The correlation between subordinate fish eye colour and received attacks: a negative social feedback mechanism for the reduction of aggression during the formation of dominance hierarchies

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Formation of beta-nickel hydroxide plate-like structures under mild conditions and their optical properties

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Formation of multiple or adventive embryos in Epidendrum nocturnum Jacq (Orchidaceae)

Under greenhouse conditions, Epidendrum nocturnum Jacq. plants produce fruits by both self-fertilization and cleistogamy. Although adapted to these reproductive processes the species respond also to cross-pollination. Seeds without embryos and with one embryo are usual but occasionally seeds with two, three or four embryos are produced. Multiple embryos are formed by polyembryony and apomixis. © 1985 Annals of Botany Company.

Formation of SnO2 gels from dispersed sols in aqueous colloidal solutions

Transparent SnO2 gels were obtained from SnCl4 aqueous solution. The sol formation from tin oxihydroxy peptization in different concentrations and by electrolyte addition in solution was measured. It was verified that the residual presence of chloride ions compromises the colloidal system stability. The sol-gel transition was investigated as a function of the quantity of solid particles in the aqueous environment and of aging time at 60°C by infrared spectroscopy and rheological measurements. The transition from plastic to pseudoplastic flow observed with the increase in loading suggests that a continuous and three-dimensional network formation is closely related to hydrogen bridges and/or hydrogen clusters, culminating in the gel formation. © 1990.

Chlamydospore formation of paracoccidioides brasiliensis strain Pb-18

Paracoccidioides brasiliensis is the causative agent of paracoccidioidomycosis and is known as a temperature-dependent dimorphic fungus. Even though several routes of transformation from a mycelial to yeast forms have been reported, the route via chlamydospore is the most important. At this time, conditions of temperature, nutrients, population of yeast cells and concentration of agar which influence chlamydospore formation are examined. P. brasiliensis strain Pb-18 was used in this experiment. Its yeast cells were mixed with agar media, and were cultured at various temperatures. The results were as follows: 1. At 25°C, more chlamydospores were formed in poor media than in rich ones. 2. At over 25°C, the number of chlamydospores increased in proportion to the increase in temperature. 3. Chlamydospores were most frequently formed when 106 yeast cell units were mixed with 25ml of medium. 4. One and 2.0‰ agars were the most adequate concentrations for chlamydospore formation.

Influence of viscoelastic characteristics of the colloidal suspensions on the formation of SnO2 supported membranes

SnO2 supported membranes have been prepared by sol-casting on alumina tubular substrate, using aqueous colloidal suspensions prepared by sol-gel route. The viscoelastic behaviour during sol ageing was analyzed by dinamic rheologial measurements. The complex viscosity and the storage and loss moduli have been followed during the sol-gel transition and the results have been correlated with the linear aggregates growth and the scalar percolation models. The scanning electron microscopy has evidenced that the homogeneity and thickness of the membrane depend on the sol ageing time. Crack-free and homogeneous membranes have been obtained for coated layers of 0.5μm thickness. © 1997 Trans Tech Publications.

Formation of colloidal particles of hydrous iron oxide by forced hydrolysis

The mechanism of formation and growth of hydrous iron oxide (FeOOH) during the initial stages of forced hydrolyses of ferric chloride aqueous solution was studied by small angle X-ray scattering (SAXS). The effect of the hydrolysis temperature (60°C, 70°C and 80°C) and of the addition of urea on the formation of colloidal particles under isothermal conditions were investigated. Based on the experimental scattering functions in the Guinier range, we suggest the presence of elongated colloidal particles. The particle diameter and length, and their variation with time, were determined by fitting the form factor of prolate ellipsoids to the experimental scattering functions. We have assumed that our solutions are in a dilute state and that all colloidal particles are approximately of the same size. The colloidal particles have geometrical shapes similar to those of the subcrystals that build up the superstructure of β-FeOOH crystals, indicating that the formation of this hydrous iron oxide is governed by an aggregation process. Otherwise, the addition of urea hinders the growth and yields smaller particles, with a reduction in size greater than 50%. © 2000 Elsevier Science B.V. All rights reserved.

Study on transient ice formation of laminar flow inside externally supercooled rectangular duct

The transient process of solidification of laminar liquid flow (water) submitted to super-cooling was investigated both theoretically and experimentally. In this study an alternative analytical formulation and numerical approach were adopted resulting in the unsteady model with temperature dependent thermophysical properties in the solid region. The proposed model is based upon the fundamental equations of energy balance in the solid and liquid regions as well as across the solidification front. The basic equations and the associated boundary and initial conditions were made dimensionless by using the Landau transformation to immobilize the moving front and render the problem to a fixed plane type problem. A laminar velocity profile is admitted in the liquid domain and the resulting equations were discretized using the finite difference approach. The numerical predictions obtained were compared with the available results based on other models and concepts such as Neumann analytical model, the apparent thermal capacity model due to Bonacina and the conventional fixed grid energy model due to Goodrich. To obtain further comparisons and more validation of the model and the numerical solution, an experimental rig was constructed and instrumented permitting very well controlled experimental measurements. The numerical predictions were compared with the experimental results and the agreement was found satisfactory.

