236 research outputs found
On geometrically equivalent S-acts
In this paper, considering the geometric equivalence for algebras of a
variety of S-acts over a monoid S, we obtain representation theorems
describing all types of the equivalence classes of geometrically equivalent
S-acts of varieties over groups S.Comment: 13 pages, some statements were corrected and improve
Phase Separation of Saturated and Mono-unsaturated Lipids as determined from a Microscopic Model
A molecular model is proposed of a bilayer consisting of fully saturated DPPC
and mono unsaturated DOPC. The model not only encompasses the constant density
within the hydrophobic core of the bilayer, but also the tendency of chain
segments to align. It is solved within self-consistent field theory. A model
bilayer of DPPC undergoes a main chain transition to a gel phase, while a
bilayer of DOPC does not do so above zero degrees centigrade because of the
double bond which disrupts order. We examine structural and thermodynamic
properties of these membranes and find our results in reasonable accord with
experiment. In particular, order-parameter profiles are in good agreement with
NMR experiments. A phase diagram is obtained for mixtures of these lipids in a
membrane at zero tension. The system undergoes phase separation below the
main-chain transition temperature of the saturated lipid. Extensions to the
ternary DPPC, DOPC, and cholesterol system are outlined.Comment: 29 pages, 4 figures, 1 table. revised versio
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