Synchronization in coupled Ikeda delay systems

In this work, we demonstrate the use of a Field Programmable Gate Array (FPGA) as a physical platform for realizing chaotic delay differential equations (DDE). Moreover, using our platform, we also experimentally study the synchronization between two time delayed systems. We illustrate two different experimental approaches – one is hardware co-simulation (using a Digilent Atlys with a Xilinx Spartan-6 FPGA) and the other is analog output (using a Terasic DE2-115 with an Altera Cyclone IV E FPGA).     

An optimal domain decomposition preconditioner for low-frequency time-harmonic Maxwell equations

The time-harmonic Maxwell equations are considered in the low-frequency case. A finite element domain decomposition approach is proposed for the numerical approximation of the exact solution. This leads to an iteration-by-subdomain procedure, which is proven to converge. The rate of convergence turns out to be independent of the mesh size, showing that the preconditioner implicitly defined by the iterative procedure is optimal. For obtaining this convergence result it has been necessary to prove a regularity theorem for Dirichlet and Neumann harmonic fields.

     

Plant Oil Bodies: Novel Carriers to Deliver Lipophilic Molecules

Oil bodies (OBs) are specialised organelles ubiquitously detected in plant oil seeds, which serve as lipid storage compartments. OBs consist of a hydrophobic core of triacylglycerol (TAGs), surrounded by a monolayer of phospholipids (PLs) embedded with some specific proteins with a size ranging from 0.5 to 2 μm. In this work, we report an easy method to reconstitute OBs starting from their constituents and to encapsulate lipophilic molecules, i.e. the fluorescent fluorescein isothiocyanate (FITC) and carboxyfluorescein (CF), into reconstituted OBs. This methods allowed us to produce OBs 4- to 10-fold smaller (50–200 nm) than the native one and to obtain a good recovery (about 40%) of both the fluorescent compounds used in the present work. The properties of reconstituted OBs were investigated by a combination of Brewster angle microscopy, scanning force microscopy, ζ-potential techniques. OBs were stable and formed ordered monolayers when patterned on hydrophobic substrates whereas they showed a higher tendency to aggregate into larger, coalescing OBs when were deposited onto hydrophilic substrates or at the air/water interface. Furthermore, we verified the uptake of FITC-loaded OBs by the MCF-7 breast cancer cell line. Our results indicated that OBs could be envisaged as novel carriers to deliver hydrophobic bioactive compounds.     

Infrared Fingerprint Engineering: A Molecular‐Design Approach to Long‐Wave Infrared Transparency with Polymeric Materials

Optical technologies in the long‐wave infrared (LWIR) spectrum (7–14 μm) offer important advantages for high‐resolution thermal imaging in near or complete darkness. The use of polymeric transmissive materials for IR imaging offers numerous cost and processing advantages but suffers from inferior optical properties in the LWIR spectrum. A major challenge in the design of LWIR‐transparent organic materials is that nearly all organic molecules absorb in this spectral window which lies within the so‐called IR‐fingerprint region. We report on a new molecular‐design approach to prepare high refractive index polymers with enhanced LWIR transparency. Computational methods were used to accelerate the design of novel molecules and polymers. Using this approach, we have prepared chalcogenide hybrid inorganic/organic polymers (CHIPs) with enhanced LWIR transparency and thermomechanical properties via inverse vulcanization of elemental sulfur with new organic co‐monomers.     

An economic and efficient tetrahydrofuranylation of alcohols, imines and alkynes

The tetrahydrofuranyl radical, generated by heating tetrahydrofuran in the presence of air and allyl or benzyl chloride, becomes a useful tool in order to transform the hydroxyl functions into ethers, or the CN double bond into amine, or the C-C triple bond into vinyl derivatives. A radical mechanism is proposed followed by a nucleophilic substitution for the alcohol substrate and a radical addition for the iminic and the acetylenic reactants.     

