arXiv subjects
Publications and source records attributed to H. Bermudez.
We determine the group of linear transformations on a vector space $V$ that preserve a polynomial function $f$ on $V$ for several interesting pairs $(V,f)$, using the theory of semisimple algebraic groups.
The bending rigidity $k_c$ of bilayer vesicles self-assembled from amphiphilic diblock copolymers has been measured using single and dual-micropipet techniques. These copolymers are nearly a factor of 5 greater in hydrophobic membrane thickness $d$ than their lipid counterparts, and an order of magnitude larger in molecular weight $\bar{M}_n$. The macromolecular structure of these amphiphiles lends insight into and extends relationships for traditional surfactant behavior. We find the scaling of $k_c$ with thickness to be nearly quadratic, in agreement with existing theories for bilayer membranes. The results here are key to understanding and designing soft interfaces such as biomembrane mimetics.
Self-assembled membranes of amphiphilic diblock copolymers enable comparisons of cohesiveness with lipid membranes over the range of hydrophobic thicknesses d=3-15 nm. At zero mechanical tension the breakdown potential V_c for polymersomes with d=15 nm is 9 V compared to 1 V for liposomes with d=3 nm. Nonetheless, electromechanical stresses at breakdown universally exhibit a square dependence on V_c, and membrane capacitance shows the expected strong d-dependence, conforming to simple thermodynamic models. The viscous nature of the diblock membranes is apparent in the protracted post-poration dynamics.