Showing papers by "Federal University of São Carlos published in 1999"
TL;DR: In this article, the effect of crystalline phase, uniaxial drawing and temperature on the real (e′) and imaginary (e″) parts of the relative complex permittivity of poly (vinylidene fluoride) (PVDF) was studied in the frequency range between 102 and 106 Hz.
Abstract: The effect of crystalline phase, uniaxial drawing and temperature on the real (e′) and imaginary (e″) parts of the relative complex permittivity of poly (vinylidene fluoride) (PVDF) was studied in the frequency range between 102 and 106 Hz. Samples containing predominantly α and β phases, or a mixture of these, were obtained by crystallization from a DMF solution at different temperatures. α phase samples were also obtained from melt crystallization and from commercial films supplied by Bemberg Folien. Different molecular orientations were obtained by uniaxial drawing of α and β phase samples. The results showed that the crystalline phase exerts strong influence on the values of e′ and e″, indicating that the αa relaxation process, associated with the glass transition of PVDF, is not exclsively related to the amorphous region of the polymer. An interphase region, which maintains the conformational characteristics of the crystalline regions, should influence the process decisively. The molecular orientation increased the values of e′ for both PVDF phases and modified its dependence with temperature over the whole frequency range studied. The influence of the crystallization and molecular orientation conditions on the dc electric conductivity (σdc) were also verified. The value of σdc was slightly higher for samples crystallized from solution at the lowest temperature and decreased with draw ratio.
465 citations
TL;DR: In this article, the 5S rDNA genes were not associated with the NORs or sex chromosomes in three anostomids, Leporinus elongatus, L. obtusidens and L. friderici, using fluorescence in-situ hybridization with PCR-obtained 5S probes.
Abstract: The large 45S rDNA chromosome sites have often been analyzed in fish. In contrast, little is known about the 5S genes in this animal group. In the genus Leporinus, the NOR chromosomal location has been shown to be very diverse. In the present work, chromosome mapping of 5S rDNA in three anostomids, Leporinus elongatus, L. obtusidens and L. friderici, is investigated using fluorescence in-situ hybridization (FISH) with PCR-obtained 5S probes and primed in-situ labeling (PRINS). Major 5S rDNA chromosomal sites were found to be subterminally located in a small metacentric pair, while minor ones were detected near the centromeric region of a medium-sized submetacentric pair in all studied species. The 5S rDNA genes were not associated with the NORs or sex chromosomes. A highly conserved chromosomal location of these genes appears to characterize the karyotype evolution of this fish group.
359 citations
TL;DR: The data suggest that this fish species has a natural preference for a dark environment and this characteristic can be very useful for the development of new behavioral paradigms for fish.
Abstract: The zebrafish (Danio rerio) has been used as a model in neuroscience but knowledge about its behavior is limited. The aim of this study was to determine the preference of this fish species for a dark or light environment. Initially we used a place preference test and in a second experiment we applied an exit latency test. A two-chamber aquarium was used for the preference test. The aquarium consisted of a black chamber and a white chamber. In the first experiment the animal was placed in the aquarium and the time spent in the two compartments was recorded for 10 min. More time was spent in the black compartment (Wilcoxon matched-pairs signed-rank test, T = 7, N1 = N2 = 18, P = 0.0001). In the second experiment the animal was placed in the black or white compartment and the time it took to go from the initial compartment to the opposite one was recorded. The test lasted a maximum of 10 min. The results showed that the animal spent more time to go from the black to the white compartment (Mann-Whitney rank sum test, T = 48, N1 = 9, N2 = 8, P<0.0230). These data suggest that this fish species has a natural preference for a dark environment and this characteristic can be very useful for the development of new behavioral paradigms for fish.
232 citations
TL;DR: In this paper, a generalized boundary condition in the solution of Fick's law for a small ac perturbation was developed for diagnostic applications and treatment of cases in which systematic deviations from the standard models for spatially restricted diffusion impedances are found.
227 citations
TL;DR: While the K49 PLA2 proteins are enzymatically inactive on artificial substrates, the toxins cause fatty acid production in cell cultures and in the latter, the PLA2 myotoxins exert at least two distinct mechanisms of action, neither of which is well-characterized.
151 citations
TL;DR: For 15 male endurance runners, it was concluded that for these subjects it was possible to evaluate the aerobic capacity by IGT and Glcmin as well as by IAT and La−min.
