52 research outputs found
Imbibition in Disordered Media
The physics of liquids in porous media gives rise to many interesting
phenomena, including imbibition where a viscous fluid displaces a less viscous
one. Here we discuss the theoretical and experimental progress made in recent
years in this field. The emphasis is on an interfacial description, akin to the
focus of a statistical physics approach. Coarse-grained equations of motion
have been recently presented in the literature. These contain terms that take
into account the pertinent features of imbibition: non-locality and the
quenched noise that arises from the random environment, fluctuations of the
fluid flow and capillary forces. The theoretical progress has highlighted the
presence of intrinsic length-scales that invalidate scale invariance often
assumed to be present in kinetic roughening processes such as that of a
two-phase boundary in liquid penetration. Another important fact is that the
macroscopic fluid flow, the kinetic roughening properties, and the effective
noise in the problem are all coupled. Many possible deviations from simple
scaling behaviour exist, and we outline the experimental evidence. Finally,
prospects for further work, both theoretical and experimental, are discussed.Comment: Review article, to appear in Advances in Physics, 53 pages LaTe
A Putative Plant Aminophospholipid Flippase, the Arabidopsis P4 ATPase ALA1, Localizes to the Plasma Membrane following Association with a β-Subunit
Plasma membranes in eukaryotic cells display asymmetric lipid distributions with aminophospholipids concentrated in the inner leaflet and sphingolipids in the outer leaflet. This unequal distribution of lipids between leaflets is, amongst several proposed functions, hypothesized to be a prerequisite for endocytosis. P4 ATPases, belonging to the P-type ATPase superfamily of pumps, are involved in establishing lipid asymmetry across plasma membranes, but P4 ATPases have not been identified in plant plasma membranes. Here we report that the plant P4 ATPase ALA1, which previously has been connected with cold tolerance of Arabidopsis thaliana, is targeted to the plasma membrane and does so following association in the endoplasmic reticulum with an ALIS protein β-subunit
Purinergic signalling and immune cells
This review article provides a historical perspective on the role of purinergic signalling in the regulation of various subsets of immune cells from early discoveries to current understanding. It is now recognised that adenosine 5'-triphosphate (ATP) and other nucleotides are released from cells following stress or injury. They can act on virtually all subsets of immune cells through a spectrum of P2X ligand-gated ion channels and G protein-coupled P2Y receptors. Furthermore, ATP is rapidly degraded into adenosine by ectonucleotidases such as CD39 and CD73, and adenosine exerts additional regulatory effects through its own receptors. The resulting effect ranges from stimulation to tolerance depending on the amount and time courses of nucleotides released, and the balance between ATP and adenosine. This review identifies the various receptors involved in the different subsets of immune cells and their effects on the function of these cells
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Optimum conditions for electrochemical deposition of 3-D mesoporous platinum framework
Here, we report a systematic investigation of the effect of experimental parameters on the structure, morphology and electrochemically active surface area of 3-D mesoporous platinum (Pt) framework. Template-assisted deposition of the mesoporous Pt framework is achieved using phytantriol-based inverse bicontinuous cubic phase of double diamond morphology (QIID) with Pn3m symmetry. Platinum is deposited electrochemically using hexachloroplatinic acid solution present within the aqueous domains of the cubic phase template. Deposition conditions, particularly the deposition potentials, are shown to significantly affect the surface morphology, porosity and electrochemically active surface area of the deposited Pt framework. Furthermore, the effect of underlying substrate on the structure and morphology of the mesoporous Pt framework is also investigated
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