[en] Epitaxial layers of iron oxides have been grown on a MgO(001) substrate by evaporating natural Fe or ⁵⁷Fe from Knudsen cells in the presence of a NO₂ flow directed to the substrate. The resulting layers have been investigated in situ with LEED, RHEED, AES and XPS and ex situ with CEMS and ion beam analysis. For substrate temperatures between 200 and 400 C we observe RHEED oscillations during deposition, indicative of layer-by-layer growth. By adjusting the flux of NO₂ at the surface, all stable and metastable cubic phases in the Fe-O system could be grown: FeO (wustite), Fe₃O₄ (magnetite), γ-Fe₂O₃ (maghemite) and solid solutions between the latter two phases. Rutherford backscattering spectra show a relatively high minimum yield in the channel directions. (orig.)

[en] In a recent study we deduced the damage profiles in Cu and Al crystals due to self implantation from the measured dechanneling cross section. On the basis of this work a model for the observed shallow and deep damage was proposed. In the present work this model is tested by comparing the damage in Cu crystals due to 100 keV self implantation at RT and due to 100 keV implantation with Ag ions at RT. In both cases regions of shallow and deep damage were found. The range of the shallow damage coincides approximately with the projected range of the implanted particles. The deep damage was found to extent to approximately 6 x this depth after Cu implantation and to approximately 5 x this depth after Ag implantation. After annealing the range of the deep damage was found to shrink. All these observations are in accordance with the proposed model. (orig.)

[en] We present the results of a computer simulation study of charged-particle interferometry, combining features of both the Aharonov-Bohm and Hanbury Brown-Twiss experiment. In contrast to a previous theoretical analysis of this experiment, we find that the Aharonov-Bohm effect is also present in the cross-correlated two-particle intensity. A simple, time-independent scattering theory that leads to conclusions that are in concert with the simulation data is given. (orig.)

[en] Radon concentrations were measured in about 60 dwellings over two consecutive periods of five and four months using time-integrating dosemeters. The dwellings were all located on the two sides of one street. During renovation, phosphogypsum plasterboards were used at only one side of the street, at the other side only low activity natural gypsum. No effect of the use of phosphogypsum was found. Differences in radon concentrations between the two sides, occurring during the spring period, could be attributed to the differences in concentration in the crawl spaces. Measurements and calculations indicate that radon concentrations at various levels in the dwelling are influenced by the concentration in the crawl space. This infuence decreases with increasing distance from the crawl space. (author)

[en] A method is presented for measuring nuclear halflives between 10^-8 and 10^-4 s with a single pulse-height-analyzing detection device, e.g. a Ge detector. If such an instrument records two cascading transitions with energies E₁ and E₂, then a sumpeak may occur in the observed spectrum at the position E₁ + E₂. The sumpeak is unperturbed if the halflife of the intermediate level is much less than the shaping time-constant of the detector signal-amplification system, but acquires a characteristic distortion by 'delayed coincidence summing' (dcs) if the halflife and shaping time-constant are comparible. Computer calculations of this dcs distortion can be used for halflife determination. The method has been tested with a 2.94 μs level in ⁷³Ge and with a 84 ns level in ⁷¹Ge, and has been applied to a level in ⁷⁴Ga, for which tsub(1/2) = (31 +- 5) ns was measured. An incidental side-effect in the ⁷¹Ge measurement may have potential as a means to measure the relative volumes of dead layers in Ge detectors. (Auth.)

No abstract available

[en] To store ions for times up to several seconds with energies in the 10 eV/amu range a table-top storage ring with a circumference of about 1 m will be constructed. The ions will be confined and guided by RF-multipoles. The first objective is the production of pure ground state beams of (multiply charged) ions. This will allow for elucidating the unknown rule of metastable ions in electron capture studies, which will be performed in a crossed beam experiment after extraction of the ion beam from the storage ring. In order to test the technique of ion storage by means of RF-multipoles a linear RF-octopole beam guide has been constructed. First results of highly charged ion injection and subsequent electron capture studies in the RF-octopole beam guide are presented for C⁴⁺ ions. (orig.)

[en] Three systems are described for chest radiograph scoring in cystic fibrosis patients: the Shwachman-Kulczycki, the Chrispin-Norman and the Brasfield method. Sixty chest radiographs of 39 patients of different ages have been independently scored by two radiologists according to the three methods. No statistical differences between the methods could be demonstrated. The Chrispin-Norman method is recommended as the best choice because differences in scoring appeared better interpretable. A significant increase in precision could be achieved by combining the scores of the three methods. (orig.)

[en] The combined treatment of irradiation followed by larynx cannulation and laryngectomy results in a severe decrease in the colonization resistance (CR) of the oropharynx. Consequently, uncontrolled growth of potentially pathogenic micro-organisms (ppm) is to be expected; this may be the major cause of infection. The authors, therefore attempted to compensate artifically for this loss of CR-capacity by local application of CR-indifferent antibiotics. This might eliminate the source, i.e., the ppm in the oropharynx. The treatment regimen was purposely extended stepwise to develop an optimal regimen. A maximal treatment regimen involving 4 daily applications of sodium carboxymethylcellulose (Orabase) with antibiotics as well as of systemic CR-indifferent antibiotics might involve an unnecessary burden for the patient. (Auth.)

[en] The term histiocytosis X (HX) refers to a spectrum of disorders varying from unifocal eosinophilic granuloma (UEG), multifocal eosinophilic granuloma (MEG), to the Abt-Letterer-Siwe syndrome. In a series of 16 patients with different types of HX and skeletal lesions, whole body bone scintigraphy was performed at the time of diagnosis and during follow up. Results were compared with radiographic findings. In patients with MEG with or without extra-skeletal dissemination bone scintigraphy revealed cold spots or hot spots, but half of the lesions were not visualised scintigraphically, resulting in false negative scans. In UEG the lesions were visualised as areas of increased uptake or as a cold spot with increased uptake at its borders. No false negative scans were encountered. The reliability of skeletal scintigraphy in patients with HX seems to depend on the type of the disorder: in UEG bone scintigraphy is a safe procedure. In MEG false negative bone scans have to be expected, and radiography is superior. (orig.)