Abstract: The equilibrium point between blood lactate production and removal (La−min) and the individual anaerobic threshold (IAT) protocols have been used to evaluate exercise. During progressive exercise, blood lactate [La−]b, catecholamine and cortisol concentrations, show exponential increases at upper anaerobic threshold intensities. Since these hormones enhance blood glucose concentrations [Glc]b, this study investigated the [Glc] and [La−]b responses during incremental tests and the possibility of considering the individual glucose threshold (IGT) and glucose minimum (Glcmin) in addition to IAT and La−min in evaluating exercise. A group of 15 male endurance runners ran in four tests on the track 3000 m run (v3km); IAT and IGT – 8 × 800 m runs at velocities between 84% and 102% of v3km; La−min and Glcmin– after lactic acidosis induced by a 500-m sprint, the subjects ran 6 × 800 m at intensities between 87% and 97% of v3km; endurance test (ET) – 30 min at the velocity of IAT. Capillary blood (25 μl) was collected for [La−]b and [Glc]b measurements. The IAT and IGT were determined by [La−]b and [Glc]b kinetics during the second test. The La−min and Glcmin were determined considering the lowest [La−] and [Glc]b during the third test. No differences were observed (P 0.05). We concluded that for these subjects it was possible to evaluate the aerobic capacity by IGT and Glcmin as well as by IAT and La−min.
117 citations
TL;DR: To examine the distribution and physiological role of CO2/pH-sensitive chemoreceptors in the gills of the tropical fish, traira, fish were exposed to acute environmental hypercarbia and subjected to injections of HCl into the ventral aorta and buccal cavity.
109 citations
TL;DR: In this paper, a straightforward combustion synthesis of pure and doped ZnO powders from stoichiometric mixtures of the relevant water soluble metal nitrates as cation precursors and urea as fuel was described.
104 citations
TL;DR: In this paper, high non-linear J×E electrical characteristics were obtained in the Nb2O5 and Cr2O3 doped CoO highly densified SnO2 ceramics.
99 citations
TL;DR: In this article, the application of pore size obtained by image analysis to estimate the cellular materials permeability through Ergun's equation was presented, and the pore distribution, cross-sectional porosity and pore density were evaluated as a function of the slice thickness.
Abstract: SiC-Al2O3 ceramic foams with 30 to 75 pores per linear inch (ppi) were used to access the application of pore size obtained by image analysis to estimate the cellular materials permeability through Ergun's equation. Samples were sliced and the pore size distribution, cross-sectional porosity and pore density were evaluated as a function of the slice thickness based on optical and X-ray computerized tomography acquired images. The average pore sizes were used to calculate permeability constants (k1 and k2) of Ergun's equation, which were compared to those experimentally obtained under water flow. Results indicated that the optical diameter distribution was very sensitive to the number of pore layers. Deviation between experimental and calculated values depended on the slice thickness. Nevertheless, the introduction of pore size obtained by image analysis into Ergun's equations seems to give fair results to assess the permeability of ceramic foams.
95 citations
TL;DR: The acidity of Beta zeolites with Si/Al ratios ranging from 18 to 33 was determined using appropriate temperature programmed desorption of ammonia conditions and their catalytic behavior was evaluated by disproportionation of ethylbenzene.
Abstract: The acidity of Beta zeolites with Si/Al ratios ranging from 18 to 33 was determined using appropriate temperature programmed desorption of ammonia conditions and their catalytic behavior was evaluated by disproportionation of ethylbenzene. Samples with greater Si/Al ratios presented higher acid strength by retaining ammonia at higher temperatures and showed a higher ethylbenzene disproportionation activity per aluminum atom. These results indicate that as the aluminum content in zeolite Beta is reduced in that range, the strength of the associated acid sites increases.
TL;DR: In this paper, the authors used scanning electron microscopy and X-ray diffractometry to show plate-like ceramics that were highly oriented (F = 0.95) after hot forging and showed that polarization reorientation was restricted to the ab plane of the orthorhombic structure.
Abstract: SrBi 4 Ti 4 O 15 ceramics were prepared via ordinary firing (OF) and hot forging (HF). Characterization using scanning electron microscopy and X-ray diffractometry shows platelike grains that were highly oriented (F = 0.95) after hot forging. Ferroelectric, dielectric, and piezoelectric characterizations revealed that polarization reorientation was restricted to the ab plane of the orthorhombic structure, parallel to the (Bi 2 O 2 ) 2+ layers. The thickness coupling factor for OF samples was only half that for HF samples oriented parallel to the HF direction (in the ab-plane), as a consequence of poling restrictions in randomly oriented grains.
