Superheavy Nuclei in the Relativistic Mean Field Theory

We have carried out a study of superheavy nuclei in the framework of the Relativistic Mean-Field theory. Relativistic Hartree-Bogoliubov (RHB) calculations have been performed for nuclei with large proton and neutron numbers. A finite-range pairing force of Gogny type has been used in the RHB calculations. The ground-state properties of very heavy nuclei with atomic numbers Z=100-114 and neutron numbers N=154-190 have been obtained. The results show that in addition to N=184 the neutron numbers N=160 and N=166 exhibit an extra stability as compared to their neighbors. For the case of protons the atomic number Z=106 is shown to demonstrate a closed-shell behavior in the region of well deformed nuclei about N=160. The proton number Z=114 also indicates a shell closure. Indications for a doubly magic character at Z=106 and N=160 are observed. Implications of shell closures on a possible synthesis of superheavy nuclei are discussed.Comment: 29 pages Latex, 13 ps figures, to appear in Nucl. Phys.

Beta-decay half-lives of very neutron rich Ni, Co, Fe isotopes produced by thermal fission of 235^{235}U and 239^{239}Pu

We study the influence of lexical subsumption on the semantic proximity of terms. By studying the semantic relation between lexically subsumed terms in an existing controlled vocabulary and those in a corpus, we formulate hypotheses on the underlying specific relations. These hypotheses enable us to propose an ordering of term variants found in the corpus, by probability of decreasing semantic proximity. Results from our experiment show that surface indices like the presence of proper names, compounds and the number of added words in a term variant are criteria for ordering the variants of the same term. The ranking obtained will enable us to form more semantically-cohesive clusters. Applications targeted are text mining, question-answering and science and technology watch

Beta-decay half-lives of very neutron rich Ni, Co, Fe isotopes produced by thermal fission of 235^{235}U and 239^{239}Pu

We study the influence of lexical subsumption on the semantic proximity of terms. By studying the semantic relation between lexically subsumed terms in an existing controlled vocabulary and those in a corpus, we formulate hypotheses on the underlying specific relations. These hypotheses enable us to propose an ordering of term variants found in the corpus, by probability of decreasing semantic proximity. Results from our experiment show that surface indices like the presence of proper names, compounds and the number of added words in a term variant are criteria for ordering the variants of the same term. The ranking obtained will enable us to form more semantically-cohesive clusters. Applications targeted are text mining, question-answering and science and technology watch

Short-Duration X-ray Transients Observed with WATCH on Granat:Are Some of Them Related to Stellar Flares?

AbstractDuring 1990-92, the WATCH all-sky X-ray monitor on GRANAT has discovered 6 short-duration X-ray transients. We discuss their possible relationship to peculiar stars. Only one source, GRS 1100-77 seems to be related to a T Tauri star.</jats:p

INTEGRAL observations of recurrent fast X-ray transient sources

Fast X-ray Transients (FXTs) are believed to be non-recurrent bright X-ray sources lasting less than a day and occurring at serendipitous positions, they can best detected and discovered by instruments having a sufficiently wide field of view and high sensitivity. The IBIS/ISGRI instrument onboard INTEGRAL is particularly suited to detect new or already known fast X-ray transient sources. We report on IBIS/ISGRI detection of newly discovered outbursts of three fast transient sources located at low Galactic latitude: SAX J1818.6-1703; IGR J16479-4514; IGR J17391-302/XTE J1739-302. The reported results confirm and strengthen the very fast transient nature of these sources, given that all their newly detected outbursts have a duration less than about 3 hours. Additionally, they provide the first evidence for a possible recurrent fast transient behaviour as all three sources were detected in outburst by ISGRI more than once during the last 2 years