Showing papers by "ICM Partners published in 1998"

Nonexistence of Solutions and an Anti-Maximum Principle for Cooperative Systems with the p-Laplacian

Abstract: We obtain a nonexistence result and an anti-maximum principle for weak solutions u = (u1,…, un) to the following strictly cooperative elliptic system, Here, Ω C IRN is a bounded domain with a C2,α - boundary δΩ, for some α ∈ (0,1), Δp denotes the p-Laplacian defined by Δpu = div (|∇u|p-2∇u) for p 6 (1,∞), and the coefficients aij (1 ≤ i,j ≤ n) are assumed to be constants satisfying aij > 0 for i ≠ j (a strictly cooperative system). We assume 0 ≤ fi, ∈ L∞(Ω) (1 ≤ i ≤ n). For ∇+ = ∇- ∇- = ∈ IR and f = (f1,…,fn) 0 in Ω, let μ1 denote the first eigenvalue of the (p - 1)-homogeneous system (S). Assuming f ≠ 0 in Ω, we show: (i) if ∧+ = ∧- = μ1, then (S) has no solution; and (ii) if ∧+, ∧- ∧ (μ1,μ1 + δ), for some δ > 0 small enough, then ui 0 on δΩ (1 ≤ i ≤ n). Our methods for the system (S) are completely different from the case n = 1 (a single equation). For n ≥ 2 and p ≥ 2, mild additional hypotheses are imposed on the domain Ω and the matrix .

CD and NMR structural characterization of ceratotoxins, natural peptides with antimicrobial activity

Abstract: Antibacterial properties of the secretion from the female reproductive accessory glands of medfly Ceratitis capitata are mostly ascribed to the presence of two peptides, ceratotoxin A and B, which exhibit a strong activity against gram-positive and gram-negative bacterial strains, and show sequence and function homology with cecropins, melittin, and magainins. CD experiments performed in different solvents indicate the presence of a significant content of helical structures in organic solvent. Two-dimensional nmr results for ceratotoxin A in methanol show a helical behavior for the 8-25 region of the peptide. A ramachandran classification of each residue for the structures obtained from distance geometry calculations lead to the definition of four structural families in which the central segment 10-19 is always helical and differences refer to residues 8-9 and 19-23. A sequence analysis of the two ceratotoxins and a systematic search on the protein data bank revealed the occurrence of a KX-hydrophobic-hydrophobic-P motif that seems to be important for helix stabilization.

Axial deformation crimping machine for cable-type end connectors

Abstract: An automated crimping machine for crimping a fitting or end connector onto an end of a cable is made up of segmental die portions which together form a die surface in the desired configuration including cylinder-operated pivot blocks to advance the segmental die portions between an open position and closed crimping position, a plunger assembly axially spaced from the die portions to support the fitting in loosely assembled relation on the cable and to automatically advance in an axial direction into the cavity formed by the die surfaces to cause the fitting to be crimped onto the cable end, following which the segmental die portions are expanded away from the fitting and the crimped fitting removed to permit insertion of the next fitting and cable which is advanced through a guide block into properly aligned relation with the plunger.

Weighted Polynomial Approximation in the Complex Plane

Abstract: Given a pair (G,W) of an open bounded set G in the complex plane and a weight function W(z) which is analytic and different from zero in G , we consider the problem of the locally uniform approximation of any function f(z) , which is analytic in G , by weighted polynomials of the form {Wn(z)Pn(z) } $\infinity$n=0 , where deg Pn\(\leq\)n. The main result of this paper is a necessary and sufficient condition for such an approximation to be valid. We also consider a number of applications of this result to various classical weights, which give explicit criteria for these weighted approximations.