[en] Extensive air showers can only be interpreted by comparison of the measured observables with simulations, using a suitable model for the shower development in the atmosphere. Due to the complexity of the phenomenon, in the past the models were quite simple and results from air showers were to interpret qualitatively, at best. With a new generation of experiments more advanced detectors became operational and the need for detailed simulations grew. In recent years several new air shower programs were developed. Using the rapid increase of the computing power they have now reached a high level of sophistication. Particle transport, electromagnetic interactions and decay of unstable particles are treated in great detail. However the most crucial ingredient to all these programs is the modeling of hadronic interactions since it requires extrapolation in energy, primary mass and kinematics to regions where no accelerator data exist and where theoretical guidelines are only vague. As a consequence of the model uncertainties, experiments using different models occasionally reached very different conclusions on energy spectra and composition of the cosmic rays. CORSIKA is an extensive air shower simulation program that contains five different hadronic interaction models (VENUS, QGSJET, SIBYLL, HDPM, and DPMJET). It is widely used throughout the cosmic ray community and allows the study of model dependencies and the systematic effects of measurement and event reconstruction. Results for different models concerning inelastic cross-sections and particle production and their influence on air shower variables are discussed and the systematic uncertainties for air shower analyses are investigated. The capability of precise multi-parameter measurements to discriminate between the models is emphasised

[en] Hadronic events including geometrically isolated high energy photons have been investigated by the CELLO detector at PETRA at √s=22 and √s=34 GeV. At √s=34 GeV the predominant source of these events was found to be initial state bremsstrahlung (75%). At √s=22 GeV are only 57% of the isolated photons coming from bremsstrahlung. The jet structure of these events has been tested using the jet measures thrust, sphericity, psub(T) and nsub(ch) as function of the energy of the photon. The agreement with QED and QCD predictions is good. (orig.)

[en] The prompt electron and muon yield was measured in hadronic events of e⁺e^- annihilation at energies of √s ≅ 44 GeV using the CELLO detector at PETRA. A cut in the transverse momentum of the lepton was used to enrich the lepton signals from b-quarks from which the semileptonic branching ratio of the b decay and the electroweak induced charge asymmetry of the banti b production was measured. One finds: Br (b → e + anti ν_e + X) = 0.11 ± 0.05 ± 0.05, Br (b → μ + anti ν_μ + X) = 0.03 ± 0.04 ± 0.04, A_b(e) =- 0.70 ± 0.52 ± 0.11, A_b(μ) =- 0.55 ± 0.59 ± 0.17. The results are found to be well compatible with the expectation of the standard model. (orig.)

[en] The incidence of dust lanes in elliptical galaxies has been estimated at approx. 40 percent by Sadler and Gerhard (1985), although the observed fraction is lower because of inclination effects. A similar percentage of ellipticals has been detected by the Infrared Astronomy Satellite (IRAS) at 100 microns (Knapp et al. 1989); these have far-infrared colors expected for emission from cool dust (S sub 60 micron/S sub 100 micron approx. 1/3). For the far-infrared detected galaxies, neither L sub 100 microns/L sub B nor L sub 60 microns/L sub 100 microns are very dependent on dust content, suggesting that the source of the infrared luminosity is the same in both cases; and hence that dust is responsible even when not detected optically. Despite this indication, L sub 100 microns does not prove to be a good indicator of the quantity of cool interstellar matter in elliptical galaxies, as measured by the mass of neutral hydrogen. There even exist several examples of ellipticals with dust, strong 100 micron flux density and sensitive limits on HI mass (Walsh et al. in preparation). Chief reasons for the lack of correlation include the existence of other important sources of far-IR power in ellipticals, such as nonthermal continuum emission extending from longer wavelengths in flat spectrum radio sources (Golombek, Miley and Neugebauer 1988); and the fact that far-infrared luminosity per unit dust mass is extremely sensitive to the temperature of the ambient radiation field, which is not accurately known. In addition to having their appearance distorted by dust, several ellipticals also show such features as shells, box-shaped isophotes or inner disks. These may be signatures of past mergers, which could also add to the ISM content of the system

[en] Short communication

[en] Following a three-day irradiation period in a neutron flux of 8 x 10¹³n/cm² the matrix is opened up in an alkali hydroxide solution and the Mo 99 is dissolved. This solution is then freed from a residue of actinides and lanthanides as well as acidified by adding mineral acid and mixed with rhodamide ions for the complex formation of Mo 99. This is followed by a treatment with an ion exchanger of the chelating agent synthetic resin type based on styrene divinyl benzene copolymers, in order to selectively absorb the Mo. (DG) 891 HP/DG 892 CKA

[en] A method to obtain a highly pure Mo 99 compound is suggested which is easy to perform even with remote handling. The matrix irradiated by neutrons is rendered soluble with aqueous alkali hydroxide solution, the Mo 99 being dissolved. The Mo rhodanide complex is collected on an organic ion exchanger. The individual process steps are described. A suitable iodine reducing agent (e.g. Na or Ka sulphite, hydroxyl ammonium sulphate) is already added to the first step and to the washing of the ion exchanger. Where necessary Tc 99 is eluated from the fixed Mo 99 mother nuclide for use in nuclear medicine. (UWI)

[en] Following a three-day irradiation period in a neutron flux of 8 x 10 n/cm the matrix is opened up in an alkali hydroxide solution and the Mo 99 is dissolved. This solution is then freed from a residue of actinides and lanthanides as well as acidified by adding mineral acid and mixed with rhodamide ions for the complex formation of Mo 99. This is followed by a treatment with an ion exchanger of the chelating agent synthetic resin type based on styrene divinyl benzene copolymers, in order to selectively absorb the Mo. (orig.)

No abstract available

No abstract available