Vibrational analysis for surge precursor definition in gas turbines

Compressor behaviour analysis in critical working conditions, such as incipient surge, represents a significant aspect in the turbomachinery research field. Turbines connected with large-size volumes present critical issues related to surge prevention especially during transient operations. Investigations based on acoustic and vibrational measurements appear to provide an interesting diagnostic and predictive solution by adopting suitable quantifiers calculated from microphone and accelerometer signals. For this scope a wide experimental activity has been conducted on a T100 microturbine connected with different volume sizes. A machine dynamical characterisation has been useful for better interpretation of signals during its transient to the surge. Hence, different possible methods of incipient surge identification have been developed through the use of different signal processing techniques in time, frequency and angle domain. These results will be useful for control system development to prevent compressor failures.

     

An anomalous mannich reaction of a trimethylsilyl enol ether

Mannich reaction between dimethyl (methylene) ammonium chloride and a silyl enol ether gives a regiochemical result opposite to that obtained from the derived lithium enolate and the same salt.     

Non-steroidal antiinflammatory agents. VI. Synthesis of 10-oxo-5H-pyrrolo[1,2-b]isoquinoline-3-acetic Acid,a conformationally restricted analogue of tolmetin

The synthesis of 10-oxo-5H-pyrrolo[1,2-b]isoquinoline-3-acetic acid 4 , a tricyclic analogue of tolmetin which might show significant analgesic-antiinflammatory activity, has been accomplished in four steps. Alkylation of ethyl 2-pyrrolylglyoxylate ( 15 ) with 2-cyanobenzyl bromide afforded derivative 16 , which was transformed by the Huang-Minion reaction into the dicarboxylic acid 6 . Cyclization of this key intermediate to 17 , followed by alkaline hydrolysis, afforded 10-oxo-5H-pyrrolo[1,2–6]isoquinoline-3-acetic acid ( 4 ). Various attempted syntheses of 6 are also discussed.     

Infrared and MÖSSBAUER spectroscopic studies on complexes of Hal2SnIV moieties with tridentate ligands

Novel complexes hal₂Sntrid, where hal ? Cl, Br, and trid^2? are dianions of ?planar”? tridentate ligands with ONO and SNO donor basic atoms, were synthesized and structurally investigated in the solid state mainly by far infrared and MÖSSBAUER spectroscopy. Possible configurations were advanced and discussed, and it was concluded that the most probable is a monomeric trigonal bipyramidal structure for all compounds, although polymers, or dimers with O or Cl bridges, were not a priori excluded, in a special way for Br₂Sntrid.     

Sub-8-fs pulses from an ultrabroadband optical parametric amplifier in the visible

Pulses with 180-THz bandwidth and 2-microJ energy were generated by a noncollinear optical parametric amplifier in the visible, pumped by the second harmonic of a Ti:sapphire laser. A portion of the amplified pulse spectrum was compressed to 7.2 fs by use of a thin prism sequence.     

Synthesis of 9H-pyrrolo[2,1-b][1,3,6]benzothiadiazocin-10(11H)-one 4,4-dioxide,a potential anti-HIV-1 agent

Starting from 2-(2-aminophenylthio)-1-ethoxycarbonylmethyl-1H-pyrrole a four-step synthesis of 9H-pyrrolo[2,1-b][1,3,6]benzothiadiazocin-10(11H)-one 4,4-dioxide, a new heterocycle related to anti-HIV-1 tricyclic non-nucleoside agents, is described.     

Simple and efficient synthesis of benzofuran derivatives from tyrosol

A convenient strategy for the preparation of compounds bearing the benzofuran skeleton starting from tyrosol, a phenol largely present in olive oil production waste, with no biological importance, is reported. A bromination/methoxylation sequence, already described for the synthetic transformation of naturally occurring compounds, was exploited. Depending on the solvent used for the methoxylation reaction together with the presence of a 4-phenol moiety respect to the side chain, benzodihydrofurans or a benzofurans derivative can be obtained.