FACTORS THAT AFFECT THE ENZYMATIC DEGRADATION OF NATURAL STARCH GRANULES - EFFECT OF THE SIZE OF THE GRANULES

In this study the relationship between the enzymatic susceptibility and the size of the com and cassava starch granules was studied. The starch granules were separated by size and classified according to their average diameter in: a) larger than 16 mum; b) between 15 and 10 mum and c) smaller than 10 mum. The starch granules of various sizes were hydrolyzed by bacterial alpha-amylase and fungal amyloglucosidase. The results showed a relationship between the enzymatic susceptibility and the size of the starch granules; smaller size of the starch granules resulted in a higher percentage of hydrolysis. A basic difference in the mode of action of enzymes on small and large granules was observed. Enzymatic attack on the large granules was characterized by considerable surface corrosion, mainly at the radial axis. For small granules, the enzymatic action occurred on the surface of the granules and was characterized by an erosion with solubilization of the granules. Chemical and physical analysis of the starches suggested that hydrolysis should occur mainly at the amorphous areas of the granules.

Effect of the composite surface sealant application moment on marginal sealing of compactable composite resin restoration

An analysis was carried out to observe whether the application or not of a composite surface sealant (CSS), as well the moment for CSS application were able to reduce marginal microleakage in compactable composite resin restoration. All the preparations were restored with a compactable composite resin. The restored teeth were randomly assessed. G1 (control group): finished and polished; G2: finished, polished, etched and cover with CSS; G3: immediately after the restoration done the CSS was applied, then finished and polished; G4: CSS applied immediately after the restoration was done, the finished and polished, etched, and covered with CSS. The specimens were isolated with nail polish, thermocycled, immersed in aqueous solution of silver nitrate, and followed in a photo developing solution. The microleakage scores obtained from the occlusal and cervical walls were analyzed with the Kruskall-Wallis nonparametric test. No microleakage was found at the enamel margins. Comparing the microleakage scores at dentin/cementum margins (p < 0.05) it was found that G3 (p = 0.0162) and G4 (p = 0.0187) were able to reduce microleakage when compared with group G2. However the results were not statistically different from the control group. The application of CSS was not able to completely eliminate marginal microleakage at the dentin/cementum margins.

Effect of the type of environmental stress on the emergence of sunflower (Helianthus annus L.), soybean (Glycine max (L.) Merril) and maize (Zea mays L.) seeds with different levels of vigor

Sowing is a critical time in the cycle of a crop and the seeds are frequently exposed to adverse conditions that may compromise the establishment of seedlings in the field. on this basis, the objective of the present study was to determine the effect of types of environmental stress on the emergence of sunflower, maize and soybean seeds with different levels of vigor. High vigor seeds were artificially aged in order to obtain medium and low vigor seeds and then they were sown in clay soil in plastic boxes and submitted to the following types of environmental stress during the germination process : 1) high temperature (35degreesC), 2) low temperature (15 or 18degreesC), 3) water excess (Psi > -0.0001 MPa), 4) water deficiency (Psi approximately equal to -1.1; -1.2 and -0.6 MPa for sunflower, maize and soybean, respectively), 5) sowing at a depth of 7 cm and 6) pathogenic infection of sunflower seeds with Alternaria helianthi, of maize seeds with Fusarium moniliforme and of soybean seeds with Colletotrichum dematium, var. truncata. The results were compared to those obtained with controls sown under optimal condition. It was concluded that: 1) the effect of seed vigor on emergence depends on the type of enviromental stress to which the seeds are exposed, 2) the stress to which the the seeds demonstrated highest sensitivity varied with species and 3) high temperature stress was the one that most impaired the emergence of the three species.

EFFECT OF THE ADDITION OF CR AND NB ON THE MICROSTRUCTURE AND ELECTROCHEMICAL CORROSION OF HEAT-TREATABLE AL-ZN-MG ALLOYS

The effect of the addition of Cr and Nb on the microstructure and the electrochemical corrosion of the weldable, high-strength and stress corrosion cracking (SCC) resistant Al-5%Zn-1.67%Mg-0.23%Cu alloy (H) has been studied. Combined additions of the alloying elements, J (with Nb), L (with Cr) and O (with Cr and Nb) and different heat treatments, ST (cold-rolled), A (annealed), F (quenched), B (quenched and aged) and C (quenched in two steps and aged), to obtain different microstructures and hardness have been performed. To correlate the electrochemical corrosion with the microstructure of the specimens, corrosion potential (E(cor)) measurements in different chloride solutions were performed and optical microscopy, SEM, TEM and EDX were applied. In chloride solutions containing dissolved O-2 or H2O2, the present alloys were polarized up to the pitting attack. It was shown that the E(cor) measurements were very sensitive to the alloy composition and heat treatment, increasing in the order H < J < L < O < Al (for a given heat treatment) and F < A approximate to ST < B < C (for a given alloy). The MgZn2 precipitates of the annealed (A) and cold-rolled (ST) specimens were dissolved in chloride solutions containing oxidizing agents and pitting attack was shown to develop in the cavities where the precipitates were present. In the specimens B and C, the compositions of the precipitate free zones was found to be equal to that of the matrix solid solution and preferential intergranular attack was not evident, this being in agreement with their SCC resistance. The addition of Cr and Nb increased the pitting corrosion resistance. The effects of Cr and Nb were additive, that of Cr being predominant, either, in the E(cor) shift or in the increase in the pitting corrosion resistance.

