On a formula for the spectral flow and its applications

We consider a continuous path of bounded symmetric Fredholm bilinear forms with arbitrary endpoints on a real Hilbert space, and we prove a formula that gives the spectral flow of the path in terms of the spectral flow of the restriction to a finite codimensional closed subspace. We also discuss the case of restrictions to a continuous path of finite codimensional closed subspaces. As an application of the formula, we introduce the notion of spectral flow for a periodic semi‐Riemannian geodesic, and we compute its value in terms of the Maslov index (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Radical cations from dipyridinium derivatives: a combined EPR and DFT study

The monoelectronic reduction of 1,1'-dimethyl-2,2'-dicyano-4,4'-bipyridinium (DCMV++) bis-methylsulphate, conducted directly in the cavity of the electron paramagnetic resonance (EPR) spectrometer at room temperature and in DMSO solution, gave the signal of the corresponding radical cation (DCMV.+) whose interpretation has been carried out with the aid of density functional theory (DFT) calculations run at different levels. The model chemistries considered yielded in general hyperfine coupling constants (hfcc) in good agreement with the experimental ones, except for the methyl protons directly bonded to the pyridinium nitrogens. The use of various computational methods accounting for solvent-solute interactions did not give significant improvements with respect to the gas phase results, while the geometry optimizations performed showed that the two pyridinium rings are coplanar in the radical cation but staggered in the parent dication, although the corresponding energy barrier involved is very low.     

Coordination symmetry-dependent structure restoration function of one-dimensional MOFs by molecular respiration

One-dimensional metal-organic compounds with cis, trans symmetry-controlled counter anions were synthesized (cis compound {[Cu(azpy)(H2O)2(OTs)2]*2H2O*(acetone)} (1) and trans compound {[Cu(H2O)4Cu(azpy)2(OTs)2(H2O)2]*2(OTs)*2H2O*2EtOH} (2)). Only 2, having trans conformation, exhibited a complete structure-restoration effect with a mechanism involving layering of molecular "bricks" of water and solvent molecules.     

Kosterlitz-Thouless Transition Line for the Two Dimensional Coulomb Gas

With a renormalization group approach, we study the pressure of the two dimensional Coulomb Gas along a small piece of the Kosterlitz-Thouless transition line, i.e. the boundary of the dipole region in the activity-temperature phase-space.     

Flow field-flow fractionation: recent trends in protein analysis

Flow field-flow fractionation (F4) is the gentlest flow-assisted separation technique for analysis of macromolecules. The use of an empty channel as separation device and of a second mobile phase flow as perpendicular field enable F4 to separate analytes under native conditions without any modification of their original structure. Because of this unique peculiarity, F4 has been shown to be ideal for "gentle" separation of biological samples, for example intact proteins and protein complexes, since its early development. Today's F4 is an appealing technique which complements most established separation techniques, for example liquid chromatography and electrophoresis. The number of applications that show the unique advantages of F4 for analysis of protein samples is constantly increasing. In particular, F4 is finding increasing application on very high-molecular-weight species such as protein oligomers, aggregates, and complexes. This review critically discusses recent literature on the application of F4 to proteins. Either stand-alone or coupled with other characterization techniques, F4 is particularly promising for quality control of protein therapeutics, characterization of amyloid proteins, lipoprotein profiling, and as a pre-MS separation step in proteomics.     

On the Existence of Forced Oscillations for the Spherical Pendulum Acted on by a Retarded Periodic Force

We show that, under mild conditions, T-periodic retarded functional motion equations on even-dimensional spheres admit forced oscillations. In this way we extend analogous results for the undelayed case due to the last two authors. A crucial role in our argument is played by a quite general continuation result, obtained in a recent paper, for forced oscillations of retarded functional motion equations on compact topologically nontrivial boundaryless manifolds.     

Laser ablation of silicon and copper targets. Experimental and finite elements studies

The ablation process induced by excimer lasers is a collective phenomenon that basically involves two phenomena: the laser radiation–matter interaction and the dynamic of the ablation plume. The laser parameters, the thermal and optical properties of the material, and the surface morphology are critical factors in the ablation mechanisms affecting the direction of the ablation plume expansion. In this study, the role of the surface roughness and the evolution of its morphology under the laser irradiation were investigated. Assuming a thermal ablation model, a theoretical study of the initial steps of the laser ablation process by a finite element method using ANSYS (6.1) was performed. Different ablation experiments were carried out on silicon and copper targets using a XeCl laser. The target surface morphology changes were observed by SEM and the plume deflection was recorded by a digital camera. An acceptable agreement between the experimental and simulated results was found. This study contributes to a better understanding of the physical processes involved in the laser ablation and the relations between the plume deflection angle and the surface roughness. PACS 79.20.Ds; 81.40.Gh; 44.05.+e     

Torsion and conformally Anosov flows in contact Riemannian geometry

We prove that on a compact (non Sasakian) contact metric 3-manifold with critical metric for the Chern-Hamilton functional, the characteristic vector field ξ is conformally Anosov and there exists a smooth curve in the contact distribution of conformally Anosov flows. As a consequence, we show that negativity of the ξ-sectional curvature is not a necessary condition for conformal Anosovicity of ξ (this completes a result of [4]). Moreover, we study contact metric 3-manifolds with constant ξ-sectional curvature and, in particular, correct a result of [13].