G. Zanella

Low-energy Antiproton Neon Interaction

Abstract By means of a streamer chamber exposed to the LEAR antiproton beams, the total reaction cross sections, the charged-prong multiplicity distributions and lower limits for the production of negative pions and K s 0 in the p-Ne interaction were measured at 19.6, 48.7 and 179.6 MeV. Annihilation was found to be dominant over all other non-elastic p-Ne processes. An analysis of Ne and other nuclei data in the frame of the Glauber theory allowed us to determine the ratio between the p-n and the p-p cross sections. An analysis in the light of INC model predictions allowed us to show up events which can be interpreted as annihilations having occurred deeply inside the nuclei.

Inelastic interaction of antiprotons with 4He nuclei between 200 and 600 MeV/c

The antiproton-helium reaction cross section has been measured at 19.6 and 48.7 MeV with a streamer chamber in a magnetic field. Charged prongs and negative pion multiplicities and cross sections for the production of 3He are given. A comparison with p 2H is performed. he previously obtained 179.6 MeV results are also taken into account.

X-ray imaging with scintillating glass optical fibres

Abstract First tests and proposals are presented regarding the use of a scintillating glass optical fibre target as an X-ray converter coupled with a CCD imager. The system appears promising for detecting X-ray images with good quantum efficiency, high spatial resolution and high dynamic range, using the high fluxes of the synchrotron radiation or in medicine, at energies over 10 keV.

Experimental apparatus for studying the interaction of antiprotons with light nuclei

Abstract A description is given of the detector system (self-shunted streamer chamber in a magnetic field) used in the PS-179 experiment at LEAR for studying antiproton interactions with light nuclei.

The detective quantum efficiency of an imaging detector

Abstract The efficiency of an imaging detector is a more extensive parameter than the quantum efficiency of a track detector or of a counter, as an image is created by the summation of many responses due to the single incoming quanta. This efficiency parameter is the so-called detective quantum efficiency (DQE). The paper illustrates the general meaning of DQE and the procedure to measure it.

DIFFERENTIAL DISTRIBUTION OF TROPOMYOSIN SUBUNITS IN FAST AND SLOW RAT MUSCLES AND ITS CHANGES IN LONG-TERM DENERVATED HEMIDIAPHRAGM

Skeletal tropomyosin, a rod-shaped protein which lies in the grooves of the double-stranded F-actin filament, is involved in the calcium regulatory system of muscle contraction [ 11. The native molecule is a dimer in which the two subunits (Y (34 000 MJ and B (36 000 Mr) are assembled as cm, Pf.3 or 43; in the slow and fast mammalian muscles the ratio of molar amount of OL and fl subunits of tropomyosin differs, the P-subunit being more represented in the slow type and during the development [2,3 1. The distribution of tropomyosin subunits has been studied in several mammalian species by immunohistochemical studies and electrophoretic analysis of extensively purified tropomyosin. Results have been collected by two-dimensional electrophoresis [6]. The position of the tropomyosin subunits have been identified in a two-dimensional electrophoretogram of crude myofibrils from rat muscle, using tropomyosin purified by standard techniques [7]. However, their relative proportion in the fast and slow muscles has not been determined. We have performed the two-dimensional electrophoresis of actomyosin from normal and long-term denervated rat muscles. The tropomyosin subunit pattern was thus compared with the myosin light chain pattern in the same preparation. The two-dimensional electrophoresis shows that adult rat soleus, a predominant slow type muscle, contains almost exclusively thee-subunit of tropomyosin, while adult fast and immature muscles contain both CX- and &subunits in about the same proportion. This is a further evidence that tropomyosin subunit ratio differs in fast and slow skeletal muscles, even though with a distribution peculiar to each mammalian species. The analysis of tropomyosin subunits and myosin light chains shows that

SCINTILLATING OPTICAL FIBERS IN MAMMOGRAPHY

Abstract Measurements of the MTF and the DQE, on images obtained using a scintillating glass optical fiber system coupled to a mammography film, are displayed in comparison with the measurements obtained by a standard mammography cassette using the same film and the same X-ray dose. The final results are favourable to the scintillating fibers. The use of a CCD read-out in the place of the mammography film is discussed.

Radiation damage of silicate glasses doped with Tb3+ and Eu3+

Abstract In this work, we studied a set of Tb 3+ (or Eu 3+ ) doped silicate glasses in which some amounts of BaO were added to increase glass density. The irradiation-induced damage was investigated by absorbance measurements performed before and after each irradiation with doses ranging from 3 to 237 Gy. Analysed glasses underwent also light yield measurements investigated in terms of light production. The results showed that radiation damage and light yield depend on glass composition and are very low for the Eu 3+ containing glass and for the Tb 3+ activated glass which contains also lead. A possible explanation could be that lead and europium favour in the glass matrix the formation of a higher concentration of defects with respect to Tb 3+ doping ions.

The role of the quantum efficiency on the DQE of an imaging detector

Abstract The quantum efficiency (QE) is unsuitable to characterise the performance of an imaging detector. Instead, the detective quantum efficiency (DQE), which indicates how much the detection process deteriorates the signal-to-noise ratio of the input image, is a more convenient parameter. Nevertheless QE plays a relevant role in the DQE formulation, as we have shown in the present paper, which is intended as a continuation and improvement of a previous paper of the same authors.

A position sensitive detector using an interline transfer imaging CCD at standard TV rate and room temperature

Abstract This paper shows the possibility of using an interline transfer (and floating gate) imaging CCD as X-ray and charged particle detector, running at standard TV rate (7.16 MHz) and room temperature (296 K). Experimental tests have been made using a Fairchild CCD 222 with exposures to 55 Fe, 90 Sr, 241 Am radiation sources. The CCD is linked to a personal computer through a video processor and the events are filtered and analyzed by digital image processing. The rms noise has been measured as a function of the temperature obtaining about 87 electrons/pixel at 296 K.