Effect of the bound nucleon form factors on charged-current neutrino-nucleus scattering

We study the effect of bound nucleon form factors on charged-current neutrino-nucleus scattering. The bound nucleon form factors of the vector and axial-vector currents are calculated in the quark-meson coupling model. We compute the inclusive C-12(nu(mu),mu(-))X cross sections using a relativistic Fermi gas model with the calculated bound nucleon form factors. The effect of the bound nucleon form factors for this reaction is a reduction of similar to8% for the total cross section, relative to that calculated with the free nucleon form factors.

Use of survival analysis as a tool for the genetic improvement of age at first conception in Nellore cattle

Restricted breeding seasons in beef cattle lead to censoring of reproductive data. In this paper, age at first conception (AFC) of Nellore females exposed to the sires for the first time between 11 and 16 months of age, was studied aiming to verify the possibility of genetically advance sexual precocity using a survival model. The final data set contained 6699 records of AFC in days. Records of females that did not calve in the next year following exposure to the sire were considered censored (77.5% of total). The model used was a Weibull mixed survival model including effects of contemporary groups, period (fixed) and animal (random). The effect of the contemporary groups on AFC was important (p < 0.01). Heritabilities were 0.51 and 0.76 in logarithmic and original scales respectively. Results indicate that it is possible to genetically advance sexual precocity, using the outcome of survival analysis of AFC as selection criterion. They also suggest that improvements of the environment could advance sexual precocity too, thus an adequate pregnancy rate for farmers could quickly be achieved.

Effect of irrigating solution and calcium hydroxide root canal dressing on the repair of apical and periapical tissues of teeth with periapical lesion

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effect of the temperature on the TMOS sono-hydrolysis and a study of the structure of the resulting aged sonogels

The effect of temperature on the oxalic acid catalyzed sono-hydrolysis of tetramethoxysilane (TMOS) was studied by means of a heat flux calorimetric method. The activation energy of the process was measured as (24.5 +/- 0.8) kJ/mol in the temperature range between 10 and 50 degreesC. The structural characteristics of the resulting sonogels, after long period of aging in saturated conditions, were studied by means of small angle X-ray scattering. The structure can be described as formed by similar to2.7 nm mean size mass fractal-like aggregates (clusters) of primary silica particles of similar to0.3 nm mean size, all imbibed in a liquid phase. The average mass fractal dimension of the clusters was found to be 2.58. The primary particle density was estimated as 2.23 g/cm(3), in good agreement with the value frequently quoted for fused silica. The volume fraction of the clusters, in the saturated sonogels was estimated as about 28%. The moment in which the meniscus of the liquid phase penetrates into the clusters under rapid evaporation process has been detected by an inflection in the first derivative of the curve of weight loss in a simple thermogravimetric test. (C) 2003 Elsevier B.V. All rights reserved.

THE INFLUENCE OF THE ELECTROCHEMICAL TREATMENT ON CU-AL-AG ALLOYS IN DEAERATED 0.5M NAOH

The effect of consecutive cyclic polarization in de-aerated 0.5 M NaOH solutions on the surface microstructure of mechanically polished Cu-Al-Ag alloys of different compositions and heat treatments has been studied using optical microscopy, SEM and EDS. The current peaks of the cyclic polarization curves do not depend on the alloy composition in the composition range studied. The repetitive potential scans between H2 and O2 evolution in alkaline media lead to preferential dissolution of aluminium, the roughness and phase composition of the surface of the alloys changing significantly. The quasistationary I-E curves of the different Cu-Al-Ag alloys studied consist in the superposition of the quasistationary I-E curves of high-purity Cu and Ag, the EDS microanalysis showing that aluminium is not present on the surface of the alloy in these conditions.

Effect of the excess of bismuth on the morphology and properties of the BaBi2Ta2O9 ceramics

In this study, the effect of bismuth content on the crystal structure, morphology and electric properties of barium-bismuth-tantalate (BBT) ceramics was explored with the aid of X-ray diffraction (XRD), scanning electron microcopy (SEM), dielectric properties and ferroelectric hysteresis loops. BaBi2Ta2O9 (BBT) ceramics have been successfully prepared by the solid-state reaction. The BBT phase was crystallized at 900 degreesC for 2 h. The excess of bismuth controls the grain size, affecting the density of the material. Measurements of dieletric constant and dieletric losses confirm that the material is a ferroeletric with a Curie temperature around 77 degreesC. The dieletric constant measured at room temperature was 400, with a dielectric loss of 0.03. Both the phase-transition behaviour and ferroelectric properties, such as spontaneous polarization (P-s), showed a dependence on Bi content. (C) 2004 Elsevier B.V. All rights reserved.

