Incorporating spatial correlations into multispecies mean-field models

In biology, we frequently observe different species existing within the same environment. For example, there are many cell types in a tumour, or different animal species may occupy a given habitat. In modeling interactions between such species, we often make use of the mean-field approximation, whereby spatial correlations between the locations of individuals are neglected. Whilst this approximation holds in certain situations, this is not always the case, and care must be taken to ensure the mean-field approximation is only used in appropriate settings. In circumstances where the mean-field approximation is unsuitable, we need to include information on the spatial distributions of individuals, which is not a simple task. In this paper, we provide a method that overcomes many of the failures of the mean-field approximation for an on-lattice volume-excluding birth-death-movement process with multiple species. We explicitly take into account spatial information on the distribution of individuals by including partial differential equation descriptions of lattice site occupancy correlations. We demonstrate how to derive these equations for the multispecies case and show results specific to a two-species problem. We compare averaged discrete results to both the mean-field approximation and our improved method, which incorporates spatial correlations. We note that the mean-field approximation fails dramatically in some cases, predicting very different behavior from that seen upon averaging multiple realizations of the discrete system. In contrast, our improved method provides excellent agreement with the averaged discrete behavior in all cases, thus providing a more reliable modeling framework. Furthermore, our method is tractable as the resulting partial differential equations can be solved efficiently using standard numerical techniques

(Re)defining learning design: a framework fit for the twenty-first century

Learning design as we know it is at a crossroads. Based on learning theories published almost a hundred years ago, it is designing for in-person learning and a student demographic that hasn’t been seen since the 1950s. In the twenty-first century, and particularly post Covid-19, the field is long overdue for an update that puts blended and online learning at the forefront, addresses the inevitable link between the internet and education and responds to the changing demographics of learners in higher education. This paper will look at pedagogy and learning design through a modern lens with an aim to redefine the field and develop a new framework for learning design that is intuitive, inclusive, and grounded in the current century

Family functioning differences across the deployment cycle in British Army families: the perceptions of wives and children

Introduction Military deployment can have an adverse effect on a soldier’s family, though little research has looked at these effects in a British sample. We investigated wives’ of UK serving soldiers perceptions of marital and family functioning, across three stages of the deployment cycle: currently deployed, post-deployment and pre-deployed, plus a non-military comparison group. Uniquely, young (aged 3.5 – 11 years) children’s perceptions of their family were also investigated, using the Parent-Child Alliance (PCA) coding scheme of drawings of the family. Materials and Methods Two hundred and twenty British military families of regular service personnel from the British Army’s Royal Armoured Corps (RAC), were sent survey packs distributed with a monthly welfare office newsletter. Wives were asked to complete a series of self-report items, and the youngest child in the family between the ages of 3.5 and 11 years was asked to draw a picture of their family. Complete data were available for 78 military families, and an additional 34 non-military families were recruited via opportunity sampling. Results Results indicated wives of currently deployed and recently returned personnel were less satisfied with their family and its communication, and children’s pictures indicated higher levels of dysfunctional PCA, whilst pre-deployed families responded similarly to non-military families. Marital satisfaction was similar across all groups except pre-deployed families who were significantly more satisfied. Non-military and pre-deployed families showed balanced family functioning, and currently and recently deployed families demonstrated poor family functioning. In comparison to non-military families, pre-deployed families showed a large ‘spike’ in the rigidity subscale of the FACES IV. Conclusion Wives’ perceptions of family functioning, but not marital satisfaction, differed between the deployment groups. The results from the coded children’s drawings correlated with the self-report measures from the wife/mother, indicating that children’s drawings could be a useful approach when working with younger children in this area. It is tentatively suggested that the differences across deployment stage on family functioning could be mediated not only by communication difficulties between deployed personnel and their families, but also by its effect on the children in the family. Larger-scale longitudinal research is needed to investigate this further

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

Closing in on the MEN2A Locus

The mapping of the locus for multiple endocrine neoplasia type 2A (MEN 2A) to chromosome 10 using linkage is briefly reviewed including a discussion of linkage strategy and reference to some of the exclusions before the assignment. The subsequent development of the map of the centromeric region of the chromosome and the linking of what appear to be the four closest flanking markers and the centromeric alphoid sequence to the disease locus are reviewed. To date no recombination has been observed between the centromeric marker and the MEN2A locus among, at least, 26 informative meioses, 11 of which are phase known. While no obligate recombination has been observed between the markers FNRB, D10S34, and RBP3 and the MEN2A locus in males, it has been observed in females and is as much as 10% for the marker RBP3. The sex difference in recombination frequency is significant. The four polymorphic flanking markers, FNRB, D10S34, RBP3, and D10S5, along with the centromeric marker D10Z1 will prove to be useful for management of the families with the disease. It will be possible in most families to give a very high (or low) probability for at risk members of the families and in some cases the DNA results will be virtually diagnostic

