A variational principle for actions on symmetric symplectic spaces

We present a definition of generating functions of canonical relations, which are real functions on symmetric symplectic spaces, discussing some conditions for the presence of caustics. We show how the actions compose by a neat geometrical formula and are connected to the hamiltonians via a geometrically simple variational principle which determines the classical trajectories, discussing the temporal evolution of such “extended hamiltonians” in terms of Hamilton–Jacobi-type equations. Simplest spaces are treated explicitly.     

An intimate polycarbonate/poly(methyl methacrylate)/poly(vinyl acetate) ternary blend via coalescence from their common inclusion compound with γ‐cyclodextrin

In this study, we successfully report an intimate ternary blend system of polycarbonate (PC)/poly(methyl methacrylate) (PMMA)/poly(vinyl acetate) (PVAc) obtained by the simultaneous coalescence of the three guest polymers from their common γ‐cyclodextrin (γ‐CD) inclusion compound (IC). The thermal transitions and the homogeneity of the coalesced ternary blend were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The observation of a single, common glass transition strongly suggests the presence of a homogeneous amorphous phase in the coalesced ternary polymer blend. This was further substantiated by solid‐state ¹³C NMR observation of the T_1ρ(¹H)s for each of the blend components. For comparison, ternary blends of PC/PMMA/PVAc were also prepared by traditional coprecipitation and solution casting methods. TGA data showed a thermal stability for the coalesced ternary blend that was improved over the coprecipitated blend, which was phase‐segregated. The presence of possible interactions between the three polymer components was investigated by infrared spectroscopy (FTIR). The analysis indicates that the ternary blend of these polymers achieved by coalescence from their common γ‐CD–IC results in a homogeneous polymer blend, possibly with improved properties, whereas coprecipitation and solution cast methods produced phase separated polymer blends. It was also found that control of the component polymer molar ratios plays a key role in the miscibility of their coalesced ternary blends. Coalescence of two or more normally immiscible polymers from their common CD–ICs appears to be a general method for obtaining well‐mixed, intimate blends. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4182–4194, 2004     

Multiscale preconditioning for the coupling of FEM–BEM

We apply multiscale methods to the coupling of finite and boundary element methods to solve an exterior two‐dimensional Laplacian. The matrices belonging to the boundary terms of the coupled FEM–BEM system are compressed by using biorthogonal wavelet bases developed from A. Cohen, I. Daubechies and J.‐C. Feauveau (Comm. Proc. Appl. Math. 1992; 45 :485). The coupling yields a linear equation system which corresponds to a saddle point problem. As favourable solver, the Bramble–Pasciak–CG (Math. Comp. 1988; 50 :1) is utilized. A suitable preconditioner is developed by combining the BPX (Math. Comp. 1990; 55 :1) with the wavelet preconditioning (Numer. Math. 1992; 63 :315). Through numerical experiments we provide results which corroborate the theory of the present paper. Copyright © 2002 John Wiley & Sons, Ltd.     

Torsion subgroups of Brauer groups and extensions of constant local degree for global function fields

We show that, for all characteristic p global fields k and natural numbers n coprime to the order of the non-p-part of the Picard group Pic⁰(k) of k, there exists an abelian extension L/k whose local degree at every prime of k is equal to n. This answers in the affirmative in this context a question recently posed by Kisilevsky and Sonn. As a consequence, we show that, for all n and k as above, the n-torsion subgroup Br_n(k) of the Brauer group Br(k) of k is algebraic, answering a question of Aldjaeff and Sonn in this context.     

The Rubin-Stark conjecture for a special class of function field extensions

We prove a strong form of the Brumer-Stark Conjecture and, as a consequence, a strong form of Rubin's integral refinement of the abelian Stark Conjecture, for a large class of abelian extensions of an arbitrary characteristic p global field k. This class includes all the abelian extensions K/k contained in the compositum k_p∞?k_p·k_∞ of the maximal pro-p abelian extension k_p/k and the maximal constant field extension k_∞/k of k, which happens to sit inside the maximal abelian extension k^ab of k with a quasi-finite index. This way, we extend the results obtained by the present author in (Comp. Math. 116 (1999) 321-367).     

Antibiotic activity of Emerimicin IV isolated from Emericellopsis minima from Talcahuano Bay,Chile

Due to the increasing emergence of resistance of bacterial pathogens to current antibiotics, we have examined the marine fungi present in sea sediments obtained 200 m offshore to discover new antibacterial compounds active against multidrug-resistant bacteria. One strain, identified as Emericellopsis minima, was isolated from sediments of Talcahuano Bay (Chile). From the liquid culture of E. minima, we isolated Emerimicin IV, a unique fungal peptaibol that exhibited antibacterial activity. The structure of this compound was assigned by interpretation of ¹H NMR and HR-LCMS data. Emerimicin IV showed bacteriostatic activity against clinical isolates of methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecalis with MIC values ranging between 100 and 12.5 μg/mL.     

The role of scavengers in the CdS film corrosion

Journal of Solid State Electrochemistry - The cadmium sulfide (CdS) is one of the most applied chalcogenides to the water splitting (WS) on photoelectrochemical cells (PEC). The CdS bandgap is...