas de produtos expandidos de inhame

Effect of extrusion parameters was studied on the expansion index, specific volume, water absorption index (WAI) and water solubility index (WSI) of expanded yam snacks. The central composite design was used to study the parameters effect. It was verified three levels of temperature in the barrel (100, 115 and 130°C), three levels of screw speed (163, 204 and 245 rpm) and three levels of flour moisture (12, 15 and 18%). The results showed that expansion properties (expansion index and specific volume) depend on flour moisture and extrusion temperature. The WSI was dependant of three parameters. Higher levels of temperature and screw speed increase the water solubility index (WSI). The studied parameters did not influence the water absorption index (WAI).

The effect of age on hematological and serum biochemical values on juvenile ring-necked pheasants (Phasianus colchicus)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Evaluación de un ALC entre EEUU y Chile

Incluye Bibliografía

Determination of BTEX by GC-MS in air of offset printing plants: Comparison between conventional and ecological inks

The use of inks containing organic solvents by the offset printing process implies in the release of volatile organic compounds to the work environment. Many of these compounds such as benzene, toluene, ethylbenzene, and the xylene isomers (well known by the acronym BTEX) are extremely toxic. In this study, the BTEX concentrations were determined in two different printing plants that use distinct types of inks: the conventional and the so-called ecological, which is manufactured based on vegetal oil. Concentration ranges were 43-84, 15-3,480, 2-133, 5-459, and 2-236 μg m-3 for benzene, toluene, ethylbenzene, m + p-xylene, and o-xylene, respectively, for the conventional printing plant. At the ecological printing plant, concentration ranges were below limit of detection (