Resistance inducing agents on the biology and probing behaviour of the greenbug in wheat

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Piezoelectric behaviour of PZT doped with calcium: A combined experimental and theoretical study

An experimental and theoretical study on the piezoelectric behaviour of PZT doped with a range of calcium ion concentrations is presented. A systematic study of the effect on the piezoelectric properties of PZT doped with various concentrations of CaO at constant sintering temperature and sintering time was carried out. The remanent polarization, planar coupling factor and frequency-thickness constant increase with calcium concentration. Ab initio perturbed ion calculations show that the lattice energy decreases with calcium addition for both tetragonal and rhombohedral phases of PZT.

Comparative procedures for the sample decomposition of rocks used in organic agriculture and the determination of Cu, Fe, Mn, and Zn by FAAS

The aim of this work was to develop an appropriate sample preparation procedure for the flame atomic absorption spectrometry determination of Cu, Fe, Mn, and, Zn in rocks used in organic agriculture as a source of macro- and micronutrients.Six different procedures were evaluated and are classified into three groups: (a) pressure digestion system with Teflon bombs, (b) conventional wet digestion in a digester heating block, and (c) closed microwave system with pressure and temperature control.Two standard reference materials and two commercial samples were analyzed. It was found that the closed microwave system required low reagent consumption, less time, and resulted in low contamination.

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.

Effects of sire breed-grazing system and environmental parameters on the behaviour of beef calves just after birth

Effects of sire breed-grazing system and environmental factors on the first activities of high grade Nellore and crossbred Canchim x Nellore, Angus x Nellore, and Simmental x Nellore calves raised in intensive production systems and high grade Nellore calves raised in an extensive production system, after birth, were studied. During 2 years, 185 calves were observed from birth until the end of first suckling, and the following variables were estimated: duration of maternal attention (cow to calf) during the first 15 min after calving, latency to first attempt to stand up, latency to stand up, latency to first suckling, duration of first suckling and the interval from standing to suckling. Data were analyzed by least squares methods, with models that included fixed effects of year and time of the year of birth (March-April (early autumn) and May-June (late autumn)), sire breed-grazing system (Sy), sex of calf (Se), category of cow (primiparous and pluriparous), time of birth, Sy x Se, year x Sy and year x time of the year interactions and the covariates weight of calf, rainfall, air temperature and relative humidity in the day of birth. Calves born from 6:00 to 8:00 h presented the longest latencies to first stand up (40.3 +/- 5.1 min) and the shortest occur from 14:00 to 16:00 h (15.8 +/- 2.7 min) (P < 0.01). Primiparous cows provided longer attention toward the calf in the first 15 min after birth than pluriparous cows (13.0 +/- 0.7 min versus 11.1 +/- 0.5 min; P < 0.05). This attention was also shorter in earlier autumn (11.0 +/- 0.5 min) and longer in late autumn (13.1 +/- 0.8 min) (P < 0.05). Relative to sire breed-grazing system, Nellore calves raised intensively did take longer to stand and to suckle after birth as compared to crossbred calves also raised intensively (P < 0.01). However, grazing system did not affect (P > 0.05) any behaviour variable studied. As regard to sex differences, female calves did take less (P < 0.01) time to suckle after standing than male calves. Results showed that even purebred or crossbred Bos indicus calves in subtropical environmental need extra care when born on rainy days, especially during the first hours of the day. (C) 2006 Elsevier B.V. All rights reserved.

Effect of modifiers on thermal behaviour of Se in acid digestates and slurries of vegetables by graphite furnace atomic absorption spectrometry

The influence of sample preparation strategy of vegetables on the electrothermal behaviour of Se without and with chemical modifiers such as Pd(NO3)(2), Pd(NO3)(2) + Mg(NO3)(2), Pd(NO3)(2) + Cd(NO3)(2), pre-reduced Pd, Mg(NO3)(2), and Ni(NO3)(2) was investigated. Acid digestates and slurries of vegetables (0.1% m/v in 1% m/v HNO3 + 0.005% v/v of Triton X-100) were used to prepare reference solutions or slurries. For 10 mul of each modifier tested, pyrolysis and atomization temperatures were evaluated using pyrolysis and atomization curves, respectively. Best conditions, such as thermal stability, signal profile, repeatability and sensitivity were attained using Pd(NO3)(2) as chemical modifier. The following heating program (temperature, ramp/hold time) of the graphite tube of the Varian SpectrAA-800Z atomic absorption spectrometer was used: dry step (85 degreesC, 5/0 s; 95 degreesC, 40/0 s; 120 degreesC, 10/.5 s); pyrolysis step (1400 degreesC, 10/3s); atomization step (2200 degreesC, 1/2 s); clean step (2600 degreesC, 2/0 s). This pyrolysis temperature is 800 degreesC higher than when measuring without any modifier. For 20 muL sample volume and 10 mug Pd(NO3)(2), analytical curves in the 3.0-30 mug Se 1(-1) range were obtained. The method was applied for Se determination in acid digestates and slurries of 10 vegetable samples and one standard reference material (rice flower) and results were in agreement at 95% confidence level. Recoveries varied from 89 to 95% for spiked samples. The lifetime of the graphite tube was ca. 250 firings and the relative standard deviations (n = 12) for a typical acid digestate and slurry containing 20 mug Se 1(-1) were 3.8% and 8.3%, respectively. The limits of detection were 2.0 mug Se 1(-1) and 0.6 mug Se 1(-1) Se for digestates and slurries, respectively. (C) 2002 Elsevier B.V. Ltd. All rights reserved.

