Parametrically excited surface wave modes on a fluid layer driven by vertical forcing can interact with each other when more than one spatial mode is excited. We have investigated the dynamics of the interaction of two modes that are degenerate in a square layer, but non-degenerate in a rectangular one. Novel experimental techniques were developed for this purpose, including the real-time measurement of all relevant slowly varying mode amplitudes, investigation of the phase-space structure by means of transient studies starting from a variety of initial conditions, and automated determination of stability boundaries as a function of driving amplitude and frequency. These methods allowed both stable and unstable fixed points (sinks, sources, and saddles) to be determined, and the nature of the bifurcation sequences to be clearly established. In most of the dynamical regimes, multiple attractors and repellers (up to 16) were found, including both pure and mixed modes. We found that the symmetry of the fluid cell has dramatic effects on the dynamics. The fully degenerate case (square cell) yields no time-dependent patterns, and is qualitatively understood in terms of third-order amplitude equations whose basic structure follows from symmetry arguments. In a slightly rectangular cell, where the two modes are separated in frequency by a small amount (about 1%), mode competition produces both periodic and chaotic states organized around unstable pure and mixed-state fixed points.

A simple methodology for the determination of the fatty acid composition of edible oils through (1)H NMR is proposed. The method is based on the fact that all fatty acid chains are esterified to a common moiety, glycerol, and the quantification is done directly in the (1)H NMR spectra through the relationship between the areas of a characteristic signal of each fatty acid and a signal of the glycerol moiety, without the use of mathematical equations. The methodology was successfully applied to determine the fatty acid composition of several edible oils, with equivalent results to those given by the AOAC Official method by gas chromatography. Its main advantages are simplicity and the lack of need for sample pre-treatment such as derivatization or extraction.

Os compostos utilizados pelo percevejo da soja Piezodorus guildinii como feromônio de alarme foram caracterizados através da análise da composição química das secreções da glândula metatorácica dos insetos adultos. Além dos hidrocarbonetos característicos, (E)-2-hexenal e (E)-4-oxo-2-hexenal foram detectados como constituintes majoritários. Tais compostos já foram previamente descritos como feromônio de alarme em outras espécies de pentatomídeos.The compounds utilized by the soybean stink bug Piezodorus guildinii as alarm pheromone were characterized by analysis of the chemical composition of the metathoracic scent gland secretions from adult bugs. In addition to characteristic hydrocarbons, (E)-2-hexenal and (E)-4-oxo-2-hexenal were detected as major constituents. These compounds were previously described as alarm pheromone in several other pentatomid species.

No abstract

The cetane number (CN) is one of the most important parameters regarding diesel fuel oil quality, mainly ignition properties. Traditionally, the CN determination is performed by a quite laborious and high-cost method on an explosion engine. On the other hand, nuclear magnetic resonance (NMR) spectroscopy is increasing as a versatile tool for quality control in several areas, such as petroleum and fuels, which permits the fast and direct investigation on samples. In this work, two NMRbased methods for CN determination based on multivariate calibration were developed with advantages of time saving, without the need of any sample treatment.

No abstract

Stability boundaries and phase-space measurement for spatially extended dynamical systems." Review of scientific instruments 59.2 (1988): 280-284.Automated methods of studying the stability boundaries and phase-space dynamics of a spatially extended dynamical system are presented. The stability boundaries are determined accurately as a function of external parameters in an automated search. The amplitudes of the individual spatial modes are measured in real time in order to determine the structure of the at tractors in phase space. Some control over initial conditions allows the basins of attraction and the transients leading to the attractors to be studied as well. The methods are applied specifically to interacting waves on a fluid surface, but should also be useful to other extended dynamical systems.Rev. Sci.lnstrum. 59 (2), February 1988 0034-67 48!88/0202~O-05$() 1.30

Neotropical Entomology 30(3): 361-364 (2001) Machos são Atraídos por Armadilhas com Fêmeas: Uma Nova Perspectiva para Manejo de Diabrotica speciosa (Germar) (Coleoptera: Chrysomelidae) Usando Feromônio Sexual RESUMO -As respostas de Diabrotica speciosa (Germar) para armadilhas com adultos foram estudadas como sugestão da produção de feromônio. Inicialmente, um ensaio para estabelecer a altura adequada para colocação de armadilhas para capturar D. speciosa foi conduzido em campo de feijão. Armadilhas colocadas a 0,25 m de altura capturaram cerca de 3,5 vezes mais adultos do que a 0,5; 0,75 e 1,0 m. As respostas para fêmeas e machos virgens de duas idades (mais novos = 24 a 72h e mais velhos = 72 a 120h após emergência de adultos), fêmeas e machos copulados foram avaliadas em campo de feijão consorciado com café, Coffea arabica L. Armadilhas com fêmeas virgens capturaram cerca de 22 (mais jovens) e 13 vezes (mais velhas) mais adultos machos do que as testemunhas (armadilhas sem insetos). Capturas foram cerca de 70% mais efetivas usando fêmeas mais jovens. Nenhum dos outros tratamentos aumentou as capturas nas armadilhas. Os resultados indicam que há um feromônio sexual produzido por fêmeas em D. speciosa. PALAVRAS-CHAVE:Insecta, semioquímico, altura de colocação de armadilhas, Luperini, Fucata.ABSTRACT -The field responses of Diabrotica speciosa (Germar) to traps baited with adults were studied as an suggestion of the pheromone production. Firstly, an assay to settle a suitable height placement to capture D. speciosa was carried out in common beans, Phaseolus vulgaris L., field. Traps placed at 0.25-m height captured ca. 3.5 times more beetles than 0.5, 0.75 and 1.0-m traps. The responses to virgin females and males of two ages (younger = 24 to 72h and older = 72 to 120h after adult emergence), mated females and males were assessed in common bean interplanted among coffee, Coffea arabica L., field. Virgin females baited traps captured ca. 22 times (younger) and 13 times (older females) more male beetles than control traps. Captures were ca. 70% more effective using younger females. None of the other treatments improved trap attraction. These results strongly indicated that there is a female-produced sexual pheromone in D. speciosa.