Shell structure of superheavy nuclei in self-consistent mean-field models

We study the extrapolation of nuclear shell structure to the region of superheavy nuclei in self-consistent mean-field models—the Skyrme-Hartree-Fock approach and the relativistic mean-field model—using a large number of parametrizations which give similar results for stable nuclei but differ in detail. Results obtained with the folded-Yukawa potential which is widely used in macroscopic-macroscopic models are shown for comparison. We focus on differences in the isospin dependence of the spin-orbit interaction and the effective mass between the models and their influence on single-particle spectra. The predictive power of the mean-field models concerning single-particle spectra is discussed for the examples of 208Pb and the spin-orbit splittings of selected neutron and proton levels in 16O, 132Sn, and 208Pb. While all relativistic models give a reasonable description of spin-orbit splittings, all Skyrme interactions show a wrong trend with mass number. The spin-orbit splitting of heavy nuclei might be overestimated by 40%–80%, which exposes a fundamental deficiency of the current nonrelativistic models. In most cases the occurrence of spherical shell closures is found to be nucleon-number dependent. Spherical doubly magic superheavy nuclei are found at 184298114, 172292120, or 184310126 depending on the parametrization. The Z=114 proton shell closure, which is related to a large spin-orbit splitting of proton 2f states, is predicted only by forces which by far overestimate the proton spin-orbit splitting in 208Pb. The Z=120 and N=172 shell closures predicted by the relativistic models and some Skyrme interactions are found to be related to a central depression of the nuclear density distribution. This effect cannot appear in macroscopic-microscopic models or semiclassical approaches like the extended Thomas-Fermi-Strutinski integral approach which have a limited freedom for the density distribution only. In summary, our findings give a strong argument for 172292120 to be the next spherical doubly magic superheavy nucleus

Potential energy surfaces of superheavy nuclei

We investigate the structure of the potential energy surfaces of the superheavy nuclei 158258Fm100, 156264Hs108, 166278112, 184298114, and 172292120 within the framework of self-consistent nuclear models, i.e., the Skyrme-Hartree-Fock approach and the relativistic mean-field model. We compare results obtained with one representative parametrization of each model which is successful in describing superheavy nuclei. We find systematic changes as compared to the potential energy surfaces of heavy nuclei in the uranium region: there is no sufficiently stable fission isomer any more, the importance of triaxial configurations to lower the first barrier fades away, and asymmetric fission paths compete down to rather small deformation. Comparing the two models, it turns out that the relativistic mean-field model gives generally smaller fission barriers

Die drei Mediengebote der Kirche. Globale Herausforderungen der katholischen Presse

Zwei Merkmale prägen den Wandel der Medienlandschaft: Das erste ist die Schnelligkeit. Vor wenigen Jahren noch hatte man Zeit, auf bestimmte Vorgänge zu reagieren. Heute hat sich das Medienangebot vervielfacht und damit auch die Konkurrenz. Der Erfolg von Journalisten wird anhand ihrer Reaktionsschnelligkeit gemessen. Man kann sagen: Das Gebot der Schnelligkeit überholt jenes der Genauigkeit. Zweitens: Auch in Deutschland umgibt uns, seit sich das Internet in beinahe jedem Haushalt durchgesetzt hat, eine Überfülle von Informationen. Hunderte von Fernsehkanälen, Hunderte von Radioprogrammen, 320 Tageszeitungen, Tausende von Magazinen und eben das Internet – so ist es in vielen Teilen der Welt. Diese Überfülle bietet Chancen, kann aber auch ratlos machen: Es fehlt die Übersicht.Für die Kirche in Deutschland ist es in einer solchen Medienlandschaft schwer, Gehör zu finden.  (...

Risse im Medien-Fundament der Demokratie. Anmerkungen zu Ursachen und Folgen einer krisenhaften Entwicklung

Der rasche Wandel der Medienlandschaft bringt Folgen hervor, die die notwendige Informationsbasis einer Demokratie gefährden. Das macht es nicht nur notwendig, entschiedene medienpädagogische Maßnahmen zu ergreifen. Man muss darüber hinaus auch über breite und tiefe Informationsangebote im Bereich Print und Online nachdenken, die über eine öffentlich-rechtliche Verfasstheit ähnlich dem öffentlich-rechtlichen Rundfunk subventioniert werden könnten. EnglishCracks in the Media-Foundation of Democracy. Comments on the Causes and Consequences of a Critical DevelopmentThe rapid transformation of the media landscape produces consequences, which endanger the required “information foundation” of a democracy. This makes it necessary to not only undertake clear media-pedagogical measures. In addition, one must also think about the breadth and depth of the information content in the fields of print and online media possessing a framework similar to broadcasting regulated by public law which could be subsidized.

