ExxonMobil

About: ExxonMobil is a company organization based out in Irving, Texas, United States. It is known for research contribution in the topics: Catalysis & Polymer. The organization has 16969 authors who have published 23758 publications receiving 535713 citations. The organization is also known as: Exxon Mobil Corporation & Exxon Mobil Corp..

Observation of a Reversible Thermotropic Order–Order Transition in a Diblock Copolymer

Abstract: The authors report the observation of a reversible thermotropic transition between the lamellar and cylindrical morphologies in a polystyrene-poly(ethene-co-butene) diblock copolymer. The nature of the intermediate structures which form as the transition progresses has been examined using two-dimensional small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Results show that the transformation from the lamellar to the cylindrical morphology proceeds in two steps. Initially, fluctuations along the interface joining the components of the copolymer grow in amplitude until the lamella transforms into a sheet of eventually spaced cylinders; cylinders which form in adjacent lamellae are usually in poor register with one another. This intermediate structure subsequently anneals into the hexagonal packing of cylinders characteristic of the cylindrical morphology. The reverse transition from cylinders to lamellae proceeds without producing any intermediate signature detectable by SAXS.

Capillary waves at liquid-vapor interfaces: a molecular dynamics simulation.

Abstract: Evidence for capillary waves at a liquid/vapor interface are presented from extensive molecular dynamics simulations of a system containing up to 1.24 million Lennard-Jones particles. Careful measurements show that the total interfacial width depends logarithmically on L{sub {parallel}}, the length of the simulation cell parallel to the interface, as predicted theoretically. The strength of the divergence of the interfacial width on L{sub {parallel}} depends inversely on the surface tension {gamma}. This allows us to measure {gamma} two ways since {gamma} can also be obtained from the difference in the pressure parallel and perpendicular to the interface. These two independent measures of {gamma} agree provided that the interfacial order parameter profile is fit to an error function and not a hyperbolic tangent, as often assumed. We explore why these two common fitting functions give different results for {gamma}.

In situ co-development of oil shale with mineral recovery

Abstract: A method of producing hydrocarbon fluids from a subsurface organic-rich rock formation, for example an oil shale formation, in which the oil shale formation contains water-soluble minerals, for example nahcolite, is provided. In one embodiment, the method includes the step of heating the organic-rich rock formation in situ. Optionally, this heating step may be performed prior to any substantial removal of water-soluble minerals from the organic-rich rock formation. In accordance with the method, the heating of the organic-rich rock formation both pyrolyzes at least a portion of the formation hydrocarbons, for example kerogen, to create hydrocarbon fluids, and converts at least a portion of the water-soluble minerals, for example, converts nahcolite to soda ash. Thereafter, the hydrocarbon fluids are produced from the formation.

Critical analysis of literature on low-dose synergy for use in screening chemical mixtures for risk assessment

Abstract: There is increasing interest in the use of tiered approaches in risk assessment of mixtures or co-exposures to chemicals for prioritization. One possible screening-level risk assessment approach is the threshold of toxicological concern (TTC). To date, default assumptions of dose or response additivity have been used to characterize the toxicity of chemical mixtures. Before a screening-level approach could be used, it is essential to know whether synergistic interactions can occur at low, environmentally relevant exposure levels. Studies demonstrating synergism in mammalian test systems were identified from the literature, with emphasis on studies performed at doses close to the points of departure (PODs) for individual chemicals. This search identified 90 studies on mixtures. Few included quantitative estimates of low-dose synergy; calculations of the magnitude of interaction were included in only 11 papers. Quantitative methodology varied across studies in terms of the null hypothesis, response measured...