TL;DR: This is the first report of preliminary crystallization data for a snake venom L-amino acid oxidase, which has apoptosis-inducing activity in an HL-60 cell culture assay and is a dimer on gel filtration.
TL;DR: In this article, high resolution TEM micrographs of a Co2SnO4 system sintered at 1210C and 1400C showed an amorphous grain boundary region low in cobalt, indicating that the Co2snO4 phase is precipitated from this region.
TL;DR: In this article, the compressive strength of α-tricalcium phosphate-based cements was improved by using polymeric additives, such as sodium alginate, sodium polyacrylate, and an in situ polymerization system.
TL;DR: In this paper, the authors identified a family of dispersed repetitive DNA sequences in the genome of a Magnaporthe grisea isolate from finger millet (Eleusine coracana).
Abstract: We have identified a family of dispersed repetitive DNA sequences in the genome of a Magnaporthe grisea isolate from finger millet (Eleusine coracana). Southern blot analyses showed that this element is present in a moderate copy number (30-40 copies) in the genome of blast isolates from wheat (Triticum aestivum). DNA sequence data suggested that this element contains a region highly homologous to the reverse transcriptase domain of MGR583, a poly A-type retrotransposon. Using the reverse transcriptase domain of this element as a molecular probe, the genetic structure of the wheat blast population was examined. DNA fingerprinting analyses revealed that the wheat-infecting isolates constitute a separate, single lineage of their own, suggesting that they are derived from a single origin.
TL;DR: A theory of the scaling of the time scale T to equipartition with E/N is presented and compared to the numerical results in the range 0.03
Abstract: We study the time scale T to equipartition in a $1D$ lattice of N masses coupled by quartic nonlinear (hard) springs (the Fermi-Pasta-Ulam \ensuremath{\beta} model). We take the initial energy to be either in a single mode \ensuremath{\gamma} or in a package of low-frequency modes centered at \ensuremath{\gamma} and of width \ensuremath{\delta}\ensuremath{\gamma}, with both \ensuremath{\gamma} and \ensuremath{\delta}\ensuremath{\gamma} proportional to N. These initial conditions both give, for finite energy densities $E/N,$ a scaling in the thermodynamic limit (large N), of a finite time to equipartition which is inversely proportional to the central mode frequency times a power of the energy density $(E/N).$ A theory of the scaling with $(E/N)$ is presented and compared to the numerical results in the range $0.03l~E/Nl~0.8.$
TL;DR: In this paper, the electrochemical properties of thermally prepared oxide films of nominal composition Ir0.3Ti(0.7−x)SnxO2 were examined as a function of x by ac impedance measurements.
TL;DR: In this article, the effects of the layer composition and preparation temperature on the electrochemical, morphological and micro-structural characteristics and durability of a new dimensionally stable electrode based on the RuO 2 -Nb 2 O 5 system prepared by a polymeric precursor method is described.
TL;DR: In this article, the authors studied the hydrothermal synthesis of Si and SiAlMCM-41 performed under both autogenic pressure and refluxing conditions and showed that a great part of the Si atoms exist as silanol groups which originate resonance peaks at -110, -100 and -91 ppm.
Abstract: The aim of this work was to study the hydrothermal synthesis of Si and SiAlMCM-41 performed under both autogenic pressure and refluxing conditions. XRD data showed that the MCM-41 phase may be formed by both processes and that the synthesized material in the presence of Al and/or under reflux presents the hexagonally arrangement of less ordered mesopores. However, as verified by XRD and physisorption data, the order was improved with higher synthesis times. 29Si and 1H - 29Si C/P MAS NMR spectra showed that a great part of the Si atoms exists as silanol groups which originate resonance peaks at -110, -100 and -91 ppm. The presence of Al atoms may generate Si(3Si, Al) and Si(2Si, 2Al) environments which might be contributing to resonance peaks at -100 and -91 ppm. The 27Al MAS NMR spectrum of the as synthesized AlSiMCM-41 showed a resonance peak of tetrahedral framework aluminum close to 53 ppm and two others, one close to 14 ppm attributed to Al(H2O)6+3 species and the other a weak signal close to 32 ppm attributed to pentacoordinated Al. 27Al MAS NMR spectra of the calcined sample showed a peak at 0 ppm corresponding to an hexacoordinated extra-framework aluminum formed during calcination.
