Verifying Weakly-Hard Real-Time Properties of Traffic Streams in Switched Networks

In this paper, we introduce the first verification method which is able to provide weakly-hard real-time guarantees for tasks and task chains in systems with multiple resources under partitioned scheduling with fixed priorities. Existing weakly-hard real-time verification techniques are restricted today to systems with a single resource. A weakly-hard real-time guarantee specifies an upper bound on the maximum number m of deadline misses of a task in a sequence of k consecutive executions. Such a guarantee is useful if a task can experience a bounded number of deadline misses without impacting the system mission. We present our verification method in the context of switched networks with traffic streams between nodes, and demonstrate its practical applicability in an automotive case study

Permeability of phospholipid membrane for small polar molecules determined from osmotic swelling of giant phospholipid vesicles

A method for determining permeability of phospholipid bilayer based on the osmotic swelling of micrometer-sized giant unilamellar vesicles (GUVs) is presented as an alternative to the two established techniques, dynamic light scattering on liposome suspension, and electrical measurements on planar lipid bilayers. In the described technique, an individual GUV is transferred using a micropipette from a sucrose/glucose solution into an isomolar solution containing the solute under investigation. Throughout the experiment, vesicle cross-section is monitored and recorded using a digital camera mounted on a phase-contrast microscope. Using a least-squares procedure for circle fitting, vesicle radius R is computed from the recorded images of vesicle cross-section. Two methods for determining membrane permeability from the obtained R(t) dependence are described: the first one uses the slope of R(t) for a spherical GUV, and the second one the R(t) dependence around the transition point at which a flaccid vesicle transforms into a spherical one. We demonstrate that both methods give consistent estimates for membrane permeability.Comment: 40 pages, 8 figures, to appear in Advances in Planar Lipid Membranes and Liposomes vol. 1

Active Membrane Fluctuations Studied by Micropipet Aspiration

We present a detailed analysis of the micropipet experiments recently reported in J-B. Manneville et al., Phys. Rev. Lett. 82, 4356--4359 (1999), including a derivation of the expected behaviour of the membrane tension as a function of the areal strain in the case of an active membrane, i.e., containing a nonequilibrium noise source. We give a general expression, which takes into account the effect of active centers both directly on the membrane, and on the embedding fluid dynamics, keeping track of the coupling between the density of active centers and the membrane curvature. The data of the micropipet experiments are well reproduced by the new expressions. In particular, we show that a natural choice of the parameters quantifying the strength of the active noise explains both the large amplitude of the observed effects and its remarkable insensitivity to the active-center density in the investigated range. [Submitted to Phys Rev E, 22 March 2001]Comment: 14 pages, 5 encapsulated Postscript figure

A 1H and 13C NMR study of motional changes of dipalmitoyl lecithin associated with the pretransition.

Motional changes of the dipalmitoyl lecithin molecule associated with the pretransition in multibilayers are investigated by proton-enhanced 13C-NMR and proton spin-locking experiments. The nitrogen-bound methyl groups of the polar head exhibit faster motion and more disorder in the intermediate phase compared with the gel phase. Although little or no change occurs in the hydrocarbon chain order at the pretransition, the corresponding motional correlation time changes by one order of magnitude. This is consistent with a model involving rotational motion of the hydrocarbon chains about their long axes: in the gel phase the motion is such that neighboring chains make an oscillating disrotatory motion, while in contrast, in the intermediate phase a quasi-free chain rotation takes place. Earlier contradicting results of Davies, J., 1979, Biophys. J., 27:339-358, and ourselves, Trahms, L., and E. Boroske, 1979, Biochim, Biophys. Acta. 552:189-193, are explained by this model

Magnetic anisotropy of egg lecithin membranes.

Magnetic realignment and rotational diffusion of cylindrical egg lecithin vesicles were measured under a phase contrast microscope. The anisotropy of magnetic susceptibility times membrane thickness was calculated from the data for several thin-walled vesicles. The resulting values were assigned to discrete numbers of bilayers. The difference between the susceptibilities parallel and perpendicular to the long axes of the lecithin molecules is deduced to be X parallel - X perpendicular = -(0.28 +/- 0.02) . 10(-8) cgs at 23 degrees C, if a bilayer thickness of 60 A is assumed

Osmotic shrinkage of giant egg-lecithin vesicles.

Osmotic shrinkage of giant egg-lecithin vesicles was observed by phase-contrast microscopy. The vesicles remained or became spherical when shrinking. Small and thick-walled vesicles formed visible fingers attached to the sphere. The water permeability of the single bilayer was found to be 41 micrometers/s. A variety of observations indicate that osmosis induces a parallel lipid flow between the monolayers of the bilayer, leading to a strong positive spontaneous curvature. They also suggest the formation of mostly submicroscopic daughter vesicles. The estimated coupling constant, 2 . 10(-6) mol/mol, is large enough to be biologically significant