We used the united-atom scheme to build three types of crystalline structures for octacosane (C28H58) and carried out molecular dynamic simulations to investigate their phase properties. By gradually heating the...

Abstract. Existence and repeatability of tornadoes could be straightforwardly explained if there existed instability, responsible for their formation. However, it is well known that convection is the only instability in initially stable air, and the usual convective instability is not applicable for these phenomena. In the present paper we describe an instability in the atmosphere, which can be responsible for intense vortices. This instability appears in a fluid with Coriolis force and dissipation and has oscillatory behaviour, where the amplitude growth is accompanied by oscillations with frequency comparable to the growth rate of the instability. In the paper, both analytical analysis of the linear phase of the instability and nonlinear simulation of the developed stage of the air motion are addressed. This work was supported by the RFBR grant no. 09-05-00374-a.

We used the TraPPE-UA [Martin, M. G.; Siepmann, J. I. J. Phys. Chem. B 1998Chem. B , 102, 2569 scheme to investigate the inhibition of crystal growth in an octacosane matrix embedded with an ethylene-vinyl acetate (EVA) inhibitor. Through elucidating the phenomena of EVA-induced morphological transitions, we demonstrated that an EVA chain needs to possess suitable configurations with an optimal concentration of polar vinyl acetate (VA) side units, minimal distance between VA units subject to the constraint that VA units remain separate, and symmetrical location distributions of VA units to achieve the best inhibition performance. Furthermore, we revealed that the EVA inhibition was triggered by distortions of the EVA backbone section due to the strong affinity of VA components to neighboring molecules. We obtained an agreement with the experimental characterizations and provided an insight into the solution for the problem of paraffin crystallizations in crude oil pipelines.