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..

Morphodynamic evolution of experimental cohesive deltas

Abstract: [1] Here we describe new techniques for creating river-dominated (birds foot) deltas with strong channelization in the laboratory. The key to achieving strong self-channelization is the addition of a commercially available polymer to the sediment mixture. This polymer enhances the substrate strength increasing the critical erosion stress, an important geomorphic threshold. More importantly it increases the rate of cohesion onset to account for increased rates of morphodynamic evolution in small-scale experiments. A cyclic pattern of delta evolution is observed. The delta “avulsion cycle” begins with channel avulsion, erosion, and channel elongation and ends with channel backfilling and abandonment. This cycle appears to be universal but is subject to a range of controls, including sediment size distribution, sediment concentration, substrate cohesiveness, and Froude number. We propose that the observed depositional cycle is characteristic of an avulsion mechanism that is more complex than current models of fluvial systems, which generally explain avulsion probability as an upstream effect dependent on channel superelevation or levee slope. The experiments suggest that in many distributary channel systems, including deltas, alluvial, and deep water fans, downstream mediated topographic effects or “morphodynamic backwater effects” may dominate over upstream avulsion processes and control the surface mechanics and stratigraphy. The experimental observations are synthesized into a new depositional model for river-dominated deltas which emphasizes the importance of self-organization and feedback in delta surface evolution and stratigraphy.

Polyvinylpyrrolidone-Agarose Gel Electrophoresis Purification of Polymerase Chain Reaction-Amplifiable DNA from Soils

Abstract: This communication describes a modification of agarose gel electrophoresis to provide a rapid and simple method for the purification of polymerase chain reaction-amplifiable DNA from soil This modification is to add polyvinylpyrrolidone to the agarose gel The polyvinylpyrrolidone addition retards the electrophoretic mobility of denaturing phenolic compounds so that they do not comigrate with nucleic acids