Microscopic Enhancement of Heavy-Element Production

Realistic fusion barriers are calculated in a macroscopic-microscopic model for several soft-fusion heavy-ion reactions leading to heavy and superheavy elements. The results obtained in such a realistic picture are very different from those obtained in a purely macroscopic model. For reactions on 208:Pb targets, shell effects in the entrance channel result in fusion-barrier energies at the touching point that are only a few MeV higher than the ground state for compound systems near Z = 110. The entrance-channel fragment-shell effects remain far inside the touching point, almost to configurations only slightly more elongated than the ground-state configuration, where the fusion barrier has risen to about 10 MeV above the ground-state energy. Calculated single-particle level diagrams show that few level crossings occur until the peak in the fusion barrier very close to the ground-state shape is reached, which indicates that dissipation is negligible until very late in the fusion process. Whereas the fission valley in a macroscopic picture is several tens of MeV lower in energy than is the fusion valley, we find in the macroscopic-microscopic picture that the fission valley is only about 5 MeV lower than the fusion valley for soft-fusion reactions leading to compound systems near Z = 110. These results show that no significant ``extra-extra-push'' energy is needed to bring the system inside the fission saddle point and that the typical reaction energies for maximum cross section in heavy-element synthesis correspond to only a few MeV above the maximum in the fusion barrier.Comment: 7 pages. LaTeX. Submitted to Zeitschrift fur Physik A. 5 figures not included here. Complete preprint, including device-independent (dvi), PostScript, and LaTeX versions of the text, plus PostScript files of the figures, available at http://t2.lanl.gov/publications/publications.html or at ftp://t2.lanl.gov/pub/publications/mehe

Natural and Induced Seismicity in the Lake Erie-Lake Ontario Region: Reactivation of Ancient Faults with Little Neotectonic Displacement

The two most prominent seismic zones in the Lake Erie-Lake Ontario region are associated with the Akron magnetic lineament and with the Clarendon-Linden fault. Both these features are recognized from geophysical data as regional basement structures related to the Grenville collisional orogen. Neotectonic displacement is not geologically evident, although Paleozoic reactivation is manifested by the Clarendon-Linden fault. We have sharpened the definition of seismic zones in the region by introducing newly discovered events, improving constraints on locations and size for many others, and omitting unreliable ones. This seismicity tends to occur on old faults with minor neotectonic displacements. Related conclusions are: 1) neotectonic surface displacement is not necessary for fault capability, 2) seismogenic faults may have geological and/or geophysical expressions, and 3) a stationary moment release at the historic level requires more capable faults than the ones active during the historic period. Waste fluid injection, oil recovery, and salt-brine recovery have been implicated in cases of induced seismicity in the study area and might have contributed a significant portion of the known earthquakes. Fluid is being injected into the basal platform formation at a depth of 1.8 km near Ashtabula, Ohio. In July 1987, about a year after the onset of injection, a mbLg=3.8 main shock occurred within a 60 km wide area with no known prior seismicity. Aftershocks detected by a short-term local seismic network define a vertical left-lateral fault in the basement just below the platform rocks as close as 700 m from the injection well, probably a reactivated pre-existing fault. Subsequent seismicity suggests a westward migration by 5-10 km, possibly along the same fault.Les deux principales zones sismiques de la région sont associées au linéament magnétique d'Akron et à la faille de Clarendon-Linden. Selon les données géophysiques, ces deux éléments sont reconnus comme étant des structures régionales du socle reliés à l'orogenèse de Grenville. On a précisé la détermination des zones sismiques dans la région en ajoutant les séismes découverts récemment, en précisant les lieux et les dimensions d'autres séismes et en éliminant ceux qui sont mal connus. La sismicité tend à se manifester dans d'anciennes failles avec peu de décalage néotectonique. On en conclut que 1) le décalage néotectonique superficiel ne met pas en cause la compétence d'une faille; 2) les failles d'origine sismique peuvent avoir des manifestations géologiques ou géophysiques; 3) un relâchement momentané localisé survenant au cours de la période historique requiert plus de compétence qu'en ont les failles actives au cours de cette période. L'injection de liquide, la récupération de pétrole ou de sel ont été impliquées dans les cas de sismicité provoquée dans la région et ont probablement causé une bonne partie des séismes connus. Près d'Ashtabula, en Ohio, on a injecté des liquides à une profondeur de 1,8 km à la base de la plate-forme. En juillet 1987, environ un an après le début des injections, un séisme de mbLg= 3,8 s'est produit dans une aire de 60 km de superficie apparamment non sismique. Les répliques enregistrées par un réseau temporaire ont laissé voir une faille verticale à décrochement sénestre, immédiatement sous la plate-forme rocheuse, à près de 700 m du puits d'injection; il s'agit probablement d'une faille réactivée. Par la suite, la sismicité indique une migration de 5 à 10 km, probablement le long de la même faille.Die zwei hauptsàchlichen seismischen Zonen in der Eriesee-Ontariosee-Region werden mit dem magnetischen Lineament von Akron in Verbindung gebracht. Mittels geophysikalischer Daten erkennt man in diesen Bildungen régionale Untergrundstrukturen, die mit der Kollisions-Orogenese von Grenville verbunden sind. Wir haben die Definition der seismischen Zonen in dem Gebiet pràzisiert, indem wir kùrzlich entdeckte Erdbeben ergànzt und fur viele andere die Definition der Ort und GroRe betreffenden Zwànge verbessert haben, und die Unzuverlàssigen weggelassen haben. Dièse Erdbeben haben die Tendenz, auf alten Verwerfungen mit geringen neotektonischen Verstellungen aufzutreten. Hieraus kann man schlieBen: 1) neotektonische Oberflàchenverstellung ist keine Bedingung fur Verwerfungsfâhigkeit, 2) durch Erdbeben entstandene Verwerfungen kônnen sich geologisch und/oder geophysikalisch ausdrùcken und 3) eine ortsgebundene momentané Entlastung auf historischer Ebene erfor-dert mehr fàhige Verwerfungen als die, welche wàhrend der historischen Période aktiv waren, In den Fallen von induziertem Auftreten von Erdbeben im untersuchten Gebiet waren Zufùhrung von Flùssigkeit und ôl- und Salzgewinnung beteiligt, und sie haben wohl einen bedeutenden Anteil der bekannten Erdbeben hervorgerufen. Bei Ashtabula, Ohio, hat man in einer Tiefe von 1.8 km Flùssigkeit an der Basis der Plattformbildung eingespritzt. Im JuIi 1987, etwa ein Jahr nach Beginn der Ein-spritzungen, kam es zu einem neuen gewi-chtigen Beben von mbM) = 3.8 innerhalb eines 60 km breiten Gebiets, in dem vorher kein Erdbeben bekannt war. Nach beben, die von einem kurzfristigen ôrtlichen Erdbeben-Netzwerk registriert wurden, ergeben eine vertikale linksseitige Verwerfung im Untergrund unter der Felsenplattform, etwa 700 m vom Einspritzungsbohrloch entfernt; es handelt sich moglicherweise um eine reaktivierte, schon existierende Verwerfung. Darauffolgende Erdbeben weisen auf eine Wanderung westwàrts von 5-10 km, moglicherweise Iangs derselben Verwerfung

