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In the present study, the fluid dynamics and phase behavior of crude-oil fouling in a closed-end heat-exchanger is studied. The deposition process associated with fouling is assumed to be due to two routes: asphaltene precipitation, and a two-step chemical reaction. The SAFT-γ Mie theory is employed to describe the phase behavior of an asphaltene-containing crude oil system, which comprises pseudo-components (C 13 ~ C 20+ ). The predicted phase equilibrium constants are used to quantify the asphaltene precipitation rate. A computational fluid dynamics framework is then used to simulate the fouling process, accounting for the multiphase flow dynamics, heat transfer, and the two deposition routes. Fouling is simulated due to the two routes individually and in concert. In the latter case, it is found that the interaction of the two routes is due to the fouling layer adhering to the heatexchanger walls, which influences heat transfer from the hot walls to the cooler oil in the bulk. The delicate interplay between heat transfer and fluid dynamics, which accompanies the flow, leads to enhancement and suppression of chemical reaction-and precipitation-driven fouling, respectively, and an overall rise in the fouling rate.

Bilayers, self-assembled by cationic surfactants and fatty alcohols in water, are the basic units of lamellar gel networks - creamy formulations extensively used in cosmetics and pharmaceutics. Mesoscopic modelling and...

Since its emergence, the Covid19 pandemic has been sustained by a series of transmission waves initiated by new variants of the SARS-CoV-2 virus. Some of these arise with higher transmissivity and/or increased disease severity. Here we use molecular dynamics simulations to examine the modulation of the fundamental interactions between the receptor binding domain (RBD) of the spike glycoprotein and the host cell receptor (human angiotensin-converting enzyme 2: hACE2) arising from Omicron variant mutations (BA.1 and BA.2) relative to the original wild type strain. We find significant structural differences in the complexes which overall bring the spike protein and its receptor into closer proximity. These are consistent with and attributed to the higher positive charge on the RBD conferred by BA.1 and BA.2 mutations relative to the wild type. However, further differences between sub-variants BA.1 and BA.2 (which have equivalent RBD charges) are also evident: Mutations affect interdomain interactions between the up-chain and its clockwise neighbor chain, resulting in enhanced flexibility for BA.2. Consequently, additional close contacts arise in BA.2 which include binding to hACE2 by a second spike protein monomer, in addition to the up-chain - a motif not found in BA.1. Finally, the mechanism by which the glycans stabilize the up state of the Spike protein differs for the wild type and the Omicrons. We also found the glycan on N90 of hACE2 turns from inhibiting, to facilitating the binding to Omicron spike protein. These structural and electrostatic differences offer further insight into the mechanisms by which viral mutations modulate host cell binding and provide a biophysical basis for evolutionary driving forces.

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