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..

Mesozoic-cenozoic paleogeographic and geodynamic evolution of southern south america

Abstract: ln this presentation, we compare the paleogeographie evolution of continental South America with the established plate tectonic history of the oceanic crust of the South American and African Plates. Major paleogeographic changes that have occurred in the last 200 million years are illustrated by reconstructions at 200, 160, 120, 100, 70, 50, 20, and 5 Ma. The se reconstructions show location and type of magmatic activity, types and arnounts of subsidence, and transgressions and regressions of shorelines. The latter are eompared with proposed eustatie sea-Ievel ehanges. The sequence of events documented by the reconstructions begins in the mid-late Triassic with the development of successor troughs and intra-plate domes and sags that represent the prelude to the rupture of Gondwanaland. Extension eontinued through the Late Jurassie resulting in widespread faulting and intra-plate volcanism. Large-seale drift occurred by the Early Cretaceous (late Neocomian) accompanied by the formation of epicontinental rifts and sags, and a well-defined magmatic are along the western margin of South America. In the mid-Cretaceous the Atlantic Basin was well developed and rimmed by trailing-margin sedimentary prisms, and global changes in plate motions led to the reorganization of the subduction system along the Pacific margin of South America. The Late Cretaceous, a time of relative tectonic quiescence in southern South America, recorded the maximum flooding of the continent by Atlantic waters. Plate tectonic reorganization in the Paleogene introduced new patterns of Andean deformation and magmatism, and coincided with general marine retreat. Magmatic arc buildup and renewed marine flooding followed in the early Neogene, with the late Neogene being dominated by pronounced shortening, Cordilleran uplift, and marine withdrawal.

Polyolefin adhesive compositions and articles made therefrom

Abstract: Embodiments of the present invention relate to article comprising 1) a functionalized component, 2) tackifier, and 3) an olefin polymer comprising one or more C3 to C40 olefins, optionally one or more diolefins, and less than 5 mole % of ethylene having a Dot T-Peel of 1 Newton or more, a branching index (g′) of 0.95 or less measured at the Mz of the polymer; and an Mw of 100,000 or less; where the functional component is selected from the group consisting of functionalized polymers, functionalized oligomers and beta nucleating agents; and where the Gardner color of the adhesive does not change by more than 7 Gardner units when the adhesive has been heat aged at 180° C. for 48 hours as compared to the Gardner color of the unaged composition.

Two or four Neoproterozoic glaciations

Abstract: A thick Neoproterozoic carbonate and glaciogenic succession of the southern Congo craton has yielded δ 13 C and 87 Sr/ 86 Sr records through the later Cryogenian (ca. 750–600 Ma) and earlier part of the Terminal Proterozoic (ca. 600–570 Ma). Sizeable negative δ 13 C excursions (to less than–5‰) occur above each of two glacial intervals and the 87 Sr/ 86 Sr values of marine carbonates shift from ∼0.7072 to ∼0.7079 at the upper glacial level. These geochemical constraints provide a Marinoan (younger Varanger) age for the upper glacial interval, previously regarded as a second phase of the Sturtian glaciation. The δ 13 C record from the Congo craton is therefore incompatible with recent global δ 13 C syntheses that have identified four or more separate ice ages during the Neoproterozoic. A cladistic analysis of geologic and geochemical characters of 12 Neoproterozoic glacial deposits identifies two distinct groups that are found in a consistent stratigraphic order whenever two glacial units occur within a single succession. We use δ 13 C and 87 Sr/ 86 Sr records from the Congo craton and other key successions to test the null hypothesis that there were only two global glaciations (Sturtian and Marinoan) during the Neoproterozoic. Placing the GSSP (global stratotype section and point) for the base of the Terminal Proterozoic within or just above a cap carbonate of the younger (Marinoan) glaciogenic succession would confine all known Neoproterozoic glaciations to the Cryogenian. The rapid shift in marine 87 Sr/ 86 Sr to more radiogenic values during the Marinoan glaciation is opposite that predicted by the snowball Earth scenario which calls for continental runoff to cease during glaciation, resulting in a shift to less radiogenic values.

Friction and Wear of Silicon Nitride and Silicon Carbide in Water: Hydrodynamic Lubrication at Low Sliding Speed Obtained by Tribochemical Wear

Abstract: This report describes experiments on friction of Si3N4 and SiC sliding against themselves and against each other in water at room temperature. The friction coefficient of Si3N4 against itself is f = 0.7 at low speeds (0.2 cm/s). At speeds above 6.5 cm/s and 4.91-N load, hydrodynamic lubrication sets in, with f = <0.002 and an estimated water film thickness of 70 nm. Between 0.2 and 5 cm/s, mixed lubrication occurs. This remarkably thin hydrodynamic film is made possible by the tribochemical wear of Si3N4 which occurs by dissolution in water and an absence of wear particles. The friction coefficient of SiC, against SiC or Si3N4 in water at low speeds is f = 0.26. Wear occurs by dissolution and fracture pitting. Small wear particles are observed. The friction coefficient of SiC against SiC is independent of sliding velocity between 0.2 and 20 cm/s. Hydrodynamic lubrication is obtained with a Si3N4 pin on SiC plate near 10 cm/s, mixed lubrication is obtained with a SiC in on Si3N4 plate at v < 20 cm/s. Prese...