485 research outputs found
Carbon capture and storage:Making fossil fuels great again?
At present, Carbon Capture and Storage, in which CO2 is captured from flue gasses and stored in geological formations, is one of the technologies to reduce CO2 emissions associated with the use of fossil fuels. Are there some good arguments to continue to invest in fossil fuels, a technology of yesterday
The order-disorder transition in model lipid bilayers is a first-order hexatic to liquid phase transition
We characterize the order-disorder transition in a model lipid bilayer using
molecular dynamics simulations. We find that the ordered phase is hexatic. In
particular, in-plane structures possess a finite concentration of 5-7
disclination pairs that diffuse throughout the plane of the bilayer, and
further, in-plane structures exhibit long-range orientational order and
short-range translational order. In contrast, the disordered phase is liquid.
The transition between the two phases is first order. Specifically, it exhibits
hysteresis, and coexistence exhibits an interface with capillary scaling. The
location of the interface and its spatial fluctuations are analyzed with a
spatial field constructed from a rotational-invariant for local 6-fold
orientational order. As a result of finite interfacial tension, there
necessarily exist associated forces of assembly between membrane-bound solutes
that pre-melt the ordered phase.Comment: Addressed the comments from colleagues, corrected typos, clarified
text, updated references. The new draft also contains new results relating to
the hexatic phas
Simulating Induced Interdigitation in Membranes
AbstractIn this study we introduce a mesoscopic lipid-water-alcohol model. Dissipative particle dynamics (DPD) simulations have been used to investigate the induced interdigitation of bilayers consisting of double-tail lipids by adding alcohol molecules to the bilayer. Our simulations nicely reproduce the experimental phase diagrams. We find that alcohol can induce an interdigitated structure where the common bilayer structure changes into monolayer in which the alcohol molecules screen the hydrophobic tails from the water phase. At low concentrations of alcohol the membrane has domains of the interdigitated phase that are in coexistence with the common membrane phase. We compute the effect of the chain length of the alcohol on the phase behavior of the membrane and show that the stability of the interdigitated phase depends on the length of the alcohol. We show that we can reproduce the experimental hydrophobic thickness of the bilayer for various combinations of lipids and alcohols. We use our model to clarify some of the experimental questions related to the structure of the interdigitated phase and put forward a simple model that explains the alcohol chain length dependence of the stability of this interdigitated phase
Improving the Mechanical Stability of Metal-Organic Frameworks Using Chemical Caryatids
Metal–organic
frameworks (MOFs) have emerged as versatile
materials for applications ranging from gas separation and storage,
catalysis, and sensing. The attractive feature of MOFs is that, by
changing the ligand and/or metal, they can be chemically tuned to
perform optimally for a given application. In most, if not all, of
these applications one also needs a material that has a sufficient
mechanical stability, but our understanding of how changes in the
chemical structure influence mechanical stability is limited. In this
work, we rationalize how the mechanical properties of MOFs are related
to framework bonding topology and ligand structure. We illustrate
that the functional groups on the organic ligands can either enhance
the mechanical stability through formation of a secondary network
of nonbonded interactions or soften the material by destabilizing
the bonded network of a MOF. In addition, we show that synergistic
effect of the bonding network of the material and the secondary network
is required to achieve optimal mechanical stability of a MOF. The
developed molecular insights in this work can be used for systematic
improvement of the mechanical stability of the materials by careful
selection of the functional groups
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