A 13C and 1H NMR study of diastereomeric α-methylidene-β-hydroxy-γ-alkoxy esters

The ¹³C and ¹H NMR spectra of α-methylidene-β-hydroxy-γ-alkoxy-pentanoates and -decanoates are presented. These data are consistent with a preferred conformation in which an intramolecular hydrogen bond is present. Very characteristic steric shifts in the ¹³C and ¹H NMR spectra provide an efficient tool for the configurational assignment for this class of compounds.     

Optical fibre amplifiers: physical model and design issues

The development of optical fibre amplifiers has caused an impressive evolution in optical telecommunications systems since the end of the 1980s. The widespread application of active fibre amplifiers requires accurate tools to design and simulate these devices in very different operating conditions. The present work describes some physical aspects of active fibre amplifiers and a numerical model for the analysis of active optical fibres that can be applied to investigate spatial and spectral properties of amplifiers for the transmission windows of optical fibre telecommunications. Finally, various design issues relevant to the investigation of optimal fibre design of silica, fluoride erbium-doped and fluoride praseodymium-doped fibres are discussed and illustrated by means of examples.     

Potent integrin antagonists from a small library of RGD-including cyclic pseudopeptides

[structure: see text]. A small library of cyclic RGD pseudopentapeptides incorporating stereoisomeric 6,5- and 7,5-fused bicyclic lactams was synthesized with the aim of developing active and selective integrin antagonists. The solid-phase synthesis and activity of these RGD derivatives is described. The approach led to two of the most active known inhibitors of alpha(V)beta3 receptor.     

One-nucleon transfer reactions induced by 32S on 34S AT Einc = 90.0 and 97.09 MeV

The one-proton and one-neutron transfer reactions in the interaction of ³⁴S with incident ³²S were studied in the 0–3.5 MeV excitation energy range of the exit nuclei. The experimental set-up (kinematic identification technique, implanted targets, etc.) has allowed an angular resolution of 0.2°, a mass resolution of 1.5% and a Q-value resolution of 0.35 MeV.Comparison with DWBA computations using an analytical approximation for the radial integral, with insertion of suitable recoil corrections, demonstrates the absorptive direct mechanisms of the reactions, even when double excitation of residual nuclei is present. The extracted values for the products of spectroscopic factors are in very good agreement with the known values and they are confirmed by EFR-DWBA computations. The selectivities of the reaction receive about the same contributions from the nuclear structure as from the specific reaction mechanism.