First decay study of the very neutron-rich isotope Br-93

The decay of the mass-separated, very neutron-rich isotope Br-93 has been studied by gamma-spectroscopy. A level scheme of its daughter Kr-93 has been constructed. Level energies, gamma-ray branching ratios and multipolarities suggest spins and parities which are in accord with a smooth systematics of the N=57 isotones for Z less-equal 40, suggesting the N=56 shell closure still to be effective in Kr isotopes. So far, there is no indication of a progressive onset of deformation in neutron-rich Kr isotopes.The decay of the mass-separated, very neutron-rich isotope Br-93 has been studied by gamma-spectroscopy. A level scheme of its daughter Kr-93 has been constructed. Level energies, gamma-ray branching ratios and multipolarities suggest spins and parities which are in accord with a smooth systematics of the N=57 isotones for Z less-equal 40, suggesting the N=56 shell closure still to be effective in Kr isotopes. So far, there is no indication of a progressive onset of deformation in neutron-rich Kr isotopes

Reaction rate for two--neutron capture by 4^4He

Recent investigations suggest that the neutrino--heated hot bubble between the nascent neutron star and the overlying stellar mantle of a type--II supernova may be the site of the r--process. In the preceding $\alpha$--process building up the elements to $A \approx 100$, the $^4$He(2n,$\gamma$)$^6$He-- and $^6$He($\alpha$,n)$^9$Be--reactions bridging the instability gap at $A=5$ and $A=8$ could be of relevance. We suggest a mechanism for $^4$He(2n,$\gamma$)$^6$He and calculate the reaction rate within the $\alpha$+n+n approach. The value obtained is about a factor 1.6 smaller than the one obtained recently in the simpler direct--capture model, but is at least three order of magnitude enhanced compared to the previously adopted value. Our calculation confirms the result of the direct--capture calculation that under representative conditions in the $\alpha$--process the reaction path proceeding through $^6$He is negligible compared to $^4$He($\alpha$n,$\gamma$)$^9$Be.Comment: 13 pages, 4 postscript figures, to appear in "Zeitschrift f. Physik A", changed internet address and filename, the uuencoded postscript file including the figures is available at ftp://is1.kph.tuwien.ac.at/pub/ohu/twoneutron.u

Detectable clonal mosaicism and its relationship to aging and cancer

In an analysis of 31,717 cancer cases and 26,136 cancer-free controls from 13 genome-wide association studies, we observed large chromosomal abnormalities in a subset of clones in DNA obtained from blood or buccal samples. We observed mosaic abnormalities, either aneuploidy or copy-neutral loss of heterozygosity, of >2 Mb in size in autosomes of 517 individuals (0.89%), with abnormal cell proportions of between 7% and 95%. In cancer-free individuals, frequency increased with age, from 0.23% under 50 years to 1.91% between 75 and 79 years (P = 4.8 × 10(-8)). Mosaic abnormalities were more frequent in individuals with solid tumors (0.97% versus 0.74% in cancer-free individuals; odds ratio (OR) = 1.25; P = 0.016), with stronger association with cases who had DNA collected before diagnosis or treatment (OR = 1.45; P = 0.0005). Detectable mosaicism was also more common in individuals for whom DNA was collected at least 1 year before diagnosis with leukemia compared to cancer-free individuals (OR = 35.4; P = 3.8 × 10(-11)). These findings underscore the time-dependent nature of somatic events in the etiology of cancer and potentially other late-onset diseases

Large-scale calculations of nuclear-structure data for simulation data bases

In the macroscopic-microscopic model we have (1) enhanced our FRDM (1992) model of nuclear ground-state masses and shapes, (2) performed a global calculation of nuclear shape isomers, in which we characterize the ground-state and isomer minima in terms of their relative energies and shapes, and furthermore provide the saddle heights between all pairs of minima, and (3) performed a calculation of fission potential-energy surfaces for more than 5 million different shapes for each of 5254 nuclei from A = 170 to A = 330. We use an immersion technique borrowed from geography to determine saddle points and minima in these surfaces. We also use this technique to establish if structures such as deep valleys separated by high ridges are present. These would then give rise to different modes of fission

