New material of three equids is described from the middle Miocene Cajon Valley Formation in San Bernardino National Forest, San Bernardino County, California. The material includes teeth of Archaeohippus mourningi, Scaphohippus sumani, and Parahippus brevidens. Scaphohippus intermontanus is considered a junior subjective synonym of S. sumani. Parahippus brevidens is identified from an upper molar that closely resembles the morphology of the holotype as well as referred specimens of Pa. brevidens from the Mascall Formation in Oregon and the Temblor Formation in California. The presence of Pa. brevidens in the Cajon Valley Formation represents a geographic range extension for the taxon of over 400 km. Interesting ecological implications emerge for the Cajon Valley Formation when compared to the nearby Barstow Formation, including the presence of chalicotheres and apparent lack of Hypohippus affinis and Megahippus mckennai.

Indoor surfaces are often coated with organic compounds yet a molecular understanding of what drives these interactions is poorly understood. Herein, the adsorption and desorption of limonene, an organic compound found in indoor environments, on hydroxylated silica (SiO₂) surfaces, used to mimic indoor glass surfaces, is investigated by combining vibrational spectroscopy, atomistic computer simulations and kinetic modeling. Infrared spectroscopy shows the interaction involves hydrogen-bonding between limonene and surface O-H groups. Atomistic molecular dynamics (MD) simulations confirm the existence of π-hydrogen bonding interactions, with one or two hydrogen bonds between the silica O-H groups and the carbon-carbon double bonds, roughly one third of the time. The concentration and temperature dependent adsorption/desorption kinetics as measured by infrared spectroscopy were reproduced with a kinetic model, yielding the adsorption enthalpy of ∼55 kJ mol^-1, which is consistent with the value derived from the MD simulations. Importantly, this integrated experimental, theoretical and kinetic modeling study constitutes a conceptual framework for understanding the interaction of organic compounds with indoor relevant surfaces and thus provides important insights into our understanding of indoor air chemistry and indoor air quality.