[en] Abstract only

[en] Recent findings suggested a possible role for pinhole collimator scintigraphy to differentiate between metastases, infection and fractures of the vertebrae. The aim of this study was to verify these findings and to ascertain whether we could identify any other specific scintigraphic patterns. The study group consisted of 58 patients. A metastatic pattern was obtained in 18 patients, while 16 showed the compression fracture pattern, 3 the tuberculosis pattern and 1 the pyogenic infection pattern. The study was considered normal in 4 patients and showed a nonspecific pattern in 4. Sensitivity was 85% for the metastatic pattern and 83% for the compression fracture pattern. Specificity was 94% for both patterns. Unique new patterns were identified in Paget's disease and in degenerative disease of the vertebrae (12 patients). Pinhole scintigraphy of the vertebrae is a valuable aid for detecting specific diseases of the vertebrae. Our findings suggest a valuable new role for skeletal scintigraphy, improving the specificity and obviating, in most cases of vertebral disease, the need for additional investigations. 3 figs., 3 tabs., 5 refs

[en] The study of non-linear problems in classical mechanics has led to the discovery of a class of classical problems which show so called chaotic behaviour. A question which arises immediately is: Can chaotic behaviour be found in quantum mechanical systems and if yes, how can these systems be identified and classified experimentally and theoretically? In this work a short introduction is given to the field of chaos and a discription of the mathematical methods which were used to do the calculations is given. The methods that are used to study chaos in classical systems are not applicable to quantum mechanical systems since quantities in quantum mechanics are normally discrete. The method which is used to study chaos in quantum mechanical systems is as follows: The behaviour of a quantum mechanical system which has a classical analog that behaves chaotially and compare the behaviour of the nearest neigbour energy level spacing distribution and Δ₃ statistics to the behaviour of the Lyapunov exponent and Poincare sections in the classical case. The case of the Hamiltonian with quartic polynomial potential is studied in detail and compared to similar studies in literature is studied. In the case of systems which have no classical analogue, the attempts which have been made in literature to characterize these systems by calculating the distribution of nearest neighbour energy level spacings is criticised and a new method of characterizing these systems is suggested. Furthermore, the use of the autocorrelation to classify the behaviour of finite spin systems and also to support arguments that chaos cannot be found in finite spin systems, is discussed. Finally experimental attempts to show that chaotic behaviour can exist on a submicroscopic level is discussed and compared to theoretical results. The applicability of these results are also discussed

[en] A sorbent was required for the extraction of uranium from a slurry of CaF₃ in solutions of HNO₃ and Al(NO₃)₃. Equilibrium results have shown Levextrel-TBP to be more suitable for this purpose than either ion exchange resins or ion exchange fibres. The undermentioned work was done with Levextrel-TBP containing 270 ml tributyl phosphate per litre of resin. The equilibria of uranium between Levextrel-TBP and solutions of UO₃(NO₃)₃ in H₂O, HNO₃, HNO₃ + Al(NO₃)₃ and in slurries of CaF₃ in HNO₃ + Al(NO₃)₃ + Mg(NO₃)₃ were measured. Strong sorption of uranium took place from these solution, but it was readily stripped with water. The dependency of the distribution coefficient of uranium on the concentrations of Al, H and NO₃ was examined at a concentration of 0,2 g U/l in the liquid. The kinetics of the sorption of uranium from solutions of HNO₃ and Al(NO₃)₃ was investigated. The equation for kinetics controlled by the rate of diffusion on the liquid side, holds when the liquid side concentration, c < 0,1 g U/l. An equation that describes the kinetics where c < 2 g U/l is also given. Diffusion in the particle determines the rate of stripping of uranium with water. The kinetics can be correlated with the equation of Vermeulen

No abstract available

[en] The aim of this study was to determine the longterm effect of the interplanetary magnetic field (IMF) on the diurnal variations of cosmic rays, proceeding from the transport equation of cosmic rays. The diurnal variation is due to an anisotropy in the propagation of cosmic rays. The anisotropy is caused by diffusion, convection and drift effects in the interplanetary medium. These effects add up vectorially and the resultant streaming of cosmic rays should result in a diurnal variation consistent with neutron monitor observations. Better knowledge of the values and directions of the cosmic ray gradients in the vicinity of the earth, as well as possible changes due to variations of the sign of the IMF is essential to explain the observed diurnal variation vector

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[en] The radiation-induced copolymerization of chlorotrifluoroethylene with vinyl acetate was investigated in the temperature range from - 30⁰C to 50⁰C over a wide range of comonomer compositions. A solid transparent copolymer was obtained in which the monomers alternate with regularity along the polymer chain over essentially the entire range of comonomer compositions. Both the rate of copolymerization and the number-average molecular mass of the resulting copolymer were found to depend strongly on the initial comonomer composition. The monomer reactivity ratios were determined and correspond well with calculated values. An apparent activation energy of 17,6 kJ/mole was obtained for the copolymerization process which exhibits a dose rate dependence of 0,54. The number-average molecular mass was found to be strongly dependent on the irradiation temperature - decreasing exponentially with an increase in irradiation temperature

No abstract available

No abstract available