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Homogeneous nucleation in supercooled liquid water. Determination of ice germ size and activation energy barrier in Molecular Dynamics simulations

Published in Molecular Simulation, 2022

Homogeneous freezing nucleation occurs in supercooled liquid water by the formation of critical-sized ice embryos. Molecular Dynamics simulations were performed ‘sowing’ a solid embryo into liquid and monitoring the subsequent system evolution. The size of critical ice embryos and the activation energy barrier associated with the incorporation of molecules into the germ were estimated using the TIP5P-E water model for three different temperatures: 237, 240 and 244 K. The results show how MD simulations provide reliable outcomes for the study of both parameters.

Recommended citation: Pereyra, R. G., Sebastianelli, P., & Ávila, E. E. (2022). Homogeneous nucleation in supercooled liquid water. Determination of ice germ size and activation energy barrier in Molecular Dynamics simulations. Molecular Simulation, 48(12), 1112–1121. https://doi.org/10.1080/08927022.2022.2068801
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Photophysical oxidation of HCHO produces HO2 radicals

Published in Nature Chemistry, 2023

At photolysis energies below the energetic threshold for radical formation we directly detect HO2 at low pressures by cavity ring-down spectroscopy and indirectly detect HO2 at 1 bar by Fourier-transform infrared spectroscopy end-product analysis. Supported by electronic structure theory and master equation simulations, we attribute this HO2 to photophysical oxidation (PPO): photoexcited HCHO relaxes non-radiatively to the ground electronic state where the far-from-equilibrium, vibrationally activated HCHO molecules react with thermal O2. PPO is likely to be a general mechanism in tropospheric chemistry and, unlike photolysis, PPO will increase with increasing O2 pressure.

Recommended citation: Welsh, B.A., Corrigan, M.E., Assaf, E. et al. Photophysical oxidation of HCHO produces HO2 radicals. Nat. Chem. 15, 1350–1357 (2023).
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Ignite your students’ interest in separable ODEs: a fire engineering application

Published in International Journal of Mathematical Education in Science and Technology, 2025

It is often desirable to have students solve a differential equation having a real application. We discuss such an equation, arising in the field of fire engineering, which models the temperature of a solid that is being heated by a radiative heat flux.

Recommended citation: Nelson, M. I., & Sebastianelli, P. (2025). " Ignite your students’ interest in separable ODEs: a fire engineering application." International Journal of Mathematical Education in Science and Technology, 1–22.
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