Concepts of lower semicontinuity and continuous selections for convex valued multifunctions

We discuss several concepts of continuity, weaker than lower semicontinuity, but still implying the existence of a continuous selection for a closed convex valued multifunction from a paracompact Hausdorff topological space into a Banach space. In this way, an extension of Michael's celebrated selection theorem is given. The behavior of -envelop approximations, as well as the localization of continuous selections, is also discussed.     

Simulations of photomodulated solute transport in doubly illuminated liquid membranes containing photoactive carriers

A steady-state model describing photofacilitated transport in liquid membranes under double illumination is presented. The model allows for the exploration of the effects of a wide range of thermodynamic and kinetic carrier properties on the control of photoinduced transport rates of solutes, called photomodulation. Most previous experimental and theoretical studies have explored the illumination of only the feed or sweep side of the membrane, while this study examines the effects of illuminating both sides simultaneously. Under double illumination, solute transport rates can be as much as five times greater than those measured in the dark and 2.5 times greater than rates obtained under single illumination. Carriers that are predominantly in the weakly binding form in the dark generally provide slightly better performance at lower light intensities than do carriers that are predominantly in the strongly binding form in the dark. The greatest enhancement in solute transport under double illumination is seen for carriers with very slow interconversion rate constants between the strongly and weakly binding forms. These results provide guidelines to help those studying photofacilitated membranes select or design photoactive molecules that will act as optimal carriers in liquid membranes under double illumination.     

Charge transfer activation energy for alkali atoms on Re and Ta

Ion and atom desorption energies for five alkali metals on Re and Ta were determined using the ion thermal emission noise method. The activation energies for the charge transfer process in the adsorbed state were calculated using a special energetic balance equation, which describes the surface ionization and thermal desorption effect. Energies for desorption of Li, Na, K, Rb and Cs from Re and Ta surfaces were determined by measuring the time autocorrelation function of the ion thermoemission current fluctuations.     

Full discretization of some reaction diffusion equation with blow up

This paper aims at the development of numerical schemes for nonlinear reaction diffusion problems with a convection that blows up in a finite time. A full discretization of this problem that preserves the blow — up property is presented as well as a numerical simulation. Efficiency of the method is derived via a numerical comparison with a classical scheme based on the Runge Kutta scheme.     

Studies on the overproduction of indole-containing metabolites by a methanol-utilizing yeast

Production of indole-containing metabolites (“indoles”) from methanol has been studied using a mutant ofHansenula polymorpha resistant to 5-fluorotryptophan. Whereas the wild-type culture produces only a small amount of indoles, the mutant is partially deregulated and overproduces indoles. Indoles production was studied in batch and continuous culture and in a washed-cell system. When the pH was above 4.0, indoles production was growth-associated, in both minimal and complex media, and batch or continuous culture. When the pH was below or equal to 4.0, a low phosphate concentration was found to improve production. In a phosphate-deficient washed-cell suspension system, the addition of an amino acid such as methionine at 5 mM increased specific productivity by more than 60%. Addition of cycloheximide at 50 mg/L decreased residual growth and increased maximum productivity of indoles by more than 60%. When the antibiotic was added at 1000 mg/L, growth was completely inhibited and indoles production continued for about 35 h.     

Cooperative domains in lipid membranes

Journal of Thermal Analysis and Calorimetry - Phase transitions of multibilayer structures of hydrated L-α-dipalmitoyl- and L-α-dimyristoylphosphatidylcholine (DPPC and DMPC) were studied...     

Dynamic shear and compressional behavior of polydimethylsiloxanes: Ultrasonic and low frequency characterization

The dynamic rheological properties of a series of entangled polydimethylsiloxanes are investigated. Rheometrical shear measurements are first reported for three different molecular weight samples, together with ultrasonic tests, thus allowing to obtain dynamic shear master curves over ten decades. Winter‘s model for slightly polydisperse polymers is used and works well in this case. This provides an example of the applicability of this model. The propagation of longitudinal waves in the MHz range for the same PDMSs is studied next. The results are analyzed and combined with static measurements of the compressibility. They indicate that different relaxation mechanisms have to be considered in shear and compression, and that the ratio between volume and shear viscosity is frequency dependent, with a preponderance for shear effects at higher frequencies. Shear and compressional relaxational mechanisms are also well separated. Moreover, it is verified that the shear and compressional moduli are independent of the molecular weight in the transition region, above a certain frequency. This frequency corresponds to a wavelength comparable to the distance between entanglements, in the case of shear waves. Received: 9 December 1997 Accepted: 30 March 1998