Reactions of 1,2-diaza-1,3-butadienes with propargyl alcohol as an approach to novel bi-heterocyclic systems.

Here we describe the reaction of 1,2-diaza-1,3-dienes and propargyl alcohol furnishing α-(prop-2-yn-1-yloxy)hydrazones that are converted into novel alkyl-1-oxa-7,8-diazaspiro[4.4]nona-3,8-dien-6-ones, by means of 2,3-Wittig rearrangement under very mild conditions. The same α-(prop-2-yn-1-yloxy)hydrazones, treated with benzyl azides furnish the corresponding α-[(1,2,3-triazol-4-yl)methoxy]hydrazones, via Cu(ii)-catalyzed 1,3-dipolar cycloaddition. Their subsequent base-promoted cyclization produces interesting pyrazolone-triazole derivatives. The impact of this work can be ascribable to the attractiveness of the bi-heterocyclic systems obtained and to the ease of the synthetic methodologies proposed.

Constraints on slow earthquake dynamics from a swarm in central italy

Several clustered slow earthquakes have been recorded by a geodetic interferometer in central Italy. The strain rise times of the events range from tens to thousands of seconds, and the seismic moment scales with the square root of the rise time. This scaling law contrasts with the conservative assumption of constant rupture velocity in fault modeling but is consistent with the occurrence of a slow rupture propagation analogous to heat diffusion in a slab.

Synthesis of biphenylyltetrazole derivatives of 1-aminopyrroles as angiotensin II antagonists.

Based on preliminary molecular modelling study, the synthesis of two different classes of biphenylyltetrazole derivatives of 1-aminopyrroles, as potentially active non-peptide angiotensin II (AII) antagonists, is reported. Some NH-Boc protected l-aminopyrroles were deprotected, N-acylated, N-alkylated with 5-[4'-bromomethyl-1,1'-biphenyl-2-yl]-1-triphenylmethyl-1H-tetrazo le, and then detritylated to give the first class of title compounds. Other 1-NH-Boc protected 1,2-diaminopyrroles were regioselectively subjected to the 1-alkylation with 5-[4'-bromomethyl-1,1'-biphenyl-2-yl]-1-triphenylmethyl-1H-tetrazo le, to the acylation of the amino group at 2-position of the pyrrole ring, and then to the detritylation process to yield the second class of title compounds.

High-resolution spectrometry with a masked Fabry-Perot interferometer.

Features of a real Fabry-Perot interferometer are severely affected by surface irregularities. A new configuration, based on appropriately masking the plates, is proposed. Theoretical results show an increase in the finesse of as much as a factor of 10 as well as an increase in the contrast factor of as much as a factor of 100, while the luminosity-finesse product is preserved. The case of nonnormal incidence is also considered, and the differences arising from that case are discussed.

Interferometric investigations of convection around cylinders at small Grashof numbers.

Experiments with a Twyman-Green interferometer have been carried out to determine the temperature distribution around a horizontal cylinder in the presence of natural convection for Grashof numbers around 10(-4) and a Prandtl number of 0.7, a region of parameters poorly covered by previous investigations. Temperature differences are recovered by digital analysis of the fringe pattern perturbation. The results indicate significant discrepancies in the temperature profile, when compared with numerical models.

Fringe pattern analysis in low-quality interferograms.

Mechanical vibrations in the frame of an interferometer can introduce a space-dependent factor throughout an interferogram, making its analysis quite difficult. This factor is formally equivalent to the modulus of the complex degree of coherence in the case of quasimonochromatic light. A simple method for retrieving the underlying phase distribution and detecting small perturbations is presented. Introducing an appropriate correction for the above-mentioned factor, good sensitivity is also achievable in noisy environments.

Automatic fringe recognition and detection of subwavelength phase perturbations with a Michelson interferometer.

Simple systems and procedures based on personal computer hardware to analyze the fringe pattern in a Michelson interferometer, retrieve information on the irregularities of the combined phase front and use it to obtain a correct interferogram are presented. In one system, where one of the mirrors can be moved piezoelectrically, good sensitivity (lambda/30) is obtained while using an economical array of 1-bit image sensing elements. In another system, based on a TV camera and a 6-bit frame grabber, images of the two separate laser beams and of the fringe patterns are stored; by adequate numerical analysis, higher sensitivity (lambda/100) is achieved.