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Bristol, United Kingdom

Montgomery W.,Wills Memorial Building | Tuff J.,Wills Memorial Building | Kohn S.C.,Wills Memorial Building | Jones R.L.,Daresbury Laboratory
Chemical Geology | Year: 2011

The stability and evolution of organic materials found in carbonaceous and ordinary chondrites in the evolution of terrestrial planet interiors are unknown. It has been determined that massive amounts of carbonaceous material fell on the early Earth during the Late Hadean, but the processes by which this material became the Earth's hydrosphere, atmosphere and biosphere are also unknown. We here demonstrate that reactions between these primordial organic molecules and the silicate mineral montmorillonite clay occur at the pressures associated with the upper mantle and planetary assembly. These reactions have consequences for the origin of complex organic chemistry on Earth. Using synchrotron-source Fourier transform infrared (FTIR) spectroscopy with high spatial resolution and the diamond anvil cell (DAC) to reach pressures up to 9.1GPa, we were able to observe the formation of new peaks (i.e., new bonds) at 952, 969, and 1026 cm-1 in situ. These peaks, which appear in formic acid (HCOOH) in the presence of montmorillonite clay, may represent either the formation of organo-silicate molecules, or the formation of more complex organic molecules via templating of the crystalline structure of the minerals. © 2011 Elsevier B.V. Source

Beckett F.M.,Wills Memorial Building | Mader H.M.,Wills Memorial Building | Phillips J.C.,Wills Memorial Building | Rust A.C.,Wills Memorial Building | Witham F.,Wills Memorial Building
Journal of Fluid Mechanics | Year: 2011

We present an experimental study of a buoyancy-driven, low-Reynolds-number (Re < 1) exchange flow of two Newtonian fluids in a vertical cylindrical pipe (length 1 m and diameter 38.4 mm) connecting two fluid reservoirs. The denser, more viscous fluid was golden syrup and the less dense, less viscous fluid was a golden syrup-water solution; the ratio of the viscosities of the two fluids (Î) ranged from 2 to 1180. Flows were initiated by removing a bung in the base of the upper reservoir or sliding out a gate positioned at the top, middle or bottom of the pipe. We observe the flows over long time durations (up to 356 h), and define the development of the flow with reference to a non-dimensional time (Ï.,). The initial transient development of the flow was dependent on which of the two fluids initially filled the pipe, but this did not systematically affect the flow regime observed at Ï., â 1. Two distinct flow regimes were observed: axisymmetric core-annular flow (CAF), in which the less viscous fluid occupies a cylindrical core and the denser fluid flows downwards in an annulus, and side-by-side (SBS) flow where both fluids are in contact with the pipe and there is a single interface between them. CAF formed at Π⥠75 and SBS flow at Î â 117. In several experiments, for 5 â Î â 59, a slowly developing transitional SBS (TSBS) flow was observed where SBS flow and CAF occurred simultaneously with SBS in the lower portion of the pipe; SBS existed throughout most of the pipe and in one case grew with time to entirely fill the pipe. Velocity profiles determined by tracking tracer particles show that the observed CAFs are adequately described by the formulation of Huppert & Hallworth (J. Fluid Mech., vol. 578, 2007, pp. 95-112). Experimental SBS velocity profiles are not well produced by the formulation of Kerswell (J. Fluid Mech., 10.1017/jfm.2011.190), possibly because the latter is restricted to flows whose cross-section has an interface of constant curvature. Despite the variations in flow regime, volume fluxes can be described by a power-law function of Î, Q1 = 0.059 Îâ̂'0.74. A comparison of experimental data with the theoretical approaches of Huppert Hallworth (2007) and Kerswell (2011) indicates that fluids are not arranged in the regime that maximises volume flux (e.g. SBS or CAF), nor do they adopt the geometry that maximises volume flux within that particular regime. © Cambridge University Press 2011. Source

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