Glass transitions and state diagram for freeze-dried pineapple

Glass transition temperature of freeze-dried pineapple conditioned by adsorption at various water activities at 25 degreesC was determined by differential scanning calorimetry (DSC). High moisture content samples corresponding to water activities higher than 0.9, obtained by liquid water addition, were also analysed. The DSC traces showed a well-visible shift in baseline at the glass transition temperature (T(g)). Besides, no ice formation was observed until water activity was equal to 0.75. For water activities lower than 0.88, the glass transition curve showed that T(g) decreased with increasing moisture content and the experimental data could be well-correlated by the Gordon-Taylor equation. For higher water activities, this curve exhibited a discontinuity, with suddenly increasing glass transition temperatures approaching a constant value that corresponds to the T(g) of the maximally freeze-concentrated amorphous matrix. The unfreezable water content was determined through melting enthalpy dependence on the sample moisture content.

Sorption isotherm, glass transitions and state diagram for freeze-dried plum skin and pulp

Differential scanning calorimetry (DSC) was used to determine phase transitions of freeze-dried plums. Samples at low and intermediate moisture contents, were conditioned by adsorption at various water activities (0.11≤a w≤0.90) at 25°C, whereas in the high moisture content region (a w>0.90) samples were obtained by direct water addition, with the resulting sorption isotherm being well described by the Guggenheim-Anderson-deBoer (GAB) model. Freeze-dried samples of separated plum skin and pulp were also analysed. At a w≤0.75, two glass transitions were visible, with the glass transition temperature (T g) decreasing with increasing a w due to the water plasticising effect. The first T g was attributed to the matrix formed by sugars and water. The second one, less visible and less plasticised by water, was probably due to macromolecules of the fruit pulp. The Gordon-Taylor model represented satisfactorily the matrix glass transition curve for a w≤0.90. In the higher moisture content range T g remained practically constant around T g′ (-57.5°C). Analysis of the glass transition curve and the sorption isotherm indicated that stability at a temperature of 25°C, would be attained by freeze dried plum at a water activity of 0.04, corresponding to a moisture content of 12.9% (dry basis). © 2006 SAGE Publications.

Proposal of an alternative transmission line model for symmetrical and asymmetrical configurations

This article shows a transmission line model for simulation of fast and slow transients, applied to symmetrical or asymmetrical configurations. A transmission line model is developed based on lumped elements representation and state-space techniques. The proposed methodology represents a practical procedure to model three-phase transmission lines directly in time domain, without the explicit or implicit use of inverse transforms. In three-phase representation, analysis modal techniques are applied to decouple the phases in their respective propagation modes, using a correction procedure to set a real and constant matrix for untransposed lines with or without vertical symmetry plane. The proposed methodology takes into account the frequency-dependent parameters of the line and in order to include this effect in the state matrices, a fitting procedure is applied. To verify the accuracy of the proposed state-space model in frequency domain, a simple methodology is described based on line distributed parameters and transfer function associated with input/output signals of the lumped parameters representation. In addition, this article proposes the use of a fast and robust integration procedure to solve the state equations, enabling transient and steady-state simulations. The results obtained by the proposed methodology are compared with several established transmission line models in EMTP, taking into account an asymmetrical three-phase transmission line. The principal contribution of the proposed methodology is to handle a steady fundamental signal mixed with fast and slow transients, including impulsive and oscillatory behavior, by a practical procedure applied directly in time domain for symmetrical or asymmetrical representations. (C) 2011 Elsevier Ltd. All rights reserved.

Tempos de infância, tempos de escola: a ordenação do tempo escolar no ensino público paulista (1892-1933)

O texto analisa a ordenação do tempo nas escolas primárias paulistas no final do século XIX e início do século XX, período em que se institui e se consolida a arquitetura temporal escolar. Compreende, pois, as primeiras prescrições detalhadas sobre o tempo constantes na reforma republicana da instrução pública de 1892, as regulamentações instituídas no decorrer da Primeira República, até o momento de criação do Código de Educação de São Paulo em 1933, quando se inaugura uma nova fase da instrução pública no estado. O texto busca mostrar como o tempo constitui uma ordem que se experimenta e se aprende na escola. Para a realização deste estudo foram utilizadas fontes documentais, especialmente a legislação e textos oficiais da administração do ensino. As análises incidem sobre dois aspectos: a formulação política do tempo escolar e a organização pedagógica e disciplinar do tempo na escola. em relação ao primeiro aspecto, mostra como a ordenação do tempo pautou-se pela aspiração de uniformização e controle. Nesse sentido, as autoridades do ensino público procuraram regulamentar a obrigatoriedade do ensino, a freqüência, a duração do curso primário e a jornada escolar. em relação à organização pedagógica e disciplinar do tempo, põe em destaque a ordenação minuciosa do emprego do tempo compreendendo a racionalização curricular - a seleção e distribuição do conhecimento por séries, aulas, lições, e a definição dos horários.

Relationship between anxiety and chronic orofacial pain of temporomandibular disorder in a group of university students

Purpose: This study evaluated the relationship between anxiety levels and severity degrees of chronic orofacial pain of temporomandibular disorder in brazilian university students. Methods: 150 volunteers (117 men and 33 women), with age ranging from 17 to 30 years, were subjects to this study. Spielberger's trait-state anxiety inventory was used to evaluate trait and state anxiety of the students, while examination for chronic orofacial pain was performed in accordance with the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). Association between anxiety levels and severity degrees of chronic orofacial pain was tested using the Chi-square test. The significance level was set at p<.05. Results: The results showed that 32.7% (n = 49) of the subjects exhibited TMD, and the intensity of chronic orofacial pain was classified as degree 1 in 85.7% (n = 42) and as degree 2 in 14.3% (n = 7) of them. Based on the results of the Spielberger's trait-state anxiety inventory, the majority of the students had moderate anxiety (48.6% and 48.1%, respectively). The correlation between trait-anxiety levels and chronic orofacial pain degrees was significant and positive (p<.05). However, no significant correlation was found to state-anxiety levels and chronic orofacial pain degrees (p>.05). Conclusion: It was concluded that chronic orofacial pain of TMD could be present in university students and anxiety may be related. © 2010 Japan Prosthodontic Society. Published by Elsevier Ireland. All rights reserved.

Novas formas de encarceramento?: os jovens e o centro de ressocialização

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Deus abençoe a América: religião, política e relações internacionais dos Estados Unidos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

A presença da álgebra na legislação escolar brasileira

Pós-graduação em Educação Matemática - IGCE

A biblioteca da Fazenda Pinhal e o universo de leitura na passagem do século XIX para o século XX

Pós-graduação em Estudos Literários - FCLAR

A presença da história antiga nos compêndios didáticos de história da Primeira República e a construção identitária nacional

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Como Esaú e Jacó: as oligarquias sul-mineiras no final do Império e Primeira República

Pós-graduação em História - FCHS

Prescrições para ensinar a ensinar leitura e escrita na escola Normal de São Paulo: circulação de saberes pedagógicos Brasil/França (1874-1889)

Pós-graduação em Educação - FFC