Processus de nucléation et de cristallisation du silicium liquide à l'aide du potentiel de Stillinger-Weber

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal

Nucleation and crystallization process of silicon using Stillinger-Weber potential

We study the homogeneous nucleation process in Stillinger-Weber silicon in the NVT ensemble. A clear first-order transition from the liquid to crystal phase is observed thermodynamically with kinetic and structural evidence of the transformation. At 0.75 T_m, the critical cluster size is about 175 atoms. The lifetime distribution of clusters as a function of the maximum size their reach follows an inverse gaussian distribution as was predicted recently from the classical theory of nucleation (CNT). However, while there is a qualitative agreement with the CNT, the free energy curve obtained from the simulations differs significantly from the theoretical predictions, suggesting that the low-density liquid phase found recently could play a role in the nucleation process.Comment: 21 page

Liquid-liquid phase transition in Stillinger-Weber silicon

It was recently demonstrated that the Stillinger-Weber silicon undergoes a liquid-liquid first-order phase transition deep into the supercooled region (Sastry and Angell, Nature Materials 2, 739 (2003)). Here we study the effects of perturbations on this phase transition. We show that the order of the liquid-liquid transition changes with negative pressure. We also find that the liquid-liquid transition disappears when the three-body term of the potential is strengthened by as little as 5 %. This implies that the details of the potential could affect strongly the nature and even the existence of the liquid-liquid phase.Comment: 13 page

A comprehensive map of the mTOR signaling network

The mammalian target of rapamycin (mTOR) is a central regulator of cell growth and proliferation. mTOR signaling is frequently dysregulated in oncogenic cells, and thus an attractive target for anticancer therapy. Using CellDesigner, a modeling support software for graphical notation, we present herein a comprehensive map of the mTOR signaling network, which includes 964 species connected by 777 reactions. The map complies with both the systems biology markup language (SBML) and graphical notation (SBGN) for computational analysis and graphical representation, respectively. As captured in the mTOR map, we review and discuss our current understanding of the mTOR signaling network and highlight the impact of mTOR feedback and crosstalk regulations on drug-based cancer therapy. This map is available on the Payao platform, a Web 2.0 based community-wide interactive process for creating more accurate and information-rich databases. Thus, this comprehensive map of the mTOR network will serve as a tool to facilitate systems-level study of up-to-date mTOR network components and signaling events toward the discovery of novel regulatory processes and therapeutic strategies for cancer