Microscopic study of the effect of intrinsic degrees of freedom on fusion

Fusion cross-sections are computed for the $^{40}$Ca$+^{40}$Ca system over a wide energy range with two microscopic approaches where the only phenomenological input is the Skyrme energy density functional. The first method is based on the coupled-channels formalism, using the bare nucleus-nucleus potential calculated with the frozen Hartree-Fock technique and the deformation parameters of vibrational states computed with the time-dependent Hartree-Fock (TDHF) approach. The second method is based on the density-constrained TDHF method to generate nucleus-nucleus potentials from TDHF evolution. Both approaches incorporate the effect of couplings to internal degrees of freedoms in different ways. The predictions are in relatively good agreement with experimental data.Comment: 6 pages, 11 figures. Invited talk to FUSION1

Evidence of microscopic effects in fragment mass distribution in heavy ion induced fusion-fission reactions

Our measurements of variances ($\sigma_{m}^2$) in mass distributions of fission fragments from fusion-fission reactions of light projectiles (C, O and F) on deformed thorium targets exhibit a sharp anomalous increase with energy near the Coulomb barrier, in contrast to the smooth variation of $\sigma_{m}^2$ for the spherical bismuth target. This departure from expectation based on a statistical description is explained in terms of microscopic effects arising from the orientational dependence in the case of deformed thorium targets.Comment: Replaced with revised version, to appear in Phys. Lett.

Effect of Pauli repulsion and transfer on fusion

The effect of the Pauli exclusion principle on the nucleus-nucleus bare potential is studied using a new density-constrained extension of the Frozen-Hartree-Fock (DCFHF) technique. The resulting potentials exhibit a repulsion at short distance. The charge product dependence of this Pauli repulsion is investigated. Dynamical effects are then included in the potential with the density-constrained time-dependent Hartree-Fock (DCTDHF) method. In particular, isovector contributions to this potential are used to investigate the role of transfer on fusion, resulting in a lowering of the inner part of the potential for systems with positive Q-value transfer channels.Comment: Proceedings of an invited talk given at FUSION17, Hobart, Tasmania, AU (20-24 February, 2017

Prescission neutron multiplicity and fission probability from Langevin dynamics of nuclear fission

A theoretical model of one-body nuclear friction which was developed earlier, namely the chaos-weighted wall formula, is applied to a dynamical description of compound nuclear decay in the framework of the Langevin equation coupled with statistical evaporation of light particles and photons. We have used both the usual wall formula friction and its chaos-weighted version in the Langevin equation to calculate the fission probability and prescission neutron multiplicity for the compound nuclei $^{178}$W, $^{188}$Pt, $^{200}$Pb, $^{213}$Fr, $^{224}$Th, and $^{251}$Es. We have also obtained the contributions of the presaddle and postsaddle neutrons to the total prescission multiplicity. A detailed analysis of our results leads us to conclude that the chaos-weighted wall formula friction can adequately describe the fission dynamics in the presaddle region. This friction, however, turns out to be too weak to describe the postsaddle dynamics properly. This points to the need for a suitable explanation for the enhanced neutron emission in the postsaddle stage of nuclear fission.Comment: RevTex, 14 pages including 5 Postscript figures, results improved by using a different potential, conclusions remain unchanged, to appear in Phys. Rev.

A practical guide for the study of human and murine sebaceous glands in situ

The skin of most mammals is characterised by the presence of sebaceous glands (SGs), whose predominant constituent cell population is sebocytes, that is, lipid-producing epithelial cells, which develop from the hair follicle. Besides holocrine sebum production (which contributes 90% of skin surface lipids), multiple additional SG functions have emerged. These range from antimicrobial peptide production and immunomodulation, via lipid and hormone synthesis/metabolism, to the provision of an epithelial progenitor cell reservoir. Therefore, in addition to its involvement in common skin diseases (e.g. acne vulgaris), the unfolding diversity of SG functions, both in skin health and disease, has raised interest in this integral component of the pilosebaceous unit. This practical guide provides an introduction to SG biology and to relevant SG histochemical and immunohistochemical techniques, with emphasis placed on in situ evaluation methods that can be easily employed. We propose a range of simple, established markers, which are particularly instructive when addressing specific SG research questions in the two most commonly investigated species in SG research, humans and mice. To facilitate the development of reproducible analysis techniques for the in situ evaluation of SGs, this methods review concludes by suggesting quantitative (immuno-)histomorphometric methods for standardised SG evaluation

An improved representation for evolving programs

A representation has been developed that addresses some of the issues with other Genetic Program representations while maintaining their advantages. This combines the easy reproduction of the linear representation with the inherita- ble characteristics of the tree representation by using fixed-length blocks of genes representing single program statements. This means that each block of genes will always map to the same statement in the parent and child unless it is mutated, irrespective of changes to the surrounding blocks. This method is compared to the variable length gene blocks used by other representations with a clear improvement in the similarity between parent and child. In addition, a set of list evaluation and manipulation functions was evolved as an application of the new Genetic Program components. These functions have the common feature that they all need to be 100% correct to be useful. Traditional Genetic Programming problems have mainly been optimization or approximation problems. The list results are good but do highlight the problem of scalability in that more complex functions lead to a dramatic increase in the required evolution time

Semantic transfer and contradictory evidence in intuitionistic fuzzy sets

The relationship between object level intuitionistic fuzzy sets and predicate based intuitionistic fuzzy sets is explored. Mass assignment uses a process called semantic unification to evaluate the degree to which one set supports another, the inverse function is semantic separation. Intuitionistic fuzzy sets are mapped onto a mass assignment framework and the semantic unification operator is generalised to support both mass assignment and intuitionistic fuzzy sets, as is semantic separation. Transfer of inconsistent and contradictory evidence are also dealt with

How the Pauli exclusion principle affects fusion of atomic nuclei

The Pauli exclusion principle induces a repulsion between composite systems of identical fermions such as colliding atomic nuclei. Our goal is to study how heavy-ion fusion is impacted by this "Pauli repulsion." We propose a new microscopic approach, the density-constrained frozen Hartree-Fock method, to compute the bare potential including the Pauli exclusion principle exactly. Pauli repulsion is shown to be important inside the barrier radius and increases with the charge product of the nuclei. Its main effect is to reduce tunneling probability. Pauli repulsion is part of the solution to the long-standing deep sub-barrier fusion hindrance proble

Evolving Perl

A list of requirements for a genetic programming representation is put forward and a representation separating the genotype and phenotype with a linear genome is presented. The target language for the genetic program is Perl. The mapping process, between the genotype and phenotype, converts blocks of four genes into program statements. This process is context-free and therefore provides inheritable characteristics. The representation is tested by evolving a selection of list evaluation and manipulation functions which are all evolved from the same language subset, with good results

Managing contradictory evidence

The paper draws on the theory of mass assignment to refine the underlying semantics of intuitionistic fuzzy sets. Inconsistency can arise from several sources and it is dealt with in different ways. All the representations of inconsistency and contradiction in this paper arise from considering restricting and positive evidence lattices. In particular this paper formally addresses the operators, intersection and conjunction in detail. Because union and disjunction are required to compute the values for intersection and conjunction these are also covered as part of the analysis