Showing papers by "Federal University of São Carlos published in 1992"

Respiratory responses to hypoxia in relation to mode of life of two erythrinid species (Hoplias malabaricus and Hoplias lacerdae)

Abstract: Predominantly, Hoplias malabaricus inhabits stagnant O2 poor environments, whereas Hoplias lacerdae occurs in well-aerated streams. The present study evaluates the influence of mode of life on O2 uptake and gill ventilation in equally-sized (300 g) specimens of this genus at 25° C. Comparing the species, H. lacerdae was characterized by the highest O2 uptake and gill ventilation combined with a relatively higher cost of breathing and a lower O2 extraction. Both species substantially increased ventilation in response to hypoxia with the difference that H. malabaricus exclusively augmented tidal volume, whereas H. lacerdae also increased breathing frequency.

B chromosomes in Astyanax scabripinnis (Pisces, Characidae)

Abstract: A karyotypic analysis was carried out using conventional staining and C-banding in 32 specimens of Astyanax scabripinnis (Pisces, Characidae) from Campos do Jordao (Sao Paulo State, Brazil). Twenty-eight individuals (87.5 per cent of the sample studied) showed 1–2 extra B-chromosomes, similar in size and shape (metacentrics) to pair 1 of the karyotype, with a high intra-individual constancy. Two types of B could be identified on the basis of their constitutive heterochromatin patterns. The hypothesis of the origin of the B-chromosome from non-disjunction of chromosome 1, followed by a heterochromatinization process, is postulated.

A highly differentiated ZZ/ZW sex chromosome system in a Characidae fish, Triportheus guentheri

Abstract: Seventeen specimens of Triportheus guentheri, a fish of the family Characidae, were submitted to chromosomal analysis, with a highly differentiated heteromorphic ZW pair being detected. Chromosome W is much smaller than chromosome Z and mostly heterochromatic. Chromosome Z is the largest in the karyotype, with heterochromatin occurring in the telomeric and centromeric regions only. The W chromosome also varies somewhat in size, the variations being probably due to its long arm. In addition to two other autosomal pairs, chromosome Z shows also an occasional Ag-NOR. Aspects of the ZW system differentiation and of the NOR presence in chromosome Z are discussed. The Characidae family includes a great deal of neotropical freshwater fish species and Triportheus appears to represent the only genus in this family having sex chromosome differentiation at a cytological level.

A new interpretation for the degradation phenomenon of ZnO varistors

Abstract: The electrical degradation phenomena of zinc oxide-based varistors were studied using a high-energy current pulse and a.c. polarization at different temperatures. Activation energy measurements during the degradation process showed that these phenomena are associated with diffusion and that the diffusion-controlling species are slower than Zn., For degradation promoted by current pulses of 8×20 μs, the Schottky potential barrier deformation was measured. A decrease in height and width of the potential barrier due to the reduction of surface states density,N s, without a significant change in donor density,N d, was observed. To explain these results, a modification of the unstable components model is proposed for the potential barrier in which the degradation is due to oxi-reduction reactions between atomic defects. These reactions promote the elimination of zinc vacancies and/or adsorbed oxygen on the grain boundaries.

Generation of squeezing for a charged oscillator and for a charged particle in a time-dependent electromagnetic field.

Abstract: Recent papers [A. Bechler, Phys. Lett. A 130, 481 (1988); M. S. Abdalla, Phys. Rev. A 44, 2040 (1991)] investigate the generation of squeezing for a charged oscillator in a constant and uniform magnetic field. Here we pursue further this line by investigating the extended system of a charged particle oscillating in a uniform and arbitrary time-dependent magnetic field. Since we do not particularize the functional time dependence, our expressions for the variances of quadratures are quite general, so the possible occurrence and amount of squeezing will depend on that specification. The corresponding results mentioned above become a particularization of ours.

Phase Characterization of Lead Zirconate Titanate Obtained from Organic Solutions of Citrates

Abstract: This paper reports that lead zirconate titanate (PZT) with several Zr/Ti ratios was prepared by the organic solution of citrates of the respective cations. The Rietveld method was applied to perform quantitative analysis of the coexisting phases. The ratio of tetragonal/rhombohedral phases increased with calcination temperature. For the composition where Zr/Ti = 53/47, the tetragonal quantity varied from 25% to 35% for temperatures ranging from 600[degrees] to 800[degrees]C. For the powder with Zr/Ti = 57/43, only the rhombohedral phase was observed after calcination at 700[degrees]C. For the powder with Zr/Ti = 49/51, only the tetragonal phase was observed after calcination at 800[degrees]C. The amount of tetragonal phase was controlled in Zr/Ti = 55/45 by seeding the powder with the tetragonal phase of PZT.

Formation of negative ions by electron impact on SiF4 and CF4

Abstract: First measurements of cross sections for the formation of negative ions by electron attachment to SiF4 and CF4 are reported for an electron impact energy range of 0 to 50 eV. The energies at which the various ions appear and the positions at which the ionization efficiency curves peak have been obtained and compared with previous measurements. Thermochemical data have been used to predict and identify the various channels of dissociation. Cross sections for the production of ion pairs through the process of polar dissociation have also been measured.

Fluid dynamics characterization of a pneumatic bed using a spouted bed type solid feeding system

Abstract: On decrit un lit qui reunit les caracteristiques des lits jaillissants et du transport pneumatique. L'appareil peut etre defini comme un lit de transport pneumatique modifie par l'introduction d'un procede de recirculation de materiaux inertes, qui conduit a une configuration semblable a celles des lits jaillissants. La dependance des vitesses de recirculation des particules avec les debits d'air et la distance entre l'entree de l'air et l'extremite inferieure du tube central (z 0 ) a ete etudiee. On a egalement etudie la variation de la perte de charge totale avec le debit, et ce pour differentes charges de materiaux inertes (spheres de verre, d p =2,8 mm) et differentes valeurs de z 0

Structure of extracellular polysaccharides produced by a soil cryptomonas sp. (cryptophyceae)1

Abstract: The Hindak strain of a Cryptomonas species (Cryptophyceae) produces extracellular polysaccharides. Because there is no information on the structure of these compounds in the Cryptophyceae we conducted structural studies. Gas–liquid chromatographic analyses showed that the polysaccharide is composed of fucose, rhamnose, xylose, mannose, glucose, galactose, galacturonic acid, glucuronic acid, and traces of 3-O-methyl galactose. The polysaccharide was separated into two subtractions by ion-exchange chromatography. Fraction A consisted mainly of 1,3-linked galactose units and 1,4-linked galacturonic acid. Unlike fraction B, fraction A did not have xylose, 3-O-methyl galactose, or glucuronic acid. Also, its degree of branching was low compared to that of fraction B. Only traces of sulfate were present infraction A, but fraction B was 10–15% sulfated. Protein was approximately 1% in both fractions. These polysaccharides appear to be a novel type of polymer in algae.

The formation of unusual glasses by sol-gel processing

Abstract: It has been claimed that one of the main advantages of the sol-gel technique relates to its potential to produce new glasses from compositions which would normally crystallize if processed by quenching a melt. This article shows that, due to the intrinsic nature of gels (high OH-content, residual carbon, high fictive state), sol-gel glasses crystallize faster than melt-derived glasses at any temperature. Additionally, gels must be (in general) slowly heated from room temperature to approximately half the liquidus temperature to densify to a glass. That is a riskier path than quenching from the liquid state because the nucleation region is crossed on heating, allowing crystal growth from a plethora of nuclei. Finally, there has been no report on a dense gel-derived glass made from systems prone to crystallize. It is concluded that the gel route is not as good as conventional processing to reach the vitreous state and is unlikely to lead to dense glasses of reluctant vitrifying compositions.

