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The performance of an energy-loss spectrometer is reported together with a detailed discussion of the basic parameters of such a system and in particular the second-order aberrations. The system we have constructed consists of two uniform-field 70° bending sectors in a configuration symmetrical to first order, with an image point in the symmetry plane. The system has been tested with the LEALE-LNF low-energy positive and negative pion beams. The magnets were set at zero degrees facing each other. The contributions of the aberrations and of multiple Coulomb scattering in air, helium and thin windows to the momentum resolution of the two magnet systems have been evaluated and the total momentum resolution compared with the experiment at various energies for positive and negative pions.

The γ-ray spectra emitted following proton capture by 51V were measured as a function of incident proton energy. The γ-ray decay of the states was observed and angular distributions were measured. The measured branching ratios and excitation energies suggest these states in 52Cr are analogues of low-lying states in 52V. Assuming these states to be analogues, the measured mixing ratios, branching ratios and normalized decay rates are compared with shell model calculations. Qualitative agreement with the mixing and branching ratios is obtained but the inclusion of 2 p 1 2 and 1 f 5 2 neutron excitations appears essential if the decay rates are to be described.

The accuracy in relative measurements of magnetic field with unclear magnetometer depends basically on the signal-to-noise ratio in the sensing coil. This ratio is evaluated in this paper as a function of the coil’s geometrical parameters, and graphs are shown which allow the optimum geometrical dimensions to be chosen. In this way it has been possible to build a coil showing an effective signal to-noise ratio of 540 at amplifier output, with a sensing volume of water of 160 cm3 (amplifier bandwidth ≃ 10 Hz).

The corrosion of four new zirconium alloys in terphenyl has been evaluated between 380 °C and 420 °C in comparison with Zircaloy-2 and Zr/2.5 wt % Nb. The new alloys tested were: Zr/1.5 wt % Cr; Zr/1.0 wt % Cu/ 0.4 wt% Fe; Zr/1.4 wt% Cu/0.4 wt% Fe; Zr/0.8 wt%Fe/0.8 wt% V. The effects of the more important parameters —temperature, time of exposure, concentrations of water and of chlorinated impurities — on the corrosion of the above six alloys have been measured according to a statistical design. The statistical analysis of the results has shown clearly the superiority in this environment of the Zr-Cu-Fe alloys, followed by Zr/2.5 wt% Nb. The oxidation and hydriding rates observed around 400 °C for the best alloys were very acceptable, although not easily estimable in the present investigation because of the smallness of their values.

A monitoring system for the LNF-LEALE positive and negative medium energy pion beams is described. The system is based upon the integral measurement of the beam charge, in analogy with Faraday-cup methods used for electron beams. Results of experimental tests are reported together with a discussion of correction methods obtained by Monte-Carlo techniques.

We describe a calorimetric monitoring system for the LNF-LEALE low energy pion beams. The apparatus measures the energy dissipated by the photons in the pion source with thermometric techniques. Numerical manipulation of the source temperature yields a relative but very stable monitor.

Isopentenylpyrophosphate isomerases in cell-free extracts from Pinus radiata and from Citrus sinensis eliminate the C-4 pro-S proton from mevalonic acid. Prenyl transferase from Pinus forms geranyl pyrophosphate, neryl pyrophosphate, 2,6 trans, trans farnesyl pyrophosphate and 2 cis, 6 trans farnesyl pyrophosphate from mevalonic acid. The 4-pro-S proton of mevalonic acid is eliminated in the formation of both trans and of cis double-bonds. The pattern is similar for the Citrus enzyme. Isopentenyl pyrophosphate isomerase from Pinus is completely inhibited by 15 m m iodoacetamide, which does not affect prenyl transferase. The pattern is the same for the Citrus isomerase, but less clear for the transferase. Previous work has ruled out direct trans-cis isomerization of C10 or C15 prenylpyrophosphates. Alternative mechanisms are proposed for the stereospecific elimination of the 4-pro-S proton of mevalonic acid in the biosynthesis of both cis and trans prenyl pyrophosphates.

The paper illustrates a new technique to define narrow windows in SiO 2 layers by means of a carefully controlled undercut in SiO 2 /Si 3 N 4 flims, The method described takes advantage of the etching propertie of the silicon nitride and of its action as a mask against oxygen diffusion. Stripe Widths less than 1µ were obtained with good definition and uniformity on the whole wafer and without the difficulties normally encountered in micron-line photoengraving. The technique gives reproducible results, requires one masking operation only and seems to be suitable as a production process.