The measurement of beta asymmetries at UNISOR/NOF using external plastic scintillator detectors

The performance of two external plastic scintillator detectors has been tested in an off-line mode using a source of¹⁰⁶RuFe at UNISOR/NOF. The measurement of beta asymmetries at various temperatures has resulted in the reproduction of the previously-determined magnetic dipole moment for the 1⁺ ground state of¹⁰⁶Rh and in addition the conclusion that the sign of this moment is positive.     

The Asymptotic Behaviour of the Fourier Transforms of Orthogonal Polynomials I: Mellin Transform Techniques

The Fourier transform of orthogonal polynomials with respect to their own orthogonality measure defines the family of Fourier–Bessel functions. We study the asymptotic behaviour of these functions and of their products, for large real values of the argument. By employing a Mellin analysis we construct a general framework to exhibit the relation of the asymptotic decay laws to certain dimensions of the orthogonality measure, that are defined via the divergence abscissas of suitable integrals. The unifying r?le of Mellin transform techniques in deriving classical and new results is underlined. Submitted: November 5, 2004. Accepted: January 6, 2006.     

On-line nuclear orientation study of184Au

The¹⁸⁴Au→¹⁸⁴Pt decay, studied on-line with the UNISOR facility at HHIRF, is discussed. Gamma-ray and conversion-electron spectroscopy of¹⁸⁴Pt as well as on-line nuclear orientation measurements of¹⁸⁴Au were done. A new low-lying level scheme of¹⁸⁴Pt is proposed. Two coexisting bands with different deformations and their respective γ-vibrational bands are established. Internal conversion coefficients for interband transitions between states with the same spin are extracted from the spectroscopy measurements. The relative E0 contents of the transitions are determined by combining internal conversion coefficients with E2/M1 mixing ratios deduced from gamma-ray anisotropies measured from oriented nuclei.     

Nonlinear forecasting and iterated function systems

The theory of dynamical forecasting can be extended to iterated function systems. An unordered set of iterates may be sufficient to construct a simulation of the unknown dynamics. The underlying dynamical system may be nondeterministic: A random element may be allowed in the dynamics, and retrieved by our proposed procedures. A first application of these extensions pertains to the reconstruction of fractal attractors, and allows us to solve the so-called inverse problem in Iterated Functions Systems.     

Turbulent particle transport in magnetized plasmas

Particle transport in magnetized plasmas is investigated with a fluid model of drift wave turbulence. An analytical calculation shows that magnetic field curvature and thermodiffusion drive an anomalous pinch. The curvature driven pinch velocity is consistent with the prediction of turbulence equipartition theory. The thermodiffusion flux is found to be directed inward for a small ratio of electron to ion pressure gradient, and it reverses its sign when increasing this ratio. Numerical simulations confirm that a turbulent particle pinch exists. It is mainly driven by curvature for equal ion and electron heat sources. The sign and relative weights of the curvature and thermodiffusion pinches are consistent with the analytical calculation.     

Beta-delayed γ-ray studies of πf7/2 - νpf shell nuclei

We have utilized the selective process of β decay to populate low-energy excited states in the neutron-rich ₂₂Ti, ₂₃V, ₂₄Cr, and ₂₅Mn nuclei. The goal was to systematically track the monopole shift of the νf_5/2 single-particle level with increased occupancy of the πf_7/2 orbital. The β-decay properties of the parent nuclides, along with the low-energy structure of the daughters, are presented and compared with the results of shell model calculations employing the GXPF1 interaction.     

Direct and inverse computation of Jacobi matrices of infinite iterated function systems

We introduce a new set of algorithms to compute the Jacobi matrices associated with invariant measures of infinite iterated function systems, composed of one–dimensional, homogeneous affine maps. We demonstrate their utility in the study of theoretical problems, like the conjectured almost periodicity of such Jacobi matrices, the singularity of the measures, and the logarithmic capacity of their support. Since our technique is based on a reversible transformation between pairs of Jacobi matrices, it can also be applied to solve an inverse/approximation problem. The proposed algorithms are tested in significant, highly sensitive cases: they perform in a stable fashion, and can reliably compute Jacobi matrices of large order.     

Dynamical systems and numerical analysis: the study of measures generated by uncountable I.F.S.

Measures generated by Iterated Function Systems composed of uncountably many one-dimensional affine maps are studied. We present numerical techniques as well as rigorous results that establish whether these measures are absolutely or singular continuous.