Estimating the masses of extra-solar planets

All extra-solar planet masses that have been derived spectroscopically are lower limits since the inclination of the orbit to our line-of-sight is unknown except for transiting systems. It is, however, possible to determine the inclination angle, i, between the rotation axis of a star and an observer's line-of-sight from measurements of the projected equatorial velocity (v sin i), the stellar rotation period (P_rot) and the stellar radius (R_star). This allows the removal of the sin i dependency of spectroscopically derived extra-solar planet masses under the assumption that the planetary orbits lie perpendicular to the stellar rotation axis. We have carried out an extensive literature search and present a catalogue of v sin i, P_rot, and R_star estimates for exoplanet host stars. In addition, we have used Hipparcos parallaxes and the Barnes-Evans relationship to further supplement the R_star estimates obtained from the literature. Using this catalogue, we have obtained sin i estimates using a Markov-chain Monte Carlo analysis. This allows proper 1-sigma two-tailed confidence limits to be placed on the derived sin i's along with the transit probability for each planet to be determined. While a small proportion of systems yield sin i's significantly greater than 1, most likely due to poor P_rot estimations, the large majority are acceptable. We are further encouraged by the cases where we have data on transiting systems, as the technique indicates inclinations of ~90 degrees and high transit probabilities. In total, we estimate the true masses of 133 extra-solar planets. Of these, only 6 have revised masses that place them above the 13 Jupiter mass deuterium burning limit. Our work reveals a population of high-mass planets with low eccentricities and we speculate that these may represent the signature of different planetary formation mechanisms at work.Comment: 40 pages, 6 tables, 2 figures. Accepted for publication in the Monthly Notices of the Royal Astronomical Society after editing of Tables 1 & 6 for electronic publication. Html abstract shortened for astro-ph submissio

Constraints on radiative decay of the 17-keV neutrino from COBE Measurements

It is shown that, for a nontrivial radiative decay channel of the 17-keV neutrino, the photons would distort the microwave background radiation through ionization of the universe. The constraint on the branching ratio of such decays from COBE measurements is found to be more stringent than that from other considerations. The limit on the branching ratio in terms of the Compton $y$ parameter is $B_\gamma < 1.5 \times 10^{-7} ({\tau_\nu \over 10^{11} sec})^{0.45} ({y \over 10^{-3}})^{1.11} h^{-1}$ for an $\Omega=1, \Omega_b=0.1$ universe.Comment: 7 pages. (figures will be sent on request) (To appear in Phys. Rev. D.

Dynamical effects in fusion with exotic nuclei

[Background] Reactions with stable beams have demonstrated a strong interplay between nuclear structure and fusion. Exotic beam facilities open new perspectives to understand the impact of neutron skin, large isospin, and weak binding energies on fusion. Microscopic theories of fusion are required to guide future experiments. [Purpose] To investigate new effects of exotic structures and dynamics in near-barrier fusion with exotic nuclei. [Method] Microscopic approaches based on the Hartree-Fock (HF) mean-field theory are used for studying fusion barriers in $^{40-54}$Ca+$^{116}$Sn reactions for even isotopes. Bare potential barriers are obtained assuming frozen HF ground-state densities. Dynamical effects on the barrier are accounted for in time-dependent Hartree-Fock (TDHF) calculations of the collisions. Vibrational couplings are studied in the coupled-channel framework and near-barrier nucleon transfer is investigated with TDHF calculations. [Results] The development of a neutron skin in exotic calcium isotopes strongly lowers the bare potential barrier. However, this static effect is not apparent when dynamical effects are included. On the contrary, a fusion hindrance is observed in TDHF calculations with the most neutron rich calcium isotopes which cannot be explained by vibrational couplings. Transfer reactions are also important in these systems due to charge equilibration processes. [Conclusions] Despite its impact on the bare potential, the neutron skin is not seen as playing an important role in the fusion dynamics. However, the charge transfer with exotic projectiles could lead to an increase of the Coulomb repulsion between the fragments, suppressing fusion. The effect of transfer and dissipative mechanisms on fusion with exotic nuclei deserve further studies.The authors are grateful to M. Dasgupta, D. J. Hinde, and A. S. Umar for stimulating discussions during this work. This research was undertaken with the assistance of resources from the National Computational Infrastructure (NCI), which is supported by the Australian Government. This research was supported under Australian Research Council’s Future Fellowship (Project No. FT120100760), Discovery Projects (Project No. DP140101337), and Laureate Fellowship (Project No. FL110100098) funding schemes

The detection and photometric redshift determination of distant galaxies using SIRTF's Infrared Array Camera

We investigate the ability of the Space Infrared Telescope Facility's Infrared Array Camera to detect distant (z ~ 3)galaxies and measure their photometric redshifts. Our analysis shows that changing the original long wavelength filter specifications provides significant improvements in performance in this and other areas.Comment: 28 pages incl 12 figures; to appear in June 1999 PASP. Fig.12 replaced with corrected versio