Monte Carlo simulation of age-dependent host-parasite relations

The death of a biological population is an extreme event which we investigate here for a host-parasitoid system. Our simulations using the Penna ageing model show how biological evolution can “teach” the parasitoids to avoid extinction by waiting for the right age of the host. We also show the dependence of extinction time on the population size.     

Coulomb excitation of neutron-rich 138,140,142Xe at REX-ISOLDE

We report on “safe” Coulomb excitation of neutron-rich ^138,140,142Xe nuclei. The radioactive nuclei have been produced by ISOLDE at CERN and post-accelerated by the REX-ISOLDE facility. The γ-rays emitted by the decay of excited states have been detected by the MINIBALL array. Recent results are presented.     

Two Kerr-NUT constituents in equilibrium

The equilibrium conditions for the superposition of two Kerr-NUT solutions are revisited. The new derivation of these conditions leads to formulas which include also the hyperextreme case. In the symmetric model of two hyperextreme constituents [3–5,8] the surfacef=0 of infinite red shift is investigated. It turns out that, for large enough distance parameter, the surfacef=0 consists of disconnected parts surrounding each source separately.     

Coexistence and mixing of spherical and deformed states in the region of light Hg-isotopes

The low-energy spectra of¹⁸⁶Hg and¹⁸⁴Hg are interpreted by a mixing of spherical and deformed states for angular momentum I=2, 4. In order to establish agreement between experimental results on¹⁸⁶Hg and¹⁸⁴Hg and potential calculations, a stronger isospin dependence of the pairing interaction is introduced. The existence of shape-isomeric states for¹⁸⁶Hg,¹⁸⁴Hg with a life-time ≈10^?8 sec is concluded from the model. The particle-vibration coupling is discussed as the probable origin for the odd-even staggering of the ground-state deformation.     

E0 transitions in 114,116,118Sn

Low-lying 0⁺ states have been excited in the (p, p′) reaction via the$\text{s}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ isobaric analog resonance in ^114,116Sn and in radioactive decay in ¹¹⁸Sn. From conversion electron measurements, values of $\text{X =}\text{B(}\text{EO}\text{;0}{}^{\mathrm{+}}\text{→ 0}{}_1{}^{\mathrm{+}}\text{)}\text{B(}\text{E}\text{2; 0}{}^{\mathrm{+}}\text{→2}{}_1{}^{\mathrm{+}}\text{)}$ are obtained from the 1953 keV state in ¹¹⁴Sn, 1757 and 2027 keV states in ¹¹⁶Sn and 1758 and 2056 keV states in ¹¹⁸Sn.     

Mössbauer study of Fe1 + xV2−xO4 spinels for the determination of cation distributions and magnetic structure

Mössbauer experiments were carried out in the temperature range of 80–500 K on the spinel series of Fe_{1 + x}V_2?xO₄. The determined cation distribution has Fe²⁺ and Fe³⁺ at both A and B spinel sublattice sites for t whole series except for x = 0. Charge hopping was observed at the B lattice sites. The present cation distribution reasonably predicts several experimentally observed constants such as the lattice constant, the oxygen parameter, the saturation magnetic moment and the Curie constant. The magnetic structure in best agreement with the experimental values shows the AA spins to be antiparallel for Fe, the BB spins to be parallel for identical ions and antiparallel for different ions, and shows a strongly antiparallel AB interaction between trivalent iron ions. Crystal distortions due to the Jahn-Teller effect were observed at 80 K for compositions with 0 ? x ? 0.75.