Optimization of the mechanical properties of low-carbon steels by formation of a multiphase microstructure

In this work five methods of heat treatments are investigated in order to obtained convenient volume fractions of ferrite, bainite, martensite and retained austenite, starting with a low carbon steel and seeking the distinction of the phases, through optical microscopy. Specific chemical etching is improved. The results in tensile and fatigue tests were accomplished and the results were related with the microstructural parameters. The results show that the mechanical properties are closely related with the phases, grains size and the phases morphology. Copyright © 2001 Society of Automotive Engineers, Inc.

Interactions of chlorine with tropical aquatic fulvic acids and formation of intermediates observed by fluorescence spectroscopy

The interactions of tropical aquatic fulvic acids (AFA) with chlorine and formation of trihalomethanes were characterized by fluorescence spectroscopy. The aquatic humic substances (AHS) were isolated from a dark-brown stream (located in a environmental protection area near Cubatão city in São Paulo State, Brazil) by means of the collector XAD 8 according the procedure recommended by the International Humic Substances Society. The photoluminescence measurements were made by using a Perkin Elmer spectrometer; AHS, aquatic humic acids (AHA) and AFA samples were assayed. The interactions of AFA and chlorine were characterized by using different reaction times (1, 24, 48, 72 and 168 h) and chlorine concentrations (2.5, 5.0, 10.0 and 20.0 mg L-1). The relative fluorescence intensity for AFA was significantly decreased with the increasing of chlorine concentration and reaction time. The reduction of fluorescence intensity in the region of longer wavelength was interpreted as an indicative of interaction between condensed aromatic groups of AFA and chlorine.

Polymer treatment by plasma immersion ion implantation of nitrogen for formation of diamond-like carbon film

Nitrogen ions were implanted by plasma immersion in Kapton, Mylar and polypropylene, with the objective of forming a diamond-like carbon layer on these polymers. The Raman spectrum of the implanted polypropylene showed typical Diamond-Like Carbon (DLC) graphite (G) and disorder (D) peaks, with an sp 3/sp2 hybridization ratio of approximately 0.4 to 0.6. The XPS analysis of the three implanted polymers also showed peaks of C-C and N-C bonds in the sp3 configuration, with hybridization ratios in the same range as the Raman result. The implanted polymers were exposed to oxygen plasma to test the resistance of the polymers to oxygen degradation. Mass loss rate results, however, showed that the DLC layer formed is not sufficiently robust for this application. Nevertheless, the layer formed can be suitable for other applications such as in gas barriers in beverage containers. Further study of implantation conditions may improve the quality of the DLC layer.

Studies on the formation of complex coacervates between chitosan and alginate during microparticles preparation

The formation of complex coacervates between chitosan and alginate was evaluated during microparticles formation. Mass ratio between polyelectrolytes and calcium chloride concentration were determinated by conductimetric analysis and by calcium ions quantification, respectively. Inert microparticles were prepared using a complex coacervation method in W/O emulsion and morphological analyses of microparticles were carried out. This method enabled the production of spherical particles, with slightly rough surface and narrow size distribution with maximal diameter of 10 μm.

The formation of the professionals for the timber industrial sector of the civil construction

The common point between the two forms of production of the wood-based sector in Brazil, one practically manufacturing and the other high technology, is in the qualification of the of the labor. In both cases, the professionals are being formed directly in the productive line and rarely with qualification in the academic area. There is not a public political education for the qualification of the labor, and the work market that does not demand qualified professionals, contributes for the sector stagnation. So, in order to excel the socio-cultural barriers in relation to the use of wood in the buildings, new attitudes are necessary in the teaching of the contents of the curricular programs, mainly, in formation of the architect and civil engineering.

Effect of brushing with conventional versus whitening dentifrices on surface roughness and biofilm formation of dental ceramics

The aim of this study was to evaluate the effect of conventional and whitening dentifrices on the weight loss, surface roughness, and early in situ biofilm formation on the surface of dental ceramics. Standardized feldspar ceramic specimens (Vita VM7 and Vita VM13) were submitted to the following experimental conditions: no brushing; brushing without a dentifrice; brushing with a conventional dentifrice; and brushing with a whitening dentifrice. A brushing machine was used to simulate brushing. The mass and surface roughness of all specimens from the test groups were evaluated prior to and after brushing. Ten participants used an oral device for eight hours to evaluate the biofilm formed in situ on the specimens. Scanning electron microscopy was used for qualitative and quantitative analysis of the biofilm. ANOVA and Tukey tests were used to analyze the results of weight loss, surface roughness, and presence of bacteria. A one-way Kruskal-Wallis test was used for bacterial colonization results. For both ceramics, brushing with a whitening dentifrice resulted in weight loss that was significantly greater when compared to brushing without a dentifrice or with a conventional dentifrice. Increased surface roughness was noticed on VM13 ceramic samples with both dentifrices, whereas only conventional dentifrice had a significant effect on the surface roughness of VM7 samples. For both VM7 and VM13, no difference was found between the experimental conditions with regard to the presence or number of bacteria. Cocci and short rods were the predominant microbial morphotypes. Granular or fibrillar acellular material partially covered the specimens. Brushing with a whitening dentifrice resulted in significant weight loss of ceramic restorations, while brushing with both conventional and whitening dentifrices can roughen ceramic surfaces. The increase in roughness was not clinically significant to contribute to increased biofilm formation.