A Sec14 domain protein is required for photoautotrophic growth and chloroplast vesicle formation in Arabidopsis thaliana.

In eukaryotic photosynthetic organisms, the conversion of solar into chemical energy occurs in thylakoid membranes in the chloroplast. How thylakoid membranes are formed and maintained is poorly understood. However, previous observations of vesicles adjacent to the stromal side of the inner envelope membrane of the chloroplast suggest a possible role of membrane transport via vesicle trafficking from the inner envelope to the thylakoids. Here we show that the model plant Arabidopsis thaliana has a chloroplast-localized Sec14-like protein (CPSFL1) that is necessary for photoautotrophic growth and vesicle formation at the inner envelope membrane of the chloroplast. The cpsfl1 mutants are seedling lethal, show a defect in thylakoid structure, and lack chloroplast vesicles. Sec14 domain proteins are found only in eukaryotes and have been well characterized in yeast, where they regulate vesicle budding at the trans-Golgi network. Like the yeast Sec14p, CPSFL1 binds phosphatidylinositol phosphates (PIPs) and phosphatidic acid (PA) and acts as a phosphatidylinositol transfer protein in vitro, and expression of Arabidopsis CPSFL1 can complement the yeast sec14 mutation. CPSFL1 can transfer PIP into PA-rich membrane bilayers in vitro, suggesting that CPSFL1 potentially facilitates vesicle formation by trafficking PA and/or PIP, known regulators of membrane trafficking between organellar subcompartments. These results underscore the role of vesicles in thylakoid biogenesis and/or maintenance. CPSFL1 appears to be an example of a eukaryotic cytosolic protein that has been coopted for a function in the chloroplast, an organelle derived from endosymbiosis of a cyanobacterium