Dependence of La2O3 content on the nonlinear electrical behaviour of ZnO, CoO and Ta2O5 doped SnO2 varistors

The effects of La2O3 on the properties of (Zn, Co, Ta) doped SnO2 varistors were investigated in this study. The samples with different La2O3 concentrations were sintered at 1400 degrees C for 2 h and their properties were characterized by XRD, SEM, I-V and impedance spectroscopy. The grain size was found to decrease from 13 pm to 9 gm with increasing La2O3 content. The addition of rare earth element leads to increase the nonlinear coefficient and the breakdown voltage. The enhancement was expected to arise from the possible segregation of lanthanide ion due to its larger ionic radius to the grain boundaries, thereby modifying its electrical characteristics. Furthermore, the dopants such as La may help in the adsorption of O' to O '' at the grain boundaries characteristics. (c) 2006 Elsevier B.V. All rights reserved.

Rehydration and shrinkage behaviour of dried pineapple

The shrinking behavior, apparent densities and rehydration indexes of fresh and osmotically pre-treated pineapple slices during air-drying were obtained. The air drying velocity varied from 1.5 to 2.5 m/s and the air temperature from 40 to 70 degreesC. By means of automatic control, it was possible to obtain drying curves under conditions of constant product temperature. Volumetric shrinkage of fresh samples was temperature independent for drying at high air velocities but, at lower velocities, increased with decreasing drying temperature. Osmotically pre-treating the material resulted in reduced shrinkage, as well as drying with product temperature controlled, due to lower drying times needed that led to shorter high temperature exposition. Moisture dependence of apparent density was highly non-linear and could be fitted by an empirical model. Fresh sample rehydration indexes were higher than osmosed ones and increased with increasing temperature, except for pre-treated samples dried at 70 degreesC, probably due to superficial sugar caramelization, which reduced surface water permeability.

Synthesis, characterization and thermal behaviour of solid state compounds of 4-methylbenzylidenepyruvate with lighter trivalent lanthanides

Solid state Ln-4-Me-BP compounds, where Ln stands for lighter trivalent lanthanides (lanthanum to europium) and 4-Me-BP is 4-methylbenzylidenepyruvate, have been synthesized. Elemental analysis, complexometry, X-ray powder diffractometry, infrared spectroscopy and simultaneous thermogravimetry-differential thermal analysis (TG-DTA), have been used to characterize and to study the thermal behaviour of these compounds. The results provided information concerning the stoichiometry, crystallinity, thermal stability and thermal decomposition. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Synthesis, characterization and thermal behaviour of solid-state compounds of yttrium and lanthanide benzoates

Solid-state Ln(Bz)(3)center dot H(2)O compounds where Ln stands for trivalent yttrium or lanthanides and Bz is benzoate have been synthesized. Simultaneous thermogravimetry-differential thermal analysis (TG-DTA), X-ray powder diffractometry, infrared spectroscopy and chemical analysis were used to characterize and to study the thermal behaviour of these compounds. The results led to information about the composition, dehydration, thermal stability and thermal decomposition of the isolated compounds.

Aging behaviour of 25Cr-17Mn high nitrogen duplex stainless steel

The precipitation behaviour of a nickel free stainless steel containing 25% chromium, 17% manganese and 0.54% nitrogen, with duplex ferritic-austenitic microstructure, was studied using several complementary techniques of microstructural analysis after aging heat treatments between 600 and 1 000 degrees C for periods of lime between 15 and 6 000 min. During aging heat treatments, ferrite was decomposed into sigma phase and austenite by a eutectoid reaction, like in the Fe-Cr-Ni duplex stainless steel. Chromium nitride precipitation occurred in austenite, which had a high nitrogen supersaturation. Some peculiar aspects were observed in this austenite during its phase transformations. Chromium nitride precipitation occurred discontinuously in a lamellar morphology, such as pearlite in carbon steels. This kind of precipitation is not an ordinary observation in duplex stainless steels and the high levels of nitrogen in austenite can induce this type of precipitation, which has not been previously reported in duplex stainless steels. After chromium nitride precipitation in austenite, it was also observed sigma phase formation near the cells or colonies of discontinuously precipitated chromium nitride. Sigma phase formation was made possible by the depletion of nitrogen in those regions. Time-temperature-transformation (precipitation) diagrams were determined.

