Lax embeddings of the Hermitian unital

In this paper, we prove that every lax generalized Veronesean embedding of the Hermitian unital ${\mathcal{U}}$ of ${\mathsf{PG}(2,\mathbb{L}), \mathbb{L}}$ a quadratic extension of the field ${\mathbb{K}}$ and ${|\mathbb{K}| \geq 3}$ , in a ${\mathsf{PG}(d,\mathbb{F})}$ , with ${\mathbb{F}}$ any field and d ≥ 7, such that disjoint blocks span disjoint subspaces, is the standard Veronesean embedding in a subgeometry ${\mathsf{PG}(7,\mathbb{K}^{\prime})}$ of ${\mathsf{PG}(7,\mathbb{F})}$ (and d = 7) or it consists of the projection from a point ${p \in \mathcal{U}}$ of ${\mathcal{U}{\setminus} \{p\}}$ from a subgeometry ${\mathsf{PG}(7,\mathbb{K}^{\prime})}$ of ${\mathsf{PG}(7,\mathbb{F})}$ into a hyperplane ${\mathsf{PG}(6,\mathbb{K}^{\prime})}$ . In order to do so, when ${|\mathbb{K}| >3 }$ we strongly use the linear representation of the affine part of ${\mathcal{U}}$ (the line at infinity being secant) as the affine part of the generalized quadrangle ${\mathsf{Q}(4,\mathbb{K})}$ (the solid at infinity being non-singular); when ${|\mathbb{K}| =3}$ , we use the connection of ${\mathcal{U}}$ with the generalized hexagon of order 2.     

Sulla disuguaglianza di Sobolev-Poincaré

Riassunto Si dimostra la disuguaglianza di Sobolev-Poincaré per una classe generale di domini che intervengono in problemi non uniformemente ellittici.

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Summary Sobolev-Poincaré inequality for general domains connected with some non uniformly-elliptic problems is proved.

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Lavoro eseguito nell'ambito dello GNAFA     

AN IMPROVED HPLC METHOD FOR THE SEPARATION OF RETINALDEHYDE ISOMERS FROM VISUAL PIGMENTS

Abstract— A method for the analytical separation of retinal isomers such as 13- cis , 11- cis , 9- cis and all- trans retinal, dissolved in aqueous solutions of detergents, is described. The retinals are extracted by means of a non-isomerizing procedure and separated by HPLC on an octadecyl silane column used in normal phase. This column retains detergents without deteriorating and gives a satisfactory separation of retinal isomers with a resolution comparable with that obtained with silica gel column. The reliability of the method is verified by analysing the chromophore of visual pigment rhodopsin in digitonin solution, before and after irradiation with white light.     

Studies on the Mechanism of the Enzymatic Photoisomerization of Retinal

The honeybee retina contains the enzyme photoisomerase that converts all-trans-retinal to 11-cis-retinal in light within the visible range. The activity of the bee photoisomerase was studied on all-trans-retinal under pulses of laser light. The experimental data were fitted with a simple equation that describes the mechanism of the isomerization reaction based on three steps having different time constants.     

Synthesis,characterization, and X-ray structure of 1,2-bis-crown-5-calix[4]arene. Modeling of metal complexation

1,2-bis-crown-5-calix[4]arene (3) was prepared by reacting calix[4]arene (1) with tetraethylene glycol di-p-toluenesulphonate (2) in the presence of cesium carbonate in 9% yield. The X-ray structure of (3) was determined. Crystal data for C₄₄H₅₂O₁₀ are as follows: monoclinic, space groupP _2/c witha=18.006(8) Å,b=10.680(4) Å,c=22.359(6) Å, =112.93(3)°,V=3958(6) ų,Z=4,D _calc=1.2 g cm^–3, the finalR value is 0.11 for the 1851 observed reflections (I>3(I)). The single crystal included two similar but slightly different molecules immobilized in a pinched-cone conformation withC ₂ symmetry. The two enantiomorphous molecules were analyzed by molecular mechanics using the GenMol program to model the selective alkali-metal complexation.This paper is dedicated to the commemorative issue on the 50th anniversary of calixarenes.     

Approssimabilità degli aperti diR n di perimetro finito

Riassunto Si provano, utilizzando certe misure di ricoprimento, risultati di approssimazione in perimetro e in misura per gli aperti limitati di perimetro finito, il cui perimetro coincide con la misura di Hausdorff (n−1)-dimensionale della frontiera.

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Summary We prove some results of approximation of a limited open Caccioppoli set, whose perimeter equals the (n−1)-dimensional Hausdorff measure of its boundary. A special geometric covering measure is employed.

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Lavoro eseguito nell'ambito dello G.N.A.F.A.     

Influence of fillers concentration on electrical properties of polystyrene matrix doped by gold nanoparticles and 8HQ

The analysis of the electrical properties of polystyrene films containing gold nanoparticles capped with 1-dodecanethiol and 8-hydroxyquinoline molecules is reported. The conductivity of the nanocomposite as a function of the doping level has been investigated both in planar and stacked configurations. While the former configuration evidenced low field tunneling between nanoparticles in the polymer matrix, stacked devices allowed us to investigate the main phenomena ruling the transport properties when switching effects are present close to critical electric fields. In particular, through the analysis of current-voltage characteristics we studied the charge transport at different fillers concentrations and sketched a physical picture of conductivity in such nanocomposite systems.     

A conducting polymer-silicon heterojunction as a new ultraviolet photodetector

We discuss on the development and characterization of a p-n heterojunction of polyaniline-silicon as a photo detector for the ultraviolet (UV) region. The hybrid heterojunction consists of micro and nano-films (<300 nm thick) of polyaniline deposited on the top of a silicon wafer through the spin-coating technique, where in the backside of silicon and on top of polyaniline, aluminum and gold were respectively deposited by evaporation to make the electric contacts. The electrical characteristics of the devices present excellent reproducibility and high rectification ratio. In addition, the spectroscopic and the photon response analysis of the devices strongly indicates that it can be used as a broad band photon detector, with good sensitivity especially in the UV region ≈2.0-3.5 eV, where it presents enhanced sensitivity (≈200%) when compared to commercial all-silicon diodes such as the OPT 301 UV detector.     

Detection of early stage damage in carbon fiber reinforced polymers for aeronautical applications using an HTS SQUID magnetometer

We present an experimental characterization of multidirectional fibre composites based on eddy current testing using HTS dc SQUID (Superconducting Quantum Interference Device) magnetometers. The correlation between the mechanical tolerance of CFRPs with different thickness and the phase gradient of the magnetic field generated by damage is shown. The eddy current based SQUID NDE is used to detect damage not visible to the naked eye and to study the effect of an impact far from the point of impact. The aim of this work is to demonstrate the capability of our technique to provide information on early stage damage due to an impact process in an unshielded environment.