Effect of the addition of ZnO seeds on the electrical proprieties of ZnO-based varistors

ZnO has the characteristic of presenting an intermediate value for the effective 3 eV barrier at room temperature. ZnO ceramics are applied in high-voltage systems or circuits. Attempts were made to reduce the number of effective barriers in the system by adding large particles of ZnO to the varistor composition. This procedure reduced the breakdown field of the varistors by values up to 90% lower than those initially obtained, and produced nonlinear coefficients as low as 20. (C) 2003 Elsevier B.V. B.V. All rights reserved.

Effect of the chronological age and sexual maturation on the time to exhaustion at maximal aerobic speed

The purposes of this study were: a) to verify the effect of chronological age and sexual maturation on the time to exhaustion at VO(2)max (t(lim)) and; b) to examine the reproducibility of t(lim) in boys aged 10-15 years. Forty boys, divided into 4 groups, in accordance to the chronological age (G10-12 and G13-15) and sexual maturation (P1-P3 and P4-P5 levels for pubic hair), performed the following tests: 1) incremental test for determination of VO(2)max and; 2) all-out exercise bout performed at VO(2)max to determine the t(lim). There was no difference of t(lim) (sec) between G10-12 and G13-15 (181.5 +/- 96.3 vs. 199 105.5). While the two measures of t(lim) were moderately related (r = 0.78), t(lim) from the second test (226.6 +/- 96.1 s) was higher than that of the first (191.3 +/- 79.2 s). We can conclude that the t(lim) is not influenced by chronological age and sexual maturation. Besides, t(lim) presents a lower reproducibility in children and adolescents.

Role of the surface state and structural feature in the thermoreversible sol-gel transition of a zirconyl aqueous precursor modified by sulfuric acid

The sols produced by admixture of ZrOCl2 acidified solutions to hot H2SO4 aqueous solutions were studied to clarify the effects of Cl- and SO42- ions on the kinetic stability of nanoparticles and to obtain some new evidence concerning the mechanism of a thermoreversible sol-gel transition observed in this system. The study of suspensions prepared with different molar ratios R-S = [Zr]/[SO42-] and R-Cl = [Zr]/[Cl-] revealed domains of composition of formation of thermoreversible gels, thermostable sols, and powder precipitation. The effects of R-S and R-Cl on the structural features of nanoparticles and on the particle solution interface were systematically analyzed for samples of thermoreversible and thermostable sol domains. Small-angle X-ray scattering measurements revealed the presence of small fractal aggregates in all samples of thermoreversible domains, while compact packing aggregates of primary particles are present in the thermostable sol. Extended X-ray absorption fine structure and elemental chemical analysis revealed that irrespective of the nominal value of R-S and R-Cl all studied samples of the thermoreversible domain are constituted by a well-defined compound possessing an inner core made of hydroxyl and oxo groups bridging together zirconium atoms surrounded on the surface by complexing sulfate ligands. zeta potentials of powders extracted by freeze-drying from the thermoreversible gel revealed a point of surface charge inversion attributed to the specific adsorption of SO42- ion. Thermoreversible gel formation is rationalized by considering the effect of the specific adsorption on the electrical double-layer repulsion together with the temperature dependency of the physical chemical properties of ions in solution.

EFFECT OF CHOLINERGIC STIMULATION OF THE AMYGDALOID COMPLEX ON WATER AND SALT INTAKE

The effect of carbachol (80 nmol/mul) injection into the amygdaloid nuclear complex (AMG) on sodium appetite and water intake was studied in male Holtzman rats weighing 240-270 g. Twenty-five satiated rats and 38 water-deprived rats were used in the experiment on water intake. In the experiment on sodium intake, 19 rats were injected with atropine + carbachol and 9 rats with hexamethonium + carbachol. After carbachol injection into the AMG, water intake decreased in rats submitted to 30 h of water deprivation (10.28 +/- 1.04 ml/120 min vs 0.69 +/- 0.22 ml/120 min). The decrease in water intake was blocked by prior local injection of a tropine (20 nmol/1 mul)(11.66 +/- 1.46 ml/120 min vs 0.69 +/- 0.22 ml/120 min), but not of hexamethonium (30 nmol/1 mul), into the AMG. In water-deprived animals, carbachol injection into the AMG caused a decrease in sodium chloride intake (6.16 +/- 1.82 ml/h vs 0.88 +/- 0.54 ml/h) which was blocked by previous injection of hexamethonium but not of a tropine. These results suggest that the cholinergic system of the AMG plays a role in the control of water and salt intake.