Temperature and solvent structure dependence of VO2+ complexes of pyridine-N-oxide derivatives and their interaction with human serum transferrin

The behaviour of the systems formed by VO(2+), 2-hydroxypyridine-N-oxide (Hhpo) and 2-mercaptopyridine-N-oxide (Hmpo) was studied both in solution and in the solid state through the combined application of spectroscopic (EPR and UV-Vis spectroscopy) and DFT methods. The geometry of solid bis-chelated complexes [VOL(2)], with L = hpo and mpo, is square pyramidal, but it can change to cis-[VOL(2)S], where S is a solvent molecule, when these are dissolved in a coordinating solvent. The equilibrium between the square pyramidal and cis-octahedral forms is strongly affected by solvent and temperature. At room temperature, the predominant species is [VOL(2)], which gives a pink colour to the solutions; at lower temperatures, the equilibrium is shifted--partially or completely--toward the formation of cis-[VOL(2)S], which is green. In an acidic environment and in the presence of an excess of ligand, [VOL(2)] can transform into the tris-chelated complex [VL(3)](+), in which vanadium loses the oxido ligand and adopts a hexa-coordinated geometry intermediate between octahedral and trigonal prismatic. 1-Methylimidazole (1-MeIm), which represents a model for His-N coordination, forms mixed complexes with stoichiometry cis-[VOL(2)(1-MeIm)], occupying an equatorial position. In the ternary systems VO(2+)-Hhpo-hTf and VO(2+)-Hmpo-hTf at room temperature and pH 7.4, besides (VO)hTf and (VO)(2)hTf, the mixed species cis-VO(hpo)(2)(hTf) and VO(mpo)(hTf) are observed, with the equatorial binding of an accessible histidine residue. Finally, the contribution of the N-oxide group to (51)V A(z) and A(iso) hyperfine coupling constants, which can be important in the characterisation of similar species, is discussed.     

Building large supramolecular nanocapsules with europium cations

A new tripodal ligand has been designed by connecting pyridine-based coordination units to a rigid triptycene moiety. Its reaction with europium(III) provides three-dimensional tetranuclear edifices, whose structural and photophysical characteristics as well as host-guest interactions are discussed in this contribution.     

Manipulation of Förster energy transfer of coupled fluorophores through biotransformation by Pseudomonas resinovorans CA10

An alkyne‐terminated anthracene and azide‐terminated carbazole were joined through a copper‐catalyzed cycloaddition to form a joined donor/acceptor pair. The photonic pair exhibited energy transfer when excited at the peak absorbance of carbazole and fluoresced with an anthracene spectral response. The fluorescent behavior was confirmed as Förster energy transfer (FRET). The lysate of Pseudomonas resinovorans CA10, a member of a predominant group of soil microorganisms that can metabolize a host of substrates, was employed to degrade the pair and alter the luminance spectral characteristics. The FRET was diminished and the corresponding, individual fluorescence of carbazole and anthracene returned. This general approach may find applications in single‐cell metabolic studies and bioactivity assays.     

Reverse Khas’minskii condition

The aim of this paper is to present and discuss some equivalent characterizations of p-parabolicity for complete Riemannian manifolds in terms of existence of special exhaustion functions. In particular, Khas’minskii in Ergodic properties of recurrent diffusion prossesses and stabilization of solution to the Cauchy problem for parabolic equations (Theor Prob Appl 5(2), 1960) proved that if there exists a 2-superharmonic function ${\mathcal{K}}$ defined outside a compact set on a complete Riemannian manifold R such that ${\lim_{x\to \infty} \mathcal{K}(x)=\infty}$ , then R is 2-parabolic, and Sario and Nakai in Classification theory of Riemann surfaces (Springer, Berlin, 1970) were able to improve this result by showing that R is 2-parabolic if and only if there exists an Evans potential, i.e. a 2-harmonic function ${E:R{\setminus} K \to \mathbb{R}^+}$ with ${\lim_{x\to \infty}\mathcal{E}(x)=\infty}$ . In this paper, we will prove a reverse Khas’minskii condition valid for any p?>?1 and discuss the existence of Evans potentials in the nonlinear case.     

On the intercalation of the iodine-iodide couple on layered double hydroxides with different particle sizes

Molecular iodine was intercalated from nonaqueous solution into microsized ZnAl-layered double hydroxide (LDH) in the iodide form, generating the I(3)(-)/I(-) redox couple into the interlayer region. Chloroform, ethanol, acetonitrile, or diethyl ether were used as solvents to dissolve the molecular iodine. The intercalation compounds were characterized by thermogravimetric analysis, X-ray powder diffraction, UV-vis spectroscopy, and scanning and transmission electron microscopy. The stability of iodine-solvent adducts and the iodine concentration affected the LDH iodine loading, and samples with I(2)/I(-) molar ratio ranging from 0.14 to 0.82 were prepared. Nanosized, well dispersible LDH, synthesized by the urea method in water-ethylene glycol media, were also prepared and successfully functionalized with the I(3)(-)/I(-) redox couple applying the conditions optimized for the micrometric systems.     

On the Poincaré inequality for vector fields

We prove the Poincaré inequality for vector fields on the balls of the control distance by integrating along subunit paths. Our method requires that the balls are representable by means of suitable “controllable almost exponential maps”. Both authors were partially supported by the University of Bologna, funds for selected research topics.     

Nonlinear programming approaches in the multidisciplinary design optimization of a sailing yacht keel fin

We consider the use of global optimization techniques for the minimization of a nonconvex function, arising from a Multidisciplinary Design Optimization problem of a ship. In ship design different disciplines must be often coupled, encompassing hydrodynamic and structural problems. This scenario requires the use of specific multidisciplinary formulations, where standard mathematical programming methods could be unsuitable. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the modeling of thermo-electro-magneto-mechanical solids at finite strains

A short overview of the mechanics of electromagnetic continua at finite strains is provided in this paper. In this framework objective thermodynamically-consistent constitutive relations are formulated for materials that exhibit thermo-electro-magnetomechanical coupling. In particular a model for an isotropic hyperelastic magnetic solid is considered, which finds application for magnetorheological elastomers (MRE). (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Interplay between structure and size in a critical crystal nucleus

We study the kinetics of crystal nucleation of an undercooled Lennard-Jones liquid using various path-sampling methods. We obtain the rate constant and elucidate the pathways for crystal nucleation. Analysis of the path ensemble reveals that crystal nucleation occurs along many different pathways, in which critical solid nuclei can be small, compact, and face centered cubic, but also large, less ordered, and more body centered cubic. The reaction coordinate thus includes, besides the cluster size, also the quality of the crystal structure.     

Reflectometric measurement of birefringence rotation in single-mode optical fibers

We present a novel reflectometric technique for the measurement of orientation and modulus of the linear birefringence vector in single-mode optical fibers. The technique provides information also on circular birefringence, although this component, if present, appears as a rotation of the linear birefringence. A detailed theoretical analysis is reported and validated by experimental results.