The origin of the Ca-Ti-Cr-Fe-Ni isotopic anomalies in the inclusion EK-1-4-1 of the Allende meteorite

The origin of the correlated Ca-Ti-Cr-Fe-Ni isotopic anomalies in the Ca-Al-rich inclusion of the EK-1-4-1 of the Allende is a longstanding puzzle. The search for a stellar environment which could explain the enrichment of neutron-rich stable Ca-...-Ni isotopes in a self-consistent way requires nuclear physics data far from stability. Recent experimental data have been obtained in the region of the shell closures N = 28 and N = 40, where the possible progenitors of these nuclei are found. Astrophysical network calculations have been updated by including the new beta-decay properties and microscopic predictions of neutron-capture cross sections. Interplay between nuclear structure far from stability and the observed isotopic anomalies is especially evident for the high entropy (S similar or equal to 150) scenario which would characterize the neutrino-driven wind in a type II supernova. (C) 2003 Academie des sciences. Published by Editions scientifiques et medicales Elsevier SAS. All rights reserved.Peer reviewe

Kernchemische Untersuchungen von Kernreaktionen und Kernzerfall. Teilprojekt 1-3: Untersuchung der Kernspaltung am Massenseparator LOHENGRIN. Schwerionenreaktionen. Kernstruktur extrem neutronenreicher Nuklide Wissenschaftlicher Bericht

Available from TIB Hannover: F97B1369+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Kernchemische Untersuchungen von Kernreaktionen und Kernzerfall Bericht der Arbeitsgruppen

Fast chemical separation methods having recently been developed for transactinide elements, it has been possible to study neutron-rich nuclides of longer half-life, and in particular the chemical behaviour of element 106, seaborgium. The report explains the online methods applied, as for instance extraction in a scintillator and measurements with pulse shape discrimination and parent-daughter correlation. (DG)Durch die Entwicklung schneller chemischer Trennmethoden fuer Transaktinidenelemente werden neutronenreiche Nuklide mit laengeren Halbwertzeiten und insbesondere das chemische Verhalten des Elements 106, Seaborgium, untersucht. Die hierzu vorgesehenen on-line Verfahren, wie z.B. die Extraktion in einen Szintillator und Messung mit Pulsformdiskriminierung und Mutter-Tochter-Korrelation, werden beschrieben. (DG)SIGLEAvailable from TIB Hannover: F94B2092+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

