Search

The most forward ring (2 ≤ θ ≤ 3°) of the INDRA multidetector has been equipped with 12 plastic phoswich detectors able to withstand the high counting rates encountered at very small angles. Each phoswich detector is composed of a 500 μm thick fast scintillator and a 25 cm thick slow scintillator. Elemental identification is achieved on a fairly large domain, ranging from Z = 1 up to Z = 37. A new method of Z separation, using an identification function technique, is described.

The magnetic spectrometer of ALICE at Orsay, has been equipped with gas counters allowing a complete identification in mass, atomic number and energy for a few MeV / nucleon heavy ions. The detection system covers the whole entrance solid angle of 4.7 msr and 20% of the energy spectrum in the focal plane for a given ion. The system is equipped with avalanche parallel plate counters giving the time of flight in the magnet and also the entrance position. Behind the spectrometer, a large ionization chamber measures two energy losses and the residual energy. The position of the particle is given by a proportional counter placed in the focal plane. The system accepts a few thousands counts per second, can give a good identification in mass A / ΔA∼80, in atomic number Z∼10–30 and measures the energy with a resolution better than 2×10−3.

Polyclonal antibodies to hamster melanoma tyrosinase were raised in rabbits, and series of immunoinhibition experiments with a purified enzyme and specific immunoglobulins were carried out. Tyrosinase activity was determined by a set of radiochemical and spectrophotometric methods utilizing tyrosine, dopa, dopamine, or dihydroxyindole (DHI) as substrates. The quantitative data obtained indicated that the complexing of tyrosinase with its specific antibody inhibited melanogenesis in a specific manner: dopachrome formation from dopa and dopamine conversion to melanin were not affected and all other enzyme activities comprising the DHI oxidation step were inhibited to various degrees. Additionally, tyrosine hydroxylation was also slightly inhibited. The data obtained implied that melanogenesis was restricted at the point of DHI oxidation. From observations on the immunoinhibition of a DHI oxidation at varying dopa-cofactor concentrations, we propose that dopa-cofactor may be bound at separate site than DHI and thus may act as a positive allosteric effector for DHI oxidation by tyrosinase. Study of tyrosinase immunoinhibition by the antibodies against the enzyme thus seems to provide a valuable system for investigating the tyrosinase-mediated melanogenesis.

We have measured the polarization parameter in πp elastic scattering with π− at 550 and 650 MeV and with π+ at 765, 895, 955 and 1025 MeV, using a polarized proton target.

Results on muon scattering in lead are given for cosmic rays in the momentum interval 200 to 1500 MeV/ c . Two Wilson chambers were used, one with magnetic field, the other with lead screens. Results are in better accord with Olbert's theory than with Moliere's.

We have undertaken an experiment on the scattering of cosmic-ray muons of 920 MeV/c momentum in lead. The scattering angles have been measured with precision by a set of acoustic spark chambers. Each muon is identified by its electron of disintegration, its momentum is determined by range measurement. The results agree with the Cooper-Rainwater predictions.

The K−p → K on partial cross section has been measured in the region of K− laboratory momenta from 1 to 3 GeV c , in steps of ∼25 MeV c and with a statistical accuracy of ∼2%.

Two new isomeric metabolites, 5-hydroxy-6-methoxyindole-2-carboxylic (a) and 5-methoxy-6-hydroxyindole-2-carboxylic (b) acids have been identified in melanotic urine: Their constitution was identified by Chromatographic and spectral comparison of the two isomers isolated from urine with the same compounds prepared synthetically.

Accurate measurements of the charge-exchange reaction K−p → Kon between 1 and 3 GeVc have been used to analyse the direct-channel formation of hyperon resonances. An overall fit to the charge-exchange data and the K−p total cross sections has been obtained, from which a set of resonant parameters (mass, width, elasticity and spin) is presented for a total of 10 resonances lying between ∼ 1.8 and ∼ 2.6 GeV.

The p p → n n partial cross section has been measured in the region of antiproton laboratory momenta between 1 and 3 GeV/ c . The implications of these results on the existence of boson resonances decaying into N N is discussed.

Measurements are reported on the cross section for the reaction π − p yielding neutral final states in the momentum range 0.7 to 1.6 GeV/ c . The π − p total cross section has also been obtained.