Neutrino Masses and Grand Unification

We discuss some models of neutrino masses and mixings in the context of fermion masses in Grand Unified Theories.Comment: Talk, 6th Int. Workshop on TAUP99, 6-10 September 1999, Paris,Franc

Shell stabilization of super- and hyperheavy nuclei without magic gaps

Quantum stabilization of superheavy elements is quantified in terms of the shell-correction energy. We compute the shell correction using self-consistent nuclear models: the non-relativistic Skyrme-Hartree-Fock approach and the relativistic mean-field model, for a number of parametrizations. All the forces applied predict a broad valley of shell stabilization around Z=120 and N=172-184. We also predict two broad regions of shell stabilization in hyperheavy elements with N approx 258 and N approx 308. Due to the large single-particle level density, shell corrections in the superheavy elements differ markedly from those in lighter nuclei. With increasing proton and neutron numbers, the regions of nuclei stabilized by shell effects become poorly localized in particle number, and the familiar pattern of shells separated by magic gaps is basically gone.Comment: 6 pages REVTEX, 4 eps figures, submitted to Phys. Lett.

Skyrme Hartree-Fock Calculations for the Alpha Decay Q Values of Super-Heavy Nuclei

Hartree-Fock calculations with the SKX Skyrme interaction are carried out to obtain alpha-decay Q values for deformed nuclei above $^{208}$Pb assuming axial symmetry. The results for even-even nuclei are compared with experiment and with previous calculations. Predictions are made for alpha-decay Q values and half-lives of even-even super-heavy nuclei. The results are also compared for the recently discovered odd-even chain starting at Z=112 and N=165.Comment: 17 pages, 8 figures, 1 tabl

Heavy sterile neutrinos: Bounds from big-bang nucleosynthesis and SN 1987A

Cosmological and astrophysical effects of heavy (10 - 200 MeV) sterile Dirac neutrinos, mixed with the active ones, are considered. The bounds on mass and mixing angle from both supernovae and big-bang nucleosynthesis are presented.Comment: 19 pages, 5 figures, 1 table. Some references adde

Elastic behavior and pressure-induced structural modifications of the microporous Ca(VO)Si4O10·4H2O dimorphs cavansite and pentagonite

The behavior of natural microporous cavansite and pentagonite, orthorhombic dimorphs of Ca(VO) (Si4O10)x4H2O, was studied at high pressure by means of in situ synchrotron X-ray powder diffraction with a diamond anvil cell using two different pressure-transmitting fluids: methanol:ethanol: water = 16:3:1 (m.e.w.) and silicone oil (s.o.). In situ diffraction-data on a cavansite sample were collected up to 8.17(5) GPa in m.e.w, and up to 7.28(5) GPa in s.o. The high-pressure structure evolution was studied on the basis of structural refinements at 1.08(5), 3.27(5) and 6.45(5) GPa. The compressional behavior is strongly anisotropic. When the sample is compressed in s.o. from Pamb to 7.28(5) GPa, the volume contraction is 12.2%, whereas a, b and c decrease by 1.6%, 10.3% and 0.3%, respectively. The main deformation mechanisms at high-pressure are basically driven by variation of the T\u2013O\u2013T angles. Powder diffraction data on a pentagonite sample were collected up to 8.26(5) GPa in m.e.w and 8.35(5) GPa in s.o. Additional single-crystal X-ray diffraction experiments were performed in m.e.w. up to 2.04(5) GPa. In both cases, pressure-induced over-hydration was observed in m.e.w. at high pressure. The penetration of a new H2O molecule leads to a stiffening effect of the whole structure. Moreover, between 2.45(5) and 2.96(5) GPa in m.e.w., a phase transition from an orthorhombic to a triclinic phase was observed. In s.o. pentagonite also transformed to a triclinic phase above 1.71(5) GPa. The overall compressibility of pentagonite and cavansite in s.o. is comparable, with a volume contraction of 11.6% and 12.2%, respectively

Cosmological and astrophysical bounds on a heavy sterile neutrino and the KARMEN anomaly

Constraints on the lifetime of the heavy sterile neutrino, that was proposed as a possible interpretation of the KARMEN anomaly, are derived from primordial nucleosynthesis and SN 1987A. Together with the recent experimental bounds on the nu_s lifetime, SN 1987A completely excludes this interpretation. Nucleosynthesis arguments permit a narrow window for the lifetime in the interval 0.1-0.2 sec. If nu_s possesses an anomalous interaction with nucleons, the SN bounds may not apply, while the nucleosynthesis ones would remain valid.Comment: Figure 7 changed. (30 pages, 7 ps-figures, 2 tables. Subm to NPB