The r-process in the high entropy bubble

Peer reviewe

Radiochemische Untersuchungen von Kernreaktionen und Kernzerfall

The neutron-induced fission of Th-233 (TRIGA Mainz), Pu-239, Am-242 and Cf-249 (ILL) was studied. The yields in the very asymmetric fission show extreme odd-even and shell effects. In the fission of Cf-249 strong deviations of the experimental mass yields from predictions were observed. With a detection system based on Rutherford backscattering of heavy ions a search for supermassive nuclei in nature was performed. Upper limits between 10"-"1"0 and 10"-"1"5 relative to the number of nucleons were found for the abundance of strange supermassive nuclei with masses A=500 to 10"7 amu. An on-line separation system was developed for studies on neutron-rich isotopes of the heaviest elements. The coexistence of deformed intruder states and spherical states in odd-mass nuclei in the mass region A=100-120 was investigated. Furthermore experiments were performed in order to study the #beta#"- decay of Rn-223, Rn-225 and Rn-227. The sharing excitation energy in binary reactions at the barrier is dominated by shape fluctuations at scission. Quasielastic transfer reactions show a complex behaviour at the barrier. Inclusive measurements of cross sections for the excitation of giant resonances at 1 GeV/u gave hints for a strong excitation of 2-phonon states. With LAND, the 2-phonon GDR was detected exclusively. In central Au+Au collisions the 'squeeze-out' of neutrons was detected for the first time. At CERN-ISOLDE 18 neutron-rich isotopes in the vicinity of "7"8Ni have been measured among them the two r-process 'waiting-point' nuclei "7"9Cu and "8"0Zn. QRPA calculations have been performed for exotic Fe-Ni isotopes. Detailed spectroscopic investigations of neutron-rich Kr isotopes indicate sphericity up to N=58 as in their Sr isotones. For "8"9","9"1Kr and "9"1","9"3Sr an I=j-1 (j=#nu#d_5_/_2) anomaly has been observed. Shape coexistence has been verified in the N=58,59 isotones of Sr and Zr. In "9"8","1"0"0Sr and "9"9","1"0"1Sr band-twinning has been shown at maximum possible ground-state deformation. In these nuclei, the usual A"5"/"3 mass dependence of the moment of inertia is cancelled. (orig.)Untersucht wurde die neutroneninduzierte Spaltung von Th-232 (TRIGA Mainz) Pu-239, Am-242 und Cf-249 (ILL). Die Ausbeuten in der stark asymmetrischen Spaltung zeigen extreme gerade-ungerade- und Schalen-Effekte. Beim Cf-249 ergaben sich gravierende Abweichungen der experimentellen Massenausbeuten von Voraussagen. Mit einem Detektorsystem, basierend auf Rutherford-Rueckstreuung schwerer Ionen, wurde in verschiedenartigen Materialien nach X-Teilchen und seltsamer Materie gesucht. Es ergaben sich keine Hinweise fuer 'supermassive Kerne'. Die Nachweisgrenzen liegen zwischen 10"-"1"0 und 10"-"1"5 schwere Elementarteilchen pro Nukleon im Massenbereich zwischen 500 und 10"7 amu. Zur Untersuchung neutronenreicher Kerne der schwersten Elemente wurde ein on-line Trennsystem entwickelt. Die Koexistenz von Intruderzustaenden und Zustaenden mit sphaerischer Kerngestalt in ungeraden Kernen wurde im Massenbereich A=100-120 untersucht. Weiterhin wurden Experimente zum Zerfall der Radonisotope 223, 225 und 227 durchgefuehrt. Die Aufteilung der Anregungsenergie in binaeren Reaktionen wird an der Barriere von Formfluktuationen am Zerreisspunkt bestimmt. Quasielastische Transferreaktionen zeigen an der Barriere ein komplexes Verhalten. Inklusive Messungen der Wirkungsquerschnitte fuer die Anregung von Riesenresonanzen bei 1 GeV/u ergaben Hinweise auf eine unerwartet starke 2-Phonon-Anregung. Mit LAND wurde die 2-Phonon GDR exklusiv nachgewiesen. In zentralen Au+Au-Stoessen wurde mit LAND erstmals der 'squeeze-out' von Neutronen nachgewiesen. Es wurden die T_1_/_2 und P_n-Werte von 18 neutronenreichen Isotopen in der A#approx#80 Gegend gemessen, darunter die beiden r-Prozess 'Waiting-Point' Kerne "7"9Cu und "8"0Zn. Fuer Fe-Ni Isotope wurden QRPA-Rechnungen durchgefuehrt. Untersuchungen der Kernstruktur von N#approx#56 Kr-Isotopen ergaben eine enge Korrespondenz der Niveauschemata mit den sphaerischen Sr-Iosotonen; ausserdem wurde eine selten auftretende I=j-1 (j=#nu#e_5_/_2) Anomalie in "8"9","9"1Kr und "9"1","9"3Sr beobachtet. Fuer "9"6","9"7Sr und "9"8","9"9Zr konnte Formkoexistenz nachgewiesen werden. Neben den Zwillingsrotatoren "9"8","1"0"0Sr wurden auch identische #nu#[411]3/2"-Banden in "9"9","1"0"1Sr identifiziert. (orig.)SIGLEAvailable from TIB Hannover: F94B1748+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman