Showing papers by "Federal University of São Carlos published in 1988"
TL;DR: In this paper, Bethe ansatz equations are formulated and solved numerically for eigenstates of the XXZ Hamiltonian on a finite chain with periodic boundary conditions and with a generalized class of twisted boundary conditions.
256 citations
TL;DR: Through class formation, B1 and B2 had apparently acquired stimulus functions similar to those shown by A1 and A2 on simple-discrimination trials, thereby leading to emergent selections of B1 on the probes, suggested the formation of stimulus classes during conditional-discrimination training.
Abstract: Three experiments examined a discrimination training sequence that led to emergent simple discrimination in human subjects. The experiments differed primarily in their subject populations. Normally capable adults served in the first experiment, preschool children in the second, and mentally retarded adults in the third. In all experiments, subjects learned a simple simultaneous discrimination: When visual stimuli A1 and A2 were displayed together, reinforcers followed selections of A1, the S+, but not A2, the S-. The subjects also learned a conditional discrimination taught with an arbitrary visual-visual matching-to-sample procedure. Comparisons were two additional visual stimuli, B1 and B2, and samples were A1 and A2. Reinforcers followed selections of B1 in the presence of A1 and of B2 in the presence of A2. After the simple-discrimination and conditional-discrimination baselines had been acquired, B1 and B2 were displayed alone (without a sample) on probe trials. Subjects had never been taught explicitly how to respond to such displays. Nonetheless, they almost always selected B1, which was involved in a conditional relation with A1, the stimulus that served as S+ on the simple-discrimination trials. This outcome suggested the formation of stimulus classes during conditional-discrimination training. Through class formation, B1 and B2 had apparently acquired stimulus functions similar to those shown by A1 and A2 on simple-discrimination trials, thereby leading to emergent selections of B1 on the probes.
161 citations
TL;DR: In this paper, the variation of heavy metal content in suspended matter (SM) during tidal cycles in a mangrove creek was described, and the stable isotope of carbon was used as a tracer for sources of SM to the system.
98 citations
TL;DR: The chemosystematics of Rutaceae is reviewed on the basis of updated surveys of various secondary metabolites and their biosynthetic derivation, and a stepwise replacement of benzylisoquinolines by simple and complex anthranilic acid derived alkaloids, and eventually by coumarins and/or limonoids is confirmed.
Abstract: The chemosystematics ofRutaceae is reviewed on the basis of updated surveys of various secondary metabolites and their biosynthetic derivation. A comparison of these data with the morphological and geographical differentiation clearly shows that the current taxonomic arrangement of the family is to a large extent artificial and needs improvement. Starting from obviously “natural” groups of genera (or single genera) as “basic taxonomic entities” a new system with informal tribal names is suggested. In particular, the subfamilyToddalioideae is broken up altogether and its former members are rearranged among several of the 17 provisional tribes within the subfamilyRutoideae s. lat. Phylogenetic progressions can be recognized from parallel changes of morphological characters and biosynthetic pathways to secondary metabolites. As a general trend, a stepwise replacement of benzylisoquinolines by simple and complex anthranilic acid derived alkaloids, and eventually by coumarins and/or limonoids is confirmed. The available data are summarized in a discussion of the possible evolutionary relationships among theRutaceae, with theZanthoxylum- andEvodia-tribes in a central position.
97 citations
TL;DR: Three mentally retarded humans first acquired a simple discrimination: Simultaneously displayed visual stimuli A1 and A2 functioned as S+ and S-, respectively, and two subjects next learned to select C1 and C2 conditionally upon B1 and B2, respectively.
66 citations
TL;DR: In this paper, the Johnson-Mehl-Avrami theory of transformation kinetics was applied to the isothermal crystallization of a nearly stoichiometric Na2O·2CaO·3SiO2 glass.
Abstract: Experiments were carried out to test the validity of the Johnson-Mehl-Avrami theory of transformation kinetics. The isothermal crystallization of a nearly stoichiometric Na2O·2CaO·3SiO2 glass was studied at 627°C and 629°C by optical microscopy, density measurements and X-ray diffraction. Both nucleation and growth rates were measured by single and double stage heat treatments up to very high volume fractions transformed and the experimental data for crystallinity were compared with the calculated values at the two temperatures. The early crystallization stages were well described by theory for the limiting case of homogeneous nucleation and interface controlled growth. For higher degrees of crystallinity, both growth and overall crystallization rate decreased due to compositional changes of the glassy matrix and the experimental kinetics could be described by theory if diffusion controlled growth was assumed. It was also demonstrated that the sole use of numerical fittings to analyze phase transformation kinetics, as very often reported in the literature, can give misleading interpretations. It was concluded that if proper precautions are taken the general theory predicts the glass-crystal transformation well.
