Numerical analysis of GeO2-concentration effects in arc-induced long-period fiber gratings under external refractive-index changes

We present a numerical analysis of the response of arc-induced long-period fiber gratings (LPFGs) under ambient refractive-index changes using standard fibers with SiO₂ as cladding material and different GeO₂ concentration in the SiO₂-GeO₂ doped core. We obtain that the LPFG-sensitivity is increased using lower GeO₂ concentrations and it follows a parabolic behavior. Also, we identify two linear regimes using an external index of 1.37: for GeO₂ concentrations between 2 and 3.5 mol %, the LPFG-sensitivity changes with a rate of 3.614 nm per mole fraction of GeO₂, while for higher concentrations the sensitivity changes with a rate of 1.39 nm/mol %. Additionally, for fibers with 2 mol% of GeO₂, the sensitivity calculated is comparable to this obtained in previous works using corrugated and tapered LPFGs in SMF28 fibers. These results are of interest for the design of improved LPFG-sensors.     

High-T c Josephson junctions for electronic applications

Summary The current status of the electronic applications of high-T _c Josephson junctions is briefly reviewed. Recent results obtained by the authors on devices employing step-edge junctions are reported. In particular the design of a microwave oscillator based on a parallel array of junctions is discussed and preliminary experimental results are presented. Paper presented at the ?VII Congresso SATT? Torino, 4–7 October 1994.     

Synthesis and stereochemistry of novel [1,2,4]oxadiazolo[4,5-a][1,5]benzodiazepine derivatives

An one-pot synthetic approach to the novel 3a,4,5,6-tetrahydro[1,2,4]oxadiazolo[4,5-a][1,5]benzodiazepine system, by 1,3-dipolar cycloaddition of benzonitriloxides to 1,5-benzodiazepine derivatives, is described. The structure and stereochemistry of the obtained adducts have been assigned by means of spectroscopic measurements.     

Tuning porphyrin/DNA supramolecular assemblies by competitive binding

Addition of an intercalating but nonaggregating porphyrin, AuT4, to a preformed adduct between DNA and a strongly aggregating porphyrin, t-H2Pagg, permits control of the extent of aggregation of the latter. The size and the intensity of the ICD and RLS signals depend linearly on the concentration of the intercalating dye and decrease markedly on increasing the concentration of the available binding sites on the biopolymer template.     

Surfactant effects on electrokinetic processes in clay-rich soils remediation

The present work concerns the realisation of an equipment suitable for the choice of surfactants to be employed in the remediation of polluted soils by soil washing processes. The experimental activity has been focused to verify the surfactants efficiency in electrokinetic processes applied in low porosity soils, polluted with used vehicle oil. The equipment consents to estimate low electroosmotic permeabilities, electrical current and to analyse the electrolytic solutions. The concentration of the chemical species reached in both anodic and cathodic cells allows a more accurate evaluation of the ion mobility through the soil. The apparatus realised has been shown to be a useful instrument capable of providing directions for the choice of surfactants in electrokinetic soil remediation. The choice of an anionic surfactant for the oil removal has shown promising result.     

Voltammetric behaviour of cis-diarylbis(triethylphosphine)platinum(II) complexes

The voltammetric behaviour of cis-[Pt(PEt₃)₂(YC₆H₄)₂] complexes in acetonitrile has been investigated by cyclic voltammetry and controlled potential coulometry. The oxidation potential increases linearly with increasing electron-withdrawing ability of the Y substituent in the platinum-bonded aryl ligand. The data are related to studies of electrophilic Pt—C bond cleavage.     

New rearrangement of 4-isoxazoline system: conversion of ketones into alpha,beta-unsaturated amides

A new rearrangement pattern of the 4-isoxazoline system is reported. The reaction, starting from 3,3-disubstituted derivatives and leading to alpha,beta-unsaturated amides, proceeds through the quaternarization of the nitrogen atom and involves the heterolytic cleavage of C(3)-N bond, assisted by the formation of a relatively stable intermediate. The overall process represents a useful conversion of ketones into alpha,beta-unsaturated amides.     

A decade of vibrational micro-spectroscopy of human cells and tissue (1994-2004)

Instrumentation used in infrared microspectroscopy (IR-MSP) permits the acquisition of spectra from samples as small as 100 pg (10(-10) g), and as small as 1 pg for Raman microspectroscopy (RA-MSP). This, in turn, allows the acquisition of spectral data from objects as small as fractions of human cells, and of small regions of microtome tissue sections. Since vibrational spectroscopy is exquisitely sensitive to the biochemical composition of the sample, and variations therein, it is possible to monitor metabolic processes in tissue and cells, and to construct spectral maps based on thousands of IR spectra collected from pixels of tissue. These images, in turn, reveal information on tissue structure, distribution of cellular components, metabolic activity and state of health of cells and tissue.     

An elastic neutron scattering on dynamical transition in hydrogen-bonded systems

Elastic incoherent neutron scattering measurements have been performed on trehalose and sucrose/D₂O mixtures as a function of temperature. The study provides an effective way for characterizing the dynamical behaviour, furnishing a set of parameters characterizing the ‘flexibility’ and the ‘rigidity’ that justifies the better cryptobiotic effect of trehalose with respect to sucrose. Elastic scans make evident a non-Gaussian behaviour of the intensity profiles, which is more marked for sucrose, with a dynamical transition at T253 and 250 K for trehalose/D₂O and sucrose/D₂O mixtures, respectively.