Squeezed states, generalized Hermite polynomials and pseudo-diffusion equation

Abstract: We show that the wavefunctions 〈pq; λ|n〈, of the harmonic oscillator in the squeezed state representation, have the generalized Hermite polynomials as their natural orthogonal polynomials. These wavefunctions lead to generalized Poisson Distribution Pn(pq;λ), which satisfy an interesting pseudo-diffusion equation: ∂P n p,q;λ) ∂λ = 1 4 [ ∂ 2 ∂p 2 −( 1 λ 2 ) ∂ 2 ∂q 2 ]P 2 (p,q;λ) , in which the squeeze parameter λ plays the role of time. Th entropies Sn(λ) have minima at the unsqueezed states (λ=1), which means that squeezing or stretching decreases the correlation between momentum p and position q.

Structure of heat-treated nylon 6 fibers. I. Application of the arrhenius equation

Abstract: The changes in lateral order, crystalline perfection index, crystallinity percentage, long period, and shrinkage denote the structural modification due to thermal effects in the heat-treated nylon 6 fibers. The application of the Arrhenius equation to these parameters resulted in two types of behavior: the parameters long period and shrinkage showed linearity in the temperature range of 100–190°C, while the others presented linearity between 150 and 190°C. The first reflects the direct dependence of crystal growth on shrinkage and the latter shows that the necessary energy to promote significant crystal growth and perfection will be reached only at 150°C. In the range of temperature from 100 to 150°C the observed increase of crystallinity is associated to chain flexibility allowing rearrangement as well as new crystal formation. This phenomenon seems to be related to the discontinuity observed in the Arrhenius plots in the same range of temperature. © 1992 John Wiley & Sons, Inc.

Geographic variation in Leporinus friderici (Bloch) (Pisces: Ostariophysi: Anostomidae) from the Paraná-Paraguay and Amazon River basins

Abstract: Morphological variation among populations of Leporinus friderici (Bloch), an anostomid fish of widespread neotropical distribution, has been hypothesized but never conclusively demonstrated. We used multivariate procedures to examine patterns of morphometric variation among populations of L. friderici from three South American biogeographic regions: the Parana-Paraguay River and Amazon River basins of Brazil, and the Marowijne River basin of Suriname. Samples from the southern Parana-Paraguay basin are completely distinct from the northern Amazonian and Suriname regions in principal components analysis, primarily on the basis of body elongation and orbit differcnces. Samples from the two northern regions were separated in a size-free canonical variates analysis by differences in relative body depth. These results emphasize a need for further studies of neotropical fish species with similar distribution patterns.

Helmintoses intestinais: o processo de comunicação e informação no Programa de Educação e Saúde em Verminose

Abstract: No trabalho sobre intervencao em helmintoses intestinais, no subdistrito de Santa Eudoxia (Sao Carlos, Sao Paulo), foi conduzido um processo de comunicacao com o objetivo de ilustrar, demonstrar e consolidar a informacao sobre o programa junto a comunidade. A comunicacao desenvolveu-se ao longo da sequencia de eventos que ocorreram durante o desenvolvimento do trabalho de intervencao, veiculando e disseminando informacao associada a participacao da comunidade.

Peptidase B polymorphism in cattle erythrocytes.

Abstract: Starch gel electrophoresis and histochemical staining withl-leucylglycyl-glycine revealed genetic polymorphism in peptidase B in cattle erythrocytes. Genetic analysis of 164 full families indicated that the three phenotypes observed are the product of an autosomal locus with two codominant alleles,PepB1 andPep B2, A sample consisting of 2630 individuals representing 5 Zebu, 13 European, and 2 crossbred breeds was studied. This polymorphism was observed in all Zebu and crossbred breeds. The frequency of thePep B1 allele was 0.89, 0.83, 0.59, 0.82 and 0.62 in the Nellore, Gyr, Guzerat, Indubrazil, and Tabapuan breeds, respectively. ThePep B2 allele appears to be fixed in the European breeds, except Marchigiana and Chianina.