The nuclear shell effects near the r-process path in the relativistic Hartree-Bogoliubov theory

We have investigated the evolution of the shell structure of nuclei in going from the r-process path to the neutron drip line within the framework of the Relativistic Hartree-Bogoliubov (RHB) theory. By introducing the quartic self-coupling of $\omega$ meson in the RHB theory in addition to the non-linear scalar coupling of $\sigma$ meson, we reproduce the available data on the shell effects about the waiting-point nucleus $^{80}$Zn. With this approach, it is shown that the shell effects at N=82 in the inaccessible region of the r-process path become milder as compared to the Lagrangian with the scalar self-coupling only. However, the shell effects remain stronger as compared to the quenching exhibited by the HFB+SkP approach. It is also shown that in reaching out to the extreme point at the neutron drip line, a terminal situation arises where the shell structure at the magic number is washed out significantly.Comment: 18 pages (revtex), 8 ps figures, to appear in Phys. Rev.

Generator Coordinate Calculations for the Breathing-Mode Giant Monopole Resonance in Relativistic Mean Field Theory

The breathing-mode giant monopole resonance (GMR) is studied within the framework of the relativistic mean-field theory using the Generator Coordinate Method (GCM). The constrained incompressibility and the excitation energy of isoscalar giant monopole states are obtained for finite nuclei with various sets of Lagrangian parameters. A comparison is made with the results of nonrelativistic constrained Skyrme Hartree-Fock calculations and with those from Skyrme RPA calculations. In the RMF theory the GCM calculations give a transition density for the breathing mode, which resembles much that obtained from the Skyrme HF+RPA approach and also that from the scaling mode of the GMR. From the systematic study of the breathing-mode as a function of the incompressibility in GCM, it is shown that the GCM succeeds in describing the GMR energies in nuclei and that the empirical breathing-mode energies of heavy nuclei can be reproduced by forces with an incompressibility close to $K = 300$ MeV in the RMF theory.Comment: 27 pages (Revtex) and 5 figures (available upon request), Preprint MPA-793 (March 1994

JISC Final Report: IncReASe (Increasing Repository Content through Automation and Services)

The IncReASe (Increasing Repository Content through Automation and Services) was an eighteen month project (subsequently extended to twenty months) to enhance White Rose Research Online (WRRO)1. WRRO is a shared repository of research outputs (primarily publications) from the Universities of Leeds, Sheffield and York; it runs on the EPrints open source repository platform. The repository was created in 2004 and had steady growth but, in common with many other similar repositories, had difficulty in achieving a “critical mass” of content and in becoming truly embedded within researchers’ workflows. The main aim of the IncReASe project was to assess ingestion routes into WRRO with a view to lowering barriers to deposit. We reviewed the feasibility of bulk import of pre-existing metadata and/or full-text research outputs, hoping this activity would have a positive knock-on effect on repository growth and embedding. Prior to the project, we had identified researchers’ reluctance to duplicate effort in metadata creation as a significant barrier to WRRO uptake; we investigated how WRRO might share data with internal and external IT systems. This work included a review of how WRRO, as an institutional based repository, might interact with the subject repository of the Economic and Social Research Council (ESRC). The project addressed four main areas: (i) researcher behaviour: we investigated researcher awareness, motivation and workflow through a survey of archiving activity on the university web sites, a questionnaire and discussions with researchers (ii) bulk import: we imported data from local systems, including York’s submission data for the 2008 Research Assessment Exercise (RAE), and developed an import plug-in for use with the arXiv2 repository (iii) interoperability: we looked at how WRRO might interact with university and departmental publication databases and ESRC’s repository. (iv) metadata: we assessed metadata issues raised by importing publication data from a variety of sources. A number of outputs from the project have been made available from the IncReASe project web site http://eprints.whiterose.ac.uk/increase/. The project highlighted the low levels of researcher awareness of WRRO - and of broader open access issues, including research funders’ deposit requirements. We designed some new publicity materials to start to address this. Departmental publication databases provided a useful jumping off point for advocacy and liaison; this activity was helpful in promoting awareness of WRRO. Bulk import proved time consuming – both in terms of adjusting EPrints plug-ins to incorporate different datasets and in the staff time required to improve publication metadata. A number of deposit scenarios were developed in the context of our work with ESRC; we concentrated on investigating how a local deposit of a research paper and attendant metadata in WRRO might be used to populate ESRC’s repository. This work improved our understanding of researcher workflows and of the SWORD protocol as a potential (if partial) solution to the single deposit, multiple destination model we wish to develop; we think the prospect of institutional repository / ESRC data sharing is now a step closer. IncReASe experienced some staff recruitment difficulties. It was also necessary to adapt the project to the changing IT landscape at the three partner institutions – in particular, the introduction of a centralised publication management system at the University of Leeds. Although these factors had some impact on deliverables, the aims and objectives of the project were largely achieved

Anomaly in the charge radii of Pb isotopes

The anomalous behaviour of the charge radii of the isotopic chain of Pb nuclei has been studied in the relativistic mean field theory. It has been shown that the relativistic mean field provides an excellent description of the anomalous kink in the isotopic shifts about $^{208}$Pb. This contrasts strongly from the Skyrme mean field, where almost all the known and realistic forces fail to reproduce the observed trend in the empirical data on the charge radii. The results have been discussed in the perspective of differences in the ans\"atze of the relativistic and the Skyrme mean-field theories.Comment: 10 pages (Latex) and 3 figures (avilable upon request); Phys. Lett. B (in print), TUM-ITP-SH93/

Ground state properties of exotic nuclei near Z=40 in the relativistic mean-field theory,

Study of the ground-state properties of Kr, Sr and Zr isotopes has been performed in the framework of the relativistic mean field (RMF) theory using the recently proposed relativistic parameter set NL-SH. It is shown that the RMF theory provides an unified and excellent description of the binding energies, isotope shifts and deformation properties of nuclei over a large range of isospin in the Z=40 region. It is observed that the RMF theory with the force NL-SH is able to describe the anomalous kinks in isotope shifts in Kr and Sr nuclei, the problem which has hitherto remained unresolved. This is in contrast with the density-dependent Skyrme Hartree-Fock approach which does not reproduce the behaviour of the isotope shifts about shell closure. On the Zr chain we predict that the isotope shifts exhibit a trend similar to that of the Kr and Sr nuclei. The RMF theory also predicts shape coexistence in heavy Sr isotopes. Several dramatic shape transitions in the isotopic chains are shown to be a general feature of nuclei in this region. A comparison of the properties with the available mass models shows that the results of the RMF theory are generally in accord with the predictions of the finite-range droplet model.Comment: 24 pages Latex, 7 figures (available upon request), Nuclear Physics A (in press)

Surface Incompressibility from Semiclassical Relativistic Mean Field Calculations

By using the scaling method and the Thomas-Fermi and Extended Thomas-Fermi approaches to Relativistic Mean Field Theory the surface contribution to the leptodermous expansion of the finite nuclei incompressibility has been self-consistently computed. The validity of the simplest expansion, which contains volume, volume-symmetry, surface and Coulomb terms, is examined by comparing it with self-consistent results of the finite nuclei incompressibility for some currently used non-linear sigma-omega parameter sets. A numerical estimate of higher-order contributions to the leptodermous expansion, namely the curvature and surface-symmetry terms, is made.Comment: 18 pages, REVTeX, 3 eps figures, changed conten

Toxoplasma gondii infection in native village chickens (Gallus domesticus) in Selangor and Melaka, Malaysia