Langmuir-Shäfer transfer of fullerenes and porphyrins: formation, deposition, and application of versatile films

Thin films consisting of a fulleropyrrolidine derivative 1 and a novel water-soluble porphyrin 2 were prepared by the Langmuir-Sh?fer (LS, horizontal lifting) method. In particular, a solution of 1 in chloroform and dimethyl sulfoxide was spread on the water surface, while porphyrin 2 (bearing peripheral anionic groups) was dissolved into the aqueous subphase. To the best of our knowledge, such a versatile method of film fabrication for fullerene/porphyrin mixed composite films has never been used before. Evidence of the effective interactions between the two moieties at the air-water interface was obtained from the analysis of the floating layers by means of surface pressure versus area per molecule Langmuir curves, Brewster angle microscopy and UV-visible reflection spectroscopy. The characterisation of the LS films by UV-visible spectroscopy reveals that the two constituents behave as discrete and weakly interacting pi systems. The use of polarised light suggests the existence of a preferential direction of the macrocyclic rings with an edge-on arrangement with respect to the substrate surface. Finally, photoaction spectra were recorded from films deposited by only one horizontal lifting onto indium-tin-oxide (ITO) electrodes and the observed photocurrent increased notably with increasing transfer surface pressure.     

Thin film construction and characterization and gas-sensing performances of a tailored phenylene-thienylene copolymer

An alternating copolymer, poly(2,5-dioctyloxy-1,4-phenylene-alt-2,5-thienylene), has been synthesized and used in this research. The behavior of the floating film at the air-water interface has been investigated by measuring surface pressure versus area Langmuir isotherms and contemporaneously by reflection spectroscopy and Brewster angle microscopy. The floating films were transferred by the Langmuir-Sch?fer (horizontal lifting) method onto various substrates. It is apparent from these analyses that the effective conjugation length is larger than those in other electroactive polymers and that a strong coplanarity and interchain association takes place above all in the floating film on the water surface and in the transferred multilayers. Such films were used as the active layers in resistive chemical gas sensor devices, thus revealing excellent sensitivity toward NO(2), reversibility, and time stability of the response.     

Shear viscosity of neutron matter from realistic nucleon-nucleon interactions

The calculation of transport properties of Fermi liquids, based on the formalism developed by Abrikosov and Khalatnikov, requires the knowledge of the probability of collisions between quasiparticles in the vicinity of the Fermi surface. We have carried out a study of the shear viscosity of pure neutron matter, whose value plays a pivotal role in determining the stability of rotating neutron stars, in which these processes are described using a state-of-the-art nucleon-nucleon potential. Medium modifications of the scattering cross section have been consistently taken into account through an effective interaction obtained from the matrix elements of the bare interaction between correlated states. Medium effects produce a large increase of the viscosity at densities rho > or approximately0.1 fm;{-3}.     

Photodetachment microscopy of

Photodetachment of ions is performed in the presence of a static electric field. A high spatial resolution electron detector is used to map out the ejected electron's wave function. Propagation over half a metre does not alter the stationary structure the electron wave possesses in the direction orthogonal to the detachment motion. Nodes and antinodes of electron current density are observed, that can be interpreted as direct imaging of the internal atomic wave function. Because detachment of a negative ion can be represented accurately in the free-electron approximation, the obtained images can also be viewed as direct experimental representations of the Green function of the uniform acceleration problem. Agreement of the measured distributions with the exact expression of this wave-function appears quite satisfactory. Received: 5 June 1998 / Accepted: 16 October 1998     

A Newly Designed Water Soluble Uranyl-Salophen Complex for Anion Recognition

A novel water-soluble uranyl-salophen (salophen=N,N‘-disalicylidene-o-phenylenediaminate) complex was obtained. Solubility was achieved in aqueous methyl-β-cyclodextrin solutions, taking advantage of the host-guest interactions established with the adamantyl moieties present on the ligand skeleton. Such an approach facilitates the synthesis of the receptor and the purification processes and, in perspective, can be definitely applicable to other molecular scaffolds. UV/Vis titration experiments demonstrate that the capacity of the uranyl-salophen core to behave as a receptor for anions is retained in water and appears comparable with that previously reported for other water-soluble uranyl-salophen systems. Hence the presence of cyclodextrins does not interfere with molecular recognition processes.