Showing papers by "University of Avignon published in 1994"

Pectin Changes in Ripening Cherry Fruit

Abstract: Pectin solubilization was studied during ripening of cherry fruit. Pectic materials were isolated at specific stages during development. The proportion of alcohol-insoluble-material decreased on a fresh weight basis with ripeness, but increased per fruit. Pectic substances were divided into water-, oxalate- and acid-soluble fractions. The oxalate-and water-soluble part increased as acid-soluble components decreased. Water- and acid-soluble fractions contained many more neutral sugar residues than the oxalate-soluble fraction. Changes in individual sugars indicated the major alterations were the degradation of galactan and the absence of arabinan solubilization in acid-soluble pectic substance. Size exclusion chromatography showed absence of pectin depolymerization during ripening, indicating that fruit softening does not depend on pectin depolymerization.

Yuan's alternative theorem and the maximization of the minimum eigenvalue function

Abstract: LetA 1 andA 2 be two symmetric matrices of ordern×n. According to Yuan, there exists a convex combination of these matrices which is positive semidefinite, if and only if the functionx∈R n ↦ max {x T A 1 x,x T A 2 x} is nonnegative. We study the case in which more than two matrices are involved. We study also a related question concerning the maximization of the minimum eigenvalue of a convex combination of symmetric matrices.

Solving cone-constrained convex programs by differential inclusions

Abstract: A differential inclusion is designed for solving cone-constrained convex programs. The method is of subgradient-projection type. It involves projection, penalties and Lagrangian relaxation. Nonsmooth data can be accommodated. A novelty is that multipliers converge monotonically upwards to equilibrium levels. An application to stochastic programming is considered.

Calculus rules for global approximate minima and applications to approximate subdifferential calculus

Abstract: We provide calculus rules for global approximate minima concerning usual operations on functions. The formulas we obtain are then applied to approximate subdifferential calculus. In this way, new results are presented, for example on the approximate subdifferential of a deconvolution, or on the subdifferential of an upper envelope of convex functions.

Double-tailed perfluoroalkyl telomeric surfactants derived from tris(hydroxymethyl)acrylamidomethane for medical applications

Abstract: A new family of perfluoroalkyl double-tailed amphiphiles was synthesized in order to develop a new drug carrying and delivery system. They were obtained by telomerization of tris(hydroxymethyl)acrylamidomethane (THAM) in the presence of various double-tailed primary and secondary thiols as chain-transfer agents, and with AIBN as the initiator. With secondary thiols, telomerization occurred in low yields (25–35% with respect to the thiol), because of the competitive formation of a disulfide by-product, but proceeded in higher yields (45–90%, depending on the stoichiometry of the reagents) with primary thiols, thus allowing the preparation of a new family of perfluoroalkyl telomeric THAM double-tailed amphiphiles. Preliminary biological tests showed no detectable hemolytic activity on human red blood cells at concentrations up to 20 mmol/L (50–65 g/L), whereas the hydrocarbon analogs proved to be hemolytic at 0,002 mmol/L. The LD50 was found to be higher than 2500 mg/kg of animal.

Approximate Euler-Lagrange inclusion, approximate transversality condition, and sensitivity analysis of convex parametric problems of calculus of variations

Abstract: We study the first-order behaviour of the optimal value function associated to a convex parametric problem of calculus of variations. An important feature of this paper is that we do not assume the existence of optimal trajectories for the unperturbed problem. The concepts of approximate Euler-Lagrange inclusion and approximate transversality condition are key ingredients in the writing of our sensitivity results.

Sur quelques formules de dualité convexe et non convexe

Abstract: La condition de qualification d'Attouch et Brezis est mise a profit pour etudier la sous-differentiabilite de l'inf-convolution de deux fonctions convexes sur un espace de Banach, sans que l'inf-convolution soit necessairement exacte. Quelques applications de cette condition de qualification a l'optimisation et a la dualite sont presentees.

Traçage chimique et isotopique (Cl−, 18O) d'une crue d'automne sur un petit bassin versant Méditerranéen incendié

Abstract: Resume A la suite des incendies qui ont ravage le massif des Maures au cours de l'ete 1990, le petit bassin du Rimbaud (bassin versant du Real Collobrier) a vu son comportement hydrologique fortement modifie. Parallelement au suivi hydrologique et hydrochimique habituel, les isotopes stables ont ete mesures sur les precipitations et l'ecoulement. La disparition de la vegetation et donc de son influence sur les pluviolessivats nous a incite a comparer l'evolution respective des teneurs en oxygene 18 et en chlorure. Au cours de la crue du 9 decembre 1990, ces deux elements presentent un comportement tres similaire et, fait original, les decompositions d'hydrogramme qu'ils permettent d'etablir sont comparables. En considerant les facteurs habituels d'evolution des chlorures et de l'oxygene 18, il apparait qu'une proportion de l'ordre de 45% d'eau “ancienne” participe aux ecoulements de crue et que la zone non saturee ne joue dans ce cas precis aucun role significatif. En outre, en s'appuyant sur l'evolution ...