47 citations
TL;DR: Foi analisada a prevalencia das helmintoses intestinais e suas associacoes com anemia, estado nutricional, renda e composicao familiar em escolares de Santa Eudoxia, subdistrito of Sao Carlos, SP, Brasil.
Abstract: Foi analisada a prevalencia das helmintoses intestinais e suas associacoes com anemia, estado nutricional, renda e composicao familiar em escolares de Santa Eudoxia, subdistrito de Sao Carlos, SP, Brasil. Foram examinadas 254 criancas: dos resultados coprologicos, 37,8% foram positivos. O parasita mais frequente foi o Ascaris lumbricoides (12,1%), seguido de Trichuris trichiura (4,8%), ancilostomideo (3,7%) e Hymenolepis nana (3,7%). Ocorreu maior concentracao de resultados positivos na faixa de 8 a 12 anos (51,9%). Foram diagnosticadas como anemicas 14,7% das criancas e 15% como desnutridas. Das correlacoes estudadas, apenas aquela entre helmintose e tamanho familiar mostrou resultado estatisticamente significante.
47 citations
TL;DR: Uma pesquisa sobre conhecimentos, atitudes e percepcao da populacao local sobre o assunto foi realizada, no Municipio de Sao Carlos, SP, para coletar subsidios que norteassem parte of um programa de intervencao em helmintoses intestinais.
Abstract: Com o objetivo de coletar subsidios que norteassem parte de um programa de intervencao em helmintoses intestinais, foi realizada uma pesquisa, no Municipio de Sao Carlos, SP (Brasil), sobre conhecimentos, atitudes e percepcao da populacao local, sobre o assunto. A pesquisa foi realizada com responsaveis por escolares, no periodo de tres meses (1984-1985), por meio de questionario aplicado em uma amostra da populacao, correspondendo a 50% + 2 do universo de estudo. Os resultados mostraram que a populacao detem uma codificacao para identificacao de helmintoses, asssim como conceituacao propria sobre sinais e sintomas, aspectos epidemiologicos e formas de tratamento. Esses achados sao de fundamental importância para o planejamento das campanhas e projetos educacionais em verminoses.
37 citations
TL;DR: In particular, considera-se que o dominio da tecnologia de ponta e fundamental for o desenvolvimento economico e autonomia do Pais, justificando medidas, such as a reserva de mercado na area of informatica as mentioned in this paper.
Abstract: Um dos pontos fundamentais do planejamento governamental brasileiro industrial e tecnologico e o incremento dos esforcos de geracao e difusao de novos conhecimentos aplicados a industria. Sao inumeros os instrumen tos de politica economica, cientifica e tecnologica sugeridos, desde a ampliacao dos recursos destinados as universidades e centros de pesquisa, estatais e privados, ate o apoio a criacao de novas empresas nos setores tecnologicamente avancados. Considera-se que o dominio da tecnologia de ponta e fundamental para o desenvolvimento economico e autonomia do Pais, justificando medidas, como, por exemplo, a reserva de mercado na area de informatica. Uma das propostas que surgiu dessa politica global foi a criacao de parques de alta tecnologia ou centros de industrias nascentes em locais que ja apresentavam determinada infra-estrutura economica e tecnologica que pudessem incorporar um potencial elevado de novos empreendedores dispostos a criar novas empresas. A experiencia dos paises industrialmente mais avancados mostra inumeros exemplos do surgimento de diversas pequenas empresas de alta tecnologia aproveitando os recursos provenientes de universidades e centros de pesquisa localizados nas proximidades.
32 citations
TL;DR: In this article, an efficient, stereoselective total synthesis of natural bakkenolide-A has been effected from (S)-1,6-dimethyl-1-cyclohexene, which can be obtained from 2-methyl-2-cycloehexen-1 one in 3 high-yield steps.
30 citations
TL;DR: In this article, it was shown that for phase space probability distributions that do not violate the Uncertainty Principle, one can associate a density matrix, ϱ( x, x '), when some conditions are fulfilled.
Abstract: Using a mapping formalism, the Wave-Packet Phase Space Representation, we show that for phase space probability distributions that do not violate the Uncertainty Principle one can associate a density matrix, ϱ( x , x '), when some conditions are fulfilled. Furthermore if condition Tr ∧ϱ 2 = 1 is satisfied it becomes possible to find a wave function associated to the probability distribution.
TL;DR: On etudie l'existence des solutions globales au probleme Lu=o, du ¬=o sur R 2, ou L est un champ vectoriel sans singularite as mentioned in this paper.
