Systematic measurements of transient fields for W,Os and Pt ions traversing Fe

Transient magnetic fields were measured for W, Os and Pt ions traversing iron hosts with average velocities in the range from approximately 1.6v ₀ to 4.8v ₀ (v ₀=c/137, Bohr velocity). Transient fields for W and Os in Fe are consistent with behaviour found for lighter rare-earth ions and are about 20% stronger than those for Pt in Fe over the majority of the velocity range examined. A measurement was made to confirm that possible heavy-ion beam induced attenuations of the transient field are negligible for low-velocity Pt ions excited by Ni beams. Results are discussed in terms of both empirical and model-based parameterizations of the transient field strength.     

FP-LAPW Calculations of the EFG at Cd Impurities in Rutile SnO2

We report an ab initio study of the electric-field gradient (EFG) at Cd impurities located at the cation site in the semiconductor SnO₂(rutile phase). The study was performed with the WIEN97 implementation of the FP-LAPW method. In order to simulate the diluted Cd-impurity in the SnO₂ host and to calculate the electronic structure of the system we used a 72-atoms super-cell, studying the relaxation introduced by the impurity in the lattice. The free-relaxation process performed shows that the relaxations of the oxygen nearest-neighbors of the impurity are not isotropic. Our prediction for the EFG tensor are compared with experimental results and point-charge model predictions. This revised version was published online in September 2006 with corrections to the Cover Date.     

The sl2 Loop Algebra Symmetry of the Six-Vertex Model at Roots of Unity

We demonstrate that the six vertex model (XXZ spin chain) with =(q+q^-1)/2 and q^2N=1 has an invariance under the loop algebra of sl₂ which produces a special set of degenerate eigenvalues. For =0 we compute the multiplicity of the degeneracies using Jordan–Wigner techniques.     

Umladungsmessungen von Li-Ionen an freitragenden Folien

Measurements of the equilibrium charge distribution of Lithium ions in the energy range 3 to 10 keV passing through very thin foils are described. For the componentsF _{0 ∞} andF _{1 ∞} a mean value of 0.5 was found.     

Solution of the SU(2)q invariant XY-Model

We consider the SU(2)q invariant version of the XY-Model, present its solution for a chain of lengthN and its relation to the XY-Model with open boundary conditions for a chain of lengthN-1, construct the representation of the generalized spin operators by fermionic operators and discuss the SU(2)q multiplets. We determine the energies of the groundstates in the subspaces with fixed spin, compare them with results for the XY-Models with periodic and open boundary conditions and extract the central charge.     

Application of stereological methods to estimate post-mortem brain surface area using 3 T MRI

The Cavalieri and Vertical Sections methods of design based stereology were applied in combination with 3 tesla (i.e. 3 T) Magnetic Resonance Imaging (MRI) to estimate cortical and subcortical volume, area of the pial surface, area of the grey–white matter boundary, and thickness of the cerebral cortex. The material comprises eight human cadaveric cerebri which had been separated into sixteen cerebral hemisphere specimens prior to embedding in agar gel. The results from MRI were compared with corresponding ‘gold standard’ values subsequently obtained by application of the same methodology using physical sectioning of the specimens.     

New Developments in the Eight Vertex Model II. Chains of Odd Length

We study the transfer matrix of the 8 vertex model with an odd number of lattice sites N. For systems at the root of unity pointsη=mK/L with m odd the transfer matrix is known to satisfy the famous ‘‘TQ’’ equation where Q(υ) is a specifically known matrix. We demonstrate that the location of the zeroes of this Q(υ) matrix is qualitatively different from the case of evenN and in particular they satisfy a previously unknown equation which is more general than what is often called ‘‘Bethe’s equation.’’ For the case of even m where no Q(υ) matrix is known we demonstrate that there are many states which are not obtained from the formalism of the SOS model but which do satisfy the TQ equation. The ground state for the particular case of η=2K/3 and N odd is investigated in detail.