Anomalous deterministic transport

We present a series of results on deterministic transport in chaotic system, obtained in the framework of periodic orbits theory. The emphasis is on intermittent systems, where deviations from complete chaos may induce anomalies on the asymptotic moments' growth.     

Reduction of systems of first-order differential equations via Λ-symmetries

The notion of λ-symmetries, originally introduced by C. Muriel and J.L. Romero, is extended to the case of systems of first-order ODEs (and of dynamical systems in particular). It is shown that the existence of a symmetry of this type produces a reduction of the differential equations, restricting the presence of the variables involved in the problem. The results are compared with the case of standard (i.e. exact) Lie-point symmetries and are also illustrated by some examples.     

DNA Binding Studies and Cytotoxicity of a Dinuclear PtII Diazapyrenium‐Based Metallo‐supramolecular Rectangular Box

The interaction with native DNA of a 2,7‐diazapyrenium‐based ligand 1 and its Pt^II rectangular metallacycle 2 is explored through circular and linear dichroism and fluorescence spectroscopies. The metal‐free ligand 1 binds through intercalation, with a binding constant of approximately 5×10⁵ M ^?1, whereas the metallacycle 2 binds and bends the DNA with a binding constant of 7×10⁶ M ^?1. PCR assays show that metallo‐supramolecular box 2 interferes with DNA transactions in vitro whereas the intercalator 1 does not. The metallacycle is active against four human cancer cell lines, with IC₅₀ values ranging between 3.1 and 19.2 μM and shows similar levels of efficacy, but a different spectrum of activity, to cisplatin.     

Preparation and Thermal Characterization of PTFE/PES Nanocomposites

Summary: PTFE/PES composites were prepared by precipitation of Radel A® into a PTFE latex containing nanoparticles with average diameters of 48 nm and spherical shape. Several samples were prepared by varying the relative ratio between the Radel A® and PTFE content. The combination of SEM and AFM analysis indicates that the precipitation of Radel A in the presence of PTFE leads mainly, if not exclusively, to a bimodal mixture of the two homoparticles. The fractionated crystallization behaviour of these samples is revealing of the PTFE dispersion degree within the Radel A® matrix. When the PTFE amount is lower than 2%, a perfect PTFE nanoparticle dispersion is obtained. When the amount of PTFE is comprised between 5 and 30%, larger PTFE clusters are obtained that, after melting, coalesce and crystallize at higher temperatures depending on the crystallization propensity of their individual heterogeneous nuclei. Finally, in case of samples 40%, only one crystallization exotherm is observed at 310 °C indicating the formation of very large clusters that after melting coalesce into wide domains.     

DNA binding and antiproliferative activity toward human carcinoma cells of copper(II) and zinc(II) complexes of a 2,5-diphenyl[1,3,4]oxadiazole derivative

The interaction of calf thymus DNA with [CuL(ClO(4))]ClO(4)·H(2)O (1) and [ZnLBr]Br·H(2)O (2) (L = 9,12,15,18,27,28-hexaaza-29-oxatetracyclo[24.2.1.0(2,7).0(20,25)]enneicosa-2,4,6,20,22,24,26,28(1)-octaene) dicationic complexes in aqueous solution at neutral pH, was investigated by variable-temperature UV-vis absorption, circular dichroism and fluorescence spectroscopy. The values of the DNA-binding constants of these complexes, determined by competitive binding spectrofluorimetric titrations of ethidium bromide (EB)-DNA solutions, are (6.7 ± 0.5) × 10(6) M(-1) for CuL(2+) and (4.7 ± 0.5) × 10(5) M(-1) for ZnL(2+). These data together with a through analysis of the spectroscopic behaviour consistently suggest that both compounds are effective DNA binders. Interestingly, the DNA-binding strength of these complexes has been found to be correlated to their in vitro cytotoxic activity toward human breast carcinoma cells, although the complex with lower DNA-binding affinity is more active. In fact, biological studies showed that when the compounds are delivered through the cell membrane by a lipidic carrier, the cell survival is sensibly reduced, up to 58% with 1 and to 31% with 2.     

Characterization and modulation of the hierarchical self-assembly of nanostructured DNA tiles into supramolecular polymers

We present a set of DNA supramolecular architectures based on the polymerization of discrete DNA tiles having the shape of parallelograms and designed to have a one-dimensional inter-tile connectivity. Tiles bind to each other with two connections, which have different thermal stabilities. We discuss how this difference in stability implies that the same monomeric tile can yield supramolecular polymers of different shapes just by changing the polymerization conditions. We show how this system reacts to external stimuli by interconverting between some of its possible states. Concurrently, we show how performing the polymerization on a surface can influence its outcome.     

Expansion Around the Mean Field in Quantum Magnetic Systems

We introduce a new definition of ordered phase in a magnetic system based on properties of the local spin state probability. A statistical functional associated to this quantity depends both on amplitude and direction of the local magnetization. We show that it is possible to introduce an expansion at fixed magnetization amplitude in the inverse of lattice coordination number if the direction is selected by an extremum condition. In the limit of infinite coordination number we recover the mean field results. First order corrections are derived for the Ising model in the presence of a transverse field and for the XY model. Our results concerning critical temperature and order parameter compare favorably with other approaches.     

Semiempirical calculations on the interaction between dimethyltin(IV) and DNA model system

The interaction between a dinucleotide triphosphate duplex (DD), mimicking the DNA molecule, and the dimethyltin(IV) cation is studied by the semiempirical PM3 method. The results show that the interaction can occur involving the tin atom and the electron-donor centres of DD, requiring in some cases the presence of water molecules. In particular, the binding of the dimethyltin(IV) moiety with two adjacent phosphate oxygen atoms is allowed by the presence of water molecules coordinating to the tin atom. In this case the tin environment shows a geometry in agreement with ¹¹⁹Sn Mössbauer and X-ray data.     

Synthesis of purinobenzodiazepine and purinobenzotriazocine derivatives,two new heterocyclic ring systems

The preparation of two new heterocyclic ring systems, purinobenzodiazepine and purinobenzotriazocine derivatives by the condensation of 8-aminotheophylline or 8-hydrazinotheophylline with o-carboxybenzaldehyde or o-carboxyacetophenone is described.