[en] Maintenance of instruments is generally of two kinds: (a) corrective maintenance, on a non-scheduled basis, to restore equipment to a functional status by repairs; (b) preventive maintenance, to keep equipment in a specified functional condition by providing systematic inspection, quality control, detection and correction of early malfunctions. Most of the instruments used in nuclear medicine are rather complex systems built from mechanical, electrical and electronic parts. Any one of these components is liable to fail at some time or other. Repair could be done only by a specialist who is able to evaluate the condition of the various parts ranging from cables to connectors, from scintillators to photomultipliers, from microprocessors to microswitches. The knowledge of the intricacies of the various electronic components required for their repairs is quite wide and varied. The electronics industry turns out more and more multi-purpose chips which can carry out the functions of many parts used in the instruments of the earlier generation. This provides protection against unauthorized copying of the circuits but it serves another purpose as well of inhibiting repairs by non-factory personnel. These trends of the instrument design should be taken into consideration when a policy has to be developed for the repairs of the hospital based equipment

[en] Bone scintigraphy is one of the most valuable nuclear imaging procedure, especially remarkable for its high sensitivity in disclosing bone metastasis of cancer long before radiographic demonstration. Bone scintigraphy is also useful in the diagnosis of covert fracture, occult trauma, bone contusion, early acute osteomyelitis, acute pyogenic arthritis and avascular bone necrosis. Measurements of bone clearance of radiopharmaceuticals, absorptiometry and quantitative bone scintigraphy are applied to the study of metabolic bone disorders such as osteoporosis and osteomalacia

[en] Nuclear Medicine is defined as a clinical specialty that utilizes the radionuclides for diagnosis, therapy and medical research. The radionuclides are used as unsealed sources of radioactivity. The diagnostic applications include both in vivo and in vitro uses of radioisotopes. There is hardly any medical research which does not use radioactive compounds. Only clinical research is considered within the purview of nuclear medicine. The Recommendations of IAEA/WHO seminar reviewed the needs of training in nuclear medicine mainly for the physicians with special emphasis on the needs of the developing countries

[en] The lepton family number violation Z boson decay, Z → e^-e^-μ⁺μ⁺ or e⁺e⁺μ^-μ^-, mediated by a dilepton, e.g. from an SU(15) theory, is calculated. The branching ratio of such exotic decay for allowed dilepton masses is found to be smaller than 10^-10. (author)

[en] It is shown that high-p_T polarized prompt photons produced by high energy longitudinally polarized electrons scattered off unpolarized protons may be utilized to determine the spin-dependent parton distributions of the photon. (orig.)

[en] The projected hedgehog approximation for baryons in models with interacting quarks and mesons is investigated. Exploiting the reduction of the Hilbert space to a subspace containing only one radial mode, we factorize matrix elements of observables into radial integrals and isospin-spin coefficients. The reduction is explicitly given for the linear σ model. In order to analyse the quality of the hedgehog ansatz the solution obtained with the projected hedgehog coherent state in the reduced model is then compared with the solutions obtained with appropriate perturbative expansions in the weak and strong coupling limits and with the solution obtained by diagonalizing the Hamiltonian in the intermediate regime. (author)

[en] The initial natural analogue studies at the Cigar Lake uranium deposit were reported at the first RCM in 1988 and additional work has been undertaken since 1989 in co-operation with the Swedish Nuclear Fuel and Waste Management Co. (SKB). Field and laboratory work was carried out on samples of ore, host rock and groundwater and cores from a new drillhole through the ore zone were examined in detail. Two new samples (CS-615 and CS-620) were analyzed by a number of methods including X-ray Photo-electron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), chemical and instrumental analysis. Analysis of plutonium-239, iodine-129 and technetium-99 were carried out at Los Alamos National Laboratory (LANL), as well as iodine-129 at the University of Toronto

[en] The 3D-visualization of the entire spatial radiation dosage in cooperation with the 3D-radiation volume requires several data volumes. The structure of the interface between the 3D-treatment planning program 'ProPlan' and the 3D-imaging system 'VOXEL-MAN' is explained. The first results in the radiological application point out the possibilities of the complex registration of dose distributions and the critical examination of the irradiation technique. (orig.)

[en] It is reported that repositories for low and intermediate level short lived wastes have been operating satisfactorily for several decades and improved disposal techniques are now in use. For long lived and high level waste, the concept of deep geological repositories is being developed. National and international programmes have investigated the feasibility of a geological confinement system, and current programmes range from laboratory studies to operation of experimental underground facilities and development of full scale repositories. The continuation of research using field and laboratory studies, plus analysis of naturally occurring migration phenomena, is seen as a means of improving the understanding of radionuclide migration related processes. International and national performance studies have concluded that releases from deep geological repositories would carry only minor quantities of radioactive products. However, several issues related to waste disposal need to be addressed. From a technical point of view, the methodologies for performance assessment are suitable for evaluation of disposal safety. Data specific to proposed disposal sites are necessary for such an evaluation in order to further improve performance assessment models. Additionally, the long time-scales associated with the disposal process introduce uncertainties into the safety analysis which need to be evaluated, and will also require site specific data from candidate sties

[en] Low-lying energy levels in ¹²⁴Ba have been investigated from ¹²⁴La β-decay by using He-jet technique. Spin and parity assignments have been deduced from internal conversion electron measurements. A β-vibrational band based on a second 0⁺ state has been identified. Experimental level energies have been compared with IBFA-2 calculations. (orig.)