First measurement of the Λ→nγ branching ratio

In an experiment performed at the CERN-SPS charged hyperon beam, we have observed the radiative decay Λ→nγ, using well identified Λ from the decays of Ο^? of 116 GeV/c momentum. Neutrons and photons from the Λ decays were observed in liquid argon and lead glass detectors. From a sample of 31 candidates, containing an estimated background of 7.3 events, the decay branching ratio was measured to be Γ(Λ→nγ)/Γ(Λ→all)=(1.02±0.33)×10^?3.     

Abnormal behaviour of some parameters revealed in the Georgian SSR before the Armenia earthquake of December 7, 1988: a preliminary report

Summary For more than ten years several measurements sites able to detect geophysical and geochemical precursory phenomena of earthquakes have been working in Soviet Georgia. On the occasion of the destructive Armenia earthquake of December 7, 1988 (M=6.9) premonitory signals relative to geophysical and geochemical parameters seem to be observed. In this paper anomalous variations of the water level in a well, of the helium content in thermal waters and of the electromagnetic signals in air, obtained in three measurements sites located at about 80 km from the epicentre, are reported. These variations appear beginning from about a month up to some hours before the occurrence of the earthquake and it seems reasonable to consider them as short-time or very short-time precursory phenomena of the earthquake.     

Surface modification and oxidation kinetics of hot-pressed AlN–SiC–MoSi2 electroconductive ceramic composite

The effects of oxidation on the microstructural modification and on the electrical resistivity and mechanical strength of a hot-pressed AlN–SiC–MoSi₂ electroconductive ceramic composite were studied. The kinetic of the oxidation was also evaluated. After the oxidation at temperatures below 1000 °C samples do not gain weight, due to simultaneous formation of SiO₂ and evaporation of MoO₃ formed by the oxidation of MoSi₂. However, the AlN/SiC matrix disables the “pesting” phenomena and strength degradation, despite the fact that at these temperatures MoSi₂ oxidizes rapidly. At temperatures above 1000 °C, the composite gains weight due to protective mullite layer formation on the surface, that provides a good oxidation resistance for use at higher temperatures. The kinetics of the oxidation follows the parabolic law. The possible rate-controlling mechanism is the diffusion of oxygen through the mullite-rich surface oxide scale.     

Projectile coulomb excitation of Ne and Ne

The static quadrupole moments of the first excited J^π = 2⁺ states in ²⁰Ne and ²²Ne and the reduced electric quadrupole transition probabilities of these states to the ground states were measured via projectile Coulomb excitation. The quadrupole moments were deduced from the shapes of γ-ray angular distributions. The results are: Q(²⁰Ne, 2⁺) = −0.20±0.05 b and Q(²²Ne, 2⁺) = −0.11±0.05 b. The transition strengths were deduced from yield measurements and by comparison with the yields of target γ-rays. The results are: B(E2; 0⁺ → 2⁺, ²⁰Ne) = 0.037±0.003 e² · b² and B(E2; 0⁺ → 2⁺, ²²Ne) = 0.025±0.002 e²· b². The results for the transition strengths are consistent with the results of accurate timing methods and resolve discrepancies between previous experiments. The results for the quadrupole moments are consistent with earlier measurements, although the mean values we obtain are slightly lower. The experimental measurements are compared with theoretical predictions and a detailed discussion is given of corrections to this type of reorientation experiment.     

Photoacoustic Generation: Optical Fiber Ultrasonic Sources for Non-Destructive Evaluation and Clinical Diagnosis

An innovative photoacoustic source for ultrasonic non destructive evaluation (NDE) and clinical diagnosis is proposed. The working principle is based on thermal conversion of laser pulses into a metallic film evaporated directly onto the tip of an optical fiber. Attractive advantages of the proposed transducer are high frequency, large bandwidth and good efficiency.     

A facile “one pot” synthesis of 2,9-disubstituted 8-azapurin-6-ones (3,5-disubstituted 7-hydroxy-3H-1,2,3-triazolo[4,5-d]pyrimidines)

A series of title compounds have been synthesized by utilising benzylazide, cyanoacetamide, ethyl or methyl esters of aliphatic or aromatic carboxylic acids and sodium ethoxide as catalyst.     

Measurement of kaonic X-rays from Li,LiH AND Be

We have observed X-rays from kaons stopping in targets of Li, LiH and Be. The strong interaction widths, shifts and relative yield of the last observed X-ray have been measured. There is evidence for a difference in the yield of the n = 3 → 2 Li X-rays in Li metal and LiH. There is no evidence in the spectra for X-rays from kaonic hydrogen formed in LiH.     

A search for K−p → Λγ and K−p → Σ0γ at rest

A search has been made for photons from the reactions K^?p → Λγ and K^?p → Σ⁰γ produced by K^? stopping in a liquid hydrogen target. No signal from these reactions was found; upper limits on the branching ratios are K^?p → Λγ/K^?p → anything ? 4 × 10^?4, K^?p → Σ⁰γ/K^?p → anything ? 4 × 10^?3. The first of these is in conflict with a theoretical prediction using recent values for coupling constants and scattering amplitudes. This may reflect the influence of the Λ(1405) on the radiative capture.