Phase transitions of fluorotelomer alcohols at the water|alkane interface studied molecular dynamics simulation.

Fluorosurfactants are long-lasting environmental pollutants that accumulate at interfaces ranging from aerosol droplet surfaces to cell membranes. Modeling of adsorption-based removal technologies for fluorosurfactants requires accurate simulation methods which can predict their adsorption isotherm and monolayer structure. Fluorotelomer alcohols with one or two methylene groups adjacent to the alcohol (7 : 1 FTOH and 6 : 2 FTOH, respectively) are investigated using the OPLS-AA force field at the water|hexane interface, varying the interfacial area per surfactant.

Structure of the Hexadecane Rotator Phase: Combination of X-ray Spectra and Molecular Dynamics Simulation.

Rotator phases are rotationally disordered plastic crystals, some of which can form upon freezing of alkane at alkane-water interfaces. Existing X-ray diffraction studies show only partial unit cell information for rotator phases of some alkanes. This includes the rotator phase of -hexadecane, which is a transient metastable phase in pure alkane systems, but shows remarkable stability at interfaces when mediated by a surfactant.

Extension of the TraPPE Force Field for Battery Electrolyte Solvents.

Optimizing electrolyte formulations is key to improving performance of Li-/Na-ion batteries, where transport properties (diffusion coefficient, viscosity) and permittivity need to be predicted as functions of temperature, salt concentration and solvent composition. More efficient and reliable simulation models are urgently needed, owing to the high cost of experimental methods and the lack of united-atom molecular dynamics force fields validated for electrolyte solvents. Here the computationally efficient TraPPE united-atom force field is extended to be compatible with carbonate solvents, optimizing the charges and dihedral potential.

End-to-end system for rapid and sensitive early-detection of SARS-CoV-2 for resource-poor and field-test environments using a $51 lab-in-a-backpack.

COVID-19 has exposed stark inequalities between resource-rich and resource-poor countries. International UN- and WHO-led efforts, such as COVAX, have provided SARS-CoV-2 vaccines but half of African countries have less than 2% vaccinated in their population, and only 15 have reached 10% by October 2021, further disadvantaging local economic recovery. Key for this implementation and preventing further mutation and spread is the frequency of voluntary [asymptomatic] testing.

Benchmarking of Molecular Dynamics Force Fields for Solid-Liquid and Solid-Solid Phase Transitions in Alkanes.

Accurate prediction of alkane phase transitions involving solids is needed to prevent catastrophic pipeline blockages, improve lubrication formulations, smart insulation, and energy storage, as well as bring fundamental understanding to processes such as artificial morphogenesis. However, simulation of these transitions is challenging and therefore often omitted in force field development. Here, we perform a series of benchmarks on seven representative molecular dynamics models (TraPPE, PYS, CHARMM36, L-OPLS, COMPASS, Williams, and the newly optimized Williams 7B), comparing with experimental data for liquid properties, liquid-solid, and solid-solid phase transitions of two prototypical alkanes, -pentadecane (C) and -hexadecane (C).