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Kuznetsova T.,University of Bergen | Sapronova A.,Bergen Center for Computational Science | Kvamme B.,University of Bergen | Johannsen K.,Bergen Center for Computational Science | Haug J.,University of Bergen
Macromolecular Symposia | Year: 2010

Summary: Development of more capable low-dosage hydrate inhibitors (LDHI) is of crucial importance to oil and gas industry. Those efforts have been severely hindered so far by lack of clear understanding of molecular-level mechanisms, both thermodynamic and kinetic, which make certain chemical compounds into efficient inhibitors. An accurate representation of intermolecular potentials between polymeric low dosage inhibitors and hydrate-water-gas surfaces is essential for modelling systems containing these components. A two-stage computational study was undertaken of two proven LDHIs, polyvinylpyrrolidone (PVP) and polyvinylcaprolactam (PVCap), in aqueous solutions under various conditions. We have first carried out ab initio density functional theory (DFT) calculations for PVP and PVCap polymers with molecular weight spanning from monomers to polymeric chains. Molecular dynamics were then employed to investigate thermodynamic and kinetic processes that affect hydrate nucleation and growth. Comparison with experiments has also shown that calculated potential is able to mimic the characteristic behaviour of methane hydrate and PVP complexes. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Botnen H.A.,University of Bergen | Omar A.M.,University of Bergen | Omar A.M.,Bjerknes Center for Climate Research | Aavatsmark I.,University of Bergen | And 3 more authors.
Energy Procedia | Year: 2013

Span and Wagner equation of state (SW EOS) have been used to investigate changes in the thermodynamic properties of CO2 during a depressurization process from a pipeline into marine environment. The process is assumed to be isenthalpic, as only the thermodynamic change at the moment of depressurization is considered. The calculations show that the depth location of the pipeline influences greatly the density, temperature and volume changes, because of the difference in the surrounding pressures. In general the two-phase area is reached at depths shallower than 600 meters, which yields for the Norwegian Continental Shelf, as it is mainly shallower than 500 meters depth. There is a rapid decrease in density in the two-phase area causing a rapid expansion in the volume of CO2 from 4 MPa to 1 MPa. At the shallowest depth considered (100m) the volume fraction consist almost entirely of gas, and the density change give a significant increase in volume. Source


Ravasi T.,University of California at San Diego | Ravasi T.,Sea For Life | Suzuki H.,University of California at San Diego | Suzuki H.,RIKEN | And 82 more authors.
Cell | Year: 2010

Combinatorial interactions among transcription factors are critical to directing tissue-specific gene expression. To build a global atlas of these combinations, we have screened for physical interactions among the majority of human and mouse DNA-binding transcription factors (TFs). The complete networks contain 762 human and 877 mouse interactions. Analysis of the networks reveals that highly connected TFs are broadly expressed across tissues, and that roughly half of the measured interactions are conserved between mouse and human. The data highlight the importance of TF combinations for determining cell fate, and they lead to the identification of a SMAD3/FLI1 complex expressed during development of immunity. The availability of large TF combinatorial networks in both human and mouse will provide many opportunities to study gene regulation, tissue differentiation, and mammalian evolution. © 2010 Elsevier Inc. All rights reserved. Source

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