Abstract.We have investigated the effects of either distorting hydrogen bonds or removing proton degeneracy on the thermodynamic properties of a minimal model for associating liquids. The presence of two liquid phases and a density anomaly is unaffected in both cases. Increasing the degeneracy of bonded structures leads to lower temperature critical points and a steeper liquid-liquid coexistence line, implying a low density liquid of larger entropy.Analysis of the hydrogen bond net accross the phase diagram indicates that the density anomaly is accompanied by a steep reduction of hydrogen bond density, which introduces a restriction on a correlation which has been preconized long ago. This feature is present independent of bond distortion or of the presence of proton entropy. § To whom correspondence should be addressed (marcia.barbosa@ufrgs.br) Liquid polymorphism, density anomaly and H-bond disruption in an associating lattice gases 2
We investigate the phase diagram of a three-dimensional associating gas (ALG) model. This model combines orientational ice-like interactions and "van der Waals" that might be repulsive, representing, in this case, a penalty for distortion of hydrogen bonds. These interactions can be interpreted as two competing distances making the connection between this model and continuous isotropic soft-core potentials. We present Monte Carlo studies of the ALG model showing the presence of two liquid phase, two critical points and A density anomaly.
A two dimensional lattice gas model with "core-softened" potential is investigated. Two liquid phases and density anomaly are found. The demixing phase transition between the two liquid phases end at a tricritical point that is also the terminus of a critical line. The density anomaly is shown to be
As Feiras de Ciências são de suma importância no âmbito da educação básica, apesar disso o número de publicações não representa esse cenário. Objetivando verificar publicações que relacione as feiras de ciências com o contexto de avaliação de resumos de trabalhos apresentados nas mesmas, através da incidência da Teoria da Argumentação de Toulmin (2006), foi realizada uma pesquisa na plataforma OasisBr. Através desta busca foi possível fazer o levantamento de publicações relacionadas e as abordagens nos trabalhos contidos na plataforma, identificando escassos trabalhos que abordam as formas de elaboração e avaliação de resumos. Identificou-se que a análise dos argumentos de Toulmin não tem sido objeto de pesquisas sobre feiras de ciências e que a forma como os resumos são escritos e avaliados tem sido tratada de maneira superficial.
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