Occurrence of Prunus necrotic ringspot virus and Prune dwarf virus in wild cherries in the locality velehrad (South Moravia, Czech Republic)

The occurrence and spatial distribution of PDV and PNRSV in a seed wild cherry (Prunus avium) orchard were studied during the period 1996 - 1999. Each year any newly infected trees were immediately removed. The cumulative infection rate of PDV-positive trees reached 4.7% and number of new infections per year was 1.2 %, on average. Although the number of centers was found to be decreasing (from 22 in 1996 to 10 in 1999), eradication of PDV was not achieved. Only one case of PNRSV infection was found in 1997.Keywords: PDV, PNRSV, ELISA, epidemiolog

Factorization of shell-model ground-states

We present a new method that accurately approximates the shell-model ground-state by products of suitable states. The optimal factors are determined by a variational principle and result from the solution of rather low-dimensional eigenvalue problems. The power of this method is demonstrated by computations of ground-states and low-lying excitations in sd-shell and pf-shell nuclei.Comment: 5+epsilon pages, 5 eps-figures. Main additions: wave-function overlaps, angular momentum expectation values, application to Ni56. To be published as Rapid Communication in PR

Local three-nucleon interaction from chiral effective field theory

The three-nucleon (NNN) interaction derived within the chiral effective field theory at the next-to-next-to-leading order (N2LO) is regulated with a function depending on the magnitude of the momentum transfer. The regulated NNN interaction is then local in the coordinate space, which is advantages for some many-body techniques. Matrix elements of the local chiral NNN interaction are evaluated in a three-nucleon basis. Using the ab initio no-core shell model (NCSM) the NNN matrix elements are employed in 3H and 4He bound-state calculations.Comment: 17 pages, 9 figure

From non-Hermitian effective operators to large-scale no-core shell model calculations for light nuclei

No-core shell model (NCSM) calculations using ab initio effective interactions are very successful in reproducing experimental nuclear spectra. The main theoretical approach is the use of effective operators, which include correlations left out by the truncation of the model space to a numerically tractable size. We review recent applications of the effective operator approach, within a NCSM framework, to the renormalization of the nucleon-nucleon interaction, as well as scalar and tensor operators.Comment: To be submited to J. Phys. A, special issue on "The Physics of Non-Hermitian Operators

Large-basis shell-model calculations for p-shell nuclei

Results of large-basis shell-model calculations for nuclei with A=7-11 are presented. The effective interactions used in the study were derived microscopically from the Reid93 potential and take into account the Coulomb potential as well as the charge dependence of T=1 partial waves. For A=7, a $6\hbar\Omega$ model space was used, while for the rest of the studied nuclides, the calculations were performed in a $4\hbar\Omega$ model space. It is demonstrated that the shell model combined with microscopic effective interactions derived from modern nucleon-nucleon potentials is capable of providing good agreement with the experimental properties of the ground state as well as with those of the low-lying excited states.Comment: 17 pages. REVTEX. 16 PostScript figure

Properties of 12^{12}C in the {\it ab initio} nuclear shell-model

We obtain properties of $^{12}$C in the {\it ab initio} no-core nuclear shell-model. The effective Hamiltonians are derived microscopically from the realistic CD-Bonn and the Argonne V8' nucleon-nucleon (NN) potentials as a function of the finite harmonic oscillator basis space. Binding energies, excitation spectra and electromagnetic properties are presented for model spaces up to $5\hbar\Omega$. The favorable comparison with available data is a consequence of the underlying NN interaction rather than a phenomenological fit.Comment: 9 pages, 2 figure

Projector operators for the no-core shell model

Projection operators for the use within ab initio no-core shell model, are suggested.Comment: 3 page