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See detailCovalent liquids: tight binding simulation versus experimental results
Gaspard, Jean-Pierre ULg; Bichara, C.; Raty, Jean-Yves ULg et al

(1998)

We show that a simple tight binding model with a repulsive potential describes the Peierls distortions in covalent systems and the well-known octet rule. The existence and the intensity of the Peierls ... [more ▼]

We show that a simple tight binding model with a repulsive potential describes the Peierls distortions in covalent systems and the well-known octet rule. The existence and the intensity of the Peierls distortion is mainly related to the hardness of the repulsive potential as demonstrated both by theoretical calculations and by the experimental systematic analysis of liquid structures. In particular, As is threefold coordinated and Sb is sixfold coordinated in the liquid; the qualitative difference is explained by the ratio of the distortion energy DeltaE to the thermal energy k BT. The As xSb 1-x alloys show continuously varying average coordination numbers showing that the semiconductor-metal transition is continuous with concentration. In addition, we illustrate in the case of liquid Se that, tight binding Monte Carlo simulations are able to describe quantitatively the structure of liquid elements provided the Van der Waals potential is added [less ▲]

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See detailThe Transcriptional Regulation of the Growth Hormone Gene Is Conserved in Vertebrate Evolution
Argenton, F.; Vianello, S.; Bernardini, S. et al

in Biochemical and Biophysical Research Communications (1993), 192(3), 1360-1366

Growth hormone (GH) gene expression in mammals is regulated by the interaction of the transcription factor Pit-1 with two binding sites within the proximal promoter. Four sequences, homologous to the ... [more ▼]

Growth hormone (GH) gene expression in mammals is regulated by the interaction of the transcription factor Pit-1 with two binding sites within the proximal promoter. Four sequences, homologous to the mammalian Pit-1 motif occur in the rainbow trout (Oncorhynchus mykiss) GHII (rtGH) gene promoter, two of which partly overlap. The three regions containing these putative Pit-1 binding sequences were protected from deoxyribonuclease I digestion by nuclear extracts of GC cells, a rat pituitary tumor cell line producing Pit-1. In gel shift assays, nuclear proteins from GC cells and from trout pituitaries were found to interact specifically with one of these protected sites. Transfection experiments showed that the rtGH promoter is transcnptionally active in GC cells, the response being strongly enhanced in the presence of a cAMP analogue. The results demonstrate that rat Pit-1 binds to and activates the rtGH promoter, indicating that the basic mechanisms regulating GH gene transcription have been conserved between fish and mammals. [less ▲]

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