TL;DR: In this paper, the effect of carbon dioxide on the electroreduction of 1,4-benzoquinone was studied by both cyclic voltammetry and double potential step chronoamperometry.
TL;DR: Single-subject-design studies may be added to supplement or replace group experimental designs in the study of infant vocal conditioning if the authors are to recognize the different learning processes that affect infant learning.
01 Jan 1988
TL;DR: In this paper, the Liapunov-Schmidt method has been used to study homoclinic and heterocliic solutions of nonlinear differential equations, using the above Fredholm Alternative.
TL;DR: The monoterpene trans-and cis-fused α-methylene-γ-butyrolactones have been synthesised from the appropriate isopulegol epimers.
01 Jan 1988
TL;DR: In this article, the authors presented a study on the use of the Fisica Universidade Federal de Sao Carlos (UniFisica UF) for the study of the effects of environmental degradation.
Abstract: Departamento de Fisica Universidade Federal de Sao Carlos, Rodovia Washington Luiz km 235, 13560 Sao Carlos, SP
TL;DR: In this paper, the physico-chemical properties of the anodic niobium oxide films grown potentiodynamically in 1M Na2CO3 solutions were studied and a phenomenological description of the oxide film behaviour was reported.
TL;DR: In this paper, the polarized Raman spectra of (NH4)2Cd2(SO4)3 were studied at temperatures from room temperature to 13 K. Several temperature-dependent variations in the phonon frequencies were observed that are related to the structural phase transitions in the material.
Abstract: Polarized Raman spectra of single crystals of (NH4)2Cd2(SO4)3 were studied at temperatures from room temperature to 13 K. Several temperature-dependent variations in the phonon frequencies were observed that are related to the structural phase transitions in the material. The existence of a ferroelectric-paraelectric phase transition was established at 91.5 K. The observed spectra suggested the existence of a new phase transition at about 162 K. This new transition is believed to be of antidistortive type, which is triggered by the softening of a phonon from the Brillouin zone boundary.
Journal Article•
TL;DR: In this paper, the chloroform extract of leaves of Virola sebifera was fractioned leading to isolation of lignans (2R, 3R) -2, 3-Di- (3, 4' -dimethoxybenzyl) -butirolactone (1) and -2-3-di- (5bromo-3, 3', 4' methylenedioxybenzinzyl), (2-2-4', 4'' -methylenedioxenzyl)-butyrolact
Abstract: The chloroform extract of leaves of Virola sebifera was fractioned leading to isolation of lignans (2R, 3R) -2, 3-Di- (3', 4' -dimethoxybenzyl) -butirolactone (1) (2R, 3R) -2, 3- Di- (3', 4' -methylenedioxybenzyl) -butyrolactone (2), (2R, 3R) -3- (3'', 4'' -dimethoxybenzyl) -2- (3', 4' -methylenedioxybenzyl) -butyrolactone (3). Transformation of these lignans intopodophyllotoxin analogs (4) was tested experimentally with negative results. In the proposed transformation (2R, 3R) -2, 3-Di- (5-bromo-3', 4' -dimethoxybenzyl) -butyrolactone (5) was obtained.
TL;DR: In this paper, the authors developed a theoretical approach based on the Alternant Molecular Orbital Model for the hydrogen molecule to predict the optical absorption spectrum of donor pairs in doped semiconductors.
TL;DR: In this paper, a natural definition of an attractor as an invariant measure is given (based on the ergodic theory of axiom A diffeomorphisms) and some results are proved which support this definition.
Abstract: A natural definition of an attractor as an invariant measure is given (based on the ergodic theory of axiom A diffeomorphisms) and some results are proved which support this definition. It is also proved that if an attractor has every characteristic exponent less than zero in a set of nonzero measure, then the support set of the attractor is an asymptotic stable periodic orbit.
TL;DR: The results obtained showed that the population in Brazil has an appropriate codefication for the identification of parasitic helminths, and accumulated knowledge concerning clinical aspects of the disease.
Abstract: A research project into knowledge, attitudes and perception regarding human intestinal parasitic helminths was carried out in Brazil. The study was conducted by means of interviews with parents of scholers during three months (November and December/1984 and January/1985). The data collected included 88 interviewed. The results obtained showed that the population has an appropriate codefication for the identification of parasitic helminths, and accumulated knowledge concerning clinical aspects of the disease. Theses results are useful for planning control programmes of intestinal parasites, based on community participation. Beside that they are also important as useful insights as a baseline for health education programmes.
TL;DR: The binding energy of the magnetic polaron in semimagnetic Cd(Mn)Te/CdTe quantum wells was calculated within a 6 × 6 k. p Hamiltonian as mentioned in this paper.