Thermal behaviour of intercalated 8-hydroxyquinoline (oxine) in montmorillonite clay

The composite montmorillonite-8-hydroxyquinoline (Swy-1-8-HQ) was prepared by two different processes and studied by using thermogravimetric analysis (TG/DTG and DSC), as well as helpful techniques as fluorescence in the UV-visible region and X-ray diffraction. The composites developed fluorescent appearance, however with quantum poor efficiency and they exhibited distinct TG and DSC thermal behavior. The fluorescence data of spectra associated to the TG/DT curves allowed to suggest that the 8-HQ was present in the composites in two different circumstances: 1 - intercalated in the interlayer spaces (Swy-1-8-HQ2), rigidly associated to the Substrate feasible as a monolayer with the aromatic rings parallel to the silica layer; and/or, 2 - adsorbed on the Surface (Swy-1-8-HQ1), either as a bilayer formation or tilting of the molecules to the silicate layer sheet. All results confirmed above are in agreement with X-ray diffraction patterns, once the interlayer space increases when 8-HQ is incorporated. The experimental results confirm the formation of the composites in agreement with the method used in the preparation.

Structural and microstructural behaviour of SnO2 dense ceramics doped with ZnO and WO3

SnO2-based varistors doped with ZnO and WO3 were prepared by mixed oxide method. Experimental evidence shows that the increase in ZnO amount increases the volume and microstrain of unit cell while the WO3 promotes a decrease. 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 in the grain boundary without influence in the densification of the samples. Besides that, an increase in the electrical resistance of the SnO2-ZnO-WO3 system was observed independent of the WO3 concentration. (c) 2005 Elsevier B.V. All rights reserved.

Influence of moisture absorption on mechanical behaviour of composites

Because of their application that normally demands high mechanical strength combined with low weight, the fibre/matrix interface became an important parameter concerning structural life. The problem of moisture absorption in materials has received attention in experimental studies on a composite systems as well as from a theorical point of view. The fibre/matrix interface plays an important role in the structural behaviour of composites due to the fact that load transfer from matrix to reinforce occurs at the interface. In this case the study of compatibility of fibre/matrix/environmental is essential to ensure a product that attend structural objectives, many times without failure possibilities. The composite used in this investigation is the carbon fibre/matrix epoxy composite, which was immersed in sea water standard during 94 days at 60 degrees C, submitted to tensile and compressive tests to study the influence of moisture absorption on mechanical behaviour. The interface was investigated through fracture surface analysis by SEM and a strong interface and a good adhesion fibre/matrix was observed.

Biology and behaviour of the neotropical ant-mimicking spider Aphantochilus rogersi (Araneae: Aphantochilidae): nesting, maternal care and ontogeny of ant-hunting techniques

Aphantochilus rogersi is an ant-mimicking spider that preys exclusively on cephalotine ants. The spiders oviposit in close proximity to nests of the model ant Zacryptocerus pusillus, and emergent spiderlings tend to remain in the vicinity of natal egg sacs. Females of A. rogersi actively defend their egg sacs against approaching workers of Z. pusillus, but the latter may sometimes destroy the eggs. Feeding specialization on these ants is confirmed by more than 300 observations of young and adult A. rogersi carrying ant corpses in the held. Although A. rogersi possesses several behavioural traits which may reduce the risk of being injured by ants during subjugation, field and laboratory observations showed that social defence by Z. pusillus may cause mutilation to the spiders. Tests in captivity revealed an ontogenetic change in the prey-capture techniques employed by A. rogersi. Early-instar spiderlings can apparently only seize the ant's petiole tightly if they are able to approach the ant from the front. As the ant is paralysed, the spiderling positions itself vertically in relation to the substratum. Larger spiders, on the other hand, attack ants most frequently from behind, and seem better equipped to seize the ant's petiole firmly with their larger chelicerae. Owing to their greater strength, late-instar spiders are able to Lift the struggling ant aloft. The selection of a suitable oviposition site, the mother's ability to defend herself and the eggs from nearby ants, and the capacity to capture and subdue ants safely from emergence to maturity, are regarded as crucial traits inherent in the mimetic and feeding specialization by A. rogersi.