TL;DR: In this article, experimental data of airflow through 10 pores per linear inch ceramic foam filters are used to show that a single sample may have completely distinct permeability constants depending on the data range chosen for analysis.
Abstract: Correct estimation of the pressure drop in filtration processes that involve fluid velocity variations is of major importance, because it allows the filtration rate and/or the energy consumed on fluid flow to be more accurately controlled. Permeability of porous filters has been often described by Forchheimer's equation, which establishes a nonlinear dependence between pressure drop and fluid velocity. Two constants, k 1 and k 2 , dependent only on the medium, quantify the viscous and inertial effects on the pressure drop curve. In this work, experimental data of airflow through 10 pores per linear inch ceramic foam filters are used to show that a single sample may have completely distinct permeability constants depending on the data range chosen for analysis. The Darcian permeability constant k 1 displays higher variation than the non-Darcian permeability constant k 2 . The conclusion is that special attention must be taken to represent permeability of highly porous structures in a large velocity range. The predictability of Forchheimer's equation generally worsens when less data are included in the curve fitting, particularly at low velocities. Careful consideration should be made if constants k 1 and k 2 are intended to be used for permeability estimation beyond the fitting range.
TL;DR: In this article, all regular solutions of the boundary Yang-Baxter equation for 19-vertex models known as Zamolodchikov-Fateev or A1(1), model, Izergin-Korepin or A2(2) model, sl(2|1) model and osp(2 | 1) model were derived and classified.
TL;DR: A polyhazard model is proposed to deal with lifetime data associated with latent competing risks, keeping enough flexibility for common lifetime data that cannot be accommodated by usual hazard-based models.
Abstract: SUMMARY We propose a poly-hazard model to deal with lifetime data associated with latent competing risks. The causes of failure are assumed unobserved and affecting individuals independently. The general framework allows a broad class of hazard models which includes the most common hazard-based models. The model accommodates bathtub and multimodal hazards, keeping enoughflexibility for common lifetime data that cannot be accommodated by usual hazard-based models. Maximum likelihood estimation is discussed and parametric simulation is used for hypothesis testing.
TL;DR: In this article, the effect of initial maleic anhydride concentration presented different types of behavior, depending on the peroxide level, in a Haake torque rheometer.
Abstract: Grafting reactions were performed in a Haake torque rheometer, according to a central composite experimental design, where the maleic anhydride and peroxide concentrations, rotor speed, and reaction time were varied. The 27 formulations were analyzed by Fourier transformed infrared spectroscopy and melt-flow index measurements (MFI). An increase in peroxide concentration caused an increase in the percentage of reacted maleic anhydride and in MFI. The effect of initial maleic anhydride concentration presented different types of behavior, depending on the peroxide level. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 247–255, 1999
TL;DR: In this article, the influence of gas velocity during filtration on cake formation and its removal was studied using a polyester felt of squared section, with an area of 0.0225 m 2, through which the dust laden air was driven.
TL;DR: The chromosomes of two neotropical freshwater fish species, namely Liposarcus anisitsi and Leporinus elongatus, were investigated by means of C-banding, Ag-NORs, fluorochrome staining and banding by hot saline solution (HSS) treatment, to reveal patterns of heterochromatin differentiation.
Abstract: The chromosomes of two neotropical freshwater fish species, namely Liposarcus anisitsi (Siluriformes, Loricariidae) and Leporinus elongatus (Characiformes, Anostomidae), were investigated by means of C-banding, Ag-NORs, fluorochrome staining and banding by hot saline solution (HSS) treatment, to reveal patterns of heterochromatin differentiation. The karyotype of L. anisitsi is described for the first time. Staining with the GC-specific fluorescent antibiotic mithramycin (MM) revealed bright signals in some C-banded blocks in both species, suggesting that these MM+ heterochromatin contains GC-rich DNA. Banding by denaturation employing HSS, followed by Giemsa staining, yielded corresponding results documenting the thermal stability of GC-rich DNA part of heterochromatin positive after C-banding. In L. elongatus the Ag-NOR also followed the above banding patterns. However, in L. anisitsi the Ag-NOR was MM+ but negatively stained after C-banding and HSS treatment. L. elongatus also showed C-banded segments that were negative for mithramycin staining and HSS treatment. The results obtained evidence the heterochromatin heterogeneity in these fish species.
