Search results for "layer"
showing 10 items of 2667 documents
On ripples and rafts: Curvature induced nanoscale structures in lipid membranes
2014
We develop an elastic theory that predicts the spontaneous formation of nanoscale structures in lipid bilayers which locally phase separate between two phases with different spontaneous monolayer curvature. The theory rationalizes in a unified manner the observation of a variety of nanoscale structures in lipid membranes: Rippled states in one-component membranes, lipid rafts in multicomponent membranes. Furthermore, we report on recent observations of rippled states and rafts in simulations of a simple coarse-grained model for lipid bilayers, which are compatible with experimental observations and with our elastic model.
Brewster angle microscopy and X-ray GID studies of morphology and crystal structure in monolayers of N-tetradecyl-γ,δ-dihydroxypentanoic acid amide
1997
First-order phase transitions from the low-density fluidlike phase to the condensed phase of monolayers of N-tetradecyl-γ,δ-dihydroxypentanoic acid amides at the air−water interface have been studied by π−A isotherms, Brewster angle microscopy (BAM), and synchrotron X-ray grazing incidence diffraction (GID). The thermodynamic differences between enantiomeric and racemic monolayers are too small to be measured. However, chiral discrimination is observable in the macroscopic domain morphology by BAM. The domains of the condensed phase grow dendritically. The characteristic shapes of domains of the pure S and R enantiomers are mirror images of each other. The domains of the racemic mixture are…
Phospholipid monolayers at water∣oil interfaces: theoretical modelling of surface pressure–molecular area isotherms
1998
Abstract The phospholipid adsorption and surface pressure–molecular area isotherms at interfaces are interpreted theoretically from two-dimensional (2D) lattice and real gas models that incorporate a minimum number of adjustable parameters. The first model is based on the lattice statistics of binary solutions and the molecular parameters introduced are the energy changes involved in the mixing process of the phospholipid and organic solvent molecules and the effective phospholipid head area. The surface pressure is interpreted in terms of the difference between the two liquid surface tensions. The second model makes use of (i) a non-localised adsorption model with a square-well potential e…
Two-Dimensional Boundary Layer Equations: High Resolution Capturing Methods
1993
In this paper we apply the piecewise hyperbolic and parabolic essentially non-oscillatory (ENO) capturing schemes (see [2] and [4]) to approximate the solution to the boundary layer equations for two-dimensional incompressible flow. We have tested several numerical examples analyzing their resolutive power and efficiency with respect to small values of the kinematic viscosity of the flow.
Large Eddy Simulations of Rough Turbulent Channel Flows Bounded by Irregular Roughness: The Role of Geometrical Parameters
2020
Almost all bounded flows, in nature and industry, are bounded by rough boundaries. Important efforts have been made, in fact, to analyse the physics of the fluids over such geometries. Basically, rough walls strongly influence the total energy dissipation, with important consequences in the form of higher costs especially in industrial applications.
Complex singularity analysis for vortex layer flows
2021
We study the evolution of a 2D vortex layer at high Reynolds number. Vortex layer flows are characterized by intense vorticity concentrated around a curve. In addition to their intrinsic interest, vortex layers are relevant configurations because they are regularizations of vortex sheets. In this paper, we consider vortex layers whose thickness is proportional to the square-root of the viscosity. We investigate the typical roll-up process, showing that crucial phases in the initial flow evolution are the formation of stagnation points and recirculation regions. Stretching and folding characterizes the following stage of the dynamics, and we relate these events to the growth of the palinstro…
Mean-Field Game Modeling the Bandwagon Effect with Activation Costs
2015
This paper provides a mean-field game theoretic model of the bandwagon effect in social networks. This effect can be observed whenever individuals tend to align their own opinions to a mainstream opinion. The contribution is threefold. First, we describe the opinion propagation as a mean-field game with local interactions. Second, we establish mean-field equilibrium strategies in the case where the mainstream opinion is constant. Such strategies are shown to have a threshold structure. Third, we extend the use of threshold strategies to the case of time-varying mainstream opinion and study the evolution of the macroscopic system.
Proliferation-associated oxygen consumption and morphology of tumor cells in monolayer and spheroid culture.
1992
The oxygen consumption rate, proliferative activity, and morphology of EMT6/Ro mouse mammary sarcoma cells in monolayer and multicellular spheroid culture have been investigated in a comparative study. During the transition of monolayer cells from the exponential into the plateau growth phase, there is a distinct decrease in the cellular volume that is associated with a corresponding decrease in the proliferative and respiratory activity of the cells. The decline in cell volume is mainly due to a decrease in the content of cytoplasm, whereas the size of the nucleus is only slightly reduced. A concomitant decrease in the number of mitochondria per cell obviously accounts for the reduction in…
Glutathione content of V79 cells in two- or three-dimensional culture
1997
The cellular glutathione (GSH) content of two- and three-dimensional cell cultures of V79 hamster lung cells has been studied. As previously described, cells in monolayer cultures show a decrease in GSH when they reach the confluent state. Three-dimensional cell cultures (multicell spheroids) allow a smoother transition from the initial proliferating to the nonproliferating status, and they show a central area of necrosis when a certain diameter is reached. Cellular GSH content in spheroids is variable throughout the culturing period: 1) GSH content (expressed per mg protein) is lower in spheroids with central necrotic areas than in smaller spheroids without necrosis, and 2) results expres…
Flow field, swimming velocity and boundary layer: parameters which affect the stimulus for the lateral line organ in blind fish
1988
The data presented support the hypothesis that the flow field supplies the stimulus to the lateral line organ (LLO) in blind cave fish (Anoptichthys jordani). Two basic predictions from the theoretical analysis of the flow field were confirmed: (i) individual blind cave fish prefer particular swimming velocities, (ii) the velocity preferred depends on the cross-sectional area (CSA) of the fish, i.e. the smaller the CSA the higher the swimming velocity. This relationship was found also in experimentally blinded fish of other species. Furthermore, when placed in unfamiliar surroundings, blind cave fish swim at higher velocities than in familiar surroundings for a certain habituation period. T…