Toxoplasmosis is a worldwide zoonosis caused by the protozoa Toxoplasma gondii which affects human and animals. Village chickens Gallus domesticus) most commonly known as Ayam Kampung or free-range chickens, have been suggested to play a role in the epidemiology of toxoplasmosis. This study determines the presence of T. gondii in the villagechicken populations in two states of Malaysia. A total of 50 serum samples from the chickens from Selangor (n=20) and Melaka (n=30) were collected and analysed using commercial serological kits. T. gondii antigen was detected in 20% (Selangor 30%; Melaka 13%) samplesusing ELISA test and anti-T. gondii antibody was detected in all positive ELISA samples using the indirect haemagglutination test (IHAT). Histopathological examination revealed tissue changes such as inflammation and degeneration in brain and liver of seropositive chickens.This is the first report of T. gondii infection in the village chickens in Malaysia

Light Nuclei near Neutron and Proton Drip Lines in the Relativistic Mean-Field Theory

We have made a detailed study of the ground-state properties of nuclei in the light mass region with atomic numbers Z=10-22 in the framework of the relativistic mean-field (RMF) theory. The nonlinear $\sigma\omega$ model with scalar self-interaction has been employed. The RMF calculations have been performed in an axially deformed configuration using the force NL-SH. We have considered nuclei about the stability line as well as those close to proton and neutron drip lines. It is shown that the RMF results provide a good agreement with the available empirical data. The RMF predictions also show a reasonably good agreement with those of the mass models. It is observed that nuclei in this mass region are found to possess strong deformations and exhibit shape changes all along the isotopic chains. The phenomenon of the shape coexistence is found to persist near the stability line as well as near the drip lines. It is shown that the magic number N=28 is quenched strongly, thus enabling the corresponding nuclei to assume strong deformations. Nuclei near the neutron and proton drip lines in this region are also shown to be strongly deformed.Comment: 49 pages Latex, 12 postscript figures, to appear in Nuclear Physics

Cell coverage analysis of a low altitude aerial base station in wind perturbations

The use of Unmanned Aerial Vehicles (UAVs) as Aerial Base Station (ABSs) is emerging as an effective technique to provide high capacity wireless networks to ground users. In this paper, cell coverage of a low altitude UAV is investigated for supporting such networks. An analytical framework for cell coverage area of an ABS is provided for Suburban, Urban and Urban high rise environments using a solid angle approach including radio link propagation effects in air- to-ground channel obtained from ray tracing simulations. Here, we account for the change in Euler angles such as roll, pitch and yaw due to perturbations by wind gusts or intentional maneuvers which leads to an increase in the geometrical coverage area by approximately 40-50 %, given same transmission power and antenna gain of the ABS

Rare-Earth Nuclei: Radii, Isotope-Shifts and Deformation Properties in the Relativistic Mean Field Theory

A systematic study of the ground-state properties of even-even rare earth nuclei has been performed in the framework of the Relativistic Mean-Field (RMF) theory using the parameter set NL-SH. Nuclear radii, isotope shifts and deformation properties of the heavier rare-earth nuclei have been obtained, which encompass atomic numbers ranging from Z=60 to Z=70 and include a large range of isospin. It is shown that RMF theory is able to provide a good and comprehensive description of the empirical binding energies of the isotopic chains. At the same time the quadrupole deformations $\beta_{2}$ obtained in the RMF theory are found to be in good agreement with the available empirical values. The theory predicts a shape transition from prolate to oblate for nuclei at neutron number N=78 in all the chains. A further addition of neutrons up to the magic number 82 brings about the spherical shape. For nuclei above N=82, the RMF theory predicts the well-known onset of prolate deformation at about N=88, which saturates at about N=102. The deformation properties display an identical behaviour for all the nuclear chains. A good description of the above deformation transitions in the RMF theory in all the isotopic chains leads to a successful reproduction of the anomalous behaviour of the empirical isotopic shifts of the rare-earth nuclei. The RMF theory exhibits a remarkable success in providing a unified and microscopic description of various empirical data.Comment: Revtex (50 pages) and 24 figures (available upon request), Nuclear Physics A (in press