TL;DR: In this paper, the Selsing model was used to estimate residual stresses in partially crystallized Li 2 O−2SiO 2 glass-ceramics for several crystallographic planes and the stresses were also determined by an X-ray diffraction method using synchrotron radiation.
Abstract: Levels of residual stresses in partially crystallized Li 2 O–2SiO 2 glass-ceramics were calculated for several crystallographic planes. The stresses were also determined by an X-ray diffraction method (XRD) using synchrotron radiation. The linear thermal expansion coefficient ( α hkl ) of a fully crystallized, stress-free, powdered sample, was measured in situ using a hot-stage XRD technique. The thermal expansion coefficient depends on the crystallographic ( hkl ) direction. For some direction, the thermal expansion coefficient of the crystalline phase is greater than that of the glass matrix, while for other direction the inverse is observed. The average thermal expansion coefficient calculated from the unit cell expansion with temperature α uc =(10.1 ± 0.5) × 10 −6 °C −1 was close to that obtained by a dilatometric method for a polycrystalline sample 〈 α c 〉=(10.8 ± 0.5) × 10 −6 °C −1 . The theoretical residual stresses were calculated by the Selsing model using experimental data for the elastic constants combined with the thermal expansion coefficient for each crystallographic plane. Experimental determinations of residual stresses were made using an XRD technique for six different sets of ( hkl ) planes in two partially crystallized specimens. The type of experimental residual stresses (tensile or compressive) for each crystallographic plane was in agreement with the predicted type. Regarding the stress magnitude, the experimental results vary from −58/−117 MPa (compressive) to 60/149 MPa (tensile), whereas the calculated magnitudes vary from −192 MPa (compressive) to 16/102 MPa (tensile). These magnitudes were confirmed by micro-Raman spectroscopy. The differences between the theoretical and experimental stress magnitudes are within the limits of experimental errors. Therefore, the Selsing model can give a reasonable estimate of residual stresses for real (anisotropic) materials.
01 Sep 1999
TL;DR: The advantage of using the egg parasitoid T. galloi in association with the larval parasitoids C. flavipes for controlling the sugarcane borer is shown, which was 3.7 times more efficient than the standard treatment.
Abstract: This work was carried out to study the effect of the association of the egg parasitoid Trichogramma galloi Zucchi with the larval parasitoid Cotesia flavipes (Cam.) to control the sugarcane borer Diatraea saccharalis (Fabr.) through inundative releases. The sugarcane variety `RB 72454' plant cane was used, with canopy height of 1 m, in Brasilândia, Mato Grosso do Sul State, Brazil. The following treatments were studied: one, two and three releases of T. galloi associated with one release of C. flavipes and two controls, the first one with no parasitoid release and the second one with only one release of C. flavipes (standard). T. galloi and C. flavipes were released at 200,000 and 6,000 parasitoids per ha, respectively. Multiple releases of T. galloi were done at weekly intervals. The association of one release of C. flavipes with three releases of T. galloi was the best treatment for the sugarcane borer control, reducing the infestation level in 60.2% in comparison with the first control (without release) and was 3.7 times more efficient than the standard treatment. These results show the advantage of using the egg parasitoid T. galloi in association with the larval parasitoid C. flavipes for controlling the sugarcane borer.
TL;DR: In this paper, the authors present the results of the influence of chemical additives (antioxidant and UV stabilizer) and pigments (titanium dioxide and carbon black) on the short-term dielectric breakdown test of high-density polyethylene (HDPE).
Abstract: In this study, we present the results of the influence of chemical additives (antioxidant and UV stabilizer) and pigments (titanium dioxide and carbon black) on the short-term dielectric breakdown test of high-density polyethylene (HDPE). These additives and pigments are commonly added to polyolefins, which are used as insulating material for medium voltage cables. The incorporation was performed in a single screw extruder and thin films specimens were obtained by hot compression from extruded materials. For the dielectric breakdown test, an automated system has been used. A voltage ramp of 500 V/s was applied to specimens immersed in a silicon oil bath at room temperature. The degree of crystallinity and chemical modification of the formulations were evaluated by X-ray diffraction and Fourier transform infrared (FTIR), respectively. The dielectric breakdown results have been analyzed by a Weibull distribution. The shape and scale parameters of this distribution have been obtained by a graphic and maximum likelihood method. These results showed that the carbon black is the component that affects the dielectric strength, that the /spl beta/ shape parameter from the graphic method can be used to evaluate additive mixing conditions, and that the weakest point for formation of the rupture channel is on the carbon black agglomerate.