Budding and Domain Shape Transformations in Mixed Lipid Films and Bilayer Membranes

We study the stability and shapes of domains with spontaneous curvature in fluid films and membranes, embedded in a surrounding membrane with zero spontaneous curvature. These domains can result from the inclusion of an impurity in a fluid membrane, or from phase separation within the membrane. We show that for small but finite line and surface tensions and for finite spontaneous curvatures, an equilibrium phase of protruding circular domains is obtained at low impurity concentrations. At higher concentrations, we predict a transition from circular domains, or "caplets", to stripes. In both cases, we calculate the shapes of these domains within the Monge representation for the membrane shape. With increasing line tension, we show numerically that there is a budding transformation from stable protruding circular domains to spherical buds. We calculate the full phase diagram, and demonstrate a two triple points, of respectively bud-flat-caplet and flat-stripe-caplet coexistence.Comment: 14 pages, to appear in Phys Rev

Determination of Electron Affinity Differences by Surface Ionization

Electron affinity differences determined by surface ionization on hot tungsten through use of polyatomic halogen molecular bea

Studies of the inner shelf and coastal sedimentation environment of the Beaufort Sea from ERTS-A

The author has identified the following significant results. Shearing periodically occurs between the westward moving pack ice (3 to 10 km/d) within the Pacific Gyre and the fast ice along the coast, forming major grounded shear and pressure ridges between the 10 to 40 m isobaths. Ridges occur in patterns conforming to known shoals. The zone of grounded ridges, called stamukhi zone, protects the inner shelf and coast from marine energy and pack ice forces. Relatively undeformed fast ice grows inshore of the stamukhi zone. The boundary is explained in terms of pack ice drift and major promontories and shoals. Intense ice gaging, highly disrupted sediments, and landward migration of shoals suggest that much of the available marine energy is expended on the sea floor within the stamukhi zone. Naleds (products of river icings) on the North Slope are more abundant east than west of the Colville River. Their location, growth, and decay were studied from LANDSAT imagery

Using genetics for social science

Social science genetics is concerned with understanding whether, how and why genetic differences between human beings are linked to differences in behaviours and socioeconomic outcomes. Our review discusses the goals, methods, challenges and implications of this research endeavour. We survey how the recent developments in genetics are beginning to provide social scientists with a powerful new toolbox they can use to better understand environmental effects, and we illustrate this with several substantive examples. Furthermore, we examine how medical research can benefit from genetic insights into social-scientific outcomes and vice versa. Finally, we discuss the ethical challenges of this work and clarify several common misunderstandings and misinterpretations of genetic research on individual differences

Evolution of particle-scale dynamics in an aging clay suspension

Multispeckle x-ray photon correlation spectroscopy was employed to characterize the slow dynamics of a colloidal suspension formed by highly-charged, nanometer-sized disks. At scattering wave vectors $q$ corresponding to interparticle length scales, the dynamic structure factor follows a form $f(q,t) \sim \exp[-(t/\tau)^{\beta}$], where $\beta \approx$ 1.5. The characteristic relaxation time $\tau$ increases with the sample age $t_a$ approximately as $\tau \sim t_a^{1.8}$ and decreases with $q$ approximately as $\tau \sim q^{-1}$. Such a compressed exponential decay with relaxation time that varies inversely with $q$ is consistent with recent models that describe the dynamics in disordered elastic media in terms of strain from random, local structural rearrangements. The amplitude of the measured decay in $f(q,t)$ varies with $q$ in a manner that implies caged particle motion at short times. The decrease in the range of this motion and an increase in suspension conductivity with increasing $t_a$ indicate a growth in the interparticle repulsion as the mechanism for internal stress development implied by the models.Comment: 4 pages, includes 4 postscript figures; accepted for publication in Phys Rev Let