Spatial optical simultons in nonlinearly coupled planar waveguides

With second-harmonic generation in surface and buried planar waveguides achieved by direct and reverse proton exchange in lithium niobate, we demonstrate a novel kind of quadratic spatial simulton: The transverse-electric fundamental input and the transverse-magnetic second-harmonic waves nonlinearly couple two superimposed planar waveguides, permitting transverse localization of light at room temperature and at excitations as low as 340 nJ in 20-ps pulses.     

Extended Scaling Relations for Planar Lattice Models

It is widely believed that the critical properties of several planar lattice systems, like the Eight Vertex or the Ashkin-Teller models, are well described by an effective continuum fermionic theory obtained as a formal scaling limit. On the basis of this assumption several extended scaling relations among their indices were conjectured. We prove the validity of some of them, among which the ones predicted by Kadanoff (Phys Rev Lett 39:903–905, 1977) and by Luther and Peschel (Phys Rev B 12:3908–3917, 1975).     

Fluorescence biosensing micropatterned surfaces based on immobilized human acetylcholinesterase

Human acetylcholinesterase (AChE) is a widely studied target enzyme in drug discovery for Alzheimer’s disease (AD). In this paper we report evaluation of the optimum structure and chemistry of the supporting material for a new AChE-based fluorescence sensing surface. To achieve this objective, multilayered silicon wafers with spatially controlled geometry and chemical diversity were fabricated. Specifically, silicon wafers with silicon oxide patterns (SiO₂/Si wafers), platinum-coated silicon wafers with SiO₂ patterns (SiO₂/Pt/Ti/Si wafers), and Pt-coated wafers coated with different thicknesses of TiO₂ and SiO₂ (SiO₂/TiO₂/Pt/Ti/Si wafers) were labelled with the fluorescent conjugation agent HiLyte Fluor 555. Selection of a suitable material and the optimum pattern thickness required to maximize the fluorescence signal and maintain chemical stability was performed by confocal laser-scanning microscopy (CLSM). Results showed that the highest signal-to-background ratio was always obtained on wafers with 100 nm thick SiO₂ features. Hence, these wafers were selected for covalent binding of human AChE. Batch-wise kinetic studies revealed that enzyme activity was retained after immobilization. Combined use of atomic-force microscopy and CLSM revealed that AChE was homogeneously and selectively distributed on the SiO₂ microstructures at a suitable distance from the reflective surface. In the optimum design, efficient fluorescence emission was obtained from the AChE-based biosensing surface after labelling with propidium, a selective fluorescent probe of the peripheral binding site of AChE.

The discovery of placenta growth factor and its biological activity

Angiogenesis is a complex biological phenomenon crucial for a correct embryonic development and for post-natal growth. In adult life, it is a tightly regulated process confined to the uterus and ovary during the different phases of the menstrual cycle and to the heart and skeletal muscles after prolonged and sustained physical exercise. Conversly, angiogenesis is one of the major pathological changes associated with several complex diseases like cancer, atherosclerosis, arthritis, diabetic retinopathy and age-related macular degeneration. Among the several molecular players involved in angiogenesis, some members of VEGF family, VEGF-A, VEGF-B and placenta growth factor (PlGF), and the related receptors VEGF receptor 1 (VEGFR-1, also known as Flt-1) and VEGF receptor 2 (VEGFR-2, also known as Flk-1 in mice and KDR in human) have a decisive role. In this review, we describe the discovery and molecular characteristics of PlGF, and discuss the biological role of this growth factor in physiological and pathological conditions.     

Universality of One-Dimensional Fermi Systems,II. The Luttinger Liquid Structure

We complete the proof started in Benfatto et al. (2014) of the universal Luttinger liquid relations for a general model of spinning fermions on a lattice, by making use of the Ward identities due to asymptotically emerging symmetries. This is done by introducing an effective model verifying extra symmetries and by relating its critical exponents to those of the fermion lattice gas by suitable fine tuning of the parameters.     

Surface studies of novel hydrophobic active carbons

The efficient adsorption of toxic organic species from humid airstreams by active carbons is impeded by the competitive adsorption of water vapour which, at low values of p/p^s, occurs at specific (polar) adsorption sites located at the edges of the carbon layer-planes and at in-plane defects. At higher pressures, adsorption in micropores and mesopores also occurs. The concentration of polar adsorption sites therefore determines the hydrophilicity of the carbon structure and their accelerated formation, by exposure to air and water vapour, is also responsible for the ‘ageing’ of active carbons. Overall, the adsorption of water reduces the volume of porosity available for the adsorption of target species and the hydrophilic nature of active carbons is recognized as a major barrier to their effective use in many applications.We present here results for the adsorption of nitrogen, organic and water vapours by a hydrophobic respirator granular active carbon produced by the thermal treatment of a base carbon, to desorb polar oxygen groups, followed by use of a plasma enhanced chemical vapour deposition (PECVD) treatment to apply a hydrophobic, fluorine containing, surface nanolayer. We show that at equivalent %RH values the treated carbon adsorbs significantly less water compared to an untreated (control) carbon and that the treatment does not reduce the levels of open porosity or impede the adsorption of a range of organic vapours at ambient temperatures. Preliminary evidence for the presence, after treatment, of constrictions at pore entrances which act as molecular gates is also presented. The treated carbon (after ageing for 6 weeks at 80%RH) is shown to have greater adsorptivity than an untreated base carbon toward hexane present in a humid (80%RH) airstream. This results in a 39% increase in break-through time. These hydrophobic properties persist one year after manufacture. The mechanism leading to the modified water adsorption properties is the partial desorption of polar oxygen sites followed by deposition at the external carbon surfaces of hydrophobic plasma polymer species. This reduces the polar surface free energy of the carbon and hence the amount of water adsorption occurring by the primary mechanism. This in turn retards the diffusion of water molecules into the micropores and leads to lower adsorption volumes at higher pressures.     

Optical properties determination at 10.6 μm of thin semiconducting layers

An optical characterization of thin semiconducting multilayers in the infrared range, using a combination ofm-lines and reflection spectroscopy techniques is exposed. Such a method, non-destructive, allows to determine the thickness and the refractive index of each component of a multilayer multimodal planar waveguide.