Improving the acquisition and implementation of in-line factory measurement systems

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1995.Includes bibliographical references (p. 79).by Michael P. Rutz.M.S

Comment on ``Structure of exotic nuclei and superheavy elements in a relativistic shell model''

A recent paper [M. Rashdan, Phys. Rev. C 63, 044303 (2001)] introduces the new parameterization NL-RA1 of the relativistic mean-field model which is claimed to give a better description of nuclear properties than earlier ones. Using this model ^{298}114 is predicted to be a doubly-magic nucleus. As will be shown in this comment these findings are to be doubted as they are obtained with an unrealistic parameterization of the pairing interaction and neglecting ground-state deformation.Comment: 2 pages REVTEX, 3 figures, submitted to comment section of Phys. Rev. C. shortened and revised versio

alpha-decay chains of Z=114, A=289 and Z=118, A=293 in the relativistic mean-field model

A comparison of calculated and experimental Q_alpha values of superheavy even-even nuclei and a few selected odd-N nuclei is presented in the framework of the relativistic mean-field model with the parameterization NL-Z2. Blocking effects are found to be important for a proper description of Q_alpha of odd mass nuclei. The model gives a good overall description of the available experimental data. The mass and charge assignment of the recently measured decay chains from Dubna and Berkeley is in agreement with the predictions of the model. The analysis of the new data does not allow a final conclusion about the location of the expected island of spherical doubly-magic superheavy nuclei.Comment: 4 pages REVTeX, 4 eps figures, accepted for publication in Phys. Rev.

Purifying selection in corvids is less efficient on islands

Funding was provided by the European Research Council (ERCStG-336536 FuncSpecGen to J.B.W.W.), the Swedish Research Council Vetenskapsrådet (621-2013-4510 to J.B.W.W.), the Knut and Alice Wallenberg Foundation (to J.B.W.W.), the Lawski foundation (to V.E.K. and J.B.W.W.), the German Research Foundation (KU 3402/1-1 to V.E.K.), the UK’s Biotechnology and Biological Sciences Research Council (BB/G023913/2 to C.R.), and the New Zealand Marsden Fund (to G.R.H.).Theory predicts that deleterious mutations accumulate more readily in small populations. As a consequence, mutation load is expected to be elevated in species where life-history strategies and geographic or historical contingencies reduce the number of reproducing individuals. Yet, few studies have empirically tested this prediction using genome-wide data in a comparative framework. We collected whole-genome sequencing data for 147 individuals across seven crow species (Corvus spp.). For each species, we estimated the distribution of fitness effects of deleterious mutations and compared it with proxies of the effective population size Ne. Island species with comparatively smaller geographic range sizes had a significantly increased mutation load. These results support the view that small populations have an elevated risk of mutational meltdown, which may contribute to the higher extinction rates observed in island species.Publisher PDFPeer reviewe

Atmospheric River Tracking Method Intercomparison Project (ARTMIP): project goals and experimental design

The Atmospheric River Tracking Method Intercomparison Project (ARTMIP) is an international collaborative effort to understand and quantify the uncertainties in atmospheric river (AR) science based on detection algorithm alone. Currently, there are many AR identification and tracking algorithms in the literature with a wide range of techniques and conclusions. ARTMIP strives to provide the community with information on different methodologies and provide guidance on the most appropriate algorithm for a given science question or region of interest. All ARTMIP participants will implement their detection algorithms on a specified common dataset for a defined period of time. The project is divided into two phases: Tier 1 will utilize the Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) reanalysis from January 1980 to June 2017 and will be used as a baseline for all subsequent comparisons. Participation in Tier 1 is required. Tier 2 will be optional and include sensitivity studies designed around specific science questions, such as reanalysis uncertainty and climate change. High-resolution reanalysis and/or model output will be used wherever possible. Proposed metrics include AR frequency, duration, intensity, and precipitation attributable to ARs. Here, we present the ARTMIP experimental design, timeline, project requirements, and a brief description of the variety of methodologies in the current literature. We also present results from our 1-month proof-of-concept trial run designed to illustrate the utility and feasibility of the ARTMIP project