Template‐Assisted Synthesis of Self‐Doped Polyaniline: Morphological Effects of Templates on the Conductivity

Self‐doped sulfonated polyaniline (PSA) has been synthesized on the surface of micellar nanoparticles made from positively charged surfactants by biocatalysis. The conformation forced by the electrostatic charge interactions between the positively charged micelle and the negatively charged PSA increases the conductivity of the PSA by three orders of magnitude. The pure PSA recovered from ion exchange, however, shows quite similar electrical properties compared with sulfonated polyanilines reported earlier. The increased conductivity of PSA complexes is as a result of the increased charge carrier concentration caused by a certain conformational locking.

     

A refined theory for laminated beams: Part II—An iterative variational approach

This paper presents a displacement-based one-dimensional model for the analysis of laminated composite beams, based on the assumption of cross sections rigid in their own planes. The proposed model is mainly focused on the boundary layer analysis. The representation of the axial displacements is given as products between line functions and warping modes of the cross section. Both the sets of unknown functions are determined by means of a variational formulation in order to obtain the ‘best choice’ for the thickness coordinate functions. The minimization of the total potential energy functional is reduced to a sequence of linear problems by means of a gradient technique. Various examples referring to simply supported and cantilever beams, subjected to distributed or concentrated loads, are solved. The results for stress distributions are found to be in excellent agreement with exact plane strain and finite element plane stress solutions even at very low distances from the end sections.

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Sommario In questo lavoro viene presentato un modello monodimens onale agli spostamenti per l'analisi di travi in laminato multistrato fondato sull'ipotesi di sezioni indeformabili nel proprio piano. Il modello è finalizzato principalmente allo studio degli effetti di bordo. Gli spostamenti assiali vengono espressi attraverso prodotti fra funzioni di linea e modi di ingobbamento della sezione. Entrambi gli insiemi di funzioni incognite sono determinati attraverso una formulazione variazionale allo scopo di ottimizzare le forme di ingobbamento della sezione. La minimizzazione del funzionale dell'energia potenziale totale viene ridotta ad una sequenza di problemi lineari mediante una tecnica tipo gradiente operando alternativamente le varizioni rispetto ai due insiemi di funzioni incognite. Negli esempi risolti, gli stati tensionali ottenuti risultano in eccellente accordo con soluzioni esatte (in stato piano di deformazione) e con soluzioni agli elementi finiti (in stato piano di tensione) anche in prossimità delle sezioni estreme libere o vincolate.

     

A refined theory for laminated beams: Part I—A new high order approach

This paper presents a new displacement-based one-dimensional model for the analysis of multilayered composite beams. The kinematic restriction of cross sections rigid in their own planes is introduced. The axial displacements over the cross sections are represented in terms of explicitly defined piecewise polynomial warping functions with discontinuous derivatives at the interlaminae, whereas the amplitude of the displacements along the beam axis is established by means of a variational formulation. It is proved that the proposed representation of the axial displacements yields the exact solution of the interior domain problem for a beam subjected to a transverse load varying according to a polynomial law. It is shown that two or three coordinate functions are sufficient to yield continuous distributions of equilibrated stresses except for small neighborhoods of the constrained cross sections, where a higher number of warping functions could be used in order to obtain a better accuracy. The numerical results show excellent agreement with plane stress finite element and plane strain exact solutions.

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Sommario In questo lavoro viene presentato un nuovo modello monodimensionale per l'analisi di travi composite multistrato. Viene introdotta l'ipotesi di indeformabilita delle sezioni nel proprio piano mentre gli spostamenti assiali nella sezione sono rappresentati facendo uso di funzioni ingobbamento definite sull'intera altezza e con derivata discontinua all'in erlamina. Infine, l'ampiezza degli spostamenti lungo l'asse della trave è determinata facendo uso di una formulazione variazionale. Si mostra come la rappresentazione degli spostamenti assiali proposta sia in grado di fornire la soluzione esatta, all'interno del dominio, per una trave soggetta ad un carico trasversale variabile con legge nolinomiale. Due o tre funzioni coordinate sono sufficienti a fornire distribuzioni di sforzi che verificano l'equilibrio anche all'interlamina, a meno di zone rislrette in vicinanza di sezioni vincolate. I risultati numerici mostrano un eccellente accordo con soluzioni agli elementi finiti in stato piano di tensione e con soluzioni esatte in stato piano di deformazione.

     

X-ray Structure and Thermal Properties of a 1:1 Inclusion Complex Between Permethylated β-Cyclodextrin and Psoralen

The phytoalexin psoralen (7H-furo[3,2-g][1]benzopyran-7-one) has been included in heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (TRIMEB) to yield a solid crystalline complex of formula TRIMEB-psoralen-H₂O. Its X-ray structural elucidation provides an accurate model for cyclodextrin–furocoumarin interaction. Thermal analysis (hot stage microscopy, differential scanning calorimetry, thermogravimetry) indicated complex dehydration in the range 40–100°C followed by melting at 137.1°C. The X-ray analysis showed that the elongated guest molecule induces elliptical distortion in the host molecule, with which it interacts via C-H ?O hydrogen bonding and hydrophobic interactions. The host molecule adopts a very similar conformation to that in the isostructural complex with l-menthol as guest. Water molecules bridge symmetry-related TRIMEB molecules by hydrogen bonding.     

The quest for hydrogen bond-based metal organic nanotubes (MONT)

Given the ability of forming homomeric amide···amide dimer by iso-nicotinamide (nda), we postulate the existence of a hydrogen bond equivalent of the iso-reticular metal organic nanotubes (MONT) built by using copper, p,p′-diphenylmethylene-diphosphinate (pcp), and bipyridine. We obtained the desired primary arrangement of Cu/pcp/nda consisting of a 1-D chain. Instead of the expected amide/amide dimer, the NH₂ groups were engaged in H-bonding networks with the phosphinate ligands in a series of 2-D slabs. The differences and the similarities of the Cu/pcp chains in known MONTs and in the reported structure are also highlighted.     

Confidence intervals in the solution of stochastic integer linear programming problems

A method is proposed to estimate confidence intervals for the solution of integer linear programming (ILP) problems where the technological coefficients matrix and the resource vector are made up of random variables whose distribution laws are unknown and only a sample of their values is available. This method, based on the theory of order statistics, only requires knowledge of the solution of the relaxed integer linear programming (RILP) problems which correspond to the sampled random parameters. The confidence intervals obtained in this way have proved to be more accurate than those estimated by the current methods which use the integer solutions of the sampled ILP problems.This research was partially supported by the Italian National Research Council contract no. 82.001 14.93 (P.F. Trasporti).     

Sc(III)-catalyzed enantioselective addition of thiols to α,β-unsaturated ketones in neutral water

This report concerns Lewis acid catalyzed enantioselective sulfa-Michael addition in neutral water by using a very efficient Sc(OTf)(3)/bipyridine 1 catalytic system. It is noteworthy that the protocol presented employs water as a reaction medium and allows us to obtain very high stereoselectivity and satisfactory yields for β-keto sulphides deriving from aliphatic thiols. The recovery and reuse of both the aqueous medium and the catalytic system is also reported.     

Reconciling phase diffusion and Hartree–Fock approximation in condensate systems

Despite the weakly interacting regime, the physics of Bose–Einstein condensates is widely affected by particle–particle interactions. They determine quantum phase diffusion, which is known to be the main cause of loss of coherence. Studying a simple model of two interacting Bose systems, we show how to predict the appearance of phase diffusion beyond the Bogoliubov approximation, providing a self-consistent treatment in the framework of a generalized Hartree–Fock–Bogoliubov perturbation theory.