Hairpin formation and elongation of biomolecules

We introduce a model of thermalized conformations in space of RNA-or single stranded DNA-molecules, which includes the possibility of hairpin formation. This model contains the usual secondary structure information, but extends it to the study of one element of the ternary structure, namely the end-to-end distance. The computed force-elongation characteristics are in good agreement with some recent measurements on single stranded DNA molecules.     

Pseudoconvex fully nonlinear partial differential operators: strong comparison theorems

We introduce a new class of curvature PDOs describing relevant properties of real hypersurfaces of . In our setting, the pseudoconvexity and the Levi form play the same role as the convexity and the real Hessian matrix play in the real Euclidean one. Our curvature operators are second-order fully nonlinear PDOs not elliptic at any point. However, when computed on generalized s-pseudoconvex functions, we shall show that their characteristic form is nonnegative definite with kernel of dimension one. Moreover, we shall show that the missing ellipticity direction can be recovered by taking into account the CR structure of the hypersurfaces. These properties allow us to prove a strong comparison principle, leading to symmetry theorems for domains with constant curvatures and to identification results for domains with comparable curvatures.     

On the subRiemannian cut locus in a model of free two-step Carnot group

We characterize the subRiemannian cut locus of the origin in the free Carnot group of step two with three generators, giving a new, independent proof of a result by Myasnichenko (J Dyn Control Syst 8(4):573-597, 2002). We also calculate explicitly the cut time of any extremal path and the distance from the origin of all points of the cut locus. Furthermore, by using the Hamiltonian approach, we show that the cut time of strictly normal extremal paths is a smooth explicit function of the initial velocity covector. Finally, using our previous results, we show that at any cut point the distance has a corner-like singularity.     

Nachweis der Salizyls?ure und Beurteilung ihrer Verwendung in der Nahrungsmittelindustrie

Ohne Zusammenfassung     

The effect of mechanical relaxation on ultra-fast charge pulses in flexible epoxy resin nanocomposites

Previously we have reported the existence of small-amplitude charge pulses in crosslinked Polyethylene (XLPE) and epoxy resin with a mobility several orders of magnitude higher than that found for the incoherent charge transport relevant to the steady state current. Here the relationship of this phenomenon to mechanical relaxation in the material is investigated by using a series of epoxy resin nanocomposites based on a resin that has its flexibility increased above that of the fully cured glassy epoxy network by the addition of a suitable flexibilizing chemical. Differential Scanning Calorimetry (DSC) measurements show that the stiffness of the nanocomposite is progressively increased as the nanoparticle concentration increases. Pulsed Electro-Acoustic (PEA) measurements reveal that both positive and negative fast charge pulses exist in the unfilled epoxy at 45 and 70°C under a field of 10?kV/mm with mobility 5×10^?10 to 9×10^?10 m²?V^?1?s^?1, amplitude between 2×10^?5 and 3.6×10^?5 C?m^?2 and repetition rates between 8 and 12?s^?1. These values are reduced progressively as the nanoparticle concentration is increased from 0% in the unfilled epoxy. A???-mode mechanical relaxation is identified in the loss modulus by Dynamical Mechanical Analysis (DMA), whose activation energy moves to higher values with increasing nanoparticle concentration. It is shown that the repetition rates of both positive and negative pulses have similar values and are correlated with the ??-mode activation energy; a similar correlation is found for the activation energy of the mobility of positive pulses. The correlation of the activation energy of the mobility of negative pulses and that of the ??-mode is weaker although both show a progressive increase with nanoparticle concentration. The modification of the fast charge pulse properties by the mechanical stiffness of the epoxy nanocomposite is discussed in terms of the theory presented previously for their formation and transport.     

Exposure to Anacardiaceae Volatile Oils and Their Constituents Induces Lipid Peroxidation within Food-Borne Bacteria Cells

The chemical composition of the volatile oils from five Anacardiaceae species and their activities against Gram positive and negative bacteria were assessed. The peroxidative damage within bacterial cell membranes was determined through the breakdown product malondialdehyde (MDA). The major constituents in Anacardium humile leaves oil were (E)-caryophyllene (31.0%) and α-pinene (22.0%), and in Anacardium occidentale oil they were (E)-caryophyllene (15.4%) and germacrene-D (11.5%). Volatile oil from Astronium fraxinifolium leaves were dominated by (E)-β-ocimene (44.1%) and α-terpinolene (15.2%), whilst the oil from Myracrodruon urundeuva contained an abundance of δ-3-carene (78.8%). However, Schinus terebinthifolius leaves oil collected in March and July presented different chemical compositions. The oils from all species, except the one from A. occidentale, exhibited varying levels of antibacterial activity against Staphylococcus aureus, Bacillus cereus and Escherichia coli. Oil extracted in July from S. terebinthifolius was more active against all bacterial strains than the corresponding oil extracted in March. The high antibacterial activity of the M. urundeuva oil could be ascribed to its high δ-3-carene content. The amounts of MDA generated within bacterial cells indicate that the volatile oils induce lipid peroxidation. The results suggest that one putative mechanism of antibacterial action of these volatile oils is pro-oxidant damage within bacterial cell membrane explaining in part their preservative properties.