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[en] Numerical codes for electron transport calculations are very important in the field of microdosimetry and thus in quantitative radiation biology. In this work electron spectra have been measured in the track of 1 KeV electrons travelling in a nitrogen atmosphere for different angles in the energy range 8-1000 eV, using a special measuring apparatus. The comparison of the results with theory (Monte Carlo simulation) is a very suitable tool for the verification of the assumptions and approximations made in numerical electron transport codes. (DG)

[en] In the analysis of neutron radiological efficiency, the quantity mean ysub(D) may play a helpful role. As the protons are dominant in the secondary particle spectrum in the majority of neutron exposure cases, in radiation protection as well as radiation therapy, mean ysub(D) was first determinated for protons. Proton tracks were computer simulated by Monte Carlo calculations in the proton energy range from 0.3 - 1.5 MeV in water vapour. From the event structure the proximity functions T(x) were derived. They are defined as weighted sums of energy transfers within spheres of radii r < = x around each event point of a track. For purposes of track analysis one may distinguish four different components: - contribution of ion events only (i) - intra track contribution of Δ-ray tracks (e) - inter track contribution of Δ-ray tracks (e-e) - ion-electron event contribution (i-e). The relative contributions are a function of radius x and of proton energy E. They have been separately calculated and the mean lineal energies have been derived from it. The results are intercompared with calculations based on track models with radial dose profiles

[en] Several proposals have been presented recently on the definition of the quality factor for charged particles on lineal energy density rather than on LET. The models of ICRU 40 and Kellerer results in a direct proportionality of the quality factor to y in the lower range of y up to about 100 keV.μm^-1 with q(y) = 0.3 y. From this, the neutron quality factor is derived to be Q_n = 0.3 y-bar_D. The version of Zaider and Brenner results in an expression Q_n = 0.03 + 0.24 y-bar_D. A similar expression was used by Bengtson in 1969. Without the knowledge of the f(y) distribution, y-bar_D can be calculated using the proximity function approach by Kellerer applied on calculated ion event tracks. Such calculations were performed for protons, α particles and heavy recoils in the energy range of 0.2 MeV.mu^-1 up to 15 MeV.amu^-1 in water vapour. From the charge particle data, y-bar_D is then calculated as a function of neutron energy in soft tissue from thermal energy up to 14.1 MeV. The new proposals are related to the f(y) distribution in a sphere of 1 μm diameter. Smaller target sizes have, however, been proven to be relevant in quantitative radiation biology. The variation of y-bar_D with target size (1 nm up to 1 μm) is shown as a function of neutron energy and the deviation from the LET approximation is discussed, which is caused by straggling effects and δ ray escape and is most pronounced at small target sizes. (author)

[en] ¹²⁵I in vitro tests especially thyroid hormone radioimmunoassays rendered it possible to study thyroidal activity of domestic animals even in large random tests. Parameters of thyroidal activity, such as effective T₄ quotient, T₃ value and total T₃ content, were investigated as to their connection to growth and environmental influence. The estimation of the hereditability yielded only low h² coefficients except in the T₃ value. All parameters studied depended to a great extent on farm conditions

[en] The spatial pattern of primary physical events was calculated for protons in water vapor by means of a Monte Carlo program. Two different cross section data sets were used to cover the proton energy range from 0.2 to 15 MeV. From the spatial pattern of primary energy deposition, proximity functions were derived and from these the dose mean linear energy was calculated. The contributions of different track components for spherical target volumes of 1-100 nm were analysed. The results are compared with the LET approximation and with analytical calculations based on expectation values of the radial energy deposition around the proton path (radial dose profiles). Finally the associated volume of proton tracks was calculated using the so called 'linear approximation', and energy deposition distributions were derived. These were compared with distributions calculated by means of restricted-LET. (orig./HP)

[en] On the basis of new radiobiological findings, the ICRP has recently revised the LET dependence of the quality factor Q(LET) for charged particles. In consequence, many in-phantom defined radiation protection quantities have to be re-evaluated. Among these, the most important operational quantity in radiation protection is the ambient dose equivalent h*(10). This study deals with the calculation of h*(10), as defined at a depth of 10 mm in the ICRU sphere for a broad parallel neutron beam. Additionally, the ratio of ambient dose equivalent to ambient dose, the effective quality factor q*_eff, as function of neutron energy, is derived. (author)

[en] The application of the radiation weighting factor w_R and the new concept of effective dose to determine a radiation risk relevant body dose, results in large differences in comparison with the old concept of effective dose equivalent of ICRP 26. Modifications of the radiation weighting factor are proposed, which will not change the general concept of ICRP 60, but will lead to a reduction of these differences. The methods are discussed and the resulting fluence-to-effective dose conversion function is calculated. (Author)

[en] For a linear sequence of stochastic events the probability distribution for energy deposition can be calculated analytically, using multiple overlap volumes of spheres of different diameters. Proton event tracks have been generated in water vapour in the energy range 0.3-1.5 MeV, by computer simulation. In these tracks the inner core of events caused by direct proton interaction and the extended part of the track caused by the delta rays have been identified. For the core and the individual delta track the number and energy distribution, as a function of target size, were determined separately. From this, conclusions on the relative importance of the different track component, as a function of proton energy, can be drawn. An often helpful classification is the applicability of the LET approximation in spherical targets. On the basis of the criteria derived by Kellerer, the calculations were extended to smaller target sizes, using realistic cross sections for the production of secondary electrons in proton and alpha tracks. (author)

[en] The calculation of microdosimetric distributions for neutrons, has so far been performed for target sizes in the micrometre region, where the LET approximation is valid. In small spherical targets, straggling and δ ray effects strongly influence the energy deposition. The dose mean lineal energy y-bar_D can, however, be calculated using Kellerer's proximity function approach from a computer simulated ion track event pattern. In such tracks, different structural components can be distinguished. The calculation was performed for the main constituents of secondary charged particle spectra produced by 14.1 MeV neutrons in tissue. The influence of δ rays on the energy deposition in small targets of 1 to 100 nm diameter is shown and the deviation from the LET approximation is discussed. (author)